Bilateral CI research findings

I will post my findings on the issue of bilateral CI on my blog. Hopefully it helps someone else too…

I want to collect the data concerning this debate, in order to get an oversight of what the medical community discover, as well as what they are writing and thinking about this issue.

Papers found in PubMed:

Patients fitted with one (CI) versus two (CI+CI) cochlear implants, and those fitted with one implant who retain a hearing aid in the non-implanted ear (CI+HA), were compared using the speech, spatial, and qualities of hearing scale (SSQ) (Gatehouse & Noble, 2004). The CI+CI profile yielded significantly higher ability ratings than the CI profile in the spatial hearing domain, and on most aspects of other qualities of hearing (segregation, naturalness, and listening effort). A subset of patients completed the SSQ prior to implantation, and the CI+CI profile showed consistently greater improvement than the CI profile across all domains. Patients in the CI+HA group self-rated no differently from the CI group, post-implant. Measured speech perception and localization performance showed some parallels with the self-rating outcomes. Overall, a unilateral CI provided significant benefit across most hearing functions reflected in the SSQ. Bilateral implantation offered further benefit across a substantial range of those functions.
(Link to more information about this paper)

Speech perception tests were performed preoperatively before the second implantation and at 3 months postoperatively. RESULTS: Results revealed significant improvement in the second implanted ear and in the bilateral condition, despite time between implantations or length of deafness; however, age of first-side implantation was a contributing factor to second ear outcome in the pediatric population. CONCLUSION: Sequential bilateral implantation leads to significantly better speech understanding. On average, patients improved, despite length of deafness, time between implants, or age at implantation.
(Link to more information about this paper)

The average group results in this study showed significantly greater benefit on words and sentences in quiet and localization for listeners using two cochlear implants over those using only one cochlear implant. One explanation of this result might be that the same information from both sides are combined, which results in a better representation of the stimulus. A second explanation might be that CICI allow for the transfer of different neural information from two damaged peripheral auditory systems leading to different patterns of information summating centrally resulting in enhanced speech perception. A future study using similar methodology to the current one will have to be conducted to determine if listeners with two cochlear implants are able to perform better than listeners with one cochlear implant in noise.
(Link to more information about this paper)

The Let Them Hear Foundation have done their own research:

Despite many insurers’ (in the US; my comment) continued erroneous assertions to the contrary, bilateral cochlear implantation is NOT an experimental or investigational procedure, and is medically necessary.  Bilateral cochlear implantation in children has been an accepted, mainstream medical practice since 1998.  Over 3000 have been performed, including over 1600 on children.

Several studies have shown that there is a vast improvement in sound localization ability in patients with bilateral cochlear implants.  In particular, the group of subjects who received a significant amount of improvement when bilaterally implanted were those who were initially implanted at a very early age, as Andrew was.  In September 2005, an international consortium of cochlear implant specialists published an article in the widely respected journal “Acta Oto-Laryngologica” formally recommending that all children with permanent bilateral profound hearing losses receive bilateral cochlear implants.  A recent publication by industry-leading otologist Dr. Robert Peters stated that:

Provision of binaural hearing should be considered the standard of care for hearing-impaired patients whenever it can be provided without significant risks. In severe to profoundly hearing impaired individuals, this can only be provided with bilateral cochlear implantation when hearing aids are inadequate. In carefully selected candidates, the benefits derived are significant, the surgical procedures well tolerated, and negative effects infrequent in both children and adults.

A second recent paper by well-known communications disorder specialist Dr. Ruth Litovsky concluded that: Bilateral CIs can offer a combination of benefits that include better ear effects, binaural summation/redundancy effects and binaural unmasking. These effects have been illustrated in numerous patients world-wide; continued work in this field will no doubt lead to further improvements and increases in the size of each of these effects, for adults and for children.Please refer to the following publications for additional information.

Another medical benefit of bilateral cochlear implantation is that it has been shown to improve speech recognition in noisy environments.  It is expected that once that a patient’s hearing with the second cochlear implant in place is maximized, they will notice a significant improvement in understanding speech in noisy environments.  Comprehending speech amidst background noise occurs commonly in real-life situations, especially in classroom settings and learning environments, at the dinner table, or while talking in a car or on a plane.  Please refer to the following studies for more details:
read more from their conclusions here…..


2 Responses to “Bilateral CI research findings”

  1. Brance Long Says:


    Thank you for the article… Its wonderful that the bilateral CI are good for post-linguistic community. It is a big step!

    I’m curious if pre-linguistic children received bi-ci and some of them don’t see it as benefit as they previous thought, then the question is what will happen to deaf children who depend on their eye for language development at later age?

    Just curious…

  2. Abbie Says:

    This is going to make a great reference Ulf!

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