Stroke: Pathology, Pathophysiology, Clinical Manifestations, Diagnosis and Investigation

my name is Remy Corre Corre and I'll be discussing the pathology pathophysiology clinical features investigation and diagnosis of strokes now as with all organs in the body the brain needs oxygen and nutrients in order to function properly these life-sustaining products are delivered to the brain via the blood that travels through the circulatory system a stroke occurs when there is a lack of blood to a portion of the brain resulting in tissue death and loss of brain function I'll come back to the causes of strokes in a moment but let's look at the blood supply first blood is supply to the brain by two pairs of arteries the anterior supply supplies blood primarily to the middle and front portions of the brain and consists of the left and right carotid arteries the posterior supply supplies blood primarily to the brain stem and the back portions of the brain and consists of the right and left vertebral arteries which then join together to form a single basilar artery rotating the brain so that we have a view of the left side we can now more clearly see how the anterior supply originating from the carotid arteries distributes blood primarily to the middle and front portions of the brain and the posterior supply originating from the basilar artery supplies most of the brain stem and the back portions of the brain and in a prime example of survival of the fittest and nature's wonderful design there is a communicating artery which joins the two systems known as the posterior communicating artery this vessel is part of the Circle of Willis and in the event that there is certain impairment of blood flow to the brain from either the anterior or posterior system the communicating order ease allow for crossover flow which may help to prevent damage to the portion of the brain affected by the impaired flow the Circle of Willis is best seen by examining the underside of the brain so let's zoom in to take a closer look the Circle of Willis is really a beautiful piece of anatomy that represents a central hub of which radiates the entire blood flow to the brain inflow is primarily via the internal carotid and vertebral arteries and outflow is via the anterior middle and posterior cerebral arteries each with a left and right branch on either side of the circle of course the basilar artery posterior communicating and anterior communicating artery is complete the circle by merging the inflow of blood to the brain from the carotid and vertebral arteries the chance is minimized that an obstruction or impairment a flow of any one of these arteries will result in a significant impairment of blood supply to the flowing arteries so as we said a stroke occurs when there is an interruption in the blood supply to the brain when a stroke occurs some brains are temporarily starved of oxygen causing them to swell and stop working properly this is why the effects of stroke are worse in the beginning and after a few days when the swelling begins to subside some cells recover and some cells will not recover there are two types of strokes one type is the ischemic stroke this happens when there is either narrowing of a blood vessel or in this animation a clot in the blood vessel that traveled somewhere in the arterial system they can be blood clots or fat embolisms or air embolisms but anyway it's preventing oxygen from getting to a segment of the brain the other type of stroke is hemorrhagic stroke this happens when there is a rupture of a blood vessel in the brain it may be caused by a blood vessel which bursts inside of the brain or a blood vessel that bursts on the surface of the brain and bleeds between the area of the brain and the skull let us now move on to the pathophysiology of stroke as we said they can be ischemic or hemorrhagic because this quemic and hemorrhagic strokes have different causes they exhibit different pathophysiology I'll start with the pathophysiology of ischemic strokes then move on to hemorrhagic strokes in the case of ischemic stroke the formation of clots known as thrombi is fundamental there are several diseases and pathologies that predispose patients to the formation of thrombi the most significant of these is atherosclerosis a compromised systemic circulation also plays a role in ischemic strokes and for hemorrhagic strokes elevated blood pressure is most commonly the underlined cause let's start with the crucial topic in the pathophysiology of ischemic stroke what exactly are the conditions in the body that leads to the formation of thrombi you see blood in the body is a constant balance between coagulating factors as well as anti coagulating factors which are proteins that keep the blood thin when the balance is tipped in the favor of the coagulant the blood is considered hypercoagulable and the risk of cloth formation and subsequently ischemic stroke increases a great scientist named Vera Kao came up with a brilliant triad to describe the conditions that lead to the formation of thrombi in the body these three key factors are endothelial injury stasis or lack of flow and blood and hypercoagulability the presence of any or all of these factors increases the chances of ischemic stroke the most important however of these is endothelial injury so let's get a visual of endothelial injury as well as clot formation even under physiological conditions a small tear can appear in the wall of a blood vessel in order to prevent blood loss platelets and coagulation factors such as the pivotal factor 10 acting in a coordinated manner close this wound the platelets are responsible for first sealing of the tear then a number of coagulation factors are activated leading to the formation of fibrin strands which stabilize the growing clot thromboembolic disorders can affect both types of blood vessels arterial or white clots are primarily triggered by the rupture of an a thorough stir on ik