Abstracts

Rationale: To investigate whether advanced dynamic statistical parametric mapping (AdSPM) for MEG could demonstrate epileptogenic zone of MRI-negative epilepsy. Methods: We analyzed four children (age 12±2.7 y.o) with intractable focal epilepsy with negative finding in 3T MRI. Children underwent scalp video EEG, MEG, intracranial video-EEG (IVEEG) and resective surgery. Advanced dynamic statistical parametric mapping (AdSPM), a noble approach for MEG to identify epileptogenic zone of bottom of sulcus dysplasia (Nakajima et al., 2018). In this study, we investigated the potential of identifying MRI-negative epileptogenic zone by using AdSPM. In AdSPM, we analyzed each 100 msec segment around MEG dipole estimated in single moving dipole (SMD) method. The area with highest threshold was defined as location of spike source. We compared spatial congruence between seizure onset zone and 1) spike source in AdSPM and 2) MEG cluster in SMD method. We defined “Hit” when MEG cluster/spike source was localized within seizure onset zone in IVEEG. We defined “No hit” when MEG cluster/spike source was remote from seizure onset zone in IVEEG. Results: Three of them had depth electrodes in the location of AdSPM spike source and the other one child had subdural grid on the location of spike source. Spike volume hit seizure onset zone in all four children (100%) whereas MEG cluster hit seizure onset zone in one of the four children (25%).All of the children underwent resective surgery. Spike sources were in the resection areas in two of four children. In these two children, one child who achieved seizure freedom had FCD type IIB. The other one child who had Engel IV seizure outcome showed oligodendrogliosis and the most populated in the region of spike source.Spike volume were not resected in the other two children. Both of them had Engel IV seizure outcome and their pathological result from the resected specimens were normal.   Conclusions: AdSPM had a potential of identifying seizure onset zone in the MRI-negative epilepsy. For successful surgery, integration analysis of SMD method and placement of subdural grid electrodes should be required to demonstrate entire epileptogenic zone. Funding: No funding