Abstracts

Rationale: Schizencephaly is a structural abnormality of congenital clefts occupying the cerebral hemisphere. Epilepsy is associated with schizencephaly. There have been reports suggest that the epileptogenicity of schizencephalic patients may differ from that of other cortical malformations such as focal cortical dysplasia. In schizencephalic patients, the lesions may point to epileptogenic zone rather than contain it. The purpose of this study is to investigate the current-source distribution (CSD) of epileptiform discharges of schizencephalic patients, and correlate it with the structural lesions. Methods: Consecutive 29 schizencephalic patients, who were diagnosed by brain magnetic resonance imagings were selected retrospectively. Ten patients among the 29 patients (34.5%) had epilepsy, and 6 of 10 epileptic patients had interictal spikes on electroencephalograms (EEGs). In 1 of the 6 epileptic patients with interictal spikes, digital EEG data were lost. Finally 5 patients with schizencephaly, epilepsy, and interictal spikes on EEG were enrolled for the current-source analysis of the interictal spikes. Scalp EEGs were taken according to the International 10-20 System with 25 channels including subtemporal electrodes (F9/F10, T9/T10, P9/P10). Sampling rate was 200 or 400 Hz and filter set was 1.6 to 30 Hz. We obtained CSDs of the peak points of the interictal spikes using standardized low resolution brain electromagnetic tomography (sLORETA). Results: Among the five patients, 4 patients showed one focus of interictal spikes, and another 1 patient had two foci of interictal spikes. Four patients had extrinsic localizations of CSDs of the interictal spikes to the brain lesions, and only 1 patient among them had an intrinsic localization of the CSD. The first patient, schizencephalic lesions were on the bilateral parietal areas, and CSD of interictal spikes was on the inferior occipital area of the left hemisphere. In the second patient, the lesion was on the right parietal area, and the CSD was on the fusiform gyrus of the right hemisphere. In the third patient, the lesions were on the bilateral parietal areas, and the CSD was on the middle temporal area of the right hemisphere. In the fourth patient, the lesions were on the both temporal and left frontoparietal areas of the brain, and the CSDs were on the right inferior temporal gyrus and the left middle temporal gyrus. The fifth patient, the lesions were on the bilateral parietal areas, and the CSD was on the middle frontal gyrus of the right hemisphere.Conclusions: Our results show that the CSDs of the interictal spikes in schizencephalic patients were mainly apart from the cerebral lesions. These findings suggest that the schizencephalic lesions may have extrinsic epileptogenicity.