An electroclinical study of absence seizures in Dravet syndrome.

We studied clinical and EEG manifestations of absence seizures (AS) in children with Dravet syndrome (DS) to clarify their characteristic features and differences from those of typical AS (TAS). The subjects were 12 children with DS. We retrospectively analyzed electroclinical characteristics of AS. We analyzed a total of 102 ictal EEGs characterized by generalized spike-and-wave (GSW) and semiology of 78 video-taped AS. The mean age at the onset of AS and at the time of the study was 16.2±7.1 months and 40.3±22.1 months, respectively. Ictal EEG showed the focality of initial discharge in 49/102 (48%), a duration ranging from 2 to 180 s (mean: 10.2±22.6 s; median: 4.0 s), frequency ranging from 2 to 4 Hz (median=3.0 Hz), and irregular and disorganized GSW morphology in 66/102 (65%). AS manifested with eyelid-myoclonus and generalized myoclonus in 9/54 (17%) and 34/78 (44%), respectively. In conclusion, AS in DS were characterized by an early-onset age, a high incidence of irregular and disorganized 3 Hz GSW morphology, and the frequent association of generalized myoclonic movement as well as the absence of automatism as compared to TAS. The results should be appreciated in the differential diagnosis of early-onset AS, the treatment of AS in DS and also a further clinical and genetic study for DS.