[Electroencephalographic foci without structural diagnostic correlates].

Abstract

On account of the increasing availability of various new, computer-aided and non-invasive imaging techniques it seems advisable to reconsider the structural-diagnostic use of the EEG which is a functional-diagnostic instrument by its nature. On the level of visuo-morphologic description local and locally accentuated patterns can only be conceived as deformations of the temporo-spatial gestalt of the EEG. On the level of interpretation, i.e. in answering the question whether such patterns are indicative of a circumscribed structural lesion or not, further information is required. In addition to clinical data such information is provided by the electroencephalographic context. Typical arrangements of the EEG-context which make improbable an assumption of a structural lesion can be demonstrated for certain anterior-left as well as posterior-right localized patterns. From such regular co-incidencies, which are illustrated by paper chart examples, we conclude that these "foci" represent local manifestations of a global functional impairment. Whereas the intermittently occurring anterior-left accentuated slow wave patterns refer to an incipient global functional disintegration, the posterior-right accentuated slow wave patterns can be regarded as a reflection of a global functional deficit of maturation. A third phenomenal domain which persistently confronts us with the structural-diagnostic limitations of the EEG consists of the focal patterns in patients with epilepsy. It may be assumed that the pronounced lateral inconsistency of these focal patterns, occurring within the recording period and even more when comparing serial recordings, is dependent both on the actual (vigilance) and the relatively outlasting level of central nervous organization (maturation).