Grand Rounds-Misadventures During Aneurysm Surgery: How to Avoid Them

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- Hello, ladies and gentlemen, the following two sessions are among the most exciting sessions we have offered through the AANS Operative Grand Rounds. Dr. Dan Barrow from Emory University, will be talking to us about Misadventures During Aneurysm Surgery and Complication Avoidance. The first part will focus on some of the common techniques to avoid these complications, and the second part, will focus on some of the technical nuances for managed complications when they occur. Thank you for joining us.

- Good evening, I appreciate you joining us tonight. Now we're going to talk about a very important, but very painful subject, the subject of managing and potentially avoiding complications during a neurosurgery with an emphasis on the management of complications during aneurysm surgery. Colin Powell, once said, "There are no secrets to success. It is the result of preparation, hard work, and learning from failure." And so what I'm gonna share with you tonight are some of my failures and the way that I manage them, and the way that I try to avoid them in the future. Certainly, the best way to manage a complication is to avoid it. And we'll talk about some tips to avoid complications, but if you do enough surgery, you're going to have complications you have to manage as well. The first step in avoiding a complication I believe, is to select patients appropriately. Not all patients need an operation, and we can save ourselves and our patients a lot of trouble by selecting patients appropriately. And there are a number of things that we can do to prevent complications, prevent direct injury to the brain, prevent incomplete obliteration of aneurysms, prevent compromise of parent vessel or branches, prevent intraoperative rupture, and then obviously we have to know how to manage those complications. And with all as with all neurosurgical procedures, meticulous postoperative care is absolutely mandatory. I wanna begin by sharing with you one of the worst complications I've ever had in my own hand, this is an image of a basilar tip aneurysm in a relatively young woman who presented with the subarachnoid hemorrhage. You might notice on the images that the posterior cerebral artery rises indicating this is a very low basilar bifurcation. So I anticipated during the opening that we would likely have to remove the posterior clinoid process in order to obtain a proximal control, and indeed, that's what we did. Aaron, could you put the first video on, please. So let me orient you here. This is a right frontotemporal craniotomy. This is the optic nerve on the right. This is the internal carotid artery upon, which is a very small retractor to protect the carotid artery. And this drill is drilling the anterior clinoid process after which I will try to chip it away with a small curette. So we're drilling the anterior clinoid process here, and the curette now will slip. And I literally tear the carotid artery in two, this is an absolute disaster. So what we do to reorient you, the carotid has now been torn literally in half. But fortunately I was able to find the proximal part of this and put a temporary clip on it, and will now attempt under barbiturate protection to re-anastomose the two ends of the carotid artery together, which the rest of this video will demonstrate. Sorry, the video went back a bit, but here I am now opening the dural ring putting a clip a little more proximately after I removed the anterior clinoid process. Now using a monofilament suture, I'm re-anastomosing two ends of the torn carotid artery together and before placing last suture, irrigating it out with some heparinized saline. Final stitches placed, and after removing the temporary clips, we actually had excellent flow through the reconstructed carotid artery, as you will see here. So here's the carotid completely reconstructed and things actually look pretty good. The patient initially did very well after surgery woke up and seemed to be making a remarkable recovery. This is the initial postoperative CT scan, but within about 24 hours of that image, the patient rapidly deteriorated from a massive infarction, presumably from a delayed illusion of that carotid artery that had been reconstructed at a decompressive hemicraniectomy and unfortunately expired.

- As you very well said then, if you do enough of this, this will happen. And the only way to avoid complication is not to operate. Let's see, in this situation, if you were unable to get proximal control, and the carotid was injured at the level of the skull base and the stump was not available, what is your thought process adenosine exposing the neck? Is there enough time? And what are those situations where there is absolutely no proximal control and you have torrential bleeding.

- Well, in this case, fortunately there was just enough of the carotid approximately I was able to put a temporary clip had that not been the case. Unfortunately, I had not exposed the carotid artery in the cervical region for a basilar tip aneurysm. This was completely unexpected. And so I wasn't prepared in that case. Certainly carotid compression could be of some benefit if you can have your assistant, or the anesthesiologist compressed the carotid. Certainly the use of adenosine is wonderful. And I'll show an example of that later in a different situation. But this is a case where had I not been able to control the bleeding with the temporary clip, adenosine would have bought me some time. The problem is that in order to really get true proximal control, I needed to drill off the anterior clinoid process, open the dural ring, something that the 15 to 20, to maybe 30 seconds of transient cardiac arrest with adenosine probably wouldn't have accomplished. That may have been a situation that would have been completely hopeless. Probably carotid compression would have been my best option, maybe rapidly opening the carotid in the neck, but I was completely unprepared for that.

- I agree. And do you think maybe your anastomosis side thrombosed, and that's why she had a delayed carotid occlusion and stroke, or what do you think the mechanism could potentially be?

