Changes in Auditory Brainstem Response in very preterm and late preterm infants.

Aim: Aim of this study was to compare the absolute and interpeak latencies of Auditory Brainstem Responses (ABR) in very preterm and late preterm infants at 1 month and 3 months of corrected age.

Method: ology: ABR traces were obtained from 80 preterm infants (40 very preterm and 40 late preterm) at 1 month and 3 months of corrected age in a prospective, comparative cohort study. Auditory click stimuli at 70 dBnHL and 30 dBnHL, with repetition rate of 11.1/s were used. Absolute latencies of peak I, III, V and interpeak latencies of peak I-V, I-III and III-V were analyzed and compared between preterm groups at 1 month and 3 months of corrected age. Wilcoxon Signed Ranks test was used to compare the ABR variables. Mann Whitney test was used to make inferences between groups.

Results: There was a statistically significant difference in absolute latencies and interpeak latencies between very preterm and late preterm infants at 1 month of corrected age (p < 0.05). Absolute latency of peak I was similar among both groups of preterms. Absolute latencies of peak III, V and interpeak latencies I-III, III-V and I-V were prolonged in very preterm infants at 1 month of corrected age. However, these latencies were significantly reduced at 3 months of corrected age. This indicated accelerated maturation/myelination of the central auditory nervous system in very preterm infants. Absolute latencies of peak III and V and interpeak interval I-V was reduced in late preterm infants at 3 months of corrected age and this was statistically significant. This reduction in latency was considered to be a normal age dependent change.

Conclusion: Findings of the current study revealed that there was no deviation in the pattern of auditory maturation among preterms; it followed the typical 'caudal to rostral' form of maturation. Very preterm infants have less mature neuronal development compared with late preterm infants at 1 month of corrected age which catches up at 3 months of corrected age.