[Mapping the spontaneous EEG in focal disorders].

It will be reported about 142 EEG spectral analytic mappings in 100 patients with focal EEG findings which were recorded already in routine EEG examinations. Drawings of the visually analysed paper recordings have been compared with the maps. We found in about 30 per cent a true gain of information. It is based on a more precise demarcation of focal findings or a better display of points of most severe dysfunction within extended disturbances. Beyond that the pictorial presentation of topographic features is a general advantage of EEG mapping. On the other side there are limits and disadvantages of topographic EEG analysis. With special reference to the analysis of circumscribed dysfunctions they will be demonstrated. Problems are related to the type of reference, to the choice of analysis time, or to "spatial aliasing effects" which are introduced by the interpolation procedure of mapping analysis. Beside the neuroradiological imaging methods the EEG mapping maintains special significance because it displays the functional aspect of cerebral processes.