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Splitting the Sylvian Fissure and MCA Aneurysm

September 02, 2015


Let's review some of the challenges we face in clip ligation of complex, partially atherosclerotic MCA aneurysms, while handling the surrounding small branching vessels and perforating arteries. This is a 66 year old female who presented with an incidental one centimeter right-sided MCA aneurysm. You can see that the broad neck of the aneurysm is more toward the temporal trunk. There's no obvious evidence of calcification, on the CT angiogram. A right-sided frontotemporal craniotomy was completed. Standard curvilinear incision was used. Here's the right temporal lobe, right frontal lobe, Sylvian fissure. Let's go ahead and review the basics for splitting of the fissure, Arachnoid knife, a round one is used to open the superficial bands, jeweler forceps dissect the superficial bands as well, in the distal to proximal direction. The fissure is open from the inside to outside direction. Here you can see the surface of M2 and insula. The dissection was deepened along the distal aspect of the insula, and then proceeded from the inside again to outside technique. Here, you can see the section primarily within the fissure. Next, the more sphenoidal or anterior segment of the fissure is further dissected. As many of the veins as possible have been protected. Now you can see the morphology of the aneurysm. Partially atherosclerotic aneurysm, with two adherent, number one, and number two, small arterial branches. Again, highly connected to the midsection, as well as the dome of the aneurysm. As you might expect, placement of the clip can be quite challenging without placing these vessels at risk. I attempted to clip ligate the aneurysm, without dissection of these branches, since they appeared to be very adherent to the very thin dome and blister of the aneurysm sac. The original the, M2 trunk on the temporal side is being looked for. I placed a temporary clip on M1 at the depth of the Sylvian fissure. So I can manipulate the sack more aggressively safely. Here you can see that any attempts of dissecting the small arterial branch from the dome of the aneurysm appears to be unsuccessful, at least portly, aneurysm is even more atherosclerotic, at its section, more medially, A fenestrated clip appear to perform well. However, upon deployment of the clip, the blades slided toward the M2 trunk, causing its partial occlusion. Here, you can see that this far part of the clip blades are compromising the M2 trunk. Before attempting further dissection of these arterial branches, I tried other clip configurations, Placing a straight clip, somewhat distal, to the neck, with dissection of this branch, did not appear to do the job and still appear to leave fair amount of aneurysm behind. Therefore, the only solution was mobilization of this arterial branch, from the dome of the aneurysm, which has expectedly led to entry into the lumen of the aneurysm and the sac. Temporary occlusion of M1 still in place. Minimal bleeding is encountered. This branch is generously mobilized away while a tentative clip is used to again, minimize the amount of bleeding. The entry site into the sack was coagulated, to avoid any further bleeding, during repositioning of the clip. Piece of cotton may also be used to achieve tentative hemostasis. Next, I settled on a curved clip, to avoid the atherosclerotic portion of the neck while achieving good occlusion of the aneurysm. There's an important concept here, that I would like to emphasize, that extraluminally, there appears to be sizable piece of neck left behind, however, due to presence of atherosclerosis, intraluminally, which is unfortunately not visible, the neck is relatively well occluded. Therefore when clip ligating atherosclerotic or calcified aneurysms, perfect clipping techniques, most often leads to compromise of the inlet and outlet of the entry and exiting vessels surrounding the neck of the aneurysm. I was relatively satisfied with the construct, the M2 trunk appeared patent, at least upon extraluminal examination. Here, you can see the temporal trunk is, well, beyond the clip plates, fluorescein angiogram demonstrates patency of the surrounding vessels. Perforating the dome did not reveal any further filling of the sac. I do believe there is some error involved in using ICG in terms of confirming complete exclusion of the sac, and there are false negative results from the ICG, when there is atherosclerosis or calcification apparent on the sac of aneurysm. Therefore, I penetrated the dome to completely assure myself that this sac has been completely excluded. Postoperative 3D arteriogram demonstrates complete exclusion of the aneurysm neck. Again, the concept here is that even though extraluminally there was evidence of aneurysm neck left behind, intraluminally, there is good occlusion of the aneurysm without an evidence of neck remnant, since thick walled aneurysms often cause more than expected collapse of the sac upon closure of the clip lights. This is obviously because of the thick wall of the aneurysms as they collapse. This patient recovered from her surgery, without any complication. Thank you.

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