Endonasal Approach to the Petrous Apex

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- Welcome ladies and gentlemen, for another session of The Virtual OR. Tonight our guest is Dr. Paul Gardner, from the University of Pittsburgh, UPMC. He is a pioneer in Endoscopic Skull Base Surgery, without a question. He has really pushed the limits and refined many of the techniques we use today, for resecting some of the most challenging lesions in the Skull Base. Paul, I really want to thank you for being with us. I know you're gonna tackle the most difficult part, which is the Petroclival region. So we're all ears and very interested in hearing your expert opinions.

- Thank you very much Aaron it's an honor to be here. The list of faculty that's gone before me and goes after me to give these talks is really simply the best in the world. So I'm very honored to be a part of it. And I want to thank Aaron for his tireless efforts, both with all of the content on the Atlas, which I think all of us can learn from, but also for just constantly keeping this dialogue going. And even in virtual times . Here I think that becomes that much more important. So thank you for all your efforts with that I know how much you put into it.

- You're welcome and thank you for being with us. It's been honor to have you as a colleague, Paul. We have worked with each other for many years and you've been huge and tremendous. We have all learned a lot from you. So let's go ahead and jump to the talk Luke and take it from there thank you.

- All right. So I'm going to talk about what I do think is one of the most challenging areas and that's the Petrous Apex and the Petroclival Region and what I call the Medial Transpetrosal Approaches, you know to contrast with the Open or Lateral Approaches. This anatomy in this area is very complex there are critical structures that essentially make up all of the boundaries of the Petrous Bone and the Petrous Apex from the Carotid artery to the seventh, eighth complex to the Fifth Nerve, et cetera, et cetera. This is a key area and as a result, one of the most challenging to access. Here's a view of that of the Petrous Apex through an Open Approach through Anterior Transpetrosal Approach. And you can really see what those boundaries are and why this is such a challenging area to access, whether it's you know, from the Carotid artery or the IAC that's limited, or the Porus Trigeminus these are all the areas that we're struggling to work around. Now this area, fortunately though, can be approached through many different varieties. We can come from anterior Approaches, posterior, inferior. All of them designed to work around these multiple neurovascular structures to try to get the greatest access. And the truth is there is no one approach that can be used for the Petrous Apex or the Petroclival junction. And the selection really in my mind varies based on two critical things. What is the pathology? And what's the goal of surgery? And that varies with different pathologies that I'll go through. And then finally, also what's the location of that pathology relative to critical structures, because that also is going to change depending on the tumor pathology relationship. So for example, you have something like this Petrous Apex Cholesterol Granuloma . Here in my mind, the goal of that is drainage and marsupialization whereas a tumor like this Chondrosarcoma, I really want to try to get a complete and radical removal to get lifelong control over it. And then finally, a tumor like this very challenging Petroclival tumor, which has surrounded by all kinds of critical structures. You may not be able to get a radical removal without having some sort of neural sacrifice. And so it's a real balancing act for many tumors like this to relieve symptoms, and yet get the maximal effect out of your surgery. Starting with Cholesterol Granuloma, just to review this is a basically a giant cell reaction either to hemorrhage or cholesterol deposits. And it's a uncommon that Petrous Apex but can occur in that location. Here's an early series, really series by Brackmann and Toh looking at 34 patients largely from inferolateral Approaches, but even a middle-fossa for management of the cholesterol granuloma. And in Infracochlear Approach really was the workhorse for this and the concept behind it was that you could drain the cyst into the mastoid, at least have some sort of marsupialization. This is a paper where we looked at this in 2011 to try to compare whether not the comparison between an Infracochlear Approach that you see demonstrated here and an Endonasal Approach to really see what the advantages and disadvantages are. In my mind for many of these tumors, the Endonasal Approach really is the most direct approach. It doesn't carry that risk of hearing loss, and you can have a large drainage window for good marsupialization. One of the keys for any access to the Petrous bone and the is a Transpterygoid Approach. And so I'll go briefly through the steps in the Transpterygoid Approach. But one of the key aspects is it's essentially an Approach through the maxillary sinus. It's not a Transsphenoidal approach but it's rather a Transmaxillary approach we just combine it with a Transsphenoidal approach. And here we see that Maxillary Antrostomy here really more of a Medial Maxillectectomy. And as we broaden that access from a Maxillary Antrostomy to a Medial Maxillectectomy we have wider and wider access out to the Pterygoid bone and the middle infratemporal fossa. Here you see the steps, the Transpterygoid Approach and again the key is that first step of the Maxillary Antrostomy, which really is what opens the window. And we can then access through the Pterygopalatine space and finally get back to the Pterygoid base. Once we opened the back wall of the Maxillary sinus now we have to work through the Pterygopalatine fossa, and the truth is other than understanding the vasculature and it's supply to for example, Nasoseptal Flap, or ability to control an IMAX artery. And again these could even be coil embolized preoperatively for this kind of approach. The main thing we have to worry about here is V2 and it's branch such as the descending Palatine. Other than that, unless you're concerned about Vidian Nerve function, which only controls lacrimation and has little impact on most patients, there's not much in the Pterygopalatine fossa that is an issue. Here you see a view into the left posterior aspect of the maxillary wall. Here you can see the Sphenopalatine artery leading to the posterior nasal branch, and essentially opening up along just like you would for a Sphenopalatine artery ligation, you can give us access into the whole Pterygopalatine fossa. Here we can see that posterior nasal branch, which is in this dissection, is attached to a Nasoseptal Flap, but the posterior wall of the maxillary sinus has been opened up to give us access into that Pterygopalatine space. We can then dissect through, critical structure identified as V2. Once V2 is identified and the IMAX can be either sacrificed or preserved. We can then work through the Pterygopalatine space into the Pterygoid. Now the truth is for many of these, the Approaches that we'll show today, unless you're really going out into the middle fossa to the Petrous Apex, we just have to do the medial aspect of the Transpterygoid Approach, which involves identify the Vidian Nerve and drilling out the Medial Pterygoid wedge, so-called Medial Pterygoid wedge, which you can see made up right here of the base of the Pterygoid where it meets the Sphenoid, this has been called the Pterygoid wedge. And at the middle aspect of this is the Vidian Nerve. We'll skip this video, looks like we've got a better one later on, but essentially once we open up this posterior aspect of the maxillary sinus and clean out or dissect aside the Pterygopalatine fossa content we're gonna have direct access onto the base of the Pterygoid. And this base of the Pterygoid is really what gives us access to widen our Approach, to be able to then get access in to it. Here we see that Petroclival junction or even the Petrous Bone. So it's that Transpterygoid Approach that's key and what you'll notice though, our limitation though really is the Petrous Carotid artery. So here's the Petroclival Carotid artery and the Petrous Apex is gonna sit right behind this bone. It widens inferiorly to give us better access to the Petroclival junction, but the Petrous Carotid artery, and understanding its relationships both from an Open Approach and an Endonasal approach really are what help define that separation between the two Approaches as well as the limitations. You'll notice from an Anterior Transpetrosal Approach, we would come over the top of the horizontal Petrous Carotid artery and lateral to the Petroclival Carotid artery to get access to the Petrous Apex, coming Endonasally, the last thing we get to is the Petrous Apex, but early on we have great access to the Petrous Body. And I'll talk a little bit later about that comparison between the two Approaches and really what's a great complementarity between the two. But if you're gonna work in this area, you have to understand the Skull Base Carotid artery and they're essentially four segments, the parapharyngeal space, the horizontal Petrous segment, the Paraclival or the vertical segment of the cavernous, and then the paraclinoidal segment of the Carotid artery. And these are the landmarks that I use and I think are important for the Petrous Carotid. If we look at the Paraclinoidal, the medial optical Carotid recess, essentially the confluence between the optic and the Carotid is the landmark there. And that Anterior Genu inferiorly where the Foramen Lacerum lies is that Medial Pterygoid Wedge is critical. The Horizontal Segment more laterally, the Vidian Nerve or if you're doing this from an Open Approach, GSPN, that give you the landmark for Horizontal Segment, and then finding the Eustachian tube again both from open-ended and nasal Approach, or what give you a landmark to the Ascending