- Department of Neurological Surgery, Goodman Campbell Brain and Spine, Indiana University, Indianapolis, Indiana, USA
Aaron A. Cohen-Gadol
Department of Neurological Surgery, Goodman Campbell Brain and Spine, Indiana University, Indianapolis, Indiana, USA
DOI:10.4103/2152-7806.92931Copyright: © 2012 Patel N. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Patel N, Wilkinson J, Gianaris N, Cohen-Gadol AA. Diagnostic and surgical challenges in resection of cerebellar angle tumors and acoustic neuromas. Surg Neurol Int 15-Feb-2012;3:17
How to cite this URL: Patel N, Wilkinson J, Gianaris N, Cohen-Gadol AA. Diagnostic and surgical challenges in resection of cerebellar angle tumors and acoustic neuromas. Surg Neurol Int 15-Feb-2012;3:17. Available from: http://sni.wpengine.com/surgicalint_articles/diagnostic-and-surgical-challenges-in-resection-of-cerebellar-angle-tumors-and-acoustic-neuromas/
Background:Cerebellopontine angle (CPA) lesions can mimic more common tumors through nonspecific symptoms and radiologic findings.
Methods:To increase the preoperative diagnostic accuracy for CPA pathologies, the authors review the full spectrum of reported CPA lesions.
Results:A wide spectrum of lesions mimics vestibular schwannoma (VS) in the space of the CPA.
Conclusion:The presence of any suspicious clinical and radiographic finding uncharacteristic of VS makes it necessary to maintain a broad differential diagnosis list. Differentiation of CPA lesions, although challenging, may be best achieved by incorporating the clinical history, physical exam findings, audiometry results, and multi-modality imaging studies to construct a comprehensive preoperative knowledge of the lesion. This knowledge will allow improved operative execution and outcomes.
Keywords: Acoustic neuroma, cerebellopontine angle tumor, ependymoma, neurosurgical procedures
Housing 6–10% of all intracranial tumors,[
The remaining abnormalities found within the CPA account for less than 1% of all lesions in this region, are exceedingly rare, and may be challenging to preoperatively diagnose with accuracy. Although the introduction of various magnetic resonance imaging (MRI) sequences has allowed for an earlier and more accurate diagnosis of intracranial masses, CPA lesions may be misdiagnosed as they can mimic VS and other more common tumors in the area through their nonspecific presenting signs, symptoms, and radiologic findings.
Inaccurate diagnosis may lead to suboptimal treatment strategies. Therefore, to potentially increase the preoperative diagnostic accuracy of clinicians involved with the care of patients with CPA pathologies, the authors attempt a comprehensive review of the full spectrum of reported CPA lesions.
The broad spectrum of unusual lesions within the CPA includes dermoid cysts, lipomas, neurenteric cysts, neuroepithelial cysts, cholesterol granulomas, paragangliomas, chordomas, chondrosarcomas, pituitary adenomas, endolymphatic sac tumors, arachnoid cysts, metastasis, non-vestibular schwannomas, gliomas, lymphomas, ependymomas, papillomas, hemangioblastomas, and medulloblastomas, among others.[
VSs are benign, slow-growing schwann cell tumors that typically arise from the inferior vestibular portion of the VIII cranial nerve.[
Resection of large VS may be challenging due to the adherence of the tumor to the surrounding cerebrovascular structures. However, the tumor does not typically invade the arachnoid membranes and those considered subarachnoid tumors are characterized by the arachnoid membrane remaining on the tumor surface after moving the arachnoid fold.[
Radiographically, VS are round or oval lesions that typically enhance after contrast administration and are located either in the internal acoustic canal or protrude into it [
Meningiomas originate from the cells lining the arachnoid villi that are predominately found along the major venous sinuses of the petrous bone.[
Radiographically, CT scan may demonstrate either bony destruction or hyperostosis due to the higher tendency of meningiomas invading the surrounding skull base bone as compared with VS. Meningiomas may present as homogenous masses with a flat base off-center from the internal auditory canal (IAC) although they can invade the IAC and cause its expansion.[
Epidermoid cysts are the third most frequent tumor of the CPA.[
