Grand Rounds-Nuances of Neurovascular Surgery
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- So thank you, Dr. Cohen. Our next speaker also needs no introduction. Dr. Mike Lawton, will speak to us on complication, management and avoidance in cerebrovascular neurosurgery. Dr. Lawton is professor and vice chair of neurosurgery here locally at the University of California, San Francisco, where he also directs the skull-based and vascular center. So, Dr. Lawton, thank you.
- Well, thank you, Cormack and thank you Aaron for the opportunity to be part of this and for all your work in getting this operative video forum to be really a part of our meetings regularly. So what I thought I would do is share with you some videos on the posterior circulation in particular, because I think there's this perception that there isn't a lot of posterior circulation aneurysm surgery going on right now and so these are just cases from the last month or two in San Francisco, just to give you a flavor for the fact that there are these cases going on and just to show some of the techniques that I've found useful. So let me start with this case. Gideon, you can roll this. This is a blister aneurysm at the basilar apex, and I want you to pay very careful attention to the films, subarachnoid hemorrhage and an abnormality at the P12 junction on the left side, that was initially thought to be the source of the bleeding. This looked to be the aneurysm and it was thought to be a fusiform aneurysm. And so going into this case, my thinking was that this would be a lesion that would need to be trapped and bypassed. He had a very poor superficial temporal artery. I was thinking I might do an insitu bypass with a PCA to SCA bypass, but you'll see as we go further along in this dissection that things didn't really turn out quite that way. This is some dissection in the carotid optic triangle to showing the extent of blood in the subarachnoid hemorrhage case, and now we're going lateral to the third nerve to get down into the inner binonchal fossa. There for the first time you're seeing the PCA at the depths, and we're just working our way through this carotid ocular motor window that can be opened by mobilizing the temporal lobe a little bit posteriorly, working along the third nerve that you see there in the center of the field, and now what we're coming on here is the PCA. This is the P12 junction, and you can see some sort of dilatation of the artery, but the walls look a little bit thin, a little bit cherry red, but really not so convincing that this is the side of the aneurysm ruptures, so you can see thalamal perforators there on that end of the P1 segment. You can see the third nerve there. And now, as I looked down further, I noticed something at the back of the apex. So this is an IC green video angiogram and this doesn't project well, but you can see some... a little bit of a blush behind the apex there. My intuition told me that that might be the site of this rupture and that maybe what we were seeing on the angiogram is really just a vasospastic PCA segment, and so as I explore this further, what I'm beginning to find here is a lot of thrombus on the back of the apex and really what amounts to a blister aneurysm. And so this is the blister aneurysm. You can see it behind the P1 and the SCA on this left side. And blister aneurysms, as you know, are very fragile. These are really a dissecting pathology, and so rather than try to clip this closed and involves that thin wall of the apex and not have a really good answer for that. My complication avoidance technique with this case was to wrap this with muslin. So what you're looking at here is a thin strip of cotton, muslin cotton, and I've worked out behind the apex the quadrification, brought it around the front and brought the tails of that muslin together. Now, once you do that, you can pull the tails up, put a little tension on the material and use these straight stacked clips to close that wrapping band. So what we've created here is basically a sling, and we've done that with a little bit of tension on the material with the clips, closing it down. And that's just a little bit of extra Tufts of cotton that go above and below where the sling ends. And so that blister aneurysm has now been reinforced. Now you can make the argument, "Is that really a securitive maneuver?" It's debatable. I think not only does it provide some reinforcement mechanically, but it also is inflammatory and can over time lead to some scar formation and thickening in the wall. Now, even though I wasn't convinced that that P12 junction was really the site of rupture, I've figured since I was there, I would do the same thing to that segment of the artery just to eliminate any doubt and give the same kind of protection to that little spot. So again, a sling. This time the clip is parallel to the P12, and again, the same idea of lifting up on the sling, sliding the clip down so that there's a little bit of counter pressure as the blades of the clip are closed down on the