VCC ICG Talk: Advances in Vascular Microsurgery

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- Hello, ladies and gentlemen, my name is Aaron Cohen from Goodman Campbell Brain and Spine in Indiana University Department of Surgery. I would like to welcome all of you guys this evening for joining us for this presentation, which will be a discussion regarding advances in vascular microsurgery with some emphasis on description of Application of Fluorescence-based, Intra-operative Video Angiography, I'm going to go ahead and call this fluorescence-based angiography from now on as ICG, and that stands for indocyanine green dye. So what is this technology of ICG? Really technically is a method by injecting a dye into the vessels and being able to evaluate by lighting up the vessels through the microscope. In other words, the microscope will only see the dye and will be able to tell us how the vessels look and how if the aneurysm or AVM still there. We'll start with a description of the disclosure, none of which really interferes with the presentation this evening. So what is the basic mechanism of ICG, is we inject the dye into the vessel and the anesthesiologist usually does that and that binds to some of the proteins in the vessel. And eventually as the blood reaches in the brain or the area of the surgery, the light from the microscope causes a special camera to only see the vessels. And that's really an intraoperative angiogram through the microscope only lighting up the vessels and nothing else. So what are the applications? Well treatment of the vascular disease of the brain and spinal cord, where we need to see the vessels very well, such as aneurysms, AVMs and revascularization surgery. So what about aneurysms? Well, if the aneurysm in this clip, we want to make sure the aneurysm isn't obliterated. So there is no dye that goes into it. So that's one mechanism for aneurysms. The other one is we want to make sure the clip doesn't cause any parent vessel compromise. So by doing the intraoperative angiography, you can assure that the vessel or the parent vessel is painted. And we'll kind of go through some of the additional applications of ICG and that includes assurance of the retrograde collaterals if you're doing trapping of the segment of the vessel that is involved with the aneurysm and also you can push the limits of ICG and assess the degree of flow, as you will see in some of the videos momentarily. So how about the AVMs, it's very simple. If you inject a dye and you don't see the dye around the resection cavity, the AVM is gone, and that's a good application for ICG in terms of AVMs. How about bypass, if you see good dye going through the vessels and the bypass graft, that means your graft is painted and it's immediate. It can give you really immediate feedback without waiting for intraoperative angiography. So what are the advantages? Again, there is no interruption of surgical workflow because you're using your own microscope to assess the vessels and do an angiogram. And there is an immediate correction of suboptimal clip results because you can see right away if they clip is compromising the parent vessel and potentially that could decrease the risk of post-operative ischemia. And it has a high temporal spatial resolution because it's very immediate and you can see the flow as it starts through the vessels and so very easy to use and potentially could decrease the need for post-operative angiography. What are the disadvantages of ICG? The structure has to be visible in order for us to assess its, you know, patency or it's compromised through the intra-operative ICG angiogram. And sometimes not all the aneurysm may be visible through the microscope and that can compromise the degree of assessment through the ICG. And more importantly calcifications or thrombi may not allow the camera to see through the vessels and see the dye and therefore that can be a problem and can mistakenly lead the surgeon to believe that the flow is compromised. So let's talk about ICG and again, the Zeiss microscopes that I use are very well-equipped to this device and I have found it personally, very useful. Let's go ahead very quickly and go through some case presentations. Let's talk about first some aneurysms and see how ICG can help. Let's start with a case of a 43 year-old male with an incidental one centimeter left MCA aneurysm. I believe we all agreed this should be treated. I think surgical treatment is mostly indicated as you can see the aneurysm has a relatively broad base and it's on the left side. Let's go ahead and start our surgical video here. This is a left frontotemporal craniotomy as you can see the Sylvian fissure and the brain, and this is the left frontal lobe and left temporal lobe. we start by opening the fissure, using microsurgical techniques as you guys are very familiar with. I have Victor Chen, one of my colleagues, who can communicate with me through my ear. So if you guys have any questions please feel free to use the chat function below the screen and he will let me know through my ear and I'll be happy to answer those questions for you. Do we have any questions, Victor, okay. So here is the aneurysm that's being exposed through the Sylvian fissure. It's a relatively sizable aneurysm, and we use the microsurgical tape holds to go around the aneurysm. In this situation, it will be very preferable if possible, to go along the anterior