Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 87. Head Injuries

Topics: Introduction | Skull Fracture | Concussion | Cerebral Contusions and Lacerations | Intracranial Hematomas

Intracranial Hematomas

Intracranial hematomas are accumulations of blood within the brain or between the brain and the skull.

Intracranial hematomas include epidural hematomas, which form between the skull and the outer layer (dura mater) of tissue covering the brain (meninges); subdural hematomas, which form between the outer layer and the middle layer (arachnoid mater (see Section 6, Chapter 76)); and intracerebral hematomas, which form within the brain. Intracranial hematomas can result from an injury or a stroke. For people who are taking aspirin or anticoagulants (which increase the risk of bleeding), particularly in older people, the risk of developing a hematoma after even a minor head injury is increased.

Most hematomas develop rapidly and produce symptoms within minutes. Large hematomas press on the brain and may cause swelling and herniation of the brain. Hematomas may cause confusion and memory loss, especially in older people, as well as loss of consciousness, coma, paralysis on one or both sides of the body, breathing difficulties, slowing of the heart, and even death.

Recovery (after prompt treatment) is more likely to be rapid and complete if the hematoma is epidural or subdural than if it is intracerebral. The reason is that the blood in epidural and subdural hematomas, unlike that in intracerebral hematomas, does not touch brain tissue and therefore does not directly irritate the brain.

Epidural Hematomas: These hematomas are caused by bleeding from an artery or a large vein (venous sinus) located between the skull and the outer layer of tissue covering the brain. Bleeding occurs when a skull fracture tears the blood vessel. A severe headache may develop immediately or after several hours. The headache sometimes disappears but returns several hours later, worse than before. Deterioration in consciousness, including increasing confusion, sleepiness, paralysis, collapse, and a deep coma, can quickly follow. Some people lose consciousness after the injury, regain it, and have a period of unimpaired mental function (lucid interval) before consciousness begins to deteriorate again.

Early diagnosis is crucial and is usually based on results of magnetic resonance imaging (MRI) or computed tomography (CT). Epidural hematomas are treated as soon as they are diagnosed, because prompt treatment is necessary to prevent permanent damage. One or more holes are drilled in the skull to drain the excess blood. The surgeon also seeks the source of the bleeding and stops the bleeding.

Subdural Hematomas: These hematomas are caused by bleeding from the bridging veins, located between the outer and middle layers of tissue covering the brain (meninges).

Subdural hematomas may be acute, subacute, or chronic. Rapid bleeding after a severe head injury can cause acute subdural hematomas, with immediate symptoms, or subacute subdural hematomas, with symptoms that develop over several hours. Chronic subdural hematomas result from a less severe head injury, in which bleeding starts more slowly, and symptoms develop after days, weeks, or even months. Symptoms are delayed because chronic subdural hematomas tend to enlarge very slowly.

Chronic subdural hematomas are more common among alcoholics and among older people. Alcoholics, who are relatively prone to falls and other injuries, may ignore minor to moderately severe head injuries. These injuries can lead to small subdural hematomas that may become chronic. In older people, the brain shrinks slightly, stretching the bridging veins and making them more likely to be torn if an injury, even a minor one, occurs. Also, bleeding tends to continue longer because older people heal more slowly. After the blood is resorbed from a hematoma, the brain may not re-expand as well in older people as in younger people. As a result, a fluid-filled space (hygroma) may be left. The hygroma may refill with blood or enlarge because small vessels tear, causing repeated bleeding.

Symptoms may include a persistent headache, fluctuating drowsiness, confusion, memory changes, paralysis on the opposite side of the body, and other symptoms depending on which area of the brain is damaged (see Section 6, Chapter 82).

In infants, a subdural hematoma can cause the head to enlarge (as in hydrocephalus), because the skull is soft and pliable. Therefore, pressure within the skull increases less in infants than it does in older children and adults.

Chronic subdural hematomas are more difficult to diagnose because of the length of time between the injury and the development of symptoms. However, MRI or CT can detect chronic as well as acute subdural hematomas.

Often, small subdural hematomas in adults do not require treatment because the blood is absorbed spontaneously. If a subdural hematoma is large and is causing symptoms such as persisting headache, fluctuating drowsiness, confusion, memory changes, and paralysis on the opposite side of the body, it is usually drained surgically by drilling a small hole in the skull. During surgery, a drain is usually inserted and left in place for several days, because subdural hematomas can recur. The person is monitored closely for recurrences. In infants, doctors usually drain the hematoma for cosmetic if for no other reasons.

Only about 50% of people who are treated for a large acute subdural hematoma survive. People who are treated for a chronic subdural hematoma usually improve or do not worsen.

Intracerebral Hematomas: These hematomas are common after a severe head injury. They are due to a cerebral contusion. Fluid accumulation in the damaged brain (cerebral edema) is common and accounts for most deaths due to head injury. MRI or CT can detect intracerebral hematomas. Because these hematomas are caused by direct damage to the brain, surgery is less likely to restore function than when the brain is damaged primarily by bleeding, as occurs with epidural and subdural hematomas.