Subdural Hematoma: Background, Pathophysiology, Etiology (2023)

The usual mechanism that produces an acute subdural hematoma is a high-speed impact to the skull. This causes brain tissue to accelerate or decelerate relative to the fixed dural structures, tearing blood vessels.

Often, the torn blood vessel is a vein that connects the cortical surface of the brain to a dural sinus (termed a bridging vein). In elderly persons, the bridging veins may already be stretched because of brain atrophy (shrinkage that occurs with age).

Alternatively, a cortical vessel, either a vein or small artery, can be damaged by direct injury or laceration. An acute subdural hematoma due to a ruptured cortical artery may be associated with only minor head injury, possibly without an associated cerebral contusion. In one study, the ruptured cortical arteries were found to be located around the sylvian fissure. [3]

The head trauma may also cause associated brain hematomas or contusions, subarachnoid hemorrhage, and diffuse axonal injury. Secondary brain injuries may include edema, infarction, secondary hemorrhage, and brain herniation.

Typically, low-pressure venous bleeding from bridging veins dissects the arachnoid away from the dura, and the blood layers out along the cerebral convexity. Cerebral injury results from direct pressure, increased intracranial pressure (ICP), or associated intraparenchymal insults.

In the subacute phase, the clotted blood liquefies. Occasionally, the cellular elements layer can appear on CT imaging as a hematocrit-like effect. In the chronic phase, cellular elements have disintegrated, and a collection of serous fluid remains in the subdural space. In rare cases, calcification develops.

Much less common causes of subdural hematoma involve coagulopathies and ruptured intracranial aneurysms. Subdural hematomas have even been reported to be caused by intracranial tumors.

It has been asserted that the primary brain injury associated with subdural hematoma plays a major role in mortality. However, most subdural hematomas are thought to result from torn bridging veins, as judged by surgery or autopsy. Furthermore, not all subdural hematomas are associated with diffuse parenchymal injury. As mentioned earlier, many patients who sustain these lesions are able to speak before their condition deteriorates—an unlikely scenario in patients who sustain diffuse damage.

(Video) Traumatic brain injury: pathology review

Using a primate model, Gennarelli and Thibault demonstrated that the rate of acceleration-deceleration of the head was the major determinant of bridging vein failure. By using an apparatus that controlled head movement and minimized impact or contact phenomena, they were able to produce acute subdural hematomas in rhesus monkeys. In all cases, the sagittal movement of the head produced by an angular acceleration caused rupture of parasagittal bridging veins and an overlying subdural hematoma.

Gennarelli and Thibault reported that their results were consistent with the clinical causes of subdural hematoma, in that 72% are associated with falls and assaults and only 24% are associated with vehicular trauma. The acceleration (or deceleration) rates caused by falls and assaults are greater than those caused by the energy-absorbing mechanisms in cars, such as dashboard padding, deformable steering wheels, and laminated windshields. [4]

Acute subdural hematoma

Investigation of brain physiological and biochemical parameters in patients with acute traumatic subdural hematoma has suggested variables that might be associated with secondary injury to the brain.

In a study of brain biochemical patterns after acute subdural hematoma evacuation, Hlatky et al found that postsurgical patients who succumbed to their injury exhibited lower values of brain tissue oxygen tension and higher dialysate values of lactate and pyruvate in the brain underlying the hematoma. They suggested that identification of this brain biochemistry pattern after surgery might signify an evolving brain injury that warrants further evaluation or treatment. [5]

Cerebral blood flow (CBF) can become markedly reduced. Schroder et al reported that in 2 patients with acute subdural hematoma requiring emergent craniotomy, the hemisphere ipsilateral to the subdural hematoma demonstrated lower CBF than the contralateral hemisphere. Furthermore, CBF in both hemispheres was lower than normal. [6]

Impressive increases in CBF and cerebral blood volume (CBV) that could not be attributed to pCO2 or blood pressure changes were noted immediately after surgery. The authors speculated that the decreased CBV caused by the subdural hematoma was a result of a compressed microcirculation, which was caused by increased ICP. [6]


Like other masses that expand within the skull, subdural hematomas may become lethal by increasing pressure within the brain, leading to pathologic shifts of brain tissue (brain herniations). Two common types of brain herniation are subfalcial (cingulate gyrus) herniation and transtentorial (uncal) herniation.

