Circulatory System | Circle of Willis: Ischemic Strokes

iron engineers in this video we're going to talk about cerebro scheming strokes so we already talked about the circle list but I want us to understand here is first off what is this scheme you how would you define ischemia ischemia is when there is a decreased oxygen supply to the tissues but not only just an increased oxygen decreased oxygen supply to the tissues but whenever they have the tissues have an increased oxygen demand okay so ischemia is defined as having a decreased oxygen supply to the tissues as well as the tissues having an increased oxygen demand whenever there is some type of ischemia of a lot of these different vessels that we're going to talk about there can be detrimental effects on the body and that's what I want to discuss in this video another thing that we're going to talk about at the end is there certain situations which are more common within certain vessels in the Circle of Willis maybe due to chronic hypertension or maybe due to connective tissue disorders those vessels can balloon out and become extremely dilated and the risk of that is it rupturing and leading to different types of like a subarachnoid hemorrhage now what I want to do is is I want to talk about clinical implications in this situation because it's good to know your Anatomy and the blood flow to the brain but it's even more important to understand what would happen if these vessels are affected so we're just gonna hit a couple of them we're not gonna hit every single vessel we'll be here all day we're gonna hit the most important ones so first thing is let's say what happens what happens if for some situation the anterior cerebral artery is occluded the blood flow to the area's occluded there's some type of stroke right occurring there so let's say first off we do the first one and we say that there is an occlusion occlusion of anterior cerebral artery if this happens we're going to give the most basic that all the most simplistic clinical consideration to this the anterior cerebral artery is going to come up and it's going to supply the primary motor cortex and it's going to pry up lie us apply the primary somatosensory cortex so I want you to remember that if it does supply the primary motor cortex and the primary somatosensory cortex then what's gonna happen you're not gonna look you're no longer gonna have sensations you're gonna have loss of sensation on the contralateral side of the body but here's where it's really particular the anterior cerebral artery supplies the medial portion of those Cortex's the primary motor and the primary somatosensory that is more specific to the legs the lower limbs so in this situation an occlusion of the anti cerebral artery could lead to most commonly contralateral loss of sensation and motor control to lower body.that is important so if there's any effect in that artery that is what can happen okay now we talk about the middle cerebral artery the middle cerebral artery if this is affected so let's say that there is an occlusion so now let's say that there is an occlusion of the middle cerebral artery I want you to keep it very simple same thing it's going to apply supply the primary motor cortex and the primary somatosensory cortex but specifically it's going to be going to the lateral side of those cortex so if that's the case then this is going to lead to contralateral contra lateral loss of sensation and motor control to upper the upper part of the body so for example the face and the upper limbs you know one other area that the middle serve artery supplies it's really really important specifically in the left side of the brain the Broca's area so sometimes if this is affected the middle cerebral artery it can even damage Broca's area and lead to Broca's aphasia which is the inability to be able to produce speech so Broca's aphasia okay now let's come to the next point the next point here is let's work our way down here these are some of the common ones that I want to hit the next one is the posterior artery think about that one think about the most simplistic way we actually talked about this if you remember and the optic nerve video we talked about the visual pathway in lesions if there is an occlusion of the posterior cerebral artery occlusion of the posterior cerebral artery do you know that this actually takes blood specifically to die except the lobe in the occipital it was important for a vision if this is effective what do you think is going to happen you're gonna have contra so remember what we talked about there was the fibers going to the occipital lobe and we say that they pick up visual fields from the contralateral side and the ipsilateral side well if this is affected let's just say that it's affecting the put of the actual right occipital lobe then the person will have remember we said that they will have homonymous hemianopia right so they'll actually lose temporal visual field and they'll lose the actual nasal visual field so we talked about this a lot in the optic nerve video when we talked about the visual pathway and lesions I'm not going to go into a lot of detail we're