A cochlear implant (CI) is an electronic device that was designed to provide sound to deaf or severely hard of hearing patients. One component is surgically implanted under the skin and directly into the cochlea. It is at this level where the CI works by stimulating the auditory nerve.
The cochlear implant also consists of an external component that is worn behind the ear. The external component has a microphone that picks up sound and a speech processor that processes the sound. The signals are then transmitted through the skin to the implanted receiver-stimulator that converts the sound signals into electric impulses. From here the electric impulses travel in a specific way along the electrode, into the cochlea where it stimulates the cochlea at different points.
It is indicated for those patients who do not benefit with conventional hearing aids. It is used for severe to profound hearing loss and deafness. It is nowadays also used in single sided deafness. For those patients who still have some residual hearing the hearing may be preserved during surgery. Electro-acoustic stimulation refers to the situation where a hearing aid and a cochlear implant are combined.
Hearing is not restored with a cochlear implant. The sound is different from normal hearing and patients must learn how to use it. Patients do however benefit in terms of sound awareness and localization, sound interpretation and improved speech understanding. Many patients may even be able to follow telephone conversations after implantation.
Unfortunately not everyone is a candidate for a cochlear implant Some patients may have structural abnormalities of their cochlea that may make it difficult and even impossible to implant. An absent nerve is a contraindication for cochlear implantation. In some of these cases an auditory brainstem implant (ABI) may be the only option.
Children should be implanted as young as possible because a critical window period for the development of speech and language exists.
Implantation for hearing loss after meningitis is considered as a medical emergency. Ossification (new bone formation) in the cochlea may prevent implantation at a later stage.
There are three devices on the market in South Africa. Dr Hofmeyr has experience in al three. A patient should enquire about all of them before deciding on a specific product.