So, this is a topic that, you know, open treatment of a poster circulation aneurysm is starting to feel like a legacy topic. It is not just a very common thing anymore. So, it's something that you really do have to work at quite a bit in order to even consider doing it. Those are my disclosures, not relevant. Thanks to my research fellows and residents and of course my colleagues. So, this is about 20% of aneurysms. We know that they have a higher rupture risk which may justify their treatment in the unruptured case more than for some other aneurysms. And they do frequently present ruptured as well naturally. And in the poster circulation really includes PCA and then everything down as you see here. You know where they are. It's no question that the advent of increasing endovascular technology has made this a very different kind of playing field. Most of these aneurysms can be coiled and most of the studies show that the results of coiling are better than for clipping in most cases. So, I always say if you know your folk music, you know, where have all the easy aneurysms gone? And they've gone to coiling every one. And the question is, the song asks us in a different way, when will they ever learn? But really the question is, when will you ever learn to do it? Because when I started doing it, it was right at the transition time and it was nice because we got to do a lot of easy ones. And after you do a bunch of easy ones, it seems to be a little bit less daunting to do a harder ruptured one. The simple ones are just not that common. Nonetheless, you can climb a lot of the learning curve just in the lab. And a lot of it is just the approach. It's getting down to those places because you know that all this area is all very constrained. It's all in the front side and it's down deep and it's surrounded by cranial nerves and bone and things that you're going to find in the way. The working angles are very limited. The viewing angles are more limited. And then of course, true proximal control is really quite challenging because there are multiple vessels coming in from every direction. When we think about conceptually the anatomy, we can divide it into three parts. So the upper basilar, the mid-basilar, and then the lower basilar. When you think about how to get there, upper, it's just in a very broad way. Some combination of tereonal, oz, or eyebrow. I do like the eyebrow too and it actually can be appropriate even for some basilar aneurysms. Then sub-temporal to come in from the side. In the middle zone, some combination of one of these, depending on how high the aneurysm is, and then down low, usually far lateral, but occasionally sub-occipital. Pike aneurysms in particular sometimes will be so far around the bend that you can approach them from straight behind, which is a little easier dissection and easier for the patient. So again, these are kind of the approaches you think of. If you have to get to that middle zone, that's probably the hard one where we get to these combined, combined, or transpetrosal. If it's lower down but still very anterior, the extreme far lateral can be in addition to the standard far lateral. But I would say in general, as you think about all these, most of the aneurysms, 90% of the posterior circulation aneurysms you're going to have to deal with is oz or some variant of oz for the upper part and far lateral for the lower. And as long as you can do those two things, you'll be able to do most anything. For upper basilar access, really three windows, right? And you have to use all of them or be prepared to use all of them. So the optical carotid cistern window, your oculomotor triangle, and then again your ICA terminus, which in some people, this can be a very big window if there's a short initial supraclinoid segment that can provide good access. If you go to the lateral window, that's the kind of view that you're looking for. And often you'll find yourself flipping back and forth between these two windows. It always seems a little kilter when you first get used to it. So if you are down there, I don't know, taking out a craniopharyngiome or doing something else, open the loquist a bit and take a look at it and just get familiar with how it looks when you're not having to deal with blood. And then from the other window, again you swing the vessel to the lateral side, you get into this window and it's optical carotid cistern and you get a nice view of the basilar apex and the P1 looking across particularly well. You know, whether you need to, what kind of craniotomy you need to do really depends on the height. If you have an aneurysm which is very high, you're more likely to add a full OZ. What we call the modified OZ, which is only the superorbital piece, is adequate for most other things to let you look high up enough. And then as you, an anterional can be adequate in some cases where you're really not trying to look up at all, just down because the OZ part doesn't help you that much for that. And then depending on the height of the tentorium and the aneurysm neck, sub-temporal can be helpful. This is the line, right? You go to the posterior clinoid and look sort of straight across and if it's well above, that's high. If it's right at, it's average. And then if it's down low, it's low. And that will tell you. So here's an approach that doesn't need the OZ, that might need the OZ, that does need the OZ. Much like you see that. So looking down versus looking across or looking up. So a lot of the maneuvers you need to know are just ways to get more exposure. So the basic steps for this region are go down and open all these windows. I never approach this region without opening everything because you