Intradural invasion of lumbar synovial cyst. Case report.

A 63-year-old female presented with a rare case of synovial cyst invading the dura mater and mimicking an intradural extramedullary tumor in the lumbar spine. She underwent posterior lumbar fusion with laminar wire fixation from L3 to S1 levels. She complained of severe pain along the anterolateral thigh in both legs for 1 year. Radiological examinations, including magnetic resonance imaging and computed tomography revealed an intradural extramedullary lesion at the L2-3 level that was compressing the thecal sac. Histological examination confirmed a synovial cyst. Synovial cyst should be considered in the differential diagnosis of an intradural extramedullary mass causing lumbar radiculopathy.