BAEP subcomponents and wave form — relation to click phase and stimulus rate

Abstract

The latency distributions of normal brain-stem auditory evoked potential (BAEP) components elicited by condensation (C) and rarefaction (R) clicks at 10 and 50 Hz were found to be double- or multi-peaked for II (10 and 50 Hz), III (50 Hz), IV (10 and 50 Hz) and V (10 Hz). A bifid component III was found in 3.5% (10 Hz) and 7.4% (50 Hz) of BAEPs. A bifid II and triple IV/V configuration were occasionally noted. The prevalences of the different IV/V complex configurations were significantly dependent upon click phase and rate. These results suggest that several subcomponent might participate in the generation of the single BAEP components and that a single generator may contribute to different BAEP components in different subjects. Early subcomponents between I and II (Ib) were found in 13% of 10 Hz BAEPs and 27% of 50 Hz BAEPs ( P = 0.002) and the latency distribution of Ib seemed to be bimodal. Ib/I relative amplitude frequently increased with 50 Hz stimulation. We suggest that the generator of Ib is partially cochlear (CM) and partially neural (equivalent to N2 of the ECochG-AP) in origin. The existence of subcomponents must be recognized in clinical use of BAEPs both to avoid misinterpretation and to decrease the normal variability in monophasic click evoked BAEP studies.