Bilateral sequential implantation in children

Abstract

Cochlear implants provide an electrical signal that may assist in the development of the central auditory system. In order to capitalize on the developmental processes associated with a maturing auditory system, many authors suggest cochlear implantation should be performed at very young ages. In order to examine the contributions associated with one versus two cochlear implants in young children, we examined performance over three years post-implantation in children who received sequential cochlear implants. Twenty-nine children sequentially implanted were studied. All children were implanted with Cochlear Corporation multichannel cochlear implants. Mean age at the first implantation was 2.31 years (range 1–9 years) and 7.55 years at the second implantation (range 3–15 years). Children were evaluated annually with audiometric thresholds and open-set speech perception testing. Data were examined in two ways. First, data acquired annually for the first three years post-implant were compared between the first and second ears implanted (chronological option A). Secondly, performances for both ears were examined for a three-year follow-up period after the second implantation (chronological option B). Thresholds were significantly higher in the second implanted ear relative to the thresholds obtained in the first implanted ear during the first two years post-implantation. Comparisons of thresholds for the two ears following the second implant also confirmed significantly higher thresholds for the second implanted ear relative to the first implanted ear over a three-year evaluation period. Analyses of speech perception performance revealed that performance with disyllable words and sentences were significantly lower in the second implanted ear at 12, 24 and 36 months after activation relative to the first ear implanted in its initial three years of use and during the three-year period following the second implantation. There is at least a five-year window to carry out a second implantation in the contralateral ear for children suffering from a congenital bilateral hearing loss, who have been unilaterally stimulated from an early age with a cochlear implant. However, the results of this work do not apply to other situations including late initial implantations or wider windows between the implantation in the first and second ears.

• neural
• audiology
• plasticity