Subdural hematoma overview

# Overview
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.

# Causes
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. 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.

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

# Treatment

## Medical Therapy
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.

## Surgery
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.

## Primary Prevention
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.