Abstracts

Rationale: The epileptogenicity of schizencephalic lesions may differ from that of other cortical malformations, such as focal cortical dysplasia. The lesions may point to epileptogenic zone rather than contain it. The purpose of this study is to investigate the current source distribution of epileptiform discharges of schizencephalic patients, and correlate it with the lesions revealed by magnetic resonance imagings (MRI). Methods: Three consecutive patients with schizencephaly in brain MRI and interictal spikes in EEG were enrolled. Seizure semiology of the patients was clinically consistent with temporal lobe epilepsy (TLE). Scalp electroencephalograms (EEGs) were taken according to International 10-20 System with 25 channels including subtemporal electrodes (F9/F10, T9/T10, P9/P10). Sampling rate was 400 Hz and filter set was 1.6 to 30 Hz. We obtained current-source densities (CSDs) of the peak points of interictal spikes using low resolution brain electromagnetic tomography (LORETA). Results: In the first patient, the schizencephalic lesions were on the parietal and perisylvian area of the right cerebral hemisphere. Interictal spikes were observed at P10 elctrode, and CSDs of them were on the temporoparietal cortex of the same hemisphere, and midline cortices of the parietal areas. In the second patient, the schizencephalic lesions were on the parietal areas of the right hemisphere, and lissencephlay was seen in the parietal area of the contralateral hemisphere. Interictal spikes were at F10 electrode, and CSDs of them were on the temporal and the parietal areas of the right hemisphere, and midline cortices of the frontal and occipital areas. In the third patient, the schizencephalic lesions were on the temporal areas of both hemispheres. Interictal spikes were at T7 and T10 electrode. Current source for T7 spikes were distributed on the temporal area of the left hemisphere. Those for T10 spikes were on the temporal area of the right hemisphere and the midline cortices of the frontal area. Conclusions: Our results show that schizencephaly may have both of intrinsic and extrinsic epileptogenicity. The current-source distributions of epileptic discharges in schizencephalic patients indicated that epileptic focus could be localized outside the lesions. In TLE with schizencephaly, the temporal cortex of the same hemisphere with the lesions which is not structurally abnormal may be the source of epileptogenicity.