Modern Skull Base Surgery: 6+1 Skull Base Approaches

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- Colleagues and friends, thank you for joining us for another session of the Virtual Operating Room. Our guest today is Dr. Juan Carlos Fernandez-Miranda from Stanford Neurosurgery. He has truly established, one of the most incredible, neuroanatomical and neurosurgical anatomy research labs. It is called the Stanford Neuro Training Innovation Center. Juan Carlos is not only a spectacular micro surgeon, endoscopic surgeon, he's also truly the protege of Dr. Lawton, and has carried the flag and the torch for him for the past decade. Juan Carlos, I cannot thank you enough for incredible work you have done. Your meteoric rise in neurosurgery is unparalleled. And I know today you're gonna talk about approaches, both open and endoscopic to sculptures and I can't find anybody better than you, who can really give us an advanced perspective on that. So, I'm looking forward to learning and let's go ahead and jump in, thank you.

- Thank you, Aaron. It's a pleasure as always to be here with you. You know how much, not only I admire you, but how much I enjoy working with you and how appreciative I am of your support to my work and the work of my fellows over the years. For listeners, you should know that, Aaron and I, we have been working together for almost two years. Almost weekly meeting, and his support has been key for many of the advances and publications you're gonna see in the next months and years coming. So, thank you for that, Aaron. Your enthusiasm, it really has been enlightening for all of us. As you said, we are gonna be talking about, what I think is my personal concept of what Modern Skull Base Surgery is about. And how we combine or how we can select approaches. I wanna start with my disclosures. These are some of the dissectors, I developed with KLS Martin sometime ago, a modification of the Pittsburgh set, we use for many years in Pittsburgh. But lately I have developed this new set of dissectors with a different company, that I think they were coming with the limitations of their KLS Martin set, and other sets, because these are good for both endoscopic endonasal, you can extend them very long and for microscopic surgery, because you can make them short and work with a microscope very well. And it has some of the key instruments to perform some of the operations we've developed, like opening an arterial wall cavernous sinus. Opening the optic canal, accurate tumor dissection, you'll see them in my videos, and this is coming up soon in the market and will be available for those with an interest. This is where I work at Stanford New Hospital, very fortunate to have a phenomenal team here, that support me and help me to do the best for our patients. And of course, a lot of the work we do in a Skull Base Surgery is about collaboration, multidisciplinary collaboration, especially with our ENT colleagues, both for endoscopic, endonasal and for lateral skull-based surgery, their collaboration is so key and so important. And as you mentioned Aaron, I've been, of course, keeping up with the traditional Professor Lawton, it is really my honor to do my best to continue his legacy. And as he used to say, the fellows inspire me everyday on the work they do and they help us so much moving the field forward. I wanna acknowledge, recognize the phenomenal world that fellows are doing in the lab, because it really takes the field forward. You can see here, some of the amazing work that they're doing, this is work by Maxi Nunez, an outstanding neurosurgeon from Argentina. We call him Max Da Vinci because of the quality of his work. We're also impressed with what he does, how talented he is. And then Vera from Italy. She's been with us also for a long time doing this 3D modeling photogrammetry. In addition to of course, dissections and the combination of the work, both together produces beauty, like this phenomenal view of the surgical anatomy, both of the white matter and the skull base, et cetera. Key for surgical education and for training the next generation of neurosurgeons. So, these models are by the way available on our website and also on the Atlas website are available or will be available and you can play with them, and really that's what makes them great. You can zoom in, zoom out, rotate and explore the anatomy as you wish. Let's go to the next slide please. There you go. So, the concept that we wanted to discuss today, is how we select approaches. And when do we do transcranial? When do we do endonasal? And we select this approaches based on, basically the anatomical location of the tumor. That is the most important factor. There are other factors; sometimes patient's age, symptoms, of course, expertise of the surgeon, but anatomical location is a key factor. When we look at how to categorize approaches, I look at Lawton of course, we all look at Dr. Lawton as a unique example of mastery and expertise. And his seven series and how the content of the seven series has impacted the field. Why? Because seven is the limit one we can remember rather easily. So do we have seven skull-based approaches as we were thinking? And as I was thinking about it, I thought, yes, we can probably talk about seven skull base approaches but I would think for a skull base in particular is more like six plus one, because there is one approach that is the endoscopic endonasal approach. That as you know, can be used instead, or in addition to other six approaches and the weight of the endonasal approach or is as heavy as the other six approaches together. So for the contemporary skull-based surgeon, we really do have to master endoscopic endonasal surgery. But of course, we need to keep up with the tradition of these six skull base approaches. You can add more, of course, but this six are, I think, basic ones and there are multiple balance within each approach, but this is what we all need to understand and master too. And often I have fellows come into my lab, and wanting to learn endoscopic endonasal surgery, of course, but I always emphasize that it's very important to first understand, master well those traditional skull base approaches. First we need to establish our traditional approaches then we need to move into endoscopic endonasal surgery. Then we'll be able to select what we think is best in our practice and for our patients. So, I'm gonna cover different areas, each approach. We gonna start with the Cribriform Region and Frontal Sinus area. We're gonna go from the front to the back, reviewing the skull-based approaches. So, here we can use both an endonasal transcribriform approach or a subfrontal transbasal approach. So, for tumors like these for example, these large Olfactory Groove Meningeoma. What should we do, endonasal or transcranial? There has been a controversial topic for a long time. And I can tell you that my opinion on this has shifted over the years. In general, we look at two aspects. One, what is the sense of smell of the patient? Is it preserved or not? Because if you do an endonasal approach, the sense of the smell will be compromised, certainly, while if you do open, you have a chance of preserving it. Not a very high chance if there's a lot of tumor, but a good chance if it's a smaller tumor. And then we'll look at the lateral extension of the tumor. Is the tumor still too lateral? Like this one. This is beyond the reach of an endonasal approach. And you're gonna leave residual tumor when you do an endonasal approach. That's another very important consideration. So, in these cases, if we compare them, so this large one with lateral extension, I'm gonna do a subfrontal transbasal approach. And I'll show you how I like to do that. But in this approach in the middle, and you see the nice, critical flap reconstruction. It is a complete tumor resection, I even resected the skull base. So it's an aggressive approach in terms of resection and really very effective. Then for this one, this is a medium size with a meningeoma. It has many tumors. We have a lot of tissue changes here, swelling in the brain. Has no sense of smell pre-op, it's completely gone. So this is when I would consider doing endonasal. The reconstruction is large, but it's not too large. This here, you see the nice septal flap reconstruction. This is a case that I think I could still do endonasally, but when they are smaller than this, usually the sense of smell is preserved. So, I would go open, sometimes through an eyebrow approach, perhaps. When they are larger, I think they are too large for endonasal. And I do not really like, I've tried before the two stage concept of going endonasal first then open or even two endonasal stages for the tumor to just collapse. I just think it's too much hassle. And I think in my