Applications of blood oxygenation level dependent-functional magnetic resonance imaging, diffusion tensor imaging and intraoperative neurophysiology monitoring in secondary epileptic surgery in M1 area

Abstract

To explore the applications of blood oxygenation level dependent-functional magnetic resonance imaging (BOLD-fMRI), diffusion tensor imaging (DTI) and cortical somatosensory evoked potentials (Co-SEP), motor evoked potentials (MEP) and electrocorticogram (ECoG) in secondary epileptic surgery of primary motor area (M1). In 19 patients, preoperative BOLD-fMRI were performed to display the relationship between active zone, fiber bundle and epileptogenic lesions. Besides, Co-SEP, MEP and ECoG were also carried out intra-operatively to direct the resection of epileptogenic lesion and epileptogenic focus. At the same time, the nervous functions were protected as much as possible. Then fMRI was performed again to ensure that the post-operative nervous function was excellent. In preoperative BOLD-fMRI and DTI examinations, active zone and fiber bundle could be seen at the edge of lesions (n = 12); range reduced, become deformed or removed (n = 6); glioma epileptogenic lesion was close-up with M1 (n = 1). The central sulcus was confirmed by Co-SEP in all cases. And two cases were inconsistent with anatomical location; Stimulating precentral gyrus, MEP were elicited post-operatively from orbicularis oris, muscle of thenar, hypothenar muscle or flexor digitorum brevis. Under the monitoring of ECoG, spike-wave was monitored in all cases. Of these, epileptogenic focus was in M1 (n = 15). After treatment, spike-wave were reduced significantly or disappeared. At a post-operative follow-up of 6 - 12 months, seizure improvement has achieved Engel III level or above (n = 18). On re-examinations of BOLD-fMRI and DTI, active zone became bigger than before and fiber bundle was symmetric with opposite side. Two of 19 cases had transient motor aphasia incompletely or hemiparesis. No permanent neurological dysfunction occurred. There was no relapse in cases of glioma. BOLD-fMRI and Co-SEP, MEP and ECoG are complementary in M1 of secondary epilepsy surgery. It is effective to preserve nervous functions and enhance the quality of life for patients with epilepsy.