Severe myoclonic epilepsy in infancy (SME) was described by Dravet in 1978 (1). In 1992, there were at least 192 published cases (2). At present, it is more difficult to give a precise figure because the number of publications has greatly increased. In 2002 (3), we counted at least 253 new cases, which represent, totally, about 445 cases. It is interesting to note that most cases are reported from Japan and southern Europe, although SME has been increasingly recognized worldwide, as shown by the description of cases in the United States (4), in China (5), and in Russia (6). According to the 1989 revised classification of the International League Against Epilepsy (7), this syndrome is characterized by febrile and afebrile generalized and unilateral clonic or tonic clonic seizures that occur in the first year of life in an otherwise normal infant and are later associated with myoclonus, atypical absences, and partial seizures. All seizure types are resistant to antiepileptic drugs. Developmental delay becomes apparent within the second year of life and is followed by definite cognitive impairment and personality disorders. It has been categorized among" epilepsies and syndromes undetermined as to whether they are focal or generalized," since the syndrome shows both generalized and localized seizure types and EEG paroxysms.

We must underline that many children have been reported by different authors with a similar picture, but without appearance of myoclonias, designated as" borderline SME"(SMEB). Most of them present with association of different seizure types (2, 8-11) whereas others have only generalized tonic clonic seizures (12, 13). They can have different EEG features but share the same course and the same outcome as the patients with myoclonias. Thus, they could be included in the same syndrome. This hypothesis seemed to be supported by the genetic studies performed by Doose et al.(13). For this reason, it has been proposed to change its name, first to" epilepsy with polymorphic seizures," and then to the" Dravet syndrome." In this chapter, we describe the typical syndrome according to the literature data completed by our present series (105 patients of which 60 selected on the basis of seizures recorded in video-polygraphic EEG have been exhaustively studied) and by the Tokyo Women's Medical University, Department of Child Neurology (39 patients). The Tokyo study (14) consists of a total of 84 patients, where only 39 patients have the typical form and 45 the borderline form. We shall then discuss the other forms.