Pathogenesis of the developmental epilepsies.

The developmental epilepsies are distinctive in that they occur in a dynamic and plastic substrate. A variety of acquired insults may present with remarkably similar seizure syndromes that are age-specific and evolve with time. This evolution may be a consequence of the brain injury itself or an alteration of normal brain maturation due to an unfavorable electrical environment. Idiopathic epilepsies are now being correlated with specific gene defects, particularly those involving ion channels and/or neurotransmitter receptors. Despite this specificity, idiopathic seizure syndromes may be caused by mutations in different genes or different mutations in the same gene, and particular syndromes may manifest heterogeneous clinical seizure types. Not all localization-dependent epilepsies are symptomatic, as a growing number of genes have been identified with partial seizure syndromes. Febrile seizures probably do not represent a homogeneous entity, but multiple disorders that may be associated with developmental abnormalities and various coexisting seizure types.