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Endoscopic Endonasal Skull Base Surgery (Coronal Plane)

Daniel Prevedello

November 29, 2021


- Colleagues and friends, thank you for joining us for another session of the Wichita Operating Room. Our returning guest today is Dr. Danny Prevedello. He is professor and director of skull base surgery at the Ohio State University Neuro Surgery Program. Danny, thank you for being with us, thank you for your immense contributions to neurosurgery and specifically endoscopic skull base surgery. I know today you're gonna talk about a very exciting topic, the limitation of the endoscopic approach, the trans-nasal approach obviously, across the coronal plane. I'm very much looking forward to learning from you, I'm sure all our viewers are at the same time. So let's get it started, and very much again thank you.

- Thanks so much Aaron, It's it's an honor and a privilege to be here with you again, and as you mentioned, what we are gonna be talking today, it's a continuation of the talk we presented several weeks ago, where now we are gonna expand the limitations and understanding the role of endoscopic endonasal skull base surgery to the coronal plane. So we divide the coronal plane and anterior fossa, middle fossa and posterior fossa the same way we will think in terms of the rationale for open approaches. So the way I'm gonna describe here, we're gonna start on the anterior skull base and go more to middle fossa, and then to the posterior coronal fossa as we present the talk. So what is in the coronal plane or perhaps sagittal in relation to the interior skull base is basically the organ. So it's one of the applications of endonasal surgery. It's the approach to lesions inside the organ. So in this location, it's very important to understand the position of the lesion in relation to the optic nerve. So when are we gonna indicate an endonasal approach for an orbital tumor? In general is if the tumor is medial and inferior to the optic nerve. Any lesion located laterally, then a lateral approach will be more indicated. So when we come into nasal in terms of anatomy, we go through the lamina papyracea first, we remove lamina papyracea. As you can see in this area here, and then once we remove lamina papyracea we have exposure of the periorbit, and with that in mind, that becomes the corridor that we can then go into the orbit. There are two corridors we can use, one between the superior oblique muscle and medial rectus muscle, but that's very narrow and superior, and it's easy to affect the anterior ethmoidal artery as one can see right there, and it's a very narrow triangle. Most of the time when we go to the corner region of the orbit, we use this triangle between the medial rectus and the inferior rectus. And it's important to understand that this is where the artery here that gives blood supply to the optic nerve is located medially, and we have to be very careful not to cause ischemia of the optic nerve. So it's very important to have that in mind. And once we enter that space, if the lesion is located medial to the optic nerve, then we can take these lesions out of the orbit, or as another example here, another tumor that we removed coming with an endonasal route to the tube. Once again, the important indication is, has to be medial to the optic nerve or and inferior to the optic nerve. Any other location is, it's an issue. In terms of the middle fossa, it's very important for every lesion we identified in the middle fossa that you have options. So you have to analyze one by one. We can use antero-medial approach or the antero door of Meckel's cave that we referred, but basically the cami-endonasal is one option, but we have to have in mind the possibility of ventral lateral approaches, lateral approaches, middle fossa, and even retro-sigmoid approaches to lesions in the middle fossa. So we're gonna try to show some of a rationale for these lesions, and it's very important to make the rational base on the pathology. So that's why I divided here in pathologies because what we would apply for one disease may not be appropriate for a different disease. So for pituitary adenomas, we have to remember that the disease starts in the pituitary gland, and from the pituitary gland, goes into the cavernous sinus, and starts from medial to lateral, and the first compartment that the adenoma will enter is the medial compartment of the cavernous sinus. So, with this in mind, we have an opportunity to come endonasal, and answer the sphenoid sinus, and then the cavernous sinus, particularly in this medial compartment to address diseases of the pituitary gland that advance into the middle fossa and cavernous sinus. So here's an anatomical example where one can see here the superior hypophyseal artery that gives the blood supply to the gland. There's the hypophyseal artery goes to the dura of the pituitary region and to the posterior gland as well. But if you look at here in this compartment, there is no cranial nerve. The cranial nerves are located lateral to the carotid artery. One here can see the sixth nerve, and the sympathetic fibers of the carotid are going to the direction of the orbit. So coming endonasal, we have access to this medial compartment of the cavernous sinus when we do surgery in the paramedial space. So this is an example of a patient that had a residual that was, patient was operated several years before I met the patient, and the residual was in the cavernous sinus 'cause it progressed from the cavernous sinus to the cellar and supercellar, and patient was losing