Subdural Hematoma

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More about Subdural Hematoma: Causes and symptoms Diagnosis Treatment Prognosis Prevention Resources

Definition

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.

Description

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.

— Carol A. Turkington

(medicine) A mass of blood between the arachnoid and the dura mater.

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

A collection of extravasated blood trapped below the dural membranes of the brain causing pressure on the brain, resulting in pain and neural dysfunction. Subdural hematomas may be life threatening.

Definition

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.

Description

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.

Demographics

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:

• headache
• episodes of confusion and drowsiness
• one-sided weakness or paralysis
• lethargy
• enlarged or asymmetric pupils
• convulsions
• increased intracranial pressure
• loss of consciousness after head injury
• coma

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

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.

Treatment

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.

Prognosis

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.

Prevention

Preventing blunt head trauma from falls, child abuse, and assaults is the most effective way of preventing subdural hematoma.

Parental Concerns

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.

See also Child abuse.

Resources

Books

Beers, Mark H., and Robert Berkow, eds. The Merck Manual, 2nd ed., home ed. West Point, PA: Merck & Co., 2004.

Organizations

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.

Web Sites

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).

Ricci, Lawrence R., and Ann S. Botash. "Pediatrics, Child Abuse." eMedicine Medical Library, September 15, 2004. Available online at www.emedicine.com/emerg/topic368.htm (accessed December 1, 2004).

Scaletta, Tom. "Subdural Hematoma." eMedicine MedicalLibrary, March 18, 2004. Available online at www.emedicine.com/emerg/topic560.htm (accessed December 1, 2004).

[Article by: Tish Davidson, A.M. Carol A. Turkington]

Subdural hematoma
Classification & external resources

ICD-10	I61.0, S06.5
ICD-9	852.2 - traumatic; 432.1 - nontraumatic
DiseasesDB	12614
MedlinePlus	000713
eMedicine	neuro/575
MeSH	D006408

A subdural hematoma (SDH) is a form of traumatic brain injury in which blood collects between the dura (the outer protective covering of the brain) and the arachnoid (the middle layer of the meninges). Unlike in epidural hematomas, which are usually caused by tears in arteries, subdural bleeding usually results from tears in veins that cross the subdural space. This bleeding often separates the dura and the arachnoid layers. Subdural hemorrhages may cause an increase in intracranial pressure (ICP), which can cause compression of and damage to delicate brain tissue. Acute subdural hematoma (ASDH) has a high mortality rate and is a severe medical emergency.

Causes

Subdural hematomas are most often caused by head injury, when rapidly changing velocities within the skull may stretch and tear small bridging veins. Subdural hematomas due to head injury are described as traumatic. Much more common than epidural hemorrhages, subdural hemorrhages generally result from shearing injuries due to various rotational or linear forces.^[1][2] It is also commonly seen in the elderly and in alcoholics, who have evidence of brain atrophy. Cerebral atrophy increases the length the bridging veins have to traverse between the two meningeal layers, hence increasing the likelihood of shearing forces causing a tear. It is also more common in patients on anticoagulants, esp Aspirin and Warfarin. Patients on these medications can have a subdural hematoma with a minor injury.

Signs and symptoms

Symptoms of subdural hemorrhage have a slower onset than those of epidural hemorrhages because the lower pressure veins bleed more slowly than arteries. Thus, signs and symptoms may show up within 24 hours but can be delayed as much as 2 weeks.^[3] If the bleeds are large enough to put pressure on the brain, signs of increased ICP or damage to part of the brain will be present.^[2]

Other signs and symptoms of subdural hematoma include the following:

• A history of recent head injury
• Loss of consciousness or fluctuating levels of consciousness
• Irritability
• Seizures
• Numbness
• Headache (either constant or fluctuating)
• Dizziness
• Disorientation
• Amnesia
• Weakness or lethargy
• Nausea or vomiting
• Personality changes
• Inability to speak or slurred speech
• Ataxia, or difficulty walking
• Altered breathing patterns
• Blurred Vision
• Deviated gaze, or abnormal movement of the eyes.^[2]

Features

Most of the time, subdural hematomas occur around the tops and sides of the frontal and parietal lobes.^[1][2] They also occur in the posterior fossa, and near the falx cerebri and tentorium.^[2] Unlike epidural hematomas, which cannot expand past the sutures of the skull, subdural hematomas can expand along the inside of the skull, creating a convex shape that follows the curve of the brain, stopping only at the dural reflections like the tentorium and falx cerebri.

