Acoustic neuroma ( Vestibular schwannoma ) : Symptoms, Causes, Diagnosis and Treatment

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Acoustic neuroma also called vestibular schwannoma is a noncancerous tumor of the schwann cells that covers the Vestibular nerve. Vestibular nerve is a branch of vestibulocochlear nerve (8th cranial nerve).
The nerve goes from the inner ear to the brain. It sends information regarding the position and movement of the head, therefore it is essential to maintain balance. 
It is usually a slow growing tumor though sometimes it may grow quickly. 
Men and women are equally affected. 1 in 100,000 people develop this tumor each year.
Acoustic neuroma may be unilateral ( 95% ) or bilateral ( 5% ).

Symptoms of Acoustic neuroma-

Symptoms of acoustic neuroma usually take several years to develop. Symptoms are due to the pressure effect of the tumor on the nearby cranial nerves and brain.
Most common symptom is hearing loss in the affected ear, usually slowly increasing .
Inability to maintain balance. Half of the affected patients suffer from this problem. Patients may fall usually towards the affected ear.
Dizziness. 
Tinnitus ( noise ) in the affected ear. Noise may be roaring, hissing or buzzing like. Tinnitus may be occasional or permanent.
Sensory loss in part of face and weakness of facial muscles. Twitching of muscles of forehead, eyebrows and face may occur. 
Changes in taste sensation and tear production.
Dull or aching headache. 
Large tumors can prevent flow of cerebrospinal fluid thereby causing hydrocephalus. Swallowing and eye movements may be affected. In very rare cases death may occur due to compression of the respiratory centre. 

Causes of Acoustic neuroma- 

There may be a genetic defect that fails to control the overgrowth of schwann cells.
Risk factors of Acoustic neuroma –
Neurofibromatosis type 2 ( a rare genetic disorder)-It is an autosomal dominant disorder. People with neurofibromatosis type 2 have bilateral acoustic neuroma.

Diagnosis of Acoustic neuroma- 

Proper history taking.
Hearing test ( audiometry )-it is done by an audiologist.
Magnetic resonance imaging ( MRI )- It can detect tumors as small as 1-2 millimeter diameter.
CT scan of the brain- Where MRI is not available or contraindicated, but It is less accurate than MRI. CT scan may miss small tumors.

Treatment of Acoustic neuroma – 

Treatment options are 
A) Monitoring 
B) Surgery 
C) Radiation

Treatment choice depends upon- 
The age and general condition of the patient 
Size and speed of growth of the tumor 
and Symptoms caused by the tumor.

A) Monitoring may be a choice- 
In case of slow growing tumor
No symptoms or few symptoms.
Older or patient with poor general condition.
Here regular checkup for symptoms, hearing test, imaging with MRI to monitor growth of the tumor every 6 to 12 months is done. Further course of intervention depends upon the results of monitoring.

B) Surgery- surgery to remove an acoustic neuroma is necessary when
The tumor is large
Tumor is causing symptoms 
Rapidly growing tumor 

Surgery is done to remove the whole of the tumor or part of the tumor where removal of the whole of the tumor carries risk of damage of facial nerve or any nearby vital structure. 
Surgery is performed under general anaesthesia through the inner ear or making an opening in the skull.

Complications of surgery- 

Damage of facial nerve 
Temporary or permanent numbness in face, weakness of facial muscles. 
Balance problem 
Leakage of cerebrospinal fluid ( fluid within the brain and spinal cord ) 
Headache
Infection in brain causing meningitis 
Bleeding in brain 

c) Radiation therapy- 
Stereotactic radiosurgery- It is usually used to treat small sized tumours less than 2.5 cm. Radiation is directly targeted to the tumor. Attempts are made to prevent damage of surrounding vital structures. It may take time to see the results of the treatment.

Complications of radiosurgery- 

Hearing loss
Ringing in the ear
Weakness or paralysis of facial muscles 
Balance problems 

Supportive therapy for Acoustic neuroma – 

Periodic check up and imaging after treatment because the tumor may relapse or grow in size.
Hearing implant or hearing aid if there is hearing loss. 
Physiotherapy, exercise of facial muscles, surgery of facial muscles and nerve grafting if necessary.
Counselling by psychologist or psychotherapist to manage stress and anxiety.