Grand Rounds-Nuances of the Expanded Endonasal Approach for Resection of Complex Skull Base Tumors:

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- Hello, ladies and gentlemen, and thank you for joining us. Today we have Dr Paul Gardner, from University of Pittsburgh Medical Center. Center for Cranial Base Surgery. He's going to talk to us about a very, very exciting field, a new field, with amazing potential, and that's expanded transsphenoidal endonasal surgery. He's a co-director of cranial based surgery there. Paul, I want to thank you for being with us this afternoon.

- Thank you Aaron very much. I really appreciate the opportunity to show this work, and I'm very excited about this web session.

- Thank you. He really has, brought in amazing videos and I encourage our viewers to see all the videos including of the agenda that you can see in this slide. We have a variety of cases, Clival Chordoma, Olfactory Groove Meningioma, Petroclival Meningioma, and particularly an amazing case of a large PCA Aneurysm, clipped through a transclival approach. I personally have a significant interests and I'm a strong enthusiast, of the expanded endonasal surgery, and I believe it will only get better. And therefore watching a master surgeon such as Paul at work, I think is going to give us a better understanding of how this procedure works. So with that in mind Paul, we'll go ahead and start. The first case. For this session will be primarily a case based approach. We're going to show cases and go through "pearls of technique." And I'll try to sort of create a discussion between you and me regarding my experience and yours. And hopefully our viewers can get a better understanding of "pearls of technique." So if you don't mind, go ahead and use your pointer there and tell us about the first case, which is a large pituitary tumor.

- Sure, so this is a middle-aged man who presented with a vision loss and bad headache from this very large tumor. And sort of the two most critical things that I think, endoscopy allows us to do. There's significant cavernous sinus invasion here with this tumor, both the medial compartment, the anterior-inferior compartment, even the lateral compartment. And then the tumor also herniates through, basically through, the oculomotor triangle and through the petroclival, petroclinoid ligament, sorry, to get out lateral here, even lateral towards the it bifurcation. But we were able to use the endoscope in this way to sort of follow the tumor into these areas in a way, I think that it was a bit unique and turned out very well for this case. Here, we sort of just see, it's not a particularly tall tumor, but more this lateral, this lateral suprasellar or lateral even medial sylvian fissure extension, really was the challenging portion of this case. Because of both the intradural extension, of this tumor, as well as the carotid involvement, we wanted to have a nasoseptal flap. We're doing, what we call a transterogoid approach or a middle fossa approach with the cavernous sinus on the right side. So this is a left sided flap that you see here, here we're dissecting Dr. Snyderman, who's my ENT partner, and co-director for skull-based dissecting, that flap out towards the left. Now we've done a very wide exposure all the way out to expose the entire cavernous sinus. Here's the paraclival carotid artery, and we're just opening directly into the tumor now. Here's the expanded sellar. And so we initially debulk the sellar portion, but then immediately start working towards the carotid artery and the cavernous sinus. Fortunately, this is a soft tumor, which allows us to work with suctions and work very carefully. Now, here we see the paraclival carotid artery, and we're opening up, this entire anterior-inferior compartment of the cavernous sinus. Now whenever we do this, we always monitor EMG's, we monitor the cranial nerves three, four, and six. But especially six becomes critical in this portion because it crosses behind Dorello's canal, to pass lateral to the carotid artery to enter the cavernous sinus. And here we see a cartouche stimulator stimulating to try to locate the sixth nerve. We found that in cases, obviously where we localized, the nerves, we were much less likely to injure them. In this case, we're able to safely and successfully localize the sixth nerve. We've protected with a Patty. You have to be very careful working in the cavernous sinus regardless of approach, for these meningeal branches. There are lateral meningeal branches, dorsal meningeal branches, and then hypophyseal branches medially. But here we're starting to work lateral, to the cavernous carotid to work up in this superolateral portion. We're doing this sort of very gingerly, and we're not going to be very aggressive with the tumor in this region, because this is where the highest risk for ocularmotor palsy comes in. This is an angled, really flexible suction. We call it shillelagh suction allows us to kind of work. Now we're working with a 45 degree endoscope looking up lateral to the parasellar carotid artery into the superior-lateral compartment of the cavernous sinus. Again the sellar is over here and this is the parasellar and paraclival carotid artery. We're working to clean out this cavernous sinus. Now we're coming back towards the midline. You can see the diaphragma with a bit of gland, normal gland here, spread over it. And here we're starting to see some of the dorsum sellar dura. This may be an inferior hypophyseal branch here. So we're sacrificing this because I know we need to get into this petroclinoid ligament area, to chase the tumor back, where it's followed through the medial cavernous sinus through the oculomotor triangle to get intradurally. So now we're working through this window, medial to the carotid artery. Cleaning off the last portion of the supersellar bit of this tumor. You can really see all the diaphragma herniating, and a normal gland right here. We deal with any cavernous sinus bleeding just by packing it off, just gently with some surgifoam. Don't want to over pack it. But a lot of times when it's full of tumor like this, you see there's very little cavernous sinus bleeding, really. And just by keeping our suctions active, we can keep the fields clear. So now we're chasing this portion as it starts to extend behind the cavernous carotid. So here's the cavernous carotid, here's that medial cavernous sinus portion, that pituitary tumors like to invade so much. And we're just starting to open up the medial cavernous wall to follow the tumor. So here's where our posterior clinoid process would be, right here. And what we're going to see is we can follow the tumor, essentially into the oculomotor triangle. Now we're working with two suctions, again, very soft tumor. Getting more lateral, I'm going to have to open up this petroclinoid ligament, that runs between the anterio-clinoid and the petrious, in order to get full access to that lateral aspect of the tumor. Again, I'm using my cartouche stimulator. I can see the third nerve extending up, above, beyond here. I can dissect it. I can stimulate it to make sure I've identified it and properly protected it. I don't like to enter in that superior-lateral compartment because I don't want to give patient ocularmotor palsy. Things like radiosurgery can treat obviously lateral tumor extension like that very easily. I'm just opening up this more of the petroclinoid ligament. And this will allow me just a little more access. Again, the advantage to the endoscope here is I can not only see behind the carotid artery, but I can sort of create an entire surgical field behind the artery, working with an angled endoscope Now the artery is really superficial here, and this is not an area that you'd be able to see otherwise. We're working behind the carotid just cleaning out that last little pocket of tumor intradurally. And what you'll see is this allows us to see all the way over towards the temporal lobe. So here now we're looking at frontal lobe, temporal lobe. We're looking out towards the medial aspect of the Sylvian fissure, really. It's a soft tumor. We have gently suction it off, and now we can look medially and we start to see even towards the brainstem. So just a last little bit of tumor here, and then we'll look back and be able to see vertebro-basilar junction. And now we're looking out laterally the final last look, and then looking medially, we see the tip of the basilar here up behind the clivus in the sellar. And this is that area where the tumor really grew through the cavernous sinus and herniated through. We can see the cavernous carotid completely laid out with tumor resection on both sides, and obviously a vascularized flap to cover all of that.

