Magnetic source imaging (MSI) in children with neocortical epilepsy: Surgical outcome association with 3D post-resection analysis

- We examine whether spike dipole clusters were located within the resection volume using 3D analysis.
- We examine MSI accuracy measures against post-operative seizure outcome.
- MSI successfully localized the perilesional epileptogenic zone in cases with localized MRI lesion.
- Cases with multiple spike dipole clusters required delineation of the epileptogenic zone by ICEEG.
- Even if MEG localizes spikes to a single focal region, confirmation with ICEEG is recommended in cases with non-lesional MRI.

SummaryObjectiveTo investigate the validity of magnetic source imaging (MSI) to localize seizure-onset zone using 3D analysis of pre-operative MSI source imaging coregistered to post-resection MRI following neocortical epilepsy surgery.MethodsTwenty-two children who had MSI and epilepsy surgery were studied (median age = 11 years, 1 year 2 months-22 years). Only seven (31.8%) had localized lesions on pre-operative conventional brain MRIs. Sixteen (72.7%) underwent intracranial EEG monitoring. Mean post-operative follow-up was 4.7 years (1 year 3 months-8 years 2 months). Fifteen patients (68%) were seizure-free. MEG spike dipole sources were superimposed onto post-operative MRIs. The number and proportion of spike dipoles within resection volume were calculated and compared between seizure free and non-free groups.ResultsBoth number of dipole clusters and proportion of dipoles in resection volume were not associated with seizure-free outcome (p > 0.05). In seven cases with MRI lesions, six of these with a ≥70% dipoles within the resection margin were seizure-free, while one with the proportion <70% was not seizure-free. Further, among the 15 cases with non-localized or normal MRI, five with both the proportion <70% and multiple dipoles clusters were post-operatively seizure free.ConclusionNumber and density of clustered spike dipole sources within the surgical resection volume is not associated with postoperative seizure-free outcome. MSI successfully localized the perilesional epileptogenic zone in cases with localized MRI lesions, but not in cases with normal MRI in this study. Even if MEG localizes spikes to a single focal region, confirmation of epilepsy localization with intracranial EEG is still recommended in cases with non-lesional MRI.