vision. So then here we have this video demonstration where we see that we first of all, remove all the bone in front of the cellar and in front of the cavernous sinus. And then we open the dura, and first we removed the tumor that was located in the cellar, that was actually narrow. Then we identify the wall of the cavernous sinus as you can see here, the medial wall, and then we opened the, we do all of the cavernous sinus to have access to the medial cavernous sinus compartment as we described earlier. Then here, as you can see, with the soft tumors, we can really follow the tumor inside the cavernous sinus using angle scopes and angle suction. I usually bend the suction to reach more laterally behind the carotid first, and we go to the posterior compartment of the cavernous sinus behind the carotid. Some of the lesions here are posteriorly, and as you can see here using the angle suction, we were able to reach and see the carotid artery more anteriorly here, as you can see this white, that's the carotid artery, and then we are able to go and follow the tumor even lateral to the carotid artery with no CSF leakage. It's very important to remember that we do all of these approaches monitoring the cranial nerves. We monitor cranial nerves six, three, four in the cavernous sinus and next, and then, to perform the resection, as you can see here, this is a postoperative imaging for that specific patient. Sometimes you see tumors involving the entire clivus as you can see here, involving the entire clivus and bilateral cavernous sinus as you can see in this, around the carotid arteries. So by following the tumor, we can actually remove the tumor in the clivus and follow into the cavernous sinus and get great resection as you can see in this MRI. This is another example of a tumor with a supercellar extension and a extension around the cavernous sinus. As you can see is a 360 degree involvement of the carotid artery, and these are examples of cases that in order to have a very good exposure of the cavernous sinus on the left side, in this case, we actually do a trans terrigoids approach to have a full exposure of the cavernous sinus on the left side. So we performed for this patient, a left side trans terrigoids approach, to have a full exposure of the anterior wall of the cavernous sinus as you can see in this corner here on the left side. Then we opened the cellar and we evacuated the tumor of the cellar to decompress the supercellar space, but not completely in order to avoid a early descent of the diaphragm. So I kept some of the tumor there and that's a technique that I usually use, and then I opened the anterior wall with the cavernous sinus extending into direction of the superior orbital fissure. And then this tumor was soft so allows us to continue with two suction technique and evacuate the tumor located inside the cavernous sinus around the carotid artery, and that's very important to have a full exposure and that trans terrigoids approach really helps in order to expose the carotid as you can see there. So for tumors, there are functional, we are very aggressive opening the cavernous sinus and trying to evacuate as much as possible of the tumor, but of course, those are the difficult ones to obtain cure or remission of the functional aspect of the disease. Once we are satisfied with the cavernous sinus then we moved here to the supercellar area. Now I'm dealing with the diaphragma as you can see here, they came down, opening the dura more superiorly, and to make sure that we obtain a complete resection of the tumor in the gutters, in this corners, and also in the anterior aspect of the cellar. I used the Q-tip as you can see, which I think is a very nice and gentle way to manipulate the diaphragma, and also to go around it without cutting or causing a CSF leakage. In this case, then I went back to the cavernous sinus and I found a couple of other pockets, opened some ligaments, and we were able to then get a very good resection for the patient even behind the carotid artery posterior in the cavernous sinus. No leakage of fluid with the performed some hemostasis with the hemostatic material, and then we performed a reconstruction, I always use a collagen matrix to give reinforcement in this case, in front of the carotid. So it put one segment of collagen matrix in front of the carotid and the cavernous sinus and another one in front of the diaphragma here to protect it and reinforce the thin diaphragma that came down to avoid a leakage afterwards. Next. So here's the post-op. As you can see with putting a very complete resection, this patient we've been following, she's doing very well with no recurrence of the disease. Next. So here we can see that the options that we have coming endonasal or laterally, or even from posterior fossa, the best example is really schwannomas trigeminal schwannomas. Trigeminal schwannomas, in my opinion is the best pathology for us to define when to do one type of approach versus another. So when the disease protrudes into this sphenoid sinus, as you can see in this example, the option of coming endonasal it becomes viable and that's usually what we prefer. If the disease on the other hand is located behind the carotid as you can see here, appealing of the middle fossa may make more sense because if you come endonasal, you're gonna have the carotid artery in front of you. And if the disease is completely posteriorly and protruding to the posterior fossa, then a retrosigmoid approach may make more sense, and you can do a supernatal approach with a drill out as well, and reach the rest