part of the Sylvian fissure and identify the M1 but unfortunately the M1 was going more medial and therefore our best chance to identify that was by mobilizing the aneurysm more anteriorly and identifying the M1. This is a very simple application or example of using ICG. We try to obtain proximal control of the M1 branch. Again, microdissection allows release of the aneurysm from the surrounding M2 structures. And you will momentarily see that the M1 branch is exposed along the lower portion of the aneurysm. A temporary clip is subsequently placed and we'll go ahead with the clip application. In this situation, we thought a cauter clip would be a reasonable option. The initial clip was used, the second clip was used because we felt the initial clip was a very long one and bots were signaling where the second one would be useful and as you can see here, it shows that the aneurysm is well clipped. Again, this is the ICG and two branches are painted. And if I remove this top clip, the smaller clip, as you will see in a second, the aneurysm fills up. So it tells you that that second clip was really important in ensuring that the clip or the aneurysm was obliterated. Let's go ahead and go to our other case here. This is a post-operative angiogram from the same patient. Again, confirming with obliteration of the aneurysm as was indicated by ICG intraoperatively. Let's talk about a 43 year-old male with a sudden onset of headache and subretinal hemorrhage. This is an interesting case. It's not a traditional saccular aneurysm. Actually, he was diagnosed with a left fusiform A1 aneurysm. This is the CT scan, this is the angiogram. Again, the CT angiogram was somewhat confusing. Subsequent 3D reconstruction of the cerebral angiogram revealed this dilation of the A1 branch proximally. Again, this is internal carotid artery. This is A1 on the left side with a fusiform aneurysm, potentially a dissecting aneurysm in the A2 branch. Let's go ahead and have a look at the surgical video and see how this surgery and ICG helped us make some decisions. Again, this is the left frontotemporal craniotomy. You can see that this is the left optic nerve, right at the tip of my arrow and these are micro scissors, which we're going use in the second to open the arachnoids over the optic nerve. We have an excellent question from one of our colleagues and he's asking if we do actually perform pre-clipping ICG. I do not, remember, if you do a pre-clip in ICG, the dye is going to stay in around 20 minutes and you cannot do an adequate ICG to assess things because everything is going to fail, so we don't do that. Here is, again, the fusiform aneurysm, as you can see at the tip of my arrow, and I'm putting a clip, I think, in this circumstance a permanent clip, because we decided that we're going to go ahead and trap the aneurysm because primary clipping was not possible. This is the section along the distal part of aneurysm, again showing the distal part of A1. And you can see ICG shows that the Heubner is open. That's very important and it shows that A1, more proximally open as you can see here. And the aneurysm is filling as you can see here, but it's very much slow flow. And that was a good indication that this stalled vessels, as you can see here, more distally are filling and so the aneurysm is filling less. It shows that the degree of flow is much less than the aneurysm and the surrounding vessels are painted. And I think that was very important information in terms of knowing that at this juncture, no further intervention was necessary. And again, critical point is that, the surrounding important vessels were painted, this is a postoperative angiogram showing no evidence of stroke on the caudate or the distribution of the Artery of Heubner and again shows complete obliteration of the aneurysm by its spontaneous thrombosis two days after surgery. So again, ICG was not only important to determine patency but it shows regular flow in an aneurysm that we wanted to thrombose spontaneously. Let's talk about another difficult case. This is a 66 year-old female with a sudden onset of severe headache and a questionable subarachnoid hemorrhage. And this really shows a right partially thrombosed, distal MCA aneurysm as you will see in the imaging modalities here. Here you can see the MRI that was performed prior to her transfer to our institution. And you can see this distalled MCA flow void, the CT angiogram clearly shows an aneurysm, very broad-based and a further 3D CT angiogram revealed again, that this aneurysm is very much involved the vessel itself and there's really no clear neck. There is a vessel that goes in and a vessel comes out, and this would be a place where potentially a bypass would be indicated. So let's go ahead and look at the surgical video in this situation before we look at the post-op imaging and here you can see a right-sided approach and you can see, I'm sorry, my video jumped over it a little bit, my apologies. I'm going to go ahead and bring my video to it's appropriate place and we can continue. Do we have any questions meanwhile, while I try to proceed with this case, Victor? Okay, well, this is the end of our last case. So we should get shortly to our next case and actually that was our second case that we just went through. And again, the ICG from our last case, the second case. So here is our case, you can see a right-sided approach and it shows that, can you