Auditory Brainstem Implant

Overview

An auditory brainstem implant (ABI) provides a sensation of hearing to deaf people by directly stimulating the brainstem. Because it bypasses the cochlear nerves, the device is most useful for people who have nonfunctioning or absent cochlear nerves.

See an animation of an auditory brainstem implant.
(Requires Windows Media Player).

The device is used most commonly in people with neurofibromatosis type II (NF-2). This disease causes tumors to form on the balance and hearing nerves, which usually results in deafness.

This procedure is offered at Mayo Clinic in Rochester, MN. Mayo Clinic specialists in Otorhinolaryngology and Neurosurgery work together to perform the procedure.

How Does it Work?

In people with NF-2, the ABI usually is placed at the same time the nerve tumors are removed, so it's completed within one surgery. The device comprises a tiny microphone positioned by the ear, a decoding chip and an array of electrodes implanted on the brainstem. The ABI connects directly to the brainstem, bypassing the damaged cochlea and cochlear nerves. The microphone picks up sounds from the environment and digitally transmits them to a decoding chip placed under the skin. The chip stimulates the brainstem electrodes, allowing the patient to hear a variety of sounds.

The placement of the ABI is just the first step in restoring some hearing. After surgery, the patient returns for multiple sessions with an audiologist to test and adjust the sound processor, and to learn and interpret new sounds. This process can take significant time, because the sound cues from an ABI are different from normal hearing.

The device doesn't give the full range of hearing, but it provides increased environmental noise awareness. Most patients are able to hear noises like a telephone ringing or horn honking, but the degree of hearing usefulness can vary greatly. Some people get good word recognition, while others get more general sound cues. In combination with lipreading, the cues help improve communication with others.