Grand Rounds-Nuances of the Expanded Endonasal Approach for Management of Complex Skull Base Lesions

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- Hello ladies and gentlemen, and thank you for joining us. My name is Aaron Cohen. And today we have with us Dr. Paul Gardner from the University of Pittsburgh Medical Center. He is the Co-Director of Cranial Based Surgery with Dr. Carl Snyderman. The first series we reviewed giant pituitary tumor and impacts on the meningioma and clival chordoma and condrosarcoma. And Paul was very kind to give us an overview of the nuance of his technique. In part two, we're going to even approach more difficult lesions, such as the petroclival meningioma and a posterior cerebral artery aneurism. I'm also going to add a case of mine, which will be a third ventricular choroid plexus papilloma. So, all again, thanks for being with us. And let's go ahead and jump into our base case, which will be a petroclival meningioma.

- So, thanks for having me again. And this is, so this is a challenging tumor and frankly one I wasn't sure that we could get a complete removal of endoscopically, or endonasally I should say, this was thought to be a schwannoma. It's a tumor that's growing in Meckel's cave and clearly has herniated through into the posterior fossa, but it has a component that's really very midline. This guy presented with some trigeminal symptoms and bad headache and retro-orbital pain.

- Yeah, definitely daunting tumor to approach through endonasal approach, especially because it really, almost goes to both sides of the cavernous sinus. So, I would be really interested in how you manage that part of it.

- Yeah, no question. So, it's just showing the initial portion. We transect the middle turbinate, which we really do for all our cases. It makes some good room for the endoscope. And obviously we'll do a vascularized flap because of both carotid as well as CSF exposure. I want to thank my fellow Francisco Vass, who's responsible for most of these videos. He and Mary Cuderuso did a lot of work to help me get this all put together. Here we see typical nasal septal flap making the upper cut now, we use a needle tip Bovie on a very low setting, about 15, maybe even 10. So we don't cut through the cartilage or we don't shrink down the flap. It's important to make the flap really as big as possible. I've never regretted having a large flap. I've regretted many times not having quite enough flap. If you can get in this proper plane, this is just like a direct transseptal approach. We're just peeling the nasal septal flap off the cartilage in the septum, making the final cut up towards the sphenoid ostium, the pedicles between the sphenoid ostium and the colina. This is fed by the posterior nasal branch of the sphenoid palatine artery. Now we're opening up the sphenoid. We've also done a maxillary antrostomy, that combination of the sphenoid maxillary antrostomy allows us to now access and drill out the vidian canal. This vidian canal and nerve, which crosses over the petrous portion of the carotid really is what gives us access to Meckel's cave. Now I'm drilling out doing this transclival approach like we saw on some of the other cases, and here we're working towards foramen lacerum. You see some of this cartilage of foramen lacerum. I'm going to have to completely skeletonize this petroclival carotid, here's the sellae, here's the clivus. This is Meckel's cave. And eventually to really access Meckel's cave, you can see here, I'm sacrificing the vidian nerve. Now, this would happen with the middle fossa approach as well, and these patients do develop dry eye, but most patients don't notice it. And the only cases I really worry about it is if I were to cause some V1 dysfunction as well. So if they have corneal, in a sense cornea, that's also dry. You could get a corneal keratopathy. Here's Meckel's cave. I'm just extending a bit up to the sellae, sort of in a reverse fashion. And here's that, extradural or intradural rather posterior clinoidectomy it's an intradural pituitary transposition. So we lift up the pituitary and resect the posterior clinoid. So now here, I've entered Meckel's cave. I'm using this cartouche electrical stimulator to identify the sixth nerve. I'm not real happy with my plane there. So I decided to look into posterior fossa, to try to understand this tumor a little better, still not sure what it is. I thought it was a schwannoma. I opened the door pretty widely, again, I'm dissecting and I just need to internally debulk this tumor. So again, using sharp and blunt dissection, internal debulking, extracapsular dissection allows me to identify, here's the sixth nerve coming around the bottom of the tumor. I can carefully dissect that free. I can put a patty on it to protect it. And the same concepts is with open microsurgery intradural or other internal debulking and extra capsular dissection. So now I start to get a sense, here's this tumor's relationship to the fifth nerve. So the fifth nerve seems to be running around this tumor and below the tumor. So what I can see here is the fifth nerve coming out and I see the tumor involving some of the upper fibers. Here's sixth going out Dorello's canal, but I can really see that the fifth nerve is below. So now I know I need to come into the top of this tumor in Meckel's cave and work down towards the fifth nerve. So that gave me a good understanding of how to attack this tumor within Meckel's cave. So again, internally debulking, I can use things like CUSA or blunt and sharp dissection. And now I can work freely in Meckel's cave, among the lateral side of the carotid artery now, and I can resect all of the Meckel's cave portion, just irrigating out to make sure everything's nice and dry. We see the fifth nerve in the floor of Meckel's cave, looking in the posterior fossa. We see complete resection here. We can see the fifth nerve as it enters Meckel's cave. Right there. You see the sixth nerve going out Dorello's canal behind the carotid artery, the petroclival carotid, dissecting a little bit more of involved dura, there's sixth nerve coming out of the retrieval basal junction, and then covering of course, both the posterior fossa and Meckel's cave openings with the nasal septal flap. He received a post-operative MRI. This thickening here is our nasal septal flap, which is external to Meckel's cave and a complete resection. He's had no sign of recurrence. There's actually a clear cell meningioma. So I'm watching him actually very closely, as you know, they have a higher rate of recurrence and really fall more in that atypical meningioma classification.

