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Role of Surgical Revascularization in the Current Era of Endovascular Therapies

Gary Steinberg

July 05, 2021

Transcript

- Colleagues and friends, thank you for joining us for another session of the Virtual Operating Room. Our guest today is Dr. Gary Steinberg from Stanford University. He's an incredible academician leader and technical neurosurgeon and he's also the former Chair of Neurosurgery at Stanford University. Today, he's going to talk to us about revascularization techniques in the era of endovascular neurosurgery. An incredibly important topic considering the advancements in endovascular therapy, but at the same time the importance of this tool in the armamentarium of the neurosurgeon facing much more challenging vascular lesions. Gary, thank you for joining us. Look forward to learning from you, please go ahead.

- Thank you, Aaron for the invitation to speak today, it's a real pleasure and here are my disclosures. So Gazi Yasargil first develop the STA-MCA bypass operation back in the '60s and he did his first bypass in a patient with an occluded MCA in 1967, and then performed this procedure on his first moyamoya patient in 1972. This is a beautiful operation and we all trained, at least during my era in this particular technique and got good at it. However, in 1985 the first bypass study was published, looking at patients who had a carotid or MCA, middle cerebral artery occlusion compared with medical therapy versus the bypass procedure and disappointing results. The study showed there was no benefit for the surgery and therefore we stopped doing this procedure for garden variety stroke. We tried to resurrect the procedure with another study, the COSS study and this was a very rigorous study, which selected patients with carotid occlusion solely on the basis of whether they had impaired hemodynamic reserve. And that was looked at with PET scan. We thought that would select the patients who had hemodynamic problems not thromboembolic problems and would benefit from the bypass. However, again, a disappointing result and you can see the surgery group did just as well as expected and they met the projected estimated stroke rate at two years, but the medical group did far better than had been projected based on the prior PET studies in these patients. And the reason probably is because of a development in medical therapy, including better control of hypertension and the use of statins. So we then witnessed the introduction of the GDC coils and endovascular therapy began to take over the treatment of aneurysms. And again, we lost the opportunity to treat many of these aneurysm patients, particularly difficult ones with a bypass in some cases and trapping of the aneurysm. And you can see here on this slide, that what happened after the publication of the COSS study was that the occlusive patients, garden variety stroke patient bypasses went down, the moyamoya patients actually increased in terms of the number of bypasses and the aneurysm patients went down slightly. So this shows the number of bypasses I've done over the years, more than 2,000. And this is what I feel are the indications for surgical revascularization in this current era of endovascular therapy, non-atherosclerotic occlusive vasculopathy and vasculitis like moyamoya disease and Takayasu's arteritis, deliberate large vessel occlusion for aneurysms, particularly the complex ones, tumors and dissections, when there's been failure of temporary balloon occlusion, recurrence after endovascular therapy or prophylactic. And occasionally for occlusive atherosclerotic cerebrovascular disease, for symptomatic brain ischemia patients, despite medical therapy, they failed that and they're not amenable to angioplasty or stenting. And here are some indications of hemodynamic compromise, watershed infarcts in it, adequate reserve on blood flow studies for angiographic flow and postural symptoms such as limb shaking TIAs. So total number of bypasses I've done since I started on faculty at Stanford, 34 years ago, over 2,000 and most of these have been direct. I think they were better even for moyamoya. Many superficial temporal to middle cerebral artery bypasses, but a number of other extracranial to intracranial or intercranial to intracranial bypass, PICA-PICA, ACA to ACA. I've done a number of interposition grafts using saphenous vein primarily, but also femoral vein, Dacron or middle meningeal artery. And you can see some of these grafts and I'll show you examples of those. And then indirect grafts, which I do usually in some of the very young moyamoya patients using different types of indirect grafts. And I'll talk some about the omental transposition, which we've developed at Stanford. So here's an example of a eight year old boy with Takayasu's arteritis I treated a while ago, he was having persistent TIAs and had a left hemisphere stroke. And you can see he's occluded both of his common carotid arteries and his left vertebral artery and he's filling his entire brain only through his right, sorry, his right vertebral