Grand Rounds-STA-MCA Bypass: Nuances of Technique

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- Ladies and gentlemen, thank you for joining us for another session of the Dublin Operative Grand Rounds. We are privileged today to have with us, Dr. Jacques Morcos from University of Miami. Our discussion will focus on management and technical nuances for STA-MCA Bypass as cerebral revascularization. Jacques, thank you for joining us.

- Thank you very much for including me in this very popular series of WNS Operative Grand Rounds. It's a real pleasure to join you.

- Thank you. So, the agenda is as follows. We are gonna go ahead and review some slides of mine and then Jacques will present some of his own slides and his takes on nuances and then we'll have three surgical videos. One of mine, and two of his that would really touch upon what the Pearls and Pitfalls of this procedure are. So, let's go ahead and discuss the disclosures. None of which interferes with the presentation today. So, what are the indications for Cerebral revascularization Flow Augmentation for Cerebral Ischemia and that's where symptomatic atherosclerotic stenosis of STA-MCA. And there's much controversy as we know a law around this, you know, issue of the study that was done. The corporative ICEC study ECIC study in 1985, that didn't show really significant difference between the medical and surgical arm for using this procedure. The recently the cost study, the carotid occlusion surgical study was also concluded due to lack of detection of any difference between the medical arm and the surgical arm. However, this procedure has remained very effective for Moyamoya disease, and for replacement for giant aneurysms and rarely tumors. Going back to the idea of use of this procedure for misery profusion, for symptomatic atherosclerotic disease, such as carotid, occlusion, or MCA stenosis occlusion. It is been our practice that still this procedure remains very effective however, for a very select group of patients. In other words even though the ECIC corporative study did not detect a difference and the recent cost study was not detecting any difference either. On very select group of patients who are on medical therapy continue to suffer from multiple strokes and have a misery profusion based on cerebral blood flow studies these procedure should still be offered. Jacques, can I please ask you to comment on that?

- Yes certainly, first of all that we all use the terms low-flow and high-flow bypass. It's really can be a misnomer. For example, certain STA can carry very significant flow up 250 CC per minutes. So, it's important to not be married to those terms and maybe think more in terms of low capacitance versus high capacitance. So, STA yes, generally is low-flow but not always so. Vein graft generally is high flow, but not always so. It all is a matter of supply and demand. So, I think it's an important distinction and the general principle would be to supply whatever the specific patient needs, not more, not less. And that's why the categorization needs to have a little nuance in it.

- And do you still offer the STA-MCA procedure to your patients who have carotid occlusion and what are your indications despite the recent studies?

- Yes, costs clearly is a very important study that we all should take into account. It's important to realize it's not published yet. So, the full analysis needs to await the paper printer it's been presented as abstracts. There is no difference in the design of the study between surgery and the best medical treatment. Clearly due to the much improved natural history of the medical arm due to the use of Statins. It is assumed if they have half the rate of strokes that they expected them to have. Surgery was still effective, the side effects, the complication rate of surgery were similar to the 1985 study. But it is interesting to note as per Dr. Greg grabbed the a copy that if the surgical side effects had been 8%, instead of the 15%, that would have been a fave benefit in favor of service. So, I do use still selectively STA-MCA Bypass for selected patients who have absolutely ongoing, probably daily TIA that may or may not have been costs handed it's because average cost candidate, I believe waited about 72 days to randomization. I, we all have anecdotal and small series cases of patient successes with properly selected patients were in extremists in spite of maximum medical therapy.

- Thank you. And for replacement for giant aneurysms. We talked about that then the other issue for indications is the donor vessel. The STA for example, for a low flow bypass is one millimeter to threshold for me, it has been technically very challenging to do a bypass with an STA that's smaller and its diameter than one millimeter. What are your thoughts on that?

- Certainly it gets harder and harder in a, probably in an exponential manner. The smaller the vessel is it is certainly possible to bypass to a recipient that is less than one millimeter surgeons who do pediatric cases. Pediatric Moyamoya are quite familiar with this. I've certainly bypassed about 0.7 millimeter. We will talk about technique a little later. I will then save the interrupted technique for 0.7 or 0.8 millimeters. Otherwise I favor the running technique. That would be my, my stance with that.

- Thank you. And patients who have had previous history of craniotomy for hematoma evacuation, or other procedures may have their STA sacrifice. And that not, that is not necessarily contraindication for STA-MCA Bypass because you can use a short radio vein into a position graph at the remaining residual stump of the STA Isn't that correct Jacques?

- Agreed, agreed absolutely.

- Thank you. And what are your indications for low flow versus high flow bypass? I know you touched upon that. It is not STA versus interposition radiograph it's about the capacity. But could you touch upon, when do you feel like when you would go an STA-MCA versus a radial interposition graft please?

- Yeah, so we all need general rules to abide the buy, but of course never to forget, to break our own rules in exceptional cases. But I think the general rules that make sense is you want to low flow bypass for all ischemic cases. Clearly it would be a major mistake. And I've certainly learned that early in my experience to give a high flow bypass for an ischemic patients. Absolutely no need to do that. You just want to augment, you don't want to replace the entire carotid three. You want to give low flow when you have peripheral branch replacement surgery. Let's say a distal MCA aneurysm all you want is replaced that branch, you don't need much a low, low so-called low flow STA Bypass would be very sufficient. High flow bypass certainly in somebody who fails that automatically their balloon test occlusion. When you're considering a carotid three replacement for a giant aneurysm, you don't want to risk not have enough flow in the critical, very operative period and have a major stroke. So, those are the cases where a high flow is warranted with radial or venous graft bypass.

