Computer generated transcript

Warning!
The following transcript was generated automatically from the content and has not been checked or corrected manually.

Um I think you're muted. Um Well, maybe I can. I Oh Perfect, perfect. Sorry, I was uh I'm muted there. So um like is what like I was saying, um this, today's presentation is on um vascular anatomy of the brain. I focused on intracranial arteries. And I've got, I've got s slides on veins as well because of course, this was a presentation I've done before when I was a resident. Um And I've got some other bits and pieces of other uh s uh presentations I've made on some clinical um uh neurosurgical problems because I know that that was one of the things you guys wanted to focus on. So we'll go through uh first just an anatomy review and then we'll focus on a couple of different things. So I apologize, the slides will all have different formats cause they're pulled from different presentations. But um I can show you essentially everything I have. Um So focusing just in terms of the arterio supply of the brain, um I presume some of this stuff is of course uh been covered. Um But just the very basics is that the supply primarily of the anterior circulation arises uh from the right and left internal carotid arteries which of course are going to be arising. Um you know, from uh coming up from your subclavian um in terms of your right. And uh and uh sorry, and then you've got my apologies, sorry, you brachiocephalic and then your right and left vertebral arteries which arise from your subclavian. Um So the uh so the best way to sort of remember is anterior circulation is coming from the IC A and then the posterior circulation is coming from the vertebral arteries. And of course, the whole point of the brain is that or sorry, the whole point of the cerebral circulation is that there are collaterals. So these vessels between the anterior and posterior circulation form loops or form connections to each other that help supply the brain in its entirety. And of course, the anastomotic ring that is formed by the IC A and the basilar artery, which is um the latter which is a um coming together of the two vertebral arteries forms the circle of Willis which I'm sure everyone here has seen enough photos of especially that uh you know, alien looking like creature. Um So the anterior circulation, the IC A largely supp supplies the supratentorial um part of the brain. So the cerebrum versus um and you know, so, but, but primarily the frontal lobe, the parietal lobe, the um temporal lobe um and then the basal ganglia, while the vertebral arteries um, and the basilar artery supply the occipital lobe, cerebellum and brain stem. Um, you know, we can continue going, you know, smaller into the AC A S, the MC A s and the PC A which are branches of the IC A and, uh, of course, you know, um, hopefully they still work. Yes, they do. Ok. Well, that's good. Uh huh. Um, I don't know how we're gonna do it with, uh, chiming in because of course, uh this is much better when it's done in person. Uh But if you want to or maybe Laura, if you want, if one of you guys wants to uh designate people to answer questions or people can type in, that's fine as well. How shall we do it? Cause I, I would like to use some of these um slide that I have is a quiz. All right. That's OK. I think maybe for the uh sake of time we'll, we'll skip it as a quiz. So first of all, just starting with the anterior circulation, you've got the internal carotid artery that is coming up. So this would be the internal carotid artery, sorry, the internal carotid artery coming up this way, uh which would branch off into the middle cerebral artery. So you've got the MC A S on each side coming here and here th this would be your anterior cerebral arteries on either side. So these would be your A ones then that communicate together with something called the anterior communicating artery in the middle. And then after that, you get your A two. So we'll talk a little bit more um specifically about the various segments of the arteries cause each of these major arteries. The anterior communicating artery, the middle cerebral artery, the posterior communicating artery. Um all have various uh segments to them. And in fact, all of them do even the ones with the posterior circulation, the vertebral artery that has four segments, the pica has, you know, five segments. So we can uh um you can keep having them further subdivided. Um And that helps not only in terms of um supplies to parts of the brain, but also in distinguishing uh you know, where certain um problems can arise such as aneurysms, one of the other branches of the internal carotid artery before it finally splits off into it, spinal bifurcation of the ophthalmic artery. So this is sort of and then uh one of, and then prior to that would be the anterior choroidal in the posterior communicating artery. So essentially what happens is as the internal carotid artery is going through the ca uh the cavernous sinus and then co comes out of the cavernous sinus and becomes the dural. The intradural segment is when you start having these branches. So the first branch of the internal carotid artery, that's a named obvious branch that we all think of would be the superior hypophysis, which isn't shown on this slide. After the superior hypophysis, you get the ophthalmic artery, which right here, followed by the ophthalmic artery. So the ophthalmic artery goes anteriorly, of course, going to the um to the eyes, um to the orbit. Um And then you've got after the ophthalmic artery, the next division of the next branch is the posterior communicating artery, which is of course, going posteriorly wrapping around the midbrain and uh connecting with the uh posterior circulation. And then lastly, the artery before you get the final bifurcation of the IC A would be the anterior choroidal artery. So the way I've always sort of remembered um this acronym and let me just see if I can get the animation bit, the acronym SOPA. And so if you remember this, this is an order from more proximal to the heart. So proximal