Visualization of ictal networks using gamma oscillation regularity correlation analysis in focal motor epilepsy: Illustrative cases.

Background: Focal motor epilepsy is difficult to localize within the epileptogenic zone because ictal activity quickly spreads to the motor cortex through ictal networks. We previously reported the usefulness of gamma oscillation (30-70 Hz) regularity (GOR) correlation analysis using interictal electrocorticographic (ECoG) data to depict epileptogenic networks. We conducted GOR correlation analysis using ictal ECoG data to visualize the ictal networks originating from the epileptogenic zone in two cases - a 26-year-old woman with negative motor seizures and a 53-year-old man with supplementary motor area (SMA) seizures. Case Description: In both cases, we captured several habitual seizures during monitoring after subdural electrode implantation and performed GOR correlation analysis using ictal ECoG data. A significantly high GOR suggestive of epileptogenicity was identified in the SMA ipsilateral to the lesions, which were connected to the motor cortex through supposed ictal networks. We resected the high GOR locations in the SMA and the patients' previously identified tumors were removed. The patients were seizure-free without any neurological deficits after surgery. Conclusion: The GOR correlation analysis using ictal ECoG data could be a powerful tool for visualizing ictal networks in focal motor epilepsy.