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Giant AVM: Nuances of Efficient Resection

October 27, 2019

Transcript

This video describes resection of giant AVMs, and reviews pearls and pitfalls for complication avoidance. This is a young patient of mine, who presented with history of subarachnoid hemorrhage. An CT angiogram demonstrated a very large or giant arteriovenous malformation in the right parietal region. Let's go ahead and review the angiogram. Here's the posterior circulation angiogram demonstrating the expected large feeders from the PCA, as well as draining veins. You can see the nidus of the malformation. In addition, these giant AVMs can carry these network or networks of deep white matter feeders along their subcortical surface. And I'll be review in the video some of the management strategies to control bleeding from these networks of the white matter feeders. Again, here is another perspective of the malformation with these rather diffuse periphery of subcortical networks of white matter feeders. I'm going to also describe the angio architecture, via the enter circulation study. Here you can see the distal MC branch, a hypertrophied branch that's feeding the small formation, with draining veins moving medially toward the superior sagittal sinus. This AVM, as you can see again, has these networks of deep white matter feeders, that can be quite challenging to handle during surgery. Here's patient positioning in the lateral position. The head turned toward the floor. I believe the lateral position provides a very nice posture for the neck to be in physiological turn, and not too much turn of the head, in terms of placing the patient in the supine position. You can see the large scalp flap that's present for adequate exposure of the malformation. Here's completion of the craniotomy. Here is anterior, posterior, superior and inferior. You can see the large draining veins, draining toward the superior sagittal sinus. I went ahead and studied this malformation via ICG angiogram and obtained a FLOW 800 analysis, to better study the early feeding arteries to the malformation, that are located along the anterior and inferior aspect of the malformation. You can see that draining veins toward the superior sagittal sinus. So I'll go ahead and start the dissection here, to dissect these early feeders superficially first. Here's the initial stages of the disconnection, again, coagulating the pia along the periphery of the malformation, and then getting under the pia to coagulate the feeders effectively, and then sharply cutting the pia and dissecting the superficial white matter from the periphery of the malformation. The pial vessels are very easily coagulable, and I go through this part of the operation very quickly. Using high magnification, I can go in through these superficial feeders very efficiently and protecting their large draining veins. Here, again the technique of subpial coagulation and disconnection. This part of the depth did not have any deep white matter of feeders next to the nidus. And I continue to use the bipolar forceps like scissors to disconnect the deep white matter. Here, is part of those networks of deep white matter feeders that I discussed, you can see that it can be quite challenging to control as they don't own coagulable walls. So the strategy in this case is if there is a fair number of these networks, to just resect it at the periphery, rather than just coagulating it. And if just one or two deep white matter feeders remove small amount of brain around them a little bit away from the malformation, in order to reach their more coagulable walls, to coagulate their lumen. Here you can see some of these deeper white matters feeders. Some can be coagulable, and some can be much more challenging to handle, as you can see here. Using neural navigation with CTA to better understand the boundaries of the malformation. I continue to, again, coagulate these deep white matter feeders, and if necessary, remove their subcortical preformed networks. Here you can see a network of these deep white matter feeders, that I'm trying to remove. Persistence on coagulation of these individual feeders within the network can be quite ineffective. Here you can see a single one more along the periphery of the malformation that's being coagulated. Again, moving slightly away from the nidus if necessary, to be able to achieve hemostasis. You can see how challenging that bleeding can be, within these networks. Ultimately, as they have been removed, you can achieve permanent hemostasis. Here's a more demagnified view. Now I'm going close to the falx. There was a large feeding vessel, that I felt I had coagulated, however, coagulation was not adequate. In these cases one has to maintain his or her composure, and use the suction to keep the field clear and coagulate the vessel. Here you can see the large draining vein. I'll go ahead and temporarily occlude it in a minute, to see if I have disconnected most of the malformation. If temporary occlusion of the vein does not lead to any significant swelling of the malformation, then I go ahead and take one of these primary veins and preserve the other ones, so I can roll the malformation now and be able to disconnect along its underneath aspect. During the later stages of resection, some bleeding is tolerable, and the only way to achieve hemostasis is to efficiently remove the malformation, rather than persisting on very strict hemostasis. Here's the final product. One point I want to emphasize is that as the malformation is removed, if there are any walls that are herniating into the resection cavity, one has to suspect some hematoma underneath them and therefore, evacuation of the hematoma is critical. Usually this hematoma means that there is evidence of residual malformation that has to be removed. This case, hemostasis was all that's needed and here's the final product. And complete remove all the malformation and preservation of some of the en passage vessels. And here's postoperative imaging. The CT scan demonstrated good resection, without a large hematoma or evidence of ischemia. Formal postoperative angiogram demonstrated complete resection of the malformation, without any evidence of AV shunting. It's important to note that I did conduct an intraoperative angiogram also, to confirm complete removal of this giant malformation. This patient made an excellent recovery. She had some mild visual field cut after surgery that completely cleared at three months evaluation. Again, for these giant AVMs, it's best to emphasize the strategies to control the deep white matter feeders as discussed, and efficiently remove the AVM as the only best mode of hemostasis, especially at the later stages of the operation is extraction of the malformation. Thank you.

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