- Great case. Paul, I have a few questions specific to this case, and then some general questions. Number one, this patient obviously had double vision after surgery. Or did the patient have it before surgery as well?

- The patient did not have a double vision before surgery. The patient did have transient six nerve palsy after surgery. Honestly, in this case, it only lasted really about one or two days. You saw, I think, we never really fully exposed the nerves in the lateral cavernous sinus. The nerves run in that layer of the lateral cavernous sinus. So it has some protection. If we were to widely open, you noticed there we were least aggressive in with that superior-lateral compartment, because that's really where the nerves are fully exposed. And so just identifying them by electrical stimulation and working close to them, we might get temporary palsies either from packing or from some minor manipulation, but not permanent palsies. We found in our overall series, I think our rate of cranial nerve palsy, even cavernous sinus dissection was only about 0.3%. So it happens, but permanent palsies are low.

- The second question I have for you is do you chase all your pituitary tumors, that are going through the cavernous sinus or only the special ones? In other words, do you remove the suprasellar component mainly to relieve the optic chiasm compression, and then will you do surgery if the cavernous sinus component close in the future.

- That's a great question. The short answer is no, we don't chase all the tumors like that. This one was unusual in about half of the tumor was in the cavernous sinus. Whenever it comes in that anterior inferior compartment, I feel that that's very accessible. The medial cavernous sinus, we always chase. Because that's the most accessible and the most common location and that superior lateral we rarely do. And usually leave that for radiosurgery. I think that we can access the medial and anterior-inferior compartments with increasing risk in those areas. And then superior-lateral has the most risk. So I would say we always access medial cavernous sinus, but not all of those other compartments. Because you're right, especially in an older patient, this is a relatively young patient, but an older patient, it doesn't make sense to go after those compartments.