of the diseases inside Meckel's cave by approaching from behind. So those are the options for trigeminal schwannomas, and we also look at the position of the carotid arteries in terms of the angle that they create, and when they protrude internally, you actually have a larger Meckel's cave and opportunity to go endonasal into that space. When they are more laterally located, then you have a narrow space and we published that. So here are some examples. You can see this trigeminal schwannoma that protrudes into the sphenoid sinus. We have a large area of contact with this sphenoid sinus. So coming endonasal in this case, it was our option, and you can see here, the post-op after several years follow up and no recurrence by approaching that with an endonasal approach, and you can see here four years later, no recurrence as well. This is an example of a tumor I did early in my career. Probably if I did this again, I will use appealing of the middle fossa, as you can see is located almost behind a carotid but we did have an advantage here because of the large pneumatization of the sphenoid sinus. We had actually a good contact of the tumor with the sphenoid sinus, and for that reason, we actually did endonasal. Here's the video. As you can see, we did a trans terrigoids, we actually transposed the vagal nerve, and you can see this is the V2 nerve that is coming in this direction, and we were able to go lateral to the carotid. The carotid is in this location right here with skeleton eyes, and in between carotid and V2, we were able to enter this corner, where is the Meckel's cave. We were able to dissect from medial to lateral, and we were able to mobilize that component of the tumor that was posterior going to the posterior fossa, and were able actually to obtain a complete resection of this tumor coming with an endonasal routes. As you can see here, this is the carotid that is a skeleton eyes, and that allows us to mobilize gently as well, and here's the resection of these trigeminal schwannoma for this patient. Here, we were able to preserve V2, and V1 is going up there, and V3 is now exposed down here. And this is the last piece of the resection, and we'll take a look here now, see how it looks like once the tumor is removed, and an overview of the approach. This is the final cuts, resection of the trigeminal schwannomas, this is a Meckel's cave, you can see the CSF coming from posterior fossa, and this is V3 here internally inside Meckel's cave that we were able to see. Next. Of course, this we have performed reconstruction with a nasal septal flap, that you can see there, and the Meckel's cave completely free of tumor, and this patient did very well. So this is another example of video here. You can see it's a larger tumor, but the same principle if we follow, once we look at the axial here, you will see, I like to look at the axial and we have all this contact of the tumor with the sphenoid sinus. Next. So for these cases, we came endonasal, skeletonized the carotid as you can see right there, and we opened Meckel's cave, and with the stimulator dissector here, we were able to dissect the tumor away from the sixth nerve, The sixth nerve was pushed here, going through the spear of the fisher, this is on the right side, and we were able to dissect that from medial to lateral, same type of maneuvers here, and you can see some of the neuro structures that were pushed up by the tumor. By dissecting medial and lateral, we were able to get this tumor all the way to the posterior fossa and very important to go around the tumor. You cannot just debulk, otherwise you end up with a residual there. Next. And here's the final view. See this is after the resection, you see how the completely resection of Meckel's cave and with the nasal septal flap covering the structures here. This patient did very well, but he did have, it's one of my only cases of my career, I think I have two that had meningitis without a CSF leakage. He had a lot of headache post-op, next, and he ended up with that, with meningitis. We had to treat him and he did very well, and he had his, no recurrence over for several years now. This is another example here of a trigeminal schwannomas that has a very large contact with the sphenoid sinus, so we decided to come here as well endonasally. So this is another example. You can see how, has that touching surface and this is the post-op after resection, and the patient did very well. Most of the time, over the, over years, I noticed that the trigeminal nerves actually pushed laterally, so when we come endonasal, is at the end of the resection, the trigeminal nerve bounces back. So for the most time, most of the time we can actually preserve it very well. So this is a cage that I learned in my career. I decided to try to go endonasal, I thought that I would have a contact here with the endonasal via a pathway, but you can see the most of the tumors really positioned behind the carotid and is not a well pneumatized as sphenoid like the other case I showed. So this one, I did endonasal and I suffered, I struggled a lot. You can see that I was able to make a little hole here, but I was not able to go around this tumor. I left all of this component posteriorly. This patient improved, he had a sixth cranial nerve palsy in the presentation, and some numbness of the face, and the sixth nerve got better but it was, I think about a year later that he started having symptoms again. Okay, so for this patient, we performed a middle fossa approach. You can see here, we exposed V2, and down here V3, and performed an extra dural