SURFACE MAPPING OF SPIKE POTENTIAL FIELDS - EXPERIENCED EEGERS VS COMPUTERIZED ANALYSIS

An EEG epileptiform spike focus recorded with scalp electrodes is clin ically localized by visual estimation of the point of maximal voltage and the distribution of its surrounding voltages, We compared such est imated voltage maps, drawn by experienced electroencephalographers (EE Gers), with a computerized spline interpolation technique employed in the commercially available software package FOCUS, Twenty-two spikes w ere recorded from 15 patients during long-term continuous EEG monitori ng. Maps of voltage distribution from the 28 electrodes surrounding th e points of maximum change in slope (the spike maximum) were construct ed by the EEGer. The same points of maximum spike and voltage distribu tions at the 29 electrodes were mapped by computerized spline interpol ation and a comparison between the two methods was made. The findings indicate that the computerized spline mapping techniques employed in F OCUS construct voltage maps with similar maxima and distributions as t he maps created by experienced EEGers. The dynamics of spike activity, including correlations, are better visualized using the computerized technique than by manual interpretation alone. Its use as a technique for spike localization is accurate and adds information of potential c linical value.