Sequential bilateral implantation in older children: Inter-implant map differences and their effects on functional outcomes.

Abstract

It is well established that sequential bilateral implantation offers functional benefits in speech in noise and sound localisation, although it can be challenging to get long-term unilateral users to adapt to the second implant. The aim of this study was to investigate programming differences between the two cochlear implants that can impact on performance outcomes. Cohort Study. Sixteen older children who received sequential implants in Ireland and with at least one-year experience with their sequential implant were included in this study. Children were categorised into two groups according to the time interval between the two implants: short if the time between the two implants was less than eight years and long if more than eight years. Dynamic ranges and current levels were compared for both implants. Functional outcome measures included sentence discrimination in quiet and in noise and sound localisation. Results show that for the children with long inter-implant delays, the dynamic range of their second implant was on average 34% less than the dynamic range of their first implant. This difference was driven by smaller comfort levels in the second implant compared to the first. Children with longer inter-implant delays also show lower speech discrimination scores with their second implant compared to children with shorter delays, in addition to no bilateral advantage in speech in noise, that is their performance in unilateral mode does not differ from the performance in bilateral mode. Finally, children with longer delays demonstrate poor performance in sound localisation compared to the children with shorter delays. Sequentially implanted older children show limited functional benefits from the second implant. The observed functional benefits are determined both by a short inter-implant delay and by having balanced dynamic ranges between the two implants.