The earliest symptom of acoustic nerve tumour is: [AIPGMEE – 1995]
1) Hearing loss
Acoustic Neuroma (Vestibular Schwannoma) is a benign slow-growing tumour.
M/C tumour of the CP angle (80%) followed by meningioma (10%), congenital cholesteatoma (5%).
10% of all brain tumours.
Site of origin of the tumour is believed to be inferior vestibular nerve a branch of Vestibulo-cochlear nerve (VIII cranial nerve).
Neurofibramatosis type 2, (autosomal dominant) has been associated with 5% of acoustic neuroma. B/L acoustic neuroma is the hallmark of NF2.
M/c symptom of acoustic neuroma is unilateral, slowly progressive, SNHL. Development of labyrinthine ischemia d/t compression of Anterior inferior cerebellar artery within the internal auditory canal. Tinnitus and dizziness may be present, but severe vertigo is rare.
When the tumour grows up to 2.5cm, absent corneal reflex may be seen d/t involvement of trigeminal nerve. further growth may even lead to trigeminal neuralgia.
Hitselberger Sign – Hypoaesthesia of the postero-superior aspect of the external auditory d/t involvement of n.intermedius (sensory branch of facial nerve). Facial nerve palsy is very rare d/t the stretch resistance of facial nerve’s motor fibres and the extremely slow growth of acoustic neuroma. So if there is a CP angle tumour with facial nerve palsy, look for more aggressive tumours.
Investigation of choice: Gadolinium enhanced MRI.
Ice-cream cone appearance can be seen in MRI (Acoustic neuroma growing into CP angle from internal auditory canal)
Treatment of choice: Surgical (Trans-labyrinthine approach, Posterior fossa approach, middle fossa approach). Stereotactic radiotherapy (Gamma knife, X-knife) can also be used in unwilling patients and patients unfit for surgery.