Less Invasive Treatment for intractable Epilepsy Combined with Magnetoencephalography and Radiosurgery

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To investigate the possibility of less invasive treatment for intractable epilepsy combined with magnetoencephalography (MEG) and radiosurgery, basic and clinical research has been performed. Animal experiment using rats showed that minimum required dose to create necrosis at the target site by stereotactic single fraction radiation is 75 Gy and even 25 Gy may create necrosis if it were followed for 1 year. Effects of irradiation for epileptic convulsion are evaluated by experiments using rat. Stereotactic irradiation to temporal lobe in amygdala kindled rats showed that ipsilateral irradiation increases threshold of after-discharge and contralateral irradiation inhibit generalization of convulsion. Accuracy of functional mapping by evoked MEG was verified in neurosurgical procedures. Intraoperative monitoring combined with neuronavigation system showed good correlation with preoperative functional mapping by MEG and verified its accuracy and value as a less invasive preoperative evaluation method. Ability of MEG for evaluating epileptic foci and its propagation is accessed. MEG successfully showed gamma-band discharge and localized its focus. In temporal lobe epilepsy, not only the focus of epileptic discharge but also its propagation to contralateral hemisphere is detected. MEG also detects mesial temporal origin of spike bursts in patient with complex partial seizure.