DIP Episode 315 - The Clutch Circle of Willis Podcast (Step 1-3)

Okay, welcome. My name is Divine. This is episode 315 of the Divine Intervention Podcast. And in this podcast, I'm going to call this the Clutch Circle of Willis Podcast. So the Circle of Willis, unfortunately, is like extremely high you to know. I mean, like if you're taking it, you're similarly exam. And you don't know about the Circle of Willis and you don't know how to think about it. You can, you know, unfortunately, run into some relatively significant problems. So hopefully this podcast is short and sweet, but very high yield. And again, useful for a new SML exam. And then for those of you that are taking the USML Es next week, actually, started on Tuesday. I have an MBME test taking. So this is for Step 2, CK Step 3. I have an MBME test taking strategy scores that starts at 2 p.m. Pacific Standard Time and Ghostio 430 p.m. Pacific Standard Time. There are still a few spots left. If you want to sign up, shoot me an email through the website. I'll give you some more instructions on cost and how to register. And then I, and it's going to be over zoom. And then for again, those taking step, just in case, Step 3, I have a 20 hour course, starting next week Wednesday. It's from 11 a.m. to 4 p.m. Pacific Standard Time. That's 2 p.m. to 7 p.m. Eastern Standard Time. It's on Wednesday, Thursday, Friday and Saturday. It's over zoom again. It's super comprehensive.

We cover a lot of Peds, Surgery, Internal Medicine, OB-GYN, Site Neural, Ethics, Bio Stats, the Step 1 material that has migrated to Step 2 CK. And also just changes from November of 2020. So again, most people take both courses together, the Test Ticking Strategies course on Tuesday, and then the 20 hour course. So it's something that you can take pretty much any time during your dedicated period. Although I usually recommend that people take it very early during your dedicated, so that you can have like a big base of knowledge from the beginning. And also have the opportunity to go through the materials from the course, because there is a ton of stuff that we cover. And then I have a Step 1 course that is going to be coming up hopefully soon. I'm going to be making an announcement on that very soon. Okay, so let's jump into the Circle of Willets. First things first, essentially, what is the Circle of Willets? Well, we know that it's basically a pretty fancy and astromoses, right? It's an astromosis of blood vessels, right? That's essentially this, though these blood vessels supply blood to the brain itself. And to the brainstem, right? I'll see primarily the brainstem, but it also does quite a bit of supply to the cortex itself, right? So I think in general, the best way to understand the Circle of Willets is first and first to understand the structure, right?

So the thing is for those of you that are taking these exams, please make sure that you can actually draw out the Circle of Willets, right? Again, it's super, super high yield. They can give you like a CT angiogram or an MR angiogram, right? And you need to identify it, right? So if we kind of start from the bottom, right? So we start from the vertebral arteries. Remember the vertebral arteries are branches of the subclavian arteries, right? So the vertebral arteries are branches of the subclavian arteries, right? So we have two vertebral arteries from the left and right subclivians, right? They come together to form the Basilar artery, right? But let's talk about the things that come off of the vertebral artery. The two big things you want to know that come off of the vertebral artery, first is Paika. Paika is the posterior inferior cerebellar artery, right? That supplies the lateral medallar. And then the second is the anterior spinal artery, which supplies the medial medallar. So those two vertebral arteries, they come together to form the Basilar artery. The Basilar artery is that strong single artery that literally runs through the ponds, right? Now the thing is the Basilar artery has a few key branches you want to know of. The first key branch you want to know about is Eika, the anterior inferior cerebellar artery. So that artery supplies the lateral ponds, right? The Basilar artery is in the ponds, right? So Eika supplies the lateral ponds.

And then there are some more medial oriented branches of the Basilar artery. They are called the pontin arteries. Sometimes you may see them refer to as the paramedian pontin arteries, right? So these paramedian pontin arteries, they supply the medial ponds. So notice, I've talked about like lateral and medial twice already, right? I said, oh, for the vertebral arteries, we have the Paika branch that supply the lateral medallar. And the anterior spinal artery branch that supply the medial medallar. And then we went up to the ponds. We're talking about branches of the Basilar artery. We said that the Eika supplies the lateral ponds. You see these things that have eye-candy names, right? I see here, right? Like the supply lateral, right? So Paika did lateral medallar, Eika does lateral ponds. And then the paramedian pontin arteries, they are paramedian, right? They are like parallel, right? To the middle of the pond. So paramedian pontin arteries, right? They supply the medial ponds, right? And then remember that for the circle of willis, there are some terminal branches of the Basilar artery, right? So the first one is the superior cerebellar is the one that comes next after the paramedian pontin arteries, right? So the superior cerebellar artery, the key thing to know about that is that it is the blood supply to the superior colliculus. Again, I'll make integrations on this as we go along, right? And then after that, we have the posterior cerebral artery.