- Precisely the temporal profile of this was perfectly consistent with that? I think that the anastomosis was probably successful. She awoke very well for a short period of time a day or a day and a half. And I think that the holo-hemispheric infarction was due to a delayed thrombosis of that newly re-anastomosed vessel. I did not keep her on any type of anticoagulant that did keep her on semantic platelet therapy, despite the recent subarachnoid hemorrhage. But I think anastomosis probably thrombosis.

- Thank you.

- So I think one of the things this case illustrates is the first step in avoiding complications, is patient selection, an appropriate patient selection. And this depends upon a number of factors, obviously factors of the patient, age, the health, the psychological impact a patient might have, knowing they harbor a lesion like an aneurysm that might shorten their life expectancy or caused morbidity. There obviously are factors of the aneurysm, whether or not it's symptomatic, size, the location, the configuration, if it's a ruptured aneurysm, whether or not there's an associated intracerebral hemorrhage. And then there are factors of the surgeon. Primarily his or her experience, with similar lesions taking into consideration what your experience has been, and how you think you might handle that particular patient and their particular pathology. And finally, we have to remember there's the selection of the appropriate therapeutic modality. In this day and age, there are a number of aneurysms that are not ideal for surgery. And in retrospect, maybe this aneurysm was one that we should have pushed and persisted, an endovascular option for. Certainly, I discussed it with my colleagues that perform excellent endovascular therapy in my institution. They felt at the time that this wasn't an ideal case for endovascular therapy, but in retrospect, maybe we should have considered that more strongly. Some of the patients that are not ideal for surgery, our elderly patients, those that arrive in poor neurological or medical condition, those that present with vasospasm, those with aneurysms and a difficult location as this one was, those with calcified necks and multiple aneurysms that might require multiple operations. We gotta keep in mind that we have alternatives. Endovascular alternatives that are less invasive and offer wonderful solutions and options for aneurysms that are difficult to deal with surgically. Surgery is not minimally invasive, but it should be minimally disruptive. We should do our very best to leave no traces from the operations that we do. And that will require avoiding complications that we'll talk about from this point forward. One of the complications that needs to be avoided, is direct injury to the brain. Sounds fairly simple, but this can happen. The slide you see here shows a contusion on the frontal lobe of the brain that occurred in turning the craniotomy flap. This is an enraptured aneurysm, and frankly, this is an inexcusable complication. But in turning the craniotomy, the drill apparently hit a portion of the brain and although this looks fairly benign, postoperatively, the patient had this contusion that caused the language dysfunction that ultimately the patient recovered from, but the patient's recovery was prolonged, and the morbidity really completely avoidable complication, just simply by paying attention to detail. There are ways to avoid direct injury to the brain. Obviously, as I mentioned, you gotta be careful. There are a number of surgical adjuncts, which we'll talk about that can help avoid direct injury. We need to appropriately expose the aneurysm, and relax the brain significantly. In this day and age, we should minimize if not eliminate the use of retractors. We need to preserve veins. Something that I think has not received enough attention in the past. And there are mechanisms to protect the brain from ischemic injury that we might subject the patient to. This is the list of some of the surgical adjuncts that have been developed before and during my career, all of which we can use to minimize the risk of injury to the brain. And we'll talk about some of these and how they can be utilized in the process of avoiding complications during aneurysm surgery. Optimal exposure is key to any neurosurgical operation, intercranial spinal, peripheral nerve. These slides show an inadequate material craniotomy. You can see that the lesser wing of the spinoglenoid has not been removed aggressively. And when one opens the dura, the Sylvian fissure is not completely exposed, requiring the surgeon to retract the brain in order to open the Sylvian fissure and get to virtually any anterior circulation aneurysm. Slide on the right if you can see, the lesser wing of the sphenoid has been removed aggressively, so that when you open the dura, the Sylvian fissure is completely exposed and the brain doesn't have to be retracted around bone. We have removed bone to expose the brain and protect it. Brain relaxation is extremely important. Even in a patient with a subarachnoid hemorrhage such as the one shown in this slide, with progressive and sequential opening of each of the arachnoid cisterns, one can achieve incredible brain relaxation, allows us to minimize the use of retractors. And that brings us to the next slide. This is a photograph that I found from a early video in my career. And I cringe when I look at the retractors pulling the frontal and temporal lobes apart, in order to visualize and clip what in this case was a superior hypophyseal aneurysm. In this day and age, I would markedly limit if not eliminate that retraction altogether. For example, here is a middle cerebral artery aneurysm that is exposed with no retraction whatsoever by opening the Sylvian fissure, exposing the aneurysm, and applying the clips through that Sylvian fissure, in a manner that really minimally affects the brain at all. If one has to use retractors and sometimes we do, as is shown in this subtemporal approach in a young child, that presented with a ruptured basilar tip aneurysm. The key here is to use multiple retractors to evenly retract the temporal lobe, away from the floor of the middle fossa to expose the free edge of the tentorium, and subsequently the aneurysm. If the surgeon puts one or maybe even two retractors, the temporal lobe has a tendency to bend around that retractor and the retractor can cut into the brain, and cause direct injury. So by evenly applying the retraction gently across a larger surface area of the brain, one can minimize the injury from the retractor digging into, or in some cases even cutting into the brain. Vein preservation is extremely important. And something that I think has largely been ignored in the past. This short video, Aaron, if you would run this, I think shows how meticulous care, through in this case a left frontotemporal craniotomy to expose a complex middle cerebral artery aneurysm. One can carefully and sequentially say even the tiny veins within the Sylvian fissure, I think a lot of the unrecognized injury, the brain swelling and venous infarction that we've attributed to excessive retraction and issues in the past, are largely related to not paying attention to the veins. Notice how now with the Sylvian fissure opened and the veins all preserved, the aneurysm can be successfully clipped and those things spared, so the patient does not experience venous infarction and importantly venous congestion.

