Test-Retest Reliability of Dual-Recorded Brainstem versus Cortical Auditory-Evoked Potentials to Speech.

BACKGROUND: Auditory-evoked potentials have proven useful in the objective evaluation of sound encoding at different stages of the auditory pathway (brainstem and cortex). Yet, their utility for use in clinical assessment and empirical research relies critically on the precision and test-retest repeatability of the measure.

PURPOSE: To determine how subcortical/cortical classes of auditory neural responses directly compare in terms of their internal consistency and test-retest reliability within and between listeners.

RESEARCH DESIGN: A descriptive cohort study describing the dispersion of electrophysiological measures.

STUDY SAMPLE: Eight young, normal-hearing female listeners.

DATA COLLECTION AND ANALYSIS: We recorded auditory brainstem responses (ABRs), brainstem frequency-following responses (FFRs), and cortical (P1-N1-P2) auditory-evoked potentials elicited by speech sounds in the same set of listeners. We reassessed responses within each of four different test sessions over a period of 1 mo, allowing us to detect possible changes in latency/amplitude characteristics with finer detail than in previous studies.

RESULTS: Our findings show that brainstem and cortical amplitude/latency measures are remarkably stable; with the exception of slight prolongation of the P1 wave, we found no significant variation in any response measure. Intraclass correlation analysis revealed that the speech-evoked FFR amplitude and latency measures achieved superior repeatability (intraclass correlation coefficient >0.85) among the more widely used obligatory brainstem (ABR) and cortical (P1-N1-P2) auditory-evoked potentials. Contrasting these intersubject effects, intrasubject variability (i.e., within-subject coefficient of variation) revealed that while latencies were more stable than amplitudes, brainstem and cortical responses did not differ in their variability at the single subject level.

CONCLUSIONS: We conclude that (1) the variability of auditory neural responses increases with ascending level along the auditory neuroaxis (cortex > brainstem) between subjects but remains highly stable within subjects and (2) speech-FFRs might provide a more stable measure of auditory function than other conventional responses (e.g., click-ABR), given their lower inter- and intrasubject variability.