"The spinal dura mater is a fibrous, non-adherent, tough layer surrounding the spinal cord. Unlike the intracranial dura mater, it only has a single layer which is continuous with the inner (meningeal) layer of the intracranial dura at the foramen magnum. It is separated from the wall of the vertebral canal by the epidural space. This space contains loose areolar tissue and a network of internal vertebral venous plexuses. The subdural space separates the spinal dura mater from the arachnoid mater. Both membranes are in direct contact with each other, apart from a small amount of fluid which lubricates the opposing surfaces 1."