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Approach Selection for Complex Skull Base Lesions

Sebastien Froelich

October 26, 2020


- Hello, ladies and gentlemen, and thank you for joining us for another session of The Virtual Operating Room from the Neurosurgical Atlas. My name is Aaron Cohen. Our guest this evening, is Dr. Sebastien Froelich from Lariboisiere hospital in Paris, France. We're so honored to have you with us, Sebastien. He's going to talk to us about the Operative Approach of choice for resection of complex skull based tumors. Sebastien, it's truly an honor again, and we're very much excited, to listen to your technical pearls. Please go ahead.

- Thank you very much, Aaron. It's an absolute pleasure to be with you today, and it's an honor to be able to speak at this wonderful sessions that you have organized, for a few years now. So subject of my talk is approach selection for complex skull base lesion. It's a difficult topic and extremely important topic in a skull base surgery. As you know we have multiple options skull based surgery to reach a lesion, located in different region of the skull base. This is what I learned, what I was trained to, when I was a young resident, we were learning different corridors and open approach possible to get to the skull base, FTOZ approach, transmitters approach, trans basil approach. And this this was our choices of options of our approach for those complex lesions. This is the example of the FTOZ approach, giving you multiple line of sight, multiple angle of you to look at a specific target. It has some advantage but over the years, there is definitely a trend towards more mini mainly invasive approach, less extensive approach, in order to reduce the morbidity of those a big open approach. We went to the Keyhole Concepts that was introduced by Perneezky. A small entry binds also multiple angle of line of sites, but everything coming from a single entry point, it's a completely different concept. And we have learned now that there's rooms for each type of approach, a big open approach for small lesions sometimes just because you need to look at this lesion from different entry points, or sometimes big lesions for which only one entry point is enough under Keyhole craniotomy is a good option. So Keyhole approach, there have been multiple duplication, multiple variations, of the technique for those small approach, supraorbital or orbitopterional, lateral supraorbital, minipterional, all these focusing on the same concept. About I would say 20 years ago or a little bit more, the endoscope was introduced, in our field bringing Keyhole endoscopic assisted technique, for tumors but also for vascular cases. And obviously it was also an opportunity to extend what's Keyhole approach whips in microscope were able to reach. And then finally we had the extended endonasal approach, which were a revolution in skull base surgery for those anterior relocated skull-based lesions, specially around the area of the clivus. All this bring us... Brought us multiple, multiple option for different lesions. Open approach using the microscope on then endoscopic assisted, open Keyhole, endoscopic endonasal approach. So this makes choice of the approach not so easy for a specific lesions, because again we have multiple options. And choosing the good approach is really trying to find the advantages, inconvenience of each approach compare those advantages and inconvenient between different option and to choose the approach that will be the best for a specific patient. This is my decision-making process, and resume of it when I am facing a specific patient. First question I think every one of us has to ask himself before choosing for a surgery kind of strategy is there an indication for surgery? Is there other options than surgeries? Medical treatment observations, all this should be in my opinions the first questions that we need to ask ourselves before starting to talk about surgery, to a specific patient. Then once we approach the surgery, surgery is decided, what is the goal of the surgery? Is the goal of the surgery is to achieve a complete resection because this is a possible cure for the patient or the goal is only a partial resection to decompress critical structure, and we know is that it's a benign tumors. And following this remnant of tumor will give many years to the patient. All this needs to be defined every time for each patient, each specific tumor. And then, once the goal of the surgery is defined, comes the choice of the approach. So choice of the surgery kind of strategy, which is the surgery kind of strategies that will give us the best chance for the patient in term of risk of in term of morbidity, in term also sometimes of mortality. Choice of the approach is based on different factors. Patient factors are obviously extremely important. Age, co-morbidities, wishes of the patient. We will not think the same way, if it's a young patient without co-morbidities he can face a very long surgery, complex approach than if it's an elderly patient that is already fragile, for which it's probably better to go fast with a simple approach with a low related risk, for the approach. Tumor factors are extremely important. I definitely strongly believe that for some tumors like large or giant petroclival meningioma being able to look at the tumor from different perspective, different entry points is really an advantage. You have a line of sight for each chronial neuron for example. So this is extremely important. For some tumors like some, planum sphenoidale or tuberculum sellae meningioma, a Keyhole approach is absolutely perfect. Anatomical factor also need to be taken into account, if you have a non-traumatized petrous bone for example, it's probably not a good idea to do a transpetrosal approach if you're not very experienced with it because skelotonizing the vestibule, the semicircular canal will not necessarily be easy. And finally surgeon factors are also extremely important. Experience with skull-base approach, experience with the anatomy of some complex region, transpetrosal approach I think is not an option if you did not have any training in a laboratory, to really train with this approach. So approach familiarities is important, and having the support of someone with more experience is also very important. So