Grand Rounds-Endoscopic Skull Base Surgery: Transclival, Transmaxillary and Transdontoid Approaches

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- Ladies and gentlemen, thank you for joining us for the second part of our video regarding discussion for endoscopic approaches for resection of skull base. Some of the details are related to more complex endoscopic approaches to the skull base, starting with a transclival approach. Ted, thanks for your time, and please go ahead.

- Aaron, thank you so much for having me. So, this is Part Two. Our first part, we dealt with a lot of the transsphenoidal approaches. We're gonna move on to a transclival approach. Now, as I mentioned before, you can get to the superior third of the clivus, or so, through the sphenoid sinus, and you can also get to the bottom of the clivus sphenoid sinus. This is an example of a transsphenoidal approach to the clivus, and what you'll see here is the dura of the sellar. And now we've opened up the dura, sorry, we've opened up the bone of the clivus between the carotid arteries below the sellar, and this gets you into your pre-pontine area. Here's another example of that, and you see the pituitary gland, the cavernous sinus, the internal carotid artery, and we've taken out this, in this example, a chordoma in the back of the sphenoid sinus that's invaded into the clivus, and also removed the dorsum sellae and the post-care clinoids. And this is the kind of view you can get coming in through the clivus of the basilar artery, the posterior cerebral artery, superior cerebellar, bilateral third nerves, and the mammillary bodies can be right up here, and this is the pons and these encephalons just above that. So, I'm gonna show you a video of how we took out this endogenous cyst in front of the pons. You go to the next movie, please. So, in this situation, we removed the bone over the sellar. We're drilling out the bone, the back of the clivus, we're opening up the arachnoid, and you can see that we get right into the cyst. We dissect around it and find the basilar artery, and then internally decompress the cyst. It's a soft cyst, so, we've exposed the entire basilar. Here you can see the third nerve on one side, posterior cerebral superior cerebellar. So, quick movie of that one. Postop, a little bit of fat graft in the area, but the tumor has been completely removed through the sphenoid. So, this is a clival chordoma that is a extradural. You can see that it presents itself to the, let's see if I can get my pointer to work, excuse me, presents itself to the back of the sphenoid sinus just below the pituitary gland. But you also note that the tumor extends behind the carotid artery on the patient's left side. Not so much on the right side, but mostly on the left side. And I'll show you how we deal with that. Can we go to the next movie? So, here we are drilling out the bone of the clivus. This is the pituitary gland here, so, we're below the pituitary gland, and you can see, we drill out a little bit of bone and we fall right into the tumor. We can get a very early frozen section and a biopsy. This is from the earlier 2D scopes that were low-standard definition. You can see the resolution's not quite as good, but we're drilling out now the bone towards the carotid arteries and back towards the dura. So, here's now the dura, and we know this is an extradural tumor. This is the sellar, and we know the tumor goes to the carotid, so, we do have to drill out the bone all the way to the carotid arteries. Here we are removing more tumor from adjacent to the carotid artery on the left side. And most of these tumors are fairly soft and fairly easy to remove. We're now removing the bone over the cavernous sinus on the left side. So, the sellar is over here. This is the cavernous sinus. Now we're working behind the cavernous sinus on the left side, and we can stay extradural and work behind the cavernous sinus up towards the posterior clinoid. There's the Doppler showing us the location of the carotid. This is the carotid artery here, and we're gonna work behind the carotid artery, retract the carotid artery laterally, and then use our angled endoscopes, angled instruments, angled suctions, to work back behind the carotid artery through eventual approach. Let's see if we can get out all of the little bits of tumor in that area. So, here's the postop scan. You can see how we've extended our resection back behind the carotid artery on the left side. Here's another example of a chordoma. It's also extradural, but you can see extends a little bit below the sphenoid, it pushes back on the dura quite a bit. There is an extension behind the carotid artery on the right side, in front of the carotid artery on the left side, and so, all that has to be studied pre-op. Let's go to the next movie. I just wanna show you an example of skeletonizing the carotid artery through the nose. We tend to use CTA navigation 'cause we wanna see the bony anatomy and the vascular anatomy, and the relationship between the carotids and the clivus. So, here we are flicking off eggshell bone over the