artery. And here you can see his vertebral artery fills his entire brain circulation. And so what we did here was we actually took a femoral artery from the groin so that we could use a live tissue in his neck because he was still growing. We replaced that with a Dacron graft and here you can see we plugged in this femoral artery into his brachiocephalic artery down here, which was open and then sew the superior aspect into his common carotid artery, which was re-canalized. Here's his occluded vessel, right carotid artery. And what you can see here post-operatively is that we've created now a new conduit to his brain, a new common carotid artery, which now fills nicely his entire anterior circulation and mark the increased blood flow. And here he is, you can see one year later here and you can see eight years later and his graft was durable at eight years. A patient I saw recently showing the same kind of strategy. This patient was an adult who presented with a stroke and you can see this is a hemorrhagic infarct pia. He has other infarcts. You can see in his posterior circulation. And the reason that he has these is he has occluded his left vertebral artery at the origin. It does reconstitute here through cervical collaterals. The right vertebral artery has a very high grade stenosis. And therefore he's not supplying his posterior circulation very well at all. And you can see his collateral flow supplied his PCA on both sides, but not his basilar artery. And this is why he was having hemodynamic strokes in his posterior circulation. And so the strategy here was to do a carotid to vertebral artery bypass. This is a little tricky, so the way we did this was to first position the patient supine to do the lateral, the left carotid exposure. And then we turn the patient on his side, so we had access to his carotid over here, but we needed access to his C1 to get to the V3 segment. And what we're doing here is we're exposing the V3 at the sulcus arteriosus which sits on top of the C1 laterally here. And I'm gonna show you the video. So this is trimming the vein, we've tunneled the vein, saphenous vein graft. This is the external carotid artery here. And I like to use the external if possible. So I don't have to clamp the internal, making an incision. And now I'm flushing it out first. This is the proximal origin of the external carotid. This is a cardiac punch with the cardiac surgeons use for their coronary grafts. The 2.5 millimeter opening, which I widened, extended. And then I'm sewing with 7-O sutures here. It's a little trickier than our normal carotid endarterectomies because the patient is slightly flexed in order to expose the vertebral artery. And the idea here is to put in the toe end and then the heel end. And then this I did with running sutures. And you can sew with a Rider or any kind of forceps that you like, I like tying with longer instruments here. And then I'm gonna run this wall over here. So this wall I'm running, and then you'll see I'm gonna flip the artery. Now, I've clamped the artery after we ensure that there was flow through the digital end. Now, I wanna show you the anastomosis to the vertebral artery at C1. This is the V3 segment, here's the saphenous vein and I'm trimming it, but leaving a little length here so that the patient could turn their neck. Now I'm clipping a small segment of the V3 vertebral artery on the arch of C1. And this is a little tricky 'cause you're sewing in a deep hole, in a confined space, opening it with a 15 blade, flushing it out after I extend the opening. And now we're sewing here with 7-O and 8-O suture. Sometimes a Cassie VA-O is better to sew with. So we've got that worn, now, you see what I've done. I put the graft on top of this clip and the clip helps to hold it back so that I can sew this wall on this side. I sometimes use this same technique when I'm doing an SCA MCA bypass for moyamoya, with smaller clips, of course. And now we're an occluding. We've got a good Doppler tone. Here's the ICG you see filling nicely. It fills the vertebral distally as well as proximally retrograde. And here's the carotid ICG, so here's the external carotid. Here's the graft going up to the vertebral artery. So a nice bypass there. And then you can see next slide, Luke. And you can see here, here's the graft coming off, saphenous vein, going up to fill the vertebral artery. Here it fills the verbal artery retrograde as well, but primarily fills up to the basilar artery and you can see it on the AP2. Here's the nice graft filling the vertebral artery up to the basilar. So nice supply that puts your circulation. Here's an example of another patient with Takayasu's where you can see a very long-term 19 year patency of the graft here. So these stay patent for many, many years. Moyamoya disease, I think is a very good indication these days, they're not a good endovascular treatment, stenting does not work for this disease. We showed that it's a progressive disease where there's occlusion of the arteries at the base of the brain, causes hemodynamic ischemia, it's not atherosclerotic, not inflammatory, at