patient counseling, discussing with the patient is extremely important in skull based surgery, explaining every aspect of the surgical approach. Explaining the surgical risk variety to the approach, and send to the tumor resection in details, is very important. I will start with some example of chordoma because chordoma is a perfect tumor to talk about selection of the approach, why? Because chordoma are really located in the soundtrack skull base, and the answer is multiple options depending on the extension of the tumor, depending on the consistency of the tumor and depending on the fact that there is classification or not. So it's a perfect tumor also in which there was very clear evolution in the choice of the approach in the last 20-25 years. This is the approach selections that we used for skull-based chordoma between 1991 and 1999. You see that it was really as a beginning up from endoscopic approach at the end of 1900, and we were mainly doing open approach like lateral transcondylear, anterolateral or was craniotomy. And then with the beginning of endoscopy, endoscopic endonasal approach for chordoma, raised a significantly, you see that in this period of time it was 24% of the approach used for those chordoma. And in 2010-2018, it was really the explosion of endoscopic endonasal approach used in 77% of patient. I have to say that in last two years I have changed and this number, has decreased significantly, because I thought that the mobidity for approach to some chordoma, endoscopic endonasal approach to some chordoma big tumor at the level of the craniocervical junction also weaves the risk of CSF leak. Other approach, other option were offering a better result to the patient. It's definitely true that with endoscopic endonasal approach if you stay in the midline if you are not going too laterally, if you are not going too deep, in fact the risk is absolutely reasonable and it's a perfect option for a midline clival chordoma for example. Whenever you go lateral, whenever you go deep, whenever you open the dura, with a big defect, then you increase the risk of morbidity. The soft tissue resection which means the resection of normal tissue to create space to work increase and the mobidity of the approach increases also with it. When you go lateral, you take higher risk with the ICA for example in the space, you take higher risk with 12 with six. So definitely the surgical footprint of endoscopic endonasal approach, I think has been a little bit under estimated for extended endoscopic approach. For those complex and big tumors. If you do a nasal septal flap it's not nothing for the patient. It's really has some consequences. The patient will have to wash his nose, for a few months in order to reduce cresting for example, and this has to be taken into account when you decide which approach you will use for a specific pedagogy. Is there other options to reduce this morbidity? Not always but if there is, it has to be think. Velopharyngeal insufficiency has been underestimated also at the level of the cranial cervical junction for big chordoma and it's not necessarily because you are doing a lot of work into the nose. It's just because you leave behind at that space, that create those source is velopharyngeal insufficiency, especially for very slow growing tumor, before the surgery. So choice of the approach is not necessarily easy and it's also push us I think to think on other options for endoscopic endonasal approach, to try to reduce the morbidity. If the morbidity is reduced, then those approach stop to be also a nicer option. And this is what we are trying to do in the last 10 years to develop some strategy, to really preserve the endoscopic, the endonasal anatomy. Working one nostril, using these chopsticks techniques that we have published, using two hands, the endoscope holding their hand left-hand holding the endoscope on the section on the right hand while holding on other instruments. Principle is based on the fact that we are not using a holder, and this gave some rooms to work and to avoid sword conflict. And I show you now some example of it. The holder in fact is the endonasal structures, that hold, the endoscope hold those sources to sections that is my label on rotative section, with just a slight movement of the finger like this in fact. I really moved the tip of my section, and it gave me really the ability to target specific point, with my section. This is an example of a chordoma. Craniocervical junction chordoma it's not a small tumor, it's going into the petrous setbacks, it's going into space or sphenoid sinus. Classic endoscopic endonasal approach in a case like this in fact, is opening everything, removing the middle doing a septectomy, maybe a constagrade approach to control the last segment of the ICA. But we've our strategy... We can stop the video. In fact the video is... Yes, in fact we just do a small incision, on the rostrum of this sphenoid on one side, we are just working one nostril, elevation here of the mucosa of the rostrum. And this will be our working space, we don't need more. We have angle instruments, angle drill, on these straps six technique we don't have an under scope, which is like a pillar, which for holder in the middle of our surgical field, I am holding everything in my hands, and I have noticed worked on flick. I can really have the tip of the endoscope, next to the tip of my instruments. So here is our drill, the cavities enlarge, and we get here to the chordoma. And then I use angular scalp, 30 degrees, 45 degrees, 70 degrees scalp here it was a 70 degree scrap looking at the back, of the petrous ICA. And slowly the tumor is completely resected. This is possible also because glaucoma soft tumors that we can suck and at the end I removed the mucosa of splenoid and I put some fat in the tumor cavity, as well as in the splenoid which has been cranialized, and we close this mucosa of the rostrum just like we would close the skin in an open approach. There was a tiny CSF leak in this case, and I think it's definitely the best closure possible for a patient like this. Closing the mucosa and like you are closing the skin. This I think is potentially the future of endoscopic endonasal approach, but obviously we need equipment. We need equipment to be able to do that and still the instruments that we have, we can move