carotid artery and removing a tumor behind the carotid. This is the carotid right here, and here's tumor going up to the posterior clinoid. And we'll get all the tumor off the dura, completely resect that. Here we are removing more and more tumor off the dura, below the pituitary gland, between the two carotids. So, here's the pituitary gland, cavernous sinus, carotid artery, dura, you see a little bit of green fluorescein from CSF. And here's that postop scan. You can see that bowing of the tumor has been resolved. We've taken out the whole tumor, it's mostly extradural. We put some fat in there because there was some CSF leaking. Here, again, you can see the fat graft and the tumor has been removed. This is just another example of an intradural chordoma extending back to the brainstem. And you can see the corridor we used to remove that, a little bit of fat graft in the way. This is an epidermoid. And what's interesting about this tumor is that it extends pretty high up into the retrosellar area, but also extends down below the clivus. If we did just a transclival approach, we would not get this whole tumor out. We could take it out probably to about here, and if we went above, did a suprasellar approach, we could take out the top part of the tumor. So, in some situations, you might do what's called a pituitary transposition and just fling the pituitary forward, and work below it. But we found that closing that large defect is difficult and we had a big CSF leak doing that. So, we decided to do another approach where we leave the pituitary in place and we work below it through the clivus to take out the bottom of the tumor, and then we work above it through a transplanum transtuberculum approach to take out the top of the tumor, and I'll show you how we did that. We go to the next movie. So, here's the sphenoid sinus. This is the floor of the sphenoid sinus that we're drilling out anteriorly. And now here's the clivus. You can see here's the sellar. These are the carotid arteries on either side. We're drilling out the bone between the carotid arteries of the clivus to the back of the sphenoid. It can be quite a bit of venous bleeding in this area from this basilar venous plexus. And we just pack that off with gel foam, elevate the head a little bit, and now we work through a transplanum approach. This is the stock, it's the pituitary gland, we're working above the pituitary gland to take out the epidermoid superior aspect of the epidermoid. You'll see the superior hypophyseal arteries on either side, one, two, we preserve those and just work in between them in order to get out the top of the tumor. And then we go below and work through the clivus below the pituitary gland to get off the bottom of the tumor. And we dissected this plane. Around this epidermoid, there's the basilar artery. And then we'll pull out that bottom piece once we've dissected it free. This gives us room to place an angle endoscope into the prepontine cistern, and then get a view working up from below through the clivus of the retrosellar area. Show you that in a second. Here's the basilar artery. Here's the pons. Another little piece of tumor we'll dissect free, and then we will advance the endoscope into the cavity and look up and you'll see the PCA, Posterior Cerebral and Superior Cerebellar Arteries. In just a minute we've dissected this free from the basilar. So, now we're looking up from below, here's the basilar tip, superior cerebellar. You can see some of the epidermoid stock. So, now we have an opening above and an opening below, but the pituitary gland is still intact, it's still in place. And that allows us just to do a gasket seal above, a gasket seal below, but we don't have this enormous defect to close, we just have to close the bottom and the top. So, we put fat inside and then we do a gasket seal above with a little piece of a Medpore and some fascia lata, and then do a second gasket seal below, here's the second gasket seal, and then we cover the whole thing with a nasoseptal flap. And the pituitary gland kind of keeps the buttress in place and helps us close that skull base in a watertight fashion to decrease the risk of CSF leak. There's that nasoseptal flap. And it's important to put the flap past the edges of the fascia lata, otherwise, it'll just stick to the fascia lata and not to the bone. And then we covered with Duraseal to keep it in place. Now, in this situation, we would leave a lumbar drain in for a day or two and drain at a low rate of about 5CCs an hour.

- Ted, I wanted to ask you a question. Is there a risk the pituitary stock can potentially DI when you work above and below and manipulate the stock?

- Yeah, absolutely, there is a risk, and we do everything we can to preserve the vascular supply, to preserve the anatomy. Sometimes we preserve everything and the patient still goes into DI, and sometimes they don't. But you're right, that is something that is at risk for this approach, but it's not something that we always see if we do a good job preserving their vascular supply. So, here's the postop scan.

- Thank you.

