Disc extrusion. A) T2W sagittal and B) T2W axial MRI demonstrate large L5/S1 disc extrusion (white arrow) elevating the PLL (black arrow). On axial image through the S1 vertebral body, disc appears to be sequestrated. C) Sequestered disc. Disc fragment (arrow) is noted posterior to the L4 vertebral body. It lacks continuity with the parent disc.