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Grand Rounds-Clip Ligation of Posterior Communicating Artery Aneurysms

B. Greg Thompson

April 03, 2012

Transcript

- Hello, ladies and gentlemen, and thank you for joining us. The following session is a discussion regarding clip ligation of posterior communicating artery aneurysms. Dr. Greg Thompson from University of Michigan will be our guest speaker. Thank you.

- Well, thank you Aaron for inviting me to participate. And let me say that you've done a great job organizing this.

- Thank you, Greg, I appreciate your time today. Let's go ahead and briefly review our disclosures, none of which interferes with the presentation today. I thought to make this talk exciting to start with a video of yours, which you would like to share with us. So I'm gonna go ahead and bring up the video and let us see the details you would like to talk to us about the posterior communicating artery aneurysms.

- Yes, this was a patient who presented with a Hunt-Hess grade II subarachnoid hemorrhage and was found on angiography to have a proximal posterior communicating artery aneurysm. He had some hydrocephalus. So as you see on this video, we placed a ventriculostomy at the time of surgery via the point of Samson and Batjer, which I always liked quite a bit because it gives you relaxation when you need it. And here we're just opening up the optic carotid cistern. And the thing that I think is notable about this case and a good starting point is that you will see as dissection goes, that the proximal neck of the aneurysm is actually under the clinoid and not accessible via the usual approach. And so here we are opening up over the internal carotid, just medial to the carotid and lateral to the optic nerve. And then looking a little bit more distally now. And I opened the fissure just to relax, give a little bit of relaxation between the optic and carotid, as well as the frontal and temporal lobe. And I try and get a medial view to see the perforators of the PCOM looking between the optic nerve and the internal carotid. You can see you have a very good view of the perforators right there. And if I'll get this arrow, can you see my arrow?

- Yes, I can.

- So here's the posterior communicating artery. The third nerve, which you can't see very well yet is out here. And the neck is here. Here's the distal neck of the aneurysm. The proximal neck is going to be up under the anterior clinoid process. And I always would like to achieve proximal control. So in this case, we're going to drill the clinoid. and I'm starting out by making an H-shaped incision over the lateral aspect of the anterior clinoid and then medial over the optic canal, and falciform ligament right here. And I've palpated previously to make sure that there's bone here over the optic canals. So you don't wanna make that cut until you felt that. And then using a small caudle, I just flapped the dura down and then use, first, a cutting, and then a diamond-tipped drill to drill the anterior clinoid away. And this ends up making a remarkable improvement in the proximal exposure of the internal carotid, as you'll see momentarily, and allowing me to see proximal in the internal carotid, proximal to the aneurysm in case we should need it for aneurysm rupture. The first thing that I try and do always is to see the internal carotid proximal to the aneurysm. I have a place that I can get a temporary clip on if I should need it. And here, actually the clinoid has been drilled away and on lateral-pointing PCOMs as opposed to posterior-pointing, I like to use a bayoneted clip, 'cause I can look through the blades of the clip as I'm putting it on the neck. And then the dome is still adherent to the third nerve. I'm gonna leave that for now and then look medially to see both the PCOM and the perforators. There's the PCOM and the perforators off of the PCOM to make sure they're free. And I actually used both the doppler ultrasonography and indocyanine green angiography on all patients. And then occasionally if I'm not certain from those two, I will use intraoperative angiography, formal catheter angiography as well. There's the third nerve. I'm just releasing subarachnoid distal. And again, you can see the posterior communicating and the perforators. And I'm trying to look distal to make sure that the anterior choroidal is free from the neck of the aneurysm, because as you well know, that's often a source of morbidity if the anterior choroidal is caught with the neck of the aneurysm. So we're looking proximally to see the posterior communicating and its perforators, distally to see the anterior choroidal and it's perforators, and then the third nerve you saw there for a second. And then I'm just taking a little bit of temporalis muscle here and putting it where I drilled the clinoid away. And then I'll just flap the dura back over the top of it. I usually use Tisseel there as well.

- I guess we have brief set et of slides that you would like to go through. I appreciate sort of pinpointing just the details very briefly so we can proceed with the other videos. I think we have about another five videos to review. Go ahead, please.

