Introduction
The vestibulocochlear nerve is a sensory nerve with two parts: the vestibular and cochlear nerves.
Sensory information regarding head position and movement is transmitted via the vestibular nerve and information relating to the reception of sound via the cochlear nerve.
Injury causes balance and hearing disturbances.
There may be ipsilateral nystagmus, ataxia and symptoms of vertigo if the vestibular portion is involved.
Sensory fibres of the vestibular nerve travel from the inner ear to the vestibular ganglion in the internal acoustic meatus of the petrous temporal bone. The nerve then enters the upper medulla.
The cochlear nerve also travels through the internal acoustic meatus, entering the lower pons.
As for CN VII, CT head scanning is needed to look for cerebellopontine angle tumours and fractures of temporal bone.
Infections such as vestibular neuritis, mastoiditis and herpes zoster can cause palsy.
The commonest tumours involving the vestibulocochlear nerve are cerebellopontine angle tumours. Approximately 85% of these are acoustic neuromas. Others are meningiomas, cholesteatomas and primary malignancies of the posterior fossa (less than 2%).
Tumours invading the temporal bone, e.g. brainstem glioma, can invade and mimic cerebellopontine angle tumours.
Vascular malformations can occur at the cerebellopontine angle.
Drugs known to cause vestibulocochlear neurotoxicity include aspirin, frusemide, phenytoin, cytotoxics (cisplatin, vincristine) and alcohol.
Paget’s disease can cause compression of the nerve in the internal auditory canal.
Fracture of the petrous temporal bone (see CN VII).