approach to the Meckel's cave. Next. We then exposed the tumor, and were able to resect the tumor located in Meckel's cave here, as you can see, using the ultrasonic aspirator. So this patient did very well, next, and we were able then with this approach to resect the tumor completely, and it's very interesting 'cause with the STU approaches, after this surgery, he actually recovered sensation that was one of the problems that he had. He recovered sensation, he had deficits in all three segments. V1, V2 and V3, all got better for him, almost normal, and he's sixth nerve normalized again. Next, to here. Good. Here you can see the post-op, he did very well. So in retrospect for that patient, if I had used just an open approach probably better. Here's a patient that if you look at these connection here, look like you could come endonasal, but the patient had this carotid, as you can see here, blocking most of the tumor they had at this medial projection. So this case I thought about and decided to come laterally here. I felt that I would probably be struggling to turn the corner like this, if I came endonasal. So in this case, I did a right away appealing of the middle fossa for resection of this tumor here, as you can see, and also an extinction to the more lateral. So there was no hesitation, and this is the post-op. It went very well, we used this approach this way, extra dural. In this case, the tumor was actually rolled into dura so I had to open the dura to get the rest of the tumor out as well. So when the tumor now, trigeminal schwannoma, that goes to the posterior fossa, all this segment here, then is different than most of the tumors in the posterior fossa. So for these, we would use a retrosigmoid approach, which makes more sense, and then we can drill the supermeatle area, and enter the Meckel's cave from behind, and that's what we did for this patient. This patient was actually pregnant and I did, so we ended up leaving a little disease in the corner there, and I watched, this has been more than I would save seven years, and there's no recurrence, very interesting case. So trigeminal schwannomas, as another aspect that I didn't mention earlier, is the fact that they can also follow V3 into the masticator space. And if you see that, actually the endonasal approach can be helpful to reach that area of the tumor extending inferiorly. This patient actually was a young gentleman with seizures. So he presented with seizures, a lot of edema in the brain, and I decided to come with an endonasal approach, and we were able to core a lot of the tumor laterally there, and also inside Meckel's, it was quite large, but it decompressed well, the edema got better, his seizures got better. Never needed any radiation, we just following this for more than five years as well with no recurrence. So now I'm gonna change one more time for meningiomas. What about meningiomas of the cavernous sinus and middle fossa? When do we do anything endonasal for them. And the role for meningiomas, in my mind, is more for decompression, and you have the options of observation if you see a patient with a cavernous sinus meningiomas, resected or some, of course you have the option of radical resection as well. And Dr. Faul Busch published in 2009, so it's been 11 years where he presented 21 patients that he did transsphenoidal approach, Most of them was actually with a microscope, but he was able to get endonasal decompression of the cavernous sinus with an amazing improvement of deficits. See, 32 of 34 cranial nerves improved, and there was something that called my attention more than 10 years ago, and I started doing decompressing, decompression for the cavernous sinus for meningiomas. So what we do is basically remove all the bone in front of the carotid and cavernous sinus, and you can see here, the way we do basically drill until it's very thin. We drill the cellar, drill the entire cavernous sinus, and expose the carotid artery as well as you can see here. Remove the bone, and that gives a full decompression of the cavernous sinus. Patients with turning nerves three, four or six, it's one of the indications. We do open the cellar and the area around the two to biopsy. So for that reason, we also work in between the two layers of dura as you can see here, and we can get specimen that can help us to orient the radiation treatment. We will be able to separate grade ones and grade twos of meningiomas in this location, and that's an advantage of having pathology instead of just empirically taking care of this patients. So, I also over the years, my idea was to see if it's soft, what if the meningiomas is soft, and I can use suction in Meckel's cave and, but my experience is they're always like a plaster and I'm not able to take them out. So this is a full decompression with the biopsy, and in this case, we hover with a nasal septal flap. Next. We use those two areas to biopsy 'cause they're safer. So around V2 and around the cellar here where the meningoma projects. Next. And you can see here, this is an example of a tumor in a patient that actually had a breast cancer history. So then would you just give radiation? Of course it looks like a meningoma, but we know based on the literature, the descriptions of annular doses, some other mimics that look like meningoma but could be a mast as well, and the patient had a kind of nerve three and six partial palsy there. So we did this approach as we are presented and here you can see how it looks like the bone removed in the medial aspect of the cavernous sinus, and this is an example of a video that