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Grand Rounds: Endoscopic Endonasal Surgery for Tuberculum Sella Meningiomas

Juan Fernandez-Miranda

February 12, 2017


- Hello, ladies and gentlemen. Thank you for joining us again for another installment of the AANS Operative Grand Rounds. Dr. Juan Fernandez-Miranda is our guest today. Again, he's returning to talk to us about endoscopic skull base surgery, and more specifically as related to suprasellar region. Juan is truly a pioneer in endoscopic skull base surgery and has truly worked tremendously on elucidating some of the anatomy of the region as well. So I'm very excited to have him with us and very much looking to hear about his surgical nuances via his surgical videos after he reviews the relevant anatomy. Juan, go ahead, please.

- Aaron, thanks so much for having me again. It is my pleasure and my honor to share this time with you. As you mentioned, we're gonna keep talking about surgical anatomy, trying to bring everything that Dr. Rhoton taught us over the years into practice in particular for endoscopic endonasal surgery. And last time we talked about anterior skull base approaches. And then today we're gonna focus more on this area right here, on the infrachiasmatic space tuberculum sellae area, and first for meningiomas, and later for craniopharyngiomas. You know, we talk about this infrachasmatic space underneath the optic chiasm. And if it's in front of the stalk, we call it the suprasellar infrachasmatic region, or pre-infundibular region. And then craniopharyngiomas, they often extend into the retro-chasmatic or retro-infundibular space here. And that we will see later. But we're gonna mainly focus about suprasellar meningiomas in that area. Now, as we all know, we have different approaches we can use to these areas. Most commonly used pterional, supraorbital or subfrontal approaches. But endonasal is definitely a very good option, alternative for tumors in this region as many we know. And the main question I always ask myself when I look at a tuberculum sellae meningioma or a suprasellar meningioma is where is the optic nerve or where are the optic nerves in relation to the tumor? Is this truly a tuberculum sellae meningioma? Are the nerves therefore laterally displaced on the posterior or superiorly? Or as a tumor like this one that looks kind of similar in size and almost location on this tuberculum sellae meningioma, but this one however is pushing the optic nerve medially. This is more a clinoidal meningioma. So this is a complete different animal. So, always first don't make the mistake on how you select your cases. It has to be a tumor that is in between the optic nerves and not displacing the optic nerve anteriorly or medially. Now, why in the nasal surgery? We have mostly some by meta-analysis and different series that the visual results for endoscopic endonasal surgery in this area might be better. Although there's always a comparison bias, we cannot make a strong argument with this. But this is the main reason we would like to do these tumors endonasally. We can do it without manipulation of the optic apparatus and perhaps there is an opportunity for improving the visual outcome. Now, I'm gonna be focusing on the surgical anatomy that is important to do these suprasellar meningiomas. As we reviewed last time, we use this very important planum right here. This is the limbus of sphenoid between the planum and the prechiasmatic sulcus. And then here we have the tuberculum sellae, and then we have the sellae itself. Laterally we have the anterior clinoid, the optic strut, which is the attachment of the anterior clinoid. So we're gonna be using this limbus of the sphenoid again to separate, differentiate the area of the planum sphenoidale from the area, that infrachiasmatic area, of the prechiasmatic sulcus, which correspond again with the infrachiasmatic space. And this difference is very important because suprachiasmatic space area on the other side what we have is the frontal lobe, the orbital surface of the frontal lobe, while in the infrachiasmatic space what we mainly have is the suprasellar system. We are gonna be just underneath the optic apparatus, the optic chiasm axes in the suprasellar space right here. And we use the limbus of the sphenoid as a reference to tell us where is the interior limit of the suprasellar space. Now, a piece of anatomy that is very important in this area is understanding what is the medial optico-carotid recess. This actually is not a true recess. So anatomically it is not a very successful name, I think, or accurate, but it is however a very important concept because we call it medial optico-carotid recess this area where the optic nerve and the carotid come together. And this area here is very important to be exposed in our approach. This area is again the conference of the optic nerve within the optic canal and the carotid artery, in particular, the paraclinoidal segment of the corridor artery. So we're gonna review the anatomy, both of the optic canal and the clinoidal segment of the carotid which is very important for these approaches. So the paraclinoidal region. We are familiar with the dorsal aspect of the paraclinoidal region. This is where we have the clinoidal segment of the carotid that we expose when we do an anterior clinoidectomy. And then we all know we have the distal ring above it and surrounding, separate actually, the carotid on the clinoidal segment from the supraclinoidal segment. And then on the bottom of the clinoid, we have this membrane, which is the so-called proximal dural ring or a carotidoculomotor membrane that forms this roof of the cavernous sinus and this proximal ring. Between both rings, we have the clinoidal segment of the carotid, that again, we expose when we do an anterior clinoidectomy. However, when we do endonasal access into the sphenoid sinus, we see the same segment of the carotid, this paraclonoidal segment. But now we're looking at the ventral aspect of this paraclinoidal carotid. And we can see right here, this paraclinoidal segment is the most anterior, the most ventral segment of all the carotid in all this area. And even more, this segment is often not well covered by bone. So the bone is often dehiscent in this area, which makes this segment of the carotid more prone to neurogenic injury when we operate in this area. So always very careful with this paraclinoidal segment of the carotid artery. On the other hand, this lack of a bone often in this area, or very thin bone covering this clinoidal carotid segment, makes it easier when we wanna expose it as we will see in a minute. So always remember we look at the lateral aspect of the parasellar region here. The three segment of the carotid we wanna understand here are the cavernous sinus segment. It's completely within the cavernous sinus. It's within the cavernous sinus up to the level of the roof of the cavernous sinus, which is formed here by this proximal dural ring, the same one we are seeing right here. Once it passes through this roof of the cavernous sinus becomes the paraclinoidal segment. And this paraclinoidal segment goes up until it crosses the distal dural ring and then becomes a supraclinoidal segment. So when we work endonasally, again, we access the sphenoid sinus and we see the paraclinoidal segment, we do not see the cavernous sinus segment yet because it's inside the cavernous sinus. We would have to open this bone and open the anterior wall of the cavernous sinus so we could see that carotid. So paraclinoid carotid is the one we see, we have the optic nerve above, and then this recess is the lateral optic carotid recess which corresponds with the pneumatization of the optic strut of the anterior clinoid. And this is also a very important anatomical concept that we will see in a minute. So, for exposure of this ventral paraclinoidal ICA, sometimes we encounter this structure. This is the middle clinoid. The middle clinoid, it is not constant. It's pressing about 50, 60%. We did a study some years ago on CTAs and something is actually quite prominent as you can see here. And this middle clinoid, as it grows, it projects towards the tip of the anterior clinoid in a way that sometimes it even forms an osseous ring around the clinoidal carotid. But removing this middle clinoid, doing a middle clinoidectomy is very important to expose this paraclinoidal segment of the corotid artery as we require sometimes in these approaches so we can expose all the bone here and have a good lateral exposure in our access. So in this video I'm gonna show you now, we are gonna be able to see how do we do a middle clinoidectomy? So this is the sellae right here. And then the thin bone the carotid here has been exposed, and now what I do is I expose the bone on the anterior wall of the cavernous sinus right here. And then this allows me to just dissect the middle clinoid. So I disconnect it from the sellae, from the cavernous sinus, from the carotid. I completely surrounded the middle clinoid so I can finally just remove the middle clinoid from there. And this is a very safe thing to do if you do it the right way. I've never really had a problem doing this. You usually get some venous bleeding that is very easy to control because this middle clinoid is located at the roof of the cavernous sinus. And remember it's gonna sometimes project posteriorly towards the anterior clinoid. And with that, I can show you this other case example where we have a true ring, carotido-clinoidal ring, where we're gonna see how this middle clinoid is completely attached to the skull base even though we have completely surrounded it. So you can see the ring. Actually this piece has bilateral rings. This is the exposure for a craniopharyngioma. And I wanna take my exposure as lateral as possible. So here this is the carotid on the cavernous sinus, and this is the paraclinoidal carotid right here, completely exposed here, and then this is the middle clinoid. This middle clinoid is very robust. As it is in the other side, it's completely still attached to the anterior clinoid forming a complete ring. So in this case, I'm gonna work up here. There is no need to completely remove the middle clinoid. In a case like this, you would say, "Why do you have to do so much exposure here?" Well, the only reason I have to do this much exposure is because for me, the safest way to expose this paraclinoidal segment of the carotid right here is to first expose the anterior wall of the cavernous sinus, which is very safe, and then surround the middle clinoid so I can finally remove it. If I see that the middle clinoid is still attached because it's forming a ring with the anterior clinoid, then I will leave the middle clinoid in there. I can maybe trim it and make it small if I really need, for example, to access the cavernous sinus. I can make it smaller. But I would not force a fracture in this middle clinoid because you are at risk of injuring the carotid artery by doing so. So remember this very important concept of the carotido-clinoidal osseous ring when you are trying to do a good exposure at the area, the tuberculum sellae medial of the carotid recess. The next concept that is very important is the anatomy of the optic canal. And the anatomy of the optic canal from the endonasal perspective. And we recently published this study where we actually try to define these two different segments on the optic canal when we're looking at it from an endonasal perspective. And this all is important because, you know, you can, endonasally, this is way you see in this panel right here. You see this optic canal prominence right on this sphenoid sinus. But not all the prominence is the true optic canal. The proximal part that you see right here actually does not belong to the true optic canal. The true optic canal starts with the optic strut. It starts right here. The optic strut of the anterior clinoid forms the floor of the optic canal. And that defines the true optic canal. The part of this proximal, we call this the preforaminal segment or the precanalicular segment. This part, the roof, is formed by the falciform ligament. You remember the anatomy from transcranial. We have this falciform ligament right here that covers this initial part of the optic canal, but underneath the falciform ligament and this segment of the optic nerve that is now osseous canal. So this is the preforaminal optic nerve and this is the most commonly invaded area by suprasellar meningiomas. So we need to learn, when we're approaching this area endonasally, we need to learn how to expose and how to remove tumors from this area. And some tumors actually cause true invasion into the optic canal. And that's a different story, and it requires a different type of dural opening as we're going to see in just a minute. So remember for the optic canal, we define two segments; preforaminal, which relates to the medial optic carotid recess and is covered by the falciform ligament, and two, the intracanalicular segment that corresponds to the lateral optic carotid recess and the optic strut. Now, if we look at the preforaminal segment right here, and we remember this dural fold of the limbus sphenoidale. This dural fold continues laterally and is gonna continue as the dura that forms the falciform ligament and covers the optic canal, the optic nerve before it enters the optic canal actually. So by exposing this dural fold, I always look at this dural fold in surgery, I know that when this dural fold becomes thicker, that is just adjacent to the preforaminal segment of the optic canal. I like to see this dural fold, and I shall show you, I like to cut through this dural fold because that is going to detach the falciform ligament and is going to make very easy for me to see this optic nerve before entering the canal and to find tumor in this area and remove it under direct visualization on not only the optic nerve, but also the ophthalmic artery that is underneath as we will see. So, how do we cut the dura to access this area? Of course every surgeon has a different way of doing things. This is just the way I like to do it. And there is a reason behind doing it this way. That works for me. And it is I like to do this first cut, again, I like to do this from dural fold on the limbus of the sphenoid, and I like to cut this dural fold just before the optic canal because I think this is gonna allow me to detach the falciform ligament. And then I like to take my cut towards the distal dural ring and also deep towards the diaphragm and towards the pituitary stalk. Why doing these cuts, one, two and three? Because if I cut it this way, I can just fold the dura. And then this is where ultimately I'm gonna just cut it and coagulate it. But the important thing is if I fold it, completely create this dural flap as you see here, as I open it, I'm gonna be able to very easily identify right here. This is very important structure. This is the origin of the ophthalmic artery. And, you see I've cut above and I've cut below. And I've never put my scissors very near, or nearby the ophthalmic artery. I've created a dural flap around it that allows me to identify very early the ophthalmic artery and allows me to get very easy and early access to the distal ring and to the preforaminal aspect of the optic nerve. So this is the reason why I like to do this dural cut. And then when there is true optical invasion in this area right here, I could do another cut longitudinally as you see right here in the upper edge of the optic canal. And when I do it, I already know where the ophthalmic artery is located. So I just put a hook here, or a right angle knife, and from here I can just cut this upper corner very safely. So again, if I created a dural flap in this side, I can see the supraclinoid artery, I can see that the distal dural ring, I can see the dura, just the beginning of the optic canal, I can see the optic nerve, and I can see the ophthalmic artery right here. If I now need to open the optic canal dura all the way, I just put my cut on the upper edge right here, and I can now see all the optic nerve running within the optic canal and the ophthalmic artery underneath now even going into these intradural segment of the ophthalmic artery within the optic canal dura. So that's the location of the dural cut that I found personally that is very safe in order to completely expose this optic canal. So I'm gonna show you this other video. This is a case of fibrous dysplasia. patient with significant fibrous displasia that is causing real compression of the optic nerve and optic neuropathy. And in a case like this, you wanna do a complete decompression of the optic nerve. And this video, I think highlights nicely this concept of the different segments of the optic nerve extradurally and how we expose these different segments. So we're doing the approach. And you will see the concept is that the segment is at the highest risk to expose is the true optic canal. So here we are in the sphenoid center. This is a unilateral approach. So I first found the carotid right here for safety. This is the periorbita. And this is the optic canal right here. So we first expose the orbital apex. We then expose the middle optical debris as preforaminal segment. And the last part we expose is the true optic canal without putting any instrument within the optic canal. And that's very important message. You don't wanna put instruments within an already compromised optic canal. So if you look at this here, this is the true optic canal. You can see this is the optic strut right here. And then this here is the roof of the optic canal. In this particular case, is hypostatic because of the fibrous displasia. But then we have this segment right here that is the preforaminal segment. It's just above the paraclinoidal ICA and is the one that is covered by the falciform ligament. So preforaminal, very common area for invasion in meningiomas, true optic canal segment, and then the orbital apex. For optic nerve decompressions, we always start on each side, so on the orbital apex. This is very safe to expose. On the preforaminal segment is also very safe to expose. Why? Because this nerve is still surrounded by CSF, is not completely within the osseous canal. And then the last part is just this area. The nerve is really compressed and there is no space. And this is the last area to safely be exposed. So I'll go back to the slides here and then we'll continue with this concept of the early optic nerve decompression. A great benefit of endoscopic endonasal surgery for suprasellar meningioma is that we can do an early bilateral optic nerve decompression. The same way when we do an anterior clinoidectomy for a clinoid meningioma, we try to get early decompression of the optic nerve. We can do the same endonasally, but bilaterally. And again, following the principles of skull base surgery, we can do it extradurally early on. So this example shows a tuberculum sellae meningioma that is small, and it has this extension here towards the optic canal. Now, many people would say this is optic canal invasion. However, this is invading just the preforaminal segment of the optic canal. And I think that's a very important difference from the surgical point of view. This is definitely easier to deal with. And I like to open the dura in a certain way when I see this extension here in this preforaminal segment. So, I'm gonna show the video of this particular case, and you will see we'll do an exposure that includes the sellae as you see right here and the carotids laterally as we explained, the optic nerve prominence, but not the whole optic canal is being decompressed. There is no need in this case. But now you see, this is the dural fold of the limbus. And I'm now cutting through the dural fold of the limbus in an oblique fashion. So I can cut the falciform ligament or better say the medial attachment or the falciform ligament. And I do this bilaterally. And this is just medial to the preforaminal segment of the optic nerve. This is very safe if you do it properly. And now the next cut goes along the diaphragm towards the pituitary aperture. And then there is another cut that goes towards the distal dural ring, this is the distal dural ring right here, and the carotid. And by doing these cuts I can have this dural flap that at the end of the operation I'm gonna transect, and I'm gonna trim, and I'm gonna coagulate, and I'm going to do so under direct visualization of this ophthalmic artery right here. So now what separates clinoidal carotid from this supraclinoidal carotid is just this dura, this distal dural ring, that is where this tumor is actually probably originating from and I'm just coagulating this dura to complete my resection. And I can explore the contralateral side, where I see no tumor, and I can see nicely the optic nerve going to the canal. This is the opthalmic artery, and this is the falciform ligament on the other side of this partially detached. And there is no tumor in this area as we can see. So we said that another very important anatomical structure to understand is the superior hypophysial artery. These arteries, or these complex of arteries from the super superior hypophysial artery, run in the same arachnoid plane as the pituitary stalk. And this is also very important from a surgical point of view because when we're doing the removal of a suprasellar meningioma, after the initial debulking of the tumor, first optic nerve decompression, and then debulking of the tumor, then we can find the arachnoid plane that allows me to separate the superior hypophysial artery branches and the stalk from the tumor itself, and allows me to preserve all these vessels coming from the carotid medially and running all the way towards the midline here. So the three branches that are most typical of the superior hypophysial artery are this descending branch right here, and we call this descending diaphragmatic branch because it goes through the pituitary aperture of the diaphragm here and goes to the upper surface of the pituitary gland. Then we have a second branch, which is sort of the continuation of the main stem. And this branch is the infundibular branch. It goes to the infundibulum, especially to the upper part of the infundiblum. And often, typically makes an anastomosis with the contralateral side. And this is a very important point. Why? Because in a case like this, for example, I could even coagulate this main stem right here, and these branches would still receive supply from the contralateral side. So this anastomosis makes a big difference in surgery. And also we have this third branch, which we call the recurrent artery that goes to the optic nerve. Now, of course here there are variations in the patterns of these branches. And a common one is that we see, for example, that this recurrent artery to the optic nerve arises directly from the carotid. Or another variation is this descending branch actually does not exist. So all those variations we can find in surgery, and it's important to understand these variations. I'm just gonna show you one here. And this is showing after the removal of a tuberculum sellae meningioma, extended to one side, we see that arachnoid plane, and here is the stalk, and here is the superior hypophysial arteries. And you can see this is the main stem, this is the infundibular branch, anastomosis with the contralateral side, and then this is the branch of the optic nerve that arises independently from the carotid in this particular case. The descending diaphragmatic branch is perhaps this one, but is very tiny in this particular case. And remember, this infundibular branch that has often anastomosis with the contralateral side provides supply to the infundibulum but also to the optic chiasm as you see here. So preserving these branches of the superior hypophysial artery is a very important doing surgery in this suprasellar region. In this other case, this is a larger tumor. I just wanna illustrate in this case how even for a tumor that is this large, is extending posteriorly even to the sellae, into the almost the retrochiasmatic space, is still this arachnoid plane is going to be there and still we can use it to preserve the pituitary stalk, and you see here, and to preserve the superior hypophysial arteries. So we'll see here this exposure as we said before. It's a wide exposure from the sellae, lateral to the clinoidal segment of the carotid, and then to the optic nerve right here, the dural flap as we described before, this dural flap allows me to early on find the carotid and the area in the superior hypophysial artery and I find the arachnoid plane which I used to dissect, find the stalk as we did there, and this is the arachnoid plane around here, with some of the super of superior hypophysial branches in this area. And after all that arachnoid plane has been defined, and I have separated the tumor from any other arachnoid attachments, I can roll it down. Only after accurate dissection of all the arachnoid around, I can roll the tumor down. And at the end of surgery, you can see the arachnoid plane is still preserved and all the small vascular supply to the optic apparatus, to the stalk, all coming from the superior hypophysial artery system, is still intact. In this particular case, the arachnoid and the stalk were displaced not only posteriorly here but also inferiorly. But if we use this arachnoid plane, we can effectively remove the tumor and preserve all these vascular structures. Also note how in this case, this diaphragm has been completely removed. And this makes a difference for these tumors that are invading often the diaphragm. We can get a more complete resection by resecting all this dura that is also involved all the way as you see here to the distal dural ring on both sides. And this brings the point of this variant of suprasellar meningioma. These are so-called diaphragmatic meningiomas. They arise not from the dura on the tuberculum sellae laterally as tuberculum sellae meningiomas do, but they arise more from the dura or arachnoid dural layer of the diaphragm itself. And they are typically more on one side than the other and you see this one is extended to this side a little bit, and they characteristically invade towards the sellae. And the difference with these diaphragmatic meningiomas is that they often encase the superior hypophysial arteries because the tumor originates often in front and behind the origin of the superior hypophysial arteries. So they grow around it and they may encase the branches of the superior hypophysial artery. And this is a more delicate situation to deal with. So always be careful with these diaphragmatic meningiomas. They are more challenging because of this reason. There are also cases of recurrent meningiomas. This is a spheno-cavernous meningioma that was resected somewhere else with three different craniotomies. The patient had different complications, also even gamma light. So this is a very complex recurrent tumor. And a tumor like this you expect to have no good planes. But this patient is presented with farther visual loss. And this is the tumor right here. Still in a tumor like this, you can try to find the superior hypophyseal artery branches, the pituitary stalk. You can see here postop the pituitary stalk preserved. And in a case like this, is definitely more challenging, but it still is possible to find this arachnoid plane, find the stalk, find the superior hypophysial arteries. Let me just pull the right video here. You will see how in this case, the superior hypophysial arteries are encased. The arachnoid planes are actually not well respected. Even the plane with the optic chiasm is really bad. So this is the pituitary gland. We cut the diaphragm because that helped me finding the stalk early on. This is the optic chiasm. You can see here we're using a 45 degree endoscope. The instrument is set on the top of the screen. And I'm doing this so I can have a better view of the interface between tumor and optic apparatus. And now I'm trying to resect the tumor, and I know that the superior hypophysial arteries branches are gonna be somewhere in here. And you can see one of the branches right there. That's probably the main one. There is no descending branches here that I can identify but I'm trying to preserve this one, although it proves real difficult. And this is the end of surgery. This is the gland down here and the pituitary stalk in this area. And then finding this arachnoid plane and trying to preserve the branches around in the arachnoid plane. So always even in recurrent cases, trying to find planes to dissect and preserve the neurovascular structures. Now, even more important are the arteries on the suprachiasmatic space above the optic chiasm. And these are the arteries of what we call the anterior communicating artery complex; the A1s and A2s, the ACom itself, and very important don't forget about Heubner artery, and the most commonly involved one, which is actually the fronto-orbital artery as we said when we reviewed the anterior skull base anatomy. You can see here, the B of this ACom complex. You can see this is a fronto-orbital artery that's looping forward. You can see a bit of the A2, the contralateral A2, the A1. And this is probably one of the Heubner arteries. You see the equivalent anatomy from arteriolar approach here. This is the Heubner artery, this is A1, this this the ACom right here. So we need to use very meticulous microvascular-like dissection to preserve these structures. There is no room for pulling blind dissection when we deal with these tumors especially when they have complex attachments to the vascular structures. And it is very important to emphasize that we need to adhere to the principles of microsurgery when we do these tumors. Doing it through an endonasal approach does not and should not change the way we do the operation. It should be done following the same principles. So you see this is after some debulking, exposure, et cetera. This is the tumor and it, you see how it is, you know, adhere to the different branches of the ACom complex. You see, this is the A1 here, this is probably Heubner, this is the fronto-orbital. And then you can see how the tumor is actually going in between both A2s. And that's the contralateral A1, contralateral fronto-orbital. But you see you can do the same meticulous dissection, contratraction with your suction and blunt, sharp dissection combining in order to be able to remove all these attachments of the tumor to the neurovascular structures. Even in complex situations like these, if you are meticulous about it, then you are gonna be able to deal with this microvascular attachment. There are sometimes challenging tumors like this one that I think only if you have significant experience doing suprasellae meningiomas through an endonasal approach you should attempt because these are more complex and they require a different skill set. For example, both A1s here, especially this one seem to be involved with the tumor. If you are careful here, you see that black dot that actually is a fronto-orbital artery that's encasing the tumor. Both A2s here, they are attached but not encased. They surround the carotid. It seems that complete encasement, but actually is not as you will see. It's like 270 degrees so we can still dissect this. But still this is a tumor that I would do endonasally just because I think when you have experience, you can achieve a very good tumor resection with minimal manipulation of the optic apparatus, trying to preserve this visual nerve function. You can see here, this a case of true optic canal invasion. The whole optic canal is invaded by tumor. And I would expect the optic nerve although you cannot see it here to be pushed all the way laterally in this case. And that's actually going to be the case as you will see with this complete invasion of the optic canal. And you will see how we open the dura for this particular case. This case actually illustrates all the concepts we have explained. You know, the wide exposure, all the way to the medial OCR, the need for microvascular dissection, and also how we open the dura of the optic canal, preserving the ophthalmic artery and being able to mobilize the tumor. So here is a wide exposure. We just cut through the falciform ligament. And in this particular case, I'm extending the cut all the way lateral above the optic canal. Debulking, finding the arachnoid plane, it's the pituitary stalk right here, and the superior hypophysial artery branches, you can see them right there right above the optic chiasm. This is the fronto-orbital artery that is partially encased by the tumor. And this is the A1. But if you are gentle, you do significant debulking and then you use microvascular light dissection, then slowly you can start removing the tumor and dissecting all the neurovascular structures around. That is the A1 here, the A2, you see there's actually a fenestrated Acom. We see both A2s. I see the right A1, I see the right fronto-orbital. And now at this point, I'm gonna change the direction. I cannot see the left A1, but I'm gonna go from the top now. Both the optic canal. Now this dural cut is key. It's the cut on the optic canal on the upper edge. And once they open the optic canal, open the attachment and I can mobilize the tumor. This