Speech perception after cochlear implantation over a 4-year time period

Abstract

Objective: To evaluate the long-term speech perception of cochlear implantees and to compare the developing auditory performance patterns of prelingual children and postlingual deaf adults.

Material and methods: Twenty-nine prelingually deaf children and 17 postlingually deaf adults who had been followed up for 4 years were included in the study. Speech perception ability was assessed by means of vowel and consonant confusion tests and the Korean version of the Central Institute of Deafness (K-CID) test (performed without visual cues). The test results were analyzed at 3 and 6 months after implantation and then annually.

Results: In the prelingually deaf children, the average results continuously improved over the 4-year period. In the postlingually deaf adults, the average results did not improve further after the first 2 years. Individuals with < 5 years of deafness had a faster rate of recovery of speech perception than those who had been deaf for > 5 years. The K-CID scores were negatively correlated with age at implantation for the prelingually deaf group and with the duration of deafness in the postlingually deaf group. Children fitted with implants at a younger age showed better speech perception ability than those fitted with implants at an older age. Interestingly, prelingually deaf children aged 5-7 years at implantation showed the widest variation in individual outcomes. Amongst this group of children with highly variable outcomes, the metabolic status of brain cortices determined by means of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) was available for three patients. The individual with the widest hypometabolic area had the best speech perception ability.

Conclusion: The extent of hypometabolism as assessed by FDG-PET seemed to be one of the major factors predicting the outcome of cochlear implantation.