Auditory brainstem responses in the full-term newborn: changes in the first 58 hours of life

The authors have studied auditory brainstem responses (ABR) in 33 full-term newborns at 0-9, 10-30, 31-58 h, in order to evaluate changes in the first hours after birth, particularly in relation to different repetition rates and recording procedures. The data obtained show that the characteristic newborn 3-peak tracing is observed in almost all the cases at the third recording session while, at the first, wave I is absent in two-thirds of the cases. The most reliable waves at birth are waves III, V and N II, which is often present even when other vertex-positive peaks are absent. Latency values of the considered peaks tend to decrease in a statistically significant way and this decrease is almost complete at the second recording session (30 h), while V-I interval values decrease, especially when the 9 stimuli/s repetition is employed. Stimulus repetition rate affects ABR replicability and synchronization, but it hardly influences latency values. Contralaterally recorded potentials are often absent at birth and become evident 58 h later. The authors conclude that the maturational processes probably affect both peripheral and central auditory structures in the first hours after birth. In this period, increasing repetition rates seem to have a greater effect on wave replicability than on latency values.