TEACHING ATLAS HEAD Gild NECK IMAGING Robert Lufkin Alexandra Borges Pablo Villablanca
Thieme
of
Teaching Atlas of H...
1259 downloads
5500 Views
46MB Size
Report
This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!
Report copyright / DMCA form
TEACHING ATLAS HEAD Gild NECK IMAGING Robert Lufkin Alexandra Borges Pablo Villablanca
Thieme
of
Teaching Atlas of Head and Neck Imaging
Teaching Atlas of Head and Neck Imaging
edited by
Robert Lufkin, MD Professor Department of Radiological Sciences UCLA School of Medicine Los Angeles, California
Alexandra Borges, MD Hospital Assistant in Radiology Instituto Portugues de Oncologia-Centro de Lisboa Lisboa, Portugal and
Pablo Villablanca, MD Assistant Professor Director, Clinical Imaging Processing Service Department of Radiological Sciences UCLA School of Medicine Los Angeles, California
2000 Thieme New York . Stuttgart
Thieme New York
333 Seventh Avenue New York, NY 10001 Editor: Jane E. Pennington Editorial Director: Ave McCracken Editorial Assistant: Todd Warnock Developmental Manager: Kathleen P Lyons Director, Production and Manufacturing: Anne Vinnicombe Production Editor: Janice G. Stangel Marketing Director: Phyllis Gold Sales Manager: Ross Lumpkin Chief Financial Officer: Seth S. Fishman President: Brian D. Scanlan Cover Designer: Kevin Kall Compositor: The PRO Group, Inc. Printer: Maple-Vail Book Manufacturing Group The Library of Congress Cataloging-in-Publication data is available from the publisher. Copyright © 2000 by Thieme Medical Publishers. Inc. This book, including all parts thereof, is legally protected by copyright. Any use, exploitation or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent. is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, mimeographing or duplication of any kind, translating, preparation of microfilms. and electronic data processing and storage.
Important note: Medical knowledge is ever-changing. As new research and clinical experience broaden our knowledge, changes in treatment and drug therapy may be required. The authors and editors of the material herein have consulted sources believed to be reliable in their efforts to provide information that is complete and in accord with the standards accepted at the time of publication. However, in view of the possibility of human error by the authors, editors, or publisher of the work herein, or changes in medical knowledge. neither the authors, editors, publisher, nor any other party who has been involved in the preparation of this work, warrants that the information contained herein is in every respect accurate or complete, and they are not responsible for any errors or omissions or for the results obtained fTom use of such information. Readers are encouraged to confirm the information contained herein with other sources. For example, readers are advised to check the product information sheet included in the package of each drug they plan to administer to be certain that the information contained in this publication is accurate and that changes have not been made in the recommended dose or in the contraindications for administration. This recommendation is of particular importance in connection with new or infrequently used drugs. Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain. Printed in the United States of America
5 4 3 2 I TNY ISBN 0-86577-691-1 GTV ISBN 3-13-107881-2
To all who have a passion in life AB RL
To my loving and supportive family PV RL
CONTENTS Preface Acknowledgme n ts
......................................... . . ................ . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ..... . . . . . . . ....................
I.
....
.
....
...........................................................................................
XI Xill
CENTRAL SKULL BASE
3
Case 1 .
Petroclival Meningioma
Case 2.
Trigeminal Nerve Schwannoma
Case 3.
Fibrous Dysplasia
Case 4.
Chondrosarcoma
18
Case 5.
Clival Chordoma
22
Case 6.
M e tastasis ..................................................... . . .. . . .. . ................................
U.
....
. . ..
. . . . . . . . . . .......... . . . . . ...................................
..................
.
.....
.
......................
. . ..
.....
..............
.
....
.
8 13
27
LARYNX AND HYPOPHARYNX
Case 7.
Epiglo ttitas ........................................................ ....................... ............. .
35
Case 8.
Laryngocele
38
Case 9.
Cord Paralysis
Case 1 0.
Posttraumatic Deformi ty
Case 1 1 .
Vallecular Cyst . .
Case 1 2 .
Chondroid Tumor of the Laryn x
Case 1 3.
Glottic Carcinoma
Case 14.
Transglo tlic/Supraglo ttic Carci noma
Case 1 5 .
Pyriform Sinus Carcinoma
Case 16.
Metas tasis
m.
.
............ . . . . ..... . . . . . .. . ........ . . . . . . . . . . . . . . .. . . .............
...
. .. ..
....
. . . .
..........
..
.
..
...
...........
...........................
.. .
...
.
. .
.. . . . .
.
. . .. ..
. . .
.
.......
..
.
......
.
...
.
. .. . . .
.
.
.. .
.....
.
.
. . . . . . . . . . . . . .. . .
.
42
. ..........
46
.. .
50
. . . . . . . . . . . . . . . . . . . . . . .. . . . .....
..........................................................
. . . . . . . . . . . . . . . . . . . . ........ . . . . . . . .........
. . . . . . . . . . . . . . . . ..... . . . . . . ...... . . . . . .. . . .........
54 58 62
.........
66
................................ ............... .............. ...............
69
.....
. . ...
........
.
................................. . . . . . . .
NASOPHARYNX AND PARAPHARYNGEAL SPACE
Case 17.
Tornwal d t Cyst
Case 1 8.
Juvenile Nasopharyngeal A ngiofibroma
Case 19.
Glomus Vagale
Case 20.
Post-Styloid
XII
Case 2 1 .
Lymphoma
...
Case 22.
Liposarcoma
Case 23 .
Rhabdosarcoma
Case 24.
Squamous Cell Carcinoma
IV.
. ..
. . . . . . . . . . . . . . . . . . . . . . ......................................
...................
....................
.
........................
.
.....
.
........
. . . . . . . . . . . . . . . . . . . .. . . . . . . . . .. . . ....................... ............... ...
...
..
. . . . .........
.. . . .
..... . . . .
.
. . . . .....
.
..
. . . . . . . . . . . . . .. . . . . . .. . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . .. . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .
Nerve Schwannoma
. . . . . . ....
....
78 82
.. . . ..... . .
86
.. . ........ . . . .. . . . . . . . . . . .. . ..... . . .. . . . . . . . . . . . . . . . . . ...... . . . . .
89
. . . . . . . .......................... ........................ ...............
92
.................. . . . . . .
. . . . ....
75
... . . . . . . . . . . . .. . . . . . . . . . ...... . . . . . . . .
..
.. . . . . . . . .. . . . . . . . . . .. . . . . . . . .. . . . . . . . . . . . . . . . . .
......
. . . .
. .
. . ... . . . . . . . .. .
.
......
.
.........
..
. . . . . . . . . . . ....
.. .
....
. . . .. . . . . .. .. . ...
..
..
..
..
..
...
..
..
96 101
NECK, THYROID, PARATHYROID
Case 25.
Thyroglossal Duct Cyst
............................................
.
.............................
1 07
I CONTENTS Branchial Cleft Cyst .... .. ... ................. ........... .. ........ .. .......... .. .. ..
Case 27.
Lymphangioma . . . . . . .. ... . . .. .. . . . . . . . . . . . . . . .. .. ... . . . . . . . . . . ..... . . ...
1 15
Case 28.
Tortuous Carotid Artery ........................................................................
1 18
Case 29.
Jug Vein Thrombosis
.. .... .. ........ .. .. ....... .... ..
1 22
Case 30.
Lipoma . ... . . . . .. . . .............................. ..... .............. . . . . . . . . . . . . . . . . .... ..
1 27
Case 3 ] .
Madelung Disease ...... . . .. . . ............... ..... . . . . .. . . . . . . . ... . . . . . . ...... .....
132
Case 32.
Retropharyngeal Abscess . ..... .. . . ..... . . . . . . . . . . . .. . .
. . . . . . . . . . . . ...
1 37
Case 33.
Carotid Body Tumor .. . ............................. .. ........... .......... . .............
143
Case 34.
Schwanoma .. .. .. . ... .. ........... . ..... . ....... .. ..... ..... . ....... ...............
147
Case 35.
Adenopathy
152
Case 36.
Reidel's Thyroiditis .
Case 37.
Goiter
Case 38.
Anaplastic Thyroid Carcinoma . . . .. . .. .. .. . . .. .... . . .... ... . .. .
1 69
Case 39.
Parathyroid Adenoma . .. . . . . . . . . . . . . . . . .. .. . . . . . . . . .. . .. ... ...... .. ...
1 74
Case 40.
Tracheal Carcinoma . . . .. ................................... . . . . . . . . . .. . . . .. . . . . . . .
V.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
..
..
.
.
. . .
.
.
.
.
..
..
..
..
.
.
.
.
.
.
.
..
.
..
..
.
..
.
.
..
.
.
.
.
.
..
.
..
.
.
.
.
.
.
..
.
. .
.
.
.
..
.......
.
.
. .
.
.
.
.
.
.
. . . . ... . . .....
..
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
. .
.
.
..
.
.
.
.
.
.....
.
..
.
.
..
.
. .
.
. .
.
.
..
.
.
. . .. . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . .. .. .. . . . .. . . ..... ......
..
.
.
.
.
.
....
..
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
..
..
. .. . . . .. ... . .. . .. . ........... .. ........ .. ...... . .
..
.
...
..
.
.
.
...
.
.
..
.
. .
. .
..
.
. . ........ . . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .................... . . . . . .......
.
.
.
.
.
..
. .
.
.
.
..
..
.
.
.
.
.
.
.
. . .
.
.
.
.
. .
..
.
.
.
. .
.
.
..
.
.
.
..
.
.
. . .
...
.
..
. . .
.
..
..
..
.
157 1 63
1 79
ORBIT AND VISUAL PATHWAYS
Case 4 1 .
Cellulitis . . . ..... . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . .. . . .. ... ... .. ..
Case 42.
Dacroadenitis .. ...... . . ... . .. . .... .. . ...... .. .............. ......... ... ....... ...
1 89
Case 43.
Pseudotumor . ............ ........ ............ . . . ... . . . . .. . . . .. .... . . . . . . . . ....... ..
1 92
Case 44.
Graves' Ophthalmopath y ................................................ ......................
1 97
Case 45.
Fat Supression Artifact . . . . . . . . . . . . .... . . . . . ..... . . . . . . . . . . . . . . . . . ... ....... ... 203
Case 46.
Optic Neuritis ..... ...... .................... .. .. ........ .............. ............. ... ... ..
207
Case 47.
Hemangioma .................. ............... ....... ........... ............... ....... . . . . . . . . .
211
Case 48.
Meningioma . . . ...... . . . . . ..... .............. . . . . ........ . . .. . . ..... . . . .. . . ....... ...
214
Case 49.
Ocular Melanoma ................................ .. .. ... . . . . . . . . . . ... . . . . . .. .. . . . ..
219
Case 50.
Retinoblastoma
V I.
.
.
..
.
.
.
.
.
.
.
..
.
.
.
.
.
..
..
.
.
..
..
.
..
.
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
..
.
.
..
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
..
..
1 85
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
..
.
.
..
.
..
.
.
.
.
.
.
..
.
.
.
.
. .
.
.
.
.
.
.
..
.
.
.
.
.
.
.
..
.
.. . ........ ... .... .. .......... ....... .. . ...... ... ... .. ,............ 223 ..
.
..
.
.
. .
.
. .
.
.
.
.
.
ORAL CAVITY AND OROPHARYNX
Case 5 1 .
Lingual Thyroid .. ..... . . . . . . . . . . . . . . .. .. . . . . . . . ........... . . ......... . . . . . . ... ... . . . . .
Case 52.
Dermoid ..... . .. .. . .. ........ . ........ . . ...... . .......... .......... .. ............... 237
Case 53.
Ranula ........... ......... ..... ........... . . . . . . ..
Case 54.
X I I Nerve Denervation Atrophy ............................. ................... . ........ 244
Case 55.
Tongue Carcinoma .... .. . . . . . . . . . . . . . . ...... . . . ... . . . ..... . ... ..
VII.
I�
III
Case 26.
.
.
.
..
.
.
. .
.
.
.
.
.
.
..
.
.
.
.
..
..
.
. .
.
.
.
.
..
.
..
. .
.
.
.
.
.
.
.
.
.....
.
.
.
..
.
. .. .. .
.
.
.
....
.
.
.. .. . .
.
.
.
.
.
..
. .....
. . .
.
.
233
.
.. .. . . . .. .. . .
..
.
.
...
. .
...
.
. .
....
241
247
SALIVARY GLANDS
Case 56.
Accessory Parotid Gland .. .... .. .... . . ....... .. .. ... .. .. . .... .. ....... .
255
Case 57.
Sialolith . . . . .. . . ......... . . . . . . .. .. . . . . .. . . ... . . . . . . . . . . . . . . . . . .. . . . . . ... .
259
..
.
.
.
.
.
.
.
.
.
..
..
.
.
..
..
..
.
..
..
.
.
..
. .
.
.
.
.
.
..
.
.
. .
.
.
.
..
. .
.
.
.
..
CONTENTSI Case 5 8.
Lymphoepithelial Cysts . . . . .. . .
................ .......... . .. ........... ...
263
Case 59.
Postoperative
. . . ........ ............ ... ................
267
Case 60.
Sjogrens Syndrome........................... . . ...................................... ...............
270
Case 6 1 .
Pleomorphic Adenoma ....... ........ ..
275
Case 62.
Warthin's Tumor
Case 63.
Oncocytoma
Case 64.
Adenoid Cystic Carcinoma
Case 65.
Mucoepidermoid Carcinoma .. . .
VIII.
.
. . . . . . . . . . .
. . .
.
.
. .... . . .. .. . . .
. .
..
.
.
....
....
.
. . . . . . . . . .
. . . . . . .
. . . .
. . ..
........
.
. . . . . .
...
. ..
.....
. .
. .. . .
....
......
.....
.
. .. . . . . ... .
.
.
. . .. . ..
.
.
...
. . . . . . . . . . . . . ........
.
.
..
.
. . . . ....
...........
.
. . .
....
..........
... . . . . ...
...
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..
..
.
.
...
. . . . . . . ......
.
. . . . . .
. .
.
. .
...
...
....
.............
...... . . . .. . ..
.
..
....
. .
.. .. ..
.....
.
.
. . . . ........ . .
. . . . . .
.
.
. . .... .
.
.....
..
.
.
. . . . . . . . . . . . . . . . . . . . . .
. .. . . . . . .. . . .. ...
. .
. .
..
.
.
..
.
279 2 82 2 86 289
SINONASAL
Case 66.
Dermoid Cyst .. .. ... . . . . .
Case 67.
Nasopalatine Duct Cyst .. ....... ..
Case 68.
Frontal Osteoma
Case 69.
Mucocele
Case 70.
Fungal Disease ..................... ......... ............. ..................... .. .. ................. 3 1 4
Case
Inverted Papilloma .
TI.
.
.
.
.
. .
.
....
.. . . . . . .. . . . . .
. . .
.
. . . . . . .
. . . .
. . . . . . . . . . . . . . . .. . . . . . .
. . . . .
.
....
. . . .
.
. . . .
.. .
..
.
.
.
. .
.
...
. . . . . .
. . .. .. . . . .
..
.
.
. . . . .
Nasal Lymphoma .
Case 73.
Carcinoma
Case 74.
Esthesioneuroblastoma
. . . . .
.
.
.
......
.
..
.. . .
. . .
..
.
.......
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.....
.....
.... ... . . .
. . . . .
. .
. . . . . . . . . . . . . .. . . . . . . . . . . . . .
. . .
.
.
. . . . .
.
. . . . .
. . . . .
. . . . . . . . .
.
.....
.. . . . .
. . . . .
... .. .. ... . ...... . . .. ... . .. .. ...... .....
.
.
.
. . . . . .
.....
.
.
..
.
.
. . . . . .....
.........
.
.. ..
. . . .
. . . . . . . . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . .
. .. . .
. .
.
. .... .
. .. . .
............
.....
..
.
. . . .
. .
. . . .
.
.
.
. . . . . . .
.
.........
.
...
.. .
295 299 303 30 8
.
. . . . . . . . . . ..............
.. .. . .
. . . . . . . . . . . ..........
......
.
.
................ . . . . . .
.
Case 72.
IX.
.
. . . . . .
....
. . . . . . . . . .
........ ..........
.. .
...........
.. .
....
.
....
..............
.
.
319 324 328 333
TEMPORAL BONE
Case 75.
Aberrant I nternal Carotid Artery ...... ..... .. ... .................. ......... ... .
Case 76.
Atresia of the External Auditory Canal ............................................ . . .
344
Case 77.
Congenital Anomalies of the I nner Ear ..
349
Case 78.
Fracture
Case 79.
Labyrinthitis Ossificans
Case 80.
Otosclerosis
Case 8 1 .
Petrous Apicitis
Case 82.
Malignant External Otitis .. .. .......... .. ... .................. .......... ....................
375
Case 83.
Acquired Cholesteatoma
38 1
Case 84.
Vestibular Schwannoma
Case 85.
Neurofibromatosis Type
Case 86.
Glomus Tympanicum
Case 87.
Mastoidectomy
Case 88.
Middle Ear Prostheses and Devices ... ... ... ... ... ..... .. .. .... ... .... ......
Case 89.
Bell's Palsy ......................... .. .. .. .. . .. .. . ..
Case 90.
Facial Neuroma ......... .... ......... . .. ... ............... .......... ............... .... ......
.
..
.
.
. . . . .
.
.
. . . . . .
.
.
..
.
....... . . . . . . . . . . . . . . . . . . . . . . .
....... ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . ....... . . . . . . . . . . . . . . . . . . . ..................
....
.
. . . . .
.
. . . . . .
..............
......
.
...........
.
.. .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
.
. . . . . . . .
.
.
. .
.. .... . .
n
...
. . . . . .
. . .
.
. . . . .
. .. . . .
.
.
. . . . . . . . .
.
. .
. .
..........
. .. . .
. . . . . . . . . . . .
. .
.
.
.
. . . . . . . . . . . . . . ....
.. . . . .
. .
.
. . . . . . . . . . . . . .
.......
.. . . . .
.. . .. .... . . . . . . . .. . .
.......
..
..
..
. .
. . .. ........ . .
.
...
.
.
. . . .
.
.
. . . . . . . . .
.
. . .
...
..
.
....
......
.
....
.
. . . . . . . . .
. ... .... . . . . . . .
.
.
.
. . .
.
.. . .. .... .. . ... . . . . . . . .
.
.
. .
..
. .
.
.
.
.
.
. .
.
.
. . . . ................ ..... ...................... ......... .... ........ .
. . . .
.
.
..
.
.. .. . .
. .
.
. . . . .......................................
. . .
.
.
. . ....
.
........
.
. .
. . ....................................................
.
....
. .
..
.
..
.
..
.
.
..
.
.
.
..
. .
.
.
. . . . .
.
.. . ..
.
.....
.
...
. .
.
. . . . .
.
. .... .. ..
..
. .. . .
.
...
.
. . . . . .
.
... . .
.
355 361 365 370
3 88 395 400
. 404
.
.
339
..
408 412 417
ixl
I CONTENTS Case 9 1 . x.
Stapes Replacement
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
423
TMJ AND MANDIBLE
Case 92.
TMJ D islocation
Case 93.
Radicular Cyst
Case 94.
Giant Cell Granulomaffumor
Case 95.
Ameloblastoma
Index
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
................................. ................ . . ...........
. . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .
43 1 437 443 448 451
Preface Vocatus atque non vocatus deus aderit. Carl lung
Head and neck imaging is more important than ever before. In the past, patients re ferred for imaging studies of the head and neck region were closely examined by primary care doctors and specialists who would obtain a focused clinical history and perform a detailed physical examination. This filtering process resulted in patients referred for head and neck imaging with finely crafted clinical questions of impor tant prognostic and management significance that the image study was well suited to answer. With changes in modern medical care, work-up of patients' complaints has been "streamlined" through a number of mechanisms that has ultimately re sulted in less access to medical resources and expertise. This results in increasing numbers of patients referred for head and neck imaging studies that have only a limited clinical work-up. I n order to adequately handle this situation, it is more im portant than ever that the radiologist have a thorough knowledge of head and neck imaging. Patients with conditions that in the past would have been diagnosed and managed in the clinic are now being sent to the radiology department for examina tion and ultimate triage. I n an increasing number of patients, the radiologist may be the only head and neck specialist that the patient sees. This book is intended for health care professionals in training and those in clinical practice interested in the head and neck. It is a case review of important examples of head and neck pathology but is not designed to be encyclopedic in scope. We hope that the readers of this casebook have as much fun using it as we had writing and preparing the material. Robert Lufkin, MD Alexandra Borges, MD Pablo Villablanca, MD Los Angeles, California 1 999
Acknowledgments We wish to express our sincere appreciation to our colleagues for sbaring their ex periences. We thank Dr. Jane Pennington and the staff at Thieme for their invalu able help. We also thank Mr. Kyu Na for his assistance with manuscript preparation and editing. Most important, this work could not have been completed without the endless support and encouragement from our families. RL
AB py I would like to thank Jeffrey Wensel and Eric Spak for all the good tips, editing help, and support, and Fernando Torrinha [or all the great images be sent me from Lisbon. AB
xiii
I. Central Skull Base
CENTRAL SKULL BASEl
Case 1 Clinical Presentation A 59-year-old female presented with a 2-year history of pain and paresthesia in volving the left side of her face.
A
B
I CENTRAL SKULL BASE
Radiologic Findings MRI of the skull base: Axial TIW (Fig. I-A) and axial enhanced T I W ( Fig. I-B) im ages at the level of the pons and axial enhanced T l W image (Fig. I -C) at the level of the middle cerebellar peduncles. These images show a well circumscribed, oval shaped mass centered upon the left prepontine cistern. This mass is isointense to gray matter on the TIW image and shows intense homogeneous enhancement on the post-contrast images. A dural tail is seen along the posterior aspect of the petrous ridge and superiorly along the left tentorium. This mass is compressing but not invading the left cerebral peduncle. The internal auditory canal is free of tumor.
Differential Diagnosis: Prepontine Cistern Mass • • • • •
Trigeminal schwan noma Clivallpetroclival ligament meningioma Parasagittal chordoma Metastasis Basilar artery aneurysm/ectasia
Diagnosis Petroclival meningioma (tentorial type)
Discussion The differential diagnosis of petroclival meningiomas includes cerebellopontine an gie (CPA) lesions and lesions arising within or in the immediate vicinity of the petrous apex. Systemic diseases such as multiple myeloma, eosinophilic granuloma, lymphoma, and metastasis should also be included in the differential diagnosis. Le sions in these locations may have components in both the posterior and middle cra nial fossa by extension over the petrous tip. Epidemiology
Meningiomas constitute approximately 1 5 to 20% of intracranial neoplasms. How ever, tumors arising from the skull base are much less common. The most frequent sites of origin are the sphenoid ridge, cribiform plate, paraseUar region, clivus, CPA, tentorium, and cavernous sinus. These tumors are more frequent in females and the peak age at presentation is in the 6th decade. Pathophysiology
Meningiomas are benign tumors that arise from meningothelial cells. Petroclival meningiomas originate from the meningeal folds surrounding the junction of the occipital bone, petrous apex, and sphenoid bone. Several classifications have been proposed because the exact location of the tumor has both clinical and thera peutic implications. The classification proposed by Kawase et al (1996) divides petroclival meningiomas into four groups: upper clival (origin in the clivus medially to the trigeminal nerve), cavernous sinus (clival origin and growth into the cav ernous sinus), tentorial (tentorial origin above the trigeminal nerve), and petrous apex (petrous origin lateral to the trigeminal nerve). This system, based on the site of dural attachment of the tumor, is useful in selecting the optimal surgical approach. Also, the location of the tumor can be inferred from the presenting
CENTRAL SKULL BASEl symptoms, which are a consequence of impingement upon the surrounding cranial nerves. Clinical Fin dings
Patients with petroclival meningiomas usually present with cranial nerve palsies or uncommonly, with signs of increased intracranial pressure, when the tumors are large enough to cause obstructive hydrocephalus. Cerebellar signs may also be present. The cranial nerves involved depend on the exact tumor location. Deafness, vertigo, and tinnitus are common presenting symptoms when the tumor impinges upon the cisternal segment of the VIIIth and VIIth nerves complex or grows along the LAC. lnvolvement of the trigeminal nerve in its cisternal segment or in the Meckel's cave results in trigeminal neuralgia or facial hypesthesia. Diplopia is also a frequent presenting symptom due to compression of the VIth nerve. This may oc cur in its cavernous segment or in its epidural course passing through Dorello's canal. The other cranial nerves coursing in the cavernous sinus ( I I I and IVth) may also be involved. Headaches, imbalance, and papilledema can be the presenting symptoms in patients with large tumors. Other focal neurologic findings may result from brainstem or cerebellar compression. W hen small and separate from cranial nerves, petroclival meningiomas can be completely asymptomatic, discovered inci dentally on imaging performed for other reasons. Imaging Findings
CT and MRI are the techniques of choice for imaging skull base meningiomas. On CT meningiomas appear as discrete, iso- or hypodense masses with a broad dural base. Calcification may be present and hyperostosis of the adjacent bone may also be seen, but these are more common with convexity meningiomas. After con trast administration there is strong enhancement. A dural tail may be recognized but is not a specific finding. Petroclival meningiomas usually show a flat base on the posterior surface of the petrous bone and a dome shaped medial surface contacting the brainstem. Unlike acoustic tumors, meningiomas show an obtuse angle with the petrous bone and are usually medial to the lAC. However, they can extend along the intracanalicular portion of the nerve sheath. CT is optimal for detection of associated bony erosion or destruction of the petrous apex, which would suggest an alternative, more aggressive process. Lesions arising within the petrous apex usually cause bony expansion. Pneumatization of the petrous apex and petrous apicitis are readily recognized on CT but can be mislead ing on MRI. Confusing petrous apicitis with tumor is common on MRI. M Rl is particularly helpful in defining the exact location of the tumor and pattern of spread, factors that are critical in selecting the best surgical approach. On M RI, meningiomas are seen as well-defined globular or plaque-like masses, isointense to gray matter on both Tl W and TIW images. I ntense homogeneous enhancement is usually seen, unless calcification is present. Due to the multiplanar capability and high soft tissue contrast of MR, it is possible to determine the site of tumor attach ment and relation to the adjacent cranial nerves. In an MRI of the skull base axial (Fig. I-D) and coronal (Fig. I-E) enhanced T1W images show an enhancing extra axial mass located posterolateral to the left cavernous sinus. This mass is well cir cumscribed and impinges upon the uncus and hippocampal formation of the left temporal lobe. The mass appears to originate from the lateral margin of the cav ernous sinus and does not involve Meckel's cave. The cavernous carotid artery is un remarkable and there is no evidence of edema in the surrounding brain parenchyma. The diagnosis is cavernous sinus meningioma. Petroclival meningiomas may extend inferiorly into the jugular foramen and along the tentorium, laterally into the lAC or anteriorly into the cavernous sinus, Meckel's cave, and medial cranial fossa. The signal characteristics of meningiomas allow ready diferentiation from petroclival cystic lesions. In an MRI of the skull
I CENTRAL SKULL BASE
D
E
base, an axial T I W image (Fig. I-F) and an enhanced coronal TI W image (Fig. J -G ) show a right petroclival lobulated mass, isointense to gray matter on Tl W images and strongly enhancing after contrast administration. The lesion is attached to the posterosuperior aspect of the petro us apex and extends superiorly through the am biens cistern into the choroidal fissure. The mass impinges upon the right ccrebral peduncle and pons. There is also significant mass efrect upon the right hippocampal rormation. An enhancing dural tail is seen along the cisternal segment of the V I I I and V I [ nerves complex. The diagnosis i s petroclival meningioma (petrous apex type).
F
G
CENTRAL SKULL BASEl
PEARLSIPITFALLS •
MRI s trongly enhances masses tha t are isoi n tense to gray matter and show a "dural tail."
•
An MRI defines the exact loca tion and e x tension of the tumor i n to the cavernous sinus, Meckel's cave, ten torium, or lA e.
•
A cr scan is optimal for d e tect ing for calcification and focal hy perostosis.
•
Whe n diagnosing this condition, the clinician may confuse a meningioma w i th a vestibular schwannoma.
•
•
Whe n diagnosing this condition, the clinician may mistake unilat eral re te n tion of secre tions for a tumor. Whe n diagnosing this condition, the clinician may fail to recog nize involveme n t of s tructures which would preclude surgery.
Management The treatment for skull base meningiomas is surgical resection. Radiation therapy is usually considered for incomple te resections and recurrences. More recen tly, s tereotatic radiosurgery has been used in the primary treatment of skull base meningiomas when surgical resection is expected to cause unacceptable neurologi cal defici ts or to tre a t postsurgical macroscopic disease. This modality appears to al low con trol of further grow th without severe morbidi ty, and is a promising tech nique in the management of these benign slow growing tumors. Surgical approaches vary according to the location of the tumor, with the focus upon functional preservation of the cranial nerves. Nevertheless, complete resection cannot be achieved in approximately 35% of cases due to tumor adherence to the brainstem, cranial nerves, or cavernous carotid artery. Compl e te removal should not be pursued a t the cost of neurologic impairmen t. Expectant managemen t is also ac ceptable for small, asymptomatic tumors in difficult locations.
Suggested Readings Couldwell, W. T., Fukushima, T., Gianno tta, S.L., Weiss, M.H. P e trocLival menin giomas: surgical experience in 1 09 cases. Journal of Neurosurgery 84( 1 ):20-8, 1996 Jan. Fazi, S., Barthelemy, M. P e troclival meningioma mimicking the prese n ta tion of a transie n t ischemic a ttack. Acta Neurologica Scandinavica 89( 1 ):75--{j, 1 994 Jan . Kawase, T., Shiobara, R., Ohira, T., Toya, S. Developme n tal pa tterns and character istic symptoms of p e troclival meningiomas. Neurologia Medico-Chirurgica 36( 1 ): 1 --{j, 1 996 Jan. Nicolato, A., Ferraresi, P , Foroni, R., Pasqualin, A., Piovan, E . , Severi, F., Masotto, B., Gerosa, M. Gamma K nife radiosurgery i n skull base meningiomas. Preliminary experience wi th 50 cases. S tereotactic and Functional Neurosurgery 66 Suppl 1: 1 1 2-20,1996. Pomeranz, S., UmanskY,I, Elidan, 1., Ashkenazi, E., Valarezo, A., Shalit, M. Giant cranial base tumours. Acta Neurochirurgica 1 29(3--4) : 1 2 1 -6, 1 994. Sekhar, L.N., Wrigh t, D. C, Richardson, R., Monacci, W. P e troclival and foramen magnum meningiomas: surgical approaches and p i tfalls. lournal of Neuro Oncology 29(3) :249-59, 1 996 Sep. Ta tagiba, M., Samii, M., Ma tthies, C, Vorkapic, P. Manageme n t of petroclival menin giomas: a cri tical analysis of surgical tre a tmen t. Acta Neurochirurgica Supplernen tum 65:92--4, 1 996. Thomas, N.W., King, T.T. Meningiomas of the cerebellopontine angle: a report of 4 1 cases. British lournal of Neurosurgery 10(1) :59-68, 1996 Feb. Zen tner, 1., Meyer, B., Vieweg, u., Herberhold, C, Schramm, 1. P e troclival menin giomas: is radical resection always the best option? lournal of Neurology, Neuro surgery and Psychiatry Apr, 62(4):341-5, 1 997.
icE TRAL SKULL BASE
Case 2 Clinical Presentation A
42-year-old female pre ented with progre sive left-sided facial pain and pares the ia.
A
I�
B
CENTRAL SKULL BASEl
Radiologic Findings On an M R I of the skull base the axial T1 W ( Fig. 2-A), and axial (Fig. 2-B) and coro nal (Fig. 2-C) post-contrast T l WI show a dumbbell-shaped lesion involving the Meckel's cave and left prepontine ciste rn, following the course of the left trigeminal nerve. The mass is of intermediatellow signal intensity on Tl WI and enhances het erogeneously, showing a nonenhancing anterior component. The coronal image shows denervation atrophy of the left pterygoid muscles. There is no evidence of tu mor extension through the foramen ovaIe.
Differential Diagnosis: Mass or Abnormal Enhancement of the Trigeminal Nerve • • • • • • • •
Trigeminal nerve schwannoma/neurofibroma Lipoma Hemangioma Perineural spread of a tumor Metastasis Inflammatory disease (sarcoid) Infection ( herpes zoster, Lyme disease, actinomycosis) Lesions in the Meckel's cave: meningioma, dermoid, epidermoid, metastasis
Diagnosis Trigeminal nerve schwan noma
Discussion Epidemiology Schwannomas are benign nerve sheath tumors arising from cranial, spinal or sym pathetic nerves. TIley occur exclusively in sensory or mixed nerves. I ntracranial schwannomas are common, comprising 8% of all intracranial tumors. Among these, 95% originate in cranial nerve V I I I . Trigeminal schwan noma, is in a distant second place, and occurs with equal frequency in men and women with a peak incidence in the 4th decade. The trigeminal nerve is the one most commonly involved in the cen tral skull base. Trigeminal schwannomas may occur in isolation or in association with neurofibromatosis.
Pathophysiology Trigeminal schwannomas are benign encapsulated tumors which originate from the nerve sheath. They are composed of two different types of tissue designated as An toni A and Antoni B (see vestibular schwannoma). These tumors grow slowly, do not tend to recur and rarely show malignant transformation. Malignant trigeminal schwannomas "de novo" are also rare with only a few cases described in the litera ture and are more common in the setting of neurofibromatosis (plexiform neurofi broma ) . TIlese malignant tumors are characterized by increased cellularity and nuclear pleomorphism and may be confused with sarcomas, speci fically with fi brosarcoma. Most malignant trigeminal schwannomas in the head and neck are localized in the retromaxillary or pterygomandibular region. Trigeminal schwannomas are classified according to their location along the course of the nerve. Location determines both the clinical symptoms and the surgi cal approach to the lesion. Type I tumors, the most common, occur in the middle cra nial fossa in the region of the gasserion ganglion. Type I I I tumors are the second most common, typically seen as dumbbell-shaped tumors with a posterior fossa
I CENTRAL
SKULL BASE component in the prepontine cistern and a middle cranial fossa component in Mecke l 's cave, separated by a waist at the level of the porus trigeminus. Type I I tu mors are limited to the posterior fossa, and involve only the cisternal segment of the nerve. Finally, type IV comprises the extracranial tumors with or without minimal intracranial extent.
Clinical Findings Most patients present with pain, paresthesias. and numbness. usually along the course of the first or second divisions of the trigeminal nerve. The association of trigeminal schwannoma with trigeminal neuralgia is controversial. Some experts as sociate this neuralgic pain with involvement of the trigeminal root, whereas others relate it to involvement of the gasserian ganglion. Headaches and symptoms of com pression of adjacent cranial nerves are common. Diplopia, facial weakness and sen sorineural hearing loss are among the most frequent, and result from compression of the cavernous segment of cranial nerve V I and cisternal segments of cranial nerves V l l and V l l l by large trigeminal tumors. Extension of a tumor along the third division of the Vth nerve may result in tris mus or weakness of the masticator muscles. Large tumors in the posterior fossa may cause cerebellar and pyramidal symptoms. Extension along the V I division may pre sent with exophthalmos and papilledema. Physical exam may reveal loss of corneal reflex.
Imaging Findings Cross-sectional imaging allows precise depiction of tumor location and extent and has largely improved the outcome of surgical treatment. Imaging is also helpful in establishing the diagnosis and in the follow-up of these patients. CT and MRI are used complimentarily to assess bony changes and soft tissue extent, respectively. Plain films of the skull base may suggest the diagnosis by showing enlargement, remodeling or erosion of the skull base neural foramina through which the three di visions of the trigeminal nerve exit the skull (superior orbital fissure-V l , foramen rotundum-V2, and foramen ovale-V3). Large tumors may also remodel or erode the petrous apex, lateral aspect of the sphenoid in the region of the cavernous sinus, an terior c1inoids or dorsum sellae. CT, due to its higher spatial resolution, shows to advantage these bony changes and at the same time depicts the soft tissue component of the tumor. Trigeminal schwannomas are usually iso - to slightly hyperdense to the brain and enhance on the postcontrast images. Large tumors may be heterogeneous due to cystic degen eration, necrosi or intra tumoral hemorrhage. Schwannomas of the Vth nerve tend to be oblong in shape following the long axis of the nerve. They may be seen any where from the nerve root, in the lateral aspect of the prepontine cistern to the pe ripheral branches of the nerve. A bilobed, dumbbell-shaped tumor is typical of trigeminal schwannomas extending from the cisternal segment in the posterior fossa into the cavernous segment in the middle cranial fossa with constriction of the tu mor mass at the level of the porus trigeminus. M RI is the best imaging modality to assess the extent of these tumors. Gadolin ium enhanced M R T may depict small tumors that would otherwise be missed. Trigeminal schwannomas tend to be isointense to t he brai n on T l WI, hyperintense on T2WI and enhance after contrast administration. Fluid-fluid levels have been re ported in these lesions resulting from hemorrhage, or layering of debris, or fluids with different protein composition. MRI better delineates the relationship of the tumor to adjacent structures, par ticularly with the brainstem, petrous apex, VU and V I l l th nerve complex, cavernous sinus and intracranial segments of the internal carotid artery. Replacement of the fat signal adjacent to the skull base foramina and pterygomaxillary fissure is a useful sign of tumor extension into these foramina and is better depicted with noncontrast T l WI .
CENTRAL SKULL BASEl
D
E
Cross sectional studies for patie n ts wi th trigeminal nerve symp toms should in clude all segmen ts of the nerve, including the posterior fossa, skull base, orbi ts, and infratemporal fossa. A trophy and fa tty infiltration of the muscles of mas tication may be seen, indicating denervation atrophy. This imaging finding should prompt a search for trigeminal nerve pathology. Differe n tial diagnosis of this lesion includes other cranial nerve schwannomas, es pecially scbwannomas of the cis ternal segme n ts of the V II and V l l l th nerves, petro c1ival or cavernous meningiomas, perineural spread of tumor, and rare infectious/in flammatory processes. Differe n ti a tion from schwannomas of o ther cranial nerves may be difficult when tumors are very l arge, but is usually possible once the radiologist is familiar wi th the anatomy of the cranial nerves. V I I and V I T I nerve schwannomas are more l a teral in position in the prepontine cistern and course in the direction of the internal audi tory canal, which may be enlarged. Schwan nom as grow along the nerve sheath by direct extension, as a single bulky lesion. The presence of "skip enhancing lesions" along the trigeminal nerve is typi cal of perineural spread of a tumor and should prompt a search for the primary neo plasm. Neoplasms mos t likely to show this pattern of spread include adenoid cystic carcinoma, mucoepidermoid carcinoma, lymphoma, and squamous cell carcinoma. The second division of the trigeminal nerve is particularly prone to perineural spread of head and neck tumors due to i ts e x tensive branching n e twork. Usually this spread is re trograde from the peripheral branches to the main trunk. Hematoge neous me tastasis to the trigeminal nerve may also occur and are more commonly seen in patients with melanoma, breast, and lung carcinoma. On an MRI of the skull base axial (Fig. 2-D) and coronal (Fig. 2 - E ) post-contrast Tl W images show abnor mal enlargeme n t and enhanceme n t of the right Meckel's cave in a patien t wi th known breast carcinoma. The diagnosis is me tasta tic breast disease (hematogeneous dissemination). Inflamma tory "neuritis" manifes ts as abnormal segmental, smooth enhancement along the course of the nerve.
I CENTRAL
SKULL BASE
PEARLSIPITFALLS •
A trigeminal schwannoma can be see n as a n e nhancing mass fol lowing the course of the trigemi nal nerve.
•
cr and M R I together give a pre cise picture of bony changes a nd soft tissue extent.
•
Image all segments of the trigem inal nerve.
•
It is importa nt not to miss the full exte nt of the tumor due to an incomplete study.
•
•
Avoid mistaking perineural spread of a tumor for a schwan noma. It is important not to miss dener vation atrophy of the muscle of mastication.
Man agement llle treatme nt for trigemi nal schwa nnomas is surgical excision. The surgical ap proach is dictated by the locatio n a nd exte nt of the tumor. As a ge neral guideline, type 1 tumors are approached through a fro ntotemporal cra niotomy via a tra nsyl via n approach. Type 2 tumors are approached through retrosigmoid cra niotomy. Type 3 tumors are approached through a combi ned subtemporal retromastoid ap proach, a nd type 4 tumors through a n extradural i nfratemporal approach. The best m a nageme nt of maligna nt schwa nnomas appears to be surgery followed by radia tion therapy.
Suggested Readings Catal a no, P., Fang-Hui, E., Som, P.M. Fluid-fluid levels i n be nign neuroge nic tumors. American Journal of Neuroradiology 1 8(2):385-7, 1 997 Feb. Charabi, S., M a ntoni, M., Tos, M .. lllOmse n. 1. Cystic vestibular schwa nnomas: neuroimagi ng a nd growth rate. Journal of Laryngology and Otology 108(5):375-9, 1 994 May. Krish namurthy, S., Holmes, B., Powers, S. K. Schwa nnomas limited to the i nfratem poral fossa: report of two cases. Journal of Neuro-Oncology 36(3):269-77, 1998 Feb. Maut ner, VF.. L i nde nau, M., Baser, M.E., Hazim, W., Tatagiba, M., Haase, W., Samii, M., Wais, R., Pulst, S.M. The neuroimagi ng a nd cli nical spectrum of neuro fibromatosis 2. Neurosurgery 38(5 ):880-5, discussio n 885-6, 1 996 May. Samii, M., Migliori, M.M., Tatagiba, M., Babu. R. Surgical treatme nt of trigemi nal schwa nnomas. Journal of Neurosurgery 82( 5 ) :7 1 1-8, 1 995 May. Tegos, S ., Georgouli, G.. Gogos. c., Polythothorakis, 1., Sa nidas. V. Mavrogiorgos. C. Primary, maligna nt schwa nnoma i nvolvi ng simulta neously the right Gasserian ga n glion a nd the distal part of the right ma ndibular nerve. Case report. Journal of Neu rosurgical Sciences 41 (3) :293-7, 1 997 Sep. Turgut, M., Palaoglu, S., Akpi nar, G., Saglam, S. Gia nt schwa nnoma of the trigemi nal nerve misdiagnosed as maxillary si nusitis. A case report. South African Journal of Surgery 35(3): 1 3 1 -3, 1 997 Aug. Yamashiro, S., Nagahiro, S., Mimata, c., Kuratsu, 1., Ushio, Y. Maligna nt trigemi nal schwa nnoma associated with xeroderma pigmentosum--case report. NeLII'ologia Medico-Chimrgica 34( 1 2 ) : 8 1 7 -20, 1 9 94 Dec.
CENTRAL SKULL BASEl
Case 3 Clinical Presentation A 35-year-old male presented w i th facial dismorphism, anosmia and pain on chewing.
A
B
/cENTRAL
SKULL BASE
Radiologic Findings Axial cr sections through the skull and facial bones (bone window) ( Figs. 3-A, 3 -B, and 3 -C) show extensive bony changes. These consist of expansion of the medullary cavi ty wi th cystic and ground glass pallerns merging imperceptibly with normal surrounding bone.
Differential Diagnosis: Diffuse Fibroosseus Lesions in the Skull Base or Facial Bones Common • Fibrous dysplasia • Paget's disease • M e tastasis • Ossifying fibroma • M u l tiple os teomas • Hyperparathyroidism Rare • Meningioma tosis • Osteogenesis imperfecta • Juvenile Paget (hereditary hyperphosphatasia) • Progressive diaphyseal dysplasia (Camura tti -Englemann disease) • Pyknodysostosis
Diagnosis Polyostotic fibrous dysplasia (leontiasis ossea)
Discussion Epidemiology Fibrous dysplasia is an idiopathic skeletal disorder characterized by a defect in os teoblastic ma tura tion. I t is a common disorder, first described in 1938, by Lichen stein and Jaffe. There are three main forms of disease, depending on the number of bones in volved and the presence or absence of other clinical fea tures. The monostotic form is the most common, accounting for 75 to 80% of all cases, and tends to preferen tially involve such long bones as the femur and ribs. Isolated involveme n t of a sin gle craniofacial bone is seen in 10 to 25% of cases with the maxilla and mandible the most freque n t s i tes. The polyostotic form accoun ts for 10 to 25% of cases and may be un i- or bilateral. Craniofacial involvement is responsible for 40 to 60% of cases and is also refered to as leo n tiasis ossea due to the characteris tic facial disfigure men t. Albrigh t - McCune -Sternberg syndrome, the rarest form, accoun ts for 10% of cases and consists of unilateral bone involveme n t associa ted with skin pigmentation and precocious puberty. This form is seen almost exclusively in females. Cherub ism is considered a special hereditary form of fibrous dysplasia exclusively involving the jaws. The disease is usually symmetrical and tends to regress spon ta neously after puberty. I n the craniofacial form the bones most frequen tly involved include, in decreas ing order of frequency, the sphenoid, frontal, maxillary, e thmoid, occipital. and tem poral bone. The peak age for fibrous dysplasia is the second and third decades. The disease tends to progress during the period of skeletal growth and to s tabilize once growth ceases, a l though this is not always the case. Milder forms of fibrous dyspla-
CENTRAL SKULL BASEl sia may manifest only in adulthood. The polyostotic forms tend to present earlier in life and have a more aggressive course.
Pathophysiology Pathologically, fibrous dysplasia is characterized by abnormal maturation of medullary bone, which is replaced by mildly to highly cellular tissue composed of a mixture of spindle-shaped fibroblasts and irregular trabeculae of woven bone with out osteoblastic lining or progression to lamellar bone. The irregularly shaped bony trabeculae have been compared to chinese characters. The "fibrous bone" merges imperceptibly with normal surrounding bone. Unlike ossifying fibroma and fibrous osteoma, these lesions are not encapsulated. The cortical bone is typically spared, al though it may be thinned and transgressed due to marked expansion of the medullary cavity. Malignant transformation has a reported incidence of 0.5 % , with most of the cases occuring after radiation therapy. The interval between diagnosis and malig nant degeneration is usually more than one decade. Sarcomas are the most common secondary malignancy, including osteo-, fibrous- and chondrosarcomas. Fifty per cent of tbe sarcomas associated with the monostotic form occur in the craniofacial region. The etiology of fibrous dysplasia is unknown. Three different theories have been proposed to explain its origin including developmental, traumatic and neoplastic. At the present time the former is the most widely accepted .
Clinical Findings Clinical findings largely depend on the extent and location of the disease. Patients with craniofacial involvement present clinically with facial disfigurement, pain, or functional problems including cranial nerve deficits. Progressive, painless facial, or calvarial swelling is the most common presenta tion. However, when severe bony expansion is present, sinonasal obstruction, mal occlusion, exophthalmus and diplopia may ensue. Obstruction of sinus drainage pre disposes these patients to mucocele formation. Cranial nerve deficits, due to stenosis and obliteration of their natural skull base foramina, are a common complication. Anosmia, visual impairment, diplopia, sensorineural hearing loss, and facial nerve palsy are among the most common neurolog.ic deficits, although all cranial nerves may potentially be involved. Physical exam of these patients should always include a full ENT evaluation and assessment of the cranial nerves.
Imaging Findings Imaging is important to establish the diagnosis and to evaluate the extent of the dis ease. CT is the preferred modality. The M R T lacks specificity and on plain films; it may be difficult to determine disease extent due to significant overlap of osseous structures in the craniofacial region. The hallmark of fibrous dysplasia is expansion of the medullary cavity by fibrosseous tissue, sparing the cortex and preserving the original shape of the involved bone(s). The woven bone of the medullary cavity may have a variety of patterns, depending on the amount of ossification of the fibrous matrix. A hyperlucent cystic appearance results when trabecular bone formation is poor or absent and is more common in the early stages of the disease. Progressive ossification, with formation of irregular bony trabeculae intermingled with fibrous matrix, leads to the classic "ground-glass" pattern. When bone formation and min eralization predominates, the involved bone becomes densely sclerotic. These dif ferent patterns may occur together or in isolation. Severely expansive lesions may develop cortical breakthrough. Periosteal reaction is usually not seen except in cases of pathological fracture or malignant transformation.
E
F
Thin cr cction through the kull ba e are mandatory to detcct tenosi or oblit eration of neural foramina. omplication uch a nasal ob truction or mucocele formation are also adequately detected on cr ·cans. Tridimcn 'ional reconstructions may provide useful information when urgical treatment is con idcrcd. Figure 3-D hows a cr of the axial section of parallasal sinuses in anothcr patient. Figures 3-E and 3-F arc coronal sections showing expansive cystic bony lesions which involve the maxilla and mandible with multiple peck led calcification . TIle cortices of the maxillary bones are thin ned with focal area of bony dehisccnce. -mere is marked
16
CENTRAL SKULL BASEl
PEARLSIPITFALLS •
I t is a painless facial deformi ty (leon tiasis ossea)/craoial nerve palsy which can occur in a young adolescen t.
•
Expansive cystic, sclerotic, or ground-glass appearing lesions involve the bone marrow, and spare cortical bone.
•
Axial cr sections show iIl defined margins wi th the abnor mal bone merging imperceptibly w i th normal bone.
•
Unilateral polyosto tic fibrous dysplasia in a young female usu ally is accompanied by preco cious puberty and pigme n ted cutaneous lesions (Albrigh t McCune-S ternberg syndrome).
•
Fibrous dysplasia is l im i ted to the jaw i n Cherubism.
•
The clinician may fail to recog nize compromise of cranial nerves due to foraminal e n trap ment.
•
The clinician may fail to recog nize mucocele formation.
•
Irradiating fibrous dysplasia le sions may lead to a malignan t transformation.
•
The clinician may mistake fi brous dysplasia for a malignan t process.
displacement of tee th , particularly in the superior alveolus, w i th tee th seen adjacen t to the orbi tal floors. The maxillary sinuses are completely obl i tera ted and there is also obli tera tion of the inferior aspect of the nasal cavi ty. On M R I , fibrous dysplasia presen ts as low or i n termediate in tensity on T l W images and bypoi n tensi ty on TIW images. Hemorrhage and cystic lesions may con tribu te to signal h e terogenei ty. I n tense enhancemen t of the medullary cavi ty is the rule. Paget disease, a p a thologic process wi th similar appearance, tends to involve the cortical bone and is more likely to cause bony deformi ty. Also, this disease occurs later in life and, as opposed to polyosto tic fibrous dysplasia, is more predominan t among males. Ossifying fibroma may be difficul t to distinguish from fibrous dysplasia bo th radiographically and p a thologically. However, this lesion tends to be more focal and to have a more aggressive course. Meningiomatosis may cause e x tensive bony sclerosis of the skull base mimicking fibrous dysplasia. Post-con trast CT or M R I of the brain shows the e x tracranial tu mor location and resolves this issue.
M anagement Fibrous dysplasia is a benign disease tha t should be managed conservatively unless significant functional impairme n t or neurologic deficits ensue. Surgery for cosmetic reasons should ideally be postponed u n til growth ceases and the lesions s tabilize. When necessary, surgical resections in the craniofacial region should be l im i ted due to the pote n tial surgical complica tions and the high recurrence rate. Recurrence oc curs in as many as 20 to 30% of cases wi thin 2 to 3 years after surgery.
Suggested Readings Ferguson, B.J. Fibrous dysplasia of the paranasal sinuses. A merican Journal of Otolaryngology 15(3) :227-30, 1 994 May-Jun. Simovic, S., Klapan, L., Bumber, Z., Bura, M. Fibrous dysplasia i n paranasal cavi ties. Journal of Oto-Rhino-laryngology and Its Related Specialties 58( 1 ) :55-8, 1 996 Jan Feb. Van Rompaey, D., Schmel zer, B., Vers traete, W., Cammaert, T. Fibrous dysplasia in the fron toe thmoidal complex: diagnosis and surgical aspects. Acta Oto-Rhino Laryngologica Belgica 48( 1 ) :37--40, 1 994.
1 CENTRAL
SKULL BASE
Case 4 Clinical Presentation A 53-year-old male prese nted with worsening headache and diplopia.
B
A
Radiologic Findings I n an M R I of the skull base. axial post-contrast Tl WI (Fig. 4-A), a nd axial TIWI (Fig. 4-B) show an e nh a nced lesio n i n the ce ntral skull base. ce ntered in the left lat eral aspect of the clivus. TIle lesion is heteroge neous on the TIW images with sev eral areas of hypoi nte nsity i nterspersed with areas of hyperi nte nsity. probaly repre se nt i ng calcificatio ns. TIle left cavernous carotid artery is e ncased by tumor a nd reduced i n caliber at the cervico-petrous j u nction. TIle mass protrudes posteriorly i nto the left prel11edullary cistern.
Differential Diagnosis: Mineralized Lesions of the Skull Base • • • • • •
118
Cho ndrosarcoma Chondroma Chondrol11yxoid fibroma Chondroid chordoma Osteosarcoma Metastasis
CENTRAL SKULL BASEl
Diagnosis Low grade chondrosarcoma of the skull base
Discussion Epidemiology Cartilaginous tumors of the skull base are relatively rare. The majority of these are chondrosarcomas, which account for 0. 1 5 % of all intracranial neoplasms and for 5 to 10% of all skull base tumors. Only 5% of chondrosarcomas occur in the head and neck region, the most common locations being the maxilla, mandible, skull base and paranasal sinuses. They can occur at any age, but there is a peak incidence between the 4th and 6th decades. There is no sexual predilection. Their benign counterpart, chondroma, is even rarer and may occur in isolation or as part of Oilier's disease (multiple enchondromatosis) or Maffucci 's syndrome (multiple enchondromas and hemangiomas ).