is the supraclinoidal carotid. That's the PCom artery right there. I can follow the artery all the way to the bifurcation of the carotid. I can see a very small artery here that I'm preserving. That's probably Heubner there. And now because I transected the dura of the optic canal, that's my last attachment. I can now roll the tumor down and I can remove the tumor from within the optic canal. This is the optic nerve that has been displaced all the way lateral, and I can identify the ophthalmic artery. This is the ophthalmic artery within the dura, this is the ophthalmic artery outside the dura. And I can remove all the tumor that is within the optic canal under direct visualization. And these are the end of the resection; the stalk, all the branches preserved, with the superior hypophysial, all the ACom complex arteries dissected and preserved. Look at this very extremely thin optic nerve that however we have not manipulated. And it goes all the way to the optic canal right here. And this patient that has, that was almost blind in this side, has recovered some vision actually in the side and now has intact vision on the contralateral side. And now, finally, this is the postop as you can see here, with a complete resection of the tumor. Now, we always argue about the dural tail of this tumor. And one can question whether the dural tail has been removed here. And it's true that we cannot remove this dura here on top of the clinoid. We can just go here and remove the tumor and maybe coagulate this dural edge here, but I cannot take all this dura. But however I can remove all the dura that has been involved around the optic canal on the base of the skull. So I think it can remove the dura that is most important or is closest to the optic nerve. This dura here, if there is ever a recurrence it's gonna grow in this direction towards the frontal lobe as opposed to recurrence here in this area around the optic nerve where the recurrence is gonna grow towards the optic nerve within the optic canal. So if I have to choose a recurrence site, I would choose this type of intraclinoidal rather than in within the optic canal, which is actually the most commonly recurrence place for transcranial approaches when there is optic canal invasion. So, you see the approach has limitations but this dural tail is one of those, but I don't think it's a major drawback of this procedure. There are others as we will see. So, suprasellar reconstruction. And these, different surgeons do this differently of course. The way I like to do these, I personally don't think you need any rigid reconstruction in this area. I don't use at all any sort of rigid support here. I think is, my personal opinion is that there are some risks associated with putting a structure that area, and especially is gonna limit my resection. I cannot put rigid structure by the optic canals, optic nerves and carotid arteries when they are exposed. The key reconstruction piece here is of course a vascularized nasoseptal flap. That's what really solves the problem here. It's a very large flap and it's a small opening. And that's why I don't typically use either multi-layer here. I just use an inlay collagen. And then the flap on top. I rarely use fascia lata in the supraciliary space. Only when I have a flap that I'm concerned about that is not good enough or a very high risk patient for different reasons; radiation, BMI that is very high, et cetera. For the same reason, I often do not use lumbar drain when I'm just doing approaches to the supraciliary space. Only on high risk profile patients. And I'll show you with this short clip why the results on leaks are so good here. And the main reason is because we have a very large septal flap, robust vascularized septal flap, that has to cover a small dural defect. And if you look at the ratio between the size of the defect and the size of the septal flap, there is a real extra flap to cover. So this is the layer of dura. Again, you saw the defect is about 1.5 by 1.5, and then this sepal flap very wildly is gonna cover the margins. It's gonna have extra septal flap around that is gonna nicely cover the whole skull that has been opened. So in the majority of patients, the septal flap is the key to prevent CSF leak. That's been my experience over the years. Of course, there are significant learning points on how to raise a septal flap, how to position a simple flap, reasons why leak rate in the past was higher than it is nowadays for meningiomas in the supraciliary space. In fact, the CSF leak rate over the last year is being is below 5% for this particular location and for this particular tumors. So the leak rate now is very small for these areas. It is different, as we said before, when we are dealing with large interior anterior skull based meningiomas, it is different when were dealing, as we will see later, with let's say clival lesions plus chordomas, but for suprasellar meningiomas, the leak rate is actually very low at this point. So just to conclude, we would say, what are the contraindications for doing this procedure? Some people talk about optic canal invasion has been a contraindication, but I just showed you how we can deal very nicely with optic canal invasion when it goes from medial to lateral. I think it's about selecting your case well. If the optic canal is invading from lateral to medial, then you need a clinoidectomy. You need a lateral approach. But if it's from medial to lateral, then endonasal is an excellent route. Secondly, the attachment or the extension of the tumor laterally. Let's