see the video okay or not yet, Victor? Here we go, we can see the aneurysm was trapped and then you can see that the distal M2 branch is filling, in a second, that actually in this situation that the ICG made sure that the retrograde flow was adequate. And that's how we knew that in this case, we can completely ligate the parent vessel proximal and distal to the aneurysm without any sequelae. So the aneurysm was subsequently opened in this case, and a shorter decompression was completed. And again, you can see that there was really no good neck for us to reconstruct this aneurysm and we turned our temporary clips to actually permanent clips. And again the further dissection shows that if we remove the temporary clip proximally, there is still a live aneurysm. And again, permanent clips were placed and post-operatively, as you can see in the images here, the patient did not have any evidence of ischemia as the retrograde was confirmed by ICG and the post-operative angiogram reveals retrograde flow through the distal MCA branches, filling in for the area that was ligated. Let's go ahead and talk about another case. This is a 60 year-old female with dizziness, who had an incidental about nine millimeter of PICA, post-cere and third cerebellar artery aneurysm. Again, these aneurysm what they are more distal as you can see, the base is relatively broad. And in this situation we felt surgical clipping is most reasonable due to the broad base of the aneurysm. As you can see the aneurysm is located along the floor of the posterior fossa and let's go ahead and start this surgical video and have a look and see, what would be the way ICG can help us, in terms of assuring aneurysm obliteration and patency of the surrounding vessels. Again, this aneurysm, as you see here, was approached through a suboccipital craniotomy. You can see the PICA going into the aneurysm and coming out. Again, this is the PICA that we're temporarily uprooting here. The cerebellar tonsils are retracted. The clip was placed parallel as you can see, to the direction of the flow in PICA. The first clip left some dog-ear as you can see, more distal on the aneurysm neck and therefore a second clip was applied to assure the complete occlusion of the aneurysm prior to performance on the ICG. And you can see the aneurysm itself looks a little bit blue right now, and here's a more sort of zoomed out view for you guys to see our approach along the posterior brainstem. As you can see the ICG momentarily, the aneurysm is occluded. You can see your clips here and there's really no feeling beyond that. And the parent vessel is very nicely open. So this is really a quick way to ensure the PICA is patent, the aneurysm is obliterated and no need for intraoperative angiography, especially in this situation the patient can be lateral or prone position. Let's go ahead and talk about our next case here. This is a postoperative again angiogram, we regularly do actually in this case, I'm sorry, we need to push up from angiogram to confirm complete occlusion. Let's talk about a 60 year-old male with a sudden onset of headache and the imaging revealed evidence of subarachnoid hemorrhage. He had this almost blister-like or a very small aneurysm off of the ACOM. This aneurysm was clipped surgically and post-operative CTA and intraoperative ICG revealed complete occlusion of the aneurysm. However, again, as you can see, even the ninth angiography revealed no residual aneurysm. Unfortunately he had a severe headache on the 21st day. And as you can see, he had a pseudo-aneurysm forming at the neck of the previous aneurysm, really much larger. And this pseudo-aneurysm obviously is a very challenging aneurysm to treat surgically. Let's review this surgical video. This is a very interesting case. This is a right frontotemporal craniotomy. You can see that the approach is obviously sub-frontal. This is the old clip that you can see at the tip of my arrow, these are the temporary clips that were placed on A1 bilaterally and here he is putting a fenestrated clip across the neck. And you can see the aneurysm right there, it's a very thin wall, almost there's no wall to the aneurysm which we would expect in a pseudo-aneurysm. And here, it was really difficult to get the neck with preserving the ACOM and we had to remove the clip a couple of times as you can see in this video to assure that the clip is really causing no stenosis of the ACOM as well as preservation contralateral A2, As you can see the clip is being moved, just a tad more anteriorly. And now the A1 and the other A2 on the other side is going to be more in view, as you can see in the tip of my arrow. So this is a pseudo-aneurysm, a difficult situation. You may have to remove your clips multiple times and you really want to have a quick feedback of this, this pseudo-aneurysm, completely obliterate it or at least somewhat, you know, has a low flow where you can keep the A1 patent or ACOM patent because the neck of the aneurysm has really incorporated the entire segment of the ACOM and is therefore postoperatively, it would spontaneously thrombose. And as you will see in a second, we use the ultrasound here and we went to ICG and as you can see, the ICG shows some flow in the aneurysm, very faint, but all the vessels are patent. This clip was ultimately repositioned to a short, complete occlusion after the pseudo-aneurysm which is more importantly secured and as you