Remember the posterior cerebral artery supplies the occipital loop. It's the primary blood supply to the primary visual cortex. Any of us know that when a person has a PC in front, right? The person will have lots of vision, but they will have macular sparing, right? Because the macula of the eye gets blood supply from two sources. It gets from the posterior cerebellar artery and from the middle cerebellar artery, right? And then that posterior cerebellar artery, right, is essentially the terminal branch of the Basilar artery, right? So the posterior cerebellar artery connects to the posterior colliculus artery, the posterior colliculus artery, right? Remember that it runs alongside cranial nerve three. I'll talk about that in a bit. And then that posterior colliculus artery, right? Essentially, bodies up with the internal corroded artery. And that internal, I mean, with the middle cerebellar artery, in some people, it's the internal corroded, that doesn't really matter much, right? And then you continue from there, right? And then you form your anterior cerebellar arteries, right? Remember, the anterior cerebellar artery is connected to the other anterior cerebellar artery on the other side by the anterior communicating artery, right? Again, if you kind of keep these things in mind, you'd be in really good shape, right?

And they remember like the internal corroded artery, again, has these things like the ophthalmic artery, the central retinal artery, which are things that also apply the eye, right? So again, if you kind of know the structure, then everything should begin to fall in line once I begin to leak integrations, right? So let's start with the first integration. The first thing I will say is, again, I see people who memorize all these brainstem syndromes, and then they are sweating and everything, and the thing is you don't need to suffer that much, right? Really, most of these brainstem localization questions are pretty straightforward in terms of how you answer them. And the way to answer them, let me teach you a method, I'm not teaching you a rule of fours or anything like that. No, like literally, this method is way simpler than a rule of fours. So what is this method? This method is, when you see a question where it's like a brainstem question, ask yourself, do I see problems with pain, pain prick or temperature, or do I see hunger syndrome? Right? I'll say that again, do I see problems with pain, pain prick or temperature, or do I see hunger syndrome? Right? And the pain, pain, pain prick, temperature problems, usually on the face and on the body, but the thing is they are opposite sides, right? So like if you have pain, pain prick problems on the right face, you're going to have pain, pain prick problems in the left side of the body, right?

Like in the left extremities, for example, right? So ask yourself that question first, do I see pain, pain prick, temperature, or hunger syndrome problems? If you do, the person has a lateral brainstem problem. If you don't, the person has a medial brainstem problem. For those of you that know you're neuroanardomy, well, you can already begin to see, oh, this is why the virus was emphasizing these rules with IKAP, IKAP and stuff at the very beginning, right? Literally, it's a very easy decision to take, right? Like, oh, the IKAP, pain prick, temperature, hunger syndrome problems is going to be lateral brainstem. If I don't, it's going to be medial brainstem, right? Medial brainstem, the modalities that go through the medial brainstem and things that form on that, the purview of like the docile columns and your cortical spinal tract, right? So once you ask yourself that first question, why do I see these pain, pain, pain prick, temperature, hunger syndrome problems? Then the next thing you ask yourself is, what are the cranium nerves that have been affected? Right? Remember, if you start from the medial brain, going up, just come by fours and you have your cranium nerves, right? So the last four cranium nerves, cranium nerves, nine through 12, they are found in the medial brain, right? For the ponds, right? If you come back by four, cranium nerves, five through eight, I end up ponds.

