Question

All of the following cranial nerves may be involved in acoustic neuroma, EXCEPT?

• A. Vagus
• B. Glossopharyngeal
• C. Oculomotor
• D. Facial

Hint:

This tumour sits at the cerebellopontine angle, far from the midbrain nerve controlling eye movement.

Answer 1

The Correct Option is C

Step 1: Acoustic neuroma (vestibular schwannoma) arises from the vestibular nerve in the internal auditory canal and the cerebellopontine angle, so it first affects the eighth (vestibulocochlear) nerve causing hearing loss and tinnitus.

Step 2: As the tumour enlarges it involves adjacent nerves. The trigeminal (Vth) is the earliest other nerve affected (reduced corneal reflex), the facial (VIIth) nerve is involved giving Hitzelberger's sign and loss of taste and lacrimation.

Step 3: Further extension affects the glossopharyngeal (IXth) and vagus (Xth) nerves, producing dysphagia and hoarseness from palatal, pharyngeal and laryngeal paralysis.

Step 4: The oculomotor (IIIrd) nerve lies far from the cerebellopontine angle and is not directly involved by the tumour (the VIth nerve may be affected late due to raised intracranial pressure). So the exception is oculomotor.