Nuclear Medicine Neuroimaging and Electromagnetic Source Localization in Nonlesional Drug-Resistant Focal Epilepsy

Abstract

Surgery is recognized worldwide as a rational option for drug-resistant epilepsy; however, it requires accurate localization of the epileptogenic zone (EZ). Magnetic resonance imaging (MRI) has dramatically changed presurgical evaluation in epilepsy. Nevertheless, MRI-negative cases still account for up to 25 % of all patients exposed to presurgical evaluation. Moreover, the absence of an MRI lesion renders accurate seizure focus localization more difficult and usually corresponds to a poorer outcome in epilepsy surgery, both for temporal and extratemporal epilepsies. Single perfusion photon emission computed tomography (SPECT) and 18F-FDG positron emission tomography (18F-FDG PET) have significantly changed presurgical epilepsy evaluation in nonlesional cases. Source analysis based on electrophysiological information, using either electroencephalography (EEG) or magnetoencephalography (MEG), has as much potential as SPECT and PET in the presurgical evaluation of epilepsy patients. In this chapter we aim to review the value of nuclear medicine neuroimaging and how the addition of source analysis based on electrophysiological information (EEG/MEG) improves EZ localization in drug-resistant nonlesional focal epilepsy, with a significant positive impact on surgery outcome.