opinion, for my business's best to just get it done in one operation, in one day you take all tumor out. And if you do a good skull base approach, and I like to do this modified subfrontal approach, and at this nicely fashion for that approach that I actually learned from James Liu, many years ago. It's a beautiful approach. This osteotomies go along the rim of the orbit or suborbital rim and then goes down to the frontonasal suture and then goes up all the other way. And this puts you right on the skull base. You look at this craniotomy here, you see the rim is not even removed, I just cut above the rim, but this follows the content of the middle of orbit frontonasal suture, in the other middle orbit, and then above remagen. The beauty of this, of course, for these, you need to learn how to do this kind of through the anterior tibial the frontal sinus into the postural table, we would just have bit blind. So you have to use an osteotome or you can use a thin drill, then you're fracture it. The beauty of this, is that you get right on the skull base and I can get crista galli at the beginning. I can detach the factory sulcus, I can coagulate the , I am all directly on the skull base here. So I have to manipulate no brain to access the skull base or the tumor. And that is, I think so important because one of the arguments in favor of endonasal was to minimize brain manipulation. But if you do a proper, a good skull-based approach, like this one, your brain manipulation is gonna be minimal and therefore the outcome is not gonna be very good for patients. Now that being said, there are some extreme cases where I do have to combine both endonasal and open at the same time. And relatively often for sinonasal malignancies is that happens when they are large. This is an extreme case, really large STC neuroblastoma. And this one you really need to combine both. You have to do endonasal and you have to do open. And what I wanna illustrate here is how the endonasal approach is really helps you get the most difficult part of the tumor, which is the posterior attachment. Just at the level of tuberculum sellae, optic canals, I can do all that work in the endonasally. And then I do all the dissection from the frontal lobe superiorly, and then I bring the tumor down and I can desegregate it completely. And I can follow my negative margins, both open and endonasally. So, don't hesitate to combine approaches when it's needed, especially for large tumors, such as this one, there are many you can do just endonasally, but once they have larger extension intracranial, you wanna make sure you get negative margins. And in that case, you can add actually autonomy to the approach and achieve the goals of surgery. A case like this with such a larger construction, actually this patient had a significant complication from an postop because this pedicle flub was not enough. This is a huge defect, but jumped very early on in drop, make microvascular eyes flap from the forearm. And this was a successful reconstruction with a very good outcome afterwards. Let's go to next. Now, there are some cases that we can do only endonasally. And this for example is a case of a young patient. You can see there was a loose, like a dermal tumor, we were not sure, but there are some still very nice case that the endonasal approach clear from played is ideal. Here we are looking at CRISTA Galli right here, that I'm drilling. And then goes on each side and you start seeing here the contents of this, actually teratoma, and for this teratoma, or dermal teratoma you have to surround the capsule. And this is coming from the faux from the crista galli to the faux. So I'm cutting the faux anteriorly, and now I'm gonna cut the faux posteriorally. And you see the beauty of this is, I don't have to do any brain manipulation in this case. I don't have to do a craniotomy in a younger kid. I can just go endonasally. And we can preserve olfactory because we were in front of the olfactory fimbriae. And here we go into the teratoma, and start dissecting it of the brain tissue. And this angle of attack endonasally. It really is ideal for such a case. And you can work in the brain, as you see right here. You see the contents of these are typical of this teratomas. And I keep dissecting until I get a good superior plane with complete dissection. You can see nice resection of the whole tumor. And now we proceed with reconstruction where becomes quite easy in this situation. And in a case like this we have good, nice dura I can even put some stitches in there and close the dura, not completely watertight, but you know enough that we know that we know the reconstruction is gonna be very solid. Then we put a flap up and there's the reconstruction. This is a nice way of avoiding having to do a craniotomy, cranalization or the frontal sinuses, et cetera. We can do it all through an endonasal approach. And there are situations... Let's go to the next one, please. So there are situations where I actually have to also combine approaches, but in a minimally invasive way. This patient had this large encephalocele, there was also pine, a bit of the edge, but a lot on the front, was going too lateral and too high for me to just do endonasal. So we combine this way, transcaruncular approach. Is a medial transfer with an approach. Have a look and play the video, please. So in this case, when I use one nostril and one medial transcaruncular approach. This is going through the nasal cavity, union aerial. You see how the defect is very lateral. Now we go transorbital and we can combine both routes. So we use these with oculoplastics. So you have a nominal team here Stanford for oculoplastic surgery. Use an to break through the medial wall of the orbit. And this directly puts me into the eighth modal, front with modal junction and can use the ultrasonic Hospira to increase my exposure. And that way I can get now into the frontal recess of the frontal sinus. And I can remove effectively all that very large encephalocele. You see, I now I'm working, combining the view from the nasal cavity, with my access to the transorbital approach. And this is all transorbital, and there was actually a lot of encephalocele. And finally, I can find a defect. This is our defect right here. And as it usually happens, they're born with defect is much smaller, but you see, it was very lateral for me to get there endonasally only, it was not possible to get there. Then we defined it, put a little dura gen, put a phinicograt and you can solve the problem this way. So this person had no incisions in the face, because the transcaruncular approach has no incision in the eye, just inside the caruncular. And then just using the one nostril. Let's go to the next look. So that covers the anterior skull-based region let's move on more posteriorly to the planum sphenoidale to tuberculum sellae area. Here there are two mainly competing approaches and one is of course, endonasal. And the other one is the orbitofrontal or supraorbital. You can use an eyebrow incision. Through a small super orbital. You can do a bigger from the orbital, you can use behind the skull depending on the case, your preference, sellae, by the access is quite similar. When to do one or the other? So for me, I look at tuberculum sellae meningoma, in this tumors the attachment is based on the tuberculum and it doesn't extend like this one on top of the clinoid canal, if the attachment stays within the tuberculum here, here in this area, I know I can get all the attachment endonasal, even if extends laterally, I can bring the tumor on as long as the attachment doesn't extend laterally. However, this tumor with the attachment right here, I know that is not going to be good for my endonasal approach because I won't be able to reach on top of the nerve and bring the tumor down. So this tumor, tuberculum, in general with attachment is still in the tuberculum sellae area. For me in the nasal is ideal corridor because you don't have to manipulate the optic nerve, secondary compressible optic nerves. I think it's a very powerful approach. For tumors that are like these one extending more lateral. Again, I prefer to use a frontal orbital approach. And when we look at these tumors, in addition to the tumor extension, we need to look at where is the optic nerve, or what is the up the chasm. In a case like this, we know the optic nerve and gut is gonna be very thin out and is gonna be displaced posteriorly, superior and posterior, right? Tuberculum sella puts the tumor back. A case like this that is more Planum is gonna approach the tumor also posteriorly, but it's going to be right here. So the relationship of the tumor with the optic nerves is much easier. The risk of manipulation of the optical apparatus in this case is much lower than in this case. And