Electroencephalographic and clinical features of typical absence seizures in children.

From July 1986 to July 1991, seventeen typical absence seizures, in patients aged 3 to 12 years (mean: 7 years 1 month), were collected for clinical and electroencephalographic (EEG) analysis. All were first-evaluated patients at the Pediatric Neurology Clinic, National Taiwan University Hospital with thorough EEG examination (including waking and natural sleep records) and detailed medical records. All had no history of any brain insult, except for one who had had febrile convulsion before. There were nine female and eight male patients. All had regular bilaterally synchronous and symmetric 3 Hz spike-and-wave discharges and absences. Nine of the 17 cases had interictal focal spike discharges, located over centro-temporal area in 4 cases, fronto-central area in 2 cases and parietooccipital area in the other 2 cases. Another patient was found to have 3 Hz posterior slow waves. Four of the 17 cases had automatisms. Only one case had photo-paroxysmal response. Hyperventilation could induce clinical spells and typical EEG findings in all 17. Normal interictal background activity on the EEG was also found in all cases.