Breaking the sound barrier: new electronic devices called cochlear implants are providing a sense of sound to children and adults with profound hearing loss.
After conventional hearing aids failed to address his steadily deteriorating hearing, physicians discovered that Limbaugh suffered from autoimmune inner-ear disease, which affects only about 20,000 of the estimated 30 million Americans with significant hearing loss. The radio personality had lost 100 percent hearing in his left ear and 80 percent in his right. For a radio talk-show host whose career revolves around listening and talking on the radio, the news was devastating. Several months later, with the aid of a device called a cochlear implant, Limbaugh reclaimed his airspace with renewed vigor, grateful to regain his hearing.
"For the first time in four months via a medical marvel ... I'm hearing this," Limbaugh announced to his fans.
Limbaugh is far from alone, numbering among the 60,000 individuals with profound hearing loss who have undergone the surgical implantation of the device.
Last August, former Miss America Heather Whitestone McCallum--deaf since infancy and the first disabled woman to receive the crown--decided to undergo the procedure after marrying and giving birth to two sons, John, now age two, and 13-month-old James.
"Hearing my children's voices and being able to communicate with them is the main reason I chose to get a cochlear implant," said Heather. "Last year, my son fell in the backyard and I couldn't hear him crying. Not being there for him really scared me, and it was then that I decided I wanted to improve my hearing."
Today, sophisticated electronic devices are helping children and adults like Rush Limbaugh and Heather McCallum restore a level of hearing to their once-silent world. Cochlear implants provide useful hearing and improved communication to those who receive little or no benefit from conventional hearing aids or other therapies. Unlike aids, cochlear implants do not amplify sound. The devices bypass the damaged inner ear, directly stimulating the auditory nerve to send information to the brain, providing patients with a sense of hearing.
To learn more about cochlear transplants, the Post interviewed Dr. Richard T. Miyamoto, chairman of the Department of Otolaryngology at the Indiana University School of Medicine.
Q: What is a cochlear implant?
A: A cochlear implant is an electronic device, part of which is surgically implanted into the inner ear. An external portion picks up sound, converting it into an electrical signal. The first part of the cochlear implantation process involves the surgical procedure, when surgeons implant a small electrode into the snail-shaped cochlea. About a month after the operation, an external piece of equipment is placed; it has a microphone that picks up sound and a processor that converts sound into coded electrical signals that are passed on to the implanted electrode.
Q: Do all cochlear implant patients suffer from severe hearing impairment or deafness?
A: When we started the project 20 years ago, all of our patients had very profound hearing losses. In fact, most couldn't benefit from a hearing aid at all, and we couldn't make a sound loud enough for patients to hear. But as the devices have improved and we have learned more about what is possible, many patients now do have some residual hearing.
Q: How many people have undergone the cochlear implant procedure?
A: The numbers have grown and grown. While there used to be just a few dozen cochlear implant patients in the whole world, once the process of cochlear implantation became accepted, the field grew dramatically. Over 60,000 people worldwide now have cochlear implants. We did our first implant at the Indiana University Medical Center in 1979 as part of an initial national clinical trial. The goal of that study for the FDA was to show that, first of all, the procedure was safe, which didn't take long to demonstrate because the risks associated with the procedure are not greater than those in many routine ear surgeries. Next, we also had to show that there was enough benefit to make this all worthwhile. It took a few years in the early '80s to get past some of these early hurdles. When the FDA approval was obtained for adults, cochlear implantation took off quickly.
Q: If you suspect hearing loss in your child, how soon should the device be implanted?
A: We are looking at this issue very carefully. The ability to hear sound is very important for speech and language acquisition, so there is no question that hearing earlier is better. We now have a newborn hearing-screening program throughout the United States. The day after birth, we know that many children have a profound hearing loss. In that situation, a powerful hearing aid is usually placed quickly, followed by a period where we observe the child. But we want to intervene as early as possible because it will ultimately make a difference in speech and language development.
We have had two major grants from the National Institutes of Health since 1987. Our children at Riley Hospital in Indianapolis have been very closely followed to document their speech and language development. This has been very important, because the research substantiates that the implants are making a difference.
