Microsurgical Clip Ligation of PICA Aneurysms: Pearls and Pitfalls

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- Hello, ladies and gentlemen, this session will be discussion regarding basic and complex techniques for open clip ligation of posterior inferior cerebellar, or PICA aneurysms. Dr. Jacques Morcos, from University of Miami, has been very kind and gracious to join me for his expert commentary. We're gonna review a set of slides to review some basic concepts after which we're gonna have about five surgical videos discussing complex technical skills, as well as interoperative ruptures. Jacques, thanks again.

- Thank you, Aaron.

- So, let's start with the disclosures. None of us have any disclosures that would interfere with this presentation. Very basic concepts, after basilar tip aneurysms, these aneurysms are some of the most common PICA aneurysms. Most of them are left sided as the vertebral is mostly dominant on the left. And the risk of posterior circulation aneurysms are generally considered to be higher than anterior circulation aneurysms, specifically for aneurysms less than 12 millimeters, Jacques, would you agree with that princ, that basic concept of the rupture, knowing these studies recently?

- Yes, I agree, particularly in Japan as well.

- Okay, so if you see intervention color hemorrhage, as you can see here, or some blood in the several pontine angle, you should really suspect a PICA aneurysm and make sure that's excluded. And obviously you need a four vessel angiogram clearly showing the origin of PICA. And obviously that's because of the close relationship of this vascular structure to foramina of Luschka and Magendie. So what is surgically important or relevant for these aneurysms? Vertebral artery enters the subarachnoid space between ring of C1 and foramen magnum, but we obviously know that. And then it really travels superiorly and transverses from lateral to anterior along the cervicomedullary junction. The PICA arms can be very variable and this variation can make the surgery very difficult. And the variation is more specifically in their route. PICA is frequently largest intradural branch, and it rises about 10 millimeter above the foramen magnum and 50 millimeter below the vertebrobasilar junction. Although that can be very variable as well. What it irrigates is very important structures, proximately PICA through its perforators does medulla, cerebellar tonsil, inferior vermis, and the suboccipital face of the cerebellar hemisphere. What is also important clinical anatomy is that the original PICA is very much associated with cranial nerve 12 and it's aneurysm. It's anterior and ventral to the lower cranial nerves. Therefore manipulation can be very tricky to preserve these nerves and it can be very small. PICA can be even up to two millimeter in its origin and clip ligation has to be very carefully managed and maybe a small piece of neck left to make sure PICA is not sacrificed. Ultimately, thanks, and it's really a gift of God to neurovascular surgeons. There is good leptomeningeal anastomosis between PICA and AICA and often if there is a thrombosis, AICA leptomeningeal collaterals can make up and avoid a stroke, although we can't count on them always. So what about endovascular techniques? Endovascular techniques have tackled PICA aneurysms effectively. However, PICA aneurysms are one group of aneurysms that remain surgically available. They often have a broad neck. They have a very small caliber associated PICA artery, and therefore really there is very small margin of error for endovascular techniques and these aneurysms remain in the realm of microsurgery, and the aneurysm often incorporates a portion of PICA, rather than vertebral, and these aneurysms can have a very fragile wall, especially fusiforms. And we're going to seek surgical video with really a catastrophic interoperative hemorrhage momentarily. CTA is not only important for the anatomy, but also it's a relationship of the aneurysm to the lower cranial nerves, jugular foramen, as it really makes a difference in terms of how you're gonna manage the aneurysm. Do you have any other details you would like to add, Jacques?

- You, maybe you talked about it a little earlier, but it's so important to make sure the PICA is not causing transdural. On your way there, you may coagulate some dural branches and before you even started the case, you sacrifice the PICA. So it's very important to understand if the, if the specific patient has one of the common congenital anomalies of PICA, up to 18% of cases have an extra cranial and possibly extra dural origin. So very important.

