Skull Base Meningiomas: Target-Based Approach Selection

James K. Liu

November 01, 2021


- Colleagues and friends. Thank you for joining us for another session for the Virtual Operating Room. Our guest today is Dr. Jim Liu from Rutgers Neuro Surgery. Jim has been a frequent speaker for this series for a very good reason. He's a very talented neurosurgeon, a dear friend, and I'm really honored to have him with us today. His topic will be selection of approaches for complex skull base meningiomas. A very difficult and challenging group of lesions that often we struggle with in terms of what's the best approach to really advance the resection as much as possible. So it's a very exciting talk, full of incredible videos. Jim, thanks as always for being with us, and I really look forward to watching your talk. So please go ahead.

- Great, thank you, Aaron. Thank you for that kind introduction. And again, it's always a great honor to be a part of this forum for this virtual OR. It's been a great resource, I know for trainees as well as neurosurgeons around the world, in terms of preparation for daily surgeries for our patients. So without further ado, let me begin and let me set the whiteboard here, so I can tell it straight as we go along with this wonderful platform that you've arranged. So skull-based meningiomas can be quite complex lesions involving very important critical structures. And what I'd like to do today is to take you through a virtual tour, a 360 degree tour, if you will, through the base of skull as meningiomas present themselves. So we'll start with the anterior skull base and the common lesion we typically see here is this large olfactory groove meningioma. And as you know, most of these tend to present quite large with significant mass effect and T2, edema in the frontal lobes with personality changes. And there's a number of approaches that can be taken the months that you've listed, that I've listed here. You can come in unilateral through pterional or orbitopterional where you extend it in front, include the orbit. Some people have tried eyebrow supraorbital approaches and even endonasal for these. And so I say for a lesion this large, I favor a midline transbasal approach, and I'll take you through how we do this and the reason why I choose this. So there is much debate as to whether we come from above or below for olfactory groove meningiomas. And I think for a lesion like this with a lot of T2 changes, A2 vessel involvement, sometimes even partial or complete encasement coming from above will give you a lower risk of CSF leak. And it can also allow you to address sinonasal involvement from above. And this gives you a wide exposure. And I typically like to do what I call a modified one-piece extended transbasal approach. It's basically a bifrontal craniotomy, but incorporates the anterior wall of the frontal sinus. And it really gives you this little basal approach so that you are pretty much in line with the contour of the anterior skull-based. And remember that the anterior skull-based contour is not flat, it's actually comprised of the orbital reus, and it forms a valley that you see here at the nasal portion at the cribriform, and then back up over the orbit. So you could see it's got this type of a shape instead of a flat sheet. And you can do this without having to remove any of the orbital rims. When you make the dural incision in order to avoid any bridging vein compromise or venous infarction, I make the dural incision quite low, right above the crista galli. And this is where the superior sagittal sinus tapers off, and it's very low flow. So you can even coagulate that anterior margin of the superior sagittal sinus before cutting it instead of the traditional suture ligature. And this really avoids any venous compromise venous infarction complications that have been described before in the literature. And I started to mobilize the frontal lobes laterally using these cottonwood patties, and really the tumor has done the work for you. You could see the frontal lobes are displaced and you really aren't using any retractive forces to get to this tumor. The tumors done the exposure for you. And so you can debulk the tumor down and then mobilize the capsule away from the frontal lobes and be aware of the optic nerves here. And they can creep up behind you. And of course the, the A2, A3 vessels on the backside. And then you could see once the tumor has been removed, this is the area of the tumor attachment. And at this point you have to decide whether or not to chase it into the sinonasal cavity. So on an elderly patient, I typically will just resect all of this dura and then thin down the bone without violating it into the nasal cavity. Of course, if the tumor extends into the nasal cavity and you're going for a gross total Simpson one, you can chase it into this cavity and then repair it with a pair of cranial flap from above, with, or without a nasal septal flap supplement from below, depending on the case. So here is the, here's a, the example where the tumor here invaded into the ethmoid sinuses. And this was a young patient. So I went ahead and resected all of this tumor and reconstructed it with a pair of cranial flap only from above. And you can see all of this edema has largely resolved and he's been stable at three years. Here's another large tumor you could see very multilobulated involving the eighth from above. These can be quite treacherous. This patient presented with papilledema, due to the high pressure with optic atrophy and anosmia, so-called Foster-Kennedy syndrome. You could see this as has the classic lion main sign, which is this T2 edema. And so again, I'm gonna show you the modified one piece transbasal approach that we do here. So I prefer to do this approach as opposed to unilateral. I think you just get better exposure. And by coming in midline, you have a great panoramic view of both orbital roofs looking straight down at the base. It's very easy to devascularize the tumor, because this approach gives you a low basal approach, where you can come in and start devascularizing the tumor early. But I also liked this approach as opposed to the unilateral approach because of better control of the A2 vessels. We do a bicoronal incision and we elevate the cutaneous flap as one layer, and then elevate the vascularized pedicle period cranial flap[ as a second layer. And I typically will undermine this flap. So it extends beyond the incision posteriorly. So you have a longer flap to work with. Remember as you're mobilizing the flap anteriorly, make releasing cuts at the interfascial area. So we do interfascial release incisions to protect the frontalis branch of the facial nerve. I'll make a burr hole in the midline directly over the superior sagittal sinus. So it flanks the normal dura across the sagittal sinus. So you don't have to strip the dura between two burr holes. You make a single burr hole and then elevate the dura and then we'll make a burr hole in each key hole. And then turn our flap that you see here. And then the anteriorly, this is where the key is, is that we use a straight B one bit, and then we'll enter the anterior frontal sinus here, download just above the frontal nasal suture or nasion. You do not have to go all the way down to the nasion just a little bit above it is adequate. And in a patient with a nice pneumatized frontal sinus. This makes this surgery very easy. You can extend the cuts just above the super orbital notch out laterally. And then you take an osteotome and you just articulate the intersinus septum, and then using a fracture technique, you can elevate this bone flap as one piece. Remember to cranialize and exonerate the frontal sinus mucosa. And then we open the dura and then we'll start to de-bulk the tumor. And here we take you to the part where we're devascularizing and then carefully detaching the arachnoid adhesions over the back of the planum. This is where it gets more critical because the optic nerves come into view. So if you're not careful, you can easily damage the optic nerves bilaterally. So here we're carefully elevating the tumor from the frontal lobe. These large tumors with T2 edema tend to have a subplial invasion. So just be aware of that and protect the A3 vessels on the backside. Here are the two optic nerves. You can see there's optic nerve. There's