Ophthalmic Artery Aneurysm-Extradural Clinoidectomy
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This video is an excellent demonstration of clip ligation of a large ophthalmic artery aneurysm via extradural clinoidectomy. This is a 50 year old female who presented with an incidental 15 millimeter left ophthalmic artery aneurysm, and subsequently underwent microsurgical clip ligation. On CT angiogram and more specifically the coronal image, you see the aneurysm intimately associated at level of its neck and more laterally to the medial aspect of the clinoid process and its associated dura. A sagittal image shows a relatively narrow neck but very much the neck approaches the area of the outer dural rank and the clinoid process. Here you can further appreciate the neck of the aneurysm on an axilla image relative to the entire clinoid process. Due to very proximal location of the aneurysm neck, an extradural clinoidectomy was deemed appropriate to expose the proximal internal carotid artery at the level of the skull base. Let's go ahead and review the basics of skull clamp placement here. I placed a two pin arm on the temple line and the single pin behind the ear over the mastoid bone. This configuration of a skull clamp placement provides ample amount of space in the area of the pterion to conduct surgery. The area of the upper neck is also exposed and prepared in case proximal control is necessary. However, the internal carotid artery is not exposed in this patient, since the aneurysm is not ruptured. Following completion of a standard left front temporal craniotomy the dura over the clinoid is mobilized. A lumbar drain was placed at the beginning of the procedure to decompress the dura sac. The frontal temporal dura fold, or the meningeal orbital band is transected for about five millimeters or so to mobilize the temporal dura away from the lateral wall of the cavernous sinus. This maneuver nicely exposes the clinoid process and allows its drilling without any obstruction. Let's go ahead and remove the lateral aspect of the clinoid and start hauling it out. Before further bony removal over the clinoid is completed, the roof of the orbit is drilled and the optic foramen is exposed and the optic nerve is released. You can see the dura over the lateral wall of the optic nerve. Bone is thinned out over the roof of the optic nerve and ring curettes are used or other forms of curettes are used to carefully remove the thin shelf bone. Now that the optic nerve is decompressed I'm going to hollow out and enucleate the clinoid process, in order to disconnect the clinoid from its last attachment, which is the optic strut. The first attachment was toward this lesser wing of the sphenoid. The second attachment is over the roof of the optic nerve. And the last attachment is to the optic strut, just lateral to the optic nerve. The optic strut essentially comes in between the optic nerve and the clinoid process. Here you can see the drilling over the optic strut to disconnect the process. Now you bluntly dissect the clinoid ligament from the tip of the clinoid posteriorly, and gently deliver the clinoid and extract it. Leading from the cavernous sinus is controlled with thrombus soft gel film. You can see the optic nerve, the area of the clinoid For opthalmic aneurysms, I open the dura only where necessary along the entry aspect of the sylvian fissure and its sphenoidal segment. And just parallel to the carotid artery exposure of the rest of the frontal lobe is unnecessary. The internal sylvian fissure is dissected. The optic nerve is exposed. The frontal lobe is released, bringing the aneurysm neck right in view. The falciform ligament is also dissected over the lateral border of the optic nerve to allow mobilization of the nerve to identify the ophthalmic artery and the entry neck of the aneurysm. Here is the ophthalmic artery leading into the optic foramen. This is the proximal neck of the aneurysm that is well exposed. You can see the turn of the ophthalmic artery just underneath the optic nerve. I continue dissection thoroughly to avoid any need for blunt dissection using the clip lights. Here's further dissection, more posteriorly of the arachnoid membranes to keep the route for the clip place open. This is the disrupt part of the carotid artery. I'm going to rotate my view in a moment parallel to the distal aspect of the carotid artery. The distal aspect of the neck is identified. Here's the neck of the aneurysm that is originating from the lateral wall of the carotid artery, leaning down or kneeling down and then turning superiorly. Therefore this neck should be further dissected. However, the bulk of the aneurysm sac is on my way. Here you can see the change in view of the microscope, the ophthalmic artery, the optic nerve and the distal carotid artery. I'm going to use a tentative clip to gather the aneurysm sac so I can carry on dissection along the neck of the aneurysm to mobilize the neck away from the dura over the clinoid process. Here's sharp dissection along the neck of the aneurysm. A piece of dura may be left on the neck to avoid any inadvertent injury to the neck of the aneurysm. This mobilization of the neck away from the dura will create a pathway for a second clip to collapse the dog ear across the neck of the aneurysm. Dissection continues over the dura of the clinoid process toward the internal carotid artery. This maneuver is relatively risky, however, necessary to make sure the aneurysm is thoroughly collapsed. Here's further dissection anterior along the neck of the aneurysm that was kneeling down and then moving further away. The second fenestrated clip allows complete exclusion of the residual neck all the way to the wall of the ICA. Let's go ahead and do an intraoperative ICG. You can see that the ICS Peyton, the aneurysm is completely excluded. Here's another view. A piece of temporalis muscle is placed within the area of the clinoid to avoid any possibility of CSF leak after surgery. Post-operative day 3 angiogram demonstrates complete exclusion of the aneurysm patency of the ophthalmic artery without any complicating features. One of the important learning points in this video is the use of tentative clips for collapsing the mid-body of the aneurysm to allow more microdissection along the neck of the aneurysm for complete exclusion of the aneurysm from the circulation. Extradural clinoidectomy is quite effective for generous exposure of the proximal ICA and the distal optic nerve entering the orbit. This patient recovered from surgery without any complications. Thank you.
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