Isthmic lumbar spondylolisthesis with sciatica: the role of the disc.

Thirty-one patients with isthmic spondylolisthesis were investigated using MR imaging. Twenty-one of these patients had selectively unilateral sciatica and no abnormalities on adjacent discs. In 18 patients there was a clear correlation between the degree of foraminal stenosis and the symptomatic side. In 20 patients there was evidence of root compression by disc tissue.