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Grand Rounds-Microsurgical Clip Ligation of Anterior Communicating Artery Aneurysms

Duke Samson

January 30, 2011


- Hello, ladies and gentlemen my name is Aaron Cohen from Goodman Campbell Brain and Spine, in Indiana University Department of Neurosurgery. On behalf of the AANS, I would like to invite you to join us for the second session of the AANS Operative Grand Rounds, which will discuss technical analysis, as they relate to microsurgical clip ligation of anterior communicating artery aneurysms. Today, we are honored to have with us Dr. Duke Samson from University of Texas at Southwestern Medical Center, who will be discussant. We are going to present a PowerPoint presentation and they will follow with four surgical videos of mine. The first one of which is an overview of technical analysis and the next three shorter videos will discuss some of the more challenging technical analysis for clip ligation of such aneurysms. Again, thank you for joining us. Duke again thanks for joining us today. We're going go ahead and proceed with our PowerPoint presentation. This is the disclosures, none of which interferes with the contents of this talk today. Anterior communicating artery aneurysms are 30% cause of a primary subarachnoid hemorrhage. Usually as we know the subarachnoid hemorrhage is basilar and interhemispheric and often along the gyrus rectus and anterior third ventricle if they're intraparenchymal. The aneurysm origin is from dominant A1 and A-comm and not just from A-comm and the vascular variations are very numerous, making clip ligation of this aneurysms one of the most challenging in aneurysm surgery. The indications of course depend upon the age and morphology of the aneurysm and the superior and posterior projecting aneurysms often may be associated with, more neuropsychological deficits after surgery, due to manipulations of their perforators from the A-comm. Do you guys clip aneurysms if the patients presents in a more delayed fashion and there's evidence of a vasospasm on the angiogram?

- Aaron, we do, because we feel like that we have good ways to treat vasospasm but all of them involve having aneurysms secured.

- Okay, so you don't feel the risk of what some authors mentioned as manipulating vessels interoperatively or risk of anesthesia and hypotension necessarily outweighs the advantages of treating aggressively with triple-H after it is clipped.

- You know, Aaron, I don't think so. I think that we tend to pay some special attention to avoiding hypotension and making sure that the brain is relaxed and things like that. But basically we feel like the major risks to the patient is the re-rupture of the aneurysm. Once that's secured, we feel like we can be very aggressive with the management of their vasospasm.

- Thank you, this is a picture from professor Yaşargil's book, Microneurosurgery, again showing the variations of A1s on both sides, as well as the origin of the aneurysm. As you can see up to 85% of patients who undergo aneurysm clipping for A-comm aneurysms have asymmetric A1's and if the preoperative angiogram reveals no or an arthritic A1 often a healthy one, and a sizable A1 is found in surgery and therefore identification of both A1's are important in surgery before proceeding with clip application. Again, you can see the neck of the aneurysm does incorporate at times part of ipsilateral A2, ipsilateral dominant A2 and therefore, that should be kept during application of clips. Go ahead Duke please.

- Oh, I think I would just reiterate that I think that there almost always a very significant contralateral A1 and if the surgeon ignores that at his or her peril, and I'd also say that as we look at these schematized drawings that it's important to remember that this anterior communicator may actually be in the sagittal plane not in the coronal plane and that really changes the exposure significantly for the surgeon.

- Thank you, again, just like what you mentioned, the variance in terms of the fenestrated variance up to 30% of patients may have two A-comms and up to 10% may have three fenestrated A-comms. And that should be kept in mind, especially if it can be seen preoperatively or intraoperatively looked for to understand the anatomy better and avoid clipping out of the fenestrated variants and some of the perforators that may come off of them. These perforators that go to chiasm, hypothalamus and septal region from A-comm or A1 or A2 are very important and no small perforator is necessarily too small or too unimportant and they very much overlap. So a large Heubner necessarily does not mean that the smaller perforators are not important, and there is significant overlap. What you very well mentioned and I think is critical is A-comm often is not in that regular, you know, transverse plane and often is in an oblique and a sagittal plane making understanding of the anatomy much more challenging, and the operator should keep that in mind in order to understand the anatomy better. These are some of the better variations of the A-comm. Again from professor Yaşargil's book, showing some of the very bizarre looking fenestrations can occur and a variation of triplicate A2s that should be kept in mind specifically during clip applications since you obviously do not want to sacrifice one of the three A2s doing clip application.

- I think that's probably one of the most common mistakes that are made preoperatively is a failure to appreciate that there is the third A2, which used to be called the artery de Corpus Callosum. And I think it's really, really important to know that's there, it's important to look for it, but it's important to always know before you operate on a patient whether or not that's an anatomical variation you're going to encounter.

- Thank you, this is again another slide showing the variations of some of the perforators off of proximal A1 or A2 and the fenestrations all of which should be looked for doing surgery to understand the anatomy better and make the surgery safer. Let's talk about preoperative evaluation. Any patient who presents with spontaneous gyrus rectus hemorrhage, should deserve a vascular study to rule out an A-comm aneurysm and because A-comm aneurysm may present with no subarachnoid hemorrhage and only a small gyrus rectus hemorrhage. A-Comm aneurysms actually have the highest false negative rate of any aneurysm and that means if a patient presents with subarachnoid hemorrhage, which is very much aneurysmal and you don't find any aneurysm on initial angiogram, the chance and the patient actually does have an aneurysm, which we did not detect on the angiogram, it is most likely an A-Comm aneurysm. That has to do with a bilateral balanced role often, or some flow from both A1 stem may prevent the dye to enter the A-Comm. And if there is a high suspicion of A-Comm over an aneurysmal subarachnoid hemorrhage, the operatives should consider a compression study to better study the anatomy in the region with an angiogram. How to approach an A-Comm aneurysm of the side is obviously controversial, I'm a left-handed surgeon. So I often find for a reason to operate from the left and if there is a dominant A1 I operate from the left side, however, you know the very experienced surgeons such as Duke I'm sure, would argue that any A-Comm aneurysm can be approached from the right side and therefore you will be manipulating only the non-dominant hemisphere. Obviously the projection and the relationship with the aneurysm dome is also important to be avoided doing surgery and again, an arthritic A1, as small A1 on angiogram does not a low the surgeon to avoid its identification or looking for it during surgery, because if there is a healthy one, which there often is a sizable A1 in surgery, and you don't find it and during clip application, you run into premature intraoperative hemorrhage without adequate proximal control that could create a very life-threatening situation for the patients.

