Grand Rounds-Transcranial and Endoscopic Microsurgical Operative Corridors for Accessing Difficult-t

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- Hello ladies and gentlemen, and thank you for joining us for another session of the Dublin Esophageal Grand Rounds. Today, our guest is Dr. Theodore Schwartz from Cornell University. He's the director of skull base surgery there, and he will be talking to us about a very exciting topic of innovation in technical aspects of neurosurgery. I will gonna review some surgical videos, discussing some more creative non traditional ways to approach lesions that are very difficult to reach. Ted, thank you for joining us.

- Thanks for having me, Aaron.

- Thank you. Ted If that's okay with you, I'd like to review some few slides, get your opinion about how can we innovate during surgery. That's a really tough topic obviously to discuss, but is one that I think is very important. What is the philosophy of innovation? I think the world is a perpetual motion and we must invent the things of tomorrow. One must go before others, be determined and exacting and let your intelligence direct life. Act with audacity. I think this coat that from this individual, I think sums up many of what we go through every day to try to come up with creative ways to do surgical solutions to difficult problems. And we have had recent innovations, all of which are well-known to us, you know, navigational radiosurgery, minimally invasive spine surgery, endoscopic techniques, endovascular approaches, intra-operative fluorescence and robotics and nanotechnology in the future. Well, when it comes to really doing the procedure you haven't done before, but we know it may help the patient how do you cross the line of challenging the dogma, what you learn in surgery and residency before, and trying to make the leap of faith to do a new approach. Those are challenges we face every day. It seems that it has worked for me, as learning from your mistake, with any confidence in the face of failure and really remembering innovation and creativity in every surgery and see how you can improve your approach to a difficult lesion. Obviously we all go through metamorphism. We all through our career can be at different stages, be a different surgeon, hopefully with increased strengths. So, let me start by asking you what you consider the ingredients for operative innovation? Obviously you have been a pioneer in a endoscopic surgery. When you started endoscopic surgery, there were no fellowships. So, how do you make that transition of saying, "you know what I've never done this before, "but I know it's the right thing to do, and I'm gonna go ahead and take the risk and do it."

- Yeah, it's a great question. And you know the way you phrased it is interesting, as you said, I know it's the right thing to do, but I think at the time, I wasn't sure it was the right thing to do. And I think when you try something new, it's hard to know for sure, whether it's the right thing to do because you really don't have enough experience doing it to know that. I was doing pituitary tumors and was frustrated with the way I was doing them. And the way I had been taught to do them, I felt that using fluoroscopy, first of all, was not a great way to know exactly where you are. You know, we do a lateral fluoroscopy, but it really wouldn't give me information in the other plane. And I sometimes didn't feel a confidence to know that I knew exactly where I was. I was trained to use a sub-lobule incision and put in a hardy retractor. And I had a limited field of view, which is disorienting. And with limited fluoroscopy, it's not that hard to get lost. And so, I was in the right spirit to try something new and try something different. And you know, endoscopy made a lot of sense. Honestly, the the first idea I had of doing endoscopically came from talking to my chairman. So, you know, Philip Stieg at the time said to me, "People are starting to do these endoscopically, "maybe you should think about doing that." And I give him a lot of credit for that and for having someone who had more global, you know, wisdom to see what was going on in the field and tried up to push me in that direction to build this department. And I took, well, the other key thing was finding a collaborator, you know, and I think we learned an incredible amount from other people when you have to be open to constantly learning throughout your training. Don't feel like you graduated from your residency training and the neurosurgery book has been written and it's formed. And it's done. But I think you have to always come into the OR saying, you know, "What is wrong with this operation?" "What could go wrong? "What can I do to make it better? "Is there somebody around me who can do an aspect "of this surgery better than I can, "and can I learn from them how to improve what I do?" So, my endoscopy fellowship was really watching my rhinologists, do the approaches and do the surgery. And I would watch for hours and hours and hours every time rhinologist would do the approach until I really knew the endonasal anatomy. And I knew what maneuvers he would do to operate with, you know, with an endoscope. I had to bring in bimanual surgery because he used to operate with one hand. And so, you know, it was that confluence of two different points of view that allowed us to evolve to bimanual endoscopic surgery, which is really more neurosurgical endoscopy. So, you know, the first cases we did were obviously very stressful and I was nervous and didn't know what was gonna happen. But if you push yourself and you sort of don't, I mean, the microscope wasn't even in the room. You know, I think you have to sort of give yourself to the new technology and allow yourself to struggle and spend time. So don't, you know, schedule 45 minutes for your first endoscopic pituitary surgery. No, you have to schedule a couple of hours because it's going to take you a couple of hours to get comfortable with it. And so, you know, being willing to put in the time and, but knowing that it needs to be done better, but there is a better way to do it. And then to be honest with yourself, and really once you sort of have done a couple of cases, say, "Is this better? "You know, is this really better in my hands?" For me being able to see with the endoscope, the panoramic view of the whole sphenoid sinus, suddenly I knew exactly where I was at all times. There was no question where the carotid was, where the optic nerve was, where the cellar was . it was all there, you could see it all. And so, I no longer needed the fluoroscopy. We've moved to using navigation, but you barely even need the navigation. Once you see that sphenoid sinus anatomy, you know, that's what orients you to where you are. I mean the endoscope provided that and it was obvious it was very apparent pretty quickly, how much better it was when the endoscope, at least in my hands. You know, some people don't agree with that, but certainly in my hands, I was much better with an endoscope than with a microscope. So, I hope that that answers some of your questions.

