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Uh Hi, everyone. Thank you for joining us today. Um For a talk on the anatomy of the spinal cord and the vertebrae. Um Just a quick reminder to fill out the post feedback form, um which we will put in the chat and we'll put a QR code at the end of the session, we will be distributing certificates at the end of the course. Um So make sure that you use the feed. I will using the feedback form as a marker for attendance. So make sure you fill them out with the same name each time. Um And if you have any questions, feel free to put them in the chat, um We'll be staying th throughout the session. So I'd like to welcome Mister Penn, a neurosurgery registrar based in London at the National Hospital for Neurology and Neurosurgery. Ok, great. Um Can you all hear me? All right. Fantastic. Ok. So thanks for the introduction. So I'll make a start. Um So those of you, I think this is the neuro neuroanatomy collaborative as I understand. So, um you're probably more interested in learning about the brain rather than the spine. So I can only assume that those of you who are here are the dedicated members of the Neuroanatomy collaborative um on a Tuesday evening. So I'll try and make it relatively to the point. Um So, hold on one second. There we go. Right. So lumbar spine anatomy, I'm gonna start with um and I might just move my screen one second. I'm gonna stop my video so you can hear me. It's gonna help with the connection. So lumbar spine anatomy, this is Florence are going to use this to represent the um the cranial anatomy that you're probably used to seeing. And on this side, we have got slough, which some of you might think of as the lumbar spine anatomy. So one is quite glamorous and exciting and one is not particularly exciting. I don't know if any of you have been to slough. But anyway, I'm gonna try and persuade you that the uh lumbar spine is um if not like Florence, it's perhaps a little bit more useful to you than slough might be. So, so the lumbar spine, the thing about the spine is that it, it's essentially a series of repeating units that subtly change over the course of the um the entire length of the, of the spinal column, which makes learning it when you're looking when you're presented with a single object quite easy. So identifying the sort of regions of anatomy that you can see here, the transverse process, the articular processes, the spinous processes, the vertical body, the vertical disc, that's all quite easy to do if you're presented with a single object. But it can be quite disorientating when you're doing an operation, which is the reason that most of us um in surgery at least are going to be learning this anatomy. So it can be highly confusing. So when you look at a textbook, you might be presented with something um similar to that. And this is actually again, quite easy to understand. But in real life, it never really looks quite like that. So it's really important to try and get a grasp of the basics before you start trying to do um an operation. That's the same for any, any surgery. But I do think the spine is especially um uh that's especially true because as I said, at the beginning, when you start to learn these things, it can be very disorientating. So the spine in the lumbar region is like a series of cups stacked on top of each other. So you can see here, imagine that's the angle of a cup there. And then you've got another cup stacked inside it here and then another cup stacked on top it here. And they're, they're arranged in that fashion. And the reason for that, if you look at the angle of the facet joint here, you can see that it supports the cup above it. And then this one here supports the cup above that the, just draw your attention to one point here, which is really important and we'll show you later on. So the transverse process, which is this bit here sticking out of the side is not an especially important part of bone. I if you fracture it, it doesn't really matter, it supports some of the paraspinal muscles, but it, it's not particularly important for the stability of your spine or not at all actually. But it's a very useful landmark for understanding where you are. If you look here, you can see that the transverse process is at the same level as the pedicle. So here is the pedicle and there's the transverse process going out. And that's important when it comes to putting, putting in metal work. So things like screws, pedicle screws when you're trying to stabilize the spine. So whilst it's not an important piece of anatomy in terms of its function, it's very useful as a landmark. So the pedicle is this area here, which is where we would put pedicle screws in which I'll show you a picture of in a little bit. And then you've got the facet complex here. Now, one of the confusing things about the facet complex is that each vertebral bone has two facets, you've got the superior facet and the inferior facet. So if we're, if this is L5, L5 has superior facet here and an inferior facet here, but the superior facet of L5 makes up the inferior part of the facet complex of L4 5. So that's important to remember because often people get confused by that when they're talking about these things. Uh and even even surgeons, radiologists, you