Abstracts

Magnetoencephalography (MEG) and electroencephalography (EEG) provide complementary neurophysiological information about the ongoing brain activity. In presurgical epilepsy evaluation, depth electrode placement and coverage is often based on relative low resolution scalp EEG aided by imaging. Depth electrode signal has been studied here together with simultaneous non-invasive high temporo-spatial resolution MEG signal in epilepsy patients. The purpose was two-fold: To assess MEG[apos]s value to optimally direct intracranial EEG placement and to address timing correlation in corregistered depth electrode and MEG interictal epileptiform activity signals., A multimodal approach was applied on three 6 to 13 year-old epileptic patients. A whole head MEG (4D Neuroimaging, San Diego, CA) registration was included to assess spike-source localization as a guide to depth electrode implantation, which was done accordingly. Both ictal and interictal intracranial EEG recordings were obtained. A second MEG was coregistered with the depth electrode signal. Interictal epileptiform events were studied according to time and compared to ictal results. Surgery of the ictal zone was done on each particular case., In all three patients, non-invasive interictal MEG localizations optimally correlated with ictal onset determined by the depth electrodes. Epileptiform events were typically registered on MEG channels earlier than in the depth electrode recordings. Postsurgical outcome confirmed the initial MEG characterization of the epileptogenic zone in all three patients., Using MEG as a routine clinical tool has proven useful to aid the optimal placement of depth electrodes. The value of interictal solid epileptiform activity as determined by MEG should be considered. For particular intracranial electrode placements and epileptogenic tissue locations i.e. tangential sources, MEG will detect epileptogenic discharges before the invasive EEG., (Supported by Centro Médico Teknon.)