artery. So there's the working window, you can see it's pretemporal right in that carotid oculomotor window. And angiographically, this is the result. Really, a nice reconstruction for a difficult problem. Now, this next case is an example of a high riding PICA, and if you look carefully, it's all the way on the distal end of the vertebral segments. So there's really a shoulder of the vertebral that bends towards the vertebral basilar junction, and what we're seeing here is an exposure to the extended retro sigmoid approach. So it's a PICA aneurysm. I think you're... all of our intuition is to approach this through a far lateral, but you have to interpret the relationship of the aneurysm to the skull base, and this is so high-riding that a retro sigmoid is really a better choice. So what you're seeing now is the PICA as it's traversing down across the cerebellum, you're seeing in the depths, the nine and tenth nerve complex, and we're just following the PICA further and further deep into that window between the ninth nerve and the eighth nerve, and we can follow that back to the aneurysm. So this is just your basic retro sigmoid craniotomy. It's a very small window, but you'll notice that there's no cerebellar retraction. It does require a little bit of manipulation of the vertebral artery forward towards the clivus that brings the aneurysm into your view. You can see it right there and that little white spot there in the depths is our aneurysm. It's enough of a working window to get the clip in. Again, it's between the cranial nerve window between eighth and nine, and with a little forward manipulation of the artery and aneurysm and working the clip across the neck, you can get those blades in and nicely take care of that aneurysm. So the clip is on. We need to inspect. We need to make sure the vertebral artery is patent. We need to make sure the PICA is patent, and we also need to make sure that the aneurysm is completely obliterated. So there's the working window. Again, IC green here in your lower corner there shows that the vertebral artery is patent, PICA is filling, and this aneurysm is secured. Small aneurysm, you could say, "Well, why did you bother clipping that?" Well, the patient presented with the ruptured ACoM six months earlier. it was called by my interventional partners, and they wanted me to clip this because they didn't feel they had a good option for this. So again, the lesson here is don't adhere to the dogma. If it's a PICA aneurysm, look very carefully where the PICA aneurysm really is. If it's medial to the seventh and eighth nerve complex, then I think you need to reconsider your approach and consider doing this extended retro sigmoid. You can see the six nerve there going in the dorello's canal at the depths. You can see the seventh and eighth nerve, more superficial in the field, and again, this is all with no brain retraction and no petrous drilling. Right, now, this is a similar case, but it's a giant aneurysm, and you can see it looks nice and clean and difficult to aneurysm. He ruptured right after the angiogram was completed, and so now that unruptured giant aneurysm has turned into a subarachnoids hemorrhage case, and we did this emergently. Now the approach that you're seeing here is a combination of the retro sigmoid that I just showed you and the far lateral. So I call this the combined far lateral retro sig. And what we're doing here is we're going actually across the foramen magnum to get exposure of the contralateral vertebral artery, because this is a giant aneurysm. I'm going to need a window of time to arrest the flow in that aneurysm. So I need to have both the vertebral arteries available to me, and they really are available to you at the foramen magnum. So this is a clip going on the contralateral vertebral artery, and this is a clip going onto the ipsilateral vertebral artery. And what that does, it basically closes the feeding flow into the aneurysm. Does not give you complete control, but it gives you a proximal floor of rest. This is just removing the temporary clip because it's taking up some of my field that I need to work through. So I've slid it more proximally, and I've used a permanent clip rather than a temporary, even though it's not going to be a permanent application. So, again, following the vertebral artery, we can work our way to the neck of the aneurysm. This is a clip going across the neck, and you can see once again, it's that same working window that's above nine and below eight, and you can just barely see the vertebral basilar junction at the tips of the clip. And the first two clips are two fenestrated clips, and the idea is drake's tendon fenestration clipping configuration, where you use the distral closing force of a fenestrated clip to close the furthest portion of the neck away from you, and then apply a straight clip proximally. Now this is where the complication comes. I'm taking my temporary clips off and I do my IC green. Everything looks good. There's flow in the vertebral artery. There's a preservation