Cochlear Implants

Children and adults with a severe to profound hearing loss who cannot be helped with hearing aids may be helped with cochlear implants. A cochlear implant is a device that provides direct electrical stimulation to the auditory (hearing) nerve in the inner ear. Patients with severe to profound sensorineural hearing loss have damage to the tiny hair cells in the part of the inner ear called the cochlea. Because of this damage, sound cannot reach the auditory nerve. With a cochlear implant, the damaged hair cells are bypassed, and the auditory nerve is stimulated directly.

The cochlear implant does not result in “restored” or “cured” hearing. It does, however, allow for the perception of the sensation of sound.

The benefits from a cochlear implant depend on many factors, such as:

  • The age of the patient when he or she receives the implant
  • Whether the hearing loss was present before or after the patient developed language skills
  • The motivation of the patient and his or her family

Cochlear implants have external (outside) parts and internal (surgically implanted) parts that work together to allow the user to perceive sound.

The external parts include a microphone, a speech processor, and a transmitter. The microphone looks like a behind-the-ear hearing aid. It picks up sounds—just like a hearing aid microphone does—and sends them to the speech processor.

The speech processor is housed with the microphone behind the ear. The speech processor is a computer that analyzes and digitizes the sound signals and sends them to a transmitter worn on the head just behind the ear.

The transmitter sends the coded signals to an implanted receiver just under the skin via an FM signal.

The internal (implanted) parts include a receiver and electrodes. The receiver is just under the skin behind the ear. The receiver takes the coded electrical signals from the transmitter and delivers them to the array of electrodes that have been surgically inserted in the cochlea. The electrodes stimulate the fibers of the auditory nerve, and sound sensations are perceived.

It is generally agreed that the best adult candidates are those who:

  • Have severe to profound hearing loss in both ears
  • Have had limited benefit from hearing aids
  • Have no other medical problems that would make the surgery risky
  • Have a strong desire to be part of the hearing world and communicate through listening and speaking
  • Have lost their hearing after speech and language development

Children can be considered for cochlear implants. Children must be at least 12 months of age to undergo this surgery.

It is generally agreed that the best child candidates are those who:

  • Have profound hearing loss in both ears
  • Have had limited benefit from hearing aids
  • Are healthy and have no medical conditions that would make the surgery risky
  • Are involved (when able), along with their parents, in all the steps in the process
  • Understand (when able), along with their parents, their role in the successful use of cochlear implants
  • Have (when able), along with their parents, realistic expectations for cochlear implant use
  • Are willing to be actively involved in their habilitation/rehabilitation
  • Have support from their educational program to emphasize the development of auditory skills

A battery of behavioral and or electrophysiological tests is given to a potential implant candidate. Imaging studies are also performed. This is done to ensure that the candidate will benefit from a cochlear implant and will have the motivation to participate in the process. It is important that the individual understands what the implant will and will not do and also understands the commitment required for care and follow-up services.

Once the decision is made to go ahead, the surgery is performed. Sometimes it involves an overnight stay in the hospital, and sometimes it is done on an outpatient basis.

About 4 weeks after surgery, the patient returns to the clinic to be fit with the external components and to activate and program (called mapping) the implant. This initial fitting process is completed over 1-2 days and will include additional visits over several months at regular intervals.

The additional visits are needed for activating, adjusting, and programming the various electrodes that have been implanted. Also, as the person develops skill in using the implant, adjustments and reprogramming are required. Usually there are annual visits to the clinic for equipment checks and test of aided hearing and speech understanding.

Both children and adults receive extensive rehabilitation services from audiologists, speech-language pathologists, teachers, and counselors as they learn to listen, improve speech, and develop better communication skills. They are taught how to use the implant and how to respond to the sounds they are receiving. For those who have heard before, sounds through the cochlear implant may seem unnatural at first. Those who have never heard before must be taught what the sounds are. Over time, most users experience more natural sound quality and benefit greatly.