Acoustic Neuroma

Condition

• Acoustic neuroma 

Definition

• Acoustic neuromas are intracranial, extra-axial tumours that arise from the Schwann cell sheath investing either the vestibular or cochlear nerve.

History 

• Unilateral hearing loss
• Tinnitus 
• Headache 
• Balance disturbance 
• Facial weakness
• Facial numbness 
• Lower CN palsy 

The most common presentation is overwhelmingly unilateral hearing loss. Assume anyone presents with sensorineural hearing loss with acoustic neuroma until proven otherwise. The following is a chart from e-medicine, here is the link to the full article

Examination

• occipital pain on the side of the tumour
• VIII nerve damage
• unilateral sensorineural deafness developing gradually over a period of months or years 
• around 5% will have sudden hearing loss
• vertigo which may be quite mild and tinnitus are common 
• caloric paresis may be demonstrable 
• V nerve damage
• depression of corneal reflex occurs early. Facial pain, paraesthesia and numbness develop
• VII nerve damage
• facial weakness is unusual 
• IX, X, XI nerve damage
• rare, presents dysphagia, change in voice, palatal weakness
• Compression effects of large tumours
• on cerebellum - ataxia, loss of coordination on ipsilateral side, nystagmus
• on pons - contralateral hemiparesis
• on aqueduct and 4th ventrcle - raised intracranial pressure e.g. headache 

Investigations

• Audiometry: selective sensorineural hearing loss in the right ear and delayed acoustic reflex (movement of the tympanic membrane in response to intense sound).
• Auditory branstem response: brainwave activity in response to sound, and tests the pathway from the cochlea to the brainstem. This should show an absence of waveforms and an increase in the latency of the fifth wave
• MRI

Murtagh's diagnostic triad

• unilateral tinnitus + hearing loss + unsteady gait = acoustic neuroma 

Treatment

• Referral to Neurosurgeon for excision 

References:

• John Murtagh 5th edition 
• Emedicine 
• gpnotebook.co.uk