The causal epileptic network identifies the primary epileptogenic zone in Lennox–Gastaut syndrome

PURPOSE Lennox-Gastaut syndrome (LGS) can be successfully treated by resective surgery in patients with a primary epileptogenic zone. This study aimed to identify the primary epileptogenic zone based on the causal epileptic network using direct directed transfer function (dDTF) analysis. METHODS We reviewed the dDTF findings for generalized sharp and wave discharges (GSW) from the preoperative electroencephalography (EEG) of 12 LGS patients (group A) with unilateral focal pathology who were successfully treated with resective surgery. These findings were compared with preoperative dDTF findings for the GSW from 15 LGS patients with bilateral non-resectable pathology (group B) who exhibited persistent bilateral independent diffuse sharp and wave discharges, even after corpus callosotomy. RESULTS The dDTF analysis of the GSW revealed concordant findings of localization or lateralization with the primary epileptogenic zone in 83.3% (10/12 cases) of group A patients and bilateral or multifocal localization in 93.3% (14/15) of group B patients (p<0.01). The regions identified by dDTF analysis were included in the resected areas of all patients in group A, and complete matches of the resected areas without other foci were observed in 7 patients (58.3%) in group A. The region of GSW most frequently identified by dDTF analysis was the frontal area, which was identified in 91.7% (11/12) of group A and in 100% of group B, while extra-frontal areas were identified in 36.1% and 24.5% of groups A and B, respectively. CONCLUSIONS The dDTF analysis of GSW could provide additional information to identify resective surgery candidates for patients with LGS.