Abstract

Background Juxtafacet spinal cysts are cystic synovial lesions that are often indistinguishable clinically or radiologically and require histopathology analysis to confirm the diagnosis. Lumbar synovial cysts usually arising from the synovium of the facet joints. They have been described posterolateral or rarely in the posterior midline. However, we describe the first synovial cyst ventral to the dural sac. Case description We report a lumbar 3-4 lesion causing cauda equina compression in a 57-year-old man who presented with 3 months history of low back pain and bilateral sciatica, intermittent urinary incontinence and erectile dysfunction. Pre-operative magnetic resonance imaging (MRI) suggested prolapsed disc, following decompression, histological analysis of the fragment confirmed a synovial cyst. Conclusion Hitherto synovial cysts have not been reported anterior to the dural sac. We describe a lumbar ventral cystic mass with cauda equina compression that mimicked a disc prolapse due to synovial metaplasia. The patient had urgent decompression with subsequent resolution of the symptoms.