Springdale : Implant surgery bypasses damage to restore hearing
Posted on Monday, July 9, 2007
URL: http://www.nwanews.com/adg/News/195215/
A surgeon at Northwest Medical Center-Springdale recently began offering cochlear implants to adults seeking to restore their hearing.
Northwest Health System officials say Dr. Michael Gluth on May 29 became the first to offer the surgery in Northwest Arkansas.
According to the world’s three major cochlear device manufacturers, a handful of doctors in Little Rock and Fort Smith offer the surgery.
“This is not for people who have never been able to hear,” said Gluth, an otolaryngologist — or ear, nose and throat surgeon.
“If someone has not ever been able to hear well enough to process speech, then some of those pathways have never developed,” he said. “You have to retrain your brain how to interpret the electrical impulses.”
And this takes dedication, practice and time — anywhere from a few weeks to a few months.
Patients cannot begin trying to use the new implant until healed from surgery, usually three to four weeks. Then, the patient might work with a team of audiologists, speech pathologists, doctors, psychologists and others to activate, program and fine-tune the implant.
The federal Food and Drug Administration first approved cochlear implants for adults in 1985 and for children in 1990, according to the American Speech-Language-Hearing Association.
As of 2005, about 22, 000 adults and nearly 15, 000 children in the United States had received the implants, according to FDA data. Worldwide, about 100, 000 people have them.
Implant patients typically have profound or severe hearing loss caused by injury, infection, disease, aging or noise exposure.
Various manufacturers’ cochlear implant systems differ in appearance but operate on the same principle. They include an external sound processor that is worn much like a hearing aid.
But while a hearing aid amplifies sound so a damaged ear can detect it, a cochlear implant bypasses damaged portions of the ear, directly stimulating the auditory nerve.
The system replaces natural hearing beginning with the processor’s microphone, which picks up sound.
The processor converts the sound into digital signals, or code, which are transmitted via radiofrequency waves to the internal implant just below the skin and behind the ear. The implant interprets the code and sends electrical pulses that bypass damaged inner-ear structures and make contact with electrodes threaded into the cochlea.
“The cochlea is about the size of a baby-aspirin tablet,” said Darla Franz, director of education and corporate communications for device manufacturer MED-EL Corp. of Durham, N. C. “And it’s coiled, like a snail shell.”
This wave of electrical impulses stimulates the auditory nerve, which transmits the signals to the brain, allowing the patient to hear sounds once again.
“Within the cochlea, there are 50, 000 hair cells,” said Franz, who also is a certified audiologist. “They sense the entire range of human hearing, from the lowestpitched sound you can hear to the highest-pitched sound.”
With most people who lose hearing, the cause is hair cells that have been damaged or become dysfunctional, Gluth said. Even more of these sound sensors will be damaged during the surgery to replace the body’s hearing system with an electronic one.
“It’s understood that when you place an implant in the ear, you’re going to lose whatever natural hearing is there, so there is some risk involved,” he said. “Those residual hair cells become damaged as the implant is placed.”
About 10 percent of patients experience complications related to either the surgery or the device, such as infection or implant malfunction.
It’s more difficult to peg the device’s effectiveness, Gluth said, because of variables such as why hearing was damaged to begin with and patient motivation. Some people can recognize 100 percent of the words they were tested on before surgery; others show no improvement.
“But most people do well,” said Gluth.
Up to 96 percent of patients can have a better quality of life after surgery, he said. “Roughly 60 percent of adult patients will gain the ability to communicate on the telephone.”
A Speech-Language-Hearing Association spokesman, Doug Plesh, said his group doesn’t break down statistics on implant patients by state. But a MED-EL spokesman, Rebecca Novak Tibbitt, said her company knows of five Arkansans who have received their devices.
“The FDA has only approved three companies,” Gluth said.
Besides MED-EL, they are Cochlear Americas of Englewood, Colo., and Advanced Bionics Corp. of Sylmar, Calif., which calls its device the Bionic Ear.
Like Gluth, most of the Arkansas clinics use devices from more than one manufacturer.
An implant’s average cost is $ 40, 000, according to the Speech-Language-Hearing Association. Gluth said the implants typically are covered by Medicare, often by Medicaid and usually by private insurers. According to the association, health insurance coverage for the implants has improved substantially in recent years. All federal health plans, including the Veterans Administration, provide benefits for cochlear implants. The group credits this to increased awareness and to federal and state laws, such as the Americans With Disabilities Act, that prohibit “exclusionary insurance policies that deprive cochlear implant candidates from the only opportunity to alleviate their hearing loss,” according to its Web site, www. asha. org.
Before coming to Northwest Arkansas, Gluth completed his internship in general surgery and residency in otolaryngology at the Mayo Clinic in Rochester, Minn., where he was chief resident and an instructor in its College of Medicine. He has published several journal articles and book chapters on cochlear implants.
Gluth anticipates he eventually will extend cochlear implant procedures to children, but for now is referring children to Arkansas Children’s Hospital in Little Rock or the Mayo Clinic.
Doctors hope cochlear implants someday can be used to correct more kinds of hearing loss, according to the National Institute on Deafness and Other Communication Disorders.
For example, studies include correcting hearing loss that is limited to the higher sound frequencies. Researchers also are exploring whether cochlear implants in both ears, or pairing a cochlear implant in one ear with a hearing aid in the other, could improve hearing.
MED-EL’s Franz said that, so far, the implants have done a “pretty good job” at transmitting speech information.
Her company is exploring ways in which the implants can better transmit the fine structure of sound.
“Fine structure is the cue that the normal ear uses to perceive music, and to understand speech and noise, and also to determine directionality of sound,” she said. “So we’re looking at ways to create different stimulation sequences that might transmit these cues to the ear.
“ Patients who get cochlear implants do well in quiet environments, and many of them can even talk on the phone,” she said. “But we want them to have a richer and fuller hearing experience.”