True PCoA Aneurysm: Clipping Strategies
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Clip ligation of true posterior communicating artery aneurysms are those aneurysms that primarily originate from the posterior communicating artery can be quite challenging. Let's review the tenets for clip ligation of such aneurysms using the case of a 51 year old female who presented initially with subarachnoid hemorrhage from a posterior cerebral artery aneurysm, and was also found to suffer from an incidental six millimeter left pecam aneurysm. She underwent call embolization of her PCoA aneurysm and later underwent clip ligation of her left pecam aneurysm. On the preoperative CT angiogram, you can see the location of the base of the aneurysm off of the pecam rather than the ICA. This is unusual as most pecam aneurysms are based over the ICA and posterior communicating artery at the division of the pecam. This is a sagittal CT angiogram. Again, demonstrating the base of the aneurysm. The set of the challenges that the surgeon has to conquer in this case is how to clip the aneurism while preserving the lumen of the pecam. A fenestrated clip, a straight one is often quite reasonable and fenestrates the ICA. However, the tip of the blades have to be short enough in order not to compromise the lumen of the pecam. Due to the working angles available and the deployment angles for the clip blades, often a small residual neck is unavoidable in order to preserve the lumen of the pecam. Let's go ahead and review the tenets in this case She underwent a left frontotemporal craniotomy. The Sylvian fissure was dissected anteriorly and CSF was drained from the optical carotid sisterns. I use a piece of rubber dell or a piece of clothe underneath a very thin cottonoid patty to slide around the sub front area and find the optic nerve. In this patient we faced significant amount of brain tension initially. That was very unusual and I suspected a secondary cause and the secondary cause upon inspection in this case was kingking of the endotracheal tube at the level of the lower teeth. And this is an important point to emphasize that if unusual brain tension is encountered in this patient with an unruptured aneurysm, a secondary cause should be sought after and aggressive brain retraction should be avoided. Here you can see the tension that we're facing on exposing the optic nerve. Some CSF is drained upon relief of kinking on the endotracheal tube brain relaxation was immediately achieved Here gain you can see the tension now that the kink is relieved. The brain is more relaxed. You can see the ICA, you can see the base of the aneurism. You can see the pecam. The base of the aneurysm is not adequately exposed. Next I'm going to find the thalamus perforating vessels off of of the posterior wall of the ICA and the pecam Gentle mobilization of the ICA allows me to identify the leash of thalamus perforating vessels. Obviously these vessels have to be dissected carefully from the posterior neck of the aneurysm to allow passage of the clip place without the compromise of these vital perforating vessels. Here you can see the atherosclerosis in the posterior wall of the aneurisym. Proximal control is not available. Here's further dissection of these thalamus perforating vessels. Easily achieved via dynamic retraction and intradural clinoidectomy was performed next. A flap of dura was cut and reflected posteriorly over the ICA. This flap of dura protects the neurovascular structures during drilling of the coronoid process. A very tailored clinoidectomy is accomplished using the intradural method. As I'm able to see exactly where the bony removal is necessary. Ample amount of irrigation is used unroofing of the optic nerve is unnecessary in this case only a very small amount of proximal IC needs to be exposed for proximal control. The bone is shelled out until a very thin layer of bone is left behind over the dura. And the angled incurates are used to mobilize the last thin shell of bond. The optic strap is located a little bit more medially between the IC and the optic nerve. You can see dynamic retraction is used now fixed retractors are avoided here is additional bony removal until the bone is thinned out Homeostasis is achieved via through a mist of gelfoam and gentle tamper knot. Ample amount of irrigation is used. Here's the use of curates to remove thin shells of bone. The flap of dura is now resected so that it does not interfere with visualization. You can see the internal carotid artery is more thoroughly exposed, just proximal to the neck of the aneurysm and origin of the pecam. Here's the origin of the pecam and the availability of space for placement of a temporary clip if necessary Arachnoid bands are obviously wildly dissected. The thalamus perforating vessels are once more inspected before the straight fenestrated clip is placed around the ICA with its distal tips, just short of the lumen of the pecam to occlude the neck of aneurysm. Obviously the neck of the aneurysm should be defined as much as possible. You can see some atherosclerosis at the neck of the aneurysm, The neck is explored as much as safely possible. Here's a final view of the leash of thalamus perforating vessels. Here's the posterior wall of the neck of the aneurysm next the straight fenestrated clip is deployed. As you can see here, just show the pecam. I moved to the little bit more proximal. I cannot advance it more. Otherwise I'll place the lumen of the pecam at risk. Here's an ICG and flouricine angiography demonstrating complete exclusion of the aneurysm. As you can see here with patency of the pecam The perforators are also inspected and you can see their patency just behind the clip. Here's another view of these perforating vessels that are left untouched. I'm satisfied with the location of the final clip ultrasound evaluation using the micro probe confirms the florescence findings post operative 3D reconstruction of the angiogram demonstrates reasonable exclusion of the aneurysm with small amount of residual neck. That is unfortunately unavoidable because of their working angles for placement of the fenestrated clip while preserving the lumen of the posterior communicating artery. Thank you.
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