- Now, it does very nicely. And I agree, and I wanna echo some of your very important points you raised about a supportive environment. You had a chairman who was supportive, obviously there's a learning curve in anything you're doing your complication is gonna be more pronounced. So, you have to have an understanding environment and you have to be conservative to select your cases extremely carefully. I think those are very essential and learn from your mistakes and keep the confidence. Ingredients for operative innovation, to be very specific, some of the things that I've written on this slide is, it creative an innovative spirit. You've gotta approach every case that is challenging knowing how can I do better, rather than saying, well, you know, that's how I was learned to do it. That's how I'm gonna do it. I don't think that's the best way to approach it. How can I minimize brand transgression? How am I kind of, how can I minimize injury to cerebrovascular structures? That has to be the first model. I wanna protect normal structures and minimize collateral damage to them, learn from mistakes and colleagues, you know, having a good senior colleague who can be a good mentor for you, when you're starting these cases through nontraditional ways can be very critical, challenging the dogma. Just because my chairman or my, you know residency director or my mentor did a parietal intraventricular tumor through a transcortical approach, doesn't mean I'm gonna always do it that way. We're gonna talk about that momentarily through a different route out. A candid evaluation of your risks and benefits. It's very tempting because you wanna publish and you're in academia and you wanna modify a technique that you wanna put your name after it. And therefore, you wanna make sure your results look good. And subconsciously sometimes we modify things that don't need modification and we make it more complex and confusing. And at the same time, try to subconsciously sugarcoat the results. And that definitely fires back later. And you need to be conservative. Just because you worked twice, doesn't mean you have to approach every case that looks anything similar to that just to build your case series. You have to be extremely important, careful about that, and never, never, ever stop pursuing excellence. I think excellence is almost reachable. It's a journey, it's not a destination, and it definitely never ends with finishing your residency. And again, just like you said, the supportive environment is gonna be critical in achieving a new horizons in surgery. So, let's go ahead and if that's okay with you, we're gonna start the first video. That's gonna talk about some of the challenges that I have had in managing difficult tumors. Here as you can see, let's talk about innovative transcranial operative corridor superior post-trip pontine tumors, or difficult to reach traditionally large midline pineal region tumors that go caudally to the superior cerebellum can be challenging. We're gonna talk about how you can come laterally to get more inferior view. Large third ventricular tumors can be also challenging. And we're gonna talk about how to expand the transforaminal approach, where atrial tumors, especially on the dominant side and obviously endoscopic expanded endonasal corridors are gonna be a critical part of any topic when we talk about expanded operative corridors through innovative techniques. So, with that in mind, I think the first case is gonna be describing posterior pontine tumor. And if I may ask you, before we do that, I wanna share some of the ideas about operating room using the mouthpiece is critical. Using the hand rest for open procedures would prevent operator's fatigue. I know you're not personally fond of a mouthpiece. Can I ask you why that is Ted?

- Yeah so, I never trained with the mouthpiece, so, I didn't get a lot of experience with it. I work now with surgeons who use it so, often the scope will be set up that way. And so, I tried it. I have a hard time moving the scope at the angle that I like to move it. I mean, I think you can move it up and down, but I'm often trynna move it kind of this way or this way. And I have trouble doing that with my mouthpiece. I also, it bothers me being in my mouth and you know, pushing the mask into my lips and teeth. So, I don't really enjoy operating with it, but you know, more power to you if you can use it. I think it's perfectly terrific to use it, but obviously I bring my hands up and I move things around often frequently. It's just like when I do endoscopic surgery, I'm constantly moving endoscope and I'm constantly moving to microscope, but it's not just up and down. I'm twisting it at weird angles. So, watch for me?