Pathophysiology Chondrosarcomas usually originate from skull base synchondroses. But they may also arise from cartilaginous remnants left behind during embryologic development, which may account for rare extraosseous locations. Development of chondroid tu mors from multi potential mesenchymal cells or from chondral metaplasia of fibrous tissue have also been postulated. Chondrosarcomas may arise de novo or result from malignant degeneration of a pre-existing chondroma. Paget 's disease, fibrous dysplasia and multiple enchondromatosis are all associ ated with an increased incidence of chondrosarcomas. This incidence is even higher when these conditions are managed with radiation therapy. Pathologically, chondrosarcomas are divided into three different SUbtypes. The conventional type is the most common and has a better prognosis. The mesenchy mal and undifferentiated types show a more aggressive clinical course and bear a worse prognosis. Conventional chondrosarcomas are further subdivided into types 1 through 4 reflecting an increasing grade of cytologic aggressiveness (increased cel lularity, pleomorphism and mitotic rate). A simpler and more useful classification system divides chondroid tumors into low, intermediate and high grade neoplasms, taking into account the difficulty in differentiating benign from malignant tumors, both pathologically and radiologically. Also, distinction between chondrosarcomas and chordomas, particularly chondroid chordomas, may only be possible with im munohistochemical analysis. I n contradistinction to chordomas, chondrosarcomas do not stain for epithelial markers such as epithelial membrane antigen and keratin. Chondromyxoid fibroma is a rare entity, that shares the same immunohistochemical features with chondrosarcomas. However, on light microscopy this tumor shows an important fibroblastic component made of stellate or spindle-shaped ceLis with scarce eosinophiLic cytoplasm, not usually seen in chondrosarcomas. Chondrosarcomas are locally invasive neoplasms, but rarely metastasize.
Clinical Findings Signs and symptoms of skull base chondrosarcomas are non-specific and depend on the location, extent, and relationship of the tumor to adjacent vital structures. The nonspecific nature of the most frequent symptoms (headache and vagueness, wax ing and waning neurologic deficits) delays the diagnosis. The mean time between the onset of symptoms and diagnosis is between 18 to 60 months. Occulomotor disor ders, decreased hearing, tinnitus, vertigo and pain, and hyperesthesia in the distri bution of the Vth cranial nerve are among the most common presenting neurologic
I CENTRAL
SKULL BASE
C
D
deficits in these patients. They relate to the typical location of these tumors laterally in the mid-skull base, and usually involve the cavernous sinus, petrous apex, and cerebello pontine angle (CPA) cistern. Whenever a patient presents with unex plainable multiple cranial neuropathies and headache, a skull base neoplasm should be suspected and appropriate imaging studies requested.
Imaging Findings Imaging evaluation of a patient with a suspected skull base neoplasm should include both CT and MRI to delineate the bony and soft tissue changes. CT is particularly valuable in the selling of chondroid tumors as it may show calcifications and tumor mineralization. Chondroid type calcifications are present in 60 to 80% of tumors and include complete and partial ringlets, as well as arciform and fine, punctiform calcifications. The degree of mineralization appears to correlate well with tumor dif ferentiation. Low grade tumors show heavy calcification and the more anaplastic high grade tumors show little or no calcification of the tumor matrix. Bone destruc tion is seen in 50% of cases and most frequently involves the clivus, petro us apex, and posterior cranial fossa. In an MRI of another patient of the orbits axial T I W (Fig. 4-C) and coronal post-contrast frequency selective fat suppression imaging (FATSAT) TI W (Fig. 4-0) images show a heterogeneously cnhanced mass in the lateral wall of the right orbit (greater wing of the sphenoid bone). This expansive mass shows well defined margins and extends medially into the lateral aspect of the extraconal compartment displacing, but not invading, the lateral rectus muscle. Di agnosis: Low grade chondrosarcoma of the greater wing of the sphenoid bone. Clival chondrosarcomas tend to occur off of the midline, an important distinctive feature from chordomas, most commonly seen in the spheno-occipital or petrociival synchondro is. The junction between the vomer and rostrum of the sphenoid is an other possible location for this tumor. Chondrosarcomas, although locally invasive. may show well-defined margins, almost geographic in appearancc, but without bony sclerosis. Most tumors show marked contrast enhancement. On M R I , tumors are of intermediate signal intensity on TI WI and fairly hyperin tense on TIWI . Calcifications, depending on their size and composition, may present as hypo- or hyperintense foci on M R l or may not be visible at all. Fat-suppressed, contrast-enhanced sequences may be helpful in determining the amount of bone
I�
CENTRAL SKULL BASEl
PEA RLS/PITFALLS •
This diagnosis should be consid ered for patients presenting with headache and vague neurologic symptoms referable to cranial nerves.
•
A CT scan will show a mid -skull base lesion located off midline with ring or arciform-like calcifi cations.
•
Predisposing conditions include: Paget's disease, fibrous dysplasia and multiple enchondromatosis syndromes.
•
Results from immunohistochemi cal analysis show that chon drosarcomas do not stain for ep ithelial markers.
•
The clinician might fail to recog nize a chondrosarcoma in the setting of an underlying diffuse pathologic process, such as Paget's or fibrous dysplasia.
•
Chondrosarcomas may be indis tinguishible from other skull base neoplasms, particularly chordoma, chondromyxoid fi broma, osteosarcoma a n d skull base metastasis.
marrow involvement. Delineation of the neoplasm and its relationship to neurovas cular structures is also optimally achieved with M R I . D u e t o the overlap o f the imaging features with other entities, particularly chor domas, chondromyxoid fibroma, osteosarcomas and mineralized metastasis, correct diagnosis requires pathologic sampling either by image-guided or open biopsy. Immediate post-operative and subsequent follow-up imaging studies are manda tory as residual and recurrent tumors are seen in a high percentage of cases.
Management The multidisciplinary approach to skull base lesions and the advent of image guided neuronavigation systems revolutionized the treatment of these tumors, allowing for more radical resections. However, several authors recommend more conservative surgical approaches with decompressive resections aimed at relief of symptoms and repeated surgeries if the tumor recurs. The goal of surgical treatment should be to achieve maximal tumor resection with the least possible morbidity. Surgical approach depends on tumor location and extent, and may require both intra- and extra-cranial approaches. Radiation has been used both pre-operatively as adjuvant therapy, and as the sole treatment modality. The type of radiation with the highest success rates are charged heavy particles and stereotactic radiosurgery. The prognosis, five year survival rate, of chondrosarcomas (95% ) is better than for chordomas (62% ).
Suggested Readings Crockard, A. Chordomas and chondrosarcomas of the cranial base: results and follow-up of 60 patients. Neurosurgery 38(2) :420, 1 996 Feb. Keel, S.B., Bhan, A.K., Liebsch, N.I, Rosenberg, A.E. Chondromyxoid fibroma of the skull base: a tumor which may be confused with chordoma and chondrosarcoma. A report of three cases and review of the Literature. American Journal of Surgical Pathology 2 1 (5):577-82, 1 997 May. Korten, A.G., ter Berg, H .I, Spincemaille, G.H . , van der Laan, R.T., Van de Wei, A.M. I ntracranial chondrosarcoma: review of the literature and report of 15 cases. Journal of Neurology, Neurosurgery and Psychiatry 65 ( 1 ):88-92, 1998 Jui. Levy, R.A., Quint, D.I, Devaney, K.O. Unusual tumours of the skull and skull base: a pictorial essay. Canadian Association of Radiologists Journal 47(6) :434-43, 1996 Dec. McDermott, M.W., Gutin, P.H. Image-guided surgery for skull base neoplasms using the ISG viewing wand: Anatomic and technical considerations. Neurosurgery Clin ics of North A merica 7(2) :285-95, 1 996 Apr. Muthukumar, N., Kondziolka, D., Lunsford, L.D., Flickinger, I e. Stereotactic radio surgery for chordoma and chondrosarcoma: further experiences. international Jour nal of Radiation Oncology, Biology, Physics 4 1 (2):387-92, 1998 May. Rapidis, A.D., Archondakis, G., Anteriotis, D., Skouteris, e.A . Chondrosarcomas of the skull base: review of the literature and report of two cases. Journal of Cranio Maxillo-facial Surgery 25(6):322-7, 1 997 Dec. Weber, A.L., Brown, E.W., Hug, E.B., Liebsch, N.J. Cartilaginous tumors and chor domas of the cranial base. Otolaryngologic Clinics of North America 28(3):453-7 1 , 1 995 Jun.
ENTRAL SKULL BASE
Case 5 Clinical Presentation A 69-year-old female presented with headaches and a right X l l t h cranial nerve palsy.
A
B
Radiologic Findings An axial T I W I ( Fig. 5-A) and agillal T2WI ( Fig. 5-B) through the the skull base show a large soft tissue mass replacing the clivus. basioccipul. anterior arch of 1 and the dens. The mass is hypointense to the brain on T I W images and hyperi ntense
22
CENTRAL SKULL BASEl on T2W I . There is inferior extension i n to the cervical spinal canal along the a n terior epidural space, to the level of the mid-C2 vertebral body. There is spinal cord com pression and kinking a t the cervico-medullary junction. The axial T l WI through the oral cavi ty (Fig. 5-C) shows denervation a trophy of the righ t hemitongue subse quent to invasion of the right hypoglossal canal by the tumor.
Differential Diagnosis: Destructive Mass in the Clivus •
•
•
Arising rrom the skull base: chordoma, chondroid tumors (chondroma/chon drosarcoma), chondromyxoid fibroma, osteosarcoma, glomus j ugulare, me tastasis, plasmacytoma/mul tiple myeloma, lymphoma, eosinophilic granuloma, fibrous dysplasia Arising above the skull base: meningioma (clivus/planum sphenoidale/tubercu lum sella), craniopharyngioma, pi tui tary macroadenoma Arising below the skull base: sphenoidal mucocele, squamous cell carcinoma of the sphenoid sinus, nasopharyngeal carcinoma, nasopharyngeal rhabdomyo sarcoma
Diagnosis Clival chordoma
Discussion Epidemiology Chordomas are relatively rare tumors of the skull base, accounting for 1 % of all i n tracranial tumors. Fifty per cen t of chordomas arise in the sacrococcygeal region. O ther common locations include the clivus and the spine which comprise 35% and 1 5 % of all chordomas respe.ctively. I ntracranially, the most common locations are the basisphenoid and basiocciput (near the spheno-occipi tal synchondrosis) and the parasellar region. Rarely, chordomas may arise in the nasopharynx or within the paranasal sinuses. The incidence of chordomas vary according to their location. Clival chordomas can occur at any age but show a peak incidence in the 3rd and 4 th decades. Sacro coccygeal chordomas tend to prese n t later in the 40- to 60-year age group. There is a predominance among males.
Pathophysiology Chordomas are histologically benign, locally invasive, and slow growing neoplasms that originate from the primi tive notochord. Because the embryonic notochord terminates a t the sphenoid bone, immediately below the sella turcica, the midline basisphenoid is the mos t common location for this tumor. However, due to the inti mate rel a tionships of the n o tochord with several neuroectodermal, mesodermal and endodermal derivatives, which give rise to the diencephalon, primi tive pharynx, Ra thke's pouch, and facial bones, o ther "ectopic" locations including intradural, nasopharyngeal, sellar and sinonasal regions are possible. Notochordal remnants in the nasopharynx are believed to be responsible for the developme n t of Tornwaldt cysts. Uncommonly, these n o tochordal remnants may give rise to a chordoma in these locations. Histologically, the tumor is composed of translucen t cells rich in mucin and glyco gen, con taining large in tracy toplasmic vacuoles. These physaliforous cells are usu ally arranged in cords or nests separated by thick fibrous sep ta. Macroscopically, the tumor forms a whi te, soft, mul ti lobula ted mass surrounded by a pseudocapsule tba t
231
I CENTRAL
SKULL BASE is composed by compressed adjacent tissue. Gelatinous mucoid fluid, necrosis, hem orrhage and sequestered bony fragments are common and contribute to the het erogeneous imaging appearance of these neoplasms. Most chordomas are cytologi cally benign. The high frequency of recurrence is explained by microscopic extensions of tumor into the adjacent tissues which, together with a difficult surgi cal access, makes complete resection problematic. Highly malignant forms of chordoma are also seen containing undifferentiated areas that may be confused with fibrosarcoma. Metastasis is seen in 7 to 14% of cases, primarily to the lymph nodes, lungs and bone. A variant rich in chondroid material, referred to as chondroid chordoma is a con troversial pathologic entity, believed by some to represent a low grade chondrosar coma. I m munohistochemical stains are very helpful in differentiating chordomas from chondrosarcomas, which may have the same appearance on imaging studies. Whereas chordomas are positive for epithelial markers such as cytokeratin and epithelial membrane antigens, chondrosarcomas are negative for epithelial anti bodies, but are positive for mesenchymal markers such as vimentin and protein S- 1 00. Confusion between chordomas and epithelial metastasis to the skull base may occur with immunohistochemical analysis.
Clinical Findings The presenting symptoms depend on the tumor location, extent, and relationship between the tumor and vital skull base structures. Most patients with clival chordo mas present with headaches and ophthalmoplegia, usually due to impingement upon the V l t h nerve in Dorello's canal. More extensive lateral extension into the cavenous sinus results in cavernous sinus syndrome with deficits of cranial nerves I I I , I V, V I and V2. Posterior and inferior extension into the jugular foramen presents with palsy of cranial nerves IX, X and XI and involvement of the hy poglossal canal results in X l lth nerve palsy. Destruction of the petrous apex and involvement of the CPA cistern may cause V l l t h and VI 1 1th nerve deficits. Ante rior growth into the sella turcica may lead to compression of the pituitary gland and hypopituitarism. Symptoms of brainstem compression and increased intracranial pressure signal advanced disease. Destruction of the occipital condyles and exten sion of the tumor through the foramen magnum into the upper cervical spinal canal may result in neck pain and quadraparesis. Subarachnoid hemorrhage is a rare form of presentation of intradural tumors.
Imaging Findings Radiologic evaluation of skull base tumors should include both CT and MRI to de termine the full bony and soft tissue extent. Depending on their location within the clivus, chordomas are classified as upper, middle or lower clival chordomas. Upper clival chordomas occur rostral to the trigeminal nerve in the region of the dorsum sella . Middle clival chordomas occur between the origin of the Vth and IXth cranial nerves and chordomas of the inferior clivus below the origin of the glossopharyn geal nerve. This classification along with evaluation of involvement of critical struc tures (cavernous sinuses, circle of Willis and brainstem ) is mandatory in determin ing the best management. Chordomas vary in size [rom I to 10cm but most are in the 2 to Scm range. Typically, these tumors arise in the midline clivus near the spheno-occipital synchondrosis. They may extend laterally into the cavernous sinus and petrous apex, anteriorly into the sphenoid sinus. superiorly into the sellar and suprasellar regions, inferiorly into the foramen magnum and/or posteriorly into the j ugular foramen and prepontine cistern. a should include post contrast axial and coronal sections through the skull base and upper cervical spine with images filmed in both soft tissue and high resolution bone windows. Chordomas are seen as iso- or hypodense soft tissue masses with lytic bony destruction and no significant sclerosis. Bony destruction may be limited
I�
CENTRAL SKULL BASE I
D
E
to the clivus or involve the petrous apex, foramen j ugulare, occipital condyles and upper cervical vertebra. Calcifications are present in 50% of cases. These are usually large, distinctive from the typical small ring like or punctiform calcifications seen in chondroid tumors, and may represent sequestered bony fragments or dystrophic calcifications. After contrast administration, these lesions may show little to moder ate enhallcemellt with non-enhancing areas corresponding to mucoid or cystic de generation. On M R I , the sigllal characteristics are quite variable depending on the presence of tumoral calcification, hemorrhage or cystic degeneration. Usually they tend to be iso- to hypointense on T l W I alld heterogeneously hyperilltense Oil TIWI . A lobu lated, boneycomb appearance after gadolinium administration has been described as a characteristic feature of chordomas. M R I is the optimal modality to detect small intraclival tumors which manifest as an area o f T I W hypointensity within the high signal intensity of fat. However, care should be taken to avoid mistaking areas of hematopoietic bone marrow for a clival tumor. To avoid this confusion, one should carefully look [or loss of sigllal void of the cortical margin of the clivus or bony erosion on CT. Axial CT sectiolls througb the clivus in another patient (Fig. 5-D and 5-E) (bone willdows) , show a destructive mass centered ill the clivus and eroding both petrous apices alld the allterior arch of the clivus. Diagnosis: Clival chordoma. M R I is also the modality of choice to evaluate the relationship of the tumor to the structure of the cavenous sinus, j ugular foramen and posterior fossa. It is particu larly useful for identifying the presence of compression or encasement of the basi lar or cavernous carotid arteries. The main differential consideratioll for dival chordomas are cbondroid tumors of the skull base. The most useful clue is the topography of the lesion. Whereas chor domas tend to arise in the midline, chondroid tumors are usually lateral in location arising from the spheno-occipital or petroclival synchondrosis. However, this serves ollly as a gelleral guidline, as chondroid tumors may be midline in location and chor domas may locate more laterally due to terminal spliting of the embryonic noto chord. Craniopharyngiomas, in addition to their typical cystic appearance and charac teristic linear, peripheral calcifications, are usually centered in the sellar region.
/cENTRAL
SKULL BASE
PEARLSIPITFALLS •
The most common location for this destructive mass is in the midline clivus.
•
A characteristic feature of chor domas is a multilobulated, hon eycomb appearance on post contrast M R I .
•
Because o f i t s embryonic origins, ectopic locations can include in tradural, sellar, nasopharyngeal and sino nasal regions.
•
When diagnosing this condition, the clinician might fail to evalu ate the fulJ extent of the tumor.
•
With MR imaging, care should be taken to avoid mistaking ar eas of hematopoietic bone mar row in the clivus for a neoplasm.
They have a predilection for postero-superior extension into the interpeduncular cistern. Clival meningiomas, show a broad dural base, tend to be isointense to the brain on all MR sequences, enhance homogenously and exhibit a dural tail . The presence o f a rim of pituitary tissue surrounding a sellar lesion suggests the diagnosis of a pituitary macroadenoma. The signal characteristics of lymphoma, iso- to hypointense on T1 WI and low sig nal intensity on T2WI due to hypercelluarity and low water content, usually allows distinction from chordoma. Mucoceles of the sphenoid sinus tend to cause bony expansion and cortical thin ing. However, late in the course of the disease cortical breaching may be indistin guishible from bony erosion. Squamous cell carcinoma of the sphenoid sinus, plasmacytoma, metastasis and re current nasopharyngeal carcinoma may be indistinguishible from a chordoma.
Management Despite the continuous advances in skull base surgery, most chordomas cannot be completely resected due to their tendency for microscopic invasion and to the prox imity of important structures such as cranial nerves and major intracranial arteries. Despite this fact, surgical excision should be attempted as radiation therapy is usu ally not effective in decreasing the bulk of the tumor. However, radiation using high dose proton beam therapy can be successful in the treatment of a residual tumor. The choice of the best therapeutic approach is based upon many factors including the tumor location, the clinical condition of the patient, and any history of previous surgery or radiation. Transphenoidal surgery may be used for upper and middle cli val tumors with only minimal or no lateral extension. Large tumors usually require extensive craniofacial and cervical approaches with increased morbidity and mor tality. Imaging is used, both guiding surgery for small neoplasms, and in planning ra diosurgery for these skull base tumors. Radiological fol low-up is mandatory due to the high rate of recurrence of these neoplasms.
Suggested Readings Casals, M.M., Hunter, S.B., Olson, J.1., Gussack, G., Blevins, L.S. Jr. Metastatic follic ular thyroid carcinoma masquerading as a chordoma. Thyroid 5(3):2 1 7-2 1 , 1 995 Jun. Doucet, v., Peretti-Viton, P, Figarella-Branger, D., Manera, L., Salamon, G. MRI of intracranial chordomas. Extent of tumour and contrast enhancement: criteria for differential diagnosis. Neuroradiology 39(8):571-6, 1 997 Aug. Kaufman, B.A., Francel, pc., Roberts, R.L., Argemand, E., Park, TS., Dehner, L.P. Chondroid chordoma of the lateral skull base. Pediatric Neurosurgery 23(3): 1 59-65, 1 995. Keel, S.B., Bhan, A . K . , Liebsch, N.J., Rosenberg, A.E. Chondromyxoid fibroma of the skull base: a tumor which may be confused with chordoma and chondrosarcoma. A report of three cases and review of the literature. American lournal of Surgical Pathology 2 1 (5):577-82, 1997 May. Maira, G., Pallini, R., Anile, c., Fernandez, E., Salvi nelli, F., La Rocca, L.M., Rossi, G.F. Surgical treatment of clival chordomas: the transsphenoidal approach revisited. lournal of Neurosurgery 85(5):784-92, 1 996 Nov. Tashiro, T , Fukuda, T, Inoue, Y, Nemoto, Y, Shakudo, M., Katsuyama, 1., Hakuba, A., Onoyama, Y Intradural chordoma: case report and review of the literature. Neu roradiology 36(4):31 3-5, 1994 May. Weber, A.I., Brown, E.W., Hug, E . B., Liebsch, N.J. Cartilaginous tumors and chor domas of the cranial base. OlOlaryngologic Clinics of Norrh America 28(3) :453-7 1 , 1995 Jun.
CENTRAL SKULL BA EI
Case 6 Clinical Presentation A 25-year-old male presented with headache, hoarseness, nasal regurgitation, and difficulty swal lowi.ng.
A
B
27 1
I CENTRAL
SKULL BASE
Radiologic Findings In an M R I of the skull base, axial T l W I , and coronal post-contrast T l WI show a de structive mass in the posterior skull base centered at the right jugular foramen. This enhancing mass invades the inferior aspect of the clivus, the right occipital condyle, anterior arch of C l , and the right hypoglossal canal. The tumor extends medially and posteriorly behind the right longus colli muscle and appears to transgress the pre-vertebral fascia (Fig. 6-A) . The axial T l W image through the oral cavity shows denervation atrophy of the right hemitongue and rightward deviation of the uvula (Fig. 6-B). The coronal T l W image through the neck demonstrates fatty replace ment and flacidity of the right lateral wall of the pharynx, con istent with involve ment of cranial nerves IX and X (Fig. 6-C).
Differential Diagnosis: Destructive Lesion of the Posterior Skull Base • • • • •
•
Neoplasm: Malignant: Primary: chondrosarcoma, osteosarcoma, lymphoma, chordoma (midline ) Secondary: plasmacytoma, chloroma, metastasis Benign: schwan noma of the lower cranial nerves, meningioma, chondroma, giant cell tumor, brown tumor, hemangioma, eosinophilic granuloma, glomus jugulare I n fectionlInflammation: osteomyelitis, radiation necrosis
Diagnosis Choriocarcinoma metastatic to the skull base
Discussion Epidemiology Although relatively uncommon, metastasis should always be considered in the dif ferential diagnosis of a central skull base mass. There is a peak incidence in the 5th and 6th decades, but they may be seen in any age group. In the pediatric population primary considerations include metastatic neuroblastoma, rhabdomyosarcoma. choriocarcinoma, lymphoma, and chloroma. [ n adulthood the major considerations are prostate, lung and breast carcinoma, and melanoma. Renal cell, thyroid and gastro-intestinal tract neoplasms should also be considered. Skull base metastasis usually occurs in the setting of a known malignancy but occasionally is the first sign of an occult neoplasm. I n the latter circumstance differential diagnosis with primary skull base tumors may be difficult. There is no gender predilection.
Pathophysiology Metastatic disease to the skull base may occur via three different mechanisms. ( 1 ) The most common is direct extension from neoplasms arising in the head and neck region, particularly nasopharyngeal, palatal. parapharyngeal, sphenoid and temporal bone malignancies. Among these, squamous cell carcinoma of the nasopharynx is the most frequent tumor presenting with invasion of the skull base. Limitation of lateral spread by the pharyngobasilar fascia directs tumor growth superiorly and posteriorly in the direction of the clivus and cavernous sinuses. The tumor may also reach the central skull base through the Eustachian tube.
1 28
CENTRAL SKULL BASEl (2) The second most common mechanism is via perineural spread from head and neck tumors, most frequently through branches of the second division of the trigeminal nerve. Neoplasms particularly prone to this type of spread include adenoid cystic carcinoma, squamous cell carcinoma, mucoepidermoid carci noma, lymphoma, and melanoma. (3) Finally, metastasis to the skull base may occur via hematogenous dissemination from distant sites. Direct and retrograde perineural spread of tumor to the skull base and intra cranial compartment is a consequence of skull base anatomy and the multiple foramina which allow for communication between the intra- and extracranial compartments. Most head and neck spaces communicate freely with the intracranial compartment t hrough one or more foramina. The main common pathway for in tracranial spread of head and neck neoplasms is the pterygopalatine fossa, a space limited anteriorly by the posterior wall of the maxillary antrum, bordered posteriorly by the pterygoid plates and containing branches of the second division of the trigeminal nerve, the pterygopalatine ganglion, vessels, and fat. Superiorly, this space communicates with the inferior orbital fissure, medially with the posterior nasal cavity through the sphenopalatine foramen, laterally with the infratemporal fossa (masticator space) through the pterygomaxiUary fissure and inferiorly, with the oral cavity through the pterygopalatine canals. Posteriorly, it communicates with the central skull base via the vidian canal and foramen rotundum. The fora men ovale opens into the masticator space and constitutes the second most com mon site of perineural spread, along the third division of the trigeminal nerve. Orbital malignancies may access the skull base through the orbital apex or orbital fissures. Perineural spread of parotid gland malignancies along the intra temporal facial nerve is not uncommon and should always be sought. Metastatic disease to the pos terior fossa may involve the jugular foramen and be confused with paragangliomas or schwannomas, the most common tumors seen in this region.
Clinical Findings Clinical presentation depends on the exact location of the lesion and on the skull base structures involved. Usually symptoms include headaches and characteristic neurologic syndromes. These syndromes were classified by Posner and Greenberg into five different categories including orbital, cavernous/parasellar, middle cranial fossa (Meckel's cave syndrome), jugular foramen, and occipital condyle syndrome. Metastasis of the central skull base tends to involve the cavernous sinus and Meckel's cave whereas metastasis to the posterior skull base usually involves the jugular foramen and hypoglossal canal . The presence of one of these syndromes should alert the clinician to the presence of a skull base lesion and prompt appro priate imaging evaluation.
Imaging Findings The central skull base, due to its anatomic complexity, is best evaluated by dedicated cross-sectional studies allowing detection of subtle lesions. CT should include con trast enhanced 3mm thick sections in axial and coronal planes, through the skull base or helical aqusition in the axial plane, followed by coronal reformations. Skull base M R I studies should include multiplanar thin sections including axial Tl W, TIW, and axial and coronal frequency selective fat suppression imaging (FATSAT) post contrast T l W images. These modalities are complimentary and should be used in combination. I n another patient presenting with headache and hearing loss, an
ICE
F
G
M R [ of the kull base. axial pre and post-contrast T l W image ( Fig. 6-0) and ( Fig. 6-E ) through the clivus show a large enhancing soft ti ue ma s replacing the the cli val bone marrow and invading the petrou and ma toid portions of the right tem poral bone. Diagno is: Skull base pia macytoma (courtesy of Dr. J.P. Wensel ) . [ n another patient a n M R I o f the kull base, agiltal T l W (Fig. 6-F) and axial post con trast T l W ( Fig. 6-G ) image show an enhancing mass in the left lateral aspect of the sellar and supraseUar regions invading the left cavernou inus. This patient pre sented with cavernou inus syndrome. Diagno is: Metastasi from brea t carci noma. CT may show subtle foraminal enlargement and ero ion of the cortical bone. Detection of intratumoral calcification and recognition of specific pallerns of calci fication may sugge t certain pathologic diagno e uch as chondroid tumors, o teosarcoma, Paget's di ease, fibrou dyspla ia or 0 teobla tic meta ta is. TIle pre ence of bony remodelisg or sclerosis suggests indolent tumors such as meni ngiomas. the Illost frequent benign tumor of the skull base.
/ 30
CENTRAL SKULL BASEl
PEARLS/PITFALLS •
The presence of a headache asso ciated with a typical skull base cranial nerve syndrome should prompt a search for a skull base lesion.
•
Metastasis to the skull base may be the first sign of an occult malignancy.
•
cr and M R I should be used i n conjunction for better assess ment of tumor extension.
•
It is possible to mistake metas tases for primary tumors of the skull base.
•
The clinician may fail to recog nize perineural spread of the tu mor.
•
It is possible to mistake a highly vascular metastasis in the region of the jugular foramen for glo mus jugulare.
M R I is very sensitive to bone marrow replacement and early perineural spread of tumor, even before foraminal enlargement can be appreciated. Focal, segmental or patchy areas of enhancement along the course of a cranial nerve, replacement of the fat hyperintensity near the foraminal openings and loss of TIWI hyperintensity within Meckel's cave are the typical M R I features of perineural spread of tumor. Clival bone marrow replacement is usually easy to detect on the non-contrast Tl W images as areas of loss of fatty signal intensity. However, incomplete replacement of the hematopoietic bone marrow of the clivus is seen in 15% of the adult population and may mimic neoplastic infiltration. Highly vascular metastases such as renal cell carcinoma, choriocarcinoma, melanoma and thyroid carcinoma may show a "salt and pepper" appearance and when located in the region of the jugular foramen are indistinguishible from para gangliomas. Melanoma metastases may show typical hyperintensity on Tl W I due to the paramagnetic effect of melanin. However, this finding is non-specific and may be seen in hemorrhagic metastases, metastases containing mucinous material or cystic metastases from thyroid malignancies which may have a high protein content. Chondroid tumors tend to be heterogeneous in signal characteristics due to the presence of chondroid calcifications and tend to occur in a lateral location centered upon the spheno-occipital or petro-clival synchondroses. The single most specific feature of clival chordomas is their location in the midline. Nuclear medicine SPECT studies using 99mTc may be performed in symptomatic patients with known malignancies, when cross-sectional imaging studies are negative.
Management Metastatic disease of the skull base is usually managed according to the cell type of the primary tumor. Radiation and/or chemotherapy may be used. Surgical resection may be considered in individual cases, particularly those with occult primaries. The surgical approach and completeness of resection depends on the location of the le sion.
Suggested Readings Ampil, FL., Hardin, IC, Peskind, S.P. , Stucker, FI Perineural invasion in skin can cer of the head and neck: a review of nine cases. Journal of Oral and Maxillofacial Surgery 53( 1 ):34-8, 1 995 Jan. Jansen, B.P., Pillay, M., de Bruin, H . G., van den Bent, M.J., Vecht, CJ., Sillevis Smitt, P. A . 99mTc-SPECT in the diagnosis of skull base metastasis. Neurology 48(5) : 1326-30, 1 997 May. Ng, S.H., Chang, T.C, Ko, S.E . , Yen, P.S., Wan , YL., Tang, L.M., Tsai, M . H . Nasopharyngeal carcinoma: M R I and CT assessment. Neuroradiology 39(10):741-6, 1 997 Oct. Sakata, K, Aoki, Y, Karasawa, K , Hasezawa, K , Muta, N., Nakagawa, K., Terahara, A., Onogi, Y, Sasaki, Y, Akanuma, A . Wide variation of probability of lo cal failure and distant metastasis among various stages of patients with nasopha ryngeal carcinoma. Slrahlenlherapie und Onkologie 1 70(4):2 1 8-24, 1 994 Apr. Sutter, CW., Masilungan, B.G., Shelton, D.K. An unusual first impression of skull base metastasis. "The sunglasses illusion". Clinical Nuclear Medicine 2 1 (4):322, 1 996 Apr.
. l
II. Larynx and Hypopharynx
LARYNX AND H Y POPHARYNXI
Case 7 Clinical Presentation Adult male presented with pharyngitis and dysphagia.
A
Radiologic Findings The lateral radiograph shows abnormal thickening of the epiglottis aryepiglottic folds, and arytenoids (Fig. 7-A). There is no evidence of radio-opaque foreign body or interstitial air.
Differential D iagnosis: Epiglottitis, Supraglottitis • • • •
Squamous ceU carcinoma Supraglottitis/epiglottitis Atypical laryngocele Post-traumatic deformity
Diagnosis Epiglottitis, supraglottitis
I LARYNX
AND H YPOPHA RYNX
Discussion Epiglottitis, or as it is increasingly known, supraglottitis, is an inflammation of the supraglottic larynx.
Epidemiology The pediatric form is due to Haemophilus influenzae virus infection and occurs in slightly older children. Its incidence in children is decreasing as childhood vaccina tions are increasing. The disease in adults is relatively uncommon but may be life-threatening. The death of George Washington is believed by many authors to represent an early recorded case of t he disease. Unlike the decreasing incidence of the pediatric form, the incidence of the acute adult form remains stable. Only a minority of adult cases are caused by H. influenza. More common pathogens are the staphylococcus and streptococcus groups. U nlike epiglottitis, croup manifests as a swelling of the subglottic larynx. trachea, and bronchi due to type I parainfluenza virus or similar organisms. Patients with croup are typically children 6 months to three years of age. Clinically. a characteris tic barking cough and stridor are present. The subglottic edema results in the signature radiographic appearance of the loss of the normal shoulder shape of the subglottic angle. I nstead there is a church steeple or wine-bottle appearance of this area on the frontal radiograph or coronal vIew.
Clinical Fi ndings Supraglottitis patients present with sore throat, dysphagia, drooling (due to failure 10 control secretions), and oflen, airway compromise. On examination, the supra glottic larynx is swollen, often with a cherry red appearance. The radiographic find ings of enlarged epiglottis on the lateral view are due to edema of this and other supraglottic laryngeal structures. Close supervision of the patient with epiglottitis is
B
L A RYNX A N D H YPOPHARYNXI
PEARLSIPITFALLS •
The epiglottis and supraglottis can appear thickened on CT or MR imaging.
•
The organism responsible for pe diatric epiglottis is usually Haemophilus influenza.
•
The organism responsible for epiglottis in adults is usually a member of the staphylococcus or streptococcus groups.
•
Cross sectional imaging will help rule out complications.
•
Epiglottitis is often a missed di agnosis in patients with impend ing acute airway compromise.
required because acute airway closure may occur, and intubation or emergency tra cheostomy may be necessary.
Imaging Findings The classic appearance on the lateral radiograph is that of a thickened "thumb-like" epiglottis (Fig. 7-A). Normally, its appearance is a thin "shoe-horn" shape (Fig. 7-B). Generalized edema of the supraglottic larynx is another finding. Although measurements are not necessary to make the diagnosis, some detailed studies have been performed. For example, the ratio of the soft-tissue parameters to the anteroposterior width of the C-4 vertebral body yields three key parameters re ported to be of high statistical significance in the diagnosis of adult epiglottitis. ( 1 ) The ratio of the width of the epiglottis to the anteroposterior width of C-4 should not be greater than 0.33 (sensitivity, 96% ; specificity, 100% ) . (2 ) The ratio of the prevertebral soft tissue to C-4 should not exceed 0.5 (sensitiv ity, 37% ; specificity, 100% ) . (3) The ratio o f the width of the hypopharyngeal airway to the width o f C-4 should be less than 1 .5 (sensitivity, 44% ; specificity, 87% ).
Because the symptoms may be nonspecific, in some cases CT or MRT may be use ful to exclude other conditions with similar symptoms such as laryngitis, foreign body, peritonsillar abscess, and tonsillitis. The most common CT/MRI findings of epiglottitis are thickening of the epiglottis, aryepiglottic folds, false and true vocal cords, obliteration of the preepiglottic fat, thickening of the platysma muscle, and reticulation of the subcutaneous fat. Multiple loculated fluid-density collections consistent with abscesses can be see!1. Although the diagnosis of supraglottitis is generally made on the basis of the patient'S history, direct endoscopy, and plain films, CT/MRJ may be used to confirm the diagnosis when an adequate clinical ex amination cannot be performed. CompLications such as deep neck abscess also may be identified easily with CT or M R I . Examinations requiring the patient to lie supine should be performed with caution as this position can precipitate acute air way closure.
Suggested Readings Barrow, H.N., Vastola, A.P., Wang, R.c. Adult supraglottitis. OlOlaryngology and Head and Neck Surgery 1 09(3 Pt 1 ):474-7, 1 993 Sep. Dawson, K.P., Steinberg, A . , Capaldi, N. The lateral radiograph of neck in laryngo tracheo-bronchitis (croup). Journal of QualilY in Clinical Praclice 1 4( 1 ):39-43, 1 994 Mar. Frantz, T.D., Rasgon, B.M. Acute epiglottitis: changing epidemiologic patterns. 010laryngology and Head and Neck Surgery 109(3 Pt 1 ):457-60, 1 993 Sep. John, S.D., Swischuk, L.E., Hayden, c.K. Jr., Freeman, D.H., Ir. Aryepiglottic fold width in patients with epiglottitis: where should measurements be obtained? Radi ology 190( 1 ): 1 23-5, 1 994 Jan. Kass, E.G., McFadden, E.A., Jacobson, S., Toohill, R.l Acute epiglottitis in the adult: experience with a seasonal presentation. Laryngoscope 103(8):84 1-4, 1993 Aug. Nemzek, WR., Katzberg, R.W., Van Slyke, M.A., Bickley, r.S. A reappraisal of the ra diologic findings of acute inflammation of the epiglottis and supraglottic structures in adults. American fournal of Neuroradiology 1 6(3):495-502, 1 995 Mar. Smith, M.M., Mukherji, S.K., Thompson, lE. Castillo, M. CT in adult supraglottitis. American Journal of Neuroradiology, 1 7(7) : 1 355-8, 1 996 Aug.
�I
I LARY
X A N D H Y POPHA RYNX
Case 8 Clinical Presentation A 77-year-old male presented with hoarsene s. On physical examination there was a bulge in the raise cord level ( Fig. 8-A).
A
B 38
LARYNX AND H Y POPHARYNXI
Radiologic Findings On a T l -weighted image (Fig. 8-B), there is an oval, sharply marginated abnormal ity in the false cord obliterating the paralaryngeal fat. The mucosa can be seen along the medial margin, indicating that this is in a submucosal position. ( Image courtesy of Dr. Hugh D. Curtin.)
Differential Diagnosis: Paralaryngeal Cyst • • • • • •
Laryngocele Congenital laryngeal cyst Cyst of the epiglottis Branchial cleft cyst Neoplasm with necrosis simulating cyst Thyroglossal duct cyst
Diagnosis I n ternal laryngocele
Discussion Epidemiology Laryngoceles are usually unilateral, although they may be bilateral in 25% of cases. Laryngoceles commonly present in adulthood and many are asymptomatic.
c
I LARYNX
AND HYPOPHA RYNX
D
Pathophysiology Laryngoceles are formed by a dilation of the small saccule (appendix) of the laryn geal ventricle. The laryngeal saccule is a small diverticulum that passes superiorly from the ventricle of the larynx. In so doing, it passes into the paraglottic space at the level of the false cord. Some experts use the term saccular cyst if it is fluid filled and laryngocele if it is air filled. For this discussion. either form will be referred to as a laryngocele. Sometimes this appendix expands superiorly in the paralaryngeal space, medial to the thyroid cartilage, where it is known as an internal laryngocele and can present as a submucosal supraglottic space mass. Figure 8-C shows a line drawing of a coro nal view of the larynx with internal (right) and mixed/external ( left) laryngocele. An axial Tl W image with contrast (Fig. 8-0 ) in another patient shows no enhancement of a cystic paralaryngeal mass. Lateral displacement of the thyroid lamina can occur. Alternatively, if the dilated saccule extends through the thyrohyoid membrane out into the soft tissues of the neck, it is a mixed (external) laryngocele. This form may present as a soft tissue neck mass. An unobstructed laryngocele is filled with air. When obstructed. high protein fluid accumulates within the dilated appendix. H the obstructed fluid becomes infected. it is referred to as a pyolaryngocele. Sometimes a small lesion near the neck of the saccule causes the obstruction and subsequent formation of a laryngocele. Laryngoceles may be associated with chronic granulomatous disease, such as tuberculosis. Laryngoceles are benign entities. However, they can result from a carcinoma of the true cord or ventricle. The laryngeal saccule is normally collapsed. but if there is a tumor obstructing its outflow into the ventricle, it can dilate, forming a laryngocele or saccular cyst. The differential diagnosis of a submucosal mass in the larynx should include var ious benign and malignant lesions. The imaging appearances of these otlier entities. however, are usually distinct from a typical laryngocele. Other cysts of the larynx include congenital laryngeal cysts, which present in newborns as smooth. mucosal
LARYNX AND HYPOPHA RYNXI
E
PEARLS/PITFALLS •
A laryngocele may be internal or mixed (external), and it may be filled witb fluid or air.
•
Laryngoceles may be seen in combination witb small glottic cancer.
•
The clinician must beware not to mistake tbe incidental laryngo cele for tumor extension in a patient with known laryngeal cancer.
•
In a patient with known laryngo cele, it is important to determine whether it is a small cancer tbat may be causing the laryngocele.
•
An extemal laryngocele may be mistaken for a branchial cleft cyst or thyroglossal duct cyst.
covered, rounded masses of the false cords and aryepiglottic folds. Congenital cysts in infants are similar to laryngoceles in adults in that both entities are lined with res piratory epithelium. They differ in that, unlike larygnoceles, congenital cysts do not have a connection with the laryngeal lumen. Cysts of the epiglottis are similar to congenital in that they do not communicate with the laryngeal lumen but they are similar to laryngoceles in that tbey typically occur in adults. All tbree of the above lesions may be associated with airway com promise.
I m aging Findings In imaging studies, a laryngocele is a rounded well-circumscribed soft tissue mass or air collection that extends superiorly from the laryngeal ventricle and false cord into the paralaryngeal space (internal laryngocele) or lateral to the thyrohyoid mem brane (rnixed/external laryngocele). In mixed laryngoceles, both internal and exter nal cystic features can be identified. Figure 8-E shows a coronal reformatted CT scan of a patient with a rnixed/external laryngocele. The signal intensity of the fluid will depend on the protein content. A typical M R appearance depends on wbether the laryngocele is filled with air or fluid. A signal void indicates that it is air filled whereas the intermediate signal is consistent with a saccular cyst. I n either situation the region of the ventricle should be carefully examined to exclude a tumor. I ntravenous contrast may be helpful in order to belp define the cystic nature of the lesion (Fig. 8-E).
Management lnternal laryngoceles may be aspirated, incised, drained, and marsupialized. Exter nal/mixed laryngoceles are often treated with an external surgical approach follow ing any internal components for removal.
Suggested Readings Curtin, H.D. Imaging of the larynx: current concepts. Radiology 1 73: 1-1 1 , 1 989. Teresi, L.M., Lufkin, R.B., Hanafee, W.N. Magnetic resonance imaging of the larynx. Radiologic Clinics of North A merica 27:393-406, 1 989.
ILARY
Case 9 Clinical Presentation A 47-year-old female presented with per istent hoarseness (Fig. 9-A).
A
B
Radiologic Findings The left true vocal cord is partially abducted and appears slightly inferior to the other cord on the axial image ( Fig. 9-B). There is asymmetry on a higher section due 42
LARYNX AND H Y POPHARYNXI to medial positioning of the left aryepiglottic fold and resultant widening of the left pyriform sinus (Fig. 9-C).
Differential Diagnosis: Vocal Cord Paralysis • • • •
Old trauma Arytenoid dislocation Laryngocele Carcinoma
Diagnosis Vocal cord paralysis
Discussion The recurrent laryngeal nerve innervates all the intrinsic muscles of the larynx. Paresis or palsy of this nerve usually results in a characteristic clinical and radi ographic appearance of the larynx as well as hoarseness or weak voice in the pa tient. Because of the long course of the left recurrent nerve around the ductus arte riosus before its ascent up the tracheoesophageal groove to the vocal cord, it is particularly susceptible to injury. Thus, vocal cord paresis may result from insult to tbe brainstem, skull base, neck, or mediastinum.
D
I LARYNX
AND HYPOPHARYNX
Pathophysiology The vagus nerve exits the skullbase via the pars nervosa of the jugular foramen and travels inferiorly j ust posterior to the carotid artery and jugular vein. Due to differ ences in vascular embryology between the two sides, the recurrent nerve loops around the subclavian artery on the right and under the aortic arch ductus arterio sus on the left (Fig. 9-0, after Jacobs et al.). ll1Us, imaging studies for right sided disease cover only to the level of the subclavian artery while evaluation of the left recurrent nerve must include sections all the way down to the aortic arch. Both nerves then ascend in the tracheoesophageal groove to the larynx. As with denervation elsewhere in the body, there is a subsequent laxity of the muscle groups following nerve injury. In the larynx, the most prominent muscle group is the thyroarytenoid muscle, which includes the vocalis muscle. Denervation results in medial rotation of the vocal process of the arytenoid cartilage and a para median position of the muscle, which the inexperienced observer on radiographic studies may mistake for a small vocal cord mass. With paresis. in addition to the arytenoid cartilage and vocalis muscle rotating into the midline in the adduction position, the structures also sag downward. This causes ipsilateral widening of the laryngeal ventricle, which may be visible on coro nal MRT imaging. Because the aryepiglottic fold is attached to the arytenoid carti lage, this downward displacement also results in ipsilateral widening of the piriform sinus. This is also visible on imaging studies. These findings strongly suggest recur rent nerve paralysis and help distinguish this entity from other causes of vocal cord fullness, which do not have these features. Although nerve dysfunction may be related to tumors or vascular conditions, or may be idiopathic, the vast majority of vocal cord paralysis is related to trauma dur ing neck or thyroid surgery. The superior laryngeal nerve exits the vagus nerve and innervates the cricothy roid muscle, providing sensory innervation of the larynx. It is usually not possible to diagnose paralysis from the radiological findings; however, due to subtle asymmetry of the larynx, the diagnosis may sometimes be made clinically with unilateral in volvemenL l maging plays a role in this case to evaluate the course of the nerve from the larynx to the skullbase to exclude pathology. With symmetrical bilateral in volvement, clinical or radiologic diagnosis is usually not possible. ll1is usually causes adduction of the vocal cords and airway compromise.
Imaging Findings Vocal cord thickening is a nonspecific finding. It does not necessarily imply tumor or edema and may be secondary to paresis. The paramedian location of the true vocal cord and the anteromedial rotation of the arytenoid process occurs due to denervation of the cricothyroid muscle (which is a tensor of the true vocal cord). The presence of ipsilateral piriform sinus and ventricle widening visible on imaging studies helps to differentiate vocal cord fullness due to paresis from other vocal cord masses. With long-standing denervation, there may be atrophy as well as subtle ratty re placement visible as increased signal on M R T l weighted images. ll1ere also may be increased signal intensity on T2W images unrelated to fatty replacement. which may be a change in water content related to loss of innervation. The value of radiology in this condition is twofold. First, the astute radiologist may make the diagnosis in the situation when the clinical picture is unclear and the imaging findings are characteristic. Second, once the correct diagnosis of laryngeal paralysis has been made, it is incumbent upon the radiologist to evalaute the entire course of the recurrent nerves from the brainstem to mediastinum to look for pos sible causes of dysfunction. Because of the course of the recurrent nerve, scans must cover down to the aortic arch if the paralysis is left-sided, whereas it is only neces sary to go down to the brachial artery if the paralysis is right-sided.
L A RY N X AND H Y POPHARYNXI
PEARLS/PITFALLS •
Radiologic findings include ipsi lateral widening of the piriform sinus and ventricle. Later, atro phy and fatty replacement are denoted by increased 1'2 signal.
•
Scans must go down to the level of brachial artery if the lesion is right-sided, and to the level of the aortic arch if the lesion is left-sided.
•
The clinician must take care not to mistake paralysis for vocal cord mass.
•
It is important to evaluate the entire course of the recurrent nerve.
Suggested Readings Decker, G.A.G., du Plessis, 0.J. Lee McGregor's synopsis of surgical anatomy. 12th ed. Bristol: John Wright and Sons Ltd., 1986: 372. Gacek, M . , Gacek, RR Cricoarytenoid joint mobility after chronic vocal cord paralysis. Laryngoscope 106( 12 Pt 1 ) : 1 528-30, 1996 Dec. Jacobs, c.J., Harnsberger, H . R , Lufkin, RB. Vagal neuropathy: evaluation with CT and M R imaging. Radiology ] 64:97-1 02, 1987. Tanaka, S., Hirano, M., Umeno, H . Laryngeal behavior in unilateral superior laryn geal nerve paralysis. A nnals of Otology, Rhinology and Laryngology 103(2): 93-7, 1 994 Feb.
I LARY
X AND H Y POPHARYNX
Case 10 Clinical Presentation A 6 1 -year-old male complained of having weakness in his voice for the pa t everal weeks. The patient denied dysphagia and hoar ene but did describe occasional pain in the laryngeal area when speaking. He did not drink or smoke and could re call no trauma to hi neck. Examination of the patient's head and neck revealed no external neck masses and no gro pathology of tbe oral cavity, nasopharynx, oropharynx, or nose. Vi ualization of the larynx showed a submucosal mass in the region of the left false vocal cord ( Fig. l O-A).
A
I�
B
LARYNX A D HYPOPHARY
xl
Radiologic Findings A cr scan at the level of the false vocal cords shows the laryngeal "rna s" to be due to a deformity of the underlying left thyroid cartilage (Fig. 1 0-B). 0 other soft ti sue rna es were noted. MR imaging at the same level also demon trates the " mas " created by the laryngeal cartilage deformity (Fig. 1 0- ). The cr and MRI scans of the larynx readily identify the cau e of the rna s to be due to di tortion and devia tion of the left thyroid cartilage at the level of the false vocal cord . 0 associated oft tissue mass or obliteration of fa cial plane is pre ent.
Differential Diagnosis: Abnormal Shape of the Laryngeal Cartilage • • • • • • •
Abnormal shape of laryngeal cartilage hronic po ttraumatic deformity Po tsurgical changes Acute laryngeal trauma hondroid neopla m of the larynx Metastasi to the cartilage ongenital deformity
Diagnosis hronic posttraumatic deformity of the larynx
Discussion Clinical Findings Unlike acute laryngeal injury where the history of trauma is usually the presenting finding. patient with chronic post-traumatic laryngeal deformities may present with a variety of vague symptom and may deny any history of trauma. Patient with chronic posttraumatic laryngeal deformitie may present to the clin ician with a ymptomatic, muco ai-covered laryngeal "masses " long after the initial
D
47 1
I LARYNX
AND HYPOPHARYNX
E
(and often forgotten) trauma. Hanson, et al ( 1 982) included six factors in their symptom complex of old laryngeal injury: ( 1 ) voice fatigue, (2) sensation of food "sticking" in the throat, (3) soreness in the side of the neck, (4) submucosal mass in the supraglottic larynx, and (5) CT or (6) M R I evidence of trauma.
Imaging Findings Posttraumatic deformity of the laryngeal cartilages can now be diagnosed by using current CT and MR scanning techniques. This is of particular aid to the clinician who is evaluating a laryngeal mass with no history of injury to the neck. CT and MR imaging are both effective in this situation, and although M R imaging allows better soft tissue contrast resolution and can produce coronal and sagittal views, CT is probably superior for visualization of the ossified cartilage and associated changes. The chronic findings of trauma of the larynx are soft tissue abnormalities due to scarring and granulation and post-traumatic deformity of the laryngeal skeleton. I t i s important t o recognize the appearance o f these chronic structural changes o n the imaging studies as tbey may occur in individuals who do not recall the initial trauma. Correct diagnosis may avoid an unnecessary biopsy or even more invasive procedure. Figure l O-D shows an M R I Axial T l W image in another patient with deformity of the thyroid cartilage presumably due to prior trauma who presented with hoarse ness and a "mass" on clinical examination. CT images (Fig. I O- E ) are shown for a third patient with post-traumatic deformity of the thyroid cartilage causing a pseudomass on the right.
Man agement These patients usually need no specific management for the laryngeal deformity. If there is airway compromise or voice changes, specific therapy may be necessary.
L A RYNX A N D HYPOPHARYNXI
PEARLSIPITFALLS •
Posttraumatic deformity of the larynx often presents as a submu cosal "mass."
•
Voice fatigue, a sensation of food sticking i n the throat, neck sore ness, a submucosal mass in the supraglottic larynx, and cr or M R evidence are the derming characteristics of posttraumatic deformity of the cartilage.
•
Many patients do not recall any history of laryngeal trauma.
•
If care is not taken, posttrau matic deformity can be mistaken for neoplasm or other pathology.
References Bent, IP. 3rd, Porubsky, E.S. 111 e management of blunt fractures of the thyroid car tilage. Otolaryngology and Head and Neck Surgery 1 1 0(2): 1 95-202, 1994 Feb. ehui, L., Lufkin, R., Hanafee, W. The use of M R I in the identification of post traumatic laryngeal deformities. Clinical Imaging 1 4 : 1 27-130, 1990. H a nson, D.G., Mancuso, A.A., Hanafee, W.N. Pseudomass lesions due to occult trauma of the larynx. Laryngoscope 92:1 249-1 253, 1 982.
I LARYNX
AND H Y PO PHARYNX
Case 11 Clinical Presentation A 69-year-old male pre ented with right neck fullness and right otalgia.
c
B
Radiologic Findings 50
Sagillal T l W (Fig. l 1 -A). axial T l W (Fig. I I -B), and axial TIW ( Fig. l l -C) MR images through the supraglollic larynx show a I .S-cm rounded. well-defined cystic
LARYNX AND HYPOPHARYNXI lesion in the left vallecula, displacing the the epiglottis posteriorly. This lesion is homogeneously hypointense on Tl W images and hyperintense on T2W images and does not enhance. There is slight impingement the tip of the epiglottis, which is dis placed posteriorly. The glosso-epiglottic fold, base of the tongue, piriform sinuses, and remainder of the larynx are unremarkable (Figs. l l -A-l l -C).
Differential D iagnosis: Vallecular Mass •
•
Cystic: vallecular cyst; cyst in the base of the tongue; dermoid/teratoma; lym phangioma/cystic hygroma; laryngocele Solid: ectopic thyroid; hemangioma; squamous cell carcinoma
Diagnosis Vallecular cyst
Discussion Epidemiology Vallecular cysts are lesions rarely seen in adulthood. In the pediatric age group, supraglottic cysts at the tongue base and vallecula comprise the majority of laryn geal cysts. Although anatomically the vallecula is not part of the larynx, pathologi cally it may be considered as such. The age of presentation is variable but usually vallecular cysts present in infants. There is no gender predominance.