And then if you go to the midbrain, the midbrain has cranium nerves, three and four, and then you know craniums, one and two, I can have special in the anion right. So the next thing you have to do is, if you know that, oh, I see pain, pain prick, temperature, hunger syndrome problems, essentially use the cranium nerves that are affected to tell you where you are, right? So if you see a problem with cranium nerves that are not nine through 12, then you know that it's very likely going to be like a haunting problem, right? But if you see problems with cranium nerves that are more nine through 12, then you know it's more going to be a medialary problem, right? But again, one of the, I guess, layer that you need to understand is, the cranium nerves in the brain, the oriented very differently, right? So there are some cranium nerves that run through the middle of the brain stem, and there are some cranium nerves that run through the more lateral aspects of the brain stem. And the thing is, there's actually an embryological reason for this, but again, I really just want to be very focused on the circle of willis. So I'm not going to say anything beyond that, right? But basically, the medially oriented cranium nerves in the brain stem, they are purely model cranium nerves, right? The medially oriented cranium nerves in the brainstem are purely model cranium nerves. And a nice role to remember them is that they are all factors of the number 12, right?

They are all factors of the number 12, right? So for example, if we're taking it from the top, if we're looking at the midbrain, cranium nerve three, the ocular motor nerve, and cranium nerve four, the trochlear nerve, those are factors of the number 12 in the midbrain, the immediately oriented, because those cranium nerves are the most part are purely model, right? Although you can't see that entirely for cranium three, just imagine cranium three is in the medial midbrain, right? If you come down to the ponds, right? If you look at between the numbers five and eight, the only factor of 12 between the numbers five and eight is six, right? Cranium nerve six, they have two cents nerve. Remember, the only function it has is that it innovates the lateral rectus muscle, which AB ducts the eye, right? That's in the medial ponds. And then if you go down to the medala, right? Remember, the medala has cranium nerves nine through 12, right? The only factor of 12 between the numbers nine through 12 is the number 12 itself, right? So that means cranium of 12, the hypoglossal nerve that innovates your tongue is in the medial medala, right? So three and four, medial midbrain, six, medial ponds, 12, medial medala, right? So basically if you know these rules have described, then you know what is going to be in the lateral medala. If I just said that 12 is in the medial medala, then in the lateral medala, that means it has to be 19 and 11.

If I just said six is in the medial ponds, then that means 57 and eight have to be in the lateral ponds, right? Three and four, those are the essentially the only midbrain cranium nerves, right? Those are in the middle. Remember, cranium four is a trochlear nerve, right? Does the superior oblique muscle, right? And then cranium three, the oculum motor nerve, pretty much does every extra oculum muscle besides the superior oblique, right? And the lateral rectus, right? So it does like medial rectus, superior rectus, inferior rectus and stuff like that, right? Okay, so now let's make these integrations, right? Let's make all your weight in worth, wow, right? So again, if we say, oh, we see a person that has a problem with pain, temporary temperature, or 100 syndrome, right? And then we notice that, oh wow, they have problems with cranium nine, right? They have problems with cranium 10, cranium 11, right? So they have like shorter droop, or they have decreased gag reflex, or they have hoarseness. Well, all those things are nine through 11 cranium of problems, and we see that the person has pain, pain, temporary temperature, and 100 syndrome issues, right? So that tells you that, oh, it's one, it's a lateral brain stem problem, and two, it's a lateral medallary problem, right? That's a wallenberg syndrome, right? And again, wallenberg syndrome, we know that Pica supplies the lateral medulla, right? So it's either a Pica problem, right?

It's a Pica problem, or sometimes on the example, the Wimput Pica has an answer, and it can put vertebrae. Remember, Pica comes off of the vertebrae, so that'll be the right answer, right? But if they put both Pica and vertebral, always go with the one that is more specific, go with Pica for your test, right? But if you notice that, oh, wow, a person has like tongue weakness, well, you notice that, oh, they don't have anything about pain, pain, temporary temperature, or 100 syndrome in the cum stem, right? You know that, oh, the fact that they don't have any of those PPTH, I'm gonna, instead of repeating the same thing over and over again, I'm just gonna say PPTH, they don't have any of those PPTH problems, right? And then, you notice that, oh, wow, they have tongue weakness, that localizes it easily for you to the medium-edal, right? That's gonna be an anterior spinal artery problem. Typically, in those questions, those people will have problems with the drossal columns, because those things run through the medial brain stem, and with a lateral cortical spinal tract, because those things also run through the medial brain stem, right? Okay, so let's go up top. So what if you see a person that has, again, PPTH problems, but then you notice that, oh, wow, this person has like facial muscle weakness, right? Like the upper and lower face are weak, right? Or they have hearing loss. Again, these are all things that follow under the purview of like five through eight, right?

