[Music] you have the m2 insular segments and these arise from the post bifurcation trunk so once the mca bifurcates into the m2 you see the insular segments the opercular segments are the branches that loop at or near the top of the sylvian fissure and then they course laterally under the parts of the opercula or the overhang of the frontal lobe so these would be the m3 or the opercular branches like i was saying earlier this is the m1 and then you see off the aca you see the medial lenticular striates and off the mca you see the lateral lenticular striates and then you get into the m2 the m3 and then the m4 are the cortical branches of the mc mca and they exit the sylvian fissure over the lateral surface of the hemisphere the next segment of the ica which we talked about or the actually the vertebral artery is the posterior cerebral artery and we always talk about the p-column communicating between the anterior and the posterior circulation so the p-column communicates between the ica and the vertebral basilar circulation or the posterior circulation and the other branch that the last branch obviously of the vertebral basal circulation that we talked about is a posterior cerebral artery and i included it within this circulation because uh this is all super tintorial or above the tumtorium so you have the p1 posterior cerebral artery the pre-communicating artery that extends laterally from the basilar artery bifurcation to the p-com junction so you have the vertebral artery that bifurcates at its apex and it gives off the two p1 branches or the two p1 p posterior cerebral artery branches and it's p1 is a segment of the posterior cerebral artery right before the p-com joins from the anterior circulation and this p1 segment lies above the oculomotor nerve or cranial nerve three which you can see right here so this is the vertebral vertebral artery becoming the basilar artery and this artery we'll talk about later it's a superior cerebellar artery but the posterior cerebral artery is right here and you can see it go back this is a sagittal view of the brain and you can see it go back and it lies right above uh the third nerve uh it has some important branches of posterior thalamo perforating arteries which supply the uh the thalami bilaterally and the walls of the third ventricle um and then we go on to the next segments which are the p2 segments which is the ambient segment this extends from the p com p1 junction it runs in the ambient or perimeter cephalic cistern and it goes posterior laterally around the midbrain so that's the part of the posterior cerebral artery that wraps around the midbrain here and this lies right above the tintorium and the cisternal segment of the fourth nerve and the p2 segment has many important branches the anterior and posterior temporal arteries the thalamogeniculate arteries the peduncular perforating arteries and then two big branches that sometimes will become important in avm surgery of the medial posterior corotal artery and the lateral posterior coronal artery and these are important to know and obviously you should know the anatomy in general but these can become larger if you have different types of avms these vessels can supply them and it's important to know these branches and know what they supply and and what happens if you take them and exactly what you know what they are and where their locations are so the medial posterior choroidal artery curves around the brain stem and courses superior immediately and it enters the telocorodia and the roof of the third ventricle and then the lateral posterior choroidal artery enters the lateral ventricle and then it travels with the choroid plexus and occurs around the thalamus so again this is these are all images from uh this book uh by dr osborne and uh you know great great great textbook in general to have if you're learning about cerebral anatomy and pathology as a first-year resident or even even now for me as chief resident it's nice to go back and and see some of these pictures the next segment of the posterior cerebral artery is a quadrigeminal segment of the p3 and this lies entirely within the quadrigeminal cistern and it begins behind the midbrain and enters where the pca enters the calcarine fissure of the occipital lobe so you can see the p3 segment is here quadrigemine cistern and then you have the p4 segment of the calcarine segment which terminates within the calcarine fissure and divides into the terminal pca trunks so here where if you guys can see my mouse that's where it is and then there's a medial trunk in the lateral trunk of that p4 segment that let's apply the occipital lobe so there's many variants of the posterior cerebral artery that you'll learn about as you go forward but the biggest ones to know are the fetal pca you know you some of you may have heard about the fetal pca and the fetal pca is just the fact that the proximal pca arises from the ica via the posterior communicating artery instead of the basilar bifurcation so i showed you guys something that looked like this image here on the bottom where you have the basil artery bifurcating into the two p1 segments so let me go back here and i'll show you that image here you can see one pca segment here the p1 segment instead of