Computer generated transcript

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

We're so, but thank you for joining us today for our fourth section, which is on ventricles. Um Just a little reminder uh for those who maybe weren't here before, um, we have a Precose form that we will put in the chat uh for if anyone who hasn't filled out, if they could do so. Now, uh there will also be a post session feedback form at the end and we'll put the link in the chat and we'll have a QR code on the screen. Um We'll be distributing the certificates at the end of the course for those who have attended over 75%. Sorry. Um And we'll be using the feedback uh form as a marker for attendance. So please fill these out um and stay consistent with the name that you enter throughout. If you have any questions, feel free to ask the questions in the chat. Um And I'd like to welcome our fourth speaker MGM Gare, um who has joined the National Hospital for Neurology and Neurosurgery as the, as a senior clinical fellow on Neuro NeuroOncology. Sorry. Thanks for having me. Let's get started. Um So the topic for this week uh for you guys is ventricles. Um And then sort of as part of that, both the sternal anatomy is um and a CS F production. So I, I'm just gonna move some of this stuff to the side. Ok. So, um the anatomy of the ventricular system. So the uh first of all ventricles are interconnected uh cavities uh within the brain uh tissue. So, within, you know, the uh cerebrum and the cerebellum that are the site of production and are of course filled with CS F. Um There are four ventricles. So we have uh paired lateral ventricles. Um We have the third ventricle and then the fourth ventricle and if only the anatomy were this simple. Um but even within the ventricles, I mean, this is something that is a very um brief presentation for you guys. I uh the, you know, there are papers and books written on this and there is anatomy that to be quite honest, I'm still wrapping my head around in terms of all of the details of, you know, where things are attached to each other in terms of the choroid plexus to certain parts of uh the ventricles and other structures. So it it is quite complex anatomy uh that is simplified with so many of the um you know, images that we see online. So seeing something like this, this is very uh a very simplified diagram. But I think for our purposes um and sort of for an introduction to the ventricular system. This is quite appropriate. Um So, so uh like I said, there are two paired lateral ventricles, each one in each uh cerebellar uh sorry, cerebral hemisphere. Um and we'll uh talk further about the subdivisions. So these would be I'm not sure, I'm sorry. Uh Despite years and years of zoom, I'm still always unclear if my cursor can be seen. Yeah, we can see it. I swear, I'm not that old and yet somehow I'm still really uh bad with zoom and teams. Um So we've got the lateral ventricles here and then the, the lateral ventricle has different parts. Uh So this is the frontal horn that sits within the frontal lobe. You've got the occipital horn that sits within the occipital lobe very appropriately named and then the temporal horns that sit within the temporal lobe and then we'll just repeat this again in a bit. Uh Then you've got the third ventricle which is a single structure and is midline and similarly the fourth ventricle, which is also a single structure and midline. And then you have connections between these and within the um ventricles uh runs the choroid plexus which is the site of CS F production. And as you can see on this diagram here, if this is the choroid plexus and this, this is the whole ventricle, choroid plexus doesn't cover the entire ventricle, it's not running everywhere. So it starts um in what's co called the choroid fissure. Well, again, I'll explain this a bit further. Um It uh in the region of the hippocampus and then runs along the uh roof of the third ventricle goes up. The interventricular foramen runs at the floor of the lateral ventricles and out into the horns. So this is sort of an important thing because I know I always sort of thought, oh, cord plexus is, you know, runs in every part of the ventricular system, but that's not true. So you're not actually gonna find corre plexus in the frontal horn. You're not going to find core choroid plexus in the occipital horn. So, um let's delve into this a little bit further and with some more details. So the lateral ventricles are c-shaped. So again, when you see this on a um s uh s uh sagittal cut of the brain, you can see that it, you know, forms a sort of c shape with, you know, a bit of an outpouching. Um again, there is one lateral ventricle in each hemisphere. The two lateral ventricles are separated in the middle by a s uh sh thin sheet of tissue called the septum pellucida. And so again, you can kind of, I'm not sure this diagram doesn't have it, but Mrs will show it and I'll uh show that in a bit. Um the lateral ventricles uh communicate with the third ventricle via something called the intraventricular foramen or the foramen of Monro. And again, there is a foramen of Monroe on each side which sort of tapers down into the third ventricle, the third ventricle is subdivided into um a different sections. So again, like I mentioned, there is the frontal or the anterior horn which sits within the frontal lobe. Uh There are the occipital horns, again, one on each side that sit uh posteriorly and then the inferior or the temporal horn that goes into the temporal lobe. And typically, and one of the things that you guys, you know uh uh at various levels of your training, we get asked uh you know, to identify on CT scans the temporal horn and typically in most young healthy adults, the temporal horn is actually something you're you usually don't see uh because it's quite small and seeing an enlarged temporal horn is an indication that there the patient has some either hydrocephalus or at least ventriculomegaly or enlargement of the ventricles. Um And so the body itself, so there's uh essentially you can think of the lateral ventricle spanning the whole of the