to distal before you get the final bifurcation, which is uh the bifurcation of the IC A into its terminal vessels of the MC A and the AC A. So, like I said, there are various segments of each of these vessels that you can name. So for example, the internal carotid artery has, if you look at various classifications, they all have them named differently. So for example, this is the Boer classification that has seven segments of the internal carotid artery starting with, you know, the cervical, the Petri, the laser, the um portion, the PETERS portion um and then you go up into your um cavernous segment, sup uh sup uh supraclinoid and then lastly communicating. But if you look at other classifications, for example, uh I think a group out of New York only classifies them in four segments. Um The f you know, there's various different classifications. I think the most important thing. Um you know, as you get to the stage where you're actually describing angiograms or you were working in neurovascular, um you know, whether it's radiology or neurosurgery is you pick a classification that is common at your institution and you go with that. Um There's, it's just a classification system and a nomenclature and really it uh at the end of the day for most of our purposes, it doesn't matter too much what segments you call them as long as it's all understood by everyone. Um Just a ca cadaveric model showing um how exactly the circulation looks like at the base of the brain. So, um this vessel here is the basilar artery and then you've got the IC A coming sort of upwards from the base of the brain as well. And you can see the relation of the vessels with relation to other neurovascular structures as well. So, for example, you've got the optic nerves here. And if you've ever been in surgery, you'll see that the internal carotid artery, which is cut here, the cut end will be seen laterally to the optic nerve. So just next to the optic chiasm, similarly, I think I kind of uh mentioned it briefly last week when we were talking about cisternal anatomy. But how you find the um the optic nerve or sorry, the oculomotor nerve, um the third cranial nerves running between your um PC A and your SC A. So your posterior cerebral artery, which is going to of course, communicate with your anterior circulation. Um and is a uh terminal branch of the basilar artery. Um and it also, and then running between the second terminal branch or the second most terminal branch of the vertebral system, which is the superior cerebellar artery. So, of course, none of this vasculature um is present in isolation. It's always there in relation to nerves as well. And the reason to remember that is if you see patients um or you know, they have particular aneurysms or they, or they have vascular malformations sitting in and around the very base of the brain or the circle of Willis, then they're going to present with certain palsies that you need to be aware of. So, for example, you know, a PCO M aneurysm is going to present with um ophthalmoplegia. So, and typically it's a third cranial nerve palsy um with, you know, uh problems with the medial rectus muscle or perhaps they may have, you know, uh ophthalmoplegia of the um if it's a cavernous segment, aneurysm, then they may have ophthalmoplegia due to um compression of the cranial nerve four, which is lateral rectus So that's one of the reasons why also knowledge of not just the arteries but what they are like in relation to other vessels is very important um in terms of the MC A. So for example, uh that's also a very important um vessel that I think typically comes up in questions as well in terms of its name segments. So starting with the branch coming right off the IC A, you have the M one segment um and then uh the bifurcation of the M one into the M two branches typically happens within the um ins uh within the operculum or within sorry, the insula. And then the M two branches will run along the Sylvian fissure before the uh both uh branches uh go along the surface of the cortex. So for example, um you're going to have the frontal branch, which is the one that will come around up along the convexity for the frontal lobe. And then the temporal branch of is going to come along outside the Sylvian fissure and go along the temporal lobe. Uh And then the M fours are the smaller branches that then run or divide after the cor uh M three segments to supply, then the um cerebral cortex or the frontal lobe and then the temporal lobe just respectively and along the MC A, you also have the lenticulostriate. So coming off the M one segment right after the bifurcation of the IC A into the MC and the AC A, you will have vessels that are called the lenticular striate. The lenticulostriate come from both the MC A which is much more visible here, but they also come from the AC A. So you have both medial lenticulostriate which are coming off the um uh primarily the AC A and also the lateral ventricular striate coming off the MC A. And the ventricular striate primarily um help supply um uh your internal capsule, your basal ganglia. So sort of your even deeper uh brain structures. This uh a side view which helps you see uh primarily the uh posterior sorry, the um the anterior cerebral artery, which is the AC A. So the AC A will also similarly have four named four or five segments. Actually, the first segment of the AC A is the branch that comes off uh directly off the internal carotid artery. So I'll kind of go back here cause I think that's probably best anatomy. So if you the uh before you get to the A A, the segment is a one, once the two A ones have come together and have that bridge between them called the anterior communicating artery, then the next um segment is then the A two, the A two then splits off in into. So this would be sort of the A two segment. Then once you have the splitting of um you know, you get the uh fronto orbital branches and then you come up here higher. So this would still be the A two branch, once you get the splitting of the Peric callosal artery which runs along the um sorry, the corpus callosum. So