The natural functioning of the ear and hearing

Sound, in the form of sound waves, enters the ear through the ear canal and causes the ear drum to vibrate.

The vibrations of the ear drum propel the three tiny bones in the middle ear to move.

The movement of the middle ear system causes the fluid of the inner ear or cochlea to bring the cochlear hair cells into motion.

The motion of the cochlear hair cells produces electrical impulses which are sent through the hearing nerve to the brain.

The auditory cortex in the brain interprets the electrical impulse and attach meaning thereto.

What is a cochlear implant?

A cochlear implant is an electronic hearing device that was designed to bypass the damaged inner ear by electrically stimulating the hearing nerve. Unlike conventional hearing aids, a cochlear implant does not amplify sound, it replaces the functioning of the inner hair cells by stimulating the hearing nerve with electrical impulses.

A cochlear implant can provide useful hearing for severe to profoundly deaf children and adults. A cochlear implant offers the opportunity for a young deaf child to learn to communicate effectively through spoken language. For adults and older children with this degree of hearing loss, a cochlear implant offers improved access to speech and sound.

How does a Cochlear Implant function??

A cochlear implant consists of two parts – referred to as the internal and external parts. The internal part is positioned surgically under general anaesthesia while the external part is worn behind the ear.

The following diagram illustrates the different parts of the cochlear implant.

1. Microphones on the sound processor pick up sounds and the processor converts them into digital information.

2. This information is transferred through the coil to the implant just under the skin.
3. The implant sends electrical signals down the electrode into the cochlea.
4. The hearing nerves fibres in the cochlea pick up the signals and send them to the brain, giving the sensation of sound.

A cochlear implant can significantly improve quality of life; however the signal received through the implant is not normal hearing and consequently patients require time and training to become accustomed to it. Rehabilitation is required post-implantation to promote optimal benefit from the device, especially young children who may have had limited exposure to sound requires intensive rehabilitation.