- You see a little bit of fat in there and the tumor has been removed, and here's the post-op by diffusion-weighted imaging, which is why those epidermides are so bright. This is an interesting case. This was a malignant recurrent ependymoma that had been operated on two or three times in the past, had radiation therapy and chemotherapy failed everything. And this is an intraparenchymal tumor. And this was growing, as you can see, deep into the brainstem and the patient was becoming hyperreflexic and couldn't move his legs and had that increased tone. But if you can see, there's a very thin rim of bone, and given the lateral extent of this tumor, it was very reasonable for us to work through a sphenoid, drill out the bone, and actually carve out an intraparenchymal tumor, work within the brainstem through an endonasal approach. This is just showing you that approach. We've taken out all the bone and we're now working within the tumor itself and dissecting it free from the brainstem. And we weren't trying to get a gross total resection because this is a three-time recurrent tumor that's been radiated and failed chemo. But you can see, we were able to get out probably 90% of the tumor, decompress his brainstem, and preserve his function to prepare him for his next adjuvant therapy that he was going to undergo. This is just some publications on the transclival approach. So, the transnasal corridor allows us to go up and avoid any sinus, if we want, go through the cribriform plate to the bottom of the clivus and through the odontoid. The key landmark here is the vertical attachment of the middle turbinate if we're working upwards. And if you look at the orange-colored area, this is the transnasal approach, comes medial to the middle turbinate up to the cribriform plate. If we go lateral to the middle turbinate, then we're in the ethmoids, and that's the green area, but for the transnasal approach, it's the orange area. So, it's good for small CSF leaks like this little encephalocele or meningocele. Here's an example of this, meningocele, it's coming off the cribriform plate. Here's that vertical attachment of the middle turbinate. You see it's medial to the vertical attachment of the middle turbinate, and here's the septum. You can see the olfactory nerve, if you go up far enough. We published on repair of CSF leak rate, which is very, very good using a purely endonasal-endoscopic approach. What about the clivus below this sphenoid sinus? Here's a lesion below the sphenoid sinus, and you can see through an endonasal approach, you really can come right back into the clivus, you have to take off this basipharyngeal fascia, and reflect that down. And you work between you eustachian tubes, here's one eustachian tube, and the other. Here's the sphenoid sinus, which we opened as a landmark, but this is the area of the clivus, and then below that would be the odontoid. We make a U-shaped flap, inverted U-shaped flap, or horseshoe-shaped flap, and pull that down. There's the clivus. So, here's an intradural tumor, another epidermoid that is ventral now to the midbrain. You can see it's below the sphenoid sinus. So, if we open the sphenoid, we're not gonna get this out, we have to open up the clivus and there's quite a bit of bone we have to drill through in order to get that out. We go to the next movie. So, here we are taking down that basipharyngeal fascia. We're working between the eustachian tubes. We're drilling out the bone now below the sphenoid sinus. Navigation is critical here 'cause you wanna have a sense of how deep you are, how far you can go. Now we just have a thin layer of bone over the dura in front of the midbrain, and we can open that up with the kah-ree-son. And here's our drill opening from the bottom of the clivus to the top. And we make a linear incision. And we know that the tumor is gonna be right behind the dura, and it'll be arachnoid first. And here we go, we fall right into the tumor right after opening the dura, and that's really the advantage of this approach. Once we take out some of the tumor, we can finish opening up the dura, cauterize back the dural edges so they don't get in our way, we're not gonna sew it shut, and then use our angled instruments and suctions to try to roll the tumor into the midline where it's safe to remove it. Make sure we dissect it free, and take the whole thing out. Here you can see the cavity when we're done, and the tumor has been removed. So, here's the postop scan. You can see a little bit of fat in that area where previously the tumor was. Here's a giant chordoma involving the sphenoid and the retrosphenoid, as well as the retroclival area. And obviously, we'd have to do a combined approach to a transnasal and a transsphenoidal approach. This is a tumor that's in the occipital condyle, and this was a squamous cell. This was actually a metastatic carcinoma, excuse me, we just wanted to do a biopsy, but it shows you that this area that might potentially be a difficult area just to do a biopsy on through an endonasal approach, we can come right into this tumor, use our navigation, figure out where the carotid artery is, where the tumor is, come right through the nose and have a straight shot right into the tumor, and literally open up through the nasopharynx. Here's the eustachian tube on one side and eustachian tube on the other side, and the tumor is just