L5 radicular pain related to a cystic lesion of the posterior longitudinalligament

A 35-year-old man with a long history of left L5 radicular pain was found t o have an intraspinal cystic lesion causing radicular compression. Magnetic resonance imaging demonstrated a round lesion situated in the anterior epi dural space, with uniform high signal intensity on T2-weighted sequences ch aracteristic of a cystic lesion. During surgery a liquid-containing cyst or iginating from the posterior longitudinal ligament was punctured and resect ed. The histologic aspect was that of a ganglion cyst without synovial laye rs. The radiologic differential diagnoses are discussed.