or Paraclival Parapharyngeal Carotid artery. So here's just showing a view of that. Again here's Foramen Lacerum and you see how the Vidian Nerve leads right back to Foramen Lacerum and that aspect of it. And the Petrous Apex is going to again, sit right behind the Paraclival Carotid artery. Here, again showing Petrous Apex relationship to the Paraclival Carotid artery. And this whole area is essentially the body of the Petrous bone. And I'll talk about that a little more later. You'll notice these landmarks that give us access to it. And I'll talk about this triangle that gives us access into the medial Petrous Apex. So this essentially is between the Paraclival Carotid artery, the Sixth Nerve and here we see what's essentially that Petroclival ligament or the Petroclival Fissure gives us the third landmark to that triangle. You can see them very nicely here. Here's the Sixth Nerve, the Paraclival Carotid artery and the Petroclival fissure. This is that medial triangle. We have triangles that are used for open surgery. This is the triangle for medial Petrous access. And these are your landmarks that essentially take you directly into the Petrous Bone and directly into the Petrous apex. This is an angle, which I think is rather interesting I'll talk a little more about the angle aspect of how you access the Petrous Apex, this is one of our former Fellows Alex Paluzzi who's now practicing for a long time in Manchester. And he basically discovered if you measure the angle between the lateral nasal wall, which is essentially your lateral access through a transnasal approach and the Paraclival Carotid artery, and did the same through the medial or posterior aspect of a Cholesterol Granuloma, as long as that was a positive angle, we could access into the Cholesterol Granuloma. I'm going to talk a little about how to increase the angle and improve that access a little later on in the talk. But here's an example of a classic Petrous Apex Cholesterol Granuloma, this patient presented with a partial Sixth Nerve palsy and some dizziness, but you can see the pre contrast hyper intensity on T1. And we can see the erosive nature of it on CT scan. So here we are looking, here's the left Paraclival Carotid artery. The Clivus has been drilled out almost essentially to the periosteal layer of dura. And then here we see the Cholesterol Granuloma. It can be easily opened up, and these tend to sit, this exposure, sits right in this triangle, this medial Petrous triangle. So here's going to be the Sixth Nerve right up above the Paraclival Carotid and there's the Petroclival fissure inferiorly. We can then drain the contents. We can leave a Silastic tube or now more and more we've gone to using a mini flap as our option. And here we see the post-op and you can actually see how nicely that many flap lies into this. And it creates essentially a sinus. So it turns this from this trapped giant cell reaction. It turns it into a sinus. So we're transforming the pathology, we're not trying to completely resect it necessarily, but rather marsupialize it and turn it into and essentially get rid of the trapped nature of it. We studied this versus the Infracochlear approach to try to understand which gave a larger access. And again, from this lateral Approach, we really couldn't get any access to the superior aspect of the Petrous Apex from infracochlear Approach. But it was great for reaching the anterior and inferior compartment of the Petrous Apex. And I'll talk a little more about how that fits into an algorithm for treating these. Conversely, Endonasal approach was able to reach the superior aspect of the Petrous Apex and essentially all of our specimens and the vast majority of the Petrous Apex was accessible at about 90%. And it created in the end a much larger window into the Petrous Apex. And it's this ability to create a larger window is what allows us to do this marsupialization and essentially open for a much wider drainage that stays open without having to limit our access or having to remove or transect things like the Eustachian tube. We wanted to look at this and try to see you know, one of the concerns obviously, we're not resecting it. There may be people who would espouse a complete and radical resection, perhaps through a middle fossa approach of a cholesterol granuloma, but long-term outcomes I think, support this drainage concept. So here we looked at over a long period of time, about 13 years, we didn't take the most recent cases because we wanted to make sure these patients had at least a year of followup, both clinical status and neuro imaging. We can play this video, this is a great example. This is a tumor in a case that had been previously resected. Someone had left, you can see a stent right there through an Open Approach. And it kept reoccurring at both and Infracochlear approach as well as a middle fossa Approach and still recurred. And so . Here we're opening right through that medial triangle below the Sixth Nerve. Here we see the Sixth Nerve up above, and then we're actually pulling out that stent that was placed previously. Because I think it ended up you know, if anything creating more of a foreign body and not allowing us to have this wide open. Now you can see with multiple prior surgeries, you can see that there's some CSF weeping out. We can get a beautiful wide view all the way out. You can see even out the IAC and branches of the Seventh Nerve crossing, but this is the kind of wide access that we can get. And just place a mini flap on the posterior aspect of the dura. We can go to the next slide now. So the concept here is not a complete resection, but rather evacuation of the cyst. And in the past, we would perhaps lead a stent behind, it could be partially a portion of a ventricular catheter or just the Silastic tube, but occasionally these do get stuck. And so we've gone more and more to using a mini flap it's a much more natural way to do it, doesn't require a second step. And as you can see . Here it creates this very nice sinus essentially out of the clival defect that we've made. And in this study . Here I think we had about 23 patients we excluded because they didn't have long enough follow-ups. So we only went with patients with long-term followup in this, and we looked at. Here you see their initial presentation and we can see that about 17% of them had previously been operated. Most of these were able to be done through a Pure Transclival approach. Some did require mobilization of the Carotid and I'll talk about ways to avoid that later. And you can see here later on in our series, we began using many more of these mini flaps. This is a current clinical status, and you can see our clinical followup is almost at 90 months and our neuroimaging follow-up is close to five years as well. And we had symptomatic recovery in almost all patients, and we only had two cases of recurrence. The meantime of relapse was 11 and 42 months after surgery. Only one of these was clinically symptomatic. Complications, Intraoperative CSF leak was considered a complication, but we only had one case that had both aseptic meningitis, as well as a post-operative leak. We did have to transient abducens palsies, this is partially just trying to peel the capsule of this, which is something I try to avoid now. And here you can see dry eye as a potential complication related to Vidian Nerve sacrifice. No Carotid injuries in this case. And you can see the Approach based on symptoms essentially, we had a good improvement, regardless of which Approach we had to take. Interestingly enough, both recurrences were prior to use of a mini flap. This could have a temporal relationship and a bias to it, but it does seem that we've not seen a single recurrence after using this mini flap concept. If you also compare this to Brackmann study, it's a very similar or higher rate of symptomatic improvement and even long-term, you know, 88 months of clinical followup, only 8% of patients recurrent. So it really holds up very well as a long-term treatment for Cholesterol Granuloma. Now, going back to the initial anatomic study, I would propose that a tumor that really sticks out into the sphenoid can be done through a simple Transsphenoidal. We might have to do where we mobilize the Carotid or the Eustachian tube. And that's a little more challenging, but can still be accessed through an more inferior approach. And then finally, if the Cholesterol Granuloma is truly hiding behind the Carotid artery, this would require either a infracochlear approach or a middle fossa approach. So conclusion, I think that endoscopic Endonasal drainage marsupialization of a Petrous Apex Cholesterol Granuloma is a very effective technique and also has great long-term efficacy. Now looking a little more complicated as we move more laterally, we can see the Petrous bone is going to articulate with the Clivus on either side. And this Petroclival region is of course famous for housing tumors, like a Petroclival Chondrosarcoma. So this is a case of a classic Chondrosarcoma crossing the Petroclival junction. Here we can see its relationship. Here's the clival dura. Here's the Paraclival Carotid artery right here. And then of course, we're working again in that same medial triangle between the Petroclival Synchondrosis between the Sixth Nerve here and between the Paraclival Carotid artery. So that triangle gives us beautiful access into the Petrous Apex, these tumors push the Sixth Nerve up. So if anything, it even widens that window, but here we are mobilizing the Carotid artery we're even working on both sides of the Paraclival Carotid artery to get to some tumor here that's lateral out in the lateral aspect of the Petrous Apex but I'll talk about how to avoid having to do this kind of exaggerated mobilization of the Carotid artery, which I do think has some potential risk to it. Here we're releasing at Foramen Lacerum the Eustachian Tube cartilage meets Foramen Lacerum cartilage, and you have to essentially disconnect the two. And here finally, because it's a Chondrosarcoma we're