Dravet syndrome: from electroclinical characteristics to molecular biology.

The onset of Dravet syndrome typically occurs within the first year, with prolonged, generalized, or unilateral clonic seizures triggered by fever. In the early stages, other types of refractory seizures usually present that include myoclonic seizures, atypical absences, and partial seizures. Electroencephalography (EEG) findings are not pathognomonic, and signs of cognitive arrest or deterioration progressively appear. In contrast, in adults, myoclonic seizures, atypical absences, and focal seizures tend to disappear, and short tonic-clonic seizures, often associating a focal component, persist particularly during sleep. The sensitivity to fever persists into adulthood, and although mental deterioration occurs in infancy, usually leaving patients with severe mental impairment, further deterioration does not occur. The identification of genes associated with Dravet syndrome and related syndromes hints at the complexity of the etiology of such epilepsies. Identifying SCN1A mutations has become useful as a means to support an early diagnosis of Dravet syndrome, to benefit counseling, and to avoid use of antiepileptic drugs (AEDs) that may have adverse effects. However, the defining characteristics of seizure type and EEG patterns initially identified by Dravet remain fundamental to diagnosis.