Subfalcial herniation may cause a cerebral infarct via compression of the anterior cerebral artery, and transtentorial herniation may cause an infarct via compression of the posterior cerebral artery. Transtentorial herniation is also associated with pressure on the third cranial nerve, causing decreased reactivity and then dilation of the ipsilateral pupil.

(Video) Epidural Hematoma | Anatomy, Etiology, Pathophysiology, Clinical Features, Treatment

With progressive transtentorial herniation, pressure on the brainstem causes its downward migration. This tears critical blood vessels that supply the brainstem, resulting in Duret hemorrhages and death. Increased ICP may also decrease cerebral flood flow, possibly causing ischemia and edema; this further increases the ICP, causing a vicious circle of pathophysiologic events.

Chronic subdural hematoma

Chronic subdural hematoma is commonly associated with cerebral atrophy. Cortical bridging veins are thought to be under greater tension as the brain gradually shrinks from the skull; even minor trauma may cause one of these veins to tear. Slow bleeding from the low-pressure venous system often enables large hematomas to form before clinical signs appear.

Small subdural hematomas often spontaneously resorb. Larger collections of subdural blood usually organize and form vascular membranes that encapsulate the subdural hematoma. Repeated bleeding from small, friable vessels within these membranes may account for the expansion of some chronic subdural hematomas.

Chronic subdural hematomas may also evolve from the liquefaction of an acute subdural hematoma, particularly one that is relatively asymptomatic. Liquefaction usually occurs after 1-3 weeks, with the hematoma appearing hypodense on a CT scan.

Some chronic subdural hematomas may also enlarge from an osmotic gradient, drawing more fluid into the subdural space, or through the separate mechanism of calcification. [7]

In 1989, Kawakami discovered that the coagulation and fibrinolysis systems were both excessively activated in chronic subdural hematoma. [8] This results in defective clot formation and recurrent hemorrhage. Katano et al reported that elevated concentrations of tissue plasminogen activator are found in some chronic subdural hematomas, and indicate a relatively high probability of recurrence. [9]

As a subdural hematoma expands in the subdural space, it raises the ICP and deforms the brain. The rise in ICP is initially compensated by efflux of cerebrospinal fluid (CSF) toward the spinal axis and compression of the venous system, expediting venous drainage through the jugular veins. During this stage, ICP rises relatively slowly, because the intracranial compliance is relatively high; in other words, the initial changes in intracranial volume are associated with small changes in ICP.

However, as the hematoma (and edema from associated parenchymal injury) expands, a limit is reached beyond which compensatory mechanisms fail. The intracranial compliance begins to decrease; small increases in intracranial volume are associated with larger increases in ICP. The ICP rises exponentially, leading to decreased cerebral perfusion and global cerebral ischemia. In a rapidly expanding hematoma, this whole process can happen in minutes.

(Video) Subdural Haematoma

In patients with chronic subdural hematoma, blood flow to the thalamus and basal ganglia regions appears to be particularly affected compared to that to the rest of the brain. Tanaka et al suggested that impaired thalamic function can lead to a spreading depression that impairs various cortical regions, thereby producing various clinical deficits. They found that a 7% decrease of CBF was commonly associated with headache, whereas a 35% decrease of CBF was associated with neurological deficit such as hemiparesis. [10]

Given that the pathophysiology of chronic subdural hematoma is often directly associated with cerebral atrophy, the fact that subdural hematomas are associated with conditions that cause cerebral atrophy (eg, alcoholism, dementia) is not surprising. In a series reported by Foelholm and Waltimo, alcoholics constituted over half of the patient population. Most chronic subdural hematomas are probably caused by head injury; other causes and predisposing factors include coagulopathy, use of anticoagulants (including aspirin), seizure disorders, and CSF shunts. [11]

Herniation syndromes

In addition to increasing the ICP, the hematoma deforms and displaces the brain. Eventually, transtentorial or subfalcine herniation can develop as the brain is pushed past the dural folds of the tentorial incisura or falx, respectively.