resecting the involved bone peeling the last bit of tumor down from below the Sixth Nerve, which we can see the Sixth Nerve entering right here through the Dorello's canal. And even using this a bone tip on the Sonopet to core out some more of the involved bone in the Petrous Apex and then cutting any dura that's been in contact to really try to get a radical removal of the tumor. Again, coming in below Dorello's canal here we see the Fifth Nerve so we're below five and six, really all the way out here in the Petrous Apex able to get a radical removal of this particular Chondrosarcoma. And so far this patient has had no recurrence. And here we can see the postop with a little bit of fat and blood in the postoperative cavity. We can go ahead and go to the next slide. So this is our early Chondrosarcoma series, 35 patients who underwent you can see about 40 procedures total, and you can see very importantly, open procedures. Endonasal surgery is not defined by getting rid of open surgery it's complimentary to it. And many of these cases for radical removal require both Approaches. Gross total resection was able to be achieved in about two thirds of patients and all of the rest had a near total resection, many lower grade Chondrosarcomas, I think can just be observed and then only radiated or re-resected through a different Approach perhaps, if they recur. Interestingly enough, when we looked at where it was residual, obviously larger tumors, middle fossa, middle cranial fossa, where we had to perhaps augment with open Transpetrosal Approach. Cavernous sinus and CP angle were all areas we struggled to get more lateral. And I'll talk though about how a different Approach, Contralateral Transmaxillary approach has gotten us more access to the lateral aspect of the tumor. To quote my good friend Jack Morcos, "Craniotomy is not a bad word." And six open procedures were a key part of getting this radicality of resection. And again, we see it's inferior and lateral is where we struggled. So when it goes out into the pharapharyngeal space and upper cervical spine, these are most likely where it would require an Open Approach. Recurrences, there were seven patients all of these were treated with radiation and four underwent repeat resection, here's just a patient who undergone craniotomy with a sacrifice of... I'm sorry this is a different patient, this a patient who had multiple recurrence of a mesenchymal Chondrosarcoma, very aggressive and after open surgery for this tumor, which you see, which is originally resected through an and then had a very nice result with just residual in the cavernous sinus, which then recurred, underwent then an Endonasal approach. They really are complimentary. And I think it's so important to be able to have access to both. Next slide, please. So we did have three deaths, one from metastatic disease, one from multiple strokes over a month after surgery, unclear etiology, but then one was unrelated several years later. Petroclival Meningiomas, this is much more controversial and much more challenging tumors, but certainly I do believe there are some Petroclival Meningiomas, which can and should be addressed Endonasally , although they are certainly among the most challenging. Again, this is something that perhaps is often misquoted, but this is not a Petroclival tumor. This is a Petrous Meningioma, and this of course should be treated through a Retrosigmoid or some version of a lateral Approach to access that. Here is Petroclival tumor. Again, the epicenter of a Petroclival tumor is going to be medial to the trigeminal nerve as this one is here and here we can see after Endonasal resection, very minimal residual left right along Dorello's canal on that right side. And a nice enhancing Nasoseptal Flap. One of the key step for many of these tumors is an extradural, is a pituitary transposition. The original way we sort of started doing this was just Extradurally. You can play this video. Here's an old video where accessing a Chondrosarcoma or a meningioma we would just lift up the dura and try to peel this down. But this is a really not a very controlled version of removing the posterior clinoid to give access for transposition, next slide. And intradural is also not a great option, but instead now we've gone to what is described as an intedural or transcavernous, this was described by Dr. Fernandez Miranda, where we essentially go through the cavernous sinus, open it, dissect out the posterior clinoid in very controlled fashion. And this, you can sacrifice the inferior hypophyseal artery as is being done here. You can sacrifice both inferior hypophyseals and not sacrifice hormone function, but that gives us beautiful access to dissect this from behind the Carotid artery and upgrade access to the posterior clinoid, next. So by doing this, we can then work behind the gland. The gland now is mobilized, we can lift it up. It still has its venous drainage through the superior cavernous and the lateral cavernous sinus superiorly. And this gives us access now all the way up to the not only the Prepontine but the perimesencephalic cisterns. And this gives us access all the way up to the Basilar Apex. Next video, please. This is just showing another one, here showing that the view that we get once we've resected tumor. Now you'll notice this very thick and stuck capsule of the Petroclival meningioma I think regardless of Approach, there are some of these where it just doesn't have the plane and the tumor itself, the tumor capsule is part of the arachnoid and I would leave that regardless of Approach, you can see how that's really part of the arachnoid. And so leaving a small rind there perhaps is often in that patient's best interest. Next slide. You can see the postop on that, that rind collapses down to the small residual that's left over on that trigeminal. And this patient had complete relief of brainstem compressive symptoms. Here's a another case of a very large Petroclival meningioma. It's a 53 year old man, actually very active man with progressive gait difficulty. He was a regular weightlifter and here you can see just dramatic impact on him and partially from brainstem compression, but also an NPH type picture, which can often happen with these Petroclival Meningiomas as they slowly block CSF Egress. And you can see here by doing this two-tier transposition, we have beautiful access to this tumor. So we would start of course, by removing the Clivus just the basic portion of the Clivus. And here now we're doing a very wide cellar exposure. Both parasellar Carotid arteries are completely exposed here. We've completely drilled out the Clivus in the clival recess. And now this is one of the things about a transclival approach is the flap often gets in the way. And so we're flipping the flap up now up into the ethmoid essentially, and we're doing. Here what's called a retropharyngeal or a rhino-pharyngeal flap, and that's just this inferior U-shaped flap that's flipped downward into for the oral pharynx. And this helps separate the oral pharynx from nasal pharynx and also gives us room to have access for the entire Clavus. So now we can access all the way down to the lower Clivus. We skeletonized both Paraclival Carotid arteries. Obviously this is a very extensive exposure, much like many open transpetrosal or combined Transpetrosal Approaches you might want to stage this. And certainly this tumor is one that we staged where we did the initial debulk exposure and debulking of the tumor on one day, and then did the final more extensive debulking and resection of the tumor on the second day. So this is the end of the first six hour day here after we've done our exposure all the way up to the floor of the Cella. We get some specimen, it's relatively soft, at least on this portion. So we're able to suction out the tumor, but again we have the same toys and tools you can use through an Open Approach, whether it's an ultrasonic or here you see us using a Niko myriad device to debulk the tumor. We wanna sacrifice many of the feeders, which obviously come off of the Carotid artery on the right side, the Petrous Carotid artery, and then without getting really much of a CSF leak we do our complete reconstruction with fascia fat and a flap. Now for the second stage of surgery, which in this case was done the next day we do this trans cavernous pituitary transposition. So we're in the cavernous sinus, do it bilaterally we pack off the cavernous bleeding with some surgicel foam dissect right next to the Carotid artery here we see the Carotid right there, and then we can carefully peel away and dissect the whole dorsum . We can safely dissect the posterior clinoid from behind the Carotid artery. And now we can open all the way up to the perimesencephalic and all the way up to the basilar apex carefully dissecting with a cartouche dissector, much as we would use during, Here we see the Sixth Nerve, much as we would use during acoustic neuroma surgery to stimulate the Sixth Nerve and identify it. And the same thing on the right side. Now this one was much more difficult to identify. And as you might see with many Petroclival tumors, it's Petroclival Meningiomas, the Sixth Nerve here is completely wrapped up in the tumor, very challenging to preserve, but we were able to identify it relatively early on, sharply dissected free. You can see the course it's taken here and he actually of course had a postoperative Sixth Nerve palsy, but that improved actually by three months. Here we can see the PCA and the third nerve and the SCA, and just working with two suctions and then blunt and sharp dissection we're able to debulk the tumor. We can see what its relationship is with the Basilar using a 45 degree scope. Here we see the third nerve up high. Again, the tumor's really plastered against the third nerve. Part of what makes the Petroclival so challenging. This would be our same window from lateral. Be a very limited window between three and six, to get to this deeper aspect of the tumor through a Retrosigmoid approach or through an