The cochlear implant is a surgically implanted device that transmits coded electrical impulses to stimulate the hearing nerve within the inner ear. It is used to provide partial hearing to children and adults who receive little or no benefit from hearing aid technology.
The cochlear implant has both internal (implanted) and external (worn outside the body) parts. An external microphone (usually mounted at ear level) picks up speech and other sounds in the environment. This sound is then converted into electrical signals by a sophisticated processing unit, called a speech processor, which is about the size of a small Walkman worn outside the body, or located on a BTE-like attachment worn on the ear. The electrical signals are transmitted through the skin to an internal receiver, which has been surgically implanted. There, the signals are sent to an array of electrodes implanted in the cochlea (inner ear) to stimulate the auditory nerve. The auditory nerve then sends these electrical signals to the brain. With extensive training, the brain learns to recognize/interpret these signals as sound. Once the implant site has healed after surgery, the speech processor requires programming or “mapping” to meet the auditory needs of the user. (Adapted from Understanding Cochlear Implants, by MED-EL Corporation.)
The cochlear implant differs from a hearing aid in that it does not
make sounds louder. Instead, it bypasses the non-functioning parts of
the inner ear and electronically stimulates the remaining hair cells
to produce a sensation of sound.
(Adapted from the article, “The Benefits and Limitations of Cochlear
Implants” prepared by the Laurent Clerc National Deaf Education
Center at Gallaudet University)
The US Food and Drug Administration (FDA) has approved several devices
for use in children ages 2-17, who meet the criteria, regardless of
the age at which they lost their hearing. Children born with congenital
deafness and who meet the criteria can receive an implant as young as
12 months of age. In order to be considered for implantation, children
must receive an extensive evaluation by a team of specialists. To be
a candidate for a cochlear implant, a child must have a profound sensorineural
hearing loss in both ears. The average hearing level in the speech frequency
range (500 to 2000 Hz.) must be 90 decibels or poorer in both ears without
hearing aids, and with hearing aids the child must not be able to clearly
recognize single words out of context without looking at the speaker’s
face. If the child has less than a severe/profound hearing loss, these
devices are generally not recommended and a properly fitted hearing
aid can be as effective.
Cochlea Illustration: Cochlear.com