Subdural hematoma

Definition

A subdural hematoma is a pooling of blood between the dura, which is a leathery membrane just under the skull, and the brain itself. Subdural hematomas usually occur following a head trauma that breaks the blood vessels that surround the brain. The pressure of the accumulated blood on the brain can cause a variety of symptoms including problems with speech, vision, or even a loss of consciousness.

Description

The bony skull encases the brain, protecting it from external damage. Between the skull and the brain itself is a tough leathery tissue, called the dura. This dura serves two purposes, forming a second layer of protection around the brain and providing vasculation that nourishes the brain with blood and spinal fluid. During a severe blunt head trauma, the bridging blood vessels that connect the dura to the skull may tear because of shear forces to the head. The broken vessels bleed into the space between the skull and the dura. This pooling of blood puts pressure on the brain, and it swells in response. Because the skull creates a defined volume, there is no extra room for the brain to swell and therefore, parts of the brain become compressed. This usually has neurological consequences including visual problems, speech dysfunction, and loss of consciousness.

The term subdural hematoma has a variety of synonyms including SDH, subdural hemorrhage, and blood clot on the brain. Physicians may use the adjectives acute, subacute, and chronic to describe the time course and volume of blood in subdural hematomas. Acute describes subdural hematomas that gather a large amount of blood

quickly. Subacute refers to subdural hematomas that occur between three and seven days following an injury to the head. In these patients, the blood clots will liquefy and in some cases the various cellular components of the blood clots will form layers that can be visualized using computerized tomography (CT ). Chronic usually refers to subdural hematomas that produce symptoms two to three weeks following an injury. In these hematomas, the blood clot has become mostly blood serum. Additionally, subdural hematomas are classified as simple or complicated. About half of all cases are simple, which implies that there is no laceration or contusion in the brain. In complicated SDH, the brain has suffered some sort of traumatic injury.

Demographics

SDH can happen to anyone who experiences a head trauma. In the United States, between 15% and 30% of patients suffering from head injuries have SDH. About half of the cases of SDH are simple SDH. The other half of the cases involves other complications such as laceration of the brain, and the mortality rate is much greater in these individuals. SDH is more common in people older than 60 because their blood vessels are more fragile than those in younger people. SDH is also associated with child abuse. People with blood disorders, such as hemophiliacs, people on anticoagulants, and alcoholics, are at higher risk for developing subdural hematomas.

Causes and symptoms

Subdural hematomas are most often caused by head trauma. Rarely, they can occur spontaneously, especially in elderly persons. Often the person will lose consciousness following the trauma, but SDH can occur when the person has remained conscious. Signs indicating the presence of SDH include headaches, dizziness , nausea, pupil dilation, slurred speech, and weakness in the limbs. More severe symptoms include loss of consciousness, disorientation, amnesia, trouble with breathing, or even coma.

Diagnosis

Diagnosis of an acute or chronic subdural hematoma is most often accomplished by using a computerized tomography (CT) scan, which is a specialized x ray. The SDH appears as a white crescent shape that lies along the skull. In subacute SDH, the shape of the pooled blood looks more lens-like and magnetic resonance imaging (MRI) is recommended to distinguish it from an epidural hematoma .

Treatment

In many cases, small subdural hematomas may be treated with observation and a series of CT scans to ensure that the blood is reabsorbing and not becoming calcified. In more severe cases, surgical intervention is necessary. The surgeon will open the skull in a procedure known as a craniotomy and remove the blood clot to release the pressure on the brain. The clot is removed with suction and irrigation.

Recovery and rehabilitation

Following surgical removal of a subdural hematoma, a patient will most likely need to remain in the intensive care unit for a period of time. Diuretics to decrease swelling of the brain and anticonvulsants to prevent seizures will be administered. Some of the complications associated with surgery are swelling of the brain, infection, seizures, memory loss, headache , difficulty concentrating, and chronic SDH. In about 50% of the cases, a hematoma may recur following surgery.

Prognosis

The prognosis for someone who has suffered a subdural hematoma depends on the size and severity of the blood clot. Acute SDH may have very high rates of death and long term disability. Subacute and chronic SDH usually have a better prognosis, with most symptoms abating following surgery. Mortality rates associated with simple SDH approach 20% as compared with 50% for complicated SDH. In all cases, persons who have experienced a subdural hematoma have a high risk of seizures, although this can usually be controlled with medication.

Resources

BOOKS

Greenberg, David A., et. al. Clinical Neurology, 5th. ed. New York: McGraw-Hill/Appleton & Lange, 2002.

OTHER

Kiriakopoulos, Elaine T. "Subdural Hematoma." MEDLINE plus. National Library of Medicine. <http://www.nlm.nih.gov/medlineplus/ency/article/000713.htm> (November 16, 2002).

"Subdural Hematoma." University of Missouri Health Care. <http://www.muhealth.org/~neuromedicine/subdural.shtml> (February 15, 2001).

ORGANIZATIONS

National Institute for Neurological Diseases and Stroke (NINDS). 6001 Executive Boulevard, Bethesda, MD 20892. (301) 496–5751 or (800) 352-9424. <http://www.ninds.nih.gov>.

Juli M. Berwald, PhD