therefore, I think endonasal has much more advantage on this case of tuberculum sellae meningeoma. So let's quickly play this video, of doing a frontal orbital approach, you can definitely do this with one eyebrow incision as you prefer, especially if the patient is bald, for example, is a great indication. But if not, you can put incision behind your hairline. I don't think it makes much of a difference. And I think this a bit bigger approach gives you the access to the whole skull base. Here we are cutting the falciform ligament. I can see the falx with a tumor it's also attached, so I can cut the falx here. Don't forget that the falx is often an area of residual tumor. So you wanna make sure you remove tumor from that area. And as you see here, I'm cutting the dura right on the bone. Digitally, I think it's been on for many years. You wanna do as aggressive resection as possible to prevent recurrence. So we cut the dura attachment. And you can see that as the optic nerve, and that is sort of olfactory nerve. You see how well we can identify the olfactory nerve and dissect it, and that's our optic nerve. And then we can remove extra dura that is covering the top of the optic canal and clinoid process, because it probably is involved here is again, touching all the dura on the falciform ligament and optic canal. And you get a very nice, complete resection in a case like this. But the difficulty comes when the tumor starts getting into the canal and underneath the optic apparatus, in that infrachasmatic space, that is always the most difficult part. And we can drill this skull base if we think there's some involvement. You can do such a nice, complete resection for a tumor just like this. And again, the difficulty is always this area here within the optic nerves. And you see this as a small craniotomy, it's all need for a case like this and for accomplishment of a good surgical resection. Let's go next, Luke. Now, play please. Opposite to this tumor on the planum, when we look at tuberculum sella meningeoma, this tumor sit, more posteriorly, in what we call the prechiasmatic sulcus. And as they grow, they're gonna push up tumor as you see there. They're gonna really stretch the optic apparatus posteriorly and to each side. And they're gonna have the stales towards the optic canals, usually both of them, sometimes more one than the other, but it can be both of them. And then the endonasal approach gives you this direct access to the tumor without having to manipulate it, see how it's stretched the optic apparatus is. So when you come from the top, transcaruncular approach, you have to work in these windows and definitely you can do it, but you see how stretched this optic nerve is here. So you do a kind of ectomy on one side, that's fine, but how we'll deal other side. You can cut the falciform ligament, but it still is gonna, you're at risk of injury in this control nerve tube. So this is why I think endonasal for these cases is ideal. Of course, if the tumor now extends in this area, then I tend to go open. But when the tumor stays in prechiasmatic sulcus region, I think endonasal is a better option. Always keeping in consideration these branches. We always think about the day one and day two on the AECOM, but don't forget the frontal lobe with all branches because these branches can look down and they are often touching the tumor or encasing the tumor. And they can be a source of major arterial bleeding during surgery. So be careful with those. A stroke on secondary to those branches is not that relevant, not very symptomatic, but bleeding can be troublesome. So be very mindful about those branches. Let's go to the next, Luke. Play, please. So this sample of tuberculum sella meningeoma is a large one, but it's still the attachment of the tumor remains at the tuberculum sellae prechiasmatic region. This patient has very poor vision. We notice he's not gonna recover one eye because he's been blind in one eye for quite a long time, but you see we're going endonasally. And I have this perfect visualization of all these neurovascular structures. And even this area that is so critical, the suprachiasmatic region, it has this small preferring branches from the AECOM complex, especially so-called Supracallosal artery. And that is key to preserve, if it goes to the septal region and it can cause a very symptomatic stroke, but also of course, you'll know the Supracallosal artery, we're bisecting them very carefully using arachnoid plane. And we have such an nice view on an access to all these neuro branches going endonasally. So you see how it's stretched the optical apparatus at the end. And we haven't touched it at all. We have decompressed both optic canals at the beginning. And I do think this approach in my experience, in my hands, in my practice, this is a better approach for these particular tumors. So then we have other tumors that I think also the endonasal approach can be of great advantage. This is a Type III Optic Nerve Sheath Meningeoma. Usually this Type III Meningeoma means that they grow outside of the optic canal into the system on the space. And these are the cases where I think endonasal has a lot to offer because we can, we normally do a wide decompression of the optic canal you see from the orbital apex, you will see in here, the whole optic canal has been exposed or with a apex of the cisterial segment, really well decompressed. But then I can open the dura. And I like to open the dura in this oblique fashion, towards the limbs of this sphenoid here in this direction. So I can fold the dura and I can see the optical apparatus. I can see the optic nerve follow it. I can see the opthalmic artery right here. This is my opthalmic artery, you're gonna see it right here and I can remove the tumor. I can open the optic canal with this red angle knife. This is one of the key instruments in our new set, the same with this straight dissector circled for dissection of these tumors. And I can keep trimming the dura, the optic canal. You can see again, the opthalmic artery here. And the opthalmic artery is gonna as you know, go and run on the floor on the dura floor of the optic canal. So be very careful, when you cut the dura to identify. That's why I'm using the doper here for, to identify where is that opthalmic artery going. And which you can see right here, this is the opthalmic artery running. The interdural segment of the ophthalmic artery. That is so important to remember. You see the beautiful resection, the optic nerve has been nicely decompressed and tumor has been removed from inside the canal. This is doing ICG visualization, overlay, white light. You can see the super hold pressure. So that's a nice resection, and patients can get better on their vision. Some others do not get better, but you might stop the progression of visual loss. And definitely you prevent the tumor extent towards the opposite side. And then you decide whether to do radiation or not. I tend to be quite conservative from recommending radiation because I worry about the risk of visual loss with radiation. Let's go to the next please, Luke. And also for this area, we have tumors that I wanna also show you, especially hypothalamic region. Here's one quick example. This patient present with this tumor you see here, it was thought to be a nongerminomatous germ cell tumor. So he was placed on real therapy, excuse me, on chemotherapy. With good response, but he had some residual tumor here and here. So the first team led by Dr. Grant did a phenomenal work, removing these pineal region tumor. This was a teratoma, but then we were left with this right here. And you cannot tell, but also there is some suspicious area here. This patient is panhyperbid. So how do you get to this hypothalamic table? What approach did you do? You either do an approach from here craniotomy. We can talk later about Transpetrosal cells. You can go this way or you go endonasal. So in my opinion, this ideal case for endonasal hypothalamic region tumors, when they're in the base of the hypothalamus, endonasal is the best. Especially if you do not have to worry about pituitary function, this patient has panhypopituitarism, he's not going to recover. So if I take the pituitary out of here, I have just such a direct exposure of this hypothalamic region, challenging place to always get into. So this was a matured teratoma that was left after chemotherapy. And you have to go after this with surgery. So you're gonna see, we're gonna take the pituitary gland because it's in our way, because he has some residual tumor and because this person has panhypopituitarism. So we dissect from the walls of the cellar, take the pituitary gland out. You see how loaded that optic chasm is. So I have to remove the dorsum sellar and I do the dorsum sellar, and I'm