- Yeah, It's very fair. I can tell again, this comes down to personal preference and I think for me, it's really mixed it and certainly much more efficient because I hardly ever take my arms out again now. You have to take the arms out and move it for gross movements, as you see momentarily in the video, but the hand rest is critical. Being able to sit and operate, I think it's a very valuable resource to be able to rest arms. Here again, it's using the mouthpiece in order to focus without minimizing, changing your arms from the instruments. So, approaching the lesion, the posterior pontine tumor, I'm gonna talk about how you can come laterally through the supracerebellar approach coming laterally, unilaterally above the cerebellum. You have a more inferior trajectory and minimizes the extreme retraction of the Coleman or midline cerebella which is more elevated. Here's two graphics showing how the patient is positioned lateral. We use the lumbar drain to avoid the sitting position. A craniotomy is elevated, we put two sutures, as you can see here, along the posterior aspect of the tentorium elevates the sinus. You can see the fourth nerve there exiting the posterolateral aspect of the mesencephalon. And as you can see how much our lateral trajectory you can get here and obviously mobilize the arteries and make an incision within that posterolateral mesencephalon and remove the tumor. How would you approach this case by the way?

- Yeah, I think very similarly, it's a beautiful approach. I actually, as a resident also never did this approach. We did a lot of supracerebellar infratentorial approaches for pineal region tumors, but never really lateral supracerebellar. And, you know, I read a couple of papers. I think maybe Sped Slur had written one or two of them. Mark Suede and also one of my partners had done this approach and I talked to him about it. So, when the right tumor came about, it looked very similar to the one that you took out. I used it and the exposure was beautiful. I think it's terrific and again, it speaks to the issue of constantly trying to learn more approaches and read the literature and read it carefully, and try to get a sense when you read what types of tumors are suitable for which approaches, and then save them, you know, the ones that you really like, you know, everything's digital now you have them, but sometimes I'll print them out if they're really, really useful and, you know, read them again and again, to make sure they're part of my surgical vocabulary.

- Very well said. You know, this was a midline tumor. I would say most people would approach it through a midline approach. but you will see that you're gonna be retracting a lot over the midline elevated, you know, some bones like a tent. You're gonna do most of the retraction in the midline, and here you come, laterally for a midline tumor, just like you approach a lateral factor movement in tumor through the trineuranal approach versus a bifocal approach. And here you can see those two sutures really elevate the sinus gently. You get a nice trajectory. You do not use any fixed retractors and you'll be able to approach the lesion without putting the other transfer sinus or trochlea at risk. And also, you preserve most of the variant midline veins where most of these veins are at anyways. And here is really the, the magnified view on the operative quarterly in this case, and a reasonable resection of this tumor. So, how about large pineal region tumors? This is another case you can see, Ted, the tumor is relatively large, it's more than three centimeters. It has a little bit of hydrocephalus associated with it. And what would you say, how would you approach this?

- So I'm first do an endoscopic third ventriculostomy. You know, when the patient first came in or put a ventriculostomy at the operation. The patient had symptoms of hydrocephalus, I would do an ETV, and then would I do the surgery, you know, a couple days later. And I learned how to do these in the seated position. And I would do a supracerebellar infratentorial approach. I think you'll get great exposure of the whole tumor. I know a lot of people don't use the seated position, but I find it comfortable if you know how to set it up, you know, and you know how to rest your arms well, because they're often extended above your head. But if you do enough of them, you can become very comfortable with it. So, that's what I would do.

- What do you do bilateral in terms of the midline suboccipital supracerebellar approach or unilateral?

- Yeah I 'll be doing midline approach.

- Good, let's begin

- A little bit on each side.