know, experienced doctors, um we'll, we'll, we'll use the wrong terminology when it comes to this. So it, it's important that you have that clear in your head that sometimes people will get that wrong and start talking about it in a different way. But there is a superior and an inferior facet for each bone. But that, that facet makes up the opposite ie the inf the inferior part of the overall facet complex that it's involved in which is a bit confusing. It took me a while to understand that. So here's a drawing which I find helpful for trying to um remember how the, the especially the lumbar spine is laid out. So if you imagine each spine um as a person, so going back, you can see here. So this is one person here and there's another person here and imagine that these people are stacked on top of each other. That's quite useful because when you're doing operations like a laminectomy, you tend to start nibbling away at the underside here. And it's much easier to remember if you can think about it in terms of some sort of memorable structure like this. So if you're doing a laminectomy, you're nibbling up on this person's leg, the, the hand here, you imagine. So this is the facet complex here. So this blue person here, his hand imagine the fingers are stretching behind the feet of the person above him. And that's important because if we go back to this picture here, this is the neural foramen where the, where the nerve itself is going to be running. So the spinal nerve root is going to be running through here. One of the main reasons you do or one of the most common reasons to do an operation of the Lumb spine is when someone has impingement of that nerve root. And you can see by these facet complexes here that it is this facet. So the the inferior facet in the complex ie the superior facet of the bone below that causes the impingement of that nerve root. So that's important to remember that when you're reaching around to try and take away that bone. So if we go back to our picture, you can see that this is the man below. So his fingers are creeping around the back of the foot of the M red man. And it's those fingers, those knuckles which are squashing into the nerve root and causing compression. So here's a couple more pictures of the uh lumbar spine. So this is the sort of image that you might see quite frequently on a um uh on a on an MRI scan something you might be looking at. So it's important to remember that the cor in the cor quer the lumbar spine, there are lots and lots of nerve roots floating in CS F that you can see here. Now, the ligamentum flavum is probably the most important thing you can learn about in the, in the lumbar spine because it protects you when you're doing operations. So the ligamentum flavum runs from the, the top of the bone below. So the ligament and flavum runs from the shoulders and the top of the arms of this man here for this woman and then runs up underneath the Lamina above and finishes about, you know, halfway up the back of this person, ok? So it starts at the shoulder of this person runs underneath, underneath, underneath the red man or red woman and then finishes about halfway up the back here. And that's important because when you're doing an operation, you're nibbling away at the bottom of this Lamina, you know that you're safe because that ligamentum flavum is protecting you from injuring the Jura. So that's why that's a safe place to start. So you can see here underneath the Lamina, you've got the ligamentum flavum, which I'm just trying to illustrate for you here. Now, the ligament and flavor is, is a sort of two leaflet sheet. So it's not, it's not one. I it's not one ligament, it's two sheets, a left one and a right one that go under the left and right side of each lamina and then stops and then starts again at the top of the next lamina and then goes underneath the one above it. So instead of one big ligament, it's not like the anterior longitudinal ligament or the posterior longitudinal ligament. It's essentially a series of lots and lots and lots of small repeating units of ligament. And that's a really, really important structure because knowing as we do now that it starts at the top of this lamina, if I drilled away the top of this lamina suddenly underneath here, there would not be any ligament to protect me from damaging the Jura and underneath the Jura, as you can see here, there are lots and lots of these nerve roots. And if during an operation, you inadvertently open the Jura with um a drill or an up cut, you, you could do a lot of damage to these nerves and it can be very serious. So it's extremely important um uh thing to remember. No one of the most common uh models for looking at spinal stability, especially in the thoracolumbar spine. Although it, it's often used for um uh for all, all levels of the spine is the three column model and that splits the spine into anterior middle and posterior columns. It's traditionally used in trauma. Um because uh they, they talk about uh uh unstable spinal injury involving two or more er columns, whereas a single column injury should still be stable. It's not quite as simple as that. And the, the posterior column is probably more important, relatively speaking. Um but it's a useful working model to be at least aware of. So you've