- I really agree with your checklist here about the important features that determine how you're going to access the aneurysm. And I think probably the most important thing is the realization that you don't have proximal control until you have good visualization of both of the A1s and whatever approach, whichever side gives the surgeon the most confidence that that he or she is going to have that, is probably the right side to approach the lesion from. I like to operate under the non-dominant frontal lobe, I'm right-handed and I think it's an easier operation from that side but certainly that doesn't preclude going on the other side when there are special cases.

- Let's talk about patient positioning and craniotomy. This is the position that we have come to use. We turn the head about 40 degrees and maybe slightly north necessary. The incision stays behind the hair-line. We do not expose more of the frontal bone with a more circular or a curvilinear incision. I think just as long as you stay behind hair-line, that will give you adequate exposure.

- I think it's really right, I don't think there's any reason to bring that vertical limb of the incision from the tragus up superiorly, because you really don't need any exposure of the temporal lobe in many times out of the sphenoid ridge. So think this is a really more physiological approach than the traditional terion exposure.

- Thank you, so this is a model that describing the approach here, again, the patient position is supine, the head is turned about 40 degrees and the incision is just behind the hair-line. Often people have discussed the issue of that other incision through the eyebrow. We like this incision because we think that cosmetic deformity is minimal. The position of the pinion is important. As you can see in this view, the pinion is placed just along the superior temporal line in the voice of temporalis muscle and inclusion of the bone and the contralateral pin is placed actually behind the ear, just on this grasp with the pinna bone. And that really leaves a large working zone for the surgeon without being sort of obstructed by the pinion.

- I agree with that, I think even though on small, unruptured intercommunicating artery aneurysms, I'll often do them through a supinal orbital bony exposure. I don't like the incision in the eyebrow. I think it looks just like that, it looks like an incision in the eyebrow, so it's better off to put the incision more posteriorly.

- Thank you, this is the way it's set up. I think placing the surgeon across from the assistant is very helpful in terms of transferring instruments. The fellow or residents will be located here, just underneath the microscope and that allows easy transfers of instruments and also provides a monitor for the assistant to watch the surgery and keep up with what would be the next necessary next instruments. This is a roadmap just showing how the surgeon starts along the Sylvian fissure, opening just the anterior limb and walks across A1 in order to expose the aneurysm. This is again the incision and the location, avoiding central and superior temporal artery, cutting the incision and full craniotomy, we place a single burr hole just below the superior temporal line and do an osteotomy or cut the bone in this direction. I've turned the heel of the dura around itself and go the same way and take the drill out. We feel this way minimizes the amount of bone loss along the key hole and some of the associated post-operative deformity. Although using multiple burr holes may be necessary in older patients who have a very adherent dura to the inner surface of the skull bone. I think it's very important to drill the bone across the floor of the roof of the orbit and the dura can be stripped away and no much, you know, skin needs to be removed as a Duke I believe that we'll mention in a second. Removing this much bone over the temporal lobe is unnecessary, removing the sphenoid too much would be unnecessary. What's most important to keep flat and a drill across the frontal, I'm sorry, orbital roof, and make sure you're very flat as much as possible and some of the bumps have been drove away.

- I really like that illustration there, because it shows us so many do not, that these bony excrescences that are a sonometer or two sonometers deep on the floor of the frontal fossa, really do get in the way as you're coming across and trying to minimize your amount of brain retraction. And if you can eliminate those preliminarily before you even opened the dura, you've really made your exposure much better.

- Right, I don't think orbital zygomatic is necessarily required. Do you use OZ or just a good terional is all you need Duke?

- Which we don't use the OZ approach very much, because we don't feel that it adds anything to the exposure. We did a series of those and found out that, it also didn't minimize the need for gyrus rectus resection. So in general, we tend not to use that exposure.

- Thank you. This is the curvilinear dural opening, as you can see. Let's talk about intradural dissection. We place the retractor just posterior to the frontal lobe and open the fissure, the anterior limb all is needed. You may have to take a bridging vein after it's coagulated. To expose A1 a carotid bifurcation exposure is necessary and to this, by not exposing the bifurcation that would minimize your frontal lobe retraction, which is very important in this procedure. And also more importantly if there is a high riding proximal A1 you don't need to expose that either, all you really need to expose is just enough of the A1 to get a temporary clip on it and whatever makes you not retract the frontal lobe, that's probably what's most important to do as long as you get the A1 under control. Exposure of both A1s is necessary and what I have personally learned from the Duke's book, The Intracranial Aneurysms Techniques, is that when you try to dissect the A1, the anatomy can be difficult, especially because you have an aneurysm, you know, that it will be on your way to the other side. And what is critical is try to identify the contralateral A1, I'm sorry, the contralateral optic nerve and follow it distally from the optic foramen and then where it joins the optic chiasm, just lateral to that junction, is where the contralateral A1 is located.

- I really think this is one of Professor Yasargil's major contributions to the intercommunicating artery aneurysm surgery and that's the demonstration of how to find the contralateral A1. We phrase it just a little differently than you do Aaron, but what we say is that you follow the ipsilateral A1 until it departs from the optic nerve and where it does that you stay on the optic nerve, cross the chasm at that level and you'll run right into the contralateral A1. It's sometimes a little difficult to identify it, especially when the system is blood-filled and because of the direction of the contralateral A1, in the position that you've outlined is as the artery is running out of the wound and kind of over your left shoulder. But once you get comfortable to looking up high on the chiasm, it's not down on the nerve, but high on the chiasm, you can always find it, even in the blood-packed system.

