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Abstracts

Widespread Reduction of HFO After Radio Frequency Thermocoagulation Extending Beyond Anatomical Boundaries to Functionally Connected Areas

Abstract number : 2.132
Submission category : 4. Clinical Epilepsy / 4C. Clinical Treatments
Year : 2022
Submission ID : 2204905
Source : www.aesnet.org
Presentation date : 12/4/2022 12:00:00 PM
Published date : Nov 22, 2022, 05:27 AM

Authors :
Daniel Lachner-Piza, Dr.-Ing. – Cumming School of Medicine, Department of Pediatrics , University of Calgary; Jonas Bruder, Dr. med. – Department of Neuropediatrics and Muscular Disease, Medical Center–University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany; Jan Schönberger, Dr. med. – Epilepsy Center, Medical Center–University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany; Philippe Kahane, MD-PhD – Univ. Grenoble Alpes, CHU Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, 38000 Grenoble, France; Olivier David, PhD – Univ. Grenoble Alpes, CHU Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, 38000 Grenoble, France; Andreas Schulze-Bonhage, Prof. Dr. – Epilepsy Center, Medical Center–University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany; Julia Jacobs, Prof. Dr. – Alberta Children's Hospital Research Institute & Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, AB, Canada

Rationale: Radio frequency thermocoagulation (RFTC) induces very focal lesions and aims to ablate seizure onset areas and reduce the seizure frequency in epileptic patients. RFTC can be performed via the same electrodes used to record the intracranial electroencephalogram (iEEG). We analyse the effects of RFTC on the activity of three EEG biomarkers of epilepsy: interictal epileptic spikes (IES); high-frequency oscillations (HFO) as a more specific but not exclusively epileptic biomarker; iesHFO as an even more epilepsy-specific biomarker conformed by HFO spatially and temporally coincident with IES. We aim to assess the effects of RFTC beyond the direct anatomical structure and hypothesize that a reduction of epilepsy biomarkers can be seen beyond the focal lesion in patients profiting from the procedure.

Methods: Our analysis is based on the pre- and post-RFTC biomarker activity from 21 patients. The biomarkers are detected using validated automatic detectors. We analyse the extent of the RFTC effects by measuring changes in biomarker occurrence and power. We considered six different brain zones varying in their anatomical and electrophysiologic connectivity to the thermocoagulation site: (1) rftcSite-the RFTC site itself; (2) rftcConnected-zones with a high electrophysiologic connectivity to rftcSite; (3) highEI-zones with a high epileptogenicity index (i.e., ictal networks); (4) rftcStructure-zones within the same anatomical brain structure as rftcSite; (5) rftcLobe-zones within the same brain lobe as rftcSite; and (6) rftcHemisphere-zones within the same brain hemisphere as rftcSite. The electrophysiologic connectivity between zones was determined by the correlation of their EEG at different frequency bands. The anatomical connectivity between zones was determined by analysing the location of the EEG channels in the MRI.

Results: The iesHFO showed a better correlation than HFO and IES with the brain zones anatomically and electrophysiologically closest to the rftcSite (p < 0.05). The iesHFO occurrence rate and power decreased after RFTC at the rftcSite (82% and 83%), rftcConnected (40% and 29%) and rftcStructure (39% and 25%) zones (p < 0.01). In patients without post-RFTC seizure improvement, the iesHFO activity decreased only in the rftcSite and highEI areas (p < 0.01). In patients showing post-RFTC seizure improvement, the iesHFO activity decreased in the rftcSite, rftcStructure and rftcConnected areas (p < 0.01).
Clinical Epilepsy