hence the name pericos and the callosal marginal artery which runs in the marginal sulcus. This these would be the vessels considered part of the A three segment. And then as you further subdivide, you'll have the A four segment, another vessel that has, in fact, actually named segments would be the pica. So moving on to this uh posterior circulation, I'll first kind of give an overview of the posterior circulation before we talk about the pica. But the posterior circulation, like I said is when the two vertebral arteries come together. So they combine prior to coming together, they will give off the um anterior um spinal artery which are two vessel uh which here, sorry, I'll the back, right. So the two vertebral arteries, when they come together, they form the basilar artery before they come together, each vert will give off a small branch that comes together to form the anterior spinal artery. This artery of course runs along the anterior ha uh part of the uh spinal cord and sits right in the median sulcus of the spinal cord and of course um supplies the anterior half and is a very, very important vessel because of course, a stroke in the anterior spinal artery will leave you with um anterior uh spinal cord syndrome, which will affect your um uh corticospinal tract. Once the vertebral artery has come together, it will first give off a branch called the I A, which is the infe anterior inferior cerebellar artery and is one of the arteries. Uh that's important in terms of supply to the labyrinthine structures or to the ear. So, um uh this will be, this is a vessel that we encounter not very frequently in, in neurosurgery, I would say. Um but it becomes important when you're dealing with uh surgery um of the lower cranial nerves and working around um the 7th and 8th cranial nerve and doing a pro um retrosigmoid approaches for Schwannoma. Once the two sorry, after the uh splitting and getting the I A, the basilar artery continues more distally. And as it does, it gives off tiny branches called the pontine arteries. Uh They're not named um But there are many of them and they of course apply the ponds as the name goes. The pontine arteries are um what uh get damaged when you have uh do um sorry, directs hemorrhages. So, for example, a shear injury where patients present with large pontine hemorrhages and of course, are nonsurgical because of the very severe um and uh devastating hemorrhage that they can present with the uh as I previously mentioned, the second last terminating branch um of the basilar is the superior cerebellar artery, which as the name goes, is of course, going to supply the superior part of the cerebellum. And then lastly, of course, you have the posterior cerebral artery or the PC A S very similar to the AC A S. And how things are named the P uh the posterior cerebral artery is named also in segments based on um uh uh its position with respect to, for example, the PCO M. So from the basilar to the peco M, this segment is called P one. After you got the PC, this segment would be called P two. And then P three segment runs as we discussed last week, we'll run along um the midbrain in the uh perimesencephalic cistern in the um ambient cistern. And then as it's going out to the cortex or going out to the parietal lobe, you get the P four segment. So as I mentioned again, ICA as you can see, this would be the 7th 8th cranial nerve complex. So when you're doing uh surgeries for CP angle meningiomas, or more importantly, CP angle Schwannoma, you have to be aware of I A which is going to be in your way as you uh decompress the tumor and decompress it off the 7th and 8th cranial nerve. Similarly, like I mentioned earlier, um you, you know, like we discussed the third cranial nerve runs between the PC and the SC A. So you can see that intimate relationship here. Um This slide of course is because specifically the segments of Pica, which is this Bassel here and is a uh like I mentioned a branch of the vertebral. So before you get to the basilar, the branch that comes off right before you get the basilar artery would be the pica and there are five named segments. Um So you've got the anterior medullary segment, you've got your lateral medullary segment, then your tonsilla medullary segment. And so the tonsilla medullary segment, and they're all named, of course, with their in relation to the medulla. So that's also quite easy and important to remember is either relation to the medulla and also their supply to the medulla. So the anterior medullary segment is going to be more anterior to the medulla and supplies that part of uh the medulla. The lateral is going to run laterally along it. And of course, um running just below the uh vagus nerve and running above segments of the um accessory nerve once you get the tonsil medullary segment. And as you can imagine the name tonsils, so now we're at the level of the cerebellar tonsils. And in fact, the um if you ever get to see a chia e decompression or any surgery where you're working, you know, below the cerebellum through the tonsils to get to uh the fourth ventricle, then you'll encounter the tonsilla medullary segment. And it does, in fact, look like that loop after the tonsil uh medullary segment, you encounter the te lolo tonsillar, which is named based on um again, the uh Tela choo and the velum and it will be something that you can encounter above the tonsils. And again, something that you have to move aside if you're doing that, uh if you're doing a surgical approach, and then lastly, of course, as it goes to uh supply the uh inferior half of the cerebellum, you get the cortical segment. So um quickly because I want to move on uh to some of the clinical syndromes. So once you've got the um cranial arteries, you're of course going to have pl vessels. So these are um I'm sorry. Um uh these would be on the surface rather than, of course, the capillaries within the cortex. But pel vessels uh will be um yes, sorry. So, pill vessels will be intracranial vessels that are actually running above along the surface of the brain and then they'll give rise to smaller and