uh supratentorial space because then the body lies within the parietal lobe and it runs from the level of the intra intraventricular foramen. So if you kind of draw an imaginary line here, this would be the start of the body as you go backwards. Uh see this. Yeah. So this would be the start of the body as it goes backward to reach towards the temporal corne. And then this section here is something called the atrium or the trigone sort of this good here. OK. And let's see the, oh right. I have to clear the eye tissue. Bye, bye. The third ventricle is like I said, a single structure, it's midline and it sits between the two thalami. So again, we have, you know, a right and left thalamus and it sits between those two and it's the central structure within the brain. Um It communicates like I said with the lateral ventricles, we have the foramen of Monroe and then um inferiorly, it connects with the fourth ventricle via the uh aqueduct of Sylvia. So there's several names for this will be called the cerebral aqueduct, the s uh Sylvian aqueduct, the cerebral aqueduct of Sylvia all means the same thing. Um And so just wrap your head around the terminology cause someone might ask it, uh you know, call it something just to not get confused. Um The roof of the third ventricle is formed by a sheet of ependyma which again, I'll describe further in the histology part. Um and it's con uh covered by a triangular fold of pia called the te la choa. So the third ventricle gets a lot of interest just because um again, it is the site of um certain tumors uh the c uh you know, certain cysts like the colloid cyst which starts off uh within the roof of the third ventricle. Um And is off and is also the site of um certain surgeries such as a uh the e end endoscopic third ventriculostomy where you make a hole in the bottom of the third ventricle. So, um it's quite an important structure and it allows you to get to various um anatomical structures as well through its VR recesses, which I'll talk about in a few seconds. Then you have the fourth ventricle um which is sort of broad and uh almost like a tent like structure when you look at it from Sagittal views. So this is again the fourth ventricle here. When you look at it in a Sagittal view, it's almost triangular in its shape. Um But when you look at it head on, sort of anterior to posterior, um it'll be rhomboid in shape. And the fourth ventricle again is a very important structure. Um And the anatomy of which is very important because of the various nuclei um that sit on the floor of the fourth ventricle, which I will not get into today because it's not the topic of today's talk and is in fact quite advanced neuroanatomy that I'm sure you guys will eventually have to learn and memorize. Um And the other important thing about the fourth ventricle is uh it's communication then with the subarachnoid space. So laterally, it is connected to the subarachnoid space via the foramen of LUSA and medially via the foramen of Magen. And I'm sure you guys have already been taught this little trick or tip. Um but the way to remember Lusa is lateral. So it starts with an L and Madi starts with an M. So it's medial, it's very basic. But still use the uh use it as a good way to remember that. And essentially for the um for both for the foramen of Lusa and Medi. But this is where the CS F then goes and then enters the general subarachnoid space. So production will start, you know, in the lateral ventricles and goes in a rostral to Caudle um pattern. So it goes from the lateral ventricle to the third ventricle to the fourth ventricle and then out laterally and medially via these foramina to go into the general subarachnoid, it the sternal space and to go down um in the uh uh fecal sac surrounding the spinal cord. So again, another review of uh the anatomy. So going over this again. So you've got your c-shaped, um ventricle or lateral ventricles, you've got your anterior or your frontal horn, this will sit. So really your anterior horn is kind of this region like I said, it is anterior to the intraventricular foramen. Then posteriorly, once you go from the level of the intraventricular foramen backwards, you are in the p um in the body of the lateral ventricle, the this would then be considered the occipital horn or the posterior horn. And then you've got the uh temporal horn here sitting within the temporal lobe and again, something that's not typically very visible. And then in between the temporal horn and um the uh occipital horn, you've got the trigone, which is again, the uh another important structure. And the reason again, it's uh differentiated is for other anatomy or other structures that run laterally or medially to it um as well as against certain t uh tumors that are found uh more within the trigone such as cord plexus papillomas in adults, et cetera. So there are reasons um you know, both based on the anatomy as well as the uh pathophysiology that these are separated into different sections. Um And then uh in between all of this, again, you've got the intraventricular foramen which is running here or the foramen of Monroe and then there would be one on the other side and it leads down to the third ventricle. Uh like I said, the third ventricle is this weird sort of um squash shape. Um And in between the and it's sitting of course, between the two thalami. The importance of that is that in between the two thalami running through the third ventricle is something called the inter thalamic adhesion or the masa intermedia. And so that will be the structure you kind of see here, almost like an eye. And you know, the face of this weird birdlike um third ventricle, the third ventricle also has various different cisterns or sorry, various different recesses. So it has 54 of which are seen here. So you've got the supraoptic recess and that's named because it sits above the optic chiasm. You've got the infundibular recess because it sits um just uh below our anterior to the infundibulum uh that goes down to the pituitary stalk itself. Then you've got two other recesses, the pineal inside of the way this record. So