Magnetoencephalographic evaluation of anterior corpus callosotomy for intractable epilepsy in a patient with Lennox-Gastaut syndrome

We analyzed the preoperative and postoperative interictal magnetoencephalographic (MEG) patterns in a 32-year-old woman with Lennox- Gastaut syndrome who underwent an anterior corpus callosotomy (CC). A 37- channel biomagnetometer was used for the simultaneous recording of electroencephalogram (EEG) and MEG. Preoperatively, interictal EEG demonstrated a bilaterally synchronous spike and slow wave bursts with a maximum amplitude on the bifrontal region. The waveforms of the MEG were similar but did not completely correspond to those of the EEG. The estimated equivalent current dipoles (ECDs) originating from bilaterally synchronous paroxysmal discharges formed a dense cluster on the bilateral frontal lobes, especially on the deep midfrontal region. After anterior CC, MEG disclosed a marked reduction of the number of ECDs. The preoperative MEG patterns were thought to be representative of interhemispheric synchrony as a large dipole orientation, and these MEG paterns were partly disrupted by anterior CC.