smaller arteries that will eventually penetrate the parenchyma. Let's move on to actually. So this just showing sort of the anatomy. I know we talked a little bit about uh last week, you know, the blood brain barrier, but this is more in terms of just the peel vessels. So here, um you can see that the glial, you know, you've got glial cells just next to the capillaries, you've also got Peric sites which also um are important in terms of, you know, keeping um again, a tight blood brain barrier and just remind me am I talking about cerebral veins today as well? Or just arteries? Someone can just let me know in the chat cause I'm happy to go through um the venous circulation as well or we can skip it and move on to uh more um clinical s uh scenarios or uh syndromes. Yes. No, anyone. OK, perfect. Um So uh we'll move uh we'll discuss the cerebral veins then. So the cerebral veins, there's more the superficial venous system, as well as the uh uh as well as the deep venous system. So, in terms of the superficial system, you've got the superior sagittal sinus which runs along the in uh which sorry, which runs just above within the interhemispheric fissure. So, you know, when essentially when you do uh convexity, meningiomas or you're doing any approach that's sort of running along the um you know, going across um the hemispheres then be below the dura, you're going to encounter the superior sagittal sinus. So, it's a very important structure to be aware of because of course, it is um draining um the um frontal and the parietal lobes and damage to. So the anterior half of the superior sagittal sinus can take some damage without ha you know, developing a large venous infarct. But if you uh if you go sort of past one third, then you can risk a very large venous infarct. Um and the patient could pre, you know, not only have a large infarct and deficit of course, but can in fact even die from having uh thrombosis or clotting or damage to uh the second two thirds of the superior sagittal sinus. So it's not all just about the arteries of the brain. The uh the venous system is very, very important um running uh sort of above the corpus callosum and the inferior structures would be the inferior sagittal sinus. The inferior sagittal sinus then becomes as the name uh shows the straight sinus because it becomes straight. Um and then it also runs posteriorly. Then you also have the transverse sinuses which are running above the cerebellum. So run between sort of the cerebellum and the occipital lobes. And of course, there's one on each side here. So that's what this uh diagram is showing. You've got a left uh sorry, a right, transverse sinus and a left transverse sinus. Um Before of course, uh the giving uh giving way to the sigmoid sinuses where the transverse sinus, the superior sagittal sinus and the straight sinus come together is called the torcula. And again, uh surgery with the uh and the uh location of the torcula is also very fraught um with risk because now you're essentially working in an area where you've got significant venous drainage from so many parts of the brain. So you have to be very careful in that region. The deep cerebral um drainage system is primarily composed of vessels uh called the internal sorry of the of the internal cerebral um veins. Um I'm just uh double-check that yeah, the next slide should talk about that. Um I'm sorry, the slide after that. My apologies. Oh I'm sorry, guys, I think I'm missing must have deleted cause I had a slide on the deep venous system. But um that's all right. We can talk about it here cause I do see the um vein of Galen. So essentially, uh you've got your thalamic striate vessels that are running within your um th of uh lateral ventricles and then as they come together, that your thrombosed vessels come together. Um and then combined with your basal vein of rosenthal. Oh Sorry. My apo, yeah, your comes together and gives rise to your internal cerebral veins. Your internal cerebral veins coming together with your basal vein of rosenthal gives rise to your vein of Galen, which is right here. You have other sinuses as well. Um That are part of still what we would call the superficial or the uh venous drainage system. So, you've got sinuses that are connecting um the larger drainage veins. So, like uh if you've got your transverse sinus here, then if you've got your superior petrosal sinus, which is gathering blood or draining into your transverse sinus, bringing over blood across from your ca cavernous sinus. So, uh the venous drainage system is just as complex as the arterial system for, you know, essentially for every artery you have, you have a vein. And likewise, for all of the collaterals that you have within the, an inter uh the anterior and posterior circulation, you similarly have collaterals that are draining the um draining the blood and feeding into the larger um uh venous system um very quickly. Um I'm sure this has sort of been part of the uh physiology lectures you guys have, but an arterial wall structure. Um of course, com is composed of different layers. So you've got the three layers, the tunica intima, the tunica media and the tunica adventitia. Um And of course, you've got some layers in between them, which is composed of elastic fibers such as the internal elastic lamina. The importance between or the difference rather between the systemic arteries and the cerebral arteries is that there is no external elastic lamina. So in um vessels in the rest of your body, after your uh between, I believe your tunica adventitia and your tunica media, you're gonna have the um external elastic lamina, which the vessels in the brain do not have the other difference. And again, this was kind of uh discussed uh last week. Um is again the fact that, you know, you've got your blood brain barrier. So you've got um uh parasites or you've got these uh tight uh junctions in between the vessels or surrounding the vessels. The other difference would be that you don't have as many elastic fibers in the medial layer. So the vessels in the brain are not as stretchy as the vessels in the