Vidyya Medical News Service
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Volume 5 Issue 215 Published - 14:00 UTC 08:00 EST 3-Aug-2003 Next Update - 14:00 UTC 08:00 EST 4-Aug-2003
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Information for patients: Cochlear implants continued...

Donna's hearing was changing . . . something was happening. When Donna was a young mother, she was a city planner who had to make a lot of speeches to groups. She needed to talk to architects and city managers and individuals on the phone most of the day. Donna had worn hearing aids since she was 17 years old, but they were no longer helping her. She started turning up the volume on the television to high, and her husband let her know it was really too loud. She couldn't hear the sounds of the voices of women or children (those are higher sounds). Her hearing became worse and worse. Donna knew her father also had lost his hearing when he was an adult. Donna was concerned about her son. She wanted to know more about her hearing loss.

Donna went to a doctor who specializes in the ear. He is called an otolaryngologist. Her otolaryngologist told her that she had inherited her hearing loss. It was the same kind of hearing loss her father had, and she was becoming deaf because of a genetic disorder. Her doctor explained that the genetic disorder was causing the tiny hair cells, those cells that transmit sounds from the ear to the brain, to die. There was no way to stop this process. He told her that, very soon, she would lose the rest of her hearing.

But there also was good news. Her doctor explained that there was a solution to her hearing loss, an amazing device called a cochlear (COKE-lee-er) implant. A cochlear implant is really a new way of hearing. The cochlear implant goes around the dead hair cells that can no longer transmit sound, and directly stimulates the hearing nerve. This is the nerve that takes sound signals to the brain. The nerve is called the auditory nerve (or the eighth nerve).

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Gathering information and making a decision.

Donna talked to experts to find out if she was a good candidate (a person who would benefit from a cochlear implant because of the kind of hearing loss she had). There are about 250,000 people who might be able to use a cochlear implant because they would be good candidates. Donna also talked to other people who had cochlear implants to find out about their experiences. Not every individual is a candidate for a cochlear implant. Each child or adult is unique. It is important to know all about each person's hearing loss or deafness before deciding how to treat or assist an individual.

For children, it is very important that a hearing loss or deafness is known as soon as possible.That should be as early as in the newborn nursery. Individuals and families with children need to make good decisions. Some of these decisions about how to work with deafness or hearing loss are language choice (English or ASL or both), desire to speak or not, programs and resources available in the child's community, and opportunities to take the best advantage of communication related to education, work, family, and community. After considering all the options, Donna decided that a cochlear implant was best for her.

Donna said, after her implant, "Just the fact that I could hear sound was amazing. It's really good sound. I can recognize individual voices again, and I can conduct business with no trouble at all. I can listen to jazz again--my favorite music. I can hear birds, and I can even identify birds from their songs."

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Understanding how we hear.

In order to understand how the cochlear implant replaces missing sound, it is important to understand how we hear. When sound waves reach your ear--for example, a doorbell or a car alarm or a crying baby--you know you've heard a soft sound or a loud sound. Your outer ear (the big flap you can see) collects sound and sends it into the middle ear. The sound waves bounce off your ear drum and are made louder by three tiny bones: the hammer, anvil, and stirrup. These are the smallest bones in your body. (Together they are smaller than an orange seed.) The sound waves travel into the inner ear. The inner ear is filled with fluid. The waves go through the cochlea (the organ of hearing), where tiny hair cells that can only be seen with a powerful electron microscope, pass on the vibration of the sound and turn it into electrical energy. Then your brain receives the energy and interprets or recognizes this energy as the "sound" of a doorbell or a car alarm or a crying baby.

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So how does a cochlear implant work?

The cochlear implant takes advantage of the things an ear can still do after hair cells have been damaged or destroyed. It also takes advantage of how smart and flexible the human brain can be. The cochlear implant creates a new way of hearing. Here's how the implant works: A tiny microphone that is easy to wear captures the sounds of the doorbell, the car alarm, or a crying baby. The microphone collects and gives the vibrations of sound to a speech processor. The speech processor is a very complex electronic instrument that makes it possible to take the vibrations of speech and provide them to the auditory nerve as electronic signals. The implant is designed so that the nerve can use these electronic signals.

The reason the cochlear implant is called an implant is that a surgeon puts it under the skin behind the ear and into the skull. During surgery, the surgeon threads the implant into the cochlea (the special organ of hearing that looks like a snail's shell), past the damaged hair cells. That allows it to directly stimulate the auditory nerve that leads to the part of your brain that interprets sounds. The cochlear implant provides information that the brain can learn to understand--like a new code.

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How many people have cochlear implants?

Lots. More than 59,000 adults and children all over the world have cochlear implants. And there are more every day. Some famous people have had this surgery, including a Miss America, a national radio talk show host, and a former professional football player. But at the beginning, twenty years ago when the earliest kinds of cochlear implants were being tested, some people did not believe they could work. Even scientists said, "That can't be done!" They did not believe that with a limited number of electrodes you could ever hope to communicate what 15,000 hair cells do for people who have good hearing.

