MAGNETOENCEPHALOGRAPHY IN PARTIAL EPILEPSY - CLINICAL-YIELD AND LOCALIZATION ACCURACY

The goals of this study were to determine (1) the yield of magnetoence phalography (MEG) according to epilepsy type, (2) if MEG spike sources colocalize with focal epileptogenic pathology, and (3) if MEG can ide ntify the epileptogenic zone when scalp ictal electroencephalogam (EEG ) or magnetic resonance imaging (MRI) fail to localize it. Twenty-two patients with mesial temporal (10 patients), neocortical temporal (3 p atients), and extratemporal lobe epilepsy (9 patients) were studied. A 37-channel biomagnetometer was used for simultaneously recording MEG with EEG. During the typical 2-3-hour MEG recording session, intericta l epileptiform activity was observed in 16 of 22 patients. MEG localiz ation yield was greater in patients with neocortical epilepsy (92%) th an in those with mesial temporal lobe epilepsy (50%). In 5 of 6 patien ts with focal epileptogenic pathology, MEG spike sources were colocali zed with the lesions. In 11 of 12 patients with nonlocalizing (ambiguo us abnormalities or normal) MRI, MEG spike sources were localized in t he region of the epileptogenic zone as ultimately defined by all clini cal and EEG information (including intracranial EEG). In conclusion, M EG can reliably localize sources of spike discharges in patients with temporal and extratemporal lobe epilepsy. MEG sometimes provides nonin vasive localization data that are not otherwise available with MRI or conventional scalp ictal EEG.