Usually the device consists of a small body-worn sound processor, a transmitter located behind the ear, and implanted electrodes. In some of the newest implant systems, the sound processor has been greatly reduced in size and can be worn behind the ear like a hearing aid.
What are the benefits of an implant
An implant cannot restore hearing to normal but it does give the sensation of sounds. Although at first the sounds are not as the person remembers them, with training they become more natural and meaningful. Implants work particularly well for adults and children who have lost their hearing after acquiring spoken language and for young children who were born deaf.
Environmental sounds are easily heard and soon become distinguishable. However, most people find that the greatest gain is hearing the human voice. The sound that is heard complements lipreading to give greater and easier understanding. More than half of those who receive an implant find they can also understand speech without lipreading to a useful extent.
After receiving an implant people are better able to regulate the volume and pitch of their own voice. Conversation is easier as it becomes possible to hear when others are speaking and understand better what is said. Most users of implants find their confidence is boosted.
Who can be considered for an implant?
Cochlear implants are suitable for those who cannot gain any useful benefit from hearing aids and who rely instead on lipreading to understand speech. Implants are of great benefit to those who have had hearing and so remember sound. However in recent years many young children who have been born deaf have received implants and benefited to a sufficient degree to have integrated into mainstream education. As the technology develops, the criteria for deciding whether somebody might be a suitable candidate for a cochlear implant also change.
There are 20 cochlear implant centres in the UK, but if you would like to find out whether you (or your child) might be a suitable candidate for a cochlear implant, you should talk to your family doctor first. If you are an adult and are referred to a cochlear implant centre, you can expect to take part in a thorough assessment, which will look at many factors including your hearing, speech and lipreading skills, your expectations, lifestyle and general health, and may involve questionnaires, tests and medical examinations. Children who are potential candidates for cochlear implants also go through a full assessment process.
How does an implant work
In a healthy ear sound waves are transmitted across the eardrum and through the middle ear to the cochlear (inner ear). Highly specialised cells within the cochlear convert these mechanical vibrations into electrical signals which travel along the auditory nerve to the brain.
Most people with sensorineural deafness, the most common form of deafness in the UK, have a functioning auditory nerve but damaged cochlear cells. Implants work by bypassing the damaged cochlear hair cells and stimulating the auditory nerve directly.
A tiny microphone worn on the outer ear picks up sound and sends electrical impulses along a cord to a sophisticated sound processor. This modifies the signal according to the individual's needs before returning it along the cord to a transmitter. The transmitter's signal is picked up by a receiver inside the skull and converted to electrical signals which are sent to electrodes to stimulate the auditory nerve.