least not acute inflammatory. And there's a compensatory enlargement of the perforating arteries, you can see here, which looks like a haziness or puff of smoke, which means moyamoya in Japanese. And you can hemorrhage from these vessels. You can also hemorrhage from aneurysms in this disease. You can see here where the occlusive process occurs at the base of the skull in the circle of Willis vessels. This is actually from a patient with moyamoya who did not survive. And you can see this proliferation, here the ventricular stripe, and here's a proliferation of the ventricular stripes in that particular patient at autopsy. So we have a large referral base. We've treated patients from 19 countries. I'm not sure why we got referrals, even from Japan and Korea and China, but we've now treated almost 1,300 patients, have done almost 2,000 bypasses in patients ranging from seven months to 74 years old. And you can see how the practice has grown since 1991 when I treated one patient. We're treating about 100 to 130 patients a year now, adult and pediatric. And as I mentioned, most of the bypasses I do are direct except for these young kids where the vessels are too small. And here's how I'd like to do the procedure. Isolate the, usually the parietal branch to the superficial temporal artery, unless it's not big enough or not present, in which case I'll use the frontal branch, isolate it with a generous couple of soft tissue, which is also vascular and then split the muscle, open the dura. And I'd like to open the dura in a cruciate manner. So there were more leaflets. I think that promotes more angiogenesis wide opening about six centimeters, not a small opening. Again, you wanna promote indirect as well as direct bypass. Try to choose a vessel that is oriented this way, coming out of the Sylvian fissure so there's no back wall, but I always choose the largest vessel, the largest M4 vessel. And then I temporarily occlude a segment about seven millimeters, open the artery and remove an elliptical portion and then fish mouth the end of the STA, sew it in in an end to side fashion, I use interrupted sutures. And of course, after you do the bypass, you have flow not only distally but also proximally back towards the Sylvian fissure and then out into the brain, it can supply the entire hemisphere. Intraoperative management is important. We use normothermia, keep the mean arterial pressure in the normal or high range, mild hypothermia. I don't monitor SEPs or MEPs anymore 'cause we never saw any changes in the OR, we just use EEG for burst suppression and very important, I like to use the Sharbell flow meter made by Transonic to look at quantitative and directional flow. I'll show you examples of that. So here you can see, go ahead and run that please, Dopplering the artery on the surface to identify it, open with verifying scissors. These are present in the bypass set that is marketed by LASIK. That's one of my conflicts, next slide. And you can see when I first started doing this, vessels can go into spasm just from manipulating them. And I used to choose another artery, but what I learned quickly is just wait, put on some nicardipine. We don't use the papaverine anymore, 'cause it may have some toxicity and the vessels will dilate up again, so not a problem. And here I'm gonna show you, this is a video of the, that's the STA, this is the MCA now. I put a little high visibility under the background, we developed with LASIK some special clips, which are smaller and finer than the commercially available ones prior to this. Fish mouth the STA, and then temporary occlude the STA. These are the special clips which are very fine. And now I'd like to remove the superior wall because we're studying this with RNA and protein analysis and found some interesting results compared to non-moyamoya patients. And then staying up with indigo carmine, put the toe end in first that allows you to adjust the heel end of the STA if necessary here. And after you put in the two ends, then you sew each wall, I like interrupted sutures so that my fellows and chief residents and actually the senior residents can put in a stitch and you'll see this does not slow us down. We do so many of these, the nurses and techs hand the stitches very quickly. Here's the final bypass. And then I measure flow with the flow meter in proximal and distal M4 and in the STA. So I wanted to show you pre-bypass, the use of Flow 800 and the ICG dye. This is what the artery looked like. This is the M4 branch that I bypassed too in this patient. Run the video and you can see, look at these competing flows in that M4 branch. First it comes in retrograde from collaterals, and then it feels anterograde. Very interesting, when we measured the flow, the maximum flow is actually anterograde, but only 1.4 mls per minute where normal for a non-moyamoya is positive 10 to 20 mls per minute. Now I'll show you the post-bypass. And here you can see in the ICG, run that video and you could see nice filling of the M4 branch from the bypass. And now the flows are negative 12 towards the Sylvian fissure proximally, 