got the anterior column, middle column and the posterior column. So two what, what an injury to one of those columns is? Ok. But an injury to two of them is not stable in reality, as I said, it's got a lot more complicated than that. And spinal stability is um is not a binary uh concept. It's not either stable or unstable. It, it's a spectrum. OK. So here's another picture where you can see what I was talking about with the ligamentum flavor. So you can see here that the ligament is split into two. You've got one on this side and one on this side. And you can see here it's starting at the top of the lamina below and it's running underneath the lamina above and finishing about halfway up and then it stops and then it will start again here. You can see that on this view here. It's lots of repeating units. OK? So which dis which nerve, this is a common um misunderstanding as well. So one of the most common issues that you'll come across in the lumbar spine would be a disc prolapse, causing impingement of the nerve and radicular pain that's often presents itself in the form of sciatica. So if you look at this, if you've got an L3 4 disc prolapse. You've got to think about which nerve is that going to be squashing? And the answer is in L3, 4, disc prolapse almost always. It will be squashing the L4 nerve root because the L3 nerve root leaves through this hole here. By the time you get to the disc, the nerve has already escaped, it's already left. So disc prolapse unless it is extremely lateral, which is very rare, will cause compression of the nerve root of L4 as it transits as it starts to leave the main um fecal sac and transits across something called lateral recess before it comes to leave here. So, an L3 4 disc prolapse will cause problems to the L4 disc. That's a really important thing to remember and you'll be doing a lot better than um a lot of um surgeons if you can remember that. Ok. So this, I'm not expecting you to learn or memorize all of the muscles for the, for the back. I just want to draw your attention to the fact that there are lots and lots and lots of different muscles involved in the stability of your spine. And the most common reason for back pain is, is muscular. So there are lots and lots and lots and lots of these muscles. When people talk about having a knot in their muscles or they, they've got severe back pain and they can't get up, they can't stand up out of bed. It's almost always due to muscular problems, muscular pain, which people often don't, don't believe they can't think it's possible to be in that much pain because of muscles. But it is absolutely true. So, really pain in your back is either due to muscles or it could be due to um, arthritic pain. So, bone rubbing against bone or in a slightly more complex fashion can go, it can be related to the nerve nerve impingement. That's probably a reasonable model in which to work with. But muscle pain is extremely common. It's also important to look at these muscles because when we do an operation, we have to strip those muscles away from the spine. So this again is a very idealized view of what it might look like to do an operation on the lumbar spine. So what people have done here is they've made an incision through the skin and they've gone down through the fat layer and then in front of them would be the fascia here underneath which is all of the paraspinal muscles. And they've opened the fascia above the spinous processes which you can see here. And then they have stripped the muscles away from the lamina of each side and then put a retractor in place here so that you can see the lumbar spine in terms of the bone. Now, in reality, it, it doesn't look as neat as that and it looks much more confusing, but broadly speaking, what you can see here is the facet joint complex here covered in a capsule, which again is what it would look like in real life. You'd have a capsula covering to it. And then here you've got this nice neat gap in between the Laminae which again, in real life is never that neat. And underneath here, it's trying to show you that this is the ligamentum flavum here that we've spoken about before. As I say, this gap between the two Laminae is usually much, much smaller in real life. Um And if you're going to be doing a laminectomy, like we said before, you'd start nibbling away at the bone here knowing that you're safe with the, um with the ligamentum flavum underneath covering you, except right in the midline where you've got to be a bit more careful because as we said, it's two sheets that come up to a tent in the midline. And you can see here this is what they're doing. They're trying to do a laminectomy, which is a very common operation for trying to decompress the lumbar spine or any part of the spine actually. And a microdiscectomy, which again, this is an idealized view of what a microdiscectomy might look like. But you can see here that they've, they basically just, well, you would nibble away at this piece of bone here. Not, not in the same way as doing a full laminectomy, but you would make a little bit of an opening here and then you would try and cut through or move aside the ligamentum flavum so that you can access the fecal sac and the nerve root underneath and find the disc fragment that would be causing uh