optic nerve. This is the chiasm and the A3 vessels are tucked away in the interhemispheric fissure. We'll reconstruct it with a pair of cranial flap and replace the bone flap. And you can see here's the post-op view. Let's go to the next slide. So here's the post-op scan. You could see improve mental status and the papilledema resolved. No CSF leak. You don't need a lumbar drain for this type of resection. And the patient was neurologically intact, went back to normal life. Here's another example, big tumor like this. Now, yes, it is a big incision. It is a big craniotomy. And people will often criticize those excessive bifrontal retraction. But what I've shown you is that you don't have to use retractive forces on the brain. And to minimize the venous infarction risk, we make that dural incision quite anterior and low. So you could see here's an example, three examples of different, large olfactory groove meningiomas. And you could see the cosmetic result is excellent. If you do very careful, meticulous closure. A note about approach selection. We wrote this paper a few years ago of my own series, and we use three different approaches for tumor large tumor, greater than four centimeters like this, I'll use the transbasal approach. Smaller tumors, less than four centimeters, but with olfaction already impaired, we use the endonasal. And then ones that are tend to recur. They tend to recur into the sinonasal cavity, and we can use a combined approach for that. And I think the role of endonasal approach for olfactory groove meningiomas remains limited. If you look at the systematic review that was published by Ted Schwartz, his group, you can see that the gross total rate is far less with a higher rate of CSF leak of up to 25%. And of course, when you come in endonasal, there's no chance of sparing olfaction, if you're doing a bilateral approach. There is a rare occasion where you do a unilateral approach and you instill spiral faction that was published by Sandy Yusuf. But those cases are very rare and the tumors tend to be small. So our results reflected those of the systematic review. And so I think the role here remains limited. So when do we use the endonasal for olfactory groove? And I think they're, they tend to be reserved for smaller tumors like this with minimal to no lateral extension, no vessel encasement. And the olfaction should already be impaired because this approach will invariably violate olfaction, which can affect one's quality of life. So here's an example of how we do an OGM with an endonasal from this approach. Here's another example. This is less than four centimeters. It's a medium size tumor, no lateral extension, and the olfaction here was impaired. So let's play the video here. So what we do is, we do an extended approach to the transcribriform region. You have to do a superior septectomy to get binostril access. And you wanna do a endoscopic modified Lothrop, which is a frontal sinusotomy. It's important to expose that frontal sinus, because you wanna open up the drainage pathway, but it also gives you the interior limit of your cribriform resection. Because you wanna be able to see the posterior table of the frontal sinus. That posterior table to the frontal sinus will allow you to have a surface to land your nasal septal flap to make contact for reconstruction. And you can see that here in this area. So after we've drilled out the cribriform plate, this allows you to remove all of hyperosmotic bone at the skull base. And then the advantage here is you can devascularize the tumor early by cauterizing the dural attachment, and then we'll incise the dura circumferentially. Start debulking the tumor, and this is like removing a convexity meningioma where you debulk the tumor internally, and then start to elevate the capsule in an extra capsular fashion, using Cottonwood patties to help dissect the tumor away from the surrounding structures. Be aware of any frontal polar or overall frontal arteries. You wanna try to preserve those. And of course you must preserve those A2 vessels and here's the resection cavity. And one of the challenges of endonasal approach is you're left with a pretty large defect, and you have to be ready to reconstruct it. And here we're using a technique of using a double AlloDerm inlay, which helps fill the dead space, but gives you an inlay flap. And then we'll rotate the vascularized pedicle nasal septal flap, but look how the flap was retracting backwards. This is due to tension on the flap. So what we've described here is it relaxing slit incision, which we've published. You make a slit incision incrementally, which allows you to release of the tension so that the anterior reach is maintained. And then the redundant posterior flap that's been in size can now be reflected upwards to make contact with the planum sphenoidale. And so we then pack it with a surgicel and gelfoam and merocel packing, which we leave for about 10 to 12 days. Next slide. So this is the article showing you the how this area gives you tension. You can release this tension by making a incremental, relaxing incision across the area of the sphenoid sinus. So we call this these sphenoidal slit incision, and then this releases the tension where the anterior reach is maintained. And then this redundant posterior portion is reflected upwards to make contact with the planum sphenoidale. And this has been very effective in our repair of anterior skull-based defects, especially with sinonasal malignancies. And so here's the post-op scan, complete removal and a no CSF leak on this case. This is a larger tumor, a little bit over four centimeters. But since the dural attachment was limited and did not extend across the orbits, I decided to do this through an endonasal approach, probably pushing the limits of it. I'd probably do it through an open approach these days, given the recent data, but I show this to show you what can be achieved. And you can see this is the devascularization, debulking of the tumor and then final removal. And of course the large defects are often a challenge to reconstruct. And so we've used this triple layered repair using a fascia lata inlay, followed by the AlloDerm combined inlay and overlay technique described by Roy Casiano from Miami, followed by a nasal septal flap. So this is a three layer repair, and we've been quite successful with this, with the CSF leak rate of only 2.4%. So something to consider. You can see here as you follow the healing of it, you can see the, the mucosalization the skull base over time to reconstruct the skull base here. And here's the post-op scan. You can see nice enhancement of the skull base and a very little to none, no brain sag, even in the absence of any structural reconstruction. So remember that the endonasal and the open approaches can be complimentary. Oftentimes olfactory groove meningiomas when they recur, they tend to present with sinonasal. Sometimes even orbital invasion. And so using an approach both from above and below simultaneously can be very useful. And so you can often just do the resection all from above. And I typically will use the endonasal portion for visual inspection of any residual tumor to resect. And then if the patient had a previous craniotomy, the pericranial flap has typically already been used. And so you need a reconstruction solution. So coming in endonasaly allows one to provide vascularized flaps from the nasal septal flap as a source for vascularized reconstruction. And so here's the pre-op, here's the post-op complete removal, no CSF leak in this case. Here's another patient 15 year old with a recurrent olfactory groove grade 2, sinonasal invasion. We did this through a combined approach. Got a near total removal, a little bit of residual left adherence to the carotid artery. And after radiotherapy had pretty good control for the last five years. Let's move on to tuberculum meningiomas. These can be quite challenging because they tend to invade the optic canal and present with visual loss. And so when you see unilateral visual loss, remember that this is probably due to optic canal encroachment or an invasion. And so in the tumor like this, I would tearfully study it, see what the vessel involvement is in. These in the tuberculum we'll typically never have a cortical cuff because of the suprasellar location, as opposed to the