- Thank you, very important point. So basic relevant anatomy, there are five segments, anterior medullary, lateral medullary, tonsillar medullary, as you can see, and there's the caudal loop, which is very important, that telovelotonsillar segment that you can see here. And then obviously the cortical segments. Clinically the most perforators are proximal to the caudal loop. And you have to remember that you cannot sacrifice any segment of the PICA proximal to that generally, although not desirable, you may be able to get away with sacrificing the distal part of PICA without untoward effects, and be able to save the distal territories, distal areas irrigated with the distal branches by the leptomeningeal collaterals, specially with distal PICA aneurysms, that may come handy. Because even recently there've been some case reports or short series of doing distal occlusions for PICA, distal PICA aneurysms. And again, this is another picture from the Roatan articles discussing the anatomy and the relevance of the caudal loop. So what are the basic management techniques, open ligation of the aneurysm, which would be ideal, proximal distal occlusion of the parent artery. This is only one area where you can actually distally occlude the PICA for a distal PICA aneurysm. And usually the occlusion is distal to the aneurysm. And the aneurysm actually gets occluded. A short series was presented a couple of years ago. You can track the aneurysm. Wrap the aneurysm, it's the fusiform. And as you very eloquently mentioned in your bypass session, you can do a bypass revascularization. And usually the trapping that occurs proximal to the caudal point where the perforators are. And here again, the perforators often come proximal to the caudal loop, as we saw momentarily. So if you have a fusiform aneurysm without any perforators, you can excise the aneurysm and do end to end anastomosis for PICA aneurysms. You, if you have perforators off of the aneurysm, you can do proximal ligation with a distal end to sine anastomosis and still irrigate the perforators. And also you can do site to site PICA anastomosis. So let's jump straight away to our micro surgical techniques for these aneurysms. The hockey stick incision has been really my preference. It's descending limb goes all the way to C3. There's also S shaped incision. I'm gonna momentarily ask you to comment on that. We leave a cuff of muscle, a cuff of muscle on the superior nuchal line, to reattach the muscle and the posterior actual C1 is often not needed to be removed, but removing it really helps with that inferior to superior trajectory, to work ventral to the cranial nerves. And that can be important. But you most commonly need to open the foramen magnum and a lateral bony removal is necessary. So while we're going through these, I would like to ask you to comment, Jacques. This is the position we use. One of the most critical factors here is this space. You have to get the shoulder moved forward and down. Otherwise it would significantly, especially in heavyset individuals, interfere with surgery. We turned the head towards the floor, almost 45 degrees. We use a hockey stick incision, and we use obviously an axillary roll. Can you please comment about your positioning and incision choice, Jacques?

- I agree with everything you said at this point. The vertex of the head, I bring it down further, to even open further the space between shoulder and head. So the axis of neck and head should be at an angle with the access of the torso. In this depiction, it seems to be in line with the torso, just a little extra help to view the occiput C1 joint once you get in there.

- Do you use hockey stick incision, or do use this question mark incision, Jacques?

- No, I like the hockey stick incision. The main advantage as far as I'm concerned is once you lift that myocutaneous flap, you're very close to the pathology. With these straight or lazy S incisions, yes, it is quicker, but once you put your retractors on that skin edge, it will lift it up. So the depth of exposure is more, with a straight incision.

- So here is the position of the head that we talked about, turning toward the floor about 45 degrees and increasing the angle between the shoulder and the head that you talked about. This is again from the book from Sampson and Bager, really showing the location of the S incision that is quicker. After using the hockey stick incision, we go ahead and do a burr hole close to the sigmoid sinus, turn a craniotomy, and we lift the muscle very lateral, up to the vertebral artery. And then in the second step, you can remove the, the bone over the posterior aspect of the foramen. You can use a Kerrison rongeurs to extend that, and really open dural in the curvilinear fashion. Any other thoughts, Jacques, on these last three illustrations?