compression. So pedicle screws when the spine is not stable, maybe that's because you've had a fracture or maybe that's because you've done an operation which is delo destabilized the spine. Deliberately, you need to find a way of securing it again. Uh And I in a tried and tested orthopedic fashion that is with screws and rods. So pedicle screws are the most common way of stabilizing the spine. This is just to give you an idea of that. So the idea of a pedal screw is just putting a big screw that runs from the sort of just to the side of the facet complex through the pedicle into the vertebral body. Now, in terms of the access points for this, this comes back to the importance of remembering about that transverse process because if you remember from before the transverse process is on the same plane as the pedicle. So your starting point for your pedicle score entry because you want to go through the middle of the pedicle is going to be approximately halfway up the transverse process that will keep you in line with the, with the pedicle. So you stand a good chance of getting in the middle of the pedicle without um breaching above or below the, the, the boundary of the pedicle, which could do damage to things like nerves. And then you want to be starting just to the side of the facet complex where there's this bulge which some people call the mammillary process. So it's approximately there and you can see um an image of it here and this involves drilling a starter hole here and then pushing something called a pedicle finder through the gap through the soft marrow of the bone. So the sort of honeycomb cancerous bone and you're pushing that pedicle binder through making sure that you don't breach any of the boundaries, the walls of the pedicle. Because if you breached this way, you'd have the, the thecal sac. And certainly if you breach the other ways you could be demining things like nerves or blood vessels. So you've got to be very careful. This is something called a, a feeler, which is just trying to, the person is um, pushing it down the hole to see if they can feel for any defects or any gaps that they've inadvertently made. And then you would put a screw in place, which is not the most glamorous thing in the world, but it is something that can be very satisfying when you get it. Right. Ok. So Cervical Spine Anatomy, this is um, supposed to represent the stairway to heaven and this is the, er, the music band led Zepplin who, who sang a song about this. And this is me trying to um suggest that the cervical spine is leading you closer to the brain, which is probably what you're all more interested in than the cervical spine. But we're not going there this week, unfortunately. So, looking at the cervical spine, the cervical spine is made of, well, seven parts to seven bones make up the cervical spine. No, this is preserved across, you know, I think virtually every mammal there are, there are, there are two except think there's a certain type of sloth and a manatee that don't have se vertebrae, but it's incredibly well preserved across across mammals. Um It has a similar type of structure whereby C one and two tend to be different to the rest of them. So it's best to think of the C one and C two complex as something that is separate to the rest of the spine, the cervical spine to the sub axial cervical spine, mainly because C 12 is is different functionally and also quite complicated in terms of the way it's set up and the bone morphology is completely different. But the the sub axial spine is perhaps the best place to start. Now, a couple of things that are notable about the sub axial cervical spine is different to the rest of the spine. So one of them is from the back, you can see that there is what was called a bifid spinous process, the spinous process has two or typically has two protrusions to it. So you can see here there's a cleft in the middle and that's important to remember because it can be a little bit misleading if you're doing an operation and you're, you're not aware of that. Um So there, there is a bifid spinous process, the orientation as you can appreciate uh when compared to the lumbar spine is, is completely different as well. Um The, I'll show you the uh an ax you in a second. But one of the most notes, noteworthy parts of the anatomy is the transverse foramen, which you can see here. And the trans foreman is there to transmit the vertebral arteries. So one on each side and that's really important because whenever you're doing operations on the cervical spine, there is this very important artery running um very close to where you're doing any sort of an operation. The vertebral artery obviously goes up uh towards the brain and it contributes to the um supplies the, the posterior circulation of, of the brain and feeding into the um into the circle of Willis that way. And also plays a very important role in in the overall blood supply of the spinal cord, which what I mentioned um in a little bit. So the vertebral artery transmitted through these lateral channels, these little holes running down the side is very, very important to be aware of. So this is slightly misleading because actually on this, on this anatomy book, they've labeled, this is C seven with the trans thrombin here. But typically it's C