January 13, 2016
This video is a detailed illustration of extradural clinoidectomy for resection of a metastatic clinoidal lesion. This is a 50-year old female with two metastatic adenocarcinoma lesions to the area of the clinoid. She unfortunately suffered from loss of vision in the right eye and presented with progressive visual decline in the left eye. The preoperative MRI evaluation reveals two paraclinoidal lesions. The larger one, which is on the right side, which already led to loss of vision in the right eye. And also a smaller lesion in the left clinoidal area that was causing progressive visual decline in the left eye. This is our surgical target as division was still somewhat functional but was deteriorating. You can see that the metastatic tumor was triangulating the optic nerve at the area of the optic foramen. And this patient had a known primary source of adenocarcinoma in the lung. A frontotemporal craniotomy was completed. A lumbar drain was placed at the beginning of the procedure to decompress the dural sac and allow extradural mobilization of the dura away from the roof of the orbit and the anterior skull base. You can see the sphenoid wing and the pterion has been drilled away. The dura is being dissected away from the lesser sphenoid wing and the area of the clinoid. The superior orbital fissure is located here. The clinoid is more in view. The lateral aspect of the clinoid is being drilled away with an air drill. The lumbar drain provided with ample amount of dural decompression. I'm going to go over through the individual steps for exposing the clinoid further. Here, we reach the lateral aspect of the clinoid. The superior orbital fissure is more thoroughly skeletonized. This is a relatively robust clinoid to expose the posterior aspect of the clinoid. One can cut the lateral aspect of the fronto temporal dura fold or the orbitomeningeal band. Only about five-millimeter or so of this band can be cut to allow reflection and mobilization or peeling off of the anterior temporal dura away from the lateral wall of the cavernous sinus. A dissector will be used next to reflect and peel off the temporal dura away from the lateral wall of the cavernous sinus. You can see the lateral wall of the cavernous sinus is just about in view. Further reflection of this outer dural membrane will reveal the lateral wall of the cavernous sinus further. Here is additional cuts through the band, and here's the lateral wall of the cavernous sinus that is more apparent as you can see here. Now, the dura is much more in view and is highly skeletonized. We don't often need that much exposure of the clinoid to allow its complete excision. So the clinoid's being hollowed out, however, before it is further cored out, I'll go ahead and decompress the optic nerve. So the nerve is decompressed and is not under any tension or risk of compression during aggressive manipulations of the clinoid process. So here's the dura over the medial aspect of the clinoid as well as the lateral aspect of the posterior, anterior skull base. Where my suction is pointing is most likely the location for the optic nerve. I'm gonna go ahead and unroof the nerve. Here's the entry of the nerve extradural into the optic foramen. You can see right here. This clearly demonstrates the location of the nerve and guides the drill for skeletonizing an area of about 270 degrees. I typically do not use fixer tractors. The suction is quite adequate with the vector of dynamic retraction to provide space where the drill is working. So the bone is shelled out and the roof is thinned out in layers. Ample amount of irrigation is used to avoid thermal injury to the nerve. This is a very relatively thick bone in this area and the nerve most likely gonna be found just along its lateral wall. The bone again is removed in thin layers to prevent any obvious injury to the nerve. A little bit of soft tissues appear at right about here. And here is again, the lateral wall of the nerve and the bone is further removed using small curettes. After, the bone is very much thinned out. Now, the nerve is more accurately localized. I can be more aggressive in terms of bone removal without injuring the nerve. Here, you can see the dura over the nerve as it joins the intracranial space and is continuous with a far dura. These curettes can be quite effective in removing the bone without it placing the nerve at the risk of thermal injury. Now the nerve and its encasing dura is more in view. You can again see the entry point into the optic foramen. Further bone removal allows aggressive decompression and release of the nerve. I avoid drilling directly on the nerve or rather I thin the bone down just to the level of the dura and then use fine curettes to remove the last piece of thin bone. I'm almost there in terms of decompression of the nerve. Now I divert my attention to the area of the clinoid, where the clinoid is very much hollowed out. The connections of the clinoid that are quite important are three. One to the lesser sphenoid wing, one to the funnel bone or the anterior skull base along the roof of the orbit and the roof of the optic nerve. And the third connection is through the optic strut, just lateral to the dura of the optic nerve. All three connections should be dismantled and thinning and hollowing out the bone within the core of the clinoid would disconnect the clinoid from the optic strut. Generous and thorough hollowing out of the clinoid is necessary before its removal. If the clinoid is not moveable, it is most likely not hollowed out accurately or thoroughly. Or the petroclinoid ligaments are not released through blunt dissection. I continue to hollow out this relatively large clinoid process. All the walls are equally thinned out. An angled thread or dissector may be used next to dissect the walls of the clinoid from the ligaments. There's fair amount of motion around the dura of the optic nerve. And this is the reason for thorough decompression on the nerve before such manipulation is undertaken. The clinoid here is relatively untethered. It's just about coming out momentarily. It is like extracting a tooth. Forceful pulling on the clinoid process is avoided. After the clinoid is removed. There is often some venous bleeding from the cavernous sinus, which can be easily controlled with gentle tamponade and packing off from a soaked Gelfoam. Here's me throwing some Gelfoam on a piece of carotenoid, which will gently tamponade the Gelfoam against the lateral wall of the cavernous sinus. Hemostasis is readily achieved. The anatomy's more in view. You can see the optic nerve. There, the clinoid. The dura is open and curving in a standard fashion. The tumor is in view. The optic nerve is compressed superiorly and mobilized superiorly by the tumor mass. The falciform ligament is cut using a colon blade knife. Further incision within the falciform ligament over the nerve will expose the fragment of the tumor, which was herniating through the optic foramen. Now the tumor is debulked and is moved away from the optic nerve. Aggressive retraction on the nerve is avoided, as such retraction is not tolerated by the nerve. This bleeding is from the tumor. However, one has to be very careful during dissection right underneath the nerve as the ophthalmic artery, since to consistently be located in the area. In this patient, the carotid artery was mobilized in posteriorly by the tumor. Bipolar coagulation may be used at low temperatures to coagulate bleeding at very focal points without injuring the optic nerve. And it's perforating branches that typically originates and travel underneath the nerve. Immobilizing the tumor on both sides of the nerve, releasing the nerve from the foramen would allow these maneuvers to deliver the tumor within the entry part of the foramen. And within the blind spot of the surgeon. The nerve looks very decompressed. Now, after this last piece is removed, I think our job is complete in terms of generously decompressing the nerve and coagulating the dura affected by the tumor. Postoperative CT scan demonstrates a complete clinoidectomy as compared to the right side. One year postoperative MRI demonstrates complete or near complete resection of the tumor on the left side. Radiation therapy led to regression of the tumor on the contralateral side. Unfortunately, this patient did not regain vision on the right side from radiation therapy. However, surgical intervention led to recovery of neurological function in the left eye. And this improvement in vision has been stable for one year after surgery. Thank you.
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