Retrodural cysts bridging a bilateral lumbar spondylolysis: a report of two symptomatic cases.

We report the MR features in two patients presenting with symptomatic thecal impingement by posterior epidural cysts linking a bilateral lumbar spondylolysis. Large fluid-filled channels bridging the ruptured partes interarticulares were present in spite of the absence of significant arthritic changes within the adjacent facet joints.