Spinal epidural cyst: theories of pathogenesis

✓ The pathogenesis of spinal epidural cyst is reexamined in the light of a case in which a small drop of contrast medium introduced by myelography 23 years before had become entrapped within a noncommunicating spinal epidural cyst. This finding suggested the diagnosis prior to surgery and reinforces the hypothesis that original communication with the subarachnoid space may later be obliterated. Two alternative theories are discussed.