On-Scalp Magnetoencephalography Based On Optically Pumped Magnetometers Can Detect Mesial Temporal Lobe Epileptiform Discharges

The validation of on-scalp magnetoencephalography based on optically pumped magnetometers (OPM-MEG) for clinical applications requires the assessment of the spatial concordance between reconstructed neural sources and intracranial data recorded simultaneously. We here report unprecedented data from an epileptic woman suffering from refractory focal epilepsy who underwent a 10-min simultaneous whole-scalp-covering video-OPM-MEG (118 channels) and stereo-electroencephalography (SEEG) recordings. The most active irritative zone involved the right amygdala despite multiple seizure-onset zones. The multimodal recording allowed to detect and localize 31 simultaneous interictal epileptiform discharges (IEDs) in OPM-MEG signals among the 52 IEDs detected in SEEG signals, and corresponded to the IEDs with the highest amplitude in SEEG. These IEDs were located at the right amygdala using both modalities, with sources distant from 14.1mm. This simultaneous recording demonstrates the ability of OPM-MEG to detect and localize IEDs from a deep mesiotemporal structure such as the amygdala with a localization value and an IED detection rate in line with previous simultaneous cryogenic MEG and SEEG studies. It paves the way for further on-scalp OPM-MEG recordings in patients with implanted materials and strengthens the potential of this growing technology for future clinical and research applications in patients with brain disorders. ### Competing Interest Statement N.H. and M.B. holds founding equity in Cerca Magnetics Limited, a spin-out company whose aim is to commercialize aspects of OPM-MEG technology. The remaining authors have no conflicts of interest. ### Funding Statement O.F. is supported by the Fonds pour la formation a la recherche dans l industrie et l agriculture (FRIA, Fonds de la Recherche Scientifique (FRS-FNRS), Brussels, Belgium). P.C. is supported by the Fonds Erasme (Convention Alzheimer, Brussels, Belgium). X.D.T. is Clinical Researcher at the FRS-FNRS. The other authors received no additional funding. The OPM-MEG project at the Hopital Universitaire de Bruxelles and Universite libre de Bruxelles is financially supported by the Fonds Erasme (Projet de Recherche Clinique et Convention Les Voies du Savoir 2) and by the FRS-FNRS (Credit de Recherche: J.0043.20F, Credit Equipement: U.N013.21F). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Institutional Ethics Committee approved the study (Hopital Erasme, P2020/664). The patient gave written informed consent. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data are available upon reasonable request to the corresponding author and after approval of institutional (Hopital universitaire de Bruxelles & Universite libre de Bruxelles) authorities.