Electroencephalographic features of patients with SCN1A-positive Dravet syndrome.

OBJECTIVE

The aim of this study was to characterize the awake EEG features of patients with SCN1A-positive Dravet syndrome.

METHODS

Between January 2002 and December 2012, clinical data of 37 SCN1A-positive Dravet syndrome patients were collected. The first interictal awake EEG features, hot water bath test induced ictal seizure patterns and the concomitant EEG results, as well as follow-up interictal awake EEG recordings were analyzed.

RESULTS

Thirty-seven interictal awake EEG recordings showed 43.2% had normal features, 43.2% had nonspecific findings, and 13.5% had abnormal epileptiform discharges. Ictal pleomorphic seizure types with a median number of three were recorded in 26 patients. In total, 42.3% exhibited myoclonic seizures as their first recognizable seizure type with simultaneous EEG findings characterized by generalized or focal spikes, generalized 2-3.5Hz spike and wave discharges, or generalized 2-3Hz high voltage slow waves, and 30.8% manifested atypical absence seizures with concomitant EEG results showing generalized or focal spikes. Fifteen patients had 45 follow-up interictal awake EEGs during a period of six years. The follow-up awake EEG recordings revealed 42.2% had normal features, 42.2% showed nonspecific findings, and 15.6% disclosed epileptiform discharges.

CONCLUSIONS

The initial and follow-up interictal awake EEG recordings showed normal results and nonspecific features in the majority of SCN1A-positive Dravet syndrome patients. Ictal electroencephalographic seizure types and concomitant EEG pictures were quite diverse and polymorphous. A low detection rate of interictal epileptiform abnormalities at awake stage might make patient management more challenging.