- Thank you. So, what are the typical preoperative imaging for a patient who's considered for STA-MCA Bypass, obviously an Arteriogram or a CT angiogram to assess the size of the STA and its location. Occasionally there are meningeal collaterals that come from the meninges at the side of the craniotomy that are already feeding the brain and you do not want to place those at risk, especially for a patient who has had previous surgery. And the Dural was that there is sort of a dural venous sinuses in progress. And I would call Ischemia if that piece of dural is, is interrupted and all of this rollout aneurysm, especially around cases, MoyaMoya disease, obviously a good cerebral blood flow studies, such as a parch SPECT scan with a Dymocks challenge may be very reasonable, especially on those select patients that are very much suffering from Missouri perfusion. And MRI or MRA in several cases to relax acute strokes and prevent an acute surgery. If the patient has had a sighted sizable stroke. Any other specific preoperative imaging studies Jacques?

- No, those are, those are pretty much the complete list. That list I would warn our listeners who have are not too familiar with this procedure, that it is very easy to get discouraged by the so-called small size STA on an angiogram. We need to remember the STA we see on an angiogram is in the skin. And very often it looks small, but you will be surprised that surgery when you free it up from its surrounding anchoring tissue, how much more it opens up. So, do not discount an STA as an inappropriate donor until you've actually dissected it during surgery. That's the date and ideally measured flow in it as I will probably show later in the video.

- Thank you. So, let's jump into the technical nuances before our video and here during the surgery, especially right when the patient goes to sleep and intubated hyperventilation has to be strictly avoided, especially in children with Moyamoya disease. Alpha Adrenergic and energetic agents or anything that causes vasoconstriction industry rule three must be at all times avoided. PCo2 as to be strictly kept to 35 to 40 and not less. And I cannot really emphasize this more because we have had a complication of a patient who was hyperventilated and did have a stroke most likely related to hyperventilation. These patients, surgical flow is really compromised. And anything else that would constrict their vessels would really decompensate and their cerebral circulation and cultural Ischemia.

- Obviously cerebral scalp and filtration with epinephrin at the site of STA avoided intraoperative EEG and evoke potentials. Do you do that routinely Jacques or not?

- Yes, yes I do. As you well know, NEP stand to be a little more sensitive than SSEP for ischemia. I do avoid barbiturates unless it's an unexpectedly prolonged temporary occlusion, particularly in aneurysms, I do use hypothermia modest hypothermia 34 or 35 degrees. I do want the patients to wake up as soon as possible, which is the reason why I do not use barbiturates routinely.

- Thank you. Linear incision over STA is ideal. If you have one that is linear and is around about six centimeter above the XR, the 28 is where you would ideally like to have your craniotomy. So, if you have a linear STA, especially in the Posterior branch of it, it may be nice to have the incision correspond to the area where you harvest St over it. Otherwise you have to do a flap and dissect STA from on your knees to flat, which can be slightly more challenging. And we're gonna go ahead through both of those techniques momentarily. Ideally you would like to manipulate the STA as least as possible and leave the soft tissue flap around it. To craniotomy, usually six centimeter above the EAC external auditory meatus. However, newer navigation we're using CT angiogram may be used to find it and three and four on the cortex and make your craniotomy much smaller. And there may be an advantage. There's been reports that even doing such procedures through a small burr hole, if you have a CT angiogram that can adequately demonstrate the size of your recipient vessel. So, when you opened the door to avoid meningeal collateral vessels, or we talked about the size of the STA 0.7, you know, usually pre the smallest possible. For us we have sort of tried to use a one millimeter because the occlusion rates could be slightly higher if the vessel of the donor is less than one millimeter or the recipient is less than one millimeter. And we try to find a cortical vessel, right perpendicular to the surgeon on the surface of the brain in order to make the sewing of anastomosis easier. Obviously using Heparinized and saline is critical for the STA and possibly for the recipient cortical vessel. Papaverine is really an amazing solution to getting the vessel sort of become more ideal and mitigate the spasm on both the STA and the recipient vessel. And therefore, the moment we, dissect the a cortical vessel, we'll go ahead and leave a papaverine soaked gelform over the vessel for a few minutes while we are getting the STA prepared in order to get the vessel diameter as large as possible, increasing the blood pressure before tranquil occlusion is a very good idea to, again decrease the risk of ischemia. And the arteriotomy length over the quarter co-recipient vessel should be usually tailored to the diameter of the fish mouth STA. Any other pacy Jacques?

- No, I, I pretty much agree with everything you said in this slide. Again, if we can avoid touching the donor in any way by using that cuff, that one centimeter cuff, it is very important.

