Figure 4

Image of a myelogram in a patient with spondylolisthesis, seen from the side. The white area behind the vertebrae represents the nerve envelope around the nerve roots (dural sac) filled with the injected contrast material. You can note the at the level of the spondylolisthesis (L5-S1), the outline of the dural sac becomes restricted (no contrast visible). This finding is associated with a significant narrowing of the space available for the L5 nerve roots and is seen in the setting of nerve irritation and pain.