A long-term follow-up study of Dravet syndrome up to adulthood

Purpose: We intended to elucidate the whole clinical course of Dravet syndrome (DS) comprehensively, from infancy through adulthood. Methods: Subjects were 31 patients with DS (14 with typical DS, and 17 with borderline DS) who were followed from childhood to at least 18 years of age. Their seizures, abilities, and electroencephalography (EEG) findings were investigated and statistically analyzed. Results: The clinical findings of the patients with typical DS and those with borderline DS became largely similar in adolescence and adulthood. Seizures were intractable in childhood in all patients, but suppressed in five (16.1%) during follow-up. Thirty-five (87.5%) of the 40 apparently generalized convulsive seizures that were captured by ictal EEG recording at 7 years of age or later were of focal origin. The seizure-free outcomes were significantly correlated with the experience of <3 episodes of convulsive status epilepticus, and also with disappearance of spikes on the follow-up EEGs. Mental outcomes involving less severe intellectual disability were correlated with the presence of occipital alpha rhythms in the background activity of the follow-up EEGs. Mean age at the recording of the follow-up EEGs was 23.8 years. Discussion: Prevention of the occurrence of convulsive status epilepticus was indicated to be critically important for the improvement of seizure prognosis in DS.