A chance to hear again
A chance to hear again |
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In mid-December at University of Iowa Hospitals and Clinics, an Indiana woman became the world's first individual to receive two cochlear implants during the same surgical procedure. "There are fewer than 10 people around the world who have one implant in each ear," says Mary Lowder, an audiologist at UIHC. "None of the other bilaterals have been done at the same time. All but three have two different implants-usually an archaic device from the early 1980s and a newer device implanted later in the other ear." Kim Afana, who lives in Evansville, Ind., was an ideal candidate for the surgery, according to Bruce Gantz, professor and head of otolaryngology, who performed the surgery. In patients needing cochlear implants, the microscopic hair cells that help transform sound waves into sounds recognized by the brain are damaged. During surgery a cochlear implant receiver is placed in the skull, and its electrodes take on the role of the hair cells. When the receiver is attached to a microphone and speech processor, an implanted patient can hear. According to Lowder, Afana was chosen because she had a significant difference in the history of hearing loss in the two ears: she suddenly lost hearing in her right ear at age 18, and then she developed a mild hearing loss in her left ear, which gradually deteriorated over the last 18 years. Although profoundly deaf, Afana wore a hearing aid in the left ear, had some sound awareness, but no speech understanding, Lowder says. "Kim was excited about the possibility, and she was willing to take more risks than others. She actually waited for more than a year while the FDA went through all of its channels to determine whether we could do this," Gantz says. "They were concerned about whether the patient would have balance problems, but we convinced them that it wasn't going to be an issue." "Once she was implanted (and her residual hearing was gone) and before the processor was hooked up, she realized how little the hearing aid was doing for her," Lowder says. Cost is another factor patients must consider before implantation. Each implant costs about $35,000, and most insurance companies will cover the cost of only one side. Fortunately, Gantz says, the Nucleus Corporation is providing one implant free for every implant purchased for the bilateral study. With a $6 million grant from the National Institutes of Health, Gantz and his colleagues are continuing research on making the devices more effective. Collaborators on the project hope to complete bilateral cochlear implants on 10 patients in the next 18 months. There are still important questions left to be answered, Gantz says. Research gathered from bilateral implants will help to fill in the gaps. "When we do a single cochlear implant, we are always wondering which is the better side to do," says Gantz, who heads the Iowa Cochlear Implant Research Center. "With bilateral implants, we can answer that question by implanting people who have two different physiologic patterns in each ear. Secondly, we wanted to address the question of whether binaural integration, or getting hearing from both ears, is really more effective in implant users. We know that as people lose their ability to hear, they lose the ability to tune finely and select information precisely. One of the biggest problems they have is they can't understand as well when there's a lot of noise around." A month after her surgery, Afana returned to University Hospitals and Clinics for her "hook-up," a colloquialism the team uses to describe what they do to make her hear. Within the speech processor, there are 22 active channels and two ground electrodes. Using a computer software program that can be attached to the processor, Lowder attempted to tune the processor by finding comfortable loudness levels for each of the channels. Rich Tyler, a professor of otolayngology, is working to improve the coding of the acoustic signals in the speech processor and is exploring whether placement of the electrodes affects the success of the implants. "There is a series of electrodes strung together in her cochlea, so we stimulate ones at one end of the cochlea with high frequencies-or pitches-and at the other end with low frequencies in an attempt to replicate the way the normal ear works," Lowder says. "That takes a fair amount of time. Lowder says Afana instantly did well-she could hear, recognize simple words, and answer simple questions without lipreading. "Even though she hadn't heard in a long time, she still had 'auditory memory,' " Lowder says. "When deafness causes stimulation from the ear to the brain to cease, those pathways remain 'available' for many years. We've implanted many people who have been deaf for a long time, but if they grew up with normal hearing, they generally do well with cochlear implants. Sometimes, recently deafened people are the tough ones because they've not developed coping strategies such as lipreading." Gantz says it's an exciting time in cochlear implant technology. "Cochlear implants are still new and offer a frontier to continue to explore," Gantz says. "This group of researchers is very enthusiastic and they continue to advance the technology." by Lesanne B. Fliehler see also A return from the world of silence |