gonna take the postnatal clinoids, both of them. First, I disconnect them. That's one of those right angle knives, opening the dura of the dorsum cellar. This is one posterior clinoid, and this is the other postural clinoid. And once you take both of them, I have beautiful exposure of the system. I opened the lagnoid layers carefully, and you can see the tumor right there. You can see the basilar bifurcation, mammillary bodies, all these key peripheral vessels. I have a unique view and I have a unique access and this is something very cool because they can now follow what was left through the pituitary stock and dissect it through, what is called the nucleus of the hypothalamus away from the rest of the hypothalamic nuclei. And then, I'd have the optic track on each side. I do the supeal dissection. You see how I'm preserving the hypothalamic tissue that is surrounding the tumor. And I can remove this tumor entirely. While at the same time, I'm preserving everything around. Such a phenomenal exposure and approach, in this very challenging area, the hypothalamus. You see both hypothalamus here per serve. You see mammillary bodies, you see all the periphery in branches, basal bifurcation. This patient did really well after the operation with no deficits. Let's go to the next, Luke. And this is supposed to have this an intraop MRI. We're doing pediatric patients. And this post-op later on usually mammillary bodies here, and a complete tumor resection, optic apparatus here, and a really good outcome. So let's move on to another area. This area of the paracliniodal region middle cranial fossa cavernous sinus plus, minus Petrous apex. So most pathology in this area is definitely such a great work force for skull-based surgeons. And I do think that the extended middle fossa approach is such a powerful approach for many of the tumors in this area, but also is the endonasal transpterygoid approach, we can choose one or the other. And I think here, as you will see, is very much based on pathology, not exclusively, but pathology also dictates what we do to detect, it is the pattern of tumor extension or the pattern of tumor involvement of all the structures. So we here, we have two type of tumors, that are more or less the same size, both young patients, both symptomatic. First patient up here, 27 year old is presenting with abducens nerve palsy. Patient was referred to me from south America with this large tumor right here. This patient has something called Ollier disease, which is that this is disease where you tend to form chondromas and Chondrosarcoma. So this we suspect is of course, a Chondrosarcoma. You can see the involvement of their . What is the ideal approach for this one? So the question I asked myself is where is the carotid artery? Is it displaced lateral like this one. You can see where the carotid artery is in here. This no question. And endonasal approach the best in my hands for this one. However, these are their tumor. Also young patient, male patient, presents with trigeminal symptoms. This is the tumor, and you see this carotid artery. The carotid is displaced, medially. This is where the carotid is located. So how do I do this approach, endonasal? Yeah, I do have a window. It is possible through this way, but it may not have much chance. All these tumors are not ideal for endonasal. So we just go through a middle fossa approach. It makes much more sense. It's a beautiful, effective approach for a tumor, such as this one. This is the post-op, and this ended up being a hemangiopericytomata. It was quite vascular, but complete resection. You see her . Here it disappear. And now completely up here, this is not a cavernous sinus tumor. This tumor was not in the cavernous sinus. It was to make a microscope. And that's why you can do a complete tumor resection with no deficit other than some mild disease neuropathy. This is at chondrosarcoma, is this tumor in the cavernous sinus? We will see. Some of these tumors invade the cavernous sinus some of those displays the cavernous sinus. So this patient, again, presents with seasonal palsy. Usually the ceratoid displays lateral. Always I'm concerned about these cases, they're related with the carotid artery. So here we're doing the transcaruncular approach. So important to understand the different steps. This is going the sphenoid process of the paratid bone expose first the palatovomer artery, not so important, but then we see this very important artery, palatosphenoidal artery, right here. Why is it important? Because if coagulated and do suprasupeal dissection, I really identify canal and the median nerve, that is the way to either... And then I follow the pterygosphen fissure. What is the pterygosphen fissure? Is between the floor of this phenoid and the bone. And I follow them, and as I follow them, I get to the formula serum. So that's the middle clinoid we're removing, exposing the whole chloroform from granola space down to formula serum. And then you see beautiful, we have a Pterygophen fissure here, in the medium canal. Some of the dissections done by our fellows in the lab. And then we dissect that fissure and I transect that fissure I cut it, and that gives the fairly, it gives me access to the foramen serum where the chondrosarcoma sits. So with this maneuver, I can identify the carotid artery in the foramen serum, it's very displaced, but that's where it's anchored. So I'm gonna find it. And once you have the carotid control, inferiorly and posteriorly I can go into the tumor, remove all the tumor, the is displaced up, it's not invaded. You saw this is the member of the cavernous sinus up here. And then I can get all the way to the pterygosphen fissure. You see this is a beautiful view of the fissure right here. And you see this is the fissure right in here. And then I have Pterygosphen one-on-one side, carotid one on the other, I can drill it extensively, get negative margins and get an extra resection of the tumor. And this patient that are presented with 6th nerve palsy, I know, she has now recovered. I do not recommend radiation postop for a case like this, complete resection with one, actually was at great two, I believe, but a low-key at 67, no radiation. Let's go to the next one, please. When I had this case recently, I thought this was a chondrosarcoma but it happened to be hypervascular. And because of that being hypervascular, I thought, should I then do open and not endonasal? Because I like to do... I've done a lot of Chondrosarcoma via endonasal approach. There are, you know, some of them huge insights, but you follow the tumor, you can bring it down, but this one, there was something unusual about it. So let's go for the next one, please. So I just had to do an open approach for this one, because he was hypervascular. And chondosarcomas are not supposed to be hypervascular. So some people were saying meningeoma, I didn't think this was a meningeoma. So I did a middle fossa approach, and as you see here and that's exposing the superior with the fissure, that is anterior clinoid, peeling the dura with the middle fossa. And I start exposing the tumor underneath. And you need to take your time to carefully expose this that's opening foramen , exposing the ESPN, and I keep dissecting the whole tumor extra durally. This is an extra dural tumor. And you know, I got the dura posteriorly and superiorly. So I try to surround the tumor as much as possible. And then I decide, okay, I'm gonna enter the tumor, let's see what this is. And once I open it started bleeding like crazy. So this became very clear, this was a hemangioma. And hemangioma is obviously a vascular tumor. You cannot remove them in a piecemeal fashion. You cannot debulk these tumors. You have to do a complete extracapsular dissection. You need to surround the tumor completely. So that increases the challenge of the case in a very significant way, especially when it's this big. So I had to go around the tumor completely. You can see the carotid artery right here, in the cavernous sinus. So I'm coagulating the branches from the carotid artery, cutting the tumor off the carotid artery. I cut . Now, I'm gonna try to find the third nerve to show it briefly here. This is the tumor going into the cavernous sinus where the tumor appears to arise from. And then that is the or third nerve is up here, superiorly some of the bleeding coming from the middle or the cavernous sinus. And then this is the petrous apex here. And what the . And there is tumor going to the pterygosphen fissure underneath. That's why I thought it was a chondrosarcoma. It was expanding the pterygosphen fissure, but hemangioma apparently can do that too. So I had to drill that pterygosphen to get underneath and detach the tumor, and finally get it all completely. This patient had a complete 6th nerve