- Thank you. And when we do the anastomosis, which is the most critical part of this operation, you have to be patient. You have to be careful and any really small mistake and trying to do it quickly without paying attention to the detail of not catching the back wall of the vessel on the other side would cause immediate occlusion at the most anastomotic site. So, at 10 millimeter interrupted monofilament suture is what we have been using. I know you use a running 10-O monofilament suture, and I would love to see your technique. I think the running one is faster and more efficient. And I will review why mine preferences for an interrupted suture in a second when we reviewed the video. Dural edges could be inverted before you close the dural and specular has mentioned about that in order to preform encephalodulosynangyosis in addition to the anastomosis. Positive flow, as you know, as much as plus 25 to 50 can be detected immediately and can even increase as to graft matures. Go ahead Jacques, please.

- No, no, that's, that's fine. I too will show in the video, the various reasons for interrupted versus running. If your fish mouth enough, there is no real danger of causing stenosis with the running techniques and which is the main detractor to some people why not use running. I clearly it is faster and I, I very much prefer it unless the vessel is really tiny 0.7 or 0.8 millimeters. I have not, I have measured slows a higher than 50 CC per minute in the STA at the completion as I said, and again, I'll demonstrate in the video, how do we use flow numbers to help us one way or another.

- Thank you. Let's briefly go over some illustrations. The patient is placed on a Mayfield health clamp as usual. Most folks talk about turning the head 45 degrees. I tried to do less because I think the angle here would really help the blood to flow out of our surgical field. As you can see here again, the angle of the head would allow the blood shorter use the gravity as a way to keep the field clear. We use a Handheld Doppler Probes to find the artery and which branch is more effective. And obviously the preoperative angiogram or CT can help you. And lenient incision would be ideal over the branch of this STA, especially the posterior branch. And that would be the same incision for craniotomy. However, if the ant the frontal branch is more dominant then you may have to do a curvilinear incision and resect the branch in thoroughly, although that's not always the case. If it is superior enough, and you have CT Neuronavigation that shows a large cortical that's underneath, you may use that. But more often, if the frontal branch is more difficult, you have to do a you have to dissect it underneath the flap. Isn't that correct Jacques?

- Yes, you do and sometimes frankly it is easier even though cosmetically not much pleasing to actually proceed with the incision on top off the frontal branch avoiding of course, the frotalis branch of the facial nerve. If you're having difficulty doing it through a skin flap from underneath, you have to be very careful that there are instances of skin edge necrosis if you end up jeopardizing the skin edges downstream from your dissection, when you end up taking both branches. So, meticulous technique is important here.

- Thank you. You can use the mixter dissector and sort of dissect from underneath the flap and then cut over it. As you can see in this illustration that will really make the work efficient in terms of dissecting way underneath. And then sort of cutting all the way along the subcutaneous tissues while the spreader is protecting the vessel. I think you're gonna have a nice nuance of by using the Colorado needle. And I look forward to seeing that during your video, Jacques. We use this vessel loop to lift up the vessel to cut underneath it, to protect it. We do try to leave the soft tissue around the vessel, the cuff. And again, we show it in the video very thoroughly craniotomy is using, is a completed and the STA disconnected. Obviously a temporary clip is placed at each fruit, and then it's fish mouth. This craniotomy size can be further minimized using navigation and CTA. And this craniotomy uses six centimeter above the external auditory meatus. go ahead, Jacques.

- I agree, I agree with that. As you show here, here is a case of an interrupted STA but clearly keeping it insight to when possible makes more sense to preserve in that vessel. If it has enough redundancy and we keep the flow in it, do the craniotomy open the dural. Identify the recipient and then at the last minute divide and decide what length is appropriate.

- Thank you. And then obviously the archeotomy completed. We try to do it at least, you know, a seven to seven millimeter to even 10 millimeters or centimeter obviously depends on the size of your STA after it's fish mouthed, you wanna measure the size and then complete your arteriotomy. It is important when you dissect the cortical vessel that there are small contributory to underneath it. And you have to try to dissect those and quite violate them. Otherwise you will have continuous oozing in your field, and that makes life very difficult. Go ahead, Jacques.

- I agree. One trick is to actually initiate the arteriotomy with the single 27 gauge needles passing in the wall into the lumen that will allow the tip of your visa blade or stylistic blade, or even scissors to initiate the arteriotomy. I am also a proponent of an arteriotomy rather than an arterioctomy. You people may see that in the literature. Some people excise an ellipse of wall here. I don't like to decrease the caliber of an already small recipient artery. That's why I do not favor excising an ellipse of wall.

- Yeah, I agree with that completely. And then again, the heal after the vessels fish mouth, the donor is sewn first and then there are the tow of the graft is completed. We use a piece of glove latex free just to create a contrast from the brain in order to start the anastomosis. We'll have jacques comments more for his technique on his videos. And as you can see, interrupted technique and completion of the, the anastomosis. It is important not to handle, especially the edges of the recipient vessel wall. It is okay because the STA usual thicker to handle the STA edges, but really at all costs avoid handling the edge of the recipient vessel. As you can see, the needle is tried, used, sorta handle the edge of the vessel and go through it and really completed a wide edge arterial anastomosis. Let's go ahead and I'll present a case and let Jacques to proceed with his two other cases. This is a 61 year old female with a history of a left carotid occlusion, Jacques and multiple episodes of speech difficulty and dizziness. I mean, this lady had TIA from left hemisphere about four or five times a day. And the studies revealed a left carotid occlusion as you can see on this CT angiogram, you can see there's no carotid artery on the left side. And it's super both for pet study with DIMA challenge revealed some misery perfusion in the area of the left frontal lobe. So, I felt this is a very good candidate with multiple, you know, TIA a day and evidence of the left carotid occlusion to proceed with STA-MCA Bypass. So, I'll show you guys in this case, how the vessel was harvested. Again, this is on the left side. You can see the areas on the left over here, and a linear incision was completed. And we start distally approximately I know some people do approximately two distally because the vessel is larger there. And again, being very careful when you dissect the vessel to prevent manipulating it. Go ahead, Jacques I'll let you comment on this, please.