- I'm gonna go through these very briefly. These are just principles of microsurgical management of PCOMs. And as an overview, I'm just gonna talk about some of the clinical, anatomic, and step-wise approaches that I use for controlled dissection and clipping of the PCOM aneurysms, and how I try and avoid complications or treat them when they come up. The one thing I wanted to say about selection of microsurgical technique, as opposed to endovascular technique was we're not talking about that today is PCOM aneurysms in general, why is microsurgery still an important arm of treatment? And the answer is because the PCOM location, for some reason tends to be a location where there's a high incidence of recurrence. In fact, 47% of all re-treatments in the ISAT trial were at the PCOM location. So younger patients, larger aneurysms, incomplete occlusion, and PCOM location are risk factors. Everyone knows the factors favoring microsurgical treatment. I'm not gonna go through those too much other than say, there was a study done at the Barrow Neurologic Institute in Phoenix, which showed that patients with PCOM aneurysms who had presented with third nerve palsy did better with microsurgical decompression than with endovascular. So that's another reason to consider it. I think everyone knows too the pterional approach, the keyhole, the inferior temporal, and posterior temporal burr hole sites and how we make that fashion that pterional incision. I'm not going to spend any time going over that. We turn the head about 15 degrees, extend it slightly, and translate it up to get a little bit of extra venous drainage. I like to prep a separate ventriculostomy site as you saw from the previous videos so that we can take it out through a separate stab wound. We use the usual scalp and mild fascial flap. I leave a myocutaneous flap to sew to when I finish, and I do not use interfascicular split, unless I'm going to take the orbito-zygomatic, which I'm not going to discuss here. The pterional bone flap begins with the in the keyhole and is done in the usual fashion that everyone at this level knows. We wanna be very careful to drill away the bone at the sphenoid wings so that we can see very flat. And so drilling down the roof of the orbit, the goal is a smooth place to look line of sight down to the optic carotid cistern. And that's the bone that we're gonna drill away. We've already seen the Samson and Batjer point insertions. So I'm not gonna go back over that. This is what I'd really like to talk about in terms of thinking about posterior communicating aneurysms. So that is the concept of surgical rehearsal that is thinking ahead about the dome projection and any irregularities, what the implications for that would be, the neck location, and the relationship to neural and skull-based anatomy. So specifically, for instance, if there's a lateral-pointing posterior communicating aneurysm, that's a case where you want to be very careful in placement of the temporal lobe retractor at the initial onset, because it can cause a rupture for those lateral-pointing as opposed to posterior-pointing aneurysms. Also, if it's bilobed, it often represents a split going around the tentorial edge. A PCOM that points lateral will be split along the tentorial edge and something we need to be aware of. The neck location, as you just saw from the previous angiogram, if it's very proximal may be under the clinoid. And I think we have to be ready to drill a clinoid as previously demonstrated. And I think of course, we need to think about the neural anatomy. The third nerve needs to be decompressed after the clipping and great care taken to avoid it during the initial neck dissection, because probably for the same reason, probably the optic nerve when looking medially, we have to be careful to avoid any injury there. And we've already talked about the anterior clinoid and tentorium. The surgical planning, I just will say very briefly that 3D angiography has become a tremendous surgical planning tool. It can show us the excrescence, the dome projection, neck accessibility, the perforators of the anterior choroidal, and the PCOM. It's really been a quantum leap for surgical planning. We can look at it as a virtual reality training station. You can turn it to look at it from the surgeon's view. It's basically a tremendous educational tool. It allows you to assess the aneurysm and accessibility of the neck, and you can see the potential rupture sites where they occurred. That's the 3D angiography view. The one thing I'd like to say about 2D angiography is that it does give us important information when we're doing posterior communicating artery aneurysms, specifically, is there filling of the PCA from the posterior circulation as you see here? Because if there's not, if this is truly a fetal trifurcation, there are important implications, obviously for ischemia with temporary clipping. So to conclude, I just wanna say that we should always think about this in the stepwise fashion, proximal control, dissection. Think about the order of neck dissection. And the here's working proximal to distal and low to high risk, but also remembering that microsurgery is an art, we take what it gives us, take the easy parts first and the high risk parts last. I like to plan a temporary clip strategy. If it's unruptured, I usually don't use temporary clips. If it's ruptured, I sometimes will. If I know I have a good feeling from the posterior circulation, I have less concerned about a trapping if the aneurysm were to rupture. If there's not filling in the posterior circulation, I prefer to use only a proximal clip and not a distal clip with the hope of getting some cross-filling and protection against ischemia. As pointed out earlier, I like to use straight or bayoneted clips for the lateral projecting aneurysms and fenestrated for large posterior pointing aneurysms like we'll see where the neck is going away from the surgeon's point of view. And so I think we can go back to the videos now.