we entered the cavernous sinus. As you see V2 here, and you see V1 superiorly there, and this is the meningoma inside the cavernous sinus, but very adherent. I tried a few cases in my career to try to remove, of course you can biopsy to get a nice specimen, but is, next, but is a very impossible to resect with this route. So here you can see how it looks like, you see a little hole, you see pre-op here superiorly and then post-op inferiorly where we make a hole into the tumor. That help to decompress, and this patient improve actually, recovery the sixth nerve was already not there, which I didn't expect. The third nerve got a little better over time and then it normalized for her, and then after these, our recommendation is to proceed with radiation. So as you can see in this algorithm here, if the patient has no symptoms, then we will attend to observe. If the patient has symptoms, then we will do this endonasal decompression with the biopsy, and we also analyze if there's a significant lateral component, because if there is one, we combine with the open craniotomy to resect all the tumor lateral to the cavernous sinus. And then after that, we basically just leave the residual inside the cavernous sinus for radiation. Only if the recurs, after all these, then we are not gonna be able to try to save function anymore, and that's when a situation that we go for a radical surgical resection when function is not the priority anymore, and the tumor is recurrent. The couple patients that I had problems in terms of recurrence of the coronal nerve palsy that improved and then got worse again, were patients early in my career that we decided to just observe because it was a meningoma grade one, and we just observed and the tumor grew back and I actually had to do more surgery to decompress and proceed with radiation. So our recommendation is to go ahead directly to radiation based on the pathology. And you can see most of the patients were able to define that were grade one for this patient, and then we proceeded with radiation knowing the pathology, which is great. And most of our patients improve their function as well with this approach. All the way from cranial nerve two, three, four, five, in some cases, and six. The two cases that had, I had one lady had eight years of sixth nerve palsy, she didn't get better, but patients that recently got deterioration on the movement of the eye, those are the ones with a high chance for improvement using this technique. Now moving away from meningoma, we're gonna talk a little bit about this other pathology that I think is very interesting. It's more common into the ENT world, and some neurosurgeons are not familiar, which is the cholesterol, petrous apex cholesterol grinaluma. As you can see they can be very large, they can cause compression of the brainstem, and the typical differentiation here in terms of understanding the differential diagnosis, if you see this dark area here, this is the bone that got moved out. So I show these to several neurosurgeons over the years, and several people told me to take these out, you should do a retrosig, but if you think about it, you have to open the dura once and you have to do the open the dura twice to get there. If you come endonasal, it's actually a simple surgery where you marsupialize, and you drain the contents of this cholesterol granuloma into the sphenoid sinus. So that's what we do. Several situations we have to go behind the carotid artery to do that. Basically the surgery is in between the carotid and the basilar artery, which is right there, of course the basilar artery will stay inter dural, so it's protected, but this is the corridor that we can evacuate this cholesterol granulomas. This is the post-op on that patient. Here's a post-op, and you can see how interesting just by my superialing, the entire capsule collapses, and decompress the brainstem in a simple surgery for this patient. So this is another example of a cholesterol granuloma here, this is not well pneumatized sphenoid sinus so we have to drill here to get to that area there. You can play the video. And here's, as we are drilling, you can see the carotid artery right there, and we now start really posterior to the carotid artery. You can see that the carotid artery is actually located anteriorly, and we are drilling posterior to the carotid artery by drilling part of the clivus as you can see this opening, and that's the petrous apex, and we are opening a mouth on the petrous apex, and we are able then to reach this cholesterol granuloma cavity and, as large as you can do this cavity is better to make sure it doesn't form scar and recurrence. So I'm here with an ingo scope, we're able to go all the way in, evacuate all the contents, but with this approach of course, we're not removing the capsule of the membrane that it has around, but just marsupializing, and then we keep this silicone projecting to the sphenoid sinus, so when we mucusilize, the mucosa around the tube here, this is a trachea tracheostomy tube, and that, next, and with that, you can see how it looks like. We leave this for several months, sometimes even six months, and then we'd take that in clinic, and the pathway becomes open for these cholesterol granuloma to drain into the sphenoid sinus. So now, moving one more time to more posterior, now to the posterior fossa aspect and jugular foramen aspect of the parasagittal or coronal plane approaches for endoscopic endonasal surgery, this is the chondrosarcoma. So petroclival chondrosarcomas, they started on this area here, the petroclival region, and