There are two things that cause a stroke. The first is where one of the vessles taking blood to your brain gets blocked, either by a blood clot or by a clump of fat. This means your brain gets starved of blood while the vessel is blocked. Eventually the block will normally remove its self or they can be given a drug and blood will flow back into the brain. Depending on how long the block is there for will depend on how bad the damage is. And what part of the brain gets starved will cause the symptoms to be different.
The second type is where a blood vessell bursts in the head and so the blood leaks out meaning it doesn’t get to the correct part of the brain. But the same thing damage occurs to the brain.
The problem for doctors is they don’t know which one has happened until they do a special scan of the head and its really risky giving them a drug without knowing which one it is. If you give someone with a burst vessel a drug to remove a clot it will cause even more bleeding and the person will die. But taking the scan takes time and therefore the person doesnt get the drug as quickly as they need it. Its a real catch 22!