- No, Aaron, again to the importance here of this, the so-called far lateral approach is the bone there laterally needs to be drilled as flush as possible. Just there exactly where you pointed and is it okay, I'm gonna use my pointer. Does, I'm not sure if my pointer shows, but yes. So here, this bone needs to be very flushed so that the whole exposure is that angle here. So by the time you make your cut here, and you pull that dura, if you haven't done enough drilling, you have a little rock of bone here, very reminiscent of a poorly drilled medial sphenoid wing, because it's such equivalence between both approaches. You can run many parallels between a transsylvian approach and a far lateral approach, but that's one of them.

- When you open the dura, you can see opening the arachnoid membrane, really following the vertebral artery intradurally. You can see where it enters the dura and then follow the vertebral artery, often the accessory nerve is superficial to that. And as you can see in this intraoperative photo, the dura has been opened. The vertebral artery has been identified, you can see the accessory nerve. And as you follow the vertebral artery and elevate the tonsils of the cerebellum, you're gonna identify the PICA. And then as you follow the PICA and the vertebral artery at their junction would be the aneurysm. And often the lower cranial nerves are superior. However, the vert can be more dural electroatatic and this aneurysm can be very ventral, and very anterior actually to the lower cranial nerves. And here's the illustration really showing the vertebral artery PICA, and the importance of the 12th cranial nerve, which very often is where the aneurysm neck is. And you have to work in different angles often below the lower cranial nerves, to be able to expose this area. Any pearls of technique, Jacques, at this juncture?

- The importance of all of these triangles, particularly for the people who have not done too many of these operations, is that don't be afraid to use every space you have. And sometimes if you feel crowded with two instruments in your hands, in one triangle, use one triangle to look through and another triangle to pass the instrument. For example, you could be below 10, with your instrument, above nine, visualization or the reverse. So many triangles, use them based on how high the aneurysm is and what the exposure is needed.

- I have to make a point here that we no longer use retractors. And I think if you can strategically use your suction, you will be able do this operation without fixed retractors. What is also, I think, a critical technical nuance here is that you stay along the medial wall of the vertebral artery to find a distal vert. And then that would also give you the neck of the aneurysm. And obviously PICA is very tortuous. It can actually move up and come down. And if you have a lot of bleeding, in the case of ruptured aneurysm, it can really lead you to do a lot of dissection, where you don't need to. So it's best to stay along the medial wall of the vertebral artery, find a distal vert, as you can see here, which is often very difficult, having proximal control and placing a temporary clip, if you need to be able to find a distal vert. You can use a fenestrated clip or a curved clip and a variety of clips, as you will see in the video to be able to clip these aneurysms and use all the little triangles Jacques mentioned about approaching these aneurysm next. Any other thoughts there, Jacques?

- Yeah, another pitfall Aaron, to mention, is that sometimes the PICA aneurysm is stuck on the dura laterally, very easy to avulse it early in the dissection. So a careful study of the pre-op angiogram to give you a hint that it may be stuck laterally. So very aware of that, too.

- Thank you, and obviously after the clip has been placed, you have to examine, make sure the distal tip of the blades have not caught the vert. And sometimes you may not be able to see that when you place the clip and then examine that area to assure nothing has been included. And again, the medial dissection along the proximal distal vert artery clipped parallel to the parent vessel. Please avoid clipping perpendicular to PICA, because that can have avulse the neck, as you will see in one of my videos. And if you cannot clearly dissect the aneurysm neck, as long as you put a clip and you spare the continuation of proximal, of the vert, proximally to to PICA, it's okay to occlude distal part of the vert compared to PICA and the aneurysm neck in one clip, as long as there is a very healthy contralateral aneurysm. So that trapping of the PICA aneurysm origin, as long as PICA is continuous with proximal vert is okay. And it's an alternative in certain atherosclerotic aneurysms. And if nothing works, you can always proximally occlude the vertebral artery sec and sacrifice it. And remember the PICA is a very small artery, and sometimes a less than perfect clip application is necessary to preserve the small vessel. Pseudomeningocele obviously is a complication, patients who undergo clip ligation should have some swallow study before they start eating next day. Even though they're doing great. Because nothing is worse than an aspiration pneumonia because of a gentle manipulation of lower cranial nerves, that can be very temporary. And if you suspect that PICA is compromised, don't put your bone flap back. And it's one way, if God forbid, there is gonna be a cerebellar stroke, to use your bony opening as a cranioectomy, any other pearls?

