Subdural space

The subdural space is a potential space between the dura and the arachnoid mater, containing a thin layer of serous fluid. It allows the dura to move over the arachnoid. This space surrounds the brain and the spinal cord, forming the cranial and spinal subdural spaces. It also briefly extends onto the nerves and connects freely with the lymph spaces of the nerves.

The intracranial subdural space has bridging veins that carry blood from the cerebral veins to the dural venous sinuses. As the brain tissue shrinks and atrophies in old age, there is increased tension on these bridging veins. Consequently, the rupture of these veins can cause venous hemorrhages within the subdural space.