- Another question that I have for you, I see that you're reconstructing your skull-based defects with an onlay and nasoseptal flap. In other words you don't have a gasket-seal that Schwartz talks about, so sort of a fat graph or something. Do you feel that just a soft tissue onlay like a fascia lata and then a nasoseptal flap, adequate for controlling postoperative CSF leaks?

- I do think so. For very, very large defects or very high flow defects, we do use inlay in this case, you know, we typically place a bit of derogem or some fascia lata or something as an inlay, if you really have arachnoid dissection. But for the most part, we've stuck with just a single vascularized layer. We're not... I think there are a lot of ways to do this reconstruction. The one commonality that I think everyone has come down to is having some portion, the last portion, be a vascularized. And this seems to have helped everyone's CSF leak rates. So there are variations on what you do below the vascularized flap. But I think that's the most important part. In general though, that's mostly what we stick to. Is that in maybe some inlay of cellulose material.

- All right, nasal septum flap, pack the nose, you put a lumbar drain, regularly, or not?

- In this kind of case again, where there's arachnoid dissection, our general policy is we consider that to be a high flow leak and we would place a lumbar drain. The short answer is, that nobody knows the answer to that. We're actually currently are doing a randomized controlled trial. We're about halfway through. We predict we need at least a 250 patients, I think, but we're about halfway through trying to determine, try to get the answer to that, in which cases does it really help?

- Okay. So your protocol is typically, really does derogem, nasoseptal flap plus or minus Lumbar drain, pack the nose, no Foley or anything, you know, ballooned up in the nose or anything. It's just the simple nasal packing, correct?

- Yes.

- Okay. Very nice. This is really a great case and I appreciate your thoughts on this. Before we go to the next one. Something that, by the way, this is a postoperative MRI, obviously showing this spectacular resection in this patient.

- Yeah. Again, you see that superior lateral compartment is the area where we left a bit of tumor and I think for, for good reason.

- And by the way, when you expose the carotid in the nose, you always cover it with something or have, has it been times when you just leave the carotid as is and plug your CSF leak and you don't worry about any sort of inflammatory dissection from the mucosal exposed carotid in the nose? So have you ever had that problem?

- We do always cover it. And I think it's important too. Although I have no evidence that it, it's certainly not like head and neck surgery where you have to exposed to saliva or a pharyngeal secretion. The nose is not like that. It likes to mucosalize and remecosalizes, but we do always cover it. Yeah.

- Okay, very good. Before we go to the next one, a central question for a novice endoscopic surgeon and neurosurgeon, what would you say is your three most important pearls, that when you want to start? Obviously taking a fellowship for six months, taking some courses with you guys. What are the other technical pearls that you personally would tell somebody who's starting to do this business.

- I think one of the most important things is understanding microsurgical technique. This isn't a new technique. What we're doing is using a different corridor that we're allowed to use because of this tool, the endoscope and the key though really is to maintain the exact same microsurgical technique you would have with an open surgery. We are trying to recapitulate that with all of our instrumentation, all of our techniques are trying to use exactly the same thing. So we make very wide openings. So maximal exposure is, is the rule. It's not minimally invasive to the sinuses. It's a maximally invasive, maximum exposure. Maintenance of microsurgical technique, which really, probably, the most important thing. So having that background of both vascular surgery and microsurgery is, I think, the most important piece of that. And then frankly, I think, you know, playing the scope-based surgery, this is just one corridor. So you have to understand all approaches. You have to understand open approaches so that you select cases appropriately. And then probably the thing that I was able to be a part of and, and that, you know, kept this from, I think being, allowed us to develop was really a respect for the learning curve that's required with it. You can't jump into cases like this, unless you're comfortable with what you may have to do if there were a carotid injury. So there's a clear learning curve with every tumor type and every, you know, anatomical boundary.

- I totally agree. And you know, I, I personally do a fair amount of these, and I think, besides careful microsurgical techniques, is patience, you cannot lose patience, start pulling out things, retracting things, and assuming that, well, it's not attached to anything behind it because you're working. This is really a small working space. It requires a lot of dexterity because the distance between the surgeon and pathology is definitely much larger here. And so you really have to be patient. And if you lose patience and start making moves that are not well calculated. If something goes wrong here, it will be really bad. And it's not like cranial surgery where you have more exposure and you can control when a bad thing happens. So the first rule here is prevention, not management. And I think that's what I personally learned through good and bad times. Let's go ahead and go to another common case or pathology that lends itself very nicely to endoscopic transnasal approach.

