FIGURE 1-18

     The layers of the dura also split to enclose the middle meningeal artery. The split is asymmetrical in that the meningeal surface - the one that the brain rubs against when it moves slightly within the cranial cavity - remains smooth, but the vessel creates a ridge in the periostial surface. The result of this asymmetrical split is that the artery erodes a "valley" in the inner surface of the skull., as shown here. If the skull fracture and the fracture line crosses this valley, then there is a good chance the middle meningeal artery will be torn and that arterial blood will leak forming a hematoma (pool of blood) between the dura and the skull.