CT myelography of a fragment of a lumbar disk sequestered posterior to the thecal sac.

The radiologic manifestations of lumbar disk herniation as seen on myelography, postmyelography CT, and, more recently , surface-coil MR have been well described (1-3). CT and MR findings of far lateral , extraforaminal disk herniation also have been reported (4]. Migratory fragments typically settle anterior and/or lateral to the thecal sac (5]. We report a case in which the sequestered migratory fragment from a herniated lumbar disk was located primarily posterior (dorsal) to the thecal sac.