of the ICA as it's coming off of the aneurysm there. You can see a filling of all the vessels, which is what I wanted to see, but the IC green isn't good enough. You have to go and inspect your aneurysm and make sure everything is taken care of. And as I was doing that, I ruptured the dome and clearly the presence of bleeding from the dome indicates that the aneurysm is not fully secured. So when you see that happening, really the problem is at the distal portion where the tips are hardest to visualize. So I'm putting a clip back on ipsilaterally and Contralaterally. So again, arrest the flow. There's the contralateral vertebral artery. So that slows the bleeding down for me, but not quite enough. I gave a dose of adenosine here, which gave me a small window of time to get this additional clip on. And that additional clip is just a straight clip that goes a little bit beyond where the tips of those two fenestrated clips were and secures that last little portion of the neck that I found very difficult to visualize at the vertebral basilar junction, and that did the trick. I am putting on one more clip for good measure, just to add an additional closing force, right at that point, distally. And there's no need to change the original clips. It's just a matter of bolstering or boostering the points of the clip more distally. And if you look very carefully at this angiogram, you can see that those last two clips were long clips that just go to the very distal portion of the neck. Sorry for the pace, it's a little quick. But anyway, we're trying to get through these cases, and this is another ICA aneurysm. This is a 72 year-old woman, small aneurysm that was not felt to be amenable to an endovascular solution. So it was referred on to me and you can see it's location right in the ponds. These are just some views that you get to orient you and some angiography pre and post, and what we're going to do to expose this is do a kawase drilling. And you really have to look carefully at this window here because that's the small window of space that we're going to open up through our exposure to get down to the ICA. So we'll go to the video now, and the view that you have here is extradural subtemporal along the middle fossa. I've divided the GSPN so that I don't put traction on the facial nerve, and I'm extending my dissection here just to the petrous ridge and falling over the edge of the cliff there and getting a retractor there to lift the temporal lobe. And with that little blade in place, this was all techniques that are standard for the ENT guys that I learned as a resident. This is me drilling by the way too. I think it's important that we, as neurosurgeons, understand this anatomy, are comfortable with the anatomy and can do it ourselves. That's the carotid canal and I was pushing up on the petrous carotid artery to get behind the carotid and extend that window of kawases as far possible, forward and inferior. So this is that working window. We're underneath the trigeminal nerve, and we're... we've maximized it as much as we can. We take it as far forward under the fifth nerve and as far back to the turns of the cochlea as we can, and now we're converting intradural. So now the door's open. This is essentially now a subtemporal exposure. And the idea here is to open up the ambient cistern, communicate the cisterns around the ponds, and then communicate the kawase space extradurally with what we're opening here intradurally. So we've got to cut the tentorium. I am lifting here the tentorium to find the fourth nerve, and I'm cutting the tent just behind the nerve where it enters the dural sleeve of the tent. And nothing fancy here, this is just an 11 blade, and the key here is just to make sure that you've identified four and have made this incision posterior to four. Now the tent, oftentimes like in Eran's video, is very bloodless, and it becomes a very nice way to communicate these compartments. Other times it can be very bloody. And here's an example of a big venous channel that doesn't always coagulate, but one little trick here that I used in this case is to inject with tisseel, so you can enter that tentorial sinus and put a little plug of tisseel and that nicely controls the bleeding. And you'll see the fourth nerve there. Now it's completely free and we can continue our incisions more laterally. And as we continue more laterally, you'll see we're going to enter that kawase space. So that hole there that's now open is what we drilled extradurally, and the idea is to communicate that extradural space with our intradural space. So it takes a little bit of extra cutting of the tent here to finish the cuts on the top side, and then extend them around the corner so that we continue onward to the door of the petrous face. So as we roll into the petrous face, we then get to the cisterns in front of the ponds, but the prepontine systems, and we drop into the posterior fossa, and that's where we're going to find our aneurysm. So here we are in the prepontine cistern now, you can see