Localizing Epileptic Focus of Patients with Epilepsy Using Post-Ictal Scalp EEG

Abstract

Localization of the epileptic focus is crucial for epilepsy surgery. Pre-ictal EEG and interictal epileptic discharges are commonly used to localize the focus. Post-ictal scalp EEG may provide useful information for localizing the epileptic focus. This study proposed a non-invasive procedure to localize the epileptic focus via the EEG source imaging (ESI) and epileptic network analysis. Scalp EEG from two patients with drug-resistant epilepsy were used, and two segments of post-ictal EEG were analyzed. The sLORETA algorithm was applied to obtain signals in source space using the patient specific head model. Then we extracted the representative source signals of each brain area by singular value decomposition (SVD). The epileptic networks of different frequency bands in the source space were constructed by Granger causality analysis. The results showed that the regions identified by in-degree feature of low-frequency post-ictal epileptic network were concordant with surgical resected areas. The preliminary result indicates that post-ictal epileptic network in low frequency may potentially be used to identify the ictal focus for surgical planning.