Tonsillar herniation through the foramen magnum may develop if the whole brain stem is forced down through the tentorial incisura by elevated supratentorial pressure. Although much less common than supratentorial subdural hematoma, infratentorial subdural hematoma can develop and cause tonsillar herniation and brainstem compression.

Characteristic herniation syndromes may develop as the brain shifts. As the medial temporal lobe, or uncus, herniates past the tentorium, it can compress the ipsilateral posterior cerebral artery, oculomotor nerve, and cerebral peduncle. Clinically, the consequent oculomotor nerve palsy and cerebral peduncle compression are often manifested by an ipsilaterally dilated pupil and a contralateral hemiparesis.

The patient also may develop a stroke of the posterior cerebral artery distribution. In approximately 5% of cases, the hemiparesis may be ipsilateral to the dilated pupil. This phenomenon is called the Kernohan notch syndrome and results when uncal herniation forces the midbrain to shift so that the contralateral cerebral peduncle is forced against the contralateral tentorial incisura.

Subfalcine herniation caused by midline brain shift may result in compression of anterior cerebral artery branches against the fixed falx cerebri, leading to infarcts in an anterior cerebral artery distribution.

(Video) Subdural Hematoma

Spontaneous subdural hematoma

Spontaneous subdural hematoma is rare. The literature is limited to sporadic case reports. These cases often have an arterial source; they are usually associated with the same pathology as that involved in subarachnoid or intracerebral hemorrhage. The blood from a ruptured aneurysm may dissect through the brain parenchyma or subarachnoid space into the subdural space.

Likewise, the blood released from a "hypertensive" intracerebral hemorrhage can dissect into the subdural space. In fact, a case has been reported of an acute spontaneous subdural hematoma precipitated by cocaine abuse.

Coagulopathy, occasionally associated with malignancy, also has been associated with spontaneous subdural hematoma. Subdural hematoma also can be caused by bleeding from intracranial tumors. The treatment of spontaneous subdural hematoma is similar to that of subdural hematoma caused by trauma, but the underlying cause must be sought and treated.

Subdural hygroma

Some chronic subdural hematomas may be derived from subdural hygromas. Brain atrophy or loss of brain tissue due to any cause, such as alcoholism, or stroke, may provide either an increased space between the dura and the brain surface where a subdural hygroma can form (see the image below) or traction on bridging veins that span the gap between the cortical surface and dura or venous sinuses.

Atrophy of the brain, resulting in a space between the brain surface and the skull, increases the risk of subdural hematoma (SDH).

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(Video) Subdural Hemorrhage | Anatomical Correlation Clinical | Features And Pathophysiology | Dr Najeeb

Hygromas probably form after a tear in the arachnoid allows CSF to collect in the subdural space. A subdural hygroma may therefore also occur after head trauma; they are frequently asymptomatic.


What is the etiology of subdural hematoma? ›

Subdural haematomas are usually caused by a head injury.

A subdural haematoma develops if there's bleeding into the space between the skull and the brain (the subdural space) caused by damage to the blood vessels of the brain or the brain itself.

What is the most common physiological manifestation of a subdural hematoma? ›

If you have a subdural hematoma, blood is leaking out of a torn vessel into a space below the dura mater, a membrane between the brain and the skull. Symptoms include ongoing headache, confusion and drowsiness, nausea and vomiting, slurred speech and changes in vision.

