Evaluating the Impact of Electrical Stimulation on Electrophysiological Biomarkers for Epileptogenic Tissue Localization
Abstract number :
3.292
Submission category :
3. Neurophysiology / 3G. Computational Analysis & Modeling of EEG
Year :
2024
Submission ID :
112
Source :
www.aesnet.org
Presentation date :
12/9/2024 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 – Institute of Scientific Instruments, The Czech Academy of Sciences, Brno, Czech Republic
Vojtech Travnicek, Ing – International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
Martin Pail, MD, PhD – Institute of Scientific Instruments of the CAS, Brno, Czech Republic
Irena Dolezalova, doc – 1 St Department of Neurology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
Milan Brázdil, MD, PhD – 1st Department of Neurology, Faculty of Medicine, Masaryk University and St. Anne´s University Hospital, Brno, Czech Republic – member of ERN EpiCARE
Rationale: Surgical resection of seizure–inducing tissue provides a significant opportunity for pharmacoresistant epilepsy patients to achieve seizure freedom. Precise localization of epileptogenic tissue is crucial for surgical success. In this study we aim to determine whether interictal electrophysiological responses to electrical stimulation can differentiate between pathological and healthy brain tissue, potentially providing a non–seizure–based method for identifying epileptogenic zones.
Methods: We analyzed 10 patients who underwent intracranial electrode implantation as part of their epilepsy surgery evaluation. During the presurgical evaluation, exploratory electrical stimulation was performed to map functional areas of the implanted tissue. Interictal EEG biomarkers, including functional connectivity (measured by relative entropy, sample entropy, and linear correlation) and power across frequency bands, were computed during the electrical stimulation epoch. The analysis focused on the effects of individual stimuli on EEG biomarkers within and outside the seizure onset zone (SOZ). To assess the impact of stimulation, we calculated the difference in biomarkers between 1–second segments before and after stimulation. The discriminative potential of EEG biomarkers for epileptic versus non–epileptic tissue was evaluated using the Precision–Recall curve and its area under the curve (AUPRC) for differences in biomarker values before and after stimulation.
Results: Analysis of individual stimuli revealed an association between changes in EEG biomarkers and the stimulated areas. In patients with Engel–IA post–surgical outcomes (n=4), the AUPRC values for contacts in the SOZ were 0.235 ± 0.210 (mean ± std) for linear correlation, 0.167 ± 0.228 for power, 0.129 ± 0.144 for relative entropy, and 0.084 ± 0.076 for sample entropy. For contacts outside the SOZ, the mean AUPRC values were 0.016 ± 0.011 for linear correlation, 0.030 ± 0.014 for power, 0.018 ± 0.007 for relative entropy, and 0.018 ± 0.015 for sample entropy. The AUPRC of the random classifier was subtracted from the resulting AUPRC values for each patient (0.124 ± 0.094).
Conclusions: We analyzed the impact of electrical stimulation on EEG biomarkers in pathological and healthy tissue. Our findings suggest that electrical stimulation can potentially assist in the objective delineation of epileptogenic tissue without the need for provoking seizures, which could improve surgical outcomes and patient well–being. However, further research is necessary to investigate the effect of stimulation parameters on EEG biomarkers and to validate our findings in larger patient cohorts.
Funding: Supported by Czech Science Foundation, project no. 22-28594K
Neurophysiology