0:00:06.956,0:00:12.525 Every two seconds, someone somewhere [br]in the world experiences a stroke. 0:00:12.525,0:00:17.878 And one out of every six people will have [br]one at some point in their lives. 0:00:17.878,0:00:20.868 Strokes deprive brain cells of oxygen 0:00:20.868,0:00:23.589 and are one of the most [br]common causes of death 0:00:23.589,0:00:26.785 and a leading cause [br]of preventable disability. 0:00:26.785,0:00:31.449 When someone experiences a stroke,[br]quick medical care is critical, 0:00:31.449,0:00:34.729 and can often help avoid [br]permanent brain damage. 0:00:34.729,0:00:37.588 But what causes strokes [br]in the first place? 0:00:37.588,0:00:40.849 And what can doctors do to treat them? 0:00:40.849,0:00:44.520 The brain makes up just 2% [br]of your body’s mass 0:00:44.520,0:00:48.958 but consumes more than 20%[br]of the oxygen in your blood. 0:00:48.958,0:00:52.751 That oxygen is carried to the brain[br]through a system of arteries. 0:00:52.751,0:00:55.638 Carotid arteries supply [br]the front of the brain, 0:00:55.638,0:00:58.688 and vertebral arteries supply the back. 0:00:58.688,0:01:00.719 These are connected to each other, 0:01:00.719,0:01:03.369 and divide into smaller [br]and smaller vessels 0:01:03.369,0:01:07.380 that get billions of neurons [br]the oxygen they need. 0:01:07.380,0:01:13.349 If the blood flow is interrupted, [br]oxygen delivery stops and brain cells die. 0:01:13.349,0:01:15.490 There are two ways this can happen. 0:01:15.490,0:01:20.641 Hemorrhagic strokes are when a perforated[br]vessel allows blood to leak out. 0:01:20.641,0:01:23.530 But the more common type [br]is the ischemic stroke, 0:01:23.530,0:01:28.518 when a clot blocks a vessel [br]and brings blood flow to a halt. 0:01:28.518,0:01:30.690 Where do these clots come from? 0:01:30.690,0:01:33.591 On rare occasions,[br]a sudden change in heart rhythm 0:01:33.591,0:01:37.900 prevents the upper chambers of the heart[br]from contracting normally. 0:01:37.900,0:01:39.809 This slows down blood flow, 0:01:39.809,0:01:45.382 allowing platelets, clotting factors, [br]and fibrin to stick together. 0:01:45.382,0:01:46.731 The clot can be carried up 0:01:46.731,0:01:50.611 towards the arteries[br]and blood vessels supplying the brain 0:01:50.611,0:01:54.092 until it gets to one [br]it can’t squeeze through. 0:01:54.092,0:01:56.297 This is called an embolism 0:01:56.297,0:02:00.665 and it cuts off the oxygen supply [br]to all the cells downstream. 0:02:00.665,0:02:05.862 The brain doesn't have pain receptors,[br]so you can't feel the blockage itself. 0:02:05.862,0:02:08.672 But oxygen deprivation [br]slows brain function 0:02:08.672,0:02:11.802 and can have sudden, noticeable effects. 0:02:11.802,0:02:15.593 For example, if the affected area [br]is responsible for speech, 0:02:15.593,0:02:18.514 an individual’s words may be slurred. 0:02:18.514,0:02:21.972 If the stroke affects a part of the brain [br]that controls muscle movement, 0:02:21.972,0:02:26.553 it can cause weakness, [br]often just on one side of the body. 0:02:26.553,0:02:30.435 When this happens, the body [br]will immediately try to compensate 0:02:30.435,0:02:33.405 by diverting blood flow [br]to the affected area, 0:02:33.405,0:02:35.885 but this isn’t a perfect solution. 0:02:35.885,0:02:39.824 Eventually, the oxygen-deprived cells [br]will start to die, 0:02:39.824,0:02:43.748 leading to brain damage [br]that may be severe or permanent. 0:02:43.748,0:02:48.390 That’s why it’s important to get[br]medical care as fast as possible. 0:02:48.390,0:02:51.370 The first line of treatment[br]is an intravenous medication 0:02:51.370,0:02:54.205 called Tissue Plasminogen Activator, 0:02:54.205,0:02:55.884 which can break up the blood clot 0:02:55.884,0:02:59.855 and allow blood to flow again[br]in the compromised artery. 0:02:59.855,0:03:02.015 If it’s delivered within a few hours, 0:03:02.015,0:03:05.415 this medication greatly increases[br]the chance of surviving the stroke 0:03:05.415,0:03:08.496 and avoiding permanent consequences. 0:03:08.496,0:03:11.646 If Tissue Plasminogen Activator[br]cannot be given 0:03:11.646,0:03:13.976 because the patient [br]is on certain medications, 0:03:13.976,0:03:15.595 has history of major bleeding, 0:03:15.595,0:03:18.336 or the clot is particularly large, 0:03:18.336,0:03:23.605 doctors can perform a procedure[br]called an endovascular thrombectomy. 0:03:23.605,0:03:28.694 Using a fluorescent dye that illuminates [br]the blood vessels under a strong x-ray, 0:03:28.694,0:03:33.146 the physician inserts a long, [br]thin, flexible tube called a catheter 0:03:33.146,0:03:35.375 into an artery in the leg 0:03:35.375,0:03:38.508 and maneuvers[br]it all the way to the blockage. 0:03:38.508,0:03:41.377 A retriever is passed[br]through this catheter. 0:03:41.377,0:03:45.867 It expands and anchors into the clot [br]when it’s just past it. 0:03:45.867,0:03:50.737 The catheter then pulls the clot out [br]when it’s removed. 0:03:50.737,0:03:53.679 These treatments need to be delivered[br]as soon as possible 0:03:53.679,0:03:55.338 to preserve brain function, 0:03:55.338,0:03:59.588 which means figuring out fast [br]if someone is having a stroke. 0:03:59.588,0:04:01.017 So how can you tell? 0:04:01.017,0:04:03.869 Here are three quick things to try: 0:04:03.869,0:04:06.558 1. Ask the person to smile. 0:04:06.558,0:04:11.118 A crooked mouth or facial drooping [br]can indicate muscle weakness. 0:04:11.118,0:04:13.879 2. Ask them to raise their arms. 0:04:13.879,0:04:19.829 If one drifts downward, that arm weakness[br]is also a sign of a stroke. 0:04:19.829,0:04:23.919 3. Ask them to repeat a[br]simple word or phrase. 0:04:23.919,0:04:26.788 If their speech sounds[br]slurred or strange, 0:04:26.788,0:04:31.489 it could mean that the language area [br]of their brain is oxygen-deprived. 0:04:31.489,0:04:37.281 This is sometimes called the FAST test,[br]and the T stands for time. 0:04:37.281,0:04:42.290 If you see any of those signs, [br]call emergency services right away. 0:04:42.290,0:04:44.331 Lives may depend on it.