- Okay, and I would say that's 99% of people, how approached this tumor. And here is a tumor that comes way caudal. And this is a case that I also approached unilaterally because I think it works very well even in large tumors. Again, the patient is lateral, you can see the outlines of the transverse and sigmoid sinus, you can see that the midline paramedian incision and you can see the stitches again, elevating a little bit of the sinus. And again, you can see this suture, how it makes the tentorium somewhat more horizontal. You find the fourth nerve laterally, you a coagulate the capsule of the tumor, as you did block the tumor. You can see the whole capsule, somewhat deflates. You can see the midline on the other side. So, this provides a really nice midline exposure and really across coat approach to remove the entire tumor. Ipsilateral into the left side, you can see we had a great view as well. This is the fourth ventricle. Third ventricle that was evident momentarily. And you can see the vein of Galen was very adherent and we were able to achieve a newer growth store resection in this case, but the fibrous tumor, it was a pineal blastoma. It was so fibrous and that's why I wanted to show this case because even though the tumor was very large, it was very fibrous. We're able to remove it through a unilateral approach without necessarily placing their venule vessels at risk. And this is a relatively good resection with a little bit of residual tumor older than midline veins. So, how about approaching the large third ventricular tumors? This is a patient who's young, a very functional person is C.E.O of young company an outside surgeon tried to approach this tumor through a right frontal transcortical approach, was able to only do a biopsy because the tumor was very fibrous. This turned out to be a cord Lloyd glioma of the third ventricle, is a very rare entity. And she came to us for a second opinion for further resection. May I ask how would you approach this one Ted?

- So, you know, depending on whether the floor of the third ventricle were intact and how intact it were, I would potentially do this through an endonasal endoscopic approach. You could get in actually underneath the chiasm is on this particular image. Is that the chiasm below?

- It is,

- Right, so, in that case, it would be challenging. You'd have to go above the chiasm So, I might actually in that situation, come through the lamina terminalis and do a bifrontal approach and come straight back through the laminate.

- Correct, and I think that's a very reasonable approach. I actually send his MRI to four very prominent surgeons, including Dr. Harris, Dr. Caldwell, Shack Marcus and Eric Book. And I got four different opinions, which tells you there are approaches that are very difficult. One of the operators that I mentioned agreed with you completely, and I think that's a very reasonable approach. I'm gonna talk about a slight modification of the transforaminal approach here. I would wanna see what you think, and if this is really effective in removing these tumors. So, we went ahead and use the previous right frontal incision. In this case, I'm going to briefly talk about the technique here, patient against supine, we're coming intro hemispheric transcallosal. We coagulate and cut the septal ring and then mobilize the fornix medially. This expands the foramen that is already expanded by the tumor. It prevents playing with the veins more posteriorly, including thalamostriate veins through the transchoroidal or subchoroidal approach. And it prevents from any manipulation of fornixes. And this really slight modification expanding of the foramen can do magic by just coagulating and cutting the septal vein. Really there has been no undo or unto work consequences from cutting this vein that is often very small, but you can see this was really a modification that I never heard of never read about, but I thought, you know, it give it a shot because I think it would work in the fellowship. And that's what we did.

- I would think on the dominant side, there would be some risk of injury to the fornix.

- I think that's definitely a reasonable concern. Here you can see the interhemispheric approach Ted. This is the corridor we are not using any fixed attractors. Here's the foramen, you can see the foramen in this case was very scoured in because of the previous surgery. You can see the septal vein right there. We went ahead and coagulate the choroid plexus. This is again in the right ventricle. We coagulated the connection of the septal vein to the thalamostriate vein, and this expanded the foramen. And you can see that thalamostriate vein right there, here's the contralateral internal cerebral vein, ipsilateral internal cerebral vein. You balking the tumor and removing the tumor using standard techniques. Again, this is emphasizing the operative corridor moving between left and right capsules, mobilizing them. And here is really essentially a gross total resection leaving a very small piece of the tumor over the hypothalamus to avoid any untoward effects there. And the patient did very well. Any other thoughts regarding this guest case, Ted?

- I mean, I would emphasize that a lot of third ventricular tumors, if they're below the chiasm, can be taken out endo nasally. We've taken out intraventricular meningiomas, we've taken out, obviously a lot of craniopharyngiomas that fill the entire third ventricle. Now I'm just going through the nose and working below the chiasm above the pituitary gland, you really can create a large enough corridor there and without any sort of brain retraction, any risk of a transportable injury. In this situation, I think the optic nerves were not helping you in that they were hurting you in that situation. So, I think coming from above is correct.

- I agree completely. I think that the moment you have one expanded endonasal large third ventricular tumor go well you think like, okay, this is like the solution to all the problems. Anytime I'm gonna have a third ventricular tumor, I'm gonna try this approach. And you have to be very careful in that case, you could see the chiasm was very much draped underneath.

