Subdural hematomas are usually the result of a serious head injury. When this is the cause, they are referred to as "acute" subdural hematomas. Subdural hematomas can also occur spontaneously or after a very minor head injury, especially in the elderly. These go unnoticed for many days to many weeks, and are referred to as "chronic" subdural hematomas. The terms acute, subacute, and chronic reflect how long it takes blood to collect. Acute traumatic subdural hematomas are among the most lethal of all head injuries (up to 50% lethality). They expand very rapidly, leaving little room for the brain, and are associated with brain injury. Subdural hematomas occur in about 15% of all head traumas. Tiny veins between the surface of the brain and its outer covering (the dura) stretch and tear, allowing blood to collect. In the elderly, the veins are often already stretched because of brain atrophy (shrinkage). Risks include: - Head injury
- Very young or very old age
- Anticoagulant medication (blood thinners)
- Chronic alcohol use
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