37.8m distally. And the total flow in the graft and the M4 branch is 50 mls per minute. So the point I wanna make is that the STA can provide a high flow bypass if necessary. You don't always need to use a saphenous vein or radial artery for other diseases. I like the STA for moyamoya because all you need is a little more blood flow. Next slide. People ask me how small a vessel can you do? And this is a pediatric case. The smallest vessel that I think one can do to stay open is about 0.7 millimeters in diameter. And here I'm gonna show you an example of that. Go ahead and run this video. So this is a pediatric case and the vessels are very thin. Sometimes the vessels can be large enough but they're too fragile to do a direct bypass. So you have to make that decision. And this one's about 0.7 millimeters and you can see it will take a 10-O stitch, but you have to be extremely gentle. And sometimes all you need are just a couple of additional stitches on each side, plus the heel and toe stitches. But you can get very nice bypasses in the kids. And I usually try to do a direct in the kids as well. Next slide. And here you can see an adult who was having multiple strokes, very severe moyamoya disease, occluded carotid with moyamoya vessels on both sides, multiple strokes. And post-bypass you can see a robust bypass two months later, filling the entire MCA distribution all the way down to the bifurcation, really on both sides. So here's the learning curve. You can see in the first decade I started doing these, bypass times were about 20 to 50 minutes with some outliers. And then in this period of time we got better and you can see here, now we've got bypasses, 2006-2009, between about 15 minutes and 37, 40 minutes. And now we do so many of these. Currently we have bypass times about 11 to 18 minutes. Last year, we had one of eight minutes, so we get very good. And this is with the residents and fellows putting a stitch in. And you can see how we increased flow. This is analysis of a number of patients, average about positive 4.4 mls per minute, very low with normal 10 to 20. Post-bypass, we increased flow in the MCA about five times. And I'm still amazed to see how these arteries can enlarge. This is pre-bypass. Look at this six months later, the STA enlarges to the size almost of a carotid and three years later is even larger than that. And as I mentioned, we can get flows in the STA, an MCA after bypass up to 80 mls per minute and even higher if you take the STA into an M2 branch for aneurysms. So again, you can use STAs for high flow bypasses. Now, here are some pearls. If you run this video, here I'm cutting it to the artery, but I need to lengthen my initial incision. You could do that just by using a small scissors. Next slide. I wanna show you another pearl, run this one, Luke, and you can see here, I've done the bypass. Now, I'm gonna take off the clips, but I've got some bleeding here from a tiny hole. See that a little jet. And so instead of re-occluding the M4 branch, what we do, I'd like to just use my suction to stabilize the artery. Someone else can provide a little suction, and then you can put in a single stitch without having to re-occlude the M4 branch. So that's a nice little trick, keeps your occlusion times down and then you finish it. I only use actually three knots now in these 10-O sutures, I think that's all you need for these interrupted sutures. Next slide. Now I wanna show you what we do if we don't have an STA, if it has been used before, and I get many redo cases or one's not available. I will use the occipital artery, very nice artery. It's more difficult to dissect out because it's torturous, it's deeper in the soft tissue and it has many branches, but it's a very good artery to use. And next, go ahead and run the video. And here you can see, I'm gonna dissect this artery using some small littler scissors. And again, we dissect it with a couple of soft tissue. There's the artery, Doppler it to make sure it's patent And then we cut the artery to anastomosis and there's no flow. And so this was an artery dissected by the resident or fellow. So then what I do is I try to irrigate it. If that doesn't work, I'll use a wire and I'll do this on an STA. And here you see what's happened is the resident occluded the graft during the dissection. So I had to open it there, restore flow, and then do a primary end-to-end anastomosis. Now, we've got good flow from the end of the occipital artery. And then again, we just do the same bypass we would do. And now we're gonna just sew the occipital artery and in the same way that we did before with the STA. So remember, occipital artery, very nice artery to use. You just have to become comfortable with the dissection in the scalp. Next slide. A couple of other points, if you don't have an occipital or STA to use or a posterior auricular, you can occasionally use the middle meningeal artery, and you can see it's a little tougher to dissect out of the dura, but you have a very nice artery here and you can achieve a very nice graft. Moyamoya can also be treated with indirect. I