WASHINGTON -- A computerized device known as a cochlear implant offers the first hope that children who are born deaf or lost their hearing soon after birth can learn to hear.
Four years after receiving their implants, 60 percent of the children involved in a small study at the University of Iowa can understand some speech without the aid of "visual cues" such as sign language, a researcher said yesterday.
The implants have not helped adults who were born deaf, possibly because they lack any memory of how words sound. But youngsters born deaf are a different story: Their formative minds appear more receptive to the stimulation of sound.
Some of the children in the test still struggle to understand spoken English, but others have learned to hear and later to talk in relatively complex phrases and sentences.
In successful cases, it usually takes two years of almost daily work with a therapist for children to develop speech that can be understood.
Dr. Bruce J. Gantz, an Iowa ear, nose and threat specialist, showed a videotape of his star pupil at a forum for science writers sponsored by the year-old Johns Hopkins Center for Hearing and Balance. Four years after his implant, the 6-year-old boy was able to tell a little story from a series of pictures.
"He got a fishing pole, and he gave it to the cashier, and he went back on the bus with the fishing pole, and he went home and wrapped it," said the boy, speaking in a monotone that was generally easy to understand.
"This is really remarkable to see this in a congenitally deaf child, but it does take time," said Dr. Gantz, one of several leading researchers who spoke at the forum.
Cochlear implants do not actually cure deafness. Rather, along with an external processor, they compensate for a defect of the inner ear by converting the spoken word into an array of electrical impulses that the brain can understand as speech.
The speech processor, worn on the belt like a doctor's beeper, receives sound through a microphone and converts it into electrical signals, which are sent by wire to a system of electrodes planted deep within the inner ear. There, the impulses stimulate the auditory nerve, which conveys signals to the brain.
Cochlear implants, which have been in use for about a decade, have been offered mainly to adults who were born with the ability to hear but lost it later in life.
Implants probably have been successful among those people because they retain some memory of sound, Dr. Gantz said.
But the implants have failed to help adults who were born deaf or who lost their hearing before acquiring language. Those people often feel the impulses as vibrations in the head and body but do not interpret them as sound.
The results have been dramatically different in some children. In the Iowa study, 32 children received the implant, 22 who were congenitally deaf and 10 who became deaf through infection or other causes before they acquired language.
The children may do better than adults because they are at a formative age when the brain ordinarily learns to process sound into language, Dr. Gantz said.
"Once they get to be an adult, they are not as receptive to new information," he said.
Children in the study range in age from 2 1/2 to 17. Younger children are not considered candidates because it is often difficult to determine the degree of their impairment.
Cochlear implants are reserved for people who are profoundly deaf.
Dr. Gantz said he is sympathetic to the hostility of some deaf people toward the implants and the doctors who offer them. Some advocates for the deaf cling to sign language and argue that cochlear implants send a message that deaf people have little value unless they can communicate in the language of the hearing world.
"We have to be extremely sensitive to this," Dr. Gantz said.
"We've never before had anything that worked" for deaf people.