Stroke is an injury to the brain that occurs when the brain's blood supply is interrupted. Blood carries oxygen which is necessary for all cells in the body to survive. The brain has one of the highest demands for oxygen. In fact, cells in the brain start to die if they are without oxygen-rich blood for more than a few minutes. The death of these brain cells can result in permanent brain damage.
Other terms for stroke include cerebrovascular accident (CVA) or brain attack.
Blood vessels that carry blood from the heart to the body are called arteries. Oxygen-rich blood is delivered to the brain through the carotid arteries along both sides of the neck. These arteries split into several smaller vessels that reach throughout the brain and skull. Damage or blockage to any of these arteries can slow or stop blood flow to the brain. The severity of brain damage will depend on the amount of brain tissue affected, the length of time the blood flow is impaired, and the area of the brain affected.
An ischemic stroke occurs when a blood vessel of the brain becomes blocked. Nearly 90% of all strokes are ischemic. Blockage may be caused by:
A stroke may also occur if a blood vessel breaks and bleeds into or around the brain. Hemorrhagic stroke is the most common type of stroke in young people. The leading causes of this type of stroke are:
A silent stroke occurs without any typical signs or symptoms of a stroke. Despite this, silent strokes cause damage to brain tissue and increase the risk of a major stroke in the future. Silent strokes tend to occur in silent areas of the brain that are not obviously active in cognitive function or mobility. Brain tissue damage is usually found incidentally during imaging tests.
Strokes can also be classified according to their course in time:
Multiple small strokes may occur over time, from days to years, and create effects similar to one big stroke.
Impact of stroke (stroke statistics). American Stroke Association website. Available at: http://www.strokeassociation.org/STROKEORG/AboutStroke/Impact-of-Stroke-Stroke-statistics_UCM_310728_Article.jsp. Updated May 27, 2014. Accessed June 12, 2014.
Stroke (acute management). EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T143427/Stroke-acute-management. Updated December 28, 2015. Accessed October 6, 2016.
What causes a stroke? National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/health/health-topics/topics/stroke/causes. Updated March 26, 2014. Accessed June 12, 2014.
What is a stroke? National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/health/health-topics/topics/stroke. Updated March 26, 2014. Accessed June 12, 2014.
What is an arteriovenous malformation (AVM)? American Stroke Association website. Available at: http://www.strokeassociation.org/STROKEORG/AboutStroke/TypesofStroke/HemorrhagicBleeds/What-Is-an-Arteriovenous-Malformation-AVM_UCM_310099_Article.jsp#.VnrryU2FPIU. Updated February 20, 2013. Accessed June 12, 2014.
Yatsu FM, Shaltoni HM. Implications of silent strokes. Curr Arthroscler Rep. 2004;6(4):307-313.
Last reviewed December 2015 by Rimas Lukas, MD
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