Q: Do you apply different approaches to implanting the device in children versus adults?
A: Yes. They require different approaches, because most adults who have received implants could hear, developed their speech and language concepts, and then through illness or injury lost their hearing. In these cases, we are trying to re-establish some of the hearing that the adults lost.
Most children who are now receiving implants were born deaf and have never heard sound prior to the cochlear implant. They must use the implant to develop their speech and language skills, We are seeing some very exciting results in very young children who gain access to sound in this way.
Q: When the device is implanted at an early age, are these children able to catch up to their peers in speech and language development?
A: There is a wide range of performance across our patient populations. We have followed our implanted children over time, and many children with cochlear implants have actually caught up with their peers. They are initially behind when they receive their implant because children are acquiring listening skills almost immediately after birth. By the time they reach school age, many of the children who received implants at one year old or so have caught up. With the aid of a rehabilitation therapist and interested teachers, many of our children in typical school settings are making good progress, so it is possible to catch up.
Q: Do benefits from the device vary, depending upon the original cause of the hearing loss?
A: That is a good question. We have spent considerable time sorting out whether some types or causes of deafness would be more appropriate for cochlear implants. In all of those studies, the type of hearing loss didn't seem to make a great difference. While there is a wide range of performance, we couldn't explain exactly why. Nearly all forms of deafness could be appropriate for a cochlear implant, as long as the patient has a hearing nerve to carry signals to the brain.
Q: What are the most common types of hearing loss?
A: First, one must understand how the ear works. Outside sound vibrations are gathered by the outer or external ear, then proceed directly through the ear canal. In the depths of the ear canal resides the eardrum, which collects sound vibrations and passes them along to three little ear bones or ossicles--the malleus, incus and stapes. These bones transmit sound vibrations from the eardrum to the inner ear or cochlea. Inside the cochlea reside microscopic hair cells that bend and, due to sound vibrations or changes in resistance, create electrical signals that are passed on to the auditory nerve and then to the brain. When hair cells within the cochlea are not working, the ear is unable to convert mechanical vibration into electrical signals. The cochlear implant takes the place of that process.
Hearing loss that occurs in the outer ear or the middle ear (eardrum or ossicles) is called conductive hearing loss. This type of hearing loss has been successfully treated with conventional measures such as hearing aids or reconstructive surgery for many years. Losses that occur in the inner ear--from the cochlea on--are referred to as sensorineural losses. Prior to the cochlear implants, sensorineural loss has been largely untreatable. In some cases, you can override that loss with a hearing aid, but as far as actually treating sensorineural loss, there wasn't anything until really quite recently with the cochlear implant.
Q: Does the cochlear implant process these vibrations and other subtleties of sound?
A: Sound has three dimensions, one is timing information--just on and off--which you pick up pretty quickly. A cochlear implant will pass timing information on very accurately as it goes on and off. There are also loudness or amplitude changes. By making the signal larger or smaller, you can reproduce loudness in that way. The tricky thing--this is what cochlear implants had to deal with early on to make the signal pertinent--is to get low--and high-frequency information the way that it is coded in the inner ear. The cochlea is snail-shaped, and different places within that cochlea respond to different frequencies or pitches. In newer implants, multiple electrodes stimulate different places in the cochlea. In the first part of the cochlea, higher frequencies are coded. Around the bend, lower tones are coded. The external processor takes a sound and splits it into frequency bands, then sends it to different electrodes inside the inner ear so we can get the frequency--the high and low--information in that way.
Q: How long does the implant procedure take?
A: The first phase is to surgically implant the device. For this, the patient comes in, and the electrode is placed. During an operation that takes about two hours, we make a small incision behind the ear to approach the mastoid bone. We drill through air "cells" in the mastoid bone, allowing access to the middle ear. Through that opening, we can drill a tiny hole into the cochlea. The electrode is then threaded around inside of the cochlea. Most patients stay overnight, then go home the next morning. We allow the skin to heal for about a month. After that, an audiologist works diligently to set the device, which involves making the device loud enough so that the patient can hear but not so loud that it is unpleasant. They tune each electrode to a comfortable listening range, which does change over time as the patient gets used to the implant. Once the device is set, the process of learning to listen to it begins, particularly in children born deaf who have never heard sound before. These children first must detect the sound, then through involvement with their environments, parents, and therapists begin to attach meanings to these sounds. Hopefully, they develop the speech and language skills that they ultimately use.