rest of the body, which becomes again important when you talk about things like plaques. Um you know, the the vessels in the brain are not as able to accommodate for hypertension in the same way. Um or uh to accommodate for the fact that, you know, you may have uh increased turbulent flow if you've got um uh carotid artery disease, because again, you don't have the strain, the same elastic fibers in the medial layer, you also have a thin adventitial layer. All of these sort of things coming together mean that you've got vessels that are less uh capable of stretching. You have vessels that are less capable of taking high pressure, which again, especially as we become older and you know, deal with things like hypertension, deal of things like, you know, um rapid blood flow due to um again, carotid artery disease, coronary artery disease, et cetera, you're at higher risk for developing things like hypertensive hemorrhages because again, these vessels are not as capable of sort of handling that pressure. We'll skip the venous wall structure um and we'll skip the cerebral blood flow cause that's not part of today's talk and we'll move a little bit to clinical relevance in terms of neurosurgical disorders. Um So, of course, we've, you know, there uh we know about aneurysms. Um And I don't think I have any particular sides of aneurysms here, but I have several notes on this. So I'll just bring up my one note. All right, I'm just gonna stop screen sharing for a bit. Ok. So, uh, we'll, we'll first discuss, um, arteriovenous malformations. Sorry, there. I see something else on the chart. Oh, is that right? Ok. That's fine. We can move on to ischemic stroke, then watershed infarcts rather than. So, um, you'll have to excuse me, most of this stuff, of course, is primarily a neurology in terms of ischemic stroke doesn't mean that of course, that we can't talk about the anatomy. But in terms of management, I won't be able to talk too much about management specifically because that's primarily a neuro a neurology rather than a neurosurgery thing. But we can of course talk about um the anatomy as well. So, and the watershed uh territories just one second. Let me see if I can grab something for you guys. So there's a beautiful diagram in Greenberg. Can you guys see this? Cause I'm just not sure if my screen is being shared correctly. Yeah, we can see. Perfect. Awesome. Um So this is a diagram in Greenberg um just under the very first section of the textbook. So if you guys have it fantastic, if not, um there are several diagrams online that look just like this. Um But I find this is actually the best one. It's high res it's good resolution and actually is very accurate. Um So in terms of the stro um in terms of vascular territories, as you can see the MC A. So, first of all, this is all anterior circulation, right? So the uh each of these hemispheres um is supplied by the IC A breaking down from the IC A, just like we talked about are the uh big branches, the anterior cerebral artery, the middle cerebral artery, um and the posterior cerebral artery, which it was sort of you can see here the PC A and then of course, you've got the anterior choroidal, the MC A is it has a very large territory and is in is, of course, obviously, the reason why when we get an MC A infarct in a patient, we see devastating clinical deficits. And uh and because primarily the MC A is supplying the um the lateral part or the second half or sorry, the lateral half of the frontal lobe and the parietal lobe as well as of course, the lateral aspect of the basal ganglia. So um the uh putamen and the Globus Pallidus ex Internus, as well as the external capsules. So, in a patient that has an MC A infarct, you may see uh you know weakness on the contralateral side because of, you know, the frontal lobe and damage to the motor strip, the primary motor cortex, you might see uh so various degrees of weakness there. Of course, you might see sensory deficit because of damage to the primary sensory cortex. Uh in the parietal lobe, you will see various forms of neglect bec uh especially if it is the do uh sorry, the non-dominant uh parietal lobes of the right side uh typically, uh because again of the secondary um uh uh somatosensory deficits and also uh damage to um these um angular gyrus and the supra marginal gyrus. So, parts of the inferior parietal lobule. So it's down here. Um and then of course, once we talk about, you know, damage to the basal ganglia, then various uh movement issues as well. And of course, the fact that if, because it's applying uh you know, parts of the internal capsule, then again, you will see profound weakness as well. Um That might actually be the whole body um because of its location. So MC A aneurys, uh sorry MC A strokes um will have devastating clinical deficits if they're on the dominant half of the brain. So the left side where language sits, and of course, you're going to get uh language disorders such as expressive or receptive aphasia um with patients struggling to uh communicate and that becomes very difficult again for a rehab uh point of view as well. Um as their day to day communication, your anterior cerebral artery, it of course um like uh occupies a much smaller area. So it is the medial ha part of the frontal lobe. And if you remember sort of the homunculus that you have of the person, you know, with their legs here in the um interhemispheric fissure, their knee here and they kind of come along here as the face then because this is the medial part, uh the anterior cerebral artery supplies the legs. So ki essentially down from the trunk all the way down to the legs. Um And so when you have an ac a stroke, you will see leg weakness more so than you will see arm weakness. And then you've got the posterior cerebral artery, which of course is the um pre predominantly uh the occipital lobe and PC A infarcts will of course, then lead to visual deficit. Um sometimes even as dramatic as blindness in or no, sorry, not blindness, um uh as devastating as having uh hemianopia or the inability to see uh one half of their visual field. Another