Classification of Epileptic Disorders

In 1997, at the beginning of the current Executive term of the International League Against Epilepsy, it was decided to review and revise the international classifications of epileptic seizures and epileptic disorders. We are now using a classification of epileptic seizures that was devised in 1981 (1), and a classification of epilepsies, epileptic syndromes, and related disorders that was devised in 1989 (2). Since then, there have been considerable advances in our understanding of the pathophysiologic and anatomic substrates of epileptic seizures and disorders, and several new epileptic syndromes have now been described. As discussed in a previous article in this journal (3), an ILAE Task Force was appointed to recommend revisions in these classifications to take into account this new information. This Task Force is completing work on four documents. The first is a glossary of standardized terms to be used to describe the phenomenology of epileptic seizures. The second is a completely new classification of epileptic seizures, which will consider ictal events as diagnostic, rather than phenomenologic, entities with implications relevant to pathophysiologic mechanisms, anatomic substrates, therapeutic approaches, and prognosis. This seizure classification will augment the new classification of epileptic disorders, which is being amended to incorporate all of the important information that has been accumulated about epileptic syndromes and diseases over the past 12 years. Finally, the fourth classification will consider the impairments associated with epileptic conditions. With respect to proposed revisions in the classification of epileptic disorders, a working group, chaired by Dr. Natalio Fejerman, has focused its recent efforts mainly on resolving differences of opinion regarding the existence, characteristics, and semiology of certain putative epileptic syndromes that remain controversial. The most perplexing issue in this regard concerns a group of juvenile idiopathic generalized epileptic syndromes currently recognized as juvenile myoclonic epilepsy, juvenile absence epilepsy, and epilepsies with grand mal seizures on awakening. Many workers question the existence of the last of these as a specific syndrome; they want also to include idiopathic epilepsies with generalized tonic–clonic seizures that occur only during sleep or without specific diurnal patterns. At the same time, there is an increasingly prevalent view that our increased understanding of inherited epilepsies blurs distinctions between these three syndromes. Consequently, one viable creative solution to what has appeared to be irresolvable differences of opinion is to recognize a single syndrome of juvenile idiopathic generalized epilepsies with multiple phenotypes, each of which might, in some cases, be identified as a discrete subsyndrome. This recognizes that a single family can have members that manifest more than one phenotype. The article by Andermann and Berkovic in this issue puts forth the argument for inclusion of a single syndrome of juvenile idiopathic generalized epilepsies in the new classification of epileptic disorders. It is the intention of the ILAE Task Force on Classification and Terminology to complete these four documents and publicize them on the Internet and in Epilepsia, before the next International Epilepsy Congress in May 2001 in Buenos Aires. All member of ILAE chapters around the world should have an opportunity to review and comment on these revisions in time to suggest appropriate amendments, before the ILAE General Assembly discusses and votes on the proposal during the next International Congress. Because we anticipate that the specific issue of juvenile idiopathic generalized epilepsies is likely to be the most controversial of all the proposed changes, Epilepsia has agreed to publish the article by Drs. Andermann and Berkovic in advance, at the same time it is being considered by the members of the Task Force, so that we may have the benefit of comments from our entire membership as soon as possible. Comments should be addressed to me, not to Drs. Andermann and Berkovic, to ensure that they are immediately distributed to all members of the Task Force. If possible, please use e-mail to correspond.