Brain-stem auditory impairment during the neonatal period in term infants after asphyxia: dynamic changes in brain-stem auditory evoked response to clicks of different rates

Objective: To explore dynamic changes in brain-stem auditory electrophysiology during the neonatal period in term infants after perinatal asphyxia. Methods: Sixty-eight term newborn infants who suffered asphyxia were studied on days 1, 3, 5, 7, 14 and 30 after birth. Brain-stem auditory evoked response (BAER) was recorded with clicks, delivered at 21, 51 and 91 s(-1) and greater than or equal to40 dB above BAER threshold of each subject. Results: During the neonatal period wave I latency in the infants after asphyxia increased slightly while later BAER components changed more significantly. On the first day after birth wave III and V latencies and I-V and III-V intervals increased significantly at all rates of clicks (ANOVA P < 0.01-0.001). On day 3, the latencies and intervals increased further. Ill-V/I-III interval ratio increased at 51 and 91 s(-1), suggesting a relatively more significant increase in III-V interval than in I-III interval at higher rates. Thereafter, wave III and V latencies and all intervals decreased progressively, although these BAER variables were still significantly longer than in normal controls on days 5 and 7 (P < 0.05-0.001). On day 30, all latencies and intervals approached near normal values, with a slight increase in wave V latency and I-V and III-V intervals at 51 and 91 s(-1). Conclusions: Perinatal asphyxia has a major effect on central auditory function, resulting in acute impairment. The impairment progresses during the first 3 days and then tends towards recovery. By 1 month the impaired auditory function has largely returned to normal. Significant increase in click rates can moderately improve the detection of auditory impairment. Significance: After perinatal asphyxia early detection of hypoxic-ischaemic damage to the central auditory system and initialisation of neuroprotective and therapeutic measures during the first hours after birth are critical to prevent or reduce deterioration of central impairment. (C) 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.