can see, you see a very bright flow, but a very faint flow in the aneurysm right there and again, that told us that this area was most likely with thrombosing this is the Heubner right here the aneurysm itself right there, and that we found very helpful in terms of assuring that this aneurysm would be excluded. We did not feel a primary clip and complete occlusion of the aneurysm atrophing was possible without preservation of the ACOM and so I think as you can see, this is the one of the further results of the positioned clip, this is again A1 contrlaterally behind my ultrasound microdropaline probing ultimately this aneurysm with thrombose post-operatively. Do we have any questions, Victor? Okay, let's go ahead to our last aneurysm case and this is actually the final result from this case again a pseudo-aneurysm, shows that the ACOM was relatively patent and this is a six months CT angiogram revealing that there was no further development in the pseudo-aneurysm and complete inclusion on the previous transcranial abnormalities. 36 year-old female with a sudden onset of headache, usual subarachnoid hemorrhage and a very interesting aneurysm, this is an intrachoroidal aneurysm as you can see here, the PCom's right there, this is a sagittal view showing the internal carotid artery Pcom, the aneurysm, therefore it's distal to the PCom or takeoff most likely, it is an intrachoroidal aneurysm. And this surgical video shows, and again, these intrachoroidal aneurysms can be often very challenging and you can see this as a left-sided, I'm sorry, a right-sided frontotemporal craniotomy and temporary clip has been placed on the proximal ICA. This is the aneurysm, very broad-based. You can see that intrachoroidal right, well, posterior at tip of my arrow and we really wanted to put a clip and very quickly assured that the intrachoroidal artery is patent, because it's sacrificed, as we all know, has significant consequences and here he's putting the fenestrated endo clip across the neck, parallel to the internal choroidal artery and in these broad-based aneurysms, I feel it's really important to put the clip parallel to the vessel, internal choroidal artery rather than the traditional clip placement. And as you can see the internal choroidal artery is patent, and this is a higher view of it showing my dissector, showing the intrachoroidal is patent and it's important to have an ICG and immediate feedback, to see is this vessel actually patent. And as you can see here, it is patent. There is no residual aneurysm and again, another way to identify patency of the stronger vessels using intraoperative angiography. One of our colleagues is asking, what is the dose of ICG per injection? And, you know, unfortunately that skips my mind. I'm happy to answer that question if they send me an email, I'm going to leave my contact information, or you guys can obviously reach Victor Chen, who is a representative from Zeiss and send him an email. He's going to leave his email for you in the chat function and therefore can be reached for technical questions. This patient actually not only underwent ICG, has an intraoperative angiography that again, showed and confirm that the aneurysm was almost completely occluded and no evidence of postoperative ischemia in the distribution of anterior choroidal artery. So now that we exhausted all the applications for any aneurysm, well let's touch upon how we can use ICG for arteriovenous fistulas. These are a class of vasculitions that are on the special interest to me and let's discuss a case of a 72 year-old male with a sudden onset of left Upper Extremity weakness, which resolved over one month. And as you can see on the images, he had this hemorrhagic, sort of somewhat calcified lesion in the right parietal area. Therefore, because this was a spontaneous hemorrhage, an angiogram was completed and you can see the internal injection shows no abnormality. And that tells you a lot because an external injection is critical. If the internal is negative and you can see how impressive external injection of internal choroidal artery reveals this very large parietal, arteriovenous fistula with a very large varices on the cortex. So let's see how we can approach this, endovascular techniques were not deemed very adequate and definitive and therefore this patient underwent surgical exploration and this entry was performed through a right parietal craniotomy as you will see in a second. In this exposure, you can see the superior sagittal sinus are retracted with sutures. Again, this is two vessels that you can see going to this malformation, but it's hard to know which one is the fistula. As you will see, there's two vessels here, one next to each other and that's why we did an ICG and you can see this is a vein, this is the fistula. And this was the use of ICG in terms of delineating artery versus vein, so you can see the bright flow in the artery right here versus a more delayed flow as you can see on the first injection when the flow came in and the dye came in and that was a guidance for us in terms of helping us identify the fistula. Ultimately the fistula was further dissected off of the folds as you can see at the tip of the arrow using microsurgical techniques. And again, the fistula has a much more sturdy and robust wall compared to the vein that's been retracted with the suction. And one of our residents, Dr. Dan Kim, as we'll see in a second is