- So in this case, Paul, you really mobilize the artery, the carotid artery immediately, and really worked sort of between the space, just lateral to the carotid artery and moved up to the Meckel's cave, am I correct?

- Yeah. I mean, you know, certainly mobilizing the carotid is not something, you know, our group even did for many years. It's, you know, working in this area I think is really on the end of the learning curve. And it's something you have to be comfortable again with managing the potential complications of carotid injury.

- And can you tell me in this case if there is a carotid injury, how would you manage it?

- Depends on the location of the injury, but the one disadvantage I found was that there really is no good way to suture. We do have hemoclip appliers. So you can, if you can oppose the edges, you can do hemoclip apply. This segment of the carotid, obviously with that kind of exposure, I can get proximal and distal control in order to control any hemorrhage, but then fixing the hole is the issue. If it's a small opening, a small tear, I'm usually able to coagulate that opening. And that's been very successful. There have been, I believe now two cases where I've been able to pinch or with a curved or an angled aneurysm clip. We have aneurysm clips we can introduce on pistol grip appliers and that way I can pinch off a bit of it, but there are some cases where we've had to sacrifice the vessel. You know, fortunately there are some percentage of people who can tolerate this, majority of people can, but I certainly don't rely on that. So packing with muscle, aneurysm clips, small hemoclips and bipolar cautery, depending from large to small, the size of, of the hole in the artery.

- Thank you. Let's go ahead. And this is a really nice case of a posterior cerebral artery that was managed through an endoscopic endonasal approach.

- So this is an older physician actually at one of our sister hospitals who presented with a progressive third nerve palsy, essentially, as I was close, by the time he got to me with this very large PCA aneurysm, you can see here, he has a pcom on the right side. He has no pcom on the left side on any view, but this is a very large aneurysm. We actually recommended to him endovascular treatment. But we did tell him probably with clipping, he would have a better chance of third nerve recovery. Although, I thought the morbidity with open surgery was higher for him, operative morbidity. He wanted to have a clipping of it. You can see this 3D reconstruction shows the relationship of the aneurysm to the PCA and the SCA, which is of course right where the third nerve runs.

- Let's go ahead and see the exciting video of this case.

