Subdural hematoma Totally Explained

Everything about Subdural Hemorrhage totally explained

A subdural hematoma (Subdural haematoma) (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). 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 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.
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. 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. The mortality rate associated with acute subdural hematoma is around 60 to 80%
   Chronic subdural bleeds develop over the period of days to weeks, often after minor head trauma, though such a cause isn't identifiable in 50% of patients. They may not be discovered until they present clinically months or years after a head injury. The bleeding from a chronic bleed is slow, probably from repeated minor bleeds, and usually stops by itself. 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".
   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.
   Other risk factors for subdural bleeds include taking blood thinners (anticoagulants), long-term alcohol abuse, and dementia.

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