Sustained depression of brainstem auditory electrophysiology during the first months in term infants after perinatal asphyxia

Objective To gain further insights into the pathophysiological processes of neuronal impairment in neonatal brainstem after perinatal asphyxia. Methods Maximum-length sequence brainstem auditory-evoked response (MLS BAER) was recorded with clicks at 91, 227, 455 and 910/s on days 1, 3, 5, 7, 10, 15 and 30 after birth in 108 term infants who suffered perinatal asphyxia. Wave amplitude variables in the MLS BAER were analysed in detail at 40 dB above BAER threshold in 86 infants who had no peripheral hearing impairment. Results On day 1 the amplitudes of MLS BAER waves I, III and V were all reduced significantly at all click rates, especially at higher ones (91–910/s, ANOVA P < 0.05–0.001). On day 3 these amplitudes were reduced further. On days 5 and 7, the amplitude reduction persisted and did not show any significant further changes. On days 10 and 15 the reduced amplitudes were increased slightly. On day 30 all amplitudes were still reduced significantly (P < 0.05–0.0001). During the first month, the reduction of wave amplitudes was more significant for the later MLS BAER components than for the earlier ones, and occurred most significantly at 455 and 910/s clicks. By comparison, the amplitude reduction in conventional BAER was much less significant. Conclusions During the first month after perinatal asphyxia the amplitudes of MLS BAER waves were reduced significantly and persistently, which was more significant at higher rates of clicks than at lower rates. The reduction is much more persistent than the increase in wave latencies and intervals we previously reported. Significance There is sustained depression of brainstem auditory electrophysiology, indicating neuronal damage of the auditory brainstem, in infants after perinatal asphyxia. This may have important clinical implications.