Cochlear Implants
Hope to Restore Profound Hearing Loss
This article is third in a series on Hearing and Hearing Loss. Suite101 takes no sides in the debate about hearing loss treatments. This article is only to be used for information and not intended in any way to replace counsel from a qualified physician nor personal decisions.
Cochlear Implants Compensate for Destroyed Hair Cells
When the hair cells of the cochlea are damaged and cannot convert sound vibrations into electrical impulses, then the auditory nerve has nothing to carry to the brain to interpret as sound. The resulting hearing loss can be severe or even total. A cochlear implant is a small, complex electrical device designed to compensate for the loss of the hair cell function.
Cochlear Implants (CIs) do not simply amplify sound the way a hearing aid does. CIs consist of three main parts:
- A small, directional microphone to pick up sound. This is worn above the ear.
- A “speech processor” worn either on the body or behind the ear.
- The actual implant with two smaller parts – a small device placed under the skin behind the ear and electrodes which are threaded into the cochlea.
The microphone captures the sound and sends the vibrations of that sound to the speech processor which filters and analyzes the sound and changes it into digital code. The coded signal is sent by FM radio signal through the transmitting coil to the implant inside the cochlea. The implant converts the signals to electrical impulses and uses them to stimulate the auditory nerve which carries the signal to the portion of the brain that interprets sound.
Sound from Cochlear Implants Not Same as Natural Hearing
The “sound” resulting from the cochlear implants is not the same as the sound heard by the natural ear. The National Institutes for Health states, “An implant does not restore normal hearing. Instead, it can give a deaf person a useful representation of sounds in the environment and help him or her to understand speech.” (National Institutes for Deafness and Other Communication Disorders, April 2008)
To get an idea of what sound sounds like with a CI, check out the House Ear Institute’s simulation.
The tonal range, clarity and other factors make it necessary for the recipient of the CI to have training to learn to “hear” with the implant.
Success with the cochlear implant varies from patient to patient. For some, the sound is clear enough to use the telephone. Lip reading is improved and even music can be understood. For others, the resulting “sound” is garbled and unintelligible.
Younger Patients More Successful with Cochlear Implants
The sooner the implantation is performed, the greater the chance of success. “Children born deaf who receive cochlear implants as toddlers show brain activity that's more normal than that of children getting the implants later in childhood, a new report shows. A separate study in animals reveals that the early implants foster development of the critical junction where the auditory nerve delivers messages to the brain.” (Science News, December 2005)
Damaged hair cells are as yet not replaceable. While science is researching possibilities in that area as well, there are ways around a non-functioning inner ear. The Cochlear Implant may not restore hearing, but it can give sound to those who have none.
Model of Ear
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