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Acoustic Neuroma

Causes of Acoustic Neuroma

The causes of acoustic neuroma depend whether the tumor is unilateral or bilateral. Also called vestibular schwannoma, it forms when the body produces too many of the Schwann cells that insulate and support the vestibular nerve in the inner ear. If tumors develop in just one ear, it is a unilateral acoustic neuroma. If the tumors develop in both ears, it is a bilateral acoustic neuroma.

Doctors believe both types are related to a genetic malfunction of a single gene on chromosome 22, which is thought to control the growth of Schwann cells. Abnormal functioning of the gene leads to uncontrolled growth of the Schwann cells and a tumor, but the underlying causes of acoustic neuroma differ for each type.

The cause of bilateral acoustic neuroma is hereditary, although some cases are the first appearance of the mutation. It relates to a genetic disorder known as neurofibromatosis-2 or NF 2. A child of a parent with NF 2 has a 50 percent risk of inheriting the condition. Tumors of the brain and spinal cord often develop in these patients, who also are at higher risk for tumors on nerves that affect eye and facial movements, speech and swallowing. The additional problems neurofibromatosis-2 causes increase the difficulty in determining the best strategy for managing a bilateral acoustic neuroma.

The cause of unilateral acoustic neuroma is not hereditary. It also arises from the genetic malfunction on chromosome 22, but it is not clear how the gene becomes faulty. Environmental factors are suspected however, at this time, researchers have been unable to link a specific agent to the condition.

Locations for Acoustic Neuroma