- Absolutely, I start also distally to approximately, you know, if particularly, if you are having an injury of the vessel, you can still salvage it. If it is distal, will you have enough length to salvage that you always want to dissect, as you're doing parallel to the vessel, whenever possible, you don't want shearing forces acting on the STA. If we leave half a centimeter on each side of the vessel, that'll give us a full centimeter cuff. And again, people need to be aware that the, these STA as are often torturous snake like do not extrapolate always a straight line. So you have to lift this in and subcutaneous tissue too, before you incise it it's very easy to injure it. If it's still anchored to the under lying layer. Again, a good assessment of the preop angiogram helps you prevent that.

- Yeah. And as you can see here, we're using the sorta this spreader, the mixter dissector sorta. Keeping the subcutaneous tissues above the vessel as you cut over it. I think that technique really helps make you more efficient by dissecting first about a centimeter or two lifting it away from the vessel. As you can see Jacques and sorta dissecting over, it includes the surgical efficiency at least for me. There tributaries from their STA has to be carefully coagulated and cut. And again, we can't evolve these because it could injure the mother branch of this TIA. This is the, I believe one of the larger pituitaries that we're gonna go ahead and tie off and then subsequently severe. Jacques what do you use as an interposition graft if the STA is not available but the stump of it is still a present?

- The radial artery is, is really the best caliber match for this. The veins are usually too large for it, even if you use the distal lower leg vein, saphenous vein.

- Okay, and I think in this case, we're proceeding to dissect the vessel from underneath its trunk. And this is usually when it can be difficult because you see some of the Tributaries and you usually try to cut down without knowing it and bleeding occurs and try to be patient and not to coagulate without knowing if you're quietly in the trunk. And here is really a sizeable STA. And as you very well mentioned, the moment you release it from its soft tissues, the vessel looks larger than you expect it, don't you think?

- Yes. It's a, it's almost always like that, yes.

- And you can see some Papaverine that we have soaked over the carotenoids and we place it on the vessel. And I think that's the method we really have used for dissecting the vessel. As Jacques you mentioned, we try not to severe the vessel or cut it until the craniotomy and dural is open. So, we put a piece of plastic around the vessel and put sutures around this plastic and use those sutures as a retraction on the vessel and the plastic would protect the vessel. What method do you use to protect your vessel during the craniotomy?

- I use something very similar. I use a Telfa. Telfa is my workhorse for retraction and brain protection. I soak it in papaverine, I wrapped the vessel as you are. And I put a vessel loops around the Telfa. So, the Telfa probably has a little more thickness than the plastic. So, there is some cushioning effect. Of course you want to make sure you don't retract so hard that you're occluding the auditory and defeating the purpose of doing this.

- And then at this time, I think we are a teen golf incision, and that's the temporalis muscle that's being cut. And usually you can open the muscle in a T shaped or in a cruise shaped fashion if necessary, and then complete the craniotomy and performed anastomosis. So, I'm gonna not show the anastomosis on this video, actually proceed with the next video, which is really completing the, the anastomosis. However, this is the video of the patient that shows the flap that is curvilinear and the STA is being dissected from underneath. So, before we proceed with this one, I'll go ahead and show the case information. For the first case as you can see, this was an STA that was ultimately anastomose right here with exuberant, really flow to the ipsilateral MCA. And this is a postoperative one angiogram. So as you can see, these anastomosis provide an amazing flow to compromise MCA circulation. And this lady actually had no, none of her TIA did they after surgery. And two years later continues to have more flow to have hemisphere from the STA. So, the one that I wanna show the anastomosis is a 61 year old male with a history of bilateral carotid occlusions, and multiple strokes. And as you can see on the CT, there is no carotid arteries. This is a CT angiogram that's been reconstructed on the skull bone, and it really shows a large frontal branch. I think these show very clearly which branch would be effective. This is the position in the operating room where the clamp is placed and the credibility or incision. And the STA was really more where was in theory or along the line that you can see. We use the CT angiogram stealth to identify this large cortical vessel. And the surgical video which as you can see here, the flap has been reflected anteriorly and in fairly, and the STA is being removed from underneath the flap. Do you have any Pearls Jacques for dissecting that STA from underneath the flat, please?

- It can be difficult as the skin flap is, is bent as it will occlude it. So the key is to really lift it in a way that it does not occlude the flow to see it. And I use a 15 blade to cut the Galea half a centimeter on each side, because you cannot, you often cannot see it as it is totally attenuated by the tissue tension. So, you release the flap on and off as you advance along the vessel. That's really the only, the only tip I can give.

- Okay, and as you can see here, that's the best STA that's been dissected off the flap with thick anteriorly, and that's where the protection is left with the plastic you use Telfa. And then we complete the craniotomy. As you can see here and proceed with the anastomosis, the craniotomy doesn't have to be large. Do you have a specific size for it Jacques?