What are the three types of subdural hematomas? ›

The three types of subdural hematomas are:
  • Acute. This most dangerous type is generally caused by a severe head injury, and signs and symptoms usually appear immediately.
  • Subacute. Signs and symptoms take time to develop, sometimes days or weeks after the injury.
  • Chronic.
17 Jun 2022

What is a subdural haematoma? ›

A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrounding the brain.

What is hematoma and its causes? ›

A hematoma is a bad bruise. It happens when an injury causes blood to collect and pool under the skin. The pooling blood gives the skin a spongy, rubbery, lumpy feel. A hematoma usually is not a cause for concern. It is not the same thing as a blood clot in a vein, and it does not cause blood clots.

Which drugs cause subdural hematoma? ›

The following increase the risk for a subdural hematoma:
  • Medicines that thin the blood (such as warfarin or aspirin)
  • Long-term alcohol use.
  • Medical conditions that make your blood clot poorly.
  • Repeated head injury, such as from falls.
  • Very young or very old age.
25 Apr 2022

What is the best treatment for subdural hematoma? ›

Craniotomy. A craniotomy is the main treatment for subdural haematomas that develop soon after a severe head injury (acute subdural haematomas). During the procedure, the surgeon creates a temporary flap in the skull. The haematoma is gently removed using suction and irrigation, where it's washed away with fluid.

What body systems are affected by subdural hematoma? ›

A subdural hematoma occurs when the tiny blood vessels within the brain's dura tear, causing blood to pool in the brain. The bleeding can quickly fill the brain, compressing parts of the brain, impeding brain function, leading to organ failure, and even causing death.

What test shows subdural hematoma? ›

Brain scans

Most people with a suspected subdural haematoma will have a CT scan to confirm the diagnosis. A CT scan uses X-rays and a computer to create detailed images of the inside of your body. It can show whether any blood has collected between your skull and your brain.

Where is a subdural hematoma located? ›

A subdural haematoma is a serious condition where blood collects between the skull and the surface of the brain. It's usually caused by a head injury. Symptoms of a subdural haematoma can include: a headache that keeps getting worse.

What type of bleeding is subdural hematoma? ›

A subdural hemorrhage, also called a subdural hematoma, is a kind of intracranial hemorrhage, which is the bleeding in the area between the brain and the skull. Specifically, it is a bleed just under the dura, which is one of the protective layers of tissue that surrounds the brain.

What are the 5 different types of hematoma? ›

Things to know about hematoma

Examples of hematomas include subdural, spinal, under the finger or toenail bed (subungual), ear, and liver (hepatic).

What are the 4 types of brain bleed? ›

Intracranial hemorrhage encompasses four broad types of hemorrhage: epidural hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, and intraparenchymal hemorrhage. [1][2][3] Each type of hemorrhage is different concerning etiology, findings, prognosis, and outcome.

What's the definition of subdural? ›

ˈsəb-ˌd(y)u̇r- : situated or occurring beneath the dura mater or between the dura mater and the arachnoid membrane.

What are the symptoms of a hematoma? ›

Pain, swelling, redness, and disfiguring bruises are common symptoms of hematoma in general. Some symptoms specific to the location of a hematoma are: Subdural hematoma symptoms: headache, neurologic problems (weakness on one side, difficulty speaking, falling), confusion, seizures.

What problems can a hematoma cause? ›

A hematoma is similar to a bruise or blood clot but, if left untreated, it can damage the tissue and lead to infection. An injury to the nose can rupture blood vessels in and around the septum where there is both bone and cartilage.

Why is hematoma important? ›

The rising importance of osteoimmunological aspects in bone healing supports the essential role of the initial haematoma as a source for inflammatory cells that release the cytokine pattern that directs cell recruitment towards the injured tissue.

What are the dangers of a hematoma? ›

Any bruise or other hematoma of the skin that increases in size over time could also present a danger. If a clot from a hematoma reenters the bloodstream, it can block an artery, cutting off blood flow to part of the body. Without prompt treatment, this can result in permanent tissue damage.

