Background: Cochlear implants provide access to the speech signal in those profoundly deaf children who derive no material benefit from acoustic hearing aids. Speech perception after implantation can vary widely--we have analysed the contribution of several factors.
Methods: We examined 40 children with mean age at implantation of 52 months who were either born deaf or became deaf before 3 years. All patients received the same multichannel implant system and were followed up for 5 years. We used connected discourse tracking (CDT) as the measure of speech perception. The effect of five potential predictors (age at implantation, number of inserted electrodes, origin of deafness, mode of communication, and socioeconomic group) on speech perception was analysed.
Findings: The mean number of words per minute perceived increased from 0 before implantation to 44.8 (SD 24.3) 5 years after implantation. Repeated-measures ANOVA showed that children significantly progressed over time (p=0.001). Age at implantation was a significant covariate (p=0.01) and mode of communication was a significant between-individuals factor (p=0.04).
Interpretation: Young age at intervention and oral communication mode are the most important known determinants of later speech perception in young children after cochlear implantation. Early identification of candidate children necessitates implementation of universal neonatal screening programmes for hearing impairment.