Radiographically, epidermoid cysts present as hypodense lesions with irregular margins eccentric to the IAC, which do not enhance with administration of gadolinium and may cause erosion of the petrous apex. They appear hypointense on T1-weighted and hyperintense on T2-weighted MRI. As opposed to arachnoid cysts, which are the primary differential diagnosis for this lesion, epidermoid cysts demonstrate high signal intensity on diffusion-weighted imaging[
Epidermoid cysts present as hypodense lesions with irregular margins eccentric to the the internal auditory canal, which do not enhance with administration of gadolinium and may cause erosion of the petrous apex. They appear hypointense on T1-weighted and hyperintense on T2-weighted magnetic resonance imaging (a). As opposed to arachnoid cysts, which are the primary differential diagnosis for this lesion, epidermoid cysts demonstrate high signal intensity on diffusion-weighted imaging (b)
The most common malignant neoplasms in the CPA include breast, lung, skin (melanoma), gastrointestinal, and genitourinary cancers.[
Non-vestibular schwannomas rarely present in the CPA. These lesions are usually easily distinguished from VSs based on different symptom patterns, neuroanatomic locations, shapes, and relationships within the skull base foramina and canals.[
Trigeminal nerve neuromas
Trigeminal neuromas are exceedingly rare tumors.[
Trigeminal neuromas are located cephalad to vestibular schwannomas (a: axial magnetic resonance imaging (MRI) with contrast). They have an anterior–posterior direction in the cerebellopontine angle cistern and may extend into the Meckel's cave (b: coronal MRI with contrast). Close association with the trigeminal nerve is noted (c: T2-weighted axial MRI)
Facial nerve neuromas
Eighty percent of facial neuromas involve two adjacent nerve segments and are often dumbbell shaped.[
Lipomas rarely occur within the CPA.[
Dermoid cysts may contain fat, hair, or sebaceous glands in addition to squamous epithelium. They are usually midline lesions that rarely invade the CPA laterally. They demonstrate high signal intensity on T1-weighted MRI sequences due to their fatty content and may have a very suggestive fat-fluid level.[
Arachnoid cysts form as a result of splitting and duplication of the arachnoid layers. These lesions can develop secondary to congenital malformation, infection, trauma, increased intraventricular pressure, or embryonic rests.[
Glomus jugulare tumors
Only the largest group of glomus jugulare tumors is found in the CPA, and when they occur, they present with pulsatile tinnitus, headaches, hearing loss, and disequilibrium along with dysphonia and dysphagia. Conductive hearing loss and a red pulsatile mass behind the tympanic membrane are characteristic signs for this tumor type. In addition to VII and VIII cranial nerve palsies, IX, X, XI, and XII cranial nerve palsies may occur.[
Enhanced MR images reveal an intense enhancement pattern which is most commonly homogenous.
Vascular lesions are rare within the CPA but include distal anterior inferior cerebellar artery (AICA) aneurysms,[
Inflammatory lesions of the cranial nerves have demonstrated both focal and diffuse enhancement patterns on neuroimaging and have mimicked VS. These inflammatory lesions have been associated with Bell's palsy[
Numerous case reports have documented infectious etiologies for CPA lesions that mimic VS. For instance, a necrotizing granulomatous inflammatory lesion cultured positive for acid-fast bacilli,[
Ependymomas usually arise from the fourth ventricle and its lateral recess and extend into the CPA by means of exophytic growth.[
Ependymomas usually arise from the fourth ventricle and its lateral recess and extend into the cerebellopontine angle (CPA) by means of exophytic growth. However, ependymomas of an extra-axial origin also exist and may grow directly into the CPA. They appear irregular and may invade the cerebellar parenchyma. Ependymomas appear as hypointense lesions on T1-weighted imaging and as hyperintense lesions on T2-weighted imaging (a and b:axial and coronal contrast-enhanced images and c: axial T2-weighted sequence)
Except for the inflammatory and infectious lesions, operative intervention remains a reasonable option for other lesions that are causing mass effect on the brainstem and cause corresponding compressive signs and symptoms. Particularly for VSs and other solid lesions, if the lesion is adherent to the important neighboring cerebrovascular structures, a radical resection is contemplated, with a small piece of the tumor left behind to avoid the associated morbidity. With the availability of radiosurgery for the treatment of residual lesions, postoperative morbidity should be minimized.
