Foramen Magnum Dural Arteriovenous Fistula (dAVF)
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Here's a nice video discussing clip ligation and disconnection of a dural arteriovenous fistula at the level of a foramen magnum. This is a 43-year old male who presented with sudden onset left facial and arm numbness. The initial CT demonstrated evidence of hyper vascularity, and on evaluation further confirmed the presence of the collection of the blood vessels at the area of the foramen magnum on the left side, with evidence of some edema at the area of the lower brainstem. Here's a CT angiogram. Again, demonstrating the hypervascular collection of the blood vessels at the region of the foramen magnum. Let's go ahead and study the lesion with angiography. You can see the Cognard IV or venous fistula at the level of the foramen magnum. The fistula is most likely at the level of the dura around the area of the foramen magnum. The fistulas connection, as you can see on this vertebral injection is most likely located just about there. Here again, the area where the vertebral artery enters the dura. Let's go ahead and review the intra-operative findings. Here the exposure paramedian linear incision was used. The patient is in the latter position. My previous videos have described the positioning and the performance of the craniotomy. Here's the craniocervical junction. The sigmoid sinus will be located here. The condyle is located here and it's not drilled. The dura is opened in a curvilinear fashion. This pattern of dural opening assists with a water tight closure at the end of the case. All the arachnoid bands are widely open. As you can see, there is a very large collection of the blood vessels that appear very abnormal. The difficult part is to find the exact location where the connection or the fistula enters the intradural space. I tried a number of different maneuvers to dissect these loops of vessels. Here's the 11th cranial nerve, craniocervical junction. I wanted to find the exact location where that fistula becomes intradural. Again, the fistulas point resides within the dura at this juncture. I'm unable to find this fistulas connection. I continue to further maneuver around these vessels to find the area where the fistula enters the intercranial cavity. One has to disconnect or ligate the fistula right at the level of the dura to be successful in completely disconnecting the fistula. Here's a vein on the brainstem. I initially thought that maybe this is the area where the fistula becomes intercranial or that this is obviously the draining vein or the brain stem. To better define the fistulas connection I went ahead and performed a dynamic fluorescence angiography. The FLOW 800 technology by Zeiss has been quite effective. Here you can see the peak of the vertebral artery, a moment ago. And you can see the nerves in the veins, but there's no evidence of a fistulas connection. Here's the vertebral artery up there just interior to the abnormal connection of vessels. Here's the 11th cranial nerve. So let's go ahead and do the ICG. This method, quantitatively measures the speed of flow, and you can see all that what I was dissecting here. The fistulas connection is most likely more superior to the area of my dissection. And I think in this case, this technology was quite helpful in guiding me where I need to dissect to further identify the fistulas connection. So I went ahead and redirect my attention more superiorly, and I was immediately able to find this thick wall vessel just at the level of the dura of the foramen magnum, which is the primary side of fistulas connection. Again, the dura foramen magnum, the fistula entering the intracranial cavity. I do not see any additional branches right at the area where it enters the dura. I circumferentially isolate the fistula so I can ligate it right at the level of the dura. Here's this straight clip across the fistula. I'll go ahead and perform another ICG injection and FLOW 800 imaging. In this case, you can see there is no evidence of filling in the abnormal venous structures over the lower brain stem and postoperative angiography revealed complete disconnection of the dural fistula. There was no complicating features and this patient's recovered from his surgery very nicely, and his preoperative symptoms completely resolved. Thank you.
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