- Dan, if you made tell us, you mentioned a very great point about the issue of retraction. Do you feel you need orbitozygomatic for every ACom aneurysm? How much do you incorporate orbitozygomatic into your aneurysm practice? Pretty much all you need as long as you drill the roots of the orbits very aggressively. Can you please comment on that.

- I will comment on that, that's a great question, Aaron. I use an orbitozygomatic approach for anterior communicating artery aneurysms rarely and sparingly. If you look at a skull and look at what taking off the orbit and what the zygoma does for your approach to an inter communicating artery aneurysm, really adds very, very little. The aneurysm where I think an orbitozygomatic approach is an incredible benefit is the high rise, the high-riding basilar tip aneurysm where one needs to look up into the interpeduncular fossa. There are occasional large, giant, complex, anterior communicating artery aneurysms, where that added benefit of looking more upward and rostrally does provide some benefit. But in my practice, I use that very rarely for anterior communicating artery aneurysms. Wide opening of the Sylvian fissure, and the basilar cisterns provides the relaxation that you need for most of them. And I don't think that approaches is necessary.

- And I really liked the nuance you just mentioned with the video, is because the banks can have such a very thin wall and handling them can be very difficult and they can rupture with the suction force on them. You grab them with jeweler forceps and grab them on the adventitial and separate them carefully. I think that's something that probably should be very well emphasized because that is the safest way to dissect these veins, don't you think?