gonna get the basic concept here because I want to want this to make sense let's say that here we have the left eye right so it's gonna be the left eye this is going to be d right eye you know that this is gonna have the optic nerve this guy's gonna have the optic nerve and then here is going to be the optic chiasma right and then this is going to come eventually to the thalamus okay so here is our thalamus same thing over here this is gonna come to the thalamus and then from here you're gonna have optic radiations and these are going to be coming to a specific area of the brain which we already know is going to be the occipital lobe here okay so this right here is going to be the occipital lobe occipital lobe now if you guys remember we said that you have two visual fields let's say that here is your nasal hemorrhage because here let's say here's the nose so this is the nasal Hemi rittany same thing this is the nasal Hemi if we do this in green this is the temporal Hemi ratney and dim portal Hemi right now if you guys remember we said that you have your left visual field over here and it's separated into two parts a temporal and a nasal same thing over here you have a nasal and it's in Portal and if you guys remember the nasal Hemi ratney picks up images in the temporal visual field and the actual temporal Hemi ratney picks up visual information from the nasal visual field and then we said that these fibers here the nasal ahem here at knee let's say that we damaged the right occipital lobe these nasal Henry Rhett knee fibers are gonna come over and they're gonna cross they're gonna go to the contralateral side and then they're gonna go to the occipital of the right occipital lobe whereas the fibers here which is picking up the nasal visual field they are going to be going and staying if see lateral and then going to the right occipital lobe if you damage the occipital lobe because of a posterior cerebral artery occlusion you're going to lose what visual field if you have here the person's eyes now you're gonna lose which one you're gonna lose this visual field this one's going to be gone okay on the left eye and then it coming over here I'm also going to lose the nasal visual field so that's what I was trying to explain here with losing the temporal visual field and losing the nasal visual field okay that covers that now let's go to this guy over here this one is really really sad if it can't happen to people it's it's an occlusion of the pasilla artery if there's an occlusion of the pasilla artery it's a very dangerous situation this can produce what's called locked-in syndrome so occlusion of the vasila artery can produce what's called locked in syndrome okay now locked-in syndrome is really really devastating and the reason why is the vasila artery there's your corticospinal tracts which are kind of running through the pons and whenever the bacilli artery is damaged the perforating branches that are going to the pons is occluded and it damages the corticospinal tracts on both sides so if there is bilateral damage to the corticospinal tracts this results in quadriplegia right so again in locked-in syndrome it results in a bilateral loss of cortical spinal tracts in other words the patient patient is completely paralyzed but here's the worst thing they somehow preserve the vertical eye movements so the person still has the ability to have what's called vertical eye movements and the person is still alert and conscious and aware of what's going on that is what's so sad is that the person is completely alert that completely conscious they can move their eyes they can blink but they can't move and it's such an unfortunate situation and the result of the collusion of the bacilli artery okay so that's that one the next one is we're gonna go down here let's say that there is the occlusion of the anterior inferior cerebellar artery let's do this one here occlusion of anterior inferior cerebellar artery this right here occlusion of the anterior inferior cerebellar artery usually results in what's called lateral ponpon syndrome lateral pontine syndrome now lateral pontine syndrome when you talk about the anterior inferior cerebellar arteries one of the big things is is it's commonly going to affect one of the specific cranial nerves cranial nerve seven the facial nerve so if you have cranial nerve seven palsy what do you think could happen to this person they might have paralysis of the facial muscles so that's an unfortunate thing another situation is it can damage the vestibular nuclei in this area too so if the damage is the vestibular nuclei it can cause vertigo and maybe even with nystagmus and another thing is depending upon the severity it can even affect the actual labyrinthine arteries and this can even possibly lead to deafness and maybe to a lesser degree some tonight is some ringing in the ears okay another thing is is it affects the actual cerebellar peduncles specifically since we're at the pons it would affect the middle cerebellar peduncles if that's the case it can cause certain cerebellar symptoms like a taxi right so it could produce loss of or let's say poor poor