important um artery of course seen here would be the anterior choroidal artery, which it doesn't get too much love from uh you know, the neurosurgeons. Again, we don't encounter it too much in terms of, you know, obvious aneurysms, et cetera. But um but is an important um uh it's uh is important in terms of its supply to the medial part of the basal ganglia. So that'll be the uh GP I as well as again, the um posterior limb of the internal capsule. So it is of course a very important vessel as well. And then it goes around posteriorly as well along the um temporal and occipital horns in terms of its blood supply. Um So let me just see, as you can see if you guys don't have a copy of Greenberg, I would highly recommend either purchasing the book or there are various, I'm not sure if I'm allowed to advertise this, but there are various copies and PDF S online. Um And I, I think it's a fantastic book as a beginner uh to have and sort of throughout your um time as med students. Um just, I mean, I think it might be too detailed as med students, but um when you get to sho level and reg level, it becomes very useful to have in terms of clinical scenarios and clinical and uh pathophysiology, epidemiology and management. Um I have notes, unfortunately not slides, but I have extensive notes on stroke syndromes which of course, you actually just kind of have to learn and memorize. Uh So let me just move with this. So this was my, all the notes I had while studying for my Royal college exam in Canada. And as you can see kind of the same diagram here uh shown in a different view that I've clearly taken from somewhere online, talking about the collateral circulation. So again, you've got your anterior cerebral artery, which you can see both on the axial section and a cross section here, your medi middle cerebral artery here and your posterior s uh sorry, your um posterior cerebral artery. And then again, your anterior choroidal, which occupies a very small area, but nevertheless, still important in terms of then your infarcts here when you have lacunar infarcts. So we've talked about the large territories, let me actually move back to the large territories and we'll go to the small territories. So again, going back if you have um MC A um strokes, if you have something as dramatic as a complete M one occlusion. So, remember we talked about the M one being the branch right after the internal carotid artery splits into the MC A and the AC A, if you've damaged right away, the M one, you're going to have profound stroke, you're gonna have contralateral weakness, um upper limbs. So again, arms more so than leg because at least your uh legs are spared because of the AC A, you'll have weakness of the lower half of the face. You'll have sensory deficits, you'll have neglect, you'll uh you'll have potentially um homonymous hemianopia as well. That's not necessarily because of the occipital. Uh But more so in terms of um you know, the pathways and the fibers that are running along um from the eye going all the way back to the occipital lobe. Um If you, if you're lucky enough not to have a stroke that early, but further down the line, then if you, the superior division, which is the division going to the frontal lobe, then of course, you'll just have some of this deficit which is, you know, weakness again, um potentially hemisensory loss as well. But you um and again, on the dominant side, you'll have expressive aphasia. That's the same with the uh M one occlusion, the inferior division um because it's the temporal lobe, um you will have risk language deficits because of uh because if uh on the dominant side, because of your sup uh superior temporal gyrus. Um and you may also develop a quadrantanopia due to um the optic radiations or even again, a homonymous hemianopia due to the optic radiations passing through this region. Another part of the MC A supply is to the inferior parietal lobule. Um And like I said, that would be the supra marginal gyrus and the angular gyrus. And you will develop uh something called Gutzman syndrome. The AC A, like I mentioned, you would primarily have leg weakness more so than arm weakness. And you may also have some sensory loss as well, although less common again, because it's primarily motor rather than uh sensory. The anterior choroidal, like I mentioned is not something we encounter too much in terms of strokes. Um Nevertheless, it's important because it supplies a lot of your limbic structure. So your hippocampus, your amygdala. Um And then, like I mentioned again, uh parts of the uh the genu of the internal capsule and the posterior limb of the internal capsule, the lateral wall of the thalamus, and then your medial part or your internal globus pala is. So again, it is quite an important uh vessel and a stroke in this region in fact, can actually lead to complete uh contralateral hemiparesis because the, the um the smaller the sections or sorry, not the small, the um the the smaller area that you have where more fibers pass through or the combination of fibers pass through the more devastating an infarct, you will actually have so a small infarct in the region of the internal capsule, the or the posterior limb of the internal capsule will actually knock out your motor entirely compared to, you know, even having a stroke higher up of the MC A branches where you may just get upper limb weakness rather than lower limb weakness. So, you know, having s infarcts in the deep brain structures can actually be very devastating. Um The PC A has various. Um and II, I will be the first to admit this, I still do not have all of these syndromes memorized because I never really encountered this as a neurosurgeon. But the PC A has some very interesting named syndromes. And of course, these were named after some random neurologists um uh from various different countries. Um But uh and uh based on where you have a stroke in the different parts of the PC A, you'll have some very di uh uh you'll have some slightly different syndromes such as, you know, Anton syndrome where you can have bilateral visual blindness and it's