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Are cochlear implants just for adults?

No. Some children are excellent candidates for cochlear implants. We are learning that if a child has a cochlear implant early, in the first few years of life, he or she seems to benefit from them more. A boy who is not famous, Will M, was born profoundly deaf. He was not developing language skills like other 2-year-olds. His parents were concerned and they found out about cochlear implants.

Will is one of the first children his age in the Washington, DC, area to have gotten a cochlear implant. "I am as good as anyone in my class at speaking and reading...and there is nothing really that I can't do." Will plays baseball and is now in the 4th grade in a regular elementary school. His mom says about Will, "... there are absolutely no limits on what he will be able to accomplish as he grows up. That's what every parent wants for their child."

Marie J's parents chose a cochlear implant for her when she was 15 months old. Marie speaks up for herself in her school classroom of 4-year-olds. She was the first member of her family to use the device; her dad now has a cochlear implant. Marie is now singing in the choir, and her mother said, "It's something we never imagined was possible for her."

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How did cochlear implants come to be?

For centuries, scientists had studied the human body and its chemistry, the process of hearing, the way sound works, the way electricity works, the way the body reacts to materials that are used inside the body, and the way that the brain works. These scientists included physicists, chemists, materials scientists, psychologists, otolaryngologists, electrical engineers, biomedical engineers, audiologists, and speech-language pathologists. They created a great deal of information that could be applied to creating an amazing new solution to hearing loss.

The National Institutes of Health (NIH) is the nation's place to support research or learning about the processes of the human body. NIH-supported scientists study diseases and disorders that affect people. They also investigate how to prevent those diseases or help the people who have them. Some diseases or disorders can be cured because of what scientists have learned through research. Part of research for one of the institutes at NIH, the National Institute on Deafness and Other Communication Disorders (NIDCD), is developing devices that assist people who have communication challenges, so NIDCD is responsible for supporting cochlear implant research.

While developing the cochlear implant, NIH also made sure that new, young scientists were getting training so they could continue to improve this amazing device. All of the research on cochlear implants has benefited other devices to help people with different sensory or medical problems.

"The reality of this device is that it not only restores hearing to those with severe to profound hearing loss, but it serves as a model for the development of devices to restore other senses, including sight," says James F. Battey, Jr., MD, PhD, NIDCD Director.

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You should be proud...

Because the cochlear implant was developed at NIH--you helped too. NIH is funded by tax dollars. NIH funds great research on heart disease, breast cancer, stroke, arthritis, and infectious diseases--all the diseases and disorders that affect people. NIDCD is extremely grateful for the contribution that you make to the research and for the resources that are given to it. At NIH, NIDCD funds research on diseases and disorders of hearing, balance, smell, taste, voice, speech, and language. Scientists are trying to find answers to tinnitus, ringing or roaring in the ears, aphasia, and speech and language problems that children have, and they also are continuing to work on improving the cochlear implant. All of this research--on all the diseases and disorders--comes from only about 2 pennies from each tax dollar.

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Are cochlear implants expensive?

Not after you think about it. The implant, the surgery, and the necessary adjustments and training that happen after the surgery cost an estimated $60,000 for each person implanted. That may seem very expensive. However, to see if it is really expensive or not, we need to look at the one-time cost of a cochlear implant and compare it to some other costs over a lifetime.

If a little girl like Marie J or a boy like Will M, who were born deaf, or another child becomes deaf before he or she is 3 years old, the services, special education, and adaptation related to his or her deafness will cost about $1,020,000, according to people who study the costs of disease (economists). Now $60,000 does not seem as expensive. If a boy or girl becomes deaf between the ages of 3 and 17, the same economists estimate that the expense in services and education and assistive devices will be $919,000 per person.

For adults, the estimates are a little different, because they have already lived part of their lives. When deafness occurs during a person's working career, as it did in Donna's case, the estimated cost over a lifetime would be $453,000. In Donna's case, the implant has already paid for itself!

For an older person--60 or older--the cost of the hearing loss over a lifetime will be approximately $43,000 per individual.

Cochlear implants may look expensive at first, but looking at cost across a lifetime, they save billons of dollars for the nation as a whole and improve the quality of life for many individuals.

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What's next for research in cochlear implants?

Scientists are always working on the next steps. Dr. James Battey, Director of NIDCD, would like to see another kind of implant that would help deaf people who have had their auditory nerves removed during surgery to take away tumors. These implants would stimulate the cochlear nucleus, the first stop in the brain after the auditory nerve. Dr. Battey also wants to see an implant that would stimulate the nerve directly.

The cochlear implant is an example of creating something that is useful for the individual who uses it and that will be important to many other developments in biomedical science. And you helped make it happen! If you want to learn more about cochlear implants, human communication research, or biomedical research, visit www.nidcd.nih.gov or call 1(800) 241-1044 (voice) or 1(800) 241-1055 (TTY).

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