you've got the pineal recess and the uh sorry, the supra pineal recess, which sits above the pineal gland and the pineal recess, which is uh just in front of the pineal gland. So those would be the two right here. Let me just drop this. So, so you've got a supra pineal and the pineal recess. And then there's another one which is sort of called the uh very lovely name, the vulva of the ventricles, which is the fifth recess that you have. And it's sort of a midline structure that I can't really point out here and haven't really personally seen in terms of, you know, actual anatomy intraoperatively as well. Um So we'll skip that for today's purposes. And then the third ventricle again connects to the fourth ventricle via the aqueduct of Sylvia or the cerebral aqueduct. And in reality, of course, it's not this longer stretch. This is a very stretched diagram, as you'll see, it's typically a very short and narrow corridor and it's, and as you can see here, this region um to just to make this a little bit interactive. What is this region pointing to in the brain? Sorry, this region here. What part of the brainstem is that? The pos so uh higher? So a little bit higher. Yeah. So it would be uh a little bit higher than that. And I'll tell you why, what would be, what can someone tell me uh what this area would be ahead of the ponds? Uh People in the chart are saying, yeah, Midbrain. So the reason is the reason I'm saying it would be a little bit higher, I might have drawn it a little bit uh too big. So I'll clear, you know what, just for the sake of everything, I'll clear all of my annotations, clear all my drawings. There we go. So the reason that I would say that this all of again, this is a very stretched picture, mind you. But the reason that this entire area would be considered the midbrain is because you're seeing these little bumps here. Does anyone know what these bumps are called? Ok. If you don't, it's the superior inferior colli. Exactly. Thank you very much. Yes. So they uh they, the superior, inferior colli, uh the superior colli involved in the um eye movement, uh pathways and the inferior colli involved in the auditory pathways. Um So this would be the midbrain uh which would mean and again, as you, so you, that's the way IC kinda always remember you see the quadrigeminal um uh sorry, you see the uh tectal plate or the um colli in the midbrain, then you see sort of this out pouching which makes this the pons and then this is the medulla. Um So within sort of uh just within the region of the pons and inferior to it, anterior to the cerebellum lies the um fourth ventricle. And again, sort of, as you can see this, these are the lateral apertures of the lateral recesses called the foramen of Lusa. And then this would be the inferior aperture. And let's clear all of these drawings. This would be the inferior one called the foramen of Madi. And then just here at the base which you can't, it's not really visible here as a label. Um but at the base of the um brain stem uh going, you know, uh to the spinal cord, the opening here is called the Cisterna Magna, which is an important structure primarily intraoperatively as well because opening the Cisterna Magna um allows you to release CS F and get some slack for uh uh doing you know surgery. Oh And of course, now I see the chat where everyone has answered. Uh Most people have answered midbrain. Good job guys. Um OK, let's move on to the next slide. Hopefully, this has been um a good review or a good uh explanation over and over again of the ventricle system. Um Does anyone have question before I move on? And you can just chime in rather than put it on the text or raise your hand or something, if not, we can move on. So this is just a superior view um of the ventricular system. So again, we've got the lateral ventricles and then you can see how the temporal horns sort of swoop out and the posterior horns or the occipital horns go posteriorly. And one of the important things here is again, for those of you um who are interested in neurosurgery uh specifically and or may have already been involved in uh doing uh EV DS or endoscope, uh sorry, external ventricular drainages. You can kind of see how um putting in an EVD sort of coming anterior to posterior lens you within the lateral ventricle or actually, this is too much of an anterior picture, never mind. Let's erase this. You would actually come anterior to posterior and end up somewhere in this region sitting just by the interventricular foramen. OK. So, uh the histology of the ventricular system uh is also pretty important, especially in terms of CS F production. Uh probably things you guys have already discussed in anatomy before, but this will be a review. So the ventricular system is lined by ependymal cells. Um They're called ependyma sites and the sheet that they form is called the ependyma. The ependyma is on the Luminal surface. So the inside of the ventricles um and uh it is cuboidal or columnar epithelium. Sorry, there seems to be a question. What are the indications to prefer it? All right. Well, uh thanks John. Uh what we'll do is I'll discuss this part towards the end. Uh when we start talking more from a surgical standpoint. Um and we'll just go through the anatomy right now. But thanks for that question. That's really good. No worries. Um It does take some time out to, to have the questions. OK. So, um right. so the ependyma sits on the Luminal surface and then on the other side of the ependyma on the vascular surface or the external surface lies the pia matter. So the, again, the same pia that's part of the, you know, the meninges of the brain. Um So, um and it's the same P I here. Uh So together the ependyma and the pia form the tela choroid and I kid you, it took me um some time throughout through the beginning of residency to really understand all of these terms because um you know, I would see tile choroid answer in places and they would talk about where it's attached. Um And you know, it's the roof of this, the floor of that um the source of CS F product, but like nothing really explained it in very basic terms because