Transcript

- Hello ladies and gentlemen and thank you for joining us today for this conference. We have a very special guest, Dr. Harry van Loveren from University of South Florida. He's the Chairman of Neurosurgery there. He's a very dynamic speaker and master surgeon who will be talking to us about techniques in surgery for surgery within the cavernous sinus. Harry, thank you for joining us.

- Aaron, Dr. Cohen, thank you so much for letting me participate in this. I'm a not so techno savvy. I know you've put a lot of work into it and I hope to be a dynamic speaker, even though I'm speaking to a small green light on a computer screen.

- Well, thank you, Harry. Before we'd start to talk. I think this is some of the most important questions for our viewers about surgery within the cavernous sinus is number one, when would you go in there to do the surgery within the cavernous sinus with all the important structures in there? And number two question, which I'm sure you're gonna address later in your talk, is what are the top three pearls technically, for the surgeon we will within their region? So, if I may please ask you maybe to answer those questions briefly, and then we're gonna go ahead and jump in your slides and your great videos.

- Well, it's exceedingly rare for me to go into the cavernous sinus. We are often around the cavernous sinus, particularly with meningioma. And I think if there is a pearl to cavernous sinus surgery, it is stay out of there, unless there is something that can be accomplished because a tumor like pituitary adenoma is suckable for lack of a better term. Generally for meningiomas and other firm tumors, that encase neural structures, it is better to use a policy of containment, where you remove all tumor around the cavernous sinus, but not within. The second pearl that I go around the country and talk about is to please realize there is no real lateral wall to the cavernous sinus. There is only temporal lobe dura. And if you treat it with the disrespect that it deserves, you'll be much more facile. So this is a presentation on surgery of the cavernous sinus, which I've done now for about 20 years experience. And let me just advance this slide. Just to disclose my educational grants with no conflict with this presentation. So just to put this in perspective, interestingly, the international society of the cavernous sinus met in 2006 to review their 20 year evolution in cavernous sinus surgery. And it was my good friend and colleague Sam Al-Mefty who started his lecture with the cover of my article on cavernous sinus meningioma. And said that this article had set back the field of cavernous sinus surgery by 20 years. So that kind of gives you a perspective that there might be some disagreement as to what is feasible and what is appropriate in cavernous sinus surgery. The reason for that disagreement is really this conclusion in our article that Hirsch grade 1 tumors can be removed and accounts for about 20% ability to remove meningiomas from the cavernous sinus so long as they involve only the lateral wall, lateral compartment. But once the tumor encases the carotid artery in a Hirsch grade two or three, it seems to me, and in my experience, it's impossible to remove that cavernous portion of tumor without incurring permanent neurologic deficit. And we were the amongst the early people to describe that problem. And our conclusion at the time, which probably still is legitimate today is that the appropriate surgical strategy should be designed to attempt a radical removal of Hirsch grade one tumors. The Hirsch grade two and three tumors really only the extra cavernous portion should be resected. Intra cavernous portion should be retained, observed, and or radiated. As any good surgeon, we looked for some excuse to explain why we were having trouble removing meningioma from within the cavernous sinus. We didn't want to blame it on lack of skill or poor technique. So Dr. Kawase, Professor Kawase, when doing a sabbatical in our lab was looking for that explanation. Here, you have a wrote in slide that shows the oculomotor nerve coming into the cavernous sinus. Here you have one of Kawase's dissection slides from our laboratory. It shows how the advent tissue that follows the nerve into the cavernous sinus eventually blends with, excuse me, the dura that follows the nerve into the cavernous sinus eventually blends with the perineurium. And so it invests the nerve sheath. The same is true here for the carotid artery. So at some point along the course of this nerve, dura is going to become perineurium. And with some of our other studies with biopsy specimens, that's what allows the meningioma eventually to infiltrate into the nerve. There was a time when we were looking for some secretory factor or tumor marker to explain how a meningioma could