[Music] okay so we've looked at uh different types of aneurysms we've looked at risk factors for aneurysm formation i'm now going to review some angiographic anatomy at a variety of levels so starting very simply uh these are angiographic views of the anti-circulation this is an internal carotid artery injection uh the left to our left is an eight what we call an ap view this is sort of a not actually a coronal view this is a little bit of a coronal plus axial view and to the right we have a lateral view of the internal injection and you can see i've lineated what is the internal carotid the mca and the aca you can see the bifurcation on the ap view a lot better than the lateral view obviously uh i'm sorry any questions oh i think uh just move on so here's a view of the poster circulation this is a vertebral injection from the right vertebral artery you can see i've labeled the pica actually the anterospinal artery in the middle uh the basilar artery and then the relevant branches of the basal artery the aika the sca and the pca as well both in a this is a more trans-facial view so this is a lot more like a coronal view on the left and to the right is a lateral view again you can see the vertebral the pica branch the asa the interspinal artery the basilar the aika the sca and the pca so getting into a little bit more of the weeds of the anatomy for the ica so here i've lineated the ica segments according to the butelier classification this is a 1997 paper that i think has significant relevance to neurosurgeons i think it's the it's probably the best and most reproducible anatomic description so from proximal to distal you can see i've labeled a petrous segment and i always say i sort of talk about this up across up that defines what is both the petra segment and then the cavernous segment has initially a superior course an anterior course and then a superior course as well akin to the teacher segment so those are the two truly extradural segments that are intracranial of the carotid artery so if you have an aneurysm of those segments it generally cannot cause subarachnoid hemorrhage it can cause problems due to mass effects but these are not locations where you can have a bleed from now distal to the cavernous segment is the easy to understand but not frequently or appropriately frequently described clinical segment that lies between the two dural rings small aneurysms in this location are still functionally extra durable meaning they can't cause intracranial hemorrhage you then have the ophthalmic segment that goes from the ophthalmic artery to the posterior communicating artery it's from this that you can have intradural aneurysms that can cause subarachnoid hemorrhage although with the exception of the blister variant aneurysms these tend to be the lowest risk aneurysms in the head you then have the communicating segment that goes from the pecan up to the ica terminus and it starts at the p-com you can see this i use this uh angiogram because there's a very large p-com and pca that are lineated 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