A subdural hematoma is a collection of blood in the space between the outer and middle layers of the covering of the brain. It is most often caused by torn, bleeding veins as a result of a head trauma.
The covering of the brain (meninges) has three main layers. The outside is a tough, fibrous covering called the dura mater. The middle layer is the arachnoid mater, and the layer closest to the brain tissue is the pia mater. Subdural hemotamas occur when blood collects in the space between the dura mater and the arachnoid mater. Subdural hematomas usually occur because veins on the inside of the dura that connect the brain cortex and the venous sinuses (bridging veins) are ruptured as the result of a blow to the head. Symptoms can occur within minutes to hours.
Subdural hematomas in children and adolescents are usually abrupt onset or acute and are brought about by accident or injury. Another type of subdural hematoma called a chronic subdural hematoma can occur in people over age 60. However, what follows applies to acute subdural hematomas in children only.
Subdural hemotamas range from fatal or life threatening to small with only minor effects, depending on the quantity of blood released and the amount of injury to other brain tissues. With small subdural hematomas, the blood may slowly be reabsorbed over several weeks without much damage. Larger hematomas, however, can gradually get bigger even though the bleeding has stopped. This enlargement increases pressure inside the skull and can compress the brain, possibly resulting in permanent brain damage or death if the blood is not drained away and the pressure relieved through surgical intervention.
In the United States, head injuries are the leading cause of accidental death and permanent disability in people under age 45. Not all these head injuries involve subdural hematoma, but it is the most common type of bleeding in the brain to result from trauma.
Infants are more prone to subdural hematoma than toddlers and older children, because the brain of infants has more room than the brain of older children to move around in the skull when shaken or hit. The neck muscles of infants are also less developed and unable to hold the head steady when shaken.
Children with blood clotting disorders are at an especially high risk of developing bleeding in the brain.
Causes and symptoms
In infants and children, subdural hematoma is often seen in physical child abuse . Its presence is one of the defining parameters (along with retinal hemorrhage) of shaken baby syndrome . Infants rarely fall until they start learning to walk, so falls account for only a small number of subdural hematomas in infants. However, many subdural hematomas in toddlers result from accidental falls, as they learn to walk and climb. In older children, a fall in which they hit their head is a common cause of subdural hematoma. All age groups are susceptible to developing subdural hematomas from vehicle accidents. In young children, even if the head does not contact a solid surface, the shaking, whiplash movement from some vehicle crashes causes blood vessels to burst in the brain.
Symptoms of subdural hematoma tend to fluctuate and include the following:
- episodes of confusion and drowsiness
- one-sided weakness or paralysis
- enlarged or asymmetric pupils
- increased intracranial pressure
- loss of consciousness after head injury
When to call the doctor
Individuals who show any immediate symptoms of subdural hematoma should be taken to the emergency room. Infants and children should be checked by a doctor if they have had a hard fall or accident in which they have hit their head or if child abuse or shaken baby syndrome is suspected.
Diagnosis is made based on history, external signs and symptoms of head injury (although external injuries may not always be present), and confirmed through magnetic resonance imaging (MRI). X rays may be done so the doctor can look for skull fracture.
Small hematomas that do not cause symptoms may not need to be treated. Otherwise, the hematoma should be surgically removed. Liquid blood can be drained from burr holes drilled into the skull. The surgeon may have to open a section of skull (craniotomy) to remove a large clot and/or to tie off the bleeding vein.
Corticosteroids and diuretics may be given to help control brain swelling, depending on the age of the child and the extent of the injury. After surgery, anticonvulsant drugs such as phenytoin may help control or prevent seizures, which can begin as late as two years after the head injury.
The outcome of subdural hematoma depends on how promptly treatment is received and how much damage the brain has received. Head injuries have a high mortality rate. The mortality rate for all patients with acute subdural hematoma is about 60 percent. Even when recovery occurs, permanent disability can occur. Headache, amnesia, attention problems, anxiety , and personality changes may continue for some time after surgery.
Preventing blunt head trauma from falls, child abuse, and assaults is the most effective way of preventing subdural hematoma.
Research in the early 2000s suggests that some of the effects of brain injury do not show up in children until several years after the injury. These include the development of social and academic skills. Parents should be alert to this possibility.
Corticosteroids —A group of hormones produced naturally by the adrenal gland or manufactured synthetically. They are often used to treat inflammation. Examples include cortisone and prednisone.
Diuretics —A group of drugs that helps remove excess water from the body by increasing the amount lost by urination.
See also Child abuse.
Beers, Mark H., and Robert Berkow, eds. The Merck Manual, 2nd ed., home ed. West Point, PA: Merck & Co., 2004.
American Academy of Neurology. 1080 Montreal Ave., St. Paul, MN 55116. Web site: <www.aan.com>.