be so aggressive, but it's really an ordinary meningioma, totally benign, doing what ordinary meningiomas do, which is following the dura, and eventually it follows it directly into the nerve. The same thing is true here for the artery, it invades the arterial wall. So given a long enough period of time of investment within the cavernous sinus, there is no hope of removing all the tumor without neurologic deficit, removing the nerve, no hope of removing the tumor without removing the carotid artery. And then it becomes a question of whether that is valuable or not. So, total resection is not compatible with remaining neurologically intact for the cavernous portion. And a previous fellow, current colleague of mine, Professor Aziz at Allegheny hospital in Pittsburgh showed in a clinical series that outcome, clinical outcome for patients is certainly much better if you take this more conservative approach. So we talk about leaving tumor in the cavernous sinus, and that is only feasible if you know what happens, long-term to the tumor that you leave in the cavernous sinus. And another acquaintance of mine, Marc Sindou from France really answered that question and showed that residual post-surgical tumor retained within the cavernous sinus has about a 20% growth rate at 20 years corrected by actuarial tables. So 80% of residual tumors in the cavernous sinus will remained stable after a resection of the extra cavernous portion. So, that led us to believe that there is not a major reason to launch into radiosurgical treatment for residual tumor in the cavernous sinus, except with specific indication. Now, for us, those specific indications include atypia, malignancy, evidence of biologic growth that is rapid either retrospectively or evidence of any growth prospectively after resection would be an indication to pursue radiosurgery. It's only interesting, and I won't make too much of it, but if you look at the other table, when you consider that residual meningioma has an 80% growth control rate at 20 years with no treatment or so, 23 year control rate with treatment. You can see like in so many other instances, how radiosurgery gets credit for oftentimes what is the natural history of the disease, or certainly the natural history is a major component in those good results. The extra cavernous portion. I fall back on the way I've been teaching this now in... I recently gave my 102nd Practical Cadever Workshop to my greater than 2000 neurosurgeons on how to mobilize the lateral wall. And this is how we do it. What you see here in this slide, after an FTOZ, and we always use an FTOZ to operate on cavernous sinus meningiomas because we found that in doing that, our frontal and temporal lobe retraction and therefore post-op encephalomalacia is much less. So we think that's a worthwhile maneuver. Strangely, it took me several years of struggle, removing anterior clinoid process, which you see here, because I failed to understand the value of cutting the orbital meningeal ligament. I didn't even understand its existence. So here you, if you get the video running, you see the periorbita, you see the anterior clinoid process, the optic nerve, the superior orbital fissure. So we are on the right side. We have an FTOZ orbitotomy. And now we have a partial exposure of the anterior clinoid process. And this will show the same thing. We are on the right side, temporal lobe dura, frontal lobe dura, orbitotomy. Now we are cutting the orbital meningeal ligament, orbital periosteum ligament. That's the orbital meningeal artery, which is essentially a constant finding. You probably should cauterize that before you cut it. This is for video purposes only according to my resident. And so then you can cauterize that, finish cutting the ligament. And you just have to overcome the fear that you're cutting the oculomotor nerve or opening the superior orbital fissure, that's one layer more deep. And then you can dissect this. Now, if we go back to the slides, you can push the dura then off of the anterior clinoid process. And we'll see which slide we're on here, let me advanced that. Once the exposure is complete, I like to unroof the optic canal. So you have the orbitotomy here, superior orbital fissure dura here, residual anterior clinoid process here. And we're gonna unroof the optic canal. Can you run that video? The reason I unroofed the optic canal at this point, and that's done with a diamond bur only, not a cutting bur under irrigation, which you'll see, is because I'm about to dissect around the clinoid process. And I like to have the optic nerve a bit mobile, so that when I put instruments in, the optic nerve has some opportunity to move away from the instrument. So here, where unroofing the optic canal, all the way into the periorbita and then we can dissect a little bit around the wall of