palsy. I found the 6th nerve at the end, and it was dissected. I was not able to save the 6th nerve, it was so thin out that I could not differentiate the 6th nerve. But all of the coronary nerves are basically intact, perhaps some of the V1 fibers could be some partial damage, but the patient has a good Cornell reflux. So that's good. And this is the post-op of the patient with a complete tumor resection, really a curve ball in this case, because you go thinking you're gonna do a debunking and it's gonna be relatively straightforward, but you have to actually do a complete extracapsular resection. Let's go to the next, please Luke. Now, if we move into meningeoma in this area, you know, meningeoma in this area, most of the time in my experience, I do them open, not endonasal, but there are some exceptions. This is the classic view of meningeoma. Is the clinoid process, the optic nerve tissue is extremely invading the canal right here. So for these, obviously with do an open approach, until . In this other case here, you see this tumor is different. It should be middle fossa, but is involving the bone. So it's a kind of meningeoma extending to the middle fossa and cavernous sinus. So this one, I'm going to do through an endonasal approach as I will show you. So this is the anterior clinoid meningeoma, and let let's play the video please, Luke. And I do think is so important that we know how to do this extra doodle and telekinetic cases in the proper way. So just going all next to doodle. And as you just saw in the previous case, you know, we go to the middle fossa, I think in the middle meningeal, we dissect the whole nerve, take the clinoid out, supraorbital fissure, this is the process. And we do all this in a fashion. As we take the clinoid out, we do a complete optic canal decompression. Optic nerve decompression, and very important for these cases is we expose the carotid space. And that is very important because we always worry about what is the carotid sometimes in case. So we can find it early on in the clinoid space. Then I know where the distal ring is. I can cut tangential to the distal ring and the falciform ligament as we're doing right here. And that is gonna expose early in the operation, the two most important structures, the optic nerve and the carotid artery. And once I have both, the rest becomes easier. So here you see the optic nerve going this direction. And I'm cutting from the falciform ligament towards the distal ring. So I know the carotid is gonna be right here. And once I have the carotid, which you see right here, I can continue dissecting the tumor. The next thing I'm gonna have here is the third nerve and the Oklahoma triangle, which is the next part I need to detach. As you see here, I haven't seen any brain yet. I'm looking directly at the brainstem, there is the third nerve here. And what I'm going to do here is, there's the Oklahoma triangle. I'm gonna cut the dura of the Oklahoma triangle in particular the pterygosphen ligament to detach the tumor. And you see happens in the brain, but this is the tumor has been all completely removed. I'm just taking the last piece of tumor, at the Oklahoma triangle, you see third nerve right here, and this is mostly an extra dual approach. And this patient had, as you see here, a lot of swelling in the brain, but by not touching the brain, barely attaching it and doing this as an extradural approach, you know, that brain is gonna recover so much better. So don't forget, I think a tumor like this defines a skull-based surgeon. If you do this approach like a skull-based surgeon, you're gonna come to the skull base first, and from here, take the tumor in this direction. If you're not a properly trained skull-based surgeon, you're gonna do the classic way coming from the brain, opening the CBM fissure, retract the brain and go from the tumor towards the optic canal and clinoid. I think that's a mistake. I don't think that's the right way of doing these cases. You're gonna do it through the skull base to get better visual outcomes, better brain outcomes. Okay, let's go to the next one, please Luke. And then we have this case that, this two Luke, have videos, you can play them. Of the pre-op imaging, and you can see the location of this tumor is involved in the meningeoma, and you can see where it sits. So this patient, one of the reasons we operated on these case is because we have evidence that tumor had grown quite fast. We have previous imaging with a tiny little tumor here, and, you know, less than a year later, the tumor had really become much larger. So it became really, we had to do surgery for them. So actually we did the biopsy first and it was a great WHO II meningeoma. So let's go to the next one please, Luke. We plan embolization of the IMaX is running. That's an important consideration, when I'm going endonasally or transmaxillary into the Terriopath fossa, and it's a temporal fossa. I worry about the IMaX because it's sometimes very lateral for me to reach it. And it's a very easy target for embolization. That's an area where I like to embolize the IMaX. Of course I do that for JNS, no question about it, but also for some other tumors in the infant temporal fossa. So you look, we're going in the nasal. This is the Vivian canal that is all full of tumor. And I'm exposing again, as you saw before, this is particular approach is deviant canal being transected. And this is a fissure here. You are seeing the carotid and I'm in the search now for V2 and V3. I like to do this transpositional in the terriod part in fossa to get more space. And again, this is the whole filament serum, here being exposed, which is key to the move into the middle fossa, this is V3. I'm going down, that was V2. So you can see now the dura of the middle cranial fossa. So I'm working into the anterolateral triangle of the skull base, between V2 and V3, okay? So B2 here, B3 here. So I'm working between both. And taking all the tumor in this area. And again, let me show you, this is V2, this is V3. So Michael's case is in this area and I've worked in between working laterally and I've removed the tumor in this area and actually even drill part of it all the way to the Petrous apex here, just in front of Michael's case. And this way we've gonna complete tumor resection, or maybe there's a microscopic disease, but mostly complete tumor resection. Go to the next one please, Luke. This actually resulted in three, not even two, and then we did radiation for these patients, definitely indicated. And the nice thing is that the patient did very well. No side effects from the operation. And it's an elderly patient with Parkinson's disease. He would tolerate this approach in my opinion, much better than doing a middle fossa approach for this particular tumor. Thanks Luke, let's go to the next one. And then we have, you know, also this type of aggressive meningeoma that extend to multiple compartments. This patient imaging here, this is an MRI done for trigeminal neuroglia about two years before, actually 18 months before. It was read as negative, but you know, you expect to have something here in the cavernous sinus. And look what that thing here became, this is the tumor in the cavernous sinus that has exploded growing into the middle fossa growing into the postural fossa. This is the epicenter of the tumor. So can we do this case endonasally, I assume we do endonasally. I mean, you have here in the . But in my opinion, in my hands, I prefer to do this open and both of these approach. And in this case, we had the . This patient is very symptomatic. Please play the video Luke. And because he's very symptomatic, he may have to mean to go into the cavernous sinus. So he has both Trigeminal neuropathy and 6th nerve palsy. And in this case I just have to be aggressive into the tumor resection because I know this is an aggressive tumor that in just 18 months has really, you know, grown a lot. So you saw the steps of the same as you saw before, GSPN is dissected, petrous apex is exposed, anterior is done. You can see the roof of the cavernous sinus full of tumor, now in the petrous apex. This is the petrous apex here that is being drilled. And this allows me to go underneath V3, underneath posterior to five, follow going through into posterior five go underneath. And this really allows me to open the door of the posterior fossa, as we said, underneath the trigeminal nerve and get all the tumor in the posterior fossa. And then we're cutting the tentorium, joining both the supra into the internal aspects of the exposure, cutting the suprasupeal sinus, the 4th nerve will find at the end. And you actually see through the arachnoid, that's the 4th nerve right there. And this is a five, that we're following. And for these case, as we said, I'm going into the cavernous