coordination coordination and tone of your muscles and maybe even balance now these things right here that I'm mentioning is primarily all ape si lateral in nature so what I mean here it's these are going to be usually produced on the same side of the body so this usually is going to be presented in an ipsilateral fashion okay but because another tract runs up through there the spinothalamic tract because the spinothalamic tract runs up through there and there's damage to the spinothalamic tract there could be con contralateral contra lateral loss of pain and temperature sensations from the body so it's unfortunate thing there right so if there's the occlusion of the anterior inferior cerebellar artery that is one damaging thing there is it can produce contralateral loss of pain and temperature sensations because it damages the spinothalamic tract okay let's go to the next one the next one that could be affected is this guy right here anterior spinal artery and the answer spinal artery let's actually do this one right here the anterior spinal artery is this is really bad this is a really really bad one the anterior spinal artery if there is an occlusion of the anterior spinal artery occlusion of the anterior spinal artery this produces what's called medial medullary syndrome so it's called medial Maji Larry syndrome now meeting Imagi Larry syndrome if you think about it this is right around the actual the medulla so because it's affecting the medulla it's gonna effect a really really important area here one is you know there's a cranial nerve that actually runs through there it's actually called the twelfth cranial nerve the hypoglossal nerve so because of that someone with medial medullary syndrome it can affect the actual hypoglossal nerve so it would produce epsy lateral cranial nerve 12 palsy which obviously could affect the tongue movements and swallowing and dysarthria affecting the pronunciation of words and speech and articulation another thing is you know right here we're gonna have the corticospinal tracts so the corticospinal tracts could be affected so it could actually produce what it could actually cause an effect on the actual contralateral hemiplegia and this could result basically in either paralysis or loss of motor control to the contralateral side of the body and the last one is you know the medial lemniscus runs up where that is - so if there's damage to the medial lemniscus which carries touch pain temperature proprioception there could be contralateral loss of touch pressure and vibrations but one more important thing really really important thing proprioception would be affected and this is super super bad okay so one of the things that you can see in people with me to measure Larry Center which is an occlusion of the anterior spinal artery is if see lateral 12th nerve palsy contralateral hemiplegia which is basically going to be loss of motor control on the opposite side of the body and contralateral loss of touch pressure vibrations and proprioception okay we come to the last and final one this guy right here posts here inferior cerebellar artery what if there's an occlusion of this sucker right here so if there's an occlusion an occlusion of posterior inferior cerebellar artery if there is an occlusion of this bad boy what could happen okay well first off it's going to go to the cerebellum so if there's damage to this it's going to alter the blood flow to the cerebellum this can produce certain types of cerebellar signs what are some of these cerebellar signs that you might see in this patient again same thing like this you might see poor coordination muscle tone and altered balance even their bounds are equilibrium might be thrown off okay what else okay well there's another cranial nerve that actually runs from out of the medulla here right out of this area right here it's actually perfectly placed it's the vagus nerve cranial nerve 10 perfect that guy right there cranial nerve 10 the vagus nerve supplies so many different structures but if he is damaged if he is damaged one of the things that you're gonna see with this guy is this is going to produce one of the classical signs is dysphasia so trouble swallowing and they might even have a negative gag reflex they might even have a negative gag reflex so that's one thing and their uvula might be actually deviated to but again tenth cranial nerve palsy can usually result in dysphagia and maybe even a negative gag reflex another really important sign here if there's the occlusion of this vessel there's sympathetic fibers that actually descend down here and if those fibers are damaged these fibers are actually going to come out and then go up to specific point specifically like the actual eye and if that is affected these descending sympathetic fibers it can produce what's called Horner's syndrome and Horner's syndrome is usually damage to the sympathetic fibers that are going to the actual eye and as a result this can produce symptoms such as pupil constriction because there's inhibition of the sympathetic fibers and you know the sympathetic fibers cause people area dilation well unopposed it's gonna lead to pupil