October 30, 2002
Cochlear implants conquer deafness
From: Purdue Exponent
Oct. 30, 2002
By Craig Davison
On a television screen in the corner of an empty waiting room a video is playing. A three-year-old girl plays with a Purdue graduate student, who is teaching her the names and shapes of animals. The girl responds, picking the right animals.
From the video, it is hard to tell how old the girl is. It is even harder to tell the three-year-old girl was born deaf.
Through cochlear implants, deaf and hearing-impaired individuals now have the chance to regain a greater range of hearing. The Purdue Audiology and Speech Pathology Center works daily to rehabilitate the hearing and speaking abilities of cases like the girl on the video.
"The biggest advantage of a cochlear implant is that it gives enough sensation of hearing to understand speech," said Mike Pachuilo, an audiologist at the Center whose interest in audiology stems from his two deaf brothers.
Cochlear implants are an involved process requiring surgery and years of rehabilitation. Each ear contains a cochlea, which is curled into a shape resembling a snail and consists of three channels. Sound enters the cochlea, sending a pressure wave through the channels, causing the membrane to vibrate. Cilia, tiny hairs on the membrane, bend creating sensations the brain identifies as sound.
For hearing impaired individuals, the cilia do not work properly. A cochlear implant places 22 electrodes in the cochlea, which circumvent the cilia and send an electronic current to stimulate the nerves.
But the implant itself is not enough.
"The therapy part is really critical," said Pachuilo. Many children get the implant at Riley’s Children’s Hospital in Indianapolis, and the Purdue Audiology and Speech Pathology Center provides rehabilitation.
For the first six weeks after the surgery, clients come to the clinic to get used to the methods and surroundings. The implants are not turned on yet so the body can heal. Pachuilo said that after six weeks the implants are turned on, so that "sound is the only new thing."
The focus of the audiology part of rehabilitation is sound detection, where the implant picks up a sound, but there is work to be done for the brain to identify what the sound is.
Megan Dunn, a graduate student working at the center, said the goal of rehabilitating children with cochlear implants is "bombarding them with language and new vocabulary words." Adults, Dunn said, work on intelligibility and articulation.
"The biggest misconception is that [cochlear implants] are the cure when it’s only the beginning," said Pachuilo, citing that a cochlear implant is placed in only one of the damaged ears and tries to replicate the work of thousands of cilia with 22 electrodes. "People say, ‘Oh, you get a cochlear implant and you hear normally.’ But it’s not true."
The years of work pay off in the end.
After enough rehabilitation some individuals with cochlear implants have the hearing range nearly equivalent to the hearing range of an unimpaired adult.
Dunn, who has worked in the center for a year, has three clients with cochlear implants this semester. She said, "It’s very rewarding to see what a difference you can make."
© Purdue Exponent 2002