Reliability and predictive value of the electrically evoked auditory brainstem response

The reliability and predictive value of the low-pulse-rate electrical auditory brainstem response (EABR) threshold and the high-pulse-rate psychophysical threshold used in electrode mapping of adult cochlear implant patients was assessed. Eight patients, all implanted with the Nucleus multi-channel cochlear implant and experienced users, participated in this study. The relationship between like pulse rates of the EABR and psychophysical thresholds was assessed and showed high correlations of 0.90 or higher. When the relationship between low-pulse-rate EABRs and high-pulse-rate psychophysical thresholds was assessed the correlation was much poorer. The best correlation of 0.75 was shown between a 30-Hz EABR and the 500-Hz psychophysical threshold. This suggests that the low-pulse-rate EABR threshold is a poor predictor of the high-pulse-rate psychophysical threshold used in electrode mapping. Hence, if the EABR is to be a clinical tool for setting the electrodes it should be used cautiously and with the proper correction formula applied.