An acoustic neuroma, also known as a vestibular schwannoma, is a tumor that develops from the Schwann cells that form the covering, or sheath, of the eighth cranial nerve. The eighth cranial nerve — the vestibulocochlear nerve — is responsible for relaying hearing and balance signals from the inner ear to the brain.
An acoustic neuroma is benign, is generally slow-growing and does not spread to other parts of the body. Studies have shown that the average growth rate of acoustic neuromas is less than 2 millimeters per year.
Acoustic neuromas affect about 10 people in one million. More women than men are affected, and they are usually diagnosed between the ages of 30 and 60 years.
Among primary brain tumors — those that originate in the brain — 6 percent are acoustic neuromas.