What Is a Cochlear Implant?
A cochlear implant IS A life-altering event in for many patients that restores or improves hearing for those with losses beyond that which can be helped with hearing aids. Specifically, it is an electronic device that is implanted in the inner ear and activated by a device worn outside the ear. Unlike a hearing aid, it does not make sound louder or clearer. Instead, the device bypasses damaged parts of the auditory system and directly stimulates the hearing nerve.
What is normal hearing?
Your ear consists of three parts that play a vital role in hearing-the external ear, middle ear, and inner ear.
Sound travels along the ear canal of the external ear causing the ear drum to vibrate. Three small bones of the middle ear conduct this vibration from the ear drum to the cochlea (auditory chamber) of the inner ear.
When the three small bones move, they start waves of fluid in the cochlea, and these waves stimulate more than 16,000 delicate hearing cells (hair cells). As these hair cells move, they generate an electrical current in the auditory nerve. This current then travels to the hearing portion of the brain which recognizes it as sound.
How is hearing impaired?
If you have a disease or obstruction in your external or middle ear, your conductive hearing may be impaired. Medical or surgical treatment can probably correct this.
An inner ear problem, however, can result in a sensorineural impairment or nerve deafness. In most cases, the hair cells are damaged and do not function. As a result, they cannot stimulate the auditory nerve fibers that are usually intact.
How do cochlear implants work?
Cochlear implants bypass damaged hair cells and convert speech and environmental sounds into electrical signals and send these signals to the hearing nerve.
The implant consists of a small electronic device, which is surgically implanted under the skin behind the ear and an external speech processor, which is usually worn on a belt or in a pocket. A microphone is also worn outside the body as a headpiece behind the ear to capture incoming sound. The speech processor translates the sound into distinctive electrical signals. These 'codes' travel up a thin cable to the headpiece and are transmitted across the skin via radio waves to the implanted electrodes in the cochlea. The electrodes signals stimulate the auditory nerve fibers to send information to the brain where it is interpreted as meaningful sound.
Specific information on brand-names of cochlear implants (e.g. Cochlear Americas, Advanced Bionics, Med-el) can be found on their respective web sites or printed literature.
Who can benefit from an implant?
Implants are designed only for individuals who attain almost no benefit from a hearing aid. They must be at least twelve months old (unless childhood meningitis is responsible for deafness). There is no upper age limit for implantation.
Ear, nose, and throat specialists (otolaryngologists) perform implant surgery, though not all of them do this procedure. The evaluation will be done by an implant team (an otolaryngologist, audiologist, and possibly others) that will give you a series of tests:
- Ear (otologic) evaluation: The otolaryngologist examines the middle and inner ear to ensure that no active infection or other abnormality precludes the implant surgery.
- Hearing (audiologic) evaluation: The audiologist performs an extensive series of hearing tests to find out how much you can hear with and without a hearing aid.
- X-ray (radiographic) evaluation: Special X-rays are taken, usually computerized tomography (CT) or magnetic resonance imaging (MRI) scans, to evaluate your inner ear bone.
- Psychological evaluation: Some patients may need a psychological evaluation to learn if they can cope with the implant.
What does the surgery involve?
Implant surgery is performed under general anesthesia and lasts from two to three hours. An incision is made behind the ear to open the mastoid bone leading to the middle ear. The procedure may be done as an outpatient procedure, or may require a stay in the hospital, overnight or for several days, depending on the device used and the anatomy of the inner ear.
When can I begin to use the implant?
Approximately one month after surgery, a patient returns to begin using the implant. The first session is referred as "activation" or "hook-up," and typically involves adjustments and programming by the audiologist, as well as instruction as to how to look after the system. This initial session takes several hours, during which the audiologist adjusts the implant to give the patient the best hearing. However, the patient returns for a series of visits over the next few months to make further adjustments to optimize the patient's hearing. During this time, the patient and his/her brain are learning how to hear through the implant. At first, sounds may be quite different than remembered prior to the hearing loss, but in time with experience and training, the patient's hearing and understanding typically improves.
Are there any alternatives to Cochlear Implantation?
A combination of lip reading, sign language, and powerful hearing aids may be utilitized to maximize communication. An audiologist can direct you to sources for counseling and assistance that emphasize these alternatives.
What can I expect from an implant?
Hearing results vary widely after cochlear implantation due to the variability of patients' hearing loss and particular situation. Nearly all patients gain sound awareness, which can provide a significant aid to lip-reading. In most cases, implantees have some additional ability to discriminate pitch and loudness, which further enhances the benefit of the device. In some patients, the implant may even provide enough hearing to understand speech without lip reading, permit use of the telephone, and enjoy music.
How does a cochlear implant differ from a hearing aid?
Cochlear implants differ from hearing aids in two important ways. First, hearing aids simply increase the volume of environmental sounds. A cochlear implant, on the other hand, transforms environmental sounds into electrical signals that stimulate auditory nerve fibers in the inner ear. Second, cochlear implants have both internal (inside the body) and external (worn outside the body) components. Surgery is needed to place the internal portion of the implant.
How are new implant devices approved?
The U.S. Food and Drug Administration (FDA) regulates cochlear implant devices for both adults and children and approves them only after thorough clinical investigation.
Be sure to ask your otolaryngologists for written information, including brochures provided by the implant manufacturers. You need to be fully informed about the benefits and risks of cochlear implants, including the device's safety, reliability, and effectiveness. Also, be sure to inquire about follow up checkups and whether your insurance company pays for the procedure.
How much does an implant cost?
More expensive than a hearing aid, the total cost of a cochlear implant including evaluation, surgery, the device, and rehabilitation is around $30,000. Most insurance companies provide benefits that cover the cost. (This is true whether or not the device has received FDA clearance or is still in trial.)
Source: The American Academy of Otolaryngology-Head and Neck Surgery