sitting right there, it's a straight shot. So, we make a little opening in the mucosa, take a biopsy specimen, and we're done, that patient can go home the same day. What about the odontoid? If you come parallel to the palate, you can get right to the bottom of the clivus, you can get to the top of the odontoid, and even down to the bottom of the C2. So, here's the opening to get to the odontoid. We have to go a little bit lower. We're working between the eustachian tubes, opening up that inverted U-shaped bit of fascia. Here is the bottom of the clivus, and now we're working below that, and this is gonna be the anterior ring of C1. Here's the anterior ring of C1, here's the odontoid, here's the bottom of the clivus. And all of that can be reached through an endonasal approach using endoscope. And show the video. The advantage of this odontoid approach is that the incision is in the back of the nose, it's not in the throat. So, these patients can be extubated postoperatively, and they can be fed the next day and they can get mobilized and out of the hospital much more quickly, because there's no incision in the back of their throat. Here we are taking down the basipharyngeal fascia between the eustachian tubes. We're using just a bovie with a red rubber catheter on it kah-ree-son-ing out the pannus, using a drill to take the anterior ring of C1. Here's the bottom of the clivus where kah-ree-son-ing, where, excuse me, cavitron-ing out some more of that pannus. Let me go back and take out more of the ring of C1. Navigation is real useful here to figure out how wide you have to be. And then once that's done, we will expose the odontoid. And here's the lateral aspect of the odontoid that we've drilled out. So, here's the cavity we've made, it's pretty deep. Here's the eustachian tubes, but we've managed to take out the entire odontoid. So, here's a preop scan. This patient was fused preoperatively, and here's the postop scan. You will destabilize a patient by doing this, so, you do need to fuse them either immediately pre-op or immediately post-op, or you can do both in one sitting. Here, just some publications on the odontoid resection. So, what about the transethmoidal corridor? The ethmoidal corridor will get you to the lateral spheroid sinus, the lateral cavernous sinus, but also we'll get you into the orbital apex in the anterior fossa. So, here we're working lateral to the vertical attachment of the middle turbinate, and you can see this green area through the ethmoids, and the roof of the ethmoid is supposed to call the fovea ethmoidalis, and your lateral limit is gonna be the lamina papyracea, the medial limit is gonna be the middle turbinate vertical attachment. This is good for lateral meningoencephaloceles lateral to the middle turbinate. Here's a bigger meningoencephalocele. This is a small meningioma that's somewhat unilateral, and, of course, a larger meningioma of the olfactory groove in a juvenile, sorry, anesthesia neuroblastoma. So, the key landmarks here are the anterior and posterior ethmoidal arteries, these come off the ophthalmic artery. The posterior ethmoidal artery, you find just in front of the sphenoid sinus, the anterior part of the planum, and the anterior ethmoidal artery is just behind the frontal recess. So, coming in from below, you see the superior turbinates, you see the inferior turbinates. This is the uncinate process, ethmoid bulla. When you open up the sinuses, you can see the dura, the cribriform plate is medially bilaterally, the fovea ethmoidalis is on either side. These are the orbits, this is the anterior ethmoidal arteries, frontal recess, posterior ethmoidal arteries, and this would be the sphenoid sinus, here with the optic nerve, optical carotid recess, and carotid artery. Take off the bone, and then, of course, expose the gyrus rectus and olfactory nerves. So, here's an actual endoscopic view of that anatomy. And we're looking up from below. This is the orbit on one side, the orbit on the other side would be here. This is the fovea ethmoidalis on one side fovea ethmoidalis on the other side, frontal recess would be up here, sphenoid sinus back here, and this in the middle is the cribriform plate that's been removed. So, to do this approach, you have to go lateral to the middle turbinate. Here's the sphenoid sinus middle turbinate, we're going lateral and doing an uncinectomy to expose the ethmoid bulla. Open up the ethmoid bulla and now we're on the other side. This is the middle turbinate, we're lateral. This is the fovea ethmoidalis at the roof of the ethmoid sinuses. This is an example of the ethmoid artery, lamina papyracea, OBF modalis. This is just a resection of a large olfactory group meningioma using this approach, and here's the brain laterally. Here's the resection cavity from fovea ethmoidalis to fovea ethmoidalis, showing the brain after the tumor has been removed. So, here's an example of an olfactory groove meningioma. When I choose cases for this approach, I don't like to do meningiomas that extend all the way up to the posterior wall of the frontal sinus, because then I think it's just as easy to use an eyebrow incision to get into it. If there's some brain between the back of the frontal sinus and the tumor, it's a reasonable one to do. We go to the video, please. So, here we've removed the middle turbinate, we've done the transcatheter approach, we're