Tumor Occupancy Ratio-An Imaging Characteristic Prognosticating the Surgical Outcome of Benign Intradural Extramedullary Spinal Cord Tumors

Background: Intradural extramedullary (IDEM) spinal cord tumors are two thirds of all spinal tumors. We have prospectively analyzed the importance of the tumor occupancy ratio as a factor for predicting the course of the disease and in prognosticating the surgical outcome in patients with IDEM tumors. Methods: We prospectively analyzed 44 consecutive cases of IDEM tumors, diagnosed as cervical, thoracic, and lumbar IDEM tumors (excluding conus/cauda equina lesion) by magnetic resonance imaging (MRI), that were operated on at our institution between 2014 and 2016. We measured the tumor occupancy ratio and noted the sagittal and axial location of the tumor in the preoperative MRI and performed the laminectomy and unilateral medial facetectomy. A primary outcome has been noted according to the gait disability score in the preoperative period and in the follow-up period of 1 year. In the statistical analysis, categorical variables were compared using a chi-square test, and an analysis of variance and student t tests were used for the continuous variables. P<.05 was considered statistically significant. Results: The tumor occupancy ratio showed a significant association to the preoperative gait disability score (P<.001) and also predicted that the surgical outcome is much better in patients with tumors with a low tumor occupancy ratio than in patients with tumors with a high occupancy ratio (P<.001). No difference in the tumor occupancy ratio was noted in 2 different pathological tumors, and there was also no difference in the tumor occupancy ratio at different sagittal and axial locations of the tumor. Conclusion: Tumor occupancy ratio has shown a significant impact on the preoperative course and also predicts the surgical outcome in patients with IDEM tumors. Hence, it is an important imaging characteristic to prognosticate the outcome in IDEM tumors and should be noted in each case.