going to go ahead and place the clip across the fistula that as you see is entering the superior sagittal sinus. Again, this is the official completely dissected around it and getting ready to receive the clip. Again, I think I'm trying to show other vessels that are going around the fistula, but the fistula remains to be the one that is entering the sinus or through the sinus. Do we have an extra question about what kind of work in distance and magnification we use? You know, to be honest, the moment he said that Zeiss scope to do the ICG, it zooms you out, but then I zoom it in exactly where I want it to be. And then I asked them to inject the dye. So I use it at any magnification I would like it to be. And here is you can see Dr. Kim, one of my residents, placing the clip across the fistula and obliterating the fistula and more importantly, we're going to do an ICG to make sure the fistula is completely excluded. So, you know, I think for different lesions, you should try to use the magnification on the microscope that gives you the field of view that you like to see. And it really depends how big your field of view is. Right now the field of view is very large compared to the aneurysm cases we presented. Therefore zoomed out to be able to see the whole structure and you can see there's no dye coming in, into the malformation, there's some thrombosis from the previous dye, the pre-treatment or pre-clip application dye and again, assured that this malformation was completely excluded. So again, this is an application for it. Parietal obliteration of fistula, not only for diagnosis of the fistula before treatment and clip application, but also after the lesion is excluded to confirm appropriate clip application. Let's go ahead and review our next case. And this is a 36 year-old male with a sudden onset of severe headache, nausea and dizziness. Again, this patient was diagnosed with a right tentorial AV fistula. This was a CT scan on admission, MRI showing T2 signal change and evidence of hemorrhage in all the studies that are present. We went ahead and did an angiogram and you can see the fistula from the internal carotid artery, along the artery of Bernasconi and Cassinari. Along the tentorial, this is where usually the superior petrosal vein is, creating a large varace infratentorial space, causing venous hypertension, leading to evidence of hemorrhage in the brainstem and therefore the presenting symptoms on the patient. This is again a CTA reconstruction, showing the abnormal connections. Let's see if the video will help us here. This is a right-sided, suboccipital retromastoid craniotomy for a dissection and identification of the fistula. As you can see, the fistula is located, the fistula is right there at the junction on the petrous tentorial junction. This is the initial clip we tried to put a straight clip, but subsequently changed our plan. This is the fifth nerve and this is the seventh and eighth cranial nerve, tentorium again is up there. And this is where superior petrosal vein usually is located and here is we went ahead and quickly put, what we'll call a vein-edit clip to assure that these connection is completed and here is you see this swollen vein and it always worries you, what is this? Did I clip the wrong vein? And a quick ICG would be very helpful in order to assure that the lesion is excluded. And so again, the lesion sitting right in the root entry zone of the trigeminal nerve, and as you can see in the ICG, there is no filling of that ugly looking vein that swole up after clip application. This is a superior cerebellar artery at the tip of my arrow. So this was a quick way, and again it shows the fistula, but the fistula really doesn't go anywhere past the clip. So, and again, this is the vessels along the brainstem and again the vessels around the seven and eight complex. So let's go ahead and discuss one of the options for arteriovenous malformations and here is our next case. It shows, and again, this is a postoperative image of that fistula along with the tentorium 3A, recently with result. So what about arteriovenous malformations? How about a 36 year-old female with headache and wide arterial AVM? And here is the MRI, MRA, and you can see the relatively large size of the arteriovenous malformation, and you can see again further angiograms, evidence of the arteriovenous malformations. We'll go through this quickly. Again, it was partially thrombose and you may have already seen part of the video and the video clearly shows the veins and arteries and can help you on the surface of the AVM to delineate what is AVM, what is not. This is a second case of another arteriovenous malformation in the right frontal which we removed. Again, this is the right frontal lobe. This is the midline and you can see the vein and the arteries. We did not perform a pre-resection ICG in this case and continued to remove the AVM. As you can see, this is again the deep part of the AVM in the white matter and where the AVM resection is often most difficult and we got into some bleeding and to make the prison exciting we thought, we show some of the challenging parts of resecting this AVM. And usually patients in the AVM resection always comes handy, again, this is the frontal lobe, this is the interpreter of the AVM, this is the posterior frontal lobe and we went ahead after isolating the AVM anteriorly or what we might say in theory, this is the funnel