Pathophysiology Vallecular cysts are retention cysts that arise secondary to ductal obstruction of mucous glands. Histologically, they are true epithelial-lined cysts. An association with laryngomalacia, probably secondary to extrinsic compression by the cyst, has been described. The condition consists of a redundant epiglottis with prolapse into the laryngeal vestibule during inspiration. Removal of the cyst usually leads to res olution.
Clinical Findings Infants present clinically with feeding difficulty, failure to thrive, stridor or respira tory distress. Early diagnosis and a high index of suspicion are required as these lesions may cause life-threatening airway obstruction. Adults may present with difficulty swallowing, fullness in the throat, referred ear pain or stridor when the lesion is large and impinges on the laryngeal vestibule. On direct laryngoscopy, these lesions manifest as a submucosal fullness, obliterating the vallecula, but may be missed if the valleculae are overlooked. D ifferential diagnosis from solid masses may not be possible on clinical exam and imaging studies are es sential in determining the exact location, extent and nature of the lesion.
Imaging Findings Lateral projection radiographs of the soft tissues of the neck are useful i n children presenting with stridor. Supraglottic cysts manifest as an abnormal soft tissue density, posterior to the tongue base that obliterates the vallecula and displaces the epiglottis posteriorly. A barium esophagram may be helpful and will show a filling defect in the vallec ula and mass effect upon the supraglottic airway. Sectional CT or M R imaging is the method of choice to evaluate the site of ori gin, extent and nature of the lesion. On CT, a vallecular cyst manifests as a fluid
21J
I LARYNX
AND H Y POPHARYNX
D
E
density. non-enhancing lesion centered in the vallecula, posterior to the base of the tongue. The degree of airway obstruction and displacement of the epiglottis are adequately assessed and may alert the surgeon to the need for a tracheostomy before any procedure is attempted. Coronal or sagittal MR imaging may better delineate the cranio-caudal extent of the lesion. Axial TI W (Fig. 11 - 0 ) and axial TIW (Fig. 1 1 -E) M R images through the supraglottis in another patient show a 2-cm cystic lesion in the left vallecula and a smaller, less than 5-mm, cyst in the contralateral side. This patient was diagnosed with bilateral vallecular cysts. When infected, vallecular cysts may demonstrate increased density and enhance heterogeneously, making them indistinguishable from an abscess. On sectional imaging, determination of the exact site of the lesion greatly assists in differentiat ing vallecular cysts from other cystic lesions such as thyroglossal duct cyst (TGDC), tongue base cyst and laryngocele. TGDC tends to be more midline and have a more anterior location between the strap muscles and the hyoid bone or thyroid ala. Internal laryngoceles grow superiorly in the paraglottic space and obliterate or push the vallecula superiorly. However, their inferior extent and connection with the laryngeal ventricle is adequately detected on imaging studies. Finally, dermoids are usually located in the base of the tongue and floor of the mouth, and typically contain fat. In children, ectopic thyroid tissue should be ruled out, and the presence of a thyroid gland in normal anatomic position confirmed by a thyroid scan with 1 - 1 3 1 , before surgery is performed.
Man agement Vallecular cysts may be managed by aspiration via an endoscopic approach. The disadvantage of this procedure is the high rate of recurrence. Marsupialization and laser ablation are the techniques of choice. Rarely. a supraglottoplasty may be necessary to remove the cyst and correct redundant epiglottis and aryepiglottic folds.
LARYNX AND HYPOPHARYNXI
PEARLS/PITFALLS •
An infant with a vallecular cyst often presents with feeding diffi culty and stridor.
•
A cystic lesion often is centered in the vallecula.
•
Patients with vallecular cysts should be evaluated carefully for any degree of airway compro mise.
•
A vallecular cyst may be mis taken for other supraglottic cystic lesions.
•
An abnormal supraglottic soft tissue mass on lateral plain films of the neck may be difficult to recognize.
Suggested Readings Oluwole, M. Congenital vallecular cyst: a cause of failure to thrive. British Journal of Clinical Practice 50(3): 1 70, 1 996 Apr-May. Wang, C.R., Lim, K.E. Vallecular cysts: report of two cases. Pediatric Radiology 25 Suppl 1 :S21 8-9, 1 995 Nov. Wong, K.S., Li, H . Y., Huang, T.S. Vallecular cyst synchronous with laryngomala cia: presentation of two cases. Otolaryngology and Head and Neck Surgery 1 1 3(5):621 -4, 1 995 Nov.
I LARYNX
AND H Y POPHARYNX
Case 12 Clinical Presentation A 40-year-old male presented with gradual onset dyspnea.
Radiologic Findings The axial CT scan (Fig. 1 2-A) shows an expansile mass centered in the posterior cricoid cartilage on the right. There are areas of speckled calcification within the lesion.
Differential Diagnosis: Expansile Lesion of the Laryngeal Cartilage • • • •
Chondroma Chondrosarcoma Metastasis Post-traumatic deformity
Diagnosis Chondroid tumor of the larynx (chondrosarcoma)
Discussion Epidemiology Chondroid tumors of the laryngeal cartilage are uncommon neoplasms. They are found predominantly in men (3 : 1 ratio) in their 4th through 6th decades. This is
LARYNX AND HYPOPHARYNXI similar to the age range of patients with cartilaginous tumors of the facial area. Chondroid tumors of the larynx are unlike other cartilaginous neoplasms (espe cially chondrosarcomas) of extralaryngeal origin, which tend to affect young and middle aged adults. Chondroid tumors are the most common mesenchymal tumor of the larynx. The specific histology may range from chondroma to chondrosarcoma. Chondrosarcoma is the most frequently encountered non-epithelial malignancy of the larynx.
Pathophysiology The location of these tumors in over 75% of cases is the posterior lamina of the cricoid cartilage. Histologically all documented cases have arisen from hyaline car tilage with no evidence of elastic cartilage. Biopsy may be difficult because of the firmness of the tumor. Interpretation of the findings is also problematic. Chondroma and low-grade chondrosarcoma are diffi cult to distinguish histologically. Some authors advocate that all laryngeal neo plasms containing hyaline cartilage should be considered chondrosarcomas until proven otherwise. They suggest that evidence of the lesion's benign nature is deter mined by either: ( 1 ) its failure to metastasize or recur over a period of several years follow-up or (2) pathologic examination of the lesion in its entirety.
Clinical Findings The clinical findings are nonspecific and tend to be due to gradual encroachment of the subglottic space. This can manifest as a neck mass or, if situated within the air way, as a slowly progressive obstruction, hoarseness or dyspnea. Because most lesions are below the vocal cords, hoarseness may be minimal, with dyspnea or stri dor the more common symptom.
B
I LARYNX
AND HYPOPHARYNX
C
D
I maging Fi ndings Chondroid tumors are characterized by focal expansion of the laryngeal cartilage. They show typical mottled chondroid calcification in 80% of lesions. It is very diffi cult to distinguish chondroma from low grade chondrosarcoma radiographically. Higher grade chondrosarcomas may show more aggressive radiographic features. cr is the preferred imaging technique because of its ability to define subtle calcifi cations. On MRI these findings are less obvious. Figures l 2-8-l 2-F show five other patients with chondrosarcoma of the larynx. The large lesion in Figure 1 2-8 is simi lar to figure 1 2-A with significant airway obstruction. Figure 1 2-C shows a densely calcified lesion. Figure 1 2-0 shows a smaller lesion with rare calcifications and Fig ure 1 2-E shows a lesion with prominent central calcifications. The small lesion in Figure 1 2-F appears as a slight widening of the cricoid cartilage without significant airway compromise.
L A RYNX A N D HYPOPHARYNXI
F
PEARLS/PITFALLS •
Chondrosarcoma presents as ex pansion of the laryngeal cartilage with chondroid calcifications.
•
The cricoid cartilage is most fre quently affected, followed by the thyroid and arytenoid cart i l ages.
•
Chondroma and chondrosar coma difficult to dist inguish
Management Although laryngeal chondrosarcoma reportedly can recur, local surgical excision without radical margins and with long-term clinical follow-up is recommended. Al though conservative therapy is acceptable i n most instances, total laryngectomy may be performed in cases of extensive tumor, high-grade lesions, and recurrences. CO2 laser excision for palliation has been shown to be a viable alternative in patients with high-operative risk.
Suggested Readings
.
•
The clinician must take care not to mistake chondrosarcoma for carcinoma of the larynx.
Bogdan, C.l, Maniglia, A . I . , Eliachar, I . , Katz, R . L. Chondrosarcoma of the larynx: challenges in diagnosis and management. Head and Neck 16(2): 1 27-34, 1 994 Mar Apr. Bough, I .DJ., Chiles, PI, Fratalli, M.A., Vernose, G. Laryngeal chondrosarcoma: two unusual cases. American Journal of Otolaryngology 16(2): 1 26-3 1 , 1 995 Mar-Apr. Browne, ID. Management of nonepidermoid cancer of the larynx. Otolaryngologic Clinics of North A merica 30(2):2 1 5-29, 1 997 Apr. Chiu, L.D., Rasgon, B.M. Laryngeal chondroma: a benign process with long-term clinical implications. Ear, Nose, and Throat fournaI 75(8) :540-2, 544-9, 1996 Aug. Lewis, IE., Olsen, K.D., Inwards, c.Y Cartilaginous tumors of the larynx: clinico pathologic review of 47 cases. A nnals of Otology, Rhinology and Laryngology 106(2) :94-100, 1997 Feb.
I LARYNX
A N D H Y POPHARYNX
Case 13 Clinical Presentation A 59-year-old male presented with progressive hoarseness over the last 4 months. Endoscopy (Fig. 13-A) shows an exophytic mass extending from the anterior com missure to the posterior third of the vocal cord.
A
B
c
LARYNX AND H Y POPHARYNXI
Radiologic Findings An axial TZW MR image (Fig. 1 3-8) through the cords of a similar patient shows a high intensity lesion invading the right true cord musculature involving the anterior commisure. A coronal T l W MR scan of the same patient in Figure 1 3-C shows that the lesion extends from the true cord to the right laryngeal ventricle. However, it does not involve the false vocal cord. The para laryngeal space also appears to be clear.
Differential Diagnosis: Vocal Cord Assymetry • • • •
Glottic carcinoma Recurrent nerve paralysis Teflon injection of vocal cord Squamous cell carcinoma of the vocal cord
Diagnosis Squamous cell carcinoma of the vocal cord
Discussion Epidemiology Glottic tumors (arising from the true cords) are the most common laryngeal can cers, typically affecting males in their fifth to seventh decades. Of malignancies of
D
�I
I LARYNX
AND HYPOPHARYNX Table
13-1
Tumor, Node, Metastasis (T M ) Staging Glottic Cancer
T l -Limited to vocal cords T2-Extends to supraglottic and/or subglottic and/or with impaired cord mobility TI-Limited to larynx with cord fixation T4-I nvades thyroid cartilage and/or extralaryngeal spread
the larynx, 90% are squamous cell carcinomas and these tumors are usually well differentiated. Glottic malignancies are slow-growing lesions that tend to metasta size late as a result of the limited lymphatic drainage of the vocal cords. Initially most patients complain of intermittent hoarseness that progressively worsens. These tumors have been linked to smoking and radiation exposure. Seventy-five percent of these tumors involve the anterior half of the true vocal cord, as is seen in this patient. Early glottic lesions have an excellent prognosis; the five year survival approaches 95% with surgery or radiation therapy. Cross sectional imaging of these lesions may show thickening of the true cords or they may be nor mal. I f the clinician has a clear view and can confirm that the lesion is an early T1 tumor, M R I is not necessary. With more advanced tumors and because the signals from tumor and muscle differ, the distinction between exophytic lesions and lesions infiltrating the true cord musculature is well demonstrated. True cord tumors spread to involve the mucosa over the arytenoids or at the anterior commissure of the cricoarytenoid joints. Figure 1 3-0 i llustrates a coronal view of the larynx with a car cinoma shown as a mass in the region of the true vocal cord (speckled pattern).
Clinical Findings Because glottic cancers involve the vocal cords, they also present very early with hoarseness. Nodal spread is rare in the case of early lesions because there is an ab sence of lymphatics along the free margin of the vocal cords. Advanced lesions with a fixed cord, however, have a higher incidence of lymphatic involvement. Since these tumors are readily accessible, the majority are diagnosed and management planned by clinical examination using laryngoscopy and biopsy. The primary role of CT and MR imaging, therefore, is to define the extent of the disease for appropri ate management.
I m aging Findings For all these reasons, despite the fact that squamous cell carcinomas are the most common laryngeal cancers, they are not the most common laryngeal cancer in radi ology departments because imaging studies add little to the diagnostic workup in most cases. The very early true cord tumor can be readily evaluated on indirect clinical examination and generally does not require an imaging study. The more advanced lesions that show extension to the anterior commissure regions above or below the vocal cord are quite a different matter. They require imaging techniques to show deep infiltration and the full extent of the tumor. Tl glottic lesions (Table 1 3-\ ) are confined to the true cords without affecting the cord's mobility. CT scan of these lesions may how true cord thickening or they may look normal. CT density differences between a nonenhancing tumor and muscle are not great enough to allow one to predict invasion of the true cord musculature in most cases. Because M R signals from tumor and muscle differ significantly, MR imaging is the more sensitive imaging modality for determining muscle invasion. The high fat content within the larynx makes T l -weighted images preferable to the T2-weighted images in which the tumor may be obscured by the intensity of the are olar tissue. T2 lesions (Table 1 3-1 ) are defined as those that have spread to either the supra or subglottic region and show normal or only slightly impaired mobility of the true
LA RYNX AND H Y POPHARYNXI
PEARLS/PITFALLS •
An early symptom of squamous cell carcinoma is voice change.
•
Lesions are usually well differen tiated and slow growing.
•
Spread to the lymphatics is usu ally limited.
•
Surgical resection or radiother apy are the preferred treatment modalities.
•
Imaging studies have limited value in this diagnosis.
•
Underestimating tumor exten sion may result in undertreat ment.
•
Squamous cell carcinoma of the vocal cord should not be con fused with paramedian cord due to recurrent nerve paralysis.
vocal cord. With CT, impaired mobility is implied in the scan by the diminished motion artifacts on the involved side. In addition, the true cord typically takes a paramedian position and the arytenoid is displaced more medially. These changes also are seen on MR i mages. True cord tumors may spread to involve the mucosa over the arytenoids or at the anterior commissure. On CT and MR imaging any more than 1 mm of thickness of the anterior commissure is considered abnormal and would require an "extended" hemilaryngectomy. One of the advantages of MRI over CT is that sagittal M R images provide an excellent view of the anterior com missure and its relationship to the supraglottic and subglottic compartments. Tumors at the anterior commissure may follow the central tendon of the vocal ligaments into the thyroid cartilage. This is very difficult to detect by clinical exam and may be difficult to detect by CT as well. Cartilaginous destruction appears as a moderate signal interrupting the normal outer rim of low signal, calcified cartilage and/or as a focal area of lower signal in the high signal central marrow. Since focal asymmetric areas of diminished density may be a normal variant in this region, an area of demineralization i n the paramedian does not necessarily indicate cartilagi nous invasion. MR imaging is more accurate in diagnosing early cartilaginous inva sion since the signal from the tumor differs dramatically from that of cartilage regardless of its state of m ineralization. Vocal cord fixation comprises a T3 lesion (Table 13- 1 ) . Since cricoid cartilage is almost invariably symmetric in its degree of ossification, any decrease in signal from one side of the cricoid cartilage is evidence of a T3 lesion. Fixation is rarely due to causes other than tumor, such as rheumatoid arthritis. Cord fixation may be the result of several mechanisms. A tumor may infiltrate the intrinsic laryngeal musculature and fix the cord to the thyroid cartilage. A bulky tumor may limit cord mobility by mass effect or may involve the cricoarytenoid joint. Scans may show an arytenoid cartilage in the median or paramedian position. MR imaging can show how the spread to the deep tissue planes and cartilage inva sion lead to fixation. Only rarely is fixation due to causes other than tumor, such as rheumatoid arthritis. Mucosal spread to the false cord may not be appreciated with M R I . However, extension across the ventricle to the false cord via the paralaryngeal space will decrease the fatty high signal deep to the cord. Coronal sections are particularly useful because bulky lesions occasionally bulge upward, distorting the false cords rather than invading them. This may be difficult to appreciate on axial images.
Management T1 and T2 lesions may be treated with surgery or radiation. Spread to the false cord and significant subglottic spread may necessitate a vertical hemilaryngectomy. Fur ther extension may fix the vocal cord to produce a T3 lesion, which may worsen the prognosis and make selection of the appropriate therapy potentially more difficult. Advanced lesions with cartilage invasion generally require surgery.
Suggested Readings Katsounakis, 1., Remy, H., Vuong, T. , Gelinas, M., Tabah, R. I mpact of magnetic res onance imaging and computed tomography on the staging of laryngeal cancer. Eu ropean Archives of Oto-Rhino-laryngology 252(4):206-8, 1995. Mukherji S.K., Castillo M., Huda w., Suojanen J., Kubilis P, Tart R.P, Dhillon G. Comparison of dynamic and spiral CT for imaging the glottic larynx. Journal of Computer Assisted Tomography 1 9(6):899-904, 1 995 Nov-Dec. Teresi, L.M., Lufkin, R.B., Hanafee, W.N. Magnetic resonance imaging of the larynx. Radiologic Clinics of North America 27:393-406, 1 989. Weinstein, G.S., Laccourreye, 0., Brasnu, D., Yousem, D.M. The role of computed to mography and magnetic resonance imaging in planning for conservation laryngeal surgery. Neuroimaging Clinics of North America 6(2):497-504, 1996 May.
I LA RYNX
A N D H Y POPHARY
Case 14 Clinical Presentation A 70-year-old male presented with hoarseness.
A
162
B
LARYNX AND HYPOPHARYNXI
Radiologic Findings The axial T I weighted M R I shows an infrahyoid supraglottic mass replacing the preepiglottic fat and narrowing the supraglottic airway ( Fig. 1 4-A). The 1'2 weighted axial image shows similar findings with improved muscle/tumor contrast ( Fig. 1 4-B). The sagittal Tl weighted image shows the mass extending inferiorly to the level of the true vocal cords ( Fig. 1 4-C).
Differential Diagnosis: Supraglottic Mass • • • • • • • • •
Carcinoma Laryngocele Post-traumatic deformity [pseudomass 1 Papilloma Chondroma Metastasis Amyloid Hemangioma Lymphoma
Diagnosis Supraglottic carcinoma of the larynx
Discussion Epidemiology Supraglottic tumors may arise anywhere [rom the false vocal cords to the epiglottis. These malignancies comprise 20 to 35% of all laryngeal cancers. Unlike glottic can cers, they tend to present later. They are also more poorly differentiated histologi cally. Because of abundant lymphatics in the supraglottic region, these tumors tend to metastasize early to lymph nodes high in the neck and involve the internal jugu lar chain and often the jugulo-digastric node. Consequently, supraglottic cancers often present as more advanced tumors than glottic lesions. Imaging studies are crit ical in their workup. For tbis reason they are the often the most common laryngeal cancer seen in many radiology departments.
Pathophysiology Histologically, the vast majority of laryngopharyngeal cancers are of squamous cell origin. Other types of malignancies found in the larynx and hypopharynx include verrucous carcinoma. pseudosarcoma, adenocarcinoma, "spindle cell" carcinoma. oat cell carcinoma, and basal cell carcinoma. Laryngeal malignancies of connective tissue and hematopoietic elements have also been documented. Examples include chondrosarcoma, fibrosarcoma, reticulosarcoma. and lymphosarcoma.
Clinical Fi ndings Carcinoma of the supraglottic region can be subdivided into two groups: ( I ) ante rior carcinomas which arise on the epiglottis and anterior false cords and (2) pos terolateral carcinomas which arise from the medial surface of the aryepiglottic folds and the para laryngeal spaces (marginal tumors). I n the anterior epiglottis group, the lesions may be either above or below the level of the hyoid bone. Suprahyoid epiglottic lesions show early invasion of the preepiglottic space, glosso-epiglottic,
�I
I LARYNX
AND H YPOPHA RYNX and pharyngo-epiglottic folds. On T l W MR images the preepiglollic space i of high intensity because of its high fat con ten!. Infiltration with intermediate-signal tumor is readily identified. Advanced suprahyoid epiglottic cancers frequently cross the midline with the paralaryngeal lymphatics and extend into the paramedian portions of the thyroid cartilage, just above the anterior commissure level. Tumors of the infrahyoid epiglottis rarely grow inferiorly to the laryngeal ventri cle. If a supraglollic laryngectomy is to be successful, a free margin must be present above the thyroepiglottic ligament with no cartilage invasion. Recalling that no ap preciable tissue thickness should be visible at the anterior commissure, the vertical extent of the lesion can be readily determined. Occasionally, the normal tissue thick ness associated with the inferior pole of the epiglottic cartilage and the thy roepiglottic ligament at the level of the false cord may be interpreted as tumor. Here, sagillal images are particularly useful (Fig. 1 4-C). Posterolateral (marginal) supraglottic tumors appear as thickened aryepiglollic folds and as a mass in the paralaryngeal space. Their natural tendency is to grow posteriorly and inferiorly to the arytenoids, rather than anteriorly to the preepiglot tic space. I nvasion of the thyroid lamina occurs late and almost invariably along the postero-Iateral-inferior margin. Tumors may also grow cephalad within the preepiglottic space to invade the tongue base without distorting the mucosa in the valleculae. Sagillal images will show spread to the tongue base to best advantage. Marginal supraglollic cancers may also arise from the surface of the aryepiglottic fold and spread to the infrahyoid epiglottis, false cord, and eventually to the cricoarytenoid joint where invasion may cause cord fixation. [ t may be difficult to distinguish an advanced piriform sinus carcinoma from a marginal supraglottic car cinoma. Axial images clearly show the limits of the tumor relative to the preepiglot tic space, tongue base, and hypopharynx. Lymph node metastasis is especially likely with aryepiglottic fold tumors. Thyroid cartilage invasion is a rare finding unless the tumor has become transglollic. The hyoid bone is usually displaced by tumor and not destroyed.
Imaging Findings Rarely does radiologic imaging play a significant role in reaching a diagnosis of ma lignancy in the larynx and hypopharynx. These regions are so readily accessible to clinical examination that the combination of cytology and visual inspection usually strongly indicates the diagnosis of cancer. Therefore, the primary role of studies in imaging the larynx and hypopharynx is to define the extent of the disease. While laryngoscopy can show mucosal surfaces and masses involving the lumen, deep extensions are difficult to detect clinically. However, these extensions can have pro found implications for the management of disease. CT. and to an even greater extent, M R [ can define this important deep anatomy. Imaging studies may detect the deep extent of tumors that have normal overlying mucosa and are not detectable on endoscopy. Sometimes large. bulky, proximal lesions obscure the view of endoscopists, who may have difficulty in viewing the infraglottic region and the apices (inferior tips) of the pyriform sinuses. Imaging is also useful to detect clinically occult laryngoceles associated with a paraventricular tumor.
M anagement Frequency selective fat suppression imaging ( FATSAT) contrast-enhanced se quences may be useful to answer the clinical questions such as the tumor extent into the fat of the pre-epiglottic and paralaryngeal spaces. Additionally. these sequences determine. to advantage, the presence of cartilage invasion, as is found in most adult patients. The laryngeal cartilages are ossified and contain bone marrow. Using CT and/or MRI for staging, a partial laryngectomy with preservation of glollic function may be possible instead of a total laryngectomy. in some cases. In others, tumor
64
LARYNX AND HYPOPHARYNXI
PEARLS/PITFALLS •
Supraglottic carcinoma presents later, is more poorly differenti ated and grows faster tban glottic lesions.
•
Lymphatic spread to upper cervi cal nodes may occur.
•
I n certain cases, voice conserva tion surgery with partial laryn gectomy is possible.
•
I maging studies are very valu able in this diagnosis.
•
I t is very difficult to recognize tbe true extention of supraglottic tumors.
invasion of the laryngeal cartilages, pre-epiglottic space, or infraglottic region may exclude radiation therapy as the sole treatment. The loss of natural voice function resulting from a total laryngectomy can be dev· astating to many individuals. Less radical laryngeal resections that allow the preser vation of natural speech and the protective sphincter mechanism of the larynx have been developed for certain smaller laryngeal tumors. Planning for any of these con servation laryngeal surgeries depends on an accurate pre-operative knowledge of the precise extent of the disease within the larynx. All surgical techniques require an intact cricoid cartilage and at least one mobile arytenoid on which to construct the functional voice box. cr and MRI can provide this essential information. To plan this type of operation, the direct coronal and sagittal imaging capabilities of MR are an advantage over axial CT images, in their ability to define critical infor mation regarding the cranial-caudal extent of the tumors. The recognition of tumor spread to other area also markedly affects patient management. In the case of spread of the supraglottic tumor to involve the tongue base, a partial glossectomy may have to be performed in addition to the primary surgery. In other areas, extraorgan spread may render the tumor unresectable.
References Katsounakis, I . , Remy, H., Vuong, T., Gaelinas, M., Tabah, R. Impact of magnetic res onance imaging and computed tomography on the staging of laryngeal cancer. Eu ropean A rchives of Oto-Rhino-Iaryngology 252 4:206-8, 1 995. Larsson, S. Y., Mancuso, A., Hoover, I., Hanafee, W. Differentiation of pyriform sinus cancer from supraglottic laryngeal cancer by computed tomography. Radiol ogy 1 4 1 :427-432, 198 1 . Myers, E.N., Alvi, A . Management o f carcinoma o f the supraglottic larynx: evolu tion, current concepts, and future trends. Laryn.goscope 1 06 5 Pt 1 :559-{j7, 1 996 May. Thabet, H .M., Sessions, D.G., Gado, M.H., Gnepp, D.A., Harvey, J.E., Talaat, M. Comparison of clinical evaluation and computed tomographic diagnostic accuracy for tumors of the larynx and hypopharynx. Laryngoscope 106 5 Pt 1 :589-94, 1 996 May.
I LARYNX
AND HYPOPHARYNX
Case 15 Clinical Presentation A 62-year-old male complained of mild dysphagia of 6 weeks duration.
A
B
c
D
I�
LARYNX AND H Y POPHARYNXI
Radiologic Findings On axial T l -weighted images (Figs. 1 5-A and IS-B), a left-sided pyriform sinus mass is seen, well delineated from the surrounding fat. Note that the t umor/muscle inter face is indistinct. In contrast, on axial T2-weighted images (Figs. l S-C and 1 5-0), the high signal intensity of the tumor allows excellent differentiation from pharyngeal and prevertebral musculature but blends with fat. At the level of the false vocal cords (Fig. IS-A), the bulky mass invades the posterolateral portion of the thyroid cartilage.
Differential Diagnosis: Pyriform Sinus Mass • • • • • •
Pyriform sinus carcinoma Post-operative scarring Post radiation edema Metastases Mesenchymal tumor Lymphoma
Diagnosis Pyriform sinus carcinoma
Discussion Pyriform sinus carcinoma is one of the most conUTIon cancers of the hypopharynx. These tumors are usually well advanced on presentation. I nitial manifestations are often subtle and include pain in the throat or referred pain to the ear, with later dys phagia, otalgia, or an isolated lump in the neck. U n like the hoarseness tbat occurs with vocal cord involvement, patients with pyriform sinus cancer often have a char acteristic alteration in their vocalization described as a "potato voice".
Epidemiology These lesions behave more aggressively than endolaryngeal lesions and comprise 1 0 t o 20% o f "laryngeal" cancers. They are actually cancers o f the inferior hypophar ynx. Early nodal disease occurs because of the rich lymphatics anterior to the pyri form si n uses.
Pathophysiology Pathologically, the majority of these tumors are squamous cell carcinomas. They tend to spread submucosally, either ( 1 ) circumferentially with extension into the posterior pharyngeal wall or (2) posterolaterally with deep invasion and associated cartilage destruction. The size of the tumor does not necessarily relate to the degree of biological aggressiveness or the tendency for cartilage destruction. Pyriform sinus tumors grow in two major patterns. ( 1 ) Tumors in the lateral wall invade the thyroid cartilage and soft tissues of the neck forming bulky masses about the pyriform sinus. (2) Tumors of the medial wall extend into the paralaryngeal space and vocalis muscle, resembling marginal supraglottic lesions. Despite the similarities, pyriform sinus tumors have several characteristics that distinguish them from marginal supraglottic lesions. Pyriform sinus tumors fre quently invade the thyroid cartilage, usually at its posterolateral margins. In addi tion, pyriform sinus lesions tend to be unilateral and submucosal. If extensive, these tumors may widen the space between the thyroid and cricoid cartilages (cricothy-
I LARYNX
AND HYPOPHARYNX
PEA RLSIPITFALLS •
Cartilage invasion is a frequent finding.
•
It is unusual for these tumors to cross the midline.
•
The clinician should keep a sharp eye so as not to overlook adenopathy.
•
Pyriform sinus masses may be mistaken for laryngeal cancer.
roid notch). This is because the tough conus elasticus tends to direct the tumor pos terolaterally and inferiorly.
I m aging Findings Clinical examination is often difficult and incomplete. Cross-sectional imaging is necessary to evaluate the extent of submucosal spread. M R I allows excellent soft tissue definition and is valuable in distinguishing a tu mor from surrounding structures. On T1 -weighted images, the primary tumor signal intensity differs sufficiently from fat so that its margins are well seen. On 1'2weighted images, the bright signal blends with fat but is clearly distinguished from surrounding musculature. Thus, T1 -weighted sequences are better at determining tumor/fat contrast, whereas T2-weighted images are helpful in determining tu mor/muscle contrast.
Management Surgical resection is the treatment of choice, often in conjunction with radiation therapy. Nodal dissection is performed as necessary.
Suggested Readings AlIal, A.S. Cancer of the pyriform sinus: trends towards conservative treatment. Bul letin Cancer 84 7:757-62, 1997 Jul. Elias, M.M., H ilgers, F.l., Keus, R.B., Gregor, R.T., Hart, A.A., Balm, AJ. Carcinoma of the pyriform sinus: a retrospective analysis of treatment results over a 20-year pe riod. Clinical Otolaryngology 20 3:249-53, 1995 Jun. Larsson, S.Y., M ancuso, A., Hoover, L., Hanafee, W. Differentiation of pyriform si nus cancer from supraglottic laryngeal cancer by computed tomography. Radiology 141 :427-432, 1 981 .
I�
LARYNX AND HYPOPHARYNXI
Case 16 Clinical Presentation A 5 1-year-old male presented with a right neck mass and hoarseness. Ten years ear lier, the patient had undergone an above-the-knee amputation for an osteogenic sarcoma of the right proximal tibia. Two years later, he was found to have a solitary right pulmonary metastasis, which was resected without difficulty. Now, eight years later, he has presented with the current lesion.
A
B
c
D
I LARYNX
AND H Y POPHARYNX
Radiologic Findings An axial T I -weighted image (Fig. 1 6-A) shows a low-intensity mass (arrowheads) originating from the marrow space of thyroid cartilage. Cricoid cartilage (C) and the left side of the thyroid cartilage (T) are preserved. A coronal T l -weighted image (Fig. 1 6- 8 ) shows a 5-cm lesion on the right side of the larynx, which is displacing paralaryngeal fat medially (arrowhead). A coronal T2-weighted image (Fig. 1 6-C) shows the submucosal location of a high intensity mass (arrow) with preservation of mucosal tissues medial to the lesion (arrowhead) . Fine-needle aspiration (Fig. 1 6-D) demonstrated a group of round to oval cells embedded in the fibrous stroma (H & E, original X 400). Nuclei are irregular and hyperchromatic, suggestive of a metastatic tumor.
Differential Diagnosis: Destructive Laryngeal Mass Centered in the Cartilage • • •
Atypical squamous cell carcinoma of the larynx Primary chondral tumor Metastasis to the larynx
Diagnosis Metastasis to the larynx (osteosarcoma)
Discussion Epidemiology Secondary laryngeal tumors are uncommon, accounting for approximately 0.02% of all laryngeal malignancies. In 1 988, Ferlito et al reviewed the world literature, which revealed 1 1 3 cases, and his series added another 7, for a total of 1 20 cases known at that time. The most common primary tumors metastasizing to the larynx are melanomas of the skin (27 to 37% ), renal cell carcinomas ( 1 3 to 1 7% ), carcinomas of the breast (9 to I I % ), lung carcinomas (8 to 1 1 % ), and adenocarcinomas of the prostate (6 to 7% ). Osteosarcoma metastatic to the larynx is rare although its appearance is simi-
E
LARYNX AND HYPOPHARYNXI
PEARLS/PITFALLS •
In general, laryngeal lesions are quite destructive.
•
Metastases are usually centered over the laryngeal cartilage.
•
Melanoma, renal cell, breast, and lung primary carcinomas com monly metastasize to the larynx.
•
Metastases to the larynx are of ten mistaken for primary squa mous cell carcinoma or aggres sive chondrosarcoma.
lar to other metastases to the larynx. A CT scan of a second patient with metastatic renal cell carcinoma to the larynx (Fig. 1 6-E) shows similar findings.
Pathophysiology Metastasis to the larynx is an uncommon event, and metastases occurring in the thy roid cartilage are rarer still, contributing to 2.6% of secondary laryngeal tumors. Metastases to the thyroid cartilage are possible only after endochondral ossification and development of a marrow space, which occurs by adulthood. Their most likely route of spread is hematogenously, either retrograde through the valveless vertebral veins, as described by Batson ( 1 940), or from the vena cava through the pulmonary circulation to the laryngeal artery.
Imaging Findings The MR appearance of the entity is unlike the appearance of most primary squa mous cell tumors of the larynx, which tend to arise from the mucosal surface rather than centered over the cartilage as in this case. Unlike most primary chondral tumors of the larynx (which are also centered over the cartilage), this lesion is very aggressive and destroys the cartilage rather than expanding or remodeling it. There is also no evidence of calcification to suggest a chondral tumor. There is preserva tion of the right side of the thyroid cartilage and of the cricoid cartilage. On coronal sections, the vocal cords appear displaced medially without gross invasion. Com paring T I - and T2-weighted images, it appears that the lesion is submucosal (Figs. 1 6-B and 1 6-C).
Management Metastasis to the larynx is almost always associated with long-standing, widely dis seminated disease, and carries a poor prognosis. General treatment recommenda tions for these lesions have emphasized a palliative approach, but there are reports in the literature of long-term survivors. I n the case of metastatic osteosarcoma, there are reports in the literature promoting metastatectomy in selected patients, espe cially those with isolated pulmonary metastases. In those patients treated surgically without evidence of disease, there is a 20 to 30% long-term survival. This case illus trates the typical longstanding history of patients found to have metastases to the larynx.
Suggested Readings Batsakis, IF., Luna, M.A., Byers, R.M. Metastases to the larynx. Head and Neck Surgery 7:458-60, 1 948. Batson, O.V. Function of vertebral veins and their role in spread of metastases. An nals of Surgery 1 12 : 1 38-49, 1 940. Cavicchi, 0., Farneti, G., Occhiuzzi, I . , Sorrenti, G. Laryngeal metastasis from colonic adenocarcinoma. Journal of Laryngology and Otology 104:730-2, 1 990. Cullen, lR. Ovarian carcinoma metastatic to the larynx. Journal of Laryngology an.d Otology 1 04:48-9, 1 990. Ferlito, A., Caruso, G., Recher, G. Secondary laryngeal tumors. A rch.ives of Oto laryngology and Head and Neck Surgery 1 1 4:635-9, 1 988. Fields, lA. Renal carcinoma metastasis to larynx. Laryngoscope 76:99-10 1 , 1 966. Grignon, 0.1., Ro, 1.y., Ayala, A.G. Carcinoma of the prostate metastasizing to vo cal cord. Urology 36:85-8, 1 990. Ikeda, M., Takahashi, H . , Karaho, T. Amelanotic melanoma metastatic to the epiglottis. Journal of Laryngology and Otology 1 05:776-9, 1 99 1 .
I LARYNX
AND HYPOPHARYNX Szmeja, Z., Kruk-Zagajewska, A., Salwa-Zurawska, W. Metastases of renal adenocarcinoma to the larynx and paranasal sinuses. Otolaryngol Pol 4 1 :221-7, 1 987. Whicker I.H., Carder, G.A., Devine, K.D. Metastasis to the larynx, report of a case review of the literature. A rch Olo/aryngoI 96: 182-4, 1 972.
III. Nasopharynx and Parapharyngeal Space
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
Case 17 Clinical Presentation An adult male presented with headaches. A rounded midline, mucosal covered na sopharyngeal mass was noted. He denied foul breath, nasal discharge. or muscular spasm with head motion.
A
B
I NASOPHARYNX
AND PARAPHARYNGEAL SPACE
Findings A 4mm rounded midline, mucosal covered nasopharyngeal mass was noted (Fig. 1 7-A) A 4 mm high signal intensity lesion on T l - ( Fig. 1 7-B) and T2-weighted ( Fig. 1 7-C) images can be seen in the nasopharyngeal midline. The surrounding soft tissues are intact. The lesion is homogeneous in signal intensity. There is no com munication with the intracranial space.
Differential Diagnosis: Cystic Nasopharyngeal Mass • • • •
Tornwaldt cyst Encephalomeningocele Pharyngeal cyst Atypical lymph node
Diagnosis Tornwaldt (or Thornwaldt) cyst.
Discussion Epidemiology G.L. Tornwaldt was a German physician from the 1 9th century who described an inflammation or abscess of an embryonic remnant cyst of the pharyngeal bursa appearing at the posterior median wall of the nasopharynx. His name is spelled both Tornwaldt and Thornwaldt in various publications although Tornwaldt appears to be the preferred spelling. Tornwaldt's cysts are found in 4% of normal autopsy spec imens. There is no gender predilection.
Pathophysiology The nasopharyngeal bursa represents the site of the caudal-most end of notocord. A Tornwaldt cyst results from an adhesion between the pharyngeal endoderm and the notocord. The bursa may appear as a midline pit or closed over as a cyst.
D
E
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
PEARLSIPITFALLS •
A Tornwaldt cyst is a midline, cystic thin walled nasopharyngeal mass.
•
It is an embryologic remnant.
•
A Tornwaldt cyst contains fluid, or occasionally air.
•
It is usually asymptomatic.
•
Symptoms may include postnasal discharge, bad taste or odor, coughing, or prevertebral neck pain with motion.
•
An encephalocele may be mis taken for a Tornwaldt cyst.
The cyst, which may have a canal that extends to the pharyngeal mucosa, is situ ated beneath the adenoid, or its remnants, and extends backward and upward to the periosteum of the occipital bone. This canal may become obstructed, resulting in infection and abscess formation.
Clinical Findings Most Torowaldt's cysts are asymptomatic. When present, symptoms can include postnasal discharge, crusting, frequent colds, sneezing, hoarseness, bad taste or odor, coughing, or prevertebral neck pain with motion. Other symptoms may be nasal speech, cervical adenitis, or symptoms relating to the ear such as vertigo, tinnitus, earache, or deafness. With infection, prevertebral muscle spasm may occur.
Imaging Findings Tornwaldt cysts vary from 1 to 5 mm in diameter and are generally rounded. M R I demonstrates high signal intensity both o n T l - and T2-weighted images, likely re lated to either proteinaceous or hemorrhagic cyst contents. On CT they are rounded cysts. Figure 1 7-D shows a CT scan of another patient with this lesion. These cysts may on rare occasions extend off the midline. They usually are fluid filled but occa sionally contain air. A CT scan of another patient with an air-filled cyst can be seen in Figure 1 7-E. The integrity of the overlying bone should always be confirmed with sagittal, coronal, or more cephalad axial views in order to rule out the uncommon possibil ity of meningocele or encepalocele.
Management Treatment consists of surgical drainage and excision for symptomatic lesions. As symptomatic lesions are usually not treated.
Suggested Readings Miyahara, H., Matsunaga, T. Tornwaldt's disease. A cta Oto-Laryngologica 5 1 7:36-9, Supplement 1 994.
I NASOPHARYNX
AND PA RAPHARYNGEAL SPACE
Case 18 Clinical Presentation A teenage male complaiJ1Cd of nasal stuffiness for 2 years and several episodes of spontaneous nose bleeds for 6 months.
A
I�
B
NASOPHA RYNX AND PARAPHARYNGEAL SPACEI
Findings In the lateral radiograph of the midface, there is a soft tissue mass which bows the posterior wall of the maxillary sinus anteriorly (Fig. IS-A). The axial CT with contrast through the same level shows an enhancing mass arising from the region of the pterygopalatine fossa and extending to the infratemporal fossa on the right (Fig. 1 S-B). An axial T l -weighted M R scan of a similar patient shows a large, intermedi ate signal intensity lesion occluding the nasal cavity and nasopharynx with widening of the left pterygopalatine fossa. There are multiple punctate areas of signal void throughout the mass (Fig. I S-C).
Differential Diagnosis: Expansile Nasopharyngeal Mass • • • • • •
Juvenile angiofibroma Chordoma R h abdomyosarcoma Schwannoma of the 5th cranial nerve Nasopharyngeal carcinoma Angiomatous polyp
Diagnosis Juvenile nasopharyngeal angiofibroma UNA)
Discussion Epidemiology Juvenile nasopharyngeal angiofibroma is a benign tumor of the nasopharynx com posed of fibrous connective tissue and an abundance of endothelium-lined vascular V
o
- ./.
��
r
I NASOPHARYNX
AND PARAPHARYNGEAL SPACE
E
spaces. The name of the disease is derived from the fact tbat it occurs during ado lescence, almost exclusively in boys. Some experts suggest that finding this lesion in a female patient should be an indication for a DNA gender test.
Pathophysiology Although the pathogenesis is not fully understood, the tumor is thought to be a mal formation of vascular tissue. TIlese tumors are believed to originate in the postero lateral wall of the nasal cavity near or within the sphenopalatine foramen. JNAs tend to follow vessels as they grow through natural foramina and fissures, expand ing as they grow. The vascular supply is primarily via branches of the external carotid artery. The characteristic angiographic appearance is shown in Figure I S-D. With intracranial extension, the internal carotid artery may also supply portions of the mass. Extension may commonly be found in the infratemporal fossa (via the pterygomaxillary fissure), orbital apex (via the inferior orbital fissure), and. less of ten, into the middle cranial fossa via foramen rotundum.
Clinical Findings The most common presenting complaint is nasal obstruction and epistaxis.
Imaging Findings Figure lS-E is an axial MR image of a patient who has a large JNA with intracra nial extension. The punctate and serpentine areas of signal void seen on MRI sug gest a highly vascular lesion. Widening of the pterygopalatine fossa is perhaps the most helpful distinguishing feature of JNA (occurring in over three quarters of pa tients in one study). cr optimally demonstrates the bony changes usually with re modeling and thinning of bone, without frank destruction. Diagnostic angiograms are no longer routinely done. Preoperative embolization is performed on almost all
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
PEARLS/PITFALLS •
Nasal mass with nosebleeds is a common symptom in a young male with JNA.
•
JNA typically widens the ptery gopalatine fossa.
•
JNA may show a vascular pat tern on imaging studies.
•
The clinician must beware not to fail to perform preoperative em bolization.
•
A biopsy of a JNA in uncon trolled fashion can lead to severe hemorrhage.
lesions. Accurate radiologic diagnosis is important since biopsy of a JNA can lead to severe hemorrhage.
Management Surgery is the treatment of choice for these lesions with preoperative embolization in nearly all cases. Radiation therapy is used in selected cases that are not amenable to surgical resection.
Suggested Readings Antonelli, A.R., Cappiello, 1., Di Lorenzo, D., Donajo, CA., Nicolai, P, Orlandini, A. Diagnosis, staging, and treatment of juvenile nasopharyngeal angiofibroma. Laryn goscope 97: 1 31 9-1325, 1 987. B rooker, D.S., Kenny, B., Gibson, R.G., Primrose, W.J. Juvenile nasopharyngeal angiofibroma in a static population: the implications of misdiagnosis. Clinical Oto laryngology 1 4:497-502, 1 989. Economou, T.S., Abemayor, F., Ward, P.H . Juvenile nasopharyngeal angiofibroma: an update of the UCLA experience, 1 960-1985. Laryngoscope 98: 1 70-175, 1988. Jamal, M.N. Imaging and management of angiofibroma. European A rchives of Oto Rhino-laryngology 251 (4):241-5, 1 994. Lloyd, GA. Phelps, P.D. Juvenile angiofibroma: imaging by magnetic resonance, cr and conventional techniques. Clinical Otolaryngology 1 1 :247-259, 1 986. Ungkanont, K., Byers, R.M., Weber, R.S., Callender, D.L., Wolf, P.F., Goepfert, H. Juvenile nasopharyngeal angiofibroma: an update of therapeutic management. Head and Neck 18(1 ) :60-6, 1 996 Jan-Feb.
1 NASOPHARYNX
AND PA RAPHARYNGEAL SPACE
Case 19 Clinical Presentation A 50-year-old female patient with a known malignancy was referred for evaluation of a new parapharyngeal space mass.
A
182
B
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
E
D
Findings A mass is demonstrated on Tl and T2 weighted axial images (Figs. 19-A-19-B). I t is located in the poststyloid compartment of the left parapharyngeal space with ante rior displacement of the carotid arteries. There are many serpentine structures, seen as signal void, within and around the mass suggesting hypervascularity. Because of the question of metastasis, under M R I guidance a 22 g needle was passed into the lesion and cells were obtained for cytologic study (Fig. 1 9-C).
Differential Diagnosis: Post-styloid Parapharyngeal Space Mass • • • • •
Glomus vagale Glomus jugulare Schwan noma Meningioma Metastasis
Diagnosis Glomus vagale
Discussion Paragangliomas and schwannomas are the two most common diagnoses for a post styloid parapharyngeal space mass (Fig. 1 9-D-normal, Fig 1 9-E-cross hatched 83 1
I NASOPHARYNX
AND PARAPHARYNGEAL SPACE mass-after Dr. Hugh Curtin) Vagal paragangliomas represent approximately 1 0% of incidence of all branchial paragangliomas and show a female dominance of 2.5 : l . Vagal and carotid body tumors are more likely to be multifocal than paragan gliomas in other head and neck locations.
Epidemiology There is a tendency of multicentricity of tumors ( 1 0%), especially in a patient with a carotid body showing familial tendency (26% ). The incidence 01' true malignancy showing metastasis varies from 2-6% . The biologic behavior or natural course of the tumors is not clearly correlated with histologic appearances.
Pathophysiology A paraganglioma is a slowly growing neuroendocrine neoplasm that arises from neural crest derivatives. T n the case of glomus vagale, this is usually from the nodose ganglion of the vagus nerve. Chemodectoma, glomus tumor, nonchromaCfin para ganglioma, and neurocristopathic tumor are other names given to this lesion. Precapillary arteriovenous shunts and nonchromaffin cells are characteristic of the histologic appearance of these tumors. Paragangliomas of the head and neck can be classified by their locations. Tumors of carotid and vagal locations are most frequent. Tympanic and jugular tumors are less frequent. Histologically, sheets of tumor cells are often divided into ball-like clusters ("Zelballen") separated by thin fibrovascular septa.
Clinical Findings The most frequent presenting symptom is a mass in the cervical or pharyngeal area, and 30% of patients have cranial nerve impairment that frequently manifests itself by neck hypoesthesia and pharyngeal pain. A woman in her forties with a painful pharyngeal mass, associated with Xth and X l l th nerve impairment has a very high likelihood of having a vagal paraganglioma. This tumor may arise from paragan-
F
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
PEARLS/PITFALLS •
Glomus vagale has a "salt and pepper" appearance on M R I .
•
A mass i s located i n t h e post styloid parapharyngeal space.
•
Performing a biopsy or surgery without preoperative emboliza tion could cause bleeding.
•
Synchronous or metachronous lesions may be detected in pa tients with glomus vagale.
glions in two locations, intravagal and extravagal, and an intravagal tumor produces rapid vagal impairment.
I m aging Findings A vagal tumor is easily delineated on CT and M R I with its well-encapsulated and hypervascular nature. The mass effect on adjacent vessels is quite different from that of a carotid body tumor and may be a clue for differentation. The internal carotid artery is displaced anteriorly by a vagal tumor (Fig. 1 9-F) whereas posterolateral displacement of the artery with separation from the external carotid artery is char acteristic of a carotid body tumor. Conventional angiography is no longer routinely used For diagnosis but is valuable for preoperative embolization. Some investigators are beginning to use color Doppler ultrasound to help characterize these lesions. Fine needle aspiration as demonstrated in this case is rarely used to make the diag nosIs. A glomus vagale is generally located more cephalad than a carotid body tumor which is characteristically located at the carotid bifurcation. U nlike glomus jugulare tumors which are located at the jugular bulb, glomus vagale tumors are more caudad. Schwannomas may occur in a similar post styloid parapharyngeal space location with similar displacement of the carotid vessels as a glomus vagale. However, they are much less vascular without the "salt and pepper" appearance of the paragan glioma.
Management Surgery is the primary treatment for these lesions with radiation therapy used as an alternative for complex cases. Preoperative embolization in order to control bleed ing is the rule.
Suggested Readings Batsakis, J.G Tumors of the head and neck: clinical and palhoiogical considerations, 2nd ed. Baltimore: Williams and Wilkins, 1 979. Cole, J.M., Beiler, D. Long-term results of treatment for glomus j ugulare and glomus vagale tumors with radiotherapy. Laryngoscope 1 04( 1 2 ) : 1 46 1 -5, 1 994 Dec. Jansen, J.e., Baatenburg de Jong, R.J., Schipper, 1, van der Mey, A.G, van Oils, A.P. Color Doppler imaging of paragangliomas in the neck. Journal of Clinical Vilra sOllnd 25(9):481-5, 1 997 Nov-Dec. Lasjaunias, P., Berenstein, A. Surgical neuroangiography, vol 2. Endovascl.llar lreal men! of craniofacial lesions. New York: Springer-Verlag, 1 987. Leverstein, H., Castelijns, lA., Snow, GB. The value of magnetic resonance imaging in the differential diagnosis of parapharyngeal space tumours. Clinical OlOlaryngol ogy 20(5):428-33, 1 995 Oct. Som, P.M., Sacher, M., Stollman, A.L. Common tumors of the parapharyngeal space: refined imaging diagnosis. Radiology 1 69:8 1 -85, 1 988. Zak, EO., Lawson, W. The paraganglionic chemoreceplor syslem. Physiology, pmhol ogy, and clinical medicine. New York: Springer-Verlag, 1 982.
D PA RAPHARYNGEAL
PA E
Case 20 Clinical Presentation A 45-year-old female who had an M R I for unrelated reasons.
B
A
Findings A well-circum cribed mas with a homogeneously hypointensc center i een in the right poststyloid parapharyngeal space on the TI W images (Fig. 20-A). 11le TIW images how a more heterogeneous interior. True flow void do not appear to be present ( Fig. 20-B). The mass extends from the level of the soft palate to the mid oropharynx. The rna di place the carotid artery medially and the medial ptery goid muscle anteriorly. There i no evidence of the infiltration of the urrounding struct ures.
Differential Diagnosis: Post-styloid Parapharyngeal (Carotid) Space Mass • • • • •
G lomu vagale Glomu jugulare Schwan noma Meningioma Metastasis
Diagnosis chwannoma in the poststyloid compartment of the parapharyngeal pace.
Discussion Knowledge of the contents of the para pharyngeal space is es ential in determining the differential diagnosis of masses in this region. The parapharyngeal pace is lat86
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
D
C
eral to the pharyngobasilar fascia that surrounds the nasopharynx. The parapharyn geal spacc can be further subdivided into prestyloid and poststyloid compartments. TIlese compartments are separated by fascia containing the tensor veli palatini mus cle fibers. The medial pterygoid muscle and fascia form the lateral border of the prestyloid compartment and separate the prcstyloid parapharyngeal space from the masticator space. The prestyloid space contains mostly fat with occasional salivary gland rests. Salivary gland tumors are rare in the poststyloid compartment, but are the most common tumor found in the prestyloid compartment. TIle poststyloid compartment contains the carotid artery, jugular vein, and the lower four cranial nerves. Some experts refer to this area as the carotid space. Post styloid lesions are generally related to the great vessels, cranial nerves (neural sheath tumors and paragangliomas) , or lymph nodes. Paragangliomas and schwan nomas are the two most common post styloid parapharyngeal space masses.
Epidemiology Schwannomas are common, usually solitary, benign tumors that peak during the third through sixth decades of life. Multiple lesions may be seen in patients with neurofibromatosis.
Pathophysiology Schwanomas are cncapsulated neoplasms of the Schwal1l1 cell. They are usually be nign. Two tissue types predominate; Antoni A (cellular) and Antoni B (myxoid) componcnts. Malignant forms may occur. One malignant type. the melanotic schwannoma, has cells that contain heavily pigmented cytoplasm. with abundant melanin pigment. TIle effects of the paramagnetic melanin may be visible on MR images. Figures 20-C & 20-0 show a patient with a melanotic schwanoma of the poststyloid para pharyngcal spacc. Thc TI W non contrast image (Fig. 20-C) shows TI shortening in the mass. The TIW image ( Fig. 20- 0 ) also shows TI shortening due to the melanin. Immunohistochemical stains are often positive for S- 1 00 protein and anti-human melanoma HMB45 marker.
I NASOPHARYNX
AND PARAPHARYNGEAL SPACE
PEARLS/PITFALLS •
Schwannomas are one of the most common poststyloid para pharyngeal space masses.
•
Schwannomas show an interme diate signal on T1 W and a high signal on TZW M R I images.
•
A schwannoma is a benign, slow growing mass.
•
A schwannoma can be confused with a glomus tumor.
----
Clinical Findings Symptoms are usually related to compression of the adjacent nerves and other structures. It is common for these lesions to present as asymptomatic parapharyn geal space masses.
Imaging Findi ngs Both M R I and CT are excellent for delineating tumor extension. Schwannomas on T l -weighted images are of intermediate to low signal intensity and enhance in tensely with contrast. They tend to have a heterogeneously high intensity signal on TI-weighted images. I f serpentine flow voids or a salt and pepper appearance is pre sent, a glomus tumor (paraganglioma) should be considered.