the clinoid process. And you can see where just controlling bleeding with bone wax, and then we can open the dura. So at this point we have the optic nerve unroofed, it's still in its dural sheath, superior orbital fissure. And now we are gonna excavate anterior clinoid process. We're gonna take a drill and we're just gonna shell it out like a canoe. The only reason you shell out the anterior clinoid process, is because you wanna get your drill inside the anterior clinoid process, so that you can get the drill underneath the optic nerve and thin the optic strut so that you can break it. And for that, you want to be inside the clinoid process. And then you can out fracture the clinoid process. So we're gonna learn a little video here. And this will show the excavation of the clinoid process. And what I like to do, you'll see with the drill on, I drill under this optic nerve. I'm trying to thin the optic strut, that I turned the drill off and push on the opposite side to try to break the optic strut. And eventually you see the optic strut breaks. So with the drill on, you drill the optic strut, with the drill off, you push in the opposite direction and fracture it, and then you can mobilize it. And there'll be a little bleeding from veins in the clinoid space. And then I always twist and out fracture the clinoid tip. And you can see that's easily done, and then bleeding is controlled with a little bit of hemostatic material for packing. You go back to the slide. So in taking out these clinoid processes, I've found it's important to know which clinoid process you really have. They're not all made alike, not all clinoid processes are equal. This is what you think you're dealing with most times. And most times that's true. It's a clinoid process that is free, and it is the continuation of the sphenoid wing. And it continues itself as the optic canal roof and the optic strut underneath. The sphenoid wing will have already been removed in the craniotomy. The optic canal roof will have been removed by drilling, and now you're thinning the optic strut. But sometimes you have this clinoid process, which has a ligament that connects it to the long forgotten middle clinoid process. And sometimes that ligament is calcified and becomes an entire optical carotid foramen, and our clinoid carotid foramen. So now you have an anterior clinoid process that is continuous with the middle clinoid process. On at least one occasion, not with me operating, but I know that someone pulled out an anterior clinoid process, just pulled it, and this ring stayed intact and put a hole, through the carotid artery. So I always rotate, grab it with a forceps or alligator forceps and rotate fracture it, just in case there's a middle clinoid process connection. This is even more severe. This is an interosseous bridge continuous with the posterior clinoid process. These two struts that exist in about 13% of patients are the reasons I always rotate fracture the anterior clinoid process. And then if you have trouble and it won't break, I go intradural and finish removing the clinoid under a direct vision of the microscope. So this just shows how the carotid artery can be trapped in this carotico-carotid foramen, and this shows the aligator forceps to twist fracture it. You also wanna be sure you don't have this clinoid process, which is aerated through the sphenoid sinus. So, it's just another part of the sphenoid sinus. When you remove this clinoid and here, you also see an aerated posterior clinoid, when you remove this clinoid and you have a hole for the mother of all leaks that you see here. That leaks immediately after surgery in the recovery room, because it's at the bottom of your funnel. It's easy to recognize during clinoidectomy, you have to palpate the clinoid space with a dissector. And if your dissector plunges through into this sphenoid sinus, you know you need to put a small muscle graft in there. What I do is a little muscle graft, cover it with a little piece of locally, harvested fascia, a little DuraSeal or fibrin glue over it, and nothing bad will happen. But if you ignore it, if you miss it, then this amazing leak will occur, which usually requires you to reopen and do exactly that muscle plugging maneuver. The alternative is an endoscopic repair from below, but usually I reopen and fix it. I say, usually it's only happened to me once. So, mobilizing the lateral wall. I like to use this 'Cavernous Sinus for Dummies', not to be insulting to anyone, but to kind of demystify this lateral wall. As I said before, this is the lateral wall, but it's also the temporal lobe dura. And once you realize it's just temporal lobe dura that continues to envelop the clinoid process, continues onto the diverticulum, continues as the dorsum sellae, then you can treat it like temporal lobe dura, dissect it