On a CT scan, subdural hematomas are crescent-shaped, with a concave surface away from the skull. Subdural blood can also be seen as a layering density along the tentorium cerebelli. This can be a chronic, stable process, since the feeding system is low-pressure. In such cases, subtle signs of bleeding such as effacement of sulci or medial displacement of the junction between gray matter and white matter may be apparent. A chronic bleed can be the same density as brain tissue (called isodense to brain), meaning that it will show up on CT scan as the same shade as brain tissue, potentially obscuring the finding.

Subtypes

Subdural hematomas are divided into acute, subacute, and chronic, depending on their speed of onset. Acute subdural hematomas that are due to trauma are the most lethal of all head injuries and have a high mortality rate if they are not rapidly treated with surgical decompression.

Acute bleeds develop after high speed acceleration or deceleration injuries and are increasingly severe with larger hematomas. They are most severe if associated with cerebral contusions.^[2] Though much faster than chronic subdural bleeds, acute subdural bleeding is usually venous and therefore slower than the usually arterial bleeding of an epidural hemorrhage. Acute subdural bleeds have a high mortality rate, higher even than epidural hematomas and diffuse brain injuries, because the velocities necessary to cause them cause other severe injuries as well.^[4] The mortality rate associated with acute subdural hematoma is around 60 to 80% ^[5]

Chronic subdural bleeds develop over the period of days to weeks, often after minor head trauma, though such a cause is not identifiable in 50% of patients.^[6] The bleeding from a chronic bleed is slow, probably from repeated minor bleeds, and usually stops by itself.^[1][7] Since these bleeds progress slowly, they present the chance to be stopped before they cause significant damage. Small subdural hematomas, those less than a centimeter wide, have much better outcomes than acute subdural bleeds: in one study, only 22% of patients with chronic subdural bleeds had outcomes worse than "good" or "complete recovery".^[2]

Pathophysiology

Collected blood from the subdural bleed may draw in water due to osmosis, causing it to expand, which may compress brain tissue and cause new bleeds by tearing other blood vessels.^[6] The collected blood may even develop its own membrane.^[8]

In some subdural bleeds, the arachnoid layer of the meninges is torn, and cerebrospinal fluid (CSF) and blood both expand in the intracranial space, increasing pressure.^[1]

Substances that cause vasoconstriction may be released from the collected material in a subdural hematoma, causing further ischemia under the site by restricting blood flow to the brain.^[7] When the brain is denied adequate blood flow, a biochemical cascade known as the ischemic cascade is unleashed, and may ultimately lead to brain cell death.

The body gradually reabsorbs the clot and replaces it with granulation tissue.

Treatment

It is important that a patient receive medical assessment, including a complete neurological examination, after any head trauma. A CT scan or MRI scan will usually detect significant subdural hematomas.

Treatment of a subdural hematoma depends on its size and rate of growth. Small subdural hematomas can be managed by careful monitoring until the body heals itself. Large or symptomatic hematomas require a craniotomy, the surgical opening of the skull. A surgeon then opens the dura, removes the blood clot with suction or irrigation, and identifies and controls sites of bleeding. Postoperative complications include increased intracranial pressure, brain edema, new or recurrent bleeding, infection, and seizure.

Risk factors

Factors increasing the risk of a subdural hematoma include very young or very old age. As the brain shrinks with age, the subdural space enlarges and the veins that traverse the space must travel over a wider distance, making them more vulnerable to tears. This and the fact that the elderly have more brittle veins make chronic subdural bleeds more common in older patients.^[6] Infants, too, have larger subdural spaces and are more predisposed to subdural bleeds than are young adults.^[2] For this reason, subdural hematoma is a common finding in shaken baby syndrome. In juveniles, an arachnoid cyst is a risk factor for a subdural hematoma.^[9]

Other risk factors for subdural bleeds include taking blood thinners (anticoagulants), long-term alcohol abuse, and dementia.

See also

• Head injury
• Traumatic brain injury
• Intra-axial hemorrhage
• Extra-axial hemorrhage
• Epidural hematoma
• Subarachnoid hematoma
• Concussion
• Diffuse axonal injury

