The usual mechanism that produces an acute hematoma is a high-speed impact to the skull. This causes brain tissue to accelerate or decelerate relative to the fixed dural structures, tearing blood vessels. Often, the torn blood vessel is a vein that connects the cortical surface of the brain to a dural sinus. In elderly persons, the bridging veins may already be stretched because of brain atrophy. Alternatively, a cortical vessel, either a vein or small artery, can be damaged by direct injury or laceration