Epidural hematoma: Whereas most subdural hematomas arise from venous bleeding, epidural hemorrhage is almost always due to arterial bleeding as a result of a tear in the middle meningeal artery (which is located on the outer surface of the dura) from fracture of the squamous portion of the temporal bone. A sizable blood clot may result within a matter of several hours, producing compression of the underlying brain and the expected edema and herniation.