Figure 1: Magnetic Resonance Imaging- Axial T1 (left) and T2 (right) images obtained without fat saturation at the level of L1/L2 demonstrate severe spinal canal stenosis with a paucity of normal CSF signal within the subarachnoid space (arrowhead). An extradural T1 isointense and T2 hyperintense fluid collection (white arrows) compresses the thecal sac. The isointense T1 signal within the collection differs from the normal epidural fat and subcutaneous fat (black!arrows).