An acoustic neuroma is a rare, usually slow-growing tumor of the inner ear, specifically of the nerve that connects the ear to the brain (the hearing nerve). Despite usually being benign, an acoustic neuroma that grows and is not treated can severely affect neurological function and become life-threatening.
This type of brain tumor develops in the eighth cranial nerve, which controls hearing and balance and is located in the inner ear near the back of the skull. One part of the eighth cranial nerve transmits sound and the other part sends balance information to the brain from the inner ear. It is one of the 12 cranial nerves that originate in the brainstem.