olfactory groove, where there can be a cortical cuff before you get to the A2, A3 vessels. So in these instances, there will almost always be no cortical cuff, but you got to look for, if there's any vessel encasement. And if these vessels can be dissected off safely. So in a case like this, I think this can be done endonasaly . And when you do the transplanum approach, I will do early optic nerve decompression with the bony opening. So you decompress the medial optic canals. Remember that when you follow the course of the optic canals, your bony opening will tend to look like a trapzoidal type opening, or a chef's hat, which has been described. And so again, the tumor removal is a devascularization of the tumor. Removal of the hyperostotic bone, and then intracapsular debulking followed by extra capsular removal. And when we have the optic canals already decompressed, we then open up the dural sleeve of the dura propria of the optic nerve, much like you would do in an open approach. And in these cases, you will often find a optic canal encroachment by the tumor. And so you can open up the dural sleeve, remove the tumor that's compressing there. And this will minimize your residual tumor and future recurrence as well as improved visual loss. Just remember to be watchful in the inframedial compartment, where the ophthalmic artery is going to be entering. So be aware of that. And then here's the final view showing the complex that pituitary stock optic chiasm and a complete removal here. And she went home post-op day two. So a very nice result. And at one month you could see complete resolution of visual loss. Here's another example, let's play the video here. This was very ideal for endonasal. So if you look at the T2 coronal here, look how the two optic nerves are situated lateral to the tumor. The tumors medial to these nerves. So coming in from below is very ideal. It's, much like a similar concept to removing a pituitary tumor of getting a better visual outcome by decompressing from above. And what I'm showing you in this video is that we can decompress these optic nerves bilaterally. Be very careful as you're drilling using a high-speed diamond drills with a lot of copious irrigation. So you don't cause thermal injury and using careful eggshell techniques. So you don't damage the optic nerves during drilling. So use eggshell technique and then out fracture those little pieces of eggshell away from the optic nerve, so you don't injure them as you're out fracturing. And use very thin curattes. I usually use a 4-O, 5-O up angled curatte. And then we open up the dura along the planum over the sellar dura. And I coagulate the intracavernous sinus and cut the diaphragma sellar. This is where some of the tumor attachment can be. And then here's a frontal polar artery that's being carefully dissected away from the tumor capsule using sharp dissection. And then after you internally, debulk the tumor, you can start to collapse the tumor and peel the arachnoid membranes off of the tumor, displacing them towards the brain side of things, and then carefully dissecting the tumor away from the critical structures. Try to resist the temptation to want to pull on the tumor. Inspect first and notice how this was still attached to a portion of the dura and diaphragma. And pulling this too aggressively you can probably tear that cavernous sinus or something even worse. So remember to inspect. We do a little bit of irrigation using this Locatelli diving technique to look under water for any bleeders or residual tumor. And inspecting both optic canals to look for any residual tumor. And so again, reconstruction is very critical here. As this can result in a potential CSF leak and meningitis. We use a double layer of fascia lata technique. I don't like to use a structural gasket. I'm always afraid that can encroach on the optic nerves and cause visual compression. So it will do an onlay fascia lata with a little fat and a nasal septal flap. And on these cases, I will use a lumbar drain typically for about three or four days and then put surgicel and so forth. During the closure I find helpful is to raise the bed. Reverse trendelenburg, it lowers the CSF pressure, and that can be useful during the reconstruction. Here's the post-op scan, complete removal and complete restoration of the visual loss. So what are the limitations? I think if you have lateral extension of dura, this tends to result in incomplete removal and higher risk of recurrence. The endonasal approach can have a higher CSF leak grade, according to the literature. And I think in cases of vascular encasement, my preference is to do an open approach because if you have vascular encasement, you get a vessel injury. It's very hard to repair the vessel from an endonasal approach, as opposed to when you have the head open, you can do anastomosis, direct suture repair, or any other type of vascular anastomosis. Underlying hydrocephalus. If you see hydrocephalus, maybe reconsider doing endonasal approach. cause this hydrocephalus without a shunt will increase your risk of post-op CSF rhinorrhea. So here's an example of a larger tuberculum meningioma that goes lateral here. Look how it goes beyond the carotids here. This is the optical carotid recess, and there's some partial encasement here as well. And so here I did this through an open approach. I initially started with a midline interhemispheric approach, but quickly adjusted to a frontal lateral approach. And here I've, unroofed the optic nerve canal and open up the falciform ligament early. And when you do this early, you can mobilize the tumor at a lower risk to the optic nerve. And the literature has shown that there's a better visual outcome, if you unroof and decompress the optic nerve early before you start manipulating the tumor. But notice how we do a no-touch technique to the nerves, mobilizing the tumor away from the optic nerve. And then as you go deeper, be aware of the pituitary stock and then follow the chiasm to the contralateral optic nerve, but also be aware of the contralateral carotid artery, which can creep into your view more medially. So remember looking contralateral, the optic, the carotid is medial to the optic nerve. And if you're not aware of that booby trap, you can injure the contralateral carotid artery. And then opening up the basal cisterns, you could see the basal apex and we'll often use an endoscope, even in an open approach to look around, to look for any residual tumor. Next slide. So here's the post-ops can complete removal and complete restoration of visual loss here. So a very nice result for this woman. So I tend to use endonasal for tuberculum for smaller to medium-sized tumors that have, are strictly midline, no to literal lateral extension and no vessel encasement. And the open approach for the larger tumors that have lateral encasement or vessel encasement in hydrocephalus. So let's move on to more laterally into the sphenoid wing. These again, can be quite complex. And I think that level of complexity increases as each adjacent compartment is involved namely the optic canal, the orbits, the cavernous sinus. If there's vessel encasement or cranium nerve adhesion. And sometimes these sphenoptrialclaval meningiomas can extend into the posterior fossa increasing more the level of complexity. And the standard workhorse approach that I typically use is an orbitalpterional or a modified one piece extended transbasal approach. I tend to harvest a very large pair of cranial flap when doing these, especially when you're resecting the lateral wall of the cavernous sinus. This is a nice solution for dural reconstruction. So the important thing is you have to unlock the cavernous sinus. When you do this, after you do a craniotomy, cut the meningo orbital band and start releasing and mobilizing this lateral wall of the cavernous sinus. This is the temporal lobe dura that's contiguous with the lateral wall, which we call the dura propria. And you can peel off the lateral wall, exposing V1 V2 and V3. And this allows you to expose the anterior cavernous sinus as well as the process for optic nerve decompression. This maneuver is also useful because does allow it allows you to peel off the extra cavernous component of the tumor while leaving the intracavernous component of the tumor behind in preparation for radiotherapy. I