A number of recent studies suggest that children with dual or bilateral cochlear implants (CIs) have advantages over children with a single implant, particularly the ability to distinguish where sound is coming from and speech in noisy surroundings.
These positive issues as well as some negative ones were discussed and debated in April at the 11th International Conference on Cochlear Implants in Children (CI 2007) hosted by the University of North Carolina. While there continues to be concern, we are seeing increasing evidence that bilateral implants have a clear benefit for some children.
Research presented by Ruth Litovsky, M.D., University of Wisconsin-Madison, Waismon Center, suggests that deaf children with a CI in each ear can more accurately locate sounds when they use both implants instead of one. Litovsky’s team studied 55 children ages five- to 14-years old who received a second implant one to seven years after being fitted with the first. At the outset of the research, it appeared the children couldn’t localize sounds. By the end of the study, most of the children developed the ability to locate speech and other sounds more accurately when using two CIs versus just one.
The team worked with children who received their implants sequentially – during two separate surgeries rather than in a single surgery. The research indicated that it took longer for the brain to combine the input from the two ears following sequential surgeries.
We also learned there is evidence suggesting that the younger a child is when receiving bilateral implants, the more benefit there is to the child. Research from the University of Oslo presented at the conference by researcher Ona Boe Wie, M.D., shows that bilateral implants in children ages 18 months to five years can improve spoken language skills more than dual implants placed in older children.
There is exciting research demonstrating the benefits of bilateral implants in children but many unanswered questions remain, including whether there really is a developmental advantage to having two implants over one. In the case of a child with significant residual hearing in one ear, a single implant combined with a hearing aid may be the best option.
Cochlear implants convert sound waves into coded electrical impulses that stimulate the hearing nerve.
The brain then interprets the impulses as sound. However, implants can’t reproduce the natural sound perceptions of acoustic hearing. If a child has significant residual hearing, a single CI and a hearing aid might produce higher quality sound than dual implants.
Another major consideration is whether the child will be able to take advantage of future technological advances that may not be compatible with the existing implants. There is no guarantee that the original implant can be removed and replaced by one that would improve the overall quality of a child’s ability to hear. For example, there is ongoing research on medical devices that combine a CI system with hearing-aid technology. However, as it is common for a child to lose residual hearing in the implanted ear, a child with dual implants might not be able to make use of a new, more technologically-advanced device that requires some residual hearing.
Also, the increased costs of a bilateral implant may be too high for some families because insurance companies typically balk at paying for a second implant. The surgery alone could cost between $70,000 and $80,000, compared with $40,000 for a single implant. If the implants are placed in separate surgeries, costs increase even more.
Moreover, costs of the additional implant device and maintenance of the hardware – such as cords, cables, batteries and speech processors – must be factored in. Implants also need to be replaced about every 10 years.
There are also higher costs for clinical services. Dual implants require programming and processing that can take five or six visits over a period of weeks following surgery. During those visits, the devices are gradually adjusted to a level of sound that the child can tolerate. And as with single implants, children must undergo years of speech and language therapy.
Until there is more research addressing these issues, parents need to have heart-to-heart discussions with their healthcare professionals before deciding whether a bilateral implant is right for their child. None of us can foresee the future, so as parents and clinicians, we must base decisions on the information we have available, our best judgment as to what the future will bring, and most importantly, the child who we wish to benefit.
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