Electromagnetic source imaging in presurgical workup of patients with epilepsy: a prospective study

Objective: To determine the diagnostic accuracy and clinical utility of electromagnetic source imaging (EMSI) in presurgical evaluation of patients with epilepsy.
Methods: We prospectively recorded magnetoencephalography (MEG) simultaneously with electroencephalography (EEG) and performed EMSI, comprising electric (ESI), magnetic source imaging (MSI) and analysis of combined MEG-EEG datasets (cEMSI), using two different software packages. As reference standard for irritative zone (IZ) and seizure onset zone (SOZ) we used intracranial recordings and for localization accuracy, outcome one year after operation.
Results: We included 141 consecutive patients. EMSI showed localized epileptiform discharges (ED) in 94 patients (67%). Most of the ED-clusters (72%) were identified by both modalities, 15% only by EEG and 14% only by MEG. Agreement was substantial between inverse solutions and moderate between software packages. EMSI provided new information that changed the management plan in 34...