[Diagnostic value of electrophysiologic studies in presenile and senile dementia].

From the therapeutical point of view, reliable differentiations of different dementia types are required. Electrophysiological methods could be advantageous for this purpose. Healthy elderly people already show slight EEG-changes as slower alpha rhythm with decreased percent time and amplitude, furtheron temporal foci predominantly on the left side. Those changes partly are correlated with age, mental abilities, and vigilance. Considering clinical psychopathological findings, the EEG pattern can to some extent differentiate dementia types. The occurrence of disorganized diffuse theta and delta waves instead of the regular alpha rhythm can signify Alzheimer's disease. On the other hand, generally well preserved but slow alpha rhythm with focal slow waves characterizes the multi-infarct dementia. Experience with evoked potential findings in dementia is still rare, compared with the relatively well established EEG criteria. An increase of latencies of early components, a decrease or disappearance of amplitudes of late components, and an increase of refractory period using double stimulus as described as typical changes. According to our own preliminary findings, the high polarity of the nonstructured late part of the EP wave could differentiate multiinfarct dementia from Alzheimer's disease, where low polarity seems to be characteristic.