- No, that sums up the most common complications. And of course be aware what the Wallenberg Syndrome looks like, oh, I guess you're gonna to talk about it, right now.

- We're gonna, I wanted to, for people to read more about it for making this presentation relatively brief and to the point. I just left the slide for people to know the symptoms. And obviously there's a variety of these and not everybody shows all these symptoms, but it's something that surgeons have to be very much aware of. Let's start with a relatively straightforward aneurism in the PICA region as a 52 year old male with a ruptured right-sided PICA aneurysm. We can see that aneurysm was off of the PICA in this case, and this was the angiogram showing the location of the aneurysm. Here is the positioning for this patient. And you very well mentioned the importance of increasing the angle here and tilting the head toward the floor, curvilinear incision here, placing a burr hole close to the sagittal, I'm sorry to the sigmoid sinus, you can see the burr hole starts a little bit over the normal dura, and then we can use a Kerrison to extend it toward the sinus. We're gonna go ahead and just very briefly outline the craniotomy, again, these are very basic techniques that I thought I'll include for our residents who are sort of seeing this video, being able to dissect the dura very carefully, specially all the way to the ridge of deployment and using a Midas Rex and turning the bone flap and doing a C1 laminectomy. Could you comment, Jacques, if you do anything different here?

- No, those are the basic principles, techniques, I use as well. As I mentioned in the webinar we did together, you and I is, if the foramen magnum is available, I use it to put the footplate of the Midas, but certainly putting a couple of burr holes as needed is perfectly fine. Very important also in elderly patients to make sure the V3 segment of the vertebral artery is not torturous and not herniating towards the skull. I've seen it happen, the vertebral artery injured, because it's actually well be, well above the sulcus arteriosus so be aware, be aware where the vertebral artery might be, as you're doing this craniotomy.

- I think that's a critical point. And I have had someone injured that during the exposure and making the case very difficult. You can see doing the C1 laminectomy here the vert can actually come up and be within the muscle, in older individuals. So if you're not very careful in your muscle resections, you can really injure the vert. Here's the critical part you were talking about, Jacques, and drilling this piece of bone very much flat to the entry point of the vertebral artery. You do not necessarily need to drill the condyle, but you really need to get very close to the entry point of the vertebral artery to have a lateral trajectory and look from inferior to superior trajectory, to approach the aneurysm. You obviously want to remove the, the ligament over the dura to be able to open the dura effectively. Here is us trying to go and then open the dura. There's a variety of way to open the dura. One way is just a curvilinear approach that is relatively easier to close. Any other thoughts, Jacques, while this video is playing?

- No, the question is often how far do you remove arch of C1 laterally? A good rule of thumb is one centimeter beyond the entrance of the vertebra artery into the dura, gives you enough room to curve it if necessary.