Q: Are cochlear implants permanent?
A: The implants are permanent and can last a lifetime. Anything man-made, however, has the possibility of failing, and there have been some mechanical failures. We place the same implant in little children as in adults. Children are born with adult-sized cochleas; the inner ear is well formed by the end of the first trimester of pregnancy.
In children we implant the electrode, curling it around on the inside of the mastoid. As the skull grows, this electrode appears to straighten out, and we haven't had any growth-related problems.
Q: Could you address recent reports of meningitis and infection linked to cochlear implants?
A: Several recent cases of bacterial meningitis have been reported, which has been of great concern. The Clarion Cochlear Implant has been withdrawn from the market for the present. This device has a separate positioning device, in addition to the electrode, which is thought to possibly relate to infections. A recommendation to vaccinate patients against pneumococcus has been made.
Q: Could you tell us about your research using positron emission tomography (PET) scans to monitor what is going on in the brain in response to auditory stimulation after cochlear implantation?
A: Hearing isn't just an "ear" thing. What we hear is a brain process. When sound enters the brain, it activates the brain. The auditory cortex in the temporal lobes is tuned to coding or decoding sound stimuli and interpreting what comes in. To better understand these brain processes, we scanned patients with normal hearing to see what would normally light up on a PET scan. We then took adult cochlear implant patients, who were very good performers, and put signals in through the cochlear implant. We found that the very same areas in the auditory cortex light up.
In a PET scan, you introduce a radioactive isotope into the circulation. When there is increased metabolic activity in the brain, like when listening, circulation to that area of the brain increases, resulting in a concentration of this radioactive material.
The PET scanner picks up areas in the brain where heightened activity occurs. Using the scan, we were able to locate the areas of stimulation in patients who received a cochlear implant. We know that brain development is going on because many patients will evolve these skills over time. We think that they are probably rewiring the auditory pathways in their brains. When exposed to signals, they learn how to interpret them. The brain has the wonderful ability to sort out these signals. What comes through a cochlear implant isn't complete by any means, so there is some interpretation going on.
Q: Can an individual take off the external portion, for example at night or while swimming?
A: The outer piece of equipment is like a hearing aid. Signals are passed through the skin. A set of induction coils--one on the implanted device and one on the outer part--line up and pass the signals through the skin. You can simply take off the outer piece of equipment at night or if you swim.
Some patients carry identifying pieces so they can explain what the device is, because many people might not be familiar with this unusual piece of equipment.
Q: Is the technology improving?
A: It is improving dramatically because we have learned a lot more about how sound is coded by the inner ear. The engineers can do just about anything you ask them to do, but the way the device really improved over the years resulted from patients' descriptions. We would make alterations or adjustments in how sound is coded, and patients would tell us whether it is better or worse. What was better would eventually be programmed into the system, resulting in better ways of passing the signal through.
Q: Are there some patients who won't benefit from a cochlear implant?
A: There are some people who were born with congenital anomalies of the inner ear where they actually don't have a hearing nerve. That is very rare, but sometimes you can pick that up on radiographic studies. We also might see an occasional patient--extremely rare--who doesn't have a developed inner ear. In Michel's deformity, there is a congenital absence of the inner ear, so there is no place to put an electrode. But almost everyone has a hearing nerve that can be stimulated.
We are working on another project with patients who have a disease called neurofibromatosis where a tumor develops on both hearing nerves, so individuals go deaf. For these patients, another type of implant, called a brain stem implant, is used. After the tumor is removed, a little pad is placed on the brain stem where the nerves enter the brain. With that device, you can get much of the same information that people with a cochlear implant receive, although the signal is not as differentiated because the cochlea has some important functions in terms of passing on high--and low-frequency information.