A wide spectrum of lesions mimics VS in the space of the CPA. The presence of any suspicious clinical and radiographic findings uncharacteristic of VS makes it necessary to maintain a broad differential diagnosis list. Differentiation of CPA lesions, although challenging, may be best achieved by incorporating the clinical history, physical exam findings, audiometry results, and multi-modality imaging studies to construct a comprehensive preoperative knowledge of the lesion. This knowledge will allow improved operative execution and outcomes.
1. Ahn MS, Jackler RK. Exophytic brain tumors mimicking primary lesions of the cerebellopontine angle. Laryngoscope. 1997. 107: 466-71
2. Berens ME, Rutka JT, Rosenblum ML. Brain tumor epidemiology, growth, and invasion. Neurosurg Clin N Am. 1990. 1: 1-18
3. Bonneville F. Unusual Lesions of the Cerebellopontine Angle: A Segmental Approach, in 1999 RSNA Scientific Assembly. 1999. p.
4. Bonneville F, Savatovsky J, Chiras J. Imaging of cerebellopontine angle lesions: an update. Part 1: Enhancing extra-axial lesions. Eur Radiol. 2007. 17: 2472-82
5. Bösel J, Klingebiel R, Schielke E. HIV-associated neurosyphilis mimicking acoustic neurinoma. J Neurol. 2006. 253: 250-2
6. Brackmann DE, Bartels LJ. Rare tumors of the cerebellopontine angle. Otolaryngol Head Neck Surg. 1980. 88: 555-9
7. Brunori A, Scarano P, Chiappetta F. Non-acoustic neuroma tumor (NANT) of the cerebello-pontine angle: A 15-year experience. J Neurosurg Sci. 1997. 41: 159-68
8. Cushing H.editorsIntracranial tumors. Springfield, IL: Charles C Thomas; 1932. p.
9. Dazert S, Aletsee C, Brors D, Mlynski R, Sudhoff H, Hildmann H. Rare tumors of the internal auditory canal. Eur Arch Otorhinolaryngol. 2005. 262: 550-4
10. DiMaio S, Mohr G, Dufour JJ, Albrecht S. Distal mycotic aneurysm of the AICA mimicking intracanalicular acoustic neuroma. Can J Neurol Sci. 2003. 30: 388-92
11. Dinh DH, Clark SB, Whitehead M, Amedee R, Bhattacharjee MB. Intracanalicular meningioma. South Med J. 2000. 93: 618-21
12. Gao PY, Osborn AG, Smirniotopoulos JG, Harris CP. Radiologic-pathologic correlation. Epidermoid tumor of the cerebellopontine angle. AJNR Am J Neuroradiol. 1992. 13: 863-72
13. Goldsmith P, Zammit-Maempel I, Meikle D. Ramsay Hunt syndrome mimicking acoustic neuroma on MRI. J Laryngol Otol. 1995. 109: 1013-5
14. Han MH, Jabour BA, Andrews JC, Canalis RF, Chen F, Anzai Y. Nonneoplastic enhancing lesions mimicking intracanalicular acoustic neuroma on gadolinium-enhanced MR images. Radiology. 1991. 179: 795-6
15. Hitselberger WE, Gardner G. Other tumors of the cerebellopontine angle. Arch Otolaryngol. 1968. 88: 712-4
16. Kohno M, Sato H, Sora S, Miwa H, Yokoyama M. Is an acoustic neuroma an epiarachnoid or subarachnoid tumor?. Neurosurgery. 2011. 68: 1006-16
17. Lalwani AK. Meningiomas, epidermoids, and other nonacoustic tumors of the cerebellopontine angle. Otolaryngol Clin North Am. 1992. 25: 707-28