- Yeah.

- And there was very little space to work through and the tumor was mobilized posteriorly. So, if you approach that tumor, you're gonna end up causing more damage to hypothalamus and the chiasm. So, even though endoscopic techniques are great, You have to know patient's selection. Otherwise, you undermine the goodness of endoscopic techniques. And some people say, well, endoscopic techniques are just not good. They don't give you enough space to see. Well, you have to use the right tumor, then they will let you see what you need to see. If you don't mind, let's go ahead and briefly review a couple of other cases. This is a case for peri-atrial tumors. You can see most of us have been taught to approach them transcortically, but when you approach these tumors transcortically, you place the vision, speech on the, especially on the dominant side at risk. So, let's talk about how we can use the posterior interhemispheric transfalcine transprecuneus approach. I'm gonna use the case of a 66 year male who presented with confusion and had this atypical meningioma. For these tumors, we have been taught to go transcortically through this superior parietal lobule. Now, when you go through there, especially in the dominant hemisphere, you place these tumors at risk, and one option is going into hemispheric, but the working distance can be often very challenging. So, here coming from here, you're gonna put speech and language potentially at risk and going sub-temporally, you're gonna require a lot of retraction. What would be the alternative approaches in this case for you then?

- So this would be a good case to use a tubular retractor and to come potentially through the superior parietal lobule or a little more posterior to that to try to avoid language. But we've adopted the metrics tubes to try to avoid damaging the deep white matter and have a custom made dilators that we use to basically get the metrics to pass through the cortex stereotactically of course, to try to, you know, make a very small opening and even sometimes come trans-sulcal. So, you get even closer to the tumor and just pass through a very small amount of white matter that gets essentially pushed laterally as opposed to interrupted.

- And I think that's a very creative way to do it rather than using the tractors and resect the gyrus and cause more collateral damage, you can do it that way, and I think that that was beautiful. The way that I thought about it is how can I come into hemispheric, violate the least amount of cortex through the procuneus here and approach this tumor. And here's the illustration showing that, how we use this approach and you actually put it, you do the craniotomy over the normal atmosphere and enter the interhemispheric space as you can see here, and you have a cross coat view in order to minimize the retraction or the normal hemisphere, and you actually put the normal hemisphere down to take advantage of gravity. And again, this is a approach that I never learned about. Obviously it has associated risks to it, but if you can find the right patient would be a good candidate, it would help. Obviously, you wanna prevent injuring the parasagittal veins, come through there again. The tumor was on the left, and coming from the right side, mobilizing the bridging veins, using those sutures to mobilize the sinus more toward the other hemisphere and come through the precuneus to the atrium. And here you can see right now this is a normal hemisphere. This is abnormal hemisphere. A T-shaped cup through the faulx, a cortical incision. You can see here again, the cross cortico stealth approach to the tumor. You get a nice exposure of the tumor and its feeders from the choroid plexus early on in the ventricle. When you come from the top, you often see the features later in the surgery, and here's really the final product with minimal transgression and relatively good results for resection of the tumor. Any other thoughts here, Ted?

- No, I think it's a great result. And I think I would emphasize that the use of stereotaxis really gives you that confidence because when you're coming through the faulx and you're seeing the normal brain presenting itself to you, it's a little daunting if you're not sure where that tumor is and what the small stomatocortex is, you can pass through to get there. So, I think the navigation is really critical in this kind of surgery.

- I completely agree that, that's a very good point. So, before we go through our endoscopic approaches, I'm just gonna briefly mention the same thing for this tumor. This is a giant tumor, the size often would lead us believe you have to remove the tumor clear bilateral approach. But again, it's not all about the size of your exposure that allows you to remove these giant tumors. You can do a very small unilateral craniotomy. It's all about working angles, working zones rather than working space. And as long as you can clearly be able to expose the tumor and use appropriate instrument such as ultrasonic aspirator here, as you can see the veins posterior to the tumor, we went again, transverse seen, remove the ipsilateral part of the tumor, cut the faulx, removed the contralateral piece of the tumor all through a small craniotomy without exposing too much brain or placing the parasagittal veins at risk. And here is the corpus collosum and some of the arteries in the region and a tumor is being removed piecemeal. Thoughts here, Ted?

