Abstracts

Rationale: Accurate presurgical epileptogenic zone localization leads to appropriate treatment strategies and good postoperative outcomes in epilepsy surgery. Although conventional methods of assessment using EEG morphology, frequency, and event-related potentials are undoubtedly useful, it is often difficult to accurately identify the epileptogenic zone using only one of these methods. High gamma oscillation regularity (GOR) is thought to correlate with increased cortical neuron local synchrony and stronger local interneuron connectivity as epileptic activity during the interictal period. Quantification of such highly localized synchronous interneuron activity during the interictal period as high GOR has been shown to accurately detect the epileptogenic zone especially in non-lesional temporal lobe epilepsy.

Methods: In 11 patients with non-lesional temporal lobe epilepsy, GOR were calculated from 20 seconds of interictal scalp EEG data. Low-resolution brain electromagnetic tomography was used to analyze the high GOR source. For validation of GOR findings, comparisons were performed with other conventional localization methods and postoperative seizure outcomes.

Results: In all 11 patients, the hippocampus and parahippocampal gyrus on the side with interictal high GOR were transected. Ten patients were seizure-free and one improved seizure after the operation. The concordance between the results of interictal high GOR on scalp EEG and other conventional localization methods was broadly consistent, but the high GOR was the most localizable.

Conclusions: The interictal high GOR is useful in presurgical epileptogenic zone localization in non-lesional temporal lobe epilepsy.

Funding: JSPS KAKENHI Grant No. JP 20K09356