The effect of electrode position on flash visual evoked potentials in the newborn.

We examined how changes in electrode position affected the visual evoked potential in 74 high-risk newborns using a multiple electrode technique. The variation in the visual evoked potential across the occiput was documented. Visual evoked potentials that were visible at one occipital electrode position were absent at a different electrode position in 21 of 87 recordings (24%). Changes of greater than 20 msec between electrodes in latency of waves P1 or N2 occurred in 34% and 29% of recordings, respectively. The amplitude of response varied by a factor of 2.36 between mid occipital and lateral occipital electrodes. The results demonstrated that large changes in morphologic characteristics, latency, and amplitude in the visual evoked potential of the newborn result from small changes in the position of recording electrodes. These findings underscored the importance of electrode position and accurate electrode placement. Our observations also indicated that recordings from a single electrode are inadequate in providing an accurate representation of the neonatal visual evoked potential.