Acoustic Neuroma

Overview

An acoustic neuroma is a noncancerous growth that develops on the eighth cranial nerve. Also known as the vestibulocochlear nerve, it connects the inner ear with the brain and has two different parts. One part is involved in transmitting sound; the other helps send balance information from the inner ear to the brain.

Acoustic neuromas – sometimes called vestibular schwannomas or neurilemmoma – usually grow slowly over a period of years. Although they do not actually invade the brain, they can push on it as they grow. Larger tumors can press on nearby cranial nerves that control the muscles of facial expression and sensation. If tumors become large enough to press on the brain stem or cerebellum, they can be deadly.

Symptoms of Acoustic Neuroma

The early symptoms of an acoustic neuroma are often subtle. Many people attribute the symptoms to normal changes of aging, so it may be a while before the condition is diagnosed.

• The first symptom is usually a gradual loss of hearing in one ear, often accompanied by ringing in the ear (tinnitus) or a feeling of fullness in the ear. Less commonly, acoustic neuromas may cause sudden hearing loss.
• Problems with balance
• Vertigo (feeling like the world is spinning)
• Facial numbness and tingling, which may be constant or come and go
• Facial weakness
• Taste changes
• Difficulty swallowing and hoarseness
• Headaches
• Clumsiness or unsteadiness
• Confusion

Causes of Acoustic Neuroma

The exact cause is unknown. Most cases seem to arise for no apparent reason (spontaneously). No specific risk factors for the development of these tumors have been identified.

A variety of potential risk factors for acoustic neuroma have been studied including prior exposure to radiation to the head and neck area (as is done to treat certain cancers) or prolonged or sustained exposure to loud noises (as in an occupational setting). Acoustic neuromas occur as part of a rare disorder known as neurofibromatosis type II.

An acoustic neuroma arises from a type of cell known as the Schwann cell. These cells form an insulating layer over all nerves of the peripheral nervous system (i.e., nerves outside of the central nervous system) including the eighth cranial nerve. The eighth cranial nerve is separated into two branches the cochlear branch, which transmits sound to the brain and the vestibular branch, which transmits balance information to the brain.

Treatment

There are three main courses of treatment for acoustic neuroma:

• Observation is also called watchful waiting. Because acoustic neuromas are not cancerous and grow slowly, immediate treatment may not be necessary. Often doctors monitor the tumor with periodic MRI scans and will suggest other treatment if the tumor grows a lot or causes serious symptoms.
• Surgery for acoustic neuromas may involve removing all or part of the tumor.
• Radiation therapy is recommended in some cases for acoustic neuromas. State-of-the-art delivery techniques make it possible to send high doses of radiation to the tumor while limiting exposure and damage to surrounding tissue.

FAQ

How is acoustic neuroma diagnosed?
A hearing test is done to access the hearing loss. Other options also include MRI or CT scan.

What are the treatments available for this condition?
The first step is to see if the tumor is growing or not. If it is growing, then it is treated either surgically or by radiation therapy.

When are these treatments given?
The treatment to be given depends on factors like the size and growth of the acoustic neuroma. The patient’s overall health also plays an important role.

How is surgery different from radiation therapy of acoustic neuroma?
When the acoustic neuroma is surgically removed, it may or may not be removed completely depending on its closeness to any vital part. The goal of radiation therapy is to ether shrink or kill the acoustic neuroma.

Is acoustic neuroma life threatening?
It is usually benign but can be life threatening if left untreated.

Can hearing be restored after acoustic neuroma surgery?
If hearing is completely lost as a result of the surgery, it cannot be restored. But there are devices that may help with the hearing loss problem of one ear.

What are the complications of the treatment?
The common complications are facial numbness, damage to other nerves leading to eye problems like drooping eyelid.

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