- I think it is or obviously if you can see the arachnoid between them even sharply dissect them is also a very safe as well. But I think to use retractors to try to pull them apart, which is what I think we used to be taught in the past, is certainly the way to avoid injury. The next point I wanna make is that one has to select the appropriate exposure and the appropriate approach. And that is a key principle of any surgical field, certainly in neurosurgery. Here's an example of a basilar tip aneurysm. And you can tell from this, this arteriogram the red arrow points to the posterior clinoid process. So you can see that this, is a very high-riding basilar bifurcation. This is a situation where we would use an orbitozygomatic approach to look up into the interpeduncular fossa to see this aneurysm. In this particular patient, she had an associated left sided middle cerebral artery aneurysm, it was not amenable to endovascular therapy. So a left sided orbitozygomatic frontotemporal approach was selected, so both aneurysms can be treated with one operation. The orbitozygomatic approach is shown in this cadaveric photograph, allows one to look way up into the interpeduncular fossa. In this particular video, you'll see that we're looking up into the mammillary bodies into which this aneurysm is embedded. So if you'd start the next video, please. So lemme just stop this for a moment and orient you. This is from the left side, this is the basilar trunk, this is the superior cerebellar artery, and here is the left or ipsilateral posterior cerebral artery. The aneurysm up here is embedded into the mammillary bodies. And this little retractor is gently retracting the carotid artery to make a window where I can look behind the basilar trunk, to sweep the perforators out the way so that this can be clipped with a fenestrated clip using the fenestration to encompass the ipsilateral pin one. So we'll proceed here. Here you can see the aneurysm, the P1 segment, at the contralateral P1, you can see the mammillary bodies up high. In this case, a fenestrated clip after the perforators had been swept out of harms way, is going to be placed in such a way that we can see the perforators. The fenestration will encompass the ipsilateral P1. This is a view of this aneurysm we really could not have without the additional exposure provided by the orbitozygomatic approach, to look up into the high portions of the interpeduncular fossa. Clip is closing here, you can see the P1 passing through the fenestration. If we go back to the slides, we'll see the intraoperative angiogram showing that the P1 passes through the fenestration, the aneurysm is completely obliterated as was the middle cerebral artery aneurysm on the carotid injection. Now, here is another basilar tip aneurysm, same aneurysm, but a completely different situation. In this case, notice how the P1 segment goes upward before reaching the free edge of the tentorium. This tells you that this particular bifurcation is a very low basilar bifurcation. As can be seen on the lateral view well, well below the posterior clinoid process. Through a frontotemporal approach with or without orbitozygomatic addition, this would be an extremely difficult if not impossible aneurysm to see. So in this case, we chose a subtemporal approach from the right side, to be able to look behind the aneurysm. And if you'll start the next video, we'll get you oriented through the right side. This is a subtemporal approach. Here's the free edge of the tentorium, here's the oculomotor nerve, and we're carefully separating the arachnoid from the undersurface of the oculomotor nerve. Stitch is being put through the free edge of the tentorium, being careful to avoid the area where the fourth nerve enters the free edge. And that little stitch will give an extra few millimeters of visualization that would become very important. The third nerve now is up here. Now we can see the contralateral P1 right here, the ipsilateral P1 here and looking behind the aneurysm where we can now through a subtemporal approach, had that same visualization as we did previously. Fenestrated clip again used encompassing the proximal part of the neck, so that the blade obliterates the distal part of the neck, being absolutely certain the perforators on the contralateral P1 or out of harms way. We get a beautiful view of that, through the subtemporal approach. There're the perforators and the clip being closed purposefully leaving a portion of the proximal neck. There's the perforator seem very well. Fenestration includes the proximal neck and the ipsilateral P1. Now that we can see the perforator as well, a second fenestrated clip is placed a little bit more proximately, so that the blades obliterate the portion of the aneurysm passing through the original clip that the P1 is spared. And two identical aneurysms in terms of their location on the intracranial circulation of requiring completely different operative approaches, because of the subtle difference in where they are in relationship to the posterior clinoid process. Finally, with regard to avoiding direct injury, we have a number of means of things we can do to avoid a ischemic injury to the brain. Despite the fact that there isn't overwhelming scientific evidence, I do in my practice typically use moderate hypothermia in patients for the scientific benefits of brain protection against ischemia. We routinely used mannitol. And when we use temporary clips, we induce hypertension and we use barbiturates or more commonly propofol. On rare occasions, we will use deep hypothermic circulatory arrest for those cases that are unusual that may require more than 15 to 20 minutes of temporary occlusion. Here's one of those examples. This is a young girl in the state of Mississippi who presented with a Weber's syndrome with hemiplegia and oculomotor palsy, from this giant rostral basilar aneurysm embedded into her midbrain. This is the all setup with the cardiac surgery team, and the patient undergoing the craniotomy before she has put on a cardiac bypass. In this case, the surgical approach we use was the so-called Kawase approach where we drill away as is shown on the postoperative CT, the petrous apex, so that the surgeon has a beautiful view down the clivus in order to be able to see proximal to this giant aneurysm. This is the preoperative arteriogram on the left and on the right, you see an intraoperative arteriogram perform while the patient is on circulatory arrest bypass. You can see that on the pump, the pump allows the blood to circulate as we turn the pump back on circulate the contrast to see that we've spared the posterior