anterior transpotrosal would be working over the top of the Fifth Nerve. And again, below the third nerve. Here we can see the Basilar. We can do IC Green just to make sure we don't have any basispasm. We check our Nasoseptal Flap to make sure our flap's still alive and then do a multi-layer reconstruction. In this case, we do a collagen inlay graft course one of the challenges with any Petroclival or clival tumor is a CSF leak with the posterior fossa, nice big piece of Fascia Lata, some fat graft, and then Nasoseptal Flap to sit on top of that. And that's our final view there. Don't know if I think we'll let this play out because I think that postoperative is in the video. He of course had a Sixth Nerve palsy, and I did shunt him given his NPH, but here we see the postoperative after the second stage, you can see our fat graft and of course a small residual along the Petrous Apex this could be treated through an anterior transpetrosal approach to get essentially a complete resection without having to really transgress or manipulate the oculomotor nerves. All right, next slide. So Petroclival generally, I think there really are three options, Retrosigmoid, Endonasal and anterior transpetrosal. And a lot of times I think the two most complimentary are Endonasal and Retrosigmoid. And so we compared patients who were resected through this about 50-50 through either Retrosigmoid, Endonasal or some combination thereof. And many of these were recurrent tumors, and a lot of them were much larger than four centimeters and at least half of them had vascular encasement. Often had to stage these and again, we did not go gross total resection, but we're able to get near total or gross total resection in about 50% of open cases, and about 40% of Endonasal Approaches. We'll skip this video in the interest of time, but that's a another you know, another to pituitary transposition. And then of course there are cases like this Petroclival tumor that is ideally either for Retrosigmoid or even in this case, a combined pre and post sigmoid Approach, posterior transpetrosal approach to get pretty close to a radical removal of this tumor. Next slide. So tumor size and encasement, of course you get very, very large tumors like this. Oftentimes it's very difficult to get a total resection, at least certainly in a single stage. And so we would do initial debulking, resect all of the osteus component, as well as debulk the posterior fossa and have the patient relieved as symptoms. And then later if the tumor grew, could do an open lateral Approach to it. Many of these underwent adjuvant radiation, depending on their age. I agree in younger patients, I tend to try to avoid that unless there's a very small target in a very unfavorable location. Here you can see the complications. And in short with Endonasal, we largely got Sixth Nerve palsies which you see as the majority of them and with Open Approaches, you're more likely to get perhaps a Seventh Nerve palsy, a eighth nerve palsy or other, a variety of complications from a lower or mid cranial nerves. Interestingly enough, the main goal of this for treating these Petroclival was trying to improve this patient's quality of life. And that's I think, best monitored in Karnofsky, if you look at a lot literature, Karnofsky scores often worse even in the short term and never even recover back to baseline. And you have to question, what's your goal of surgery in these very indolent tumors. But were able to improve the Karnofsky to almost 90 and essentially alter all patients, even in very short term followup so by 12 to 14 months, patients were actually improved and almost never worsen using this particular philosophy. So again I think it's showing the complimentarity of a particular Open Approach with an Endonasal approach and understanding when these are best applied, which patient, which relationship with the tumor of the cranial nerves it can be used for. And here's just showing a diagram, again these are tumors inevitably, which by definition Petroclival meningioma would originate medial to the Fifth Nerve. And so tumors where the epicenter is medial to the cranial nerves if we can access Endonasally, which has all the way from two to 12, I would tend to treat primarily with an Endonasal Approach to debulk, but obviously if the epicenter is largely lateral to this and the tumor is extending out to the Petrous bone than I would choose an Open Approach for those. Of course the CSF leak has been a major issue with Endonasal which was a largely I think, overcome by the Nasoseptal Flap. But you do have to understand with a Transpterygoid Approach, your flap has to be on the opposite side, because if you're doing a Transpterygoid Approach, you are inevitably manipulating or destroying the posterior nasal artery, which gives supply from the SPA, the sphenopalatine artery to the Nasoseptal Flap. Now you can mobilize these in some cases, but we always try to, if possible, do the on the opposite side. Of course once we started doing these Transpterygoid Approaches, we worry about Carotid artery injury. Here's a case of a chordoma in a child. If we can play this video and here we can see the Paraclival Carotid and Foramen Lacerum right there. And we're trying to get to more tumor, which is hidden back in this Petrous Apex and the Petroclival junction and in doing so, we then expanded our Transpterygoid Approach. But when I came back in and tried to make this cut through Foramen Lacerum I was disoriented and ended up cutting right into the Carotid artery. We can go onto the next video. And we had actually exposed the Carotid in the neck because this child had an extensive tumor and with brisk and tried with hypotension, there's brisk back bleeding, which indicates a Peyton Circle of Willis. And I could have tried to pack this off with muscle, but you can see here, my primary modality here was to sacrifice this. So here's the open cut end of the Carotid artery. I cannot suture Endonasally. This is a major limitation, my ability to repair an artery in this kind of situation, mind you with an open Transpetrosal Approach a Carotid injury is often equally difficult to manage, it can just be packed off with muscle, but I still think most of us would be a little more comfortable trying to suture or repair this through an Open Approach as we would through an Endonasal approach. All right, next slide. Fortunately, the sacrifice was well tolerated. There's again, brisk back bleeding. This is a child so he has a fortunately, a persistent trigeminal artery as well as good crossbill across the circle of Willis. Again, I can't emphasize enough the importance of understanding, you know, the levels of the Carotid artery, a the Parapharyngeal, horizontal Petrous, that Foramen Lacerum and again the Paraclinoidal segment of the Carotid artery. Again, these are the landmarks that I choose to use. And I think they're really critical landmarks to try to understand the Carotid artery and safely access this area. Now, one of the other things you can try to do is avoid having to manipulate the Carotid artery and try to work around it. And this what I was talking about before about the angles of access. Now, this is a concept that Dr. Snyderman came up with where rather than coming from a nasal corridor, we come from a Contralateral Transmaxillary corridor, and this was recently published. And again, we can gain access to that same triangle into the Petrous Apex, but now our angle is even more favorable. So here we can see again that triangle to the needle Petrous Apex . But if you look at the angle that Paluzzi described originally, where we're coming from the lateral nasal wall, that puts us at most having to mobilize the Carotid artery, and we just can't get as lateral. But if you come from this Contralateral Transmaxillary Approach, it almost puts us directly parallel to the horizontal Petrous Carotid artery. And this is absolutely beautiful. It gives us a direct access all the way straight down the Petrous Apex up to the IAC and gives a beautiful reach advantage to this area of the Petrous Apex reaching through this Medial Petrous triangle to gain access all the way out to the IAC. Here's again as mentioned the publication from 2018, and this is just looking at the difference in angle, the angle between the horizontal Carotid artery and the Paraclival Carotid artery from an Endonasal Approach is about 45 degrees. Whereas we come Transmaxillary, we're nearly parallel to it. So really a significant angle and reach advantage. This can be used for tumors like this Petroclival Chondrosarcoma here we can see a significant clival segment that would be challenging to access around the Carotid artery from an open Transpetrosal Approach conversely, from an Endonasal Approach, we're really not able to get lateral around this corner, but by using Contralateral Transmaxillary Approach, we can come behind the Carotid artery, follow the tumor, which is essentially come through the Petroclival junction around the Carotid artery and get a complete removal or near complete removal of that tumor. This is showing intraoperatively the reach advantage. This is showing our Endonasal access, and this is showing the CTM access directly into the lateral aspect of that exact tumor I just showed you, working behind the Carotid artery here we're gaining access all the way up and up toward Meckel's Cave and the middle fossa dura. Here's another example of a Chondrosarcoma and again just look at the angle advantage. It really puts us directly in line with the long axis of the tumor. This is the specular two point concept where if you take two points in the long axis of the tumor and you follow down the length of that tumor, that's probably the best Approach to choose. And I think that certainly fits for the CTM for many of these. If we can play this video, this is an example of a large Chondrosarcoma that was treated through a Contralateral Transmaxillary approach. Again, requires a Maxillary Antrostomy on the side of the anterior Maxillary Approach, opposite of the