six where you would, you would have the um uh vertebral artery starting to go through its journey, that journey gets a little bit more complicated as you get to the top. And I'll show you a picture of that uh in a short while. The other thing that's um different is the something called the Unna the UN process. So here, it's quite slightly difficult to appreciate. But if you're looking straight on at the, at the spinal um vertebral body on in the spal spine, they have these sort of um it's like a cup where they have another type of cup, but they um the uncinate process is like a little lip at the lateral edge of each vertebra and that stops too much um lateral movement of the cervical spine. So you don't sort of hyper uh flex or extend uh in the lateral plane. But it's also a very important uh part of the anatomy because it can contribute to uh impingement of uh nerves as they travel out again through the neuroforamin um that you can see here and here. OK. So the, the uncinate process is actually an important part of degenerative spine anatomy because it does lead to radiculopathy. So, nerve pain. OK. Um And just also worth mentioning, it is an important point to remember that C seven uh is what's sometimes called the vertebra prominence. So the, the, the, the, the, the spinous process you can feel at the base of your neck uh is, is traditionally um thought to be um C seven. So it's typically C seven that you can feel there. So that's a useful piece of surface anatomy as well. Ok. So th th this is something that um is, is a little bit confusing um which I always found confusing for a long time actually. So you, you have um seven cervical bones, but you have eight cervical nerve roots which seems, you know, confusing. Um And um the reason for this is, is simply an error when they, they, that they, they did the naming of these things. So C one nerve root travels above C one. So it comes out above C one, all of the other nerve roots come out in much the same way they do in the lumbar spine below the uh in the neuroforamin of that level. So it's just below the pedicle. So because C one is called C one, it means that the, the numbering for all of the other nerves is out of sync by one. So what they should have done is called C one nerve root, Cze nerve root. And then all of the other nerve roots would have been appropriately named and then you would just have seven cervical nerve roots. So it, it, it, it is confusing but you've just got to remember that the anomaly there is C one, c one is an error essentially in the way it's named. Uh and if that weren't the case, then everything would be well with the world. OK. So in the sub axial spine, the if you look at this from above or be, yeah. So you can see here this is an axial view of the spine. So we can see here the transverse foreman where the vertebral artery is being transmitted. And here is the body obviously much, much smaller than the lumbar spine because it's not uh load bearing in the same way. It has much, much more to do with flexibility and movement and less to do with load bearing. There's not so much weight. Now, if you look at this, the pedicle is a very, very different structure. If we remember in the lumbar spine, the pedicle was a big fat structure. Um It's not not the case in the cervical spine. It's, it's a very small thin structure that you can see here. The lamina is, is orientated slightly differently as well. It's flat up, but you still have the concept of ligamentum flavum that exists there as well. So the pedicle being smaller has implications for fixation uh which I'll mention um in a little bit. Um what else? The transverse process is not quite so relevant? Um And er we've already spoken about the bifid process there. The facets are aligned in a very different way, much closer together and the nerve root. So when we were talking about which nerve root is affected in the cervical spine, the nerve root that is affected by some sort of disc prolapse is the nerve root that comes out at that level. So, in the lumbar spine, if you remember what, by the time the disc prolapse had occurred, the nerve root would already come out somewhere up here. But in the cervical spine, because the depth of the vertebral body is much shorter, it means that the nerve root that's coming out at this level is indeed the one that's affected by a disc prolapse. However, because of what we said before, the misnaming of C zero or C 12345678, that means that despite that, it's still the number of the vertebral body below that is affected. So, in ac 56 disc prolapse, it is the C six nerve root that is compressed for different reasons to uh to what you would find in the lumbar spine. That is quite confusing and I wouldn't expect you to remember that. Um But it's more just your interest. Um And this, I just wanted to mention about fixation in the cervical spine. So I won't go into all the details of it. But the cervical spine typically, when someone is doing a fixation, it will be what's called a lateral mass fixation. So instead of a pedicle fixation because those pedicles are very, very small. Uh And it's not so effective at holding and it's more difficult to access. Typically, instead, if you wanted to do a fixation for the lumbar spine, you would be putting a screw into the lateral