Splitting of the intervertebral disc in spondylolisthesis: a magnetic resonance imaging finding in two cases.

Two patients with grade III spondylolisthesis of L5 on S1 underwent magnetic resonance imaging (MRI) as part of their preoperative evaluation. The nucleus pulposus of the involved intervertebral disc was noted to be divided into anterior and posterior halves. The signal intensity of the involved nucleus pulposus was decreased, a finding correlated to degenerative changes of the disc material. Moderate narrowing of the thecal sac was noted at the level of spondylolisthesis. Both patients underwent in situ posterolateral spinal fusion from L4 to S1 without decompression. We were not able to correlate the MRI findings to etiology of pain in spondylolisthesis.