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Article

Validating EEG, MEG and Combined MEG and EEG Beamforming for an Estimation of the Epileptogenic Zone in Focal Cortical Dysplasia

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Institute for Biomagnetism and Biosignalanalysis, University of Münster, 48149 Münster, Germany
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Computing Sciences, Faculty of Information Technology and Communication Sciences, Tampere University, 33014 Tampere, Finland
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School of Electrical and Computer Engineering, Technical University of Crete, 73100 Chania, Greece
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Ruhr-Epileptology, Department of Neurology, University Hospital Knappschaftskrankenhaus, Ruhr-University, 44892 Bochum, Germany
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Department of Neurosurgery, University Hospital Knappschaftskrankenhaus, Ruhr-University, 44892 Bochum, Germany
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Department of Neurosurgery, University Hospital Erlangen, 91054 Erlangen, Germany
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Department of Neurosurgery, University Hospital Halle (Saale), 06097 Halle, Germany
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Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, 48149 Münster, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Giovanni Pellegrino
Brain Sci. 2022, 12(1), 114; https://doi.org/10.3390/brainsci12010114
Received: 2 December 2021 / Revised: 4 January 2022 / Accepted: 6 January 2022 / Published: 14 January 2022
MEG and EEG source analysis is frequently used for the presurgical evaluation of pharmacoresistant epilepsy patients. The source localization of the epileptogenic zone depends, among other aspects, on the selected inverse and forward approaches and their respective parameter choices. In this validation study, we compare the standard dipole scanning method with two beamformer approaches for the inverse problem, and we investigate the influence of the covariance estimation method and the strength of regularization on the localization performance for EEG, MEG, and combined EEG and MEG. For forward modelling, we investigate the difference between calibrated six-compartment and standard three-compartment head modelling. In a retrospective study, two patients with focal epilepsy due to focal cortical dysplasia type IIb and seizure freedom following lesionectomy or radiofrequency-guided thermocoagulation (RFTC) used the distance of the localization of interictal epileptic spikes to the resection cavity resp. RFTC lesion as reference for good localization. We found that beamformer localization can be sensitive to the choice of the regularization parameter, which has to be individually optimized. Estimation of the covariance matrix with averaged spike data yielded more robust results across the modalities. MEG was the dominant modality and provided a good localization in one case, while it was EEG for the other. When combining the modalities, the good results of the dominant modality were mostly not spoiled by the weaker modality. For appropriate regularization parameter choices, the beamformer localized better than the standard dipole scan. Compared to the importance of an appropriate regularization, the sensitivity of the localization to the head modelling was smaller, due to similar skull conductivity modelling and the fixed source space without orientation constraint. View Full-Text
Keywords: epilepsy; beamformer; MEG; EEG; regularization; validation; source analysis epilepsy; beamformer; MEG; EEG; regularization; validation; source analysis
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MDPI and ACS Style

Neugebauer, F.; Antonakakis, M.; Unnwongse, K.; Parpaley, Y.; Wellmer, J.; Rampp, S.; Wolters, C.H. Validating EEG, MEG and Combined MEG and EEG Beamforming for an Estimation of the Epileptogenic Zone in Focal Cortical Dysplasia. Brain Sci. 2022, 12, 114. https://doi.org/10.3390/brainsci12010114

AMA Style

Neugebauer F, Antonakakis M, Unnwongse K, Parpaley Y, Wellmer J, Rampp S, Wolters CH. Validating EEG, MEG and Combined MEG and EEG Beamforming for an Estimation of the Epileptogenic Zone in Focal Cortical Dysplasia. Brain Sciences. 2022; 12(1):114. https://doi.org/10.3390/brainsci12010114

Chicago/Turabian Style

Neugebauer, Frank, Marios Antonakakis, Kanjana Unnwongse, Yaroslav Parpaley, Jörg Wellmer, Stefan Rampp, and Carsten H. Wolters. 2022. "Validating EEG, MEG and Combined MEG and EEG Beamforming for an Estimation of the Epileptogenic Zone in Focal Cortical Dysplasia" Brain Sciences 12, no. 1: 114. https://doi.org/10.3390/brainsci12010114

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