Most sacral cysts are accidentally found on lumbar myelograms and are
usually asymptomatic. We operated on two patients with giant sacral cy
sts from S3 nerve roots who complained of neurogenic bladder and peria
nal sensory disturbance as well as buttock pain. Morphology of these c
ysts and intraoperative electrophysiological findings of nerve conduct
ion 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 du
e to degeneration of nerve root fibers involved in the sacral cyst wal
ls. Postoperatively, buttock pain and perianal hypesthesia were resolv
ed, but the neurogenic bladder showed only partial recovery.