if you look at all the old text books, they go into detail right away. Um And then finally, I found some like very basic no anatomy uh website and it was just like ependyma plus P equals to choroid. And I was like, that makes so much sense. Um So, you know, all these Latin term and technology, it's a bit harder to understand, but it's as simple as that. It's the combination of ependyma and P A and it's a double layer membrane and then this double layer membrane surrounds on the vascular side or the external side, uh Tufts of permeable capillaries that form the choroid plexus. So what happens during um embryology is that these permeable capillaries um actually invaginated. Uh the tela choroid are the walls of these ventricles at sites called the choroidal fissure um and become the actual sites of CS F production. And of course, the combination of vessel plus ependyma plus P A is the choroid plexus. So um just kind of in very simplistic embryology views. I do have a slide later on embryology. Um But if you're looking at this as the fourth ventricle uh during embryogenesis, uh then kind of zooming in further and further, you've got uh the connective tissue of the pia matter which again is on the vascular surface and the ependyma which is on the um Luminal surface, you got an artery. Then I think someone uh needs to do to correct you. OK? I think that was a mistake. We've muted him. OK. Um uh So the uh sorry, so an a so an artery at the site of a choroidal fissure will I invaginated? Uh this tela choroid. And of course, if you, you know, you have multiple invagination and it forms the choroid plexus as you know, a collective um uh you know, the multiple small um parts of the choroid plexus will be vili and they have um and then they're actually the vili are these specific small subunit structures that are responsible for CS F production. So um a little bit more again, in terms of the histology. So the Sue, so then there's another layer called the subependymal or the ependyma are the subependymal glial cells which sit below the ependyma. So they're going to in fact be here on the inside and these uh structures or sorry, these ependymal cells um form tight junctions that then create what you guys have already heard of the blood brain barrier or for the purposes of this talk, the blood CS F barrier because that's really what it is. Um And uh these, these tight junctions or the blood CS F barrier is what helps CRE uh control the composition of CS F. So that um you know, substances from the blood, some of these substances can go into the CS F um which are small, you know, ions and small molecules that can uh permeate or pass through this barrier and through the tight junctions to get into the CS F and make the CS F versus large substances such as cells, proteins and glucose, which cannot cause these tight junctions. So, what you end up having is not, not exactly like osmosis cause. Of course, that would mean that they pass freely, but you have um you know, substances going from a higher gradient within the blood to a lower gradient within the um lumen of the ventricles or the CS F um across to make uh the cerebrospinal fluid and of course, water um is able to again cross freely as a small molecule. So again, like we talked earlier, uh choroid plexus doesn't sit in all parts of the ventricle. So it starts here um in the um choroidal fissure uh of the third ventricle within the region of the hippocampus. And then it goes up along the roof of the third ventricle, uh up in the posterior part of the foramen of Monroe will turn the corner and then go posteriorly along the floor of the lateral ventricle. Again, keeps going posteriorly posteriorly. And then again, following the curve of the wall, then goes to the superior part of the temporal horn. So this is one continuous region um where the choroid plexus kind of runs like a band. And then there is another area where chore plexus sits and that's within the uh what's uh within the roof of the fourth ventricle. And again, the reason that we call this the roof certainly let me, yeah. So this would be the roof of the fourth ventricle. Can someone tell me why, why this this region is called the roof and why this is called the floor. Someone can raise their hand rather than typing up the answer. If you know it's ok. If you don't, I'll give it a second and if not, then I'll explain. All right, I gonna take that as a no. Oh wait, someone's got a Yeah. So the super, so the superior inferior medullary bellum isn't going to actually form. Uh So that's part of, yeah, it forms a roof like structure, although it would be kind of in this region. But the reas uh the the I'm just going in a very simplistic um way here to kind of make you guys understand why the posterior part is called roof, why the anterior part is called floor. And it's very simple um and very basic neuroanatomy. And that's just going in terms of talking about how we determine, you know, ventral and dorsal surfaces. So if you remember how um you know, the, the way the embryo forms, we talk about this almost as a um uh what's the word I'm looking for? Sorry. So almost as a, you know, basic ver uh vertebrate structure where the or as an animal, right? So if you've got this is the surface of any sort of flat creature, this is the um ventral, oh sorry, this is the dorsal aspect and this is the ventral. And so if we think about as we're erect, you know, two legged creatures, but if you were to think of us, you know, walking on all fours, then our heads and our spine would be our dorsal surfaces. And uh you know, the front part of our face, uh our abdomen, et cetera would be the ventral surface. So if you were to take, you know, this head and kind of rotate it so that this is facing the floor, this is facing, you know, the roof or the ceiling, then you can understand why this is called the floor of the fourth ventricle. This is called the roof. I just wanted to get that across because I know that a lot of the times uh you know, students get confused between the terminology of why something is rostral versus caudal, why something is dorsal or