generally don't chase meningiomas into the cavernous sinus. I'll show you this in a moment. And the studies show that these tumors are quite invasive and will invade the cranial nerves and even the adventia of the carotid artery. So you're not gonna get a surgical cure here. So another advantage of doing this peeling approach of the lateral wall is a very hypervascular meningioma like this. You could see there's large flow voids, and I don't have the angiogram, but I'll show you, how tell you that these feeders were not from extracranial vessels. They were all from intracranial feeders, from the cavernous ICA. And it was very difficult to control by debulking this tumor and up until I started to peel the lateral wall and devascularizing the tumor the resection became much more easy. So here's an example of a sphenocavernous meningioma. You could see the MCA is displaced and here's some intracavernous tumor. Here again, you could see it's a straddling the sphenoid wing compressing the frontal, as well as the temporal lobes. Let's play the video. This was done through a left modified OSI. We're cutting the meningo orbital band here, and then starting the peeling technique with a stiff Mizuho Fukushima A dissector. It's a nice stiff dissector for skull-based dissection for this peeling portion. And after we expose the process, you wanna decompress the optic nerve first. And once you've unroof the optic nerve, you identified it, you can now safely with more confidence, drill out the intracliniod process extradurally. Here I'm able to remove all of the clinoid, but if the cliniod is too big, I have a low threshold of stopping just short and doing the remainder of the cliniodonectomy intradural the so-called hybrid cliniodonectomy technique. And so we open up the Sylvian fissure widely. Find the MCA and then start debulking the tumor intracapsularlly. And here are the tumors primarily pre temporal on the temporal lobe side, lateral to the ICA. And so we can isolate the tumor and then I'll cut the dura towards the orbital apex into the falciform ligament. Unroof and disconnect the falciform ligament to decompress the optic nerve that you see right there. And then this will allow early decompression of the optic nerve. And then you can cut the dura laterally towards the roof of the cavernous sinus over the ICA. So you're now recreating the distal ring of the ICA. There's the ICA right here. There's the picalm. And remember you wanna look for the next artery, which is the choroidal artery. So now we're doing the Dolans technique, cutting along the roof of the cavernous simus where we had peeled the dura propria. And then you have to make a backside decision from the back here to resect that lateral wall. So now the dural attachment has been removed, and we'll now debulk the tumor with the Metzenbaum scissors. By debulking the tumor, it makes the tumor more manageable, meaning it's easier to roll the tumor and to look for these small critical perforators that you must interrogate and decide if these vessels or tumor feeders. And here, this is not a tumor feeder. This is the antichoroidal artery. So be aware of the antichoroidal artery if you inadvertently sacrifice this, you'll have a dense hemiparesis. A difficult deficit to recover from. And then use the tentorial edge, find the tentorial edge and follow it to detach the rest of the tumor. And then you can get a complete tumor removal here. Now we know that there's some microscopic invasion into the cavernous sinus. There's the ACA vessels and the brainstem. There's third nerve right here in ICA. Let's go to the next slide. So here is a near complete removal. There's some residual tumor here in the cavernous sinus, which will leave for radiotherapy. So the important anatomy here is knowing this paraclinoid anatomy. And I like this illustration from here, because it shows that doing this extradural drilling an extradural cliniodectomy, you have what I call proximal control of the optic nerve and carotid artery, meaning you have normal anatomy on the outside. And this is important when you're dealing with a tumor like this. This tumor is very treacherous because it encases the carotid artery here in a 300, almost a 360 degree fashion. Extends into the cavernous sinus and a little bit into the posterior fossa. And so it is easy to get lost in here, if you start debulking the tumor and you have no idea where that ICA is. And it can probably result in a sub optimal tumor removal or even worse, avascular injury. So here we're showing the left modified OSI, we've done the clinoidectomy and optic nerve decompression. We'll open up the dura and open the Sylvian fissure widely, and then you wanna follow the MCA to the carotid. And here the tumor has a great arachnoid plane over the carotid artery. And this is important because as you're debulking, you want to see exactly where that carotid is. Look how I'm using the suction and knowing that every step of the debulking, I know where that carotid is. Because you don't want that or sona pet to go right through the tumor capsule into the carotid. So now I carefully divide the tumor directly over the carotid. The carotid is like the yellow brick road. It shows you the path of safety. And we'll go ahead and open up the optic nerve canal, dural sheath to release the optic nerve. And now that I have the carotid protected, I can now debulk the tumor with more confidence because I know where the ICA is. And now I can do it systematically where I work on the lateral component, lateral to the ICA. Resect this lateral wall cavernous sinus finish the peeling off of the lateral wall. There's no the lateral wall, there's the intracavernous component. This is the Gasserian ganglion, V1, V2, and V3, and then cut the roof of the cavernous sinus using the Dulens technique. Now that I've debulk the tumor, it's easier to mobilize that tumor. Find the lateral component of the tumor, which is right along the tentorial edge. Protect the fourth nerve, protect the brainstem there, and then just de-bulk the tumor piecemeal. So I can carefully peel off PICAM and choroidal. When the tumor is so big and you're trying to roll this thing, you can cause some traction on those important perforating vessels. And so by making the tumor smaller, it makes it more manageable. Here's the brainstem coming into view. And then here's the SCA vessel as well. And so there's the SCA vessel. And then third nerve was quite displaced. It was up against the carotid artery here. And here, we're showing you a three hands technique where your assistant holds the sona pet and you as a surgeon are hands free, you can deliver the tumor into the vacuum of the aspirator. And this is a nice three hands technique. And so now we're gonna work on the medial component of the tumor. There's the optic nerve. And on these tumors, the optic nerve tends to be displaced, medially and inferior on these cases. And so be aware of the potential position of that optic nerve and it's quite flat here. And so we'll hear we're looking for the third nerve. It's coursing right here, up behind the coronary artery. Very displaced medially. Using careful microdissection to get that tumor off of the third nerve as much as possible. Here's the final view. This is the ICA. Here's the posterior circulations. This is the SCA tentorial edge. And again, we'll use this vascularized paracranial flap to reconstruct this large dural defect. Next next slide. So here's the final view. This is the residual tumor in the cavernous sinus. Again, you separated the extra cavernous from the inter cavernous and reserve this for radiotherapy. So a comment about a cavernous sinus meningiomas what I just showed you are secondary cavernous meningiomas. And of course there are primary cavernous meningiomas. And typically majority of these get radiated, but sometimes they can present with optic neuropathy or a third nerve or six nerve palsy. And so generally this Dwight Parkinson has taught us that this is the anatomical jewel box. And we've seen from the literature that there is high morbidity in resecting cavernous meningiomas, especially primary and it has to do with this. You can't really get a cure on cavernous meningiomas cause histologically we've demonstrated that these invade fascicles of the cranial nerves and infiltrate the ICA wall. So the other option is the