just never know what you're going to need. And I've so far not found a time when you had too much room. You can often take off the anterior clinoid. It really depends on the anatomy. And then even mobilize the internal carotid artery somewhat. That gives you a little bit more room to move it back and forth and makes approaching the basilar apex a little easier. You can take off the posterior clinoid. I'll show you that in a minute. You can divide the posterior communicating artery. How many people have done it? Good. So it's actually not a difficult thing to do. It's a very important basic tool to have in your toolbox. You can open the cavernous sinus and mobilize the third nerve. Actually this works very well. It only buys you a few more millimeters, but it's sometimes more than enough. You can give adenosine. Adenosine is real nice. So we used to do a lot of this. We have I think 106 cases at the Barrow, but we don't do it almost at all anymore because usually with some combination of adenosine and other techniques, we just don't need it. So in terms of bone removal, we talked about this, the OZ osteotomy, and then anterior clinoidectomy, and then posterior clinoidectomy. If you do this, you can do kind of upper clivectomy as part of that posterior clinoidectomy and get quite a bit more room to get proximal control. And it is helpful to have proximal control. It isn't going to stop somebody from bleeding, but it will soften the aneurysm considerably, and it may slow things down if you have trouble. But mostly it's really to soften the aneurysm. So this is the anatomy. Here you see optic nerve. This is a right-sided approach, optic nerve, carotid artery. So this is oculomotor triangle. You see third nerve here. And this bone right here is what we're talking about. And if we can get that out of the way, then that lets us have a little bit more access into this zone here. So we're talking about bone there and there. The third nerve I talked about, so here's the third nerve. You're used to seeing it on these approaches. If you just come to this side and size the cavernous sinus, it bleeds quite a bit, but actually mobilizes very nicely. And when that happens, it allows it to follow the temporal lobe a little bit more and just swing slightly laterally. Again, very small maneuver, but can be extremely helpful. And we just talked about posterior communicating artery. So where is the perforator free zone? Posterior communicating artery. Can we just take it with impunity? No, because it has branches that go up from it. Medially, they feed a lot of important things. But at the back end of it, there's almost always a zone. So close to the PCA, there's a zone that can be sacrificed. Typically, the branches come off on the more anterior part. They're often quite a number of them, like this. But when you get back underneath here, there's a zone right here. In fact, this is one where this is the last big branch. There's a zone there. It's usually somewhere between two and six millimeters long. And you really need only two or three millimeters. So again, that is the zone. Obviously not with fetal anatomy. So here's the temporary clip on the basilar there looking down. And this thing is just crossing the path. So quite simple to take a bipolar. And just on a relatively low energy at first, bipolar at posterior, that branch get a nice segment so it doesn't open up. And then just cut it. And what it doesn't do actually is increase your working area. What it does do is gets the PCOM out of the way. Because the PCOM often will obstruct the clip access. So it's not so much that you get more room. It's that this thing which is hanging across your view is moved out of the way. So yeah, you can see just how much that improved access to the basilar apex. We talked about this, but the other thing is if you do induce hypotension, the basilar will usually come down a little bit, sort of as it deflates. And it can give you a couple extra millimeters of room, too, for clipping. In terms of clip selection, I have a personal bias about this that you can, if you use a low profile clip applier, you can put a regular small clip onto the basilar apex like on any other aneurysm. But I personally, unless you don't have the closing force, like these big long clips. So often you'll see that I have a long clip. And I mean a long clip, 12 millimeters, 15 millimeters, and just use the front part of it. Generally, it's more than long enough. So you can see like here, here's the clipping. The clip is right there. And we're only using the front 6 millimeters. But that keeps the back end of the clip out of your view. It's much easier to work through the window that way. And then frequently, you have to stack clips if it is a larger aneurysm, either like a fenestrated clip that puts the force on the backside and then a front clip that closes the front half of the aneurysm. By then, it's easier because the first clip has made it a little easier for you. For basilar, perforators, and perforators. So the most un-reassuring thing is not to find them. You have to find the perforators on the basilar apex. And they are very unforgiving. If you get a perforator, you will know and regret it forever. It's very tempting sometimes to clip early. You see it finally, you've got the neck out, you've got the clip on. But in this case, that's the one part of the operation where you spend some time and kind of grit your teeth and move it around because they're frequently not right on the front side where you can find them. They're on the side or on the back. And again, sometimes by softening the aneurysm, it will let you peek around to the backside of it. All these perforators come