L5 radicular pain related to a cystic lesion of the posterior longitudinal ligament.

A 35-year-old man with a long history of left L5 radicular pain was found to have an intraspinal cystic lesion causing radicular compression. Magnetic resonance imaging demonstrated a round lesion situated in the anterior epidural space, with uniform high signal intensity on T2-weighted sequences characteristic of a cystic lesion. During surgery a liquid-containing cyst originating from the posterior longitudinal ligament was punctured and resected. The histologic aspect was that of a ganglion cyst without synovial layers. The radiologic differential diagnoses are discussed.