Dorsal compression of the epidural cord due to free sequestral lumbar prolapse. Diagnostic problems in magnetic resonance imaging and computed tomography.

Due to the anatomical situation, intervertebral disc herniation usually results in compression of the anterior epidural space, with lateral or medial irritation of nerve root or cauda equina. Rare locations are an intra- or extraforaminal position or dislocation dorsally. Three patients with dorsal cauda equina compression caused by a sequestered herniated nucleus pulposus (HNP) are reported. The patients complained mainly of severe back pain. In two patients nondermatome-related leg pain was observed; one patient suffered additionally from incomplete cauda equina syndrome. In all cases magnetic resonance imaging and computed tomography diagnosed neoplastic tissue.