Brain Injury Association of America. 8201 Greensboro Dr., Suite 611, McLean, VA 22102. Web site: <www.biausa.org>.
Brain Injury Resource Center. 212 Pioneer Bldg., Seattle, WA 98104–2221. Web site: <www.headinjury.com>.
Meagher, Richard J., and William F. Young. "Subdural Hematoma." eMedicine Medical Library, June 8, 2004. Available online at <www.emedicine.com/neuro/topic575.htm> (accessed December 1, 2004).
Moojain, Bhagwan, and Nitin Patel. "Neonatal Injuries in Child Abuse." eMedicine Medical Library, September 16, 2001. Available online at <www.emedicine.com/neuro/topic238.htm> (accessed December 1, 2004).
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Tish Davidson, A.M. Carol A. Turkington
A subdural hematoma is a collection of blood in the space between the outer layer (dura) and middle layers of the covering of the brain (the meninges). It is most often caused by torn, bleeding veins on the inside of the dura as a result of a blow to the head.
Subdural hematomas most often affect people who are prone to falling. Only a slight hit on the head or even a fall to the ground without hitting the head may be enough to tear veins in the brain, often without fracturing the skull. There may be no external evidence of the bruising on the brain's surface.
Small subdural hematomas may not be very serious, and the blood can be slowly absorbed over several weeks. Larger hematomas, however, can gradually enlarge over several weeks, even though the bleeding has stopped. This enlargement can compress the brain itself, possibly leading to death if the blood is not drained.
The time between the injury and the appearance of symptoms can vary from less than 48 hours to several weeks, or more. Symptoms appearing in less than 48 hours are due to an acute subdural hematoma. This type of bleeding is often fatal, and results from tearing of the venous sinus. If more than two weeks have passed before symptoms appear, the condition is called a chronic subdural hematoma, resulting from tearing of the smaller vein. The young and the old are most likely to experience a chronic condition. This chronic form is less risky, as pressure of the veins against the skull lessens the bleeding. Prompt medical care can reduce the probability of permanent brain damage.
Causes and symptoms
A subdural hematoma is caused by an injury to the head that tears blood vessels. In childhood, hematomas are a common complication of falls. A subdural hematoma also may be an indication of child abuse, as evidenced by shaken baby syndrome.
Symptoms tend to fluctuate, and include:
- episodes of confusion and drowsiness
- one-sided weakness or paralysis
- enlarged or asymmetric pupils
- convulsions or loss of consciousness after head injury
A doctor should be contacted immediately if symptoms appear. Because these symptoms mimic the signs of a stroke, the patient should tell the doctor about any head injury within the previous few months.
In an infant, symptoms may include increased pressure within the skull, growing head size, bulging fontanelle (one of two soft spots on a infant's skull), vomiting, irritability, lethargy, and seizures. In cases of child abuse, there may be fractures of the skull or other bones.
A chronic subdural hematoma can be difficult to diagnose, but a slow loss of consciousness after a head injury is assumed to be a hematoma unless proven otherwise. The hematoma can be confirmed with magnetic resonance imaging (MRI), which is the preferred type of scan; a hematoma can be hard to detect on a computed tomography scan (CT scan), depending on how long after the hemorrhage the CT is done.
Small hematomas that do not cause symptoms may not need to be treated. Otherwise, the hematoma should be surgically removed. Liquid blood can be drained from burr holes drilled into the skull. The surgeon may have to open a section of skull to remove a large hematoma or to tie off the bleeding vein.
Corticosteroids and diuretics can control brain swelling. After surgery, anticonvulsant drugs (such as phenytoin) may help control or prevent seizures, which can begin as late as two years after the head injury.
If treatment is provided soon enough, recovery is usually complete. Headache, amnesia, attention problems, anxiety, and giddiness may continue for some time after surgery. Most symptoms in adults usually disappear within six months, with further improvement over several years. Children tend to recover much faster.
Because a subdural hematoma usually follows a head injury, preventing head injury can prevent a hematoma.
Brain Injury Association of America. 105 North Alfred St., Alexandria, VA 22314. (800) 444-6443. 〈http://www.biausa.org〉.
Head Injury Hotline. P.O. Box 84151, Seattle WA 98124. (206) 621-8558. 〈http://www.headinjury.com〉.
Head Trauma Support Project, Inc. 2500 Marconi Ave., Ste. 203, Sacramento, CA 95821. (916) 482-5770.
Corticosteroids— A group of drugs similar to natural corticosteroid hormones produced by the adrenal glands. The drugs have a wide variety of applications, including use for inflammatory disorders and swelling.
Diuretics— A group of drugs that helps remove excess water from the body by increasing the amount lost by urination.
Fontanelle— One of the two soft areas on a baby's scalp; a membrane-covered gap between the bones of the skull.
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.
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.
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 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 .
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.
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.
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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