cerebral arteries, superior cerebellar arteries, and the aneurysm is gone. Not a beautiful arteriogram, but it gives us the information we need to know that we've achieved our goal of eliminating the aneurysm, and preserving the parent vasculature. The next complication I wanna talk about avoiding and managing is the incomplete obliteration of the aneurysm. One advantage that surgery has over endovascular therapy is its durability. So it is imperative that when we clip an aneurysm, we do everything humanly possible to be sure that it's a durable treatment. This arteriogram as you can see, shows an aneurysm that was clipped in the distant past, that is now recurred likely due to the fact that it was not obliterated appropriately during the initial operation. And there are a number of things we can do to avoid this. First of all, we can observe the aneurysm under the operating microscope. We can puncture it. We can use a variety of intraoperative imaging techniques, but ultimately a goal of completely eliminating the aneurysm has to be tempered with good judgment. And we'll talk about that. Observation under the operating microscope is absolutely imperative. Here is a middle cerebral artery aneurysm, beautifully visualized through the Sylvian fissure, which has been carefully opened. And under the operating microscope, we can observe the clip in perfect position. We can observe the M one and the M two segments. And this is a very, very important first step in documenting that we completely obliterated the aneurysm. We all know from experience that observation under the operating microscope alone is oftentimes insufficient. One of the other options we can use is to puncture the dome of the aneurysm. This is a patient with a basilar tip aneurysm that is operated on, from a right frontotemporal craniotomy. And you'll see on the video as it comes up, lemme just stop for a moment. This is through a right frontotemporal craniotomy, here's the aneurysm being carefully dissected forward. Here's the posterior communicating artery, and here is the internal carotid artery just for orientation. So we're looking at the aneurysm the basilar tip aneurysm being clipped here's the contralateral P1 segment. Aneurysm is clearly that clip is clearly across the aneurysm, but when we puncture it, notice how it continues to bleed. So despite the fact that I can see the clip is across the aneurysm, the closing pressure obviously was inadequate, the second clip was added, and the aneurysm completely obliterated. Something I wouldn't have known, had I not puncture the dome or perform some other form of intraoperative imaging. And that brings us to the subject of intraoperative angiography. This is an intraoperative angiogram performed on a patient with a fairly large anterior communicating artery aneurysm after we had clipped it. And I thought it was completely obliterated. You can see there is residual aneurysm that we identified on the intraoperative arteriogram, could immediately with the patient's still under the same anesthesia within a matter of minutes, re-clip the aneurysm, and document that it's now completely obliterated. We rely heavily, in fact, we rely on intraoperative angiography on every aneurysm that we operate on. And I've done that for a number of years, working out a system with our interventional neuroradiologist, where it's very, very simple, and straightforward adding literally no more than about 10 minutes to each case. Another adjunct that has been very useful in helping us document, that we completely obliterated the aneurysm is ICG videoangiography. This is an intraoperative picture showing a middle cerebral artery aneurysm that has been exposed to the Sylvian fissure. The ICG videoangiogram here before clipping the aneurysm shows us the anatomy, the aneurysm, the two M two segments, and after we clip the aneurysm, we can then repeat the ICG videoangiogram. We have to wait about 15 minutes or so, for the indocyanine green to completely wash out of the system. After that we can repeat the study. And in this case you can see that even though the aneurysm is clipped, and the clip appears to be a completely across the aneurysm, notice the fluorescence within the dome indicating that that aneurysm is incompletely obliterated, allowing us to re-clip it and completely obliterated during the initial operation. There are a number of clipping strategies we can use to ensure or completely we have eliminated the aneurysm from the circulation. As one measures the pressure on an aneurysm clip from proximal to distal, the closing pressure decreases as we walk out or distally. That led Sugita to first describe the tandem clipping technique illustrated in this cartoon where a fenestrated clip is used to allow the higher closing pressure, to be pushed more distally, and then a second clip used to obliterate that part of the aneurysm that passes through the fenestration. These and other clipping strategies are very, very useful to obliterate complex aneurysms. Here is a real life case, showing a complex anterior communicating artery aneurysm. Here's the A one, the temporary clip, and the ipsilateral A two, and this large aneurysm being exposed from the right side. In the second pane, you can see the fenestrated clip reconstructing the A one, A two junction, allowing a portion of the aneurysm neck to pass through the fenestration. And then the straight clip, clipping that portion of the aneurysm passing through the fenestration to completely reconstruct the anterior communicating complex, yet obliterate the aneurysm completely. Finally, I wanna close this segment by saying that a goal of complete obliteration of aneurysms has to be tempered by good judgment. This is a very complex carotid aneurysm I operated on many years ago, and the initial intraoperative angiogram looked pretty good, but I felt like there might be a little bit of residual aneurysm right here. I re-clip the aneurysm, immediately repeated the intraoperative arteriogram and you can see that I've completely occluded the carotid artery. This also illustrates again, the beauty of intraoperative angiography and immediately prefigured the clips. And now you can see that I was left with the arteriogram that is not a trophy arteriogram maybe not perfect, but the ophthalmic artery fills, and what may be a little bit of residual aneurysm was wrapped with cotton. And this patient had long term follow up, now, well over a decade and a half, has not had any recurrence of that aneurysm. And as they say, the enemy of good is better. This was a case where we settled for something that was good, but not absolute perfection.

