Clip Ligation of Large ACoA Aneurysms: Technique

December 02, 2015


Let's go ahead and review technical analysis for a clip ligation of the large ACoA Aneurysms. These aneurysms can be quite challenging due to their location and the large size that they can often reach. We're going to go ahead and use the case of one of my patients who is 50 years old with an incidental 14 millimeter ACoA aneurysm. You can appreciate on the axial CT angiogram, this aneurysm is pointed to the right side, which means that the left A1 is dominant. A 3D reconstruction angiogram reveals a large size of the aneurysm. It's broad base across a common core putting more of the A1 on the left side. And therefore this aneurysm was approached from the left side. Of note, there is the dome and the most sort of vulnerable portion of the dome located more superiorly and anteriorly. We'll go ahead and expose this aneurysm through a left front temporal craniotomy. And here's the position of the patient in a Mayfield pinning. You can appreciate that the single pin is ipsilateral to the size of the incision, and the two pins are contralateral to provide the surgeon with ample amount of working. So the head of the patient is minimally turned contralaterally in order to allow a good operative working angle toward the midline aneurysm. Standard pterional incision is used after a left frontal temporal craniotomy is completed. We drilled the bone over the super orbital area and the roof of the orbit to get an unobstructed view toward the parasellar areas. I'm going to go ahead and show the details of splitting the fissure, reaching the midline without using a rigid fixed retractors. Here you can see a thin piece of cottonoid is being used to dynamically elevate the frontal lobe using the shock suction apparatus. The anterior limb of internal capsule is being open, generously using a microdissection and sharp techniques. Here is the optic nerve that is being free then released away from the frontal lobe arachnoid membranes. Ultimately the arachnoid membrane of this severed fissure and the supra optic area are connected to each other to complete our arachnoid dissection. And here you can see the ipsilateral optic nerve whose arachnoid are being dissected away. Here's the chiasm. And we're going to go ahead contralaterally and generously open all the arachnoids membranes to be able to mobilize from the lobe without use of aggressive fix retraction. Here's the ipsilateral A1, over the chiasm, as you can see that. And now we're going to open the interhemispheric fissure arachnoid membranes over the aneurysm. Due to the large size of the aneurysm, A small amount of gyrus rectus is being removed subpialy, and the pia is then being sharply cut; being obviously very careful about the artery of Huebner. Here's the ipsilateral, A2. Here's posterior to the aneurysm, and ACoA where you can appreciate the hypothalamic perforators. Here's again, the contralateral A1 over the chiasm. And now the more difficult part of the aneurysm is to go over the dome of the aneurysm, which as we discussed, is the most problematic part and the thinnest part of this aneurysm. We'll go ahead and place bilateral temporary clips. You can again see the hypothalamic perforators more posteriorly, which should be protected. We'll go ahead, under temporary occlusion mobilize this superior dome of the aneurysm Here you can see the dome is being delivered more inferiorally for me to be able to see the contralateral A2 during funnel clip placement. Sharp dissectors are used and sharp scissors are used to the dissect the ipsilateral A2 from the dome of the aneurysm. Now we're mobilizing the dome and ultimately we'll be able to find the contralateral A2 which is right here and dissected off of the dome of the aneurysm. This allows an unobstructed passage of the clip across the neck of the aneurysm, all the way contralaterally, toward the contralateral frontal lobe. Here's placement of the fenestrated clip. We use a tandem clip because this aneurism is very long and one clip most likely will not be able to close the entire neck of the aneurysm. Small amount of "dog ear" across the neck had to be left in order to protect the ACoA due to presence of atherosclerosis along the neck of the aneurysm. As you can see, we use intraoperative fluorescence angiography, which has a higher resolution and more clear image in terms of showing that perforators and patencies of the A1 ipsalaterally, as well as occlusion of the aneurysm completely. You can also see the ipsilateral A2 here. We'll go ahead and also look at ICG angiography and that you can see the image is somewhat degraded and out of focus. These techniques, a short, complete exclusion of the aneurysm and preservation of surrounding vasculature and postoperatively. We were very satisfied with the recovery of the patient without any deficits. As you can see here, the clips have excluded almost the entire aneurysm with the exception of a small residual "dog ear" that had to be left in order to avoid the first clip from sliding over the ACoA. Again, this patient did recover from surgery without any complications. Thank you.

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