off all along the P1 segment. But mostly, it's these middle ones that are the problem. And unfortunately, they go to a very high rent district. So you have to just watch all of them. Some people have a pressure on, one dominant one. In some ways, that's easier because as long as you protect that one, you're protecting most of everything. All right. Here's a case. This is one where, interestingly, the patient preferred to have clipping. It certainly would be a coilable aneurysm. The neck is just mildly broad, but I think it's nice to illustrate what a basic kind of case looks like. So looking down inside, first thing, of course, is just like the anterior circulation. Howard talked about optical crotted window, open, let out CSF, relax everything. We usually open quite a bit of fissure, which we didn't really show that, but to get a little bit more room. And then, just go down and find the neck. And if you're lucky, the neck actually turns out to be right where you want it to be. This one, the neck is just a hair on the low side. Here, we're dissecting the P1 off and then looking for all these little perforators. The funny thing about these aneurysms, of course, is that you, at the end of the case, you always picture the entire clipping, but when you go back and look at the videos, you're almost never seeing everything at once. You're seeing a little bit through one window, a little bit through another. But if you're lucky, you have this kind of situation. On a ruptured aneurysm, a little tougher, we might have removed more bone, because if it bleeds, you don't really have proximal control here, as you see. The height is not acceptable for that. But here, you can see the perforators under ICG. And that's probably the most crucial thing, is to make sure that those are flowing properly. So, again, patients like this, especially on the elective ones, can do very, very well. Another aneurysm. So here's, again, right side, optical carotid cistern, oculomotor triangle, freeing up the carotid, getting everything loose, opening liloquist pretty widely, just to get the space and be able to see. And then, again, working through both windows. So here we go on one side, free everything up a little more, and then figure out where all the anatomy is, where the neck is, find the SCAs. Yep, clear everything up. And again, a lot of it is just checking, finding out where all the perforators are, and making sure you have your anatomy straight. Again, this is all optical carotid cistern window. But frequently, what will happen is, you'll go and get one view, and then that view is all the view that you have, and if you put a clip in, you lose that view. So usually, as I say, we'll free everything up more even than it seems like you need to in order to have the access, and then use the other window. So maybe switch the view to this window, or switch the clipping to that window. And it is very common to do what I'll do here in just a moment, which is bring the clip in through the other side. So I'll be looking through here, watching the tines, but bringing the clip from the other side with the carotid in the foreground. And I usually will zoom out just a little bit, so that you can keep an eye on the carotid at the same time. But you can see that the real key here is watching that. There's really nothing to hurt in between, so it's just a matter of keeping track of that. And again, long clip, right? Only the front few millimeters of clip are really working. So that's basilar aneurysms. So that is not an aneurysm that most people are going to clip a lot of anymore, just really less and less. Now, an SCA aneurysm, sometimes these are harder to coil. Not always. They're frequently coilable. But sometimes the SCA's relationship to the neck is such that it's not simple. And so they come up. And the one thing I would say about this is, is on the scale of things, if a giant basilar tip aneurysm is a 10, right? An SCA aneurysm is like a three. These are beautiful aneurysms. No one should ever be afraid to clip this aneurysm. So here's a case of this. There are no perforators on that zone in between. This is one where one of my colleagues did try to coil the aneurysm and was not able to do it because it kept closing off the flow in the SCA, where it came off. And here you can see the kind of height here. Not bad. Just a little bit of clinoid down towards the neck. But we do have to be a little lower because it's SCA. So here we are again, right-sided approach. I'm a right-handed surgeon. I will approach most things from the right. But for an SCA, you really have to approach from whatever side the aneurysm is on. So here it is. Have you ever done one from contralateral? I have, but I have to say you don't see the neck as nicely. Yeah, you don't see the neck as nicely. Because often they're slightly rotated back, I find. So I have done one from contralateral when I was clipping some other aneurysm and looked across. But I have to say, having done it, I wouldn't by preference do it from that side. I like to use a rubber glove when I drill. So I put a little piece of that there. And then this is just drilling away some clinoid, putting in some bone wax, and then drilling again. And then packing a little more down and drilling again. And then that lets us get that little bit of extra room to see to the, where the SCA is. And then putting a clip on. And then just again, re-inspecting, re-inspecting down there to find the branches and make sure it's not kinked. Again, looking and looking. The after clipping part is just as important after as the clipping part. In fact, there I thought that it was a little bit kinked, so I backed it up. And then just check the