plaque arterial clots are platelet rich venous or red cloth on the other hand mainly consist of red blood cells and fibrin vascular injury hypercoagulability of the blood and venous stasis virchow's triad play a crucial crucial role in their development it's important to note that the formation of both types of clots arterial and venous always involve platelets as well as coagulation factors so let us go back to our pathophysiology when we talk about endothelial injury atherosclerosis is the disease that comes to mind atherosclerosis is defined as the thickening in the walls of large blood vessels due to the accumulation of fatty materials atherosclerosis of disease is the most common way that arterial thrown by occur and therefore it presents a major risk for ischemic stroke in atherosclerosis injured endothelial cells in large and and medium-sized arteries become chronically inflamed LDLs that are found in cholesterol are retained by the injured and O thulium and become oxidized these oxidized lipoproteins trigger an immune response which are attract which attracts cells called macrophages these macrophages become trapped inside the endothelial lining forming what we call foam cells eventually the body tries to heal this chronic inflammation forming a plaque or fibrous clap cap over the area if some things such as turbulent blood flow causes the plaque to rupture a blood clot can form causing a blockage the plot the plot can also break off and travel in the circulation the following animation will help us visualize this very important disease atherosclerosis is a life-threatening disease that may have begun to develop during childhood this condition is a process in which deposits of fatty material called build up inside the walls of arteries reducing or completely blocking blood flow although the exact causes of atherosclerosis are not clear many scientists think it begins with damage to the inner wall of an artery called the endothelium substance is traveling in the blood such as cholesterol fats and cellular waste products appear late inside the damaged area of the arterial wall chemical reactions occurring within the build-up of material cause cholesterol molecules to oxidize this initiates an inflammatory response in which the endothelial cells at the damaged site release chemicals that signal a call for help in response monocytes from the bloodstream travel to the damaged site stimulation from oxidized cholesterol converts the monocytes into macrophages the macrophages eat and digest the cholesterol molecules as a result of this process the macrophages change into foam cells which accumulate to form plaque as the plaque increases in size the arterial wall thickens and hardens at the same time smooth muscle cells within the arterial wall begin to multiply most of the smooth muscle cells move to the surface of the plaque these cells contribute to the formation of a firm fibrous cap covering the plaque eventually the passageway through the artery narrows enough to reduce blood flow and the amount of oxygen received by the organs it supplies over time the cap may erode and break open releasing plaque into the bloodstream the plaque can flow downstream and contribute to the formation of a blood clot which can stop blood flow as a result limited blood supply is available to the area surrounding the partially blocked artery degrading and potentially killing the neighboring tissue let's come back and take one last look at the pathophysiology of stroke a compromised systemic circulation in a weak heart can also increase the chance of an ischemic stroke when the heart is weakened blood does not flow as effectively as it used to when the flow of blood is reduced the chance that various clotting factors in the blood can interact and form a thrombus increases our condition like atrial fibrillation is a major risk factor for stroke making a patient five times more likely to suffer one atrial fibrillation is when the top two chambers of the heart the atria do not fully contract instead they sort of quiver or fibrillate this irregular contraction means that pump blood is not pumped fully out and into the ventricles and some of it pools and then can clot and then these clots can be pumped out of the heart and into the brain causing an ischemic stroke returning to a diagram of a blood vessel let's look at how different injury to the blood vessel can lead to a hemorrhagic stroke if a patient has high blood pressure then their arteries are always under a lot of strain and the blood pushes on the vessel and that causes the walls to eventually weaken causing a bulge called an aneurysm these weakened walls are more likely to burst especially if they continue to be put under the same pressure as before if the blood vessel that bursts is in the brain we call it a hemorrhagic stroke hypertension is therefore a crucial risk factor for stroke and needs to be well managed to prevent weakening of blood vessels the symptoms of a stroke depend on the type of stroke and what area of the brain is affected as early as 400 BC the Greek philosopher Hippocrates described the stroke phenomenon as sudden paralysis he used the term apoplexy which is the Greek word meaning struck down with violence Hippocrates had the right idea one of the most common signs of a stroke is sudden numbness or weakness of the face arm or leg especially when it's on one side of the body people who are having a stroke can also experience trouble moving due to dizziness loss of balance or loss of coordination stroke victims may experience trouble speaking or understanding sudden confusion is also common other possible indicators of a stroke include sudden difficulty seeing sudden severe headache of unknown cause let's look at how a stroke and each of the different areas of the brain might affect a survivor a stroke in the right hemisphere of the brain often causes paralysis in the left side of the body this is known as