- You know, I think that when you're working around corners like that, the endoscope can be helpful. And we'll often put the endoscope in at the end of the operation when the only tumor that's left is that tumor that's on the contralateral side. It's hardest to see and put it up, someone hold a 45 degree endoscope and keep operating. With that view that you really can't get with a microscope, and then a lot lot allows you of course, you don't have to take quite as much faulx maybe not violate as much of the cortex on the other side, the inner hemispheric cortex. But I would just emphasize that if you're doing smaller craniotomies and working cross coat, to always keep in mind that you can use the endoscope to help you see beyond what you could see with just the microscope.

- Very well said. And again, this is another variation, you know, talking about how we can go transfalcine, can we do this awake? This is a tumor that often is very difficult to approach here. You know, this is posterior faulx. If you go ipsilateral, or you often end up with tracting the motor cortex significant to reach. Again, this is sort of a peri atrial tumor, and this is close to the motor cortex, as you can see here. So, how are you gonna approach this tumor without causing morbidity? Coming back to the same theme, minimizing retraction, brain transgression, and here is sort of a DTI demonstrating how the tumor has displaced the white matter tracts. And obviously the leg region is not easily remarkable on MRI because the movement of the leg in the MRI machine would cause too much artifact. So, in this case, again, we came contralateral from the left side to the right side map the region of the brain just superior to the tumor. And we're able to actually map the medial posterior faulx area to maximize tumor resection. And here are the details of this case coming again from the left side, the tumor is on the right side, you can see the cross coat approach cuttinng the faulx would allow us to minimize, exposed it cortex. And we're now mapping the contralateral hemisphere, which is normal, to estimate the location of the motor cortex. And then we mapped a medial frontal area. As you can see, we map the SMA, worked around the callosomarginal artery and pericallosal arteries to achieve a goal to a resection without any transgression of the brain. And here are other lesions that can be approached through a transfalcine approach. Again, transfalcine, a through sounds counter-intuitive, you're exposing the normal hemisphere to remove a tumor on the abnormal hemisphere. That's counter-intuitive. Number two, you're increasing the working distance significantly. So, it makes it technically more challenging, but you know, it minimizeS brain transgression. And that's the ideal of in my opinion being creative in approaching these lesions. I think endoscopic techniques, have revolutionized neuro surgery for many good reasons. A 32 year old female presents with this large meningioma, most often people say, well, there's potential vascular encasement. This tumor could not be approach through an endonasal approach. What would be your impression there?

- So we've gone back and forth on all factor group meningiomas. And there's no question you can take it out endonasally and we have done so. There are a couple of very important issues that you need to take into account. First of all, in order to take this out completely endonasally, obviously olfaction is gonna be sacrificed. Anytime you're going through the cribriform plate, the patient will not be able to smell. So ironically, some of the smaller olfactory group meningiomas that are easier to take out endonasally. We may elect to take out through an eyebrow incision because we think we can preserve their sense of smell. This is such a big tumor that I think no matter how you take it out, it's gonna be very difficult to preserve their sense of smell. You can see there's a lot of hypertrophy of the bone of the skull base, and that is an advantage coming in from below, because all that's gonna be removed as you take out the tumor from below. If you look at the very anterior limit of the tumor, though, it's really right in the back of the frontal sinus and the back wall of the frontal sinus. And in order to get that out, your rhinologist is going to have to do a draft three or well, a lateral really open up the frontal sinuses bilaterally to get in there. And if they don't do that, [Theodore coughing] excuse me, you may not have the proper exposure. Both the middle turbinates will have to be taken out, for sure, and we can see on the coronal that the tumor extends just above the orbits, but it really doesn't go past the mid line. And I would say, this is on the border. You know, I think you would probably could get this all out, but it's possible that some of that dural attachment may be too lateral because the laminate perforation of course is gonna prevent you from going very far lateral. You can get a little way it's probably a centimeter past, but any more than that I think is challenging. So, I think if you do the correct approach, that this is very removal endonasally, the other issue of course is closure. The nasal septal flaps really have to be very long to close the defect like this. So, you have to make sure that your rhinologist gets a very very long nasal septal flap. If you wanted to reach far enough anteriorly to close this adequately. And if you don't think you can get that long of a flap, your closure may be a bit of an issue. So, a lot of things to take into consideration.