18. Little JR, Gomez MR, MacCarty CS. Infratentorial arachnoid cysts. J Neurosurg. 1973. 39: 380-6
19. Mahaley MS, Mettlin C, Natarajan N, Laws ER, Peace BB. Analysis of patterns of care of brain tumor patients in the United States: A study of the Brain Tumor Section of the AANS and the CNS and the Commission on Cancer of the ACS. Clin Neurosurg. 1990. 36: 347-52
20. Marple BF, Milchbrub S, Meyerhoff WL, Roland PS. Necrotizing granulomatous inflammation of the superior vestibular nerve mimicking an acoustic neuroma. Otolaryngol Head Neck Surg. 1998. 118: 862-5
21. Michaels L. Origin of congenital cholesteatoma from a normally occurring epidermoid rest in the developing middle ear. Int J Pediatr Otorhinolaryngol. 1988. 15: 51-65
22. Moffat DA, Ballagh RH. Rare tumours of the cerebellopontine angle. Clin Oncol (R Coll Radiol). 1995. 7: 28-41
23. Moffat DA, Saunders JE, McElveen JT, McFerran DJ, Hardy DG. Unusual cerebello-pontine angle tumours. J Laryngol Otol. 1993. 107: 1087-98
24. Morris DP, Ballagh RH, Hong A, Moffat DA, Hardy DG. Thrombosed posterior-inferior cerebellar artery aneurysm: A rare cerebellopontine angle tumour. J Laryngol Otol. 1995. 109: 429-30
25. Morrison AW, King TT. Space-occupying lesions of the internal auditory meatus and cerebellopontine angle. Adv Otorhinolaryngol. 1984. 34: 121-42
26. Nedzelski J, Tator C. Other cerebellopontine angle (non-acoustic neuroma) tumors. J Otolaryngol. 1982. 11: 248-52
27. Piedra MP, Scheithauer BW, Driscoll CL, Link MJ. Primary melanocytic tumor of the cerebellopontine angle mimicking a vestibular schwannoma: Case report. Neurosurgery. 2006. 59: E206-
28. Samii M, Gerganov VM, Samii A. Functional outcome after complete surgical removal of giant vestibular schwannomas. J Neurosurg. 2010. 112: 860-7
29. Saunders JE, Kwartler JA, Wolf HK, Brackmann DE, McElveen JT. Lipomas of the internal auditory canal. Laryngoscope. 1991. 101: 1031-7
30. Shramek J, Gray L, Wilkins R, Rengachary S.editors. Tumors of the cerebellopontine angle: Imaging. Neurosurgery. New York: McGraw-Hill; 1996. p. 1049-63
31. Smirniotopoulos JG, Chiechi MV. Teratomas, dermoids, and epidermoids of the head and neck. Radiographics. 1995. 15: 1437-55
32. Srinivasan V, Anandacoomaraswamy KS, Atlas MD. Sterile abscess mimicking recurrent tumour in the cerebellopontine angle. J Laryngol Otol. 2002. 116: 379-81
33. Tien R, Dillon WP, Jackler RK. Contrast-enhanced MR imaging of the facial nerve in 11 patients with Bell's palsy. AJNR Am J Neuroradiol. 1990. 11: 735-41
34. Wong ML, Larson TI, Brackmann DE, Lo WW. Lipoma of internal auditory canal. Otolaryngol Head Neck Surg. 1992. 107: 374-6
35. Zager EL, Shaver EG, Hurst RW, Flamm ES. Distal anterior inferior cerebellar artery aneurysms. Report of four cases. J Neurosurg. 2002. 97: 692-6
36. Zulch K.editorsBrain Tumours: Their Biology and Pathology. 1957. New York: Springer-Verlag: