Symptomatic intraspinal synovial cysts of the lumbar spine: correlation of MR and surgical findings.

The purpose of the study was to determine the frequency of associated MR imaging findings in patients with symptomatic lumbar intraspinal synovial cysts, and to correlate MR with surgical findings. MR imaging studies of 18 patients with surgically and histopathologically proven lumbar intraspinal synovial cysts were retrospectively analyzed and correlated with surgical findings. The diameters of the synovial cysts ranged from 10 mm to 28 mm, with a mean of 16 mm. A nonhemorrhagic cyst was found in 15 patients (83%), and a hemorrhagic cyst in three patients (17%). Degenerative spondylolisthesis was found in six patients (33%) at the level of the synovial cyst, with displacement ranging from 3 to 5 mm, mean 4 mm. Surgery revealed instability and hypermobility of the facet joint at the level of the synovial cyst in all patients with degenerative spondylolisthesis, and in five additional patients. Symptomatic synovial cysts of the lumbar spine were associated with degenerative spondylolisthesis in six of 18 patients (33%) and with instability of the facet joint in 11 (61%). These findings may support the theory that increased segmental motion plays a role in the pathogenesis of synovial cysts.