Combined electroencephalography and magnetoencephalography of interictal spikes in benign rolandic epilepsy of childhood

Objective The neurogenesis and functional organization of the interictal spikes in benign rolandic epilepsy of childhood (BREC) still remains controversial. Methods We performed a combined neuroelectric and neuromagnetic study in 24 consecutive patients with BREC using a 143-channel whole-head magnetoencephalography (MEG) system simultaneously with electroencephalography (EEG) recorded from 40 closely spaced scalp-EEG electrodes. Isopotential and isofield maps were calculated over the time window from 250 ms before to 250 ms after the maximum of the negative peak of the spike. We then performed principal component analysis (PCA) and spatio-temporal dipole modeling in order to estimate the number, location and temporal activity of sources. Results EEG and MEG spikes were characterized by a stereotypical appearance both within and across patients showing a stable dipolar field distribution over the entire time window. The spikes were generated by a single tangential dipolar source located in the precentral gyrus with the positive pole directed frontally and the negative pole directed centro-temporally. Conclusions One source located in the precentral gyrus can adequately explain the spike complex in BREC. Significance Simultaneous EEG and MEG provide comprehensive information on functional organization of spikes in BREC.