A cochlear implant works by stimulating remaining auditory nerve fibers. But if disease or tumor removal leaves no functioning auditory nerve, the patient would not be a candidate for a cochlear implant. The auditory brainstem implant (ABI) was developed to restore some hearing to people in this situation. In most cases, these are people with neurofibromatosis type II (NF2) who have tumors in both ears. As a result of the tumors or their surgical removal, hearing is lost and the hearing nerves are destroyed. The ABI bypasses even the damaged hearing nerves by placing electrodes in the next center up the pathway to the brain, the cochlear nucleus complex in the brainstem.

At House Clinic, ABI surgery has been performed for over 30 years. The ABI is usually placed at the time of surgical removal of your acoustic tumor. It can be placed during the first tumor removal to give you time to adjust to the sound before losing all of the hearing in your other ear. The tumor is removed using the translabyrinthine approach. After removal of the tumor, the ABI electrode array is placed completely within the cochlear nucleus and tests for electrical auditory responses are performed. These tests are helpful in determining whether you’ll be able to hear sounds from the device.

Initial device stimulation usually occurs 4 to 8 weeks after implantation. The overall hearing ability of people who have received ABIs is generally similar to that of people with earlier simple cochlear implants. Eighty-five percent of people who have received an ABI do have auditory sensations. When combined with lipreading cues, most people with an ABI have improved sentence understanding at 3 to 6 months after initial stimulation. They also hear environmental sounds and can understand words when a limited set (like multiple choice) is presented.