- Thank you, Greg, those were very enlightening. So let's go ahead to, I think one of your videos that talks about some of the general concepts, and then we'll follow with a giant aneurysm in the same location. So please go ahead.

- So this is a gentleman who presented with a giant PCOM aneurysm, a wide-necked aneurysm, not a good candidate for endovascular treatment, and had a grade III Hunt-Hess, but only a grade II Fisher scale bleed. And because of the hydrocephalus replacing ventric again, via the point of Samson and Batjer. Sometimes on these I will do a zygomatic approach in this particular case, because it was a supraclinoid aneurysm that I thought would be distal to the anterior clinoid process. I chose to do that. I like to use telfa to decrease abrasion over the frontal lobe as is commonly done. And here I'm opening the optic carotid cistern and you can see that there's a fair amount of a subarachnoid blood. And we will work from proximal to distal obtaining proximal control of the internal carotid, proximal to the aneurysm. The fissure is rather full with the subarachnoid blood. And after I've opened proximally sometimes with a very full fissure, I'll work from distal to proximal just to make the brain relaxation a little bit easier. And here we're working out the supraclinoid segment trying to identify the aneurysm and the proximal posterior communicating branch. And again, I'm using the technique of going medial to the internal carotid and looking medial for the perforators coming off the PCOM proximally. And also for the anterior choroidal distal to the aneurysm. And there's the PCOM you can see as we lift up on the parent vessel and its perforators coming off. Very key step is seeing the posterior communicating. This was actually a fairly wide-necked aneurysm. And I haven't shown you that picture, but it had an excrescence very near the neck, and it pointed posterior lateral with a bit of bilobed or at least a daughter excrescence. And you can see how thin it is here near the neck, rather translucent. And now I'm working distal to the aneurysm, trying to demonstrate the anterior choroidal. And here I'm simply lysing arachnoid adhesions on the distal side of the aneurysm dome. The anterior choroidal would be right here. This is the proximal M1. Yeah, that's the M1 segment right there, just at the end of the supraclinoid segment here. The anterior choroidal is directed away from us much like the PCOM itself. And again, I like the bayoneted clip because I can look through the clip blades at the time of placement and see the neck very well and try and place it slowly. The dome is pushing the carotid medially and the third nerve laterally. And now I'm dissecting between the aneurysm and the third nerve. And I've actually in the interim bipolar this aneurysm down quite a bit as well.

- And you can see almost part of the PCOM there, can't you?

- Yes. And I think if I remember correctly that the PCOM I also look for medially here and actually see the clip blades excluding the posterior communicating branch itself. I don't think that was actually the giant one that was, I think, a large, but not giant bilobed one.

- Well, perfect. Let's just go ahead and jump into the giant one and see that. I personally really enjoy watching this one, so please take us through it.

- So this gentleman is about 38 and had presented with diplopia, and sudden severe headache, and had a very large wide-necked aneurysm proximally.

- And if I may orient our viewers, this is a right-sided approach, right carotid, optic nerve. Apparently there's a smaller aneurysm that you've just clipped before that, is that correct, Greg?

- That's correct, there is a small distal ICA bifurcation aneurysm. This is the internal carotid on the right as you pointed out. I believe that's a perforator off the PCOM that you're seeing medial to the internal carotid. And there's this very wide-necked supraclinoid aneurysm. And if you look underneath the M1 segment, from time to time you'll see the anterior choroidal. Just running down here there's a branch coming down here where the arrow is, off the anterior choroidal. And I think when I first put the clip in, you could actually see the anterior choroidal distal to the neck as well.

- One important point here, Greg, is that you're trying to clip the aneurysm parallel to the carotid artery. So in these giant and the large aneurysm, it's very important to do that, to get a good closure because perpendicular may be not enough to close the aneurysm neck. Go ahead, please.