don't think it works as well. And we showed this in a recent publication that we did from Stanford patients, in adult patients. In the kids, it works much better. I still like to do the direct graft. And remember, anytime you do a direct graft, if you harvest enough artery that you can lay it on the surface of the brain, it will induce indirect grafts too. So you've basically done a combined direct plus indirect, but if we just do an indirect in the very young kids with the small arteries, you isolate the STA, do your craniotomy, take the bone off, open the dura, and then lay the graft, which is still connected on the surface of the brain. You can open the pia and arachnoid if you want. I'm not sure it's necessary. Close the dura over the STA and then put the bone back, leaving holes for the graft to enter and exit. And you can achieve a nice bypass, indirect bypass or remember it takes at least three to six months for that to work. And it doesn't work as well as the direct plus the indirect graft which we usually do. You can use muscle. Here's an example of someone who failed a EDAS, indirect graft and burr holes. The muscle works nicely, I've never seen seizures caused by the muscle. I like to use the omentum, it's become one of my favorite choices for redos, where there's no other vascular substance to put on the surface of the brain. And remember the omentum is a very vascular substance in the abdomen that also secretes neurotrophic factors, growth factors, angiogenesis factors and neurotransmitters. You must detach it from the stomach and the colon and what we do, it has two blood supplies, gastroepiploic artery in the left. And so what we do is, and all of these cascades, we take down to lengthen it. We end up cutting the left gastroepiploic artery, leaving it attached to the right gastroepiploic artery here, that's very important to preserve. And then we take down the cascades. When I first started doing this in 1990 to 2000, a general surgeon health. And we did a laparotomy, here you could see taking it down from the greater curvature of the stomach and from the colon, leaving it attached, and then you lengthen it. It's amazing you can actually leave it attached and lengthen it so that it stretches up to the brain. Then you have to tunnel it and you tunnel it and bring it out and place it on the surface of the brain here. And you wanna thin it out, but it covers the brain. And we use that to close the dura actually. I've also done free grafts where I take it out of the abdomen and anastomose the gastroepiploic artery and vein to the superficial temporal artery and superficial temporal vein. I abandoned that procedure in the 2000 to 2010 era, but resurrected it because the general pediatric surgeons have become wizards, being able to harvest the omentum laparoscopically. And so now we do it laparoscopically, and I've done 21 of these with laparoscopic harvesting. And you can even revascularize both sides of the brain with a single transposition. I'll show you very quickly, run this video. This is how we positioned the patient. And the endoscopic approach is through some small transverse incisions. We dissected off the transverse colon and greater curvature of the omentum with these endoscopic instruments. You have to partner with a general surgeon who is faster with these techniques and make sure you don't interrupt the supply to the spleen, the splenic artery. And then you take down the cascades, leaving the main gastroepiploic artery on the right attached. So you don't compromise the blood supply, and then you tunnel it laparoscopically, bring it up to the brain surface. And then we open the dura, you wanna thin out the omentum. So reset the dura, thin the omentum here, not interrupting the blood supply. And we close the dura with the omentum. You don't need to use anything else. It's a very good substance to close. Next slide. And here's an example of someone that failed indirect bypass is done elsewhere. And you can see, we use the omentum and here's the gastroepiploic artery going from the abdomen all the way up to the neck. Here it goes up to the neck, to the brain and it's spilling the entire brain that was not filled previously by the indirect grafts. And you can see here years later, three years later, it's still a filling from the abdomen of the chest to the head and nice revascularization of the brain with a patient who's doing quite well now. She's now a teenager actually, I saw her recently. So I wanna show you something I recommend you don't do. Here was a patient who had bilateral bypasses from moyamoya, was having bilateral hemisphere TIAs, and the indirect graft feeds where EDAS is done did not take and this is why I don't think it works. The patient continues to have bilateral hemisphere TIAs, so I did a vein graft from the external carotid artery in the neck, and it worked on the left side, but then I did the right side 'cause we still have the TIAs. And you can see I used the vein graft here. This is one of my very early cases. And next slide, run the video. You can see the mismatch between the saphenous