M an agement Surgery is the treatment of choice for these lesions. To approach the parapharyngeal space a transcervical approach is most often used. This minimizes the morbidity fol lowing manipulation of the facial nerve that may be present with a transparotid ap proach.
Suggested Readings Curtin, H. Separation of the masticator space from the para pharyngeal space. Radi ology ] 63: 1 95-204, 1 987. Leverstein, H., Castelijns, 1. A. , Snow, G.B. The value of magnetic resonance imaging in the differential diagnosis of parapharyngeal space tumours. Clinical Otolaryngol ogy 20(5):428-33, 1 995 Oct. Marco, v., Sirvent, 1., Alvarez Moro, 1., Clavel, M., Muntal, M.T., Bauza, A. Malignant melanotic schwannoma fine-needle aspiration biopsy findings. Diagnostic Cytopathology 18 4:284-6, 1 998 Apr. Pensak, M.L., Gluckman, lL., Shumrick, K.A. Parapharyngeal space tumors: an algorithm for evaluation and management. Laryngoscope I 04(9):1 1 70-3, 1 994 Sep. Som, P.M., Curtin, H.D. Lesions of the parapharyngeal space. Role of MR imaging. Otolaryngologic Clinics of North A merica 28(3):5 1 5-42, ] 995 Jun.
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
Case 21 Clinical Presentation A 59-year-old male presented with a history of progressive hearing loss on the left side. The patient also noted bilateral neck swelling.
A
B
Findings A T l -weighted axial sequence of the nasopharynx (Fig. 2 1 -A) shows diffuse soft tissue infiltration of the vault of the nasopharynx with low to intermediate signal in Tl -weighted images. There is obliteration of the fossae of Rosenmtiller and also opacification of the mastoid air cells on the left side. Extension of this lesion beyond the pharyngobasilar fascia is present on left. The longus colli muscle is invaded. Mul tiple bilateral lymph nodes are presented in the neck (Fig. 2 1 -8). Incidental note is also made of medial location of the carotid arteries.
Differential D iagnosis: Nasopharyngeal Mass • • • • • •
Carcinoma Lymphoma Rhabdomyosarcoma Adenoidal tissue Tornwaldt cyst Retropharyngeal adenopathy
Diagnosis Nonhodgkins lymphoma of the nasopharynx.
I NASOPHARYNX
AND PARAPHARYNGEAL SPACE
c
o
Discussion Epidemiology Nonhodgkin's lymphoma is the second most common histologic diagnosis (after squamous cell carcinoma) made in nasopharyngeal malignancies. l1le lesion usually appears as smooth. exophytic, submucosal. and non ulcerative. One should be aware that extranodal lymphoma in the head and neck region increases the probability of systemic disease below the clavicle or diaphragm. and the majority of patients have involvement of cervical lymph nodes. The tonsils are most often involved, followed by the nasopharynx and the lymphoid tissue of the base of the tongue.
Clinical Fi ndings In the nasopharynx. symptoms related to the ear usually lead to early detection of the tumor when it is fairly small because of the proximity of the lesion to the orifice of the eustachian tube. Figure 2 1 -C shows a nonhodgkins lymphoma in another pa tient. The T I W MR image depicts left mastoid nuid and left sided nasopharyngeal mass invading the prevertebral muscles. A large right retropharyngeal node is pre sent ( » . Figure 2 1 -D is an MRI of a patient with non hodgkins lymphoma of the na sopharynx. A bulky left sided nasopharyngeal mass is present with left sided ob structive ear disease.
Pathophysiology Of head and neck lymphomas 75% are non hodgkin and 25% are hodgk in. The nodal form is most common for both types. l1le majority of cases of extranodal lym ph om as of the head and neck are histiocytic lymphomas and lymphocytic lym phomas of the diffuse type. Involvement of extranodal sites of the head and neck by Hodgkin's disease is rare. Extranodal lymphoma may be either lymphatic ( Waldeyer's ring) or extra lymphatic. WaJdeyer's Ring of lymphoid tissue consists of: ( I ) Adenoids ( nasopharyngeal lymphoid tissue). ( 2 ) Palatine tonsils. and ( 3 ) Lin gual tonsils. Most of the patients with lymphoma limited to the head and neck are in the fourth to eighth decades of life.
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
E
PEARLSIPITFALLS •
Lymphoma of the nasopharynx shows up on imaging studies as a bulky mass with extensive adenopathy.
•
Of head and neck lymphomas, 75% are nonbodgkin type.
•
Chemotherapy and radiation therapy are the primary modes of treatment for lymphoma.
•
Lymphoma of the nasopharynx may be indistinguishable on imaging studies from carcinoma of the nasopharynx.
•
Care should be taken to avoid mistaking a lymphoma for nor mal adenoidal tissue.
I maging Findings The pharyngobasilar fascia is the superior fascial continuation of the constrictor muscles of the pharynx. It separates the pharyngeal mucosa from the deeper mus culature and serves to hold the airway open as it attaches to the skull base. It is com posed of the deep layer of the deep cervical fascia. On MRI or contrast enhanced CT scanning it can often be identified by its "whale tail" configuration. Figure 2 1-E depicts a right sided nasopharygeal lymphoma [> 1 in another patient seen on contrast enhanced CT. The pharygobasilar fascia is lat erally violated by the tumor but is intact posteriorly [->1 and on the left. It pro vides an important imaging landmark to help differentiate benign from more ag gressive nasopharyngeal masses. Normal adenoidal lymphoid tissue does not cross this boundary while more malignancies such as carcinoma and lymphoma and ag gressive infections do. Lymphoma of the nasopharynx may be indistinguishable on imaging studies from nasopharyngeal carcinoma. A bulky nasopharyngeal mass with extensive adenopathy should suggest the diagnosis. Similar findings (na sopharynx mass and adenopathy) may be seen with H I V positive patients and in younger patients with infectious mononucleosis.
Management Radiation therapy a n d chemotherapy are t h e primary modes of treatment for lym phoma.
Suggested Readings Braull, I . F. M R I of the nasopharynx. Radio Clin North Am 27:327, 1989. Kieserman, S.P., Stern, 1. Malignant tran formation of nasopharyngeal lymphoid hy perplasia. Otolaryngology and Head and Neck Surgery 1 1 3(4) :474-6, 1 995 Oct. Yanagisawa, E., Citardi. M.1. Endoscopic view of malignant lymphoma of the na sopharynx. Ear, Nose, and Throat iOLirnaI 73(8):5 14-6, 1 994 Aug.
D PA R A P H A RY N G E A L
PA E
Case 22 Clinical Presentation A 69-year-old female pre ented \ ith a rna in her right lateral neck. On phy ical exam a oft. non tender. mobile rna was palpated underneath the right mandibular angle and in the right ubmandibular reg.ion.
A
B
c
D
Findings An M R I wa done of the neck. Figures 22-A and 22-8 show the a ial TI W I . Figure depict the axial T2WI. aDd Figure 22-D how the enhanced axial TI W I . M R I
22-
92
NASOPHARYNX AND PARAPHARYNGEAL SPACE! of the neck shows a 6 em hour glass shaped mass centered in the right prestyloid parapharyngeal space (PPS), extending posterolaterally into the parotid space through an enlarged stylomandibular notch. Medially, it bulges into the right lateral wall of the oropharynx. This well defined lesion causes mass effect but does not appear to infiltrate the adjacent structures. The mass is predominantly homoge neous except for the presence of l i near septations within the most lateral and infe rior components. The signal follows that of the subcutaneous fat, although it appears slightly hyperintense to the remainder of the subcutaneous fat on T2W images. There was no evidence of cervical lymphadenopathy ( Figs. 22-A, 22-B and 22-C).
Differential Diagnosis: Fatty Lesions in the PPS • • • • • • •
Lipoma Angiolipoma Dermoid cyst/teratoma Hibernoma Lipoblastoma/Lipoblastomatosis (pediatric patients) Benign symmetric lipomatosis (Madelung disease) Liposarcoma
Diagnosis PPS Liposarcoma
Discussion Epidemiology Fatty tumors are common in the body, but only l 3% occur in the head and neck re gion. I n the head and neck, they can be subcutaneous or submucosal and the most common location is in the subcutaneous soft tissues of the posterior neck. They tend to grow with age and are more common in obese people. Although they e nlarge with increasing body weight, they do not decrease in size with weight loss. Age of presentation and location varies with gender. In males, they tend to occur in the head and neck region after the 6th decade of life, whereas in females they tend to present earlier (4th decade) and are usually found below the clavicles. Liposarcomas are much less common than lipomas and are exceedingly rare in the head and neck. The ratio of liposarcoma to lipoma has been estimated as 1 : 20. The incidence of l iposarcomas above the clavicles is low, around 5 % , and there are only 80 cases described in the literature. There is a slight male predominance with a male to female ratio of 3 : 2. The age range is broad with a peak incidence in the 6th decade.
Pathophysiology Liposarcomas are malignant tumors which arise from lipoblasts or totipotential mes enchymal cells, usually adjacent to muscle or fascia. They are much more common in the deep-seated fat, rarely arising in the subcutaneous soft tissues. They do not origi nate from pre-existing lipomas. The histologic classification of these tumors is con troversial as the biological behavior of adipose tissue neoplasms depends not only on morphology but also on location. According to some experts, fatty neoplasms arising in deep fatty spaces tend to behave in a more aggressive fashion than their histologic counterparts do in subcutaneous fat. Therefore, deep adipose tissue neoplasms should be considered malignant even in the absence of cytologic features of malignancy. Depending on their histologic features, liposarcomas are usually classified into four categories: well-differentiated, myxoid, round cell and pleomorphic. Whereas
ASOPHARYNX A D PA RAPHARYNGEAL SPACE the former two categories rarely metastasize and have a high five year survival rate, the latter show a high recurrence rate and a high rate of distant metastasis.
Clinical Fi ndings Lipomatous lesions in the PPS present as any other mass in the same location. They cause few. if any symptoms until they become large and compress adjacent neu rovascular structures or compromi e the airway. llley may grow laterally into the parotid or submandibular spaces and present, as in this case, as a neck mass. On physical exam, detection of a fatty PPS mass can be difficult as this neck space usually contains primarily fat. Usually, a medial bulge of the lateral pharyngeal wall is the only visible sign and often is only detected after the lesion has reached 2.5 to 3cm in size. Earaches, tubal dysfunction, fullness or foreign body sensation in the oropharynx may be the presenting symptoms and are nonspecific. When large enough, these le sions may cause airway obstruction. When palpable, they manifest as soft. lobulated masses that may or may not be mobile. Rarely, neurologic deficits due to compres sion of neurovascular structures may ensue. Differential diagnosis of a PPS mass in cludes abscess, atypical branchial cleft cyst, benign and malignant salivary gland rest tumors, mesenchymal tumors, such as lipoma and hemangioma and, less commonly. neural sheath tumors. Pseudomass, due to asymmetry of the pterygoid plexus. should also be considered.
I magi ng Fi ndings Imaging is crucial in the diagnosis of lesions seated in the deep spaces of the neck, which are not accessible to clinical examination. It is common for a PPS mass to be detected as an incidental finding in a study performed for unrelated reasons. Both cr and MRJ are well-suited to detect masses in the PPS and may be diagnostic when a lipomatous lesion is seen. Although the imaging appearance of lipomas is pathognomonic on cr scans. li posarcomas may be difficult or impossible to diagnose based on imaging, as they may mimic any other soft tissue tumor (malignant fibrous h istiocytoma. lymphoma, plasmocytoma, rhabdomyosarcoma). Depending on their histologic subtype they may contain varying amounts of fat intermingled with other soft tissue components. Therefore, the density of the lesion depends on its composition and vascularity. and may be similar to that of muscle. On contrast enhanced cr scans, liposarcomas often manifest as heterogeneous masses containing a combination of fat and enhancing soft tissue elements. llle at tenuation value of fat characteristically varies between - 65 and - 1 00 Hounsfield units. It has been stated that the attenuation value of fat seen in liposarcomas is higher than that of subcutaneous fat. When liposarcomas are exclusively composed of fat, demonstration of contrast enhancement is useful in differentiating them from lipomas, which usually do not enhance. However, angiolipoma, another benign fatty tumor, may show contrast en hancement and be indistinguishible from a liposarcoma. Fibrous septations may be seen in both benign and malignant fatty lesions. I ll-defined margins and infiltration of adjacent structures are the most reliable differentiating features, but are incon sistent. The MRI appearance of liposarcomas in the head and neck is not well docu mented due to the rarity of this entity. However, it has been reported that the ap pearance of liposarcomas differs from subcutaneous fat in that the signal character istics of fat within a liposarcoma tends to be of lower signal intensity on T I W sequences and higher signal intensity on TIW sequences. M R I is less specific than cr in diagnosing fatty tumors, because the signal char acteristics may overlap with those of mature hematomas. Several techniques have been used to separate these entities including calculation of T l W and TIW relax-
194
NASOP HARYNX AND PARAPHARYNGEAL SPACEI
PEARLS/PITFALLS •
Fatty tumors in the deep spaces of the neck should be considered to be liposarcoma until proven otherwise.
•
Demonstration of contrast en hancement and iU-defined mar gins with infiltration of adjacent structures are the most reliable differentiating features, but are inconsistent.
•
Care should be taken not to con sider all fatty tumors with well defined margins as benign lipo mas.
•
Care should be taken not to ex clude liposarcoma from the dif ferential diagnosis when the tu mor is predominantly soft tissue density/intensity.
ation times, gradient echo imaging and several techniques of fat suppression. How ever, even using these techniques, a definite diagnosis is not always possible because hemorrhage within a fatty lesion is common. The most reliable technique to detect fat on M R I is frequency selective fat suppression imaging ( FATSAT) in which a spe cific saturation pulse in the resonant frequency of fat is given. The advantages of M R I in the evaluation of liposarcomas include a better delin eation of the neoplasm, and demonstration of the presence or absence of cleavage planes between the tumor and adjacent structures, due to its multiplanar capability. Metastatic lymphadenopathy is rarely seen. In the pediatric patient, lipoblastoma and Iipoblastomatosis should be consid ered. These tumors have a similar imaging appearance as liposarcoma and, although rare, are more common than liposarcomas in the pediatric age group. The differen tial diagnosis is important as lipoblastomas are considered hamartomatous lesions and should be managed accordjngly. Both discrete and diffuse forms have been de scribed. Other fatty tumors that show contrast enhancement and soft tissue compo nents include hibemomas, angiolipomas and teratomas.
Management Liposarcomas of the head and neck should be managed surgically by wide local excision. Tn the PPS several approaches can be used depending on the size of the lesion and surgeon's preference. These include transcervical, submandibular. transparotid, transoral, and infratemporal approaches. In selected cases adjuvant radiotherapy may be of benefit. Palliative radiation therapy may prolong survival in inoperable cases. Neck dissections are not performed routinely as cervical metasta sis are rare.
Suggested Reading Abdullah, BJ., Liam, C.K . , Kaur, B., Mathew, K.M. Parapharyngeal space lipoma causing sleep-apnoea. British Journal of Radiology 70(838):1 063-5, 1997 Oct. Collins, M.H., Chatten, 1. Lipoblastomallipoblastomatosis: a clinicopathologic study of 25 tumors. American Journal of Surgical Pathology 2 1 ( 1 0): 1 1 3 1-7, 1 997 Oct. Elango, S. Parapharyngeal space Ijpoma. Ear, Nose, and Throat Journal 74( 1 ):52-3, 1 995 Jan. Kraus, M.D., Guillou, L., Fletcher, C.O. Well-differentiated infla=atory lipo sarcoma: an uncommon and easily overlooked variant of a common sarcoma. Amer ican Journal of Surgical Pathology 2 1 (5):518-27, 1 997 May. Saddik, M., Oldring, OJ., Mourad, W.A. Liposarcoma of the base of tongue and ton sillar fossa: A possibly underdiagnosed neoplasm. A rchives of Pathology and Labo ratory Medicine 1 20(3):292-5, 1 996 Mar. Stewart, M.G., Schwartz, M.R., Alford, B.R. Atypical and malignant lipomatous le sions of the head and neck. A rchives of Otolaryngology and Head and Neck Surgery 1 20 ( 1 0 ) : 1 15 1-5, 1 994 Oct.
Case 23 Clinical Presentation three-year-old female pre ented with history of chronic na al ob truction.
A
B
c
D
1 96
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
E
F
Findings An axial cr section through the basiphenoid (bone window) (Fig. 23-A) shows a large soft tissue mass occupying the nasopharynx, nasal vault and nasal cavity, ex tending through the left sphenopallatine foramen into the left pterygopallatine fossa. There is bony destruction involving the left basisphenoid, medial wall of the left maxillary sinus and nasal septum. An axial cr section through the low na sopharynx (soft tissue window) (Fig. 23-B) shows a large left-sided retropharyngeal nodal conglomerate that appears separate from the midline nasopharyngeal mass. In an axial TIW M R image (Fig. 23-C) at tbe same level as the CT section showing the large midline nasopharyngeal mass is seen as separate from bilateral retropha ryngeal lymphadenopathy ( Fig. 23-0). The coronal enhanced T1 W MR image ( Fig. 23-0) shows the craniocaudal extent of the mass and homogeneous contrast en hancement. There is no evidence of meningeal spread or intracranial invasion through the cranial nerves foramina ( Fig. 23-E). The sagittal Tl W MR image (Fig. 23-F) shows a bulky soft tissue mass occupying the nasopharynx, nasal cavity, nasal vault and oropharynx, obstructing the choana and oropharyngeal airway.
Differential Diagnosis: "Aggressive" Nasopharyngeal Mass in a Child •
• • • • • • • • •
Rhabdomyosarcoma (includes other soft tissue sarcomas such as fibrosarcoma, angiosarcoma, mesenchymal chondrosarcoma, malignant mesenchymoma) Lymphoma Chloroma Langerhans' cell tumor Nasopharyngeal carcinoma Metastatic neuroblastoma Esthesioneuroblastoma Hemangiopericytoma Minor salivary gland malignancy Aggressive infection (fungal, TB, Cocci)
I NASOPHARYNX
AND PA RAPHARYNGEAL SPACE
Diagnosis Nasopharyngeal rhabdomyosarcoma (embryonal type)
Discussion Epidemiology Rhabdomyosarcoma is the most common malignant soft tissue tumor in children under 1 5 years of age. In the head and neck, it is the most common sarcoma and the third most common malignancy following lymphoma and retinoblastoma. Two peaks of prevalence are noted, one between 2 and 5 years of age and the other be tween 1 5 and 20 years. Seventy percent of tumors occur before age 10. In the head and neck, the most common location is the orbit followed in decreasing order of fre quency by the nasopharynx, paranasal sinuses, and middle ear cavity.
Pathophysiology Rhabdomyosarcoma is a malignant mesenchymal tumor that originates from undif ferentiated mesenchymal cells, the precursors of skeletal muscle. The tumor was first described in 1 854, by Weber and further characterized by Stout. who described the histology of this tumor more precisely. 0 predisposing factors are recognized, but a chromosomal translocation is noted in almost half of the children with rhab domyosarcoma. Pathologically, three main types of spindle cell tumor are recognized. The most common is the embryonal type, which comprises 75% of all cases and is the form most commonly encountered in the head and neck. This cell type is een in younger children and carries a better prognosis, with a 5 year survival rate of 65% after com bined treatment with radio- and chemotherapy. H istologically, the embryonal cell type may be confused with anaplastic carcinoma, large cell lymphoma. esthesioneu roblastoma and melanoma. Botryoid rhabdomyosarcoma is not histologically dif ferent from the embryonal type and its name is derived from its macroscopic grape like appearance. The second most common, the alveolar type ( I S% ). tends to occur in older patients (second decade) . I t spreads to lymph nodes and carries a worse prognosis with only a 2% S year survival rate. Finally, the least common form is pleomorphic rhabdomyosarcoma, considered to be an adult form as only 6% of cases occur before age 6. The most important diagnostic criterion is the identifica tion of rhabdomyoblast . within the tumor. D i fferent stains help to characterize the tumor, such as desmin, myoglobin and muscle specific actin.
Clinical Findings Clinical presentation depends on the location of the tumor. asopharyngeal rhab domyosarcomas tend to grow silently and present as large destructive masses at a late stage. Very young children may present with difficulty breathing and eating and failure to thrive. Older children present with sinonasal symptoms similar 10 those of sinus infection which further delay the diagnosis. asal obstruction. rhinorrhea. and epistaxis are the most common presenting symptoms. Hearing impairment due to obstructive serous otitis is also common. Local pain appears late in the course of the disease and usually indicates bony destruction. Cranial nerve and other neurologic signs and symptoms imply skull base invasion with intracranial extension. ENT examination usually discloses a nasopharyngeal mass which may extend into the nasal cavity. Because the tumor itself is submucosal, the clinical findings are non-specific and may mimic hypertrophic turbinates and hypertrophic adenoids. common findings in pediatric patients. Tumor subsite and tumor. node, metastasis (TN M ) staging have important impli cations in management and prognosis. Subsites are classified into orbital. para-
198
NASOP H A RYNX AND PARAPHARYNGEAL SPACEI meningeal, and miscellaneous tumors. The parameningeal group includes the na sopharynx, paranasal sinuses, pterygopallatine fossa, infratemporal fossa, and tem poral bone. The close proximity to the skull base and meninges makes this group of tumors particularly prone to intracrarual extension and meningeal spread, worsen ing the prognosis. The TNM classification for soft tissue sarcomas of the impacts and Use Committee ( IUAC) divides these tumors into two groups according to their lo cal invasiveness. Tl includes tumors confined to the muscle group of origin, 1'2 in cludes tumors which have spread through the fascial planes outside the muscle group of origin , and invading neurovascular structures or bone. Overall, lymph node metastasis are seen in 50% of cases at presentation and distant metastasis in 58% . The most common metastatic sites include the lungs, bone marrow and brain.
Imaging Findings Imaging is crucial for the diagnosis, determination of local and distant tumor extent, treatment planing and detection of local recurrence. Cross sectional imaging may disclose the aggressive nature of a nasopharyngeal mass by showing deep invasion and bone destruction, which can not be assessed on clirucal exam. This can differ entiate adenoidal hypertrophy from more aggressive lesions. However, lack of specificity in tissue characterization necessitates biopsy to confirm t he diagnosis. On CT, the main findings include a bulky mass, isodense to muscle, with little to moderate homogeneous contrast enhancement, expansion or erosion of skull base foramina, or destructive bony changes of the skull base. The low yield of CT in soft tissue characterization makes it difficult to separate tumor from post-obstructive changes in the paranasal sinuses and mastoids, to detect meningeal spread, and sep arate residual scar tissue from recurrent mass. Poor prognostic signs on CT include skull base destruction and intracranial spread. M R I is the modality of choice in evaluation of soft tissue tumors of the head and neck. It allows multi planar delineation of the tumor, differentiation between the tumor and post-obstructive inflammatory changes, and detection of meningeal and cranial nerve spread in post-contrast images. Rhabdomyosarcoma tends to be of intermediate signal intensity on Tl WI, hy perintense on T2WI and enhances homogeneously. Cervical and retropharyngeal lymphadenopathy should be surveyed. Imaging follow-up should include a scan after completion of treatment, then follow-up scans every 2 months during the first year, every 4 months for 2 years, and once a year, thereafter. Imaging should also be performed any time symptoms ap pear or a clinical exam disclnses new findings. It has been demonstrated that the presence of a post-therapeutic residual mass (defined as a region of soft tissue thickening at the original tumor site with en hancement and absence of mass effect) is a poor prognostic sign heralding an in creased probability of tumor recurrence. Differential diagnosis from other aggres sive looking nasopharyngeal masses, such as lymphoma, Langerhans' cell tumor, chloroma, nasopharyngeal carcinoma, metastasis from neuroblastoma and other soft tissue sarcomas is not possible based solely on the imaging findings, and biopsy is mandatory.
Management The overall prognosis of rhabdomyosarcoma markedly improved, with the advent of multidrug chemotherapeutic regimens and external beam radiotherapy, from a 55% to an 80% 5 year survival rate in patients with non metastatic disease. These regimens had their major impact in the treatment of parameningeal tumors, not amenable to curative surgery or requiring major craniofacial resections with inade quate surgical margins. Surgery plays an important role in many patients. A sagittal Tl W MR image (Fig. 23-F) shows the same patient after radiotherapy and chemotherapy. There was complete resolution of the soft tissue mass.
ASOPHARYNX AND PARAPHARYNGEAL SPACE
PEARLS/PITFALLS •
A nasopharyngeal mass can of ten be found in a child with chronic sinus symptoms.
•
Rhabdomyosarcoma can show signs of deep invasion.
•
•
•
•
cr imaging may show bony de structive changes in the base of the skull and erosion of cranial nerves foramina.
Care must be taken not to mis take an aggressive nasopharyn geal mass for adenoidal hyper trophy. Care must be taken not to mis take post-obstructive changes i n the paranasal sinuses a n d mas toids for tumor extension. Care must be taken not to miss i n tracranial and meningeal spread of the tumor.
Suggested Reading Gilles, R., Couanet, D., Sigal, R., De Baere, T. , Tardivon, A, Masselot, 1., Vanel. D. Head and neck rhabdomyosarcomas in children: value of clinical and cr findings in the detection of loco-regional relapses. Clinical Radiology 49(6):41 2-5, 1 994 Jun. Kowalski, L.P., San, c.l . Prognostic factors in head and neck soft tissue sarcomas: analysis of 1 28 cases. Journal of Surgical Oncology 56(2):83-8, 1994 Jun. Kraus, D.H., Saenz, N.C., Gollamudi, S., Heller, G., Moustakis, M., Gardiner, S., Ger ald, w.L., Ghavimi, E, LaQuaglia, M.P. Pediatric rhabdomyosarcoma of the head and neck. American Journal of Surgery 174(5):556-60, 1 997 Nov. Lee,J.H., Lee, M.S., Lee, B.H., Choe, D.H., Do, YS., Kim, K.H., Chin, S.Y, Shim, YS., Cho, KJ. Rhabdomyosarcoma of the head and neck in adults: MR and CT findings. American Journal of Neuroradiology 1 7 ( 10):1 923-8, 1 996 Nov-Dec. Lyos, A.T., Goepfert, H., Luna, M .A, Jaffe, N., Malpica, A Soft tissue sarcoma of the head and neck in children and adolescents. Cancer 77( 1 ): 1 93-200, 1 996 Jan I . Odell, P.E Head and neck sarcomas:a review. Journal of Orolaryngology 25( 1 ):7-13. 1 996 Feb. Park, Y W. Evaluation of neck masses i n children. Americall Family Physician 5 1 (8): 1 904- 1 2, 1 995 Jun. Yang, W.T., Kwan, W.H., Li, C.K., Metreweli, C. Imaging of pediatric head and neck rhabdomyosarcomas with emphasis on magnetic resonance imaging and a review of the literature. Pediarric Hematology and Oncology 14(3):243-57, 1 997 May-Jun.
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
Case 24 Clinical Presentation A 42-year-old male presented with unilateral serous otitis media.
A
Findings The axial Tl W MRI shows (Fig. 24-A) a right sided nasopharyngeal mass which in vades the prevertebral musculature.
Differential D iagnosis: Nasopharyngeal Mass • • • •
Adenoidal tissue Lymphoma Carcinoma Tornwaldt cyst
Diagnosis Squamous cell carcinoma of the nasopharynx
Discussion The nasopharynx remains an area that is occult to casual clinical examination. Its proximity to the skull base makes cancers in this region particularly devastating.
ASOPHARYNX AND PARAPHARYNGEAL SPACE
Epidemiology Malignancies of the nasopharynx can be divided into three groups. Seventy percent are carcinomas and 20% are lymphomas. The remaining 1 0% are made up of a va riety of lesions including adenocarcinoma, rhabdomyosarcoma, melanoma, adenoid cystic carcinoma, and others. Squamous cell carcinoma of the nasopharynx is a tumor not commonly seen in the United States. However, in certain portions of the world, (Canton, China) it is one of the most common cancers. Human leukocyte antigen A-2 and B-sin histo compatibility loci have been identified as possible markers in the Chinese popula tion for susceptibility to this disease. While the incidence of the disease in American born Chinese decreases, it is still seven times higher than for other Americans. Antibodies against Epstein-Barr virus have been associated with the undifferen tiated form of nasopharyngeal carcinoma. Other risk factors for nasopharyngeal carcinoma include nitrosamines (found in dry salted fish) and exposure to polycyclic hydrocarbons (found in burned foods).
Pathophysiology Carcinoma of the nasopharynx based on histopathology, is classified according to the World Health Organization into three types. Type 1 is squamous cell carcinoma which is similar to other lesions found in the upper aerodigestive system. Type 1 1 lesions have little or no keratin production and are referred to as a non keratinizing carcinoma. Because of their similarity to urinary tract tumors they are sometimes referred to as transitional cell carcinomas. Type I I I carcinomas include lymphoep ithelioma, spindle cell and clear cell squamous carcinoma. While Type I and I I lesions are usually found i n adults, type I I I lesions have a bimodal age distribution.
Clinical Findings Nasopharyngeal carcinoma may present as a change in voice quality, impaired hear ing, or a mass in the nasopharynx. Often the first sign of abnormality is the accu mulation of fluid in the middle ear or mastoid caused by obstruction of the eu stachian tube.
B
I J.Q?
NASOPHARYNX AND PARAPHARYNGEAL SPACEI
D
c
Lymphadenopathy is also very common in nasopharyngeal carcinoma and is seen in approximately 70% of patients at presentation. Nodal extent ion to the nodes of Rouviere (lateral retropharyngeal nodes) is frequent. Figure 24-B shows large lat eral retropharyngeal lymph nodes (» in a patient with squamous cell carcinoma of the nasopharynx. A common presentation of nasopharyngeal carcinoma is a mass in the nasopharynx and spinal accessory lymphadenopathy.
I m aging Findings An M R I examination of the nasopharynx is indicated to: ( I ) delineate the extent of a known malignancy, (2) search for the presence of the tumor in a patient with symptoms or clinical findings, and (3) follow treated patients with a history of na sopharyngeal cancer to rule out recurrence. Figure 24-C shows a recurrent right sided nasopharyngeal carcinoma in a 21 year old who had undergone radiation therapy for her original disease (note atrophic changes on the contralateral side). Anatomical routes hy which tumors extend from the nasopharynx to the middle cranial fossa may be shown by imaging studies. By following the eustachian tube, nasopharyngeal carcinoma can pass through the tough pharyngobasilar fascia at its only natural defect, the sinus of Morgagni. From this point, a tumor may enter the parapharyngeal space and extend to the floor of the middle cranial fossa by ex tending along the course of the eustachian tube in the sphenoidal sulcus, following it to the region of the foramen lacerum and ova Ie, and then extending into the cav ernous sinus. Figure 24-0 shows a large nasopharyngeal carcinoma extending through a widened foramen ovale to invade the middle cranial fossa. Note that the internal carotid artery is encircled by the mass on this section. Tumors high in the nasopharynx may also gain access to the middle cranial fossa via either the pterygoid canal or sphenopalatine foramen. Through the pterygoid canal, tumors may extend directly to the foramen lacerum, or erode through the thin lateral wall of sphenoid sinus, entering the cavernous sinus. Through the sphenopalatine foramen, tumors may extend directly to the pterygopalatine fossa, inferior and superior orbital fissures, and into the cavernous sinus. I n cases of na-
1 03 1
I NASOPHARYNX
AND PARAPHARYNGEAL SPACE
PEARLSIPITFALLS •
•
The clinicians should search for an occult nasopharyngeal mass in patients presenting with nodal extension to the posterior trangle. The clinician should identify in tracranial extension and adenopathy which may have treatment and prognostic signifi cance.
•
Care should be taken not to miss a nasopharyngeal mass in adult patients presenting with unilat eral serous otitis media.
•
Care should be taken not to con fuse carcinoma with adenoidal enlargement.
sopharyngeal carcinoma with neck metastases, MR images may show an extranodal tumor abutting and surrounding the carotid artery and jugular vein.
Management The role of surgery in this disease is limited to biopsy and staging. Radiation ther apy is the standard treatment for nasopharyngeal carcinoma. Advanced lesions may also require chemotherapy.
Suggested Readings Teresi, L.M., Lufkin, R.B., Hanatee, W. MR imaging of the nasopharynx and floor of the middle cranial fossa. Part 1 . Normal anatomy. Radiology 1 64:8 1 1 , 1 987. Teresi, L.M., Lufkin, R.B., Hanatee, W. MR imaging of the nasopharynx and floor of the middle cranial fossa. Part I I . Malignant tumors, etc. Radiology 164:81 7, 1 987.
IV. Neck, Thyroid, Parathyroid
ECK, THYROID, PA RATHYROI DI
Case 25 Clinical Presentation An adult male patient presented with painles midline swelling adjacent to the hy oid bone.
A
Radiologic Findings CT cans revealed a thin walled midline cy tic mass adjacent to the hyoid bone
(Fig. 25-A).
Differential Diagnosis: Anterior Cystic Neck Mass • • • • • • • • •
Branchial cleft cyst External laryngocele Thyroglossal duct cy t Necrotic lymph node Ab ce s ySlic hygroma Dermoid llHombosed anterior jugular vein Aneurysm
Diagnosis Thyroglossal duct cyst
Discussion 11lyroglossal duct cy ts are more frequently found in children. but they also may present in adulthood. They can be found anywhere along the thyroglo sal tract, ex-
1 07 1
I NECK,
THYROID, PARATHY ROID
pyramidal lobe thyroid
B
tending from the foramen cecum to the thyroid gland, and most frequently present as anterior, midline or paramedian neck masses. Although they are reported most commonly in the low to mid-neck, up to 20% occur above the hyoid bone. They may be seen as a mass at the root of the tongue. The cyst is often associated with the body of the hyoid bone, and in order to avoid a surgical recurrence, the body of the hyoid bone should be removed along with the cyst.
Pathophysiology The thyroglossal duct is an epithelial lined tubular structure extending from the foramen cecum, around the inferior border of the hyoid bone to the pyramidal lobe of the thyroid bed (Fig. 25-B). It is formed by the 3rd week of gestation and nor mally involutes by the 1 0th week. If any portion fails to involute, the secretory epithelial lining may cause a cyst to be formed. Although these are congenital lesions, they often do not present until there is inflammation or blocked drainage.
Clinical Findings Most patients present with asymptomatic neck masses within the anterior triangle. Fistulas are uncommon but can occur related to surgery or complicated infection. Most cysts ( >75% ) are midline and are most common at or near the level of the hyoid bone.
Imaging Findings Thyroglossal duct cysts typically appear as a cystic thin-walled midline mass on CT or M R T scanning. They may be intimately associated with the hyoid bone. Tby-
1 1 08
o
c
as ell-circums ribed fluid-den it tructures in roglossal ducI cy t' appear on the midline. The cy I are u ually large I at the b oid level but aJ lrack inferiorly adjacent to tbe laryngeal kelelon Fig. 25- ). On M R I tbe nuid content may be expected to demon trate tbe same anatomic and gro morph logic features. yst nuid ill how both long Tl and 1'2 in appro priately weighted pin echo image The ignal of the nuid depend on its content or M R l un Ie (e.g protein. hemorrhage). The cy t rim ill be nonenhancing on inflammati n i pre ent. which i often the ca e on mplomatic Ie ions. Perhap the mo t significant morphol gic feature to be determined by or M R I i evidence of internal or external fi tulae. adherence I underlying lruclure or lobulati n ince the e eem to be the mo t important cau e f urgical recurrences. agina! TI WI in another patient (Fig. 25-D) how a characteri lie cyst (arrow). n axial T2WI ( Fig. 25- ) in another patient show cy tic signal (arrow) adjacent to the hyoid bone. \
0
\
.•
\
Management
When pos. ible, surgery is the treatment of choice. The goal or the surgery is to remove all the epithelial lining. Becau e of their e tent, complete rem val rna be 1 09
/ NECK,
THYROID, PARATHYRO I D
PEARLS/PITFALLS •
A thyroglossal duct cyst appears as a thin walled midline cystic mass on cr and M R I scanning.
•
A t hyroglossal duct cyst is lo cated along path of thyroglossal duct.
•
A thyroglossal duct cyst has a characteristic appearance on cr and M R images.
•
Surgical removal is the treatment of choice.
•
Care should be taken not to mis take a thyroglossal duct cyst for a thin walled abscess or necrotic node.
difficult and may recur. Extensive resection (Sistrunk procedure), which removes the entire duct, midportion of the hyoid bone and a portion of the tongue base, has decreased the recurrence rate from 50% to 20% .
Suggested Readings Johnson, u., Smith P., Akintunde, M.O., Robson, A.K., Stafford, F. W. Assessment of pre-operative investigations of thyroglossal cysts. fournal of the Royal College of Surgeons of Edinburgh 41 ( 1 ):48-9, 1 996 Feb. Kawanaka, M., Sugimoto, Y., Suehiro, M . , Fukuchi, M. Thyroid imaging in a typical case of acute suppurative thyroiditis with abscess formation due to infection from a persistent thyroglossal duct. A nnals of Nuclear Medicine 8(2) : 1 59-62, 1 994 M ay. Lim-Dunham, lE., Feinstein, K.A., Yousefzadeh, D.K., Ben-Ami, T. Sonographic demonstration of a normal thyroid gland excludes ectopic thyroid in patients with thyroglossal duct cyst. A merican fournal of Roentgenology 1 64(6) : 1 489-9 1 , 1 995 Jun. McHenry, c.R . , Danish, R . , Murphy, T., Marty, 1.1. Atypical t hyroglossal duct cyst: a rare cause for a solitary cold thyroid nodule in childhood. American Surgeon 59(4):223-8, 1 993 Apr. Urao M . , Teitelbaum, D.H., Miyano, T. Lingual thyroglossal duct cyst: a unique sur gical approach. fournal of Pediatric Surgery 3 1 ( 1 1 ): 1 574-6, 1 996 Nov.
/2 2 9
E K, THYRO I D PA R ATH Y RO I DI
Case 26 Clinical Presentation A 36-year-old male presented with a history of progressive swelling in his neck. Phy ical examination revealed a round. painless. mass just inferior to the mandible on the left.
A
B
Findings There is a well-circum cribed cystic rna in the right lateral neck ( Figs. 26-A, 26-6, & 26- ). TIle submandibular gland is displaced anteriorly. The sternocleidomastoid
111
I NECK,
THYRO I D, PARATHYROID
D muscle is displaced posterolaterally, and the carotid artery and jugular vein are dis placed medially. (Case courtesy of Dr. Andrew Berger.)
Differential Diagnosis: Cystic Neck Mass • • • • • • • •
Thyroglossal cyst Branchial cleft cyst Cystic hygroma Necrotic lymph node Laryngocele Sebaceous cyst Jugular vein Lipoma
Diagnosis Second branchial cleft cyst.
Discussion Epidemiology Second branchial cleft cysts are the most common congenital cystic neck masses. These cysts usually present during the second to fifth decades of life. Second branchial cleft anomaly comprises a spectrum of cysts, sinus tracts, and fistulae that are caused by incomplete obliteration of the branchial apparatus.
Pathophysiology Branchial cleft cysts represent a congenital cystic anomaly of the branchial appara tus (Fig. 26-0, 5-week embryo). TIle branchial apparatus begins to develop in the third week of gestation, surrounding the primitive pharynx. The branchial appara-
N ECK, THYRO I D, PARATHYROIDI tus consists of five transverse mesodermal ridges, separated by clefts. Each cleft is met by an outpouching of the pharynx, called the pharyngeal pouch, with a thin membrane separating the structures at their interface. The branchial apparatus de velops into the main structures of the face, nasopharynx, oropharynx, and neck. The first branchial arch ( I in Fig. 26-0) gives rise to the maxilla and mandible, as wel l as the facial artery and mandibular and maxillary divisions of the trigeminal nerve. The first cleft pinches off and gives rise to the external auditory canal, with the thin membrane separating it from the pharyngeal pouch, becoming the tym panic membrane. Cysts associated with this cleft are uncommon and occur in the re gion of the external auditory canal. The second branchial arch ( I I in Fig. 26-0) forms, among other structures, the sty loid process, anterior base of the tongue, and posterior belly of the digastric muscle. The fate of the second branchial cleft is controversial, but in conjunction with rem nants of the second pharyngeal pouch, it is believed to be responsible for 95% of branchial cleft cysts. Second branchial cleft cysts occur via the persistence of the cleft as an epithelium lined tract ( * in Fig. 26-0) that courses between the second and third branchial arch ( I l l in Fig. 26-0). If the tract exists in its entirety (i.e., there is a complete fistula), its internal opening usually lies in the tonsillar fossa. From there, the tract runs beneath tbe stylobyoid muscle and posterior belly of the digastric muscle, and above the glossopbaryngeal and hypoglossal nerves. Further on, it crosses between the inter nal and external carotid arteries (see Fig. 26-D). Below the carotid bifurcation, it courses along the carotid sheath a nteromedial to the sternocleidomastoid muscle. The external opening appears along the anterior edge of the sternocleidomastoid, usually in its middle third. If the tract is incomplete, it may present as an isolated cyst anywhere along tbe course of the tract, or as a cyst in communication with an internal or external fistula. There is a spectrum of cysts, sinus tracts, and fistulae that arise from incomplete obliteration of this branchial apparatus. Cysts are much more common than fistulae or sinuses.
Clinical Findings The second branchial cleft cyst most often presents as a smooth, nontender, fluctu ant mass located along the upper third of the sternocleidomastoid. Wben not in
E
F
I NECK,
THYRO I D, PARATHYROID
PEARLS/PITFALLS •
Second branchial cleft cysts are the most common congenital cys tic neck masses.
•
Second branchial cleft cysts may have internal oral or external lower neck fistulae.
•
Ninety five per cent of second branchial cleft cysts are from sec ond branchial cleft.
•
A second branchial cleft cyst can pass between the internal and external carotid arteries.
•
Care should be taken not to mis take a second branchial cleft cyst for an abscess.
communication with an external fistula, the cyst may go unnoticed until the second to fourth decades. The discovery of the cyst is often related to an upper respiratory infection, which causes transient enlargement of the cyst. Cysts may become in fected and progress to abscess formation, with the possibility that spontaneous rup ture or incision and drainage will lead to a permanent fistula. Patients with a branchial fistula may present with persistent mucous discharge from a skin opening in the neck.
I maging Findings The introduction of ultrasonography, CT, and M R I has improved the accuracy of di agnosis of these lesions. The course and extent of a fistulous tract may be demar cated by fistulography, which may be followed by CT scanning. The cysts are well demonstrated on cr and M R I scanning. On cr, they are usually sharply mar ginated, centrally hypodense masses with thin enhancing capsule. On M R I a noninfected second branchial cleft cyst presents as a homogeneous, low to intermediate signal intensity cystic mass on T l -weighted images (Fig. 26-E; s-submandibular gland, m-branchial cleft cyst, sm-sternocleidomastoid muscle: image courtesy of Dr. E l len K. Tabor). They are usually high signal on T2 weighted images (Fig. 26-F; image courtesy of Dr. E l len K. Tabor). The lesion is well circum scribed and thin walled. If there has been previous infection, there will be varying degrees o[ wall thickening, increased signal intensity and obliteration of the sur rounding [at planes. The radiographic differential diagnosis includes neck abscesses, branchiogenic carcinoma, lipoma, tuberculous adenitis, cystic hygroma, paraganglioma, and metastatic neoplasm. The benign, thin walled, cystic appearance, classic location, and T l and T2 parameters usually allow correct radiographic diagnosis, with differ entiation from an abscess presenting the greatest difficulty. Thyroglossal duct cysts tend to be close to midline and laryngoceles usually have an obviolls association with the larynx.
Management Complete excision under general anesthesia is the treatment of choice. The proce dure is associated with a low incidence of local complications and neurologic sequelae. The overall recurrence rate is less than 5% after a follow-up of 2 years.
Suggested Readings Agaton-Bonilla, F.e., Gay-Escoda, e. Diagnosis and treatment of branchial cleft cysts and fistulae. A retrospective study of 1 83 patients. lnternatio ll al Journal of Oral and Maxillofacial Surgery 25(6):449-52, 1 996 Dec. Batsakis, J.G. Tumors of the head and neck: clinical and pathological considerations, 2nd ed. Baltimore: Williams and Wilkins, 1 979;5 1 4-520. Chandler, J.P, Mitchell, B. Branchial cleft cysts, sinllses, and fistulas. OlOlaryngologic Clinics of North America 1 4: 1 75-1 86, j 98 1 . De, P.R., Mikhail, T. A combined approach excision of branchial fistula. Journal of Laryngology and Otology 1 09( 1 0) :999-1 000, 1 995 Oct. De Schepper, A.M., Monheim, P, Degryse, H . R . , Van de Heyning, P. cr of second branchial cleft cysts and fistula: comparison with M R I in three cases. Annals of Ra diology 3 ] : 1 4 1-1 48, 1 988. Reynolds, J.H . Y, Wolinski, A.P Sonographic appearance of branchial cysts. Clinical Radiology 48(2): 1 09-10, 1 993 Aug.
ECK, T H Y ROID, PA RATHYRO I DI
Case 27 Clinical Presentation An adult female pre ented with a painless lower neck mass.
B
A
Findings A homogeneous mass is pre ent in the posterior triangle. It conforms to surround ing oft tissue structures ( Figs. 27-A and 27-B). (Case courtesy of Dr. Andrew Berger.)
Differential Diagnosis: Cystic Neck Mass • • • • • •
Branchial cleft cyst Lymphangioma Thyroglossal duct cyst External laryngocele Necrotic lymph node Lipoma
Diagnosis Lymphangioma
Discussion Lymphangiomas are benign malformations of the lymphatic sy tern.
CK, T H Y RO I D. PARATH Y RO I D
Epidemiology Mo t lymphangioma occur during childhood with 60% present at birth. and 0% presenting by 2 years of age. This corre pond to the period when the greate t de velopment of the lymphatic ystem OCCUJ . There i no gender predominance. orne of tho e that occur in adult may be of traumatic rather than developmen tal origin.
Pat hophy iology Lymphangioma are nonencap ulated lesions of lymphoid ti ue. Mo t researcher in thi area feel the e Ie ion a re malformation rather than true neopla m . For the record, they are cia sified into three group , ba ed on the size of the I mphatic pace within the rna : ( I ) lymphangioma implex are compo ed of thin walled capil lary sized channel , (2) cavernou lymphangioma have more dilated lymphatic with fibrous adventitia and (3) cy tic hygroma have large cy ts up to everal cen-
c
11 16
D
N ECK, THYRO I D, PARATHYROIDI
PEARLS/PITFALLS •
•
Most lymphangiomas occur dur ing childhood with 60% present at birth, and 80% presenting by 2 years of age. A lymphangioma is a cystic neck mass that classically occurs in the posterior triangle.
•
A lymphangioma is a non en hancing, soft pliable mass.
•
Care should be taken not to mis take a lymphangioma for a necrotic lymph node.
•
Care should be taken not to fail to recognise the full extent of the lymphangioma for adequate sur gical planning.
timeters in diameter. I n practice, the radiographic appearance of these types over lap and, in fact, all three tissue types may occur in the same lesion.
Clinical Findings Lymphangiomas are generally painless, compressible neck masses. Cystic hygromas classically occur in the posterior triangle but may extend more anteriorly.
Imaging Findings U ltrasound is valuable in imaging these lesions especially in the perinatal period. CT and M R I are useful for defining the full extent of the lesions. Accurate delin eation of lesion extension is important for preoperative diagnosis, surgical planning, and assessing recurrence. Lymphangiomas are characteristically soft and conform to existing tissue spaces rather than distorting surrounding structures. Because of their large cystic spaces, they do not typically enhance with contrast. They are low signal on Tl WI (Fig. 27-C) and high signal on TIWI ( Figs. 27-D and 27-E). With infection or hemorrhage, these signal characteristics may change.
M anagement Surgery is the therapy of choice for most patients with this condition. Imaging is es pecially valuable to define the full extent of the lesion to allow full excision at surgery.
Suggested Readings Borecky, N., Gudinchet, E, Laurini, R., Duvoisin, B., Hohlfeld, 1., Schnyder, P. Imag ing of cervicothoracic lymphangiomas in children. Pediatric RadioLogy 25 2 : 1 27-30, 1 995. D ubois, 1., Garel, L., Grignon, A., David, M., Laberge, L., Filiatrault, D., Powell, 1. Imaging of hemangiomas and vascular malformations in children. A cademic Radi ology 5 5:390-400, 1 998 May. Fung, K., Poenaru, D., Soboleski, D.A., Kamal, I . M . I mpact of magnetic resonance imaging on the surgical management of cystic hygromas. Journal of Pediatric Surgery 33 6:839-41 , 1 998 Jun. Vazquez, E., Enriquez. G., Castellote, A., Lucaya, J., Creixell, S., Aso, C, Regas, 1. US, CT, and MR imaging of neck lesions in children. Radiographies 15 1 : 1 05-22, 1 995 Jan.
I NECK,
THYRO I D, PARATHYRO I D
Case 28 Clinical Presentation An adult female was brought to the clinic after sustaining a fall and complai ning of neck pain and a sore throat. Physical examination demonstrated slight muscle spasm in the cervical region without point tenderness. An exudative pharyngitis was also present. There was no evidence of a pulsatile neck mass.
B
A
Radiologic Findings Cervical radiographs (Fig. 28-A) demonstrated prevertebral soft tissue widening. 1l1ere was no evidence of cervical fracture. Prevertebral vascular calcifications were not present. Because of the radiographic and clinical findings, an MRI was per formed of the upper neck (Fig 28-B). There was no evidence of abscess. A tubular structure with signal void on all sequences was seen in the prevertebral soft tissues.
Differential Diagnosis: Prevertebral Soft Tissue Widening • • • • •
Abscess Neoplasm Post-traumatic change Lymph fluid Tortuous carotid artery
Diagnosis Medially deviated (tortuous) carotid artery
N ECK, THYROI D, PARATHYROID1
Discussion The cervical prevertebral soft tissues are made up of the prevertebral space and the retropharyngeal space. The prevertebral space is bounded posteriorly by the anterior longitudinal ligament of the vertebral column, and anteriorly by the prevertebral fascia (deep layer of deep cervical fascia.) This space extends the entire length of the vertebral column. The retropharyngeal space is bounded posteriorly by the prevertebral fascia and anteriorly by tbe buccopharyngeal fascia (middle layer of the deep cervical fascia.) The retropharyngeal space extends from the skull base to the level of tbe sixth tho racic vertebral body. The retropbaryngeal space normally contains only lymph nodes. Several other spaces border the retropharyngeal space. The pbaryngeal mu cosal space of the nasopharynx, oropharynx, and hypopharynx are located anteri orly. The carotid space (i.e., poststyloid portion of the parapharyngeal space) is located lateral to the retropbaryngeal space. It contains the carotid artery, internal j ugular vein, the lower four cranial nerves, as well as most of the external carotid artery branches.
Epidemiology Congenital tortuosity of the internal carotid artery has an estimated incidence of < 1 % of the population. This abnormal course results from failure of uncoiling of an embryological bend present at the junction of tbe embryonic dorsal aorta and the third aortic arch. The aberrant vessel will course adjacent to the tonsiLlar capsule of the pharyngeal wall in close apposition with the superior constrictor muscle. Medial deviation of the carotid artery also is seen with normal aging as an inci dental finding. Redundency of the carotid arteries also has been related to a de crease in cerebral flow with rotational motion of the neck and stroke.
Pathophysiology The retropharyngeal space is an area that is frequently involved by pathologic processes arising from contiguous spaces or primarily in that space. A large number of abnormalities involving the retropharyngeal space have been reported, such as abscess, benign and malignant neoplasm, lymphedema, post-traumatic processes, and ectatic carotid arteries. Tortuous carotid arteries and congenital aberrant course of the carotid arteries are relatively less well known. Awareness of these entities becomes significant be cause of procedures that may be performed sucb as oropharyngeal intubation, biopsy, abscess drainage, or other surgical procedures. All of these procedures could result in vascular injury, witb potentiaLly disastrous results.
I maging Findings The presence of this finding in older patients may sometimes be associated with vas cular calcifications on lateral and frontal cervical radiographs. Calcified carotid arteries in normal position overlie the vertebrae on the lateral radiograph and can be seen lateral to the vertebrae on tbe frontal views. In patients with medial devia tion of the carotid arteries, the calcified vessels are anterior to the vertebrae on the lateral view and are usually not visible or superimposed upon the vertebrae on the frontal view. CT or M R I scans with or without intravenous contrast enhancement may be needed for proper localization of the medial position of the carotids. This is espe cially true when vascular pulsations are felt on pbysical examination, but no definite
1 191
INECK,
THYROID, PARATHYROID
c
D
calcifications are seen on plain radiographs. Prior to biopsy, an M R I of another pa tient with metastatic lung carcinoma to the right medial pterygoid muscle and pha ryngeal wall (Fig. 28-C, arrow) revealed a carotid artery adjacent to the mass, in denting the posterior pharyngeal airway. Figure 28-0 shows an enhanced view of a CT scan of another patient with a tortuous carotid artery (arrow). A reformatted coronal enhanced CT scan in another patient (Fig. 28-E) shows the medial position of the vessel.
Suggested Readings Cheung, Y.K., Sham, J.S.T., Chan, F.L., Leong, L.L.Y., Choy, D. Computed tomogra phy of the paranasopharyngeal spaces: normal variations and criteria for tumor ex tension. Clinical Radiology 45: 109-1 13, 1 992. Daniello, N.J., Goldstein, S. l . Retropharyngeal hematoma secondary to minor blunt head and neck trauma. Ear, Nose, and Throat lou.rnaI 73:4 1-43. 1 994.
N ECK, THYROID, PARATHYROml
PEARLS/PITFALLS •
A tortuous carotid artery can show up as a pre vertebral soft tissue mass on radiographic imaging.
•
A tortuous carotid artery bas a characteristic cr and MRI ap pearance.
•
Do not biopsy! ! ! ! ! !
