Interictal High Gamma Oscillation Regularity as a Marker for Presurgical Epileptogenic Zone Localization
Yosuke Sato1, Yoshihito Tsuji2, Madoka Yamazaki3
1Department of Neurosurgery, Showa University School of Medicine, Tokyo, Japan.
Background:
To ensure that epilepsy surgery is effective, accurate presurgical localization of the epileptogenic zone is essential. Our previous reports demonstrated that interictal high gamma oscillation (30-70 Hz) regularity (GOR) on intracranial electroencephalograms is related to epileptogenicity.
Objective:
To examine whether preoperative GOR analysis with interictal high-density electroencephalography (HD-EEG) improves the accuracy of epileptogenic focus localization and enhances postoperative seizure control.
Methods:
We calculated GOR from 20 seconds of HD-EEG data for 21 patients with refractory focal epilepsy (4 with nonlesional temporal lobe epilepsy) scheduled for epilepsy surgery. Low-resolution brain electromagnetic tomography was used to analyze the high GOR source. To validate our findings, we made comparisons with other conventional localization methods and postoperative seizure outcomes.
Results:
In all patients, the areas of interictal high GOR were identified and resected. All patients were seizure-free after the operation. The concordance between the results of interictal high GOR on HD-EEG and those of source estimation of interictal discharge was fully overlapping in 10 cases, partially overlapping in 8 cases, and discordant in 3 cases. The concordance between the results of interictal high GOR on HD-EEG and those of interictal 123 I-iomazenil single-photon emission computed tomography was fully overlapping in 8 cases, partially overlapping in 11 cases, and discordant in 2 cases. In 4 patients with nonlesional temporal lobe epilepsy, the interictal high GOR on HD-EEG was useful in confirming the epileptogenic zone.
Conclusion:
The interictal high GOR on HD-EEG is an excellent marker for presurgical epileptogenic zone localization.
