Abstracts

Rationale: It has been reported that patients with a single MEG spike cluster had better postoperative outcomes compared to patients with multiple clusters. However, the issue of how to determine a genuine source in the multiple MEG spike clusters remains unsolved. Therefore, we aimed to figure out where the focus of epileptic activity would be in a situation of the multiple MEG spike clusters. Methods: Six patients with intractable epilepsy who showed multiple MEG spike clusters were retrospectively investigated. All patients had pathologically proven type Ia FCD with no MRI lesion and discordant multimodal presurgical evaluations, and all of them showed a favorable postoperative outcome. With spontaneous recording of MEG signals, MEG spikes were localized and clustered using a hierarchical clustering method. Then, effective connectivity referring to the causal interaction between distant structures in the brain was applied to the source waveforms extracted from the multiple MEG spike clusters. We adopted a phase-slope index (PSI) method to estimate the direction of information flux between source waveforms. Finally, the information source, i.e., the driver location between multiple clusters could be identified. Results: Through the present study, we found that 5 of 6 FCD patients showed that the information sources, i.e., driver regions between multiple clusters were coincident with the resection area, which was also a quite consistent at different epochs. Conclusions: Our results suggest that the effective connectivity analysis would have a potential value in a presurgical evaluation when multiple MEG spike clusters were found. To the best of our knowledge, this is the first study that evaluated the value of the effective connectivity in discerning a real source in the multiple clusters.