Neurological Disorders: Acoustic Neuroma

Introduction

Acoustic Neuroma, also called as vestibular schwannoma is an example of brain tumor. This tumor actually does not arise from the brain tissue itself rather it arises from the 8th cranial nerve which is also called as vestibulocochlear nerve or statoacoustic nerve. This 8th cranial nerve is related with our hearing and balance so this tumor may cause deafness and balance problems in the affected patient.

Schwannomas are not unique for this cranial nerve, they can arise from other cranial nerves, peripheral nerves, or from spinal nerve roots as well.

For the 8th cranial nerve schwannoma now a days vestibular schwannoma is the preferred term because of these two reasons;

1) Majority of schwannomas when they arise from the 8th cranial nerve they actually arise from the vestibular component of this nerve rather than the acoustic componest

2) The term schwannoma describes its origin; it arises from the schwann cells. These cells produce a substance called myelin.

These tumors are extraaxial, means arise from outside the brain issue within the skull cavity but can grow towards the brain tissue. They are also benign tumors means they are no cancers (they do not spread from its place of origin to other places), however that doesn’t mean they cannot create any problems (please see below).

They are the commonest tumors in an area called cerebellopontine angle of the brain stem region.

Who gets this tumor?

The incidence of this tumor is highest in late middle age and early late age group (around 6th and 7th decades). Both genders are affected almost equally. This tumor may arise at an early age when it occurs in patients with neurofibromatosis (NF). Although both type 1 & 2 of NF patients can develop this tumor but it does more with type 2 and in fact bilateral vestibular schwannoms are one of the requirements for defining type 2 NF.

How do patients present?

The following manifestations are seen (case to case basis)

• Vertigo (spinning type dizziness)
• Hearing deficits
• Ringing sound in the ear (tinntus)
• Facial numbness
• Facial paralysis
• Focal extremity weakness and/or numbness
• Headache
• Nausea and/or vomiting etc

Diagnosis

A CT or preferably MRI of the brain with and without contrast is the investigation of choice. A biopsy may be necessary to confirm the diagnosis. Audiometric studies are necessary to detect the hearing problems.

Management

The management aspects for these tumors are similar to many other intracranial tumors including (decided on case to case basis);

• Surgical excision of the tumor as much as possible
• Radiotherapy as necessary
• Sometimes just wait & watch policy (for small tumors)

A neurologist and/or a neurosurgeon are frequently involved in the care of acoustic neuroma patients.



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