Cochlear implants (CI) are designed for individuals with severe to profound sensorineural hearing loss. These individuals receive little or no benefit from hearing aids. CIs bypass the non-functioning part of the cochlea in order to deliver electrical signals directly to the auditory nerve. They can be used effectively by both prelingually and postlingually deafened children and adults.
A cochlear implant consists of two parts, an external and an internal component.
The implant consists of a housing, which contains the electronics, and the electrode array as well as the receiving antenna and a magnet that holds the coil in place behind the ear.
- Audio processor
The audio processor is worn behind the ear and consists of a control unit, a battery pack, and a coil that transmits information through the skin to the implant.
How do Cochlear Implants work?
Cochlear implants convert everyday sounds into coded electrical impulses. These electrical pulses stimulate the auditory (hearing) nerve so that the brain can interpret these signals as sound. As the brain receives sound information very quickly, sounds are heard as they occur.
- Sounds are picked up by the microphone of the audio processor.
- The audio processor analyses and codes sounds into a special pattern of electric pulses.
- These pulses are sent to the coil and transmitted across the skin to the implant.
- The implant sends the pulses to the electrodes in the cochlea.
- The auditory nerve picks up the signal and sends it to the auditory centre in the brain. The brain recognises these signals as sound.
Benefits of a Cochlear Implant System
Cochlear implant systems can offer a wide range of benefits including hearing speech, environmental sounds and music. Results reported with today’s cochlear implants consistently indicate speech understanding for the majority of implanted patients. Benefit from a cochlear implant is most readily measured within the scientific community by the percentage of speech a cochlear implant user can understand in a laboratory setting without lip-reading.
Although openset speech understanding is a very imporant measure of hearing ability, it is by no means the only benefit cochlear implant users report. The perception of environmental sounds, such as doorbells, alarm signals, etc. can make a substantial difference in the life of a person who is severely hard of hearing.
Who Can Benefit from a Cochlear Implant System?
The following guidelines may be helpful when deciding if a CI is right for you.
- Implantation at a young age is highly recommended because hearing is important for language development and because research has shown better outcomes for children implanted at an early age.
- Older children and adults with previous speech and language development generally perform better with a cochlear implant.
- A long period of profound hearing loss may limit the benefits of a cochlear implant.
General Candidacy Criteria
- For children, a profound sensorineural hearing loss in both ears.
- For adults, a severe to profound sensorineural hearing loss in both ears.
- Age at implantation may be as young as several months, depending on individual circumstances and local practices.
- Receive little or no benefit from hearing aids.
- No medical contraindications.
- High motivation and appropriate expectations.
- Access to education and (re)habilitation follow-up.