- Thank you and for inferior pointing aneurysms, it is important to avoid aggressive frontal lobe retraction and aversion of aneurysm dome. Maybe a remover of a little bit extra gyrus rectus to minimize retraction may be necessary. And also earlier, you know, ipsilateral A1 dominant A1, temporary occlusion may be necessary to just avoid any aggressive manipulation of the dome. This is again a illustration showing the internal carotid artery and approach from the right side. In this case, the internal carotid was short and bifurcation was exposed upon retraction where they illustrated from the video. And you can see just staying right on the optic chiasm as you as you cut the arachnoid is important. If you get too close to the brain and try to use blunt dissection that may interfere with the dome and cause pre-mature rupture.

- This is a good picture and kind of makes the point that we were talking about a minute ago, is that the route to the contralateral A1 is to follow the ipsilateral A1 and then stay tight on the chiasm and up high, it should cross over. I think it's interesting that when you look at the variety of projections almost none of these aneurysms project interiorly and posteriorly. Almost none of them come back into the chiasm itself. And because of that, there's almost always an easy pathway there if you're just willing to take it. Right exactly where Aaron's dissecting here, staying up high on the chiasm, not down on the nerve, the contralateral A1 is not down here, it's up here and just gradually elevating the gyrus rectus and staying flat with the chiasm will take you always, to the contralateral A1 and after that, things become a whole lot easier.

- Thank you, so the step two after finding A1 would be to position the retractors efficiently, protect the Heubner, avoid, you know, aggressive pulling of the gyrus rectus that could place this important perforator at risk and untether it, and don't put your retractor aggressively on the Heubner to cause it's occlusion and the longitudinal and cortical incision. So up here resection and then coagulation of the medial pial and sharp dissection is important and do not shortcut and do not make yourself struggle by trying to remove very little gyrus rectus. I think just enough to give you good exposure is important because trying to struggle with a little bit of brain removal may have much more disastrous consequences if you're struggling and run into premature rupture, because you are not able to see what's going on very well.

- I really agree with you, I think that as long as you're respecting the perforators especially the Heubner, I think that a really aggressive gyrus rectus resection, especially in a ruptured aneurysm, serves a surgeon very well. We tend to do this operation as Aaron talked before with two retractors, we placed one right here on the posterior aspect of the orbital cortex here, and we place the other one anteriorly as Aaron is showing here so that the tip of the retractor crosses the olfactory tract and is placed right at the scene where the aneurysm must be a fissure. And then the question about how much gyrus rectus should be resected is very simple. You back both of the retractors off until you can see the olfactory tract and then this hernia that Aaron's illustration is showing you so well, is exactly what needs to be removed. And I kind of tell my residents and fellows when I'm teaching the really important thing here as you're doing this is to have in your mind what you're doing is not to show yourself the aneurysm, but it's to show yourself the origin of your A2. So you need to take out enough of this gyrus, so that you can see the superior aspect of the A1. Otherwise it's very common to just float on out here onto the aneurysm and not recognize that you've passed the origin of the A2, which would be tucking on your retractor back here.

- After exposure and thank you again for your detailed discussion, which I think was very helpful is the most important part is really the exposure of A1, A-Comm and A2 junction in the aneurysm neck and often we try to move across from A1, find the ipsilateral A2. Again, it's important that A-Comm can be oblique and just looking at you across its length or in a sagittal plane rather than moving away from you. Anterior pointing aneurysms, dissect across a A-Comm and stay above and below A-Comm to find a contralateral A1 and A2. Again, depending on how the dome of the aneurysm is located or projecting, this dissection is going to be different, so from an anterior pointing aneurysm, identify A1, remove gyrus rectus, find A-Comm and then stay above and below, if it's anterior pointing aneurysm and then this keeps you out of trouble of the dome. If it's an inferior pointing aneurism, obviously you can aggressively retract the frontal lobe and you may dissect above A-Comm, stay above that and then find a contralateral A1 from distal to proximal, in other words, you may be able to stay above A1, and then stay above the A-Comm, find the contralateral A2, and then follow it more proximally to find the contralateral A1. For superiorly and posteriorly pointing aneurysms, the hypothalamic perforators are critical because they're often adherening to the dome or the neck of the aneurysm and temporary clipping and deflation of the aneurysm would allow dissecting the animals away from the perforators, rather than the perforators away from the aneurysm and this would prevent you from putting too much distraction force on that perforators.

- Aaron, I agree with that, I think I did this just a little bit differently in the sense that, I really never take out gyrus rectus until I've identified the contralateral A1. I think that just works better for me. And I'm really more comfortable then with removal of the gyrus rectus, knowing that I have proximal control. I think most of the time, the Newberger's complex is the hardest for me to identify, is the contralateral A2. And so if I have both A1s I'm willing to go on to temporary occlusion relatively early for a short period of time to allow me to manipulate the dome in the aneurysm and identify where the contralateral A2 is. But I think that it's important that a surgeon remember always both A1s, both A2s, the communicator, both Heubner's and the hypothalamic perforators, all have to be identified before you begin really seriously thinking about how are you going to put your clip on.

- Thank you and here is a view of the protruding quarters, now you may be approached to find the A1 on the other side. And often we try to go in fairly to avoid manipulation or below A1 to avoid manipulations of the perforators from A-Comm, but if it is absolutely a transverse looking A-Comm, as you can see here, which we ideally all like to see, often maybe staying a little bit more posteriorly, you find A1 contralaterally there and then you dissect above A1. Again, what Duke very well mentioned is I have been called from the operating room of another surgeon in another state, asking me how to find a contralateral A1, because they couldn't find it and they were looking for it here across the falciform ligament. It is not there, again, follow the contralateral optic nerve where it joins the chiasm, right at junction laterally. If you lift up the complex here, you will easily find it and often a very healthy one before you dissect the gyrus rectus as very well mentioned by Duke.

