Glioma surgery using intraoperative tractography and MEP monitoring

In surgery of gliomas in motor-eloquent locations, it is essential to maximize resection while minimizing motor deficits. We attempted to identify the cortico-spinal tract (CST) by intraoperative-diffusion tensor imaging (DTI) tractography, combined with electrophysiological mapping using direct subcortical stimulation during tumor resection. Our techniques and preliminary results are reported. Tumors were removed from twelve patients with gliomas in and around the CST using high-field intraoperative MRI and neuronavigation system (BrainSUITE). DTI-based tractography was implemented for navigation of CST pre-and intraoperatively. When the CST was close to the manipulating area, direct subcortical stimulation was performed, and motor evoked potential (MEP)-responses were examined. Locations of CST indicated by pre- and intraoperative tractography (pre- or intra-CST-tractography), and locations identified by subcortical stimulation were recorded, and those correlations were examined. Imaging and functional outcomes were reviewed. Total resections were achieved in 10 patients (83.4%). Two patients developed transient deterioration of motor function (16.6%), and permanent paresis was seen in one (8.3%). The distance from intra-CST-tractography to corresponding sites by subcortical stimulation was 4.5 mm in average (standard deviation (SD)=4.2), and significantly shorter than from pre-CST-tractography. That distance correlated significantly with the intensity of subcortical stimulation. We observed that intraoperative DTI-tractography demonstrated the location of the pyramidal tract more accurately than preoperative one. The combination of intraoperative tractgraphy and MEP monitoring enhanced the quality of surgery for gliomas in motor-eloquent area. (author)