- Of course, discussed open options with him. I felt this was a relatively direct approach to this aneurysm. Again, we see the sellae, we've done a pituitary transposition to remove the upper clivus, the dorsum and the posterior clinoid, especially on the side of the aneurysm. And this allows me now to open the clival dura, here you see the periosteal layer of dura has been stripped and that venous plexus between the two has been open has been, packed off rather. And here I'm opening the dura, this little micro through cutting device. It's very nice for opening dura, I think pretty safely. Now I'm opening toward the side of the aneurysm. You can see that posterior clinoid and dorsum resection, allows me to open the dura very widely and work towards the basilar apex, which inevitably lies right behind the sellae and the pituitary gland. We resect the dura and you can see here I have nice control over the basilar and the PCA. So I do have proximal and distal control. I dissect the associated vessels, the SCA, atherosclerotic neck, of course, here we see the third nerve just being crushed by the aneurysm. And you can see here just trying to compress the aneurysm with my sachs dissector and see the mammillary bodies there in the distance. Just trying to dissect there. It gets pushed up just by the sheer weight and magnitude of this aneurysm. So I decided to do a brief temporary clipping. Remember no pcom on this side. So, all I have to do is trap with the right PCA and the basilar and now this aneurysm is much softer. So, for about two minutes here, I have the patient, his bet suppressed, this temporary clipping of the basilar and the right PCA. And then I'm just placing a clip here to take some of the weight away from the aneurysm. This isn't I realized my final neck, but I want to kind of reduce this to a much smaller aneurysm. So I'm not fighting the turgor of the aneurysm. Remove my temporary clips. It's going to be one of the trickiest parts, because these are obviously free floating. And my angle of access is, is limited coming through the nose. Now I want to place really, my neck clip. I've dissected between the PCA and the aneurysm and the SCA. I know this is a very thick neck, so I know I don't want it to look perfect on the outside, because if I do, I'll have to nose it on the inside. So I'm pretty happy with leaving this amount of external remnant, because I think, but what I see here is that there's still some filling of the aneurysm. And I think that's just purely, largely, the weight of the aneurysm. So what I try to do here is reposition these, these clips that I have in place, really put them a bit deeper even, in case it was filling on the backside that I couldn't see well, I reposition this distal clip. I was pretty happy with this proximal clip on the neck. You can see the area that's filling here. This atherosclerotic portion is not going to be filling, not when it's pinched together that way. Carefully checking my tips. Make sure I don't get any perforators on the backside. We see a small perforator has to be dissected free checking with a Doppler, my SCA is still patent, but aneurysm is still filling so I can still Doppler the aneurysm. So, what I did is just placed eventually one more booster clip, just this little ones I had, and that was adequate for some reason, just the closing pressure of these clips and this atherosclerotic neck, in this size of an aneurysm wasn't enough. You know, this isn't a new concept. These are all the same concepts from open aneurysm surgery. And so, all the concepts are exactly the same. It's just a corridor through which they're applied. Fortunately, all of these clips are intradural. So, the aneurysm no longer Dopplers, all of these fall within the intradural space. I can just cover them with a nasal septal flap. Again, we see patent vasculature, flush things out and make sure everything, nothing's bleeding inside there, and then place a collagen DuraGen inlay, and my nasal septal flap. In this case because of the size of the opening. and because of my concern with the aneurysm, I did place a, this is like a fascia lata type material. I think it's a pig intestine layer, and then the vascularized nasal septal flap. So again, for these larger defects, we have gone to this multi-layer reconstruction in cases where we're not sure the nasal septal flap will cover the entire defect well.

- If I may ask, how about if you aneurysm clips stick out through your bone defect? How are you going to manage sort of handling the hinge?

- Sure. So, this was a nice case in that we didn't have that problem. But, for example, when we've done super hypophysial immediately pointing supraclinoidal aneurysms, like the case, when I finally got points immediately, your aneurysm clip will be sticking out. First of all, I use as short of a clip as I can, but what we do is place fat around it. So, you have the aneurysm clips sticking out, we place fat around it and then the flap over that, I don't put the flap directly on a clip. We do have one of our first cases where the clip eroded through the flap. And so we ended up placing fat around that. So, now we've gone to placing fat first around the aneurysm clip and then the flap over that. So it's protected from that eroding.

- I got you. And these aneurysm clip appliers are the regular appliers, or do you have specific appliers for this kind?

- These are pistol grip appliers I think, I believe we use ASCO clips, but most companies make pistol grip appliers I actually don't even know if ASCO makes them anymore. We've bought enough of them that we have some backups, but there are both these pistol grip appliers there are some nitinol single shaft appliers that are on the market now, but a standard clip applier, you won't be able to open and close in the nose.

- Thank you.

- I think we have a post-op angio. There's our preoperative, Here's our intraoperative final impression angio, we see a preservation, so it turned out. I think that clip was a nice placement. We had the SCA patent, the PCA patent on the side, and we can see all the perforators still patent there. He has recovered his third nerve palsy. He still, he did have a long postoperative course, which is, I don't think surprising, but he's doing quite well at this point.

- Very nice. So I think this is a case where no angiectomy was necessary. Please go ahead.