- So this is a craniopharyngioma again. This is, I think, a 65 year old man who presented with he had nausea, hemianopsia, confusion, lethargy. He was found to basically I have a cortisol level of zero. And we can see this is a purely suprasellar, but not purely third ventricular tumor. It's lifting up the floor of the third ventricle with this large cyst. And the solid portion is basically filling the upper, the stock and growing into the tuber cinereum. Now the chiasm is pushed forward. We can see the chiasm right here. And so I think this would be, you would have to go trans-lamina terminalis and have a bit of a blind approach from an open approach for this. So I, I personally think, especially in someone who's hypo-pit, we don't have to worry about the gland function, just going directly into this tumor, endonasally through this trajectory is a great option.

- I totally agree for retrochiasmatic craniopharyngiomas, which we're talking about right now. The best approach without a doubt, is an endonasal approach. The working angle is beautiful. The exposure is nice and the risk to the cerebrovascular structures are less. So I cannot emphasize more than for retrochiasmatic craniopharyngiomas, the endoscopic approach really proves itself to be so valuable and so superior than any other approach. Go ahead please if you would like to add something with this MRI, Paul.

- Nothing much here, just showing how there's a large cystic component, but there is some edema, even the hypothalamus, which is a little bit of a worrisome feature. It just indicates that probably there's a little bit of significant adhesion or maybe a little bit of invasion of the hypothalamus. And my preference, my biases in those cases to leave a bit of tumor behind, if I must. Rather than potentially affect hypothalamic function. So this is another very nice exposure. This is a case, my partner, Dr. Fernandez-Miranda, helped with quite a bit. He's the other neurosurgeon I work with, but here we see the sellar and we see this wide suprasellar exposure. We're opening the dura out over the right optic nerve. And over the left, we've exposed the medial optic nerve. Here we see the gland and here you see these critical microvasculature. And why this is important as these superior hypophyseal arteries give a branch to the optic, they give a branch to that chiasm, and then they give a branch to the stalk. Now the stalk branches don't matter here. This is a patient who's hypo-pit already, but preserving these perforators, these subchiasmatic perforators, I think, is a great rule and having a good visual outcomes after these approaches. And I think potentially an advantage coming from below. So here we've entered into tumor, which is essentially the blown out stalk. The entire stalk is just blown out tumor. Here we're just carefully dissecting. Here's one of the hypothalamic hypophyseal branches that's feeding into the tumor itself. We're preserving the subchiasmatic branches and just internally debulking the tumor here. One of the things that you may notice... Sorry, what was that?

- I may ask you using Laney at 30 degree scope here, is that correct?

- We do almost everything with the a zero degree scope. This is a zero degree scoping used here. It's a direct trajectory into the tumor. Usually endonasally. It depends on the slope of the skull base, but generally working through this area of the tuberculum below the chiasm, we're able to work with a zero degree scope. It's easy to work with, it's comfortable, but you do need to be able to go back and forth. But this right now is still zero degree scope.

- May I ask when I use the zero degree scope, I run into trouble doing micro, using micro scissors and my suction when I'm really magnified and the endoscope is very close. Do you have the same problem because everything's such a small hole? And you're trying to mobilize your micro scissors, you hit the head of the endoscope if you're using zero degrees, and therefore you need to use the 30 degrees facilitate that. Is that a good Pearl?

- Yeah, I think, I think it absolutely is. I mean, I think there are times where you find, you just can't do what you need to do with the zero. And so that's when we switched to a 45. One of the things, I think, that's very important is whenever we do the surgery, we're doing it with two surgeons, an ENT surgeon and a neurosurgeon. And you'll notice there's a lot of dynamic endoscopy. So sometimes the endoscope is even working between and you're working together as one surgeon where the three instruments are working together. There's this sort of dance that you learn over time. And it's that ability that allows you to do some things that you wouldn't, I don't think, be able to do with a static scope holder and not to mention that you have another surgeon there working with you, thinking through the problem of solving this tumor.

- Thank you, please go ahead.