mass, which is this thing here in between the facets. So if we look back here, so you can see here this is the lateral mass. So screws would go in either side, facing upwards, sort of parallel to the facets. Ok. Actually angling slightly outwards as well. So it's a very, very different uh way of inserting screws in the cervical spine compared to the lumbar spine. And one of the main reasons for that angulation is that this is a big chunk of bone that you can push it into. And you also want to be very careful of damaging the uh vertebral artery that's running up and down here. If you tried to dig around finding a way of getting the um uh the screws into the pedicle here. A it would be very slim and also there would be a um higher risk of damaging the vertebral artery. So typically lateral mass screws are the way we would fix the cervical spine. So, C one and two, as I mentioned to, you are quite different in terms of the way they're orientated and indeed what they look like. So this is c one that you can see here, this is C two. So if we start with C two, the most obvious thing to mention is the dents of the odontoid uh peg which sticks out and then C one articulates with it like a ring around, um A spoke or, you know, there's like, like a, um just this peg and C one just sits on that. Um So you can see here um, that the transverse for is orientated in a slightly different plane. And I'll show you a slide after this to demonstrate why that is. But the vertebral artery goes on a slightly strange course around C one and C two. And then C one, that's not a very good picture of C one actually. Um If we move on to the next slide, I think you can see slightly better representation of what the C 12 complex looks like. And I think it's best to think of the C 12 complex as a complex rather than those two bones because they, they really do exist um in a symbiotic um sense. So it's much better to think of them as one unit that, that moves. Um So there are lots and lots of ligaments that you, you see around about this, this craniocervical junction. So probably you can't remember all of them necessarily. Um But the important ones to remember are the, if you look on this slide here on the right. So the, the um transverse ligament which is a ligament that stretches on the backside of the anterior arch of C one and it passes posteriorly to the peg. So the role of that ligament is to push the peg forwards and hold it up against uh C one. OK. So it, it keeps that peg nice and stable up against C one. If you have a damage to the transverse ligament of the Atlas, then it significantly compromises the stability of the craniocervical junction. And it's a very, very important ligament when it comes to that. So in the, in the context of cio uh cervical junction trauma, one of the reasons for an MRI scan, apart from looking at the extent of perhaps any nerve damage or anything like that is also to look at the damage to ligaments. So MRI is good at looking at soft tissue. Uh CT is good, good at looking at hard, hard tissue. So you can use an MRI scan to help you assess the integrity of the ligaments and the transverse ligament um of the Atlas is a very important part of that. The. Now here on this side, you can see that there are, they've also got the alar ligaments here which you can see running up and down here. So ali like wings, they run from the dens. So from the odontoid peg and they fan upwards and they attach on the inside of the um occipital bone. So in in the head. So in the inside the skull, they attach um on that sort of inner edge of the foramen magnum. And then you've got the um uh this sort of apical ligament here uh which runs from the top of the dens up to the, again, the, the insi inside of the foreman magnum. So it's quite a complicated set set of ligaments there. Uh Oh yeah. And the tector membrane here, which is, you know, really a funny name for just a continuation of the posterior longitudinal ligament. Um But there are lots of ligaments going on there. But I think the important ones to probably remember are the transverse ligament to the Atlas, the stability and the alar ligaments because they're, they're often um identified in these, in these drawings. OK. Um Is there anything else I wanted to say on that slide? I probably not. OK. So the vertebral artery, so looking at the vertebral artery here, you can see if we look at the origins. So the vertebral artery arises from the subclavian artery broadly. There are variations, but basically that's where it comes from. So it comes from the subclavian artery. It rises up and then usually in C six, it enters into the um uh transverse foreman. OK. And then it runs up parallel to the vertebral bodies in the transverse foreman. And then when it gets to C two, it has this bend laterally which you can see here, which is why the uh transverse for is a strange orientation in C two and then it goes out to the transit foreman of C one, which lies further laterally and then it bend, bends back inwards before it goes into the um foreman Magne. And that's really important because when you're doing operations at this level, so if you're doing a Foramen Magne decompression or you're doing an operation that involves doing a decompression as a laminectomy of C one, you need to remember that