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

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

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Strokes deprive brain cells of oxygen

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and are one of the most [br]common causes of death,

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and a leading cause [br]of preventable disability.

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When someone experiences a stroke,[br]quick medical care is critical,

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and can often help avoid [br]permanent brain damage.

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But what causes strokes [br]in the first place?

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And what can doctors do to treat them?

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The brain makes up just 2% [br]of your body’s mass

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but consumes more than 20%[br]of the oxygen in your blood.

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That oxygen is carried to the brain[br]through a system of arteries.

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Carotid arteries supply [br]the front of the brain,

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and vertebral arteries supply the back.

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These are connected to each other,

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and divide into smaller [br]and smaller vessels

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that get billions of neurons [br]the oxygen they need.

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If the blood flow is interrupted, [br]oxygen delivery stops, and brain cells die

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There are two ways this can happen.

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Hemorrhagic strokes are when a perforated[br]vessel allows blood to leak out.

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But the more common type [br]is the ischemic stroke,

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when a clot blocks a vessel [br]and brings blood flow to a halt.

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Where do these clots come from?

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On rare occasions,[br]a sudden change in heart rhythm

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prevents the upper chambers of the heart[br]from contracting normally.

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This slows down blood flow,

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allowing platelets, clotting factors, [br]and fibrin to stick together.

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The clot can be carried up

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towards the arteries[br]and blood vessels supplying the brain

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until it gets to one [br]it can’t squeeze through.

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This is called an embolism,

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and it cuts off the oxygen supply [br]to all the cells downstream.

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

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But oxygen deprivation [br]slows brain function

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and can have sudden, noticeable effects.

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For example, if the affected area [br]is responsible for speech,

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an individual’s words may be slurred.

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If the stroke affects a part of the brain [br]that controls muscle movement,

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it can cause weakness, [br]often just on one side of the body.

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When this happens, the body [br]will immediately try to compensate

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by diverting blood flow [br]to the affected area,

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but this isn’t a perfect solution.

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Eventually, the oxygen-deprived cells [br]will start to die,

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leading to brain damage [br]that may be severe or permanent.

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That’s why it’s important to get[br]medical care as fast as possible.

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The first line of treatment[br]is an intravenous medication

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called Tissue Plasminogen Activator,

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which can break up the blood clot

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and allow blood to flow again[br]in the compromised artery.

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If it’s delivered within a few hours,

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this medication greatly increases[br]the chance of surviving the stroke

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and avoiding permanent consequences.

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If Tissue Plasminogen Activator[br]cannot be given

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because the patient [br]is on certain medications,

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has history of major bleeding,

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or the clot is particularly large,

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doctors can perform a procedure[br]called an endovascular thrombectomy.

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Using a fluorescent dye that illuminates [br]the blood vessels under a strong x-ray,

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the physician inserts a long, [br]thin, flexible tube called a catheter

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into an artery in the leg,

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and maneuvers[br]it all the way to the blockage.

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A retriever is passed[br]through this catheter.

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It expands and anchors into the clot [br]when it’s just passed it.

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The catheter then pulls the clot out [br]when it’s removed.

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These treatments need to be delivered[br]as soon as possible

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to preserve brain function,

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which means figuring out fast [br]if someone is having a stroke.

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So how can you tell?

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Here are three quick things to try.

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1: Ask the person to smile;

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A crooked mouth or facial drooping [br]can indicate muscle weakness.

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2: Ask them to raise their arms;

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If one drifts downward, that arm weakness[br]is also a sign of a stroke.

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3: Ask them to repeat [br]a simple word or phrase;

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if their speech sounds[br]slurred or strange,

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it could mean that the language area [br]of their brain is oxygen-deprived.

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This is sometimes called the FAST test,[br]and the T stands for time.

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If you see any of those signs, [br]call emergency services right away.

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Lives may depend on it.