Davis, W.L., Harnsberger, H.R, Smoker, W.R.K., Watanabe, A.S. Retropharyngeal space: evaluation of normal anatomy and diseases with CT and MR imaging. Radi ology 1 74:59--64, 1 990. Gianoli, GJ., Espinola, T.E., Guarisco, J.L., Miller, R H . Retropharyngeal space in fection: changing trends. Otolaryngology and Head and Neck Surgery 1 05:92-100, 1 99 1 . Poe, L.B., Manzione, 1. Y. , Wasenko, J.1., Kellman, R M . Acute internal j ugular vein thombosis associated with pseudoabscess of the retropharyngeal space. A merican Journal of Neuroradiology 1 6:892-896, 1 995. Silver, A.J., Mawad, M.E., Hilal, S.K., Sane, P., Ganti, S.R . Computed tomography of the carotid space and related cervical spaces. Radiology 1 50:723-728, 1 984. Som, P.M., B iller, H.F., Lawson, W., Sacher, M., Lanzieri, c.F. Parapharyngeal space masses: an updated protocol based upon 1 04 cases. Radiology 1 53 : 1 49-156, 1 984. Wong, Y K., Novotny, G.M. Retropharyngeal space-a review of anatomy, pathol ogy, and clinical presentation. Journal of Otolaryngology 7:528-535, 1 978.
E K, T H Y RO I D. PA RATH Y RO I D
Case 29 Clinical Presentation A 56-year-old female with nonHodgkin lymphoma presented with discomfort and a palpable mass in the right anterior neck.
A
B
Radiologic Findings An axial IT section at the in fragloltic level (Fig. 29-A) shows an enlarged right mass lacking enhancement. The central portion i hypoden e with a surrounding rim of enhancement. An axial ection at the supraglottic level ( Fig. 29- B ) hows a peripheral area of enhancement. There are no inflammatory change urrounding the mass. The carotid arteries and left internal jugular vein ( U V ) are unremarkable.
Differential Diagnosis: Anterolateral Neck Mass •
•
•
•
Pseudomasses: hypertrophy of the sternocleidoma lOid muscle, status poSt unilat eral radical neck di section Vascular masses: asymmetry of the j ugular veins, jugular vein ectasia, aneurysm of the jugular vein, jugular vein thrombosis (bland, septic or metastatic clot). aneurysm of the carotid artery, arteriovenous fistula. hemangioma. lymphan gioma y tic ma es: branchial cleft cy t, external laryngocele. cy tic adenopathy. thy roid cysts olid masses: adenopat hy. paraganglioma, schwannoma, ab ce s, neurofibroma. thyroid tumors, lipoma
Diagnosis (' mernal jugular vein thrombo is
1 22
N ECK, THYROID, PA RATH YRO l Dl
Discussion There is a long List of differential diagnoses for a patient presenting with an antero lateral neck mass. Although these masses are easily amenable to diagnostic FNA due to their superficial location, care should be taken to avoid puncturing a normal vessel or a vascular mass. As such, a thorough physical examination and diagnostic imaging should be performed before more invasive maneuvers are undertaken. Asymmetry of the venous drainage of the neck is fairly common either in the number or size of the vessels. The most common and striking of these normal vari ants is asymmetry in the size of the IN's. I n 80% of cases the right IJV is larger than the left. The IJV can be congenitally absent or there may be more than one vessel on the same side.
Epidemiology In the preantibiotic era, septic [JV t hrombosis (lJVT) was a frequent complication of local and regional infectious processes occuring in the head and neck. Lemierre's syndrome, also known as necrobacilosis, was a well known lethal entity referring to suppurative thrombophlebitis of the TlV, secondary to an oropharyngeal infection. With the widespread use of antibiotics, vascular involvement from an infectious process of the head and neck has became rare. However, there has been a resur gence of IJV thrombophlebitis in the past few decades, due to the more aggressive and invasive care of critical patients and the increasing number of intravenous drug abusers. At the present date, the more frequent causes of IJV thrombophlebitis are placement of central venous lines and puncture of the lJV by intravenous drug abusers. The incidence of jugular vein thrombosis i n patients with indwelling catheters is as high as 60% in most series and this number is thought to be an un derestimate, as the diagnosis may be easily overlooked.
Pathophysiology TIle pathogenesis of IJVT involves several factors. Causes relating to endothelial damage include placement of indwelling catheters, central venous lines, direct puncture of the IlV (usually by intravenous drug abusers), surgical damage during head and neck procedures, cervical trauma (open or blunt trauma), radiotherapy and infection. An infection may result from direct in noculation or from hematogeneous or lymphatic spread through the vasa vasorum, which ultimately leads to intimal disruption. In cases of an infected thrombus, the entity is referred to as thrombophlebitis and has more ominous implications. Ton sillitis, otomastoiditis and odontogenic infections are the leading causes of IJV thrombophlebitis. Causes related to hypercoagulable states include malignancies, paraproteinemias, connective tissue disorders (systemic lupus erythematosus), pregnancy, and defects in the coagulation cascade (e.g., protein C and protein S deficiency, deficency of antithrombin TIl, etc. ). The final factor potentiating thrombosis is blood stasis, which is present in states of dehydration, hypotension and prolonged imobilization. lJVT can result from extension of a thrombus arising in intracranial venous sinuses, par ticularly the sigmoid and transverse sinuses. Pathologically a thrombus seen within the LJV may be bland, infected or neo plastic in nature. Clinical history and imaging findings usually allow [or discrimina tion of these entities.
Clinical Findings The clinical presentation of IJVT may be quite nonspecific and not infrequently asymptomatic and detected as an incidental finding. Neck discomfort, pain and a
I NECK,
THYRO ID . PARATHYROID cervical mass are the most frequent presenting symptoms. When there is associated infection. symptoms of sepsis may dominate the clinical picture. Physical exam usu ally reveals a palpable mass along the anterior border of the sternocleidomastoid muscle which may be firm and tender ("cord sign ) . I nflammatory changes in the overlying skin indicate thrombophlebitis. In such cases, fever, elevated white count and elevated sedimentation rate are usually present. Complaints of headaches and other neurologic signs suggest intracranial deep venous thrombus propagation with impending risk of hemorrhagic infarction. Fundoscopic examination will reveal pa pilledema. Complications of IJVT include pulmonary and systemic thromboembolism, su perior vena cava syndrome, and chylothorax. "
I maging Fi n dings The diagnosis of IJVT is most often established based on imaging findings. Imaging is also mandatory for defining the extent of the thrombus and identifying any asso ciated complications. U ltrasound is the modality of choice in the initial evaluation of a patient pre senting with a lateral neck mass. 11lis modality will rapidly determine the location of the mass and reveal whether it is vascular, cystic or solid. Sonographic signs of thrombosis include the presence of an incompressible, dilated vessel with filling of the lumen by hypoecboic material and loss of respiratory phase changes in the cal iber of the vessel. Using Doppler, it is possible to make the diagnosis and to identify any residual flow suggestive of partial thrombosis or recanalization. Collateral cir culation can also be depicted. Limitations of US include the inability to evaluate the vessel above the mandiblular angle and below the supraclavicular notch. and less conspicuity of the surrounding soft tissues and vessel wall. CT with and without contrast enhancement has been advocated as the preferred noninvasive diagnostic modality. The CT appearance depends on the age of the clot and whether the clot is infected or contains a tumor. Acute thrombus ( less than 24 hours) is hyperdense relative to flowing blood and may go undetected if precontrast images are not obtained as it blends with the contrast enhanced blood. Subacute and chronic bland clots appear as hypodense material partially or completely filling the lumen. A surrounding hyperdense rim is frequently noted corresponding to enhancement of the vessel wall . lllis is due to dilation of the vasa vasorum, although local inflammation may also contribute to this phenomenon. Neoplastic clots usu ally cause irregular vessel dilatation due to invasion of the vessel wall. In the enhanced scan enlarged venous collaterals are easily depicted. CT adequately determines the full extent of the thrombus and in some cases also reveals the un derlying cause such as an abscess or tumor of the head and neck. The presence of an ill-defined vessel wall witb surrounding inflammatory changes (e.g., soft tissue thick ening, fatty stranding and loss of fascial planes) is diagnostic of thrombophlebitis. Less commonly, a fluid collection can be seen within or surrounding the vessel wal l representing an abscess. Enlargement of the retropharyngeal space by hypodense material is sometimes seen and is thought to be related to interstitial edema. This should not be mistaken for a retropharyngeal abscess as the cause of the venous thrombosis. Care should be taken with the timing of the contrast bolus in order to avoid a false-negative result. Vascular flow phenomena result in asymmetric and heteroge neous enhancement of the IJV, which may be mistaken for thrombosis or may make it impossible to ensure an accurate diagnosis. This problem became more frequent after the introduction of power injectors and faster scaning times (helical CT). Whenever the diagnosis is in doubt the study should be repeated with a longer de lay between the bolus injection and image acquisition. Another potential pitfall for the inexperienced radiologist is mistaking IJVT for a necrotic lymph node. The ver tically tubular nature and smooth peripheral enhancing rim seen with the former
1 1 24
ECK, TH Y RO I D, PA RATH Y RO I DI
C
hould preve nt thi confusion. Disadvantages of cr include radiation exposure and the need for intravcnou contra t admini tration. An en hanced cr scan of the neck (axial ection at the level of the hyoid bone) in a patient with thromboph lebitis of the left IJV demonstrate a lack of enhancement of the left IJ V, which show a central area of hypodensity surounded by a rim of pe ripheral enhancement (Fig. 29- ) . The wall of the vessel i indistinct and there i oft ti sue den ity and fany tranding encircling the vein. The fa cial plane with the ip i lateral sternocleidomastoid muscle is indistinct. The left common carotid artery is smaller than the right. but patent. There are no abnormalitie in the right jugular vein. On M R I . J VT may be more difficult to detect because slow flow or transient sta is in the ve el may mimic clot as they both appear as intraluminal hyperinten ity. The signal intensity depends on the age of the thrombu becau e of the biochemi cal changes undergone by clotted blood. The multiplanar capability and high oft tis ue re olution make M R I an ideal tool to evaluate the extent of the thrombu and any a ociated soft tis ue changes. M R venography with a two dimensional time of flight gradient echo acquisition has hown excellent correlation with Doppler US and conventional venography in the detection of venous thrombosi . onventional venography wa abandoned as a diagno tic tool due to the inva ive nature of the procedure and the potential for complication related to embolization of the clot.
M anagement IJVT is managed with ant icoagulant therapy, primarily for prevention of pulmonary thromboembolic events. When ant icoagulants are ine ffective. intravascular proce dure may be attempted to remove the clot. In the ca e of an infected clot. broad spectrum antibiotics should be init iated after blood culture are pcrformed. 111c presence of purulent thrombophlebitis with intraluminal absces formation man date' excision of the I1V to prevent serious complications. oncomitant i n fected collections in the head and neck region hould be debrided and appropriately drained. eopla tic thrombus is usually resistant to oral anticoagulation but may repond to hcparin the rapy. However, primary thcrapy should target the malignancy itself with chemotherapy or radiation therapy.
1 25 1
INECK, THYRO I D, PARATHYROLD PEARLS/PITFALLS
An INT appears as a "cord like" mass in the anterolateral neck on radiographic imaging.
•
•
Predisposing factors to INT in clude indwelling catheters, cen tral venous Lines, i ntravenous drug abusers, head and neck in fections, cervical trauma, and hy percoagulable states.
•
E nhanced cr shows an enlarged vessel, lacking contrast enhance ment.
•
Care should be taken not to per form an FNA before excluding a vascular origin for a lateral neck mass.
•
•
•
Care should be taken not to mis take asymmetric and heteroge neous enhancement of the IJV for thrombosis. Care should be taken not to mis take IIV thrombosis for necrotic nodes.
A clinician should take care not to perform an i.ncomplete study which does not not include the full extent of the clot.
1 1 26
Suggested Readings D uffey, D.C, Billings, K.R., Eichel, B.S., Sercarz, 1.A. Internal jugular vein throm bosis. A nnals of Otology, Rhinology and Laryngology 104( 1 1 ):899-904, 1 995 Nov. Finn, 1.p., Zisk, 1.H., Edelman, R R, Wallner, B.K., Hartnell, G.G .. Stokes, K.R .. Longmaid, H.E. Central venous occlusion: MR angiography. Radiology 1 87( 1 ): 245-5 1 , 1 993 Apr. Gudinchet, F., Maeder, P., Neveceral, P., Schnyder, P. Lemierre's syndrome in chil dren: high-resolution cr and color Doppler sonography patterns. CheST 1 1 2( I ):
27 1 -3, 1 997 Jul.
Kalan, A., Tariq, M., Harar, R P.. Gatland, D. Spontaneous internal jugular vein thrombosis and recurrent laryngeal nerve palsy: a rare simultaneous presentation of an occult malignant neoplasm. Joumal of Laryngology and OTology 1 1 0( 1 2): 1 1 66-8, 1 996 Dec. Leontsinis, TG., Currie, A.R., Mannell, A. Internal jugular vein thrombosis follow ing functional neck dissection. Laryngoscope 1 05(2): 1 69-74, 1 995 Feb. Poe, L.B., Manzione, 1. Y., Wasenko, 1.1., Kellman, RM. Acute internal jugular vein thrombosis associated with pseudoabscess of the retropharyngeal space. Americall Journal of Neuroradiology 1 6(4 Su p pl ) 892-6 , 1 995 Apr. Sakai, 0., Nakashima, N., Shibayama, C, Shinozaki, T , Furuse. M. Asymmetrical or heterogeneous enhancement of the internal jugular veins in contrast-enhanced CT of the head and neck. NeLiroradiology 39(4):292-5, 1 997 Apr. Stocks, RM., Milburn, M., Thompson, 1. Unusual neck masses secondary to jugular venous abnormalities: case report and discussion. American Surgeon 63(4):305-9, 1 997 Apr. Terada, Y. , Mitsui, T , Jikuya, T , Kaminishi, Y., Watanabe, K. Infected throm bophlebitis of the right internal jugular vein. Journal of Vascular Surgery 24(6): 1 066-7, 1 996 Dec. Tovi, F., Fliss, D.M., Noyek, A.M. Septic internal jugular vein thrombosis. Journal of Otolaryngology 22(6):41 5-20, 1 993 Dec. :
NE
K, THYROID, PA RATHY ROIDI
Case 30 Clinical Presentation A 65-year-old male presented with a painle s mass in the left po terior neck. On clinical exam a oft, mobile mass was palpated in the left occipital region.
A
B
Radiologic Findings An enhanced cr scan of the neck ( Fig. 30 A ) hows a 2 x 1 .5 cm well-circum scribed, fat density mass in the subcutaneous soft tissues of the left occipital region. A thin enhancing rim is noted. There a re no areas of central enhancement and no internal septations. The attenuation value within the lesion was -85 HOllnsfield units ( H U ) the same as subcutaneous fat. Figure 30-B is a photograph of the surgi cal pecimen from the patient. -
Differential Diagnosis: Fatty Tumors of the Neck •
•
Solitary fatty tumor • With no evidence of contra t enhancement: lipoma, dermoid cyst • With contrast enhancement: angiolipoma, hibernoma, lipobla tomaJlipoblas tomato i , liposarcoma Multiple fatty tumors • Benign symmetric lipomatosis ( Madelung disease) • ushing syndrome
Diagnosis Posterior neck lipoma
1 27
1 N ECK,
THYROID, PARATHYROID
Discussion Epidemiology Lipomas are benign, encapsulated, mesencbymal tumors. Although highly prevalent in the body, only 13% of lipomas occur in the head and neck, most frequently in the subcutaneous soft tissues. Submucosal lipomas also have been reported in the phar ynx, oral cavity and larynx, but are much rarer. The most frequent location is the posterior neck. There is a male predominance, with a peak incidence in the 7th decade. Lipomas are more frequent in obese people. ll1ese tumors tend to increase in size with age and body weight, but do not decrease in size with weight loss.
C
1 1 28
D
NECK, THYRO I D, PA RATH YROIDI
Pathophysiology Pathologically, lipomas are encapsulated, benign tumors composed of adult fat cells, separated into lobules by septae of connective tissue ( fibrolipomas). When highly vascularized, these lesions are classified as angiolipomas. Angiolipomas may be of the infiltrating or non-infiltrating sUbtype. The latter may infiltrate adjacent muscles and neurovascular bundles, demonstrating a more aggressive appearance. However. angiolipomas are rare in the head and neck. Another histologic subtype of lipoma is the spindle cell lipoma, which is charac terized by a mixture of fat cells and spindle-shaped fibroblasts in a collagenous ma trix. This subtype of tumor, has a more aggressive cytologic appearance than the conventional lipoma, with considerable nuclear pleomorphism, and may be con fused with a well-differentiated liposarcoma. Submucosal Lipomas may arise within a muscle or from intermuscular fascial septa. These deep seated lipomas may be sessile or pedunculated. Although benign, these lesions may recur when not completely resected. Malig nant degeneration of a lipoma has never been fully proved. Most experts agree that liposarcomas arise de novo and not from pre-existing lipomas. Lipomas may be congenital or acquired, and are thought to arise from a multi po tential mesenchymal cell. TIlere are several congenital and acquired diffuse, 110n encapsulated lipomatoid lesions which are not true neoplasms. These include, among others, lipoblastomatosis, which is a growth of embryonal lipoblasts seen in children, and benign symmetric lipomatosis, which is a disease of middle-aged men characterized by multiple symmetric accumulations of fatty tissue in the neck.
Clinical Findings Neck lipomas usually present as subcutaneous soft, non-tender, freely movable masses that may have a lobulated surface. TIle most common location is the poste rior neck, but other subcutaneous locations are possible. Axial TI W (Fig. 30-C) and T2W ( Fig. 30-D) images in another patient with a subcutaneous lipoma show a large
F
G
1 NECK,
THYROID, PA RATHY RO I D mass in the anterolateral and inferior aspect of the right neck, insinuating between the thyroid gland and the strap muscles and splaying these structures. There is also posterior deviation of the neck vessels and leftward deviation of the airway. The mass shows well defined margins and follows the signal intensity of subcutaneous fat on both sequences. Coronal T l W image (Fig. 30-E) shows the craniocaudal extent of the mass in the right cervico-thoracic j unction. There are linear areas of hy pointensity within the mass representing fibrous septa. Patients usually present for cosmetic reasons, very rarely with compressive symp toms. Even submucosal lipomas are frequently asymptomatic. The presence of symptoms depends on tumor size and location. They are usually related to airway obstruction, compression of the pharynx or visceral space of the infrahyoid neck, and include dysphagia, dysphonia, stridor, sleep apnea, foreign body sensation in the throat, and irritating paroxysmal cough. On clinical exam, submucosal lipomas are non-specific in appearance and mani fest as any other submucosal mass bulging the walls of the pharynx or larynx. Coro nal M R I of the larynx of another patient with submucosal lipoma of the larynx (Fig. 30-F) shows a submucosal mass centered in the right paraglottic space. The mass has the same signal intensity as the subcutaneous fat and insinuates itself through the adjacent laryngeal structures, including the ipsilateral true vocal cord. An axial Tl W image at the supraglottic level (Fig. 30-G) shows a decrease in the transverse diam eter of the airway caused by this submucosal mass. I n the oral cavity, lipomas may cause discomfort during speech or mastication, and manifest as a yellowish submucosal mass located in the tongue or cheek. Multiple lipomas may be seen in association with several syndromes, such as mul tiple familial lipomatosis, Birt-Hogg-Dube syndrome, Gardner's syndrome, multiple familial and nonfamilial spindle cell lipomas, etc.
Imaging Findings Fat has unique characteristics on both CT and M RI allowing for the diagnosis of most lipomatoid masses. The diagnostic role of imaging is especially important in submucosal lesions, which are non-specific on clinical exam, and have a vast differ ential diagnosis. I maging is also necessary to evaluate the extent of the tumor, which may be transpatial, and to look for any aggressive features. On CT, lipomas manifest as well-circumscribed fat density masses with -65 to - 1 00 HU, with a thin and smooth e n hancing capsule and, eventually, thin intratu moral septations. M R l gives better delineation of the tumor, showing to advantage any infiltrative behavior or transpatial extent. Lipomas follow the signal characteristics of fat, hy perintense on Tl WI and intermediate signal intensity on T2WL When the diagnosis is in doubt additional fat-suppression sequences may be used. Characteristically, lipomas do not show contrast enhancement. This is an important distinguishing fea ture from liposarcoma. Lipomas also tend to displace and compress rather than in filtrate adjacent structures. Lipomas also may be an incidental finding.
M anagement Surgical excision is the treatment of choice, when warranted. Care should be taken to do a complete resection due to the high rate of recurrence. The rate of recurrence is believed to be secondary to microscopic foci of lipomatous inflltration of adjacent soft tissues. The recurrence rate of infiltrating lipomas is as high as as 62% . Lipo suction assisted excision of lipomas may be used in cervico-facial lesions to improve the cosmetic result and the technique can be repeated as needed in case of recur rence, with no increasing risk. Submucosal lesions, depending on their size and lo cation, may be removed endoscopically, or via an external approach.
1 1 30
NECK, THYROID, PA RATHYROIDI
PEARLSIPITFALLS •
•
A lipoma presents as a soft, non tender mass in the posterior neck. 0.n cr and MR i mages a lipoma can be seen as a homogeneous, well-defined, fat density or fat signal intensity mass.
•
•
Care should be taken not to fail to evaluate the full extent of the tumor. The clinician should take care not to mistake diffuse lipomatous processes with true, encapsulated lipomas.
Suggested Readings Abdullah, B.1., Liam, C.K., Kaur, H., Mathew, K.M. Para pharyngeal space lipoma causing sleep apnoea. British fournal of Radiology 70(838 ) : 1 063-5, 1 997 Oct. Calhoun, K.H., Bradfield, 1.1., Thompson, C. Liposuction-assisted excision of cervicofacial lipomas. Otolaryngology and Head and Neck Surgery 1 1 3(4):401-3, 1995 Oct. Eckel, H.E., JungehUlsing, M. Lipoma of the hypopharynx: pre-operative diagnosis and transoral resection. fournal of Laryngology and Otology 1 08(2): 1 74-7, 1 994 Feb. Elango, S. Parapharyngeal space lipoma. Ear, Nose, and Throat fournaI 74( 1 ) :52-3, 1995 Jan. Kransdorf, M.J., Benign soft-tissue tumors in a large referral population: distribution of specific diagnoses by age, sex, and location. A merican fournal of Roentgenology 164(2) :395-402, 1995 Feb. Murty, K.D., M urty, P.S., George, S., Balakrishnan, R., Mathew, K.I., Varghese, G. Lipoma of the larynx. A merican fournal of Otolaryngology 1 994 Mar-Apr, 1 5(2):149-5l . Tsunoda, A . Lipoma in the peri-tonsillar space. fournal of Laryngology and Otology 108(8):693-5, 1 994 Aug. Worsey, 1., McGuirt, W., Carrau, R.L., Peitzman, A.B. Hibernoma of the neck: a rare cause of neck mass. A merican fournal of Otolaryngology 1 5(2):1 52-4, 1 994 Mar Apr. Zeiger, B.w., Zeiger, B.G., Plorer, A., Steiner, H., Fritsch, P.o. Dermal spindle cell lipoma: plexiform and nodular variants. Histopathology 27(6):533-40, 1995 Dec.
�I
INE
K . THYRO I D.
P
RATHYRO I D
Case 31 Clinical Presentation A 66-year-old male presented with a 5-year history of progre ive generalized neck welling and a recent onset oC hoarsne and nonproductive cough. The patient a lso complained of facial congestion upon exertion. On clinical exam there was a disfig uring oft. non-tender. non-mobile, generalized neck swelling with a lobulated ur face. 0 discrete masses were palpated.
A
B
Radiologic Findings cr of the neck demonstrates massive accumulation of homogeneou' fat-density tis 'ue in all the infrahyoid compartments of the neck, the submandibular and sub mental spaces. TIlere is no demarcation from the subcutaneous fat and no encap u lated areas or fibrous septalions. Thi fally tissue infiltrate the visceral pace involving the glollic and upraglollic larynx. with definite infiltration of the true vo cal cord . TIlere is also infiltration of the retropharyngeal and prevertebral space by thi fat tissue. TIle ternocleidomastoid muscle and trap mu des are displaced and
1 132
NECK, THYROID, PARATHYROI DI compressed. The neck vessels are displaced posterolaterally. There is mediastinal ex tent of this increased fat which displaces the thoracic vessels laterally and com presses the mediastinal trachea. The tranverse caliber of the trachea is slightly de creased at this level due to extrinsic compression ( Figs. 3 1 -A, 3 1 -B and 31-C).
Differential Diagnosis: Diffuse Lipomatosis of the Neck •
•
Without inflammatory signs: benign or multiple symmetric lipomatosis, multiple familial lipomatosis, morbid obesity, Cushing's disease/syndrome, lipoblastomato sis (children), liposarcoma With inflammatory signs: Weber-Christian's disease (painful adipositis), Dercum's disease (acute panniculitis), progressive nodular lipomatosis
Diagnosis Benign symmetric lipomatosis (Madelung disease)
Discussion Epidemiology Multiple symmetric lipomatosis is a rare lipodystrophy characterized by the pres ence of multiple non encapsulated fatty infiltrative lesions that occur in a symmetric distribution. The disease has several eponyms including Madelung disease, madelung collar, lipomatosis of Launois-Bensaude, and benign symmetric lipomatosis. Men are affected more often than women with a male-to-female ratio of 1 5 : 1 . For unclear reasons Mediterranean males are predominantly afflicted. The fatty deposits usually appear after 20 years of age and the peak age at pre sentation is between the 4th and 6th decades. Typically, there is rapid progression of the lipomatous tissue over a variable period of time foLlowed by a period of stabi lization or slow progression over many years. A familial incidence has been described with an autosomal dominant mode of in heritance, but most cases are sporadic.
Pathophysiology The etiology of Madelung disease is unknown and various theories have been pos tulated to explain its pathophysiology. There is an unequivocal relationship with al coholism, with 65 to 90% of cases seen in patients with a prolonged history of ethanol abuse and some with chronic liver disease. The accumulation of fat is ex plained by the lipogenic and antilipolytic effect of alcohol, through a decrease in B adrenergic receptors. Another theory is based on a genetic defect in catecholamine-stimulated lipoly sis, which has been associated with hypertrophy of adipocytes in animal models and related to functional sympathetic de nervation. The mechanism of denervation may be related to the alcohol-related neuropathy or to other unknown factors. However, the defect appears to be at the post-receptor level, because the lipolytic response to cyclic AMP is preserved. Finally, another theory places Madelung disease in the group of the phakomatoses. Several metabolic defects have been associated with this disease including hyper lipidemia, glucose intolerance, diabetes mellitus, hyperinsulinism, hyperuricemia, hypertension, hypothyroidism, polyneuropathy, and abnormalities in liver [unction tests. Some of these biochemical defects may be associated with alcoholism itself, al though most have been reported i n patients with Madelung disease who have no history of ethanol abuse. The frequent association with upper aerodigestive tract neoplasms leads some experts to consider this disease a paraneoplastic syndrome.
PatllOl gically, the fat depo its ar nonencapsulated and compo ed of mall. ma ture adipo e cell with a light increa e in fibro a cular troma. 0 cellular pleo m rphi m or atypia are een. There i only one rep rt in the ngli h literature of malignant degeneration of the fatty ti' ue in Madelung di ea e. Once pre nt. the fat dep its do not spontaneousl re 01 e. li nical fi nding
Most patient pre ent ith cervical welling ovcr a peri d of ears taU ing disfig uremcnt. re triction of motion and. ometime I cal pre ure mpt m "Madelung collar" r "bo e collar" were the term used to de crib the appearance pr duced by large p terior cervical lump extending int the anterior neck, ·ubmandibular. ubmental. parotid and upracla icular region When there i in olvcmenl of th deep and vi ceral pace of the ncck. patient may pre ent with dy pnea. hoar ene or d phagia. Media tinal involvement ha been a iated ilh uperi r vena cava yndrome. On phy ical exam, tbe fat dep it are nontender and nonencap ulated. NT ex amination ma di clo e ubmuco al bulge in the pharynx and/or larynx due to ub muCO 31 infiltration and extrin ic compre ion of the e ructure linicall . the main differential diagno i i made with ma ive lymphadenopathy. According to the di lributi n f fat dep it Madelung di ea.e i di ided into two ubI pe In 1 pe I, the fatt dep it are focally circum cribed and di tributed ym metricall in the upper part of the b d , paring the extremitie There may be me\
\
D
1 1 34
E
NECK, THYROID, PA RATHY R O I DI diastinal extention and involvement of the deep spaces of the neck, including the upper aerodigestive tract. Type I l-disease is characterized by a more diffuse in volvement with accumulation of lipomatoid tissue in the entire subcutaneous fat layer, mimicking simple obesity.
Imaging Findings The role of imaging is three-fold: ( 1 ) distinguishing this disease from other causes of diffuse neck swelling when the clinical findings are not clear, (2) evaluating the ex tent of fat accumulation and its relationship to adjacent neurovascular structures for therapy planning, and (3) identifying complications due to compression. CT and M R I are the preferred methods for evaluation of this disease and are both diagnostic, demonstrating nonencapsulated deposits of fatty tissue involving several compartments of the neck. The density and signal intensity of the fat de posits are similar to that of subcutaneous fat with no demarcation between the two. The most common sites of accumulation of fat tissue are the subcutaneous soft tis sues of the posterior and lateral neck, paraspinal region, supraclavicular fossa, an terior neck, prevertebral space, parotid region, submandibular and submental re gions, and mediastinum. Submucosal fat deposits also may be detected in the visceral space of the neck, even when not clinically apparent. Sectional imaging de tects compression and displacement of adjacent structures and allows quantification of airway compromise. M R I , having the advantage of multiplanar capability, better depicts the extent of the fatty deposits and compression of adjacent structures. An enhanced axial CT scan of the neck of another patient with Madelung disease at the glottic (Fig. 3 1 -D ) and supraglottic (Fig. 3 1 -E ) levels show diffuse accumula tion of fatty tissue in the anterior and lateral compartments of the neck, sub mandibular space, prevertebral, and visceral spaces of the neck. The submandibular glands are displaced anteriorly and compressed, and the sternocleidomastoid mus cle and neck vessels are displaced posteriorly by these fat deposits. The supraglottic larynx and true vocal cords are infiltrated by fat. Direct laryngoscopy (Fig. 3 1 -F) of the same patient shows fullness of the paraglottic spaces bilaterally with a smooth yellowish surface. The main distinguishing features from other forms of diffuse lipomatosis include the absence of encapsulation, absence of inflammatory signs in the adjacent soft tis sues, and the distribution of fatty deposits. According to some experts fat suppres sion and chemical shift imaging can be used to distinguish encapsulated lipomas that are seen in multiple hereditary lipomatosis, and progressive nodular lipomatosis from Madelung disease. Imaging may also be used to monitor medical therapy and to detect complications of surgical procedures, such as hemorrhage and infection.
M anagement 1l1erapy may be required for cosmesis, for functional problems, or to alleviate com pressive symptoms. Correction of metabolic imbalances and alcohol abstinence may help to control the disease, but do not reduce the fatty deposits. Medical therapy us ing a B2 agonist (salbutamol) has been used with variable success and may help maintain a certain degree of normal lipolysis. Liposuction is tbe preferred treatment for subcutaneous involvement as it can safely be performed under local anesthesia. 1l1is is an important advantage in this patient population, usually poor surgical candidates, due to respiratory distress and chronic liver disease. Also, tbe amount of scarring is much less when compared to open lipectomy, allowing repeated procedures for recurrent disease. Both open and closed resection of these fat deposits have a high recurrence rate and are considered palliative. Open lipectomy is the modality of choice for deep-seated fatty deposits, and when the proximity of the airway or major vascular structures makes liposuc tion unsafe.
INECK,
THYROID, PA RATH YROI D
PEARLSIPITFALLS Madelung disease often presents with diffuse neck swelling and the appearance of a "horse col lar."
•
Madelung disease is most often seen in middle-aged males with history of chronic alcohol intake.
•
•
•
Accumulation of non-encap u lated fat i n the subcutaneous soft tissues, deep spaces of the neck, visceral space, or mediastinum is commonly seen in Madelung dis ease. Care should be taken not to mistake the disease for simple obesity.
•
Failure to recognize submucosal deposits of fat can cause airway compromise or other compres sive symptoms (superior vena cava yndrome).
•
There is sometimes insuffi c ient coverage of the neck and medi astinum, when imaging this dis ease.
1 36
Suggested Readings Borges, A., Torrinha, E, Lufkin, R.B., Abemayor, E. Laryngeal involvement in mul tiple symmetric lipomatosis: the role of computed tomography in diagnosis. Ameri can Journal of Otolaryngology l 8(2): l 27-30. 1 997 Mar-Apr. Chung, J.Y., Ramos-Caro, EA.. Beers. B.. Ford, M . I .. Flowers, E Multiple lipomas, angiolipomas, and parathyroid adenomas in a patient with Birt-Hogg-Oube syn drome. Il11ernational Journal of Dermatology 35(5):365-7, 1 996 May. Feldman, D.R .. Schabel. S.1. Multiple symmetrical lipomatosis: computed tomo graphic appearance. SoLt/hern Medical Journal 88(6):68 1-2, 1 995 Jun. Kitano, H., akanishi, Y.. Takeuchi, E., agahara. K. Multiple symmetrical lipo matosis: no longer just a Mediterranean disea e? Journal of Oto-Rhino-Iaryngology and Its Related Speciallies 56(3): 1 77-80, 1 994 May-Jun. Martin, OS, Sharafuddin, M., Boozan, 1., Sundaram, M., Archer, C MUltiple sym metric lipomatosis (Madelung's disease). Skeletal Radiology 24( I ):72-3. 1 995 Jan. Murty, K . D., Murty, P.S., George, S., Balakrishnan, R., Mathew, K.I., Varghese. G. Lipoma of the larynx. American Journal of Otolaryngology 1 5(2): 1 49-5 1 , 1 994 Mar Apr. Parmar. C. Blackburn, C Madelung's disease: an uncommon disorder of unknown aetiology? British JOllrnal of Oral and Maxillofacial Surgery 34(5):467-70. 1 996 Oct.
NE
K, T H Y RO I D, PA RATH Y RO I D1
Case 32 Clinical Presentation A 30-year-old male pre ented with malai e. dy phagia. and neck pain and stiffnes . linical exam revealed a eptic patient with erythema of the po terior pharyngeal wall and no definite mass. The neck was painful with motion. l1le patient's prior clin ical history was uneventful.
A
B
Findings Lateral plain films of the cervical region how marked full ness of the prevertebral soft t issues, which measure approximately 20 mm in lhickness at the level of C2. The airway is di placed anteriorly, but appear adequate in caliber. No soft t issue em physema i noted. There is a l 0 mild traightening of the cervical pine with 10 s of tbe normal lordosis. The cervical vertebral bodies and di k paces showed no ab normalities ( Fig. 32-A). An enhanced cr scan performed the same day shows a hy poden e mass with an enhancing wall extending fTom the level of the nasopharynx to the post-cricoid region. No mediast inal exten ion wa noted ( Fig. 32- 8 ) .
Differential Diagnosis: Enlargement of the Prevertebral Soft Tissue • •
Ma s within the prevertebral space M ass in the retropharyngeal pace: adenit is/celluliti . ab cess, edema, hematoma, lipoma, metastatic lymphadenopat hy, direcat invasion from na opharyngeal or oropharyngeal squamous cell carcinoma, Kawa aki' disease. atypical third branchial cleCt cyst, hemangiomallymphangioma.
Diagnosis Retropharyngeal absces
1 37 1
1 NECK,
THY RO I D, PA RATHYROID
Danger S pa c e
M i d d l e L a y e r of t h e Deep C e r vi c a l
Fascia
( B u c c o - P h a r y ng e a l F a s c i a )
A l ar F a s c i a
Ret rophar yngea l
(Deep L a y e r of t h e Deep C e r v i c a l F a s c i a )
Space
Pre- Vertebral Fasci a J u gul a r Vei n
(Deep L a y e r of t h e Deep C e r v i c a l F a s c i a )
P r e - Vert ebral Space
C
Caroti d Artery
Discussion The retropharyngeal space ( RPS) is a midline space in the deep neck bounded an teriorly by the middle layer of the deep cervical fascia (buccopharyngeal fascia) and posteriorly by the deep layer of the deep cervical fascia (prevertebral fascia). This space extends from the base of the skull to the level of the body ofT4 and is a route for disease extension into the mediastinum. Lymph nodes and fat are the only con tents of the retropharyngeal space and, therefore, primary disease processes of this space are uncommon. A midline raphe separates the right and left chains of lymph nodes lying in this space (nodes of Rouviere). Posterior to the RPS lies a virtual space between two slips of the deep layer of the deep cervical fascia, often referred to as the danger space. This potential space can serve as a conduit for spread of dis ease to the level of the diaphragm, where these two leaflets join together. The most posterior midline space is the prevertebral space which extends from the skull base to approximately T3 (Fig. 32-C). It has been argued that the retropharyngeal nodes regress by the age of 6 years, which would account for the higher incidence of RPS infection in children. How ever, retropharyngeal adenopathy is commonly seen in older patients with head and neck malignancies, especially nasopharyngeal carcinoma.
Epidemiology The incidence of retropharyngeal space infections dropped dramatically during the antibiotic era. However, there has been a recrudescence of this disease in the past 3 decades due to an increasing population of immunocompromised patient . Children are particularly prone to retropharyngeal abscesses due to the spread of infection from adenoidal, tonsillar or middle ear disease. Some series report 95% of retropha ryngeal infections occurring before the age of 6 years. In adults. males are more fre-
1 1 38
N ECK, THYRO I D, PARATHYROIDI quently affected then women (2 : 1 ) and predisposing factors should be carefully searched.
Pathophysiology A retropharyngeal infection can result from spread via lymphatic drainage, direct extension of prevertebral space infection or from direct inoculation related to pen etrating trauma. I n fection of the retropharyngeal space may also be iatrogenic (sec ondary to surgery), may result from foreign body penetration, or from esophageal perforation. The areas whose primary lymphatic drainage is the retropharyngeal lymph nodes include Waldeyer's ring, the sinonasal tract, the oral cavity and the middle ear. I n the pediatric population upper respiratory infections involving these sites are very com mon and may extend into the deep spaces of the neck when untreated. Other pos sible etiologies in children include blunt trauma to the oropharynx and impacted foreign bodies. Toddlers are especially prone to oropharyngeal trauma due to unsteady gate and tendency to walk with sharp objects in their mouth. Trauma may result in undetected oropharyngeal hematoma which may secondarily become infected. The organisms most commonly cultured from these deep space infections are group A beta-hemolytic streptococci, Staphylococcus aureus and Hemophilus in fluenza. I n adults spread of infection to the deep spaces of the neck is quite infrequent in the absence of predisposing factors. Odontogenic infection due to poor oral hygiene and spread from a peritonsillar abscess are the most common associations. Under lying illnesses such as diabetes mellitus, chronic alcoholism, malignancy, H I V infec tion, and other causes of immunocompromise are usually present. Spread from cervical osteomyelitis is not uncommon and mycobacterial and fun gal infections should be considered in the differential diagnosis. I n the iatrogenic group the most frequent causes are endoscopy and orotracheal intubation which may lead to pharyngeal mucosal tears and subsequent infection. Impaction of for eign bodies and esophageal perforation also should be considered i n an adult patient. A great variety of organisms are cultured from retropharyngeal abscesses in adults, depending on the cause of infection and underlying clinical status. These range from Gram negatives to anaerobic organisms and acid fast bacilli.
Clinical Findings Symptoms vary with the patient's age although in most cases patients are septic at presentation. I nfants and young children usually present with difficulty feeding and drooLing. I n older children, obstructive symptoms, particularly stridor, are the most typical presentation. Gastrointestinal symptoms such as nausea and vomiting also may occur and may draw the attention of the clinician away from the head and neck region. The onset of symptoms may be insidious and the patient may not come to medical attention until there is impending airway obstruction. Adults usually present with sore throat, odynophagia, dysphagia and neck pain. On clinical exam there may be inflammatory changes in the pharyngeal walls and a pharyngeal bulge, although these findings are inconsistent. Therefore, a normal ENT examination does not exclude the diagnosis of a retropharyngeal abscess. Fever, leucocytosis and elevated sedimentation rate are the rule.
I maging Findings A lateral plain film of the neck should be performed in any patient with suspected retropharyngeal abscess. Fullness of the prevertebral soft tissues is the hallmark of
K. T H Y ROID. PA RAT H Y RO I D this condition. As a rough guideline. there i prevertebral oft ti ue welling when the distance bet' een the anterior a pect of and the posterior pharyngeal wall is greater than 7 mm for adult and children or when the same distance at 7 meaurc greater than 22 mm in adult or 14 mm in children. I nterst itial air may be een within the prevertebral soft tissue and, although infrequent, is a valuable diagnos tic sign. The film should be obtained during quiet respiration becau e with forced expiration (especially i n children). the thickne s of the pharyngeal oft tis ues i
D
1 1 40
E
NECK, THYROID, PA RATHYROIDI overestimated. Plain films of the neck are also useful to rule out other pathologic processes with similar clinical presentations such as supraglottitis and cervical os teomyelitis. Cross sectional imaging is the only way to distinguish between retropharyngeal and prevertebral space infections, and this distinction is based upon the location of the mass or fluid collection with respect to the prevertebral fascia. Retropharyngeal masses displace the fascia and prevertebral muscles posteriorly. Conversely, prever tebral masses displace these structures anteriorly. Another distinguishing feature of retropharyngeal space masses is that they tend to be lateral in position due to the presence of the median raphe as opposed to prevertebral masses, which are usually midline. However, inflammatory processes may violate fascial planes, making it im possible to accurately determine the site of origin. CT is superior to M R I in the evaluation of infectious processes in the head and neck region because it is more accurate in distinguishing adenitis and phlegmon from a true abscess. For this purpose contrast administration is mandatory. Adenitis presents as enlarged lymph nodes, which may or may not show a central area of necrosis and ill-defined margins, suggesting extracapsular spread. A phlegmon appears as an ill defined enhancing soft tissue density, whereas a hypodense lesion with an enhancing rim defines an abscess. Enhanced axial CT at the level of the oropharynx in a patient with retropharyngeal abscess due to a fungal infection (coc cidioidomycosis) (Fig. 32- 0 ) shows a large bilobed mass in the retropharyngeal compartment, displacing the longus colli muscles posteriorly and the airway anteri orly. This well circumscribed mass is cystic and shows a thick enhancing wall. The largest component of this mass lies on the left side and compresses the airway at this level. Axial T 1 WI (Fig. 32-E) and axial TIWI (Fig. 32-F) of the same patient at the level of the nasopharynx show the superior extent of this lesion, which involves the left longus colli muscle. The signal characteristics are those of a fluid collection. TIlis distinction has important consequences in the management of these patients, be cause only an abscess is amenable to surgery. Air-fluid levels and the presence of gas pockets are also more easily detected with CT. Figure 32-0 depicts an enhanced axial CT of the neck at the glottic level in a patient with retropharyngeal abscess that shows retropharyngeal fullness with interstitial gas. The fascial planes between the retropharyngeal space and the carotid sheath are obscured bilaterally. Anaero bic organisms were isolated on culture. Another important consideration for surgical planning is the delineation of the full extent of the lesion. Therefore, a cross sectional study should be performed from the skull base to the diaphragm. Extension of an infection into the mediastinum is not uncommon and can be accompanied by pleural and pericardial effusions. Eval uation of airway patency is also mandatory and may alert the clinician as to the need for tracheostomy placement. A CT may localize the primary site of infection, detect radiopaque foreign bodies and localize esophageal perforations (using oral contrast administration). I nvolvement of the carotid space by infection may have disastrous complications such as jugular vein thrombosis and spasm or thrombosis of the internal carotid artery. TIl is is another reason to perform an enhanced CT study. I n children, helical CT may circumvent the need for sedation. It should be kept in mind that a CT is not 1 00% accurate in the evaluation of deep space infections. A recent study showed a significant rate of false-positive results for the presence of abscess ( 13% ) and proposes that the decision for surgery should be based on both clinical and imaging data. M R I is especially useful when the primary site of infection is the prevertebral space, as it is the method choice to detect epidural abscesses and to evaluate the in tegrity of the spinal cord. On MRT, a retropharyngeal abscess appears hypointense on TI WI (Fig. 32-E ) and hyperintense on TIWl (Fig. 32-F). When intravenous contrast is used. ring en hancement is seen. Gas and foreign bodies are more difficult to detect and the im ages more difficult to interpret due to susceptibility artifacts.
1 41 I
ECK, THYROID, PARATHYROID
PEARLSIPITFALLS A retropharyngeal abscess is more frequently found in chil dren and immunocompromised patients.
•
•
Do not exclude a retropharyn geal abscess on the basis of a normal ENT/clinical exam.
•
A lateral plain film of the neck should be the first imaging study.
•
An enhanced cr scan is manda tory to: (1) distinguish retropha ryngeal from prevertebral space infections, (2) distinguish adeni tis, flegmon and non-infected fluid collections from abscess, and (3) evaluate the full extent of the inflammatory process.
•
Care should be taken to perform a complete study (including the mediastinum).
•
Care should be taken to not con fuse adenitis or phlegmon with an abscess.
•
Care should be taken for the clinician to recognize vascular complications, especially throm bosis of the ICA
M R I is the only imaging method that adequately depicts the layers of the deep cervical fascia allowing a more precise localization and better anatomic delineation of the lesion ( Figs. 32-E and 32-F).
Management The management of retropharyngeal infections depends on both the patient's clini cal status and the imaging findings. Adenitis and phlegmons are managed conserva tively with antibiotics and antiinflammatory drugs. When the clinical response is not adequate, tissue should be obtained for culture and sensitivity tests. When the pres ence of an abscess is certain, the lesion should be drained surgically or under imag ing guidance. Complex, multi loculated abscesses and those with extremely viscous secretions should preferably be managed surgically, because they would require multiple drains and longer hospitalization. Surgery is also preferred when patients are severely septic or when there is mediastinal extension.
Suggested Readings Babl, EE., Pascucci, R. I mages in clinical medicine. Retropharyngeal abscess. New England Journal of Medicine 337(7):472, 1 997 Aug 14. el-Sayed, Y. , al Dousary, S. Deep-neck space abscesses. Journal of OIO/aryngology 25(4):227-33, 1 996 Aug. Gidley, P w. , Ghorayeb, B.Y., Stiernberg, CM. Contemporary management of deep neck space infections. OlOlaryngology and Head and Neck Surgery 1 16( 1 ): 1 6-22. 1 997 Jan. Goldenberg, D., Golz, A, Joachims, H.Z. Retropharyngeal abscess: a clinical review. Journal of Laryngology and Otology 1 1 1 (6):546-50, 1 997 Jun. Hewel, K., Kioumehr, E, So, G., Wang, M . Infected third branchial cleft cyst: retropharyngeal extension to the superior mediastinum. Canadian Association of Radiologists Journal 47( 2 ) : 1 1 1-3, 1 996 Apr. Karkanevatos, A, Beasley, N.1., Swift, A.C Acute non-tuberculous retropharyngeal abscess in an adult. A case report and review of the literature. Journal of Laryngol ogy and Otology 1 1 1 (2) : 1 69-7 1 , 1 997 Feb. Lazor, 1.B., Cunningham, M.J., Eavey, R.D., Weber. A.L. Comparison of computed tomography and surgical findings in deep neck infections. Otolaryngology and Head alld Neck Surgery 1 1 1 (6):746-50, 1 994 Dec. Marra, S., Hotaling, A1. Deep neck infections. A merican Journal of Otolaryngology 1 7(5):287-98, 1 996 Sep-Oct. Nokes, S.R., Adametz, J., Gardner, G., Beaton, J.N. Radiological case of the month. Blastomycosis osteomyelitis with epidural and retropharyngeal abscess. Journal of the A rkansas Medical Society 92(5):253-4, 1 995 Oct. Sakaguchi, M., SalO, S., [shiyama, T., Katsuno, S., Taguchi, K. Characterization and management of deep neck infections. in ernational Journal of Oral and Maxillofacial Surgery 26(2 ) : 1 3 1 -4, 1 997 Apr.
1 1 42
NECK, THYROID, PARATHYROIDI
Case 33 Clinical Presentation An adult male presented with a 5-year history of an asymptomatic left cervical mass, which was non tender and without bruit. The patient denied dysphagia, stridor, and neurologic symptoms.
A
Radiologic Findings An axial T l W image ( Fig. 33-A ) through the level of the valleculae shows a left sided mass with a heterogeneous "salt and pepper" appearance. The internal and ex ternal carotid arteries are displaced anteromedially and splayed.
Differential D iagnosis: Neck Mass • • • • •
Schwannoma Carotid body tumor Adenopathy Branchial cleft cyst Lymph node
Diagnosis Carotid body tumor
ECK, THYRO I D, PARATHYROID
Discussion Epidemiology Paragangliomas are benign tumors arising from paraganglion cells. The most com mon paraganglioma in the head and neck is a carotid body tumor. An increased incidence of carotid body tumors has been found in people living at high altitudes. The carotid body tumor arises at the bifurcation of the common carotid artery. As it grows it becomes adherent and difficult to separate from the major vessel. There is a tendency to a multicentricity of tumors ( 10% ) , especially in a patient with a positive familial history (26% ). The incidence of true malignancy showing metastasis is higher in a carotid body tumor ( 1 0% ) than the overall incidence, vary ing from 2%-6% . The biologic behavior or natural course of the tumors is not clearly correlated with histologic appearances.
Pathophysiology A paraganglioma is a slowly growing neuroendocrine neoplasm that arises from neural crest derivatives. Chemodectoma, glomus tumor, nonchromaffin paragan glioma, and neurocristopathic tumor are the most common names given to this lesion. Precapillary arteriovenous shunts and nonchromaffin cells are characteristic of the histologic appearance of these tumors. Paragangliomas can be classified by their locations: tympanic and jugular tumors are less frequent; tumors of carotid and vagal locations are more frequent. Sheets of tumor cells are often divided into ball-like clusters ("Zelballen " ) separated by thin fibrovascular septa.
Clinical Fi ndings Paragangliomas often present as slowly growing and compressible masses, or cranial nerve paralysis, according to the location. A vertically fixed and laterally movable mass is a characteristic finding in a carotid body tumor.
c
B 1 44
NECK, THYRO I D, PARATHYROIDI
E
o
Imaging Findings Radiological diagnosis of this tumor is based on location and characteristic byper vascularity. M R I has some advantages over CT in delineating and characterizing the lesion witb its superb soft tissue contrast. The hypervascular nature of the tumor can be demonstrated by MR with signal void of flowing vessel. MR angiography can show the major vascular structures adjacent to the tumor as well as tumor vascular ity. The characteristic splaying of the carotid bifurcation is characteristic of a carotid body tumor. The most characteristic findings on an M R I are multiple low signal intensity ar eas that represent vascular flow voids throughout the tumor. H igh and low signal intensity regions on MR images are called a "salt and pepper" appearance. This appearance is not specific for paraganglioma but may be seen with a number of hypervascular lesions. Figures 33-B and 33-C show another patient witb a less common appearance of a carotid body tumor. The mass is circumferentially located around the common, in ternal and external carotid arteries. Figure 33-B is through the common carotid artery and Figure 33-C is slightly more cephalad through the level of the hyoid bone.
M an agement Surgery is the tberapy of choice for most patients with this condition. While con ventional angiography is generally no longer used for diagnosis, preoperative em bolization is used in most cases to limit bleeding at surgery. The arterial pbase of an angiographic study in a patient with a carotid body tumor (Fig. 33-0) shows the typ ical appearance of the displacement of the internal and external arteries by the mass at the bifurcation. During the capillary phase (Fig. 33-E) dense contrast enbance ment is noted. Radiation therapy is used in some patients who are not surgical can didates.
I N ECK,
THYRO I D, PA RATHYROID
PEARLS/PITFALLS •
The carotid body tumor is a mass tbat is centered at tbe bifurcation of the carotid arteries.
•
A carotid body tumor has a "salt and pepper" appearance on MRl.
•
Do not biopsy or perform surgery without a preoperative embolization.
•
Care must be taken to detect synchronous or metachronous lesions.
Suggested Readings Batsakis, J.G. Tumors of the head and neck: clinical and pathological considerations, 2nd ed. Baltimore: Williams and Wilkins, 1 979. Olsen, WL., Dillon, WI', Kelly, WM. MR imaging of paragangliomas. American Journal of Neuroradiology 7: 1039-1 042, 1 986. Shugar M.A., Mafee M.F. Diagnosis of carotid body tumors in dynamic computer ized tomography. Head Neck 5urg 4:5 1 8-521 , 1 982. Vogl , T., Bruning, R., Schedel, H. Paragangliomas of the jugular bulb and carotid body: MR imaging with short sequences and GD-DTPA enhancement. AJNR 1 0:823-827, 1 989.
Case 34 Clinical Presentation w grov ing rna in the right lal53-year-old female presented with a painlc eral neck. n clinical exam the rna i firm, non-lender and non-pul atile.
A
B
147 1
I NECK,
THYROID, PA RATHYROID
Radiologic Findings A sagittal T l W image ( Fig. 34-A) shows a 2.5 X 1 cm well-circumscribed, oval mass, with its long axis parallel to the neck vessels. The mass is located within the right carotid sheath, displacing the common carotid artery and jugular vein anteri orly. The axial T2W image (Fig. 34-B) shows heterogeneous T2W hyperintensity and anterior displacement of the neck vessels. No relationship with the cervical nerve roots is noted. Coronal post-contrast Tl W image (Fig. 34-C) shows intense, homo geneous enhancement.
