Inherited epilepsies of childhood.

Recent advances in neuroepidemiologic and molecular biological techniques have facilitated a growing understanding of the role that inherited factors play in epileptogenesis. During the last few years linkage analysis has mapped gene loci associated with the following epilepsy syndromes: benign familial neonatal convulsions, juvenile myoclonic epilepsy, Unverricht-Lundborg/Baltic/Mediterranean progressive myoclonic epilepsies, the juvenile form of ceroid lipofuscinosis, sialidosis I, and the myoclonus epilepsy with ragged red fibers (MERRF) syndrome. In addition, characterization of the inheritance patterns of other syndromes such as childhood epilepsy with occipital paroxysms and febrile convulsions has improved. It is apparent that a significant amount of clinical and genetic heterogeneity exists, which emphasizes the importance of accurate clinical classification. As genetic markers are found for well-defined groups of patients, traditional means of classification (seizure type, pathologic markers, progressive course, etc.) become less meaningful. It is proposed that the components of the phenotype of an epilepsy syndrome (eg, age of onset, seizure type, electroencephalographic pattern) may be controlled by multiple genes.