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.