Histology revealed a schwannoma. What is remarkable in this case is the relatively minor clinical signs associated with this huge mass, i.e. foot drop and no pain. This is presumably due to the slow growth of the tumor causing pressure erosion on the spinal canal. The contemporary preliminary CT (not available to me in this case) apparently did not show an obvious mass in the spinal canal. Look at the T1 sagittal images and perhaps you could make the same mistake.