- If I may a echo that concern in the middle cerebral artery aneurysms, which has personally happened to me, MC aneurysms, and I think the middle cerebral artery complex requires a good atrium of a vessel for the two M to fill. So if you were clipping an MC aneurysm, and if you feel there is a little bit of the neck is there and you try to make the clip look perfect. I think that's when one of the branches, at least either right away or in a delayed fashion can thrombose, especially in anterior colloidal artery aneurysms as well. So as I would like to echo that at least based on the smaller experience that I have had that perfect is definitely the worst enemy of good in aneurysm surgery in my opinion.

- Good point. The next complication I wanna talk about is a compromise of the parent artery or its branches, which can lead to ischemic injury. This CT scan has an arrow pointing to an area of infarction in a patient that I operated on for an ruptured carotid aneurysm. I felt that everything went absolutely perfectly. Intraoperative arteriogram was completely normal. And despite everything going beautifully and good, this patient obviously had some injury, some compromise of a perforating artery that left her with an infarction that ultimately she made a good recovery from. But again, the recovery period was prolonged, and for an unruptured aneurysm is really as an unacceptable complication that we have to go to great lengths to try to avoid. And as with the other complications, there are a number of adjuncts we can use to try to be sure we don't compromise the normal vasculature. And they include some of the same adjuncts that we discussed in making sure that the aneurysm is completely obliterated. Observation under the operating microscope, intraoperative imaging, microdoppler, clipping strategies. And sometimes we have to resort to reconfiguring the parents circulation through bypass surgery, and those aneurysms that are recalcitrant to our endovascular or surgical treatments. Observation under the operating microscope, as I said in the last segment can be notoriously misleading. Particularly when you have aneurysms that are large or giant, and particularly, when they look like this intraoperative image with a calcified or atherosclerotic aneurysm. In that case what can happen, is even though from the outside, it appears that your clip is well above the neck of the aneurysm. You can't see what's going on inside the lumen and a thick wall aneurysm may be compromising the lumen, even though it looks perfect from the outside. This is also the case when complex aneurysms like this carotid bifurcation aneurysm, require multiple clips to reconstruct them. By the time this aneurysm was clipped, one couldn't tell by observation whether there was any residual aneurysm, whether lumen of the carotid is patent or not, because of the large array of clips that was required to reconstruct this very complicated aneurysm. This is when we have to rely on other means to determine that we've maintained patency of the parent vessel and its branches. Traditionally neurosurgeons relied on postoperative angiography. Problem with postoperative angiography is illustrated beautifully on this case. This is a large complex carotid bifurcation aneurysm that at the time of surgery, it appeared the clip was in perfect position. But obviously sometime between placing the clip and the patient waking up poorly in the recovery room, that clips slipped down onto the carotid bifurcation. By the time that's recognized, the patient goes to the angiography suite for a postoperative angiogram. Well that cat is out of the bag and this patient suffered a massive infarction because of the delay in the time of the intraoperative occlusion and the postoperative angiogram demonstrating the occlusion. This is the beauty of intraoperative angiography illustrated by this case. Here's a gentleman with a giant partially thrombosed middle cerebral artery aneurysm with some specks of calcification. You can see on the arteriogram only a small portion of that aneurysm fills on the angiogram. I clipped that aneurysm with a complex set of fenestrated and straight clips and thought I'd done a perfect job but you can see on the intraoperative angiogram right here in the Sylvian fissure, there is a branch missing. That was recognized immediately while the patient was still under proper fall protection, and we rapidly reconfigured the clips, and now you can see, that the aneurysm is completely obliterated, and you can see that the entire Sylvian triangle is now patent. This patient did perfectly well because of the rapidity with which, the intraoperative arteriogram demonstrated the problem and allowed us to fix it. This I think is a terrific case to illustrate the beauty of intraoperative angiography. This is a young man who has a superior cerebellar artery basilar trunk aneurysm. You can see the aneurysm here on the right side between the posterior cerebral, and the superior cerebellar arteries. The three-dimensional angiogram off to the side, shows the aneurysm well. My first mistake, was that I didn't have an appropriate axial image on this patient. And didn't appreciate that this aneurysm was actually much bigger, than what the arteriogram suggested because there was a thrombotic portion. I didn't learn that until we operated on the patient. So the next video, Aaron, if you would start that, shows exposure of this aneurysm through a right frontotemporal craniotomy. So let me orient you here in one moment. We stop this. This is the carotid artery, the carotid bifurcation, the optic nerve on the right, this small retractor is gently retracting the carotid artery to expose the basilar trunk here. And the oculomotor nerve will be over here. So we proceed with a dissection. Here's the basilar trunk, under high magnification we separate the oculomotor nerve from the free edge of the tentorium because it's obscuring our view, of this superior cerebellar artery aneurysm. Now we see the superior cerebellar artery here. Here's the aneurysm, and here's the posterior cerebral artery. So it's got a very narrow neck, looks like a simple straightforward case. That clip is being