"Extradural neural axis compartment (EDNAC) exists from the tip of the coccyx all the way to the back of the globe, and yet it is relatively unknown as a concept. It is bounded externally by the periosteum of the vertebrae and sacrum inferiorly and the skull superiorly, and the visceral (meningeal) layer of the dura (dura propria/theca) internally."
"spinal epidural haematomas are within the EDNAC, whereas intracranial extradural haematomas are external to it (actually subperiosteal haematomas); note that intracranial haemorrhage within the EDNAC is exceedingly rare, sometimes known as intralaminar dural haematoma"