The phenotype: seizures and epilepsy syndromes.

The coincidence of recent advances in human genetics and the development of an international classification system in the field of epilepsy, mostly for practical reasons, has resulted in unexpected progress in syndrome-related epilepsy genetics. This review of the International Classification of Epileptic Seizures as well as of Epilepsies and Epilepsy Syndromes, in addition to presenting up-to-date clinical views on epilepsy classification, tries to draw special attention to problematic areas of the classification and its underlying concepts, particularly to those to which genetic studies could be expected to contribute. These questions include, amongst others: are there genetically different non-specific basic mechanisms for the generation of focal epileptic discharge on one hand, and ambincipient or generalized discharge on the other?; are absence epilepsies, juvenile myoclonic epilepsy, and grand mal on awakening genetically separate or identical disorders?; how do genetically determined precipitating factors such as photosensitivity and, perhaps, pattern and eye closure sensitivity, interact with other genetic factors?; what is the place of idiopathic localization-related epilepsies in relation to idiopathic generalized epilepsies?; and what is the possible role of age-related, regional or diffuse gene action? Further areas of investigation may include the study of regional distributions of 'generalized' spike wave discharge as a possible indicator of subsets of this genetically determined trait; the search for a possible relation of West syndrome to chromosome 21; and the collection of precise data on the phenotype of the occasional later remanifestations in syndromes with age-related offset.