What Is a Subarachnoid Hemorrhage?
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A subarachnoid hemorrhage occurs when blood leaks into the narrow space between the pial and arachnoid membranes that surround the brain. It is a severe condition that requires immediate treatment. Most patients are hospitalized for 10 to 20 days, and 40% of patients do not survive.
Five percent of all strokes and half of all instances of spontaneous bleeding inside the brain are caused by SAH. Although it does have a genetic component, the condition is thought to largely preventable. Learn how to recognize symptoms, what to expect from treatment, and ways to prevent SAH.
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1. Causes
Swollen areas of an artery, called aneurysms, are responsible for 80% of cases of SAH. The swelling stretches the blood vessel walls, causing them to become thin to the point of bursting. Once the vessel bursts, uncontrolled bleeding results.
Bleeding from an aneurysm is referred to as non-traumatic SAH, to differentiate it from internal bleeding from a head injury. Lesions on the brain or spine also sometimes hemorrhage. In rare cases known as benign perimesencephalic SAH, a leaking vein or a blood clot is responsible.
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