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Subdural hematoma
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<p>A subdural hematoma (SDH) is a type of bleeding in which a <a href="/facts/Hematoma/p5xtzwaJ">collection of blood</a>—usually but not always associated with a <a href="/facts/Traumatic_brain_injury/DTq110vw">traumatic brain injury</a>—gathers between the inner layer of the <a href="/facts/Dura_mater/vcb6bz93">dura mater</a> and the <a href="/facts/Arachnoid_mater/fmWI3KT0">arachnoid mater</a> of the <a href="/facts/Meninges/IcxhShYH">meninges</a> surrounding the <a href="/facts/Brain/EKla9NkJ">brain</a>. It usually results from rips in <a href="/facts/Bridging_vein/l9vnhXSN">bridging veins</a> that cross the <a href="/facts/Subdural_space/1WLzwgq8">subdural space</a>. </p><p>Subdural hematomas may cause an increase in the <a href="/facts/Intracranial_pressure/GVyhAWpH">pressure inside the skull</a>, which in turn can cause compression of and damage to delicate brain tissue. Acute subdural hematomas are often life-threatening. Chronic subdural hematomas have a better <a href="/facts/Prognosis/3DEGwPag">prognosis</a> if properly managed. </p><p>In contrast, <a href="/facts/Epidural_hematoma/IKc0VwH8">epidural hematomas</a> are usually caused by rips in <a href="/facts/Arteries/Y1Yj0jat">arteries</a>, resulting in a build-up of blood between the dura mater and the <a href="/facts/Skull/A9Wp63Np">skull</a>. The third type of brain hemorrhage, known as a <a href="/facts/Subarachnoid_hemorrhage/otbJ6CcK">subarachnoid hemorrhage</a> (SAH), causes bleeding into the subarachnoid space between the arachnoid mater and the <a href="/facts/Pia_mater/8Kt6sdD1">pia mater</a>. SAH are often seen in trauma settings, or after rupture of intracranial aneurysms. </p>