Epileptic seizure localized by whole head MEG

1 Introduction Magnetoencephalography (MEG) is currently used clinically for presurgical localization of epileptic tissue, based on signals from interictal spikes, using single equivalent current dipole (ECD) modeling [1,2,3,4]. There has been a long-standing question " Do interictal spikes co-localize to the same area as epileptic seizures? " Minassin, et al. found that the interictal MEG localization of spikes corresponded to ictal zones mapped by the ECoG in ten of eleven patients [5]. MEG was able to map interictal activity equally well as intracranial electrodes (ECoG). This suggests that the localizing information obtained by the invasive intracranial monitoring may also be available by noninvasive MEG. Mappings of epileptic seizures by MEG are rare since patient movement typifies most seizures, and localizing brain activity after the patient moved is not accurate. In one study, performed by Ko et al. [6], in which an epileptic seizure was monitored by MEG, the data was compared to EEG localizations. The MEG data localized the active source more mesial in the temporal lobe than the EEG. The mean difference in localization between MEG and EEG interictal spikes was 2.1 cm (patient 1) and 3.8 cm (patient 2). The mean difference in localization between the ictal and the interictal data from EEG was 3.5 cm (patient 1), whereas the mean difference in localization between the ictal and interictal data from MEG was 1.8 cm, (patient 2). That study suggests that the MEG may be more reliable in comparing the interictal spikes with the ictal spikes. We report a case study of localization of MEG data from both interictal spikes and an epileptic seizure captured by MEG in the same subject. A male patient (27 years old) with complex partial and secondarily generalized seizures was monitored with 148 channel Neuromagnetometer (4D Neuroimaging Magnes WH2500) and 21 channels of EEG. This patient has persistent intractable localization-related epilepsy despite two previous left frontal lobe resections. The patient changed into a hospital gown and removed all metal articles from his body, except for dental work, which was adequately demagnetized with a commercial videotape eraser. Three small electrode coils, used to transmit subject location information to the neuromagnetometer probe were taped to the forehead with two-sided tape. Disposable ear molds of the correct size were placed in the ears and an additional localization coil was attached to each ear mold. The EEG electrodes were applied with collodion adhesive using the International 10-20 …