vein. And after I opened the vein, I saw extensive hyperemia and pulsations the brain I didn't like. So I occluded the graft and I gradually let it open. And I was satisfied there wasn't extensive hyperemia. Next slide. And sent the patient home. And she did well for 10 days and then had a reprofusion injury. And so I think saphenous vein provides way too much blood flow. I think radial artery is too much blood flow for these moyamoya patients. So I don't recommend using those. And I just wanna show you, we just recently submitted a paper in a large number of patients that we've treated with moyamoya patients over many years, this is the largest series published in the Western hemisphere or Europe, in Western moyamoya. And you can see four factors out of many, highly correlated with post-bypass stroke. Age, I'll show you the digital subtraction angiography score, where we looked at the extent of ICIC collateralization or worse, ECCI. The MRI score, where we gave points for ischemia hemorrhage atrophy, or more importantly, if there's a DWI infarct, even a punctate infarct like that, within a month before surgery can lead to this kind of a stroke. So I delayed patients at least a month if their pre-op MR shows this, and then the hemodynamic reserve score where they have impaired reserve after Diamox or even steel, which has worse leads to worse outcomes. So those are our risk factors for a stroke. Age is a very important determinant. You see, we have about a 4% risk of peri-operative major stroke after bypass overall, but it's very low in the kids. 1% increases in the 19 to 39 years old. 5.8%, which I still think is acceptable, 40 to 59. But when you get over 60, I worry. And so I don't do many patients unless they're really failing medical therapy and continuing to have strokes. Most of these are ischemic strokes and 50% do improve at least one score on the mRS scale. But I still lose sleep over these peri-operative strokes, even though it's a low rate. It's a great disease to treat, it's mainly young patients. They get back to normal activities, sports, they get married, they have children, they win debating contests and even participate in high-impact sports, like ice climbing, skydiving, trapeze acrobatics, and maybe one of the highest risk sports, becoming a physician. I wanna show you how else I think revascularization is important in this current era where we treat a lot of patients with aneurysm endovascularly. Here's a patient who ruptured a dissecting aneurysm. You can see here in the right vertebral artery and we coil the aneurysm, patient did well. You could see there's a little flow into a retrograde from the contralateral but over six weeks the aneurysm enlarged. And so what I did was to do a PICA graft using the occipital artery, which I think is a good artery. And you can do a PICA-PICA graft. But here let me show you, so here's the PICA and we use the tonsillar loop where there are no perforators. Here's the occipital artery, a good match. And we'll temporarily occlude the PICA sewing with 10-O suture again. The advantage of this over the PICA-PICA graft is you don't need to include both PICAs. So you're not putting both PICA distributions at risk. And here the completed graft on occlude, make sure the flow is okay. Here's a measuring flow and you can see the post-bypass flow is actually greater than the pre-bypass flow, trap the aneurysm. And now we've got a, next slide, a nice result. You can see we do an intra-op angio showing the occipital artery filling the PICA distribution, same post-op and the other vert fills the basilar artery. PICA-PICA grafts are actually technically easier I think, 'cause the occipital artery dissection is more difficult, but I think this is a nice alternative. And I wanna mention, I do not use this S shaped incision, which Roberto Heros popularized to the far lateral approach anymore. There's too much muscle dissection. I do all my far lateral incisions. Just bringing it down through a midline incision here, and the plains are much nicer. Usually you don't even have to extend the incision laterally here but you can if you need to, but anatomic planes are much better. Here's another example of a patient with a, we thought it was a tumor, he came in with seizures and extensive edema but this is a giant aneurysm. Here you can see it's an M2 aneurysm and this is only about a third of the aneurysm filling angiographically 'cause the rest of the aneurysm is stretching the M2 branch here. And so what we did here is we did a bypass, I'll show you that we did a couple of bypasses. Here's the temporal lobe, here's the frontal lobe, here's the giant aneurysm just peeking through, this was so difficult to expose. I thought about maybe just leaving the patient alone, but the residents and fellows said, "No, you gotta do this case" 'cause of course they wanted to see how we did it and the anatomy. Go ahead and run the video. So here you can see gaining control, this is the M2, sorry, the M1 and the M2 going into the aneurysm. Here's the aneurysm, it's four centimeters. And so I control the M2 and the