Simultaneous eeg-fmri in epilepsy

Abstract

Simultaneous recordings of electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) signals are technically demanding, but offer a unique view onto the spatiotemporal dynamics of large-scale epilepsy-related networks. In this chapter, we present a detailed methodological overview of simultaneous EEG-fMRI, and provide examples of two clinical applications: (i) identification of syndrome-specific functional correlates in idiopathic generalized epilepsies (IGE) and (ii) localization of potentially epileptogenic tissue in patients with pharmacoresistant focal epilepsy syndromes. Studies using EEG-fMRI have shown that there are bilateral areas of deactivation during generalized spike-wave discharges (GSW) in IGE within the thalamus, precuneus, anterior cingulate cortex and inferior parietal cortex. These results underscore the importance of thalamo-cortical interactions in GSW generation, as well as the role of the so-called default mode network in sustaining attention and consciousness. In focal epilepsies, EEG-fMRI provides complementary information during the presurgical work-up of refractory epilepsy, especially in patients with mul-tifocal or non-lesional epilepsies. Overall, simultaneous EEG-fMRI has become an invaluable tool to elucidate the neurophysiology of human epilepsy, and shows promise as a clinical tool for specialized epilepsy centers.