References

1. ^ ^{a b c d} University of Vermont College of Medicine. "Neuropathology: Trauma to the CNS." Accessed through web archive on August 8, 2007.
2. ^ ^{a b c d e f g h} Wagner AL. 2004. "Subdural hematoma." Emedicine.com. Retrieved on August 8, 2007.
3. ^ Sanders MJ and McKenna K. 2001. Mosby’s Paramedic Textbook, 2nd revised Ed. Chapter 22, "Head and facial trauma." Mosby.
4. ^ Vinas F.C. and Pilitsis J. 2006. Penetrating Head Trauma. Emedicine.com.
5. ^ Dawodu S. 2004. "Traumatic brain injury: Definition, epidemiology, pathophysiology" Emedicine.com. Retrieved on August 7, 2007.
6. ^ ^{a b c} Downie A. 2001. "Tutorial: CT in head trauma". Retrieved on August 7, 2007.
7. ^ ^{a b} Graham DI and Gennareli TA. Chapter 5, "Pathology of brain damage after head injury" Cooper P and Golfinos G. 2000. Head Injury, 4th Ed. Morgan Hill, New York.
8. ^ McCaffrey P. 2001. "The neuroscience on the web series: CMSD 336 neuropathologies of language and cognition." California State University, Chico. Retrieved on August 7, 2007.
9. ^ Mori K, Yamamoto T, Horinaka N, Maeda M. "Arachnoid cyst is a risk factor for chronic subdural hematoma in juveniles: twelve cases of chronic subdural hematoma associated with arachnoid cyst." J Neurotrauma, 2002 Sep;19(9):1017-27. (PMID 12482115)

Circulatory system pathology (I, 390-459)
Hypertension	Hypertensive heart disease - Hypertensive nephropathy - Secondary hypertension (Renovascular hypertension)
Ischaemic heart disease	Angina pectoris (Prinzmetal's angina) - Myocardial infarction - Dressler's syndrome
Pulmonary circulation	Pulmonary embolism - Cor pulmonale
Pericardium	Pericarditis - Pericardial effusion - Cardiac tamponade
Endocardium/heart valves	Endocarditis - mitral valves (regurgitation, prolapse, stenosis) - aortic valves (stenosis, insufficiency) - pulmonary valves (stenosis, insufficiency) - tricuspid valves (stenosis, insufficiency)
Myocardium	Myocarditis - Cardiomyopathy (Dilated cardiomyopathy, Hypertrophic cardiomyopathy, Loeffler endocarditis, Restrictive cardiomyopathy) - Arrhythmogenic right ventricular dysplasia
Electrical conduction system of the heart	Heart block: AV block (First degree, Second degree, Third degree) - Bundle branch block (Left, Right) - Bifascicular block - Trifascicular block Pre-excitation syndrome (Wolff-Parkinson-White, Lown-Ganong-Levine) - Long QT syndrome - Adams-Stokes syndrome - Cardiac arrest Arrhythmia: Paroxysmal tachycardia (Supraventricular, AV nodal reentrant, Ventricular) - Atrial flutter - Atrial fibrillation - Ventricular fibrillation - Premature contraction (Atrial, Ventricular) - Sick sinus syndrome
Other heart conditions	Heart failure - Cardiovascular disease - Cardiomegaly - Ventricular hypertrophy (Left, Right)
Cerebrovascular diseases	Intracranial hemorrhage/cerebral hemorrhage: Extra-axial hemorrhage (Epidural hemorrhage, Subdural hemorrhage, Subarachnoid hemorrhage) - Intra-axial hematoma (Intraventricular hemorrhages, Intraparenchymal hemorrhage) - Anterior spinal artery syndrome - Binswanger's disease - Moyamoya disease
Arteries, arterioles and capillaries	Atherosclerosis (Renal artery stenosis) - Aortic dissection/Aortic aneurysm (Abdominal aortic aneurysm) - Aneurysm - Raynaud's phenomenon/Raynaud's disease - Buerger's disease - Arteritis (Aortitis) - Intermittent claudication - Arteriovenous fistula - Hereditary hemorrhagic telangiectasia - Spider angioma
Veins, lymphatic vessels and lymph nodes	Thrombosis/Phlebitis/Thrombophlebitis (Deep vein thrombosis, May-Thurner syndrome, Portal vein thrombosis, Venous thrombosis, Budd-Chiari syndrome, Renal vein thrombosis, Paget-Schroetter disease) - Varicose veins (Hemorrhoid, Esophageal varices, Varicocele, Gastric varices, Caput medusae) - Superior vena cava syndrome - Lymph(Lymphadenitis, Lymphedema, Lymphangitis)
See also congenital (Q20-Q28, 745-747)

Injuries, other than fractures, dislocations, sprains and strains (S00-T14, 850-929)
Head (head injury) and neck	Black eye - Traumatic brain injury (Concussion, Cerebral contusion, Epidural hematoma, Subdural hematoma, Subarachnoid hemorrhage) - Brachial plexus lesion
Thorax (chest trauma)	Traumatic aortic rupture - Pneumothorax - Hemothorax - Hemopneumothorax
Abdomen, lower back, lumbar spine and pelvis	Ruptured spleen
Shoulder and upper arm	Rotator cuff tear
General	Bruise - Spinal cord injury

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