Two parts of a cochlear implant system
Who would benefit from a cochlear implant?
When sound passes through to the cochlea of a hearing person, the inner ear’s microscopic hairs convert the sound energy into nerve energy.
The hearing nerve fibres then carry this energy as information to the brain.
People who are profoundly or totally deaf have very few or no hair cells in the cochlea, so the sound energy is unable to travel in this way.
For these people, a conventional hearing aid is of very little or no benefit as it can amplify sound, but cannot turn it into the electrical nerve messages needed by the brain.
However, a cochlear implant can bypass the missing hair cells in the cochlea and electrically stimulate the nerve endings directly.
The cochlear implant system has two parts - the implant device and the external apparatus:
The implant device is made up of:
It cannot be seen from the outside.
The external apparatus is similar to a hearing aid. When it is worn it receives sound like a conventional hearing aid but instead of amplifying the sound it converts the messages into FM radio waves.
A small external aerial is held in position on the head, by a magnet. It transmits the radio waves to the aerial of the implant device.
Messages are decoded in the microchip and then conducted through the electrodes into the inner ear where they stimulate the nerve endings.
Like any other hearing aid the external device is left off for swimming and usually for sleeping.
A cochlear implant is not suitable for everyone. Suitability is always determined on an individual basis. Contact your doctor to discuss in the first instance.
However, as a guide:
Children (aged 0-18 years) with
Adults (aged 18 years +) with
The earliest cochlear implants had only a single electrode.
They could give an awareness of rhythm and loudness, and so help a person who had become deaf, monitor the loudness of their voice and gain extra clues to help in lip reading.
No single electrode devices were implanted in New Zealand.
The Deafness Research Foundation monitored the development of cochlear implants until clinicians and scientists felt that the implants had become so sophisticated and reliable that the time was appropriate for a New Zealand cochlear programme to begin.
New Zealand’s first cochlear implant operation was in December 1986 at Auckland’s Mercy Hospital.
The Australian designed and manufactured implant was chosen and is still the only implant being used in New Zealand.
It has 22 electrodes which extend to 22 different depths within the inner ear.
The latest models have 2 additional electrodes on the surface of the skull bone. Some are pre-curved to fit more snugly within the spiral of the inner ear.
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