very easily, and stop worrying about these mythological landmarks of where is the anterior limit, where is the posterior limit. It's just temporal lobe dura, and it's easily dissectable. The way that I mobilize the lateral wall. There's three different methods we use for three different indications. And they are the ways that I learned to do it from three of my cavernous sinus mentors, who I operated with Dr. Akira Hakuba, Takeshi Kawase, and Vinko Dolenc. And they all approach the cavernous sinus differently. And it took me a decade to figure out what the unifying theme is and how three different great neurosurgeons, all experts at the cavernous sinus could have such a different approach and they all worked. So I'm gonna go through that a little bit. Hakuba, Kawase and Dolenc. And when I send a resident or fellow to the OR to mobilize the lateral wall to the cavernous sinus, this is our language of communication. I want you to do a Hakuba, I want you to do a Kawase or I want you to do a Dolenc. So this is a chondrosarcoma that comes up through the floor of the middle faucet and pushes its way up into cavernous sinus. And this is the poster child case for Hakuba approach. Because in a Hakuba approach, you can, after craniotomy, dissect the anterior temporal lobe dura, keep pushing the dura off anteriorly until you reach the orbital fissure. And then you can push the entire dura, so-called lateral wall of the cavernous sinus off of this tumor without ever opening the dura. So, it's a technique that pushes the dura open from front to back or pushes the dura off of cavernous sinus. And you are never intradural, never in the subarachnoids space. This is that dissection, you're just pushing this dura back, from front to back, pushing it open. This is orbital fissure and it's cranial nerves. Just how aggressive that dissection is, because you're only pushing dura, possibly temporal lobe, possibly some meningioma attached to the lateral wall. You're able to very aggressively with a Penfield dissector push the dura off of the cavernous sinus. Okay, can we go back to slides. A bit of cautery to control bleeding because there may be infiltration with meningioma here. So that is the Hakuba method, Hakuba approach, pushing it open from the front. And you see here, the tumor before surgery and after surgery, the tumor material is gone. The dura has never been opened, and you see the line of dura put back here, it swings around, was on the surface of the tumor and came back to the petrous apex. So now you've removed a chondrosarcoma completely, and the patients never had a dural opening. So that's the Hakuba the method. This is the Kawase method. And it's the method we've adopted to, or adapted to all trigeminal schwannomas that start in Meckel's cave and extend either into the back lower portion of cavernous sinus and or extend through an enlarged pores, trigeminal into the posterior faucet. As we said, the Hakuba method pushes the dura open from front to back, the Kawase method pushes it off the cavernous sinus from bottom to top. So in this technique, we come across the dura, dissecting it from the floor of the middle faucet and then push it straight up off of Meckel's cave and the cavernous sinus. But in order to accomplish that, when you're pushing the dura up from below, at some point you have to release the dural sleeves for V2 and V3, the maxillary and mandibular divisions of trigeminal nerve because those nerves take sheaths out through the floor with them. So you have to cut them loose to continue the dissection. We'll go from there. This is Dr. Kim, the great Korean neurosurgeon who did a fellowship in our laboratory and did these wonderful dissections that helped us understand the dura in this region, which is very complex. And one of his diagrams that shows that there's temporal lobe dura that covers Meckel's cave. And that there's a second layer of dura that invests the ganglia, that the nerve took when it left the posterior fossa. So the Meckel's cave is in a cave of a double layer of dura that confuses some people. Then this just demonstrates that two layers, we've got one layer of temporal lobe dura retracted, and then you find a second layer of dural investments and casing the trigeminal, which will now have to be cut. And on the next video, you'll see that cut being made in the second deeper layer of trigeminal dura. And now we're opening the second layer of dura that the trigeminal took with it theoretically from posterior fossa. And then you finally see the tumor, which you can excavate with a CUSA, because the nerve is generally on the deep surface of the tumor. And once the tumor is smaller, you can begin to dissect its capsule. And finally, on the last video, you can see the elevation of the tumor, which stretches only those fibers that give origin to it. And