arising from the top of the basilar artery arises from the posterior communicating artery so this is an angiogram a lateral angiogram of the ica circulation uh so you see the ica here coming up in the we talked about the first branch of the intradural ica being up the the ophthalmic artery which this is the back of the head this is the front of the head this is the top this is the bottom so this is where your eyes would be up here so this is the ophthalmic artery going to the eye but if you look here there's a very large posterior communicating artery and usually the pecan runs from here to here just about there and so the fetal pca is a variant where the fetal circulation is preserved and the posterior communicating artery supplies the posterior cerebral artery circulation meaning that the pca comes off the posterior communicating artery instead of the vertebral artery and it's an important variant to appreciate and recognize especially during aneurysm treatment so you'll learn about that as you go forward uh this is seen in about 10 to 30 percent of cases uh and then the other variant of the posterior cerebral artery is called the artery of percheron and that just shows you that there is a single dominant phalamoperforator artery which arises from the p1 segment and supplies the rostral midbrain and the bilateral medial thalamide so if you look here this is your basilar artery you have a lot of perforators in the in the middle of the basil artery that supply the pons or the pontine perforators you have this superior cellular artery and you have the posterior cerebral artery here at the top so the artery of percheron is a variant that can be devastating so if you think about a basilar artery stroke or a stroke that affects the top of the basilar artery if you have this variant which is the artery of pressure on and that gets occluded then you've knocked out bilateral phalamine so that's devastating because we all know that you have the reticular activating system and and if you knock out the bilateral thalamide the patient is is is going to be in the coma so that's an important variant to recognize and it's also a very uh important board's question for neurosurgery residents then we go to the vertebrobasilar system or the posterior circulation as everybody calls it uh and you have the verteb the vertebral artery runs through the cervical spine so it starts from the subclavian artery goes posteriorly and enters the transverse foramen at the sixth cervical vertebra or c6 and it runs within the transverse foramina of the c6 to c3 so you can see it running up here and running up here bilaterally and at c2 it uh it sort of comes outwards and goes continues superiorly so um you see the foraminal segment which i talked about which is v c3 to c6 and then it makes this inverted l and it turns upward to pass through the c1 transverse spring which is right here the biggest branch from here is the anterior meningeal artery and that just supplies the uh the dura so the v3 segment or the extra spinal segment begins after the vertebral artery exits the c1 foramen and eliza it stays on top of the c1 ring right here which we call the j groove uh and this the the v3 segment curves posterior medially so it goes back and immediately as you see here around the atlanta occipital joint which you see here and it makes a sharp anterior superior turn to pierce the dura at the foramen magnum uh right here and the big branch from the v3 segment is the posterior meningeal artery so the v4 segment or the intradural segment is here point depicted by this arrow is actually pointing to another branch but this is the v4 segment and off the v-sort v4 intra-dural segment you have the anterior and the posterior spinal arteries the medullary perforating branches and the segment that you see here is the the pica depicted by this artery of the the pica curves around the tonsil of the cerebellum and it gives off the perforating medullary choroid tonsillar and inferior cerebellar branches so a pica stroke you you probably already learned in medical school or if some of you are going to medical school you learn this causes wallenberg syndrome so ipsilateral loss of pain and temperature in the face contralateral loss of pain and temperature in the body just because of the way uh the pain and temperature tracks are the ipsilateral larynx pharynx paralysis ipsilateral horner syndrome vertigo ataxia and nausea because of the way the pica supplies the medulla and the the nuclei and the medulla these are the symptoms that you get so you just have the main things you have to remember about a pike a stroke the buzzwords are ipsilateral loss of pain and temperature on the face and then contralateral loss of pain and temperature in the body so those are generally the ones that are the the topics that are tested it with the pica stroke the basilar artery so the vertebral arteries unite at or near the ponto medullary junction so the two verts become the basilar and the basilar artery courses superiorly in the pre-pontine cistern and it terminates in the interpeduncular fossa by dividing in the pcas as we talked about earlier so the first major branch off the basilar once the two verse unite is the ica and the aika courses ventromedially to cranial