A subdural hematoma (SDH) is a form of traumatic brain injury in which blood gathers between the dura (the outer protective covering of the brain) and the arachnoid (the middle layer of the meninges). Subdural hemorrhages may cause an increase in intracranial pressure (ICP), which can cause compression of and damage to delicate brain tissue (also known as a mass effect). Acute subdural hematoma (ASDH) has a high mortality rate and is a severe medical emergency.

Subdural hematomas are most often caused by head injury, when fast 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, especially aspirin and warfarin. Patients on these medications can have a subdural hematoma with a minor injury.

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. Infants, too, have larger subdural spaces and are more predisposed to subdural bleeds than are young adults. 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.^[3] Other risk factors for subdural bleeds include taking blood thinners (anticoagulants), long-term alcohol abuse, and dementia.

Medicines used to treat a subdural hematoma depend on the type of subdural hematoma, the severity of symptoms, and how much brain damage has occurred. Diuretics and corticosteroids may be used to reduce swelling. Anticonvulsion medications, such as phenytoin, may be used to control or prevent seizures.

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.

Always use safety equipment at work and play to reduce your risk of a head injury. For example, use hard hats, bicycle or motorcycle helmets, and seat belts. Older individuals should be particularly careful to avoid falls.

The first case of subdural hematoma was discovered by Johan J.Wpfer, in 1657. Trephination is the process of creating a hole in the skull. The evidence of these procedure is found all over the world starting from late paleolithic period also known as late stone age (50,000 years ago).

• The first case of subdural hematoma was discovered by Johan J.Wpfer, in 1657.^{[1][2][3][4][5]}

• Trephination is the process of creating a hole in the skull. ^[6][7][8]

• The evidence of these procedure is found all over the world starting from late paleolithic period also known as late stone age (50,000 years ago).
• Until 19^th century scientists used to think that these holes were made by accident or weapons, but further studies showed that they were actually surgical procedure.
• The number of holes were different in every person and evidence of healing from edge of the holes was shown a 70% cure rate with limited infection or any complication.
• In old stone age the old people with brain atrophy would developed chronic subdural hematoma.
• One of the symptoms of subdural hematoma is ataxia.
• These people were more susceptible to fall and heading their head into a sharp object (natural trephination).
• Old stone age people observed a dark liquid comes out of the brain from puncture wound of these people, and the symptoms of the patients starts to go away.
• It created the idea of “demonic brain” and established the trephination procedure.

The following are a few famous cases of subdural hematoma:

• Former fox news president Roger Ailes
• Ann B. Davis’s the center square of the Brady Bunch tic-tac-toe grid
• Alex Trebek the Canadian-American television personality

There are 3 classification system for subdural hematoma. Subdural hematoma may be classified according to symptom onset and duration into 3 subtypes including acute, subacute, and chronic, according to midline shift and thickness into 4 subtypes, and based on imaging findings into 6 subtypes.

There are 3 classification system for subdural hematoma:^[1][2]