- Excellent point. I try and clip, you know, parallel to the long axis of the aneurysm so that I can avoid a dog-ear. And if I were perpendicular to that, I could count on it getting a dog-ear. So that's an excellent point. Sometimes it kinks aneurysm. I think that was what I was trying to avoid in this particular case, actually not the aneurysm, it kinks the parent vessel. And you can actually see the third nerve lateral to the aneurysm over here as well. I think an important aspect is on giant aneurysms with high flow through these wide necks, it's a good idea to put the temporary clip proximally. This patient had good filling across the Acom. So he was not aschemic with that, it just simply soften the aneurysm. And I'm looking for the anterior choroidal here underneath as I looked up on the M1 segment. The major morbidity of this case is the anterior choroidal. And you can see that I've actually widened the clip away from the parent vessel. And if I remember correctly, I think I'm gonna put a very small clip to strengthen that little dog-ear area. Here it comes.

- Canister clips sometimes work real nicely too, because you can fenestrate the carotid and then really nicely closes the aneurysm for you, but you can always incorporate the perforators because you don't see very well.

- And there you have the indocyanine green, and you could see that's a very effective. This was a partially calcified aneurysm and you kind of get a sense of that as well because the edges, which calcification is not seen through as well, tend to be not quite as smooth on the ICG angiogram.

- And here you can see PCOM right there, very patent, no aneurysm is left. So everything looks very nice.

- And the anterior choroidal coming down as well.

- So, Greg, if you don't mind, I thought we can review some slides and basic concepts adding very much to what you eloquently mentioned about these aneurysms. Obviously, PCOM aneurysms are the most common aneurysm and they may present with third nerve palsy or embolic ischemia if they don't rupture. And issue of the 20% fetal origin of PCOM is really important as you mentioned. The fact that if the P1 segment of the PCA is not very viable and the PCOM provides most of the irrigation to the occipital lobe, you really have to be careful when you manage these aneurysms not to compromise them. And even temporary occlusion has to be very caution. The anterior thalamuperforators are critical, life runs through them, and they have to be carefully protected as they come off of the posterior communicating artery. And these aneurysms to posterior communicating aneurysms really to remain clippable. They are relatively surgically accessible without much morbidity. And therefore, it is best if we can, as surgeons, provide the patient with the best nuances to make this procedure safe, even in the era of advancements in endovascular techniques. My thoughts is a frontotemporal craniotomy just above the superior temporal line is all you need, aggressive drilling of sphenoid wing to the superior orbital fissure or meningo-orbital artery would be very advantageous to decrease the need for frontal lobe retraction. I do like splitting the fissure because more and more we do not use fixed retractors anymore. And we're using only dynamic retraction with the suction. And so the more we can split the fissure, the less chance of using fixed retractors. Well, the dissection is usually on the anterior medial aspect of the ICA, just like you mentioned to avoid getting into the aneurysm too early, without proximal control. After the proximal control is secure, the PCOM and the anterior choroidal are identified and really you laterally retract the ICA to find the PCOM to get a good idea of how big it is, and make sure how much you can protect it after you clip the aneurysm to make sure the flow is adequate. Again and again, temporal lobe retraction should be avoided until good proximal control is secure. And clip application parallel to the ICA is the rule if you can do it. I will show you a video of mine where I get into huge trouble, Greg. I tried to put a clip and forcing the clip perpendicular on a broad-based aneurysm. That could potentially cause premature rupture that leaves dog ears. And to be honest with you, it's just not a good practice because one of the major rules of aneurysms surgery is to place a clip across the neck of the aneurysm parallel to the parent's vessel. Do you have any other thoughts about these details, Greg, please?

- No, I think those are all very good points and I'm looking forward to seeing the video.

