Background: Synovial cysts have a synovial lining, contain fluid and communicate with the facet joint itself. The exact etiology of this condition is not known, it probably is the degeneration and instability of the joint that plays an important role. They project into the lumbar canal, causing its narrowing and signs of nerve root compression and/or low back pain. The choice of treatment has changed over the years: from surgical excision to percutaneous aspiration. Surgical removal of the cyst is usually performed for the treatment of this disorder.Case Report:A 51-year-old woman suffering from conservative therapy resistant right lower extremity pain with numbness in the right foot and mild low back pain. CT revealed a spherical extradural pathological mass with a diameter of 10mm with calcification in L5/S1 right recessus. A right fenestration under operative microscope was performed at L5/S1 and the cyst was completely resected. Right extremity pain, low back pain, and numbness disappeared immediately after the procedure.Conclusions: Surgical excision is still the definitive treatment, especially for recurrent cysts, cysts causing intractable pain or neurological deficits and has low risk for complications.

Keywords: lumbar spine, facet joint, Synovial Cyst