ventral or why things are called roofs and floors when really it makes no sense that this isn't actually, you know, the bottom of the human being and this isn't the top of the human being. But if you were to think of us as you know, four legged creatures, then that's where that term she comes from. So I'm not so unlike John here, I'm not getting into the very specific detailed anatomy of superior, inferior medullary Veum, which is actually very important and does come up uh in, you know, within neuroanatomy and uh surgery in terms of um connections uh to the cerebellum and how I'm sorry to the cerebellar peduncles as things that hold up the um or sorry, the connections to the ventricle and the cerebellum. But we will skip that for today also because I don't really have notes on that for to show you guys. But if uh John wants, we can go into it a bit in detail later. Um in terms of total CS F production uh in terms of volume. So at any given time, we have about 100 and 50 CCS of CS F in an adult. Um What that means though is that uh we make about 450 to 500 CCS of CS F in a day. Um And so that means that we're turning over, you know, 4 to 5 times within the day. Uh 20% of the CS that's about 25 CCS. Um uh 25 to 30 CCS sits within the ventricles. Um And then 100 and 25 CCS sits within the subarachnoid space. So our ventricles in the brain actually don't hold up. Um So don't hold out much CS F. Um And the rest of it is sort of within the cisterns and uh surrounding the spinal cord. Um We produce CS F, sorry, that's my toddler. Uh Just one second. She is also very excited about my neur anomic talk. Um So produced about uh and so we make about 20 CCS of CS F every hour. Now, in certain patients, of course, this may be something that's overproduced. So, um there are various forms of hydrocephalus. There's, there's, you know, obstructive hydrocephalus, but clearly CS F isn't going all the way across, um you know, through the system and is blocked uh somewhere. Um But you can also have uh communicating hydrocephalus, which can happen because potentially of overproduction of CS F or under absorption of CS F. Um And then again, this diagram here is again, showing re uh for another time, the anatomy of the choroid plexus. So if you were looking at this as a single uh villa um or tuft of the choroid plexus, then again, you can see that the uh on the Luminal surface of this being the Luminal surface where CS F is um getting made or the ventricle. You've got um sorry, I'm getting myself confused. Yes. No, that's right. So you've got the ependyma sites on the inner surface. You've got the capillaries uh that are actually what we consider the external surface and you, you get flow or you get substances going across from the blood out into the CS F uh through these tight junctions within the appendis. So, composition of CS F compared to blood. So, um CS F contains higher concentration of uh sodium chloride and magnesium and a lower Conte concentration of potassium and calcium. And again, this becomes important. Um you know, for, again, various uh things within the brain. Um But also very importantly, um a clinical example that I can think of where this concentration becomes something useful to think about is um when we do procedures within the ventricles and we're washing, you know, blood out. So, for those of you who have ever seen um in person or, you know, online a video of doing an endoscopic third ventriculostomy or uh taking out a tumor within the ventricles. Um And you, you might see us doing some sort of endoscopic procedure and of course, in order to wash out the blood, um we, you know, continuously irrigate with saline. Um And why might that be a problem? Ok. Uh So, oh, there's a check there. Yeah, exactly. It's not the same composition of minerals, right? So if I if you look at just regular saline, right? It, it's um first of all, it's not the same concentration as it is in blood. So it's 100 and f you know, we have 100 and 54 mill equivalents of sodium within regular sort of normal saline. The uh but in blood, uh of course, our composition is low. We're looking at 100 and 35 to 100 and 45. But in CS F, it'll be even higher. So, in fact, what happens is because the composition is different, not against speaking specifically just to sodium, but in general, this sometimes can be a cause or trigger of patients not feeling well, having um you know, having seizures even because you've now changed the composition, not of CS F just in the ventricle. But of course, the CS F that is now are fluid that is now going around within the whole um CS F space, which can trigger exactly. It's exactly, it's kind of like CS F being diluted. Um which if you can imagine um all these cells are bathed in or surrounded by CS F and its part, you know, is going to be part of the um the action potentials, et cetera. So, one of the things that can sort of trigger cause problems. And then again, CS F contains very trace concentrations of cells proteins and immunoglobulins. Sometimes what becomes very important then is in clinical scenarios when we do lumbar punctures, right? So obviously in lumbar punctures in settings of infection, we'll see that, you know, protein is raised. Oh, that's very good. Yeah, Ringer's lactaid is probably a better sorry, that was sala one of the uh people has mentioned how their center uses Ringer's lactaid, which I think is actually again, it is a more biologic um uh fluid and is probably better and something actually in my center back in uh Canada, we often ended up switching to Ringer's lactate as well for this reason. Um But anyways, going back to um you know, the utility of doing things like lumbar punctures then is if something is abnormal, like having an infection, having meningitis in meningitis, um you know, a patient will have higher concentration of protein. Um and So that is again, something that's not normal, we can pick that up. Similarly. Um You know, in an infection, if you see more white cells will typically um in CS F, you should barely see any, um you shouldn't see any blood cells really and you see about only five if