[Symptomatic lumbar intraspinal synovial cyst: a case report].

Synovial and ganglion cysts, also known as juxta-facet cysts, are intraspinal lesions that may mimic disc herniations and cause radicular symptoms. A 75-year-old male patient presented with a 6-month history of left leg pain and numbness in the foot that increased in severity within the past week. Physical examination showed motor deficit of the left extensor hallucis longus muscle (4/5) and hypoesthesia on the left L4-5 dermatomes. Magnetic resonance imaging revealed an intraspinal cyst originating from the L4-5 facet joint. Medial facetectomy and cyst excision were performed, which provided immediate relief of pain. He had no loss of strength of the extensor hallucis longus muscle and his neurologic examination was normal during the first postoperative year.