Effects of electrode placement on the auditory brainstem response using ear canal electrodes.

The effects of electrode placement on the latency and amplitude of the auditory brainstem response (ABR) were investigated in normal-hearing subjects. Ear canal (EC) electrodes were used in conjunction with surface electrodes to obtain ABRs. Three electrode combinations were evaluated: (1) vertex-EC-EC; (2) vertex-EC-neck; and (3) forehead-EC-neck. Absolute and interwave latencies and absolute and relative amplitudes were computed for Waves I, III, and V at 75 dB SL. Standard errors of measurement (SEmeas) revealed excellent test-retest reliability for latency (SEmeas = 0.06 ms) but only fair reliability for amplitude (SEmeas = 55 nv). No reliability differences were observed among the three electrode combinations. No significant latency or interwave latency differences were found among the three montages. No amplitude differences were found for Waves I and III among the montages. However, the Wave V amplitude was larger for the vertex-EC-EC and vertex-EC-neck montages than for the forehead-EC-neck montage. Because the vertex-EC-EC montage does not require additional electrodes on the contralateral neck, this montage is recommended.