outflow, which is the M3, I thought that was the only outflow. And then I cut into the aneurysm using a cuzosana pick to take out all the thrombus. Now there's bleeding. And so obviously there's another M3 branch coming out. There's the orifice of it right there. So I found that on the outside of the artery to temporarily occlude that. I realized I couldn't clip this, so I ended up cutting off the aneurysm and then I cut the M2 going in and I cut the M3 coming out, the proximal M3. And I did an end to end anastomosis between the M2 and the M3 with 10-O suture and made sure that was patent with a flow meter. And then I used the STA, which I'd isolated. And I sewed that into the other M3 branch over here, again with 10-O sutures, so two bypasses. Next slide. And the patient did well and you can see here's my STA. This is the STA to the M3 branch. And here's the direct anastomosis between the M2 and the M3 and the aneurysm's gone. Nice resolution of the edema. Another case quickly I just wanna show you. And this was a very large P2, three aneurysm, and here you can see the aneurysm. It's a very dysplastic artery right here that needed to be resected. This is actually the superficial, this is the SCA aneurysm, the SCA artery rather. So what I did was temporarily occlude the PCA here. I took out this, I resected that portion and I took a small piece of superficial temporal artery vein. You can use saphenous vein and I anastomosed that to the posterior cerebral artery end to end and that worked nicely. And the final case here I'm gonna show you is a recent case I treated. This was a patient of my colleague, Robert Dodd, with a giant parasellar sphenoid aneurysm that resulted in multiple episodes of epistaxis. Here's the complex aneurysm in the parasellar sphenoid area. The problem was no flow from the contralateral injection via the AECOM and no good STA branch. Occipital artery was too small. Attempted flow diversion robs also a endovascular surgeon could not deploy various devices. So he got me involved in what I decided to do was a extra cranial external carotid to M2 bypass using a saphenous vein. And here I'll show you, this is the very atherosclerotic disease segment with the aneurysm of the ICA. This is the right temporal lobe, right frontal lobe. This is actually the M2 segment and this is the M1 segment. And I'll show you that was not a good segment to bypass too. So here you can see, this is not a good segment over here. It's too atherosclerotic right here. And so I decided to go to the M2, measured 2.5 millimeters. Here's the saphenous vein, which I've tunneled already. And this was a nice match, it's about three millimeters, sorry, three centimeters in diameter, clipped a segment avoiding the perforator. Again, I reset a small elliptical portion of the superior wall, flush it out, stain it. And now we're going to sew this with 8-O suture is what I use to sew here. And sometimes I think actually this was 9-O suture. You just figure out what is the best match. So this was 9-O suture for this and this is a pretty straight forward anastomosis. You could run it. I like interrupted sutures and then flip it, do the back wall. And then here's the external carotid artery again. And we're opening it up. Now, we're gonna sew the saphenous vein proximal segment, and remember the ankles segment goes into the external carotid. Here we're measuring flow in the graft and here you can see nice flow into the middle cerebral artery M2 on ICG. And then we did actually, next slide. You can see the flow before we included the ICA in the neck, 38 mls. And we opened the graft completely, 85.9 mls per minute, and that was enough to carry her. You could see postoperatively she did well, and you can see here's the graft up to the brain. There's a graft filling the MCA distribution after we coiled off the aneurysm. So in my opinion, I think patient selection is critical for doing revascularization. You need to decide on the need for a low flow versus high flow bypass, but STA can supply a high flow bypass if it's large enough. I'd like to use the native anatomy as much as possible to reconstruct. The fewer bypasses you do the fewer anastomosis sites, the better. Develop proficiency with various arterial grafts and interposition graft techniques, and choose the revascularization technique that will provide adequate blood flow, highest patency but with the lowest risk. So I wanted to thank everyone at Stanford for the success of our program over the last 31 years. Many of the people we started with, including Greg Albers and Michael Marks are still here. Michael just retired, but the three of us have been directing the Stroke Center for 31 years. And I wanna thank our patients particularly. We have an annual moyamoya picnic and patients come from all over the country with their families. And this of course is the reason that I went into neurosurgery to help patients and the most gratifying aspect of what I do every day. So thank you again for your attention and thank you, Aaron, for inviting me to give this talk.

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