tumor. On the same side of the tumor we also do a Maxillary Antrostomy, so we do a Transpterygoid Approach on the side of the tumor and a Maxillary Antrostomy or a medial maxillectomy on the Contralateral side to get access. Again Contralateral flap harvest, cause we're doing a Transpterygoid Approach, we do the Nasoseptal Flap on the side of the anterior Transmaxillary approach on the side of the CTM. So this is a right sided tumor so we're doing a left sided CTM approach. Here on the right side though, we're opening up for the Transpterygoid Approach to gain access to the Pterygoid and then the Petroclival junction. Sacrificing the posterior nasal branch in this case, we now would probably use reverse flaps during the posterior Septectomy resecting the Rostrum to gain access to the Sphenoid. And then of course the rest of this is a standard Transsphenoidal Approach all done Endonasally until we get to the tumor. Here showing the reverse flap being wrapped around the anterior aspect of the nasal septum. And we see that really to help limit nasal septal morbidity. This prevents things we think like nasal dorsal collapse and certainly limits the amount of nasal crusting in these patients post-operatively. Now opening the lateral recess on the right side. Here's our Vidian, going to be right there. So now we're drilling out the medial Pterygoid wedge on the right side. Remember the medial Pterygoid wedge is what lines us right up with a Paraclival Carotid. Here's our Vidian right there. And now we drill out the Clivus. We can start to see the tumor poking in to the Petroclival area. We'll skeletonize the Paraclival Carotid artery, but I can help avoid mobilizing it as much although I will do some mobilization here. Here you see detaching, the eustachian tube very carefully from Foramen Lacerum . You really have to be precise with that cut and understand where the location is. And now finally getting into the tumor medial to the Paraclival Carotid artery. Here's our Paraclival Carotid artery, and then drilling out the bone lateral this includes the lingual process right here. There's removing with the and the lingual process and removing that bone lateral allows us to mobilize the Carotid from lateral to medial. Cutting a little close for on Foramen Lacerum now that I can really see the angle of the Carotid artery and mobilizing Foramen Lacerum again, here's that triangle between sixth, Paraclival Carotid artery and that Petroclival junction. You can see our beautiful access here into the Petrous bone, the Petrous Apex and here's all working Endonasal. But now I come from the left side at Contralateral Transmaxillary Approach, and that suction brought in through the CTM gives me beautiful access, right in line with the horizontal Petrous Carotid. Here's the horizontal Petrous where we're looking out now with an angled scope turned sideways, working with angled instruments through the CTM, have access all the way from the IAC and the porous trigeminal superiorly all the way down to the jugular frame and inferiorly. So here's our Petroclival junction completely blown out by tumor and we're cleaning it out all the way to the jugular frame and inferior petrosal sinus. You can see a little bit of bone involvement laterally right where the Parapharyngeal Carotid artery enters the Skull Base. You can see we're all the way out to the IAC right here. And then inferiorly all the way down to the inferior Petrosal sinus. There's no real CSF leak here but we fill it in with fat and then cover it with a flap. Next slide. So this really allows us to get this kind of beautiful, direct access all the way out to the IAC through this Contralateral Transmaxillary approach. It can be used for tumors like this recurrent chordoma. Here we see Endonasal versus CTM access again, and here's the post-op. And again, just beautifully takes us right down, right to that medial Petrous triangle directly down into the lateral aspect of the Petrous bone. Here's our early experience with the CTM, 29 different ones, largely chordoma's and Chondrosarcomas. So Clival tumors or Petroclival tumors that we're extending out towards the Petrous bone. We're able to get 75% of time gross total resection, that Petrous portion of these chondromatous tumors. These are purely tumors extending out into the Petrous bone. And again, Nasoseptal Flap on the same side as the CTM. Now, a lot of times there's this battle between Endonasal versus transcranial, but I really think it's important to understand how they're complimentary with each other and how to apply them. This was a study, absolutely wonderful study done by Dr. Hernandez from Spain who spent a year with us. And this is her PhD project essentially, where she compared the volume metric resection of bone, depending on Approaches. And this is essentially comparing a full Anterior Petrosectomy through an open transcranial approach with different versions of Endonasal versus CTM and evaluated the amount of bone removed using a CT scan and 3D volumetric measurement of the amount of bone removed on CT scan between each a separate step. And here you can see the progressive Endonasal Approaches and compare it with a full anterior Petrosectomy. Here you see the dissection done for a full Anterior Petrosectomy through an Open Approach, including mobilization of the trigeminal and a skeletonization of the Carotid artery to maximize our access to the Petrous Apex. And then this is a simple, a purely Transclival Approach, which gives you a little bit of access to the Petrous Apex not a tremendous amount. And then lateralizing the Carotid artery, mobilizing like I showed, improves your access a little bit more, but then adding the Contralateral Transmaxillary Approach, which you see here and then finally using an angled endoscope, just showing again, that view into that medial Petrous triangle. And then finally the most extreme which is Contralateral Transmaxillary with a mobilization of the Carotid artery and seeing what's the maximum access we can get. The 3D reconstructions were done using this technique, which has been previously published, where we do essentially using CT and using a volumetric analysis done by a specific computer program allows us to measure the amounts of Petrous bone resected. And here we see looking at the Petrous Apex and of course look what a beautiful job the Hakuba-Dolenc anterior petrosectomy Approach does of resecting Petrous Apex. But interestingly enough, CTM or CTM plus Carotid mobilization really comes quite close and essentially gives us the same access and the same amount, as statistically the same amount of Petrous Apex resection as does Hakuba-Dolenc obviously coming from a medial perspective. We look at the body of the Petrous Bone not the apex. However, this Contralateral Transmaxillary approach really starts to stand out for gaining access to that inferior aspect of the body. Whereas the Hakuba-Dolenc has a harder time reaching over the top of the Carotid artery to get lower down towards the petroclival fissure and towards the lower aspect of the Petrous body. So if we compare this, the percentage resected in Contralateral Transmaxillary, what you'll notice is that a standard Endonasal with Carotid mobilization essentially is equivalent to Hakuba-Dolenc for the Petrous body, not the Petrous Apex, but the Petrous Body and the Contralateral Transmaxillary really starts to stand out when it comes to accessing the Petrous Body. This is just showing that in short, the Hakuba-Dolenc gave beautiful access to the very top of the Petrous Apex. Although with a CTM plus Carotid mobilization, we could essentially get the exact same access. When it came to the Petrous body however, the CTM really starts to stand out for gaining a resection of that inferior and medial aspect of the Petrous body. So I think the CTM really does provide great access for these paramedian tumors. It's a great thing to add on to an Endonasal approach. And the CTM, especially with Carotid provides really very similar access to a classic open anterior Petrosectomy for the Petrous Apex and provides superior access to the Petrous Body for a tumor that extends, for example, from the Clivus all the way through the Petrous body. So in the end I think Endonasal endoscopic Approaches or Transinus Approaches to include the CTM, would provide a very novel way to access lesions, including the Petrous Apex and Petroclival junction. The very novel trajectory, but they do have their own set of novel complications and has to be compared with an Open Approach. Again, you have to understand the relationship of the tumor to those nerves in your ability to avoid manipulating those nerves and understanding what is the pathology, what's the goal of surgery? Is it drainage? Is it radical resection? What's the location relative to neurovascular structures. And very importantly, what's your experience and your ability to provide safely one of these particular Approaches and then of course, patient preference, In the end I think Endonasal and transcranial are very complimentary, especially when it comes to difficult areas like the Petrous apex. And it really is important to understand your own ability and your learning curve, which we've demonstrated many times. I think Endonasal is really starting to understand where it falls as a standard treatment on Scott's parabola, but I really think it does have a place in experienced hands for accessing the Petrous Apex. And I think that these Approaches really go beautifully hand-in-hand, that's one of the goals of this book with many authors that you've heard on the Atlas are in this book, espousing both open and Endonasal Approaches to try to understand which are best for our particular approach. Of course, we're all shifting to virtual teaching. So we're hoping to have some virtual courses available soon, and I invite everyone to join and be part of the Skull Base Congress. Certainly things like Skull Base Congress and Neurosurgical Atlas, or how we all try to learn from each other are a great resources for anatomy.

- Great work, really tremendous, very impressive, truly pioneering Paul. We're truly honored to be listening to all your great pearls. There were some questions during your session that I like to ask you, one of them is a very good one. If you are operating on a patient who has had previous surgery, radiation, Nasoseptal Flap is not very functional. What is your sort of second and third tier reconstruction technique in the Petroclival area?

- Yeah, great question. And actually there's a great option in the Petroclival area, assuming that you at least will have a pedicle and that's a lateral nasal wall or inferior turbinate flap. It really doesn't have the same kind of reach as a Nasoseptal Flap. So it doesn't work well for the anterior cranial base, but for mid or lower Clivus or Petroclival, it's a beautiful rescue option. It's nicely vascularized, a very thick pedicle. It really actually has a very thick, stubborn pedicle to rotate. It is not an easy flat to harvest, but that's a very nice option. Another wonderful option is the temporoparietal fascial flap also somewhat challenging to harvest because essentially you're talking about harvesting Galea. You have to rotate that through the Pterygopalatine space through the Pterygomaxillary fissure, but that can be done through a simple incision laterally here. It can be extended all the way up even to the Contralateral side, if you're willing to take that much Galea. And then finally, very rarely, we'll even take a Paraclival cranial flap, which has to be quite long, bring it through an unilateral ethmoidectomy and run it down to the Clivus. So I'd say that there are options, but probably lateral nasal wall flap is probably the primary option. And then the truth is of course, if you're running out of reconstructive options that can change your Approach access also, you may want to choose a fresh approach. One that has better reconstructive options. One that doesn't have as much scar.