- This nice illustration points up another thing that I think is a side point that's very easy to remember, and that is that if the brain is the tight and your ventriculostomy is not working as well as you'd like or your lumbar drain or whatever you have, this is an optimal time to open the lamina terminalis and my friend Raphael DiMargo believes that that routinely opening the lamina reduces the incidence of a post-subarachnoid, hemorrhage hydrocephalus dramatically. We've not found that to be the case here at Southwestern, but what we have found is that very often evacuation of the third ventricle will give you just that little, extra bit of brain relaxation that will allow you to ease up on your retractors during the operation.

- Thank you again, I routinely try to clip contralaterally first before it's a lateral because, if there is an aneurysm ruptured pre-maturely, it's often most difficult to get the contralateral A1 under control as you can see here in this situation, over ipsilateral A1 but most commonly below ipsilateral A1. And after you do that, really, that gives you a very nice relaxation.

- I think that's really true and I think that's an important point that very frequently, a unexperienced surgeons don't get. And that is if you could put this first clip on, if you could expose the contralateral A1 and put the first clip on there, then this clip is really out of your way, and you don't have to worry about it anymore. If you put your ipsilateral clip on, then you're always battling with your ipsilateral clip when you're trying to get to the contralateral side. The other thing I would say is that in a ruptured lesion, when I expose the contralateral A1, I take a very small amount of cotton and I just place it on the A1. If you have an intraoperative rupture, the cistern fills with blood and very often, it's difficult to find the contralateral A1, but if you have a piece of cotton on it, it's always right beneath the cotton. You can pick it up and put a clip on it easily there, but this is a nice demonstration. The other thing that very often I think people forget is it's nice to see how Aaron has avoided Heubner with both this clips, I think that's really, really important in the long haul.

- Thank you, let's talk about nuances of clip application. Now, again, the aneurism projection is important for anteriorly and inferior projecting aneurysm, I think a straight clip just does, parallel to A-Comm, those are pretty straightforward aneurysms. Superiorly projecting aneurysms are very difficult due to the fact that how much attention has to be given through those small perforators, off of the A-Comm specifically and often a fenestrated clip is your best friend. For posterior projecting aneurysm, obviously, a deflation early on is important and a straight clip may be all is needed. After the clip is applied, we inspect the perforators and other vessels very carefully. We use a micro-doppler and then we have come to really like using the indocyanine intraoperative angiography. As long as you can see the aneurysm, well, you can see if it's filling or not. In this region, it can be difficult because often the dome is in the gyrus rectus and you want to remove as less as possible. But again, it's been a very useful tool. And may I ask Duke to comment on ICG for us?

- Well Aaron, I think ICG has really changed aneurysm surgery for the better. We've had it now, I guess for a couple of years and just routinely use it. I think it's, as you mentioned, I don't think it's as good for identifying an aneurysm patency as it is for making sure that even the smallest vessels in the complex patent after your clip is applied. If you can't really determine what you've got, then I think you're pretty much obliged to rely on what Roberto Heros calls the Turo Test and that is sticking at 26-gauge needle in the fundus of the clipped aneurysm. And I think that's an important part of the thing although sometimes it provides some relatively unpleasant surprises.

- Thank you and you know, I have a very generous about clip re-application, this is an area where it is so important to just get the clip right. And I think some people have trepidation saying, well, the clip is applied, you can't move the clip now. I think you've got to be very open to that and understand this is a challenging location. It's across the midline of the skull base, there's a small amount of space to work through and that there's a lot of important perforators that make this challenging, this clip application very challenging.

- I think that's really important and I think, you know, having watched Dr. Yasargil do a lot of aneurysms, he has never been satisfied with one clip application and really, really is demanding about making sure that you've got as good anatomical solution to the problem as possible, which involves routine clip application. One of the things that we found that's been very, very beneficial in situations like this and at the basilar apex is that we have a set of clip appliers in which we've removed all the ratchets. So there is no additional effort required to either open or close the clip. And we use those to simply crack the clip open and adjust it by a millimeter or so and it's been very, very helpful. So I think that if you know that you're going to use a lot of clip re-applications and modifications, having a set of those ratchetless appliers is very helpful.

- Thank you and as you remove the retractors, you've got to make sure that clip is not getting displaced. It's not stenosing A-Comm or A1, it's not compressing the optic nerve that really can disappoint the surgeon who did a perfectly good technical operation.

- And as I told Aaron before on this latter point, I've had four patients who woke from surgery with normal vision and then suddenly as the brain re-expands after the dural closure have developed unilateral optic nerve difficulty and in three of them an immediate return to the operating room has demonstrated that there was pressure on a nerve, and we've been able to alleviate that by repositioning the clip and the other one despite that, the patient's unilateral amaurosis persevered.

- Thank you. For a transverse A-Comm or anterior pointing one, you can see I'm fenestrated clip is the most often used clip here. You've got to make sure that your temporary clips are out of your way and that's really important, just have your permanent clip push your temporary clip and distort something and evoles the vessel, just would disappoint everybody.

- I think this is another point where having the sufficient amount of gyrus rectus resection makes all of this necessary manipulation much easier and much safer. The smaller the hole in which this is being done, the bigger the risk of making an awkward move. And that's why I think that the gyrus rectus' section is really essential in any kind of significant size and to your communication.

- Thank you, at this point, very pointing aneurysm. I think that temporary occlusion is very important and as you can see a straight clip applied. For a straight pointing aneurysm, often it's difficult to see the contralateral A2 and it's the most difficult one to identify. We have to put this one, the contralateral A1 clip, most commonly from the bottom of the ipsilateral A1. And then often as you close the clip, the last seconds, you're going to identify the A2 and that's how you avoid it contralaterally. Because again, this is such a challenging pointing aneurysm.