then you can cut only those fibers t hat are a component of the tumor, sparing the rest of the ganglion. And that is a huge difference to the way we used to do it, where we just removed the ganglion with the tumor and incurred an amazing amount of numbness. Now, there's very little numbness with these tumor resections. That's the Kawase approach, and it's used particularly for trigeminal schwannomas. And we go back to the slide show and finally, you can chase the tumor then into the posterior fossa. Okay, so just finishing the Kawase approach on this slide, there will be a component, small, medium, or large that extends into the posterior fossa. And you will have to cut the dura of Meckel's cave right across the superior petrosal sinus, which you can clip or cauterize, and then you can cut the tentorium right into the inside. And that's how you expose from middle fossa to the posterior fossa component. I once actually literally walked a surgeon on the telephone through that incision when he called me from his operating room in another country, to say he was staring at that superior petrosal sinus and didn't quite know how that cut work based on an article he had with him in the operating room. So that was an exciting maneuver for us. That leads us to the final approach. But for neurosurgeons my age, this was the first approach we all learned. And it is the Dolenc approach to cavernous sinus. In the Dolenc approach, you make this classic cut along the superior edge of the ocular motor nerve all the way across cavernous sinus, that would be on right here. And once that is released because the dura continues over the tumor, over the plane and across the diaphragm muscle and other neural structures. When you cut along the third nerve, you're able to take the lateral wall down from above. So that finalizes these approaches. The Hakuba is a front to back dissection. The Kawase is a bottom-up dissection. And finally, the Dolenc is a top-down dissection. And if you dissect the dural wall, the lateral dural wall is right here. And all of this extra cavernous tumor will come out with your dural wall dissection and all of this intracavernous tumor then remains. And the patient's nerve function, ocular motor function remains intact. That's kind of the modern way we look at the Dolenc approach. So we should have a video. This is a rather complicated case, but we're working on this tumor on this side that invests the cavernous sinus on the patient's left. And we're going to remove that tumor along with the lateral wall at the cavernous sinus using a Dolenc methodology, but what you were really gonna see besides the messiness of it all, this is the actual key to the Dolenc approach, which is finding the oculomotor nerve and dissecting front to back along its superior margin. So here you see a thickened oculomotor nerve, and we're going to expose it and release the lateral wall, so that we can use a top-down approach. So here we just show where cutting along the superior aspect of the ocular motor nerve. But when you come here to the front, you'll see that it blends in to the need to do a little bit of Hakuba to push the dura from the front to back. It will blend into a little bit of Kawase, where you need to release the nerve roots sleeves at the bottom. So all these approaches blend. And finally, there's one cut across the back behind the tumor, and once you bring all these together, this entire lateral wall and whatever tumor is attached to it, comes out and tumor in the cavernous sinus around the nerves and artery remain in position. So we'll show the video. And it will briefly show, a little bit of Hakuba being used front to back, just pushing the dural wall from front to back. And this is that cut across the back. So the remaining tumor and dural investment is here, and now you're making the cut around the back of the tumor. So that's a very clean resection after which there is no residual tumor. And of course, you have to do a dural reconstruction, which we simply do these days with two layers of Duragel and some sealant. So that's the end of that tumor removal, again, without neurologic deficits. This is a typical tumor then, and you see a clinoidal-cavernous meningioma, and the removal of that meningioma with the lateral wall. Well, I appreciate that. Well, that's the patient post-op. I think that's a day one or two post-op. And I only show you that video with the patient's permission to show you that in spite of all that aggressive dissection and a swollen eyelid, you have a patient whose cognitive function is intact, and we'll show you in a moment that his ocular motor function is intact as well. I'm just gonna turn and... He's a good guy. And then look way to the right to the right, way to left, way to the right. Way up, way down. Okay. Can you see, well with that eye?

