Stroke
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Stroke is an injury to the brain that happens when its blood source is stopped. Blood carries oxygen that cells in the brain need to live. Cells start to die if they are without oxygen for more than a few minutes. This can cause lasting harm to the brain.
Other terms for stroke are cerebrovascular accident (CVA) or brain attack.
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Blood vessels that carry blood from the heart to the body are called arteries. Oxygen rich blood is brought to the brain through the carotid and vertebral arteries along both sides of the neck. These arteries split into smaller vessels that reach throughout the brain and skull. If they are harmed or blocked, it can slow or stop blood flow to the brain. The amount of harm depends on how much tissue was affected, how long blood flow was slowed or stopped, and the part of the brain it was in.
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| Copyright © 2002 Nucleus Communications, Inc. All rights reserved. |
Types and Causes of Stroke
An ischemic stroke is when a blood vessel of the brain is blocked. Most strokes are ischemic. Blood may be blocked by:
- —Narrowing of the carotid arteries that bring blood to the brain. It happens from atherosclerosis. This is the buildup of plaque inside artery walls.
- —A blood clot that forms in the arteries of the brain. It is often from atherosclerosis.
- —A blood clot that travels from some other part of the body. Often, the clot travels from the heart and gets trapped in the arteries that bring blood to the brain. It is often due to atrial fibrillation, a type of heart arrhythmia.
- —Blood vessel walls can tighten or loosen to help blood flow. Problems with nerves, blood vessel structure, injuries, or stimulant use can cause them to do this. This makes it hard for blood to flow. Spasms can cause problems on their own, but they may be more likely to cause blockages in blood vessels with atherosclerosis.
A stroke may also happen 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 main causes are:
- —Blood pressure is the force of blood on artery walls. High blood pressure harms and weakens blood vessels.
- —An aneurysm is an outpouching of a blood vessel wall in the brain that forms in places where the artery wall is weak or thin. The bulging, blood filled pocket can put pressure on parts of the brain. Aneurysms that burst can be deadly.
- (AVM)—This is a rare problem due to unusual links between arteries and veins. Instead of an artery bringing blood to the brain, it is linked to a vein that takes it away and goes past the brain tissue that needs it. The blood vessels may get weaker over time. This may cause the vessels to widen or burst.
A silent stroke happens without any of the usual signs or symptoms. They cause harm to brain tissue and raise the risk of a major stroke in the future. They tend to happen in silent parts of the brain that are not clearly active for thinking or moving. Brain tissue damage is often found during imaging tests.
Classifying Stroke
Strokes can be grouped by their course in time:
Strokes can be grouped by their course in time:
- Completed stroke—Reaches its most harmful point right away or over a few hours.
- Transient ischemic attack (TIA)—A brief loss of blood supply to the brain that gets better on its own within 24 hours. It is a warning that a more severe stroke is likely.
- Stroke in progress—One that gets worse over time, likely over days.
Many small strokes may happen over time, from days to years. They can cause as much harm as one big stroke.
References
- Stroke. National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/health-topics/stroke.
- Stroke (acute management). EBSCO DynaMed website. http://www.dynamed.com/management/stroke-acute-management-1.