drilling out the bone of the anterior fossa, we're drilling it out, and here's it's laterally. This is just in front of the sphenoid sinus, this is anteriorly. And once we drilled out the bone circumferentially, we're removing bone toward the lamina papyracea, which is here, taking its entire attachment. We remove the cribriform plate on block. These patients will definitely lose their sense of smell, so, you have to know that this is a tumor where you're not gonna preserve smell. And then you're just looking at the tumor, it's just hanging right in front of you and we can dissect it off the brain. Sometimes they can be a little stuck. Here we're using a standard bipolar to dissect it off the brain on either side, and then we'll internally decompress it with the cavitron. Here's our cavitron. You can see there's absolutely no brain retraction whatsoever, we're just retracting on the tumor and pulling it away from the brain. And here's the brain in the frontal lobe. And we fill that with fat, cover it with fascia lata, use our Medpore graft, and then also use a nasoseptal flap. Here's the Medpore going in. So, here's a postop scan. Here's the fat in place. This was the edema that was present beforehand, and that fat will eventually resorb. But just because we can take all these olfactory group meningiomas out doesn't mean that we should. And in some circumstances I do like to use an eyebrow incision. And I just wanna go over that to show you that this is a great minimally invasive approach for taking out olfactory groove meningiomas. This is the view you get. This is the tumor before resection and after resection. And you see all the arachnoid planes preserved and the carotid, and the optic nerve. Here's an example of a meningioma that we took out also through an eyebrow incision, just showing you we can take out pretty big ones. You can harvest the nasoseptal flap through an eyebrow incision and use that to repair the skull base. This is the attachment of the temporalis muscle, and here's the bone flap. I like to take the orbital rim. It's a fairly minimally invasive minimal-access approach to take out pretty big tumors. Here's the postop scan. But sometimes we do like to go through the nose, and sometimes we combine the two. So, this is olfactory group meningioma that was above the cribriform plate, and went through the cribriform plate into the nose. So, it had a anterior fossa component and a nasal component. So, we did an eyebrow incision, went in from above, took out the tumor, and then went into the nose and took out the rest of the tumor. We made a separate incision here in order to get a nice big pair of cranial flap, and then made an eyebrow incision. Let's go to the video. So, what you're gonna see is once the craniotomy has been done through the eyebrow and the orbital rim has been removed, we drill off the superior aspect of the orbital rim, and then we start to internally decompress the tumor. This is that eloquence device. Now, when you go through an eyebrow incision, it's hard to get to the cribriform plate. Here we are. We can't really get our instruments to the cribriform plate using a microscope, we can't see around that corner, but we can bring an endoscope in and do endoscope-assisted surgery through an eyebrow incision, and then we can see very nicely into the cribriform plate. And here we are using that eloquence device in endoscope-assisted eyebrow micro supraorbital craniotomy, and then we're coming in from below and you're doing an endonasal approach to get out the rest of the tumor, and using that eloquence device in here, a tissue shaver to take out that meningioma within the nose. So, that's a combined above-and-below approach, which then we closed with a nasoseptal flap and a pericranial flap. And here's the postop scan showing the tumor removed. Esthesioneuroblastomas can also be removed through endonasal-endoscopic approaches. This is an embryonal rhabdomyosarcoma, similar tumor that we took out. And it is important to get negative margins in these malignant cases. They do not need to be removed on block, but they do need to have a complete resection with negative margins. Can we go to the video? So, if you cannot achieve that through an endonasal approach, you probably should be doing a craniotomy or a combined approach, a cranionasal approach. But in some circumstances, you can achieve a complete resection with negative margins through the nose, and those are well-selected appropriate cases. Here we're working between the middle turbinates. We've taken out the bulk of the tumor, we're taking out the ethmoid arteries. You can see the dura below the interior fossa. And we dissect the dura because the tumors do extend towards of the olfactory bulbs through the dura, and that has to be resected. There we've removed the crista galli, we're working in the interhemispherically along the faux. Here's the frontal recess, the tumor removed, here's the lamina papyracea removed, and the sphenoid sinus behind, and that's the cavity. So, here's the postop scan. And here's just a description of a paper of that transethmoidal transorbital approach. Now, it turns out the orbital apex also presents itself to this sphenoid sinus and to the ethmoid sinuses, and you can remove things, but only from the medial orbital apex. The first thing you'll encounter is gonna be the medial rectus muscle, so, you