that of white blood cells. So, um you'll see uh that uh you know, you'll see a higher concentration which will tell you that there is an abnormality or there is something wrong. Similarly, if the blood brain barrier is broken down um due to a certain, you know, um tumors of the brain, um or tumors of the uh central nervous system, then sometimes you can actually pick up abnormal cells within the CS F. So for example, lymph uh central nervous lymph, uh central nervous system, lymphomas. If you do, you know a large volume CS F type, you can catch CS F. Um sorry, you can catch lymphocytes within the CS F. It may not 100% be diagnostic or um enough for hematology, oncology to give certain uh chemotherapy. But it does help us know that there's something wrong. Similarly, for example, in uh m multiple sclerosis, which not my area of expertise as not being neurology. But again, they'll look for like oligoclonal bands. So the CS F can give us a lot of insight into, you know, something being wrong uh with a patient. Oh, is that what a liquid biopsy? Is, I'm actually not sure. I've never heard that term before. Um So uh one of our students, Mohammed Avis asked what a liquid biopsy is and I'll have to get back to you on that because I'm not, I've never heard of that as a term. Um So I'll have to look that up. Um I'll be honest. Uh Someone else asked how long does it take for naturally produced CS F to replace all the Saline? So, I mean, uh that you would use meth. So if we're making about 25 ccs every hour, um and again, not in the exact same spot where we gave, you know, where we did the washout. But um you would essentially um depends on how much fluid you use. So if you used uh you know, a liter, that's going to be a lot that's already more than the um amount of CS F you're holding, right. So if you have only 100 and 50 ccs of CS F in your body and you have now done a wash of a liter, um then that's going to take quite some time and I would do the math. Um but I won't because my brain is no longer that good. So someone else can do the math for us and tell us how long it would take if you had a leader. Um And I will move on. I'm only a brain surgeon. You guys uh not a mathematician. So um cisterns. So, cisterns are in large pockets of po po in large pockets of CS F and they're created during, again, uh um within embryogenesis. I can't remember um specifically what stage or what week. But what happens is you have a separation of the P A matter uh from this ano space. And what happens is the P A uh remains sticking close to the brain and to the spinal cord. Um whereas the um so Arachnoid space is a bit looser. And so it uh sort of uh separates or disassociates a bit. But uh and so the space between them becomes a pocket of CS S and there are various places within our ventricular system or within our brain that you have these enlarged um CS F pockets or cisterns. Um Primarily the most important for us, of course, is, you know, all of the cisterns that contain major arteries and veins. So, thinking of, you know, the inter pedunculated cistern um uh which will contain, you know, the basilar um and our third nerve, for example, um you know, the quadrigeminal cistern where um at various parts will be the various um segments of the um posterior cerebral artery. So the PC A, so that would be so they are important in various um because of the major arteries and veins that they contain um as well as the fact that uh cisterns can be used to access certain neural structures. So again, go you know, as someone had asked or we talked about the Cisterna Magna. So I'll kind of go back here. Um So let's first of all, just do a review of the cisterns before I get ahead myself. Um And then we can talk about some clinical relevance and hopefully I can answer those questions. So you've got, there are many, many cisterns um and sort of, some of them are, of course, very obviously named. So you've got the interp cistern which sits between the cerebral peduncles um and contains the um you know, obviously the uh bifurcation or the end of the basilar artery, uh the segments or the pedunculated segments or the P one P two segments of the um posterior cerebral artery. Um It's also got uh the optic chiasm and that's a little bit sort of anteriorly within it. Um as well as again, like I mentioned the third cranial nerve which sits between the uh PC A, the poster uh cerebral artery and the sc a the superior cerebellar artery. So the interp sister, even though it's sort of this, you know, you think of this as a small space, but there are many, many things housed within the space here and this is the space, sorry, I trying to find something to drop. This is the space. So if the basilar artery is sort of running here, then this is the space that for those of you who've seen the surgery or aware of it, this is where we do our E TV S or endoscopic third ventriculostomy. We make a hole in the floor of the third ventricle going into the in interp cistern just in front of where the basilar artery sits. And now you've made this new connection where CS F can go if you have a block here, you know, some block somewhere in here. Um So that's one very obvious named um Cistern. Essentially the way to think about it is anywhere along the brainstem, there are named parts um or Cistern. So there's the Ponto Melly Cistern, which just like the name uh shows it's surrounding the ponds and the medulla. Uh you've got the cistern of the lamina terminalis which sits anterior to the lamina terminalis. Um And then within the, another very obvious name or so sorry, not obvious, but a very common thing that you guys will encounter will have been quizzed about uh during, you know, case rounds or something like that would be the quadrigeminal cistern or the basal cisterns. And the quadrigeminal cistern is named that because of the fact that it's sort of surrounding the quadrigeminal part of the midbrain or the superior inferior colli and the quadrigeminal cistern has uh different parts. So it's got the in interp cistern, then the ambient cistern and then the lateral cistern. Here, I'll go to the next