the six nerve there traveling forward to dorello's canal. You can see the aneurysm being dissected there with the number six, and we've got to take down this arachnoid of the prepontine cistern, and as we do that, we can start to see the aneurysm. So there's the aneurysm. We've got a couple of things to find. We've got to find the proximal basilar trunk, We've got to find the distal basilar trunk, and we need to see ICA as it originates from the base. And so just by working through those arachnoidal bands, we can start to see that anatomy. And again, tight windows mean that you have to manipulate the tissues a little bit. There's the distal basilar, there's the distal neck. You have to move the aneurysm a little bit, so it makes this kind of an approach a little bit less favorable if you're dealing with a ruptured aneurysm. This was unruptured, so there's that confidence that you can do that safely, but here's the clip going in. You can see it's a very steep trajectory, not lot of wiggle room. So it's the reason why I find that you really do need to go intradurally rather than completely extradurally to get that angle and that right clip application. But there we have it. It's a slightly curved clip. It goes right across the neck. The basilar trunk is preserved. You can see ICA dropping out underneath, there it is, coming underneath the clip blades. And we'll go to IC green here, just to confirm that ICA is patent, and also that basilar is patent, and it is. And also that the aneurysm no longer fills. And so at the end of it all, this is the working window. You can see the fourth nerve. You can see the temporal lobe. You can see the fifth nerve there. So this approach essentially goes underneath the fifth nerve into that kawase space and takes care of the aneurysm. Now, I'm going to change gears a little bit. This is a very fascinating case, intraventricular hemorrhage. If you look closely at the angiogram, there's this feeding lenticulostriade artery aneurysm to this very diffused basal ganglia AVM. So this is not an AVM that I wanted to treat surgically it's too diffused and it's too spread out through the central core. So it's not something that I would attack surgically, but she presented with the hemorrhage from her aneurysm. So we can't ignore that. So the treatment of this aneurysm is not one that can be dealt with endovascularly, it's to distill on that lenticular stride, and I think taking out that artery would have been too risky. So we're going to go at that surgically and that anatomy, if you study it carefully, leads you essentially right to the ventricular floor across from the frame of the monroe. So this approach is a interhemispheric transcallosal approach. This is the corpus callosum here being divided, and we're now finally entering the ventricle. You can see blood in the ventricle and it immediately takes you to the aneurysm. So that round thrombotic thing there is aneurysm, and it's basically adherent to the floor of the ventricle. Now this is an aneurysm that I'm intending just to trap. There's no way to directly clip this or to reconstruct it, and it's feeding an AVM so it really doesn't have to be. But this is the outflow artery. And just in order to get out the imfolite, cauterize the outflow, roll the aneurysm forward, and now you can see the aneurysm is bleeding. It's fairly brisk because it's an AVM feeding artery, even though it's small. And you can see that you just have to be patient, keep your sucker right at the bleeding point and follow it right to the point where it's bleeding. And as you keep moving a little bit further forward, you can see that point of bleeding and you just put a little clip on it, right at that point where it's coming out and going into your sucker and that'll control it. And that's really all it takes. There's your proximal occlusion. Right at that point. A little bit of bipolar cautery for good measure, and you're done. So here's the aneurysm, it's been completely trapped. I can take it out now. And just to be sure that I haven't missed it, I wanted to open it up, make sure that it had the features that I had appreciated on the angiogram, and it did. You can see the inflow into the aneurysm right there. You can see that the aneurysm is quite a bit bigger than it looked angiographically, so this was sort of a thrombotic pseudo aneurysm, and perfectly matched the site of the hemorrhage, the intraventricular distribution, et cetera. So no question that the pathology had been addressed. There's the clip, there's the view into the ventricle straight shot. No brain retraction, head is turned to the side so that gravity retracts the frontal lobe, very beautiful approach for a very deep aneurysm that might have seemed a little overwhelming. Okay. This is a coral occurrence, not an uncommon problem that we deal with. These aneurysms that are coiled can recur and as they recur and are... as they are ignored, they grow bigger and bigger. You can see from those MR images that this had extended all the way down into the posterior