A blood clot is seen over the external surface of the dura within the cranial cavity after removing the top of the skull at autopsy. Thus, this is an epidural hematoma. Such a location for hemorrhage is virtually always the result of trauma. The most likely source of bleeding is a tear in the middle meningeal artery. The arterial source means that the bleeding is brisk and blood collects quickly, leading to neurologic signs and symptoms within minutes to hours. [Image contributed by Jeannette J. Townsend, MD, University of Utah]