the vertebral artery is actually quite medial at that level. So if you start buzzing away with a drill or your up cut and you get too lateral and you didn't think about it, you could do an injury to the vertebral artery which could be catastrophic, uh and potentially even lead to a, you know, cerebellar stroke, uh which can, can be fatal. So it's a really important piece of anatomy to remember that the vertebral artery has this strange curvy course around C one and C two. This is just showing you some C one screws which you don't need to worry about at all. That's quite a um a subspecialist thing to be doing. Ok. But the vertebral artery is a really, really important part of the anatomy of the cervical spine. Uh And to remember where it comes from where it goes, where it lies. Ok. Uh And roughly what it does. So here you can see at the top it's going up and they feed in towards the basilar artery and here, you can see the spine, it's coming to supply the spine through the spinal artery there as well. So the blood supply of the spinal cord again, you don't really need to know too much information about this. It's more, more for your interest, but it's actually very complicated. And if you ask the vast majority of people, um, who are fully qualified doctors or even people working in, in neurosurgery or, you know, surgery in general. Um very few of them would have an accurate idea of the blood supply of the spinal cord. It, it is complicated uh and it can get quite confusing. Um So don't worry too much about it, but just to give you a rough idea of it. So the the main, the supply for the spinal cord comes from the three arteries, you've got two posterior spinal arteries and one central anterior spinal artery. The anterior spinal artery does sort of the, the front two thirds or so. And the posterior spinal arteries is do the back, the the blood comes from the um vertebral arteries. It's best to think of it. Primarily coming from the vertebral arteries feeding into the anterior spinal artery here and every now and then an extra artery comes in to give it a boost. So essentially, there are lots of segmental arteries that break off from the aorta. And then, for example, through the intercostal arteries, it branches off that and then gives each level of the spine, its own radicular arteries or sometimes called uh segmental medullary artery. And that basically feeds into the existing spinal blood supply and sort of gives it a boost basically. Right. So it's best to think of it as one long artery that is being fed from the vertebral arteries. And every now and then it's getting a boost from some other arteries. That's, that's probably the easiest way to think of it. And again, I, I really wouldn't worry about the, the in depth um uh vascular anatomy of the spine. But it's useful to have a general idea that that's how it works. The, the 11 thing that is worth remembering is probably the artery of a ACUs, um which is essentially a um the major, the major boost, major vascular boost for the lower part of the spinal cord. So, from the sort of lower thoracic region down into the sort of um lumbar sacral regions of the spinal cord, most of its blood supply comes from th this artery here. So if that artery is damaged, for whatever reason, um you can have um quite rapidly a vascular injury to like a basically a spinal stroke of the lower reaches of the spinal cord. So you and you can end up being paraplegic as a result of that. So I think that's an important one to remember that you've at least heard of the artery of Ede uh Ede Carris, ok. But that's just just to give you an idea. Now, the uh yeah, this is what I'm saying. So, segmental reinforcement. OK. So this is another view of it here. So you can see the aorta, here's a segmental artery coming off. Uh We must be somewhere in the thoracic region here because we've got a rib. OK. So you can see here, here's a segmental artery, it's giving off branches that's going towards the um uh the intercostal artery here. And then you've got branches going up to the paraspinal muscles here. And then it's also giving off branches that are your um radicular sort of segmental medullary branches here that are giving that boost to the spinal cord blood supply at that level. OK. And you can see that it's got a close relationship to the spinal nerve root itself. Again, that, that you don't need to worry too much about that. But that can become important when you're talking about um things like fistulas involving the CSF space and the venous drainage of that region, which is very rare and very specialized, but it is actually quite interesting. Um Here is just another view of the same thing that we've been talking about that you can see here and this is the artery of the em Critz that we can see here again, uh providing that major vascular blood supply to the, to the lower reaches of the spinal cord here. Ok. Uh Autonomic, I'm not gonna go into too much detail over this. This is the sort of thing that you, you can, you can learn about separately in textbooks as well. Um But just to remind you that the anatomy of the sympathetic versus the parasympathetic nervous system is quite different. So the um the the the sort of nuclei feeding into the sympathetic chain, which is this chain of ganglia sitting