say, for example, on top of the clinoid or lateral to the carotid. You have seen cases where the tumor can still be removed when it extends laterally. And often is not just an attachment. It's just an extension that you can bring down as you debulk the tumor. But there is a limitation when the attachment and the dural tail extends laterally because we cannot completely remove that lateral dural tail. And third, we saw also the problem of the vascular encasement and adherence. So most tumors will just have adherence to the vessels, and that's easier to deal with once you debulk and you do careful dissection. Then you can bring the tumor down. Vascular encasement is another degree of difficulty. We can deal with it endonasally, the same way we deal with it through a transcranial approach. But it's technically, I believe, more difficult endonasally so unless you are comfortable doing, if there is vascular encasement, transcranial approach is perhaps a better option unless you are very comfortable managing these microvascular dissection through an endonasal approach. Not only the vascular dissection but also the vascular repair or the vascular control if you have vascular injuries. It's also something important to master before doing these cases. And last, as we just saw, CSF leaking rates are not a limitation nowadays for approaches in area. The leak rates are very low when you know how to raise a flap and you know how to position this flap, the leak rates again are very low. I guess wanna finish by showing a complication and something that I think could be a potential contraindication. At least it might be for me in my practice, because this is an unfortunate case I had to deal with. And this patient had this relatively small suprasellar meningioma. And at the same time, she had this partial empty sella. And in breath respect, you can also see that she has a bit of a Chiari right here. She is a very obese patient. Her BMI was 60. Now, she didn't have papilledema. She just was referred with a right optic neuropathy. So actually, you know, one of the students that does these tumors transcranially referred this patient to me to do this through an endonasal approach thinking it was a better option. I definitely agreed with that. And I did this endonasally. And so it did went really well, but in the post operative period, in the immediate post operative period, the patient had a bilateral visual decline. And this canceled, no clod, intraop, we didn't have any problems at all. So I just brought the patient back to the sender that same day to see what was going on. And what I found, which actually cannot illustrate well with imaging, but what I found was the brain herniating down through the opening in the prechiasmic sulcus in the craniectomy. The brain was herniating down and actually pressing on the optic nerves. This is something I've never seen before. I've talked to many colleagues and none of them have seen this before. So, maybe it was a unique case combination of this patient having intracranial hypertension that was occult. And that's one of my hypothesis. But for this patient, I went back, I put an EVD, I tried to free more the optic nerves as much as I could but it was a real problem and she had significant visual decline that recovered only partially. So I would just bring up word of caution. If you see a patient that is very obese and has these signs of potentially intracranial hypertension with an empty sellae, with a Chiari, you can still do it endonasally if you want but maybe put an EVD or just don't do endonasal and do transcranial approach. It may be a better option for this particular case. So just to conclude, the endonasal approach provides a natural corridor into these tumors that provide both early devascularization of the tumor. We can take all the dura where the tumor is arising from, that dura that is around the distal rings, underneath the optic nerve, in the optic canal, where the tumors arising from, we can take all the dura and we can do a bilateral early optic canal decompression, which I think is very important for these tumors. We decrease the optical manipulation. As we saw the CSF leaks have dramatically improved, vascular microdissection is difficult and only after significant experience should be attempted. And as we just said, be aware of the risk of brain herniation in various specific patient profile. Thank you.

- Juan, thanks so much for really a very thorough presentation about how the technique works. I think tuberculum sellae meningiomas are especially well suited for the endonasal approach in that they present in a smaller size because obviously they cause optic apparatus compression early, they are very accessible, you can decompress the optic nerve early. You're addressing a subchiasmatic lesion via subchiasmatic approach which makes a very complete sense. And as you well mentioned, because the exposure is limited, the closure is very effective therefore the rates of CSF leak are very small. So it's just a perfect lesion to approach via the endonasal approach unlike the olfactory groove meningiomas that only a very limited selection should undergo endonasal resection. So I think overall, it's really a nice approach, well-suited. I'd say that I'm rarely removing any tuberculum sellae meningiomas through the head anymore unless they're very giant. So, we sincerely thank you for your very worthwhile pearls. I look forward to your next session on craniopharyngiomas. Thank you again.

- Thanks a lot.

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