- Okay, and here is doing the microdissection intradurally. That's the vertebral artery. When there is hemorrhage, obviously things are a little bit more difficult because you can see every detail elevating the cerebellum. Here as you can see the PICA loop, it always leads you as if the OICA vertebral origin is up here, but actually that's not the case. Often the vert starts down here and it moves up. I'm just showing this part of the video to show how the resident can become somewhat disoriented and continue dissection much more superiorly than necessary. As you can see, this is just a loop, nothing more than that. And here you can stay medial to the wall of the vertebral artery, find the distal vert, and be able to carry on the dissection on the aneurysm. In this patient, this vert actually was very much stenotic at the level of the origin of the vert in the neck, and this was retrograde flow. So we had to place a clip on the distal vert to obtain proximal occlusion, which is really very unique, in this situation. So we're gonna go ahead and put a clip around this artery. And as you can see here, a longer clip, to be have it out of the way, and be able to dissect the neck of the aneurysm. One mistake that I've often see is people get nervous without dissecting very thoroughly, around the neck of the aneurysm, place the clip prematurely, and cause intraoperative rupture, because the clip is not completely across the neck and actually increases the jet of the lock into the aneurysm that way. Any other details you would like to add here, Jacques?

- No, the critical importance of in your case here, it sounded like you only needed one end of the vertebral control, but by, you know, proximal and distal control is so critical in PICA because when it bleeds, even if you have a clip on the proximal vert, as if you didn't have any clip, because that retrograde grade flow is almost always so vigorous. So absolutely the clipping portion of the aneurysm should be the easiest and absolutely last step. The dissection is the key.

- I can't emphasize that more, and many people sort of avoid using temporary clips. I think temporary clips are absolutely critical because if you can't really dissect well and deflate the aneurysm, that's when you can place clips most safely, if you have complete local or regional surgical arrest, even for a short period of time on there accommodate suppression, you can do a lot of work without causing significant injury. And here he is, again, you see taking your time and looking across the neck of the aneurysm anteriorly rather than placing the clip blindly. And assuming that it clip blades would go ahead and do the dissection for you. Again, replacing the distal clip in this case, we're gonna go ahead and place a proximal clip also, and this gives us such a nice decompression of the aneurysm, as you can see, and this way you can put the clip, I really enjoy clip application because it is becoming effortless and so safe, so effective, and make sure you can get every abnormal part of the neck of the aneurysm that is incorporated to the parent, into the parent vessel. And here is momentarily, the clip will come in again. I'm doing all I can to see all the way across the neck of the aneurysm and there is nothing that is moving blindly. You put the angle clip, you grab a little bit of abnormal part of the vessel that is incorporated in the neck. And the ICG shows that the, all the relevant vessels are patent. You look around to make sure you haven't grabbed anything. Or the neck of the aneurysm is not beyond the tip or the tip of the blade of the, of the clip. And here's the ICG showing flow and complete occlusion of the aneurysm. And this was the post operative angiogram showing complete occlusion of the aneurysm itself. So let's now talk about a little bit more straightforward, 48 year old female with an unruptured six millimeter right PICA aneurism, in this case, and let's review the images. You can see the location of the PICA aneurism, relative to the foramen magnum. Here you can appreciate the opening. This was using a question mark incision as Jacques, you mentioned, there's often a very large depth to the working zone of the surgeon because the muscles almost lift up with the retractors and increase the working zone of the surgeon. But again, for very simple, straightforward PICA aneurysm, this works well. Any other thoughts for the dural opening or details you would like to add, Jacques?

- No, I'm sorry, this was a non ruptured aneurysm, correct? Or it was ruptured?

- Unruptured, yes.

- Yes, yeah, you see, compared to your other case. The view is less here. It's, it's more crowded. I mean, I'm sure the job will get done, but it just, you're more tunnel vision. I'm not sure if it's because of the incision, the craniotomy, but it's less viewing than the previous case.

- And I think that comes down to what you mentioned. If you use a curvilinear and a hockey stick incision, you'll be able to move the flap out of your way. But in this case, the muscles almost move up in your way with the retractors and here is in an unruptured case, a very easy to expose the aneurysm, stay on the medial part. You can see the neck of the aneurysm, you can see PICA and you can see most of the aneurysm is located on the PICA portion rather on the vert, vertebral artery portion of the vascular tree in the area. And again, it's important to really carefully examine this aneurysm before placing the clip, it's a very small amount of space, and immature placement of the clip usually causes either intraoperative rupture, or potentially intra-aneurysmal thrombosis and distal embolization. If the clip is repositioned. Here is a placement of a straight clip right across the neck of the aneurysm. Would you have used a different clip in this case, Jacques?