Can high blood pressure cause subdural hematoma? ›

Hypertensive crisis presenting with acute spontaneous subdural hematoma prompts tight blood pressure control in timely manner to prevent permanent neurological sequalae. Rapid and severe elevation in the blood pressure might be a potential etiology of spontaneous bleeding into the subdural space.

What are the after effects of a subdural hematoma? ›

Many people are left with some long-lasting problems after treatment for a subdural haematoma. These can include changes to your mood, concentration or memory problems, fits (seizures), speech problems, and weakness in your limbs.

Can subdural hematoma heal without surgery? ›

People with an acute subdural hematoma typically do not need treatment because the hematoma will break down in the body over time. However, in some cases, following a head injury, an acute subdural hematoma will need to be treated immediately with surgery to relieve pressure on the brain.

Can subdural hematoma be treated without surgery? ›

Conclusions: Chronic subdural hematoma can be treated with tranexamic acid without concomitant surgery. Tranexamic acid might simultaneously inhibit the fibrinolytic and inflammatory (kinin-kallikrein) systems, which might consequently resolve CSDH.

When is surgery needed for subdural hematoma? ›

INDICATIONS FOR SURGERY An acute subdural hematoma (SDH) with a thickness greater than 10 mm or a midline shift greater than 5 mm on computed tomographic (CT) scan should be surgically evacuated, regardless of the patient's Glasgow Coma Scale (GCS) score.

What is the treatment for hematoma? ›

Treatment for a bruise or a hematoma

First-line therapy is rest, ice, compression and elevation (RICE method). If the injured area is painful, the injury can be treated with OTC medications like Tylenol or Advil.

Will an MRI show a subdural hematoma? ›

Magnetic resonance imaging

An MRI is helpful in imaging chronic subdural hematoma when CT scans are difficult to interpret (eg, when suspecting an isodense hematoma). MRI may be particularly helpful in diagnosing bilateral chronic subdural hematoma because a midline shift may not be apparent on CT scan.

Can MRI see subdural hematoma? ›

Chronic subdural hematoma (CSDH), which generally occurs in elderly patients, is a frequently diagnosed condition in neurosurgical departments. Computed tomography (CT) and magnetic resonance imaging (MRI) are the most preferred diagnostic modalities for CSDH assessment.

Which hematoma is most common? ›

Acute subdural hematoma is the most common type of traumatic intracranial hematoma, occurring in 24% of patients who present comatose. This type of head injury also is strongly associated with delayed brain damage, later demonstrated on CT scan.

What is hematoma medical term? ›

A pool of mostly clotted blood that forms in an organ, tissue, or body space. A hematoma is usually caused by a broken blood vessel that was damaged by surgery or an injury. It can occur anywhere in the body, including the brain.

What is the stage of hematoma? ›

The Inflammatory Stage

This tells the body to stop using the injured part so it can heal. Other cells that come to the area during this stage form a hematoma (blood clot) around the broken bone. This is the first bridge between the pieces of the broken bone.

Is subdural hematoma a stroke? ›

If a subdural hemorrhage involves significant amounts of blood, the pressure can cause a stroke. In severe cases, significant pressure can lead to loss of consciousness or even death. This can happen if the blood is located near the brainstem, which controls breathing and other important automatic functions.

Can stress cause a brain bleed? ›

New IRP research shows that psychological stress not only triggers depression-like behavioral changes in mice but also causes tiny ruptures in their brains' blood vessels.

What were your first signs of a brain bleed? ›

Brain hemorrhage
  • Sudden or severe headache.
  • Weakness, tingling or numbness in the arms or legs (often on one side)
  • Nausea or vomiting.
  • Changes in vision.
  • Changes in balance.
  • Difficulty speaking or understanding speech.
  • Difficulty using fine motor skills.
  • Seizures.

