[Synovial cyst in the lumbar facet joint. A rare cause of lumbar-sciatic pain].

Synovial cysts of the facet joints are uncommon lesions which may be asymptomatic or present as low back pain, with or without radicular symptoms. They are considered to be secondary to trauma or degenerative joint disease, and they occur more frequently in patients with spondylolisthesis. Diagnosis is normally achieved with computed tomography or magnetic resonance, which show a cystic lesion located laterally adjacent to the facet joint. We review the literature and report a patient who presented with first sacral nerve root symptoms attributable to a ganglion cyst of the left L5 S1 facet joint. Treatment was curative and consisted in excision of the cyst.