- Straight works or possibly a fenestration around the nerve, as you know, a fenestration can be around the vessel or around the nerve. I sometimes use fenestrated clips around the third nerve, but looking at the way you're applying it, I guess you're applying it left-handed. I probably would have used bayoneted clips so I can see better around the clip applier. I'm not comfortable with the view I have right now because the clip applier head is a bit in the way. So I like to use tandem or fenestrations.

- Okay, so that's very good pearl to know. Using the clip that is in the form of a bayoneted instrument, often gives you extra space to look around, to make sure you're not catching anything. And here it is, again, looking, making sure that the distal vert is not, I placed it within the clip, you can see a little bit of the neck is still left, and we're gonna go ahead and reposition the clip a little bit more towards the feet of the patient, in order to make sure that a portion of the aneurysm is also occluded. But as you can see, you can not always rely on seeing the distal vert. Here again, showing that not only the clip was a little bit short, but also aneurysm is filling. And that could be a reason because I couldn't see around the aneurysm very well, just like very well you mentioned. And we positioned the clip a little bit more distally and a little bit closer to the neck of the aneurysm. And actually the second ICG revealed a complete occlusion of the aneurysm. We use a powder and soaked gel foam over the PICA before the closure to make sure the PICA is not necessarily effected by vasospasm due to manipulation. Another case, this is an interesting case, a 55 year old female. Now with an unruptured left distal PICA aneurysm, you can see the reconstruction of the CTA. This aneurysm is relatively incorporating portion of the vessel. Here as you can see the aneurysm almost at the bottom of the fourth ventricular space, and this is an angiogram demonstrating again, the aneurysm, very distal, one would say, you can almost sacrifice this portion of the PICA, but it's best to preserve as much as you can. Any other detail you would consider important looking at these pictures, Jacques?

- Well, certainly if you can see the perforators on the angiogram, you want to pay attention to them. It's as you, we also know as the more distal the aneurysm is the less you need a far lateral approach, and the more you can get away, you do get away, and that's all you need in those distal cases is simple midline, suboccipital craniotomy, maybe slightly eccentric to one side. That would be my comment on this one.

- And that's exactly what we did, Jacques, as you can see, there's no, this is really a standard suboccipital craniotomy midline approach to cerebellar tonsils, we open the space between the two micro surgically. And go ahead and follow the PICA distally. Again, these are very basic techniques to preserve the artery. And as you can dissect the two tonsils, obviously the aneurysm comes in your view, this is the choroid plexus at the base of the fourth ventricle, very adherent to the distal portion of PICA. Trying to open the PICA very widely to avoid any undue traction on the tonsils.

- Aaron, may I make a comment? I forgot on the angiogram, that hairpin turn of the PICA, that also should tell you it may be difficult to clip reconstructed. I have an identical case where I ended up doing an end to end anastomosis. So the fact that the curve of the PICA at the neck of the aneurysm is very sharp. You need to be wary that you may not be able to clip it easily.

- I think that's a great point. And here, you can see the aneurysm along that hairpin, that you very well mentioned, a very much fusiform nature of this aneurysm, how we use the two angle, fenestrated clip in this case. And it seemed that it did the job, but again, you can see that hairpin turn. You can see the aneurysm, a very or temporary occlusion of distal PICA, and then use the angled fenestrated clip. These fenestrated clips come extremely handy. We use two of them, and they work very well. What are your thoughts in this situation using these clips?

- Yeah, no, it works fine. I just don't like to put them against tension. So do you have only a proximal clip or a proximal and distal trapping clip here?

- No just a proximal and it's really deflated the aneurysm well enough, as you can see here.

