Methods: A case of bilateral symptomatic facet joint synovial cysts arising in association with calcium pyrophosphate deposition disease is reported. Objective: To present a previously unreported cause for symptomatic synovial cysts of the lumbar spine.

Background: Synovial cysts of the facet joints occur most commonly in association with degenerative disease of the spine in older individuals. The association of these cysts with trauma, rheumatoid arthritis, spondylolysis, and kissing spinous processes also has been reported. These cysts can cause symptoms and signs from direct compression of the dura. Chondrocalcinosis has not been previously reported to cause symptomatic synovial cysts.

Methods: A 67-year-old woman presented with right lower limb sciatica caused by a right L4-L5 facet joint cyst, which resolved after surgical decompression. A year later, she presented with left lower limb sciatica caused by development of a new L4-L5 facet joint cyst, which also resolved after surgical decompression.

Results: Histopathologic examination of each cyst showed a cyst wall of fibrous tissue with synovial lining, inflammation, and granulation tissue. Examination of the tissue under polarized light showed positively birefringent, short blunt crystals of calcium pyrophosphate dihydrate.

Conclusions: In patients with a history of gout or pseudogout, a rare possibility of a synovial cyst should be considered in the differential diagnosis during investigation for the cause of neural compression resulting in sciatic syndrome.