fossa, almost to the foramen magnum, even though it originated from PCoA. So they'll see how easy this is, even though it's a giant aneurysm at that kind of distribution, this couldn't be easier. It's a standard posterior communicating artery approach, which is opening up the cisterns, opening up the spaces in the carotid optic window, and the reason to go here is to find posterior communicating artery. So most of the time you'll find it lateral to the carotid heading behind and along the third nerve in this case, because the aneurysm bulk we're finding immediately in that carotid optic window, and as we open up the arachnoid we find it. Now with these giant PCoAs, the thing that I worry about the most is the intrachoroidal. And nine times out of ten, you're going to find the intrachoroidal artery completely plastered to the back wall of the aneurysm. And this was a really pleasant surprise, you can see the choroidal is completely free and just by taking down some adhesions and opening up that plane between choroidal and the back wall of the aneurysm, choroidal came completely off the aneurysm. So that's a huge relief. And you can see that now with the choroidal-free, we can go at the aneurysm. There's a temporary clip just to close the inflow, and we free some of the adhesions on the proximal neck, and this is just a straight clip across a very simple neck with the blades going underneath the PCoA medially, and going in front of choroidal posteriorly. And this is just one simple straight clip, but with the joint and particularly a giant thrombotic aneurysm, you have to expect that one clip isn't going to do it. And so I'm applying here a fenestrated clip. Same principle I mentioned before, using the fenestration to get around some tissue on the proximal neck, but preserve that closing force distally. And here I'm adjusting the clips forward to make sure that I get that tip underneath PCoA all the way forward, where I want that closing force to be. And that seals that proximal portion of the neck. And now this aneurysm is basically done. IC green here in the corner showing that the carotid flow is preserved, showing that our perforators look good and that we've got this thing essentially taken care of. Now, one of the things that I wanted to do at this point was to make sure that his mass effect was relieved. He presented with chronic third nerve deficit. I didn't have much hopes for that, but he had also developed some hemiparesis. And so the idea was to debulk this aneurysm and take some pressure off of the midbrain and the cerebral peduncle. So with the clips in place, you can just work behind it. I'm going to open the dome. I'm going to get into that thrombus, and I'm going to use a ultrasonic aspirator to break apart and debulk this aneurysm. There's the ultrasonic aspirator. It's a very nice application of a tumor instrument, but basically you can get all the way down deep into the posters circulation by just working inside the aneurysm sack. So there's the desired result. You see the coils there, very poorly coiled and an expected recurrence. So this is a interesting aneurysm of very distal M2 segment aneurysm. I haven't seen many like this. Most of these fusiform aneurysms tend to be more proximal, but this is one that going into this, you have to expect to need a bypass, and so you can't expect to clip these. You need to think about bypass options. Those options include an SDAMCA bypass, they include insitu options like excision reanastomosis, or reimplantation or a side-to-side. So it's good to kind of enter the arena with a whole choice of a whole list of possibilities and make your decisions on the fly from a menu that you've already put together. This is just a sylvian fissure dissection, and as you can see, we're coming down on this very unusual aneurysm. It's like a little bird's egg. You can see the outflow vessel there leaving the side of the aneurysm, and as we work our way around the aneurysm, you'll see the inflow artery here. And my decision here is to do an end-to-end reanastomosis after excising the aneurysm. So the two arteries were pretty much side-by-side, and this is a nice, simple anastomosis, because it's a little shorter than the endocides, and it doesn't require that you harvest the temporal artery. So you can see both the inflow and outflow are being cut from the aneurysm. The aneurysm is removed, and now we're left with these two stumps. They're only about five millimeters or so apart. And I first place a stitch that will approximate the ends. And that will very... You have to be very gentle with this first knot that you don't pull your suture through, but this brings the vessels together, and now we can throw a second suture on the other side. And then the suture lines, there are two suture lines, it's basically just running continuous suture from one knot to the other. And these end-to-end reanastomosis, there are fewer throws than the usual. It's about half a dozen, and I like to place them all in sequence and then go back and tighten them