resection cavity for arteriovenous malformation and again, the ICG shows intraoperative no residual AVM in the resection cavity with normal vessels patent on the normal cortex. So this is really a simple application of ICG for arteriovenous malformations. And this really is the MRI of the patient whose images we just reviewed and discussed some of the nuances in terms of using ICG for arteriovenous malformations. That was a surgical video. Let's talk about revascularization. How does ICG help with cases where we need to do bypass? This is a 61 year-old male with a history of bi-lateral carotid occlusions and multiple strokes. This was his CTA, again, revealing there was no flow, intracranially through the bilateral carotid arteries. This shows and reconstruction of this superficial temporal artery revealing the anterior branch is much more robust than the parietal or the front branch is much more robust than the parietal branch. And again, you can see, we use intraoperative CT angiography to identify the cortical vessel that is very healthy and can receive our graft. So let's go ahead and talk about how to do a STA-MCA bypass and how can ICG help with this procedure? What we'll be seeing would be a left-sided approach. Again, a craniotomy has been completed. The cortical vessel has been prepared and again, the vessel, the arteriotomy is being performed to prepare this side of a recipient and here we've using the scissors to do the arteriotomy along the cortical and fore branch. Again, using the highest magnification of the microscope. And here as the arteriotomy is relatively completed, it looks okay. Here is the STA vessel and I'm trying to complete the first anastomosis suture. After that's completed, we're finishing our first knot. Any other questions Victor that I can help add, please? What focus techniques do I use to optimize my picture? And this is one of the questions came in. Really, that depends what procedure you're doing. I typically just try used the appropriate button on the handle of this scope to assure that the picture is obviously in focus and also adequate magnification is available. What's most important is that I try to carry vascular procedures at the highest magnification possible because it gives you a good lighting and it really allows you to do my microsurgical techniques very well. And it really makes for a prettier, you know, image, because you really have excluded all the distraction or distracting factors. Here, you can see we're proceeding to complete the anastomosis with one side placing sutures. We're using 10-hole sutures here, all across. This is finishing the anastomosis on the contralateral side. Some people may use 9-hole but I have found it to be helpful to use 10-hole although we can be much more challenging. This is the end of our really bypass, showing really adequate suture placement and here is the ICG showing very nice patentized STA, patent cortical vessel, patent distal vessel. And then this is really important to get this feedback that your STA is booming, this is the dual closure. And again, you can further confirm the flow, with your micro-doppler And this is a postoperative CT, so a postoperative angiogram really showing how the STA goes through the bony defect and joins really your MCA construct and here you can see it's coming through the defect. And this is the anastomosis between the STA and fore branch, really a very satisfying operation, obviously in very selected patients. Let's talk about a 41 year-old female with a history of an MC dissection about 15 years ago, suffering from a giant M1 and A1 aneurysm is really is not primary clipable as you can see, we have seen the second internal carotid artery, joining A1 and M1, the aneurysm is fusiform and involves both, you know, segments and we felt that a high flow bypass across the MCA would be reasonable with a ligation of A1 distal to the aneurysm, because there was a patent ACOM and let's go ahead and review this video of performing a high flow bypass. Again, the bypass is being conducted on the right side, and this is the M2 branch or these are the M3 branches, the M2 branch, as you can see has already received their recipient and this is the high flow graph. In this case, we used the vein graft. You can see the vein graft that's going into the fissure and ultimately being subcutaneously passed along the anterior part of the ear to external carotid artery, where a anastomosis between the vein graft and the external carotid artery is being completed. After the anastomosis is completed, as you can see to the external carotid artery, we'll proceed to restore flow. Again here, removing a clip, distal clip, and this is the fissure obviously and you can do an ICG and assure that your graft is patent and your MCA territory is patent and as you can see, here we go, the ICG showing the patent graft, patent MCA branches, and really this immediate feedback, showing patency on the vasculature, I think is very important for the surgeon to receive a confirmation if the anastomosis is adequately performed. That this patient ultimately underwent proximal ligation of the carotid artery in the skull base, just distal to the anterior carotid artery. And again, we can go through different techniques of bypass, but I think at this time, for the sake of time, we'll proceed to further applications of this method of ICG. And there are other applications besides, and if