- Thank you. Very briefly the positioning, we turned very little, everybody puts the Mayfield head clamp differently, but again, not much turning is required because then the temporal lobe would be on your way. We position the assistant or the surgical nurse across from the surgeon for easy transfer on the instruments. Again, this is the usual incision. I use one burr hole below the superior temporal line. And I just turn to cuts and turn the heel around. And this really minimizes the bony loss around the pterion and potential cosmetic deformity. Again, if the dura is very stuck, obviously you may not be able to do that, and you may need more burr holes. Also where you're away from the muscle, you can use your number three penfield and go really far to dissect the dura away. If you put a burr hole here, you may not be able to have the right angle just to dissect the dural widely. Open the dura. And as you can see, in this case, the bony removal is just above the superior temporal line. You really don't need much for Acom or other aneurysms. And let's jump into a very basic procedure for a 55-year old female with an incidental eight millimeter PCOM aneurysm. Just to review the basic concepts for management of this very favorable aneurysm. And again, this was a left frontotemporal craniotomy. You can see the left frontal lobe, left temporal lobe, sylvian fissure, the dural opening, and really removing the bone until you're flat through the roof of the orbit. You can see the carotid artery has been exposed here. And really looking around finding the PCOM. Again, just like you eloquently mentioned, the PCOM, the perforators, the optic nerve, the carotid artery at the edge of the tentorium. As you can see this aneurysm is below the tentorium, which can happen in this very inferiorly and posterior-looking aneurysms. And you can see the origin of the choroidal artery right there, where you just see the knuckle. And you can see here, it's very difficult to see the origin of PCOM. And that's why I proceeded to cut the edge of the tentorium carefully so you can better appreciate the origin of the PCOM. Any thoughts here, Greg, please?

- That's as you point out a little bit unusual to be under the tentorium, but not so much that anyone's doing this won't see it commonly. My guess would be maybe one posterior communicating artery and X will be completely underneath the tentorium. And in fact, have seen a posterior fossa subdural as well as a middle fossa subdural actually from PCOM aneurysms. But the posterior fossa one is the one that can be surprising when you see that.

- Thank you. And you can see the origin of PCOM here. I put a temporary clip just to be able to decompress everything and really appreciate the origin of PCOM, which you see just as a knuckle. And as you see using an angle clip, sort of a more untraditional way of putting this clip on these aneurysms, you can see the anterior choroidal right there. But again, this is really my goal, to put the clip parallel to the ICA rather than perpendicular. And really does a nice job. It's not perfectly parallel, and it's not really perpendicular, it's sort of an angle. And I think really it does a nice job. Using the mini clips in this area can be challenging because of the high flow in the ICA and potentially the aneurysm may not close. So we use whatever we can to avoid mini clips. I'm gonna share with you a new study we're doing here in a moment. Let me just show you the PCOM again by retracting the ICA laterally and protecting the perforators. I use fluorescein with a special camera, yellow 560. And this really doesn't show the aneurysm filling anymore. And you can see the carotid artery filling. The advantage of the fluorescein is the surgeon can operate and there's no camera that's separate, it's a filter. So you can easily see what you're doing while you're looking through your binoculars. And this is the comparison to ICG. As you can see, the definition is much more in my opinion, with the fluorescein because you can focus more and you can zoom in a lot more as compared to ICG where you have to stay away because of their wavelength requirements. So as you can see here, the fluorescein and the PCOM there, the perforators are much better appreciated compared to the ICG because of the higher definition of the filter used for fluorescein angiography. And as you can see, the brain is minimally affected and the patient did very well.

- Very nice.

- Thank you. Yes, go ahead, Greg.

- I liked the technique with the side-biding aneurysm clip. I've tried that on a number of occasions. The one difficulty I would caution our listeners too about that is that it's hard to get the distal end of the tip underneath and around the carotid to kind of tow in. One can leave a small dog-ear of aneurysm if you don't tow in enough underneath it. And sometimes it actually helps to pull the aneurysm up and lift the neck into the clips as you place that side-biding clip on.

- Thank you, Greg. Here was the pre-op angiogram that I should have shown prior before going to video. And here's the postoperative 3D angiogram. As you can see really doing this as much as you can parallel leaves almost no neck and really the inlet into the PCOM. So it works very well. I like to 3D angiogram after surgery because it really is a great teaching point for the surgeon. A 3D angiogram never lies. And I tell you, you can miss a neck remnant and feel like you did a great job, but then actually a 3D angiogram shows you could have done a lot better. So we really use this as a very strict teaching point for the surgeon to know how to do better next time.

- I agree with you. As a rule obtain post-op angiography, I think not only for the patient's benefit, but as a quality assurance issue for the surgeons. It a lifelong learning.

- I could not agree with you more. I think that's the most important thing about a neurosurgeon to keep in mind. 26-year old female with a severe headache six years prior to admission. So this lady presented to us a little bit later, Greg. A little bit of blood on MRI. Obviously we don't do MRI for these cases, it was done before the patient was transferred on flare images. And you can see rather bulbous multilobular aneurysm on CTA. A 3D angiogram was performed because the CTA was a little bit difficult to understand the morphology of the aneurysm. And the 3D is so effective, just like you mentioned about the origin of the PCOM, their relationship in 3D, and more importantly, you can add the bone windows and appreciate where is the anterior clinoid, which you can see right here compared to the aneurysm. And preoperatively, you can assess if you need to be ready to remove the clinoid. This is a right frontotemporal craniotomy optic nerve, and you can see right frontal lobe, a gentle retraction, temporal lobe, securing the proximal control just like you very well mentioned, and cutting the arachnoid over the blood that is around the aneurysm. And then here is the aneurysm, and I'm trying to find the origin of the PCOM in this situation. Again, the carotid artery, aneurysm, origin of the PCOM. And really a temporary clip helps so much, especially in the case of a ruptured aneurysm to deflate the aneurysm and let you see around it. So you can protect the PCOM. In this situation, especially with a ruptured aneurysm a lot of blood, it maybe difficult to see around it to put a clip parallel to the ICA. So we're really putting a clips sort of perpendicular, although this is a small-neck aneurysm and we should be okay. Any thoughts there, Greg, please?

- Well, I think first of all, your point is very correct about the difficulty in achieving obliteration of these posterior-pointing aneurysms, particularly without intraoperative imaging. I recently went back and looked at both our results and in the literature, and although we all think of PCOM aneurysm as amongst the most straightforward, it turns out that in the majority of studies reported that the most common location to have residual aneurysm on postoperative angiography was in fact the posterior communicating artery. So I think it just demonstrates that particularly for those posterior-pointing aneurysms where you don't see the neck as well as the ones that point lateral into the temporal lobe, it's incumbent upon us to use angiography and whatever imaging techniques we have available. And I think if one feels uncertain that you have to go beyond ICT and angiography as well, you have to do a true 3D angiogram, much like what you just said, you know, three minutes ago.

- Thank you. And we did the fluorescein angiography, the aneurysm was failing. You could compare that to ICG just to see the detail of definition between the two. And here is the most common part where we leave an aneurysm residual is distal at the edge of our clip. And here's me trying to advance the clip a little bit more. Again, the PCOM is more evident and here is the fluorescein redone. And you can appreciate that the temporal clip was on. Unfortunately, we'll removing it momentarily. And you can see, you can repeat the fluorescein and no longer it's filling. Everything is filling nicely and fluorescing, but the aneurysm remains unfilled. And again, a surgeon can manipulate, you can see the PCOM origin there. You can see the origin of the anterior choroidal. And here is removing the clip. And you can see the flow is reconstituted. The dura does pick up fluorescence and fluorescein. Therefore, the image is not as clean as ICG. But again, we like it because it lets the surgeon to play with the structures while the dye is in the system. And this is the postoperative angiogram, again, showing the aneurysm has been secured and the PCOM is patted. Let's do a review of some of the more difficult situations, including a large intraoperative rupture. This is a patient of mine early in career of mine and a 40-year old female with a ruptured four millimeter PCOM aneurysm. Some of these small aneurysms can be very challenging because there's no dome. And the moment you lift the temporal lobe, you're looking at the dome. Obviously, there's no neck. And the moment you lift up the temporal lobe, you're looking at the dome. And you can see a little bit of hemorrhage on CT, Greg. And here is this very small aneurysm mostly off the PCOM actually. let's go ahead and see her video. It's sort of a good learning experience.

- Good in retrospect.

