Every two seconds, someone somewhere in the world experiences a stroke.
每两秒，世界某个角落就会有人中风。
And one out of every six people will have one at some point in their lives.
而每六个人当中就有一个在一生中的某个时刻中风。
Strokes deprive brain cells of oxygen and are one of the most common causes of death and a leading cause of preventable disability.
中风会使脑细胞缺氧，是最普遍的死因之一，也是可预防残疾的主要原因。
When someone experiences a stroke, quick medical care is critical, and can often help avoid permanent brain damage.
当一个人中风时，迅速得到治疗至关重要，而且通常能够对避免脑部永久性损伤起到帮助。
But what causes strokes in the first place? And what can doctors do to treat them?
但是，人究竟为什么会中风？医生又如何医治中风？
The brain makes up just 2% of your body's mass but consumes more than 20% of the oxygen in your blood.
大脑只占身体质量的百分之二，但却会消耗血液中超过20%的氧气。
That oxygen is carried to the brain through a system of arteries.
这些氧气通过动脉系统运输到大脑。
Carotid arteries supply the front of the brain, and vertebral arteries supply the back.
颈动脉把氧气运输到大脑前半部分，椎动脉则负责后半部分。
These are connected to each other,
这两种动脉互相连接，
and divide into smaller and smaller vessels that get billions of neurons the oxygen they need.
并细分成越来越小的血管，为数十亿个神经元提供它们所需的氧气。
If the blood flow is interrupted, oxygen delivery stops and brain cells die.
如果血流受阻，氧气运输停止，脑细胞就会死亡。
There are two ways this can happen.
发生该情况有两种可能。
Hemorrhagic strokes are when a perforated vessel allows blood to leak out.
穿孔的血管导致血液流失，进而引起出血性中风。
But the more common type is the ischemic stroke, when a clot blocks a vessel and brings blood flow to a halt.
但是更普遍的是缺血性中风，就是当血凝块阻塞了血管，使血液循环停滞。
Where do these clots come from?
这些血凝块是从哪儿来的？
On rare occasions, a sudden change in heart rhythm prevents the upper chambers of the heart from contracting normally.
在极罕见的情况下，心律的突然失常阻碍上心房正常收缩。
This slows down blood flow, allowing platelets, clotting factors, and fibrin to stick together.
这会使血液流速减慢，导致血小板、凝血因子和纤维蛋白粘结成块。
The clot can be carried up towards the arteries and blood vessels supplying the brain
凝块可以被运输到提供大脑氧气的动脉和血管，
until it gets to one it can't squeeze through.
直到它抵达某个无法通过的血管。
This is called an embolism and it cuts off the oxygen supply to all the cells downstream.
这种现象叫做栓塞，会切断下游所有细胞的氧气供应。
The brain doesn't have pain receptors, so you can't feel the blockage itself.
大脑并没有痛觉感受器，所以你是无法感受到血流阻塞的。
But oxygen deprivation slows brain function and can have sudden, noticeable effects.
但是氧气的缺乏会使大脑功能变慢，从而造成突发的、极为明显的影响。
For example, if the affected area is responsible for speech, an individual's words may be slurred.
例如，如果受影响的区域负责言语，那个人的言词就会模糊不清。
If the stroke affects a part of the brain that controls muscle movement,
如果中风影响到大脑控制肌肉运动的部分，
it can cause weakness, often just on one side of the body.
身体机能将会衰弱，通常只有身体的一侧受影响。

When this happens, the body will immediately try to compensate by diverting blood flow to the affected area,
当这种情况发生，身体将马上实施补救，把血流转移到受影响的部位，
but this isn't a perfect solution.
但这并不是个完美的解决方案。
Eventually, the oxygen-deprived cells will start to die, leading to brain damage that may be severe or permanent.
最终，缺氧的细胞会逐渐死亡，导致严重或永久性的脑损伤。
That's why it's important to get medical care as fast as possible.
这就是为什么尽早寻求医治至关重要。
The first line of treatment is an intravenous medication called Tissue Plasminogen Activator,
中风的第一线治疗方法是静脉注射一种叫做血浆组织纤溶酶原活化剂的药物。
which can break up the blood clot and allow blood to flow again in the compromised artery.
它可以溶解凝血，使血液重新在受阻的血管流通。
If it's delivered within a few hours,
如果将药物在几小时内注入身体，
this medication greatly increases the chance of surviving the stroke and avoiding permanent consequences.
可大大地提高中风的生存率，并避免永久性后遗症。
If Tissue Plasminogen Activator cannot be given because the patient is on certain medications,
如果因某些原因无法使用这种药物，例如病患正服用某些药物、
has history of major bleeding, or the clot is particularly large,
有大出血的病史，或者是血凝块太大，
doctors can perform a procedure called an endovascular thrombectomy.
医生也可以进行一种叫血管内栓塞切除术的手术。
Using a fluorescent dye that illuminates the blood vessels under a strong x-ray,
病人先服用一种荧光染料，使血管在强X光照射下发光，
the physician inserts a long, thin, flexible tube called a catheter into an artery in the leg
然后医生将一条细长、可弯曲的导管插入大腿中的一条动脉，
and maneuvers it all the way to the blockage.
并操纵导管使之抵达血凝块。
A retriever is passed through this catheter.
再将一个捡拾器穿过这条导管。
It expands and anchors into the clot when it's just past it.
捡拾器在穿透血凝块时膨胀并把凝块勾住。
The catheter then pulls the clot out when it's removed.
导管最后被拉出体外时，血凝块也跟随着被排出。
These treatments need to be delivered as soon as possible to preserve brain function,
这些治疗方法必须尽早施行以保护大脑功能，
which means figuring out fast if someone is having a stroke.
也就是说，需要快速判断一个人是否中风
So how can you tell? Here are three quick things to try:
。那么怎样判断呢？可以尝试这三个快速的方法：
1. Ask the person to smile.
一、让对方微笑。
A crooked mouth or facial drooping can indicate muscle weakness.
不对称的嘴巴或脸部下垂可能警示着肌肉衰弱。
2. Ask them to raise their arms.
二、让对方举起双臂。
If one drifts downward, that arm weakness is also a sign of a stroke.
如果一只手持续下垂，也可能是中风的征兆。
3. Ask them to repeat a simple word or phrase.
三、让对方重复一个简单的词或句子。
If their speech sounds slurred or strange, it could mean that the language area of their brain is oxygen-deprived.
如果对方的言词听起来模糊不清或奇怪，那就表示其大脑的语言区域在缺氧。
This is sometimes called the FAST test, and the T stands for time.
这些测试有时叫FAST测试，T代表时间。
If you see any of those signs, call emergency services right away. Lives may depend on it.
如果你发现这些症状中的任何一个，马上请求紧急救助。生命也许就掌握在你的手中。