Subdural Hematoma

What Is It?

A subdural hematoma or hemorrhage is an accumulation of blood between the brain and its tough outer lining, caused by a ruptured blood vessel. A subdural hematoma is a close relative of other hemorrhages that can occur at the surface of the brain, including epidural hematoma and subarachnoid hemorrhage. These hemorrhage types each cause blood to collect beneath a different layer of the meninges, the three-layer protective covering of the brain. In the case of a subdural hematoma, blood collects immediately beneath the outermost layer, named the dura mater. A subdural hematoma is a threatening problem because it can compress the brain.

Most subdural hemorrhages are caused when trauma to the head damages tiny veins within the meninges. In young, healthy people, bleeding usually is triggered by a significant impact, such as might occur in a high-speed motor-vehicle accident. In contrast, older people may develop a subdural hemorrhage after minor trauma, such as a falling out of a chair. Bleeding within the head after a minor injury is also more common in people taking medications that thin the blood and in people who abuse alcohol or have seizures.

Subdural bleeding that develops shortly after a serious blow to the head is known as an acute subdural hemorrhage. Acute subdural hemorrhages develop in 5 percent to 20 percent of people with severe head injury, typically those who fall from a considerable height. This type of bleeding occurs three times more often in men than in women. In acute subdural hemorrhage, the rapid accumulation of blood causes pressure to rise within the brain, and can result in loss of consciousness, paralysis or death. The force required to trigger this type of bleeding can cause several different injuries to the brain and spinal cord at the same time.

When bleeding develops slowly, typically over a period of weeks to months, it is known as a chronic subdural hemorrhage. This form of bleeding is much more common in the elderly, with most of those affected over age 50. The head trauma that causes chronic subdural hemorrhage is often minor, and up to one-half of those affected cannot recall a head injury.

Symptoms

Acute subdural hemorrhage usually develops after severe head trauma. Injuries that result in a subdural hemorrhage are typically forceful enough to cause a temporary loss of consciousness (concussion). Bleeding associated with a subdural hemorrhage occurs slowly, because the damaged blood vessels are small veins. Usually, in the minutes to hours after head injury, recovery from a concussion may be followed by a gradual loss of consciousness from subdural bleeding. Other common symptoms include severe headache, weakness of arms or legs on one side of the body, seizures and changes in vision or speech.

Chronic subdural hemorrhages produce more subtle symptoms, which may continue for more than a month before the diagnosis is recognized. These symptoms include: