Minimally Invasive Corridors to the Suprasellar Region: The Endonasal and Supraorbital Approaches

Gabriel Zada

May 23, 2022


- Colleagues and friends, thank you for joining us for another session of "The Virtual Operating Room." Our dear guest today is Dr. Gab Zada from USC Neurosurgery. I've known Gab for many years, and I can tell you that he is one of the truly most successful rising stars in neurosurgery. He's not only an incredible super surgeon, technically gifted, but also an incredible academician. He's on the editorial board of "Journal of Neurosurgery" and at the same time very prolific. I can hardly know an issue of "The Journal" without having a very impactful publication from him. A very busy neurosurgeon, is in fact the director of the Brain Tumor Center. He's the director of skull-based surgery and a tenured professor at USC. Gab, I have been following your career for the time you were resident, and I cannot be more proud from your incredible accomplishments and many more that I would like to witness, and without a question, you will be an incredible legacy to neurosurgery in general. So with that, I'd like to learn from you today. I know you're gonna talk to us about operative corridors to the suprasellar region, something that is very complex. The anatomy there is fertile, you know, plenty of what we call controversy there and I know you have huge experience there. So take it away, and I look forward to it.

- Excellent. Thank you so much, Dr. Cohen-Gadol, for having me. It's quite an honor. You mentioned the word legacy and as I've told you this, "The Neurosurgical Atlas" is going to be one of the most unique and longest lasting legacies that I think have been left in our field thus far, and so just trying to follow in in your footsteps, Aaron.

- That's very kind. Please go ahead.

- Okay, so I thought today we'd talk a little about approaches to the suprasellar region. There are so many options available, and these are evolving all the time, especially in the last few decades. So wanted to review the current catalog of surgical techniques for anterior skull-based pathology, but mostly focusing on the suprasellar region. Talk a little about endoscopy, but also about the role of craniotomy and keyhole craniotomy and what some of the differences are about endonasal versus more traditional craniotomies for suprasellar cisternal exposure, and then talk about some of the most commonly used approaches for lesions of this region. It's pretty amazing when we look at the evolution of endoscopy going back about a century now and some of the key players and the evolution of our technology going from people like Walter Dandy to Harold Hopkins and then out of our own shop here at USC in 1977 was one of the first reported uses of the use of the angled endoscope, and you can see even in the first figure here, there're looking into the suprasellar region right here with an angled lens, a practice that we still use today, as well as some roles for aneurysm surgery and spine surgery, and then of course the first purely endoscopic approach for a pituitary tumor, now over a quarter of a century old in 1996 out of the Pittsburgh team, of course, where a lot of this was developed. So on the left we're seeing one of the oldest known videos of endoscopy by Professor Guiot in the early 1960s via a transphenoidal speculum-based approach, and you'll see shortly on the right, a more modern endoscopic video of a transclival surgery for chordoma, and you can see how much evolution has taken place in the optical technology and the instrumentation and the panoramic views and illumination, and this will only continue moving forward. So we've come a long way in this time, and just to show you this transclival procedure as well. Okay, well, using minimally invasive techniques and the endoscope, we're now able to gain access really to all aspects of the skull base, 360 degrees as well as to the subcortical space and intraventricular region, and in our adult practice in Los Angeles at the University of Southern California, this has really lent itself to developing a practice, and about half of my practice is now endoscopic or minimally invasive. You can see how it's broken down here among some of the categories, with traditional intraventricular channel neuro-endoscopy, endonasal procedures, endoscopic assisted keyhole craniotomy, and port-based approaches, which are really the latest addition to this. So we treat about half of our patients with brain tumors with minimally invasive approaches, and just talk a little about the endoscopic, endonasal approaches. Of course, over the last several decades, we've developed the ability to gain access really to the entire midline skull base going along the anterior skull base back to the sella and then down the clivus to the upper cervical spine. So all of these are now within our reach via extended or to the pituitary gland itself, direct approaches, and also a variety of lateral transpterygoid, transmaxillary approaches that can get us to a variety of parasellar and middle fossa pathology, and what's important here is we maintain the principles of skull-based surgery, which include bony removal to provide adequate exposure, avoiding brain retraction, and focusing on two-handed microdissection and of course, reconstruction. The direct approach to the sella is used mostly for pituitary adenomas, occasional Rathke cleft cysts, and many centers are now routinely performing full endoscopic surgery for Cushing's tumors. We still focus on capsular approaches, so not that much new as far as what's going on here. For this talk, I wanted to focus more on the suprasellar region and some of those nuances, and here you're seeing an extracapsular removal of a ACTH secreting pituitary adenoma, and we can go on to the next slide please. So, fortunately, even pituitary adenomas that are macroadenomas or giant adenomas rarely require an extended approach. Only about 15% of our pituitary tumors undergo an extended approach, and that's for a variety of reasons. It's usually because the aperture of the diaphragmic sella is widened, and so you can get this suprasellar component to descend, and the consistency of pituitary tumors really lends themselves to being removed just via direct sellar approach. So only in rare circumstances do we need to do an extended approach. When you see the arachnoid descend into the sella in a macroadenoma case, it means you've most likely done a good job of decompressing the suprasellar cistern and the optic apparatus, and you can be fairly confident that you've removed that suprasellar component. Next slide, please, and even when you have tumors that have almost finger-like projection into the suprasellar cistern and compression of the optic chiasm and optic nerves, you still don't that necessarily need an extended approach. Here we've done a direct approach and we're using a 30 degree angled scope to look upwards and make sure that we've removed this suprasellar component right in this area that's compressing the chiasm and right optic nerve, and so the angled endoscope really lends itself to removing some of the pituitary tumors that grow into adjacent anatomical components without the need for an extended approach. Next slide please. We can usually preserve pituitary gland function fairly well, especially when you see where the gland is located ahead of time. We also focus very much on the consistency or fibrosity of these tumors and we found that the fibrosity of the tumor really dictates how the approach and resection will proceed. So for more firm adenomas such as this one, we usually will perform an extracapsular approach and remove the tumor on block, whereas with the softer tumors, we're able to use suction and chase them into adjacent components without requiring an extracapsular approach. So that's something that we're studying systematically now, and next slide please. So these are just some of the factors that we have noticed may change your approach and may dictate that an endonasal approach may not be the preferred approach, and you'll notice number five here, firm tumor consistency, something that we've been studying quite a bit, and so this is something that we ultimately would like to predict on MRI but currently do not yet have the ability to do so. However, we grade these tumors in terms of consistency pretty systematically and have developed an objective grade for doing so, and we found that the fibrosity or consistency of these tumors is associated directly with the extent of resection as well as intraoperative complications such as intraoperative CSF leak and even rates of new hypopituitarism. So we think it's a very important operative characteristic that can help you plan your approach, and certainly more work to be done there. The extended approaches have really allowed us to gain access to the suprasellar region and to gain access there, we usually rely on a transtuberculum and transplanum approach, and this has really changed the way that we practice surgery, especially for craniopharyngiomas and selected meningiomas of the anterior skull base, as well as the occasional pituitary tumors that require an extended approach, and there are many approaches available that surgeons who are doing skull base and sellar region surgery should be familiar with. They should have the versatility of going back and forth and for a variety of tumors, there are certain approaches that are preferable. The pterional and OZ are still required in a surgeon's armamentarium for selected tumors, especially those with lateral extension. Rarely do we use a bifrontal craniotomy for, mostly for giant olfactory groove cases, and I'm gonna talk today about the super orbital craniotomy, which is a keyhole craniotomy that we rely on quite a bit for exposure to the anterior skull base and suprasellar region, as well as of course the endoscopic endonasal approach. So when you're doing this type of extended surgery, you wanna make sure you have all your ducks lined up in a row. You wanna make sure that every one of these is functioning and ready to go, otherwise it can threaten the outcome of the case. So this video in this slide shows the case of an epidermoid tumor of the cavernous sinus going back to Meckel's cave that we treated with a transpterygoid more lateral endonasal approach, and again, you just want to be ready to address anything that comes your way, whether it's a complex high flow CSF leak or the rare vascular injury that neurosurgeons will encounter here, just making sure that you have all of these modalities ready to go at any time, and next slide please, and of course, occasionally we have to be prepared to deal with encephaloceles of the anterior skull base, and if we could play this video please. This was a patient sent to me after a surgery at another institution for a pituitary tumor where they had a large meningoencepholocele, and occasionally we'll see these going all the way back to the planum, sphenoid alley, et cetera, or in the sphenoid sinus we'll see spontaneous meningoencephaloceles. So these are a great place to start for surgeons who are just starting to do endonasals and extended operations. Next slide please. Moving back along the skull base towards the suprasellar region that we're going to focus on, we now thankfully have access to the entire anterior skull base. We can treat olfactory neuroblastomas, which this is an example of here, and just correlating that to the anatomy here of the anterior skull base, focusing on the ethmoidal arteries, anterior ethmoidal artery and posterior ethmoidal artery, cribriform plate on the midline, and then going back to the planum and tuberculum sella here. So we can now access this region endonasally, and occasionally we'll do these in combination with open craniotomies and use a paracranial flap and or nasal septal flaps for reconstruction here, and just to show you what this type of case and video would look like. So this is an invasive olfactory neuroblastoma, and the first thing we'll do is harvest a flap here, make sure it's free of tumor, and here we're doing a frontal sinus drill out. We're now removing bone lateral to the cribriform plate. The next thing you'll see is the crista galli here. We're opening the dura, removing the crista galli, detaching it from the falx, and then working around the plane of this tumor to dissect it from the gyrus rectus and olfactory tracts and bulbs and trying to get a complete resection here, which we were able to do to follow this up with radiation and chemotherapy, and next slide please. So as I mentioned, nowhere perhaps has extended approaches become more useful than for suprasellar pathology and has really been a game changer. Although the extended approaches were initially described via the microscope by some of our mentors, Dr. Marty Weiss, Dr. Ed Laws, Dr. Bill Caldwell and others, the endoscope really was a game changer for especially cranial pharyngiomas and meningiomas, and now you see us removing a suprasellar cranial pharyngioma. We've exposed the suprasellar dura, we've cauterized the superior intercavernous sinus. We're working to really try to preserve the superior hypophyseal arteries to preserve vascularity to the optic chiasm, and then usually this involves a decision of whether the pituitary stalk can be preserved and in most cases we attempt a gross total resection and therefore are willing to sacrifice the pituitary stalk, and our colleague Ted Schwartz at Cornell had a great paper a couple years ago that showed that even when you try to preserve the pituitary stalk in craniopharyngioma cases, you're often unable to remove the entire tumor and pituitary function is usually compromised anyway. So we're pretty aggressive about attempting a gross total resection even at the expense of taking the infundibulum when needed, and next slide please. So for the trainees who are watching, especially the medical students and residents, when we learn neuroanatomy at first, it's often not in a surgical context and that's okay, but as you develop your surgical skills and acumen, it's very important to see anatomy from multiple perspectives, and this is just a great illustration of that by an artist, M.C. Escher, who I happen to really like, showing different perspectives of various landmarks, and this relates a lot to how we see relevant anatomy. In this Rhoton dissection, we can understand that the typical relationship we see with the craniotomy of the optic nerve to the carotid artery and anterior glenoid process, and of course the optic strut between them, and then seeing the exact same anatomy via an endonasal perspective with the optic nerve, more medial carotid artery, more lateral, and then the usual bony removal for transtuberculum approach. So I mentioned earlier that most pituitary tumors do not require extended approaches. Well, there are exceptions to that. Here's a great example of a non-functioning adenoma growing over the tuberculum sella here and into the anterior cranial fossa, and this is a telltale sign that an extended approach may be needed because a direct approach is simply not sufficient enough for working in this corridor and making this turn and safely removing this tumor from this region. In addition, you'll notice extension into the oculomotor cistern here, and this patient did have a right third nerve palsy in addition to vision loss. So this for us is a classic indication for an extended transtuberculum approach, which you'll see here. I usually just expose the sella to start and open that, and that's because I want to get a sense of what the consistency of the tumor is like and how much of it will descend. So you'll see that first. This happened to be a pretty average consistency and we were unable to remove it all just with that exposure. So we've removed the bone over the tuberculum sella and posterior planum and opened the dura. Now we're dissecting the pseudocapsule of the tumor sharply from the carotid artery, which is right here, and then you'll see the sharp dissection from the thinned out optic chiasm, which is right here, and right above that you'll see the ACOM complex, but these tumors can be very adherent and even invasive, and here we were able to remove, I'd say, nearly all the tumor with maybe just faint microscopic residual. It was read as a gross total on the imaging preservation of the normal pituitary gland, which you see right here, and decompression of the optic apparatus, which is here. So this patient's vision got dramatically better after the operation. So this is an example of when we would use an extended approach to access the suprasellar cistern for a non-functioning giant pituitary adenoma, and next slide please. So I mentioned earlier that almost nowhere has this been a bigger game changer than for cranial pharyngiomas, and the reason for that is multifold. Number one is, again for the trainees in the room, when someone shows you a slide of a suprasellar mass, which this is here and it's happens to be distinct from the normal pituitary gland, which is below it, and it appears to be a cystic and solid mass, the first thought that should come to your mind is a craniopharyngioma, and because they're often partially cystic, they lend themselves to minimally invasive approaches. They're often retrochiasmatic with the chiasm often sitting right around here, and then finally, the long axis of the tumor is often in line with the trajectory offered by an endonasal case, which is another reason why they really lend themselves to endoscopic endonasal resection. So as this slide also illustrates, that long axis of the tumor is critical. So here's an example, and this is an article I wrote with Dr. Cohen-Gadol and Dr. Schwartz several years ago, just showing some of the steps we take for craniopharyngioma removal. We've opened the suprasellar cistern, we then slack in the inside of the tumor and debulk it from within the capsule and then work around the tumor circumferentially, dissecting it laterally from the PCOM arteries and third nerve, superiorly from the optic chiasm, and then more posteriorly from the mammillary bodies and third ventricle. Here we see the tumor is not separable from the pituitary stalk, so we make a deliberate decision to sacrifice the entire stalk and tumor and then inspect within the cavity where there's no evidence of residual. You're looking into the third ventricle, you see the under surface of the chiasm and it's a complete removal of the tumor. There are many ways to reconstruct the sella. We like using fat to obliterate the dead space. Often we'll do dural reconstruction with either fascia lata or dural substitutes such as DuraGen, and then of course the pedicle nasoseptal flap is really the workhorse of reconstruction for extended approaches and has been an absolute game changer. I still will use a lumbar drain usually at five to 10 cc's per hour for 48 hours depending on the body habitus of the person. If it's a smaller person or more elderly person, we'll use five cc's an hour, and there's of course a pretty robust level one data from the Pittsburgh group in the "Journal of Neurosurgery" supporting the use of lumbar drainage for extended approaches. Here's another case of a craniopharyngioma that occupied the sella and suprasellar region, another case where the long axis of the tumor is very favorable for endonasal resection, so we proceed with bony removal, removing the bone over the tuberculum sella. We always use a doppler on every case to identify the carotid arteries. Here we're sacrificing the superior intercavernous sinus. We're doing a French-door opening of the sellar dura. We're debulking the tumor from within so as to slacken it and then sharp dissection laterally around the tumor. We try to really preserve these superior hypophyseal arteries and then mobilize the tumor away from the surrounding structures. We're able to dissect it and pull it downwards, and then again inspection, third ventricle mammillary bodies, PCOMs, and then often the tumor will require additional dissection from the basilar apex and the perforating arteries, which is a very important step. When they do descend down into this retrosellar region, that's a good move for either removing the dorsum sella or posterior glenoid processes or taking out the whole gland itself to give you this access to the retrosellar region. Make sure you can use two-handed dissection to dissect the tumor away from the basilar apex and all of these small thalamic perforating arteries that come up this way in addition to the P1 vessels, and next slide please. So even larger craniopharyngiomas can be removed with endonasal approaches as long as you have sufficient bony exposure and slackening and debulking the tumor really helped. So this was a larger transtuberculum, transplanum approach. Again, we're getting inside the tumor to debulk it so that we can start to fold it in. Here we're dissecting the tumor off the undersurface of the chiasm and now off the basilar apex we've removed the dorsum sella. We're being very careful to identify any small perforators. We're now dissecting the tumor away from the third nerve and here's the P1 vessel that we saw there, and then we use a 30 degree angled scope to look superiorly, dissect the tumor away from the third ventricle and undersurface of the chiasm, and then of course do our inspection. Here we're using fat to occupy the dead space and our dural reconstruction with a single piece of fascia lata and of course followed by a very robust flap, and here's a complete tumor removal. In this case, we've been observing this young gentleman and has not had a recurrence to date. We will reserve radiation therapy either if there's residual or a target or if it's a recurrent tumor. Otherwise we'll hold off on radiation therapy to the cavity, and next slide please. So I mentioned meningiomas earlier and I think with meningiomas we have to be very selective. I think a craniotomy is still an excellent approach for many skull-based meningiomas. This was a fairly well circumscribed tuberculum sellae meningioma, not a lot of lateral extension beyond the carotid arteries. This was an excellent target for an endonasal approach. So here's my ENT colleague Dr. Roble elevating a left-sided pedicle nasal septal flat. Now we're doing our vomer removal and sphenoid rostrum widening. Here I'm using a ultrasonic aspirator bone removing device to thin out the bone over the tuberculum sella and posterior planal sphenoid alley, removing bone from the medial optical carotid recess region and then having a good bipolar cautery, really critical for this area. We're using a micro doppler as we do on every case, especially to identify the carotid as it takes this medial bend intraorally. We're now cauterizing and cutting the superior intercavernous sinus and then devascularizing the meningioma early on, then working over it to develop a sharp plane between the tumor and the optic chiasm, which you'll see here. Here's the optic chiasm up there and then you'll see a two-handed micro dissection, and then finally we'll roll the meningioma downwards and delateral dissection with preservation of the infundibulum, which is right here and preservation of the pituitary stalk, and this patient had a complete removal with improvement in her vision, and you can see our reconstruction here with fascia lata. We call this the cargo net technique. I'm using a little Surgicel to tuck it under the bone and then of of course a flap which would go over that, and next slide please. Here's a larger tuberculum sella meningioma with a dural tail, so this one would mandate a posterior planum removal as well, and there's also some hyperostosis right in this region that you'll note. This one also had some invasion of the optic canal. So just to show kind of what we can do endonasally, here are the same steps that I've showed already, devascularizing the tumor, debulking this tumor. This one was more firm and calcified even, and then trying to find the optic apparatus very early to protect it. You can see the optic chiasm behind us. The pituitary gland is preserved, and now two-handed dissection of this tumor away from the chiasm, and then what we'll do is we'll unroof the optic canal as you see here on the left side and we'll follow the tumor into the left optic canal, and as you can see that we were able to remove this tumor, including the dural tail and decompress the structures in the suprasellar cistern, preserve the gland and her vision got much better with no hypopituitarism, and next slide please. So that is currently a lot of what we're doing with extended approaches to the suprasellar region, and there are many cases when I feel that either a patient has already had an endonasal approach or extensive reconstruction or as I mentioned for some meningiomas, my preference is a craniotomy, and that's because we can avoid sinonasal morbidity, don't have to worry about a CSF leak, olfaction may not be jeopardized, and patients can go home sooner sometimes with a craniotomy. So for carefully selected anterior skull base meningiomas, I think a keyhole or eyebrow or a standard craniotomy is even better sometimes in terms of patient recovery, and so I think we have to be very careful about that. The OZ is a great example of an alternative, but can be extensive for a lot of these lesions. What it does offer is a very nice more anterior to posterior trajectory than a pterional approach, which is a more lateral to medial trajectory, and that's one reason I love the supraorbital approach. It takes you almost directly along the midline as a endonasal approach would, and it allows you to work between the optic nerves. So it's almost an approach we're used to seeing from below, but gives you a different trajectory from above, which is why I think it's such a powerhouse approach. So I use these for a lot of salvage procedures and a lot of new anterior skull-based meningiomas. I use it for a lot of frontal sinus work. The key landmarks here are avoiding immediately the supraorbital nerve, which is of course a sensory nerve, and then perhaps even more importantly, the frontals branch of the facial nerve, which is laterally in the fat pad here, but you need to be careful in that area. We do a single burrhole at the McCarty keyhole, which is adjacent to the zygoma here. You can do your skin incision either in the eyebrow or in the eyelid as some people do, or often in more elderly people or in women who tend to have less thick eyebrows, we'll do a standard frontotemporal hairline incision and still do a very small supraorbital craniotomy. So you have a lot of versatility as in terms of what you can do here. So just an example, this was a planum sphenoid alley and tuberculum sellae meningioma. I thought that this would be better approached with an eyebrow procedure for some of the reasons I mentioned, so here's our eyebrow approach. Here's the right-sided burr hole in the McCarty keyhole. We then turn about a three by two centimeter bone flap, do not take the orbital rim down, but I do drill the undersurface of the orbital rim to make it flush with the anterior frontal fossa, and here we are working already on the tumor, devascularizing it. This is sped up a little bit, but dissecting it off the right, now off the left optic nerve, which is right there, and so we're able to work contralaterally to remove the tumor and get a complete resection, and then of course the reconstruction, and next slide please. So you can see that this also offers a phenomenal view. As I mentioned, it gives you a great anterior to posterior subfrontal trajectory. The brain relaxation is tolerated very well on the gyrus rectus, and even though we love splitting the Sylvian fissure, technically you can avoid a trans-Sylvian approach and retraction associated with that in some cases and you don't need to do any sinonasal flaps or reconstruction, and so I think for carefully selected meningiomas, this is for me a preferred approach, especially the ones that tend to go under the optic chiasm or are redo-type approaches, and these patients do really well cosmetically. A lot like me, this gentleman was, is follicularly challenged, and if you look very closely, you can see his scar right here in the right eyebrow. Hard to see if you're not aware of it, and so with a multilayer closure, these patients seem to do very well. So here's an example of a patient with, that I treated several years ago with a non-functioning adenoma, and what you can't recognize on this is that this tumor was very firm and was even invading into the arachnoid, and I was only able to remove a component of this. You can see the residual here. He did have a flap and an extended approach, and so our options at this time in a young man are either to radiate this tumor, which we prefer not to do upfront because its proximity to the optic chiasm and to the normal pituitary gland, which is down here. So we would avoid, we would prefer to completely remove this. We could of course go back in through the nose. I wouldn't, I don't think that would be the wrong approach here either, but you'd have to go back through your reconstruction, and perhaps there was a little bit of tumor descent here, but we decided to go in with an eyebrow approach, gave us a great trajectory to this tumor, and you can see the postop scan. Chiasm's decompressed, gland is intact, and patient is doing well. Here's another example. So this is a pure, mostly planum sphenoid alley tumor with its base here. Would not fault anyone for going endonasally, although olfaction is a consideration here, but we did this with an eyebrow approach. It's about a two-hour operation coming in subfrontally here, complete removal and this patient went home post-op day one. So I think you have some options with a tumor such as this one, and it's definitely surgeon's preference, but for those reasons we prefer to do a craniotomy on that, on this particular tumor. I'd also say we can use the endoscope to our advantage even on a supraorbital keyhole approach. So we've removed in part a tuberculum sellae meningioma, but a hard place to inspect is often under the optic nerve in the canal, and now we're using a 30 degree endoscope through a supraorbital approach to look under this optic nerve, make sure it's decompressed, just get a different view of it, see if we can identify the ophthalmic artery anywhere, and we think that this is another added benefit that with versatility can give you a little more confidence in how much tumor you've removed, and next slide please. All right, so as I start to wrap up here, I think an important point to convey is that we've heard kind of an evolution of optical technology purported by some people going from the microscope maybe to an endoscope. Lately we've heard a lot about exoscopes and I don't necessarily think that this is true. I think all of these are extremely valuable pieces of equipment that we can use interchangeably and I think versatility is really key, putting a plan together for every patient, every tumor where you can use these interchangeably or whatever's needed to provide the best outcome is really critical. So in conclusion, I hope I've conveyed to you that surgeons have a lot of advanced options for accessing the suprasellar region and anterior skull base as a whole. I think endoscopy has certainly lent itself to doing so, and of course we have to focus on principles of microdissection and reconstruction, but there still remains a very viable role for craniotomy and keyhole craniotomy, especially for, I would say meningiomas of the anterior skull base, whereas cranial pharyngiomas really lend themselves to endonasal resection and that this technology will continue to get better and better as we continue to push these approaches forward. So just a shout out to a couple of my mentors here, Dr. Ed Laws, Dr. Paolo Cappabianca, and then just to really thank and congratulate Dr. Aaron Cohen-Gadol and on so many contributions to neurosurgery, but the atlas in particular and it's quite an honor for me to be here today and join you here, Dr. Cohen-Gadol. Thank you so much.

- Beautifully done. I really like the microsurgical techniques. Gab, you really are very meticulous. You use the same skills that we use, transcranial through the nose, which is really important. I think not pulling, not pushing, really that two-handed technique is just such a powerful method that can provide so much flexibility in terms of safe tumor removal and pushing the boundaries of endonasal microsurgery. There were a few things that I think worth mentioning again. You mentioned about the fact that you gotta be more aggressive with cranial pharyngiomas. It is very true. We often try to protect every structure, but when the tumor is really encasing the stalk, you can spend as much time as you want. You're gonna leave some tumor behind and they really wake up having a very sort of affected pituitary access anyways. So might as well provide the patient with good growth resection and then let them enjoy that rather than leave tumor behind, make the surgery extended, and usually it's not that easy to leave a sheet of the tumor the moment you lose the plane. So you often come back, post-op MRI looks a lot more tumor than you thought you left. So it makes the whole thing very complicated. I think that's just a good technical pearl one should not forget. The other thing that I want to add is that we often worry too much about the floor of the third ventricle in these kind of pharyngiomas. If the tumor really has eroded and has affected the floor of the third ventricle, and I'm interested to hear your thoughts, Gab, is that if you really remove a little bit of gliotic margin that is very discolored from the normal hypothalamus, you can get away with and the patients actually do very well and you can get an excellent cross-zonal section. So I think some surgeons get really lost in this fine detail that everything at the floor has to be protected when in fact the discolored tissue that is very adherent to the tumor can be removed safely without any hypothalamic dysfunction side effects. What are your thoughts there, Gab?

- Yeah, I think that's a great point, Aaron. So I would completely agree with you. When I see either the capsule or tumor or cystic capsule invading the hypothalamus, I will try to remove it, especially in adults. I think that there's a difference in between kids and adults, how they tolerate hypothalamic dissection and recovery. Obviously in kids there, the potential for hypothalamic obesity and puberty-related changes is much more of an issue than in adults. So we have to take that with a grain of salt, but I think there's also a difference if it's unilateral or bilateral and I think we can get a away with a lot more with unilateral hypothalamic injury than bilateral, but I could not agree more with you. The first operation is your chance to remove the whole tumor. Once there's been an operation, radiation, recurrence, it's a much more difficult operation. It can still be done as you know, of course, but it's much more challenging and and riskier, and then we have to keep in mind that the different types of craniopharyngiomas, of course now. We do have salvage options for the papillary types now that we have to be mindful of as well.

- I agree with you. I think those are critical factors that I always say the first chance is the best chance at cure. So you've gotta respect that. Really going back in these kind of pharyngiomas, if there is residual tumor, the morbidity is significant, the challenge is significant, and the patient gets hurt.

- Absolutely, and once they have a second operation, and that as we've seen, that can lend itself to multiple recurrences and cystic expansion. So that first operation, really what it's about.

- Yeah, it's the best chance at cure. The other point that you all mention is the fibrosity, how fibrous tumor is. Sometimes, believe it or not, it's as important as the location of the tumor.

- Yes.

- Because if you have a tough tumor, oh boy, you got a challenge ahead of you, and you could have a very soft tumor in a very relatively inaccessible endonasal route, but in fact you'll do very well because the tumor, you know, drops down. You can use Valsalva maneuvers. So in those blind spots with a 45 degree or 70 degree or 30 degree as you very well showed, you really can extend your reach, and that's really goes down to what I tell a lot of my fellows and residents, that almost the tumor determines how successful you can be, not yourself or technical skills. Obviously that's an exaggeration, but the tumor is such a critical aspect of what you can do, and Dr. Weiss always says it's not about how you get there, it's about what you do when you're there, and so I can't emphasize more that there's so much literature about how to get there, endonasal, transcranial, orbital, but then there's not much discussion about what to do when you're there. So I think the emphasis you put on fibrous aspect of the tumor is critical. Do you want to add anything else there, Gab?

- Yeah, thank you for bringing up that point. I, as you mentioned, it's often as important as the pathology itself and the location, and I think that's will become more important moving forward because ultimately the goal, the dream would be to be able to predict this on MRI and that will tailor your approach. So if you can say something with confidence is very soft, by all means minimally invasive approach would be great, but you know, if you know something's gonna be calcified firm, not gonna fold in, not gonna descend, then maybe you wanna plan something more definitive or that gives you better exposure, et cetera. So I think that's a, it's a very important aspect of it, and just to follow up about what you said about the approach versus what to do when you're there, definitely one of my favorite quotes, of course from Dr. Weiss, and that just really points to, I think understanding the biology of the tumors as well, and you know, we are now studying our cavernous sinus resection outcomes and we've noted that the softer tumors can be removed from the cavernous sinus, but the more firm ones, not worth trying to be as aggressive with. So as you mentioned, some of those characteristics dictate the approach but really understanding what the biology of the tumor is. Why do Cushing's cases tend to recur so frequently or have, you know, multiple adenomas, double adenomas, et cetera, and making those intraoperative decisions absolutely key.

- Yeah, I agree and I know that's a focus for your research is the predictability of the fibrous nature of the tumor, which is so critical so.

- Not there yet though. A lot of work to do still.

- Oh I know, but it's a great start, and the other thing about versatility, you mentioned that don't push the boundaries with many tumors. Couldn't be more, more agreed. Cannot agree more with you on that. I think, you know, we all are innovative. We sometimes try to push the limits too much, especially meningiomas through the nose. I think the supraorbital approach is an excellent approach. I really do believe there is significant limitations in removal of the meningioma through the nose in a gross total fashion. As you know, when you remove these tumor transcranially, there is a mushroom and there's part of the dura of two centimeter almost away from the tumor base that is affected that we clean out. We coagulate, we really try to clean it out. Such exposure is not available through an endonasal route, and I do believe the recurrence rate is higher. No question for a focal sub-tuberculum sellae meningioma, it's an excellent approach. This is a focal subchiasmatic lesion and therefore subchiasmatic approach is ideal. However, for a more extended tumors, extensive tumors, this can be quite a challenge. So I would say to standard of care and also the ideal approaches for pituitary adenomas, for craniopharyngiomas and confined tubercular sellae meningiomas, is endonasal. I would say that is ideal, that's true, that's prudent, and I think that's a great good way to do it. I would say large olfactory meningiomas, petrous clival meningiomas, clival meningiomas, or other meningiomas, I think one has to be very, very exercise caution and a lot of justice in terms of approaching them and pushing limits just because you wanna become an innovative surgeon per se. What are your thoughts there?

- I couldn't agree more. I think we have decades of substantiated outcomes for craniotomy for meningiomas and we have to be selective and just because we can do something doesn't mean it's the right thing or, and of course we all, as you mentioned, want to be innovators and push the envelope, but you know, I think we're finding that for selected meningiomas, even of the anterior skull base, even as you mentioned, non-confined tuberculum sellae lesions, that there's still a major role for craniotomy, I think, especially in terms of patient recovery and even length of stay and things like that, that I think a good old-fashioned craniotomy outweighs in certain cases outweighs an extended endonasal approach.

- Very well said. So with that, I wanna really thank you, Gab. Tremendous accomplishment, really meteoric rise in neurosurgery that I so much like to see in our younger generation. You exemplify that. I'm really proud when neurosurgeons stand up and really move so quickly with their own accomplishments, not because they have followed someone else. They do it with their own sweat and their own hands. They really finish, they demonstrate their skills, they rise and they contribute and you are an example of that, which is so tremendous. So I want to again congratulate you and look forward to having you with us in the near future.

- Thank you for your kind words. It's been awesome being here, Aaron and I'm, so many of us are trying to follow in your footsteps, so.

- God bless you. God bless you. The feeling is mutual. Thank you.

- Thanks.

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