Proximal ICA Aneurysm: Intradural Clinoidectomy
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This video describes techniques for clip ligation of a proximal paraclinoid ICA in more specifically posterior communicating artery aneurysm and also demonstrates the technique of intradural clinoidectomy. This is a 28 year-old female with an incidental 6 millimeter left proximal paraclinoid internal carotid artery aneurysm. As you can see on preoperative imaging, this is a posterior communicating artery aneurysm very much related to the PCoA on the sagittal CTA. You can see that the neck of the aneurysm is intimately associated with the anterior clinoid process. The left frontotemporal craniotomy in standard fashion was completed. The dura was opened very flat to the floor of the orbit. An orbitozygomatic craniotomy is not necessary. The anterior aspect of the Sylvian fissure was generously exposed. The optic nerve is released from underneath the frontal lobe and the internal carotid artery is exposed. You can see the aneurysm is barely visible along its distal neck. Generous arachnoidal dissection in the subfrontal area, obvious the need for use of fixed retractor blades. Again, you can see the distal dome of the aneurysm located there. An intradural clinoidectomy was completed. Dura over the process was coagulated and a round knife was used to open the dura over the area in a cruciate fashion. The flaps of the dura were peeled off and reflected and subsequently coagulated. An air drill was used to hollow out the clinoid process and this articulate the process from its three attachments. Number one, the lesser sphenoid wing; number two is the poster aspect of the anterior skull base over the roof of the orbit; and number three from the optic strut. This process in this patient is relatively small and should be easily removable. I continued to shell out the bone within the clinoid process. You can see that the dura over the lateral aspect of the optic nerve is exposed. I continued to hollow out the clinoid process more posteriorly. Bleeding is controlled using pieces of thrombin-soaked Gelfoam. Here is the last piece of the clinoid that was extracted like a tooth. Further bleeding from the bed of the bone removal can be controlled with thrombin-soaked Gelfoam and gentle tamponade. Here is the optic nerve and the carotid artery. There's still some bone overlying the lateral aspect of the optic nerve that is being removed. More specifically, it is first shelled out, thinned out, and a curette, an angled one, is used to remove the bone over the nerve. Direct drilling over the nerve is avoided to prevent thermal injury to the structure. Now that the dura over the internal carotid artery is further exposed, I incised the dura parallel to the access of the internal carotid artery and slightly tore the neck of the aneurysm until the outer ring of the dura is exposed. This is the last thin shell of bone over the lateral aspect of the optic nerve. A fine Kerrison Ronegeur is used to remove the least last piece. And I continued to excise the dura toward the outer dural ring. Sharp dissection mobilizes to dura over the lateral aspect of the ICA. Here's the exact location for the outer dural ring. I leave a piece of dura over the dome of the aneurysm to avoid premature rupture. The arachnoid membranes are now sharply dissected Now the dome is more in view. However, the very proximal neck of aneurysm is still not visible. This aneurysm is relatively fusiform and involves the posterior wall of the internal carotid artery. I spent ample amount of time dissecting around the entire neck of the aneurysm. A circumferential dissection is mandatory to avoid the use of the clip lights to carry on further dissection during their deployment. Now the dome is more visible. The area of the outer dural ring is identified. Next I'll be using a round knife to dissect over the dural ring and expose the more proximal aspect of the aneurysm neck. Now I'm beyond the outer dural ring. Any bleeding from the cavernous sinus is controlled using thrombin-soaked Gelfoam packing. The arachnoid membranes around the internal carotid artery are thoroughly dissected so the clip lights can be placed without any resistance. An angled Fenestrated clip should be ideal to fenestrate the internal carotid artery and close in the curve the aneurysm parallel to the posterior wall of the parent vessel. This clip configuration avoids any dog ear and is physiologically most effective in avoiding any residual aneurysm while providing curable exclusion of the aneurysm. Here is the optic nerve. It's mobilized away from the medial neck of the aneurysm. A proximal neck of aneurysm is now visible. The internal carotid artery is identified more distally. Now we are just about ready to apply the clip. I did not feel proximal control was mandatory in this patient. A Fenestrated T-clip was more appropriate. You can see that this clip closes the neck of the aneurysm parallel to the internal carotid artery. The posterior communicating artery is most likely stenosed with this clip configuration. However, the very robust P1 vessel in this patient obviated the need for a PCoA. If the patient harbored a fetal PCoA, obviously they posterior communicating artery has to be strictly protected during clip deployment. The postoperative angiogram demonstrates complete exclusion of the aneurysm without any complicating features. They internal carotid artery is quite patent. This patient recovered from surgery without any untoward effect. Thank you.
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