- So in this aneurysm, in this picture, it's maybe a little bit difficult to make out that Aaron has already dissected the hypothalamic perforators away from the aneurysm. And he's got his temporary clip placed beneath his own A1, which basically gets the entire body of the temporary clip out of the way of this permanent clip application. You can just imagine what this would look like if you had the temporary clip for the contralateral A2, sticking out above the ipsilateral A2, it'd make this much more complex.

- Some of the aneurysms that are straight pointing can be approached by the right of other angles clips, which would make things easier, obviously as long as you don't cause the accordiong effect across A-Comm.

- This is a beautiful illustration of the use of a clip that we use very frequently in anterior communicators. This is a clip that Dr. Yasargil designed for proximal and distal clipping of internal carotid aneurysms, so we call it the atomic clip, but it very frequently, especially in a sagittaly situated intercommunicating artery is the ideal clip to completely embrace the aneurysm neck while avoiding the contralateral A2s. Sometimes you don't need quite as much angle as that and there is a clip that has less angle than that, which for lack of a better term, we call the semiaphelmic and it is also very good where for this orientation.

- Let's talk about some of the variations. Again, the key component here is the surgeon is looking from this direction, this is the dominant A1. The aneurysm is from really the junction of A-Comm and A2 and this is the area that the surgeon is most commonly blindfolded. And often we put a clip across here without knowing there is a residual here and that's why the clips should always come from the front to the back to get that piece that comes more often from the proximal A2 and occasionally there are aneurysms that come more pre-dominantly from A-Comm. And this is a very nice illustration, showing how the surgeon who's coming from here puts a clip across A-Comm parallel to it to make sure the A-Comm is not stenose, but actually, you know, misses the portion of the aneurysm that's filling from A2 so really the operator has to adjust the hand from front to back and get that portion of the aneurysm and often you may need multiple clips or a straight clip after a fenestrated clip.

- I really agree with that, I think that this area here is most frequently the area that the surgeon has most difficulty dissecting and also difficulty including and the fenestrated clips are an excellent answer to that. I've had a couple of cases in which, they're trying to dissect this area, developed a rent in the aneurysm neck right here at its origin and the only possible way to occlude that, is as Aaron has shown here with a distal to proximal fenestrated clip. I would say that I think almost always it's better to use the shortest fenestrated clip that you can, because I think that it's often difficult to tell where the blades are going on the other side and often difficult to see that, once your clips are in place, so we like the very, very short bladed fenestrated clip with a very small hole.

- Thank you and for atherosclerotic aneurysms, you may need two clips to have the second clip assist the first clip or occluding the neck of the aneurysm. Let's talk about complications. As you see, when does enough A-Comm aneurysms, you will see these perforator injuries across the caudate, especially on the left side, it can be very problematic. And you know, the surgeon may say, well the Heubner looked great, why do I have a caudate stroke? And that's because there is so much perforators along the region, all of which have to be protected. And so if you say, well, I took a small perforator off, it was attached to the aneurysm neck, but the Heubner looked good, well, unfortunately that's not even good enough, the margin of error is so small in the aneurysm in this region and as you can see, the Heubner starts off in from A2 and then goes parallel to A1 and irrigates the entire perforator substance. There is a number of perforators in this region, but the complication abulia, contralateral neglect, transient hemiparesis and memory difficulty, always can be problematic and again, this is the region where some of the perforators A1 and A-Comm and proximal A2 feed.

- Let me just say a thing about that Aaron. The other thing that makes this really treacherous is that you never have any idea about what kind of depths that it's going to accrue to a patient with these kind of perforator infarcts. Sometimes you'll be very lucky and nothing obvious will happen. I've told Aaron previously I had a gentleman who I operated on for bilateral carotid bifurcation aneurysms and who ended up with bilateral Heubner infarcts. He had no noticeable deficit. He was a lawyer and that may be the reason, but in other patients, simply a single small Heubner infarct will be devastating in terms of their recent memory, their cognition and their ability to understand complex ideas.

- Well said, let's start with our first case in the video, a 35 female year-old who was a professor at our college here in Indiana University had incidental seven millimeter A-Comm aneurysm and this is the 3D angiogram, a very standard interior pointing aneurysm with a broad base of the A-Comm. This is a more anatomical view from the surgeon's point of view and this is looking from below again, showing A2s, dominant A1 from left and the aneurysm.

- It's a nice case, it also shows the kind of heart-shaped course that the proximal A2s often run around a decent-sized intercommunicating artery.

- Thank you. This is a left-sided frontotemporal craniotomy that was performed for clipping up the angiogram we just showed you. A bone has been really drilled away. The optical carotid system was just open and you can see the retractor has been placed along the posterior part of the frontal lobe and just the anterior of the Sylvian fissure has been opened. Not much temporal exposure is necessary, I think this case too much of the temporal lobe was exposed. I think it good anterior fissure exposure and dissection would make your job much easier in terms of frontal lobe retraction later in the procedure.

- I think especially in patients who don't have a lot of cerebral atrophy and huge spaces, this opening of the mesial part of the fissure, it's very, very helpful in diminishing the amount of retraction necessary on the gyrus rectus and on the aneurysm itself.

- Thank you, the second step would be on tethering the optic nerve as you can see by sharp dissection and making sure you identify the A1.

- We tend to think that the best place to find the ipsilateral A1 is right here on the lateral margin of the nerve. If you look at most angiograms that's where the A1 starts it's course to descend the inner hemispheric fissure. And so by just opening gently across here, back and forth, normally you'll pick up the A1 right here and as Aaron said, you don't need a lot of the A1. All you need is enough to put a temporary clip on. And we like to prepare the A1 for temporary clipping as far away from the hemisphesric fissure as is reasonable, because this gets awfully crowded down here with a couple of temporary clips.

- Thank you and I think at this point, I'm just trying to show the retractor placement. It is so critical just to have the retractor perfectly right here and you can see the herniation of the cortex Duke, you very well mentioned.