- Usually three to three and a half centimeter epicenter at the six centimeter point that you mentioned earlier works very well as it catches the district Sylvian fissure and the temporal and frontal cortex.

- Thank you. And sometimes if the brain is tense, I try to open one of the anterior sorta fissures next to Sylvian fissure, to release some CSF, as you just saw in order to help with cerebral decompression. And here is really trying to make the distal part of the vessel naked to prepare it for the anastomosis. I don't have any special, you know, pearls about it. It's just takes patients in my opinion. And you do wanna have a good length of the vessel naked, and you don't wanna have any soft tissue that would interfere with your anastomosis. This is the fish-mouthing technique that would try to increase the size and the diameter of the anastomosis to decrease the risk of occlusion. Temporary clips have been placed, and a piece of plastic has been inserted underneath the cortical vessel. Here you can see a very healthy vessel, especially after some gelfoam soaked with papaverine has placed on the vessel. It's amazing how they can expand and make our life easier. Again, this we measure how much we fish-mouth STA and I know you use a needle. Here is 11 blade to start the anastomosis. This is a series of sectors or micro scissors that can be used to dissect the vessel and perform the arteriotomy. I like this micro scissors because they really give you a lot of control in order to cut the vessel and keep the edges as clean as possible. Obviously you wanna remove any material that would interfere with your anastomosis from the edge of the arteriotomy. Inject heparin and flush both the STA with heparin and again, complete first the heal off the anastomosis first. Usually you have to be on under the highest magnification of the operating microscope. Isn't that correct Jacques?.

- Yes, certainly for this part. And I may make another comment too, maybe because we're were very magnified. You're the STA the way you have it is making a heparin turn. I guess you have enough redundancy but it's so important to lie the STA in the natural way that it wants to lie in to avoid kinking once floor is established. So now it's looking a lot better. So obviously you have quite a bit of redundancy in it and obviously you want the shortest possible STA graft since resistance is totally proportional to linear length of a vessel. So you don't want, you want a shortest possible graph that gives you enough redundancy to work on both sides of the anastomosis.

- And no one can emphasize that pal more than in the morning, I guess enough. And I really appreciate you bringing that up. You want your estate to be very relaxed and give you ability to go from side to side in order to complete your anastomosis. Here is the interrupted technique. And one of the reasons I like to interrupt the technique, it gives you more control over the edges where you were completing your suturing. I think again, the running technique is very efficient. It works beautifully our preference has really been because it gives you so much control on every stitch. And if in the middle of your anastomosis, this is again, the final result. As you can see right there at the middle, if you have a problem, it would, you have to review your anastomosis often. And here is the ICG showing a nice flow through the STA and the cortical vessel without any evidence of stenosis there and the closure, obviously you want the dural to be loose and you don't want it to be under tension as Jacques very well mentioned during any time your closing your craniotomy.

