A longitudinal study of brainstem auditory evoked potentials of preterm infants.

Brainstem auditory evoked potentials (BAEPs) of nine 'healthy' preterm infants were recorded at weekly intervals between 32 and 36 weeks conceptional age to study the relationship between stimulus intensity and central transmission time through the subcortical auditory pathway (i.e. the interval latency between peak I and peak V) as a function of conceptional age. Stimulus intensities of 70, 80 and 90 dB nHTL were used. Changes in click intensity produced changes in the absolute latency of all BAEP peaks, but the interval latency I to V remained constant. The absolute latencies and interval latencies reflected maturity, but varied widely between these preterm infants. The peak V latency and the I to V interval latency decreased with increasing conceptional age. Exponential regression analysis suggested that, above 70 dB nHTL, the time-constant of the calculated exponential function most likely represents maturation and function of the central subcortical pathway, and may give an indication of the infants' development.