A 40-year-old presents with unilateral progressive sensorineural hearing loss, tinnitus, and unsteadiness. MRI with gadolinium shows a 1.8 cm mass in the internal auditory canal/CPA with intense enhancement. The superior vestibular nerve is identified as the nerve of origin. This is best classified as:

• A Vestibular schwannoma (acoustic neuroma) arising from the superior vestibular nerve — most common (55%) origin; NF2 gene mutation if bilateral ✓
• B Facial nerve schwannoma — differentiated by facial weakness and CT bone changes
• C Meningioma — differentiated by dural tail, calcification, and origin from inferior vestibular nerve
• D Epidermoid cyst — differentiated by low T1/T2 signal and DWI restriction, no enhancement

Explanation

Vestibular schwannomas (acoustic neuromas) arise in 55% from the superior vestibular nerve and 45% from the inferior vestibular nerve — despite being called 'acoustic' (cochlear), the cochlear nerve is rarely the origin. The characteristic MRI is a gadolinium-enhancing, T1 hypointense/T2 hyperintense mass with an ice-cream cone shape in the IAC/CPA angle. When bilateral, it is pathognomonic of NF2 (neurofibromatosis type 2), caused by loss-of-function of the Merlin protein (NF2 gene, chromosome 22q12). Meningioma has a dural tail and no IAC expansion; epidermoid shows DWI restriction without enhancement.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.