left hemiplegia right hemisphere stroke survivors may have difficulty with spatial and perceptual abilities resulting in trouble picking things up misjudging distances difficulty dressing and falling down survivors of right hemispheric strokes often have judgment difficulties they often develop impulsive dangerous habits like driving a car when they do not have the special ability to do so right hemispheric stroke survivors may also experience left-sided neglect causing them to ignore objects on the left for example a person with this condition naughty food on the left side of their plate conversely a stroke on the let's hemisphere of the brain can cause paralysis on the right side of the body or right hemiplegia survivors of left hemispheric strokes may develop aphasia which is difficulty speaking or understanding language patients who have had a left hemispheric stroke often develop a slow cautious style of behavior and they may need frequent instruction on biofeedback of the most basic of tasks a stroke that occurs in the cerebellum affects reflexes and balance cerebellar strokes can result in difficulty standing nausea dizziness and even vomiting the most physically devastating of strokes are those that occur in the brain stem brain stem is responsible for all involuntary function of the body like blood pressure heartbeat and breathing damage to this area may require life support brain stem strokes can also lead to problems of hearing talking and swallowing let us now turn our attention briefly to T IAS transient ischemic attacks are just like many strokes which are just like a regular ischemic or blood clot stroke it's when a blood vessel to the brain becomes blocked or leaks and there's a halt of oxygen to a segment of the brain but the difference is that T is are reversible with normal body repair mechanisms now even though cia's disappear on their own they are an indicator that a major stroke may occur it's important to receive immediate treatment because about 1/3 of people will end up having a full blown stroke soon after so let us turn our attention to the important clinical manifestations and warning signs of T IAS a person may suddenly feel weakness numbness or heaviness even in a small part of the body like the hand the face or the foot it may be hard to speak or understand words things may look blurry or dim and a person might feel dizzy or clumsy on their feet they might also experience sudden headaches which feel like severe migraines here's a look at how a TIAA may manifest in a day to day activity like playing basketball how pretty was that not bad but not half as pretty is it bring it off haha my the old folks home is looking for a ringer look no further I'm in the prime of my life I'll have you know and these are your jeans too pal let's take a good long look at your future huh I don't know about my future but I think I can see my reflection scotch disrespect come on free shot I bet you can't make it from here what you're afraid of losing our bet dad are you okay good hmm dad what what sit down okay going away now what was that I mean one second you were fine in the next year old limp as you can see having a stroke can be a very scary experience when a stroke strikes is spreads like a fire in the brain in the sense that the longer it goes undetected the more damage is done to spot the signs of a stroke you have to think and act fast F face has their face fallen on one side can they smile on a-arms can they raise both arms and keep them elevated s speech is their speech slurred t time to call 9-1-1 or 999 and it's important to remember this mnemonic device and to educate your patients so remember if you're suspecting a stroke act fast finally once we've established that our patient is indeed suffering from a stroke there's a variety of diagnostic imaging tests that we can do CT scan CT perfusion MRI MRA cerebral angiogram carotid ultrasound or just to name a few the idea being that we want to try to see the stroke and assess how bad the damage is or how reversible the damage is and what can we do now one of the things we can do is called a perfusion scan and this shows how well the blood is getting to parts of the brain the images in the lower-left are what you see in a CT perfusion notice the highly colorful images the regular CT scan which is in the top right image it shows bleeding and if it's been going on long enough might show at a regular ischemic stroke in this image we see a normal perfu scan in each individual scan we can see that there is equal perfusion to both sides of the brain on each of the images as opposed to this image where you can see that the color is not symmetrical anymore and on all three images in fact you can see that one side is more perfused better than the other and this is really one of the things that we do when a patient comes in we want to try to find out are they having a stroke where is the stroke located and what's going on and of course we can do MRI scans as well you can see in the lower left image how the part of the brain that's suffering from the stroke that is light and very bright on imaging you can see the white region there that's where the ischemia is occurring and then we have techniques to look at the blood vessels with an MRI scan you can see in the top right image the blood vessels going up into the brain and we have ways of color coding it as well and the quantitative MRI can not only show us where the blood is going but can also tell us about the rate and speed and velocity at which the blood is going and this concludes my lecture so thank you very much for watching

Channel: Rammy Korkor

Views: 162,571

Keywords: Stroke: pathology, pathophysiology, clinical manifestations, diagnosis, investigation, stroke, Stroke (Disease Or Medical Condition), Diagnosis (Literature Subject), Health, Pathology (Medical Specialty)

Id: k_p0aASogkU

Length: 23min 41sec (1421 seconds)

Published: Sun Aug 30 2015