nerve seven and eight and it loops in the iac so this is a nice axial image showing the ica and and the different branches off the icah uh around cranial nerve seven and eight so these are your lower cranial nerves here nine ten uh eleven coming up and then these are the branches of the aika that you see here so the ica supplies both nerves as well as a thin strip of the cerebellar hemisphere right behind the petrocentral bone and some of the big well the big branch that you have to know off the ikea is the labyrinthine artery or the ia internal auditory artery and this arteries uh this arteries accompanies cranial nerve eight or the vestibular nerve into the internal auditory canal and this artery supplies the vestibular apparatus and the cochlea so the board question will be what artery is this that you know patient had hearing loss afterwards and that's the labyrinthine the sca is the next major branch of the basal artery right before the pca and this course is laterally right below the third nerve we talked about the pca running above the third nerve the sca runs right below the third nerve and it goes posterior laterally around the midbrain just below the tutorial um so you know we talked a lot about the anterior circulation and then the posterior circulation obviously but i talked about the branches before um so i will uh ask you guys again if you can use the chat i'm i'm trying to figure out let me see how i can use a chat function here but uh so the c1 branch how many uh it's a c1 segment of the ica how many branches does it have if anybody can write in the in the chat can't seem to pull up the chat but anyway we talked about the c1 being cervical c2 petrus c3 lacerum c4 cavernous and we talked about the cavernous segment of the ica having two major trunks the c5 running between the proximal and the distal dural rings and you have the ophthalmic segment and then you have the communicating segment so here is a nice depiction where you can see the p-com coming off the anterior coral coming off and then this is the ic8 terminus here where you see the anterior cerebral artery and the middle cerebral artery here and here you see the mca has a bifurcation it's another nice image online showing the extensive anastomoses this is a very complicated picture but if you just break it down you can see the ica here coming coursing this way and it labels all the segments but you see the c4 the petra segment coming up and we talked about the cavernous segment having sorry the c4 being the cavernous segment you see it having the major branches of meningo hypothesial trunk or the infra lateral trunk and then become in the clinoidal segment and then you see the ophthalmic artery coursing here going through the optic canal with the optic nerve c6 and nc7 and the poster communicating art right here and this is a nice picture just showing how you know we always like i showed you guys a picture before of the circle of willis and it being a flat diagram showing all the vessels which like i said is important to recognize the names of all the arteries from that image but that's not how the vasculature looks and one thing that i appreciated as i became a resident i learned more about the anatomy is that there are extensive anastomoses between various circulations so the external uh carotid artery the eca has many branches and as a bunch of branches obviously in the face and scalp and all that and these branches have a lot of anastomoses which you guys will all learn about it it's beyond the scope of this lecture with the ica so as i mentioned earlier when you have a carotid internal carotid artery occlusion that occurs over time many of these anastomoses can become more prominent or can reverse their flow depending on the pathology so these are some eca branches that you can see are communicating with ica branches um then i wanted to see if this would have been a little if i you guys could unmute then we would have gone through all the the names of all these vessels but if you look at this image this is an anterior or an ap view of the vertebral artery and the basilar artery this is a lateral view of the vertebral and vascular arteries and number one here is the basilar artery number two is the uh sorry number two is uh an ic the left icah number number three is the loop of the pica coming off it's a an ika pika sort of variant here number four is the right ica number five is the uh left number six is the hemispheric branches of the pica number seven is the superior cerebellar artery here number eight are the superior vermin branches of the sca and number nine under the hemispheric sca branches so may all in all for you guys to remember this is a vert this is a vert the two verts combine to cause to form the basser the icas come off the basilar first and you have the sca bilaterally here left and right and then you have the pcas and then the major branches off the the vert are the picas and like i said the first major branch off the basser is the ike this is on the lateral view the basser arteries here this is one vert this is the other vert [Music] hey everyone ryan rad here from neurosurgery training.org if you like that video subscribe and donate to keep our content available for medical students across the world