sinus. I have the carotid, I know is displaced medially. I worry about six. So I follow five, so V1. And if I look medial, that's what I find the 6th nerve, medial to the virus of V1. And I use the Doppler of course, to map the course of the carotid and try to do as aggressive resection as possible. Go to the next one, please. At the end, we left, just side of the tumor with this posterior carotid cavernous sinus, you know, stuck to the carotid. As you know, meningeoma are different pathology. They often have such an intimate, exclusive relationship to the carotid that is difficult to do a complete clean resection. But this an excellent resection of all the other areas because of the being a great tool. This patient was also sent for radiotherapy. Now as you've seen, we cover, you know, anterior scope is all the way to the middle fossa. Now let's talk about this other three approaches that involve mostly the posterior skull-based or the patient with all the tumors at the posterior skull-based. And we're talking about combined transpetrosal, the retro sigmoid with a different variance and extreme far lateral. Versus or in addition to combine with an endonasal approach. So here you have three tumor that are relatively small in size. And it is one of the most fascinating exercises with assertiveness is choose approach. You know, what is our strategy? What approach are we gonna use? And these cases are different, and there are different subtleties within them that made me use a different approach for each of these tumors. And if you see the first one, as you will see, I'm not sure this getting more and more detail, the longest of the tumor is like this. And I thought, should I go in the nasal this way? But I thought I can also go supracerebellar, you know, right here. And I also, I have the long axis to the tumor, and that's what I did, supracerebellar transtentorial for this case. And it was a great choice as you will see. Then how about this one, this tumor you can do a retro sigmoid simply, right? But as I'll saw you, this was a redo, recurrence. This tumor was very stuck to the brainstem. And I don't have a good visualization of this side of the brainstem right here. So I chose doing a transpetrosal approach for this one. And then this one here, you look, this is the interface of the tumor with the brainstem. So retro sigmoid, definitely not a good idea to go there. I don't have good visualization at all. I could do transpetrosal, but that's what this patient had years before. And I worry about all this skull tissue I'm gonna find in my way, and still, I'm not sure I'm gonna have such a great view of all these areas, the basilar. So I decided, okay, it looks tight, but I'm gonna do an endonasal approach like this. Within the carotid endovascular, as you will see, I have space and the most important thing, I have excellent view of this brain. And that's why I chose an endonasal approach for this particular one. So let's go for the first one. Let's play the video. This is Dada, he'd actually ended up being . He was sent to me also from central America with the diagnosis of meningeoma. But I thought this is not meningeoma, this tumor does have the dura attachments. This tumor had been radiated twice and it had grown and it had more and more swelling in the brainstem. So what this tumor ended up being is a trochlear schwannoma. And as you will see, I'm gonna find the 4th nerve, right here, and I can see the forth nerve, I'm cutting it right now. The forth nerve just becomes a tumor. So this is no question. I'm going to present a velour. And then you see that was the brainstem. What I'm seeing here is the third nerve and the PCA above the third nerve. And you can see the beautiful view of this is gonna... Petrous apex is here, supracerebellar, tentorium. And I can see all the way to the third nerve, entering the cavernous sinus. And this is my resection near, complete resection along the long axis of the tumor in a patient that did very well. I think that was the right choice for this case. Definitely endonasal could have not been a good choice for this, go to the next one please, Luke. So this is a case, you know, someone else did, this going retro sigmoid, is not an easy tumor to do. He had unfortunately, severe neuropathy post-op, and he was left with this tumor, probably because it was very stuck to the brainstem, very stuck to the trigeminal nerve. So when the patient came to me, I just say, okay, we're gonna watch it. You just had an operation, they did a good decompression. That's fine. But the tumor actually grew in just six months, increased in size. And not only that, but the brainstem here had increased swelling and the patient had worsening attacks here. So I said, well, it's time for another operation, unfortunately, but I think if they had so much trouble, retro sigmoid before, I might have the same trouble, so why don't we do, you know, a different approach. So we'll do a combined transpetrosal approach for this case. And this is what we did. Combined the petrosal approach and please take a look. And it really work, you know, very well. It's a relatively small tumor, which makes the operation more enjoyable because it's not that long. So first I'm doing the middle fossa approach. You see that the B3, now we have our neurotology team doing a beautiful mastoidectomy. This patient no hidden before surgery. That is a no-brainer, that makes the combined hospital even a better choice because you can drill through the opened internal acoustic analogy. You can drill through the inner ear. You don't have to worry about it. And then I have beautiful exposure. It puts me right on the spot on where the tumor is. I'm cutting above from below the tent lagging in the superior petrosal sinus, very important to preserve this veins, the best you can. And then I can cut the tent, remove the tentorium, and then I'm looking at the tumor right on. So a tumor that before endonasal procedure was very far away with no good planes that I can identify. Now I'm super close to the tumor because of the drain of the petrous bone, I can identify the fifth nerve, which is actually really stretched by the tumor. And I can go direct to the bottom of the tumor, right on the Petrous bone. I can find the Batchelor, I can detach it from the Petrous bone. I can detach it from the brainstem because I can see beautiful interface between brainstem and tumor. And that, you know, really allows me to do a complete tumor resection on this case. Even I can see the attachment, remove the dura, coagulate it. And at the end of the resection, rheumatoid reconstruction is really important. These are vascularized flap, posteriorly pedicle, and the fat flaps to fill up the empty space. And this was ultimately a patient that did very well. Some partial postop, but he recovered completely after surgery. Let's go to the next please. You can see the nice resection for this recurrent meningeoma. And this one, this was a really ugly case because it was an atypical meningeoma, combined the total approach very well done years before, like 10 years before. And this tumor with this dark area, a lot of brainstem swelling. And again, the tumor is stuck from the front. So as you saw there, I have three portals both through the nostrils, one through the transaxillary approach. And we're not contralateral transvascular approach to get more lateral access. And I wasn't sure this was gonna be a great idea, but it ended up being actually a good idea. You know, this is the Vascular right here, and I have the carotid here. So that's my window, between vascular and carotid. And the beautiful thing of this approach is that I have direct visualization of the brainstem interface right here, which is a terrible interface. I can do ICU also and see the periphery vessels that I worry much about. And I was able to do a very good resection, not complete by any means that is this ream of tumor that is stuck to the brainstem surface that I cannot take without injuring those periphery vessels. But a good decompression clinical improvement on this patient. He had a recurrence later on, because of , we had to do a retro sigmoid approach for some of the tumor burden that went posterior sellae. But we solved the problem at that point, I think in a very satisfactory way. So yeah, those are different cases, but Petroclival meningeoma in particular, probably they serve a whole new set new webinar, right. But briefly just wanna make a few comments on petroclival meningeoma. These are such fascinating tumors. One of the most difficult we do as surgeons. And the options are several. Basically combined petrosal vessel retro sigmoid with different variations versus endonasal. I'm asked often how about endonasal approach for petroclival meningeoma and I've done a quite number of