MEG Useful In Finding Seizure Source

Magnetoencephalography (MEG) is a controversial diagnostic tool, because it is expensive and data on its effectiveness are lacking.

Reporting at the American Epilepsy Society's 69th Annual Meeting, researchers H. Barka and colleagues did a retrospective review of case reports in 60 cases. The cases involved pediatric patients, all of whom had intracranial monitoring and resection, and in whom MEG was used to aid decision-making as to the feasibility of surgery, and to guide intracranial implant placement.

The team reviewed localization data for available modalities - long-term scalp video-EEG monitoring (LTM), imaging (MRI), intracranial EEG recordings (iEEG) ictal and interictal data, and intraoperative monitoring (IOM) data, in a few cases where it was both available and definitively localizing, and MEG.

They found that long-term scalp video-EEG monitoring was the least successful way to find the source of seizures in children with intractable epilepsy.

Their conclusions focused on two endpoints, seizure localization by various modalities, and localization vs postsurgical outcome. They noted that multiple previous studies have shown that successful ictal localization and the clinical outcome are closely correlated. But they found that connection to be "equivocal." With respect to successful localization," iEEG is the golden standard, and this study shows consistently the concordance of iEEG, a perisurgical invasive modality, and MEG, a pre-surgical noninvasive one, as demonstrated statistically". Further, they said, "MEG is indeed a valid and valuable pre-surgical evaluation tool in pediatric patients with intractable epilepsy, and ought to be used for lateralization and lobar localization prior to implant placement, especially in the patients in whom scalp EEG (LTM) findings were equivocal."