concept that my mentor Bill Caldwell has talked about, which is decompressive surgery for primary cavernous meningiomas. And what you can see here is the, when you do the decompression, your cranial nerve improvement rate is much higher than if you were to do SRS alone. So I think there is a role for decompression, and in our experience as well. This I'll walk you through the operation of how to do this. It's very similar to what you've seen before. This patient presented with the third, fourth, and sixth nerve palsies and no visual loss. And so instead of radiating this by itself, with the risk of not getting cranial nerve improvement, what we're going to do is to do the decompression operation, which is basically what you've seen already, cutting the meningo orbital band. Peeling the dura propria off the lateral wall of the cavernous sinus. Exposing V1, V2 and V3. And then we'll decompress the superior orbital fissure, V2, and V3 by drilling that infratemporal bone releasing the nerve fascicles that V1, V2 and V3. And then we will unroof the optic nerve and drill off the intraclinoid process. In these cavernous meningiomas you'll often find tumor in the clinidectomy bone, as you're drilling it, you'll see soft tumor. And then here was skeletonizing the optic just along the lateral aspect of the optic nerve. Be careful of the depth of the cliniod where the clinoidal segment of the carotid will be. So be aware of that, so you don't injure the clinoidal middle segment of the ICA. So there's the olfactory nerve crossing the optic nerve, and we'll open up the dura propria with a hook over the optic nerve. Again, this illustrates the concept of early optic nerve decompression, and I'll cut the dura towards the orbital apex. And then there's the hybrid clinoidectomy. This is the remainder of what was left. That's a little bit easier to remove once the dura is open. And then here's the tumor over the carotid bifurcation. You can see there's a good portion of intradural resectable tumor on this primary cavernous meningioma. Look how it's compressing the optic nerve medially here right here. So if you radiate this alone, you would not be able to, you'd have more radiation exposure to that optic nerve, but by decompressing, and actually being able to remove this component, you're reducing the tumor volume in preparation for radiotherapy or radiosurgery. And so here we're, de-bulking the rest of this tumor that's safe to remove before reaching the limit of where the margins of the cavernous sinus are. And then here's the complete resection of that lateral wall. And you can see the tumors quite soft, quite suckable, So you can even, in tumors like this, that are not too fibrous, you can resect the portions that are intradural and then follow them into the different triangles of the cavernous sinus. So here we're gonna open up the oculomotor trigone and decompress the third nerve. 'Cause the third nerve here is what tends to get strangulated. Here's the third nerve going into the oculomotor trigone. These nerves tend to be strangulated by the tumor impacting the cavernous sinus causing those preoperative third nerve palsy. And we can work in between the third nerve and the carotid artery in this carotid oculomotor window. And this is where tumor tends to extend posteriorly. And if it's soft tumor like this, you can debulk it and readily with a Fukushima seven suction, and then resect the remainder of this lateral wall of the cavernous sinus that you see here. So we'll continue the peeling and using that technique cutting the, making that posterior cut on the, posterior temporal side, and then communicating it with the cut on the superior side, along the roof of the cavernous sinus here. And that completes the removal. There's the fourth nerve. You can see here's some tumor around the fourth nerve here as well. And then let's go ahead and advance the slide here. So sorry, the picture's not showing up well, but this was an excellent decompression of the cavernous sinus. You can see here's the residual tumor that's intracavernous that we've left for radiotherapy. So let's move to the last component, which is the posterior fossa. And the posterior fossa has a number of approaches, a number of lesions where the tumors can arise. And I tend to divide the clivus into fourths, according to my friend and colleague Jack Marcos. And you can see an FTOZ subtemporal, we'll get you to that upper fourth. And as you walk down, Kawase approach gets you between the fifth and seventh nerves. And then adding a posterior petrosal component gives you that combined approach to get lower around the capsule towards the ninth and 10th nerves. And the lower clivus is generally reserved for a far lateral approach. And we must not forget the retrosigmoid, which is really the workhorse of CPE angle surgery. And in some cases you may want to come endonasal endoscopic to the clivus if needed. And so this is what we're used to seeing. This is the standard retrosigmoid approach. As you see in Rodin's collection. And for a tumor like this, this is an anterior petrous or a petrotentorial meningioma. This is very readily removed through a retrosigmoid approach. Remember to study the bone, nuero anatomy. There's a large suprameatal tubercle here where the tentorial portion extends. And so we can come at this entirely through this retrosigmoid approach. Your first step is to really drain the CSF at the lower cerebella medullary systems to allow brain relaxation. And then after we identify the tumor, we can start to debulk the tumor internally, and devascularize it. And now this patient had a large suprameatal tubercle. That was in the way. So you can really drill this down with a three or two diamond burr to give you more anterior access around the hump of that meatal tubercle. And then devascularize the tumor along the petrous dura and the tentorial dura. And then sequentially de-bulk the tumor. There is the seventh and eight nerves on the inferior side of the tumor. And then as the tumors debulk can sequentially come around and extracapsularly, and then peel the tumor away from the brainstem and away from the critical structures, the cranial nerves. So what you'll see here is that the fifth nerve is being displaced inferiorly just next to the seventh nerve. So there's the root leads to five, and look at the position of five. Normally it's a block higher, close to the tentorium. So this tells you the origin of the tumor, which is really the tentorial area, where it displaces the fifth nerve down. And so this is not a petroclival meningioma by definition. This is more of a tentorial feature tentorial and there's the six nerve medially with the basilar artery coming into view here. Here's a nice view of the lower cranial nerves. And then here's the fourth nerve towards top. And you can do a nice watertight dural closure. I tend to like to use a fat graft over the suture line technique that we've published, which really eliminates any pseudomeningocele, next slide. And here's the post-op scan, complete removal, normal facial nerve result. The Kawase's approach, the Kawase's approach is a very nice approach. I think it's under utilized, but you have to have a good understanding of the indication and the anatomy. So the key to knowing them the middle fossa Kawase's approach is to know the middle fossa rhomboid, which is bordered by V3 GSPN RQ and eminence, and the medial petrous ridge. So when you bisect the geniculate ganglion here, this is where the cochlea is, at the cochlear angle. And lateral to this as Glasscock triangle, which houses the horizontal petrous ICA. So when you drill it out, you get a view like this. You've drilled out the petrous apex. You've preserved the cochlea here. And when you open up the dura, you get great access to the brainstem between the fifth and the seventh nerves, as well as the and sometimes the basilar trunk. And so we did this through Kawase approach for tumor like this. This is an upper petroclival meningioma, video that we published in neurosurgical focus some years ago. And I call this petroclival because look at the Fiesta scan the tumor originates medial to the fifth nerve. So true petroclivals are medial to the fifth nerve. And if they're not, it's not a true petroclival. So we do this through a frontal temporal approach, and then let's play the video. After we do the craniotomy, we begin to elevate the dura propria, sub temporarily. Remember to coagulate and divide the middle meningeal artery at the foremen spinosum because this will allow you to release the dura and we'll peel the dura from a posterior fashion, protecting the GSPN. And then this will allow us to expose the intrapertous apex. We're now elevating the dura propria of V3. And the periosteal dura can be quite adherent in this region. And so will you sharp the section with a 15 blade here and micro scissors to really release those adhesive fibers, to separate the two layers of the cavernous sinus. And this is important because the more you release the less tension and retractive forces, there are on the temporal lobe. You wanna mobilize the temporal lobe. And so we'll decompress the foramen ovale, V3 here. And this will allow you to mobilize V3 anteriorly to get more exposure of the petrous apex in that retrogasserian space. So we have the rhomboid in our mind's eyes. So now we can begin drilling. These landmarks are much better than your image guidance. These landmarks will really guide you as to where to drill and expose the critical structures, namely the ICA and the cochlea. So now we're drilling the area that we call the premeatal triangle. The bone that's anterior to the IAC. Your inferior limit of drilling is the inferior petrosal sinus. Will then come and sub temporarily and this will allow us access to the supratentorial component of the tumor. This is the tumor that's on the upper surface of the tentorium on the medial temporal region. And so we'll, de-bulk the tumor with an ultrasonic aspirator, and then begin to peel the tumor away from the critical structures. Again, when you're working around the tentorium, the structure you wanna look for on the medial side of the tentorium is the fourth nerve. And so there is the fourth nerve right here. You can see the fourth nerve is right here, this white structure. So when you're cutting the tentorium, you wanna stay behind the entrance of the fourth nerve. We cut from the lateral side as well, and we'll get into the superior petrosal sinus. I generally like to use a bipolar to just wheel off the opening. Alternatively, you can use a suture ligature, but if the flow is very low flow, shutting it down with a bipolar is very efficient to do. You can even squirt a little bit of surgy flow in there to get it to slow down. You wanna be careful not to inject too much, cause you don't want to inject that into the sigmoid sinus, which can go to the heart. So again, be very careful on what you inject and how hard you inject it. This is this dandy's vein, superior petrosal of vein, which we will divide right at the tentorium and then open up the fibrous ring of the posttrigeminus into Meckel's cave. This gives you access into that Meckel's cave medial to the fifth nerve. This approach allows us to land right in front of the cranial nerves or working in front of the fifth nerve, in front of the brainstem here. And this is a much different view from the retrosigmoid. This is a very wide exposure working in front of the fifth nerve. You don't have the tentorium in your way. You're not working in a deep hole, deep corridor, and this is a very nice versatile approach for these types of upper petroclival meningiomas. You could see we're now dissecting the tumor away from the tumor arachnoid and pushing that arachnoid towards the brainstem surface. This is what I call undressing the tumor. This is a concept I generally teach my residents when we're doing any kind of skull based tumor surgery. A lot of people say maintain the arachnoid plains. And I think that term is often vague. I think the better term is to undress the tumor by peeling the arachnoid off of the tumor capsule towards the critical structures. So multilayered repair is very critical using a fat graft here to plug up the dural opening followed by some dudging and a nice vascularized pericranial flap. Let's go to the next slide. Here's the postop scan, complete removal neurologically intact. And if you want to extend the Kawase you can combine it with a posterior petrosal approach. And this will become the combined petrosal approach, also known as the Double Martini approach that professor taught us. And here we're showing preservation of the capsule in a hearing preservation type of petrosal variation. There are different variations of the petrosal that you can do based on, hearing status preoperatively. Hearing status was intact preoperatively. You could see this large tumor that I chose to do a combined petrosal we'll approach. We'll do it through a C shaped incision here in the lateral position. And this is comprised of a temporal craniotomy with an extended retrosigmoid transmastoid approach. And here we'll show you this video that we published not too long ago. Here we're drilling out the capsule. Skeletonizing the superior posterior and lateral canals, and you really need to hug those canals when you're drilling. So you don't have any bony overhang blocking your line of sight. And so we'll cut the dura along the temporal region, open up the presigmoid dura and then ligate, the superior petrosal sinus. When you're doing this, be very careful of where those veins of labbbe are. And I say veins because you can have more than one vein of labbe. And so after you ligate the superior petrosal of sinus, there's the seventh and eighth nerves. And luckily this tumor was a soft and suckable. And you can start to dissect the tumor away from the brainstem. So this approach really gets you close to the target in the petroclival region, right on the brainstem. We're now finishing the tentorial cut towards the posttrigeminus to open up Meckel's cave. And opening the tentorium is very important and cutting that tentorium because oftentimes the blood supply can be from the tentorium. So when you cut the tentorium, you're devascularizing, it you're cauterizing it. And with time it makes the tumor softer, with time during the operation. And you'll notice a change as you're removing these tumors earlier on, it can be a little more vascular, but as you sequentially cut that tentorium. You'll notice the tumor become progressively softer, more devascularized. And here we're, we're moving that last portion of the tumor near the brainstem. And again, you can see all the arachnoid adhesive fibers. Undressing the tumor, appealing that arachnoid off of the tumor capsule. And here is the final view with the endoscope. You can see big cavity where the brainstem has been displaced. We'll use a fascial lata sling technique, or the sling can hold the fat grass or the fat graph doesn't fall into the brainstem cavity. And this serves as a nice plug. Next slide please, for CSF leak prevention. And here's the post-op scan. You can see excellent decompression. The brainstem is re expanded to its physiological alignment and she's restored her normal gait. So here we're showing some variations of the petrosal. This is the retrolabria where the capsules preserve in a patient who has intact hearing. But if you need further exposure, you can do a transcrusal approach, where you remove the superior and posterior canals, and you can still have the ability to potentially preserve hearing. And if the hearing is out, you can do a translab. And in the most extreme case, you can mobilize the facial nerve to get access to the cochlea, to do a transcochlear. We've largely abandoned this approach because of the inherent facial nerve palsy that recovers to Brachman grade 3. But it is an option that if should you choose that. Now when you're doing a transcrusal approach, as you're drilling the canal, you have to plug and wax off the membranous canal as you're reducing it. But this gives you that additional exposure which we did in this particular large petroclaval meningioma. You could see that if you did a retrosigmoid approach here, you would have to mobilize a lot of brainstem to get them the most medial aspect of the tumor. But coming in from a lateral projection, from a combined anterior and posterior route petrosal route. You really minimize and avoid any cerebellar or brainstem retraction. This approach really lands you right on the tumor after we cut the tentorium. So here's the seventh nerve coming in from the left side of the prons. These are the lower cranial nerves. This is the seventh nerve right here. So the tumors largely above the seventh nerve. We can decompress the tumor, start to peel it off the fifth nerve here that you see. Here's the brain stem where the root of the fifth nerve arises. And you can see the tumor is readily dissected and peeled away from the fifth nerve going into Meckel's cave. Here's the basilar artery that you see here. And we'll open up the posttrigeminus here in the Meckel's cave. And now that we get into Meckel's cave here using a McElveen knife to deliver that tumor that's in Meckel's cave, the were some microscopic remnants of tumor adherent to the rootlets of five, which were small residues left behind. But here's the top part of the tumor. We're looking for the origins of of the brain stem. Here, this is the top part of the tumor, and here's an SCA vessel at the top. And so you have to be careful of where the fourth nerve is going to be. And so what we're doing here, we're using that undressing technique. Using the scissors to deliver that tumor and mobilizing the arachnoid away from the tumor capsule. So it goes towards the brain structures. And by doing this, we can now find the fourth nerve. Here's the fourth nerve stretched over the top of the, of the tumor. And using the sharp dissection to cut these arachnoid bands so that you free the tumor away from the fourth nerve and then you can deliver it safely. So there's the other side of the fourth nerve and removing this tumor safely. And so here is the SCA vessel human being preserved. Again, using those sharp dissection with the scissors, and you can use the scissors in a very versatile fashion. I teach the residents that you can use the scissors as your dissector using a closed blade technique or a single open blade technique. And then you can cut on demand. It really makes you more efficient. You're not switching instruments with a rotund six blunt dissector, which I think tends to be very ineffective for these types of tumors. And you could see the final view. Here's the fascial sling technique reconstruction of the skull base. And then the final view. Let's go to the next slide. Complete removal near total removal rather, but excellent decompression to the brainstem. And we were able to preserve the patient's hearing. Here's another combined approach. Again, this is the concept of taking out all of what's extra cavernous, and then knowing when to stop is very important in these petroclaval meningioma especially when there's cavernous invasion. And I tried to make the residual radiosurgical target as small as possible. Here's, a more elderly patient who had gait ataxia. And this one I did just through a retrosigmoid approach because it tended to follow the curve of the petrous bone. And I had to leave some residue that was adherent to some critical structures, and it's been well controlled with post-op radiotherapy and he's regained his improved gait function after decompression. So let's move to the last compartment of the posterior fossa, which is really the foramen magnum and jugular foramen. And these foramen magnum meningiomas can be treacherous. They tend to cause severe spinal cord, cervical medullary compression, where patients present with severe gait ataxia. You can see the cord is completely compressed here. And so the choice of approach here, I know some colleagues favor an endonasal approach for this, but when you consider an endonasal approach for this, remember the target is quite deep. And you're also going to remove some components of the top of the odontoid, which can contribute to instability. And then you have also have a higher risk of CSF leak. And so notice how the cord is stretched over the tumor and the C1 arch is right here. So when you're doing this from a far lateral approach, remember to remove the hemiarch of C1, because that's going help decompress the spinal cord early. And you're choosing the sign of approach, look for the laterality of the tumor. So here, the tumor creates a window towards the right side of the tumor, and it's situated between the two vertebral arteries. And this patient was wheelchair bound with spastic quadriparesis. We do this through a right sided approach using this so-called Fukushima lateral position. Look how the tumor presents itself to the right side. So we're going to choose to come at it from a right-sided approach, because this is the wider corridor with good control of the verts. This is an illustration showing the typical far lateral approach. And when you remove the hemiarch of C1, this allows you this inferior to superior viewing angle to get to the tumor. And the vertebral artery can be readily found by following the vertebral sulcus. And this is also called the J group because it's shaped like the letter J on a right sided approach. And I think there's a misconception of the far lateral approach. Foramen magnum meningiomas tend to displace these lower cranial nerves superiorly where, so the top the tumor is situated here and the nerves are draped over the top of the tumor. And I've seen comments made that the far lateral approach, the nerves are dorsal to the tumor. And I don't think that's true. I think the nerves are over the superior pole of the tumor, and you're working underneath these lower cranial nerves using this approach. So remember that you may need to drill the bone, doing a partial condyle removal. I don't think you need to remove the occipital condyle in these. I always try to preserve this OC 1 articulation. You can see it right here. This OC 1 articulation on a post-op CT scan, but focus the drilling here.. What I call supracondylar drilling above the hypoglossal canal. So as you're drilling, stay on the medial side, hug the spinal dura and just follow this bone laterally. And all you need to do is remove a little bit of this that will prevent your obstruction of line of sight. So let's look at this video here of this foramen magnum meningioma. We've approached it from the right side. Here's the right retromastoid craniectomy. You have to completely unroof the foramen magnum and drill enough medially sometimes beyond the midline of the keel so that you get a good decompression of that compressed spinal cord. I think it's critical to remove that C1 arch. Be careful of where the vertebral sulcus is. So you don't violate the vertebral artery. And in a tight neck, tight space, I'll remove just the top of C2, just to get a little bit more inferior exposure. We're cutting the atlanto occipital ligament here in preparation for the dural opening. You can see the foramen magnum is nicely decompressed. The cord has been decompressed extradurally. There's a vertebral artery going into the entrance, and now we're drilling the suprahypoglossal jugular tubercle. So this is actually reduction of the jugular tubercle, as opposed to the condyle. I try to keep that condyle OC 1 joint articulation intact. And again, these tumors largely create the corridor for you. So you only need to remove the bone that's needed that's gonna prevent you from having obstruction of your line of sight. So we open up the dural widely, open up the arachnoid widely, release CSF. And you wanna look for the PICA arteries, the verts. You also wanna to look for the C1 and C2 nerve rootlets. Neuromonitoring is very important. Those are the C1 and C2 nerve rootlets. There's the spinal accessory nerve. Lower cranial nerve monitoring is very important, monitoring the seventh and eighth and ninth through 12th nerves. So there's the tumor that's pushing the cord medially. And so we'll open up these arachnoid membranes. It's okay to divide these C1 rootlets to get better access. Be very mindful of the contributions to spinal accessory that those are preserved, but this widens your corridor safely. So you can work in between these nerves. I'll typically we'll de-bulk the tumor and devascularize the tumor along the base. Always look for where the vertebral arteries. I know it's tempting to try to want to remove this all as one big piece, but it's safer to break the tumor down into components so that you don't cause any unnecessary stretch on the cord. And then cause a quadriparesis post-op. Especially in this area, you don't want to avulse any anterior spinal artery. So it's very important to carefully dissect the tumor away from the ventral cord and make sure it's free from the vertebral artery