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Basilar Apex Blister Aneurysm

December 16, 2015


This video reviews management of a basilar apex blister aneurysm, and also describes techniques for dissection through the interpeduncular cisterns. This is a 64 year-old female who presented with acute onset headache, and suffered from subarachnoid hemorrhage. The initial 3D cerebral arteriogram demonstrated a small blister aneurysm on the left side of the basilar artery bifurcation. This small pseudoaneurysm, or blister aneurysm, grew on the subsequent 3D arteriogram about three days later. Due to the gross growth of the pseudoaneurysm, as well as consistent pattern of subarachnoid hemorrhage with this lesion, the patient underwent a craniotomy for clip ligation, or management of this lesion, based on intraoperative findings. A left frontotemporal craniotomy was performed. You can see the minimal amount of head turn, and the standard incision for reaching the interpeduncular cisterns. The anterior limb of the severed fissure was generously dissected. The carotid artery and the optic nerve are in view. The retro carotid space was used. You can see the posterior communicating artery is being followed through the membrane of Liliequist. The blood within the interpeduncular cisterns are evacuated. The posterior circulation territory is exposed. Here is the trunk of the basilar artery, and one of the perforating vessels. A small part of this artery was skeletonized, full placement of a temporary clip and proximal control, and a dissection was pursued distally, along the basilar trunk, toward the basilar artery bifurcation. You can see a small blister at the level of the bifurcation, but there is no obvious evidence of hemorrhage right at the level of this blister, and, therefore, I was not convinced that this small blister is actually the source of hemorrhage. The aneurysm is most likely pointing slightly posteriorly and superiorly, and therefore, dissection was continued along the basilar apex. You can see the contralateral P1. Here is the ipsilateral P1 and the PCoA joining the P1. Here is the origin of the aneurism on one of the perforating vessels. Further dissection is necessary to understand the morphology of the aneurism and the adjacent important perforators along the basilar apex. The PCoA is more mobilized, so I can expand my operative corridor. It's another one of the circumflex branches off of the P1. There is another perforator at the posterior aspect of the P1. Again, because of the history of hemorrhage, it's quite difficult to work within the fibrinous material, and the scarred clot here is potentially an aneurysm or a perforating vessel that is just lateral to it. I continued to carefully mobilize the fibrinous material, and carefully investigate the region of the basilar apex for the aneurysm. The temporary clip is applied, as I'm getting to a suspicious area that could be the aneurysm itself. I suspected the wall of the aneurysm to be quite thin. I've included the details of dissection here, because of the challenges involved with working through the basilar apex and identifying the important perforating vessels before exposing the aneurysm. Even though this structure was initially suspected to be the aneurysm, it's actually a perforating vessel, and that is why it's so important to continue dissection thoroughly in this area before inadvertently placing the clip across a vial perforator. There is a suspicious structure right medial to that perforator, which has to also be exposed further. I try to continue some dissection posterior to the area of the basilar apex. There's some dilatation of the bifurcation area. However, no obvious aneurysm is present. Now, I continue my dissection posterior to that initial perforator at the level of the bifurcation, and now you can appreciate the true blister aneurysm just medial to it. I'm more convinced that this is actually the aneurysm just medial to the perforator, but, again, the neck of the aneurysm is not clearly identified. So, now I can more appreciate this perforator, and also an aneurysm just pointing posteriorly, related to these perforators. Again, this is most likely the neck of the aneurism at the tip of the arrow. The anatomy is not a hundred percent clear yet because of the presence of these perforators. I use papaverine-soaked pieces of gel foam to relieve the spasm on the perforators that are being manipulated. I explored the option of working through other triangles, including the optical carotid triangle to further explore this aneurysm. However, the space was more limited within these triangles. The superior carotid triangle obviously proved to be more risky because of the presence of the perforators there. So, I persisted to work within the retro carotid triangle, dissect the perforating vessel more, and finding the neck of the aneurysm more clearly. So, here is the aneurism, now more within view. You can see the two perforating vessels just anterior to it. Both perforating vessels were initially suspected to be potentially aneurysmal tissue. Again, emphasizing important dissection to carefully reveal the pathoanatomy. Placement of the clip appears to be quite challenging with the presence of these perforating vessels. I felt that the clip could actually sacrifice at least one of the perforating vessels. Here's one of the thalamo-perforators. Here is another one. The aneurysm is behind these perforating vessels. As you can see, in this area, placement of the clips seemed too risky, and therefore, I proceeded with placement of a permanent clip across the basilar trunk to complete a hunterian ligation to prevent future risk of hemorrhage. The posterior communicating arteries were both robust from the anterior circulation, and I believe that this, applied to the basilar apex region, will be adequate, despite hunterian ligation of the upper basilar trunk. Here is a definitive clip across the perforative-free section of the upper basilar trunk. Post-operative angiogram demonstrated patent posterior communicating artery feeding the upper basilar region without any complicating features, and the CT scan did not show any evidence of ischemia. This patient recovered from surgery without any new deficits, and has made an excellent recovery. Again, this technique demonstrates the use of hunterian ligation in management of basilar artery aneurysms at the level of the bifurcation that are not safely clip ligated. The hunterian ligation will relieve some of the pressure over the aneurysm dome, and significantly decreases the risk of future rehemorrhage. Thank you.

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