Background: Preoperative diffusion tensor imaging (DTI) is used to demonstrate corticospinal tract (CST) position. Intraoperative brain shifts may limit preoperative DTI value, and studies characterizing such shifts are lacking.
Objective: Using high-field intraoperative magnetic resonance imaging (iMRI), we examined tumor characteristics that could predict intraoperative shift in tumor-to-CST distance.
Methods: We retrospectively evaluated preoperative and intraoperative DTIs, tumor pathology, and imaging characteristics of patients who underwent resection of an intra-axial tumor adjacent to the CST to identify covariates that significantly affected shift in tumor-to-CST distance. For validation, we analyzed data from a separate, 20-patient cohort
Results: In the first cohort, the mean intraoperative shift in the tumor-to-CST distance was 3.18 +/- 3.58mm. The mean shift for the 20 patients with contrast and the 5 patients with non-contrast-enhancing tumors was 3.93 +/- 3.64mm and 0.18 +/- 0.18mm, respectively (P < .0001). No association was found between intraoperative shift in tumor-to-CST distance and tumor pathology, tumor volume, edema volume, preoperative tumor-to-CST distance, or extent of resection. According to receiver-operating characteristic analysis, non-enhancement predicted a tumor-to-CST distance shift of 0.5mm or less, with a sensitivity of 100% and a specificity of 75%. We validated these findings using the second cohort.
Conclusion: For non-enhancing intra-axial tumors, preoperative DTI is a reliable method for assessing intraoperative tumor-to-CST distance because of minimal intraoperative shift, a finding important when interpreting subcortical motor evoked potential to maximize EOR and preserve motor function. In resection of intra-axial enhancing tumors, intraoperative imaging studies are crucial to compensate for brain shift.
From: Preoperative Imaging to Predict Intraoperative Changes in Tumor-to-Corticospinal Tract Distance: An Analysis of 45 Cases Using High-field Intraoperative Magnetic Resonance Imaging. by Shahar et al.