London Cochlear Implant Clinic

 

What is a Cochlear Implant?

A cochlear implant is an electronic device that can restore hearing by directly stimulating the nerve endings of the cochlear nerve.  People who get no benefit from the most powerful hearing aids can have their hearing “restored” with a cochlear implant (CI). 

There are two discrete parts to a CI. The internal component consists of receiver/stimulator package from which a thin wire extends. This wire has an array of up to 22 electrodes which is inserted into the cochlea surgically (see diagram).  The stimulator/receiver package (S/RP) is placed in a pocket under the skin behind the ear (see diagram).  Inside the cochlea the electrode array lies very close to the cochlear nerve endings (spiral ganglia).  These electrodes can stimulate the spiral ganglion cells electrically and this sends a nerve impulse to the brain which is perceived as sound.

The external component is made up of a speech processor that is usually worn on the ear like a conventional hearing aid (see diagram) (although can be body worn in children with very small ears – see diagram).  The speech processor has a microphone that picks up sounds.  These sounds are then processed and broken up into different pitches (frequencies) and delivered to the second part of the external component – the coil (see diagram).  The coil is simply a circular coil of wire with a central magnet.  This magnet is attracted to a second magnet within the implanted  S/RP.  The electronic impulses are then transmitted across the skin from the external coil to the S/RP and from there to the electrodes within the cochlea.