Dr. Sudeeep K.C.

 Acoustic neuroma is also known as vestibular schwanoma or VIIIth nerve tumour.  INCIDENCE: Acoustic neuroma constitutes 80% of all cerebellopontine angle tumours and 10% of all brain tumours.

 PATHOLOGY:  It is benign encapsulated, extremely slow growing tumour of viii th nerve.  Microscopically, it consists of elongated spindle cells with rod shaped nuclei lying in rows. Bilateral tumours are seen in patients with neurofibromatosis.  PATHOLOGY:  It is benign encapsulated, extremely slow growing tumour of viii th nerve.  Microscopically, it consists of elongated spindle cells with rod shaped nuclei lying in rows. Bilateral tumours are seen in patients with neurofibromatosis.

 CLASSIFICATION ◦ DEPENDING UPON THE SIZE, THE TUMOR IS CLASSIFIED:-  INTRACANALICULAR(CONFINED TO INTERNAL AUDITORY CANAL)  SMALL SIZE (UP TO 1.5 CM)  MEDIUM SIZE (1.5-4CM)  LARGE SIZE(> 4 CM)

1) Age and sex: 40 to 60 yrs of age, both sexes are equally affected. 2)Cochleovestibular symptoms: It is the earliest symptoms when tumour is still intracanalicular. Progressive unilateral SNHL, often accompanied by tinnitus. Marked difficulty in understanding speech, out of propotion to the pure tone hearing loss.There is imbalance and unsteadiness.

3)Cranial nerve involvement :  Vth nerve is the earliest to be involved Reduced corneal sensitivity, numbness or parasthesia of face.  VIIth nerve  sensory fibres are affected early.  Hypoaesthesia of posterior meatal wall(Hitzelberger’s sign),loss of taste. Reduced lacrimation.  IXth and Xth nerves  Hoarsness  Other cranial nerves  affected when tumour is very large.

 4) Brainstem involvement: Ataxia, weakness and numbness of arms legs with exaggerated tendon reflexes.  5) Cerebellar involvement : Pressure symptoms on cerebellum are seen in large tumours.  6)Raised intracranial tension : late feature, having headache, nausea, vomiting, diplopia,papilloedema with blurring of vision.

 AUDIOLOGICAL TESTS a)PURE TONE AUDIOMETRY SHOWS SNHL. b)SPEECH AUDIOMETRY SHOWS POOR SPEECH DISCRIMINATION & DISPROPORTIONATE TO PURE TONE HEARING LOSS c)RECRUITMENT PHENOMENON IS ABSENT. d)SHORT INCREMENT SENSITIVITY INDEX (SISI) TEST WILL SHOW A SCORE OF 0-20% IN 70 –90% CASES  STAPEDIAL REFLEX DECAY TEST

 VESTIBULAR TEST  CALORIC TEST WILL SHOW DIMINISHED OR ABSENT RESPONSE IN 96% OF PATIENTS.WHEN TUMOUR IS VERY SMALL,CALORIC TEST MAY BE NORMAL.  NEUROLOGICAL TESTS ◦ COMPLETE CN FUNCTONS EXAMINATIO AND FUNDUS EXAMINATION  RADIOLOGICAL TESTS ◦ PLAN X-RAY,CT-SCAN, MRI WITH GADOLINIUM CONTRAST, VERTEBRAL ANGIOGRAPHY.

 ELECTRIC RESPONSE AUDIOMETRY ◦ VERY USFUL TEST OF RETROCOCHLEAR LESION. ◦ IN THE PRESENCE OF VIIITH NERVE TUMOUR, A DELAY OF>0.2MSEC IN WAVE V BETWEEN TWO EARS IS SIGNIFICANT.  CSF EXMINATION ◦ PROTEIN LEVEL IS RAISED, LP IS AVOIDED.

 Surgery: S urgical removal of tumour is the treatment of choice.  Radiation : Radiotherapy has no role in treatment of acoustic neuroma due to low tolerance of CNS to radiation. Gamma knife surgery for patient unfit for Surgery or who refuse surgery.