Differential Diagnosis: Solid Mass in the Carotid Sheath • •
Inflammatory/Infectious: lymphadenopathy, traumatic neuroma Neoplasm • Benign: nerve sheath tumor (schwannoma, neurofibroma, ganglioneuroma. ganglioblastoma, ganglioneuroblastoma), paragangLioma (glomus vagale, carotid body tumor, glomus jugulare), bpoma, hemangiolymphangioma, granu lar cell tumor (rhabdomyoblastoma), thyroid and parathyroid tumors • Malignant: metastatic lymphadenopathy, lymphoma
Diagnosis Vagus nerve schwannoma
Discussion Epidemiology Twenty-five to 45% of nerve sheath tumors occur in the head and neck region. [ n the neck, these tumors may arise from the vagus nerve, sympathetic chain o r cervi cal nerve roots, including the brachial plexus. Often the nerve of origin is difficult to determine preoperatively. Benign peripheral nerve tumors include two basic tumors with different patllo logic features: schwannomas and neurofibromas. Over the past decades, these tu mors have been known by a multitude of names, such as neurilemoma, neurinoma, perineural fibroblastoma, fibroma of the nerve, peripheral glioma, and gliofibrosar coma. Schwannomas may present at any age although a peak incidence is noted between the 4th and 6th decades. Neurofibromas tend to occur earlier in life (2nd and 3rd decades), especially when associated with neurofibromatosis type [ (NF- [ ) . Neuro fibromas may occur as a solitary lesion or, most often, be multiple. Only 1 0% of pa tients with neurofibromas have N F type I. Schwannomas may also be multiple.
Pathophysiology Nerve sheath tumors originate from Schwann cells or neuroectodermal perineural cells. Pathologically, there are two distinct types of nerve sheath tumors with distinct histologic patterns and clinical behavior. Schwannomas or neurilemomas are well encapsulated tumors characterized by the presence of two different types of tissue: Antoni A, which is the cellular component made by Schwann cells and fibroblasts, and Antoni B, which is composed of myxoid elements. Hemorrhage and cystic de generation may be seen in larger tumors. Neurofibromas are well circumscribed nonencapsulated nerve sheath tumors composed of Schwann cells, fibroblasts and swirls of neuronal elements running through the bulk of the tumor. Plexiform neurofibromas are a histologic variant, pathognomonic of NF I, with a more aggressive behavior. Whereas schwannomas
N ECK, THYROID, PA RATHYROIDI rarely, if ever, undergo malignant degeneration, neurofibromas show a 5% to 15% rate of malignancy, which is higher in patients with N F type 1.
Clinical Findings Symptoms and signs depend on the location of the tumor and nerve of origin. The most common clinical finding is a painless, slowly growing mass in the anterolateral neck. Neurologic symptoms may arise from direct involvement of the nerve by tu mor or from adjacent nerves due to compression and ischemia. Involvement of the cervical sympathetic chain may infrequently present with Horner's syndrome (myosis, ptosis and anhydrosis). Vagus nerve tumors may present with dysphonia, dysphagia, hoarseness and arrhythmia. H owever, the presence of these symptoms does not allow for topographic localization of the tumor, because the same symp toms may result from compression by an adjacent tumor. Tumors located higher up, near the skull base may involve the jugular foramen causing neuropathy of the lower cranial nerves. Nerve sheath tumors arising in the cervical nerve roots present with sensory and motor deficits in the distribution of the involved root, usually paresthesia and mo tor weakness. Pain may occur with large tumors, particularly when there is significant compres sion and bone remodeling. On physical exam, the mass is usually non-tender. A sensation of electric shock may be elicited by palpation. The mass is often mobile laterally but not along the axis of the nerve. Pulsation and bruits should be sought to exclude highly vascular lesions, such as a carotid artery aneurysm and a paraganglioma. A biopsy should not be performed before imaging studies rule out these diagnostic possibilities. A biopsy of nerve sheath tumors may be hazardous, causing excruciating pain or nerve damage. A complete physical exam, including a thorough neurologic examination, is rec ommended for all patients, especially when neurofibromatosis is a consideration. Electromyographic testing with evaluation of nerve conduction may be helpful in the diagnosis and localization of lesions involving the cervical nerve roots.
Imaging Findings The main purpose of imaging masses in the anterolateral compartment of the neck is to distinguish between solid and cystic lesions and to detect vascular or highly vas cularized lesions. These goals may be achieved by using ultrasound with Doppler or cross-sectional imaging. Once the solid nature of the lesion is established, several imaging features should be assessed to narrow the differential diagnosis. These in clude the exact location of the lesion, the level of the lesion within the neck, direc tion of displacement of adjacent structures (especially the neck vessels), and the de gree of vascularity. Schwannomas of the vagus nerve present as fusiform, well-circumscribed soft tis sue masses, located in the carotid sheath, dorsally to the internal carotid artery ( lCA), displacing the neck vessels anteriorly. The long axis of the mass parallels the course of the n erve. On CT, schwannomas are typically iso- to hypodense to muscle, depending on tumor cellularity, degree of Antoni B myxoid tissue and presence of hemorrhage or cystic degeneration. In addition, the degree of enhancement is vari able. Although most lesions show little to moderate enhancement, one third of schwannomas are highly vascularized and may mjmjc the appearance of a paragan glioma. Contrast enhancement appears to be related to extravascular leakage with stagnation and pooling of contrast into the tumor bed. Dynamic CT and M R I stud ies usually show a flat, hypovascular curve contrasting with the early arterial peak of paragangliomas. When the lesion is centered at the skull base or extends superiorly into the jugu-
ECK, THYROID. PARATH Y RO ID lar foramen, it may cau e calloping of the bone, a opposed to the permeative change usually een with paraganglioma. M R I bener demon trate the fusiform morphology of the tumor on sagillal and coronal sections. Schwannomas are usually hypointense to muscle on T l W images. bright on T2W image and how intense and uniform enhancement. Rarely these tu mors show How voids. In the rare instance where a schwan noma is highly vascular and how How void or a small. Ie s than 2 cm, glomu tumor contains no How voids. differential diagnosis between these lesions may not be po ible. However, the man agement is the same, with a t ranscervical urgical approach and preoperative em bolization, if required. Large chwannomas may undergo significant cystic degeneration cau ing diag nostic problem with other acquired or congenital cy tic lesions of the neck. Glomu jugulare tend to be centered in the region of the jugular foramen and only rarely extend below t he level of the hyoid bone. Permeative bony changes of the jugular foramen are helpful in the differential diagno is. arotid body tumors have a typical location, centered in the carotid bifurcation and splaying apart the I A and external carotid artery (E A). Ultrasound is useful in differentiating cervical nerve sheath tumors from lym phadenopathy. Ultrasonic features that favor a neural origin include the pre ence of a olitary, oval shaped hypoechoic lesion with po terior enhancement and ab ence of a fally hilum. Exophytic thyroid nodules and parathyroid adenomas are al 0 a con ideration in the differential diagnosis. Parathyroid adenoma tend to be located more medially in the tracheoe ophageal groove. eurofibromas are u ually indi tinguishable from chwannomas with imaging, but a low, almost water den ity lesion is characteri tic of neurofibromas. Typically, the plexi.form variant of this tumor has a central area of low density/intensity that correspond to the central fibrou core. Fatty degeneration i also a classic feature of neurofibroma . When extensive, it may mimic a lipoma. The pre ence of aggressive imaging features such as ill-defined margin, bony de struction, or the presence of distant spread, indicates a malignant nerve sheath tu mor (neuroectodermal sarcoma). However, the ab ence of these aggressive features does not confirm a benign nature. Nerve sheath tumors arising from the cervical sympathetic chain are indistin guishible from vagus nerve tumors, as the sympathetic chain is located posterome dially to the ICA and tumors in this location also displace the vessels anteriorly. Glomus vagale tend to occur within the carotid sheath at the skull base.
D
1150
E
N ECK, THYROID, PA RATHYROIDI
'pEARLSIPITFALLS •
•
•
•
•
A vagus nerve schwan noma is a painless, slow-growing mass in the carotid sheath, that displaces the neck vessels anteriorly. The typical imaging appearance of a cervical nerve tumor is a dumbbeU-shaped mass bridging and scalloping the cervical neural foramina. A dynamic cr or M R I study shows a flat arterial curve. Care should be taken not to mis take a nerve sheath tumor for lymphadenopathy. If the clinician fails to recognize multiple lesions the diagnosis of neurofibromatosis may be missed.
Peripheral nerve sheath tumors arising from the cervical nerve roots or brachial plexus manifest as soft tissue masses in the lateral neck, retroclavicular area, or ax illary region. The typical imaging appearance of a cervical nerve root tumor is a dumbbell-shaped lesion that bridges and scallops the neural foramen, with in tradural and extraforaminal components. The extraforaminal component may ex tend between the anterior and middle scalene muscles into the posterior cervical space and axillary apex. Axial postcontrast T1 W (Fig. 34-D) and TIW (Fig. 34-E) M R r of the neck of a patient with solitary neurofibroma of the right C5-6 nerve root through the level of the true vocal cords show a fusiform mass posterolaterally to the right carotid sheath, along the course of the right C5-6 nerve root. There is no evidence of intracanalar or intraforaminal components. Imaging also is required for surgical planning and follow up of asymptomatic pa tients treated conservatively. Tumor growth and interval appearance of aggressive features should prompt intervention.
Management Nerve sheath tumors are managed surgically. Although most schwannomas may be resected without damaging the nerve of origin, resection of neurofibromas is more hazardous and may result in severe morbidity. When it is not possible to preserve the nerve of origin the surgeon should be prepared to perform an end-to-end anas tomosis or interpose a nerve graft. Several experts advocate conservative manage ment of asymptomatic lesions and imaging follow up to evaluate for growth. The transcervical approach is the most commonly used for lesions located in the lateral neck. When the pathologic diagnosis reveals a malignant nerve sheath tumor, post operative radiation should be offered.
Suggested Readings Catalano, P, Fang-Hui, E., Som, P.M . Fluid-fluid levels in benign neurogenic tumors. American Journal of Neuroradiology 1 8(2):385-7, 1 997 Feb. Furukawa, M., Furukawa, M.K, Katoh, K, Tsukuda, M. Differentiation between schwannoma of the vagus nerve and schwan noma of the cervical sympathetic chain by imaging diagnosis. Laryngoscope 1 06( 1 2 Pt 1 ) : 1 548-52, 1 996 Dec. Ganesan, S., Harar, R.P., Owen, R.A., Dawkins, R.S., Prior, A.J. Horner's syndrome: a rare presentation of cervical sympathetic chain schwan noma. Journal of Laryn gology and Otology 1 1 1 (5)493-5, 1 997 May. George, B., Lot, G. Neurinomas of the first two cervical nerve roots: a series of 42 cases. Journal of Neurosurgery 82(6):91 7-23, 1 995 Jun. Kumchev, Y, Kalnev, B. A neurofibroma affecting the first right cervical sympathetic ganglion and entering the jugular foramen of the skull base. Folia Medica 39(2) : 15-9, 1 997. Sairyo, K, Henmi, T., Endo, H. Foramen magnum schwannoma with an unusual clin ical presentation: case report. Spinal Cord 35(8):554-6, 1 997 Aug. Sheridan, M.F., Yim, D.W. Cervical sympathetic schwannoma: a case report and re view of the English literature. Otolaryngology and Head and Neck Surgery 1 17(6):S206- 1 0, 1 997 Dec.
INECK.
T H Y R O I D. PA RATH Y R O ID
Case 35 Clinical Presentation A middle-aged male with a history of tongue carcinoma pre ented with a new neck mas on the right.
A
1152
B
N ECK. TH YROID , PA RATHYROIDI
Radiologic Findings An axial TI W M R image ( Fig. 35-A) shows bilateral masses posterior to the sub mandibular giands.llley appear nearly isointense to muscle on this pulse sequence. Following contrast administration there is enhancement of both lesions with a cen tral area of nonenhancement on the right ( Fig. 35-B). The T2WI ( Fig. 35-C) shows the central area to be high signal.
Differential Diagnosis: Neck Mass with Central Lucency • • • • •
Branchial cleft cyst Lymphangioma ecrotic lymph nodes Abscess Benign node with fally degeneration
Diagnosis Necrotic lymph node from squamous cell carcinoma metastases
Discussion Epidemiology Squamous cell carcinoma is the most common malignant neoplasm of the upper aerodigestive tract. One of the most important factors that influences therapeutic outcome in the management of patients with this disease is the presence of cervical lymph node metastases. A single nodal metastasis reduces the patient's survival by approximately 50% , regardless of location. or size of the primary tumor in the head and neck.
D
I NECK,
THYROI D, PARATHYROID Table 35-1
Correlation between the Rouviere. UICC, and Numeric classifications.
Rouviere
U ICC
Numeric
Submental
Level I
Submandibular Superior jugular nodes Midjugular nodes Inferior jugular nodes Spinal accessory nodes Prelaryngeal nodes Para tracheal nodes Retropharyngeal nodes Parotid and buccal nodes Retroauricular and occipital nodes
Level l Level I I Level I I I Level IV Level V Level VI Level V I I
Submental Submaxillary Lateral cervical group Lateral cervical group Lateral cervical group Lateral cervical group Anterior cervical group Anterior cervical group Retropharyngeal nodes Parotid and facial nodes Mastoid and occipital nodes
Clinical Findings Before the development o f CT, assessment o f cervical nodal metastasis was based completely on palpation of lymph nodes as detected by physical examination. TIle inaccuracy of the physical examination has been documented in a number of stud ies. False-negative and false-positive rates of the physical examination are 1 5-20% and 30-50% , respectively. CT and M R I have improved the accuracy of nodal stag ing over physical examination. Both techniques allow visualization of nonpalpable nodes deep into the sternocleidomastoid muscle or in the retropharyngeal space.
Pathophysiology Clinically, occult normal-sized nodes with central necrosis or with extracapsular spread can be identified as metastases by CT or MR. Borderline-sized nodes with out necrosis or extracapsular spread remain indeterminate by both CT or MR. Size has been a widely used criterion to determine the presence of nodal metastases. Because size data are a continuum, the relative sensitivity and specificity of any size criteria can be adjusted by changes in the threshold dimensions, depending on a clinical setting. Small metastatic nodes can be missed. Conversely, large reactive nodes cannot be differentiated consistently from metastatic nodes. Lucency in lymph nodes by CT can sometimes be seen with normal fally hilus or with fatty replacement of nodal parenchyma following inflammation or irradiation. Post treatment fally density signal is usually peripherally located. Central necrosis also can be seen with lymphoma, papillary thyroid carcinoma. and tuberculous adenitis (Fig. 35-0). The nomenclature of cervical nodes has been complicated by variations among several different nodal classification systems. Cervical nodes were initially catego rized by Rouviere into one of 1 0 principal groups based on their precise anatomic location (Table 35- 1 ). Today the most widely accepted classification has been that of the Union I nternational Contre Ie Cancer ( International Union Against Cancer; U lCC) , organized by the American loint Commillee on Cancer (AlCC), wherein cervical lymph nodes are subclassified into 1 2 regions. Head and neck surgeons have increasingly used a more simplified numeric classification based on physical examination, which was established and adopted by the Academy of Otolaryngol ogy-Head and Neck Surgery, in 1 99 1 . This simplified classification aims to eliminate misinterpretation due to variation in terminology of cervical nodes as well as to pro vide standardization of variable modification of neck dissection. Major cervical nodal groups are classified as level I through level V I . This classification is useful for understanding recent applications of conservative or selective neck dis-
I�
NECK, THYRO I D, PARATHYROIDI section, in which a part of the cervical nodal groups are removed. Some nodal groups, such as retropharyngeal nodes and intraparotid nodes. are not included in this numeric classification and must be referred to by their U I CC classification.
Imaging Findings [ n the early era of CT, size criteria for nodal metastases were established by inves tigating the range of normal variation in size of lymph nodes in subjects without cancer. The initial criterion was that "discrete lymph nodes larger than 1 .5 cm are considered metastases." More recently, size criteria have been reassessed with ex tensive pathologic analysis. One study suggested that a minimum (short) axial diameter of 1 1 mm for the j ugulodigastric nodes and 10 mm for all other nodes more accurately reflects the presence of metastases. Sensitivity and specificity of the size criteria in this study were 89% and 73% per specimen and 4 1 .7% and 99.3% per node, respectively. These results indicate that more than one-half of metastatic nodes are smaller than 10 mm. Small metastatic nodes missed by this simple size criterion are seen fre quently in a specimen that already contains a large metastatic node. Considering partial voluming effects and the limits of spatial resolution in cross-sectional imag ing, there are a substantial number of indeterminate "borderline-size" lymph nodes. Another multicenter study analyzing nodal size in 1 00 neck dissections revealed that 46% of pathologic nodes were less than 1 em and 22% of pathologic nodes were between 1 and 1 .5 cm in diameter. Another pathologic analysis of 750 lymph nodes in patients with head and neck cancer demonstrated that most normal nodes are small (less than 5 mm in diameter) but that metastatic nodes vary in size with out having any peak in size distribution. Thus, a significant number of metastatic nodes are missed (false-negative) by simple size criteria. In patients with squamous cell carcinoma, central nodal low attenuation with ring enhancement is likely to represent the presence of necrosis or tumor itself, within metastatic nodes. Tumor cells replacing the medulla of lymph nodes generally show less contrast enhancement than the remaining nodal cortex, resulting in a heteroge neous appearance. This finding is highly characteristic of metastatic squamous cell carcinoma. In a large clinical series, 74% of metastatic nodes contained necrosis or cystic areas on pathology, whereas central necrosis was visualized only in 32% of metastatic nodes on imaging studies. Therefore, a homogeneous appearance of lymph nodes on CT or MRI does not exclude the presence of nodal metastasis. Moreover. the incidence of central necrosis in positive nodes was reported to be di rectly proportional to the size of the nodes. Even though small metastatic nodes may contain necrotic foci, central necrosis is seen more commonly in larger nodes, which usually are diagnosed as metastases by size criteria alone. Normal fat deposi tion. as well as abscess formation in patients with infectious disease, may mimic cen tral necrosis of lymph nodes. Spread of the malignancy beyond the lymph node "capsule" has a strong negative impact on patient prognosis. One study reported that the presence of extracapsular spread reduces the 2-year survival of patients by approximately 50% . They con cluded that histologic evidence of extracapsular spread is a more sensitive prognos tic indicator than is the stage of the head and neck cancer. I ndeed. when extracap sular spread is pathologically evident. postoperative radiation therapy is mandatory. CT and MRI findings indicative of extracapsular spread include irregular nodal boundaries and obliteration of the adjacent fat planes, if there has been no recent infection, radiation therapy, or surgical intervention in this region. All of these processes cause irregular nodal borders and obliteration of fat planes.
Management A variety of cervical nodal dissection procedures have been developed for treat ment of nodal metastases in head and neck cancer. Radical neck dissection (RND),
I NECK,
THYROID, PARATH YROID
PEARLS/PITFALLS •
•
•
Large size lymph nodes with cen tral necrosis, and extracapsular extension all suggest metastatic involvement. These findings can also be found with infiammatory disease. Care should be taken not to mis take metastasis for a benign con dition.
involves en bloc removal of aU lymph nodes from level I through level V along with the sternocleidomastoid muscle, internal jugular vein, and spinal accessory nerve. Significant morbidity is associated with RND, uch as shoulder dropping and pain . The idea of a less invasive neck dissection has been developed to minimize func tional and cosmetic deficits while maintaining adequate disease control. As more conservative neck dissections have become available without sacrificing prognosis, more accurate and tissue specific presurgical imaging studies are necessary. Radia tion therapy is added in selected cases.
Suggested Readings Anzai, Y, Brunberg, J.A., Lufkin, R. Imaging of nodal metastases in the head and neck. Journal of Magnetic Resonance Imaging 7:774-783, 1 997. Don, D., Anzai, Y, Lufkin, R.B., FU, Y S., Calcaterra, T., Lufkin, R. Evaluation of cer vical lymph node metastases in squamous cell carcinoma of the head and neck. Laryngoscope 1 05:669-674, 1 995. Som, P. M . Detection of metastases in cervical lymph nodes; CT and MR criteria and differential diagnosis. American Journal of Roentgenology 1 58:961 -969, 1992.
NECK, THY ROID, PARAT H Y ROIDI
Case 36 Clinical Presentation A 58-year-old female presented with a rapidly enlarging neck ma s, progre ive hoar enes, in piratory dyspnea and dysphagia. On phy ical exam a hard woody ma wa palpated in t he right lateral and anterior neck, and was fixed to the sur rounding structures. On laryngoscopy right vocal cord paraly i wa noted.
B
c 1571
1 N ECK.
THYROID, PARATHYRO I D
Radiologic Findings An MRI of the neck shows an asymmetric thyroid gland due to enlargement of the right thyroid lobe, which extends posteriorly into the retrotracheal region. The mar gins of this lobe are ill-defined and there is obscurity of the fascial planes with the right sternocleidomastoid muscle, strap muscles, anterior aspect of the right internal jugular vein and prevertebral muscles. The retrotracheal component obliterates the tracheo-esophageal groove and blends with the proximal esophagus, which cannot be separated from this mass. A nodular area of hyperintensity is noted in the medial aspect of the right thyroid lobe, adjacent to the trachea, possibly representing a pre existing nodular goiter with high protein content or hemorrhage. The remainder of the right lobe is markedly hypointense compared to the contralateral side. The tra chea is deviated anteriorly and to the left, and its tranverse lumen is decreased (Fig. 36-A). The cranio-caudal extent of this lesion is best appreciated in the coronal sec tion ( Fig. 36-B). The axial section at the supraglottic level shows right vocal cord paralysis (Fig. 36-C).
Differential Diagnosis: Ill-defined Enlargement of the Thyroid Gland with Extrathyroid Extension •
• •
Infectious/Inflammatory: acute suppurative thyroiditis ( bacterial or fungal), Riedel's thyroiditis (also called invasive fibrous thyroiditis) eoplastic: anaplastic thyroid carcinoma, thyroid lymphoma Iatrogenic: postsurgical changes, postradiation therapy ( radiation induced thyroiditis)
Diagnosis Riedel's thyroiditis
Discussion Thyroiditis is a general term to designate a variety of inflammatory conditions occurring in the thyroid gland. They are classified according to their clinical presen tation into acute, sub-acute and chronic forms, and further subclassified according to etiology or pathology. The acute form is usually associated with an infectious process due to bacterial or fungal agents and is also called acute suppurative thy roiditis. The subacute category comprises two different conditions: subacute granu lomatous thyroiditis (Quervain's thyroiditis), which is thought to result from a viral infection. and subacute lymphocytic thyroiditis, which likely represents an autoim mune entity. It differs from Hashimoto's thyroiditis by the fact that it is self-limited and does not tend to cause irreversible hypothyroidism. This entity may be seen in the postpartum period and tends to reccur in subsequent pregnancies. Chronic thy roiditis includes Hashimoto's (chronic lymphocytic thyroiditis), an autoimune process that usually results in irreversible hypothyroidism, and Riedel's thyroiditis ( invasive fibrous thyroiditis). With the exception of acute suppurative thyroiditis, all other forms of thyroiditis are limited to the thyroid gland and do not commonly cause vocal cord paralysis. although they can cause compressive symptoms due to gland enlargement. For these reasons they are excluded from the current differential diagnoses. The main clinical and imaging diagnostic mimic of Riedel's thyroiditis is anaplastic thyroid car cinoma, which may present in the same age group and with an indistinguishable clinico-radiologic picture. Thyroid lymphoma with a florid reactive desmoplastic reaction. and the fibrosing variant of Hashimoto's thyroiditis may also be very difficult to distinguish from
1 1 58
N ECK, THYROID, PARATHYROID1 Riedel's thyroiditis pathologicaUy. However, thyroid lymphoma does not tend to have a hard consistency on palpation and Hashimoto's thyroiditis, even the scleros ing variant, does not cross the boundaries of the thyroid gland.
Epidemiology Riedel's thyroiditis was first described by Bernhard Riedel in 1883. It is best de scribed as a benign fibrotic process with aggressive features, partially or completely involving the thyroid gland and extending beyond the confines of the gland into the soft tissues of the neck. Since first described, multiple terms have been used to refer to this entity such as Riedel's struma, struma thyroiditis and invasive fibrosing thy roiditis. It is a rare condition, with an estimated incidence of 0.05% determined in the largest series of thyroid resections reported to date. The female-to-male ratio varies between 3 to 5 : 1 and the age group most commonly affected is between the fourth and seventh decades, with a peak incidence in the late forties. The disease may be uni- or bilateral. There is a well known association with other fibrosclerosing dis eases including retroperitoneal and mediastinal fibrosis, orbital pseudotumor (scle rosing variety) and Addison's disease.
Pathophysiology The etiology of Riedel's thyroiditis is unknown. There are two main theories, one suggesting an autoimune process, which may be the same or different from the one responsible for Hashimoto's thyroiditis, and the other suggesting a localized or sys temic fibrosclerosing inflammatory process. Evidence to support an autoimmune pathophysiology includes the presence of thyroid autoantibodies (anti thyroglobulin and antimicrosomal), the coexistence of histologic features of both Riedel's thy roiditis and Hashimoto's in the same gland, and some land, and some isolated re ports of other autoimune diseases, such as pernicious anemia associated with Riedel's thyroiditis. Therefore, some experts characterize Riedel's thyroiditis as the end spectrum of chronic lymphocytic thyroiditis. The association with and similari ties to other fibrosclerosing diseases support a primary systemic fibrosclerosing
D
1 59 1
INECK, THYROID, PARATHYROID process. Recently, an autoimune mechanism. mediated by eosinophils and their highly fibrogenic degranulation products has been proposed as the basis of this sys temic fibrosclerosing process. Potential mechanisms for eosinophilic recruitment have been proposed such as adhesion molecules expressed by the vascular en dothelium, connective tissue cells and thyroid follicular cells after local stimulation by inflammatory mediators. Macroscopically, Riedel's thyroiditis is characterized by a tony-hard fibrous mass effacing the normal glandular architecture. Microscopically, there is extensive re placement of the normal thyroid tissue by paucicellular bands of dense fibrous tis sue, with bundles of collagen fibers and a hyalinized matrix invading the capsule and extending into the surrounding tissues. A scarce inflammatory infiltrate may be seen, primarily composed of lymphocytes, plasmocytes and polymorphonuclear (PMN) leukocytes. Recently, attention has been put on the presence of eosinophilic infiltrates in fibrotic regions and in the perivascular spaces. Histologic section of the same patient (Fig. 36-0) shows compressed and atrophic follicles surrounded by dense collagenous bands and scarce inflammatory infiltrate. It is important to note that fibrotic tissue may be found in a variety of other con ditions, including other forms of thyroiditis (radiation-induced and Hashimoto·s). nodular goiter, desmoplastic reaction associated with lymphoma, post-trauma. scle roderma, amyloid deposition. and neoplastic processes such as undifferentiated thy roid carcinoma. Therefore, the presence of three diagnostic criteria is required to make the diag nosis of Riedel's thyroiditis. These include the presence of fibrosis of all or part of the thyroid gland, near complete destruction of the involved portion of the gland, with absent or destroyed follicules, and extension beyond the capsule. The major pathologic differences between Riedel's and Hashimoto's disease is the absence of lymphoid germinal centers, the presence of extra thyroid extension. vascuJar changes, and loss of thyroid lobulation in the former. FNA results are often nondiagnostic due to the increased consistency and hypocellularity of the gland. They also may be misleading with a few described cases of false-positives for carcinoma. Surgical biopsy is usually required for accurate di agnosis. Clinical Findings
Patients with Riedel's thyroiditis typically present with a rapidly enlarging neck mass, causing compressive symptoms such as hoarseness. inspiratory dyspnea, stri dor and dysphagia. Hoarseness may result from direct laryngeal extension. but more commonly results from involvement of the recurrent laryngeal nerve in the tracheo esophageal groove. Mediastinal extent may occur and be responsible for venous hy pertensive yndromes such as superior vena cava syndrome. The disease may appear first in an otherwise normal gland or a preexisting goiter. Rarely. the gland may be normal in size and show a single nodular lesion. Symptoms and signs of hypothy roidism should be sought, although these tend to appear in the later phases when there has been extensive replacement of the thyroid gland parenchyma by fibrotic tissue. On clinical exam, the thyroid gland is diffusely or focally enlarged, with a rock hard consistency and most likely a lobulated surface. Typically, the gland is fixed to surrounding structures, including the skin, and may be impossible to mobilize. Un like anaplastic carcinoma, lymphadenopathy is not a feature of Riedel's thyroiditis, an important distinguishing feature. Laryngoscopy may disclose vocal cord paraly sis or submucosal laryngeal infiltration. stenosing the laryngeal lumen. Esoph agoscopy may demonstrate esophageal stenosis due to extrinsic compression. On clinical history, it is important to ask for symptomatology related to other fi brosclerotic processes, such as renal problems, hypertension, visual deficits or jaun dice. Laboratory tests may be useful in the differential diagnosis. They should include 1 1 60
NECK, THYROID, PARATHYROIDI erythrocyte sedimentation rate, evaluation of thyroid function and detection of an tithyroid antibodies. In some cases, there is an elevated ESR. Euthyroidism or hy pothyroidism is the rule and a positive reading for antithyroid antibodies occurs in as many as 67% of cases. Further diagnostic tests should include imaging studies and FNA or surgical biopsy to make a definitive diagnosis and, especially, to exclude malignancy. Imaging Findings
I n addition to providing useful diagnostic information, imaging studies are required to determine the extent of disease and to exclude other sites of systemic involve ment. Cross-sectional imaging of the orbits, mediastinum or abdomen may be re quired in selected cases. Plain films of the neck and chest may disclose enlargement of the thyroid gland, thyroid calcifications and airway deviation or stenosis. However, cross-sectional imaging better depicts the presence of extrathyroid extension, which is the hallmark of this disease. Ultrasound is the optimal screening test for thyroid disease. Typically, the in volved portions of the gland are homogeneously hypoechoeic, but a nodular ap pearance, indistinguishable from multinodular goiter, may also be seen. US may also detect extra thyroid fibrotic masses and exclude the presence of lymphadenopathy. Limitations of this modality include the evaluation of mediastinal extent and inva sion of air-containing structures such as the larynx, esophagus and trachea. Due to its multiplanar capability, MRI adequately depicts the extent of the lesion and does not necessitate intravenous contrast. The gland may be partially or dif fusely enlarged and the involved portions tend to be hypointense on both T l W and T2W images. These are the signal characteristics of fibrotic tissue, although amyloid deposits and hemochromatosis may share these same features on MRI. Addition ally MR1 may allow distinction from Hashimoto's thyroiditis, which tends to be markedly hyperintense on T2WI . Less commonly, the gland is heterogeneous in sig nal intensity, especially when the disease is superimposed upon a pre-existing goi ter. Solitary or multiple nodules may also be present, as in the case presented (Figs. 36-A and 36-8). Extracapsular extension manifests as an irregularity of the margins of the gland, obscurity of the fascial planes, and obvious invasion of the surround ing structures. When the isthmus of the gland is involved, infiltration of the strap muscles and skin may be seen. Other structures frequently invaded include the ster nocleidomastoid muscle, carotid space, tracheoesophageal groove and postcricoid and retropharyngeal regions. Airway deviation and stenosis is a frequent finding, as well as indistinctness of the esophagus. Vocal cord paralysis, when present, manifests as a paramedian vocal cord, ipsilateral anteromedial deviation of the aryepiglottic fold and enlargement of the pyriform sinus (Fig. 36-C). The presence of cervical lymphadenopathy favors malignancy, most likely anaplastic thyroid carcinoma. As recurrence is seen in a high percentage of cases, imaging follow up is usually re quired. CT requires intravenous contrast administration and the only advantage over MRI is the detection of dystrophic calcification, an inconsistent and nonspecific finding in Riedel"s thyroiditis. Scintigraphic studies with Tc pertechnetate show non specific decreased activity in the affected portions of the gland. Management
Surgery may be required to alleviate compressive symptoms and for cosmetic rea sons, or to make the definitive diagnosis when the FNA is nondiagnostic or doubt ful. Tracheostomy may be required for life threatening airway compromise, includ ing cases of bilateral vocal cord paralysis. When malignancy is excluded, surgery should be limited, to avoid complications resulting (rom attempted dissection of the invasive fibrotic tissue from surrounding structures. Potential complications include
E K, TH YROID, PA RATHY ROIDI
Case 37 Clinical Presentation A 72-year-old male with a long tanding anterior neck mas pre ented with recent onset of dysphagia, hoar ene s and stridor.
A
B Radiologic Findings Coronal Tl WI (Fig. 37-A) and axial T2Wl (Fig. 37-B) of the neck show multinodu lar, diffuse enlargement of the thyroid gland extending into the superior and ante-
163
ECK, THYROID, PARATHYROID rior mediastinum and compressing and displacing the trachea and esophagus. TIlere is a dominant nodule in the left thyroid lobe extending posteriorly into the left tracheo-esophageal groove. The signal characteristics of these nodules are heteroge neous, which is consistent with the presence of cystic degeneration, calcification and hemorrhage. The gland is lobulated in contour, but shows well-defined margins with no evidence of invasion of the adjacent neck structures. No lymphadenopathy is apparent.
Differential Diagnosis: Multinodular Thyroid Gland Enlargement • • • • • • •
Multinodular goiter Thyroiditis (subacute, Hashimoto's, Quervain's, post-partum) Primary or secondary lymphoma Metastatic disease Undifferentiated/anaplastic carcinoma Thyroid sarcoma Graves disease
Diagnosis Multinodular goiter
Discussion Epidemiology
Goiter is a nonspecific term meaning diffuse enlargement of the thyroid gland, which may be seen in a large variety of pathologic processes affecting the thyroid gland. However, it is commonly used as a synonym [or nontoxic or euthyroid goiter. Endemic goiter, defined as goiter in at least 10% of the population, is the most common cause of goiter worldwide. Seventy five per cent of cases occur in third world countries, which lack iodine prophylaxis, and the remainder in mountainous regions of Europe and Asia. In the United States, endemic goiter is virtually non existent and most cases of goiter are termed sporadic goiters. The incidence of goiter in iodine-replete populations has been estimated between 4 and 6% . Non-endemic goiter is more common in women and in the elderly. The incidence of malignant de generation varies from I to 4% and increases with age and prior exposure to radiation. Pathophysiology
The pathophysiologic mechanism common to all causes of goiter is an excessive stinlUlation of the epithelial follicular cells leading either to excessive replication and formation of hyperplastic [ollicules, or to hyperfunction with excessive produc tion and accumulation o[ colloid material. I n endemic goiter, the gland hypertro phies in an attempt to produce more thyroid hormone with less available iodine. Most goitrogens act through the hypothalamic-hypophyseal loop, producing an increase in thyroid stimulating hormone (TSH). Another common mechanism is the stimulation by thyroid antibodies that act directly on the TSH receptors in the follicular cells such as long acting t h yroid stimulator (LATS) in Graves' disease. These thyroid antibodies can also damage the thyroid cells as seen in HashinlOto's thyroiditis. Goiter may also result from congenital enzymatic deficiencies impairing iodine uptake, or organification, or be part o[ congenital syndromes such as Pan dred's syndrome (congenital deafness and goiter). Common goitrogens include iodine rich foods (soy beans, sea weeds), iodine containing drugs (amiodarone, con trast material, antiseptics), and drugs containing salts, which compete with iodine for thyroid absortion (lithium). The typical progression of goiter is from diffuse enlargement of the thyroid gland to increasing nodularity. 11 64
NECK, THYROID, PARATHYROIDI Pathologically, goiter is characterized by follicular hypertrophy and hyperplasia with accumulation of colloid, resulting in cystic degeneration. When the expanding gland outgrows the blood supply, follicular necrosis and hemorrhage may occur. Dystrophic calcification and psammous calcification of stagnant colloid material are also typical features of goiter. Nodularity results from the presence of small subsets of follicular cells with abnormal growth potential at different sites through out the gland. These autonomous replicating follicular cells are thought to be rem nants of fetal thyroid tissue or to result from somatic mutations resulting in cell lines with a preferential growth advantage accounting for the formation of a few well-encapsulated nodules. Mutations in the TSH receptor gene account for the development of hyperfunctioning adenomas. It should be stressed that autonomous growth and autonomous function are separate features of follicular cells further contributing to the heterogeneity of multinodular goiter. Depending on its mor phologic and functional characteristics, goiter is classified into diffuse or nodular and euthyroid, hypothyroid or hyperthyroid respectively. Cytologically, it is impossible to separate follicular adenomas from carcinomas. 1l1erefore, the general term "follicular tumor" is commonly used. Malignancy can only be diagnosed in the presence of vascular or capsular invasion which requires evaluation of the histologic specimen. Clinical Findings
Seventy five percent of patients who have a goiter present with a chronic asympto matic anterior neck mass and seek medical attention for cosmetic reasons. Most commonly, goiters are detected by physicians during routine physical examination. A small percentage present with compressive symptoms, symptoms of thyroid dys function (either hypo- or hyperthyroidism) or sudden growth associated with pain. Compressive symptoms include dyspnea, stridor, dysphagia and hoarseness and are seen more often in patients with substernal or intrathoracic goiter. These patients may rarely present with superior vena cava syndrome and rupture of esophageal varices. Although vocal cord paralysis usually signals the presence of malignancy, it may occasionally result from benign compression of the recurrent laryngeal nerve when the goiter grows posteriorly and medially into the tracheo-esophageal groove. Even though 80% of patients with goiter are euthyroid at presentation, subclinical hypo- or hyperthyroidism may be present and therefore thyroid function tests should be performed in the initial evaluation. Sudden enlargement and pain are usually associated with hemorrhage into a follicular cyst, but also may signal malig nant transformation. The clinical history should address not only the possible causes of goiter (recent viral infection, pregnancy or recent delivery, autoimune disorders or exposure to goitrogens) but also the risk of malignancy (rate of growth, family history of thyroid cancer, presence of MEN syndromes, etc). The nationality and res idence of each patient should be ascertained to rule out the possibility of iodine deficiency. On physical exam the volume, mobility, and consistency of the gland, and the presence of any dominant nodules or cervical and supraclavicular lym phadenopathy should be evaluated.1l1e volume of the gland should be recorded in the patient's clinical chart to allow for future comparison and determine the success of therapy. Auscultation of the thyroid gland may detect the presence of a bruit, in dicating increased vascularity, typical of Graves' disease. Direct or indirect laryn goscopy also should be performed to evaluate vocal cord mobility. Examination of other major organs and systems (particularly the cardiovascular system, skin and eyes) is important to determine the presence of clinical thyroid dysfunction. Bio chemical analysis including determination of blood levels of TSH, free triiodothy ronine (T3) and tetraiodothyronine (T4), and antithyroid antibodies may be re quired. After an adequate history is taken and physical examination and biochemical testing are performed, most patients do not require further diagnostic tests. When the goiter is multinodular at palpation, FNA of any dominant or en larging nodules is advised to exclude malignancy.
ECK, THYROI D, PARATHYROID Imaging Findings
Imaging of a goiter has five major goals: ( 1 ) to provide an accurate assessment of glandular volume and morphology; (2) to evaluate compression of adjacent struc tures including the airway; (3) to determine the functional status of clinically suspi cious nodules; (4) to detect imaging features suggestive of malignant degeneration; and (5) to direct FNA. However, the cost-effectiveness of imaging and the preferred modalities for addressing these problems are the subject of controversy. Surgical candidates should have a cross sectional imaging study to determine the anatomy of the gland and its relationship to adjacent structures. MRI is preferred over CT as it does not involve ionizing radiation, does not require contrast administration, and al lows for multiplanar evaluation. The use of iodine based contrast materials on CT not only may precipitate a hyperthyroid crisis but it will interfere with subsequent scintigraphic studies, laboratory tests and radioiodine therapy. TIle only advantage of CT is better sensitivity in detection of thyroid calcifications that, although non specific, may be of diagnostic value. M R I gives optimal delineation of the size and configuration of the gland. TIle coronal and sagittal images are particularly helpful in assessing the cranio-caudal extent of the gland, detecting the presence of any me diastinal components (plunging goiter) and assessing the status of the airway and esophagus. The use of scintigraphic studies to evaluate the functional status of thyroid nod ules is questionable as FNAB is more accurate than scintigraphy in the assessment of thyroid nodules. Scintigraphic studies may be performed with 1 1 23 or Tc99m. The former is used to evaluate glandular function whereas the latter is used to evaluate glandular morphology. According to the amount of radiotracer uptake, nodules may be classified as hot (hyperfunctioning), warm (normally functioning), or cold (hy pofunctioning). The importance of this classification lies in the fact that 10 to 25%
c
11 66
NECK, THYROID, PARATHYROIDI
D
E
of cold nodules are malignant whereas the risk of malignancy in warm or hot nod ules is 9% , and I to 4% , respectively. Scintigraphy also may be helpful in patients with hyperthyroid goiter as it differentiates Graves' disease (characterized by a dif fuse increase in iodine uptake), toxic multinodular goiter, (presenting with multiple areas of increased uptake), and Plummer's disease (manifesting as a single toxic nodule causing near total suppression of the remainder of the thyroid gland). How ever, scintigraphy shows a lot of overlap between benign and malignant nodules and is not sensitive to nodular lesions that are smaller than 1 cm. Ultrasound is the optimal imaging modality for evaluation of the thyroid gland. I t is widely available, rapid, and inexpensive. Ultrasound is very sensitive in the de tection of focal thyroid lesions and may show additional lesions in a patient with a single thyroid nodule on palpation. 11 is also very accurate in distinguishing solid and cystic lesions and can provide guidance for FNAs of any suspicious nonpalpa ble lesions. Although early studies suggested a higher risk of malignancy in solitary thyroid nodules, most recent series do not confirm these data. [n patients with non diagnostic "blind" FNAs, ultrasound may assist in directing the needle to solid com ponents of the lesion and increase diagnostic accuracy. The major drawback of US is an inability to evaluate substernal goiters, requiring further assessment with cross sectional imaging. Plain films of the chest or soft tissues of the neck may give a gross evaluation of the extent of the gland and detect airway compromise. The imaging features of a goiter include an enlarged heterogeneous thyroid gland with single or multiple nod ules and areas of cystic degeneration, hemorrhage and calcification. A lateral plain film of the soft tissues of the neck in a patient with papillary carcinoma arising within a multinodular goiter, (Fig. 37-C) shows a large soft tissue mass in the ante rior neck extending inferiorly into the mediastinum. This mass displaces the cervi cal trachea posteriorly and decreases the anteroposterior diameter of the trachea. A large nodular area with multiple punctiform calcifications is noted bulging anteri orly in the soft tissues of the anterior neck. Larger, coarse calcifications are also noted projecting posteriorly to this mass. Cystic lesions may show fluid-fluid levels due to intracystic hemorrhage or debris. A longitudinal section of a thyroid ultrasound in a patient with colloid goiter (Fig. 37-D) demonstrates a large predominantly cystic nodule in the inferior aspect of the right thyroid lobe with some posterior acoustic enhancement. Echogenic material is seen layering in the dependent portion of the lesion, probably representing debris or hemorrhage. The margins of the nodule are well defined. A transverse section of the right thyroid lobe in another patient (Fig. 37-E) shows an US-guided FNA of a dominant solid nodule in a multinodular goiter that had recently increased in size. The small hyperechoic foci with acoustic shadowing represent calcification. The margins of the nodule are well defined, surrounded by a hypoechoic halo. The mar-
1 NECK, THYROID, PARATHYROID PEARLS/PITFALLS A goiter can presen t as a long standing, asymptomatic anterior neck mass.
•
•
•
•
•
•
•
The imaging features of a goiter include a diffuse, heterogeneous enlargement of the thyroid gland with mUltiple nodules and areas of cystic degeneration, calcifica tion or hemorrhage. Possible mediastinal extension causing compressive symptoms can be seen in a small percentage of patients. FNA studies should be per formed in patients who have dominant or rapidly enlarging nodules.. A clinician shouLd take care not to fail to recognize a malignant nodule within a goiter. A clinician shouLd take care not to fail to evaluate the full extent of the gland.
It's important not to mistake other diffuse thyroid processes such as thyroiditis, thyroid lym phoma or anaplastic carcinoma for goiter.
1 1 68
gins of the gland are usually lobulated but well defined with no evidence of invasion of adjacent structures or regional lymphadenopathy. Graves' disease manifests as an enlarged thyroid gland. Sonographically, the gland shows lobulated margins, a dif fusely hypoechoic texture and increased vascularity better appreciated on Doppler US (thyroid inferno). Differential diagnosis of a goiter includes several other lesions that present with an enlarged heterogeneous gland. These include several forms of thyroiditis, anaplastic thyroid cancer, lymphoma and metastatic thyroid disease. In the acute inflammatory phase Hashimoto's thyroiditis and Quervain's thyriditis may be par ticularly difficult to differentiate from a goiter, requiring adequate clinical and biochemical correlation. Management
Therapy of a goiter should be directed to its cause. Therefore, it may include dietary iodine supplements, elimination of goitrogens, anti-infammatory drugs and anti thyroid drugs. Treatment should also address problems associated with hyper thyroidism including management of hypertension. arrythmia and ophthalmologic problems. Most patients with euthyroid goiters can be managed conservatively with clinical monitoring of the volume of the gland. However, surgical treatment may be re quired for cosmesis, alleviation of compressive symptoms or malignant degenera tion. Decrease in glandular volume may be achieved with antithyroid drugs such as levothyroxin, radioiodine or surgery. US guided ethanol ablation of hyperfunction ing thyroid nodules has also been used with high success rates.
Suggested Readings Daniels, G.H. Thyroid nodules and noduJar thyroids: a clinical overview. Compre 1996 Apr. Dworkin, H.J., Meier, D.A., Kaplan, M. Advances in the management of patients with thyroid disease. Seminars in Nuclear Medicine 25(3):205-20, 1 995 Jul. Hurley, D.L., Gharib, H. Evaluation and management of multinodular goiter. 010laryngologic Clinics of North America, 1 996 Aug, 29(4):527-40. Naik, K.S., Bury, R.F. l maging the thyroid. Clinical Radiology 53(9):630-9, 1998 Sep. Petrone, I.R. A primary care approach to the adult patient with nodular thyroid dis ease. Archives of Family Medicine 5(2):92-100, 1 996 Feb. Singh, B., Lucente, F.E., Shaha, A.R. Substernal goiter: a clinical review. American Journal of Otolaryngology 1 5(6):409-16, 1994 Nov-Dec. hensive Therapy 22(4):239-50,
N ECK,
THYROI D, PARATHYROIDI
Case 38 Clinical Presentation A 76-year-old female with a long history of neck swelling reported a rapidly en larging right neck mass.
B
D
Radiologic Findings An axial CT through the level of the cricoid ring (Fig. 38-A) shows a large inhomo geneous mass within the right lobe of the thyroid gland. This mass is predominantly
1 NECK, THYROID, PARATHYROID hypodense and shows a gross calcification. TIle margins of the gland are indistinct with no cleavage plane between the mass and the strap muscles. Extension into the postcricoid region also is seen with leftward deviation of the in(raglottic larynx and cervical esophagus. Laterally, the mass surrounds and distorts the internal jugular vein, which is otherwise patent. An axial view at the level of the proximal trachea (Fig. 38-B) shows inhomogeneity of both lobes of the thyroid gland, an annular cal cification in the right lobe, and two hypodense lymph nodes in the right internal jugular chain. An axial section at the level of the thoracic inlet (Fig. 38-C) clearly shows the strap muscle infiltration. An axial section at the level of the glottis (Fig. 38 D) demonstrates right vocal cord paralysis, with the right vocal cord paramedian in position and a patulous piriform sinus. There is no evidence of cartilaginous in vasion. -
Differential Diagnosis: An Aggressive looking Thyroid Mass • • •
Infection: Acute suppurative thyroiditis Inflammatory: Reidel's thyroiditis Malignant tumors: anaplastic carcinoma, lymphoma, sarcoma, squamous cell car cinoma, metastasis
D iagnosis Anaplastic thyroid carcinoma
D iscussion TIle differential diagnoses of an enlarged thyroid gland include diffuse and multin odular goiters, infectious and inflammatory thyroiditis and benign and malignant tumors (Table 38- 1 ). Rapidly enlarging thyroid masses are usually associated with signs of compression and pain, and are due to acute infection/inflammation (acute thyroiditis), hemorrhage in a benign or malignant lesion, or aggressive malignancies such as anaplastic carcinoma or lymphoma. The presence of aggressive features in a thyroid mass, as seen in this case, suggests malignancy, one exception being Reidel's thyroiditis, which is a benign condition with malignant features. Clinically aggressive lesions manifest rapid growth, hoarseness, dysphagia and dyspnea. Characteristic imaging features of these lesions include ill-defined margins, invasion of adjacent structures with loss of cleavage planes between muscles, airway and the carotid sheath, vocal cord paralysis and associated adenopathy. A variety of histologic types are seen with thyroid malignancy including. in order of decreasing frequency, papillary, follicular, medullary, anaplastic, lymphoma, epi dermoid, sarcoma and metastasis. Although these cannot be differentiated clinically or on the basis of imaging alone, certain features can suggest the correct diagnosis. In the present case, the patient's age (seventh decade), previous history of long standing goiter, rapid growth and the presence of a ill-defined mass with aggressive features in a background of an heterogeneous, enlarged gland and nodal metastasis point to anaplastic carcinoma. Other thyroid carcinomas should be considered in the differential diagnosis although most tend to occur in younger age groups. Follicular tumor also can be associated with goiter and is usually unifocal. Nodal involvement is rare but the remaining features are indistinguishable from the other forms of malignancy. Papillary carcinoma occurs most frequently in the fifth decade and generally pre sents as a unifocal lesion with well- or ill-defined borders (40 and 60% of cases re spectively). This lesion can show cystic degeneration, hemorrhage and calcification. Nodal spread is very common and can display the same features as the primary tumor. Medullary carcinoma usually presents with benign features and most are sus pected clinically due to an elevated calcitonin level. These tumors are easily distin1 .129
NECK, THYROID, PARATHYROIDI guished from the other differentiated thyroid cancers on the basis of their lack of iodine uptake on scintigraphic studies. Lymphoma can present as a diffusely enlarged gland, mUltiple modules or, more commonly, as a solitary mass (80% of cases). It also may behave as an aggressive/ infiltrative mass and can have associated adenopathy. A previous history of Hashimoto's thyroiditis is the rule, and the presence of necrosis or calcification is rare (less than 7%). Sarcomas are rare tumors i n the thyroid gland and are not associated with a prior history of goiter. The most common variants are angiosarcoma and fibrosarcoma. Imaging findings do not allow distinction from other tumors. Metastases to the thyroid are usually not clinically apparent and are a late event in a patient with known history of cancer. The most frequent presentation is multi ple discrete lesions and the most common tumors that metastasize to the thyroid are breast, lung, renal cell carcinoma and melanoma. Reidel's thyroiditis is a rare chronic inflammatory condition that is characterized by extensive fibrosis of the gland infiltrating the capsule and adjacent structures. The clinical presentation can be similar to that of a malignant condition and imaging fea tures can also be misleading. Enlarged nodes are not usually present. M RI can be helpful in differentiating this condition from malignancy due to the typical signal intensity of fibrous tissue (hypointense on T1 W and TIW images). Acute thyroiditis is usually clinically apparent with signs and symptoms of in flammation being prominent features. It is usually unilateral, limited to one thyroid lobe. When there is abscess formation and rupture, indistinctness of the adjacent structures and nodal involvement can be confused with malignancy. Anaplastic carcinoma of the thyroid can be indistinguishable from an exten sive esophageal carcinoma in a patient presenting with dysphagia. This is often the case when the bulk of the tumor grows posteriorly and involves the cervical esophagus. Epidemiology
Anaplastic thyroid carcinoma is a rare tumor ( 1 to 10% of all thyroid malignancies) and is one of the most lethal tumors of the head and neck region. I n areas of en demic goiter the incidence is considerably higher with some series reporting an i ncidence of 30% . I n addition, patients with longstanding goiter have an increased susceptibility to this tumor. Coexistence with other histologic variants, particularly with follicular and papillary tumors, suggest that anaplastic carcinoma can result from dedifferentiation of these well-differentiated tumor types. It tends to occur in older patients than other thyroid gland tumors and a slight female predominance is consistently reported in large series. Association with radiation exposure has never been proven. Clinical Findings
The most common and specific clinical presentation is a rapidly growing thyroid mass i n a patient with previous stable thyroid gland enlargement. Other symptoms such as dyspnea, dysphagia and hoarseness are equally frequent in patients with simple goiter or other thyroid masses, both benign and malignant. Weight loss is a frequent associated symptom. On physical examination the most frequent finding, aside from the neck mass, is vocal cord paralysis. Mediastinal extension can also be responsible for superior vena cava syndrome. I maging Findings
A thyroid mass or enlargement should initially be assessed by ultrasound. Ultra sound delineates the gland's morphology, identifies focal lesions and their charac teristics, detects enlarged nodes, and allows assessment of patency of the neck ves-
I NECK, THYROID, PARATHYROID sels using Doppler mode. Anaplastic carcinomas usually present as ill-defined hypoechoic masses within an inhomogeneous and enlarged gland. CT or M R I should be used to determine invasion of adjacent structures, medi astinal extension and to further characterize enlarged lymph nodes looking for evidence of necrosis, calcification and extra-capsular invasion. CT easily detects cal cifications which are common in this tumor. Internal areas of necrosis are commonly seen and present as ill-defined regions of hypodensity on CT and areas of hy pointensity on T1 W and hyperintensity on T2W M R images. The pattern of spread is easily recognized with both imaging techniques. Initially, there is capsular invasion with infiltration of the extraglandular fat, followed by involvement of the strap mus cles and sternocleidomastoid muscle and carotid sheath. Invasion of the larynx and trachea are not uncommon and mediastinal extension is also a possibility. On M RI there are no specific signal characteristics to suggest the diagnosis. Anaplastic tumors present as masses hypointense on Tl and hyperintense on T2W images and show no specific pattern of enhancement. However, MRI can be useful in distinguishing anaplastic carcinoma from Reidel's thyroiditis and lymphoma. In Reidel's, fibrosis of the gland makes it hypointense on both T1 and T2W images. The high cellularity of lymphoma makes it less hyperintense on T2W images than other thyroid malignancies. Recent studies using MRI with gadolinium enhancement showed that another distinguishing feature of primary thyroid lymphoma when compared to other thyroid tumors is poor enhancement. Scintigraphic studies show no evidence of radioactive iodine uptake which is not specific for this tumor. Although clinical and imaging features can suggest the diagnosis of anaplastic tumor, histologic confirmation is mandatory. Tissue can be obtained from FNAB or from open biopsy. FNAB is a safe procedure with high accuracy rates and should be preferred to open biopsy whenever surgery is not considered the treatment of choice. Several samples should be obtained, preferably with imaging guidance to avoid areas of necrosis or hemorrhage. Manage ment
The treatment and prognosis of thyroid cancers depend on the extent of the disease. The staging systems utilized for well differentiated tumors are not very helpful in anaplastic carcinoma that usually presents with more aggressive features. Prognos tic factors that proved significant in anaplastic carcinoma include gender, tumor size and complete surgical resection. Female gender and tumor size less than 6 cm are associated with a better prognosis. Tumors that are amenable to complete surgical resection also carry a better outcome. Although there is no consensus as to optimal therapy for this type of tumor, ag gressive treatment seems to be associated with a slightly better mean survival rate. Surgery should be offered to all patients amenable to this type of therapy and should be used as palliation of respiratory and upper digestive symptoms. Com bined treatments with chemotherapy and hyperfractionated radiotherapy with or without debulking surgery also have a role in those patients with extensive locally invasive lesions. The mean survival rate for this tumor varies between 4 and 1 2 months and the 5 year survival rale ranges from 1 to 7 . 1 'Yo . Death usually results from respiratory failure or inanition because of invasion of the tumor into the up per aerodigestive tract or pulmonary metastasis.