alongside the spinal column that that chain is, is um uh is, is largely supplied from the lower reaches of the cervical spine, going down to the upper reaches of the lumbar spine. Ok. In terms of the um uh the the the anatomy of the cord, whereas the parasympathetic supply comes from a series of nuclei at the top and the bottom, so sympathetics in the middle, whereas parasympathetics come from these brainstem nuclei. Um you know, these pontine medullary, you know, brainstem nuclei and also these sacral lower region nuclei. Ok. So it's top and bottom for the parasympathetics and in the middle for the sympathetic. Um and all of this stuff which, you know, actually, you know, I'm sure you guys are probably better, better than better than us as um surgeons at remembering this sort of stuff because it, it, you, you, you tend to learn this sort of anatomy when you're at medical school more than you do when you're um when you're practicing. Although it's still important. Um the, you can see here, there are um these are the ascending So sensory uh fibers here, tracts that you can see. And here are the descending um tracts. So probably the most important ones to remember are the um uh the corticospinal tract. So you can see here, there is the corti corticospinal tract there. Uh This is the anterior corticospinal tract which is a little bit more complicated, has more of a role to play in, in things like posture. And then in the sensory tract, you've got the um uh well, probably the most important one being the spinothalamic tract, which you can see here and here and then the posterior columns. Um So this bio thalamic tract is doing your pain sensation, um temperature, things like that. Um And then the posterior columns are doing things like proprioception and vibration sense. The it's quite a useful diagram here to remind you that all of these fibers cross, but it's well, most of them cross, but it's, it's all about when they cross in terms of what that, what implications that has for the clinical syndromes that you might see. So on the descending corticospinal tract that you can see here. This is just to remind you that the decussation. So the crossing over of the fibers happens higher, but the decussation of the pyramid is in the medulla. Ok. So the decussation of the corticospinal tracts is in the medulla. That's not the case for the, this, this curious thing, the anterior corticospinal tract. But that's a much much, much more minor part of the, of the tract. It only represents about 10% of the fibers. So I wouldn't worry too much about that, but 90% of the corticospinal tract decorate up in the region of medulla. And then they run along down the side that they are ultimately going to supply, ok in the ascending tracts. So, the sensory things, if you're looking at the um spinothalamic tract that we can see here, they decussate um either right here or just by going up a little bit and then decussate. But basically, they're all decco at the level of the spinal cord that they go in roughly. And that has big cli clinical implications because of um the frequently tested Browns card syndrome. So remember with the bra car syndrome, you're damaging half of the spinal cord. So if you think about it, if you're damaging this side of the spinal cord here, you're going to be taking out the um motor supply to the same side that you've damaged because those fibers have already crossed. Whereas if you damage the spinal cord here, you are going to be taking out the pain and temperature sensation, the fibers on the opposite side because they decussate early in the spinal cord. So damage to the spinal cord to half of the spinal cord will cause the Brown Sicard Syndrome. So damage to the motor fibers on the same side of damage, but on um the opposite side when it comes to pain and temperature sensation. Ok. Um Right. Ok. So that, that's, that's probably the main things that I wanted to cover for you. Um, there's a lot, there's a lot of information and a lot of it, you can obviously learn yourself. It's just to try and give you a, a sort of an overview. Um And to, um, well, an overview of the things that I think are probably most important from a practical perspective. I know that some of that is not necessarily the same with what you examined on at medical school. Um But I think it's important to also, you know, keep, keep in touch with what the clinical implications to these things are and why we might learn about them as surgeons, um which some of you may be interested in, but um some of you clearly may not be all right. Um Does anyone have any particular questions about that? I can't promise that I can answer uh everything, but I might be able to um touch on something that you're interested in if, if there is anything you want to ask and don't worry if there aren't any questions that's fine. OK, if there aren't any questions left, um I'd just like to say thank you, Mr Pen for delivering such an informative talk. I'm just going to put the feedback form in the chat for everyone. Um We'd be really grateful if you could fill, fill this out and I'm just going to put the QR code as well, right? Ok. Um I'll, I'll I'm gonna make a move now, so I if that's ok, I'll I'll I'll say say goodbye to everybody. All right. Thank you. Thank you again. Thank you.