Abstracts

Evaluating Cortical Excitatory and Inhibitory Activity Through Interictal Intracranial Electroencephalography: Insights from Gamma Oscillation Regularity and Cortico-cortical Evoked Potentials

Abstract number : 3.291
Submission category : 3. Neurophysiology / 3G. Computational Analysis & Modeling of EEG
Year : 2024
Submission ID : 207
Source : www.aesnet.org
Presentation date : 12/9/2024 12:00:00 AM
Published date :

Authors :
Presenting Author: Keisuke Nagata, MD, PhD – the University of Tokyo

Naoto Kunii, MD, PhD – Jichi Medical University
Ako Matsuhashi, MD – the University of Tokyo
Toshiya Aono, MD – the University of Tokyo
Shigeta Fujitani, MD, PhD – the University of Tokyo
Seijiro Shimada, MD, PhD – the University of Tokyo
Nobuhito Saito, MD, PhD – the University of Tokyo

Rationale: Excitatory-inhibitory balance in epileptic patients has been focused on as an underlying mechanism for epileptic seizure generation. Gamma oscillation regularity (GOR) indicates the synchronization of inhibitory interneurons, the enhancement of which is quantified as a decrease in multiscale entropy (MSE). On the other hand, the reactivity of cortico-cortical evoked potentials (CCEPs) in the vicinity of the stimulus site has been reported to reflect local cortical excitability. By combining two parameters, we aimed to visualize cortical inhibitory and excitatory activity and utilize them to predict epileptogenic regions.


Methods: Five patients with mesial temporal lobe epilepsy who underwent intracranial electrode implantation participated in this study. GOR was quantified using MSE derived from long-term video electrocorticogram recordings, while CCEP reactivity in the vicinity of the stimulation site was measured by cortical electrical stimulation. These parameters were compared on an electrode-and-electrode basis and spatially visualized on a brain surface as indicators of cortical inhibitory and excitatory activity. Written informed consent was obtained from all participants preoperatively. This study was conducted in accordance with the Declaration of Helsinki and was approved by the Institutional Review Board of the University of Tokyo (approval number 1797).


Results: Elevated GOR and CCEP reactivity, indicative of enhanced inhibitory and excitatory activity, were observed in the epileptogenic regions. An increase in CCEP reactivity was observed in the localized region around the seizure onset area, accompanied by a decrease in MSE in the surrounding region, indicative of increased GOR. These parameters independently predicted the epileptogenic zone with high specificity, while their combination predicted the epileptogenic zone with increased specificity.


Conclusions: In this study, we demonstrated that GOR and CCEP reactivity can quantitatively visualize the distribution of cortical inhibitory and excitatory activity as well as the relationship between the two parameters. By combining them, they are expected to serve as biomarkers for localizing epileptogenic zone from interictal intracranial electroencephalogram.


Funding: This work was supported in part by a Grants-in-Aid (No. 19K09452) for Scientific Research (C) from the Japan Society for the Promotion of Science.


Neurophysiology