[MUSIC] Okay, so let's talk about what can go wrong in, in the brain? And one, the biggest the most common thing that can go wrong, the most common neurological event that sends a person to the hospital and the most common neurological event that results in a person dying is stroke. And stroke is a general term. It, there are two different broadly speaking there are two very different types of stroke. There are ischemic strokes and ischemia means no oxygen. Okay? And this is, about 90% of all strokes are ischemic. And then there's hemorrhagic strokes which is where the blood vessel actually opens up and bleeds. And brain tissue does not like blood. It can't survive being in a, in a sea of blood. And so this is also devastating to neurons. A key piece about a stroke is that it's very sudden onset. So, it's going to happen on a rapid timescale. And I just want to show you a quote, from a woman who was working down at the South Pole. She was at the research station at the South Pole. She was sitting at her desk and then she says I looked at the screen and, oh my God, half the screen is missing. This was a woman who had a stroke I don't actually know if it was her left or her right but she clearly had a stroke in the occipital cortex. So that either the left half of the world or the right half of the world was no longer visible to her and that sudden onset loss of function is very very typical for a stroke. And the effects of a stroke are going to be different, depending on where in the blood supply the stroke hits. So if the stroke is going to, let's say that we're looking at an ischemic stroke and what that means is that this blood vessel has blocked. Well if the blood vessel is blocked here that means that this entire area that derives its blood flow from that root vessel. This is all going to be without oxygen. So as you may imagine, that's going to have a big effect. That's going to effect a large part of the brain. Let's contrast that with what would happen if there was a blockage out here. You may not even know that a stroke had occurred. So strokes can be very massive, they can be smaller depending on where they affect. And what, what is it that blocks blood vessels? Well, there's a lot of different stuff in the circulatory system that can block it. Plaques, artha, arthrosclorotic plaques, very hard for me to say, but they can block it. Artener, arterio-venous malformations are congent, is a congenitial condition where the vessel wall is, is compromised and it can burst. And that can give rise to a hemorrhagic stroke. So importantly the, the what you would do. Let's go back to the board for a moment. What you would do if you have an ischemic stroke and a hemorrhagic stroke are very different. Remember that if this is a blood vessel, in an ischemic stroke, there's a blockage. And so blood is flowing here, but there's no blood flow after the blockage. Well, in that case, what do you want to do? You want to give a blood thinner. You want to try and get this clot out of there. Well, imagine what you, what would happen if you gave a blood thinner to somebody who has a hemorrhagic stroke. In that case, there's a blood vessel and now the wall bursts and blood is just flowing out here, and if you stop it from clotting then that is, that is very inadvisable. And one of the remarkable things that it, that we need to figure out is a way of discriminating between an ischemic stroke and a hemorrhagic stroke that does not depend on a picture, a some kind of clinical imaging. And so, we don't really have that and that's something that I hope that maybe one of you will figure out in the, in the years to come. And we need to know which type of stroke it is in order to treat it correctly. While the, while strokes are cardiovascular in cause, it's, this is a cardiovascular event. When I first studied this stuff, I, I wondered why we talked about strokes because it was such a cardiovascular event. But the fact is that even though it's cardiovascular, it is completely neurological in its effect. And so where the stroke hits is going to determine what is going to go wrong in the person. So, for instance, if there's a, a left hemisphere stroke, the person may become aphasic, may lose the ability to control the right side of their body and so on. And make lose the ability to see the right, the right side of the visual world. Now, the effect of these strokes is on the tissue around here. So remember that we have all these neurons around here. Well, if they're really close and they are sitting there without oxygen for a long time. Or if they were sitting bathed in blood for a long time, they're going to die. And so if the stroke happens in one place, there's an area around it where the, where the neurons die. And what treatment is aimed at is at this surrounding area called the penumbra, where the neurons don't die but they're at risk. And what is, what treatment is aimed at is trying to prevent these at risk neurons from dying. Another thing that can go wrong besides strokes is tumors, and this is a picture of a tumor. It actually started as a skin tumor and it ate through the skull and, and into the frontal lobes. So, this is an area where there's just no brain. The neurons have been completely destroyed there. So tumors tend to be much more gradual in onset. But they can suddenly cross some threshold and result in a in symptoms. So you can't automatically know from the sudden onset whether something's a stroke or a tumor. So in the next segment, we're going to look at different types of intracranial bleeds. [MUSIC]