flow. And although it's hard to see what everything is, you can see that there is flow in that branch, which timed normally. And then there was a little dog ear left. And what you can see is that this is not a big window. It's not like you have a wide open view, on an anterior circulation aneurysm that's so beautiful. You really have a very small one. And every one of those maneuvers I discussed gives you another millimeter. And so here again, one very long clip, even though this wasn't a huge aneurysm, and then a smaller clip for that other piece. But you can get a really nice reconstruction. And again, these kind of people do well. I'm going to zip through the others. Posterior cerebral aneurysms are, first of all, very rare. Well, there's a lot more to this than we can fit in this time, so I'm going to zip over that. The mid-basilar ones will come up, and basically what you have to know is that they're terrible aneurysms. The results are not great for any treatment modality. But there are a number of options for them. Some of them, if they're small, things can actually be primarily clipped, like this. The big thrombosed ones, nobody really has the right answer for. We will sometimes do flow diversion of some kind. So proximal clipping with a STA SCA, for instance, or some other version of clipping. Or we do this sometimes where we do flow reversal. So a clip below pica, that keeps flow coming down to go out this pica, and then a clip above pica, which keeps flow going through pica, but minimizes the flow through the aneurysm. The reality is that sometimes reversal of flow is reversal of fortune. You cannot predict very well what's going to happen. We think that reducing flow will reduce growth. When we looked at our series recently of these larger aneurysms like this that were treated in a variety of ways with some kind of parent-vessel occlusion, what you discover is that the average person ends up worse overall. A number of patients die. Some of them have because of regrowth and retreatment. But occasionally you can stabilize someone's disease. And so really when we do this, you're rolling the dice and hoping that you don't. You're not one of the people who dies and you end up in the stable group. In the group of people we do nothing with, virtually all of them will go on to die in a relatively short period of time. So really that's the whole lesson. You can possibly stabilize this disease, but at a high cost to the patient. We've been looking at flow alteration and preoperatively modeling what would happen if we added a bypass or cut it with some nice smart people down at ASU in Phoenix. And what we discovered was that our ability to guess what was going to happen inside the aneurysm as a result of interventions without this is totally wrong. We are completely unequipped to guess. We found that in this particular aneurysm, it was actually better to open a stenosed vessel and increase the flow through the aneurysm than to decrease the flow through the aneurysm, which actually worsened the shear situation and created these eddy pockets. So naturally we need a lot more aneurysms to prove that this works, but I think it shows you how little we know. I want to get to pica, because this is one you actually will see. So again, I said for the upper part, if you can do some OZ and its variant approaches, you'll be able to do the upper part and then down low. Pica is a common aneurysm, and they come in many, many forms. No two picas are exactly alike. Usually the brainstem and the hypoglossal nerve are in the way. This time you can get good proximal control. Distal control can be challenging. And you should always be prepared for bypass for this, because at least in my hands, I find there are many times when it turns out to be helpful. You have something like this where there is no real neck. You know, this is truly a fusiform aneurysm, however it may look like this. So the far lateral you know, you position park bench. Again, flex, rotate, and lateral bend. You really want to open up this angle. There are a couple of choices. You can use a direct incision or even a smaller version of that. Hold on a second here. Boy, a smaller version of that. But when you do that, you come across the occipital artery. So if you want to save it as a potential for bypass, then it's not so good. So even though I generally do a lot of keyhole surgery, this is not a case where I do that usually. I keep this and find the occipital artery up here, put a temporary clip on it, and I even open and close it a few times during the case just to keep it flowing, just in case you would happen to need it. You want to take off bone down to the bottom, and usually a C1 laminectomy. You don't have to do a condylectomy in everybody, but a partial condylectomy, or at least right up to the very back, is helpful. And you are never as far anterior as you think. Every time you look at a scan afterwards, you think, God, I must have been all the way to the clivus, and you're not. So, whoops, there we go. So that, you know, here, so what, if you have a pica like this, what approach? It's just suboccipital, right? No reason to do a far lateral. If you have one like this, fairly high, in fact, fairly high, you almost can do a low retro-sig to reach that. As you get down to the typical low location, so here's the condyle here, then that's where your far lateral really comes into play. And this is the sort of direction for the direct approach, that you're going like that. Gives you that kind of opening. And again, this is about as much condyle as I've ever removed. On one side, you can still do that and not destabilize someone. The rule is supposed to be 50%. One thing to