- So I will add now some different concepts that compared to what we've already covered. Really, to discuss more about general aspects of bypass surgery, and then special cases about STA-MCA. Again, in deference to our great anatomical teacher, R.Rotan, who has taught many of us to categorize various structures. And to remember them, he, as you know, he has a rule of three, for example, for foster structures. So I thought, I noticed that you can approach bypass surgery with the rules of threes. So let's talk about those rules of three. There are three components to a bypass, the planning, the execution, and the verification. the planning has three components. What is the purpose of the bypass? What is, what are you going to do with the aneurysm? If it's for an aneurysm, the purpose itself has three components really pleasing. So augmenting flow, or just protecting some part of the territory. The type of the bypass is it insight meanings generally intracranial to intracranial? Is it short graft, or is it a long graph? The Aneurysm, are we gonna trap it? We're gonna partially three shifts, or we're gonna do nothing with it at all. Then comes the Execution of the bypass. And again, there will be, say components to that. What is the donor? What is the recipient? And what is the graft If there is one the donor. Are we gonna go from afferent vessel? Are we gonna go from extra cranium or intracranial? Your Recipient again, three categories. Are we gonna shoot your into the efferent vessel? The main one, are we gonna shoot you into a branch of the Efferent, or are we gonna go very distant where the pathologist? And lastly, the third component of the execution is the Graft itself. Generally it ends up being an STA as were discussing here today, Zane graphs, saphenous vein, or radial artery graft. And finally the third component of the execution is a very important, and it's generally neglected. And that is the Verification of your bypass. How, do we verify what we've just done? We've can visualize it with ICG, with operative DSA angiography, or with Doppler. We can measure flow, which is certainly my bias is to try to be quantitative and slow measure. We should measure before we do the bypass we should measure after the anastomosis is completed. And finally, after the bypass, after you've released all temperate clips. And this applies again, to Ishmania, to aneurysms. Lastly, in verification, if you uncover complications, you need to reverse them. And again, there is systematic way of going about that is addressing the donor vessel, the recipient vessel or the anastomosis itself. Again, that's kind of beyond what today, but this is a generally out I wanted to convey that goes through my mind every time I approach a bypass operation or email any of this. So, replacement bypass is generally a permanent bypass. Remember, we are substituting native afferent flow. Argumentative bypass with simply subsidizing the difference between the Native Afferent Flow and Collateral Flow. And that's generally what we're doing in ischimia bypasses. It is with substituting the degree of hypoperfusion. The protective bypass much are used is temporary bypass. So, some people get confused about where to categorize a certain bypass. I think this a three by two table helps organize our thoughts. If we think of the type of the donor we're using is it from intracranial? Is it a local, extra cranial, such as STA or occipital artery, or is it a distant extra cranium, common carotid, external carotid, ICA vertebral artery. If we're doing one anastomosis or more than one, you can categorize all known bypasses. This is I'm not gonna go in detail over those, but you can visualize these would be insight to bypasses. These would be short graft bypasses. The STA-MCA or occipital artery to PICA bypass would fit in this category. And lastly, the long grafts would fit in here and G stands for graft for intervening graft. And my final slide, which were relate to some of the things I will discuss on the video from a recent chapter I've written earlier this year, not to confuse you with any complicated math. This is really quite simple high school algebra. I wanted to show what links and what cross sectional area gains do we get by fish melting assessment. We're gonna compare a straight cut from a donor end to side, to a recipient. We're gonna compare a 45 degree slant casing the donor or the fish mouth single side fish mouth, assuming the fish, the fish mouths here equal in length to the flatten diameter. If you work out the math again, very simple. This construct is a huge advantage. Why? Because compared to this one, it is four times the cross sectional area only at the cost of twice the length of the arteriotomy. Again, comparing this is This is the length of the arteriotomy here. This is the length of the arteriotomy here. So you double the length, but you gain four times the cross section area. Therefore, if you are like me and you use a running technique, you really don't have to worry about stenosis. And if knows, you're still four times more than the straight and side 90 degrees bypass. I'd like to move on to case one. This is a 32 year old ironically nurse in a stroke unit, a neuro nurse who developed right arm and speech TIA Weiss. By the time she came to me, you can visualize on her angiogram. She has early Moyamoya disease with occlusive, distal, ICA and early M1 A1 disease. Here is her left side. It's an eclectic cervical left ICA was really very severe hypoperfusion of her left hemisphere with a typical Moyamoya vessels and the presence of STA arteries, anterior and posterior branch. And this is her left vertebral injection showing an attempt at collateralization. I proceeded with, again, the physiologic studies we tend, I like to prefer, I prefer to use generally two modalities, the SPECT scan of the brain with and without Diamox, but a word of caution. If somebody is really very brittle, Diamox can certainly induce a stroke. So you have to be very careful when you use it. I thought in her, she was not that bad. She was not having TIAs daily, for example. So, we did use Dymocks and it did show the 30 to 40% decreased perfusion compared to the opposite side and CO2 transcranial Doppler visual motor reactivity study, which our stroke neurologist does also show decreased bilaterally. So our VMR is impaired bilaterally. She is a perfect candidate for an left STA-MCA bypass tracing of her branches at surgery. It is a measurement of the actual flow. This is not Doppler this is CC full minute quantitative flow of her donor. We are getting, this is a so-called cut flow. We are measuring the flow that maximally can be given by this STA after it's been released from the skin. Now we're measuring her recipient flow before we've done anything you can see it's only 3.1 CC per minute clearly hypoperfused. Now after completion of the end to side bypass, we are measuring much better numbers. Now she has total flow of 64 CC per minute, which is divided retro gravely, and empty gravely into the recipient. Again, a word of caution. These two numbers don't always add up. They should add up, but generally a gentle pink of the vessel as you're measuring may not give you the perfect math, but these two numbers should generally add up to the total STA flow you've provided. Which takes us to the next slide, which is our post-op STA excellent patency of this anastomosis. And then here it is on the source images, good flow and then I brought her in a few weeks later to do her right side, and that's after doing a right side STA-MCA Bypass. You can see the mirror image bone flaps, and this is her left side again, angiogram. And she has done extremely well continues to work as a nurse in a stock in it. And if I could move on to her video, that is the recipient vessel, a very similar technique to harvesting the STA as Aaron has described again, here is a baseline measurement. Get your numbers early on after you avoid all the kinks, you register those numbers, you create a naked area for the temporary clip and for measurement. Then you tailor your graft to the lengths that you need. This is the anterior STA branch, which is not needed. So I sacrificed it. Here is our background material. And a very useful device is the SPECTS micro suction device. This is kind of your third hand to suck all the deputies and blood, and then irrigation fluid to try to keep your field dry and clean, By the way, all the movements you see in the video of course are the mouthpiece of the microscope. Again, I am a convert to the mouthpiece and it does allow you to move your hands, your mouth, the microscope all in unison, instead of interrupting the flow of work to handle the microscope. So we're cleaning very important to clean the distal end. And again, a good assistant can provide you with excellent counter traction and hid we ought to