confabulation. So they actually have all their in uh anterior pathways are intact, but they don't think they can see. Um you can have Weber Syndrome uh due to the PC A as well. And that'll be due to primarily the first part of the basilar. Of course, the PC A which will have more of the perforating branches running along the cerebral peduncles and they'll present with contralateral hemiparesis, which again, you wouldn't because you are thinking, oh, well, it's not, you know, it's not the MC A and yet because it's applying um the midbrain. Then again, you have your cortico uh spinal fibers, your cortico um bulbar fibers all passing through this region. So you'll have contralateral hemiparesis as well as having an ipsilateral oculomotor nerve palsy because coming back to this, a stroke in this region will also affect the oculomotor nerve as it's passing through this area and picking up supply because the nerves also need blood, right? So there are various different um syndromes that we unfortunately, uh won't be able to go through. Um And I can tell you that listening to me, tell you about them is still not going to put them in your head. Really, the best way to learn about stroke syndromes is you need to start, need to understand and appreciate the anatomy of the blood vessels and the area it supplies. Once you figured that out, um you know, if this vessel is supplying this region Well, what does this region do when I have a stroke? Then these are going to be the deficits I have. Um I think one of the I don't want to leave without talking about lateral medullary syndrome cause this is such a favorite of neurologist to quiz you about. It shows up on so many exams. So lateral medullary syndrome, I also known as Wallenberg Syndrome, uh is due to primarily an infarct from Pica, but in 80 to 85% of cases, the vertebral artery is also involved. Um And this is again, a very typical like neurologists love this because they can quiz you on so many of these syndrome symptoms that the patient can have and they can present with so many deficits. So, uh due to damage um of, you know, cranial nerve five, which is work, you know, in this region, you'll have facial sen and sensory loss. So the nucleus of cranial nerve five is here. Um The uh you'll have ipsilateral uh gait ataxia due to uh uh you know, damage to the restiform body and parts of the cerebellum. You'll have ipsilateral nystagmus due to the vestibular nucleus. Similarly, you'll have nausea and vomiting again due to the uh uh vestibular nucleus, you'll have vertigo, you'll have dysphasia, which of course is going to be uh not lateralized and you have ipsilateral corners. So this will be a stroke syndrome where you actually get more ipsilateral syndromes rather than contralateral um what you will. Uh So again, it's the only location where a lesion will actually produce as uh you know, so many symptoms on the ipsilateral um uh side in terms of face finding. So, um facial sensory loss, um but then you'll have contralateral sensory loss in the body. So this is one of those diagrams where, you know the ha one half of the face on the ipsilateral side and the contralateral side of the body is affected. Um So this one would be one that I would very much urge you to read about cause it shows up a lot and in fact, clinically, it's also something that we see because pica um infarcts can and do happen. Um Sorry about the rush guys. Um I, I know that it's around eight o'clock. Um But I, if you guys have any questions, I'm happy to um stick around in terms of sharing these notes. Um I, I, I'm happy to, but I don't think that this will be so helpful simply because my notes are just a um composite of, you know, uh textbooks like Greenbergs or neuroanatomy. And I think reading my notes is not going to provide you the same benefit as writing your own notes. So, and I say this with experience because I had seniors share their own notes with me and it, I never really uh benefited from them. Um But if you know, I, I'm happy to share specifically this um if people want cause I think that this, you know, this is a lot uh of good condensed information. I won't be sharing the slides though mostly because they're not complete any other questions. I know it's eight o'clock and I'm really sorry that this was, this ran really late. No, thank you so much. Yeah, sorry. I was a bit fragile today between uh you know, between rushing home et cetera. So I'm really sorry guys. No, it's cool. It's completely out of your control. Thank you so much for still making it. And this is super helpful. Um If anyone um is it fine if I just quickly take over sharing? Absolutely. Please do. Uh sorry one second. Perfect. OK. So this is the QR code for the post feedback form. Um And if anyone has any questions, you can still ask them in the chat. Thanks everyone. You guys are too kind. You just explained it perfectly. No one has a single question. Yeah, I, I really think, you know, take, take the time and of course it's not easy because it comes like I said, I still don't have any of the PC A ones memorized. But um as you learn anatomy, remember so much, I mean, all of the brain works in concert. So um learning vascular anatomy has to come in relation with understanding the cerebral or the, the brain, the parenchyma anatomy. Um And I think as you learn that it all kind of fits together. Yeah. Yeah. I think it's very helpful to unders, I think understanding the anatomy helps you understand symptoms. And, yeah, the actual pathology is so much better. Yeah, there's gonna be no, um, oh, external carotid anastomosis. Ok. Oh, this is a whole other topic. Um, external carotid. Um, anastomoses are, um, anastomoses. So, primarily there's four. and now you're quizzing me essentially on stuff I had learned from my Royal College exam. But um essentially, there are connections that you have at various parts between your external and your internal system. Um There's the hypoglossal trigeminal shoot. I don't remember all of them, but essentially, there's four and they are remnants essentially uh due to the fetal uh circulation, not