• Subdural hematoma may be classified according to symptom onset and duration into 3 subtypes:
  • Acute: Develop less than 24 hours after head trauma (or other subdural hemorrhage causes)
  • Subacute: Develop between 1 to 10 days after head trauma (or other subdural hemorrhage causes)
  • Chronic: Develop weeks or months after head trauma (or other subdural hemorrhage causes). It can be further divided into 5 grads:
    • Grade 0: Normal patient with no symptom
    • Grade 1: Patient has headache and mild or no neurological abnormalities but is alert
    • Grade 2: Decreased level of consciousness (drowsiness) with neurological abnormalities
    • Grade 3: Sever focal neurological deficit and loss of consciousness but response to pain stimuli
    • Grade 4: Coma with no response to pain stimuli
• Subdural hematoma may be classified according to mid-line shift and thickness into 4 sub-types:
  • Type A: Thickness ≤ 1cm, midline shift ≤ 5 cm
  • Type B: Thickness > 1cm, midline shift ≤ 5 cm
  • Type C: Thickness > 1cm, midline shift > 5 cm
  • Type D: Thickness ≤ 1cm, midline shift > 5 cm
• Subdural hematoma may be classified according to imaging findings into 6 subtypes:
  • Type 1: Hyperdense lesion, relatively homogeneous (describes acute subdural hemorrhages)
  • Type 2: Isodense lesion, relatively homogeneous (describes subacute hemorrhages)
  • Type 3: Hypodense, relatively homogeneous (describes chronic hemorrhages)
  • Type 4: Isodense to hypodense, relatively heterogeneous (describes recent rebleeding)
  • Type 5: Hypodense in its liquefied component, relatively heterogeneous; internal septations and loculations (higher risk for recurrence after surgical treatment)
  • Type 6: Calcified hyperdense, relatively homogeneous (describes subdural hemorrhage with calcified component)

It is understood that subdural hematoma is the result of rupture in bridging veins (mostly due to head trauma) and hemorrhage between dura matter and arachnoid, leading to subdural hematoma, or rupture of small cortical atreries and hemorrhage into the space between dura matter and arachnoid, leading to subdural hematoma or intracranial hypotension (mostly due to lumbar punctue) and traction of bridging veins which leads to subdural hematoma. Genes involved in the pathogenesis of subdural hematoma include ADPKD, osteogenesis imperfecta, fabry’s disease, mucopolysaccharidosis IIIB, and type B Niemann–Pick disease. On gross pathology, crescentic shape blood in the subdural potential space are characteristic findings of subdural hematoma. On microscopic histopathological analysis, blood in subdural space is characteristic findings of subdural hematoma.

The normal physiology of bridging veins can be understood as follows:^[1]

• In embryonic period, there is lots of anastomosis between brain and dura matter venous drainage.
• After 12 weeks of gestation these anastomosis will disappear and what is left from them create bridging veins.
• These vein s will drain venous blood from underlying brain tissue to the dural sinuses.

• It is understood that subdural hematoma is the result of:
  • Rupture in bridging veins (mostly due to head trauma) and hemorrhage between dura matter and arachnoid, leading to subdural hematoma.
  • Rupture of small cortical atreries and hemorrhage into the space between dura matter and arachnoid, leading to subdural hematoma.
  • Intracranial hypotension (mostly due to lumbar punctue) and traction of bridging veins which leads to subdural hematoma
• Subdural hematomas as a result of arterial rupture accounts for 20% of SDH cases and are mostly in temporoparietal region.
• Since most of the SDH cases are due to vein rupture, the bleeding will stop on its own as a result of a clot formation or increased intracranial pressure.

Genes involved in the pathogenesis of subdural hematoma include:

• ADPKD^{[2][3][4][5][6]}
• Osteogenesis imperfecta
• Fabry’s disease
• Mucopolysaccharidosis IIIB
• Type B Niemann–Pick disease

Conditions associated with subdural hematoma include:^{[7][8][9][10][11][12][13][14][15]}

• Elderly
• Anticoagulant use
• Alcoholics
• Seizure
• CSF shunt
• Arachnoid cyst
• Meningioma
• Cocaine
• Dural metastase
• Roller coaster

On gross pathology, crescentic shape blood in the subdural potential space are characteristic findings of subdural hematoma.

On microscopic histopathological analysis, blood in subdural space is characteristic findings of subdural hematoma.

The most common causes of subdural hematoma include head trauma and neurosurgical procedures.

• Head trauma
• Aneurysmal rupture
• Meningioma

• Head trauma
• Neurosurgical procedures

• Cocaine
• Dural metastase
• Roller coaster

• ADPKD
• Osteogenesis imperfecta
• Fabry’s disease
• Mucopolysaccharidosis IIIB
• Type B Niemann–Pick disease

Subdural hematoma must be differentiated from other disease that causes headache,seizures and loss of consciousness such as Meningitis, encephalitis, brain tumor, hemorrhagic stroke, neurosyphilis, migrain, hypertensive encephalopathy, wernicke’s encephalopathy, brain abscess, drug toxicity, conversion disorders, metabolic disturbance, multiple sclerosis, and seizure.

