[EEG changes in type I and type II lissencephaly]

Lissencephaly syndromes are rare disturbances of the neuronal migration with agyria and/or pachygyria. Typical patterns in the EEG of 5 children with lissencephaly are presented. Rhythmic alpha- or beta-waves with high amplitudes of diffuse or fronto-precentral localisation are characteristic in type I lissencephaly. In type II lissencephaly initially theta- or delta-waves of somewhat lower amplitude are observed. Sharp and slow wave-complexes of very high amplitude are found more often in type I lissencephaly. They seem to correlate with the severity of the brain malformation and the epilepsy. In both types of lissencephaly the spatial organisation of the background activity and the sleep-wake differentiation are absent. The EEG of most type I lissencephalies show no reactivity to intravenous benzodiazepines. With increasing age the frequency of the background activity and of the high amplitude rhythmic waves decrease in type I and increase in type II lissencephaly. A complete dedifferentiation of the EEG tracings has been observed in the course of type I lissencephaly. Lissencephaly is diagnosed by imaging techniques. However, with a high probability lissencephaly can be suspected already by its EEG.