- Yes.

- Awesome.

- Yes I can see.

- Okay. That'll be all. We can go back to the slides. And I actually, I just wanna say something about those day one post-op videos. I think it's important to get permission from the patient to do that. It maps the patient's time to recovery. It's grossly underestimated. So you really have to try to have a patient that's neurologically intact day one, and then kind of show that progression. Many more people are intact and well, of course, by three months or six months after surgery. But that doesn't show some of the extreme problems you have in the early phases. So I showed this other typical case, lateral spheno cavernous meningioma completely resected. And the primary reason I show it is two-fold, one, just to show you these amazing pseudomeningocele we sometimes get after surgery that are usually remarkably and wonderfully self limited. But also to show you that cosmetic results are not perfect. She looks pretty when her hair is down, but she's got this indentation that we so often get in the tarion. And that is in spite of rebuilding the tarion in every case with either titanium mesh or some type of a graft material, whether it be silastic or POREX. We keep all of that in the OR and we do our best to reconstruct, and we still get these somewhat minor indentations, minor, meaning it's not in my head, it's in someone else's head. So we're still trying to perfect that. This is an other case and shows how tumor is removed. And Dr. Sebastien Froelich, one of my previous fellows, who's now the professor in Paris showed extremely well in a series of cases, how you almost always see exactly where the lateral dural wall actually runs through the tumor. And so you can predict with great accuracy that after surgery, in this technique, this portion of tumor will be removed along with that lateral wall. And this portion of tumor will be your residual. So you know exactly what the residual will be. And then if you use Marc Sindou's data, you can observe that until growth is seen, unless there's a biologic predictor. So, surprisingly I've come to the end. And it alludes back to the beginning that I made an early career out of learning how to, and then teaching how to operate on the cavernous sinus and then spent the rest of my career explaining to people that that was not a good idea. And trying to have some influence on this concept, that containment is better for the cavernous sinus tumor than attack. So, Aaron, that's my little bit on how I approach cavernous sinus.

- Well, I really appreciate this very valuable lecture, Harry. I wanna go back if that's okay to with you and focus on, because that remains a big issue. Let's say this patient shows up with progressive sixth nerve palsy, she's young, she has this tumor. Would you offer her surgery or would you let that oncoplastic surgeons fix her eye and just follow the tumor? She has no other symptoms otherwise.

- Well, first of all, the indication for surgery in this young woman was T2 signal, oedema in the temporal lobe and seizure. So there's usually an indication. If she presents with sixth nerve, I would still offer surgery, because I think even if you don't fully remove tumor from cavernous sinus, you do open and decompress a compartment syndrome that can benefit the nerve. And at her young age, I think the onset of a sixth nerve palsy is a surrogate marker for growth. So you have a tumor in a young person that is by surrogate marker is growing and producing neurologic deficit that might be benefited. So I think you have all the indications in the world. Sometimes we see a much smaller tumor and a sixth nerve palsy, in which there is not much extra cavernous portion. And in that situation, if the sixth nerve palsy is intermittent, or I can reverse it with steroids, I would consider radiosurgery alone. Otherwise I would operate to open a compartment syndrome and then probably proceed to radiosurgery.

- Thank you. How about if this patient shows up with no symptoms and absolutely incidental findings for headaches, would you offer redo surgery or just observation?

- Well, first I would have to decide whether I thought her headaches were related or unrelated. I'd have to admit that in most cases, it's migraine or some other diffused form of headache that's not related to the tumor. Tumors in this case, irritate the dura, produce V1 pain that shows up as forehead and retro orbital headache, rather specifically, if they're symptomatic. So if she walks in and she is completely asymptomatic, I would still probably lean more towards surgery than radiosurgery because of tumor size and young patient age. If you give me this, this tumor is probably close to three centimeters. So, let's pretend the tumor is two centimeters and is in a 75 year old, I'd probably offer radiosurgery. But in this case you have a three centimeter tumor in a 24 year old, I'm gonna recommend surgical removal. I will give every patient, even a young patient, some opportunity to wait to show growth. A significant percentage of tumors, regardless of patient age will fail to grow. I wouldn't predict that for this young woman, but I might give her the chance and put her in surveillance.

- If the tumor is one centimeters asymptomatic in a young patient, do you follow with surveillance imaging or do you recommend radiosurgery upfront?

- I usually follow with surveillance imaging. And by surveillance imaging, I mean, I always do one mystical three months scan to prove it's not one of my bizarre cavernous sinus, lymphomas, sarcomas, tuberculomas, something very strange. But once I have the three months scan stable under my belt, I go to yearly scans. I do not go quickly to radiosurgery in the asymptomatic patient, because I think there is a low rate of patient irritation from radiosurgery to the occasional trigeminal neuropathy, dural inflammation, temporal lobe necrosis. I think the risks of radiosurgery are low, but not zero.

