Basic And Clinical Research On Combined Use Of High-field Intraoperative Magnetic Resonance Image-guided Functional Neuronavigation And Intraoperative Neurophysiological Monitoring For Cerebral Motor Pathway Mapping

Background:Glioma surgery in eloquent areas remains a big challenge for the risk of postoperative motor deficits.Objective:To prospectively evaluate the efficiency of using combination of diffusion tensor imaging (DTI) tractography functional neuronavigation and direct subcortical stimulation (DsCS) to yield the maximally safe resection of cerebral glioma in eloquent areas.Methods:A prospective cohort study was conducted in58subjects with an initial diagnosis of primary cerebral glioma within or adjacent to the pyramidal tract (PT). The white matter beneath resection cavity was stimulated along the PT which was visualised using DTI tractography. The intercept between PT border and DsCS site was measured. The sensitivity and specificity of DTI tractography for PT mapping was evaluated. The efficiency of the combined use of both techniques on motor function preservation was assessed.Results:The postoperative analysis showed gross total resection in40patients (69.0%).17patients (29.3%) experienced postoperative worsening, one-month motor deficit was observed in six subjects (10.3%). DsCS verified a high concordance rate with DTI tractography for PT mapping. The sensitivity and specificity of DTI were92.6%and93.2%, respectively. The intercepts between positive DsCS sites and imaged PTs were2.0-14.7mm (5.2±2.2mm). The6-month Karnofsky performance scale scores in postoperative50subjects were significantly increased compared with their preoperative scores. Conclusion:DTI tractography is effective but not completely reliable in delineating the descending motor pathways. It is recommended that integration of both techniques favors patient-specific surgery for cerebral glioma in eloquent areas. Objective:To evaluate the clinical feasibility of intraoperative neurophysiological monitoring (IONM) within3.OT high-field intraoperative magnetic resonance imaging (iMRI) system by quantifying and comparing the image artifacts caused by different electrodes in the phantom.Methods:Four different needle electrodes made from nonferromagnetic or weakly ferromagnetic materials (Ag-Mn, Al-Ti, Ag-AgCl, Cr-Ni alloy) and one standard routine steel electrode were chosen. The electrodes were attached to the custom phantom which was marked with a scale bar to easily quantify the scope of image artifacts. After various electrodes were implanted in the phantom, T2, Fluid attenuated inversion recovery (FLAIR) and diffusion weighted images (DWI) were acquired. The image quality was then analyzed for artifacts by measuring and comparing the scope and depth of the image artifacts caused by different electrodes. By analyzing the image quality, we chose the electrode which had the smallest image artifacts. To verify whether the electrode could be safely implanted in any position in the head, we evaluated the changes in image quality due to implantation of the electrode in several different locations in the phantom.Results:DWI was not further used to quantify the image artifacts for the artifacts were too severe to quantify. Whereas, the Al-Ti alloy and Ag-AgCl alloy electrodes demonstrated unobvious artifacts on DWI. Electrode-related artifacts, which were primarily caused by steel electrodes, were clearly identified. The image artifacts caused by the Al-Ti alloy electrodes were minimum. The areas of different electrodes that settled in the phantom on T2and FLAIR weighted images were:Steel)20×20mm2, Al-Ti alloy)0, Ag-AgCl alloy) 10×5mm2, Ag-Mn alloy)20X20mm2, and Cr-Ni alloy)15×10mm2, respectively. The Al-Ti electrode has little effect on the image quality, regardless of the position in which the electrode was implanted in the phantom.Conclusions:Routine steel electrodes can not be used for IONM within high-field iMRI environment for the severe image artifacts, however, the Al-Ti alloy electrodes can be used within high-field iMRI environment without influencing the intraoperative image quality Objective:To evaluate the clinical efficacy of combined use of3. OT intraoperative magnetic resonance imaging (iMRI) and intraoperative neurophysiological monitoring (IONM) for the surgery of cerebral gliomas within motor areas.Methods:57patients with gliomas in motor areas underwent tumor resection assisted by iMRI and IONM. Self-designed MRI-compatible electrodes were attached to the patient’s scalp and muscles for intraoperative monitoring. Adverse effects caused by IONM and image distortions of iMRI were recorded; the monitoring waveform and MRI image datasets were analyzed. Tumor volume and extent of tumor resection were quantified before and after continued resection following iMRI. Motor function were assessed preoperatively and postoperatively.Results:IONM and MRI can be performed with good quality. No adverse effects caused by IONM or MRI scanning were observed. The rates of radiological gross total resection before and after continued resection following iMRI were63.2%and75.4%, respectively. The mean residual tumor volume before and after continued resection was3.9cm3and1.8cm3, respectively. Volumetric analysis of pre-and post-operative imaging data revealed that the mean extent of resection in the first and final iMRI evaluation was94.8%and97.5%, respectively. A statistically significant difference before and after continued resection was observed in the residual tumor volume (P=0.003) and in the extent of resection (P=0.005).8patients (14.0%) experienced a transient postoperative motor deficit;2subjects (3.5%) suffered from post-op late motor deficits at the one-month follow-up. Conclusions:IONM can be performed with standard quality within3. OT iMRI environment with MRI-safe electrodes. The combined use of high-field iMRI and IONM can increase the extent of tumor resection and decrease subsequent motor deficits.