Intracranially it is formed by two layers:
- outer endosteal layer, continuous via sutures and foraminae with the periosteum
- inner meningeal layer continuous inferiorly with the theca of the spinal cord.
These two layers are adherent except were separated by the dural venous sinuses which are analogous to the epidural venous plexus of the spinal canal.
In the young the extension across unfused sutures makes the dura inseperable from these, thus limiting extradural haemorrhages to the sutrures. As the calvarial bones fuse the suture layer involutes. The dura however becomes thicker and more adherent to the overlying bone with age, also accounting for the decrease of EDHs in the elderly.
- Gray's Anatomy 39th Edition, Elsevier