- Okay, well, if you don't, if you're not fighting the wall, then that's perfectly fine. If you were fighting the wall, it's a good case to puncture the aneurysm between trapping clips to apply the fenestrated clips.

- And you can see the distal PICA fill in very well, proximal PICA, the aneurysm here is not filling at all, and really worked well in this situation. But I agree. It doesn't always work this way and you may have to excise a portion of the vessel incorporating the aneurysm and do end to end anastomosis, which can be very difficult in these circumstances. Let's quickly jump to our next case and this, this was actually the post-op angiogram showing good flow from our last case. This is a difficult case where I toured the neck of the aneurysm. And I like to know your opinion here. Really a very difficult moment in surgery, 48 year old female with a ruptured four millimeter left PICA aneurysm. These smaller PICA aneurysms are almost more difficult than the bigger ones, because before you expose them, you're almost exposing the dome, and you don't have much aneurysm to work with. And I think everything is actually in the video here. So let's go ahead and jump to the case here. A 52 year old female with a ruptured small four millimeter left PICA aneurysm. You can see the hemorrhage in the cerebellum pontine angle and this very small aneurysm. These aneurysms can often be blister aneurysms. This is the positioning, increasing the angle. The hockey-stick incision, as you can see, the turn of the head toward the floor. Here's the opening. This lady has a very deep posterior facet, opening the arachnoid, finding the PICA, moving along the 11th cranial nerve and the vertebral artery. And here as you can see this aneurysm. This is the PICA. This is the vert. This is the aneurysm, embedded medially into the brainstem. And I tried, I tried to clip and I should have stuck with using this clip rather than doing it perpendicular. But you can see the, I'm putting a temporary clip. You can see the 12th cranial nerve on my way. So there was no way to put a parallel clip along the neck because the nerve was going parallel to the neck of PICA. So I went ahead and put a clip across here and it worked okay. But when I repositioned it, I tore the neck. How would you have clipped this aneurysm, Jacques?

- I'm trying to understand. Oh, I see. Yeah, no, I agree. You should have stuck with your original plan forcing that lower blade here. Your left blade is a dangerous maneuver, being 90 degree to the PICA. I would have put that angled fenestrated clip I believe you were holding in your hand first. An angle fenestrated, so the blades are totally parallel to the PICA, as opposed to 90 degree to it. Also, you know, let's not forget. I'm not sure if you have distal control or not. If you don't have distal control, adenosine is very handy to give you temporary deflation, particularly in a ruptured case, just during the clip application.

- Right, you know, the reason I didn't put that initial clip and I stopped the video here, because the nerve was in the way, you see that if I had put that clip, I would have grabbed the neck with it. At least that was my initial impression. I do have the distal controlled. You can see the neck and initially that curved clip worked well, but it left a little bit of neck of the aneurism because I clipped perpendicular. And that's well-known fact, when you do perpendicular. So I try to now the neck was already a little bit weak because of the first clip. I try to create a little more space, but because I had already injured the wall of the aneurysm from the first clip, I injured the neck with my dissector. So you can see momentarily that the hemorrhage is coming from the neck of the aneurysm. And in this situation, obviously one solution is trying to force a clip, which I initially tried. And that's not a good technique at all. You have to get a second suction in your hand and work with a dryer feel, and try to see if you can repair the tear at the neck. The technique that's always worked for me is putting a piece of absorbent cotton and doing what we call the cotton clip technique across the neck of the aneurysm. Would you have managed it differently in this case?

- You know, my first instinct in cases like this is just stop the bleeding by temporary trapping. I'm not sure which temporary clips you have on now. Let's just do that, so we don't tear the neck further. This cotton technique, as you know, published by a Barrow And Spetzler is very handy as a last resort. At four tears at the neck, as you incorporate the cotton with the clip, it increases surface area against the bleeding point. But if you end up managing it this way, it's perfectly fine. But my, I would have given either temporary trapping or adenosine, I need to see what's going on rather than clipping through blood. That would be my general strategy.

