UW News

January 14, 1997

UW Medical Center seeks patients for clinical trial of improved cochlear implant to restore hearing

People with severe hearing loss, as well as profoundly deaf persons, may be candidates for a new cochlear implant about to undergo clinical trials at University of Washington Medical Center.
Cochlear implants bypass damaged or destroyed hair cells in the ear, stimulating the auditory nerve directly and restoring useful hearing in most recipients.

The new investigational device, the CI-24, has an increased number of channels compared to earlier models, and can be more finely programmed for various hearing situations.

Whereas the cochlear implant was once considered appropriate only for people who are profoundly deaf, its expanded use was recommended by experts at a 1995 conference convened by the National Institutes of Health. The device is now considered appropriate therapy for people with severe hearing loss — from whatever cause — who receive only marginal benefit from hearing aids.

The NIH conference was chaired by Dr. George Gates, director of the University of Washington’s Virginia Merrill Bloedel Hearing Research Center. Gates, who is professor of otolarygology/head and neck surgery, is leading the clinical trial of the CI-24 at UW Medical Center.

“Many people have been reluctant to consider the implant,” said Gates. “Not all deaf and severely hard-of-hearing people are candidates for implants, but for those who are, it is a safe and effective therapy.”

Candidates for the implant are people who, in their best hearing-aided condition, can hear no more than 30 percent of key words in normal conversation. Studies show that the average comprehension after six months with the cochlear implant is 76 percent. About one-quarter of recipients have better than 95 percent comprehension, unaided by lip-reading. (A small number of recipients who were totally deaf do not achieve comprehension above 15 to 20 percent.)

Even for those who achieve only a small improvement, the ability to hear sounds in the environment, like the doorbell and the vacuum cleaner, is a benefit, said Gates.

“People are concerned that they will lose what little hearing they have left,” said Gates. “The good news is that no one is worse than they were pre-operatively. The cochlear implant is no longer experimental, and we’re now more confident in telling patients not to wait.”

Age is not a significant factor in the decision whether to implant. A large number of recipients are senior adults, and Gates’ oldest patient was 84. Nor is the source of deafness a factor in the decision whether to implant. However, noted Gates, in about 99 percent of cases, the hearing impairment is caused by loss of hair cells.

Children are not candidates for the clinical trial of the CI-24. However, profoundly deaf children aged two and up are candidates for another cochlear implant undergoing trials at Children’s Hospital and Medical Center in Seattle. “Some children implanted before they develop language are now progressing at norms for their age,” said Gates. “They develop normal speech.”

The CI-24 is made by the Cochlear Corporation. Like other cochlear implants, it consists of an external microphone, a signal processor and a coupler, worn outside the body. The implant itself includes a transmitter and a receiver with a number of electrodes implanted in the cochlea (24 in the case of the CI-24). The surgery is performed under general anesthesia with an incision behind the ear into the mastoid bone.

For information on the clinical trial, call Gates at (206) 685-2962.