Identification of the epileptogenic tuber in patients with tuberous sclerosis: A comparison of high-resolution EEG and MEG

Purpose: We compared epileptiform activity recorded with EEG and magnetoencephalography (MEG) in 19 patients with tuberous sclerosis complex (TSC) and epilepsy. Methods: High-resolution (HR) EEG, HR-MEG, and 1.5-T MRI scans were performed. Epileptiform spikes were identified in EEG and MEG recordings offline by three observers. Spikes for which the interobserver agreement (spike consensus) was > 0.40 were used for source localization with CURRYV 3.0 software. MUSIC analysis was performed. The distance between the source determined from EEG and MEG recordings and the border of the closest tuber was calculated and compared. Results: Consensus spikes (kappa > 0.4) were identified in 12 patients in the EEG recording and in 14 patients in the MEG recording. MEG sources were closer to tubers in all but one patient. Three patients underwent epilepsy surgery, two of whom are seizure free after complete resection of the tuber. Conclusions: In patients with TSC, epileptogenic sources identified on MEG are closer to the presumed epileptogenic tuber than are similar sources identified on EEG. Moreover, spike consensus is greater with MEG. Clear identification of the epileptogenic zone may offer opportunities for surgery in patients with TSC with intractable epilepsy.