- So this is a, I believe it's about a 65 year old woman who had a Chiari decompression about 20 years earlier. She had basilar invagination at the time, but it's progressed significantly. And she has some significant bulbar symptoms from this brainstem compression. So, she obviously needs a fusion as a part of this with progressive basilar invagination, but because of the bone decompression of the brainstem, we wanted to do an endonasal odontoid resection as well. The access is directly through the nasal pharynx between the eustachian tubes. We simply resect the nasal pharyngeal mucosa as well as the longus capitis and rectus capitis anterior muscles. Just the attachments here at the foramen magnum. And now we have direct access onto the anterior ring of C1. Here I'm drilling out the ring of C1. This is a very low, this is the absolute most caudal access we can get. So this is a curved MIS, a drill attachment allows us to get a little bit lower. It's just using a Kerrison to resect. Some of the atlantoaxial joint capsule, do some of the atrial ligament attachments. This view really shows how deep this is. A little trick here, you can drill off some of that maxillary crest where the nasal septum attaches more to get a little more caudal access. Just like a transdural approach, the resection of the dens is no different. We drill from the top down. You don't want to disconnect the den and then have to try to cut away the tip of the dens from those ligamentous attachments. Here we're just drilling away a little, getting a little wider access doing a little more than medial lateral mass of C1, resecting some of this ligamentous attachment until we really see tectorial membrane, making sure we have a nice wide exposure. And here we see a nice pulsatile tectorial membrane at the end of the case, just be reconstructed with Tisseel, doesn't require anything else. There's no CSF leak. I don't resect back to dura when there's just bone decompression because the tectorial membrane is nice and pulsatile and decompressed.

- I can go back to the pre-op images here Paul. Did you have to use a 30 degree scope to work most of the time, or 45 degrees or a 0 degree scope was fine?

- Yeah, we're really forced even to use a 0 degree scope in this case, the problem with an angled scope is really looking down. Doesn't get you an angle to anywhere you want to see it. You could see down perhaps to C2, but not to areas you can reach. So this is one of the most difficult areas to keep a view, but we do use a 0 degree scope and simply work just below the scope. It is difficult. Occasionally, if there's a lot of basilar invagination, we'll have to work with a 30 degree scope to sort of reverse that angle. But in this case, we have direct access. You can drill off some of the foramen magnum, you can drill off some of this assimilated ring of C1, and then we have direct 0 degree access to the tip of the band.

- Very nice.

- Here we see the, there's actually an intraoperative CT during a nice wide decompression. And we've clearly resected all of the dens as well as any portion of the foramen magnum that was affecting the craniovertebral or the cervicomedullary junction. And reconstruction is just with Tisseel and it fills in very nicely heal secondarily and it mucosalises.

- Paul, I wanted to share a case with you. And the reason I share with you is because this is a 45 year old female with a visual dysfunction, and this is the tumor that she had, a choroid plexus papilloma. She had a previous history of papilloma and, you know, a lot of my colleagues feel like a very highly vascular tumor, which typically a choroid plexus papilloma is, may not be very well amenable to endonasal approach. Because if you get into breathing, it's very difficult to control it. Can I ask you, first of all, would you approach this endonasally? What are the pearls you would share with your colleagues? And, before we review the video, that you would say, make this a difficult case of a highly vascular tumor.

- Yeah, I guess one question obviously is, what's the patient's pituitary function at this point, because I think any approach you do this will, it may potentially affect that.

- She didn't have a DI before surgery, but she had some hypopituitarism, and she had the same of those after surgery and her DI was only temporary. So, through an endonasal approach, we did not affect her pituitary function.

- That's great. You know, I think the main things that I would be, and it's not necessarily intuitive. The obvious pathway to this is between the chiasm in the gland, in the suprasellar between, and in the tuberculum across the superior intercavernous sinus, but to work safely there, you really got to remove the bone. I think below the sellae, in order to safely, kind of sit on or press on the gland. You know, a vascular tumor in this location, this deep location is tough, no matter how you get to it, as long as you make sure you have the same instruments available and the same mobility to work with microsurgical technique, I would be comfortable resecting this. You know, one of the things about these tumors is if you use the long access the two point rule that's best for, I think, you know, very importantly, spouses, this is the, the most direct access in that long axis of this tumor is endonasal and anterior corridor based on that concept is the right corridor for this.

- One of the things that worried me a lot about this case is, the kind of such a small space there is to work on. And for vascular tumors such as this, that could be a challenging small corridor, but just like you mentioned, we transpose the pituitary posteriorly by removing the bone and that lets you increase your operative corridor. When we talked about the petroclival meningioma, one of your cases you just mentioned, you talked about the pituitary gland transpositioned anteriorly. Can you tell me a little bit more about that instance that you removed over the sellae? Are you really open to do over the pituitary? And to talk about transposition? So, you really mean about pushing the pituitary up, but not necessarily removing the dural, is that correct?

- So, you know, when we initially described pituitary transposition, we described an intradural, so you completely disconnect the gland and lift it out of the sellae. I think that's a very high rate of pituitary dysfunction. What we've gone to more as for lesions, especially behind the dorsum sellae and this retro dorsal space or retro-infundibular tumors, we'll drill out the, the upper clivus and then just lifting up the dura here. You can access the dorsum. So you leave the gland with its venous plexus and the dura around it, you protect the vasculature of the gland and really protect the gland by leaving at least that inner layer of dura there.