How can a subdural hematoma lead to brain injury or death? ›

The bleeding is under the skull and outside the brain, not in the brain itself. As blood pools, however, it puts more pressure on the brain. The pressure on the brain causes symptoms. If pressure inside the skull rises to a very high level, a subdural hematoma can lead to unconsciousness and death.

What is the most common cause of a brain bleed? ›

Bleeding in the brain (also called a brain hemorrhage or brain bleed) can happen because of an accident, brain tumor, stroke, or high blood pressure caused by congenital or other health conditions. Brain bleed can reduce oxygen delivery to the brain, create extra pressure in the brain and kill brain cells.

What is the most common cause of intracranial bleeding? ›

The main causes of intracranial hemorrhage are: Hypertension (high blood pressure). High blood pressure can weaken the blood vessels in your brain, causing them to leak or rupture. Head trauma.

What is the most common cause of a subdural empyema? ›

Subdural empyema most often occurs due to the direct extension of local infection. The infection can spread to the intracranial compartment due to the valveless diploic veins of Breschet. As a result, blood may flow in either direction, causing the spread of bacterial infection intracranially.

What causes non traumatic subdural hematoma? ›

The majority of acute subdural hematoma (SDH) occur due to head trauma, and nontraumatic or “spontaneous” acute SDH is rare, which is caused by various etiologies such as cortical artery bleeding, vascular lesions, coagulopathy, neoplasms, spontaneous intracranial hypotension, cocaine, and arachnoid cyst.

How do you treat a brain hematoma? ›

A craniotomy is the main treatment for subdural haematomas that develop soon after a severe head injury (acute subdural haematomas). During the procedure, the surgeon creates a temporary flap in the skull. The haematoma is gently removed using suction and irrigation, where it's washed away with fluid.

What are 3 types of hemorrhage? ›

These three types of bleeding, or hemorrhaging, differ not only in location but also in how they flow and their severity. Specifically, arterial bleeding comes out in spurts, venous bleeding flows steadily, and capillary bleeding trickles from the body. Bleeding from the arteries and veins can be severe.

Who is at risk for brain hemorrhage? ›

Intracerebral hemorrhages can occur in anyone at any age. However, people with high blood pressure are at an increased risk of developing an intracerebral hemorrhage. High blood pressure, particularly unrealized or untreated high blood pressure, is the most common cause of intracerebral hemorrhage.

What is risk subdural hematoma? ›

A subdural haematoma is a serious condition that carries a high risk of death, particularly in older people and those whose brain was severely damaged. Acute subdural haematomas are the most serious type because they're often associated with significant damage to the brain.

Can subdural hematomas cause infections? ›

In addition, surgical results revealed an infected subdural hematoma. A bacterial culture of the purulent specimen identified E. coli. In view of the urinary complaint and leukocyturia, the cause of the infected subdural hematoma was postulated as a urinary tract infection.

Can drug use cause a subdural hematoma? ›

There are multiple risk factors associated with spontaneous subdural hematoma (SDH), including substance abuse, hypertension, vascular abnormalities, and neoplasms. The illicit drugs typically cited as risk factors for spontaneous SDH are alcohol and cocaine.

How are subdural hematomas diagnosed? ›

Brain scans

Most people with a suspected subdural haematoma will have a CT scan to confirm the diagnosis. A CT scan uses X-rays and a computer to create detailed images of the inside of your body. It can show whether any blood has collected between your skull and your brain.


1. Epidural and Subdural Hematoma
(Nursing School Explained)
2. What is subdural hematoma? | Neuroaholics
(Faldi Yaputra)
3. Epidural Hematoma, Subdural hematoma, Subarachnoid hematoma, Intracerebral hemorrhage
(the study spot)
4. Acute Subdural Haematoma - what is it and how do brain surgeons evacuate them?
5. Subdural Hematoma: Presentation and Management
(Brain & Spine Group)
6. Chronic Subdural Hematoma, SDH
(Dr.S.N.Gautam Neurosurgeon)
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