they project to the middle fossa, and they project to posterior fossa, and the also project to the cervical region. As you can see in this area here, it goes around the carotid artery and jagular foramen. So if you look at these imaging here on the axial, the tumor is assignation to the petrous apex cholesterol granulomas. The same thing here, to remove this tumors, if you come with a retrosig, not only the cranial nerves may be in front of you, but you have to open the dura once and you have to open the dura twice to reach there. So not an ideal approach When we come endonasal, we actually start on the petroclival synchondrosis, and we can actually follow the tumor to posterior fossa and middle fossa, as well we can follow to the cervical region there. So that's a, for us our preference. Play the video, and here you can see, most of these tumors are soft. I have seen several that are actually very firm and calcified and you have to drill them, but the majority that you will find they are soft. So here we are dissecting the periosteal of the middle fossa, where the tumor eroded, and we are coming endonasal. This is a trans clival region, you can see this dura in the back, that's the posterior fossa dura, and we are evacuating the tumor. The cellar is superiorly here, and now we are going posteriorly and laterally. So very important to drill with angle drills behind the carotid. In this case here, we also use the Q-tip to retract the dura and progressively evacuate that, the tumor that was located into the posterior fossa and middle fossa. So as we start going more lateral, then we use a endoscope with an angle behind the carotid artery, and you can see here taking the tumor. And as we dissected more laterally, you can see the herniation of the dura of the posterior fossa and the middle fossa there. So then we drilled more of behind the carotid, and we were able then here to dissect the region of the petrous bone. Then here's the relis canal area or going to the relis canal. That's where the sixth nerve appears right there. You can see appears right there, that's the sixth nerve on top of the petrous bone, and then as we went in front of the petrous bone, after drilling more of the bone here, we were able to see the jagular vein, and the tumor that was dissecting under and going to the cervical region. We follow that and we were able to resect this whole tumor completely, and staying extradural. So then we cover with the nasal septal flap and no leakage of any fluid here. Next. And you can see the post-op, you see the flap located inferiorly. The flap is down there and all that component of the middle fossa, we got resected and the posterior fossa component got resected as well. Next. Perfect. Here you can see in the axial, this is immediately post-op MRI. So Meckel's cave got decompressed, and the brain still with the memory where it was located by the tumor, this eventually came back to normal position. So this is another example how some variants of this chondrosarcomas. This is a tumor that not only was invading all those regions, but also was invading through the dura, going to the posterior fossa and CP angle, and also invading the jagular vein. It actually invaded jagular vein, it was sealing the jagular vein inferiorly there. So here in this case, we actually opened the trans terrigoids, and then this is how we removed the station tube. We went lateral to station tube, removed all the bone of the terrigoids, used the doppler to identify the carotid posterior, that's the parafrengio carotid artery. See this is the soft valet down here, and we're able to then to go around and remove the station tube by disinserting the station tube. By performing that maneuver, really opens a corridor, and we were able to see the jagular vein with tumor inside, and then we opened that jagular vein, and we removed the tumor that was going down through the jagular vein. We got some gush of venous bleeding at the end, and then we put some surges cell deep down there once we got that resected. The beauty of this approach is that the vein here in this area protects the cranial nerves. So currently the inferior cranial nerves are actually coming posterior from the vein perspective. This is the hypoglossal canal now, and we are looking behind the carotid artery in the petrous bone here using angles scope. This is the tumor that was going to the posterior fossa, and you can see here is, this is the raw surface of the cerebellum, and we were able to get the tumor that was herniating through the dura there. We got the, this as a complete resection actually for this patient, you see the final view here, a little hole there in the dura, the petrous area totally open, that's the area where the tumor was going through, and we plugged those defects with a collagen matrix, and then for the petrous area where the tumor was located, we put a fat graph, then we covered everything with the nasal septal flap. Next. And this is the post-op. You can see that we were able to get that component that was going cervical as well, and the entire part that was going intracranial. This patient, he is probably seven, eight years when we saw him last with no recurrence of the tumor. So some other limitations, in this case for the posterior part of the tumor, we were able actually to get this whole tumor out here, this is a chondrosarcoma. In order to take that out, I have to remove all this bone of the clivus to get a direct approach here to be able to get to the tumor. The problem we had in this case, it was actually not in the intracranial. It was the fact