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Abstracts

Investigation of Epileptogenic and Non-epileptogenic Brain Tissue Reaction to Direct Electrical Brain Stimulation

Abstract number : 3.168
Submission category : 3. Neurophysiology / 3G. Computational Analysis & Modeling of EEG
Year : 2023
Submission ID : 957
Source : www.aesnet.org
Presentation date : 12/4/2023 12:00:00 AM
Published date :

Authors :
Presenting Author: Zuzana Formankova, Ing. – International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic

Jan Cimbalnik, PhD – International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic; Petr Klimes, PhD – International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic; Vojtech Travnicek, Ing – International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic; Martin Pail, PhD – 1 St Department of Neurology, Faculty of Medicine, Masaryk University, Brno, Czech Republic; Irena Dolezalova, PhD – 1 St Department of Neurology, Faculty of Medicine, Masaryk University, Brno, Czech Republic; Milan Brazdil, PhD – 1 St Department of Neurology, Faculty of Medicine, Masaryk University, Brno, Czech Republic

Rationale: Surgical resection of seizure generating tissue offers pharmacoresistant epilepsy patients a significant chance at achieving seizure freedom. Precise localization of epileptogenic tissue is crucial for successful surgery. In this study we analyzed the reaction of brain tissue to electrical stimulation and evaluated whether pathological tissue reacts differently to stimulation compared to healthy tissue in terms of interictal electrophysiological (EEG) biomarkers.

Methods: We analyzed eleven patients who underwent intracranial electrode implantation as part of their epilepsy surgery evaluation. Exploratory electrical stimulation was performed to map the functional areas of the implanted tissue as a part of their presurgical evaluation. We calculated EEG features represented by high frequency oscillations, interictal spikes, power in frequency bands and functional connectivity (relative entropy and linear correlation) in resting state and during electrical stimulation epoch. First, we evaluated whether there is a difference between resting state and stimulation period within and outside of the seizure onset zone. Second, we performed analysis of the same areas one second before and after the stimulation. Additionally, we explored whether the site of the stimulation has any effect on the change of EEG features.

Results: The comparison between resting state and electrical stimulation epochs did not reveal a distinct effect, as the difference between EEG features was statistically significant both within and outside the seizure onset zone. Analysis of periods before and after the stimulation showed on average across all stimulation locations a significant difference in relative entropy outside the seizure onset zone (p=2.959e-10) and an insignificant difference in relative entropy within the seizure onset zone (p=1). Examination of individual stimuli indicated a relationship between the change in EEG features and the stimulated location where stimulation of certain brain areas resulted in greater differences between SOZ and non-SOZ EEG features.

Conclusions: We analyzed the impact of electrical stimulation on EEG features in pathological and healthy tissue. Electrical stimulation can potentially assist in objective delineation of epileptogenic tissue without the need for provoking seizures which could lead to better surgical outcomes and improved well being of the patients. Further research is needed to investigate the influence of the stimulation site and parameters on the EEG features.

Funding: None

Neurophysiology