ИСТИНА

Background and Purpose/Objectives: Although the goal of presurgical MEG evaluation is accepted to be localization of the ictal-onset zone,the reports on ictal MEG recordings are extremely rare in the literature. Here, we investigated seizure-onset patterns recorded by MEG with regard to its prognostic value for favorable surgical outcome. Methods We analyzed seizure onset patterns in presurgical MEG recordings of twelve patients within a broad age range 0.5 40 years with temporal and extratemporal intractable partial seizures who subsequently underwent resective surgery with favorable outcomes (Engel I, II). For all patients the site of seizure onset could not be confidently predicted from the long-term video-EEG or other evidence (MR imaging, seizure semiology), and their further examination with interictal and ictal MEG contributed to a planning of the resective surgery. The MEG preictal patterns were defined according to the criteria accepted for intracranial recordings. The sources localization was applied using multi-dipole modeling. Source localization results were retrospectively compared with the site of the resected cortical area. Results The concordance of the MEG-defined putative seizure-onset zone (SOZ) with the cortical area, whose resection led to favorable outcomes was observed in nine out of 12 patients. In two patients with mistakenly identified SOZ , it was located in temporal lobe, in third preictal pattern wasn't identified. Conclusion The source localization for preictal MEG pattern proved to be a useful tool for presurgical evaluation of SOZ, although temporal sources may be underestimated. The results provide an argument in favour of incorporating ictal MEG into the process of presurgical evaluation.