- Yeah and now you can see here's the A1 and it's right on the margin of the nerve here. And so now you've got your 50% to proximal control and ultimately the surgeon is going to end up resecting this segment of the gyrus rectus to give himself adequate exposure of the communicating complex.

- You surely read my mind. Here it's me trying to remove the gyrus rectus. You can see the Heubner on the white arrow. Duke is the blue arrow, by the way, for our viewers. And you can see the Heubner has to be protected, maybe a little bit more irrigation here would have been helpful during bipolarization, but a small portion of gyrus rectus has been removed. Again, this is an unruptured aneurysm. So if the vein is tight, you may need to remove more gyrus rectus, but the perforators here the Heubner, coming back it is just so important to be preserved.

- As you look at this video and you're thinking about where you're going to find the contralateral A1, it's going to be right here where the A1 segment leaves the nerve, this is where you cross over the chiasm and at that spot on the contralateral side, you'll pick up your contralateral A1 and then you'll be in complete control of the communicator complex.

- Thank you. I think in this juncture we removed a little bit more gyrus rectus and I agree with you, probably finding the ipsilateral A1 would be nicer before we use gyrus rectus. This is again in that side of frontotemporal craniotomy, this is ipsilateral A1, contralateral A2, I'm sorry, contralateral A2, ipsilateral A2 and again, the Heubner and the aneurysm is located right there. This is somewhat a hypothalamic perforators. This is a better view, this video has been taken from a more wide field of view specifically to keep our viewers oriented during the procedure. We typically do operate at a higher magnification. As you can see this as a contralateral A1 here, ipsilateral A1, contralateral A2, ipsilateral A2, Heubner and the neck of the aneurysm. I'm placing a temporary clip control laterally, under contralateral A1 because that's usually the most difficult place to place a temporary clip. And then I think this is showing the neck of the aneurysm and portion of the aneurysm.

- So I think that maneuver right there, that Aaron just showed us is really, really important. Whenever you put a temporary clip on a feeding vessel, I think the first thing you should do is take dissector and just nudge the aneurysm and see whether there's any effect to what you've done or not. If there's not any effect, you may not have the vessel in the temporary clip and you may be proceeding as if you do and down that road, lot of disasters. So I think really it just takes a second to nudge the aneurysm and see if it's softer.

- Thank you and this is a fenestrated clip placed across the neck of the aneurysm, Duke. I really liked that new nuance of making sure that temporary clip is on the vessel. I can't tell you how often when the space is small, the surgeon is nervous because he sees an aneurysm staring at him, one may just say, let me just put this on there and get out of here and they run out of patients. I think this is such a critical part of the operation to be patient to assure and triple check everything that's occurring in the field because every little mistake could have disastrous complications.

- I think when you're using the fenestrated clip like this, and this one looks like it's really nicely placed, but I never can actually tell whether the fenestration may have narrowed the artery and the fenestration down until I actually take off my temporary clips and get complete flow in the thing. Sometimes when it looks like it's been stenosed, it looks great and certainly it looks great here on your ICG.

- Right, you can see in the ICG Duke, the aneurysm was filling in this case. And that's, again, that part of the aneurysm from A2 ipsilaterally that I could not clip well, because I was not able to see the very well. So as you very well mentioned here is the straight or a slightly curved clip grabbing that residual piece of the aneurysm that is coming off the neck of aneurysm that's coming off the portion of ipsilateral A1. And again, gently moving the clip and the whole complex and placing it right on the residual neck coming off of A2.

- That's another good example of what the professor Yasargil has talked about so often, that when you put your first clip on very frequently, you'll find out it's not adequate, but what it does do is it shows you what you really need to do next and it really it really simplifies things, rather than being a failure. So just because the first shot didn't go out of the park, it's not a time to wring your hands.

- Thank you and here I guess again the low threshold to just get it right, right across, I think I was leaving a little bit on neck left. So here it is just to make sure it is as good as one can get. Obviously trying to be perfect in this situation is not good because it can stenose the A-Comm or cause other complications. As you can see here and no longer the aneurysm is filling, this is the tip of my dissector and again, there's no dye, the idocyanine green that is really filling the aneurysm dome. And that's again proximal A2 ipsilaterally and Heubner, well illustrated right there. So let's go to our second case and discuss some of the nuances in a shorter video. This is again the postoperative angiogram on the first patient showing adequate clip application. The second case is a 55 year-old male with an incidental 15 millimeter atherosclerotic A-Comm aneurysm. And here's the CT angiogram showing a very sizable A-Comm aneurysm that was incidental. And this was approached also from the left side because the dominant A1 was located there. And this is again, the ipsilateral optic nerve, ipsilateral frontal lobe on the left temporal lobe, very atherosclerotic aneurysm and this is contralateral A1, again, Duke very well mentioned. You lift up the complex and right underneath, across from the chiasm on the other side is where the contralateral A1 is located. In this situation an ipsilateral clip was placed first because we felt the chance of, you know, early rupture would be minimal in this very highly atherosclerotic aneurysm. This is again, the Heubner, part of the gyrus rectus on the left side was removed. This is a very sizable aneurysm, you can all see a portion of it. This is the optic nerve and removing gyrus rectus, we identify the contralateral A2 here. This is again a more transverse looking A-comm and this is again the contralateral A2.

- This is a very large and giant aneurysm, so anything, 15 millimeters and up in this area, pose a lot of of problems, not so much for exposure, but for clip obliteration because they all have densely atherosclerotic walls and very frequently contain intramural promise. And so in most of these situations you're going to have to have a minimum soft in the aneurysm very often, and you're going to have to empty it with application.

