In a multicenter study of 188 cochlear implant recipients from around the country, 96 children received bilateral implants, allowing for comparison of outcomes of those with bilateral implants to those with a unilateral implant (JAMA. 2010;303:1498-1506). Literature shows that children with early cochlear implantation develop language within one standard deviation of their hearing peers—good enough, typically, to allow them to sit in the same classroom.
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April 2015The study found that, after eight years, 26% of the kids are performing at or above the norm, 16% are within one standard deviation, and 18% are on a trajectory in which it appears likely that they’ll get to within one standard deviation of their hearing peers. So the bottom line, he said, is that a child who received a cochlear implant 12 years ago has a 60% chance of being in an age-appropriate mainstream classroom with his or her hearing peers, without assists. This carries a tremendously positive societal imact generally, as well as expanded life opportunities for implanted children.
But, he said, while vocabulary and semantics developed at normal rates, grammar and the pragmatics of language were attained in this study consistently only when the implant was placed at less than 18 months of age and, even more importantly, when children were immersed in a language-rich environment.
When adjustments are made for a variety of factors to give each child an equal footing, Dr. Niparko said, “we see that bilateral implantation falls away—it’s not a predictor of strong language learning—whereas maternal sensitivity, age at implantation, baseline language comprehension, and the child’s IQ, in fact, are predictive.”
Also, he said, while there might be right-versus-left differentiation with bilateral implants, true effective spatial hearing is limited. Speech and noise are improved, but not likely with the same effect that could come with continued improvements in technology.
Cost is also an important consideration. The average implant costs $50,000. In a cost-effective analysis in which the cost-utility ratio of normal hearing is 0.9 to 1.0 and severe sensorineural hearing loss drops that ratio about 0.5 on average, the first cochlear implant brings much more benefit—an increase in 0.2—than the second implant, which brings an additional increase of approximately 0.05, Dr. Niparko said. “It is substantially unimpressive compared with the first implant’s impact,” he said, “and this suggests that, in fact, we have to look for better ways to provide a binaural benefit.”