those. The ideal meningeoma for endonasal is the one that is purely clival or predominantly clival. This one, the incision of this tumor goes from here to here. This is excellent for endonasal approach. Especially considering it's an older patient. A combined transpetrosal is an option for this. You see, look at the brainstem surface here and it's here. So I do think endonasal is superior for this case. A case like this, well, this is a no-brainer, endonasal, you know, you could do it, it's possible, but you know, there is no need for that. I think you can do in this case. And I prefer a retro sigmoid, why? Because it's an elderly patient with what I think is a very slow growing tumor. The patient is not very symptomatic, has ataxia, but not that symptomatic. That is middle fossa, I know, but I can leave that disease. I can do a quick retro sigmoid, do an nice resection, decompress the brainstem, that's all this patient is going to need. So the goals of surgery are so important in this case too. However, this other one, this is a 47 year old only, she's young. And she presented with a lot of symptoms, which tells me this tumor has grown quite rapidly. And you see it's very ugly extends to the middle fossa, of course, to the posterior fossa, but also has a lot of potential extension is a tall tumor. So this is not good for retro sigmoid in my hands. There is too much middle fossa extension, too high, quite vascular, I worry about this retro sigmoid only. Can I do this endonasal? Yes, I can do this endonasal. I can do a lot of work endonasallly, is possible. And I've done cases like this, perhaps not with such large, middle fossa but, not good for endonasal. I think I wanna go for all the tumor as possible or as much as possible. I'm gonna do a combined Transpetrosal for this particular case. Let's play the video please Luke. So when a tumor is this large, and the goals of surgery society is a complete or near complete resection, I think combined transpetrosal is the best option. And if you're lucky, as we were in this case, the tumor was relatively soft. Then you can do a phenomenal work with this approach. Just to review, you know, the concept is to combine both posterior and anterior petrosectomy. In this case, the hearing is intact. So we're gonna preserve the hearing. We're gonna leave the island of the cochlear elaborate in bones intact. We start with a pedicle flap, so important for reconstruction and good exposure. You wanna have your landmarks well, laid up. I like to do this with a craniotomy first. I think it expedites the case, I think it's quicker. They'll leave the marks for our colleagues that really master it masterfully. I'm so lucky to have a phenomenal group of neurotologists at Stanford, really superb, because not only are they good, but they're quick. And it's important to be quick in this operation because they become too long. And then you start taking tumor, you know, late in the afternoon, you don't want that. You wanna start taking tumor early afternoon the latest. And here we are combining now with the middle fossa approach. I really like to have a good middle fossa exposure. I know you can do this smaller, but I do like to have a lot of good mobilization of the temporal lobe to feel that the temple is really free and not really putting a lot of tension on it when I'm working. Often, we consider, should we do this into stages? So we do it in one stage? Whenever it is possible, I like to do it in one stage, but for whatever reason, if the approach is taking very long and we're gonna start taking tumor very late, I might consider, you know, closing and bringing the patient back the next day to start a tumor resection early on. But whenever possible, I like to do it all at once, even if it's a late case. So here we are drilling the petrous apex and we know we're gonna be opening the interlocutory canal. This part, I think it's very important to identify the nerves in the canal. We're opening the dura on the middle fossa, sorry, on posterior, Oklahoma triangle. We can see that seven and eight complex is starting to separate one from the other, malware lagging in the sinus again. We open the dura in the middle of canal fossa. We can cut it a tentorium. Add tend to our brackets are gonna cam and coagulate them there. Of course, careful with the fourth nerve as you going into that area. The good news with anterior that is quite vascular like this is that they are often softer. I'm identifying now the trigeminal nerve, I always wanted into the trigeminal nerve early on and then follow it into the middle fossa and cut the dura ring of Merkel's cave. So I come free up with trigeminal nerve from the posterior fossa into the middle fossa, and then I can follow the tumor along. And once I started moving tumor away from five, I started looking at the Petroclival junction, and I think about six nerves going toward the canal. So I again, this is five right here. This is where six is going to be. We have a little bit of six exposed right there. And now working below five, at both seven and eight, looking at the brainstem interface, this patient thankfully had a good interface with the brainstem. That is good arachnid plane preservation, not like the other case that we had before. And that allows me to once I did bulk and I do some arachnoid dissection the tumor will come out really nicely, and at the end, you have this gorgeous view of cameras from three, five, seven, eight, down to lower canal nerves here. That's the cochlear bone intact. And this is a near complete resection in a patient that actually had a very good recovery. As you see, she's still suffering from trigeminal neuropathy. Let's go to the next one please. But no other no electron deficit, a backseat up all that much improved on it for a shunt. So actually it really, really, really without grunting. Okay, let's finalize because this is getting too long, I know. And just a few words on the lower clival region from a Magnum, a lower clivus. So two case examples. Again, we could spend another hour on talking on tumors in this area, but two quick concepts is, I like to look at these tumors. And are they above or below the foramen Magnum? So obviously this tumor here is above the foramen magnum. It is probably called a lower clival tumor. These for me, as I look at this is ideal for endonasal. It's not an easy case, these are difficult cases, but I think they are superior than retro sigmoid far lateral combined approach. Because you have bilateral access you don't have lower clival nerves in your way, they are are all outside. You don't have the vessels in your way, they are outside. You have excellent access right there. These are the case here. You know, you look at the foramen Magnum and you know, I have, you know, more than half of the tumor below the filament Magnum, can I do it endonasal, is it possible? Yes, it is. And I actually thought about this patient doing endonasal, but I decided not to do it endonasal. You know, I would have to drill this, which is fine, a typical advantage. You can drill this and it's still not causing stability, but I thought, you know, it's low. And the real benefit of the endonasal approach here as it happened with the optic nerves on the infra-cosmetic space, the real benefit of endonasal approach here is minimize manipulation of the lower cranial nerves. And that really has a role when we are on the lower Kleiber's here, not here, because if this tumor is gonna be below the lower nerve, the lower nerves are gonna be up here. They're not gonna be my way, this is 12 right here. So I'm gonna do the low nerves, yes, but I can work below them. And they are not at risk or they are not at significant risk. However, here, I think there are at very high risk. If you go from a lateral approach and that's the rationale for me to do one approach versus the other. So this is the approach for this filament Magnum meningeoma. Yeah, it's small, but it's a young patient. I follow this patient for two years and the tumor had... Play the video please, Luke. The tumor had grown minimally. Yes, some growth, but the patient had this persistent neck pain. Oh, actually no video here, I'm sorry, proceed. So I use this incision that I copied from Dr. Bill Cowell. I often have done, you know, of course, as you know, your a hockey stick incision here, for better say, hockey stick incision will be something like this. And I like this incision a lot, but sometimes this is a very quick incision. This obligation, you need to center it on the a big process here that you see, where is it? Right here? And that's the epicenter of your approach. And that is where the artery is. And it is a quicker approach. And I think the problem is when the tumor goes through a C2, you start having difficulties getting low. But when the tumor is center in the filament Magnum, I think this oblique incision works really well for me. So here we are seeing, we are cutting, C1 sensory root, to get access to the tumor. We cut the ligament, the dented ligament, and we're taking the tumor. And I want you to pay attention to this artery here. So important because that's the posterior spinal artery right here, you have to preserve this artery because if you don't, the patient can get a stroke in the cord. And it could be a depleted stroke. This is a near complete or complete resection of this tumor, it was heavily calcified. I was very happy we did this endonasal and not open. I mean, open and not endonasal, sorry. Because it was very calcified. I would have a hard time, but it's true that endonasal, you have the benefit of these artery not being in your way. So it's something to consider. Let's go to the next one, please. And this is the post-op and this patient has been doing phenomenal with no symptoms whatsoever and no neck pain, which is amazing. This tumor do or can cause neck pain. This patient's her neck pain resolved after surgery. And I'm gonna end up finally with this case of this lower clival tumor, almost into the filament Magnum. I think this is where the endonasal is powerful. Again, because of the lower nerves. This tumor was unusual. 