remember is, if you leave the joint intact, and just hollow out everything above, you can get just as much room and not destabilize them. So not always necessary. You can get extradural control of the vert very easily. And I highly recommend in the cadaver, you just practice finding the vert that way. Every year, someone at the barrel finds it with a bovie. I don't recommend that. So, yeah, condylectomy, we usually put it back. Occasionally, the 12th nerve does get beat up, and 9 and 10 and 11, especially in ruptured aneurysms. And in fact, when you look at the morbidity of this surgery for ruptures, what we find is that the quality of life effect that's greatest is this. It's the effect on their ability to swallow. So I will say, in the barrel ruptured aneurysm trial, surprisingly, the pica group did very poorly in terms of actual quality of life afterwards. Much worse than we would have guessed they would do. Very quickly now. Can you talk about that for just a minute? Yeah. I remember maybe seven or eight years ago, presenting a Jackson Hole case where I tried to coil a pica and tore it and ended up hurting the patient. And Robert really took me to task and said, I know you, you can clip these. These all need to be clipped. And then I was shocked last year when I heard him talk about Brad and say, one of the reasons we have the results we have is that pica aneurysms are really bad aneurysms to clip. There's got to have been some evolution of thinking there, and I struggle with pica aneurysms. I really do. I've ended up clipping a fair number of them, and sometimes I get away with a great result, and other times I don't. And they're not always easy to treat endovascularly. No, in fact, I mean, so despite the, so what he's referring to, Adam's referring to the, in the BRAT study, if you look at the outcome for posterior circulation aneurysms, for whatever reason, a large number were randomized, I mean, a much larger number randomized to clipping than to coiling. And strangely enough, that group did really poorly. The poor outcome, MRS, most of them were not devastated, but a lot of them were threes, were, was like 67% of patients. They had a poor quality of life. And when you look at why, a lot of it has to do with, like I say, these other things. So if you look at the surgical result, meaning how well it was clipped, preservation of the pica, all that, they, it seems like you did a good job, but they just don't do well. They have a lot of other problems. So it has evolved our thinking somewhat. But you're right, I mean, there are a lot of these aneurysms that you would have to sacrifice pica. We get, all the time, cases where somebody has just sacrificed pica somewhere else, and then we get a patient with a big posterior fossis stroke. I don't think it's necessarily better than that, but I would say if you, if you can, you know, coil one, probably it should be coiled. And we do, you know, rely on that as much as possible. But that being said, we still find lots to clip. And getting better at it, being really, really cautious about the lower cranial nerves, I think that's something we've done a lot more since Brad ended, is take, just not take it for granted that a little stretch of those nerves is not going to be a problem. So, but... So you think you've moved towards more endovascular... More endovascular, or in some cases, we've moved more towards doing things like sacking the vessel open and bypassing it so we don't manipulate, yeah, so we just don't manipulate it too much. Because it does seem like it's all that manipulation around the brainstem. You either end up with, you know, infarct along the brainstem, or you end up with lower cranial nerve problems. And those seem to be the really, the, you know, the MRS changing factors. But it was surprising to me too. I would say that Brad happened when I was first at the Barrow, the actual time of that in those first few years. And so most of my cases were not in that because you had to have been, have a certain number in practice before you could start. And my results after Brad were actually better than the results during Brad. So it's a little hard to say why exactly. But we take them with more respect because the clipping is not hard. You get out of the case and think, okay, we're, I mean, it's not easy. But you get out of the case and think, well, you know, it wasn't so bad. But then they don't do as well as you'd think. I think for the ones that are very high and very anterior to the cranial nerves, that those are ones that if they can be coiled, they probably ought to be coiled. And just real quickly to mention that, so there's pica pica side to side, pica pica end to end. This is just a fusiform aneurysm. It's actually one of the ones I showed you on a previous slide. But here's a clip on one side. And then there's a whole big thrombosed dome. You can see it there on the side there. And then looking at this, I had the OA out so we could use the OA. The other pica wasn't a good match. But sometimes you'll find that you can just go and cut off the aneurysm and find that the vessel on the other side is okay. And if it is okay, you really have two options. But if there's enough slack, the best thing to do is just take the aneurysm out and then sew the two ends together, which is exactly why you've got turkey wings downstairs, so you can feel completely comfortable to do this. This is a relatively easy end to end bypass. And again, you've got to really make sure you get all the sick stuff out. It's kind of deep, so that's a problem, but really not a bad option. So this goes on for a little bit, so I'm not going to really show the whole thing to you. But you'll find that