- Okay, that's very well said. As you can see that cotton really works well, holding it against the wall. And this aneurysm was really small enough that one clip, and even if you go perpendicular it did the job fine, as you can see, everything is patent, but it's critical to not to panic and either use adenosine, in this case, we also use fluorescing for interoperative angiography here. It gives you a more high definition image, but we didn't have pacers on the chest of the patient. And you can see the postoperative angiogram shows good filling of PICA. And that's why we really didn't use necessarily adenosine. Well, let's go ahead and go to our last case in this case. 42 male with a ruptured right fusiform PICA. And he was in with history fibromuscular dysplasia. This is actually a case of one of my colleagues and this patient had a very, very awful pseudo aneurysm almost. And you can see, again, the blood in the fourth ventricle, this is the aneurysm. Very fusiform slightly more distal, and incorporating the PICA itself. Hockey-stick incision, dural opening, arachnoid opening. It's gonna quickly jump into showing where the vert comes in and the PICA join each other. And here as you can see PICA, you can see vert and the aneurysm is hiding, just caudel to the lower cranial nerves. And as you can appreciate, it's right here. It's very much the neck of the aneurysm is broad. It's located here. And we decided to go ahead and clip from the side of PICA, distal PICA toward the vert. And here is again, working underneath the vertebral artery to see if we can fenestrate it. That was not fruitful because the birch was very adherent to the lateral wall of the brainstem. This is the aneurysm, this is PICA. And here is placing that clip again, parallel to PICA, but look what happens. The aneurysm neck avulses, and that's because this was really a pseudo aneurysm, due to previous history of collagen vascular disease in this patient. Really a very difficult situation that I don't have a good answer to deal with. It really startles the surgeon in this case, you can see the neck and that's one of the reasons, while a tear happens, you should be very calm and not necessarily pull your clip too quickly because it can tear the neck. In this case. I don't think there was any option besides proceeding with trapping of the aneurysm and sacrificing PICA, both proximally and distally, as you can see. So if there is a lot of bleeding going on, one approach is use adenosine, thank you. However, again, these patients are often in lateral position and there's no pacing, but still you can use it, using a piece of cotton. It's a very good absorbent and can suck the blood and provide good clearance of the field to put the proximal clip, to decrease the bleeding, and then obviously a distal clip and trap that portion of PICA. Obviously not an ideal situation. In this case, you can see the neck is torn. It would have been ideal, maybe use the cotton technique, potentially repair the neck with sutures. But again, that segment of the vessel was so sick. We didn't feel that was the case. And in this point, at this juncture, we're really relocating a temporary clip for a permanent clip to complete permanent exclusion of this portion of AICA from circulation. Any comments there, Jacques?

- Yeah, Aaron, I mean, the angiogram probably told us that this was either a dissect, it's probably a dissecting aneurysm due to his collagen disease. So I was gonna ask on your way in what was the plan, because it did not look clippable on the angiogram. I would have gone in with exposing the midline for a possible PICA to PICA bypass because clearly you cannot repair those with flow preserving clip on that vessel. So hopefully it ended up well, but, you know, trapping the PICA probably is, was the right choice under the circumstances. Ideally I would have had, I would have wanted the option of revascularization within my bone flap confines.

- Very well said. And that's what I was trying to save for the end. But you obviously stole the thunder. We did do a balloon occlusion test of that part of PICA and this patient had very good collaterals. And as you can see, there is some leptomeningeal collaterals, and also AICA collaterals and this patient did not have a stroke. But you're very right. In this situation for dissecting pseudo aneurysms, you have to prepare to do a revascularization procedure as direct clipping can be very problematic, Jacques. Thanks for expert opinions. And I really enjoyed working with you.

- Great cases, Aaron, great job. Thank you very much, congratulations.

- Thank you.

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