ABR in newborns: effects of electrode configuration, stimulus rate, and EEG rejection levels on test efficiency.

OBJECTIVE

This study investigated the effect of electrode configuration, stimulus rate, and EEG rejection level on the efficiency of ABR testing in babies.

DESIGN

ABR to click stimuli at 40 dB nHL were simultaneously recorded from two electrode configurations, ipsilateral mastoid to high forehead (Mi-Fh) and nape to high forehead (N-Fh), with two EEG rejection levels (± 5 μV and ± 10 μV). Stimulus rates were between 39.1 and 69.1 per second. Efficiency was measured by confidence in the ABR for a given test time.

STUDY SAMPLE

Thirty babies who had passed a targeted newborn hearing screen with ABR thresholds ≤ 40 dB nHL.

RESULTS

The N-Fh configuration, as expected, gave on average a larger response amplitude compared to the Mi-Fh configuration but was only marginally significantly better in terms of test efficiency. There was no significant effect of stimulus rate on test efficiency between 39.1/s and 59.1/s. The lower ± 5 μV EEG rejection level was more test efficient.

CONCLUSIONS

This study provides some evidence that, for ABR threshold testing in babies, alternatives of ipsilateral mastoid or nape electrode and a range of stimulus rates have little or no effect on test efficiency. The results support the use of low EEG rejection limits.