What is a Cochlear Implant

A cochlear implant (Bionic Ear) is an artificial hearing device, designed to produce useful hearing sensations by electrically stimulating nerves inside the inner ear.

The multi-channel cochlear implants designed by the University of Melbourne and Cochlear Limited, consist of 2 main components: 1) the cochlear implant package and electrode array (or receiver-stimulator) and 2) the speech processor and headset. The model shown in the Figures below is the Nucleus® 24 cochlear implant system.

The implant package (or receiver-stimulator) contains the electronic circuits that control the flow of electrical pulses into the ear. It also contains an antenna that receives the radio-frequency signal from the external coil and a magnet that holds the external coil in place. Attached to the package are wire leads that join to electrodes. The 22-electrode array is inserted into the shell-like structure in the inner ear known as the cochlea. The ball electrode is placed under a muscle near the ear. There is also a plate electrode on the outside of the receiver-stimulator package. All of the parts shown in Figure 1. are placed under the patient's skin behind the ear during the implant operation.

Figure 1. The internal component of the cochlear implant

The other parts of the implant system are worn externally. The coil is held in position against the skin by a magnet and the microphone is worn behind the ear. The body-worn speech processor (SPrint^TM) can be worn in a pocket, in a belt pouch or in a harness. The ear-level processor (ESPrit^TM) is worn behind the ear. These parts, which are shown in Figure 2. are normally fitted two weeks after the operation.

Figure 2a. SPrint^TM speech processor

Figure 2b. ESPrit^TM speech processor

There are currently two cochlear implant systems made by the Australian company Cochlear Limited. The Nucleus® 22 system uses the CI22M implant and the Spectra 22 speech processor. This system has been available world-wide since 1984. Early in 1997, the Nucleus® 24 was released. This system (shown above) offers the choice of a body level (the SPrint^TM) and an ear level (the ESPrit^TM) speech processor with its CI24M implant. The Nucleus 24 system utilizes up-dated technology in both the implant and the speech processors.