Frontal AVM: Principles of Microsurgery

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This video reviews, the basic principles for AVM surgery. Before we proceed the video, I would like to review very briefly the steps involved in resection of an Arteriovenous Malformation. These steps involve exposure. Subarachnoid the section of the feeding vessels and draining veins. Peel the section of the malformation, parenchymal the section of the malformation. At the deep sections of the malformation the appendimal dissection is quite important. And obviously the last step involves confirmation of complete disconnection of the Nidus before the draining vein or the draining veins are disconnected. And the whole lesion is extracted. Let's go ahead and review the basic principles in this 14-year old boy who presented with intractable seizures. On MRI evaluation, typical left frontal wedge-shaped arteriovenous malformation, approaching the ventricle is obvious. You can see that the draining vein has remodeled the bone. Cerebral arteriogram demonstrates the angio-architecture of this malformation, which as expected is fed primarily by the ACA and MCA branches. It drains via a large parasagittal vein into the superior sagittal sinus. This patient underwent a left frontal craniotomy as guided by MRI neuronavigation. I did use a lumbar drain in this case to achieve early brain relaxation. You can see the location of the AVM marked with an X. We also prepared for an intraoperative angiogram. A large craniotomy was elevated for generous exposure of the malformation. You can see the large draining vein that had eroded into the inner aspect of the calvarium. Upon opening the dura. You can see the large draining vein and most likely the location of the malformation residing just underneath the cortex. This patient had previously undergone slide embolization of his malformation. The first step would involve arachnoidal dissection identification of the draining vein. And in this case, following into the malformation, since this malformation is not very evident on the surface of the brain. Jeweler's forceps and micro scissors can be used to open the arachnoid bands, protecting the arterialized vein and some of the feeding arteries. Here's a draining vein. Moving deeper into the white matter. Some of the feeding vessels around the draining vein were initially disconnected. The Gliotic margin of the malformation is apparent. After the peel section of the malformation, the parenchymal step involves disconnection of the Nidus from the gliotic parenchymal areas. Here you can see how the malformation is evident and the nidus, I was able to stay right on the nidus of the malformation without any evidence of bleeding, to preserve as much of a normal brain as possible. This maneuver is not always possible. Some of the larger feeding vessels from the MCA are being coagulated and cut. The deep white matter feeders are most problematic. They have a very thin wall and are not readily amenable to bipolar coagulation. These white matter feeders have to be pursued slightly away from the nidus of the malformation. So their relatively normal wall can be found and coagulated so that bleeding can be controlled. We'll see that in a moment. Again, some of these vessels are quite robust in their walls and amenable to bipolar coagulation. This is a white matter of feeders that is not amenable readily to a bipolar coagulation. It has a very thin wall. I continue to pursue the malformation in the white matter and secure hemostasis, packing the area of the bleeding from the white matter is not advised. As this can lead to remote subcortical hemorrhages. Your further pursuit of the vessel into the white matter, led to its control as the wall of these white matter feeders contain more normal contents, the farther one moves away from the nidus. Here is again, the draining vein. Some of the architecture of the malformation is being more clearly revealed. Here you can see the nidu, the draining vein. I continue again, going around the malformation, staying right on the surface of the nidus, disconnecting the malformation from the surrounding white matter. This malformation did not extend all the way to the level of a ventricle and therefore undermal disconnection was not necessary. Here are some of the other white matter feeders at the apex of the malformation that are being controlled. Here you can see the malformation is relatively free. It's only attached to the draining vein that is now being coagulated and cut. Postoperative angiogram demonstrates complete exclusion of the malformation without any early AV shunting. Thank you.

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