Cochlear Implants

A cochlear implant is a small, electronic device that can help provide a sense of sound to a person who is profoundly deaf or severely hard of hearing. The implant is surgically placed under the skin behind the ear. A cochlear implant does not restore or create normal hearing. Instead, it can give a deaf person a useful auditory understanding of the environment and help him or her to understand speech. Since 1990, thousands of children and adults have received cochlear implants. Cochlear implants were designed for persons with severe to profound hearing loss who obtain little benefit from hearing aids.

Cochlear implants compensate for damaged or non-working parts of the inner ear. The inner ear converts sound waves into electrical impulses. These impulses are then sent to the brain. A cochlear implant works in a similar manner. It electronically finds useful sounds and then sends them to the brain. Hearing through an implant sounds different from normal hearing. However, cochlear implants allow many people to communicate orally in person and over the phone.

How does a cochlear implant work?

In order to understand how a cochlear implant works, it is important to understand how we hear. The outer ear collects sound waves and sends them to the middle ear. The sound waves bounce off your eardrum and are made louder by three tiny bones: the hammer, anvil, and stirrup. The sound waves travel into the fluid filled inner ear. The waves go through the cochlea (the organ of hearing). Microscopic hair cells in the cochlea turn the vibrations into electrical impulses. Then your brain receives and interprets this energy as a sound or speech.

Cochlear implants take advantage of the things an ear can still do after hair cells have been damaged or destroyed. It also takes advantage of how smart and flexible the human brain can be. The cochlear implant creates a new way of hearing. A cochlear implant consists of five basic parts; these are a microphone, a speech processor, a transmitter, a receiver/stimulator, and an electrode array.

Here’s how the basic parts of a cochlear implant work:

⁽¹⁾ Sound is captured by the microphone on the processor
⁽²⁾ The sound processor converts sound into detailed digital information
⁽³⁾ The magnetic headpiece sends the digital signals to the cochlear implant
⁽⁴⁾ The cochlear implant sends electrical signals to the hearing nerve
⁽⁵⁾ The hearing nerve sends impulses to the brain, where they are interpreted as sound

How do I know if I am a candidate or if my child is a candidate?

To determine if a person is a candidate for a cochlear implant, a comprehensive evaluation will be conducted by a team of experts at centres of excellence that offer the Advanced Bionics Cochlear Implant system.

The first step is to contact the Ear Institute in Pretoria at (012) 333-3130, to locate your nearest centre that provides a specialist evaluation for this procedure. Cochlear implantation is a licensed procedure needing a team of experts. There aren't many centres that do it, and you may need to travel some distance to your nearest centre. You will be booked for a comprehensive assessment.

The evaluation assesses the type and level of hearing impairment, as well as how well you or your child performs with hearing aids.

In addition to the hearing evaluation, the assessment will include medical tests such as an MRI. During these tests, the radiologist takes special images of the inner ear, to check that it is possible to implant an electrode array. You may also be asked to undergo other medical tests to ensure that you are able to undergo surgery without risks to your general health.

Candidacy for a cochlear implant is evaluated by a multidisciplinary team of professionals: audiologist(s), rehabilitation specialist(s), surgeon(s) and sometimes other team members, like psychologist(s).

A typical assessment will involve an audiological and hearing aid evaluation to determine the degree of loss and to assess the benefit derived from amplification. Sometimes recommendations are made for a trial period with more powerful hearing aids. In addition, the audiologist performs a battery of speech perception tests to assess an individual's current ability to understand speech using audition alone.

With young children, an auditory brainstem evaluation is done while the child is sedated or sleeping naturally.

An adult candidate for a cochlear implant is typically someone who has:

A moderate/severe to profound hearing loss in both ears
Very little/no benefit from hearing aids
Spoken language

A baby/child who is a candidate for a cochlear implant is typically someone who has:

A moderate/severe to profound hearing loss in both ears
Very little/no benefit from hearing aids
Has a speech and language delay

Remember other factors not mentioned here are also used to determine whether a person is a candidate for an implant. The Cochlear Implant Team will discuss these unique factors with you.

Why do people get a cochlear implant?

People get a cochlear implant because they want to hear better or they want their child to hear better. Adults want to be independent and to feel included instead of isolated: to take part in conversation, to hear their children or grandchildren talk, to listen to music or simply to listen to the sounds of nature. They want to be confident that they can hear in all listening situations even in background noise.

Parents want their child to hear the sounds of life. They want to provide their child with the opportunity to learn to listen, talk and communicate freely and independently. They want their child to participate fully in the world of sounds that surrounds them.

Ear Institute Cochlear Implant Team

From left: Dr Jannet Izeboud (ENT Surgeon), Jayne Barnard (Audiologist and Rehabilitation Co-ordinator), Dr Gerrie Moolman (ENT Surgeon), Prof Louis Hofmeyr (ENT Surgeon) and Dr Catherine van Dijk (Audiologist/Team Manager).