Frontal AVM: Staying out of Trouble
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I would like to use this video to describe some of the challenges that we face in resection of large arteriovenous malformations. This is a young patient who presented with intractable epilepsy and was found to have a left frontal arteriovenous malformation as you can see on T2 weighted images, as well as the sagittal and coronal enhanced sequences. An arteriogram demonstrates the angio-architectural malformation including the large feeding vessels, both from the MCA and the ACA territories as expected. The large draining vein is obviously joining the Superior Sagittal Sinus. The patient underwent a left Frontal Craniotomy through the incision demonstrated here. Neuronavigation was used. The malformation was generously exposed. Arachnoid dissection using jeweler forceps exposes the large feeding MCA branches to the malformation. Following sacrifice of some of the larger branches, I continued parenchymal and white matter dissection while staying out of the Nidus The larger MCA branches were first clipped, coagulated and then cut. I ran into some bleeding from the nidus of the malformation. Small amount of bleeding may be controlled by gentle coagulation. However, if this maneuver is ineffective, a piece of cotton may be used along with gentle tamponade to control the bleeding. Aggressive coagulation should be avoided at all costs. As aggressive coagulation can lead to hemodynamic changes within the Nidus that can cause premature rupture of the malformation. Therefore, if you face Nidul bleeding during the surgery, it is best to use thrombin soaked cotton or gel foam, but preferably cotton, to seal the bleeding via gentle tamponade. And strictly avoid the temptation to aggressively coagulate the nidus, again causing sudden hemodynamic changes that can lead to premature rupture. If the dominant feeding vessels are not completely excluded. In this case, the ACA branches were still alive. Here's one of them that has been clipped and then coagulated and cut. Subsequently the draining vein was coagulated and cut, and the AVM was removed. Post operative Angiogram demonstrates gross total removal of the malformation without early AV shunting. Some of the larger feeding arteries are present, however, they're are not shunting and they are ending without entering any residual malformation. The final learning point about this case is really the control of Nidal bleeding as mentioned via gentle tamponade and thrombin soaked cotton avoiding the temptation for coagulation of the Nidus, or any other maneuvers, that can place the flow within the NIdus at risk before the dominant feeding arteries are sacrificed. Thank you.
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