we're using it in vascular cases let's talk about tumors. A 62 year-old male with a generalized seizure in bilateral frontal meningioma and this is his meningioma. It shows that the sinus is relatively occluded and we do know how far it's occluded and the MRV shows that it's way up there, but there is some drainage, some cortical veins that can be very important because that's the vein of Trolard and in this situation, we felt that it would be a good idea to use intraoperative angiography to assure patency of the sinus and the surrounding cortical vessels. And the cortical veins more specifically. Here, you can see the craniotomy, which was by frontal. This is folds being cut away. This is that vein I was talking to you about right there, going to the sinus right there. And this is your residual part of the sinus. It's important to me with this vein is patent, because you don't want to sacrifice it if you don't need to. And in this case, we went ahead and did ICG and you can see the vein to be patent, and it's actually going to the sinus. And therefore we left the portion of the sinus there intact with a small amount of tumor attached to it. So this is one way, another way, this is a right side, is suboccipital craniotomy for MVD and you can see there is a vessel here right next to the nerve, the fifth nerve and it's hard to know, is it a nerve or an artery, can I take it or not? It's really in sheath within the arachnoid and stuff, very visible and this is again, mobilizing the nerve. And here you can see the vein has the same phase as the superior petrosal vein and you can see that this small structure that we're questioning is most likely a vein because it appeared at the same time as superior petrosal vein. And so, again, this is one way to identify veins versus arteries by when the dye shows up in the unknown vessel compared to the surrounding structures that you are sure to be vein or an artery. And again, ultimately we decided not to take that vein because it did have a loop that went ahead along the entire brain stem. This is a another case where there could be some pitfalls to ICG and we would like to review those, because I think it's important to realize that although ICG is a great tool, it has its own limitations. This is a 55 year-old female with history of headaches and an incidental 1.6 millimeter wide MCA aneurysm and she underwent surgical exploration as you will see here. And first of all, let's define the lesion. You can see the MCA coming in here, a very broad-based, large aneurysm, and in showing partial incorporation in two branches. And you know that in surgery, there will be multiple clips placed. You really want assure patency of the vessels and here is what we did during surgery and what we felt ICG, maybe in this situation could have done better. This is the first clip that was placed. And I'm going to go ahead and make sure we reach the white part of the video. I apologize again, some of the videos can have a their mind of their own. We initially placed the clip as you will see in a second across the neck of the aneurysm. Here's the clip that you will see in a second, placed across the neck of the aneurysm. And this is the M1 branch and here you see it's patent. And these are M2 branches on its sides, showing how the parent vessels or patent and the aneurysm itself looked really not filling in ICG. And here you just use the ultrasound and you just have it fill in this aneurysm and spill it. And so, even though the other vessels are patent, we felt like there was just something wasn't right. That even though ICG was telling us, the aneurysm was not filling, this aneurysm could be filling somewhere and therefore we put a fenestrated clip, due to the very broad base of the aneurysm. And as you can see here, I'm trying to place this clip across the more distal part of the neck. And so we thought the ICG is negative. We put a third clip, we felt very good about everything. And let's go ahead and penetrate the aneurysm with a needle and you can see the blood coming out the aneurysm. So even though the ICG was not indicating any flow, there was a flow into the aneurysm and therefore we had to remove all our clips, we refashioned the clips with a more distal application. So there was no residual neck across the distal edge, and eventually this aneurysm was completed or obliterated without further flowing the aneurysm as you can see. So if the aneurysm is very atherosclerotic, has a very thick wall in this situation, you may have a hard time seeing what's going on inside the aneurysm with ICG. And as we say, there is no perfect method. There is no one method that can replace, you know, every hunch of a surgeon or every decision and make the final decision. You really have to be careful how you use the ICG in order, making a decision if the vasculition has been excluded and this is the post-operative 3D angiogram, showing that the aneurysm was completely occluded with no residual neck across the aneurysm. So I want to thank all of you guys for joining us this evening. I know there were a lot of cases, pretty much going through them very quickly, trying to indicate what are the indications and perils and pitfalls for use of ICG in improving the care of cerebrovascular patients. So I want to thank you again, all of you guys for joining us this evening and giving us your valuable time.

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