- Okay. I agree do me a favor. What do you do to avoid vasospasm in the Carotids, especially on the ones that are very small caliber, do you use Papaverine? What are the strategies?

- I haven't had much trouble with Carotid itself, but Papaverine is my go to, what I do worry about on for example, those Petroclival Meningiomas is spasm of the Basilar and some of the mid Basilar branches. Some of those preforators, what I'll do then is I'll soak my collagen graft, whether it's Duragen or DuraMatrix, whatever I'm using in Papaverine, dilute Papaverine and place that directly as my first layer of reconstruction. So I have a Papaverine soaked collagen resting on the Basilar for example. I found that to be, at least makes me feel like I'm doing everything I can, but I'll use Papaverine, I'll spray it on the Carotid artery. If I need to, if I get some spasm in it intraoperatively, but I honestly haven't had much trouble with spasm from an Endonasal approach or from an Open Approach in the Carotid itself. Smaller vessels, intercranially, Absolutely.

- I agree with you. I think Carotid is too big to have vasospasm. Take us through, you're doing a Chondrosarcoma, you get bleeding from Carotid. It looks relatively small. I know you have done beautiful work in your courses to simulate it, but for people who can't go to a course unfortunately with a pandemic right now. I know you use the bipolar first, try to see if it's a perforated, it's been avulsed. Can you take us through what you're thinking and what you do if the initial steps are not working?