- True, in this one, a fenestrated clip was initially placed Duke and then it was not adequate. It was filling, the aneurysm was on ICG. So we placed the repositioned clip, moved it a little bit more proximately because that's often A2 where it's filling. It was filling again, so for these atherosclerotic aneurysms we augment the first clip with a second clip and trying to preserve all these important perforators through the fenestration and in this case, the second clip did close the neck completely and we did not need to deflate the aneurysm, although that's often unnecessary. This is the postoperative angiogram. This is a third case, a 56 year-old male, with a sudden onset of headache and confusion and was non-vocal and confused on arrival. This patient had a dominant A1 on the left, but their hemorrhage on the right as most often is because the dome is contralateral to dominant A1. And even though the dominant A1 was on the left, we approached from the right to prevent bilateral gyrus rectus injury. And I think that's an important nuance in my mind. Do you have any thoughts Duke?

- Well, I think that's right and I think that in a situation like this, even if you had a large gyrus rectus clot, you'd be able to evacuate it from the contralateral side. So I think it would be nice to avoid giving them that kind of problem bilaterally.

- Thank you and this is again the dominant A1 on the left angiogram showing the anterior looking or pointing aneurysm. Let's go to the video for this case. This is a right-sided craniotomy to orient our colleagues. And as you can see, this is contralateral A1, ipsilateral A1, temporal clips on both. This is a frontal polar artery, which is more approximately located on A2 and it's being dissected away from the aneurysm neck. It travels behind the aneurysm, as you will see in a second, and this is again, the A-Comm is rotated, it's in a more of a sagittal or how ever you call it? You know, playing rather than more in a transverse plane.

- That's really nice picking that frontal polar off. I think that there are a lot of people that would just go ahead and set the clip on that, but I think that's absolutely a really nice job. And it's so much easier to do when the aneurysm is going soft, secondary to your temporary clip placement.

- Thank you and I think generous use of temporary clipping as long as adequate brain protection is used, is really important in this case. So let's go to our next case which I think is very intriguing. This is again, a post-op angiogram on that patient, showing an adequate result. This is a case that was included in this presentation after the initial recording with Dr. Duke Sampson and therefore I present it by myself. This is a partially coiled intercommunicating, artery aneurysm and general, clipping partially coiled aneurysms can be very challenging due to the fact that the coils often extrude through the wall of aneurysm as they're exposed in surgery. And these extruded coils can interfere with dissection around the important vessels. The clip application can be very challenging also, since the coils often occlude portion of the aneurysm and not all of the aneurysm and therefore it is difficult for sure to know from outside where the surgeon is looking at surgery, where the coils are within the aneurysm. Preoperative 3D angiography can be critical to assure a neck exists, an adequate neck to apply the clip, since it will be unfortunate to expose an aneurysm during surgery that is deemed unclippable since adequate neck is not present and then surgeon may attempt to do a coil embolectomy or in other words, remove the coils through the dome of the aneurysm, which is often fraught with complications, since these coils are very much embedded in the wall of the aneurysm and their removal can significant injury of the wall and potentially shear off the neck of the aneurysm, placing the parent vessel at risk. Managing partially coiled aneurysm acutely with potentially mobilizing some of the coils can be much easier since the area on these coils may not be as much embedded into the wall of the aneurysm. So what are the management strategies? Primary clipping is most ideal but often a number of clips have to be tried and often requires multiple clips for complete occlusion of the residual aneurysm. Revascularization may play a significant role in partially coiled aneurysm treatment and completion of the bypass may be necessary prior to tackling the aneurysm if the coils are in a position where the parent vessel could be at risk during clip application. Proximal collusion of course, is an option as well and it well may change the hemodynamics in the aneurysm and cause complete occlusion or thrombosis of the aneurysm. Wrapping with muslin or cotton is an option as well. However, this method is associated with an unknown efficacy. This illustration reveals a partially coiled, intracommunicating artery aneurysm. In this situation, the coils have compacted through the dome and there is a residual aneurysm more approximately in this situation, this part of the aneurysm is most likely least populated with coils and therefore the first clip, clip number one is placed initially, and then additional clips are applied distally and the distal clips may not close completely due to presence of some of the coils in this region. In this situation that you can see in the second illustration which you will see in the surgical video in a second, the closed or occluding the upside of the aneurysm. However, the dome has remained unprotected. In this situation it may be most prudent and that's what we have done is place a clip distally across the dome, protect the dome, decrease the chance of intraoperative rupture and then leave yourself with more opportunity to use different clips, to assure complete occlusion, more proximally where there are coils and these coils may make clip application much more difficult. If you initially placed the clip more proximally, since there is a chance to blade would not close completely since you are not sure if some of the claws would prevent the closure of the blades, incomplete closure of the blades could be associated with intraoperative rupture since the dome is not protected. Let's go ahead and discuss the case of a 62 year-old female with a ruptured complex, multiloculated intracommunicating artery aneurysm. She presented with a grade IV Hunt and Hess and due to her poor neurological status underwent partial coiling of the suspected superior dome of the aneurysm responsible for the hemorrhage. The more inferiorly anteriorly pointing dome or lobe of the aneurism was not treated since it was suspected not to cause the hemorrhage and also had a broad-based neck which made endovascular treatment more risky. Fortunately, she made an excellent neurological recovery and subsequently underwent a left frontotemporal craniotomy for a complete occlusion of the aneurysm. This is her initial angiogram which she presented at hemorrhage and you can see the A1 which was dominant and no A1 contralateral report was present and the angiogram on her end was not having surgery either. As you can see, there is a superior lobe the aneurysm, as well as an anterior inferior lobe. This is from the back and this is from the front. Again you can see the superior pointing lobe that was initially treated endovascular, the air was noted noted to be most likely the cause of the initial hemorrhage. This is her postoperative endovascular retreated aneurysm that you can see the lobule securely has been very well treated with the coils. However, there is a residual inferior lobe that has been untreated. She subsequently underwent a surgical clip ligation, and this is the surgical video. This is a left frontotemporal craniotomy. This is the left frontal lobe. This is the retractor over the left from the lobe. This is the lobe of the aneurysm that was located anteriorly and inferiorly, which was not treated. This is the superior lobe that was treated. This is approximately A2, A1 and artery of Heubner, the dissector, the tip of the suction and one of the frontal funnel to pull the branches off of A2. In this situation, the superior lobe that was previously treated with the coils is being mobilized with the dissector. There is much amount of scarring and as you can see, extrusion of the coils through the wall of the aneurysm as often present in these partially coiled aneurysms. This does increase the risk of dissection. As you can see, we're trying to use the tip of the dissector to dissect through the scar and identify the contralateral A2 prior to placement of the clip across the neck of the aneurysm. And then you can see the coils clearly extruding through the wall of the aneurysm. Ultimately were able to dissect through the scar, identify the frontal polar artery and a peek of the A2. This is more proximally, you can see lamina terminalis, contralateral optic nerve, ipsilateral optic nerve, A1. Inspection did not reveal any evidence for contralateral A1. For this picture posteriorly you can see the hypothalamic perforator without any evidence of contralateral A1, again, the hypithalamic perforators, Heubner, ipsilateral A2. Further dissection over the aneurysm and the partially coiled part of the aneurysm, you can see the frontal polar branch and also A2, I'm sorry, contralaterally. A temporary clip was placed across A1 to deflate the aneurysm, the residual aneurysm, as you can see, the morphology of the coils has been defined, compared to the residual part of the aneurysm. A permanent clip was initially placed across the aneurysm to protect the dome. As you can see, I tried to put the clip and it didn't seem at the time that was completely closed. The blades did not seem to be sitting up properly, so I did not like the position and therefore repositioned the clip more anteriorly as we discussed, during the second illustration, to assure complete closure of the blades more distally so the dome is excluded. Considering the morphology of the coils here, the disclosure was much more satisfactory. As you can see, the second clip can be now placed as the dome is protected. And while taking into account the coils that are present at the tip of my pointer and this second clip, a short satisfactory occlusion with some of the cores are remaining more medium. Postoperative 3D angiogram reveals adequate clip occlusion of the aneurysm with some of the coil present, occluding the rest of the aneurysm. Let's talk about tips and pitfalls to wrap this session up. Exposure of bifurcation, again, the ICA bifurcation is not necessary, with aneurysm is pointing inferiorly please be aware of the aggressive frontal lobe retraction risks and short the section across and close to the superior aspect of the chasm is important. And again, the contralateral A1 can be found just across the chiasm on the other side. Respecting the perforators, superior pointing aneurysms can be very challenging and the perforators have to be protected, again, as Duke very well mentioned, the shortest fenestrated clip you can use, that's often your best friend in preserving everything and occluding the aneurysm. Don't struggle, remove enough gyrus rectus if necessary. Coagulation of the aneurysm mid-portion is important. Obviously you don't want to quietly the neck of the aneurysm because that will make the aneurysm neck weak and maybe expose the patient for chance of a future recurrence. And then remember, that dissecting the aneurysm neck, be patient, do not slip the clip as fast as possible. Some A-Comm aneurysm may have a secondary lobe or aggressive dissection may puncture a portion of the aneurysm and it runs just medial to A2 ipsilaterally as well mentioned by Duke, so watch for those smaller lobes and watch for injuring the dome and often, especially for unruptured aneurysm, although bilateral A1s maybe, bilateral ones have to be exposed for proximal control an ipsilateral temporal occlusion of the dominant A1 is all that's needed to deflate the aneurysm any quickly. The pitfalls, the Heubner, the proximal control of contralateral A1, avoiding premature clip application and getting the rupture because what happens is you don't see the whole neck of the aneurysm, you don't have it exposed, you put in a permanent clip, what happens is you left part of the aneurysm neck alone and it's open, therefore the flow within the aneurysm actually increases. It's really a hose effect, if you have a hose in your hand and you put your finger on a portion of the diameter of the water hose you're going to find the pressure of the hose is going to go a lot higher. Therefore you have to have the whole neck exposed. If you blindly put a clip across the neck and you get only two third of it, you will get bleeding, you will make a very difficult case out of a case that was relatively under control. And again, keep your dissection along the A-Comm. Any thoughts on that Duke?