- So here we're just further debulking the tumor. You see some calcified portions. We're protecting the chiasm with cotton patties. We've preserved the subchiasmatic perforators. We've left the gland in place, there's probably no good reason to have done that, but we did. And now here's the tricky part we're coming up towards the hypothalamus and the posterior aspects. So now we can't really see, so we've switched to a 45 degree endoscope. We've introduced that into the cavity. Here you see the chiasm, you can see we're looking up now, at the back of the chiasm, we can resect the remainder of the tissue, leaving just a little bit of thickened stuff on the edge of the hypothalamus here. But this is an area where you really need the 45 degree scope to make sure you've cleared third ventricle and the floor of the third ventricle, where the cyst has expanded.

- Very nice case. Again, I think, for craniopharyngiomas, this is really an amazing approach. Go ahead, please.

- You can see there's a little bit of residual here, which I think shows up also on the coronals. Just in that wall of the hypothalamus, you would see maybe a hint of it here, and there's some pretty good studies that show, if you treat a small residual like that with gamma knife, the results so far seemed to hold up just as well with a 95% resection plus radiosurgery as would a complete resection.

- Let's go ahead and move to the next case. A case of chondrosarcoma. Will you share your info with us on this one?

- So this is a young girl. She was actually a nurse here, who basically almost went blind in her left eye and she began to even develop a right-sided temporal hemianopsia. And you can see here, the glands actually right here, and this is really growing, almost exclusively here, interdurally in the cavernous sinus, really crushing the left optic nerve and lifting up the chiasm. That's a very heterogeneous and also very calcified. So obviously very slow growing for her to tolerate this. It's slowing growing cause it's calcified. We don't have the T2's here. It was very bright on T2. So T2 calcified paramedian we were suspicious this could be a chondrosarcoma. Our exposure consists of a sphenoidotomy. Obviously we do a contralateral right-sided flap. We've done a wide sphenoidotomy and also a left sided maxillary antrostomy because that gives us advantage all the way out into the cavernous sinus. Now here, we're looking up at the 45 degree endoscope. And this is because of that suprasellar extension of the tumor. We're removing the tuberculum sellar here. Now this girl has a very flat skull base. So we had to use an angled endoscope to see that. Here we're just finishing exposing. This is the actual sellar here. This is all a cavernous sinus, that's been greatly expanded. You'll notice we don't open the dura supersellar, but we just remove the bone. That allows me to retract the dura upward and work in this space. So we open this, we encounter some soft tumor and then there's this rock in the middle of the tumor. Here's a, I think normal gland. And so here's a carotid artery off to the side. I ended up having to drill through this tumor. It was so calcified. Again I'm using that cartouche stimulator. I get some bleeding from the lateral cavernous sinus now. So I now decompress this, and it turns out this was actually growing. You know, these grow from the petroclival synchondrosis. So they naturally liked the inter dural space. So this is growing between the meningeal layer and this periostial layer that we know always surrounds the gland in the cavernous sinus. This is using all kinds of tricks we've stolen from open skull-based surgery. That was a SONOPET, an ultrasonic bone aspirator. I used to, again, cut more of this tumor in half. So how calcified fibrotic tumors, there a challenge, no matter how you approach them. But we have some of the, sort of the same tools and tricks. Here we see the carotid and we're just like, we dissected that portion of the tumor from, again, the cavernous segment of a carotid, and here I'm dissecting it from the pituitary gland. So here we see normal gland and you can really tell this tumor has grown completely interdurally. Now, this girl also has a sixth nerve palsy. Obviously this tumor is growing almost exclusively next to Dorello's canal. So she has six nerve palsy from that. And we start to see a hint of the sixth nerve, which is coming into Dorello's canal down here. There's a little bit of dura that looked involved, so I resected that. But otherwise I think we're able to get a nice resection, again, some inlaid duragen, a nasoseptal flap, that Dr. Schneiderman harvested for us, and then complete coverage of that area. Here we see the postop. Here's the T2 showing no more of that abnormal T2 signal. We see a nice normal gland and a complete decompression of the chiasm. She's had no sign of recurrence and has no sign of residual at this point.

- That's great work Paul. Well, that's really spectacular work. And I can tell you transcranially it will be impossible to achieve such a nice resection. And again, using the microsurgical techniques, we have learned so much. Intradurally and transcranially applying the same techniques through the nose, really, make the big difference. So here's a case of a clival chordoma that you want to share with us, please.

- Sure, so this is a young girl, I think about 20 years old presented with a sixth nerve palsy. And I think we can see this is just around where Dorello's canal is. We have tumor herniating intradurally, and we have tumor growing out towards the Dorello's canal. You can see that intradural herniation, although chordoma sometimes can fool you, because they like to grow in the interdural space between the meningeal and periosteal layers. So a lot of times there's very little dural involvement, even though a tumor looks like it's extensively intradural here. And here, again, we can see that herniation out into Dorello's canal. Dorello's canal is an interdural space. Chordomas like intradural spaces so that's why we end up with this kind of six nerve palsy so frequently. So we've done a sphenoidotomy, but we've also exposed all the way down to the foramen magnum through the nasal pharynx. So the sellar is going to be all the way at the top of our field. Here we see the sellar and we're just removing some of the eroded bone. This is the left paraclival carotid artery. Here's the right paraclival carotid artery. And we've started to expose the carotids on either side of the exposed sellar. I'm just testing here to see if I can figure out, make sure the sixth nerve isn't somewhere in the middle of this tumor. I suspect it's on the backside, but not always. So here, this is the upper clivus. The upper clivus is made up of the dorsum and the posterior clinoid. So what I like to do in these cases is involved bone, it includes the upper clivus. So here I'm performing a resection of the posterior clinoid. On the right side to do that I have to do what we call an interdural resection. So that was an extradural, by lifting up the poster clinoid. Here I have to go into the cavernous sinus between the layers, so interdurally, pack off the cavernous sinus. Because this posterior clinoid on this right side was just taller than the other side. I couldn't quite safely dissect, over the top of the posterior clinoid, to dissect off those ligamentous or the dural bands, rather that hold it in place. So here I'm opening that the cavernous sinus. Here's where the cavernous carotid would be. Here's the sellar. And now by opening in that way, I can see the very top of the clinoid to make sure I do a controlled dissection. Here we see the inferior hypophyseal artery. Try to preserve it. Not critical if you have to coagulate and cut it, that's okay. Here I'm just grasping this with the kerrison slowly, peeling it out. There I've peeled out the posterior clinoid after dissecting it off. So now I know all involved possible bone has been removed. There's a little more involved bone here on the medial aspect of the paraclival carotid canal. And now I can start to peel this tumor out of the interdural space. It has grown through the periosteal space. And so now it's just herniating into the meningeal layer of the dura. I can gently peel it out. Again I'm using that cartouche stimulating dissector. Same thing I would use during an acoustic or other open skull-based surgery. And as long as this inner layer, meningeal layer, is protected. I feel comfortable gently peeling the tumor out. Again I'm not grabbing at it. I'm not just pulling it out. I'm gently dissecting it out. I think there's a big difference. Here. I recognize now. Here, it's very apparent to the dura. I'm not sure it's not herniating through the dura, so I'll kind of amputate it in this region. So what we actually see here, is this was just a herniated segment. Now you obviously have involved dura here that needs to be resected, but the tumor itself is barely intradural. And this is happens frequently with chordoma. I want to resect the involved dura. And so my concept in chordoma is to always resect any involved tissue. So if the tumor touches dura, that dura has to be resected, you shouldn't be limited because you're worried about CSF leak. If that's the case, you should be using a different approach. So you still need to make sure you resect all involved tissue. This is something, you know, Dr. Shaker has taught us and Dr. Sen, from doing lots and lots of chordoma's 'cause you got to remove all the involved bone. You got to remove all the involved dura and all the involved tissue that you possibly can in order to try to prevent recurrence. Here. We're resecting that inner layer of dura, and I'll resect this as really as widely as it is physically possible. Only limited by the carotid artery and the sixth nerve Here, we see the left sixth nerve. This was not the sixth nerve that was affected by tumor. It stimulates nicely at the end of the case. So I know I preserved that. Here I'm stimulating to localize Dorello's canal. The Dorello's canal again is interdural, a little more involved dura. And again, I find some more tumor here, that's in the interdural space. I'll even send dural margins around the edge here to make sure I get complete resection. Here's the left six nerve. We can see the right six nerve just buried next to the basiler, on this side. Then the sixth nerve originates at the vertebra-basilar junction, always. So this is I think, a complete resection, at least as far as I can get, microscopically negative margins. The imaging confirms that this integral space has gone. There's no more T2 hyperintensity behind the carotid artery. You can see our packing in place and a nice nasoseptal flap, which shows up on the contrasted images.

- I see that a lot of times, Paul, while your exposing the carotids, partly because knowing where they are, is going to make your procedures safer rather than say, well, I'd rather not play with them because I put them at more risk. I think in endonasal surgery, it's best to know where they are, especially in these procedures. I assume you just use a diamond drill over them and then use it to curette to, move out the thin piece of bone cortical bone. Is that right?

