title: Seizure Onset Zone Localization from Ictal High-Density EEG in Refractory Focal Epilepsy.
abstract: Epilepsy surgery is the most efficient treatment option for patients with refractory epilepsy. Before surgery, it is of utmost importance to accurately delineate the seizure onset zone (SOZ). Non-invasive EEG is the most used neuroimaging technique to diagnose epilepsy, but it is hard to localize the SOZ from EEG due to its low spatial resolution and because epilepsy is a network disease, with several brain regions becoming active during a seizure. In this work, we propose and validate an approach based on EEG source imaging (ESI) combined with functional connectivity analysis to overcome these problems. We considered both simulations and real data of patients. Ictal epochs of 204-channel EEG and subsets down to 32 channels were analyzed. ESI was done using realistic head models and LORETA was used as inverse technique. The connectivity pattern between the reconstructed sources was calculated, and the source with the highest number of outgoing connections was selected as SOZ. We compared this algorithm with a more straightforward approach, i.e. selecting the source with the highest power after ESI as the SOZ. We found that functional connectivity analysis estimated the SOZ consistently closer to the simulated EZ/RZ than localization based on maximal power. Performance, however, decreased when 128 electrodes or less were used, especially in the realistic data. The results show the added value of functional connectivity analysis for SOZ localization, when the EEG is obtained with a high-density setup. Next to this, the method can potentially be used as objective tool in clinical settings.
authors.affiliation: MEDISIP, Department of Electronics and Information Systems, Ghent University, De Pintelaan 185, Building B Entrance 36, 9000, Ghent, Belgium. Willeke.Staljanssens@UGent.be.|iMinds Medical IT, Ghent, Belgium. Willeke.Staljanssens@UGent.be.
authors.forename: Willeke
authors.initials: W
authors.lastname: Staljanssens
authors.affiliation: MEDISIP, Department of Electronics and Information Systems, Ghent University, De Pintelaan 185, Building B Entrance 36, 9000, Ghent, Belgium.|iMinds Medical IT, Ghent, Belgium.
authors.forename: Gregor
authors.initials: G
authors.lastname: Strobbe
authors.affiliation: MEDISIP, Department of Electronics and Information Systems, Ghent University, De Pintelaan 185, Building B Entrance 36, 9000, Ghent, Belgium.|iMinds Medical IT, Ghent, Belgium.
authors.forename: Roel Van
authors.initials: RV
authors.lastname: Holen
authors.affiliation: Functional Brain Mapping Laboratory, Department of Fundamental Neurosciences, University of Geneva, Campus Biotech, Geneva, Switzerland.
authors.forename: Gwénaël
authors.initials: G
authors.lastname: Birot
authors.affiliation: Functional Brain Mapping Laboratory, Department of Fundamental Neurosciences, University of Geneva, Campus Biotech, Geneva, Switzerland.|EEG and Epilepsy Unit, Neurology Department, University Hospitals and Faculty of Medicine of Geneva, Geneva, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Gschwind
authors.affiliation: EEG and Epilepsy Unit, Neurology Department, University Hospitals and Faculty of Medicine of Geneva, Geneva, Switzerland.
authors.forename: Margitta
authors.initials: M
authors.lastname: Seeck
authors.affiliation: MEDISIP, Department of Electronics and Information Systems, Ghent University, De Pintelaan 185, Building B Entrance 36, 9000, Ghent, Belgium.|iMinds Medical IT, Ghent, Belgium.
authors.forename: Stefaan
authors.initials: S
authors.lastname: Vandenberghe
authors.affiliation: Functional Brain Mapping Laboratory, Department of Fundamental Neurosciences, University of Geneva, Campus Biotech, Geneva, Switzerland.|EEG and Epilepsy Unit, Neurology Department, University Hospitals and Faculty of Medicine of Geneva, Geneva, Switzerland.
authors.forename: Serge
authors.initials: S
authors.lastname: Vulliémoz
authors.affiliation: MEDISIP, Department of Electronics and Information Systems, Ghent University, De Pintelaan 185, Building B Entrance 36, 9000, Ghent, Belgium.|iMinds Medical IT, Ghent, Belgium.|Functional Brain Mapping Laboratory, Department of Fundamental Neurosciences, University of Geneva, Campus Biotech, Geneva, Switzerland.
authors.forename: Pieter
authors.initials: P
authors.lastname: van Mierlo
mesh_terms: D000328:Adult; D000465:Algorithms; D001921:Brain / Q000503:physiopathology*; D004566:Electrodes; D004569:Electroencephalography / Q000379:methods; D004828:Epilepsies, Partial / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging; D012640:Seizures / Q000503:physiopathology*
keywords: EEG source imaging (ESI); Functional connectivity; Granger causality; High-density electroencephalogram (hd-EEG); Refractory epilepsy