the topic for today. Um So I don't have anything prepared, but essentially there's four. And uh some of them and the reason that they become important is we'll never encounter them with so many of our patients because of course, you know, we don't deal with fetal circulation except for if any of them are persistent. So, you know, persistent trigeminal artery um will be something that you'll randomly happen to see on an angiogram and you'll be like, what the heck is this. Um And it's someone who's got a persistent, uh you know, anastomosis that's still left uh something similar with the persistent hyp hypoglossal. So there's four of these that I can't remember all of them off the top of my head. Um, but they become important just when you see them and sometimes they may help, um, you know, um, circulate blood and you might actually a patient may be protected from a particular stroke if they have this. Otherwise, of course, we run into some of these anastomoses, um, in, you know, uh, problem, uh, problems such as dural, a v fistulas, et cetera. But again, that's a different topic and, uh, not uh something that I was able to chat about today. Anything else? 00 Man, in the Barrel syndrome. Ok. So man, in the Barrel syndrome is um a stroke that you have um in the, in the, in the, in the spinal cord. So it's not, uh it's not necessarily the cranial syndrome, of course, but essentially what you have is you're going to have uh preserved you, your face is all. Ok. Uh But because you have a stroke into the cervical spinal cord, um you may end up having more weakness um in your upper extremity more so than your lower extremity. And the reason that is, and again, I don't have the specific slides for this, but when you look at a cross section of your spinal cord and you look at, there's a homunculus within the spinal cord as well. Um You know where your s uh where you arms are in relation to your legs and um your arms are sort of more medial vers and your legs are more lateral when you're talking about corticospinal. Oh my gosh. OK. You guys have a lot of questions that are very specific about neurosurgery, which is fantastic, but I would very much recommend that you guys take a step back and, and, and focus more about um uh you know, the neuroanatomy, which is the talk for today rather than some of these very specific neurosurgical questions. I'm really happy to come back as a guest and talk about neurosurgical management of, you know, things like scalp A VM, which um I have done once and a lot of the time um uh or sorry, not scalp A V MS uh A scalp A VM. Um I think I've only clipped one and it was coming right off the scalp onto the surface. Um And the majority of the time you don't need to do anything about them. Um And I think when you say scalp A VM, you also probably mean um from a neurosurgical side, we would talk about as a dural, a V fistula. If you mean a true scalp like a skin, a VM in within the scalp, then that's not a neurosurgical problem because it's um outside the, outside the brain, outside the cranium. Um It may be something plastics encounters. I've never dealt with a scalp A BM. So I'm not, I'm not quite sure what that uh how to best respond to that. Um Men in the Barrel syndrome. Sorry to get back to uh Sam's question. Uh You're going to essentially have um lower extremity strength. You're going to have facial strength, but you're going to be weaker in your arms. And similarly, you're going to have sensory problems in your arms. So the reason it's called man in a barrel is because if you as uh um imagine a, you know, a guy or a, you know, a patient with their arms stuck in a barrel as if a barrel was slid onto their body, then their arms are stuck. So they can't move their arms especially proximally, more so than distally. So if the barrel was going over their body, uh right underneath their neck, then they would be stuck. So they'd be able to walk, but they wouldn't be able to move their arms. And that's pre predominantly um due to um uh um anterior spinal artery issues um or cerebral hypo that can sometimes happen due to brain infarcts. But then that'll be within watershed regions again in the MC. A more so than the AC A. But I've encountered it more when we're talking about spinal cord infarction rather than brain infarction. All right. Very good. Um Lastly neuroanatomy textbook. So I'll write it here. So uh neuroanatomy through clinical cases and that's by Blue Hales. Um That's a very good one. I think it's one of the best ones out there. There are color. Um uh Not that you heard it from me, but there are copies of the book floating around on the in EDS um as and with color diagrams, which is very, very helpful. I think that's probably my favorite one. In fact, you know what I know, I'm not sharing my screen, but I'm just gonna take a look at some of the textbooks I have. So, um I think uh that's probably one of the best ones. Um There's, there's also an Sevier uh like publisher book called Neuroanatomy. And that's another, it's, it's as simple as that. Neuroanatomy. Um Netters is also very good. I'll be quite honest. I think everyone learns differently. So for me, Blumenthal's is very helpful, but everyone loves it. Some, some people just like seeing diagrams and they're more picture people, some people like a wall of text. So I found, and at various stages during my training, I found some books were way too basic and I needed more. So I think at various times you'll, you'll just need to sort of see what your library has. Um And kind of pick and choose between them. No one neur anatomy textbook is going to be perfect cause. And then Neuroanatomy textbook that focuses more on vasculature may not talk enough about white matter tract gray or white matter anatomy, for example. So I don't think there's one catch all. But as a beginner, I do think neuroanatomy through clinical cases is fantastic. All right. Thanks, everyone. I think you guys have stayed really late. Yeah, thank you so much. You're welcome. Bye. Good luck with the rest of your stuff. Thank you. Have a lovely evening. Thanks. You too. Bye bye.