before we fish mouth. And then we're gonna in this case, anger at 45 degree. To again, we have to thank Alexi Corral in the first couple of decades of the 20th century to have shown us the various techniques in vessel anastomosis mostly for transplant surgery, but a lot of that they can instead he described, we all use today in those various principles. I cannot overemphasize how important it is to clean. When you start suturing, particularly running technique. If you have redundant fascia, it will slow you down. It will prolong ischemia, there is a cup flow we're measuring occasionally I use elastic tubing to provide an angle approach to irrigating. You see, we can irrigate into the recipient. Here is a 27 gauge needle, which I should show the briefly earlier, which I made the entry into the recipient. And I do anchor the heel first, like Aaron does. But probably unlike some other surgeons will have a preference of anchoring both the heel and the toe. I only anchor the heel. It gives me better viewing of the artery of the anastomosis on half a wall. Of course, that means you do have to have measured appropriately and the donor and the recipient edges so they're equal. You want to run the suture in a way it's like a spiral on a, on a binder. Then you tighten them one by one hand over hand technique, pulling on the part of the loop that links you to the preceding loop. You have I generally have to use of course, diamond dusted forceps, because anything that is very jagged and sharp can, can rupture this suture. It is a 10-O BV or V 75 dash three is the name of the needle. It is a three eight of a circle, not half a circle. I find that much easier to turn your wrist and run into the anastomosis. So you complete half a wall. You flip over, make sure you've not caught the other edge. Make sure there is no debris. And now you do the second half in an identical manner. And this is your chance to correct any deficiencies. Of course, near the APCs is where the weakness is, where leaks can happen. So, I always put the stitches and the pin closer together. You know, the APCs little further apart near the mid segment. At completion, remove the distal clip first. And then the approximately and here is an important point. Measure your flow in the recipient before you've opened your STA this way you isolate a problem if there is one. If you're stenosed in the recipient, then release the donor and you make your measurement and you've seen the closure. And I think I'll move on to the next slide, next case and the video of that case. And again, I'm not, I was not going to show any slides. It's a 53 year old man with a carotid artery occlusion that is similar to Aaron's case. And in home we're doing an STA-MCA Bypass similar to work repeated TIA and we've doing, I believe a left STA. Now again, in the opening slightly different techniques than what Aaron described, yes it's of course you have to lift this up from the STA. But what I find very useful and efficient is use of the Colorado needle to both cut and coagulate. As you move along, you see here is a tiny bleeder. You don't have to change an instrument. You coagulate and you keep going. Of course, keep it at a low current don't don't coagulate too close. Here is I'm showing how the STA could be left inside too. And here is creating a naked segment to both apply a temporary clip and make a measurement of blood flow. Now, here, we're going to divide this parietal branch fill it with Heparinized saline. Here is 10 font that is soaking in papaverine is going to wrap this and we are going to flip it over excellent flow. I measured it to be 28 CC per minute. This is the cup flow of this STA. In this case, we flipped it over covered it with a telfa. And then the opening of the muscle you noticed I did not do a tea cut I did the first cut. I do believe you save more muscles from the motivation and really an ugly cosmetic appearance, a single bird hole. And then you turn your bone flap in a traditional manner. You tack your dural you are careful about meningeal vessels. Escalate that dural opening, and then I'm measuring the distance that I need. Here is a, the peeling technique of the arachnoid. Sometimes you use sharp, sometimes you use the feeling technique between the four steps. I identified a nice recipient. There will be tiny branches coming out from it, and we are going to sacrifice them. Now, here is another technique. Often, the brain sinks in it's nice to elevate that recipient over gelform and the background, it brings it closer to you. Here is again, the SPECTS micro suction. So, there is a cleaning of the distal STA and we are going to mark in this case with ink, with the ink to show better, the edges of the arteriotomy. We have fish mouth did. Sometimes it's helpful to round the sharp corner. It is the flow of the recipient. It's negative two CC per minute. Again, clearly hypoperfused so we proceed again, same technique. And here is a needle, 27 gauge needle. I bent it a little bit. I hook it to a transducer and I'm measuring perfusion pressure. The recipient in this case, 57 millimeter mercury, this tiny hole is in a good initiation point to the beaver blade, which will then allow a good arteriotomy, clean all the blood. It is a needle, a V 75 dash three. You have to load it. The nurse cannot really load it efficiently. You have to load it under the microscope. We're going to the heel. So out in, on the recipient. And then of course, in out on the donor at the end, we are going to secure this. And another question is, how long do you make that suture? About eight times the length of the arteriotomy. It ends up being about two and a half inches for an STA-MCA Bypass. So I secure this notice. I guess we have to go to the next half of the video Aaron. And so we are now suturing the heel end of the anastomosis. And now we are beginning the back wall. Again, you notice that the toe end of the donor is free floating to improve really the visualization. As you are running the suture from away from you to near you. You leave those loops a little bit loose, so you can grab them at the completion of half of the anastomosis. And as you come to the vertex, I'm sorry to the toe end turn your hand towards yourself. So, really the loops are parallel. Remember, it's really an end lips It's not a straight line. Now we're doing hand over hand tightening traction, counter traction. And then after the last loop is tightened down on the vessel wall, you suture it, you tie it to itself. When that is completed, you will flip the vessel over to do the other half of the anastomosis. It is a good idea to leave a little length of it, to be able to handle it that suture. I'm inspecting the inside of the Norman to make sure there are no irregularities. This is a time to fix them. Now we're starting the second walls. Remember, I'm sorry. Notice that I am very close in my first stage to the other stage. You don't want the leak in between those two at the apex. Again, you use a curved needle holder. That's my preference because it gives me one extra degree of freedom to apply the needle. Then I run it with a simple four steps because it's simply quicker. You hold the forceps to hold the needle. And generally you want to hold it at the one third, two third point along its curvature. Again, notice this is not half a circle needle. This is three eight of a circle. It's less than half a circle. I think it's easier to handle under high magnification, make sure the loops don't interlock. And as you near the end, you may have to apply the suture backhanded, to really be parallel to the incision line. Again, we're going to do hand over hand tightening of those loops and you are going to suture it either to itself or to the three end of the first suture in the first half of the world. And it is always comforting when you're going to release the temporary clips to see a little leak. If you see nothing, I'm actually worried when I see no leak whatsoever, the little leak is comforting that it's not occluded. Notice I'm doing the hemostasis before I release STA I measure the flow, it's the same as when we started. Now we released STA and we remeasure flow and look, we got 35 CC permanent it's even slightly higher than the cap flow we measured before. And now the recipient is getting 18 CC retrograde and six CC integrates clearly much better than what we started with. And notice the LF foot, what is called LF foot design each, where that you get that is absolutely no chance of stenosis. If you try to strive for this geometric configuration, we put the little Surgicell on the donor and try to bridge a little bit that your leaflets, that is your Urogyn, that is your bone flap with a tunnel through it, and then make sure you don't occlude the STA with your muscle closure when you close it. And I think that's the end of my presentation, Aaron. Thank you.