- Yes. Well, go ahead and enlarge the video, Michael, please. And you can see when I retract the temporal lobe here, the hemorrhage occurred and here is me. Obviously the first thing is to have a second suction in there. I did have a temporary clip on there. This is a right frontotemporal craniotomy, temporal lobe, frontal lobe, ICA, really getting a lot of bleeding and it's more internally gets worse. And I really can't see the aneurysm and you see something here. And the worst thing you can do is place a clip because you get nervous. And this is a lesson for me is not to put a clip unless you're absolutely sure you have identified the aneurysm. The bleeding is coming from there. It makes you feel like the aneurysm is there, but actually the aneurysm is way down here. And you can see the aneurysm sort of shows up itself now as bleeding sort of pushes it out. And when I remove my suction, you're gonna see a lot of bleeding. So that's the key part, that where you have a lot of bleeding, it's best to keep calm and make sure you're not clipping an anterior choroidal artery or another important vessel just because you're not sure what's going on and the blood making you make a decision very quickly. So here is a suction coming in. One of my residents trying to clear the field for me until I can ask for a clip. And again, really keeping calm and getting the right clip. Again, the aneurysm is right underneath the suction. Any thoughts there, Greg?

- Well, I think that the point that's already been made that you said is the most important one, which is the worst thing to do when an aneurysm rupture is to start throwing in clips indiscriminately. In this case, it would have been nice, I'm sure you did know. It'd be nice to know for myself and the viewers was there a good cross filling because if there were, I think with a high-volume rupture like that, it would be nice to actually trap the segment so that you could see well enough to find out where the hole was exactly the side of the aneurysm rupture and the appearance of aneurysm so that you could get the optimal clipping on this in a fairly expeditious fashion. This is a very difficult aneurysm as you point out maybe surprisingly so to some, because it's four millimeters and it's wide-neck, and it's hard to get an aneurysm clip sometimes to sit on those wide-neck thin aneurysms, particularly when they're bleeding, unless you stop the bleeding with a trapping, you know, set up clips. So personally I would try and handle this by having both a proximal and distal clip stop the bleeding, and then try and get an ideal clip across the aneurysm at that point. The patient is well with some burst suppression and trying to keep it less than just a few minutes.

- Well, I think those are great points. And in this situation, maybe I should have more of the ICA distally exposed. I didn't, and so that's one good learning point. You've gotta get a good segment of the ICA exposed. This patient did have good cross-filling. And when we put a temporary clip it burst suppression was instituted. I think the key point you were saying is have the option of distal control, which in this case may have not been adequately done by myself. And, you know, after such a case, Greg, you wish you had a nice trip away from work, maybe in Northern Minnesota in Boundary Waters, dog sledding. I really enjoy this kind of trips and really keeps your sanity together after these tough cases.

- You look no worse for the wear. In fact, very healthy there.

- Thank you. Let's go ahead to the next case. 51-year old female with incidental bilateral PCOM aneurysm. It's about six millimeters each. The right side was actually carrying a nice neck and we decided to coil endovascularly the right side to avoid a bilateral craniotomy on this patient. And the left-sided aneurysm was much more broad-based. And since there was a strong history of subarachnoid hemorrhage and aneurysm in this family, we proceeded to clip the left and coil the rights. Would you have done it any differently, Greg?

- Well, I think that's very reasonable. Looking at those angiogram views, I think that's probably what I would have done as well.

- Okay, thank you. And this was really the aneurysm from the left side, very broad base, very small PCOM. And I clicked this aneurysm, I'm not gonna review this surgical video, and the clip came off on the postoperative angiogram although we had a good clip application. And intraoperative, the ICG was very clearly good and I'm not filling. This is the point I'm trying to make that in these very broad-based aneurysm, if you go perpendicular to the carotid, your clip can come off, even as it's very small one. If the base is very broad use this small clip, the clip can come off. That's why doing it perpendicular is so important. And I'm not gonna show the video here for the sake of time, but I put a fenestrated small clip across the carotid and fenestrated the ICA and the aneurysm was excluded. Let's go ahead and talk about another case. You very well mentioned about clinoidectomy. A 58-year old female with acute right third nerve palsy. And this is how she presented. This is with the consent of the patient to use the picture. As you can see the droopy eye and the third nerve palsy really deviated to the right, and this can be very well a first presentation of a PCOM aneurysm and should not be disregarded, because the patient may return shortly with a devastating hemorrhage. This was the CT and the CTA really showing this aneurysm and the region of the PCOM. And here is their CTA reconstruction showing this very small aneurysm, however, causing a lot of symptoms by causing the third nerve. The positioning of the patient, as you can see. And you can see the incision right there that sort of shows with the placement of the pinion behind the ear. And let's go ahead and review the surgical video, which I think is interesting in this case. Here is really the right frontal lobe, right temporal lobe, the clinoid, and this is the anterior choroidal. And here we can see the PCOM aneurysm is completely covered by the clinoid. You can barely see the distal part of the neck of the aneurysm under my suction. And we really did exactly what you very well mentioned. I did a little bit of less dural opening than you did. I liked the way you did it because it gives you a very nice sort of panoramic exposure of the clinoid process. And we'll go ahead and drill the clinoid process at this juncture. You can use a variety of instruments including drills or sonapet if necessary. Any pointers here, Greg?

