A patient with a vestibular schwannoma (acoustic neuroma) at the cerebellopontine angle presents with unilateral sensorineural hearing loss and tinnitus. The nerve most at risk of compression SECOND (after CN VIII) as the tumour enlarges is:

• A CN VII (facial nerve) ✓
• B CN V (trigeminal nerve)
• C CN VI (abducens nerve)
• D CN IX (glossopharyngeal nerve)

Explanation

At the cerebellopontine angle, CN VII runs just anteriorly alongside CN VIII through the internal acoustic meatus; it is thus the second most commonly affected nerve by acoustic neuromas, causing ipsilateral lower motor neuron type facial palsy. CN V is affected as the tumour grows further anteriorly, causing ipsilateral facial numbness. CN IX and X are affected when very large tumours involve the jugular foramen region. The anatomical proximity of CN VII and VIII within the internal acoustic meatus is the key point.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.