Suggested Readings Brooke, P.K., Hameed, M., Zakowski, M.E Fine-needle aspiration of anaplastic thy roid carcinoma with varied cytologic and histologic patterns: a case report. Diag nostic Cytopathology 1 1 ( 1 ) :60-3, 1994. Greval, R.S., Goyal, S.c., Goyal, R. Chemotherapy and combination therapy in anaplastic thyroid carcinoma. indian Journal of Medical Sciences 47( 1 1 ):269-71 , 1993 Nov.
NECK, THYROID, PARATHYROIDI Hadar, T., Mor, c., Shvero, 1., Levy, R., Segal, K. Anaplastic carcinoma of the thyroid. European Journal of Surgical Oncology 1 9(6):5 1 1 -6, 1993 Dec. Levendag, P.c., De Porre, P.M., van Putten, W.L. Anaplastic carcinoma of the thy roid gland treated by radiation therapy. International Journal of Radiation Oncol ogy, Biology, Physics 26(1 ): 1 25-8, 1 993 Apr 30. Mathai, v., I dikula, 1., Fenn, A.S., Nair, A. Do long-standing nodular goitres result in malignancies? Australian and New Zealand Journal of Surgery 64(3):180-2, 1 994 Mar. Melliere, 0.1., Ben Yahia, N.E., Becquemin, 1.P., Lange, F., Boulahdour, H. Thyroid carcinoma with tracheal or esophageal involvement: limited or maximal surgery? Surgery 1 13(2):166-72, 1993 Feb. Nakahara, H., Noguchi, S., Murakami, N., et al. Gadolinium enhanced M R imaging of thyroid and parathyroid masses. Radiology 202(3):765-72, 1 997 Mar. Peters, 1., O'Reilly, S., Barragry, 1.M. Anaplastic carcinoma of the thyroid following radio-iodine therapy. Irish Journal of Medical Science 1 62(1 ):3-4, 1 993 Jan. Russell, P., Lean, c.L., Delbridge, L., May, G.L., Dowd, S., Mountford, C.E. Proton magnetic resonance and human thyroid neoplasia. I : Discrimination between be nign and malignant neoplasms. A merican Journal of Medicine 96(4):383-8, 1 994 Apr. Salabe, G.B. Aetiology of thyroid cancer: an epidemiological overview. Thyroidol ogy 6(1):1 1-9, 1 994 Apr. Staunton, M.D. Thyroid cancer: a multivariate analysis on influence of treatment on long-term survival. European Journal of Surgical Oncology 20(6):613-21, 1 994 Dec. Tan, R.K., Finley, R.K. 3rd., Driscoll, D., Bakamjian, v., Hicks, w.L. Jr., Shedd, D.P Anaplastic carcinoma of the thyroid: a 24-year experience. Head and Neck 17(1):41-7, discussion 47-8, 1 995 Jan-Feb. Tennvall, 1., Lundell, G., Hallquist, A., Wahlberg, P. , Wallin, G., TibbLin, S. Combined doxorubicin, hyperfractionated radiotherapy, and surgery in anaplastic thyroid car cinoma. Report on two protocols. The Swedish Anaplastic Thyroid Cancer Group. Cancer 74(4): 1348-54, 1 994 Aug 15.
I N ECK, THYROID, PARATHYROID
Case 39 Clinical Presentation A 47-year-old female presented with fatigue, weakness and diffuse bone pain. Bio chemical analysis showed hypercalcemia.
A
B
Radiologic Findings Axial T1 W (Fig. 39-A) and TZW (Fig. 39-B) coronal (Fig. 39-C) poslconlrasl TJ W sections show a small, well-circumscribed, homogeneously enhancing lesion in the left tracheo-esophageal groove. (Case courtesy of Dr. Fernando Torrinha.)
NECK, THYROID, PARATHYROIDI
Differential Diagnosis: D iscreet Mass in the Tracheosophegeal Groove • • • •
Exophytic thyroid nodule Lymphadenopathy Parathyroid adenoma/ carcinoma/ cyst Nerve sheath tumor (cervical roots/ vagus nerve)
Diagnosis Parathyroid adenoma
Discussion Epidemiology
Primary hyperparathyroidism has a prevalence of 0.037% , with 100,000 new cases diagnosed annually in the United States. The disease is more prevalent in post menopausal women with a peak incidence between the fifth and sixth decades. Patients with MEN syndrome tend to present earlier. Clinical Findings
Most cases of primary hyperparathyroidism are diagnosed in asymptomatic pa tients. When symptoms occur, the most common complaints are fatigue, bone pain, and recurrent renal stones. The classic association of "stones" (renal calculi), "groans" (abdominal cramps), "bones" (osteopenia and arthritides), and "moans" (psychiatric disturbances) is rarely seen. Although hypercalcemic crisis and compression symptoms may occur with large parathyroid adenomas, paticularly when they undergo hemorrhage or necrose, they are more commonly associated with parathyroid carcinoma. Hoarseness, dyspnea, stridor and dysphagia are the most common symptoms, resulting from compression of adjacent structures. Pathophysiology
Primary hyperparathyroidism results from increased secretion of parathyroid hor mone (PTH) and subsequent hypercalcemia. Parathyroid adenoma acounts for most of the cases of primary hyperparathyroidism (80 to 85% ), followed by parathy roid hyperplasia (15%), parathyroid cysts « 5%), and parathyroid carcinoma « 1 % ). Multiple adenomas are present in 2 to 3% of cases. Ectopic adenomas are not uncommon, representing 10% of all cases. To localize the lesion, it is important to know the anatomy and embryology of the parathyroid glands. Normally, four parathyroid glands are present in each individual (two superior and two inferior) but, supranumerary glands, up to six in number, are seen in 13% of people. The superior parathyroids originate from the endoderm of the fourth pharyngeal pouch along with the thyroid gland. Because their descent to the normal position is minimal and intimately related to the thyroid gland, their position behind the upper lower third of the thyroid is relatively constant with only 2% of ectopic locations. These include ectopic locations at or above the superior thyroid pole, posterior and medially in the retropharyngeal region and below the inferior thyroid artery. Mediastinal locations are rare and usually in the posterior mediastinum. The inferior parathyroid glands originate from the 3rd pharyngeal pouch in close relationship to the thymic anlage. Because they migrate a long distance along with the thymus, ectopic locations are more frequent (50% ). The most common anatomic location for the inferior parathyroid glands is lateral to the lower pole of the thy-
E K, T H Y RO I D. PARATHY R O I D roid. Ectopic location may be anywhere from the angle of the mandible to the low anterior media tinum. I ntrathyroid and intrathymic locations are een in 2% of cases. Histologically, parathyroid adenoma are rather monomorphic, compo ed of chief cells and oxyphil cells embedded within fibrou and adipose ti ue.
Imaging Findings The optimal imaging modality [or asse sment of primary hyperparathyroidism, and whether imaging is necc ary in all patients, are topic of debale. Because the diag nosis is u ually made on the basis of clinical and biochemical dala, Ihe primary role of imaging i to localize the di ease pre-operatively, and detect any other head and neck pathology that may be t reated simultaneou ly. However. becau c most parathyroid adenomas are peri thyroidal in location, surgical treatment al ne with out preoperative localization i ucces ful in 70 to 90% . depending on the erie , and experience of the surgical team. Although pre-operative imaging improves this uc ce s rate to 97%, opponent of thi approach argue that it doc not significantly change surgical morbidity or operative time. I n addition. some studie suggest that the co t of preoperative imaging outweighs its benefits. Arguments to support pre operative imaging include the need for only unilateral cervicotOmy when a single adenoma is delected, identification of ectOpic adenomas. and reduction in operating r om time. Therefore. the approach should be tailored to each particular in titution depending on the experience of bOlh the head and neck surgeon and radiologi I , and availability of imaging modalities. Longitudinal U of the neck i n a patient wilh
E 1 76
F
NECK,
THYROID, PARATHYROIDI
parathyroid adenoma (Fig. 39-0; courtesy of Dr. Fernando Torrinha) shows a fairly homogeneous, hypoechoic mass posterior to the right thyroid lobe. The mass is oblong and shows increased through transmission. Two small hypoechoic lesions are noted in the inferior third of the right thyroid lobe. The options for imaging the parathyroid glands are multiple and include US, CT, M R I and nuclear medicine stidies. Studies comparing the accuracy of these imaging modalities alone and in several different combinations show conflicting results in different series. Far from being consensual, general guidelines suggest the use of a functional study (parathyroid scintigraphy) in association with an anatomic study (cross-sectional imaging). In the newly diagnosed patient, US should be used as the screening modality because it is the least expensive and most widely available of all modalities, followed by MRI, when the results are negative or doubtful. The ap proach for residual and recurrent hyperparathyroidism includes M R I and parathy roid scintigraphy. For difficult, conflicting cases intraoperative US and invasive stud ies such as angiography and venous sampling for PTH levels, are recommended. On US, using a linear array 7.5 to 10 Mhz transducer, parathyroid adenomas man ifest as round or oblong well circumscribed lesions, peri thyroidal in location. Arathyroid adenomas are usually small, ranging from a few millimeters to 2 cm in size, and homogeneously hypoechoic due to their hypercellularity and cellular monomorphism. Increased through-transmission of the US beam is common due to the lack of acoustic interfaces. Limitations of this modality include inability to de tect ectopic adenomas in the mediastinum or near the airway or osseous structures, and low accuracy in differentiating adenomas from exophytic thyroid nodules and cervical lymphadenopathy. The use of color Doppler may be useful in distinguishing parathyroid adenomas from thyroid nodules, because the former lack Doppler sig nal. In addition, the presence of a bean-shaped lesion with a central area of hyper echogenicity is more likely to be a lymph node. CT has the advantage of allowing simultaneous imaging of the neck and the me diastinum and allows for the detection of most ectopic adenomas. Parathyroid ade nomas present as well-margined lesions, hypodense to the thyroid gland, enhancing in 25% of cases. Limitations of CT include the need for intravenous contrast ad ministration to differentiate parathyroid adenomas from adjacent vessels, artifacts from breathing and swallowing, and beam hardening artifacts, particularly from the shoulder. The inexperienced radiologist may also be confused by tortuous vessels or a tortuous esophagus. Differentiation between adenoma and enlarged lymph nodes may be imposible. MRI is the most accurate of the cross-sectional modalities in detecting eutopic or ectopic parathyroid adenomas. These lesions are of intermediate signal intensity on Tl WI, hyperintense on TIWI and show intense, homogeneous enhancement in most cases. However, highly cellular lesions may be of higher signal intensity on Tl WI and show intermediate signal intensity on TIWI due to a low water content. The most common M R l pitfall is confusion with an enlarged lymph node. Parathyroid adenomas can be heterogeneous with areas of cystic degeneration and hemorrhage, causing further confusion with exophytic thyroid lesions. Calciii cation of a parathyroid adenoma is, however, uncommon. Concomitant thyroid le sions are seen in 41 % of patients diagnosed with primary hyperparathyroidism. Ill defined margins, invasion of adjacent structures and the presence of cervical lymphadenopathy are all suggestive of malignancy. The diagnosis of parathyroid hyperplasia is based solely on enlargement of the parathyroid glands, and the imaging diagnosis is difficult. Normal parathyroid glands usually measure 5 x 3 x 1 mm. When parathyroid hyperplasia is present, MEN syndrome should be considered as it is the underlying cause in 30% of cases. Parathyroid cysts are rarely the cause of primary hyperparathyroidism. Although congenital epithelial parathyroid cysts may occur, most are thought to represent cys tic adenomas. When present, they manifest as peri thyroidal or mediastinal cystic le sions and the differential diagnosis includes congenital cysts such as third and fourth branchial clefts, bronchogenic and thymic cysts. A variety of scintigraphic studies are
1 NECK, THYROID, PARATHYROID PEARLS/PITFALLS
Primary hyperthyroidism is most prevalent in post-menopausal woman.
•
On US, parathyroid adenomas manifest as small, homogeneous, well circumscribed, perithyroidal or mediastinal in location.
•
Imaging evaluation with US and possibly M RI should be used in the newly diagnosed patient.
•
•
•
•
•
•
Evaluation with MRI and Tc ses tamibi studies sbould be used for the palient with residual or re current disease. Consider MEN II (Sipple's syn drome) as a possible diagnosis in patients with parathyroid hyper plasia.
available for parathyroid imaging. The most accurate include technetium 99m and thallium 201 subtraction studies and technetium sestamibi studies with or without thallium 201 or 1 131 subtraction. The most recent literature reports high accuracy for the sestamibi study using delayed (2 bour) images, precluding the need for imag ing subtraction, which can be a source of error and technical difficulty. The increased fixation of thallium 201 and sestamibi in parathyroid adenomas results from the high level of mithochondria in the oxyphilic cells. Limitations of tbe scintigraphic studies include poor detection of small lesions, particularly those smaller then 1 cm, even wben associated with SPECT imaging. Detection of parathyroid hyperplasia and intrathyroidal parathyroid adenomas is also problematic. When evaluating a pa tient with residual or recurrent primary hyperthyroidism of the parathyroid glands aU imaging modalities are less accurate due to post-operative changes, including dis tortion of anatomy, presence of post-inflammatory granulation tissue and reactive lymphadenopathy. Enhanced axial CT section througb the superior mediastinum of a patient with ectopic Parathyroid adenoma (Fig. 39-E; courtesy of Dr. Fernando Torrinba) shows a well-circumscribed enhancing mass in the prevascular compart ment. Enhanced axial CT section in a patient with parathyroid carcinoma (Fig. 39-F; courtesy of Dr. Fernando Torrinha) shows an ill-defined mass in the left tra cheoesophageal groove infiltrating the left thyroid lobe. No clear cleavage plane with the esophagus is noted. Management
Care should be taken not to fail to recognize ectopic adenomas due to limited imaging studies.
The gold standard for treatment of parathyroid adenoma is surgical resection. When a single lesion is successfully localized preoperatively, a unilateral cervicotomy is performed. However, some experts recommend intra-operative determination of PTH levels to exclude the possibility of a second missed lesion. When no presurgi cal imaging is performed, bilateral cervicotomies are routinely performed and, if no lesions are found, an anterior cervicotomy or mediatinostomy may be required. For high surgical risk patients or patients who refuse surgery, parathyroid adenomas may be managed by image guided therapies such as ethanol ablation, laser ablation or electrocautery. Parathyroid carcinoma is managed by radical surgery followed by radiation therapy.
Care should be taken not to fail to recognize multiple lesions.
Suggested Readings
Care should be taken not to mis take enlarged lymph nodes, ves sels, or tortuous esophagus or ex0phytic tbyroidal lesions for parathyroid adenoma.
---
Hodin, R.A., Silen, W.W. Detection and management of parathyroid tumors. Cur 9( 1):75-8, 1997 Jan. Hopkins, CR., Reading, CC Thyroid and parathyroid imaging. Seminars in Ultra sound, Ct and Mr 1 6(4):279-95, 1995 Aug. Loevner, L.A lmaging of the parathyroid glands. Seminars in Ultrasound, Ct and M,. 17(6):563-75, 1 996 Dec. Norton, I.A Reoperation for missed parathyroid adenoma. Advances in Surgery 31 :273-97, 1997. Santos, E., Higgins, CB., Clark, O. Clinical image. Recurrent hyperparathyroidism caused by a paratbyroid cystic adenoma: localization by MRI. lournal of Computer Assisted Tomography 20(6):996-8, 1996 Nov-Dec. Shah a, AR., Sarkar, S., Strashun, A., Yeh, S. Sestamibi scan for preoperative local ization in primary byperparatbyroidism. Head and Neck 19(2):87-91, 1 997 Mar. Shen, w., DUren, M., Morita, E., Higgins, C, Duh, O.Y., Siperstein, AE., Clark, O.H. Reoperation for persistent or recurrent primary hyperparathryoidism. Archives of Surgery 131(8):861-7, discussion 867-9, 1996 Aug. Yousem, D.M., Scbeff, A.M. Thyroid and parathyroid gland pathology. Role of imag ing. Otoiaryngologic Clinics of North America 28(3):621--49, 1995 Jun. rent Opinion in Oncology
1 1 78
NECK, THYROID, PARATHYROIDI
Case 40 Clinical Presentation A 49-year-old female presented with hemoptysis and cough. After clinical examina tion, a CT scan was requested to evaluate a possible mass.
A
B
Radiologic Findings Axial CT images through the level of the upper trachea (Fig. 40-A) and slightly lower (Fig. 40-B) show a right sided posterolateral soft tissue mass which extends into the lumen and causes some airway compromise. There is no evidence of calci fication. The mass appears to erode the cartilage and extend into the adjacent tra cheal bed.
Differential Diagnosis: Primary Tracheal Carcinoma • • • • • • •
Papilloma Granuloma Foreign body Primary tracheal carcinoma Secondary invasion from adjacent neoplasm Amyloid Ectopic thryoid
Diagnosis Primary tracheal carcinoma
1 NECK, THYROID, PARATHYROID Discussion Epidemiology
Primary neoplasms of the trachea are rare, especiaUy when compared with neo plasms of the larynx or lung. Depending on the series reported, there is approxi mately one carcinoma of the trachea for every 20 carcinomas of the larynx, and for every 1 80 lung carcinomas. Why this is so remains unclear. Secondary involvement of the trachea by carcinomas is much more common with 1 0-20 cases for every case of primary tracheal carcinoma.
c
1 1 80
D
NECK,
PEARLSIPITFALLS •
•
•
•
A primary tracheal carcinoma appears as an invasive tracheal mass which narrows the tracheal lumen. In patients with primary tracheal carcinoma, 20% may have metacbronous or synchronous tumors. Hemoptysis is a presenting symp tom in half the patients with pri mary tracheal carcinoma. Care should be taken not to mis take primary tracheal carcinoma for a more benign tracheal process.
THYROID, PARATHYROIDI
Pathophysiology
Primary tracheal tumors in the pediatric age group are distinctly uncommon with 90% of tumors occurring in adults. In the pediatric population, less than 10% of tumors are malignant. In adults, 50% of primary tracheal neoplasms are malignant. Of these most are carcinomas. Half of these carcinomas are the familiar squamous cell carcinoma. It should also be noted that in patients with primary tracheal carci noma, 20% will manifest synchronous or metachronous tumors. Benign nonneoplastic soft tissue masses such as granulomas may occur in the tra chea but they do not tend to have an aggressive radiographic appearance. Clinical Findings
The clinical manifestations of tracheal tumors are primarily through the effects of partial airway obstruction. Cough is present in half the patients and dyspnea and wheezing are common. Approximately 25% of the tracheal lumen must be occluded before obstructive symptoms become dominant. Hemoptysis is present in 10% of patients with benign tracheal tumors, and in over 50% of those with malignant tu mors. Imaging Findings
The diagnosis is suggested by the presence of a destructive mass narrowing the tra cheal lumen. Secondary invasion by malignancies of adjacent structures may have a similar appearance and are much more common than primary tracheal carcinoma. MR images in another patient with thyroid carcinoma (Figs. 40-C and 40-0) show secondary tracheal invasion. The axial T l WI (Fig. 40-C) shows the destructive thy roid mass invading and narrowing the tracheal lumen. The coronal T1 WI (Fig. 40-0) shows similar findings. With a more benign appearing tracheal mass, other considerations such as granuloma or papilloma should be considered. When tra cheal lumen narrowing is due to cartilage changes without a discrete mass, chon dromalacia should be considered. An axial CT in another patient with chondroma lacia of the trachea (Fig. 40-E) shows angular narrowing of the lumen and the absence of a soft tissue mass.
Suggested Readings Holbert, I.M., Strollo, O.c. Imaging of the normal trachea. lou al of Thoracic 10(3): 1 7 1 -9, 1 995 Summer. Weber, A.L. Radiologic evaluation of the trachea. Chest Surgery Clinics of North America 6(4):637-73, 1 996 Nov. rn
Imaging
v. Orbit and Visual Pathways
O R B I T A D V1SUAL PATHWAYSI
Case 41 Clinical Presentation A 96-year-old female presented with left orbital pain, swelling and decrea ed vi ion. On phy ical exam there was swelling and erythema of tbe periorbital soft ti sue proptosis and chemo i . Fundo copic examination bowed papilledema.
c
B Radiologic Findings
Axial cr cans of t he orbit (Fig. 4 1 -A and 4 1 -8) show marked swelling and soft tissue thickening of the pre eptal compartment of the left orbit. There i also soft tissue thickening and enhancement surrounding the globe. Fatty stranding i noted in the extra- and inlraconal compartments. No fluid collections are een. Coronal section (Fig. 4 1 -C) how enlargement of the left lateral rectus mu de with ill defined margin . Also note the stranding of the retrobulbar fat.
1 85
I ORBIT AND VISUAL PATHWAYS Differential D iagnosis: O rbital Swelling • •
Orbital infection (bacterial, viral, fungal) Orbital inflammation: orbital pseudotumor; granulomatous diseases (sarcoid, Wegener's granulomatosis); vasculitides, connective tissue disorders
Diagnosis Orbital cellulitis (serratia isolated on culture)
Discussion Epidemiology
Although the incidence of infections has markedly decreased with the availability of antibiotic therapy, it is still the most common primary orbital disease process, accounting for more than 50% of orbital pathology. It may affect all age groups, although children are especially susceptible. Pathophysiology
Orbital infection may occur by three different mechanisms, which include in de creasing order of frequency, spread from adjacent structures, penetrating trauma and hematogenous spread. Sinusitis is the most frequent cause of orbital cellulitis, accounting for two thirds of all cases of orbital infection, usually spreading from the ethmoid sinus. Spread of infection occurs via the thin, often dehiscent, bony orbital walls and natural foramina. Other sources of direct spread include infection of the facial soft tissues, pharynx and teeth, which may extend into the orbit by means of interconnecting venous plexuses. Orbital involvement also may result from infec tion arising in the lacrimal apparatus (lacrimal sac and lacrimal gland). Penetrating trauma, particularly in the presence of an intraorbital foreign body, is the second most common cause of orbital cellulitis. Hematogenous spread of infection to the orbit may be a late event in patients with septicemia. Orbital infections may be acute, subacute or chronic. The majority of acute infec tions are bacterial in origin and the most frequent agents include staphylococcus, streptococcus, hemophilus, neisseria and pseudomonas. Viral infections can also pre sent acutely and are usualy due to herpes viruses (herpes simplex and herpes zoster). Mycobacterial, fungal and parasitic infections tend to be subacute or chronic at onset. Immunocompromised and diabetic patients are especially prone to fungal infections. Mucor and aspergillus species are the most common opportunis tic agents. They may involve the orbit by direct extension from the nasal cavity and paranasal sinuses, through bone destruction. Pathologically, acute infection is char acterized by polymorphonuclear leucocytes infiltration, leading to necrosis and rapid destruction of the tissue planes. In chronic infections a mononuclear infiltrate predominates with or without associated multinucleated giant cells. Mycobacterial infection is characterized by the presence of caseating granulomas. Angioinvasion and infarction are the hallmarks of fungal infection. Clinical Findings
Presenting symptoms depend on the severity and extent of the orbital involvement. Orbital infections usually spread in a fairly constant fashion from periorbital in flammatory edema to pre-septal cellulitis, followed by retroseptal involvement. Sub periosteal abscess, orbital cellulitis and, eventually, an intraorbital abscess may en sue. Acute inflammation is characterized by rapid onset of orbital pain and periorbital soft tissue swelling and redness involving the preseptal compartment. The orbital septum, a fibromembranous structure within the eyelids and contiguous
ORBIT A N D V ISUAL PATHWAYS1 with the periorbita, prevents spread of infection into the retroseptal compartment in the early stages. Retroseptal involvement presents with more striking symptoms such as loss of visual acuity, diplopia and exophthalmus. A mass in the superotem poral aspect of the orbit suggests the presence of dacryoadenitis, which may be the origin of orbital infection. Physical exam may disclose chemosis, ophthalmoplegia, papilledema, and inflam matory signs in the periorbital soft tissues. Signs and symptoms of sinusitis or other head and neck infections are usually present. In children, orbital cellulitis may be the first sign of sinus infection. History of prior trauma, or the possibility of an intraocular foreign body should be elicited. Complications of orbital cellulitis in clude thrombosis of the superior orbital vein and cavernous sinus and intracranial spread of infection, with development of epidural, subdural or intra parenchymal abscesses.
Imaging Findings Imaging studies are performed to determine the etiology, extent and complications of the disease. One of the major goals is to differentiate between pre- and retrosep tal involvement. which have different prognoses and management. CT is the modal ity of choice, as it nicely depicts cortical bony changes and radiopaque intraorbital foreign bodies, and differentiates phlegmon from drainable fluid collections. Thin, 3mm axial and coronal sections should be obtained through the orbits and paranasal sinuses after intravenous contrast administration. M R I is useful in the evaluation of intracranial complications and magnetic resonance venography ( M RV) may dis close thrombosis of the superior ophthalmic vein and cavernous sinus without the need for intravenous contrast administration. Imaging cannot differentiate between inflammatory periorbital edema and pre septal cellulitis, as they both present with soft tissue thickening of the periorbital soft tissues and stranding of the subcutaneous fat. These inflammatory changes involve the eyelids and adjacent soft tissues. There may be associated uveoscleral thickening and enhancement. Progression to orbital cellulitis manifests as stranding of the intra- and extraconal fat, proptosis and, eventually, as enlargement of the extraocular muscles (EOMs). Subperiosteal phlegmon or abscess is not uncommon when infection spreads from the ethmoidal sinuses. Accumulation of inflammatory
o
E
1 87 1
I ORBIT
AND VISUAL PATHWAYS tissue and edema beneath the periorbita manifests on cr as a soft tissue density located between the lamina papyracea and the medial rectus muscle. Displacement of a thickened periorbital membrane and medial rectus into the orbit is usually seen. cr of the orbits of another patient ( Fig. 4 1 -0) shows soft tissue thickening and fatty stranding limited to the preseptal and periorbital soft tissues on the left. These inflammatory changes extend to the medial canthus and prezygomatic soft tissues. 111is patient was diagnosed with orbital cellulitis secondary to ethmoidal sinusitis. Progression to a central area of hypodensity surrounded by an enhancing rim indicate abscess formation. This is usually accompanied by increasing mass effect upon the EOMs and optic nerve. Enlargement of the EOMs with ill-defined mar gins also may be depicted on cr. Enhancement along the optic nerve sheath indi cates perineuritis. An intraconal abscess is rarely seen. Thrombosis of the superior ophthalmic vein and cavernous sinus manifest on CT by e nlargement and absence of contrast enhancement. The hallmark of fungal infection is the presence of bone destruction and rapid progression, whjch can be noted in Figure 4 1 -E. This axial T2W image from another patient hows a crescentic region of hyperintensity in the preseptal compartment of the right orbit, extending laterally into the suprazygo matic masticator space. The right globe is slightly proptotic. 111ere is diffuse hyper intensity of the intra- and extraconal fat. The right ethmoidal air cells are opacified and there appears to be bony disruption of the medial wall of the right orbit. The diagnosis in this case was mucormycosis of the paranasal sinuses invading the orbit in a diabetic patient. (Case courtesy Dr. J.P. Wensel. )
Management Medical therapy with antibiotics should be directed against the causal agent. according to the results of orbital cultures and antibiograms. Retroseptal involve ment may require intravenous therapy, especially when the optic nerve is in danger. Subperiosteal and intraorbital abscesses should be drained surgically. Early surgical debridement is also required in cases of fungal infection to avoid the devastating consequences of intracranial extention.
Suggested Readings Davis, P.C.. Newman, .1 . Advances in neuroimaging of the visual pathways. Amer ican Journal of Op/lIhalmology 1 2 1 (6):690--705. 1 996 Jun. .
Haugen, J.R., Ramlo, J. H., Serious complications of acute sin usitis. Posigraduare Medicine 93( 1 ): 1 1 5-8, 1 22, 1 25, 1 993 Jan. Klapper. S.R., Patrinely. J.R., Kaplan, S.L., Font, R.L.. Atypical mycobacterial infec tion of the orbit. Op/1fhalmology 102( 1 0) : 1 536-4 1 . 1 995 Oct. Mauriello. lA. Jr .. Yepez. .. Mostafavi, R .. Barofsky, J.. Kapila. R .. Baredes. S., or ris, J. Invasive rhinosino-orbital aspergillosis with precipitous visual loss. Canadian Journal of Ophlhalmology 30(3): 1 24-30, 1 995 Apr. Mitchell, C.S., Nelson. M.D. Jr., Orofacial abscesses of odontogenic origin in the pe diatric patient. Report of two cases. Pedialric Radiology 23(6 ):432-4. 1 993. Moll, G.W. Jr .. Raila, EA .. Liu. G.c.. Conerly. A.W. Sr. Rhinocerebral mucormycosis in 1 0 0 M. Sequential magnetic resonance imaging of long-term survival with inten sive therapy. Diabeles Care 1 7( I I ): 1 348-53, 1 994 Nov. Sullivan, T.l, Patel, B.c., Aylward, G.W., Wright, J.E. Anaerobic orbital abscess sec ondary to intraorbital wood. Auslralian and New Zealand Journal of Ophthalmol ogy 2 1 ( 1 ):49-52. 1 993 Feb.
ORBIT A N D V ISUAL PATHWAYSI
Case 42 Clinical Presentation The patient is an adult male who presented with new onset proptosis on the right.
A _........ .
I ORBIT
AND V I S UA L PATHWAYS
Radiologic Findings An axial T l W, noncontrast MR image through the orbit (Fig. 42-A) shows a ho mogenous enlargement of the right lacrimal gland. There is no evidence of bony in vasion. The above findings were confirmed in the coronal ( Fig. 42-B) and axial TIW (Fig. 42-C) images.
Differential Diagnosis: Lacrimal Gland Mass •
•
Lymphoid/I nflammatory: acute (viral, bacterial, orbital pseudotumor, lymphoma) or chronic (sarcoid, Wegener's, thyroid opthmalopathy, Sjogrens's syndrome, Mickulicz syndrome) Epithelial neoplasms: pleomorphic adenoma or malignant tumors (adenoid cystic carcinoma, mucoepidermoid carcinoma, adenocarcinoma)
Diagnosis Lacrimal gland enlargement due to acute dacroadenitis
Discussion Pathophysiology One useful approach to diagnosing masses of the lacrimal glands is to consider that approximately 50% are of the Iymphoidlinflammatory type and 50% are neoplasms of epithelial origin. Dermoid cysts are not included in this scheme. This is because although dermoid cysts may arise near the lacrimal fossa, they are not true lacrimal gland lesions, but, instead, arise from embryological rests in the orbit. Metastases to the lacrimal gland have been reported, but they are rare. The lesions in the lymphoid/inflammatory group run the spectrum from mild in flammatory conditions all the way to lymphoma (usually nonhodgkins). Lesions in this group tend to result in diffuse enlargement of the gland and usually show no bone erosion. It is useful to group these lesions according to their time course. The acute group includes bacterial and viral dacroadenitis and tends to involve younger age groups. Orbital pseudotumor and lymphoma can also present with this picture. Entities in the acute group can also have a more chronic course. Other more chronic conditions to be considered are sarcoid, Wegener's, thyroid opthmalopathy, Mickulicz, and Sjogrens's syndromes. Mickulicz's syndrome is non specific lacrimal (and salivary) gland swelling associated with leukemia, lymphoma, TB, syphilis, or sarcoid. Sarcoid Sjbgrens's disease is lymphocytic infiltration and enlargement of lacrimal (and salivary) glands associated with connective tissue diseases. This infiltration may
D
1 1 90
ORBIT A N D VISUAL PATHWAYSI
Half the cases are lymphoid/in flammatory and half are epithe lial neoplasms.
be associated with decreased lacrimation (xerophthalmia) and xerostomia (dry mouth). The other 50% of lacrimal gland masses tend to be epithelial cell tumors. Radi ographically this group is more likely to show aggressive behavior and occasionally bone involvement. Fifty percent of the tumors in this group are pleomorphic ade nomas. A reformatted sagittal CT scan in another patient with a pleomorphic ade noma of the lacrimal gland is seen in Figure 42-D. The remaining 50% include adenoid cystic carcinoma, mucoepidermoid carci noma, adenocarcinoma, and others.
Epithelial tumors tend to be more aggressive.
Imaging Findings
PEARLS/PITFALLS •
•
•
•
•
Lacrimal gland enlargement is often a non-specific radiographic finding.
Dermoid cysts may occur in this location but also occur through out the orbit and in other loca tions in the head and neck. Avoid mistaking other (non lacrimal) masses for lacrimal gland enlargement.
-
Enlargement of the lacrimal gland is usually a nonspecific radiographic finding that may be due to either inflammatory (dacroadenitis) or neoplastic conditions. The lacrimal glands may be involved with a variety of disease processes. However, because of the histologic similarities of the lacrimal gland with salivary gland tissue, these two groups of glands share many of the same pathologies. Although the radi ologic findings are usually nonspecific, the clinical setting may help suggest the diagnosis.
Management Clinical management of lacrimal gland masses depends on the pathology involved. While a specific tissue diagnosis is often not possible based on the CT or M R I find ings, these studies provide valuable information about the extent of disease and involvement of adjacent structures.
Suggested Readings Bilaniuk, L.T., Farber, M . Imaging of developmental anomalies of the eye and the orbit. American loumal of Neuroradiology 1 3(2):793-803, 1992 Mar-Apr. Carmody, R.F., Mafee, M . F., Goodwin, lA., Small, K., Haery, C. Orbital and optic pathway sarcoidosis: M R findings. American lournal of Neuroradiology 1 5(4):775-83, 1 994 Apr. Krzystolik, M., Warner, M.A. Orbit and adnexal neoplasia. Current Opinion in Oph thalmology 6(5):78-85, 1995 Oct. Shields, c.L., Shields, lA. Lacrimal gland tumors. International Ophthalmology Clinics 33(3): 1 8 1 8, 1 993 Summer.
10RBIT
A
Case 43 Clinical Presentation A 9 1 -year-old female pre ented with acute left orbital pain. On clinical exam, there was no proptosis. No inflammatory changes were noted in the anterior orbital com partment.
A
1 1 92
B
ORBIT AND VI SUAL PATHWAYSI
Radiologic Findings An axial enhanced TI W image with fat-saturation (Fig. 43-A) shows enlargement of the lateral and medial recti, with involvement of the anterior tendinous insertion on the globe and abnormal enhancement of the intraconal fat. Coronal sections (Figs. 43-B and 43-C) also show generalized enlargement of the extraocular muscles (EOMs) which have ill-defined margins and enhancement of the retrobulbar fat. Abnormal enhancement also is seen along the optic nerve sheath. These changes are more pronounced near the orbital apex. There is no evidence of extension into the optic tracts or cavernous sinus.
Differential Diagnosis: E nlargement of the E xtraocular Muscles • • •
• •
•
I n fection (bacterial, viral or fungal) Thyroid orbitopathy Inflammatory conditions: orbital pseudotumor, Sjiigrens's syndrome, Mickulicz's syndrome, granulomatous conditions (sarcoid, Wegener's granulomatosis), con nective tissue disorders (rheumatoid arthritis, lupus, scleroderma), retained for eign bodies Vasculitides (PAN, giant cell arteritis) Tumors: hemangioma, rhabdomyoma, plasmacytoma, lymphoma, leukemia, rhab domyosarcoma Amyloidosis
Diagnosis Orbital pseudotumor
Discussion Epidemiology The term orbital pseudotumor was first used by Birsch-Hirschfeld in 1 905 to de scribe an idiopathic inflammatory condition involving the orbit. This entity is the third most common ophthalmologic disease after thyroid orbitopathy and Iympho proliferative disorders, and is the most frequent cause of an intraorbital mass in adults. [t is the underlying cause of unilateral exophthalmos in 25% of patients. Only 5 to 15% of cases of orbital pseudotumor occur in the pediatric age group.
Pathophysiology Orbital pseudotumor defines a clinically and histologically heterogeneous group of lesions for which an identifiable cause cannot be found. I t is a diagnosis of exclusion, after other local or systemic disease processes with similar c1inico-radiographic find ings have been ruled out. Proposed etiologic factors include an autoimune process and Iymphoproliferative disease. Histologic changes define two different types of orbital pseudotumor and may vary in the course of the disease. In the acute inflammatory type there is infiltra tion of the orbit by polymorphous acute inflammatory cells dispersed in a matrix of granulation tissue, whereas in the chronic sclerosing form, inflammatory changes are replaced by fibrotic tissue with subsequent stretching and deformity of the intraorbital structures. There is also a predominantly lymphocytic variety of pseudo tumor, thought to be a prelymphomatous condition. The presence of germinal follicles and increased vascularity helps in differenting this condition from true lymphoma. 1 93
1 0RBIT
AND VI SUA L PATHWAYS
Clinical Findings The symptoms in orbital pseudotumor depend on the degree of inflammatory re sponse, the stage (acute, subacute or chronic), and on the affected orbital structures. The most common symptoms in the acute inflammatory form of disease include abrupt onset of orbital pain, swelling of the periorbital tissues, double vision and, occasionally, decreased vision. This form of presentation is easily confused with orbital or periorbital infection, and it is common for patients to be treated initially with antibiotics for several days. On physical exam, there may be chemosis, sclero uveitis, papillitis and exudative retinal detachment. The chronic sclerosing form has a more indolent course. Patients typically present with ophthalmoplegia, diplopia, proptosis and progressive visual loss. Several clinico-radiographic classifications based on the involvement of different orbital structures have been proposed, but these normally overlap. The most fre quently used separates orbital pseudotumor into six different categories: acute and subacute idiopathic anterior orbital pseudotumor, acute and subacute idiopathic diffuse orbital inflammation. myositic form, apical orbital inflammation (Tolosa H unt syndrome), idiopathic dacryoadenitis, and idiopathic perineuritis. The Tolosa Hunt syndrome is a variant of pseudotumor characterized by an inflammatory infil tration of the orbital apex, with extention into the superior orbital fisure and cavernous sinus. Clinically, it manifests with painful ophthalmoplegia involving cra nial nerves I l l, I V and VI and hyposthesia of the periorbital tissues due to involve ment of the first division of the trigeminal nerve. Isolated involvement of the lacrimal gland may be acute or chronic, presenting as either a painful or painless mass in the superolateral orbit. Differentiation from dacryoadenitis, lymphoma or other lacrimal gland tumors may require tissue sam pling. Perineuritis presents with orbital pain on extraocular movement, decreased vision and papilledema. I ncreased pain upon retrodisplacement of the globe and the pres ence of proptosis differentiates perineuritis from true optic neuritis. I rreversible ophthalmoplegia and amaurosis are dismal complications when the disease is not promptly recognized and treated.
Imaging Findings I maging of orbital pseudotumor, although nonspecific, is useful in defining the ex tent of the disease and excluding true orbital tumors. When the differentiation from orbital tumor is not possible, FNA may be required. CT and M R I are best suited for these goals, with M R I being superior to CT in the evaluation of the optic nerve, cav ernous sinus and globe. Fat-saturated TI W sequences after contrast enhancement are required for evaluation of inflammatory changes in the retrobulbar fat, optic nerve and cavernous sinus. Ocular ultrasound is a good method to evaluate the globe, but much less accurate for assessment of the retrobulbar structures. The structures involved by orbital pseudotumor are, in decreasing order of fre quency, retrobulbar fat (76% ), extraocular muscles (57% ), optic nerve (38% ), uvea and sclera (33% ), and lacrimal gland (5% ) . I n the anterior variety o f pseudotumor, the inflammatory changes are seen i n the preseptal orbital compartment and in the globe itself. There is swelling, thickening and enhancement of the preseptal soft tissues. Ocular findings include uveoscleral thickening, blurring of the ocular-optic nerve junction and accumulation of fluid in Tenon's capsule. An accumulation of fluid beneath Tenon's capsule. anechoic on ultrasonography (T sign), appears as a crescentic area of hyperintensity on TIW MR images. Retinal detachment may also be present. Diffuse orbital pseudotumor, also referred to as a tumefactive or infiltrative type of pseudotumor, is characterized by increased soft tissue density and abnormal enhancement of the retrobulbar fat, which molds itself around the globe without distorting the surrounding structures. The globe may be slightly proptotic, but is nor-
1 1 94
ORBIT AND V ISUAL PATHWAYSI mal in shape. I n the sclerosing variety of pseudotumor, the extensive desmoplastic changes manifest as regions of bypointensity on both Tl W and T2W images and a greater amount of distortion and retraction of the orbital structures is seen. These findings harbor a poor prognosis. The absence of mass effect and bony invasion are the main diagnostic clues to differentiate pseudotumor from a true orbital tumor, although distinction from orbital lymphoma may be impossible based on imaging alone. In the myositic form, the inflammatory changes involve one or more EOMs on the same side. Bilateral muscular involvement is less common and, when present, may be confused with thyroid orbitopathy. The main characteristics are enlargement of the muscle(s), involving both the belly and tendinous insertions, and ill-defined margins. The snperior muscle complex and the medial rectus are the most com monly affected. Apical orbital inflammation presents as irregular, infiltrative, enbancing soft tis sue involving the orbital apex, which may compress the muscle cone and optic nerve, leading to ischemic neuropathy. Extension of this abnormal soft tissue into the cavernous sinus and superior orbital fissure is a hallmark of the Tolosa-Hunt syndrome. Lacrimal adenitis manifests as a nonspecific and diffuse enlargement of the lacrimal gland, with ill-defined margins, and associated inflammatory changes in the surrounding soft tissues. The morphology of the gland is usually preserved. Idiopathic perineuritis usually occurs in association with other inflammatory find ings, but occasionally as an isolated finding. The hallmark is enlargement and en bancement of the optic nerve-sheath complex, which may show ill-defined margins. I n general terms, the most important imaging features in differentiating pseudo tumor from true neoplastic disease are the absence of mass effect, confinement to tbe space of origin and the lack of bony destruction. However, there are a few reported cases of extraorbital extension of pseudotumor, including intracranial extension. As opposed to lymphoma, orbital pseudotumor shows intense enhance ment and is hyperintense on T2W images (except for the sclerosing variety). When tbe diagnosis is in doubt, imaging guided FNA, followed by flow cytometry or Southern blot analysis of tbe cytopatbologic specimen, usually allows differentiation between the lymphocytic variety of pseudotumor and true lymphoma. M R I of the orbits in another patient (enhanced Tl W images with fat-saturation,
D
E
( ORBIT
AND VI SUAL PATHWAYS
PEARLS/PITFALLS Sudden onset of unilateral
•
painful proptosis or ophthalmo plegia in an otherwise healthy patient suggests an orbital pseudotumor. •
•
•
•
Rapid and lasting response to steroids usually indicates a pseudotumor. Imaging shows abnormal en hancing soft tissue. with ill defined margins, confined to the space of origin and little or no mass effect. Do not mistake an orbital pseudotumor for a neoplastic process. Partial response to steroids does not exclude the possibility of an orbital neoplasm!
Fig. 43-D) show intense enhancement in the region of the orbital apex with indis tinctness of the muscular cone, intraconal fat and optic nerve sheath. This patient was diagnosed with orbital pseudotumor (apical variety). For another patient with an orbital pseudotumor (anterior variety), an axial CT of the orbits (Fig. 43-E) demonstrates swelling and soft tissue thickening of the pre septal compartment of the left orbit. There is thickening and abnormal enhance ment of the ocular layers, representing uveo-scleritis. The retrobulbar fat adjacent to the globe also shows stranding, consistent with inflammatory change. An enhanced frequency selective fat suppression imaging ( FATSAT) T1 W, coro nal M R image shows enlargement and enhancement of the medial, inferior, and lateral recti of the left orbit. The muscles show ragged margins with slight enhance ment of adjacent fat. Note also enhancement surrounding the optic nerve. This patient has orbital pseudotumor (myositic variety with associated perineuritis).
Management Orbital pseudotumor usually has a dramatic and rapid response to steroids. Thus. not infrequently, a course of steroids is attempted when the diagnosis is in doubt. However, several other diseases, including tumors, may have a partial response to steroids. Close follow-up of patients is mandatory whenever the diagnosis is in doubt. The acute inflammatory variety of the disease is particularly sensitive to steroids. TIle subacute and chronic forms. including the sclerosing variety. are unre sponsive. Radiation therapy and immunosuppressors may be used in patients unre sponsive to steroids, but are not successful in treating fibrosclerosing lesions. When the optic nerve is in danger of compressive ischemic neuropathy, surgical decom pression should be attempted.
Suggested Readings Atabay, c., Tyutyunikov, A., Scalise, D., Stolarski, c., Hayes. M.B .. Kennerdell, 1.S., Wall, 1. Serum antibodies reactive with eye muscle membrane antigens are detected in patients with nonspecific orbital inflammation. Ophthalmology 1 02( 1 ): 1 45-53, 1 995 Jan. Berger, 1.W, Rubin. P.A .. Jakobiec, F.A. Pediatric orbital pseudotumor: case report and review of the literature. international Ophthalmology Clinics 36( I ): 1 6 1 -77, 1 996 Winter. Char, D.H., Miller, T., Orbital pseudotumor. Fine-needle aspiration biopsy and re sponse to therapy. Ophthalmology 1 00( 1 1 ): 1 702-10, 1 993 Nov. de Jesus, 0., Inserni. 1.A., Gonzalez, A., Colon, L.E. Idiopathic orbital inflammation with intracranial extension. Case report. Journal of Neurosurgery 85(3):5 1 0-3, 1 996 Sep. Mombaerts, I.. Goldschmeding, R., Schlingemann, RO., Koornneef, L. What is or bital pseudotumor? Survey of Ophthalmology 4 1 C I ):66-78, 1 996 Jul-Aug. Mombaerts, 1 . , Schlingemann, R.O., Goldschmeding, R, Koornneef, L. Are systemic corticosteroids useful in the management of orbital pseudotumors? Ophthalmology 1 03(3):52 1 -8, 1 996 Mar. Mombaerts, I . , Schlingemann, Ro., Goldschmeding, R., Koornneef, L. Idiopathic granulomatous orbital inflammation. Ophthalmology 1 03 ( 1 2):2 1 35-4 1 , 1 996 Dec. Notter, M., Kern, T., Forrer, A., Meister, F; Schwegler, N. Radiotherapy of pseudo tumor orbitae. Frontiers of Radiation Therapy and Oncology 30: 1 80-9 J , J 997. Osguthorpe, 1.D.. Hochman, M. l nflammatory sinus diseases affecting the orbit. 010laryngologic Clinics of North America 26(4):657-7 J . 1 993 Aug. Weber, A.L., Jakobiec, F.A., Sabates, N.R Pseudotumor of the orbit. Neuroimaging Clinics of North America 6( 1 ):73-92, 1 996 Feb.
( 1 96
ORBIT A N D VISUAL PATHWAYSI
Case 44 Clinical Presentation A 5 1 -year-old female presented with progressive bilateral painless exophthalmus.
B
A
Radiologic Findings An axial CT through the optic nerve canal (Fig. 44-A) shows bilateral enlargement of the medial recti and crowding of the orbital apices. The lateral recti appear nor-
I ORBIT
A N D VISUAL PATHWAYS mal in thickness. A mild degree of proptosis is also noted. Coronal sections ( Figs. 44-B and 44-C) show bilateral enlargement of the extraocular muscles (EOMs) with relative sparing of the lateral recti. The section near the orbital apices ( Fig. 44-C) again shows crowding, which is more pronounced on the right side. Note that the right optic nerve is surrounded only by a thin rim of fat.
Differential Diagnosis: Extraocular Muscle E nlargement •
Endocrine • Thyroid ophthalmopathy • Acromegaly • I nflammatory • Pseudotumor • I n fection: bacterial, fungal, parasitic (cysticercosis, trichinosis) • Plasma cell granuloma • Sarcoid • Neoplastic • Benign: rhabdomyoma • Malignant: lymphoma, rhabdomyosarcoma, metastatic disease • Vascular • Carotid cavernous fistula • Extradural arteriovenous fistula • Deposition diseases: amyloid
Diagnosis Thyroid orbitopathy
Discussion Enlargement of the EOM may result from three basic mechanisms: infiltration by abnormal cells (inflammatory or neoplastic), deposition of abnormal material (amy loid, mucopolysaccharides), or edema from vascular congestion. The extent of involvement, and un i- or bilaterality of the process are valuable clues in the differential diagnosis. While neoplastic tumors vascular processes and pseudotumors tend to be unilateral, endocrine diseases tend to affect both orbits. When the clinical and imaging findings are non diagnostic, fine needle aspiration (FNA) guided by imaging is a valuable tool for therapy planning.
Epidemiology Thyroid orbitopathy is also referred to as thyroid associated ophthalmopathy, au toimmune thyroid disease, endocrine exophthalmus and Graves' ophthalmopathy. It is the most common orbital disorder, affecting approximately 0.5% of the US population. Thyroid orbitopathy is the most frequent cause of exophthalmus in adults, representing 80% of bilateral and 15 to 28% of unilateral exophthalmus. It usually presents in adulthood with a peak incidence in the fourth and fifth decades of life. Only 5% of cases occur before age 1 5 . Females are more frequently affected. The EOMs are the most common orbital structures to be affected. The involve ment is bilateral in 70 to 85% of cases, although asymmetric in 20 to 30% . Isolated involvement of a single EOM is much less common, only seen in 1 0% of patients. Hyperthyroidism is present in the majority of patients (70% ), with increased lev els of triiodothyronine (D) and tetraiodothyronine (T4). However, thyroid oph thalmopathy may be the first sign of Graves' disease and preceed any hormonal changes by a year or more. TIle incidence of proptosis varies widely in different se ries, ranging from 35 to 93% .
1]2?
ORBIT A N D V ISUAL PATHWAYSI Table 44-1
Werner's Modified Staging System for Thyroid Orbitopathy
I-Asymptomatic eyelid retraction I I-Symptomatic eyelid retraction I II-Proptosis greater than 22 mm without diplopia I V-Proptosis greater than 22 mm with diplopia V-Corneal ulceration VI-Loss of vision
Pathophysiol ogy Thyroid ophthalmopathy is due to deposition of abnormal material in the orbital contents, predominantly involving the EOMs and retrobulbar fat. This process is thought to have an autoimune origin due to cross-reactivity between the eye muscle and thyroid autoantigens. Several autoantibodies have been implicated, including long acting thyroid stimulating factor (LATS) and thyroid stimulating immunoglobulins (TSI), which are now recognized as antibodies against the thy rotropin receptors of the thyroid gland. In the early acute i nflammatory stage of the disease, there is deposition of hygro scopic mucopolysaccharides and glycoproteins, and infiltration by inflammatory cells (lymphocytes and mast cells). With disease progression, there is replacement by collagenous tissue, necrosis of muscle fibers and fatty degeneration. These changes result from chronic increase in orbital pressure, which leads to ischemia and subsequent edema and fibrosis of the EOMs. The fibrotic phase of the disease is usually irreversible. Several factors contribute to the development of proptosis, in cluding enlargement of the EOMs increased volume of retrobulbar fat and vascular congestion. Ischemia of the optic nerve, due to compression by the enlarged mus cles in the orbital apex, may result in optic neuropathy. The degree of orbital involvement does not correlate with the degree of thyroid dysfunction or the levels of circulating LATS. Thyroid orbitopathy also has been associated with hypothyroidism and Hashimotos' thyroiditis.
Clinical Findings The most common presenting symptoms are proptosis and double vision. On clini cal exam, lid lag due to retraction of the upper eyelid, restricted ocular motility and loss of sight may be noted. In the acute phase of the disease periorbital swelling and chemosis are common. Blindness from ischemic optic neuropathy is a dismal conse quence of thyroid orbitopathy if early decompression is not undertaken. Corneal ul ceration, due to exposure keratitis, is another possible complication of the disease. A family history should be elicited, because 30% of patients have other familial autoimune disorders. Staging systems to evaluate the severity and progression of the disease have been devised. The most commonly used is based on clinical findings and classifies patients into six different stages (Table 44- 1 ) .
I maging Findings U l trasonography, CT and M R I may be used to evaluate orbital involvement in Graves' disease. As orbital involvement may be subclinical, all patients should have an imaging study as a screening test for thyroid orbitopathy. Imaging is useful for detection and serial follow up of proptosis and is crucial for detection of optic nerve compression. The degree of proptosis is measured in the axial plane at the level of the lens, from the interzygomatic line to the anterior margin of the globe. Another important role of imaging is providing guidance for FNA of undeterminate masses.
