Giant sacral cysts with neurogenic bladder.

Most sacral cysts are accidentally found on lumbar myelograms and are usually asymptomatic. We operated on two patients with giant sacral cysts from S3 nerve roots who complained of neurogenic bladder and perianal sensory disturbance as well as buttock pain. Morphology of these cysts and intraoperative electrophysiological findings of nerve conduction block showed two kinds of pathogenesis causing these neurological symptoms. One was attributed to conduction block of more caudal sacral nerves squeezed between these giant sacral cysts and the other was due to degeneration of nerve root fibers involved in the sacral cyst walls. Postoperatively, buttock pain and perianal hypesthesia were resolved, but the neurogenic bladder showed only partial recovery.