- Yeah, I mean, that's always the big challenge and you've absolutely nailed it on the head, especially with this kind of Approaches. If you're going to access tumors out to the Petrous Apex you better be comfortable managing a Carotid injury. And that cannot be emphasized enough, but I think not only do you have to be ready, but your team has to be ready. We run simulations with the OR team. We have a checklist that we'll go through, but long and the short is I'm thinking a couple of different things. First thing is what is this patient's anatomy? Refreshing any one of these cases, I'll review it in advance. If it's post radiation, I'll do a balloon test to see if I can sacrifice it. If not I'll re-review the anatomy or have someone in the OR who knows what they're doing, re-review it and tell me, is there an ACOM, is there a PCOM? What are my odds of being able to sacrifice this? I don't want to do that, but I want to know if that's an option. If it's small, I'll see if I can get a bi-polar on it. And the truth is you can oftentimes aneur the Carotid artery, edges of it together. And remember the Carotid is a large vessel. If I lose part of that lumen by coagulating it, or using an aneurysm clip for example to pinch it, that's not the end of the world, but many times you get a sidewall injury, don't have great access, or we all have great videos when we had beautiful access and we could pinch it or coagulate it. If it's more on the back wall, you're either stuck sacrificing it or muscle. The one thing I learned from looking at our Carotid artery injuries is there were too many times I tried to get too cute and try to do something really clever. And I wish and I just learned if I don't have quick and easy control, just put some muscle on it, get it packed off and let my endovascular colleagues save the day because they often can. They have so many good options now to try to salvage a Carotid injury. So I would say that, try some of these other things, but go quickly to muscle as a packing agent.

- I got you. I use Adenosine too. When I get into the bleeding, I love Adenosine because it really gets everything quiet for 30 seconds a minute. And it really allows me to look at the Carotid, what is torn, what's happening and then react appropriately rather than just sort of you know, how your blood pressure and heart rate goes up and you just don't think well, no matter how much.

- You're guessing, you're absolutely right. You're guessing otherwise that's a great point.

- Yep. So you know, you've been truly a pioneer Paul. We know that Endonasal surgery started for short form pituitary tumor standard, I would say the best approach. for craniopharyngiomas it's proven itself to be really, in my opinion, more superior, to transcranial Approaches craniopharyngiomas are perfect. They fit, they are cystic. There are very extra axial, they're originating in the region of Supracellar space. And no matter how big they are, you really can decompress and pull the tumor in. So Endonasal Approach really has proven itself superior for pituitaries, for craniopharyngiomas, for Tuberculum sellae Meningiomas, they are small, they're subgaleal matic, a beautiful approach. For Olfactory Groove Meningiomas you and I disagree, I know you have done a beautiful job and you can take it out. I just think if the olfaction is still somewhat there the transcranial Approach is the way to go. So that's sort of a gray area for some of us who do Endonasal surgery. You have pushed the limits in terms of Petroclival Meningiomas, that's a really a new area for anything extra dural in the Petroclival region, like Chondrosarcoma, chordomas, it's essentially standard of care. I don't know why you would you not Approach Endonasally for an extradural region Petroclival area. The vascular areas are sort of a different level and we're not going to touch that tonight. So Petroclival area are really there. You have pioneered, and I know a Fernandez Miranda has done the cavernous approach. What do you think is the future? If we're going to look five years from now, what would you say? And you give this talk, what do you think we'll be looking at?

- Wow, I think the real question is, are we going to be able to come up with instrumentation that is improved and are we going to be able to come up with ways of training people so that this really can be, you know done more ubiquitously because you know, Petroclival tumors are at the very end of the learning curve. They require the most difficult microsurgical dissection. They have the highest potential complications. And I think the comfort with managing that is really the most challenging. So I think there are... And another limitation also is having a team that's available to do these and having an ENT that's committed to staying there for an eight to 10 hour case. These are limitations. I do think there are things like robotics that maybe not five years from now, but perhaps 10 years from now, we're able to recapitulate some of the things that you know, a Carl Snyderman or an Eric Wong can do intuitively during a surgery like this. And start to replace some of those functions, so the ENT doesn't perhaps have to stand there the whole time. Robotics could perhaps allow us to shorten our learning curve by making some tasks easier in a crowded space like that. My hope would be that that would be perhaps one of the advantages. And then just further training. I'm very interested to see what happens when, you know the next generation who comes along who's training and has a open mind to, "I could do this Endonasally or microsurgically, I have to develop those skill sets" and what they're able to do, you know, as the next generation with how they see this falling out. I think those are really what's going to define the future for us. Technology and then training.

- You know, I agree with you. I think something that's very important that we're not an Endonasal surgeon or we're not a transcranial surgeon. It's not a separate specialty. I come across too often that people feel like, you know, Endonasal Skull Base surgery is separate profession, it isn't. we really have to adjust our expertise to the legion rather the legion obeying our expertise. I think too often people say that, "Okay I'm an endovascular surgeon. Therefore I coil all aneurysms. I'm an Endonasal surgeon. So every tumor should be Endonasally removed." I think we will become super sub-specialized. And I think subspecialization has very much great disadvantages. It gets us separated from our colleagues, it narrows our scope of expertise and really narrows our set of our operative skills. So I agree with you that we have to be very broad, very multi dimensional in intracranial surgery and be able to react to the legion based on our expertise rather than having the legion react to us. So with that in mind, Paul, I want to really thank you for how much you have done for Skull Base surgery in general and Endonasal surgery in particular, we hope to have you with us in the near future and hear more of your accomplishment and pioneer work that we can follow closely.

- Thank you so much Aaron, for having me. I really appreciate it. And thanks for everyone for staying late tonight. And again, thank you for all your efforts with the Atlas. Really very valuable work. Thank you.

- You're welcome, God bless you. Thank you so much.

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