placed across the neck with the posterior cerebral artery here and superior cerebellar artery underneath here. Watch carefully as the clip is released. Watch how the thrombotic material that I didn't recognize, moves the aneurysm clip proximately towards the basilar truck. That's a very, very key element. Watch right here and you'll see the clip move this way as I release it. Here's the posterior cerebral artery and boom, there it pops forward. Everything still looks okay. Now, take a look, and if you move back to the slides, please, we'll show the next slide, which is the next. This is the first intraoperative angiogram. Notice the aneurysms completely gone. Here's the superior cerebellar artery, but notice that the posterior cerebral artery only fills up to the posterior communicating, and there's no filling of the distal posterior cerebral artery. Now perhaps is filling through the posterior communicating artery, but in a young man, this is an unacceptable result. So we immediately go back to the operating microscope, you can go to the next video. Now we will explore the aneurysm with clipped a small carotid aneurysm in the meantime, that was also there. But as we explore the aneurysm, we realize that it's filled with thrombus. And so without removing the clip, leaving this one where it is, I use the number 11 knife blade to open the sack, and evacuate the thrombotic contents, not all of them, but just enough that I have a soft neck distal to the original clip. Here you can see the thrombotic material being moved and removed out of the sack of the aneurysm, an aneurysmorrhaphy if you will, once that's removed, now I've got a nice soft neck distal to the original clip. Simply put clip just distal to the original one, where I wanted the first clip to be, and then remove the first clip. Now watch the posterior cerebral artery right here as that clip is released. Watch it engorge with blood, look right there. As the clip is removed, fill up with blood. Now I've left a little tiny dog ear that I simply will clip with a mini bayoneted clip to pinch that dog ear, but keeping the posterior cerebral artery paint. Now that I've taken the thrombotic contents out, and move the clip blood back to where it should have been in the first place. Can we go back to the slides, please. So here's the second intraoperative angiogram, all of this done with a matter of minutes. Now you see the aneurysms completely obliterated, the superior cerebellar artery fills well, and the entire posterior cerebral artery fills well, illustrating the beauty and versatility of intraoperative angiography. Here's another instance of a thrombotic posterior cerebral artery, a little different situation. This is an elderly woman who has on this left posterior cerebral artery, the P1 segment, here's the P2 segment. In this aneurysm as you can tell from this axial imaging study is substantially bigger than what the arteriogram demonstrates. If we were to put endovascular coils in this aneurysm, they would migrate into the thrombotic portion rapidly leading to a recurrence, and to try to clip this aneurysm, we would certainly run the risk of compromising the posterior cerebral artery because the thrombotic material would cause the clip to slide approximately. So in this video, I'll orient you in the beginning. Here is a left subtemporal approach. Here is the P1 segment, here is the posterior communicating artery, and here's the P2 segment. And this is the large aneurysm embedded into the brainstem. So these are the retractors gently elevating the temporal lobe. So here's the posterior communicating artery, here's the P2 and the P1 back here. So I'm putting a temporary clip on the P1 segment right here. Here's the aneurysm here separating the P2 segment from the sack itself, to find a location the second temporary clip. And now with a number 11 knife blade, I'm opening the sack above and below the P2 segment to evacuate the thrombotic contents, perform an aneurysmorrhaphy. Here's the thrombus within the aneurysm, which is being removed with a microdissector, and small micropituitary rongeurs to remove the thrombus and soften the neck of the aneurysm. And now with the aneurysm tract, a fenestrated clip is used to reconstruct that P1, P2 junction. P1, P2 junction is passing through the fenestration, temporary eclipse being removed from the P1, the P2, and the posterior communicating artery. And we've got a reconstructed posterior cerebral artery, an aneurysm that's completely obliterated simply by taking the time to remove the thrombotic contents. There's the P1, there's the P2, the brainstem decompressed. Let's go back to the slides, please. Another way to avoid branch or parent artery occlusion is by using ICG videoangiography. This is an interesting case where on the right side, you see the small middle cerebral artery aneurysm, and you see this perforator running parallel within the Sylvian fissure to that small aneurysm. We now move to the intraoperative photograph. Here's the Sylvian fissure opened, here's that small aneurysm, and here's that perforator running adjacent. In fact, it's even adherent to the dome of the aneurysm. Something we didn't appreciate on the arteriogram. ICG videoangiography now shows us the aneurysm before clipping and shows us how well at perforator fills. It shows its dense adherence to the dome. In order to clip the aneurysm, I sharply dissected this perforator off of the dome, and clipped it as seen in the next series, the clip is on and here is the perforating vessel. When we repeat the ICG videoangiogram, notice two problems. First of all, the aneurysm is still filling, despite the fact that the clip looks like it's completely across it. But even more importantly, that perforator is very, very faintly if at all filling. Maybe vasospasm, it maybe that the clip has somehow compromised it, but it's not acceptable. And so we immediately remove the clip, re-clip the aneurysm in a more secure manner, apply some papaverine to the vessel. And when we repeat the ICG videoangiogram again, knows the aneurysms gone, and now we have robust filling of the perforator and a patient that wakes up without the aneurysm and healthy.

