Optimal Timing of Postoperative Magnetic Resonance Imaging (MRI) in Patients With Extradural Spinal

Primary aim: Assess if Magnetic Resonance Imaging (MRI) at 2 to 3 weeks after surgery leads to the same clinical decisions and has the same probability of being chosen by a physician for guiding the subsequent management of the patient, compared with immediately postoperative MRI. Secondary aims: Investigate the differences between early and late MRI by comparing: * Size of tumor in three dimensions; * Extent of edema; * Presence and extent of fluid collection; * Spine Oncology Study Group score; * Involvement of adjacent levels; * Progression of tumor; * Patient's preference/performance scale right after each image had taken: level of discomfort at around the time each MRI was performed. Study Design: This is a prospective diagnostic study for which no standard of care currently exists.