But again, because we see PPTH problems, we know that, oh, it's a lateral brain stem problem. So this has to be a lateral pointin problem, right? A lateral pointin problem. And again, what supplies the lateral points? It's EIKA, it's the anterior inferior cervical artery, right? But again, what if you see a person having like weakness of IA Bduction, right? And you notice that they don't have PPTH problems. Again, the fact that they lack those PPTH problems tells you that, oh, wow, I am dealing with the medial brain stem. And the fact that you're seeing that it's a cranial six problem, which is a factor of 12, that tells you that it's a medial pointin problem. So what's the blood vessel that's impacted there, right? That's gonna be your, that's gonna be your pyramidian pointin arteries, right? Your pyramidian pointin arteries at the affected blood vessel in that case, right? So let's keep going up in the circle of willis, right? So again, let's maybe deal with the basilar artery. Again, remember, if you mess up the basilar artery, what's gonna happen? Well, you're gonna infarct the entire ponds. You're literally gonna infarct the entire ponds. So all those ascending tracts and all those descending tracts are gonna be all messed up, right? That person is gonna have locked in syndrome. So those people, they'll be completely quadriplegic. The only thing that you'll be able to move will be their extracurlomosols, right? So remember, that's a vascular cause of locked in syndrome.

Remember, another thing that can cause locked in syndrome is osmoid dimelination syndrome, right? Where essentially, if you're correct, when it's rimming too quickly, you can mess up the presence of ponds, right? So let's keep going up. So we go to the superior cerebellar artery, right? So the superior cerebellar artery, remember I said that it's the blood supply to the superior colliculus, right? It's the blood supply to the superior colliculus. And remember, your superior colliculus is your vertical conjugate gase center, right? It's the thing that says, oh, look up with both eyes and you're able to look up, right? So if, for example, you've infarcted the vessel that feeds to superior colliculus in this case, the superior cerebellar artery, guess what? What are we gonna be dealing with here? We're gonna be dealing with parynod syndrome. That's a vascular cause of parynod syndrome. Remember, parynod syndrome can also be caused by a brain tumor, right? Like a paineloma, because remember, the painel gland is superior to the superior colliculus, right? I'll say it again, the painel gland is superior to the superior colliculus, right? So if a person has a paineloma, that can compress the presence of superior colliculus and also cause parynod syndrome. Usually those people have like what we call the sun downside, right? Down, they have troubles looking up on endemic exams. And then the posterior cerebellar artery, again, what's the key integration to know for endemic exams?

Remember, the posterior cerebellar artery, it's the blood supply to the occipital loop, and that's where your primary visual cortex is, right? So when a person has a posterior cerebellar artery problem, right? Those people are on your endemic exams, they're gonna have cortical blindness, but again, they'll have macular sparing because they're a collateral blood supply from the middle cerebellar artery. And then if we keep going up, right? So remember the posterior collocidin artery runs alongside cranial nerve three, the oculumodon nerve. So if a person has like a rupture of an aneurysm of p-com, right? Or an aneurysm of p-com itself, it can compress cranial nerve three. So those people will have like a blum pupil, right? So they'll have that down and out I, right? They'll have that down and out I, they'll have that down and out I, right? The I's down and out, it's down because superior oblique is working on a pulse. Superior oblique, one of the, it's jobs is to pull down the, pull down the eye, right? And then lateral rectus is also working on a pulse. Remember that's cranial six country, right? They have two sense nerve. So if a person has a p-commanurysm, they'll have an oculumodon nerve pulsing, right? And then if we go up top, right? To the anterior cerebral artery. If we're looking at the homonculus, remember the homonculus is almost like a geography map of the, of different parts of our bodies and the blood vessels that supply them.

