Abstracts

Rationale: MEG utility in children has been thus far limited to small pediatric series with variable results.  To date MEG has been underutilized in children with epilepsy due to lack of experience and availability. The aim of our study was to describe MEG experience (utility, feasibility, and unique contribution) without sedation in a large number pediatric cohort at a tertiary care epilepsy center.  We evaluated the results of interical MEG in combination with simultaneous EEG (MEEG) acquired during MEG study, and compared it to Video EEG (VEEG), MRI, and other supplementary presurgical evaluations. Methods: 411 consecutive children (concordant (MEG dipoles occupied the same region as the test over no more than two lobes), concordant+ (MEG dipoles in the same region but MEG occupied a larger area than the test result), concordant- (MEG dipoles in the same area but MEG occupied a smaller area than the test result), partially concordant (partial overlap between MEG and TEST), and discordant (no overlap between MEG and the test result). Results: Of 411, the 82.7 % patients showed a positive MEG epileptiform activity during a one hour MEG with a total of 589 dipole sources was. 164 patients had one, 110 had two, 37 had three, 16 had four, and 6 patients had five MEG sources.  MEG dipoles were localized to frontal (32%), fronto-central (16%), perisylvian-opercular (20%), parieto-occipital (16%), and temporal (26%) lobes. When compared to MEEG, MEG dipoles were concordant in 50%, concordant- in 28%, discordant in 12%, and partially concordant in 6.2%. 70% patients had focal, while 30% had generalized or multiregional MEEG spikes.  Of 106 (30%) patients with MEEG multiregional spikes, MEG showed a focal epileptiform dipolar source in 45 (43%) patients. When compared to VEEG, interictal MEG was concordant in 37% were, concordant in 30.4%,  concordant+ in 20%, and  discordant in 16.%. 73% VEEG patients had focal and 27% had generalized and multiregional spikes.  Of 100 (27%) multiregional VEEG spikes, MEG refined the localization in 75 (75%) patients leading to a more precise surgical hypothesis. Overall, 90% of VEEG were localized as a focal epileptiform dipolar pattern on interictal  MEG. When compared to co-registration of  brain MRIs for each patients, MEG dipoles were  concordant- in29%, concordant in 29%, partially concordant in 10.5%, and disconcordant in 14%. Of 79 (22%) patients with multilobar foci, MEG dipoles showed a more restricted region of epileptogenicity in 31 (40%) patients. Conclusions: MEG in children was useful in determining a dominant or solitary focal epileptiform dipolar sources. Even when MEEG and scalp VEEG showed a multiregional and generalized epileptiform abnormalities, MEG can identify, separate, and refine the epileptic zones from a more widespread picture on scalp VEEG. Funding: None