Lumbar intradural arachnoid diverticulum with cauda equina compression.

An unusual case is reported of an intradural lumbar arachnoid diverticulum causing mild compression of the cauda equina and producing debilitating symptoms which were relieved by inadvertent drainage. A survey of the literature indicates that lumbar arachnoid diverticula are very rare. Only one other report of an intradural lesion of this type has been found. These lesions cause back pain or radicular pain and sensory disturbances when the patient is upright of bending forward. These symptoms are relieved by lying down. Percussion tenderness over the level of the diverticulum is a consistent finding. The key to the diagnosis is supine myelography.