Maturation of the auditory brain stem response (ABR): additional perspectives.

A retrospective, cross-sectional analysis of component latencies of the auditory brain stem response (ABR) was performed on 466 patients ranging in age from 30 weeks postconception to adulthood. The ontogeny of ABR component wave latencies was adequately described by two exponential curves having different slopes; the steeper curve represented an early, rapid maturation ending by 8 to 10 weeks post partum, and the ensuing, more gradual curve corresponded to developmental events which were completed by the beginning of the third year of extrauterine life. These observations conform to previous maturational concepts of peripheral versus central segments of the auditory pathway and to the gradual decrease in interwave latencies with increasing age. Unlike interwave latency, however, the ratio of the latencies of selected component waves was constant with increasing age. This was especially apparent in developing newborns less than 50 weeks postconception. The nonlinear bases of this phenomenon are outlined, and the insights which stem from this perspective are discussed.