have to be very, very careful not to damage the medial rectus. This is an ethmoid osteoma that went into that medial orbital apex. And the post-op cavity, this was an extradural tumor, so, we were able to take it out through the nose. She went home pretty quickly. But you can also get a little more anteriorly through the ethmoids. Here's the back of the orbital apex with the sphenoids. And this is a intracranial tumor. Obviously, the orbital fat's gonna come out when you do this kind of surgery. What about the transmaxillary corridor? This is the last corridor we're gonna talk about. This is what gets you lateral in the skull base and can get you to the infratemporal fossa, pterygopalatine fossa, the petrous apex, the lateral sphenoid sinus, and the lateral cavernous sinus. It's very good for these CSF leaks of Sternberg canal, these lateral sphenoid sinus CSF leaks. You might think you can get this through a transsphenoidal approach, but it's very hard to see this for a lateral through a standard transsphenoidal approach. You really need to drill off some of the pterygoids in order to see this. This is Meckel's cave, which we can get to through a transpterygoidal approach. Here's a juvenile nasioangiofibroma that's in the pterygopalatine fossa. Here's a petrous apex cholesterol granuloma, which we can also get to through an endonasal-endoscopic approach, and drain them that way. You have to know the anatomy of the pterygopalatine fossa, the infraorbital nerve, the Palatine nerve, the pterygopalatine ganglion, and the sphenopalatine artery draining into the internal maxillary artery, as well as the descending Palatine artery. This is just an example now on the other side. So, here's the sellar, here's the ICA, here's the optic nerve. And what you'll see is the back of the maxillary sinus has been removed, and you can see the infraorbital artery, infraorbital nerve, maxillary artery, sphenopalatine artery, and here's the pterygopalatine ganglion. And this just shows you the sphenopalatine artery coming through. This is gonna be the blood supply to the nasoseptal flap. And this is the crista ethmoidalis, which also has to be drilled out in order to get inferiorly in that maxillary sinus. So, here's a juvenile angiofibroma taken out through a purely endonasal-endoscopic approach. Here's your postop film. Here is a lesion in Meckel's cave. And I'll show you how we took that out. I'm just showing you that you have to open up the maxillary sinus lateral to the medial terminate. Your otolaryngologists can do an uncinectomy, an antrostomy, and open that up. Here's the sphenopalatine artery and the pterygoid bone, and you need to cauterize and cut the sphenopalatine artery. Here's the perpendicular plate. Here's the back wall of the maxillary sinus. And here we opening up into Meckel's cave. This is the sphenopalatine sinus, so, we're now lateral to that. We're looking at the lateral cavernous sinus here. We go to the video. So, here we're doing our uncinectomy and antrostomy opening up the back wall into the medial wall, excuse me, of the maxillary sinus. We're gonna expose the sphenopalatine artery, we'll cauterize and cut that. Drill out the pterygoid bone and expose Meckel's cave. Here we are in Meckel's cave taking out the tumor, we're dop-ling the carotid artery from lateral to medial, it's the lateral wall of the cavernous sinus. And here's our postop scan with the tumor removed. This is tumor in the infratemporal fossa. And I show this case as an example of how we can do just a purely endonasal-endoscopic approach, take out the back of the septum, work laterally, work through the back wall of the maxillary sinus to get into the infratemporal fossa, pterygopalatine fossa that's been expanded here, and take out this whole tumor. So, we're working our way around this juvenile nasioangiofibroma. They bleed quite a bit, so, we like to work our way around them before getting into it. This is the crista ethmoidalis, we're still on the nose, this is the maxillary sinus up here. And we're drilling out the crista ethmoidalis so we can open up the maxillary sinus widely. Most of the tumor is back here in the pterygopalatine fossa. We're starting to get drilling towards the pterygopalatine fossa. Now we're in the back wall of the maxillary sinus. We just flick that forward 'cause it's very thin by the tumor. We're looking all the way into the maxillary sinus, and we're gonna dissect our way around the lateral aspect of this juvenile nasioangiofibroma, try to come not through it, but around it. You'll see that it's white because it's been embolized, particularly the IMA branches have been embolized, and that's why this lateral infratemporal fossa component is very white. So, are dissecting the musculature off the margin of the tumor, keep working our way around it, preserve the plane to try to preserve all the muscles, the infratemporal fossa and take it out in one piece, and kinda roll it forward into the nose. Now we're cutting the last attachments of the tumor sharply. And then finally, we'll take the excuse me, I'm not gonna get that. We'll take the sphenopalatine artery that's giving the blood supply to most of the tumor. We'll cauterize and cut that at the end. So, here's the postop film. And you can see that we remove the tumor from within the infratemporal fossa and there's no more tumor there. Here, just some