13 year old, not age for meningeoma. And you see eating into the bone like this, not clear dura tales, very dark in T2. Let's go to the next one please. As you will see very dark in T2, something was not right for meningeoma here, so we did a biopsy. The biopsy gave us the diagnosis of meningeal melanocytic cytoma. So surgery is a treatment for this case. You see there is disease here also. So what do we do here? I started, well, yeah, you certainly can do retro sigmoid here and go after this tumor and then go after this tumor too. But you know, here we have nerves and vessels, same here. And I didn't think it was a good idea. I thought let's get here. I'm going endonasal to remove all the tumor here. And then when I come retro sigmoid, and remove this tumor here, we'll do the operations apart. You know, actually within like a couple of months apart. So this is the endonasal approach, lower clivals we detached the . It's still important to expand your approach all the way lateral to the pterygosphen, just below the BDM canal. I can see here the pterygosphen fissure. Again, I'm gonna expose it. And this is important because I wanna see the formula serum. And that is the way for me to do the maximum width of my exposure, exposing the filament serum. That is what limits my exposure. So pterygosphenoidal fissure, pterygosphen median canal, always this constant triangle, this land mark very important. So drill the whole clivals, all the way down to filament Magnum. Look at the dura, it's all dark. This is typical of menengiocytoma. but then I opened. And the beauty of this is I don't have any structure in my way, I'm directly to the tumor. The vessels are around, the nerves are around, the brainstem is behind. This was extremely difficult tumor, it was so fibrous. And so you'll see that endonasally, we can do very fibrous tumors still the same as open. And the same as open is painful. You just need to deal with it. Very consistent, very meticulous, don't lose your temper. Just keep working, keep the bulk in piece by piece. It will be a long case, but if you're careful, it will be a successful case. You saw the sixth nerve was displaced on one side per serve. This is the ICA here. You can see the Vassar, this is the other sixth nerve here or lower nerves are gonna be just in this area, but laterally, we don't even see them. They are not in our way, they are not an issue. And this is the vascular of course, is concerning, you know, see how it stuck the tumors to the vascular. So very slowly, you always to split the tumor and split it as many times as you have to split it, right? But in this case, you start with the medial. So I have one team on each side of the vascular artery, and then I can gradually, and painfully, dissect this tumor, this is a vein, there are so-called inferior petrosal vein that I can take, is not an important vein at this level. And this is tumor extended lateral, I can get some of it. And the loaners are gonna be just behind this. This part of the tumor was a bit softer, thankfully, but all nerves you can see them down there. This is a loaner right here. So you can see the unique view that they endonasal approach has given me to the particular artery, and the interface. And this is sure incision in this case, because I need to decide when I stop, I had to leave a little bit of tumor stuck to the bachelor and to those peripheral branches. Just tiny pieces, but I think justified to prevent injuring those. But it's a near complete dissection of this tumor with an excellent outcome. ] No complications at all. Let's go to the next one, please. So this is the postop and you see complete resection of the stimulus samples, those are the bits that you maybe, if you wanted something here, then we went retro sigmoid, you can see the approach, and then we'll remove all the tumor from this area. Also difficult, very stuck to the facial nerve, but also almost complete resectioned with no deficit preserve hearing. And this 15 year old kid that came from out of state here to Stanford, had a very good outcome. He's intact, he went into radiation for this tumor, which is not that clear that it's beneficial, but there is a concern for tumor progression. But as he's juggling with this soccer ball around all these options, you know, it's the same thing we do with them with skull visually, it's all about trying to consider what you think is best for each particular case. We cannot be dogmatic about one approach or the other. We can not be narrow in our expertise. We need to expand our expertise to both endonasal and open approaches, because this is only to the benefit of our patients to try to get the best outcome, the best resection and the less morbidity. Thank you again, Aaron, for inviting me and for having me. It is my pleasure to service this time with you. Thank you.

- Juan Carlos, spectacular presentation. Do me a favor, Carlos, can you mute me when I'm talking and then I'll mute... Thank you for this piece. Okay, here is the start for after the presentation, Luke. Juan Carlos, beautiful, gorgeous videos, spectacular techniques, fun to watch, really fun to watch, and it demonstrates how important it is for you to be very comfortable with different approaches. So that you're really using the best approach now, rather than using your best expertise to approach tumor. Obviously one has to be careful in terms of using approaches that one is comfortable with it as well, in order to minimize the risk to the patient. May I please ask, what do you think is the future of skull-based surgery or are we just gonna get more minimally invasive? And are we just gonna be able to hopefully have a robot who helps us through the nose and even expand or reach further that way? Could you comment on that please?

- You know, the answer is I am not sure. I don't know what the future will bring us. I do think that the future for the younger generation is so important that they get trained on all approaches, especially endonasal and open, you need to combine both. In terms of the minimal invasiveness, I think it's important to be kind of less, less invasive, but I think that come with expertise as you become more comfortable with an approach, you can do it through a smaller corridors. You're comfortable working through smaller approaches, but at the beginning for the younger generation, I think it's good that they get comfortable first with the bigger approach, then make smaller as you come on and you have more expertise. I think it's also important to put in perspective the importance of less invasiveness. Certain less invasiveness is what? On the skin or on the bone flap, or is it on the brain and the vessels? To me, what is most important is that you are less invasive for brain and vessels than the size of your skull flap or the size of your bone flap. So I think that's another important concept to remember. And in terms of robotics, I really hope we could get a true robot, like a DaVinci that is good for minimal access or for the type of micro surgery of what we do. But I'm not sure how far away are we from that because really technically those small instruments, they are not there yet. They're not robotic at this point, but they will be. And I think we'll probably see that in the next 10, 20 years.

- Again, beautiful presentation Juan Carlos, really enjoyed it. Look forward to having you with us again soon. And again, thanks for all you do for neurosurgery.

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