The subdural space of the spine: A lymphatic sink? Myodil's last message.

Following the radiological study of a large number of myelograms, starting over 50 years ago when the only clinical contrast medium available to show the contents of the spinal canal was an iodized oil, the author has collected a number of examples where the oil was inadvertently injected into the subdural area, rather than the intended subarachnoid space. By taking follow-up films at various intervals following the inadvertent injection, it has been possible to study the extent to which the subdural space could become visualized from a lumbar injection, the contrast medium sometimes passing to the top of the cervical region and the lower part of the sacrum. Also, the contrast passed outward along the peri-neural lymphatic sheaths or spaces of the issuing spinal nerves, where it might remain for months, and under the influence of gravity it could extend for a considerable way. It also passed into abdominal and thoracic lymph vessels and nodes. Considering the morphology, predictability, and ease with which the demonstrated subdural space fills, the author concludes that the subdural region is a true and functionally significant "space," and an important conduit or functional part of the body's lymphatic system. He also considers that it has implications for the spread or dissemination of various organisms, substances or pathological conditions, as well as being part of the normal conduit for reabsorption of CSF with implications for hydrocephalus, and with potential for misplacement of spinal anaesthetic agents.