Subdural HemorrhageSubdural Hemorrhage is bleeding within the two membranes that surround the brain: the dura mater and the arachnoid mater. This bleeding can often separate these two layers and accumulation of blood can lead to increased intracranial pressure, or pooling and clotting of blood known as a hematoma. When this happens it can be very damaging to brain tissue and is considered a medical emergency. Subdural bleeding is often caused by sudden and violent changes in velocity that can stretch and tear the vessels of the dura and arachnoid mater. Veins are more likely to tear than arteries, resulting in a slower accumulation of blood. This means that symptoms of Subdural hemorrhage can show up anywhere from 24 hours to two weeks after the injury. The elderly and patients on anticoagulant (prevention of blood clots) medication are at higher risk for this type of injury. Computed tomography (CT) and magnetic resonance imaging (MRI) scans are used to diagnose subdural hemorrhage. Careful monitoring and allowing the body to heal on its own can treat small hemorrhages. Large hemorrhages, however, require a procedure called a craniotomy where the skull is opened and the blood clot is removed from between the dura and arachnoid mater. Acute hemorrhages have high rates of death and permanent injury. Sub acute hemorrhages present fewer problems with people often recovering completely when the blood is cleared.