individually. The trick here is to once you've got that first suture line, rotate your clips away from you, bring the back wall up into the field, and then you can do the back wall in the same manner. There you have it, nice flow in the artery. So we've reconstructed that the way we want, aneurysms excluded completely, and really not too bad, not too bad of a case. And there's the post-op angiogram. You can't even see where the bypass is. Okay. So two more cases. I'm going to switch gear a little bit and just go to some cavernous malformations. This is a nice approach for this kind of a lesion. The teaching point in this is that you can go through a little bit of the middle cerebellar peduncle for lesions like this. Again, just to continue on this theme of the posterior circulation, the posterior fossa, we're just going through an extended retro sigmoid approach. You're looking at the eighth nerve down there, and that we just get a little bit above that, to that surface of the middle cerebellar peduncle, and you can see the hemosiderin stain there. This is a very tolerant entry zone for access to pontine cavernous malformations, and we can get in. There's no brain retraction, as you can see, this is all done through that window of the retro sigmoid approach. I think my recommendation for these is to be aggressive in drilling out the sigmoid sinus so that you can completely skeletonize that. Pull the dura as far forward as can possibly be pulled, and that really opens up that window for you. Now with brainstem cavernous malformations, the secret there is to really get inside the lesions capsule and do all of your work on the interior. That way, the capsule and that thin layer of the malformation forms a protective barrier from you harming anything in the brainstem. So as you see all this manipulation, you have to remember that it's all on the inside. It's from the interior of the lesion, and so, because we're working through small windows between delicate nerves, these lesions often come out piecemeal, this is a piecemeal or a piece right here, our first piece. And you just can never be satisfied, even though it looks like a big chunk you have to have in your minds eye this sense of what volume you're expecting and keep looking for more if you feel like you're not at that level. And so sure enough, there's more. Again, we're working above the seventh and eighth complex through the peduncle there, and there's an additional piece which comes out very nicely. No fixed attraction. And you have a nice panoramic view. There are five, seven and eight and nine, ten and eleven, all through just a basic retro sigmoid craniotomy. And there's our postoperative result, complete resection. She did well, and I think that's really the way to go for many of these in the ponds. This is another example. I think my last case. It's a transventricular resection of this medullary cavernous malformation, and I want you to notice that there's a little bit of a flow of the fourth ventricle. I really hesitated to do this case. And I normally like to see the lesion on T1 actually at the surface or exophytic into the ventricle. And it was with some reluctance that I did this, and also some persistence by the patient to want to get this dealt with because she had had multiple hemorrhages. And as you see, as expected, the flow of the fourth ventricle is pristine and that's really not what you want to see. Now, you want to see some hemosiderin staining, you want to see a venous malformation. You want to see something that will really dictate your entry site. And so the little nuance here is I've got my bypass set out. These are very fine jeweler forceps, and I think if you're really strict about going right in the midline at this level down by the vagal trigone and really keeping that opening small, you can get yourself through that normal floor and to the lesion in a manner that's safe. I've got a little Tuft of cotton there to suction on. This is a number three sucker. Everything's really as small as you can possibly take it. But by going through those two millimeters of normal tissue, ultimately we here, we hit the malformation. These are these very nice spatula instruments that I love. This is a number one, that's got a little bit of an angle to it that allows you to kind of work into a little blind edge and free things up. And in any event, that's the small working window, that's the little technique for getting through what was a normal floor. You can't mess with the floor of the fourth ventricle, and I'm showing this to you because it's an exception to that rule. You really need to be cautious with the floor, particularly as you go more cephalad. But here it is, it comes out very nicely, thankfully, and we got a good result with this lady. She had no new deficits. You see a nice room around the resection cavity, no evidence of any residual there and no retraction either. You can see it's all just between the tonsils. And there's her postoperative MR.
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