Developmental course of brain-stem auditory evoked potentials in the first days of full term infants

Modifications of brain-stem acoustic evoked potentials (BAEPs) in the first 5 days of life of normal full-term infants are reported. BAEPs were recorded using rarefaction clicks at 70, 60, 40, 20 dB HL. Multiple linear regression analysis was performed to evaluate chronological and gestational age differences for all positive and negative peaks, interpeak latencies, amplitudes and amplitude ratios. The percentage of newborn infants with auditory threshold of 20 dB HL increased with the number of days. At all intensities the latency of PIII and PV decreased significantly between the 2nd and 3rd day, while the latency of PI decreased significantly between the 3rd and the 4th day; PIII and PV latencies decreased also between the 4th and the 5th day. The longer the period of gestation the longer was the PI latency recorded between the 2nd and 5th day after birth. The anatomical and physiological changes developing shortly after birth are probably responsible for the above findings. These changes most probably appear firstly in the cochlear and trapezoid nuclei and later on in the organ of Corti.