Acute subdural hematoma results from violent trauma and is almost always associated with underlying brain damage. Unlike chronic or subacute subdural hematoma where the bleeding is usually from a vein, the source of bleeding in acute subdural hematoma is usually arterial. The rapidity of expansion of the blood clot which is in turn determined by the size of the bleeding vessel and the degree of underlying brain damage determines the patients outcome.
Patients may arrive at the Emergency Room with signs indicating severe brain damage caused by the development of vector of forces and "herniation" discussed previously and even rapid surgical evacuation does not lead to recovery. In other instances, if the degree of associated brain injury is small and the rate of bleeding is slow, excellent recovery can result from rapid evacuation of the blood clot. The blood is essentially always clotted in acute subdural hematoma and therefore twist drill craniostomy cannot be used. Instead, craniotomy, which consists of removal of circular or rectangular piece of skull, opening of the brain membranes (the dura matter) under which the blood clot is located, its evacuation and subsequent replacement of the previously removed bone are required. In some instances such as in high speed vehicular accidents, there is often a thin layer of subdural hematoma which does not require surgical evacuation and where the primary damage is caused by the closed head injury.
The treatments include ICP pressure monitoring, controlled respiration and supportive treatment. (See Brain Surgery:Basic Principles, Closed Head Trauma)
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