slide to show that there we go. So um it's got various parts uh to it um that you can um you know, rhyme off or name to your uh seniors during, you know, morning rounds and it will be a bit impressive. So again, if you've got your midbrain sitting here, you've got, you know, your mickey mouse ears or your cerebral peduncles and your interpreter cistern is this most medial part. So you kind of go around here to, you know, the edge of the ped uncles or the um kind of where your p one sits. So the first segment of your poste uh sorry, of your postero cerebral artery. Then as you go around, you've got your Ambien cistern which sits actually, you know what, let's go back here and just zoom out or sorry, I'm going to um and my slide show just because I think this is cut out a little bit. Um Let's start the slide show again. OK. It's not there we go. So the Ambien cistern sit laterally. Um And then this is again where this would be where the P three segment sits of the posterior cerebral artery. Um Again, different people will name for different things. So sometimes you'll have, you know, people will call this the crural cistern as well. So just around the crew of the cerebral peduncles before you hit the ambient cistern. Um And then this is con this would be considered the quadrigeminal cistern or behind the tectal plate. Like I said, um you've got, like I said earlier in the last slide you've got the prepontine cistern, which is ahead of the Pons, but also part of the Pontomedullary Cistern, which is the whole thing. So you'll, you'll essentially, what I'm trying to say is that there's different terminology uh for the cistern. So someone may specifically just call this the prepontine and then call this the premed Lly, someone might call this the pontomedullary, but it's the same region in continuity with each other. And they're named these because of the structures that they're in front of or behind or below or whatever. And then again, the things that they contain. So the chiasma cistern, um as I mentioned earlier is, you know, the optic chiasm sits here but then also starts um or it's also part of the interred ocular system. Um one of the other and again, the quadri cern or this particular region of the brain um is important also for um the fact that a lot of the aneurysms that we see will bleed or will have blood within this region. So, again, sort of that death star that you guys see on CT scans, um you'll see blood primarily within this region and you know, a lot of aneurysms. So, aneurysms of the basilar aneurysm A PC M PC A um less of course, uh uh SC A et cetera will occur within this region. Uh You've also got the Sylvian fissure of like my, my, my images moved. So it's not doing a very good job of showing you where things are. But the Sylvian fissure which is here, um which you can sort of think of um not as a cistern because of course, it's not separate of um the pia from the Arachnoid, but is a poor space between um the lobes of the brain, the frontal parietal and the temporal. But again, the Sylvian fissure which houses um you know, the MC A and the branches of the MC again, is another space filled with CS F and also a region where blood can accumulate during a Aach noid hemorrhage. And then lastly, one of the other cisterns I mentioned and is, you know, an important cistern would be the cisterna magna and also, which is also known as the cerebellar medullary cistern. Um And uh this contains importantly in terms of vessels, the vertebral artery and Pica um as well as uh the exiting 9, 10 and 11 cranial nerve, sorry, 9, 10, 11 and 12 cranial nerves. Um And I think one of the questions we had was why do you open the Cisterna magna? Um I rarely. So in any case where I am actually accessing um the, you know, need to do something within the cerebellum or need to do something um you know, around the cerebellum. So you, so let me just sort of think, let me gather my thoughts. So for example, if I am doing a surgery that is just um you know, a decompressive uh procedure, say for someone who's had a posterior fossa stroke. Um and I just need to remove the bone here, right? I just need to remove the bone. I just need to open the dura so that this person who is potentially dying from all of the um yeah, uh from all of the pressure in their brain, whether it's a hematoma or it's just an infarct. Um I won't be opening the cisterna Magna because I don't need to slack in the brain to reach something else. So there's no point in opening the cisterna magna there. So I leave it alone. OK? And uh opening the Cisterna magna, it's not some for, again, for those of you who've ever seen these surgeries, it's not um you know, some big thing. It's really like this thin sheet of um you know, arachnoid that you just open up with the sharp hook and then all of a sudden you get a gusher CS F and it's just here at the uh just at the base of the cerebellum uh befo in the at the cerebral tonsils, sorry, stuck here. So I'm just trying to see how I can. There we go see the chart. OK. I'm not sure if there's been any further question. Um But so that would be the instance where I would not need to open the Cisterna Magna if however, I need to uh access a tumor. So for example, I am um you know, I've got a large mat in uh you know, either of the cerebellar hemispheres or I need to um you know, get to a tumor. Um say like am uh Schwannoma at the CP angle then helping, then opening the cisterna magna helps really CS F for me. Um And by releasing CS F I have now reduced IC P, right? Because what is IC P? It's a combination of the uh or sorry, it's, you know, the Kelly Monroe doctrine. So it's blood plus CS F plus tissue, brain tissue. So, by releasing CS F I have now helped uh reduce my IC P, the brain slacks a bit and I can maneuver without things herniating out at me. So those would be the re the reasons why I would open up the Cisterna magna. It's not just a reflex knee jerk thing because if I don't need to in a surgery, then it's, then I won't do it and then, you know, have to encounter a post-op CS F leak. So I wonder if that answers your question, John in