that we got all the tumor from the petrous apex and petrous bone, but not the portion of the tumor that was going down into the cervical area because it was going too low. See this component of the tumor was going to the masticator space, it was really just a finger projecting inferiorly. So this is a limitation of the endonasal 'cause there is, if it goes too inferior in the cervical area, there's no way you can follow all the way down there. So in this case we actually came transoral. You see the tooth here, and we opening this incision with the upper corral in between here the soft palate and the posterior aspect of the mouth. Next. And by dissecting here, you can see that we were able to expose the component of the tumor that was forming like a sac going down. We opened that up. Next. And you can see here once we opened that up, we actually got that same type of aspect of tumor that we normally see with a chondrosarcoma, and we we're able to get that out of there, and resect it nicely for this patient. So with this complementation of approaches, endonasal followed by this trans oral, next, we were able to get a complete resection for that patient. So another limitation here, I'm gonna show you this example. This patient, this is a chordoma now, but with a lateral coronal plane extension. You can see here, this is the carotid artery right there, and all this is lateral to the carotid artery right here, and a component medial. This was going to the cordial as well, this patient had several surgeries in another country, and if I remember correctly had twice a Cyber Knife, and we decided to start with an endonasal approach. This, I was paralyzed when I met her, was frozen, and because chordoma there are midline for the most part. So we started with a midline approach endonasal. So I'm not gonna go through this video for the most part here, can play just for a second just to see how it was not easy, there was disease everywhere. And in one point during this surgery, I saw a membrane at the end there, and I thought we were done with the resection. Next. So then here what happened, I removed basically the medial and medial lateral component of the tumor, but this membrane here, I really thought I was done, and there was all these disease past lateral there, and this is a patient that will benefit from a complete resection of the tumor because she was already coming from another country with multiple resections, so in order to optimize, few days later I actually took her through another surgery, and I came this way with appealing of the middle fossa to resect the rest of the tumor. And this is here the example where we came down there, we used the doper, identified the carotid. You can see here if I remember this correct, this is a V3, and we used the windows of the middle skull base here to go around. Next. And, next. You can play. And then you can see here that we used this scissors we're able to dissect more posteriorly, and really cut this tumor with the goal of a complete resection for this patient. It's very interesting. We saw the sixth nerve that was traveling through the tumor, that we, it looked like it was gone already. She had a set of paralysis, next, of the eye. And so the sixth nerve, she never recovered. Next. Play. And, but interestingly, part of the third nerve was pushed up, and she actually recovered by decompression the function of the third nerve. So she was able to open her eyes again. So this is the post-operative MRI on this patient. You can see that we were able to resect the tumor lateral and medial to that carotid artery, got a complete resection for the patient and we sent the patient then for a proton beam radiation. She, like I said, improved her third nerve palsy, never improved the sixth nerve palsy, but the third nerve improved which was a surprise for us. So I wanna finish with this video which is interesting video here where you can see, it's a combination of an endonasal and an open approach. So in this case, we, this was a low grade sarcoma and it shows that you cannot do everything endonasal but you can actually combine in the same anesthesia in the same case. So this is a mixed of a view of coming endonasal and open approach with the endoscope, taking some of that low grade sarcoma that was attached. It was interesting, it was in the epidural space, but was going into the sphenoid sinus. Here, you can see a spatula, that means we are with an open approach. In a second you will see a view coming from outside, like right now, see the craniotomy there, and we came epidurally, and down here you can see a V3 going down, and a V2 going up there, and basically we were able to work in between the triangles of the middle foster here. This is with the open approach, and able to confirm a resection, this is actually going to the sphenoid sinus. Now we're with the endoscope inside the sphenoid sinus, and we're looking laterally. See this here, we are dissecting connecting the dots, as you can see here having some fun as well. As you can see the surgeon outside, and here's the cavity of where the tumor was removed, and we basically connect the dots by using the endonasal and the open approach as they complimented each other. So next. This shows the, really the fact that they compliment each other, I'd like to invite people that wanna come to our course. It was gonna happen in May if we don't have another wave of COVID of this coming year. So once again, Aaron thank you so much for the opportunity, and to allow us to share a little bit of our experience with the entire world. Thank you so much.