IORBIT A
F
H
12 00
ORBIT AND V ISUAL PATHWAYSI Ocular US is well-suited for orbital screening in patients with Graves' disease as it is innocuous, inexpensive and rapidly performed. The major finding on cross sectional imaging is enlargement and enhancement of the EOM, which is usually bilateral and asymmetric. Typically, the muscles most fre quently involved are, in decreasing order of frequency, the inferior, medial, superior, and lateral rectus. In patients with isolated involvement of a single muscle the su perior rectus and levator palpebrae complex is most commonly affected. Classically, the swelling is maximal in the belly of the muscle, sparing the tendinous attachment to the globe, and the margins of the involved muscles are smooth. These are impor tant distinguishing features from orbital pseudotumor, which usually involves the entire length of the muscle and shows ill-defined margins. Other CT findings include increased volume and increased density of the retrobulbar fat and uveoscleral thick enmg. Crowding of the orbital apex is usually associated with dilatation of the superior orbital vein and increased diameter of the optic nerve sheath due to CSF trapping in the subarachnoid space. On M R imaging the enlarged muscles are hyperintense on TIW images due to edema and inflammation. Fat-saturated enhanced Tl W images are very sensitive for detection of muscle enlargement due to the increased vascularity of the muscle. The better contrast resolution of M R I makes it the best method to evaluate for optic nerve compression. A "tram track" sign on TIW images may be seen representing dilatation of the subarachnoid space surrounding the optic nerve and is suspicious for optic nerve compression. Differential diagnosis of this sign includes increased intracranial pressure and pseudotumor cerebri. Scintigraphic studies using I I 11n labelled octeotride have proven helpful in iden tifying and following patients with inflammatory eye disease as the tracer accumu lates in the retrobulbar space. TIle radiotracer fixates in the cell membrane of activated lymphocytes expressing somatostatin receptors. Axial CT of the orbits in another patient (Fig. 44-0) shows symmetric bilateral enlargement of the medial and lateral recti, more prominent at the muscular belly and tapering toward the tendinous insertion on the globes. The margins of the mus cles are well-defined. The volume of retrobulbar fat appears increased and shows scanty linear hyperdensities consistent with increased vascularity. There is bilateral proptosis more prominent on the right side. Axial (Fig. 44-E) and coronal (Fig. 44-F) CTs of the orbits in another patient show the appearance of the orbits after decompressive surgery. There has been bilateral resection of the medial wall of the orbits and the markedly enlarged medial recti are seen to herniate through the surgical defect, decompressing the optic nerves. Axial (Fig. 44-G) and sagittal TIW (Fig. 44-H) M R images of the orbits show en largement of the muscular bellies of the medial, superior and inferior recti, sparing the tendinous insertions in the globe. There is some crowding of the orbital apices but a thin rim of fat is seen surrounding both optic nerves. There has been prior or bital decompression with partial resection of the lamina papyracea bilaterally.
Management Left to its natural course, the disease resolves spontaneously in the majority of patients. However, in 1 0% of cases the progression of orbital involvement leads to recurrent corneal ulcerations and loss of vision. Some local measures may relieve orbital symptoms, particularly in the acute phase of the disease. TIlese include head elevation at night, and lubricating eyedrops and ointments. Steroids and radiation therapy are also useful in the acute inflammatory stage and should be administered to patients with progressive disease that is unresponsive to local measures. Im munosuppressive drugs have been used with varying success rates, although the in herent risks of this kind of therapy limit their use in this benign condition. Surgery is the only successful therapy in the chronic fibrotic stage of the disease and may be used to correct eyelid retraction or to decompress the optic nerve. Surgical proce-
I ORBIT
AND VI SUAL PATHWAYS
PEARLS/PITFALLS
Bilateral or unilateral painless proptosis is one of the most com mon presenting symptoms of thyroid orbitopalhy.
•
M R images of the orbit show EOM enlargement involving the
•
muscular belly, sparing the tendi nous insertions on the globe. findings include an increased volume of the retrobulbar fat.
cr
•
Do not exclude the diagnosis in euthyroid patients!
•
•
•
Do not fail to recognize muscle enlargement (when bilateral and symmetric). Avoid failing to recognize optic nerve compression.
dures attempt to increase the bony orbit in order to decompress the orbital con tents. One or more orbital walls may be ressected depending on the degree of com pression.
Suggested Readings Cangiarella, J., Cajigas, A., Savala, E. et al. Fine needle aspiration cytology of orbital masses. Acta Cytological 40(6): 1205- 1 2 1 1 , 1 996 Nov-Dec. Kao, S.C, Kendler, D.L., N ugent, PA., Adler, J.S., Rootman. J. Radiotherapy in the management of thyroid orbitopathy. Computed tomography and clinical outcomes. Archives of Ophthalmology 1 1 1 (6):8 1 9-23, 1 993 Jun. McNab, A.A. Orbital decompression for thyroid orbitopathy. Australian and New Zealand Journal of Ophthalmology 25( 1 ):55-6 1 , 1 997 Feb.
Postema, P.T., Krenning, E.P., Wijngaarde, R., Kooy, P P., Oei, H.Y., van den Bosch, WA., Reubi, J.C, Wiersinga, WM .. Hooijkaas, H . , van der Loo T. et al. 1 1 1 In-DTPA-D-Phe l octreotide scintigraphy in thyroidal and orbital Graves' disease: a parameter for disease activity? Journal of Clinical Endocrinology and Metabolism 79(6): 1 845-5 1 , 1 994 Dec. .
Rosen, CE., Kennerdell, J.S. Extreme eyelid swelling as an unusual presentation of dysthyroid orbitopathy. Journal of Nellro-Ophthalmology 1 5(2):84-9, 1 995 Jun . Sendrowski, D.P. Hyperthyroidism. Optometry Clinics 3(4):87-97, 1 994.
Shokeir, M.O., Pudek, M.R., Katz, S., Rootman, J., Kendler, D.L. The relationship of thyrotropin receptor antibody levels to the severity of thyroid orbitopathy. Clinical Biochemistry 29(2):1 87-9, 1 996 Apr. Villadolid, M.C, Yokoyama. N., Izumi, M. et al. Untreated Graves' disease in pa tients without clinical ophthalmopathy demonstrate a high frequency of extraocular muscle enlargement, JOllrnal of Clinical Endocrinilogy and Metabolism. 80(9):28302833, 1 995. Weber, A., Dallow, R., Sabates, N. Graves' disease of the orbit. Nellroimaging Clin ics of North America 6( 1 ):6 1 -72. 1 996 Feb. Wilson, WB., Prochoda, M . Radiotherapy for thyroid orbitopathy. Effects on extraocular muscle balance. Archives of Ophthalmology 1 13( 1 1 ): 1 420-5, 1 995 Nov.
1202
O R B IT
D VISUAL PATHWAY
Case 45 Clinical Presentation A 58-year-old female presented with nonspecific left orbital pain. The ophthalmo logic exam was normal.
B
A Radiologic Findings
Axial ( Fig. 45-A) and coronal ( Fig. 45-B) fat- uppre ed TI WI M R I cans how an ill-defined area of hyperinten ity in the medial and inferior aspect of tbe left orbit. involving both the extra- and intraconal fal. There is no ignal abnormality or mass effect on the adjacent extraocular mu c1es ( EOM). I ncidentally, prior cataract urgery is noted bilaterally.
Differential Diagnosis: Diffuse Hyperintensity in the Extra- and Intraconal Fat on FATS AT Tl WI • •
Artifactual: art i fact due to failure of fat suppression Pathologic: orbital p eudotumor. orbital cellulitis. orbital neoplasm
Diagnosis Artifact due to a ymmetric failure of fat-suppres ion
Discussion Epidemiology Artifacts associated with M R fat uppre sion imaging are relatively frequent in orbital studies and may mimic orbital pathology. These include complete or partial failure of fat suppression. which may be symmetric or asymmetric.
Pathophysiology Fat uppressioo M R J techniques provide a method of improving patial resolution by decreasing t he 110rmal hyperinten ity of the orbital fal. which may ob cure
203 1
/ORBIT
AND VISUAL PATHWAYS equally hyperintense lesions on enhanced or nonenbanced T l WI sequences. 1l1cre are several techniques of fat suppression available on M R I scanners which are based on frequency selective pulses ( FATS AT) phase difference descrimination. saturation of signal from short Tl relaxation times (STIR) and variation of phase encoding gradients. The former technique, FATS AT, is the most commonly used and is subject to this artifact. The FATSAT sequence consists of delivery of a 90 degree radiofrequency ( RF) pulse, followed by a RF pulse at the resonant frequency of fat to selectively suppress the fat signal. When two substances with a large difference in magnetic susceptibil ity, such as air and fat, share an interface, the main magnetic field ( BO) around this interface is distorted due to a different amplitude of magnetization on each side of the border. This results in a shift of the resonant frequency of the fat protons near the interface toward that of water protons. The result is failure of the presaturation pulse to suppress fat protons. ,
Imaging Findings Failure of fat-suppression manifests as ill-defined regions of hyperintensity. ll1e magnitude of these areas of fat suppression failure are known to depend on the
c
/204
D
ORBIT AND VISUA L PATHWAYSI
PEARLS/PITFALLS •
•
•
I ll-defined area of hyperintensity on FATSAT images could be a result of an artifact due to fat suppression. When an artifact is present, there is an absence of mass effect or signal abnormalities on otber se quences. Take care not to mistake fat sup pression failure for orbital pathology.
geometry of the interface and its orientation in regard to the main magnetic field, being maximal where the interface is perpendicular to BO. A FATSAT artifact is not difficult to recognize when there is complete or sym metric failure of fat suppression. However, it may be misleading when asymmetric. Asymmetry of this artifact is seen in any circumstance that alters either the geome try or the orientation of fat-water or fat-air interfaces. This includes physiologic asymmetry of the paranasal sinuses or configuration of the orbits, asymmetric dis ease of the paranasal sinuses (with soft tissue or fluid within the sinus) or asymmet ric positioning of the patient'S head in the scanner. Differential diagnosis from orbital pseudotumor, orbital cellulitis and orbital neo plasm in clinically doubtful cases may be a challenge. Distinguishing features of the artifact vs pathology include a location near fat-air interfaces, ill-defined margins with fading of the hyperintensity towards fat-water interfaces. absence of mass effect on adjacent structures and absence of signal abnormalities on SE T l W and T2W images. Both orbital cellulitis and orbital pseudotumor are inflammatory conditions that are typically hyperintense on T2WI. Orbital neoplasms tend to be more focal and, in general, are also hyperintense on T2WI. To avoid misinterpretation of a FATSAT artifact for orbital pathology, it is im portant to correlate the imaging findings with clinical examination. It may also be necessary to use an additional technique of fat suppression, less sensitive to suscep tibility artifacts such as STIR, repeat tbe same sequence, changing the orientation of the patient's head in the scanner, and correlate the FATSAT images with T l W and T2W SE sequences. Coronal FATSAT enhanced Tl WI (Fig. 45-C) shows an ill-defined region of hyperintensity along the medial and inferior aspects of the orbits bilaterally. The hyperintensity is maximal near the interfaces with the ethmoid and maxillary sinuses and fades gradually towards the center of the orbit. Axial (Fig. 45-D) and coronal (Fig. 45-E) FATSAT contrast enhanced T l WI show hyperintensity of the intraconal fat in the left orbit, along with marked enlargement of the extra-ocular muscles.
Suggested Readings Anzai, Y., Lufkin, R . B., labour, B.A, Hanafee, W.N. Fat-suppression failure artifacts simulating pathology on frequency-selective fat-suppression MR images of the head and neck. American journal of Neuroradiology 1 3(3):879-84, 1 992 May-Jun. Barakos, J.A Advances in magnetic resonance imaging of the head and neck. Top ics in Magnetic Resonance Imaging 6(3): 1 55-65, 1 994 Summer. Barakos, J.A., Dillon, W.P., Chew, W.M. Orbit, skull base, and pharynx: contrast enhanced fat suppression M R imaging. Radiology 1 79( 1 ): 1 9 1 -8, 1 99 1 Apr. Borges, A.R., LufkiJ1, R.B., H uang, A.Y., Farahani, K., Anold. A.C. Frequency selective fat suppression MR imaging. Localized asymmetric failure of fat suppres sion mimicking orbital disease. journal of Neuro-Ophthalmology 1 7( 1 ): 1 2-7, 1 997 Mar. Kaldoudi, E., Williams. S.c., Barker, G.1., Tofts, P.S. A chemical shift selective inver sion recovery sequence for fat-suppressed M R l : theory and experimental valida tion. Magnetic Resonance Imaging 1 1 (3):34 1 -55, 1 993. Lee, D.H., Simon, J.H . , Szumowski, J., Feasby, T.E., Karlik, S.1., Fox, AJ., Pelz, D.M. Optic neuritis and orbital lesions: lipid-suppressed chemical shift MR imaging. Radiology 1 79(2):543-6, 1 99 1 M ay. LUdeke, K.M., Rbschmann, P., Tischler, R. Susceptibility artefacts in NMR imaging. Magnetic Resonance Imaging 3(4):329-43, 1 985. Mintz, E., Kline, L.B., Duvall, E.R. Diagno tic misinterpretation of fat suppression
I ORBIT
AND VI SUAL PATHWAYS orbital magnetic resonance scanning [ letter1 American Journal of Ophthalmology 1 1 5(2):262�, 1 993 Feb 1 5 . Simon, J., Szumowski. 1., Totterman, S.. Kido, D., Ekholm, S., Wicks, A., Plewes, D. Fat-suppression M R imaging of the orbit. American Journal oj' Nellroradiology 9(5):96 1 -8, 1 988 Sep. Tien, R.D .. Chu, P.K., Hesselink, J. R., Duberg, A., Wiley, C. Intracranial cryptococ cosis in immunocompromised patients: CT and M R findings in 29 cases. American Journal of Nellrorndiology 1 2(2):283-9. 1 99 1 Mar-Apr.
ORBIT
AND V1SUAL PATHWAYS1
Case 46 Clinical Presentation A 48-year-old female with a hi tory of prior surgery and radiation therapy for a left frontal lobe neoplasm, now pre ents with a new onset of decrea ed vi ual acuity.
A
B
207 1
I ORBIT
AND VISUA L PATH WAYS
Radiologic Findings Coronal noncontrast Tl WI ( Fig. 46-A), coronal post-contrast frequency selective fat suppression imaging (FATSAT) T l WI ( Fig. 46-B), and axial post-contrast FATSAT T I WI ( Fig. 46-C) show enlargement and abnormal enhancement of the retrocanalic ular segment of the optic nerve and optic chiasm, with the left greater than the right.
Differential Diagnosis: Optic Nerve E nlargement and E nhancement (Optic Neuritis) • • •
•
• •
' Demyelinating disease : multiple sclerosis Inflammatory: collagen vascular disease, orbital pseudotumor, sarcoid I nfectious: H I V-related optic neuropathies, tuberculosis, fungal infection, toxo plasmosis, syphilis ' Neoplastic : optic glioma, optic nerve meningioma, metastasis, leptomeningeal carcinomatosis ' Vascular : ischemic neuropathy (severe hypertension, systemic vasculopathies) Others: radiation induced optic neuropathy, optic nerve trauma
Note:
'
indicates that the process is usually unilateral.
Diagnosis Radiation-induced optic neuropathy
Discussion Epidemiology Optic neuritis is a general term used to describe an acute inflammatory condition involving the optic nerve. usually presenting as rapid onset of visual loss. While it occurs as an isolated entity, its greater significance results from its association with mUltiple sclerosis (MS). In fact, the term optic neuritis is often misused as a syn onym of optic nerve involvement in MS. Optic neuritis is a relatively common disease affecting young adults (mean age of 30 years). There is a slight female predominance. The disease is rare in children.
Pathophysiology Optic nerve inflammation may be due to mUltiple pathologic processes including demyeLinating disease, infection, systemic inflammatory processes. optic nerve ischemia and toxic insults. Because the optic nerve is an extension of the CNS, con sisting of bundles of myelinated axons, it is not surprising that it is affected by the same demyelinating diseases as the brain. Approximately 35 to 40% of patients with MS develop optic neuritis and in 15 to 20% optic neuritis is the initial manifestation of MS, meaning that 20% of patients with optic neuritis will develop MS over a short or longer term. Concurrent optic neuritis and cervical myelitis is known as Devic's syndrome, and is uncommonly seen in patients with MS. Infectious processes involving the CNS and meninges may spread to the optic nerve. The conduit for spread may be the nerve itself (e.g., neurotropic viruses such as H IV) or the CSF in the optic nerve sheath. Basilar meningitides such as tuberculosis and fun gal meningitis are the most common infectious processes spreading to the optic nervc. Systemic vasculopathies of small and medium sized vessels may also be responsi ble for optic neuritis. The optic nerve is fairly sensitive to radiation injury, and radiation necrosis of the optic nerve is a well known complication when the optic nerve is included in the
1208
O R B IT AND V I SUAL PATHWAYSI radiation field. This is usually encountered after radiotherapy for orbital, sinonasal, sellar and orbitofrontal neoplasms. 1l1e effects of radiation are dependent on the total dose and the amount of fractionation.
Clinical Findings Optic neuritis may be asymptomatic, although typically, patients present with sud den loss of visual acuity, pain with eye movement, and dyschromatopsia. The visual loss tends to be of sudden onset, but may be more gradual, progressing over a period of 1 to 2 weeks. Slow recovery over a period of 6 to 1 2 weeks is the rule. A rare chronic progressive unremitting variant of optic neuritis has also been de scribed, eventually leading to blindness. Symptoms are unilateral in 70% of cases. Diagnosis is based on clinical history and ophthalmologic evaluation, including assessment of visual acuity, color vision, and visual fields. Fundoscopic examination may show optic disc swelling. A thorough clinical history and neurologic exam should be performed in order to exclude MS. Even when optic neuritis is seen in isolation, patients should be closely followed because a significant percentage will eventually develop MS. Radiation induced optic neuropathy has no specific clinical features. Ophthalmo logic evaluation may show disc swelling, prepapillary exudates, hemorrhage, and subretinal fluid. The onset of symptoms is usually remote from the time of radiation therapy, and may be confused with recurrence of the primary neoplasm.
I m aging Findings Abnormal imaging findings are not required for the diagnosis of optic neuritis and, when present, the findings are nonspecific. The main role of imaging is to exclude other pathologic processes and to detect other white matter abnormalities in the eNS, making the diagnosis of MS more likely. I maging is also important in the eval uation of treatment efficacy and in long-term follow-up. 1l1e best imaging modality to evaluate the visual pathway is M R l . The study should include the orbits and brain. Postcontrast fat-suppressed axial and coronal
D
E
I ORBIT
AND VISUAL PATH WAYS
PEARLS/PITFALLS •
•
•
•
•
•
•
Typically, young adult patients with optic neuritis present with sudden onset of visual loss. MR1 of the orbits including post contrast FATSAT Tl W sequence is mandatory. It is important to perform M R I of t h e brain to look for otber evi dence of demyelinating disease. The most common MR1 findings for optic neuritis are smooth en largement and enhancement of the optic nerve. Avoid mistaking non-neoplastic optic neuritis for neoplastic processes. I t is important to confirm radia tion necrosis of the optic nerve with recurrence of the primary tumor. Avoid failing to evaluate tbe brain and miss tbe diagnosis of MS.
T I W images of the orbits are mandatory. The most common findings are optic nerve enlargement and optic nerve enhancement, which may be focal. segmental or dir fuse. Single or multiple discontinuous lesions may be seen. More nodular enhance ment suggests neoplastic involvement, although sarcoid and some infectious processes (such as tuberculosis and fungal infection) may have a similar appearance. M R I may also show T2W hyperintensity in the optic nerve, optic chiasm and in the parenchymal white matter. T2W abnormality and/or optic nerve enhancement is present in 56 to 72% of pa tients with isolated optic neuritis and in 90 to 98% of patients with definitive MS. The diagnostic yield is increased with the use or inversion recovery or FATSAT postcontrast sequences and a surface coil. The number, site and size of the lesions should be reported. These data are useful to evaluate the success of treatment. The retrobulbar segment of the optic nerve is the most commonly involved segment of the optic pathway in MS. CT imaging may also detect optic nerve enlargement and enhancement, but has a lower accuracy when compared to MRI. Radiation necrosis manifests as a focally cxpanded. enhancing optic nerve and optic chiasm. Contrast enhancement is thought to be due to vascular injury result ing in increased permeability of the blood-brain barrier. Axial T2WI in a 40-year-old woman with lupus (Fig. 46-0) shows diffuse en largement and hyperintensity of the intraorbital segment of the left optic nerve. FATSAT post-contrast T l WI (Fig. 46-E) shows optic nerve asymmetry due to en largement of the left optic nerve. 1l1ere is no apparent abnormal enhancement seen .
Manage ment Steroids are used as the "gold standard" treatment for optic neuritis, regardless of cause. Several studies have shown a quicker recovery of vision and a transient pro tective effect from development of MS with the use of intravenous methyl pred nisolone.
Suggested Readings Cornblath, W.T., Quint, OJ. M R I of optic nerve enlargement in optic neuritis. Neu rology 48(4):82 1-5, 1 997 Apr. Kortvelesy, S. Recent advances in the management of optic neuritis. Hawaii Medical Journal 56( 1 0):28 1 , 1 997 Oct. Villablanca, P., Curran, J., Arnold, A .. Lufkin, R. Orbit and optic nerve. Topics in Magnetic Resonance Imaging 8(2):87-1 1 0. 1 996 Apr. Weber. A.L., Klufas, R., Pless, M. Imaging evaluation of the optic nerve and visual pathway including cranial nerves affecting the visual pathway. Neuroimaging Clill ics of North America 6( 1 ): 1 43-77, 1 996 Feb.
O R B IT AND V ISUAL PATHWAYSf
Case 47 Clinical Presentation A 64-year-old male presented with gradual proptosis of the right globe over several years.
B
A
Radiologic Findings A well-defined mass in the intraconal space is present 011 the right ( Fig. 47-A). The mass effect causes a slight proptosis. The mass is homogeneous on all sequences. On the TI-weighted sequence, it is hyperintense (Fig. 47-B) ( Image courtesy Drs. Andrew Berger and Ed Helmer). Figure 47-C shows it to be clear of the optic nerve.
1 0RBIT
AND VI SUAL PATH WAYS
Differential Diagnosis: Retrobulbar Intraconal Mass • • • • • • • • •
Hemangioma Schwanoma Metastasis Pseudotumor Meningioma Hemangiopericytoma Lymphangioma Varix Hematic cyst
Diagnosis Cavernous hemangioma
Discussion Epidemiology A cavernous hemangioma is one of the most common tumors of the orbit and the most common benign primary orbital tumor in the adult. There is a female prepon derance, and it usuaLly presents in the third to fifth decade of life. The majority of cavernous hemangiomas are solitary.
Pathophysiology Cavernous hemangiomas are round or oval in shape and may have a slightly nodu lar surface. Macroscopically, they are purplish-red in color, well circumscribed, and are encapsulated by a fine fibrous capsule. Microscopically, cavernous hemangiomas have numerous blood-filled vascular channels that are lined with flattened en dothelial cells that are surrounded by smooth muscle. The vascular channels are of ten separated by fibrous septa. Rarely, phleboliths may be present. Intramuscular hemangiomas may also occasionally occur.
Clinical Fi ndings 1lle clinical course is characteristic: a slow, progressive enlargement with findings related to displacement or compression of orbital structures. This is in distinction to capillary hemangiomas which tend to decrease in size over time. The sign/ symptom at the time of diagnosis is usually proptosis. I f the tumor is in the orbital apex, it may produce diplopia and optic nerve compression. Typical M RI and CT ap pearance is that of an oval or round, well-defined enhancing tumor in the intraconal space. The mass is soft and conforms to the shape of the orbit without distorting that structure. Occasionally, a small portion of the lesion may extend into the extraconal space. On MRI it is usually homogeneous in intensity on T l W sequences and heteroge neous in appearance on T2W images. On a T I -weighted image. the intensity is greater than muscle and globe and much less than fat. On a T2-weighted image it is more intense than any other tissue. The marked hyperintensity on T2 weighting is due to the high fluid content of the numerous blood-filled microscopic spaces. 1llis intensity component predominates over that of the fibrous and supporting tissues and results in marked hyperintensity. Enhancement with contrast agents occurs dif fusely and moderately. A cavernous hemangioma grows insidiously and may be come so large that it can expand and remodel the orbital walls.
1212
ORBIT AND VISUAL PATHWAYS( PEARLS/P ITFALLS •
•
•
•
Management
A cavernous hemangioma pre sents as a retrobulbar, intraconal mass.
Surgical excision is the treatment of choice. The encapsulated tumor can easily be totally removed. Cavernous hemangiomas generally do not recur, even after in complete excision.
Typical MRl and cr appearance is of a well-defined, contrast en hancing tumor.
Suggested Readings
Take care not to mistake a cav ernous hemangioma for a more aggressive process. Avoid mistaking a cavernous hemangioma for a varix of the ophthalmic veins.
Bilaniuk, L.T., Rapoport, R.1. Magnetic resonance imaging of the orbit. Topics in Magnetic Resonance Imaging 63: 1 67-8 1 , 1 994 Summer. Forbes, G. Vascular lesions in the orbit. Neuroimaging Clinics of North America 6 1 : U 3-222, 1 996 Feb. Mukherji, S.K., Tart, R.P., Fitzsimmons, 1. , Belden, C, McGorray, S., Guy, 1., Man cuso, A.A. Fat-suppressed MR of the orbit and cavernous sinus: comparison of fast spin-echo and conventional spin-echo. American Journal of Neuroradiology 1 59: 1 707- 14, 1 994 Oct. Sweet, C, Silbergleit, R., Mehta, B. Primary intraosseous hemangioma of the orbit: CT and M R appearance. American Journal of Neuroradiology_ 1 82:379-8 1 , 1 997 Feb.
IORBIT A
Case 48 Clinical Presentation 47-year-old female pre ented with progre ive loss of vi ion in her left eye. Phy ical examination revealed propto is and impaired mobility of the left globe. Fundo scopic examination wa unremarkable.
A
12 1 4
B
O R B IT AND V ISUAL PATHWAYS/
Radiologic Findings Axial T l W (Fig. 48-A), axial frequency selective fat suppression (FATSAT) T1 W (Fig. 48-B) images after gadolinium enhancement, and coronal FATSAT T I W im age after gadolinium enhancement (Fig. 48-C) show a round, weLl-circumscribed intraconal mass in the left orbit. This mass is intimately related to the optic nerve, which is displaced inferiorly and abuts the posterior aspect of the globe anteriorly. The lesion is isointense to the gray matter and shows vivid enhancement after con trast administration. There is no evidence of posterior extension to orbital apex and the extraconal muscles are also uninvolved by this mass. A mild to moderate degree of proptosis is noted (Courtesy Dr. Howard Krauss).
D ifferential D iagnosis: E nlargement of the Optic Nerve or Sheath •
• •
Tumors: optic nerve glioma, optic nerve meningioma, optic nerve neuroma, lym phoma, leukemia (chloroma), metastasis (hematogeneous: breast and lung, direct in vasion: retinoblastoma, uveal melanoma), hemangioblastoma, hemangiopericytoma I nflammatory lesions: orbital pseudotumor, optic neuritis, sarcoidosis Others: pseudotumor cerebri
D iagnosis [ntraorbital meningioma
Discussion In the assessment of orbital lesions accurate localization is critical. In the intraconal compartment, lesions can arise from the globe, extraocular muscles, intraconal fat, optic nerve or sheath. This distinction significantly reduces the list of differential diagnoses. The optic nerve is enveloped by the meninges from the optic chiasm to the pos terior aspect of the globe where they merge with the sclera. This meningeal enve lope provides an anterior extension of the subarachnoid and subdural spaces. I n the superior intracanalicular portion of the optic nerve, the pia mater, arachnoid mem brane, and dura fuse with each other and with the optic nerve, providing an attach ment to the optic canal.
Epidemiology Optic nerve meningiomas comprise 5 to 7% of aLl primary orbital tumors. Females are more frequently affected than males (4 : 1 ) and, although there is a broad range, a peak incidence is seen in the fourth and fifth decades. I ntraorbital meningiomas can also occur in children, usually in the first decade of life. TIlese meningiomas show more aggressive behavior than the adult form. Bilateral meningiomas are a diagnostic criteria for neurofibromatosis type 1 .
Pathophysiology I ntraorbital meningiomas may originate within the orbit or on rare occasion, result from direct extension of an intracranial tumor usually arising from the sphenoid ridge. Intraorbital meningiomas can arise from the meningeal sheath of the optic nerve, or from remnants of meningoepithelial cells left behind during embryologic development. The most common location is the optic nerve sheath and the orbital apex. However, meningiomas of the extraconal compartment can be seen, usually arising from the periosteum of the orbital walls. Intracranial meningiomas gain ac-
1 0RBIT
AND VISUAL PATHWAYS cess to the orbit either by extension along neural and vascular foramina, or through invasion of the bony walls of the orbit. The most frequent pathologic varieties of intraorbital meningiomas are menin goepithelial and transitional cell types. Pathology may be useful in distinguishing the rare angioblastic meningioma from hemangiopericytoma. As the clinical and imaging findings are often nonspecific, FNA should be per formed prior to therapy planning. Because most of the lesions are not readily accessible, imaging guidance is usually necessary.
Clinical Findings The clinical presentation of intraorbital meningiomas is non-specific, similar to any other intraorbital mass. The most frequent presenting symptoms include decreased vision, proptosis and constriction of the visual field. However. the clinical presenta tion largely depends on the size and location of the tumor. Small meningiomas aris ing along the optic nerve sbeath may be asymptomatic for long periods before they come to clinical attention. Clinical examination may reveal papilledema, optic atro phy, scotomata, and decreased motility of the extraocular muscles. Canalicular and chiasmal meningiomas are usually not associated with significant proptosis and often present as central scotomata. Clinically, there are a few findings that may help to distinguish a mass arising i n the optic nerve itself from the optic sheath and other i ntraorbital locations. A sig nificant visual impairment associated with mild proptosis is more likely to be related to an optic nerve lesion. Conversely, extrinsic lesions tend to produce significant proptosis before compromising visual acuity. It is also typical for primary lesions of the optic nerve to produce transient visual obscurity in the extremes of gaze, or with change in head position due to vascular compression.
Imaging Findings CT and M R I have complementary roles in the evaluation of intraorbital masses. Although M R I has superior soft tissue contrast resolution, in the case of an intra orbital meningioma, CT is superior in detecting intratumoral calcification and asso ciated bony changes which may be important clues in the differential diagnosis. Beam hardening artifact due to adjacent bone is one limitation of CT, particularly in the evaluation of small perioptic meningiomas. On CT, a meningioma of tbe optic nerve may appear as a tubular thickening, an eccentric mass, or a fusiform enlargement of the optic nerve-sheath complex. Stip pled or ring shaped calcifications, although rare, may differentiate these tumors from optic nerve gliomas. Typical associated bony findings include sclerosis and scal loping of adjacent bony structures, seen primarily in intracanalicular meningiomas and in those arising from the sphenoid ridge and secondarily invading the orbit. A spongy appearance of the bone around the optic canal, sphenoid wing and chias matic sulcus may be the only finding when the tumor is too small to be detected radiographically. Diagnostic dilemmas such as confusion with fibrous dysplasia and Paget's disease occasionally occur. Meningiomas near tbe orbital apex, however, tend to cause demineralization and enlargement of the optic canal. Another finding is the associ ation with pneumosinus dilatans, usually of the sphenoid sinus. The cause of this as sociation is controversial. Some experts believe meningiomas produce irritation of adjacent bone and cause progressive thinning of the bony walls of the sinus. which then expand. Others suggest that pneumosinus dilatans is the primary process which stimulates the growth of arachnoid cap cells to produce a meningioma. Meningiomas show moderate to marked homogeneous enhancement. The classi cal "tram track" sign consists of linear enhancement along the nerve sheath sepa rated by a central area of hypodensity which corresponds to the optic nerve.
ORBIT AND V I SUAL PATHWAYSl
D
E
However, this sign is not specific for meningioma and can be seen in a variety of in flammatory conditions including optic neuritis and pseudotumor. M R I is more accurate in the detection of optic nerve/sheath complex enlarge ment, especially when enhanced coronal T l W images with fat saturation are per formed. This sequence provides better contrast resolution between the enhancing lesion and the intraconal fat (also hyperintense on TI W I ) and is crucial in the diag nosis of small perioptic tumors. Orbital meningiomas are usually slightly hy pointense to the brain parenchyma on botb T I W and TIW images and enhance vividly and homogeneously, being clearly distinguishable from the optic nerve. Coronal images are particularly well-suited for evaluation of the optic canal, the optic chiasm and the precise relationship between tbe lesion and the optic nerve (Fig. 48-C). Meningiomas are well circumscribed unless tbey breach the dural Lining and infiltrate the surrounding fat. This is seen more frequently in pediatric patients and represents more aggressive behavior. Associated bony sclerosis may be depicted on M R I as an enlarged area of absent signal corresponding to the enlarged cortical bone. Dilatation of the subarachnoid space, usually due to increased intracranial pres sure, may appear as a halo surrounding the optic nerve, following the signal charac teristics of CSF. This should not be confused with a tumor as the post-contrast images will show no evidence of enhancement. Diffuse enhancement along the optic nerve is more likely to be related to an inflammatory process, altbough sometimes it is impossible to distinguish from a tumor. Ultrasound is a good screening test for detection of intraorbital lesions because it is readily available and easy to perform. Although the findings are nonspecific, US may be used in FNA guidance and Doppler US may be belpful in the diagnosis of vascular lesions. Axial FATSAT T l W images of the orbit after contrast enhancement (Figs. 48-D and 48-E) show a large hourglass-shaped mass with a larger component centered in the left cavernous sinus and a smaller component in the intraorbital component. The mass extends into the orbit through the optic canal which is markedly enlarged. The cavernous segment of the ICA is medially displaced and compressed by this
I ORBIT
AND VISUAL PATHWAYS
PEARLS/PITFALLS Optic nerve meningiomas are seen most often in middle aged women.
•
The most frequent presenting symptoms include proptosis and slowly progressive loss of vision.
•
An optic nerve meningioma ap pears as a tubular, fusiform or eccentric enhancing lesion along the optic sheath without involve ment of the nerve itself.
•
•
•
•
•
•
Perform enhanced M R l of the orbits with fat saturated Tl W images to get a more accurate picture of the optic nerve/sheath complex. Take care not to miss involve ment of the chiasm. Avoid misdiagnosing for an optic nerve glioma. Take care not to confuse dilation of the subarachnoid space around the optic nerve for a tumor. Differentiation from inflamma tory conditions is not always possible.
lesion. The lesion extends laterally into the medial cranial fossa compressing and displacing the medial aspect of the temporal lobe.
Management The management of lesions involving the anterior optic pathways is controversial. TIle treatment of intraorbital meningiomas depends upon their location, extent and associated symptoms. As opposed to nerve sheath meningiomas, extradural or "ec topic" meningiomas are usually easy to resect without endangering the optic path way. Intracanalicular and nerve sheath meningiomas, with some rare exceptions, are not amenable to complete resection without considerable risk of optic nerve dam age due to the close proximity of the ophthalmic and central retinal arteries. There fore, the decision to perform surgery depends upon the severity of symptoms and disease progression. Surgery is indicated when there is loss of visual acuity, in creased proptosis, pain or radiographic evidence of further growth. Intracranial le sions with intraorbital extension require a multidisciplinary approach with surgery performed by a team of neurosurgeons and skull base surgeons. Lesions involving the chiasm carry a significant risk of postsurgical blindness. Radiotherapy may be considered in cases of chiasmatic involvement and for recurrence.
Suggested Readings Biesman, B.S.. Heilman, C. Surgical management of lesions affecting the anterior optic pathways. Seminars in Ophrhalmology 1 0(3):260-4, 1 995 Sep. Delfini, R., Missori, P., Tarantino, R., Ciapetta, P., Cantore. G. Primary benign tumors of the orbital cavity: comparative data in a series of patients with optic nerve glioma, sheath meningioma, or neurinoma. SlIrgical Neurology 45(2): 1 47-53. dis cussion 1 53-4, 1 996 Feb. Gunalp, I.. Gunduz. K., Duruk, K .. Kanpolat. Y. Neurogenic tumors of the orbit. Japanese Journal of Ophrhalmology 38(2): 1 85-90, 1 994. Hashimoto, M., Tomura. N., Watarai. 1. Retrobulbar orbital metastasis mimicking meningioma. Radiarion Medicine 1 3(2):77-9. 1 995 Mar-Apr. l ng, E . B .. Garrity, 1.A .. Cross, S.A., Ebersold, MJ. Sarcoid masquerading as optic nerve sheath meningioma. Mayo Clinic Proceedings 72( I ):38-43. 1 997 Jan. Johnson, T.E . , Weatherhead, R.G., NasI', A.M .. Siqueira, E.B. Ectopic (extradural) meningioma of the orbit: a report of two cases in children. Journal of Pediarric Oph r/1almology and Srrabisl11us 30( 1 ):43-7, 1 993 Jan-Feb. Miller, N.R .. Golnik, K.C., Zeidman, S.M., North, R.B. Pneumosinus dilatans: a sign of intracranial meningioma. Surgical Neurology 46(5):471 -4, 1 996 Nov. Reid, D.. Ngo, H . H . , Lamarche, 1.B. Primary post-traumatic intraorbital menin gioma. JOllrnal of Orolaryngology 23(4):298-30 I . 1 994 Aug. Rose, G.E. Orbital meningiomas: surgery, radiotherapy, or hormones? 8riri.l'/1 Jour nal of Ophrhalmology 77(5):3 13-4, 1 993 May. Ruscalleda. 1., Feliciani, M., Avila, A., Castaner. E., Guardia, E .. de Juan. M. Neuro radiological features of intracranial and intraorbital meningeal hemangiopericy tomas. Neurodiology 36(6):440-5, 1 994 Aug.
I�
ORBIT A N D V I S UAL PATHWAYSI
Case 49 Clinical Presentation A 65-year-old male consulted his ophthalmologist because of a 2-week history of decreased vision in his right eye. Opthalmic examination revealed a right choroidal mass.
B
A
Radiologic Findings There is a choroidal mass in the right that is seen on the axial CT image (Fig. 49-A). The lesion is hyperintense (arrowhead) on TI W images both before ( Fig. 49-B) and after ( Fig. 49-C) contrast. The contralateral globe is unremarkable.
I ORBIT
A
D
V I SUAL PATHWAYS
Differential Diagnosis: Choroidal Mass • • • • • • • • • • • • •
Melanoma Hemangioma Hemorrhage RetinaUchoroidal detachment Choroidal metastasis Sarcoidosis Retinal cyst Retinoblastoma Retinal gliosis Nevi Leiomyoma Schwanoma Neurofibroma
Diagnosis Choroidal (uveal) melanoma
Discussion Uveal melanomas are the most common primary ocular neoplasm in adults with an annual reported incidence of seven case per million. There is no gender predilec tion. It is more common in individuals witb light skin coloring and is almost always unilateral.
D
1 220
ORBIT A D V I SUAL PATHWAYSJ
Pathophysiology The tumor arises from malignant transformation of melanocyte in the uveal tract, which is made up of the ciliary body. iris, and choroid. Melanomas in the ciliary body and choroid are believed to originate from preexisting nevi. Choroidal nevi are con genital lesions, usually recognized late in the first decade of life and most commonly located in the posterior third of the choroid. TIley are usually not visible with high resolution CT or M R I techniques.
Cli nical Fi ndings Diagnosis is usually accomplished using the standard opthalmologic examinations of opthalmo copy, sonography and/or f10 urescein angiography. CT and more often M R I are valuable, however, to evaluate extracapsular extension, which may occur in 1 0 to 1 5% of patients and may be difficult or impossible to evaluate with the prior techniques. Direct opthalmologic visualization may be impo sible in patients with "opaque media" (i.e. cataract, vitreous hemorrhage).
Imaging Fi ndings The CT and M R I appearance of choroidal melanoma is that of an enhancing choroidal mass ( Figs. 49-A-49-C). I nitially there is a smooth contour as the mass elevates Bruch's membrane (lamina vitrea; Fig. 49-D left). With more growth and rupture of the membrane, the tumor assumes a more characteristic mushroom shape (Fig. 49-D. right). TIle adjacent retina also becomes elevated (detached) on either side of the tumor. These fluid collections can usually be differentiated from the primary mass on T2W M R I . The imaging appearance of the melanoma may be mimicked by retinoblastoma, choroidal metastases. hemangioma. or intrachoroidal hemorrhage. Electron-spin resonance studies have shown that melanin produces a stable, free radical signal. These radicals cause a proton relaxation enhancement that shortens both T l and 1'2 relaxation time values. Damadian, et al ( 1 974), reported that, unlike other tumors, melanomas have a short T l value, which they attributed to paramag netic proton relaxation enhancement by a stable radical in melanin. Because of the relatively shortened TI and 1'2 relaxation time values, owing to paramagnetic prop erties of melanin. uveal melanomas may appear relatively hyperintense (to vitre ous) on T l W, proton-weighted MR images, and become hypointense on T2W MR scans. On M R I . associated retinal detachment can be easily differentiated from the uveal melanoma. Choroidal hemorrhage may be mistaken for malignant uveal melanoma on clinical examination as well as on various imaging techniques. On M R I , the acute choroidal hemorrhage appears a a moderately hypointense image on T2W MR scans. Subacute choroidal hemorrhage may be seen as an area of het erogeneous signal intensity on both T l - and T2-weighted MR images. Chronic choroidal hemorrhage appears as hyperintense areas in both TI W and T2W M R scans. Uveal metastases may b e very difficult t o differentiate from uveal melanoma. Most metastases, however, often appear hyperintense on T2W MR images. Metas ta es from primary mucin-producing carcinoma may be very difficult to differenti ate from uveal melanomas. Although T l and 1'2 shortening has been seen in some MRI studies of patients with melanoma, the finding is neither particularly sensitive nor specific in the diag nosis of melanoma. It is insensitive because not all melanomas contain large amounts of melanin (amelanotic melanomas). The finding is nonspecific because other tissues such as blood breakdown products can also cause relaxation enhance ment.
I ORBIT
AND VISUAL PATHWAYS
PEARLSIPITFALLS •
•
•
•
•
Management
Tl shortening for melanoma is neither particularly sensitive or specific.
Treatment is based on the size. location and extent of the tumor. Brachytherapy with or without local excision. enucleation. orbital exenteration. or percutaneous proton irradiation are all treatment options.
Amelanotic melanomas may have relatively low levels of the paramagnetic stable free radical.
Suggested Readings
Subacute hemorrhage with methemoglobin is paramagnetic. Proteinaceous fluid may cause T l shortening. Care should be taken not to con fuse a choroidal melanoma with choroidal metastasis or other mimics.
Damadian. R .. Zaner. K . . Hor. D.. DiMaio. T. H uman tumors detected by nuclear magnetic resonance. Proceedings or the ational Academy of Sciencc SA 7 1 : 1 4 7 1 - 1 473, 1 974 . Gomori. JM. et al. Choroidal melanomas: correlation of NMR spectroscopy and MR imaging. Radiology 1 58:443-445, 1 986. Mafee. M.E Malignant uveal melanoma and simulating lesions. MR imaging evalu 1 60:773-780. 1 986.
ation. Radiology
Potter, P. O., Shields. C.L .. Shields, JA., Flanders. A.E. Thc role of magnctic reso nance imaging in children with intraocular tumors and simulating lesions. Oplulwl111010gy 1 03 1 1 : 1 774-83. 1 996 Nov.
Romani. A .. Baldcschi. L., Genovesi - E be rt F. . G re mi g ni . E .. Ragone. M.e.. Rizzo. S .. ardi, M. Sensitivity and specificity of ultrasonography. fluorescein vidcoangiogra phy indocyanine green videoangiography. magnetic resonance and radioim munoscintigraphy in the diagnosis of primary choroidal malignant melanoma. Oph thalmologicnl 2 1 2 Suppl 1 :44-6, 1 998 . Scott, l .u.. Murray, T.G . Hughes. JR. Evaluation of imaging techniques for detec tion of extraocular extension of choroidal melanoma . A rchives of Ophthalmology 1 1 6 7:897-9, 1998 luI. .
.
.
222
Case 50 Clinical Presentation n
J
-month-old child pre ented with leukocoria and trabi mus.
A Radiologic Findings An axial nonenhanced cr of the orbit (Fig. 50-A) hows a gros ly calcified retro lental oft ti ue mass in the po teromedial a pect of the left globe. There is no evidence of extraocular exten ion along the optic nerve or into the retrobulbar fal.
Differential Diagnosis: Intraocular Mass in a Child •
•
eoplastic conditions: retinoblastoma and retinocytoma -, uveal melanoma, metastases (neurobla IOma, mo t common), p eudoglioma (retinal a trocytoma or a lrocytic hamartoma) onneopla tic conditions: per i tent hyperpla tic primary vitreous (PHP ) retinopathy of prematurity or retinal dysplasia ( Ropf, Coat's disease. toxocari a is or larval granulomato is·, chronic retinal detachment·, uveiti
.
•
ote: The pre encc of calcification in an intraocular mas further limit
po ibilities. The lesions most likely to calcify are marked with
·
t he diagnostic
.
223
I ORBIT
A
A L PATHWAY
Diagnosis Retinoblastoma
Discussion eparating retinobla toma ( R B ) from benign nonneopla tic condition . uch a tho e Ii ted above, i one of the major challenge in pediatric ophthalmology. In orne ca e . thi differentiation is impo ible both clinically and radiologically, lead ing to delay in t he treatment of this highly malignant tumor and. ometimes, to ocular enucleation for benign pathologie Differentiation of RB from it more benign variants ( retinocytoma) and from uveal melanoma is not mandatory a patient management i the arne. Ocular meta ta e u ually appear long after detection of the primary tumor making the diagno i obviou . Retinal a trocytoma or astrocytic hamartoma is commonly a ociated with tuber ou c1ero i and may be the pre enting ign of the di ea e. hronic retinal detachment can appear a a dense retrolental rna s on , which may show dystrophic calcification, mimicking R B. However, this p eudoma s d e not cros the optic nerve head, and i limited anteriorly by the ora serrata. sually, the clinical hi tory and the presence of a predi po ing factor for retinal detachment allow for the correct diagno is. Mo t benign congenital ocular di ease are a socia ted \ ith malformed globe . mi crophthalmia and hallo\ anterior chamber nlike RB. they rarely calcify and do so only in the late stage of the disease (dystrophic calcifications in phthisis bulbi ).
B
c
224
ORBIT AND VISUAL PATH WAYSI Retinopathy of prematurity or retinal dysplasia is associated with prematurity. low birth weight and exposure to supplemental oxygen therapy. which may be elicited from the clinical history. It is typicaUy a bilateral and asymmetric condition which rarely calcifies. With progression of the disease. the globes become micro phthalmic with shallow anterior chambers. Persistent hyperplastic primary vitreous is the second most common cause of leukokoria in the pediatric population and may pose diagnostic problems with RB. Distinguishing features include the presence of microphthalmia at birth and a more anterior location within the globe, sometimes manifesting as a triangular shaped mass extending [rom the posterior aspect of the lens toward the optic di c (along the Cloquet's canal). It does not usually calcify. Coat's disease is more common in males and tends to present later in life. between 4 and 1 0 years of age. Like retinoblastoma the globe is normal in mor phology and size. On US, a definite solid mass is usually not identified. and on M R I the more solid component of the lesion i s located anterior t o t h e detached enhanc ing leaves of the retina, while in RB the tumor arises from the retina and projects into the subretinal effusion. The subretinal effusion in Coat's disease are hyperin tense on both T l W ( Fig. 50-B) and T2WI due to its lipoproteinaceous content (Fig. 50-C). Ocular toxocariasis or sclerosing endophthalmitis may be radiologically indistin guishable from RB, presenting as solitary or multiple calcified ocular masses (Fig. 50-D). Involvement of other organs and systems and a positive enzyme-linked immunoadsorbent assay (ELISA) for Toxocara canis usually allows an accurate diagnosis.
Ep idemiology Retinoblastoma is a rare congenital intraocular malignancy with a reported world wide incidence varying between I : 15,000 and 1 : 34.000 live births, and comprising approximately I % of all pediatric malignancies. It is the most common intraocular malignancy in children and the most frequent cause of leukocoria, responsible for 60% of cases. Although congenital in origin, the median age of presentation depends largely on the efficiency of pediatric health care systems. In the United States, the median age of presentation is 18 months and 98% of all cases are diag nosed before age 5 years. There is no gender predominance. Among all forms of RB. 65 to 75% are unilateral and 25 to 33% are bilateral. In the presence of a positive familial history of RB the incidence of bilaterality increases to 65% .
Pathophysiology Retinoblastoma is a primary malignant congenital neoplasm that arises from prim itive embryonal retinal cells that are located in the nuclear layer of the retina. These embryonal cells are primitive neuroectodermal derivatives and. therefore, RB is classified within the primitive neuroectodermal tumor (P ET) group. According to their etiology, four different groups of RB are recognized. Non hereditary forms comprise 60% of aU cases and result either from a sporadic postzy gotic mutation in the retinoblasts or from anomalies involving chromo ome 1 3 (monosomy, deletions. etc). I n these cases, subsequent generations are not affected and RB is more commonly unilateral. Hereditary forms comprise 40% of all cases and may result from a sporadic germinal mutation or an autosomal dominant anom aly involving band 14 of chromosome 13 ( R B I gene). Penetrance of the RB I gene in familial RB is high, approaching 95% . 1l1e most common genetic anomaly associated with RB is the deletion of band 1 4 of the long arm of chromosome 1 3 , responsible for codification of the enzyme es terase 0, which has been implicated in the tumorigenesis of several malignancies. The RB I gene is thought to act as a tumor supressor gene or antioncogene. Ac cording to Knudson's theory, an individual with a familial predisposition inherits
IORBIT
AND VISUAL PATHWAYS one inactive gene so that only one other mutational event during the susceptible stage of embryonic development is necessary for retinoblasts to become apparent. When larger deletions of chromosome 13 occur, systemic dysmorphic features also may be apparent. These include microcephaly, ear anomalies, mental retardation and genital anomalies. Trilateral RB is a rare variant of RB, consisting of bilateral intraocular RB and an ectopic tumor in the pineal gland, suprasellar or parasellar regions. These tumors are known to be different primaries with a common embryonic origin in primitive neuroectodermal cells. It comprises 4% of all cases of RB and 8% of familial cases. The RB I gene also has been demonstrated to predispose to second nonocular malignancies, which are unrelated to the primary tumor and may occur in locations outside standard radiation ports. Most commonly these tumors are bone or soft tissue sarcomas, including osteo-, chondro- and fibrosarcomas or malignant fibrous histiocytomas. The prevalence of a second tumor in non irradiated areas is estimated to be 1 0% at 10 years of age and increases to 70% at 30 years with a cumulative life risk of 32% in bilateral RB survivors. Pathologically, RB is characterized by the presence of Winterstein rosettes ( neu ronal cells linning a central zone of polysaccharides) and fleurettes (flowerlike groups of cells which are markers of photoreceptor differentiation). Hower-Wright rosettes. a group of neuronal cells lining a central area of cobweb filaments. are found in other P ET and are not specific for retinal differentiation. RB is a small round cell tumor. Prominent foci of calcification are typical of this tumor and result from the formation of calcium complexes when DNA is released from necrotic cells. Areas of glial differentiation may also be seen in this tumor. Retinoblastomas metastasize in approximately 10% of patients. The most fre quent site is meningeal seeding via the subarachnoid space surrounding the optic nerve. Hematogeneous spread occurs primarily to the bone marrow and liver. Lym phatic spread to the preauricular, submandibular and internal jugular chains may occur.
Clinical Findings The most frequent presenting sign of retinoblastoma is leukocoria (60% of cases). Leukocoria, or white pupillary reflex, is a non pecific finding with an extensive dif ferential diagnosis, which includes, besides the pathologic conditions listed above. congenital cataracts and coloboma. I n these circum tances all efforts should be made to reach an accurate diagnosis. The importance is twofold: avoiding unneces sary enucleations for benign lesions and avoiding delayed diagnosis of RB, leading to increased mortality and precluding ocular salvage therapies. Other common presenting signs include strabismus and pain, secondary to closed angle glaucoma (when the tumor obstructs the irido-corneal angle). Decreased visual acujty, heterochromia iridis, hyphema and phthisis bulbi may develop with progression of the disease. Patients with trilateral RB may first present with headache and other symptoms of increased intracranial pressure, due to noncom municating hydrocephalus, in the absence of ocular symptoms. Ophthalmologic examination is the mainstay of the diagnosis, able to detecl tumor beyond the resolution of imaging, as small as 0.02mm. [t may also detect metastatic seeding of the vitreous. Limitations of ophthalmoscopy include the pres ence of hyphema, cataracts or vitreous hemorrhage, precluding visualization of the retina and evaluation of tumor extent beyond the globe. Ophthalmoscopic exami nation of the contralateral eye is mandatory. Screening of the progeny of patients with bilateral RB and genetic counseling should be provided. RB can be divided into four clinical stages, modified by Prat, et al: limited to the retina (stage I ) , extraretinal intraocular disease (stage I I), extraocular disease lim ited to the adnexal structures (stage I l l ) and extraocular disease with distant metas tasis (stage IV). A metastatic workup should be performed in clinically advanced
ORBIT A N D VISUAL PATHWAYSI lesions including a complete physical exam, liver function test, lumbar puncture and bone marrow aspirate.
I maging Findings In addition to helping in the differential diagnosis, imaging is mandatory in ad vanced lesions to determine local extent and evaluate for the presence of intracra nial disease or distant metastasis. Imaging modalities include US, CT and MRI for local disease, and liver and bone scanning to rule out metastatic involvement in advanced cases. The imaging appearance of RB depends on the size of the lesion and pattern of growth. Endophytic lesions are the most common, manifesting as a soft tissue mass protruding into the vitreous chamber, and sometimes associated with floating islands of tumor within the semiliquid vitreous and anterior chamber. The exophytic form appears as a soft tissue mass prot