constriction on meiosis okay the next thing is that actually there's no sweating because the sympathetic nervous system actually innervates the sweat glands it's weird because those glint those nerves that are going to the sweat glands are actually cholinergic so they release it on to muscarinic receptors which produce sweat well the damage and this would no longer produce sweat so this is going to cause an hydrosis another thing is it's gonna cause the upper eyelid to droop and if the upper eyelid droops this will cause ptosis of upper eyelid now one more thing that I want to mention here and I'm just gonna mention I'm not gonna write it down but I want you to think logically and try to visualize this there's two tracks that are going to be running wherever the posterior inferior cerebellar artery go okay one is called the spinothalamic tract now if you remember the spinothalamic tract is gonna be carrying what pain and temperature sensations but if there is damage to the posterior inferior cerebellar artery what do you think's gonna happen there's going to be contralateral loss of pain and temperature sensations from the actual contralateral side of the body that's one thing another thing that can happen is there's another track that actually runs up through here to the spinal nucleus you know there's the nucleus the spinal nucleus of the trigeminal nerve system that's gonna be carrying pain and temperature from the face but if the post your inferior cerebellar artery is occluded guess what's gonna happen they're gonna have FC lateral loss of pain and temperature sensations on the side of the face right that same side so I want you to remember that okay last thing that I want to hit here last thing that I want to hit here is going to be aneurysms now aneurysms there is of different types the ones that occur and the Circle of Willis are usually in the form of what's called berry aneurysms or there's another name so there's actually what's called berry aneurysms or we call them saccular aneurysms so these are usually a result of two different situations two main causes of berry aneurysms or saccular aneurysms is of two common causes one is chronic hypertension so that's one reason one reason is chronic hyper tension someone is hypertension it puts a lot of force on the blood vessel walls it causes them to become fibrotic it actually damages the actual elastic lamina and eventually over time they can start ballooning out another case which is obviously not as common is connective tissue disorders so if someone has some type of connective tissue disorder for example Marfan syndrome or ehlers-danlos syndrome it can alter the normal actual histology of those blood vessels and again if they don't have that elastic fibers of the collagen fibers they're not going to be as resilient or elastic so whenever the pressure is pushed through these vessels is going to cause them to balloon out now the damage of that is if these aneurysms rupture it can be very very serious it can cause a subarachnoid hemorrhage right now the most common areas of Barry or saccular aneurysms is this sucker right there the anterior communicating artery this is the most common site of berry aneurysms out of all of them he accounts for around 40% so if we were to say here the anterior communicating communicating artery this guy is going to account for approximately 40% of the berry aneurysms that occur within the central nervous system right or the Circle of Willis in this case the other one is going to be the middle cerebral artery the middle cerebral artery and we already talked about the occlusion of those vessels but what happens if there's an aneurysm in ruptures this around the area of approximately 34% so if there's an aneurysm that develops within the middle cerebral aneurysm here in the anterior communicating or an aneurysm out here within the middle cerebral there's another one too which can happen in the internal carotid artery not as common but that can actually cause an aneurysm here and that's around 20% so approximately 20% for an internal carotid artery aneurysm and another one again not as common you know we have the vasila artery here and it branches into the posterior cerebral arteries here at that point there where it bifurcates into the posterior cerebral this p1 segment right there in the middle that is the most common site for the berry aneurysms also in this situation but that only accounts for about 4% of the berry aneurysms in the circular Willis all right an engineer so in this video we covered the ischemic stroke of the cerebral blood supply I hope it made sense I hope you guys really did enjoy it and I hope you guys learn something from myself you guys did please hit that like button comment down the comment section and please subscribe guys also you guys get a chance go check out our Facebook or Instagram maybe even our patreon account RN engineers as always until next time [Music] you [Music]

Channel: Ninja Nerd

Views: 217,914

Keywords: circulatory system, ischemic strokes, circle of willis, brain aneurysms

Id: CaOPBuP3VkA

Length: 26min 15sec (1575 seconds)

Published: Tue Feb 27 2018