- Well, I've sonapet on occasion. I tend to use drill still just because it's an old habit, but I think it's a very good instrument. If one does use a drill and I think the sonapet as well, the key is irrigation has to be continuous because I think sometimes the injury is not a direct mechanical injury, but in fact, a heat injury.

- Yeah, I think so. And one important point here is the surgeon to take his or her time and get proximal control. One big mistake is just to try to force the clip just to shorten your surgical time. And I think disaster lies at the end of that road by just forcing the clip because you cannot see very well the proximal neck of the aneurysm.

- I completely agree. The extra 45 minutes or half an hour, whatever it takes to take down the dura and drill the clinoid is well worth the effort, and actually saves you a lot of time as well for the clip application. Sometimes when you drill the clinoid, it becomes a very simple, straightforward aneurysm.

- Very well said. And here's me trying to really look around the neck. One other mistakes is the surgeon may sometimes just say, "Well, I'm just gonna pass the clip, I'll get it." You really have to sit around the neck of these aneurysms. You have to be sure how far are you, because it is really easy to try to force a clip here not knowing how far you are without microsurgically dissect the arachnoid and only get a partial clipping and aneurysm ruptures, because as you know, it's a hose effect. If you put your finger at the tip of the hose, the pressure goes a lot higher. So if you partially clip an aneurysm, you have a much higher risk of intraoperative rupture. And so you have to really be very sure how far are you with your clip. Here is the PCOM, is very evident. The knuckle of the PCOM around the aneurysm and put the clip really comfortable. Don't force the clip. The clip blades are not dissectors. I think some people feel like the clip blade can be used as a source of a dissector at the end of it. And I never found that very, very safe.

- I would agree, I think that's a real problem is that when one doesn't see proximately well, then you cannot know if the anterior aspect of the aneurysm neck has been adequately lysed from its adhesion to the skull base or to the third nerve if it's lateral. So I think what you're doing here is really necessary.

- And here you can see, yeah, the PCOM is very large here. And as I can see I'm spending extra effort just to dissect the PCOM, maybe a little bit more sharp dissection would have been helpful. But if I had just passed a clip here, I would have compromised the PCOM, which is very large. And again, this is why you have to take at the time, use micro scissors, it doesn't matter how far and how deep it is, and just really understand pathoanatomy of this structure. And here really you see the aneurysm is so clearly now defined, which makes the clip applications so much easier.

- Yes. Sometimes this is a point at which when I'm trying to see the trajectory of the posterior communicating artery, I'll look from the medial side as well and see the PCOM and its perforators. And just so that the anterior tine of the aneurysm clip avoids that PCOM as well as it comes inferior to the carotid.

- I think that's very important. Here, you know, the carotid was so large and when I retracted laterally, I couldn't see the PCON. The PCOM was sort of running away from me. And that's why we really went ahead and just clipped it that way and couldn't see the PCOM medially. You can see we're just gonna place a needle into the aneurysm because this patient had a third nerve palsy. We do not dissect the aneurism off of the third nerve, I think that causes more injury. And you just have to give the patients some time for the third nerve to recover. So in closure, thank you for your time and expertise, Greg. Avoid temporal lobe retraction, don't forced the clip blindly, see around the neck and you fenestrated clips if you can. It really works well. Fenestrated carotid, if the perforators of the PCOM are not on your way, it can really do a nice job for you. And you may need to drill the anterior clinoid process. Again, Greg enjoyed working with you and as always, thank you.

- Aaron, thank you very much. Enjoyed it too.

- Thank you.

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