- I really liked the way you went through this case. It is very astute, obviously an expert way of going through it. Thinking about the problems you're gonna run into, rather than just saying, you know what, what can go right? You went through things that can go wrong, and that's what it takes when you really wanna tackle unknown territories removing large meningiomas through the nodes. Obviously you don't want to get into that, get into trouble, injure the patient, and obviously persuade yourself endoscopy is not the way to go. And that's exactly how we approach this tumor and how we resected it. We moved bilateral middle turbinates. We also did a very radical ethmoidectomy. We opened bilateral frontal sinuses as you can see here, these are bilateral frontal sinuses. Here is the ethmoid sinus, you are coagulating the entire ethmoidal arteries, and here's the dura, very wide exposure and removal of the lamina papyracea And again, removing this hypostatic area and using much surgical techniques. I think one argue that the only way to get a sense on one grade resection for this tumor is through the endoscopic route. And here, as you can see the optic nerve momentarily, we use the very same techniques wiping the brain, using carotenoids, using endoscopic methods, debulking, finding the anterior cerebral arteries that you saw momentarily. And here's the final view. This was significant amount of appeal invasion here on a gross total resection, a very large craniofacial and skull base osteotomy requiring a very solid reconstruction in this case, that we did. And you can see a gross total removal of the tumor with minimal morbidity. And the patient was discharged three days after surgery and has done extremely well. Let's go through another case. A 42 year old female with visual dysfunctional papilledema. If you look at this case right now, Ted you can see this is a choroid plexus papilloma. And because the patient had another lesion that was resected years ago, the exposure through the lamina terminalis is gonna be very small. Choroid plexus papilloma is notoriously vascular. Would you tackle this endoscopically?

- Yeah, I think you could get this through an endonasal approach. It looks like it comes down a bit longer stalk heading down towards the cellar. And I think you will be able to go through, you know, just around the stalk. I would be curious about the pituitary function of patient preoperatively. If there's any hypopituitarism.

- There was moderate hypopituitarism but no DI

- You know, I think you have to tell the patient that there's a significant risk of DI taking this out through the nose. You know, the CPR about to see all arteries could be involved in feeding the tumor and you're gonna be working around them. And you worry about interrupting the supraoptic cells, but often there are corridors above and below are usually below the supraoptic cells that allow you to get into the third ventricle. And then as a choroid plexus papilloma, you should be able to start cauterizing it and shrinking it before getting into it and just sort of slowly work your way around it and find your margins. You know, I think it's gonna be stuck to the up and the underside of the chiasm and the posterior part of the chiasm and doing in endonasally is one of the only ways to really see that. Well, as well as the whole third ventricular wall that is gonna be attached to, you know, coming from below, you're gonna see the entire third ventricle from below both walls back up chiasm, which really is where you want to see top of basilar, all of that's gonna be visible to you from below. I don't know if embolization was a possibility. That's something I consider.

- Yeah we did an embolization in this case, I wanna reemphasize and echo what you said beautifully. And that's for retrochiasmatic tumors. Endoscopy is just the best way to go. There's just no better way to reach retrochiasmatic space. And here is the chiasm in front. This is most likely going to be a retrochasmatic tumor, and I can tell you it was because you're gonnna see that video momentarily and a working angle that you have is the key. Here is the chiasm, using our surgical techniques, working behind the chiasm delivering this tumor within the capsule, and ultimately working along the capsule. From there, you can see the bimanual resection, cutting the tumor segments and be able to ultimately see the foramen and roll by bilaterally. Even the lateral ventricles there stalk was left intact here as you see, you can see the postoperative MRI. The top stalk is sort of hanging in the breeze. The patient had the eye after surgery, however, has recorded a very minimal amount of DDAVP and had her pituitary function has worsened. However, collosal resection was possible because again, you're working angles along the long axis of the tumor, transcranially it will be almost very difficult to work along the long axis of the tumor in this case.

- I also emphasize that the closure of these cases really is not that difficult because the opening you make is quite small. You're limited by the chiasm from above and the pituitary gland below. And so, you really can't make a very big opening in the bone there, and closing it, you know, we use a gasket seal with fascia lata medical cover with the nasal septal flap. I think your leak rate would be very very low here.

- I very much had read. You'll be amazed how small of a space you need to work when you're along the longer axis of the tumor, you really need very little space. And that really is the beauty of endoscopy. So, this is a tumor in a inferolateral aspect of clivus. I would say it was almost impossible for me to fashion an approach to remove this chondrosarcoma with minimal morbidity, even the trasectomy unnecessarily would not get us there because this is to inferior. Can you think of a transcranial approach here, Ted, that would get us and provide a chance for gross resection?