- Thank you, Jacques. This was really a technically superb operation. I personally enjoyed watching this video. I thought we'll finish with some basic, you know, questions that folks may have in terms of how to handle post operative care of these patients. And here's our previous presentation. So we'll jump to the end of it if you don't mind, and, so regarding a postoperative care of these patients that's has always been a interesting concepts for us and I'm gonna try to get myself there. Here's the postoperative management, obviously normal tension afterwards. You wanna avoid hypertension to avoid the leakage around the anastomotic site, and also avoid hypotension after surgery because he would cause graft occlusion. We typically place the patients on an aspirin after surgery. We try to restart her Plavix or Coumadin as soon as possible within, within the first four or five days, since these patients have been on them for a long time, usually and we use a daily Doppler investigation on the STA through this skin. And it is very interesting that at least temporary neurological worsening on these patients who are very much compromised on their cerebral perfusion is not uncommon after surgery. Isn't that correct Jacques?

- Yes. It's actually quite, quite an interesting phenomenon. There could be of course, hypoperfusion causing worsening. And as you well know that is a hypoperfusion syndrome, not too dissimilar from the post carotid and penectomy hypoperfusion syndrome. Now, unfortunately in several of the papers that have addressed this, it's not always a very strong correlate to patients who have had hypoperfusion have not necessarily had the highest Interoperative flow measurements that as I was alluding to earlier. So there is still a little bit of a mystery as to which patient might develop hypoperfusion worsening. in addition Aaron, I'm not sure if you meant Coumadin earlier when you said you restart Coumadin four or five days, post-op, I'm not sure if you meant Plavix aspirin. Yes, of course. Aspirin for three or four ischemia cases. There is no need interrupted. I keep it a pre op inter op post-op. I would not necessarily start Coumadin sort of tweak or stop.

- Yeah, I agree. I think for Coumadin we have to be more conservative because of its complication. I think for Coumadin is a weak Plavix, maybe four or five days, five days Is that a reasonable guideline or not?

- Yeah, I don't have problem with five days yes of anti-platelets yes.

- Okay, thank you for correcting that. How about if, if I do an angiogram next day and the graph is occluded, do you think I should take the patient back Jacques?

- It all depends what the basis for doing the surgery. If frankly it was a marginal indication where let's say an indirect anastomosis for a Moyamoya is, would have been acceptable? I probably wouldn't, but generally an acutely accrued to the graph. If we are being honest with ourselves and we're doing the surgeries for the appropriate indications, it means we've not achieved the goals. We go back to the OR and try to figure out what is going on and isolate the problem.

- Okay, I appreciate that. And, I think you briefly mentioned these indications for low flow versus high flow. I think low flow bypass for ischemia. We wanna definitely avoid high flow bypass for ischemia and really high full both passes for acute occlusion for a giant aneurysm or really occlude occlusion of a large vessel in the brain. That's those are really clear indications for a bypass. What's the future Jacques is STA-MCA gonna continue to stay for Moyamoya and giant aneurysms? Or do you think there will be more indications in the future for misery perfusion.

- Not withstanding the cost data. And again, we're talking about it before it's officially published. I think that we remain indications. There are things that we're not measured in cost. How about that nebulous concept of cognitive improvement that are, I have several patients and I'm sure other surgeons do as well. Patients who are running on no carotid flow that simply cannot think clearly. And I bet you asked several micro surgeons who have done this operation. Most patients when the bypass is successful come and tell you, Doc, I can think clearer now. Now, these are executives who are on companies. So, besides stroke prevention, I think the future here is somebody to look at neurocognitive improvements, if any, with the hyper, with the increasing profusion in a carotid occlusion or other forms of ischemic disease. Moyamoya remains the mainstay of that treatment. Giant aneurysms of course, you all know the advent of flow diversion, and that will be a very interesting debate as to how to do that. And that's another whole topic to be discussed probably separately another time. But I have no question that bypass is here to stay, to be expanded in different indications, but clearly needs to be regionalized in the hands of people who do them on a regular basis. It's not, as we all know, it's a very practice dependent operation and we can't just do one or two a year.

- I agree with you completely. And I wanna thank you again Jacques, for your expert opinion on this very interesting topic.

- Thank you Aaron for having me.

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