- No, I just think there's nothing that beats complete exposure. Complete exposure of the A1s, complete exposure of the early A2s, complete exposure of the entire communicator. And then the nice complete dissection of the neck, so that the surgeon really has in his mind what he's trying to close with his clip, rather than just, hoping and sticking it down there.

- Right and saying, well, on the angiogram, it looked like a five millimeter neck. I'm going to use a seven millimeter aneurysm, you know, clip blade, and well, I don't see all the neck, but I bet it's right there. Let me just go ahead and slip it there. I have personally paid heavily for that. Intraoperative rupture, please stay in control and understand the anatomy. If you expose a complex and something just doesn't look right and you can't find something, saying, well, let's just put a clip on, we'll be okay, that just has never worked, at least for me. And understanding the variations in morphology of the area and understanding that, you know, studying the preoperative angiogram effectively is so important. If patients don't have seizures before surgery, if they're ruptured A-Comms, how long do you put them on seizure prophylaxis, Duke?

- A week.

- For a week, same for us. Do you use the intraoperative EEG, SSEP or no?

- We don't use SSEP, we do use intraoperative EEG and we use it to verify the depth of our barbiturate or propofol coma.

- Thank you, we generously do use the temporary clips and length of time for temporary clipping, although none known, I think with less than five to 10 minutes, it's considered safe in this region. I would like to thank Dr. Samson, who is one of the leaders in aneurysm surgery. I know his book, the Intracranial Aneurysm The Techniques, will be coming out soon with a new edition, I personally, very excited to see it. It's the Bible of aneurysm surgery as I've talked to anybody who does a lot of aneurysms and again, I would like to thank him for his expert opinion to make this session worthwhile. Again Duke, thank you again.

- Thank you, I appreciate it.

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