Abstracts

Rationale: Precise localization of epileptogenic zones is essential for surgical planning in patents with Lennox-Gastaut syndrome (LGS), which has been generally determined by epileptologists based on visual inspection of EEG, intracranial EEG (iEEG), and diverse neuroimaging modalities. However, accurate localization of epileptogenic zones has not always been possible in LGS patients, which reflects the need for new additional techniques to enhance success rate of the respective epilepsy surgery in LGS patients. Methods: Four pediatric patients with LGS who became seizure-free after the resective epilepsy surgery without cerebral infarctions, progressive underlying metabolic diseases, or chromosomal anomalies were selected. Four other pediatric patients with LGS whose surgical outcomes were not favorable were also selected. iEEGs of these patients prior to the resective surgeries were acquired. We investigated iEEG of LGS patients with successful surgical outcome before the surgery, and performed time delay analysis, directed transfer function (DTF) method, source imaging of high gamma oscillation, and graph theoretical analysis. Results: Both the results of time delay analysis and functional directional connectivity networks among the intracerebral electrodes using DTF method applied to four iEEG data of patients with favorable outcome corresponded well with the surgical resection areas identified using conventional methods. Combined use of these two iEEG analyses resulted in a more accurate estimate of epileptogenic zones than the use of a single method, when compared with patients with unfavorable surgical outcomes. iEEG-based frequency domain source imaging of high gamma oscillation (60-100 Hertz) was applied to LGS patients with favorable outcomes whose iEEG contained some ictal events with distinct high gamma oscillations before seizure onset, and the results coincided with the surgical resection areas. In graph theoretical analysis, among various graph theoretical measurements such as local efficiency, participation coefficient, and eigenvector centrality, only betweenness centrality (BC) showed fair correspondence with surgical resection areas. Conclusions: Time delay analysis, DTF, source imaging of high gamma oscillation, and BC in graph theoretical analysis of iEEG can serve as a new auxiliary tool to localize epileptogenic zones in LGS patients. Funding: There is no funding to declare.