Abstract:
The provision of bilateral cochlear implants for children with bilateral sensorineural hearing loss has reached a common consensus in the last few years. In New Zealand, public funding of bilateral cochlear implants was approved for all newly referred children staring in 2014; prior to that time it was practice to implant one ear only. Also, at this time, children who had received one cochlear implant previously and were under age 6 became eligible for a second device. Most did proceed to bilateral use. The inter-implantation interval is the time between the first and second ear surgeries. In this thesis, its importance as a factor for predicting speech perception ability is considered. Firstly, the aim of this research was to examine whether an improvement in speech perception ability occurred when children received a second cochlear implant. Secondly, this research aimed to investigate the relationship between the timing and consequences of sequential bilateral cochlear implantation in children. Speech perception performance data was collected from 15 paediatric participants who underwent sequential bilateral cochlear implantation. Performance was measured in the bilateral condition and in each unilateral condition using words in quiet, and sentences in background noise. The 15 participants were grouped for further analysis according to the length of the inter-implantation intervals. As a group, participants with an inter-implantation interval of less than 1 year demonstrated significantly higher speech perception performance in quiet in the bilateral condition compared to either ear alone. This was not the case for children with longer interimplantation intervals; bilateral performance was similar to performance with the first ear of implant in all listening conditions for this group. A trend of increasing differences in performance between the first and second ear of implant was evident as the inter-implantation interval increased. Shorter inter-implantation interval should be advised for children who need a sequential implant to ensure access to binaural advantages and therefore better speech perception outcomes. Gathering this clinical data supports policy decisions made by the Ministry of Health regarding bilateral cochlear implants in children. The data also supports recipient and family counseling during candidacy evaluation.