Subdural hematoma must be differentiated from other disease that causes headache,seizures and loss of consciousness such as Meningitis, encephalitis, brain tumor, hemorrhagic stroke, neurosyphilis, migrain, hypertensive encephalopathy, wernicke’s encephalopathy, brain abscess, drug toxicity, conversion disorders, metabolic disturbance, multiple sclerosis, and seizure.

The incidence of subdural hematoma is approximately 14.7 per 100,000 individuals in USA. The case mortality rate of traumatic subdural hematoma is approximately 14%. Patients of all age groups may develop subdural hematoma. The incidence of subdural hematoma increases with age. There is no racial predilection to subdural hematoma. Men are more commonly affected by chronic subdural hematoma than female.

• The incidence of subdural hematoma is approximately 14.7 per 100,000 individuals in USA.^[1]

• The case mortality rate of traumatic subdural hematoma is approximately 14%.

• Patients of all age groups may develop subdural hematoma.
• The incidence of subdural hematoma increases with age.

• There is no racial predilection to subdural hematoma.

• Men are more commonly affected by chronic subdural hematoma than female.^[2]

Common risk factors in the development of subdural hematoma include elderly, anticoagulant use, alcohol use, Seisure, and any other disease with gait and balance abnormality.

• Common risk factors in the development of subdural hematoma include:^[1][2][3][4]
  • Elderly
  • Anticoagulant use
  • Patients who are at risk of falling such as:
    • Alcoholics
    • Seizure
    • Any disease with gait and balance abnormality

• Less common risk factors in the development of subdural hematoma include:^[5][6][7]
  • CSF shunt
  • Arachnoid cyst

If left untreated, 14% of patients with subdural hematoma may progress to serious complications including death. Common complications of subdural hematoma include memory loss, dizziness, headache, anxiety, difficulty concentrating, seizures, temporary or permanent weakness, numbness, difficulty speaking, brain herniation, coma, death. Depending on the extent, type, and locationat of hematoma at the time of diagnosis, the prognosis may vary.

• The symptoms of chronic subdural hematoma usually develop in the sixth and seventh decade of life.^[1][2]
• In acute subdural hematoma, the symptoms of SDH typically develop 24 hours after head injury.
• In subacute subdural hematoma, the symptoms os SDH typically develop between 1 to 10 days after head trauma.
• In chronic subdural hematoma, the symptoms of SDH typically develop weeks or months after head trauma
• If left untreated, 14% of patients with subdural hematoma may progress to serious complications including death.

Common complications of subdural hematoma include:

• Memory loss
• Dizziness
• Headache
• Anxiety
• Difficulty concentrating
• Seizures
• Temporary or permanent weakness
• Numbness
• Difficulty speaking
• Brain herniation
• Coma
• Death

• Acute subdural hematoma prognosis is generally poor, and the case mortality rate of traumatic subdural hematoma is approximately 14%.
• Acute subdural hematomas has high rates of death and injury.
• Depending on the extent, type, and locationat of hematoma at the time of diagnosis, the prognosis may vary.
• However, the prognosis is generally regarded as poor in acute subdural hematoma and good in chronic subdural hematoma.
• Subacute and chronic subdural hematomas have better outcomes in most cases, with symptoms often going away after the blood collection is drained.

• There is a high frequency of seizures following a subdural hematoma, even after drainage.
• These seizures are usually well controlled with medication.
• Seizures may occur at the time the hematoma forms, or up to months or years afterward.
• A period of rehabilitation is sometimes needed to assist the person back to his or her usual level of functioning.