Acoustic Neuroma Introduction A K A vestibular schwannoma

Acoustic Neuroma

Introduction A. K. A. : vestibular schwannoma / neurilemmoma Benign, encapsulated, slow growing tumour arising from Schwann cells of superior vestibular division of 8 th nerve within internal auditory canal Rarely from inferior vestibular or cochlear division

Tumour growth Tumor expansion within internal auditory canal causes widening & erosion of I. A. C. appears in cerebello-pontine angle (> 2. 5 cm) involves 5 th, 7 th, 9 th, 10 th, 11 th cranial nerves displacement of brainstem & cerebellum raised intracranial pressure Involvement of 6 th & 3 rd cranial nerves

Classification as per size 1. Intra-canalicular: confined to I. A. C. 2. Small: up to 1. 5 cm 3. Medium: 1. 5 to 4 cm 4. Large: over 4 cm

Tumor size

Intra-canalicular

Small

Medium

Large

Epidemiology l 10% of all brain tumors l 80% of all Cerebello-pontine angle tumors l Age: 40 -60 yrs l Male : Female = 3: 2 l Unilateral (90%); Bilateral (10%) l Bilateral = von Recklinghausen’s neurofibromatosis

Clinical Staging 1. Otological stage: due to pressure on 8 th nerve 2. Other Cranial nerve involvement 3. Brainstem + Cerebellar involvement 4. Raised intra-cranial tension 5. Terminal stage: failure of vital centres of brainstem & cerebellar tonsil herniation

Otological symptoms & signs 1. Progressive, unilateral sensorineural deafness 2. Poor speech discrimination (disproportionate) 3. Tinnitus 4. Mild vertigo 5. Nystagmus Vestibular symptoms appear late due to slow

Other Cranial nerve palsy Trigeminal: first nerve to be involved l Loss of corneal reflex l Pain, numbness and paresthesia of the face Facial: l Hypoaesthesia of posterior external auditory canal wall (Hitselberger’s sign) l Facial weakness, Loss of taste, ed lacrimation

Other Cranial nerve palsy Glossopharyngeal, Vagus & Accessory Spinal: l Dysphagia l Hoarseness l Nasal regurgitation l Decreased gag reflex Abducent & Oculomotor: l Diplopia

Brainstem involvement Ataxia Weakness of arms & legs Tendon reflexes exaggerated Cerebellar involvement Ataxic gait (fall on affected side) Intention tremors Past-pointing Dysdiadochokinesia Increased Intra-cranial tension Headache Projectile vomiting Blurred vision Papillodema Abducent nerve palsy

First Symptoms Hearing loss: 80 -100 % Vertigo: 10 -50 % Tinnitus: 5 -10 % Ear ache: 5% Sudden hearing loss: 5% Facial paralysis: 1 -2 %

Investigations l Pure Tone Audiometry: high frequency SNHL l Speech audiometry: SD scores < 30% l Tone decay test: positive l Stapedial Reflex: Decay > 50 % in 10 sec l B. E. R. A. : wave V >4. 2 ms; inter-wave V >0. 2 ms l Caloric test: I/L canal paresis or no response l C. T. scan with contrast: for tumor > 0. 5 cm l M. R. I. with gadolinium contrast: best

Pure Tone Audiogram

Speech Audiometry Roll over phenomenon

Calorigram

Brainstem Evoked Response Audiometry (B. E. R. A. )

Contrast C. T. Scan

Contrast M. R. I. : neuro-anatomy

Contrast M. R. I. : intra-canalicular

Contrast M. R. I. : small

Contrast M. R. I. : Medium

Contrast M. R. I. : Large

Bilateral tumor: small

Bilateral tumor: large

Treatment 1. Observation 2. Microsurgical removal: (partial or total) l Trans-labyrinthine approach l Retro-sigmoid or Sub-occipital approach l Middle Cranial Fossa approach l Combined approach 3. Stereotactic Radiotherapy 4. Brainstem Implant: after B/L tumor excision

Observation Indications: 1. Age > 60 years with small tumor & no symptoms 2. Tumour in only hearing / better hearing ear Serial MRI used to follow growth pattern. Treatment recommended if hearing is lost or tumor size becomes life threatening.

Incisions Middle cranial fossa Retro-sigmoid Trans-labyrinthine

Retro-sigmoid Approach

Sub-occipital approach

Trans-labyrinthine approach

Middle cranial fossa approach

Surgical Approach Protocol 1. Intra-canalicular: Middle cranial fossa approach 2. Small (<1. 5 cm): Retrosigmoid approach 3. Medium (1. 5 - 4 cm) a. Hearing fine**: Retrosigmoid approach b. Hearing bad: Trans-labyrinthine approach 4. Large (>4 cm): Trans-labyrinthine / Combined ** Pure Tone Average < 30 d. B, S. D. Score >70%

Intra-operative photograph

Proton stereotactic radiotherapy Single high dose of radiation delivered on a small area to arrest or kill tumor cells. Minimal injury to surrounding nerves & brain tissue Gamma Knife: radioactive cobalt LINAC X-knife: linear accelerator Cyber-Knife: robotic radio-surgery system Indication: 1. Surgery refused / contraindicated 2. Post-operative residual tumour

Treatment Planning

Treatment Planning

P. S. R. T. in progress

Pre & Post treatment

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