- One thing that I have personally run into Dan is, if you have your retractor on the distal segment of the artery, we're hoping I'm not retracting that hard, but occasionally that occludes the artery. And on ICG it may look like as it's not filling, but if you just lose some of your retractor, you're gonna find out a vessel is perfusing very well. Have you had that experience with ICG or no?

- I have seen that. And I think that's a very good point and all the more reason to not use retractors or if you use them use it very sparingly with minimal retraction of the brain. The retractors really, if they're used at all, should be used to protect the brain from our instruments moving in and out, more than actually retracting the brain. There are those instances where you simply have to use a retractor, but we should try to minimize it and that's another reason why.

- Thank you.

- Another adjunct to be sure that we maintain blood flow in the parent vessel in its branches, is microvascular doppler. This is a case of an elderly woman with a large superior hypophyseal aneurysm that was causing progressive visual loss. And you can see from the series of arteriograms, she underwent multiple endovascular causes, none of which completely got rid of the aneurysm and obliterated it, and in fact, she continued to have progressive visual loss. We anticipated we might be required to perform a high flow bypass, something we weren't excited about doing in this woman who was elderly. And although we were prepared for that, we elected to explore the aneurysm first before proceeding with the bypass. This series of photographs beginning in the upper left, demonstrates the optic nerve here through a right frontotemporal craniotomy. This is the large aneurysm, and you can see the coils through the sack. And here's the distal internal carotid before the intracranial bifurcation. The carotid is also been exposed in the neck so we are at this point, trapping the aneurysm. If you move over to the right, you see that the first step is to place a series of fenestrated clips to use the fenestrations to reconstruct, to reconstruct the lumen of the carotid artery. Using microvascular doppler in incinerating this, we recognize that there's no flow through this artery that's been newly reconstructed 'cause the lumen is just too small. So if you move to the next frame, you can see that what we then do is take another set of fenestrated clips and put it distal to the first clip set, removing the initial set. So we essentially walk these fenestrated clips further and further distally along the neck of the aneurysm as is illustrated in this next figure. And finally, we end up with fenestrated clips that are much more distal on the neck than they were originally. And with microvascular doppler, we now insulate a beautiful flow through the newly reconstructed carotid artery. And the intraoperative arteriogram verifies that in fact, we have completely reconstructed the carotid, eliminated the need for bypass, and the use of microvascular doppler along with intraoperative angiography allowed us to document an appropriate time, when we created a lumen large enough to carry flow to the right hemisphere. As with incomplete obliteration of aneurysms, making sure that we maintain flow through the parent vessel and its branches also utilizes a number of very innovative and complex clipping strategies. Some of these photographs show a variety of flipping strategies we can use even with very complicated aneurysms to reconstruct the lumen of the parent vessel, yet maintain a complete obliteration of the aneurysm. And so I think this illustrates the versatility of surgery that we can use all kinds of strategies to accomplish our goals if we pay attention, and remain creative. Sometimes however aneurysms are simply recalcitrant to even our best endovascular or surgical attempts. And we have to eliminate either the parent vessel or one of the branches emanating from an aneurysm and rely on some type of an intracranial to intracranial, or extracranial to intracranial bypass. Here's an example of a complex aneurysm occurring right at the anterior skull base, that was not able to be treated. by any surgical means or at the point that this patient was treated, there were no endovascular options. And in this case, a saphenous vein bypass graft the proximal and anastomose to the internal carotid artery, the distal and the middle cerebral artery completely replaced the carotid circulation and provided this patient with a long-term cure of her aneurysm. This is a complex problem. This elderly gentleman presented with this huge vertebral aneurysm, which you can see on the CT angiogram is markedly compressing the brainstem. If we look at the video, you can see what our solution was. And I'll orient you here in a moment. Here is the brainstem. This is the right side, this is the left side. And the cerebellum up here. This is the vertebral artery here and the aneurysm you can barely see ventral to the brainstem markedly, compressing and distorting the brainstem posteriorly. So what we did in this case, we knew we needed to trap the vertebral artery, but PICA on this side on the ipsilateral side, you can see it right here is coming right out of this giant aneurysm. Here's the proximal vertebral, here's the origin of PICA. And so we did in this case is we identified PICA on the other side and notice how at the side of the tonsillar loops, they come close together. We put a permanent clip on this PICA since we're going to sacrifice it. And three temporary clips, and we do a PICA, PICA side to side bypass. Here you can see an arteriotomy being created with an ophthalmic knife, and the arteriotomy here. And this particular bypass is not technically difficult, but you've gotta think through it. So an anchor stitch is placed at one apex of each of the arteriotomies. And this is sewn in place. This will bring the two PICAs together by sewing, by tying this first knot, bring the apex of each of the arteriotomies together here. Obviously for this bypass one must use a running suture, otherwise you would have knots on the inside of the bypass. So after tying this knot, we leave a small tail, to tie the suture to in the end. And we sew the back wall of the bypass from the inside. So you can see here, in this case a 9-0 monofilament suture is being run in the back wall of the right PICA to the back wall of the left PICA, all the way to the next apex of the arteriotomy. Once we reached the apex of the next arteriotomy, then we simply using the same suture in a running fashion. Then go back on the outer wall, which you can see here, the outside wall, the right to the left PICA, back to the original stitch to the apex here, where we can then tie to the tail we left from the original stitch. Once that is cut, we now have a PICA PICA bypass, temporary clips are removed. The permanent clip is left on the PICA we're sacrificing an ICG videoangiography demonstrates excellent filling of the right PICA through the left. One of the dangers of this bypass is that you do put both PICAs at risk of ischemia. So that is something to take into consideration. Now that we know the bypass is patent we trap, the vertebral artery, proximally, and distally above and below our PICA bypass. And once we've trapped it, we can open the aneurysm. You can see the mark decompression we get of the brainstem as we evacuate the blood from this giant sack. We can go back to the slides, please. Next slide shows the intraoperative arteriogram, showing that the vertebral is indeed a completely sacrifice. And here is the left PICA filling the right PICA back to vertebral artery where we put the permanent clip, demonstrating the aneurysms completely obliterated and the bypass is still in.

- This is a spectacular talk full of amazing pearls. And I really appreciate your words of advice. I think the second part we're gonna start soon in a separate session, which even will be more exciting, full of amazing videos of showing how to get out of some of the most difficult troubles in aneurysm surgery. Dan, thanks again.

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