Our first patient who received a brain stem implant was a young boy whom I followed since he was about ten years old when a tumor was discovered on each hearing nerve. We removed the tumor out of one ear that he really never heard out of. On the other side, we decompressed a small tumor. He maintained hearing for several years, but gradually lost it. By college age, he was totally deaf. After his freshman year in college, we did a brain stem implant, putting an electrode pad on the cochlear nucleus on the brain stem. With only that hearing, he graduated magna cum laude, then entered law school, received a law degree, and passed his bar exam.
Q: Are cochlear implants covered by insurance?
A: Once the device achieved FDA approval, it became an accepted procedure, and little by little almost all insurance companies have lined up behind that and now cover the device.
Q: If individuals suspect that they or their children might qualify, where can they learn more about this device and the procedure?
A: Almost every major medical center in the country now has a cochlear implant team. The growth of the field has been quite exciting, In the original study, there were only seven centers, so we did about ten percent of all the implant patients in the world at Riley Hospital, at least among the children. The corporations that developed the cochlear implants host Web sites on the Internet, and that basic information is pretty accessible to all individuals.
Q: Radio and TV personality Rush Limbaugh was in the news recently about his loss of hearing and subsequent cochlear implant. Could you talk about his case as an example of the process of cochlear implantation?
A: Rush Limbaugh had an autoimmune sensorineural neural loss, an unexplained inner ear problem that resulted in his hearing going down rapidly in both ears. People who listened to Rush Limbaugh's radio program said that he seemed unable to monitor his own voice, and one of the major functions of your own ears is to monitor your voice. You can modulate your voice and adjust loudness due to a feedback mechanism, and your ears are part of that whole process. As he lost his hearing, Limbaugh was not able to modulate his voice. People who were used to listening to him picked up on that fairly quickly and knew something was going on. It became apparent that his hearing was deteriorating rapidly, until Limbaugh became profoundly deaf. After undergoing a cochlear implant, he very rapidly regained most of his skills.
Adults like Limbaugh are what we call post-lingually deafened--meaning they have all of their speech and language skills and have a good memory bank so they know how things are supposed to sound, even though they can't hear them. After much of the signal was replaced through a cochlear implant, he quickly regained that ability to listen and speak again, and the result has been quite dramatic. At least half of our adult cochlear implant users, using the current devices, gain enough listening skills that they can talk on the telephone again. We didn't think that we would ever see that take place, but it happens often enough that we kind of expect it now.
Q: Could you tell us about your ongoing research projects?
A: Our NIH-funded research is primarily with young deaf children. A huge payoff will occur if children can acquire enough speaking and listening skills by the time they reach school age to be educated in conventional school systems, because most of the world lives in a speaking, hearing world. However, not everybody attains these skills, and many of our children use sign language in addition to what they get with their implant. Our focus in all these children is primarily the development of a functional language that works for them.
In another project, we have been following the production of speech-spoken language. I thought very early on that if this cochlear implant worked, it would be reflected in vocal productions. You speak by reproducing what comes through your ears. We took voice recordings of all our young children. Out of these voice recordings, we were able to conduct very sophisticated analyses of what was happening in their speech. One focus of our research studies is to see how intelligible the children's speech becomes. We take voice recordings of standard samples and then we have people who haven't focused on listening to deaf people listen to the recordings, then rate the intelligibility of these voice recordings so we can monitor the progress of speech skills.
Q: Do cochlear implants cure deafness?
A: The implants do not cure deafness. You can think of the device as a hearing aid. Deafness is still present. In fact, if you want to be deaf, you just turn it off, then you are totally deaf again. We haven't fixed the ear at all, but it is a way of dealing with the condition.
Videotape: To order a copy of the "Saturday Evening Post Health Show" featuring an interview with Dr. Richard T. Miyamoto on cochlear implants, send $24.95 (includes s&h) to: The Saturday Evening Post Video Library, P.O. Box 1144, Dept. 1102. Indianapolis, IN 46206-1144, or call 1-800-558-2376.
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|Publication:||Saturday Evening Post|
|Date:||Nov 1, 2002|
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