Interictal and Ictal Magnetoencephalographic Study in Patients with Medial Frontal Lobe Epilepsy


Address correspondence and reprint requests to Dr. H. Shiraishi at Nuclear Magnetic Resonance Center, Massachusetts General Hospital, Room 2301, Building 149, 13th Street, Charlestown, MA 02129-2060, U.S.A. E-mail:


Summary:  Purpose: To determine whether magnetoencephalography (MEG) has any clinical value for the analysis of seizure discharges in patients with medial frontal lobe epilepsy (FLE).

Methods: Four patients were studied with 74-channel MEG. Interictal and ictal electroencephalographic (EEG) and MEG recordings were obtained. The equivalent current dipoles (ECDs) of the MEG spikes were calculated.

Results: In two patients with postural seizures, interictal EEG spikes occurred at Cz or Fz. The ECDs of interictal MEG spikes were localized around the supplementary motor area. In the other two patients with focal motor or oculomotor seizures, interictal EEG spikes occurred at Fz or Cz. The ECDs of interictal MEG spikes were localized at the top of the medial frontal region. The ECDs detected at MEG ictal onset were also localized in the same area as those of the interictal discharges.

Conclusions: In medial FLE patients, interictal and ictal MEG indicated consistent ECD localization that corresponded to the semiology of clinical seizures. Our findings demonstrate that MEG is a useful tool for detecting epileptogenic focus.