The normative basis for click and frequency-specific BERA in high-risk infants

The use of brainstem electric response audiometry (BERA) for early detection of hearing loss is predicated upon large-sample normative data. Auditory brainstem response (ABR) thresholds for click and notch-masked tonepip stimuli were examined in 230 normal infants with no risk factors for hearing loss, tested under audiometrically ideal conditions at between 48 and 56 weeks post-conception. The ABR threshold distributions for clicks and tonepips differed considerably. Almost all infants had click thresholds consistent with normal hearing on adult criteria, whereas many appeared to have hearing loss at 500 Hz. ABR latencies for 70 dBnHL clicks were more variable than expected, even in infants with click thresholds of 30 dB or better. In males, wave V latency was about 0.2 ms larger than in females, but there was no such difference for wave I. For both sexes, there was a linear decrease in wave V latency with age at approximately 0.1 ms per month, but wave I latency was constant.