What is subdural hematoma?

Quick Answer
Collection of blood (clotted and partially clotted) in the subdural space.
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Causes and Symptoms

Subdural hematomas are caused by either a major head injury (acute subdural hematomas) or by a relatively minor head injury (chronic subdural hematomas). Acute subdural hematomas usually occur after a major head injury in which the rotational or linear forces cause veins in the subdural space to break. These types of subdural hematomas are the most common form of sports-related brain injury, especially in professional boxers because of the multiple head blows that they receive. Chronic subdural hematomas, on the other hand, typically develop days to weeks after relatively minor head injuries. This type of hematoma mainly afflicts the elderly, who are more likely to have brain shrinkage, which causes the subdural veins to stretch in order to cover the greater distance created between the brain and the dura mater. These stretched veins are more vulnerable to breakage, even from a minor head injury. Some cases of subdural hematomas occur without apparent head injury, which may be due to the fact that many minor head injuries go unnoticed. Blood-thinning drugs such as Coumadin, alcohol abuse, seizures, repeated falls, shunts draining excess cerebrospinal fluid (CSF) from the brain, and very young or very old age increase the risk of developing a subdural hematoma.

A subdural hematoma can compress the brain, frequently leading to brain injury. Symptoms in adults and older children include a persistent headache, drowsiness, loss of consciousness, paralysis on the opposite side of the body, seizures, memory problems, confusion, nausea, numbness, visual abnormalities, slurred or confused speech and language, and weakness. An elderly person with memory loss or drowsiness may be mistakenly thought to have dementia when he or she actually has a subdural hematoma. In professional boxers, symptoms include neurological abnormalities, deteriorating dementia, and death.

In infants, subdural hematomas occur as part of shaken baby syndrome. Symptoms of a subdural hematoma in infants include swollen fontanelles (“soft spots” in a baby’s skull), focal seizures, generalized tonic-clonic seizures, increased sleepiness, irritability, and vomiting. In all cases, acute subdural hematomas carry a high risk of death and are considered medical emergencies. The cause of shaken baby syndrome remains controversial. Initially, shaking was thought to induce shear forces that cause breakage of the bridging veins in the subdural space, resulting in the subdural hematomas, retinal hematomas, and encephalopathy characteristic of shaken baby syndrome. However, more recent research suggests that these symptoms are more likely caused by vein damage due to impact and hypoxia. Subdural hematomas may also be caused by the birth process.

Treatment and Therapy

Computed tomography (CT) scanning and magnetic resonance imaging (MRI) can detect most subdural hematomas. MRI is more sensitive and may be able to detect hematomas that may not show up on CT scans.

Treatment is based on the type and size of hematoma and the amount of pressure that has accumulated in the brain. Small subdural hematomas may resolve when head injuries heal. For small subdural hematomas that do not resolve, a hole may be drilled in the skull and the blood mass drained from the subdural space via a catheter. This procedure can be performed at the patient’s bedside. Large hematomas, however, may require a surgical procedure known as a craniotomy, in which the skull is surgically opened and the blood mass removed. Surgical removal of acute subdural hematomas is associated with a significant risk of death. On the other hand, treatment of chronic subdural hematomas has a relatively good prognosis.

Perspective and Prospects

In 1946, pediatrician John Caffey described the relationship between long bone injuries and subdural hematomas. Since then, subdural hematomas have been reported in the elderly, professional athletes such as boxers and hockey players, and in abused children.

There is considerable uncertainty about the long-term effects of subdural hematomas. Although it is not known if suffering a subdural hematoma puts someone at greater risk of experiencing subdural hematomas in the future, boxing commissions in several states have banned boxers with a history of subdural hematomas from competing. Boxers diagnosed with subdural hematomas risk being banned from boxing, a fact that prevents some professional boxers from seeking a diagnosis. A well-known case involves a thirty-one-year-old boxer, Joe Mesi, who was suspended by the Nevada Athletic Commission after he developed subdural hematomas as a result of head injuries sustained in a March, 2004, fight. Mesi lost an appeal to lift his medical suspension in 2005. Another athlete, a professional hockey player, suffered a subdural hematoma after receiving a hit to the head during a game. However, his wounds healed and his doctors allowed him to return to professional hockey, believing that there would be no negative consequences. Until more is known about the long-term effects of subdural hematomas, there will continue to be controversy over whether athletes with a history of hematomas should be allowed to compete.


Heller, J. L. “Subdural Hematoma.” MedlinePlus, July 4, 2012.

Miele, V. J., et al. "Subdural Hematomas in Boxing: The Spectrum of Consequences." Neurosurgical Focus 21, no. 4 (October 15, 2006): E10.

Neff, Deanna M. "Subdural Hematoma." Health Library, November 26, 2012.

Squier, W. “Shaken Baby Syndrome: The Quest for Evidence.” Developmental Medicine & Child Neurology 50, no. 1 (January, 2008): 10–14.

Squier, W., and J. Mack. “The Neuropathology of Infant Subdural Hemorrhage.” Forensic Science International 187, nos. 1–3 (May 30, 2009): 6–23. Describes the neurological symptoms of subdural hematomas in infants.

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