of our clinical papers on the transpterygoidal approach. We've talked a little bit about closure. I wanna give some more detail on this gasket-seal closure that we've developed. The idea is in order to get a watertight closure, we take a piece of fascia lata that is larger than our opening, and we countersink a piece of bone into this area to prevent CSF from coming out, and get a watertight seal because the fascia lata is sort of pooched around the outside. Now, in our early iteration of this, we just put Duraseal on top of it, now we put a nasoseptal flap on top and put Duraseal on that. And if we're not in the third ventricle, we'll put fat intracranially, if we're in the third ventricle, we won't put fat because I'm always afraid it's gonna fall into the third ventricle and obstruct the aqueduct of Sylvius. So, here's an opening. Here's the fascia lata moving in. It's bigger than the opening. And we buttress it with a piece of Medpore, or a piece of Volmer. And you can see how it cauliflowers out around the outside so that it prevents any fluid from leaking out. And here we're covering it with Duraseal. Here's an actual example of a surgery where we're up into the third ventricle. You can see the opening in the bone, it's about this big, above the normal size sellar. We take a big piece of fascia lata, put a piece of Volmer in this situation, and countersink it. And you can see the fascia lata around the outside making a watertight seal, cover it with Duraseal. Nowadays, we would do our gasket seal, use Medpore instead of Volmer, and then cover it with a nasoseptal flap, and then cover the flap with the Duraseal. Patient selection is everything, I can't emphasize that enough. You have to choose the right patient for this. You have to know where you can reach with an endonasal approach, and where you can't. So, I've tried to highlight in green the areas where I think it's reasonable to do an endonasal-endoscopic approach. The carotid arteries are really our lateral border for a lot of these surgeries. It's very hard to work lateral to the carotid artery. It is possible, but it's very challenging. As you can see, we extend lateral through the maxillary sinuses 'cause that provides a safe corridor. And coming in in a sagittal plane, there's quite a large area we can reach, but again, it's not everything. So, at 400, we sort of looked at our cases to see, what was our rate of CSF leak, what were our complications? So, I'd just talk like to talk a little bit about that. About half the cases we've done have been pituitary tumors. Now, our CSF leak rate for all 400 of these cases has been 4%, and it's not that different for pituitary tumors and other tumors. At the beginning of our learning curve, we had 16 CSF leaks and 12 of these stopped with lumbar drains. Two required craniotomies, two required repeat endonasal surgery. So, the rate of re-operation was only 1.2%. And what we learned from this was that a lot of these leaks would stop with a lumbar drain. So, now we started to put more lumbar drains in beforehand. Now, pathology is important. This is for the whole series. You can see that our meningioma CSF leak rate was really fairly high, about 10%. Cranios was acceptable at 4%, encephaloceles 3%, and chordoma, 0%. But the learning curve is important. In the first half of our series, we had a 6% CSF leak rate in the first 200 cases. In the next 200 cases, we only had a 2% CSF leak rate. So, that's really quite good. And if you look at the meningiomas, it was actually 20% in the first 200 cases and 0% in the second 200 cases, encephaloceles, the same thing, it came down dramatically from about 9% to 0%. So, there is a learning curve here, but hopefully you will learn from the mistakes that we made and other experts have made, and you guys can hit second half of the learning curve and just skip the whole first half. This is our learning curve for CSF leak after extended transplanum transtuberculum approaches. When we used just a fat graft, CSF leaked much too high. So, we started to do more advanced closures, fat graph plus sellar reconstruction, nasoseptal flap, gasket seal, and nasoseptal flap plus a gasket seal. In this consecutive series of 61 cases, the last 13, we had no CSF leaks. Here's some more data, the gasket alone, in a larger series of 65, 3%, gasket plus nasoseptal flap, 40 cases, 2.5% CSF leak. And these two leaks that we had, both of them stop with the lumber drain, so, we didn't have to do any re-operations. So, lumbar drains now were placed intra-op pre-surgical. We didn't do it that much in the beginning, now we do it in everybody who has a giant tumor or definitely an intradural tumor. So, if we know we're gonna get a CSF leak, guaranteed to get a big leak, we'll just put a lumbar drain in beforehand. We'll only drain it at 5CCs an hour for 24 hours, and then we'll pull it out. And I think it allows that dural sealant to harden in the first 24 hours to hold the flap in place. And we leave it open during extubation so that a pressure wave of them coughing goes out the lumbar drain, and doesn't go out the nose. You do get some epistaxis, although not a high rate, 1.5%, DVTs and PEs fairly low. Infection, now here, you'd think you get a lot of infections, we're working through the nose to the brain, you'd think we're going through an unsterile field to a sterile field, but it turns out we have