Performance over time of adult patients using the Ineraid or nucleus cochlear implant

This study examined the average and individual performance over time of 49 adult cochlear implant subjects. Subjects were randomly assigned to receive either the Ineraid cochlear implant, with analog processing, or the Nucleus cochlear implant, with feature-extraction processing. All subjects had postlingual profound bilateral sensorineural hearing loss and received no significant benefit from hearing aids before implantation. Group data were examined in two ways, First, only subjects who had complete data over the test period were examined. Second, an analysis of all available data was carried out by mixed linear-model analysis. In this analysis, to account for missed fellow-ups at the planned intervals, data consisting of the observations closest in time to the planned test times were modeled by natural splines with knots at the planned follow-up times, Contrasts between all pairs of planned follow-up times for each device were tested, as were contrasts between devices at each planned follow-up time, Results indicated little difference between the performance of the Ineraid and Nucleus subjects in their level of performance or their rate of learning. Postimplantation performance was typically superior to preimplantation performance within 9 months, and continued to improve up to 18-30 months depending on the speech perception measure. In some subjects, improvements in speech perception measures were observed up to four or five years postimplantation. There was also evidence that three subjects had a decrement in overall speech perception performance, although their postimplantation scores were always higher than their preimplantation scores. In at least one subject this was likely a result of age-related cognition decrements. (C) 1997 Acoustical Society of America.