The outcome of cochlear implantation in patients with deafness of prelingual onset is largely unpredictable due to high individual variability. This study evaluated speech perception performances in a group of 18 prelingually deafened subjects (aged 13–30 years) which was homogeneous with respect to duration of deafness, hearing aid use before cochlear implantation, mode of communication and administration of auditory-oral speech therapy. Word discrimination length, word and sentence identification, phoneme identification and word and sentence recognition were tested before cochlear implantation and at 6 months, 1, 2 and 3 years of cochlear implant use. Scores on all tests significantly improved after cochlear implantation, although mean values were lower compared to those achieved by postlingually deafened patients. Speech performances on both word and sentence recognition continued to increase over time also beyond 1 year after cochlear implantation. Moreover, scores on sentence recognition tests were significantly higher compared to disyllabic words at 3 years of cochlear implant use. The presence of an auditory input delivered by hearing aids before cochlear implantation associated with auditory-oral therapy and a good level of education may positively influence the cochlear implant outcome in prelingually deafened adults.

Serial comparisons revealed that that speech perception performance evaluated in children aged 5 to 15 years was superior with the Freedom than previous generations of Nucleus sound processors. These differences are deemed to ensue from an increased input dynamic range, a feature that offers potentially enhanced phonemic discrimination.