Epileptic hub in MRI-negative focal cortical dysplasia using advanced dynamic statistical parametric mapping and magnetoencephalography

Objective Localization of epileptogenic MRI-negative focal cortical dysplasia at the bottom of the sulcus (FCDB) is challenging. This study evaluated the utility of advanced dynamic statistical parametric mapping (AdSPM), a magnetoencephalography (MEG)-based source analysis method, for detecting epileptic MRI-negative FCDB. Methods We retrospectively analyzed MEG data using AdSPM in four patients with pathologically confirmed MRI-negative FCDB, whose seizure onset zones were identified by intracranial video-EEG (IVEEG). The most active area identified by the AdSPM was designated as the AdSPM spike source. We compared the spatial concordance of the AdSPM spike source, single moving dipole (SMD) findings, and 18 F-FDG PET/MRI findings with seizure onset and resection areas. An additional MRI-negative patient without seizures during IVEEG monitoring was analyzed separately for concordance with the resection area. Results The AdSPM spike source localized to the seizure onset zone and was included in the resection area in all four patients with an identified seizure onset zone. SMD findings were mislocalized relative to the seizure onset zone and resection area. PET/MRI was concordant with the seizure onset zone in one of three evaluable patients and with the resection area in three of four patients. In the patient without seizures during IVEEG, AdSPM and PET/MRI were concordant with the resection area; however, the SMD findings were mislocalized. Conclusions AdSPM noninvasively and neurophysiologically localizes epileptic MRI-negative FCDB and may provide useful information for presurgical evaluations. Significance This is the first diagnostic application of AdSPM for MRI-negative FCDB.