CORTICAL AUDITORY EVOKED POTENTIALS IN TWO PRELINGUALLY DEAFENED ADULTS

Background: It has been reported that in prelingually deafened adults there is maturation of the late latency response (LLR) after rehabilitation using cochlear implants. Other evidence suggests that the auditory system, like any other sensory system, receives multimodal stimulation, a factor which could help the auditory system mature even in the absence of any auditory input. The current study was done on two prelingually deaf adults who had not received rehabilitation, and their latencies were within the normal mature range, suggesting their auditory cortex responses were maturely developed prior to rehabilitation. Material and methods: Two male participants took part in the study: one was 21 years old and the other was 36, and both had congenital profound hearing loss. Using pure tone thresholds obtained earlier, a strong class hearing aid (Siemens Infiniti Pro SP) was programmed using NOAH software and fitted to the right ear using the NALNL-1 fitting formula. As an objective measure of verification of hearing aid effect, auditory P1, N1, P2, and N2 were recorded using the free-field facility available in the IHS SmartEP system: a 1000 Hz pure tone was presented at 70 dB SPL (30 dB SL) and 50 dB SPL (10 dB SL) from a loudspeaker at a distance of 1 m and 45° angle. Results: The latencies of P1, N1, P2, and N2 for both participants were recorded for 70 and 90 dB HL; all latencies were well within normal limits. Conclusions: The results indicate that, with adequate amplification, a mature response from the auditory cortex can be obtained even in adults who have profound hearing loss and who have been deprived of auditory stimuli since a prelingual age.