What is a cochlear implant?
The cochlear implant is a prosthetic replacement for the inner ear (cochlea) and is only appropriate for people who receive minimal or no benefit from a conventional hearing aid.
The cochlear implant bypasses damaged parts of the inner ear and electronically stimulates the nerve of hearing. Part of the device is surgically implanted in the skull behind the ear and tiny wires are inserted into the cochlea. The other part of the device is external and has a microphone, a speech processor (that converts sound into electrical impulses), and connecting cables. It is battery powered, adjustable, and expensive.
Cochlear implants have been performed for over 20 years and have become the standard treatment for people with profound hearing loss, who desire to use spoken language. Today, over 12,000 adults and children worldwide have received a cochlear implant.
The American Medical Association and the American Academy of Otolaryngology - Head & Neck Surgery have approved the use of this medical procedure for adults and children over the age of two years. The most widely used device is the Nucleus 22 Channel Cochlear Implant. Another implant, the Clarion, is in review by the Food and Drug Administration for adult use, and is available, as an investigational device, for children.
The Nucleus 22 Channel Cochlear Implant System. The various components are: 1. The electrode array (which is placed in the inner ear). 2. The receiver for the electrode array. 3. The speech processor, a small electronics package that typically is placed in the wearer's pocket. 4. Tranmitting coil and 5. Microphone, both of which are worn behind the ear.
1. Sounds in the environment are picked up by the small directional microphone.
2. A thin cable (cord) sends the sound from the microphone to the Spectra 22 speech processor.
3. The speech processor amplifies,filters and digitizes sound into coded signals.
4. These coded signals are sent from the speech processor to the transmitting coil via the cables.
5. The transmitting coil sends the signals across the skin to the
implanted receiver/stimulator via an FM radio signal.
6. The receiver/stimulator delivers the correct amount of electrical stimulation to the appropriate electrodes on the array.
7. The electrodes along the array stimulate the remaining auditory nerve fibers in the cochlea.
8. The resulting electrical sound information is sent through the auditory system to the brain for interpretation .
Today, cochlear implant devices are very sophisticated. The multichannel implant stimulates the hearing nerve in a variety of places to give information about pitch, which is essential for understanding speech. The externally worn processor is designed to incorporate advances in technology, so there is no need to wait for next year's upgrade. The sooner the person receives the implant after becoming deaf the better he/she will do with the implant.
Who is a candidate for a cochlear implant?
Candidates for implants are adults or children (two years or older) with all of the following:
Profound or severe hearing loss in both ears (this includes people with so-called "nerve" deafness).
Hearing aids but receive little or no benefit from them in understanding speech by listening alone.
No medical reason to avoid surgery.
A desire to interact with the hearing world and to communicate with spoken language.
Realistic expectations about results.
Factors related to successful use:
Functioning auditory nerve
For adults: Good speech, language, and communication skills
Good motivation
Short amount of time without hearing sound
Support from family and friends
What is involved in the evaluation and surgery for a cochlear implant?
A. Evaluation: Evaluation procedures used to determine whether individual is an appropriate candidate include:
Ear examination to determine cause of hearing loss and absence of infection.
Medical examination for eligibility for surgery and anesthesia.
Hearing ability testing, with and without best-fit hearing aid.
Evaluation of communication skills.
CT scan to determine patency of the inner ear (cochlea).
In adults - balance tests to determine the risk of postoperative dizziness.
Optional tests:
Promontory stimulation test to determine if the hearing nerve can be stimulated.
In adults - psychological evaluation to assess motivation and expectations.
Testing can be discontinued at any point if the candidate and/or evaluation team feels it is not appropriate to continue.
B. Review:
Results of tests are reviewed by the cochlear implant team before a decision is made on whether to implant. Parents are considered an integral part of their child's team.
Implantation is recommended only for people we believe will benefit from an implant.
Pre-authorization for implantation from the third party payor is requested. Often several weeks are required for authorization and scheduling.
C. Surgery:
The surgical risks are the same as for any other ear surgery and are considered minimal. The surgery takes approximately 1 1/2 hours, and the hospital stay is usually 1 day for adults and 1 or 2 days for children.
D. Fitting:
In adults, the headset and speech processor are fitted 4-6 weeks after surgery. The audiologist obtains soft and comfortable listening levels for each of the electrodes and uses this information to create a MAP or program. The fitting is done over several days.
In children, the fitting procedure continues over a 3-month period. Young children are typically seen 2 to 3 times a week for the first month and 1 or 2 times a week for the next 2 months to obtain a stable MAP.
Hearing speech for the first time with the implant may sound unnatural during the fitting but over many days to weeks it begins to sound familiar. People who have never heard before require longer times to adjust to the new sounds. For adults who have heard speech before, the MAP is put onto the speech processor and is adjusted as necessary to custom fit the individual.
For children who have never had hearing, the intitial reaction to sound varies. Some children do not respond to sound at first. Other children may show surprise, fear, inquisitiveness, or happiness. Dramatic changes in auditory and speech skills are typically not observed initially. Performance usually continues to improve over time with auditory and speech training.
• Electrodes are checked and adjusted, and instructions in use and care of the implant are given.
E. Follow-up:
For adults - weekly adjustments of the MAP and communication therapy are done for the first month after fitting. The treatment focuses on auditory training, speech reading, music, telephone use, and communication strategies. A family member or friend is encouraged to attend the weekly sessions to learn how to communicate most effectively with the implant recipient.
For children - After the initial 3-month period, children are seen every 3 months for the first year and every 6 months for the second and third years. Thereafter, the child is seen annually. The child's MAP as well as his/her auditory, speech, language, and social-emotional development are closely monitored.
For children: Every effort is made to work with the school teacher and other professionals working with the child. In-service training about the implant and participation in the child's IEP meetings are available.
What can be expected after a cochlear implant?
Adults hear medium level and even soft sounds, and can differentiate among many environmental sounds.
It is important for children to receive auditory and speech training to maximally benefit from a cochlear implant. A child's performance will usually continue to improve over an extended period of time with training.
Understanding speech in combination with speechreading (lipreading) improves. Speechreading becomes less stressful and more accurate.
Speech understanding ability increases over time with continued treatment and experience.
Most people who had normal hearing at one time are able to understand some speech without speechreading. The degree to which they are able to do this depends, in part, on the success factors mentioned earlier.
Understanding speech over the telephone varies greatly. Some people are able to carry on conversations, while others may recognize only a limited number of words.
Most people experience a positive effect on their feelings of involvement in daily life, self-worth, and relationships with family, friends, and co-workers.
Most people experience an improved ability to monitor the quality and volume of their own voice
Adults who lost their hearing completely as children may not understand speech without speechreading, but experience all the other benefits and may be able to tell the difference between some speech sounds. They often feel more connected to the world around them because of the sounds they now hear.
Performance and benefits vary from individual to individual and it is not possible to predict how much benefit any one person will obtain. The impact of a cochlear implant on a young child's social-emotional development is not known at this time.
Other benefits reported by some users:
Richer relationships with family and friends
Increased confidence and ease of communication
More social opportunities
Improved job performance or opportunities
Music appreciation is noted by some users