- Danny, thanks so much. This was very useful, spectacular cases. Something that's really important to emphasize here is that the tumor selection here is really important. You're using tumors that are relatively suckable, relatively can be removed around the corner safely, and really you're providing adequate exposure. So you're not pulling on things without having a reasonable visualization around what they could be attached to. So really the tumor selection is so critical. Don't you agree on that?

- I agree a hundred percent, and that's what I try to show some nuances of cases where I decided to go with an open approach and others that I actually failed that I used, like I tried, that case example of a trigeminal schwannoma where I went endonasal first, and it was not ideal for an endonasal and I had to kind of compliment with an open approach. So, but in general is true, for chondrosarcoma for instance, we always look at T2, and if you see a lot of calcifications on CT as well, you know that they may be more calcified, and I still, for the most part for petroclival chondrosarcomas because they start on the synchondrosis more immediately, I usually go endonasal independent of the consistency for chondrosarcoma, but it's true that if I look at my series, the cases that I was not able to have a complete resection were more often on the ones that had more calcification and the consistence was not favorable. I agree a hundred percent. So, and I think another example of that is what I showed on meningiomas where, because they are very firm for the most part, it's unusual for us to get a complete resection when they're in the cavernous sinus. Different when they're like in the system, if they're petroclival or on the anterior skull base, but once they are inside the cavernous sinus those are, for me, the goal of surgery is a decompression followed by radiation because of the consistency as you said.

- Yeah. So eventually the important point to emphasize again, as you very beautifully did, is it's important the tumor consistency, how much you can do endonasally not just location and size, and importantly, having a low threshold to know that you may need a craniotomy later to finish the job.

- Yeah.

- I think you don't wanna push an immature endonasal more than necessary. Obviously you're extremely talented in what you do, and as you can see, you're being very careful about what you're gonna do through the endonasal route, and not try to push the limits and make the procedure become too risky to the patient.

- Yeah, absolutely. I think that case selection is the most important aspect, always trying to do the best for our patients.

- With that I wanna thank you again for being such a gracious speaker for us Danny. Really proud of what you have done for neurosurgery, and we look forward to having you with us in the new future as well.

- Thank you and I appreciate.

- You're welcome.

- Thank you so much.

- Thank you, Danny. Thank you.

- Thank you.

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