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

また6人中1人が、人生のどこかで脳卒中を起こします。

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

脳卒中が起きると、脳細胞から酸素が奪われます。

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

脳卒中は最も多い死因の1つであり

But what causes strokes in the first place?

予防できる障害をもたらす主因です。

And what can doctors do to treat them?

脳卒中が起きた時には迅速な医療ケアが重要で

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

それにより、脳への後遺症を防ぐことができます。

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

でもそもそも、何が脳卒中を引き起こすのでしょうか？

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

その治療のために、医者は何ができるのでしょうか？

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

脳は体重のたった2%しか占めませんが

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

血中の酸素の20%以上を消費します。

There are two ways this can happen.

その酸素は動脈系を伝って脳に運ばれます。

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

頸動脈によって脳の前側、

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

椎骨動脈によって脳の後ろ側に酸素が供給されます。

Where do these clots come from?

これらはつながっていて

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

細い毛細血管にどんどん枝分かれし

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

何十億というニューロンに、必要な酸素を供給します。

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.

血流が遮られると、酸素の運搬が止まり、脳細胞は死にます。

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

これが起こる原因には2通りあります。

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

出血性脳卒中は、穴の開いた血管から血液が漏れ出るものです。

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

より一般的なのは虚血性脳卒中で

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

血塊が血管を塞ぎ、血流が止まってしまうものです。

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.

この血塊はどこから来るのでしょう？

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.

まれに、心拍リズムが突然変わることで

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

心臓の上半分で通常の収縮ができなくなることがあります。

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

これにより血液の流れが遅くなり

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.

血小板、凝固因子、フィブリンがくっつきます。

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

血塊は

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.

脳に必要なものを供給する動脈や血管を上っていき

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.

通り抜けられない部分まで進んで詰まります。

A retriever is passed through this catheter.

これは塞栓症と呼ばれ

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

下の方にある全細胞への酸素供給が絶たれます。

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

脳には痛みの受容体がないので、血栓そのものは感じられません。

These treatments need to be delivered as soon as possible

しかし酸素を失うことで、脳の機能は低下し

to preserve brain function,

突然、顕著な影響が出ることがあります。

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

例えば発話能力を司る部分が影響されると

So how can you tell?

ろれつが回らなくなるかもしれません。

Here are three quick things to try:

脳卒中が、筋肉の動きをコントロールする脳の部分に影響すると

1. Ask the person to smile.

筋肉が衰弱します。大抵体の半分にだけです。

A crooked mouth or facial drooping can indicate muscle weakness.

こうなると、体は即座にそれを埋め合わせようとし

2. Ask them to raise their arms.

影響を受けた部分に向けて血流を変えます。

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

でもこれは完璧な解決策ではありません。

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

最終的に、酸素を奪われた細胞が死に始め

If their speech sounds slurred or strange,

重度、または後遺症となるような脳のダメージへとつながります。

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

だから、医療ケアを出来るだけ早く受けることが重要なのです。

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

まず行われるのは静脈内投薬で

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

組織プラスミノーゲン活性因子と呼ばれます。

Lives may depend on it.

これで血塊を破壊し

We are on the non-profit mission to revolutionize education. Click here to learn how you can get involved.

影響を受けた動脈内に再び血液が流れるようにします。