- Yeah, very much. We, we use a, so almost blue lining technique. It's a coarse diamond bur, so it is a little more of a rough edge than a typical diamond, but it's still basically a diamond bur and it's a tedious process exposing a carotid to a tee, it's not fun, but I think it's necessary for many of these, to get really that wide exposure and to be able to access the tumor that's behind the carotid. So you're absolutely right. I don't just bite with a kerrison or something, I very much thin the bone overlying the carotid and then gently dissect it or flip it off. That's, I think, that's the safest way to do it.

- And it seems like you often do that in terms of exposing the carotid. Because you want to know where they all are very well early on the process. Am I correct?

- Yeah

- Very good. Let's go ahead. And you have one more case. Before we sort of divide the talking to two pieces, and this would be an olfactory groove meningioma, please go ahead.

- So this is a middle-aged man who presented to us, who had this discovered, actually a few years ago and kind of forgot about it a bit. Was loss to follow up and over about eight years, this essentially tripled in size. He represented when he had dysosmia, had almost essentially lost his, completely his sense of smell. He had headaches and he also had some personality changes with irritability and depression and mood swings. And he's found that this moderate size meningioma. It's, you can see here, to access this through a craniotomy would require nearly some degree of frontal lobe attraction. It's a rather wide tumor, but I'll show you one of the tricks we use to get out over the top of the orbit. There's also a little bit of ACA involvement, essentially touching the backside of the tumor.

- Before we go to the video. You're all, it seems like the endoscope would have a hard time seeing along this angle, because, am I correct, you're going to talk about how you get around this area, because you're working space with this, you know, it's clinoid sinus and it's ethmoid you invading there.

