Panel expands use of cochlear implants.

A panel of experts convened by the National Institutes of Health recommends expanding the role of the hearing devices known as cochlear implants. Currently, implants can be used only for adults and children who hear nothing with normal hearing aids. The panel now endorses implant use by adults with severe hearing loss who receive marginal benefit from hearing aids.

While cochlear implants were designed to aid the completely deaf, several studies indicate that "ironically, some adults with profound hearing loss using implants could perceive speech and sounds better than adults with less hearing loss using standard hearing aids," says panel chairman George A. Gates of the University of Washington in Seattle.

Standard hearing aids amplify sounds that go through the normal hearing channels from the outer ear through the middle ear to the fluid-filled cochlea, which turns them into electrical impulses to the brain. However, deafness ordinarily results from tissue damage that limits the amount of sound getting through, regardless of how loud it is. Cochlear implants bypass normal hearing channels by transforming useful sounds into electrical impulses and transmitting them directly to the brain. With training, people can perceive these impulses as sound, in some cases "hearing" so well that they can use the telephone.

Not all people achieve that level of proficiency, however. The panel notes that adults who lose their hearing after learning to speak and who receive implants soon after becoming deaf attain the clearest speech perception. Children who get implants at age 2 to 3 years also tend to improve their speech and language skills. Adults who were deaf before learning to speak usually gain the least from implants, but even they "can obtain some awareness of environmental sounds and danger sounds," says Gates.