Abstracts

Rationale: There was previous evidence that the location of generalized-spike-and-wave discharges (GSWDs) generator was different according to the responsiveness to valproic acid in idiopathic generalized epilepsy. The aim of this study was to compare current source distribution (CSD) of GSWDs between childhood absence epilepsy (CAE) patients with seizure free and the patients with seizure recurrence after use of optimal dose of valproic acid. Methods: Six consecutive children with CAE and GSWDs in electroencephalogram (EEG) were enrolled in this study. We classified the patient into 2 groups: 1) drug-responsive group including children with seizure free after treatment with optimal dose of valproic acid, 2) seizure recurrence group including children with seizure recurrence in spite of use of valproic acid with adequate doses. Scalp EEGs were taken according to International 10-20 System with 25 channels. Sampling rate was 400 Hz and filter set was 1.6 to 30 Hz. We selected artifact-free EEG segments of 500 msec before and 500 msec after the peak points of spikes of typical GSWDs in the enrolled patients. We obtained an averaged spike from the 18-50 interictal GSWDs in each patient. At the peak point of the each averaged spike, we obtained the CSD by current source analysis. We observed the location and lateralization of the CSDs and compared them between the drug-responsive group and the seizure recurrence group. Results: The CSDs of 3 patients in the drug-responsive group (patient 1, 2, 3) were relatively symmetric than the other 3 patients (patient 4, 5, 6) in the seizure-recurrence group. In addition, the most maximal point of CSD was in the frontal lobe in the all 3 patients in drug-responsive group in contrast that the point was outside of the frontal lobe in 2 of 3 patients in seizure-recurrence group. The location of CSD was the anterior-inferior-medial fontal area across both hemispheres and the anterior-medial temporal area of the right hemisphere in the patient 1. In the patient 2, the CSD was in the anterior-medial fontal area across both hemispheres and the inferior-medial temporal area of the right hemisphere. In the patient 3, the CSD was in the anterior-medial fontal area across both hemispheres. The lateralized shift of CSD was observed in 2 of 3 patients in seizure-recurrence group. In the patient 4, the CSD was in the inferior and medial temporal area of the left hemisphere. In the patient 5, the CSD was in the temporal area of the right hemisphere. In the patient 6, the CSD was in the anterior-medial fontal area across both hemispheres. Conclusions: The irritative zones of epileptic brain in CAE may distribute differently according the seizure control states. In well controlled CAE patients with valproic acid, the CSD of interictal spikes may tend to distribute in the frontal area with bilateral symmetricity. However, the distributions may shift to the lateral direction in CAE patients with drug-resistance. This electrophysiologic difference may be helpful to speculate the prognosis of nave patients with CAE.