had three cases of questionable meningitis, and the reason I say questionable was because they seemed like they had meningitis, but the lumbar punctures were negative, but all of these patients had CSF leaks. So, if we didn't have a CSF leak after surgery, we never saw a case of meningitis. However, we did have one intracranial abscess around a fat graft, and that was in a pediatric case. So, the rate of infection is about 1%. And the rate of sinusitis, which we can treat with antibiotics postoperatively, was about 5%. Vascular injury, again, about 1%. These also were very early in our series. We had the carotid injury I mentioned, which, luckily, we had no neurologic sequela, one ophthalmic artery injury which had no neurologic sequela, and two strokes, one of which was silent, and one of which caused a brainstem infarct. And this patient did have neurologic deficits. Mortality, about 0.75%. We had one patient with a meningioma of the tuberculum sella and she had diabetes, end-stage renal disease, hypertension, and she had a skull-based defect before we did our extended closures, where we put a buttress in there and it just fell out into the nose, and we just could not close it. And we tried a craniotomy endoscopic surgery, we were not successful. We had a macroadenoma that died on postop day seven of a massive cardiac event, and one olfactory groove meningioma who died postop day seven of a hematoma, but overall was less than 1% mortality. What about quality of life? We've started to measure quality of life in our patients. And we can look at sinonasal quality of life and skull-based quality of life. It turns out at about three weeks, their sinonasal quality of life is a bit worse. Three weeks after surgery, their nose, they have some complaints, but if you look over time, it actually gets much better, and it goes back to about its baseline. If you look at the ASBQ, which is an Anterior Skull-Based Surgery Quality of Life, it turns out that it's six months. If you compare it with pre-op, these patients actually have improved quality of life. So, if you measure their quality of life, it actually gets better after surgery, if you can wait six months. However, we do use a lot of foot pedals, and it can be painful to do these cases. So, we're trying to minimize the number of foot pedals that we use. What's the future? Well, 3D stereoendoscopy may be very useful. This will overcome the issue of depth of field, which you don't have with a 2D endoscope. 2D can be misleading. And there are commercially available systems out there that use a 3D sensor with a chip on the tip of the scope, and we have been involved in helping them develop it and using it clinically. We give courses every years, we have some books that we've written, and hopefully this has been informative for you all. And I hope that you can slowly start to embark on these approaches, take your time, and see if they're useful for you. Thank you very much, Aaron.

- Thank you, Ted. I think this is a spectacular technical job, really pushing the limits safely, and at the same time, really doing a superb job. If I may ask, the three elements that was most important to you in the first 200 cases and the second 200 cases, one of which was really the gaskets, the nasal flap, that nasoseptal flap that you talked about, what are the other two that you saw were so instrumental for people who wanna really get going with endoscopy that would help, sort of pearls of advice that you really can't write in your papers but you really wanna share it with others, please?

- Well, I think one of the things that I often tell the residents when they're doing these approaches is that's important to remove a lot of bone. You can't make a little tiny bone opening. If you do, you're gonna not see what you're doing and you're gonna end up pulling on something. But you only gain the confidence to make a big bone opening if you can close it. So, you first have to establish that you can do closures and establish ways of closing so that you're not worried, because what keeps you making a small-bone opening is you're worried about a CSF leak. But if you're no longer worried about a CSF leak, and you don't even care, and you say, "I'm gonna take as much bone as I need to get this job done safely," then you're much more likely to get the job done safely than if you're hindering yourself with a small-bone opening. The same can be true of the sphenoid sinus, the sphenoid sinus entry wall has to be completely opened. You don't wanna see any bone obstructing your field of view. In fact, the whole keel of the sphenoid sinus, or the rostrum, we take out the whole thing, particularly if we're gonna use a nasoseptal flap, because you don't want that flap going over a big lip of sphenoid sinus 'cause it's just gonna be hanging in the breeze. And the other key pearl is if you're using a nasoseptal flap, you have to take out all the mucosa in the sphenoid sinus, because if you leave mucosa behind a nasoseptal flap, you'll get a mucocele, right, 'cause it's just gonna start producing mucus behind your flap. It'll pull your flap off and you may have to go back in and drain that mucocele. So, those are some of the key things that we've learned that have really helped us over the years.

- Thank you, again. I really enjoyed the discussion, Ted.

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