Analysis of auditory brainstem response waveforms derived ipsilaterally and contralaterally to monaural stimulation.

The auditory brainstem responses (ABRs) obtained from 28 normal healthy adults were studied using the ipsilateral and contralateral recordings from the positions of vertex and each mastoid to monaural stimulation. Each wave of ABRs recorded by ipsilateral and contralateral derivations to stimulation site showed slightly significantly differences. Comparing the ipsilateral and contralateral data, the latencies of waves II and V showed a slightly small reduction in the ipsilateral recording, while these of waves III and IV showed a small increase. Next, the distributions of potentials and latencies of waves II to V were investigated from ABRs situating different electrodes in mid-coronal array of the scalp and non-cephalic reference electrode on the seventh cervical vertebra (CVII). The results of latencies showed the reverse relation to the data obtained from the ipsilateral and contralateral recordings using the reference electrodes on each mastoid. These facts suggest that the comparable differences of latencies in the bilaterally recorded ABRs are explained by the pseudo-phenomena of differential recordings, which the phase delayed or advanced potential propagated to each mastoid being reference electrode position.