Automatisms in absence seizures in children with idiopathic generalized epilepsy.

BACKGROUND Automatisms are well recognized to occur in complex partial seizures; however, their occurrence in generalized epilepsies is not always appreciated. There has been considerable debate regarding the nature, triggers, and timing of automatisms in absence seizures. OBJECTIVES To examine the frequency and nature of automatisms in new-onset absence seizures and assess the influence of the state of arousal, provocation, age, and epilepsy syndrome on the presence and type of automatisms. DESIGN Analysis of absence seizures through video electroencephalogram (EEG) recordings. SETTING British Columbia's Children's Hospital, Vancouver, British Columbia, Canada. PATIENTS Seventy consecutive children with new-onset untreated absence seizures in idiopathic generalized epilepsy recruited between January 1, 1992, and June 30, 1997. MAIN OUTCOME MEASURES Each seizure was analyzed for the presence and characteristics of automatisms. The influence of the following variables on the presence of automatisms was statistically analyzed: state of arousal (awake, drowsy, asleep), provocation (hyperventilation, photic stimulation), age, and epilepsy syndrome. RESULTS Automatisms occurred in 163 of 405 seizures (40%) in 53 of 70 children (76%). Automatisms were more likely in longer seizures and hyperventilation. Only 23% of spontaneous awake seizures had automatisms. Automatisms were similar for an individual child; however, automatisms were not present in all their seizures. Age, epilepsy syndrome, or state of alertness had no effect on the presence of automatisms. CONCLUSIONS Automatisms are frequently seen during childhood absence seizures. The high frequency of automatisms during EEG recordings is predominantly due to the effect of hyperventilation. Their preponderance during longer seizures may relate to opportunity for automatisms to occur. The characteristic pattern of automatisms suggests a reactive phenomenon to internal and external stimuli.