Variables Affecting Speech Perception in Postlingually Deaf Adults Following Cochlear Implantation

Objective--To evaluate the time span over which there is greatest improvement in postlingually deaf adults undergoing cochlear implantation. Additionally, to quantify potential patient and device factors that may predict the postoperative results. Material and methods--A longitudinal study was conducted. Numbers, monosyllables and sentence test results were collected for 66 cochlear implant subjects [Combi 40/40+, n=60; Clarion HF2, n=2; Nucleus 24m/k, n=4] at regular intervals for up to 6 years following cochlear implantation. Results--All patients showed a steady improvement over time on all tests. Progress during the first 12 months was statistically significant, with further improvements being recorded after the 12-month testing period. The duration of deafness and the number of electrodes (8 for the Combi 40, 12 for the Combi 40+) appeared to be weakly correlated with postoperative performance. Re-implantation after device failure had no negative effect on speech reception. Subjects who were "upgraded" from an analogue to a digital cochlear implant improved their test results almost twofold. Conclusion--All the patients in our study gained substantial benefit from their cochlear implants. It is encouraging to note that the factors examined were not deemed to be relevant predictors of performance. Even long-term deaf subjects and re-implantees are able to achieve an excellent level of speech perception.