Daphne Peacock was born deaf, but it was not discovered until she was 2. Her parents enrolled her in a program for hearing-impaired toddlers at Northwestern University in Evanston, IL, but despite that excellent program, her parents' tireless efforts on language development at home, and speech therapy, Ms.Peacock, now 40, said her speech skills just “are not great.”
When her son, Joash, now 5, failed his second hearing screening as an infant, Ms. Peacock found herself considering cochlear implantation for him. An American Sign Language (ASL) speaker, she was wary of cochlear implants (CIs) until she saw an online posting by the deaf mother of two children with implants who are bilingual in ASL and spoken English. “At the time, my son was wearing hearing aids in both ears,” Ms. Peacock recalled. “He also started auditory verbal therapy and was beginning to pick up a little spoken English, which showed me that he was capable of learning to listen and speak. He was limited by his hearing aids, however, which were not strong enough for him. I began to think it would be helpful if he was bilingual in ASL and spoken English so he could communicate easily with hearing and deaf people.”
Joash was 23 months old when he received his first implant in March 2009. Ms. Peacock wanted both implants done simultaneously, but Joash surgeon preferred not to do bilateral surgeries at that time. Joash was given a second implant in November 2010 when he was 3.
Ms. Peacock noticed the difference immediately. “After the second implantation, my son's spoken language skills increased,” she said. He is hearing more with both CIs. I believe that bilateral CIs are much better than one for sound localization in noisy environments. It is interesting that there are a lot of articles and data on one-sided deafness and its effect on education and language development, but at the same time some still resist bilateral implantations.”
USE OF BILATERAL IMPLANTS MAY RISE
The first CIs were approved by the U.S. Food and Drug Administration in 1985 for adults and in 1990 for children. More than 40,000 adults and nearly 26,000 children in the United States have received them, according to December 2010 statistics from the National Institute on Deafness and Other Communication Disorders. (See FastLinks.)
Bilateral implants like Joash Peacock's remain less common. NIDCD did not report on bilateral implants with its December 2010 statistics, but between 6,000 and 7,000 individuals had bilateral implants as of fall 2007, according to figures from implant manufacturers compiled by the ASL-Cochlear Implant Community. (See FastLinks.)
That figure may start to go up dramatically. A growing body of data indicates that — as Ms. Peacock noted — bilateral implantation provides significant advantages, particularly for children and for those who receive both implants as young as possible, ideally in their prelingual years.
EFFECTS ON LANGUAGE AND SPATIAL HEARING
A recent prospective cohort control study found a significant gain in disease-specific quality of life (P=<.05) as measured by the Glasgow Children's Benefit Inventory; the Speech, Spatial, and Qualities of Hearing Scale; and the Nijmegen Cochlear Implant Questionnaire. (Arch Otolaryngol Head Neck Surg 2012;138:134.) The study included 30 bilaterally implanted children and a control group of nine with unilateral implants; those with bilateral implants had a mean age of 5.3 years at the time of their second implantation.
It is more difficult to quantify the speech and language benefits of a second CI compared with the dramatic changes after a first implant, said lead investigator Marloes Sparreboom, PhD, from Radboud University Nijmegen in the Netherlands. “For most children in our study group, the benefits for speech and language development were already obtained by the implantation of the first CI,” Dr. Sparreboom said. “There might be a benefit, but I think it is difficult to verify this in the whole group because all the children were implanted at different ages with the second CI.
“I think that bilaterally implanted children, because of their benefits for hearing in noise and spatial hearing, are better able to learn language more incidentally than children with a unilateral implant. In the long term, this will lead to better performance in school.”
She said her team is currently studying children implanted simultaneously with bilateral CIs to evaluate the effects of bilateral cochlear implantation on cognition, language, and school performance.
Ruth Litovsky, PhD, the director of the Binaural Hearing & Speech Lab at the Waisman Center at the University of Wisconsin in Madison, has spent years studying outcomes in patients with bilateral cochlear implantation. She and her colleagues found that bilateral CIs improved children's spatial hearing skills even if the children received their second implant several years after the first. (Otol Neurotol 2010;31:1287.) “This finding supports the notion that the auditory system of children who are born deaf and do not receive bilateral hearing for a number of years is highly capable of processing spatial cues relevant for sound location discrimination,” she wrote, adding that this “lends support to the notion that bilateral implantation may have a protracted window of opportunity for emergence of spatial hearing benefits.”
Dr. Litovsky added that earlier bilateral implantation has been shown to offer advantages. “[C]hildren who receive a second CI by ages three to five years are more likely to have speech scores in the second implanted ear that catch up to speech scores in the first implanted ear than children whose second CI is activated at ages five to eight years and more so compared with activation at ages eight to 13 years,” she noted.
Dr. Litovsky compared the performance of 45 bilaterally implanted children on numerous standardized measures with the average population of age-matched peers. “When the children with CIs have had minimal experience with their implant, their scores on expressive and receptive language skills are about one standard deviation below the mean, normed by age. As they gain more experience, they have, on average, a score that is actually one standard deviation above the mean.”
Dr. Litovsky also found that children with bilateral implants can use information about sound location to separate speech from noise better with two implants than with one, which is useful in a noisy classroom.
THE EARLIER, THE BETTER
Susan Myers (not her real name), a mother from Fort Wayne, IN, has normal hearing, but her two sons, James and Phillip (not their real names), are deaf. James, now 11, received his first implant when he was 9 months old, and was the youngest infant in Indiana to receive one. His parents wanted him to receive a second implant when he was 3, but overturning insurance denials delayed the process for two years. Bilateral implantation had become more accepted by the time Phillip, now nearly 6, was born, and he received his first implant at 6 months and the second at 9 months.
“I think the bilateral makes a big difference in the school setting. They do not seem to struggle much in noisy settings,” Mrs. Myers said. “Although James hears really well on both sides, I can tell a lot more quickly if the batteries go dead in his first implant because he doesn't hear quite as well with the other side as he does with the earlier implanted side.”
Even now James prefers the hearing in the first implanted side. “He claims that the old side is ‘more colorful,’ which I think says a lot about neural development,” Mrs. Myers said. “There is a certain amount of what happens in the brain when you're implanted young, and can use the regular pathways for hearing that we can't really quantify. Phillip, on the other hand, does not really distinguish between his left side and his right side.”
Some parents choose to wait to get a second implant for their child, hoping that future technology will improve the implants, but Dr. Sparreboom advised against this. Like James, most of the children in her study performed better with the first CI than the second one as long as 24 months after implantation. “Children with larger differences in performance had more difficulties wearing the second implant,” she said. “Because there is only a limited sensitive period for the auditory system to mature, I would recommend bilateral cochlear implantation simultaneously in congenitally deafened children before the age of 2 years.”
Dr. Sparreboom added that sequential bilateral cochlear implantation might be an option to decide whether a contralateral conventional hearing aid would be beneficial for a child with residual hearing. “Every month, every week in a baby or toddler's life that they do not hear can make it that much harder,” said Mrs. Myers, who is a strong advocate for early and bilateral implantation.
The importance of this decision was brought home to her when she learned that her sons have Usher syndrome type II. Approximately 10 percent of the deaf population has Usher syndrome, which ultimately leads to severe retinitis pigmentosa, making them legally blind in adulthood. “They already have night blindness now,” she said. “If gene therapy trials for this disorder do not go well, they will be totally reliant on hearing through CIs.”
* View NIDCD's 2010 hearing loss statistics at http://1.usa.gov/NIDCD2010.
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