June 29, 2006 "Bye-bye, bye-bye," said one 3 and a half-year old child, born deaf but with a cochlear implant that partially restored hearing nine months earlier. That's the most complex speech the child uttered during a testing session that involved play with a toy train set.
In contrast, a child of the same age who had a cochlear implant 31 months earlier made more sophisticated statements: "OK, now the people goes to stand there with that noise and now — Woo! Woo!" and "OK, the train's coming to get the animals and people."
The testing session was part of research that indicates the earlier a deaf infant or toddler receives a cochlear implant, the better his or her spoken language skills at age 3 and a half. The research was conducted by Johanna Grant Nicholas, Ph.D., research associate professor of otolaryngology at Washington University School of Medicine in St. Louis and colleague Ann E. Geers, Ph.D., from the Southwestern Medical School at the University of Texas at Dallas.
"Ninety percent of children born deaf are born to hearing parents, and these parents know very little about deafness," Nicholas says. "They don't know how to have a conversation in sign language or teach it to their children. Many of these parents would like their children to learn spoken language."
The researchers tested the spoken language skills of 76 children, all 3 and a half years old, who had cochlear implants and compared those results to the length of time each child had his or her implant. They found that with increased implant time, children's vocabulary was richer, their sentences longer and more complex and their use of irregular words more frequent. The researchers' work was reported in the June issue of Ear and Hearing.
Nicholas notes that many of the children who received cochlear implants at the youngest ages have nearly the same spoken language skills as children with normal hearing. The researchers' further studies — not yet published — suggest that by age 4 and a half, children who had cochlear implants very early often have normal speech and can potentially enter kindergarten with their hearing peers.
"Kids with residual hearing can get some help from hearing aids, but cochlear implants give a tremendous hearing advantage over hearing aids — the implants provide more sound information," Nicholas says. "For example, high-frequency sounds are magnified more with cochlear implants, so kids can hear 's' sounds and 'ed' endings better. So they tend to catch on to plurals and verb tenses faster."
While studies like this and others favor early implantation, the decision for or against cochlear implantation is frequently put off, Nicholas indicates. Hearing parents often find they need time to learn about deafness and potential treatments. Implantation also may be delayed to make certain an infant's deafness has not been misdiagnosed.
Even when deafness is confirmed, the idea of head surgery for their baby makes many parents hesitate. And they may be daunted by the fact that a cochlear implant is forever — the device destroys any residual hearing so that hearing aids are no longer an option.
"Studies like ours are meant to help answer parents' questions about cochlear implants," Nicholas says. "Our overall goal is to focus on the best age for implantation. If the window of time for the best outcome is small, we want parents to know that. With the results we've seen so far, we believe that it is best to implant when the child is younger than 24 months if parents want a deaf child to use spoken language at the same level as their hearing peers."
Nicholas is also on the faculty of the Program in Audiology and Communication Sciences (PACS) at Washington University School of Medicine. The PACS program is part of a consortium of programs formerly operated by Central Institute for the Deaf and now collectively known as CID at Washington University School of Medicine.
Nicholas JG, Geers AE. Effects of early auditory experience on the spoken language of deaf children at 3 years of age. Ear and Hearing 2006;27(3):286-289.
Funding from the National Institute of Deafness and Other Communication Disorders supported this research.
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