EEG/MEG source reconstruction in non-lesional epilepsy

Background: The postsurgical outcome of non-lesional epilepsy is worse compared to that of lesional epilepsy. Electric and magnetic source imaging (ESI/MSI) are very important methods for the presurgical identification of the epileptogenic focus. Objective: The aim of this article is to provide an overview on the current state of knowledge on ESI and MSI in non-lesional epilepsy. Material andmethods: The article presents a non-systematic literature review. Results and conclusion: Source imaging has proven its usefulness in the localization of the epileptogenic focus in non- lesional epilepsy patients. The concordance of the resection zone or intracranial EEG and the source imaging in patients with a good surgical outcome was high. It provides non-redundant information in a relevant proportion of patients by identifying unknown lesions; however, only 9 of 25 surveyed European epilepsy centers reported using ESI in their presurgical evaluation. Semiautomated source reconstruction and limitation of the number of spikes and electrodes needed could help to improve its practicability and increase its use in epilepsy centers.