All but one of the idiopathic epilepsies with a known molecular basis are channelopathies. Where the ion channel defects have been identified, however, they generally account for a minority of families and sporadic cases with the syndrome in question. The data suggest that ion channel mutations of large effect are a common cause of rare monogenic idiopathic epilepsies, but are rare causes of common epilepsies. Additive effects of genetic variation, perhaps within the same ion channel gene families, are likely to underlie the common idiopathic generalized epilepsies with complex inheritance. The genetics of epilepsy is progressing rapidly toward a more detailed molecular dissection and definition of syndromes.

a Centre for Medical Genetics, Department of Laboratory Genetics, Women's and Children's Hospital, and Department of Molecular Biosciences, University of Adelaide, South Australia; b Epilepsy Research Institute and Department of Medicine (Neurology), University of Melbourne, and Austin & Repatriation Medical Centre, Heidelberg, Victoria; and c Department of Physiology, University of Melbourne, Victoria, Australia