there's often enough slack. The pica has those big loops to it, and I've done this a number of times, just cut out a fusiform aneurysm rather than trying to wrap it. The one place you can't do this is if the aneurysm is very close to the vert, naturally, because that's where you're going to lose your perforators. And the one thing you also can't do, I learned through painful experience, is expect those perforators to stay open through backfilling. Even if you provide a bypass distal and then have them fill in reverse, they don't have enough flow. You'll get too much stasis, and even though the bypass may be open, you'll get a back occlusion. Here's another, and again, you look at the aneurysm, decide that it's very anterior. It would be just as easy to close it, so having the occipital artery ready to get out. And then this is just an end-to-side. It's really not much different than doing STAMC, except it's a deeper hole. And generally, if you just push the blood pressure up during this time, you won't have any trouble with cerebellar ischemia. And this is beyond the brainstem perforators, so it really is a nice technique to have. I mean, again, I always like to emphasize the importance of having those bypass techniques. This is not an aneurysm at all, but a vertebral artery stenosis. My partner, Dr. McDougall, tried and tried to get this open and just couldn't pass anything past it, and after a shower embolizing, distally gave up. The guy, whenever his blood pressure would fall below 180, he had no contralateral vert, and he had that stenosis. He would fall down. It was amazing. You could just play with his blood pressure, raise it and lower it, and make him go asleep or wake up. So this is just getting a hold of the vert right where it comes in, freeing it from the dural sleeve so it's out of the dura completely, so we have complete control around it. And then this is opening the vert. I want to see. I was prepared for a bypass, but what turned out was it was just like a carotid enderectomy. There's the inner part coming out. But this is a very sick vessel, so I bypassed it. Well, I didn't bypass it. I just sewed it up primarily. And what you see here is blood coming through a muscular branch. No flow through it. So I reopened it, washed it out with some TPA. Amazingly, during this time, with the blood pressure up high, the vox didn't really change. Eventually, I sewed a patch in. And then all while I sewed it, I kept opening and closing the clips to let blood go so that it wouldn't get stasis in it. And in fact, once that was done, I ended up with this, which has created a little fusiform aneurysm for him with excellent flow. And actually, he went right back home and like nothing happened, apparently unaware that this is nothing, something that happens very often. I think in the interest of time, I will not show you more cases unless we have time. But I will say these are more difficult aneurysms, but they are often still surgical. And you really have to learn everything and then even get better at it all the time. Just because we've hit this endovascular era, it just raises the bar for what you need to know. It means you have to practice a lot more to do fewer cases. Particular for upper basilar and SCA and also pica, these should be considered regular approaches. These are not exotic approaches. These are approaches that you should absolutely be able to do if you're doing any vascular at all. And again, you can climb a lot of the learning curve out of surgery so that when you get there, it doesn't seem so daunting. I always love this quote from Charlie Drake, that the learning curve is hard, and as much as you can learn before you get there, the better. As he says, if we could only have those back who we treated before, we know what we know now. Since there's a lot of expertise out there, I would say avail yourselves of it. When you get into surgery, as you often know, and I've felt this all throughout my life, there's never a time you wish you had spent less time preparing on one of these cases. Lastly, I am a big fan of endovascular therapy, but it should never be that the reason why you decided it was better for the patient of endovascular therapy be because you can't do what we already could do. I think it should be an intolerable thing for all of us to think that we would someday be worse at doing something than people used to be. An era has passed. You look at Charlie Drake's 1700 posterior circulation aneurysms, nobody gets to do that anymore. It's just impossible, but you still need to practice and practice and practice so that you can take a good shot at it. That was long. I appreciate your attention. Do you have any questions at all about any of that? No. How many people are in an institution where you think you do more than 10 open posterior circulation aneurysms a year? Good. I would just say go to every case. I mean, go to every case. Don't miss a case because you need a lot of them. I think, well, Mike, what was in your series that you published in 2002, right? Was 27 the break point? Was between when your complication rate for basilar aneurysms shifted from higher to lower, keeping in mind that it wasn't that high to start with, and then it became a lot lower than most people can expect. Now, I know most of you are probably better than Mike Lawton, but the reality is for most people, the learning curve is probably a lot longer than 27, so you really have to take every opportunity to soak up every case. All right. Thank you. Thank you.

posterior circulation aneurysms

endovascular technology

clipping methods

accessing posterior circulation

exposure and control

bypass procedures

surgical outcomes