Assessment of the utility of optically pumped magnetometer magnetoencephalography in preoperative localization of refractory epilepsy: A prospective study

Objective: Precise localization of the epileptogenic zone (EZ) is crucial for epilepsy surgery success. Optically pumped magnetometer magnetoencephalography (OPM-MEG) is a promising noninvasive technique requiring rigorous clinical validation. Methods: In this prospective diagnostic study, 68 patients with refractory epilepsy underwent 90-min interictal OPM-MEG. Dipoles were fitted to interictal epileptiform discharges for localization. The primary objective was to evaluate the spatial concordance between OPM-MEG and the EZ defined by intracranial electroencephalography (iEEG; stereo-EEG or electrocorticography), assessed at the sublobar level using Gwet AC1. The secondary objective was to evaluate the diagnostic value of OPM-MEG for surgical outcome. This analysis included 51 patients who underwent curative intervention (resection or thermocoagulation). The reference standard was a composite of the treated brain region and seizure freedom (International League Against Epilepsy [ILAE] class 1 or Engel class I) at ≥12-month follow-up, from which sensitivity, specificity, and diagnostic odds ratio (OR) were calculated. Results: OPM-MEG showed almost perfect agreement with iEEG-based EZ localization overall (AC1 =.885, concordance rate = 90.0%), with substantial agreement in temporal (80.1%, AC1 =.723) and almost perfect agreement in extratemporal regions (92.0%, AC1 =.926). The Euclidean centroid distance between OPM-MEG and iEEG localizations was significantly shorter in concordant versus discordant cases. In the assessment of diagnostic value, OPM-MEG demonstrated a sensitivity of 85.7% and specificity of 65.2% (OR = 11.25) under ILAE criteria, and a sensitivity of 73.0% and specificity of 64.3% (OR = 4.86) under Engel criteria. Significance: OPM-MEG demonstrates high concordance with iEEG for EZ localization and provides robust diagnostic value for predicting postoperative seizure freedom, supporting its utility in the presurgical evaluation of refractory epilepsy.