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  • Every two seconds, someone somewhere in the world experiences a stroke.

  • And one out of every six people will have one at some point in their lives.

  • Strokes deprive brain cells of oxygen and are one of the most common causes of death and a leading cause of preventable disability.

  • When someone experiences a stroke, quick medical care is critical , and can often help avoid permanent brain damage.

  • But what causes strokes in the first place?

  • And what can doctors do to treat them?

  • The brain makes up just 2% of your body's mass but consumes more than 20% of the oxygen in your blood.

  • That oxygen is carried to the brain through a system of arteries.

  • Carotid arteries supply the front of the brain, and vertebral arteries supply the back.

  • These are connected to each other, and divide into smaller and smaller vessels that get billions of neurons the oxygen they need.

  • If the blood flow is interrupted, oxygen delivery stops and brain cells die.

  • There are two ways this can happen.

  • Hemorrhagic strokes are when a perforated vessel allows blood to leak out.

  • But the more common type is the ischemic stroke, when a clot blocks a vessel and brings blood flow to a halt.

  • Where do these clots come from?

  • On rare occasions, a sudden change in heart rhythm prevents the upper chambers of the heart from contracting normally.

  • This slows down blood flow, allowing platelets, clotting factors, and fibrin to stick together.

  • The clot can be carried up towards the arteries and blood vessels supplying the brain until it gets to one it can't squeeze through.

  • This is called an embolism and it cuts off the oxygen supply to all the cells downstream.

  • The brain doesn't have pain receptors, so you can't feel the blockage itself.

  • But oxygen deprivation slows brain function and can have sudden, noticeable effects.

  • For example, if the affected area is responsible for speech, an individual's words may be slurred.

  • If the stroke affects a part of the brain that controls muscle movement, it can cause weakness, often just on one side of the body.

  • When this happens, the body will immediately try to compensate by diverting blood flow to the affected area, but this isn't a perfect solution.

  • Eventually, the oxygen-deprived cells will start to die, leading to brain damage that may be severe or permanent.

  • That's why it's important to get medical care as fast as possible.

  • The first line of treatment is an intravenous medication called Tissue Plasminogen Activator, which can break up the blood clot and allow blood to flow again in the compromised artery.

  • If it's delivered within a few hours, this medication greatly increases the chance of surviving the stroke and avoiding permanent consequences.

  • If Tissue Plasminogen Activator cannot be given because the patient is on certain medications, has history of major bleeding, or the clot is particularly large, doctors can perform a procedure called an endovascular thrombectomy.

  • Using a fluorescent dye that illuminates the blood vessels under a strong x-ray, the physician inserts a long, thin, flexible tube called a catheter into an artery in the leg and maneuvers it all the way to the blockage.

  • A retriever is passed through this catheter.

  • It expands and anchors into the clot when it's just past it.

  • The catheter then pulls the clot out when it's removed.

  • These treatments need to be delivered as soon as possible

  • to preserve brain function,

  • which means figuring out fast if someone is having a stroke.

  • So how can you tell?

  • Here are three quick things to try:

  • 1. Ask the person to smile.

  • A crooked mouth or facial drooping can indicate muscle weakness.

  • 2. Ask them to raise their arms.

  • If one drifts downward, that arm weakness is also a sign of a stroke.

  • 3. Ask them to repeat a simple word or phrase.

  • If their speech sounds slurred or strange,

  • it could mean that the language area of their brain is oxygen-deprived.

  • This is sometimes called the FAST test, and the T stands for time.

  • If you see any of those signs, call emergency services right away.

  • Lives may depend on it.

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Every two seconds, someone somewhere in the world experiences a stroke.

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B2 US TED-Ed clot oxygen stroke brain blood

【TED-Ed】What happens during a stroke? - Vaibhav Goswami

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    Jenny posted on 2018/03/12
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