- Yeah. I mean, to some degree working with a zero degree endoscope we do more sinus exposure, we basically ended up doing almost complete ethmoidectomies, which certainly has some sinus morbidity to it. And so that's one of the ways we do extend that, is by doing ethmoidectomies. And that and using 45 degree endoscope more so even for this case, than we would normally, those are essentially the only things that we change. So, for this exposure, again, we'll have to resect both middle turbinates as the patient's already anosmic, it's just showing the resection of the right middle turbinate. And we'll obviously do, need a nasoseptal flap for this, the nasoseptal flap, if you do measurements, which we've done in a couple of studies, as have others, really can cover the entire skull base. This flap is being done on you'll see, I believe, the right side. And it's being extended down onto the floor of the nose, even. So we're even getting a little bit of mucosa down onto the floor. It has the same blood supply, and then we can dissect it back, off the nasal septum and tuck it down into the nasal pharynx, out of the way. So we'll start with a sphenoidotomy. The upper sphenoid puts us directly onto the planum This tumor comes right back to the optic nerves and the tuberculum. So we need that access via this sphenoid. So now here, we're just seeing the ethmoidectomy. One of the great advantages of this. Here's the anterior ethmoidal artery on the left side. So we've resected the lamina papyracea, and we, on both sides will coagulate the ethmoidal arteries, the anterior and the posterior ethmoidal arteries. This will, devascularize the tumor. Here's the final step, which is to open up the frontal sinuses. And that gives us our most anterior aspect of our exposure. Here we see the anterior ethmoidal on the left side. I guess, that must've been the posterior ethmoidal before. But by dissecting the lamina papyracea, transecting these ethmoidals, we can gain access over the orbital roof. What we call a medial orbitotomy, in order to retract the, to the, the periorbital over and really expand our access. It requires a small superior septectomy and able to gain bilateral access to the skull base. But here we've resected lamina papyracea. Decompress the orbits. We have a frontal sinus opening, on both sides. And now we have access to the full cranial base. We've essentially turned this into a devascularized convexing meningioma. So now I'll do an osteotomy along the left cranial base, just medial to the orbit. I'll extend this up to connect to the cribriform plate and the crista galli. Posteriorly, I need to do an osteotomy across the planum. Here I'm doing the osteotomy with the drill across the planum. Again, you notice the constant dynamic endoscopy. I really couldn't do most of what I do without working closely with very skilled ENT surgeons. They develop these approaches with us. I think it's critical. So after doing those osteotomies on both sides, now I need to connect them in the middle by drilling away and resecting the crista galli. So I've done osteotomies bilaterally that allows me to peel out the entire cranial base. Here's peeling out the last portion of the posterior cribriform. You can see this bones involved. So for a true Simpson grade 1 resection of this, you need to drill away all the involved bone and all the involved dura. And this approach naturally gains that for you. This is showing how we gain that more lateral access to remove the medial orbit, the so-called medial orbitotomy, that Dr. Fernandez described. And by dissecting over the periorbita, we gain access to that orbital roof. And you can see that here. So here we've preserved the bone of the optic canal. So that's preserved, and we have this very wide access to the cranial base. Well, beyond the medial orbit. So now I can open directly onto the tumor. Again, in theory, this is like a convexity meningioma. What you can see here is the tumors completely devascularized, it's dead. It's kind of a, it's got some venous bleeding in it, but other than that, it's really not very vascularized at this point at all. It's a little bit fibrous. So I'm using a ultrasonic aspirator there. And then again, the same concept I internally debulk the tumor. And then I do extracapsular dissection. The first thing I want to do is get proximal vascular control. So I dissect the lower portion of the tumor to identify the ACA's as they enter the interhemispheric fissure. Here, we see the Acom-complex. Here I'm dissecting out, what I think is probably hoidner or another small recurrent perforating branch. That's along the aspect of the tumor, the lateral aspect of the tumor. Using a 45 degree endoscope, microsurgical instruments. And then anteriorly after I've dissected the lateral portion to really release the tumor. You have to transect the faux. So the final attachment for this tumor is the faux. I want to calculate the faux. I'm using this straight through cutting instrument here to transect the faux. But before that, I need to debulk tumor a little more. So the same concepts, constant internal debulking, extra capsular resection. I'm not just reaching up and pulling this tumor out here. I'm resecting this last a little bit of a falcine attachment. Now I just have the portion of the tumor left that has subpial invasion. And you can really see it's not just peeling out. We have a fair amount of adherence to this subpial surface. You can see the olfactory tract on the right side, coming into view here. And again, the same kind of thing. I'm just carefully not pulling this tumor out. I'm dissecting the edges of it. Blunt and sharp dissection. Here, I'm using my scissor. You can see how the tumor really has some pretty decent subpial invasion in a couple of these areas. Using cotton patties to protect the brain. All the same sort of techniques we do with open microsurgery. Just the very last attachment you can see we've preserved another small branch of the ACA here. Here's our very final attachment, a little bit of a, of a feeder vessel there. And there's the final portion of the tumor being resected or detached. And if you just pull this tumor out, you'd have probably some pretty decent ACA injuries. Here we're looking at the angled endoscope. Checking all of our dural margins, making sure there's no involved dura left, whatsoever. We protected the ACA during this portion. Now removing the patties. We see the Acom-complex. We see the hoidner vessels completely protected. Olfactory tracks. And here we see that area of subpial invasion. So obviously we need a nice reconstruction here, place a duragen inlay graft, and a, and in this case, our nasoseptal flap, I was worried, didn't quite reach all aspects. So we placed an onlay graft here, sort of a triple air closure, and then even fat to fill the sphenoid. And this is to make sure that our vascularized tissue can meet all edges around here. So these are some tricks that we use as part of the reconstruction to ensure that our vascularised flap has contact around all edges. Just because you use a vascularized flap doesn't mean it will always cover, and sometimes we have to use these other tricks in order to make sure we have the entire covered. I know earlier you were asking me, do we always just use an inlay graph? I think it depends on the size of the defect and how well it's covered. Here's the post-operative MRI. We just did this case this week, actually He's left the hospital after a couple of, after two days. And he's, he's doing very, very well, but hopefully he'll get that to heal up.

- How long did it take you to this case, Paul?

- This particular case, to be honest with you, I knew I was doing this for this, so I didn't, usually my fellows will do a fair amount of the case. So Dr. Schneider and I just did this case and we were finished honestly by one o'clock in the afternoon. So I think that's pretty reasonable. I think between the, you know, two surgeons who've worked together for a long time, we're able to do these cases very efficiently.

- And you sit down, you were holding two days down. That means the lumbar drain wasn't involved before he leaves, which is 48 hours only of lumbar drains.

- Correct. We do three days. Our protocol in our lumbar drain trial is three days. So I typically do three days. I think, I think probably that's adequate. Four and five days, you start running into a higher risk of infection.

- Okay. Thank you. So this would be the end of part one. Let's go ahead and to have our viewers also watch part two. Thank you again, Paul.

- Thank you.

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