Acoustic neuroma Chunfu Dai M.D & Ph.D
Background Originate from vestibular branch of aucoustic nerve Histologic feature: schwanoma, neuroma, neurolemmoma Predilection: 30-50y Unilateral: majority Bilateral: Type II acoustic neuroma
Pathology Predominate: internal auditory canal Extension to CPA Compression on brainstem and brain hydrops Anterior: trigeminal nerve, Medial: abducent nerve Inferior: IX, X, XI, XII
Clinical presentations Hearing loss and tinnitus Progressive HL 90% SDS reduction 10% of patients complain of sudden HL. Unbalance Otalgia and compression due to depression of sensor fiber of facial nerve Involvement of trigeminal nerve Compression of cerebellum and brainstem: ataxia, nystagmus and intracranial hypo-pressure
Work-up Audiometry PTA: threshold elevated in high frequency tone decay test: positive Speech audiometry Acoustic impedance ABR: latency of wave V prolongs, or wave V disappears Acoustic emission
Work-up Vestibular function: Neurologic exam Image study CT shows enlargement of internal auditory canal MRI
Managements Surgery Middle cranionectomy: useful hearing Translabyrinectomy: no useful hearing Nice exposure of facial nerve
Managements Retro-sigmoid sinus approach: Inferior occipital approach: Big tumor >3cm Nice exposure tumor
Managements No surgical intervention -Knife observation