- Do you believe that there is a potential for differentiation of these tumors with radiosurgery?

- I don't know. I mean, I'm aware of Bill Caldwell and Sam Al-Mefty's paper with six cases that appear to have had growth of previously dormant meningiomas stimulated by radiosurgery. It is one of the reasons that I delay radiosurgery until I have specific indication or demonstrated growth. On the left-hand side of that equation is... On left we have Caldwell's warning that radiosurgery could stimulate growth. And on the right side of that equation is Sindou's warning that not all meningiomas grow. Given those two warnings, I usually also want a specific indication for radiosurgery. So this is our final submission of a case that demonstrates all the elements we were talking about. A total spheno cavernous meningioma and its complete resection, including the entire lateral wall. And all tumor that is attached to the lateral wall in the lateral compartment and in the middle fossa. This is that first small component, the Hakuba approach, where we push the wall open from the front. We are still extra dural. We are at the orbital fissure area and we're simply pushing the anterior temporal lobe dura opening the cavernous sinus from front to back. Essentially, I might say tearing through the tumor. That is part and parcel of the exposure of the clinoid process. And this is part of the unlocking of the bony elements that confine the dural attachments. This is what we call the lens opening of the dura, right down the sylvian fissure. This is the debulking of the tumor with the CUSA or with sharp instruments or with a Bovie loop or with a laser, whatever tools you wanna bring to the project, dissecting the dome capsule of the tumor from brain. Again, more debulking. It shows the aggressive aggressiveness you can use to debulk the tumor. So long as you know where all the critical anatomy is based. Oculomotor nerve, trochlear nerves. You have to have regional knowledge. So now were opening the optic sheath, sectioning the distal dural ring, so that we can mobilize the anterior attachments of the tumor. This is optic sheath being opened, mobilizing the tumor attachments to vascular structures, getting our first view of the oculomotor nerve. A bit of the Dolenc approach where you section dura by following the oculomotor nerve. So that's that infamous cut that the Dolenc makes to release the dural attachment superiorly. Now we're going anteriorly again, to push the tumor away from front to back, that's a bit of Hakuba. Releasing the tumor at its base inferiorly, which we refer to as a bit of Kawase coming up from below. So we keep going around the tumor releasing and resecting the entire lateral wall while allowing the cranial nerves to be protected by the inner membranous layer. You can see the cranial nerves within the inner membranous layer. Oculomotor nerve here, constantly keeping the intramembranous layer and the cranial nerves in view, mobilizing the lateral wall along with all tumor. And again, once you know where all these nerves are, you can remove all extra cavernous tumor. This is a patient I might add, that had no cranial nerve deficits immediately after surgery and improved vision. So this is probably because it's being done by my fellow and my partner Dr. Hegarty. And here they're just demonstrating the exposure of various cavernous sinus elements. So that is that composite approach that we like to teach, where you mobilize the lateral wall in three different methodologies, anteriorly in what we call Hakuba, inferiorly in what we call Kawase and superiorly in what we call Dolenc, along the oculomotor nerve. And then once the tumor is elevated, you have to make one final cut of dura posterior to the tumor, and then you've lifted the entire lateral wall out with all middle fossa sphenoid tumor. Your residual then is whatever tumor cells are left encasing the cavernous sinus nerves, and that we tend to leave behind in order to protect nerve function. So that was our final case.

- Images please, for this particular case.

- And again, you can see it's early post-op, there is a swelling of soft tissues, but you can see the excellent resection around cavernous sinus. We never say that this is a Simpson one resection. We don't see any visible tumor, but we always anticipate that cells are left within the cavernous sinus. As you know, sometimes a significant, massive tumor is left within cavernous sinus encasing the carotid artery. In this case, we were able to accomplish the resection. Dr. Hegarty was without neurologic deficit to the patient who presented with seizure and optic nerve visual impairment that improved. So for us, that's about the best result that we can achieve.

- Thank you again, this was really a spectacular session and we look forward to having you with us in the near future.

- Thank you for all your great work.

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