- You know,I guess you could come subtemporal and open quasis triangle and,

- Well but I agree I think I certainly would do this endonasally, but you know, that the part that's going into the posterior fossa in front of the ponds, you may not get out endonasally, depending on how big and opening you wanna do. And if you wanna just stay extradural, one option is to take out everything that's extra dural and leave that intradural nodule for radiosurgery. You could take it out into intradurally, as well. You know, you just have to talk with the patient about the risks and, you know, whether you're sure it's a chondrosarcoma and how well you think it's gonna respond to radiation but, was there a sixth nerve palsy in this case?

- Very subjective, mild periodic diplopia.

- Yeah. And that's exactly what we did. We did this endoscopy, I don't think you can use it through a quasi triangle and do the resectomy because the tumor goes below level of the IAC. So, really the endoscopy has revolutionized the resection of these tumors because there really wasn't a good transcranial approach previously. Here's the midline clevis, here is drilling the bone, and here's the tumor, you can see that petrous choroida. We're gonna go ahead and debulk the tumor. Again, another point that you have emphasized beautifully in your talk is using angled instruments. Using angled endoscopes. It opens a new polarizing endoscopy, and I don't think people who haven't done endoscopy appreciate as much. This is using a 45 degree endoscope. This is a midline, and you can see how much you can get for lateral exposure using angle instruments to deliver the tumor and to find the petreous choroida. Here again, the chondrosarcoma is relatively soft, lend themselves beautifully to this kind of procedure. You can see the entire carotid artery has been exposed. This is their dural over the middle fossa. And so posterior fossa, this is a jugular tubercle. You can see the vein in that area. Now we go into the cavernous sinus, follow the carotid artery into the cavernous sinus. This is the dura of the middle fossa. This is the dura entering the carvenous sinus and the wall of the cavernous sinus and really providing us a beautiful panoramic view, a relatively great resection of the tumor, even it's into dural aspect, because I think it had, it's really the tumor was extradural, but it pushed it to a more posteriorly and really provides a magnificent result and the patient can go home within two days. Any other closing thoughts you have, Ted?

- Yeah, I mean I think, you know, we've had the same experience with chondrosarcomas of the petrous apex that it takes what, when I finished my training would have been an incredibly complicated, difficult, daunting surgery and makes it similar to taking out a pituitary macroadenoma. I mean, it's, it becomes even even less so because a lot of it is just extradural and people don't realize when you're coming in through the nose, you know, how easy it is to drill up the clivus and get into the petrous bone, and you know, that you can be nervous about the carotid, but often the tumor is soft. And once you take the tumor out, you see the carotid. And once you know where the carotid is, it gives you a confidence to be more aggressive because you're only tentative and hesitant when you don't know where the carotid is. But if the tumor has eaten away the bone, once you start taking out that soft tumor, the carotid becomes immediately apparent, you can follow it, you can trace it, you know, and it's got a fairly robust, you know, fibrous adventitia around it that allows you to work around it without worry of carotid injury. Now, you could argue that you should be prepared to take the carotid, you know, some people would cut down on the carotid before they did this operation, or have embolization already, a balloon in place. We probably wouldn't do that. Obviously, if there is an injury, you need to have your interventional radiologists available, but we've had so few injuries doing these cases endonasally. And again, you're choosing the right tumors to do. I mean, you know that these are often gonna be soft tumors. And so, the soft tumors are the ones where you're less likely to damage the carotid because the manipulation you're doing in that area is, you know, sort of bluntly with the rain curates. And that's very unlikely to puncture a hole in the carotid. So, I think it's a perfect case for endoscopy and really shows what an advantage that is. And the angled endoscopes are gonna be key to getting you to the back of the petrous bone. You will not see that with a zero degree scopes, you have to have those angled into scopes available and long angled instruments available in order to reach back there. So, a lot of doing this successfully, is putting together a good tray of instruments that you can rely on and you're comfortable using to get around.

- Very well said and first of all, I sincerely thank you for participating. You know, you have been a pioneer who has been not only very creative and innovative, Ted, you have been also very conservative. And that conservatism mixed with a very astute sense of creativity leads to really giants in your surgery. And I wanna truly congratulate you. And I also wanna tell the younger neurosurgeons that always remain creative. Just because you were taught something one way, it's surely not the best way to do it. And remember, for vitality of our beautiful profession, neurosurgery innovation and creativity are most important foundation for survival. Again, thank you for joining.

- Aaron, thank you so much for having me.

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