Contributions of Magnetoencephalography to Characterizing Brain Function in Pediatric Epilepsy: Evidences of Validity and Added Value

Abstract

Magnetoencephalography (MEG) and magnetic source imaging are considered among the few available noninvasive modalities that can address, in pediatric populations, clinically relevant questions at the individual level. The contribution of MEG to the localization of the irritative zone (based on interictal epileptiform discharges), and the characterization of function-specific cortex (i.e., functional mapping), has proven to be as accurate as those derived from invasive “gold standard” procedures like the intracarotid amobarbital procedure and cortical stimulation mapping. Here, we will review some of the evidences supporting the added value of MEG in the study of pediatric epilepsy with special interest in the seminal studies where the clinical validity of MEG has been established after comparing MEG-derived estimates with those derived from the well-established invasive “gold standard” procedures. In the first section, we revisit a study where MEG is applied to characterize distinct patterns of propagation of interictal epileptiform discharges in relation with the clinical evolution of children with typical and atypical variants of benign rolandic epilepsy. This study serves to illustrate the additional value of MEG's high spatiotemporal resolution. Intralobar, interlobar, and interhemispheric patterns of propagation were demonstrated using MEG and associated to the clinical features exhibited by children with rolandic epilepsy. The second section of this article reviews part of the experience accumulated, in more than 800 clinical cases, by the MEG Laboratory at the University of Texas-Houston. In different studies, MEG-derived estimates for language and sensorimotor functions were compared with those derived from the gold standard invasive procedures (i.e., intracarotid amobarbital procedure and direct cortical stimulation) and tested against surgical outcome measurements. In these studies, authors benefit from some of the strengths of MEG as a valid, and noninvasive, tool to characterize brain function in pediatric population, demonstrating the utility of MEG in studying the issue of epilepsy in the developing brain.