TSBVI logo | Home | Site Search | Outreach |

Winter 2004 Table of Contents
Versión Español de este artículo (Spanish Version)

Cochlear Implants

Jim Durkel, CCC SLP/A and Statewide Staff Development Coordinator
Texas School for the Blind and Visually Impaired Outreach Program

Abstract: This article describes the cochlear implant device and discusses the considerations for candidacy for an implant, benefits and limitations of an implant, controversies and problems, and specific issues when thinking about implants for people with deafblindness.

Keywords: deafblind, cochlear implant, amplification, hearing aid, hearing loss, deafness

What is an implant?

A cochlear implant is a device used to make auditory information available to people with some types of hearing losses. The degree of information an implant can offer may be better than what can be achieved using conventional hearing aids. The cochlear implant can be considered a different type of amplification. It is not some type of "corrective surgery".

If you would like to hear a simulation of what speech through an implant may sound like, go to <http://www.bsos.umd.edu/hesp/zeng/simulations.html>. Remember, this is a simulation and the actual listening experience of the user may be different. But you will hear that hearing through an implant is not "restored". Instead, we are giving the implant user an opportunity to have access to information he or she did not have before.

The implant consists of internal (implanted) and external parts.

Implanted is an array of electrodes (fine wires) that are inserted into the cochlea. These electrodes deliver electrical impulses to the nerve fibers that run into the 8th cranial or auditory, nerve. Early cochlear implants (25 years or so ago) had a single electrode (or channel). Modern implants can have as many as 22 channels. Please note: the electrodes are implanted into the cochlea, not the brain. A cochlear implant does not involve brain surgery!

Also implanted is a receiver/transmitter. This part of the implant is implanted just under the skin behind the ear and is used to conduct information between the electrodes and the externally worn part of the implant.

Externally, the implant has a microphone, a speech processor, and a transmitting coil. The microphone takes in sound and the speech processor converts the sound into electric energy. The transmitting coil is worn on the outside of the skin behind the ear. A magnet attaches the external transmitting coil to the internal receiver/transmitter. The transmitting coil and the receiver/transmitter serve to convey information from the outside of the ear to the electrodes inserted into the cochlea.

The speech processor may be worn on the body, similar to a body hearing aid, or behind the ear, similar to a behind the ear hearing aid.

The role of the speech processor is to take auditory information, change that information into electronic form, and then send the information to the various electrodes implanted in the cochlea.

Candidacy for an Implant

Who is a candidate for an implant? There are recommendations but not legal requirements. A general bottom line seems to be that individual physicians can use their own judgment when deciding to perform an implant. Insurance reimbursement may not occur if the physician does not follow recommended practice, however.

In general, here are some recommendations and considerations for candidacy:

Benefits and limitations of an implant

Not all implant recipients end up with the same auditory, speech, and/or language skills. Unfortunately we can't totally predict future levels of success before implantation. Some implant users are able to use the implant so well that they can carry on open-ended conversations over a telephone, a very difficult listening situation. Other implant users, however, may be limited to receiving some general environmental information through the implant.

It is important to state that an implant does not "cure" hearing loss. Successful implant users who had hearing and lost it report that listening with an implant is not the same as listening with unimpaired hearing. An implant is not restorative!

After the implant surgery, there is a need for regular and frequent follow up to ensure that the implant is working and that device has been programmed to deliver the most benefit to the implant user. There are different coding strategies the processor can be programmed to use to break apart auditory information and deliver it to the electrodes. The best coding strategy for one user (the strategy that provides the best speech discrimination) may not be the best for another user. And the best strategy for one user may change over time. Only through on-going assessment and reevaluation of the implant can this strategy be determined. At the least extreme, a processor may be providing little or no benefit because of an inappropriate coding strategy. At worse, the strategy may result in sensations of pain to the user and result in a total rejection of the implant.

In addition to follow up for adjusting and setting the device, there is a need for intense training (speech, language, and listening) for the recipient to learn to use the information provided by the implant. A speech-language pathologist, a teacher of the deaf or hard of hearing, and/or an audiologist can best provide this training.

Wearing an implant does not necessarily mean that sign language should not be used. It may be that an implant user prefers sign as an every day communication mode. Or an implant user may want sign when learning new concepts and words or when in group or lecture situations. These are all difficult listening situations and even experienced implant users may want visual or tactual communication support.

One training technique for learning to use information from an implant "sandwiches" visual (or tactual) and auditory information. So, a word might be given in sign, then repeated orally only, then again in sign. This helps the learner associate what he or she is hearing with what he or she already knows. The sandwich can work the other way, too. That is, a word is given orally only, then in sign, then orally only again. It is so important to remember that the implant is not a cure; it is a tool that can support learning but it does not replace good teaching.

There needs to be a strong commitment for the implant to be of any benefit. An implant that is broken, has dead batteries, or is not consistently worn will provide no benefit.

Controversies and Problems

There has been some controversy in the Deaf culture about the use of implants. Some Deaf feel that an implant is an intrusive medical procedure and is done to "fix" what is perceived by the Hearing to be a medical problem. These Deaf feel that deafness is not a medical problem requiring this type of solution. On the other hand, most children with hearing loss have Hearing parents who would like their children to use speech and hearing to communicate. These are very emotional issues! You can read the NAD (National Association of the Deaf) position paper on cochlear implants at <http://www.nad.org/infocenter/newsroom/positions/CochlearImplants.html>.

There is a report of increased risk for contracting meningitis following implantation. (For more information, see <http://www.tsbvi.edu/Outreach/seehear/winter03/fda.htm>).

A cochlear implant can be disrupted by exposure to static electricity.

The external components of the implant can be removed and normal bathing and swimming will not damage the internal components. Internal components may be damaged by scuba diving.

Deafblind specific issues

There are two considerations when thinking about implants for a person with deafblindness.

First, one of the main benefits for implant recipients who are sighted is better communication because of combined auditory and visual information during lipreading. Individuals with deafblindness may not receive this benefit.

Second, most implants in America are unilateral. That is, only one ear receives an implant. That means that the typical implant user cannot localize sound. This has profound implications for orientation and mobility training. It would be easy to overestimate how safe a high-level implant user really is when making street crossings while relying just on hearing.

Because the implant is unilateral, listening in noise may be quite a problem. Cochlear implants can be used with assistive listening devices to compensate for this.

Some implant centers are starting to provide implants to both ears but this is not yet a common practice in the United States.

Resources

A great resource is "Cochlear Implants: Navigating a Forest of Information…One Tree at a Time" by Debra Nussbaum from the Laurent Clerc Deaf Education Center at Gaullaudet University in Washington DC. This document can be downloaded from <http://clerccenter2.gallaudet.edu/KidsWorldDeafNet/e-docs/CI/index.html> or call (800) 526-9105. This document contains loads of information as well as additional resources. The document is in English and in Spanish.


| Winter 2004 Table of Contents | Send E-Mail to SEE/HEAR|

Please complete the Comments! form or send comments and suggestions to Webmaster

Last Revision: September 1, 2010