a roundabout way. Oh OK. So John has asked another question between an ependymoma and a choroid plexus tumor. Um So uh without going specifically into too much of this. Um But yes, so an ependymoma is simply going to have uh started from the ependymal cells as simple as that where a choroid plexus tumor will be an overgrowth of all of those components. So it's um in an ependymoma, um these cells are still capable of making um CS F. So if you see an ependymoma, sometimes there are little pockets of CS F because they have, they have made that. But as you don't see the frs of choroid plexus in an ependymoma and an ependymoma can occur anywhere. So you do have um you know, ependymoma occurring, but they're primarily within the posterior fossa and the fourth ventricle for Children. And then sometimes you will see them, uh you know, in lateral ventricles uh for adults. Uh but you can have ependymoma occur um within, you know, other parts of the brain. Uh um you know, due to errant um ependymal cells that you can see versus a choroid plexus tumor um is going to arise from, you know, the totality of choroid plexus and under the microscope will look like tiny choroid, like will look like tiny little ventricles because it is all of the components of the choroid plexus and they will have little FRS under the microscope. Um And this will very much secrete CS F. Um And in fact, in patients, you will see when they have choroid plexus tumors, even if it's not obstructive because it hasn't blocked off, say the foramen of Monroe. Um the patient will potentially have more CS F just because they're making mo um they're making more CS F from this tumor. Um And then choroid plexus um tumors will occur primarily within um uh the lateral and third ventricle, uh third ventricles for pediatric patients and, and less um are tumors that you see in adults. Although ependymoma can occur in adults, uh uh again, less so than Children, but uh you certainly see them more than you see choroid plexus tumors. Um And then another difference between ependymoma is that you will see them all along, like I said, all along the um CS F pathway. So you will see ependymoma within the spinal cord versus the fact that you will not see cord plexus, you know, um down in the thoracic or the um lumbar spine. Yeah, I uh sorry, you didn't ask again. Um I didn't realize I was giving a neur oncology talk. Yeah. So, ependymoma, as you would say, arise solely from ependymal cells. Um whether, you know, you would see some other cells, I'm not sure. Uh But that, that is the general idea that that's their cell of origin versus from choroid plexus. Um uh You, it's a combination or an overgrowth of the poro plexus um in itself is a tumor. I'm happy to come back and give more of a neur oncology talk as you know, my specialty. Um But we'll have to p you know, pre uh prepare things a little bit better. Um I let me see if I have any more slides. I don't have too much more after this. Um So lastly is the embryology and uh pardon me? But this, this is something that I have, of course, forgo since my own Royal college exam. But essentially, um this is kind of around the time that the various um vessels and uh the cavities of the um the brain or the central nervous system will form. So the neural tube will form the vesicle wall. Um And, you know, you start having these indentations. So initially, you have the three primary vesicles, which is the forebrain, the midbrain and the hindbrain. Um and then they sort of form by fifth week into um you know, further secondary vessels. So that's when you start forming um you know, your diencephalon, your mesencephalon, um the uh sorry, your telencephalon diencephalon, which come from your forebrain. Um your mesencephalon stays the same and then you've got your metencephalon and myelencephalon and it's around this time uh that the lumen of these vesicles or the inside is starting to form the ventricle. So, um it's around the 5th and 6th week. Uh and then primarily the choroid plexus will arise from the medial wall wall or so, like I said, the Luminal wall um of the lateral ventricle. So here um at the sixth week and I think that concludes my talk, um I didn't really think this was going to take, you know, almost an hour and yet here we are. Um So, uh I'll take this for questions and for now, maybe we can focus a little bit on the um on the anatomy that I presented or this uh uh CS F pathophysiology. And then if you guys have any questions, you know, sort of more clinically, we can move to that in a bit also bearing in mind that it is 7 30 I'm sure you guys have other things to do as well. Any questions? OK. Is there more of clinical questions if you guys have any? Otherwise we can uh lo as this sort of the end of the talk? Oh, no, if anyone has any questions. Um Yeah, there are no um questions then. Yeah. Thank you so much for to, for taking the time to teach us today. It was very helpful. Absolutely happy. Sorry. I know I said absolutely. Um uh I am, I'm giving you guys a ques uh sorry a talk next week on uh the anatomy. I think of the vasculature. Uh Do you guys want to just because I'm assuming it's gonna be the same group um Whether people wanted it to be focused again on, you know, this kind of content where it's sort of a, a little bit basic but simplified or do you guys wanna see more um you know, clinical images? Um You know, more CTS, more MRI Ss talk more about clinical stuff. So if you guys just wanna chime in a little bit about what you'd like to see, um I can tailor that a little bit. Um I mean, I know personally I quite like seeing also like a um the clinical side um and doing a bit of both. Perfect. Ok, so I'll, I'll try to bring in a little a few clinical cases or at least, you know, some more um CT or MR imaging and that might be helpful. Perfect. I'm just gonna quickly um for everyone, if you could please fill out the um QR code for the post session feedback, that would be very helpful. Thank you. Um Yeah, and I think people on the chat are also saying um clinical correlations. Absolutely. We'll do that for next week. Thank you so much was.