Diagnostics

• Cochlear nerve (CN VIII): sensorineural hearing loss

  • Audiometry

    • Hearing loss with a greater deficit for higher frequencies

    • Best initial test: > 90% of patients will have some type of hearing loss. [2]

  • Weber test: lateralization to the normal ear

  • Rinne test: air conduction > bone conduction in both ears

  • Brainstem-evoked audiometry: delay in cochlear nerve conduction time on affected side finding

    • Can be used as an additional test in patients with asymmetric audiometry findings

    • More cost-effective but less sensitive than an MRI

• Trigeminal nerve (CN V): ipsilateral decreased corneal reflex

• Facial nerve (CN VII): ipsilateral facial twitching or weakness

Contrast MRI

• Recommended in patients with abnormal audiometric testing or high clinical suspicion of acoustic neuroma (cerebellopontine angle syndrome)

• CT with and without contrast is an alternative for those who cannot undergo MRI.

• Shows an enhancing lesion by the internal auditory canal, with possible extension into the cerebellopontine angle

• Gross findings: encapsulated firm mass

• Microscopic findings

  • Spindle cells in palisades (Antoni A tissue) alternating with myxoid hypocellular areas (Antoni B tissue)

  • S-100 positive