Remember the anterior cerebral artery actually supplies the leg, like our legs, basically, right? But the middle cerebral artery supplies the face and the hands, the upper extremities, right? The face and the upper extremities. So the thing is, if a person has an anterior cerebral artery problem, they're gonna have issues with the legs, right? If, if, if, if they have an anterior cerebral artery problem, they'll be issues with the legs, but if they have an MC problem, it's gonna be issues with the mouth, with speech, right? And with the upper extremities, right? In fact, if you see a person having an ephagia on an MDM exam, remember, those speaking centers, those understanding speech centers, those are in the lateral cerebral cortex, right? That's MCA country, right? That's MCA country, in fact, when a person has an ephagia, that tells right off the bat that it's a left MC problem, right? Because remember, for most people, especially a person that is right-handed, the dominant cerebral hemisphere is the left cerebral hemisphere, right? So that's gonna be a left MCA problem, right? If you notice that a person does not have ephagia, but you have like upper extremity problems and mouth problems, then that tells you that it's likely gonna be a right MCA problem, right? Because they are right, they are right cortex is the non-dominant side of their body, right? Again, very high yield to keep that in mind.

And then the artery that connects the two anterior cerebral arteries, that's the anterior comichydin artery. Remember, that artery is the most common location of an aneurysm in the circle of willis. If you have an aneurysm of that, right? And it pops, right? That can cause a sub-artinoid hemorrhage, which will present as the worst headache of a person's life. But remember, an anterior comichydin artery aneurysm can also compress the optic chiasm, right? And that can cause a bite-temporal hemianopsy, right? That'll cause a bite-temporal heteronimus hemianopsy, right? And then the last thing I'll talk about, again, remember the ophthalmic artery, right? Or like the central arachnal artery, right? People can get like a painless, very quick, sudden vision loss, right? Because usually people can have like thrombi or embolite from the internal chloride artery that flake off and then go and embolize those vessels, right? And that'll cause like a central arachnal artery occlusion, those people have like fondle, paler, and things of that nature, right? So hopefully this really, really helps you if you listen to this podcast. Again, I know I'm trained very intentionally to keep it short. I mean, one, because I'm in a hurry, but two, because I just want this to be something where you're like, I struggle with a struggle of willis, I listen to this like 20-ish mini podcast and I'm good to go, right? So again, I try to explain all the mechanisms here.

So again, I would encourage you to just maybe listen to this like once or twice and you should be in pretty good shape, you should be in pretty good shape, I'm going forward. So thank you for listening to this. I'd offer one on one tutoring for many exams. Step one, step two, CK, step three, preclinical medical exams, 30-ish-off exams. And then I also again, offer step two CK courses and a comprehensive step one course. I'm going to be making an announcement on the step one course soon, God willing. And then I also work with people for like the ERAS applications or the ANCAS applications. Again, I've worked with people with very tricky applications, having red flags or having new USMLS scores that again, I've matched into some very competitive specialties. So please subscribe to the website, divininginterventionpodcast.com. If you're subscribed, whenever I make a new podcast, you'll get an email notification. And then I also have a You Tube channel, the Vine Intervention USMLS podcasts and videos. That's why I placed my videos, so subscribe to that You Tube channel. And then I also have these podcasts on Apple podcasts and Google podcasts on Spotify. If you're interested, again, just subscribe to those. And again, you'll get the latest podcasts as I upload them to the podcast feed. So thank you for listening. I'll see you next time. God bless you. Thank you.

An anastomosis (network) of arteries supplying blood to the brain and brainstem.

The vertebral arteries.

PICA (Posterior Inferior Cerebellar Artery) supplies the lateral medulla, and the anterior spinal artery supplies the medial medulla.

Lateral brainstem problem.

CN IX through CN XII (all factors of 12).

Facial weakness/sensory loss; Anterior Inferior Cerebellar Artery (AICA) or PICA.

Superior Cerebellar Artery (SCA); Parinaud syndrome.

CN III (Oculomotor), CN IV (Trochlear), and sometimes CN VI (Abducens).

Lateral = Problems with pain/proprioception on opposite sides; Medial = Lack of these contralateral signs.

Posterior Cerebral Artery (PCA); Macular sparing (due to collateral supply from the MCA).

Locked-in syndrome (quadriplegia with only eye movements preserved).

Cranial Nerve III (Oculomotor nerve).

Anterior Spinal Artery (medial medulla).

CN III (Oculomotor), CN IV (Trochlear), and sometimes CN VI (Abducens).

Lateral = Problems with pain/proprioception on opposite sides; Medial = Lack of these contralateral signs.

Posterior Cerebral Artery (PCA); Macular sparing (due to collateral supply from the MCA).

Locked-in syndrome (quadriplegia with only eye movements preserved).

Cranial Nerve III (Oculomotor nerve).

Anterior Spinal Artery (medial medulla).