- So it's really immobilizing the pituitary out of your way.

- It is, it sounds a bit fancy, but really you're just removing the bone and lifting up the dura, protecting it.

- Well, making it fast. It's a nice point to do. So, this video is definitely not nice as your videos because there's going to be bleeding in there, partly that because of this very highly vascular trauma. So, bear with me and I will try to sort of, go over the video, which is a little bit on the long side. I would love to hear what your opinion is, in terms of how to manage a vascular lesion through the endonasal approach. So here it is, we did approach this through the endonasal approach and this lady had some visual dysfunction. You will see momentarily that again, the same images that we reviewed and the very dense tumor, that most likely is highly vascular with some of the choroids within the tumor. Again, this is her visual fields, more of it in barrier quadranopsia, because this is, the push is from up or the pressure is from top of the chiasm to impair direction. So, we did a nasal septal flap, it's very standard, here is to the sellae, right from sellae and planum, standard technique of drilling and removing the ball. I tried to be very conservative with my bone immobile just to avoid any cebocephaly postoperatively. I feel you guys like the more expanded volume removal. I really tried to be very stingy and only removing it as I need it. This is again the pituitary gland right here. You talked about removing some bone over it and then opening the dura, using very much similar techniques in terms of opening the exposure to the tumor. Would you have removed more bone here, Paul?

- I would have opened it. I wouldn't have opened any higher, but I would have opened a little more widely, just because I feel then I can move my instruments more. Once I get into the intradural space, because it's the bone that limits me more than anything. I don't know if I would have opened the dura any wider, but the bone I might've opened a bit wider.

- I got you. And here's using again, techniques to coagulate the dura. We talked about those perforators. Unfortunately, I had to take some on one of these perforators from the suprafascial, just to be able to open my working zone into the optic chiasm and this patient vision actually significantly improved after surgery, which was nice. Again, the opening was very small by pushing that pituitary back or in a little bit of gentle elevation of chiasm, which chiasm neatly, nicely tolerates. I think transcranially, optic nerves and chiasm seem to tolerate their mobilization a lot less, but endonasally, just the gentle elevation seems to be very well tolerant. Do you agree on that topic, Paul?

- Aaron, I think you're following the pathway of the tumor. And so, to some degree you have some laxity of the chiasm that's been created by the tumor, but you know, that's sort of been my experience is that working through this corridor has much better visual outcomes. And I think part of it though, is visualization of, some of the areas of the tumor that you just can't see. And so, while we may be, you may be retracting the chiasm it's under visualization as well.

- Thank you. So here is microsurgically cutting the lateral edges of the tumor and delivering and sort of the heart of the tumor and debulking it using, we had to disconnect another branch of suprafascial. This is the posterior left wall of the third ventricle. This is using a 45 degree endoscope and working again to the perennial mandrel. And this is really a beautiful way of dissecting this tumor, which was attached to the choroid plexus over that lateral ventricle. So again, they're a part of the tumor and trying to dissect and preserve the mucous membrane to protect the posterior fossa and vascular stretches. Again, looking up with it 45 degrees scope and seeing all the way through the lateral ventricle and confirm that everything has been removed. Here's talking about preserving the memory of the request and this is the stock that was currently preserved here, showing the, with a 45 degree scope, very small, maybe amount of turn left just to protect the walls of the ventricle. And this is a post-op MRI. She did really well, vision improved, between function and then stable. I really enjoyed doing it this way, and I think it's really the best way and safest way. Do you have any other thoughts about how you would have done this differently, now you saw the video?

- I don't, I mean, that's a, that's an amazing case. That's really neat. And you know, I think one of the things about it is, you know, when you come from this approach, you could see that stock at the end, you knew you had preserved that, you can see it here on the MRI. You can see how this was something that was growing forward from the four, from the third ventricle. You know, I don't, that's an amazing case. I don't think I have much to say about it, it's really, really nice case. I think, I personally think that was the right approach for you taking advantage of the corridor that the tumor's created. Very nice job.

- Thank you. And you can see the pituitary stock nicely preserved on the post-operatory MRI. So Paul, I really appreciate all your great pearls really master work that you do there. Pushing the limits. You're one of the pioneers of endoscopic surgery, and I really want to thank you for your time.

- Thanks again. I really appreciate this opportunity. I want to, you know, also thank my fellow Francisco Vass, he really helped me a lot putting this presentation together and you know, this whole program is really remarkable, so, thank you very much.

- Thank you, Paul.

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