Vestibular Schwannoma

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Diagnosis Definition

Vestibular schwannoma (VS), often referred to as “acoustic neuroma,” arises from the vestibulocochlear (8th cranial nerve) sheath; median age of presentation is 50 years
VS is the most common extra-axial cerebellopontine angle (CPA) mass (70%–80%), followed by meningioma (10%–15%) and epidermoid cyst (5%)
VSs may remain within the internal auditory canal (IAC) or extend into the CPA; those with both an IAC and CPA component are the most common
Symptoms are related to compression of adjacent cranial nerves, brain stem, or posterior fossa structures; chronic asymmetric sensorineural hearing loss is more common than tinnitus or unsteadiness
VS is unilateral in >90% of patients, with an equal incidence on the left and right

Imaging Findings

Due to superior contrast resolution, MR imaging is the standard of care in evaluating VSs
VS is typically T1 isointense relative to the cerebellar parenchyma and demonstrates avid enhancement on postcontrast T1 images
T1 hyperintense signal and susceptibility artifacts on T2* gradient-echo sequences may represent hemorrhage
Larger VSs often demonstrate heterogeneous enhancement secondary to hemorrhage and cysts
Important findings on MRI include mass effect on the middle cerebellar peduncle or extension to the cochlear aperture

Pearls

CPA meningiomas are dural-based enhancing masses that grow along the petrous ridge and can extend into the IAC; they often have a characteristic dural tail and may be associated with bony changes
Unlike a meningioma, a VS does not have calcifications
Bilateral VSs are diagnostic of neurofibromatosis type 2

References

Lin EP, Crane BT. The management and imaging of vestibular schwannomas. American Journal of Neuroradiology 2017; 38(11):2034-2043
Gentry LR, Jocoby CG, Turski PA, et al. Cerebellopontine angle-petromastoid mass lesions: comparative study of diagnosis with MR imaging and CT. Radiology 1987;162:513–20

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