Discal cysts of the lumbar spine: a case report.

Discal cysts--intraspinal cysts communicating with an adjacent intervertebral disc--are an uncommon cause of lumbar radiculopathy. We report a case of discal cyst of the lumbar spine. The cyst contents were bloody and clotted rapidly; no disc materials were seen. Communication between the cyst and the intervertebral disc was detected. Histopathology of the cyst wall revealed fibrous connective tissue without synovial lining cells. We hypothesise that the discal cyst was formed by haemorrhage of the epidural venous plexus caused by separation of the peridural membrane by mechanical force transmitted by an annulus fibrosis fissure. The minute segmental motion caused by the affected disc may have stimulated continuous bleeding.