Choice of the reference for EEG mapping in the newborn: an initial comparison of common nose reference, average and source derivation.

The instantaneous amplitude of different EEG patterns found in a 36 week newborn baby were mapped by isopotential display, using 3 different references. We found that in certain cases, the nose reference recalculated average and source derivations give the same results. If the different EEG activities on the skull have too an high amplitude, and are not in phase opposition, the average reference differs from the zero potential of the common reference. In this case, the nose may be a better reference. However, it is possible that under other conditions high amplitude activity contaminates the nose, rendering the other references as better choices. From these preliminary results, we recommend the simultaneous display of maps obtained with the different references, and the comparison of the maps with the tracings for topographic studies in babies. It is absolutely necessary to record at least two polygraphic derivations to be able to recognize the sleep stages in which the analyses were performed. The eyes movement lead lets us to see if the EEG activity contaminates the face with multiple displays. It is then possible to decide which reference system is most appropriate.