Vestibular Schwannoma

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

KEY IMAGES

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

1. Lin EP, Crane BT.  The management and imaging of vestibular schwannomas.  American Journal of Neuroradiology 2017; 38(11):2034-2043
2. 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