before you deliver it. So here's a nice delivery of a large component of that tumor. And then here's the last component I believe of the tumor. Working in between these small rootlets. And again, there's the vertebral artery here. And look at the lower cranial nerves. The tumor was here, elevating the lower cranial nerves above. So we're working from low to high. The cranial nerves are not in our way and that's a misconception. So here's the dural closure. We'll put a little bit of fat graft and a med pour plate to prevent pseudomeningocele formation. And I think technique is very useful. It's worked quite well for us. Next slide. Here's the postop scan. Look at the decompression of the cord. This patient regained the ability to walk and no longer needed a wheelchair. Here's another large foramen magnum meningioma with partial encasement, 270 degrees of this avert right here. And of course the same approach that you see here, same concepts. There's the vertebral artery, the spinal cord, spinal accessory. And after removal, you can see both vertebral arteries. Here is the clivaldura and the spinal cord has been decompressed. And again, look at where the tumor used to be. Tumor was down here. Largely lower cranial nerves are up here. So the lower cranial nerves are not in your way. And here's the final resection, excellent decompression restoration of quadriparesis. This foramen magnum meningioma also has this vertebral encasement here. And so let's go to the video. This is a left sided approach. We're now drilling that jugular tubercle just underneath the sigmoid sinus. And I'm drilling off a portion of that condyle. We'll go ahead and open up the dura over the C1, dura up into the retro mastoid region and then open up the cisterna magna arachnoid membrane to expose the tumor. And the spinal accessory nerves. Spinal accessory nerve here is draped on the posterior side and we're debulking the tumor here with an ultrasonic aspirator. And then finding the inferior pole of the tumor here. And this is the critical part here. I'll show you that the tumor here is quite adherent to the pia arachnoid of the spinal cord. So what I'm doing here is I'm undressing the tumor by cutting the arachnoid bands on the tumor capsule and then peeling it towards the spinal cord. This is that concept I mentioned of undressing the tumor, but look how I'm falling into this plane where I can now peel it away from the spinal cord. If you don't do this, you are at risk of avulsing the vasculature on the pia arachnoid of the spinal cord and risking a quadriparesis complication. So that's very important to recognize. So stay on that tumor capsule and then you can devascularize the tumor on the ventral side and then start to de-bulk and decompress the tumor. So on the superior side, you can see here, spinal accessory wrapped over the top of the tumor. You saw the 12th nerve there, and now we have more confidence that the spinal cord is now free of the tumor adhesions. You could see, we can now appeal it off of the spinal cord and then start to decompress the tumor and in a variety of ways here. So now we're just going to lift up the inferior pole of the tumor. You can see the tumor is quite large and so avoid the temptation of wanting to deliver it all in one piece. So sequential debulking is important. Here's the vertebral artery entering, entering the dural compartment. So we wanna sharply dissect the tumor away from the vert. Make sure the vert is protected on the ventral side and carefully detached all of these tumor adhesions. There's the vertebral artery again. And we're gonna detach the tumor here. Now this is the C2 nerve root where the tumor is straddled against. So we'll cut the inferior half of this, and then we're gonna deliver this top part of the tumor underneath this C2 nerve root. And you can see the tumors largely devascularized. Now it's a lot softer. And then we can just mobilize it into this larger corridor away from the vert, away from the spinal accessory nerve. So it's a lot easier to decompress, okay. And here's the final view. You could see the ventral spinal canal. There's the 11th nerve draped over the top. Again, the tumor here is low below the lower cranial nerves. Here's the lower cranial nerves. And then we'll use an endoscope to look inside this cavity. You can see there's the cavity in front of the brainstem and spinal cord. There's a vertebral artery coming into view. And there's the final view. Let's go to the next slide. So here you can see decompression of the spinal cord and the patient regained her strength after decompressing it. Lastly, we'll talk about jugular foramen. This is a much more rare tumor of the skull base. This is patient with a left side weakness with gait ataxia with some dysphasia. And it's important to study the venous outflow. 'Cause you wanna know if this tumor is invading the jugular bulb and you could see the venous outflow is not filling. So this gives you the suspicion that this tumor is in the jugular bulb. And typically I would do a infratemporal fossa or what I call an extended infralabyrinthine antral lateral approach that you would do for glomus jugulare tumor. This involves a infralabyrinthine mastoidectomy and a high cervical approach to completely skeletonized the sigmoid sinus and jugular bulb so that you have control of the jugular system to access the tumor that's in the jugular bulb. And the tumor will be intradural as well as extradural within the lumen of the internal jugular vein. So here's the video that we'll show you. This is the left sided approach. And we've tied off the internal jugular vein, and we're now occluding the sigmoid sinus with a piece of gel foam. And we're opening up the jugular system. And there's the tumor inside the jugular bulb. That's all meningioma. And then we'll open up the dura in the posterior fossa and then expose the tumor here, that's in the posterior fossa. There's the tumor along the lower cranial nerves. And here we can peel the tumor away from the lower cranial nerves. Expose the vertebral artery that you see here. And they're seven and eight. This is seven and eight draped over the top of that tumor. And then we'll remove it in a piecemeal fashion. And then follow the tumor right over towards the jugular foramen. And this is the tumor that's in the jugular fossa. And then we can go extradural intraluminal in the jugular vein. This is in the lumen of the jugular vein. When we preserve this medial wall. This is the medial wall of the pars nervosa. If you preserve that, you have a higher chance of maintaining lower cranial nerve function. Here's the final view. We'll do a dural sling, a fascial dural sling closure technique, but the fact graft on, and then plate. Next slide. Here's the post-op scan complete removal. And she regained all her function back with her gait and maintain the lower cranial nerve function. So a few concluding points. I think it's very important when you're dealing with meningiomas that, you know, both endoscopic and open approaches. You should know all the approaches, I think, which can be helpful in your armamentarium, in dealing with these types of difficult and challenging lesions. And we have to remember to be tailors and tailor our approach to each individual based on their pathology and scan. And I think it's also important to know when to stop so that if we have to leave residual, we leave the least amount ready for radiosurgical targeting. And it's also important to preserve cranial nerve function as this can affect our patients quality of life. And with that, I thank you for your attention.

- Great work, Jim really illuminating really enjoyed it. I think we just refer someone on the answer skull-based as I used it for all even giant olfactory meningioma. Obviously I think that's supraorbital allows you to preserve olfaction, and that's an important thing to do and would really limit any significant endonasal approach for that because they, a sense of smell will be sacrificed automatically. So overall I really, really thank you. A little bit of a long lecture, but on great stuff. So we really enjoyed it so far matter of time, I keep the closure relatively brief and we look forward to having you with us again.

- Great, thank you, Aaron. It's great to be here again.

- Thank you.

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