What is an acoustic neuroma (vestibular schwannoma)?
An acoustic neuroma is a noncancerous tumor that grows on the vestibular nerve, which connects the inner ear to the brain. This nerve sends hearing and balance information to the brain. As the tumor grows, it can disrupt those functions and facial movement and sensation, in some cases.
Acoustic neuromas are rare, affecting one in 100,000 people in the United States each year. These tumors are usually diagnosed in adults in one ear and are not hereditary. Vestibular schwannomas are similar to acoustic neuromas but are rarer still. They can affect both ears or be associated with other benign growths in connection with a genetic disease called neurofibromatosis-2. The tumors usually grow slowly.
Diagram of an acoustic neuroma
Left: This cross-section diagram of the skull base shows a small acoustic neuroma (vestibular schwannoma) on the right side of the head. The tumor develops on the vestibular nerve, which sends hearing and balance information from the inner ear to the brain. The tumor's volume fills the inner bony ear canal (internal auditory canal) and extends to the trigeminal nerve, regulating facial movement and feeling.
Right: When the acoustic neuroma grows larger, as shown here, it enters the space between the inner ear canal and brainstem. This large tumor pushes on the brainstem, cerebellum, and trigeminal nerve, affecting facial functions.