Abstracts

Rationale: To evaluate the performance of automated ictal EEG Source Imaging (ESI) for localization of epileptogenic zone in the patients with extratemporal lobe epilepsy (ETLE). Methods: The analysis was done in 17 patients (8 cortectomies, 5 disconnections, 4 lesionectomies) of the Epilepsy Database Unit (St. Luc Hospital, Brussels, Belgium). All patients had ETLE operation and 11 (65%) of them were seizure-free at 1 year follow-up. Sixty-seven seizures were analyzed using a semi-automated method. The electrographic seizure onsets were marked by an expert electrophysiologist in the EEG with the following inclusion criteria: (1) rhythmical discharges in the canonical frequency bands (2) rhythmical spiking activity, (3) fast paroxysmal low voltage activity. EEG signals were recorded with 19 electrodes of 10-20 system in 13 patients and Ft9/10 and Tp9/10 were added for recording of 4 other patients. For each seizure the band of rhythmic discharges was also indicated.An epoch of 1s before to 3s after the marker was segmented. EEG source localization was performed at each time point to estimate the activity of 50 sub-lobes. The sub-lobe with the highest activity in the provided frequency band was identified as seizure onset zone (SOZ). All results were compared to the resection at sub-lobar level given the surgical outcome. Results: The analysis of 67 seizures led to sensitivity, specificity and accuracy of 57.45%, 75% and 62.69%, respectively. At patient level, we localized the SOZ correctly for all seizures in 3/11 and for more than half of the seizures in 7/11 patients. Conclusions: The results indicate that ictal EEG source localization has potential to be used during the presurgical evaluation, especially in challenging extra-temporal lobe cases. Funding: No funding