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.
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.
Diuretics—A group of drugs that helps remove excess water from the body by increasing the amount lost by urination.
See also Child abuse.
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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>.
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Tish Davidson, A.M. Carol A. Turkington