When Hearing Aids fail, Cochlear Implants Used

Q: My grandson was born with a severe hearing impairment, and he will likely receive a cochlear implant. How does a cochlear implant work? Could I get an implant to help with my age-related hearing loss?

A: While a cochlear implant may make sense for your grandson, it's not an alternative to a hearing aid for people with mild to moderate hearing loss due to aging or other common causes. Cochlear implants are used for adults and children with hearing loss in both ears that's so extreme that even the best hearing aid has little effect. Tens of thousands of people who once had no hope of improving their hearing have been helped with cochlear implants. Thanks to universal newborn-hearing screening, more children receive them.

A cochlear implant differs from a hearing aid. A hearing aid amplifies the normal transmission of sound through the ear to the hair cells in the cochlea and then to the auditory nerve. An implant sends an electrical signal from an external antenna to the implanted receiver and then to electrodes in the inner ear that stimulate the auditory nerve.

To find out whether a cochlear implant is right for you, talk with an otolaryngologist or otologist who performs this surgery. The doctor will require you to have a hearing test and medical exam to determine the cause and severity of your hearing loss.

Even though people who have cochlear implants are deaf in both ears, the operation is usually done on just one ear. Early research showed that people who had two cochlear implants didn't end up hearing better than those with just one, but this practice may soon change. Research suggests that there is an advantage to having cochlear implants in both ears or, at least, to having a cochlear implant in one ear and wearing a hearing aid in the other.

To perform a cochlear implant, the surgeon makes an incision behind the ear and into the mastoid bone. Some of the bone is removed to make room for electrode wires to be inserted through the middle ear and into the cochlea in the inner ear.

The term cochlear implant is somewhat misleading because not all of the components are implanted. You will be fitted for the external components that operate the implant a month or two after the surgery. (This allows the soft tissue around the implant time to heal properly.) You will wear a small microphone behind your ear to pick up sounds. You'll also wear a speech processor. Older models hang on a belt or go in a pocket. Newer models fit behind the ear.

The speech processor converts sound waves from the microphone into electrical signals, which are sent through a wire to a transmitting coil attached behind the ear. This coil converts the signals into radio waves and sends them through the skull to a receiver, which is connected by wires to the electrodes in the inner ear. The electrodes stimulate the auditory nerve, allowing the signal to be sent to the brain.

Once all the components have been attached, you must work with an audiologist to learn how to listen to and interpret sounds. Speech may sound mechanical, and other sounds may be unrecognizable at first. Some people can understand words and carry on a conversation following a cochlear implant. Others have to learn how to interpret speech by using visual cues, like lip reading. During rehabilitation, you'll learn to associate the way different sounds are heard with your surroundings -- the doorbell, the telephone, a car starting and so on.

Learning to use a cochlear implant is hard work. Rehabilitation can take six months to a year for an adult and many years for a child. In the end, however, most people can understand some speech and hold conversations that were impossible before.

Cochlear implants cost about $25,000 to $30,000. That includes the preoperative testing, the surgery, and the implant itself, as well as the training sessions. Most insurance plans cover the cost for people with severe hearing loss.

One note of caution: People with cochlear implants are at increased risk of bacterial meningitis, the inflammation of the tissue surrounding the brain. That's why the Centers for Disease Control recommends that people with implants receive the pneumococcal polysaccharide vaccine. People age 5 and older should get one dose. Children between ages 2 and 5 should get the pneumococcal conjugate vaccine series and one dose of the pneumococcal polysaccharide vaccine. You can find more information about vaccines online at www.cdc.gov.

Cochlear implants are a great advance for people with severe hearing loss like your grandson. You should be glad for him -- and glad for yourself if you can get by with a conventional hearing aid.

Copyright 2007 the President and Fellows of Harvard College . Developed by Harvard Health Publications (www.health.harvard.edu). Distributed by UFS. Submit questions to harvard_adviser@hms.harvard.edu.