to the next slide. Are not completely made for this type of strategy. We need smaller endoscope, we need smaller camera. We need instruments that do not take such place into the nasal cavity. We need angel instruments, my labor instruments, my labor drill. So this is a cartoon showing the technique, that we use, we remove the tumor, doing a small incision at the end after having put some fat into the tumor cavity, we close the rostrum mucosa, we stitch this to do a kind of what the uptight closures. There is different way to open and close this mucosa, depending on the anatomy. This is the post-operative results with the fat, into the tumor cavity, and the outcome for this patient was really, really nice. Here is another case of a very small tumor, located here in the jugular foramen medial aspect. This patient was complaining of an XI nerve parsy. He was a failure man. And it was really a problem for him, for his professional activity. It was a young patient. It was a slowly growing tumor, but growing tumor bringing some symptoms. So I thought it had to be removed. The diagnosis I thought it was a combo sarcoma but not completely sure. Here you have different options either going with an open approach, a complex surgery, coming from lateral, complex approach with draining of the petrous bone to opens the jugular foramen. I think it was too much for these tiny tumor. So we did exactly the same things and before, one nostril approach from the opposite side, draining the rostrum, on progressively getting to the tumor. We can stop the video here. So chopsticks technique, one nostril approach, opposite side, getting to the paraclavial ICA, from the opposite side. Following vagus nerve here that is an arrow pointing on the last segment of the ICA, and once we have it we've got some cartilage, fibro cartilage below last serum to get to solution. When you're from CMRI is that it would be soft, because it was very hyper T2. On progressively we get to the lesion, we suck it and at the end we stimulate the cranial nerve in the jugular foramen. Next the slide. So this was a quite straightforward approach. You see the corridor is very narrow, but we didn't really need it more, and the endonas anatomy was very preserved with this patient. This is another case of a clival chordoma, it's a quite big tumor, as you can see here it's purely intradural and there's some kind of lateral extension. I was not so confident in this patient, going with an endoscope, why? First because it was purely intradural and I thought I would need a big dural opening to really have access to the different, compartment of these tumor. Big defect means higher risk of CSF leak, and on the top box is this patient was obese with a high BMI, which we know is a very increased significantly the risk of CSF leak. So here I use the classic open approach for petroclival lesion, which is a combined petrosal approach. Combined petrosal approach is described for decades and it's a fantastic approach to reach this region and to really, have control of the critical structure around. We can stop the video. So this was a mastoidectomy. The concept of combined petrosal is based on working between posterior falx, cerebellum temporal lobe. You need really to open the space just like you work between frontal and temporal lobe, it's the same concept. And you drills the petrous reach just like you would drill the spinal reach you don't have to use zeal. Dura opening is different because you need to get the tentorium, you need to mobilize the sigmoid and transverse sinus, but you see here that they have a short walking distance. I can really dissect the tumor away from the nerve, from the vessel. And I was able to achieve here what I believe was a complete resection. Outcome for this patient was I think better we've almost zero risk of CSF leak, if you close properly the middle here. Next slide. This is another case, a little bit similar from the previous one. You may tell me why don't you use your combined petrosal you did it before. Here it's a bit different because you see that there is some tumor in suspended sinus. If I do a combined petrosal approach, and at the end I set this piece of tumor, I will have a leak. So then I have the combined petrosal but I have also a big opening into the sphenoid sinus which may be difficult to close if I go to trans finally. So here, I decided to do on endoscopic endonasally and it was also tumors that was really midline without going too much laterally like before. So I did endoscopic endonasal approach we can stop the video. It was in fact the approach it's the same, it's a one nostroid approach but we did a nasal paraclival here, and chopsticks technique exactly the same and before, same concept. We are resecting here as a tumor, but we had separate to see that the vessels on brunches where completely uncased and infiltrated by the tumor. It was endoscopic endonasal for tumors that we thought would be soft and in fact it was really a nightmare. We dissected the brunches of basilar one after the other away from the tumor. Very high risk, this patient went fine we had no vascular issue, but we were really on the edge, for the entire case. We closed with the technique from Napoli which is a 3F technique. Just putting a piece of fat focusing them as a post-operative period on the intracranial pressure, keeping the patient at 45 degree, on never a supine to really lower the intracranial pressure. Combination of both I think is a very clever way to close. We can go to the next one. This is a fat that we put into the defect, big piece of fat like the snow snowman on them keeping the patient 45 degree minimum upright position for at least two weeks. And this patient did not leak. This is another case of clival chordoma, big tumor, you can see that it's going in multiple compartments in through the central basal system. There is tumors going here into the until it pushes a little bit seven and eight. There is a big piece also into the cavernous sinus. And there is a piece that is going quite up here, probably having some tight relationship with the third nerve. So here on endoscopic endonasal is an option, but endoscopic endonasal extradural it's easy, but once you need to resect those species here it's another story. That tumor may come easily into the section but do you have a good control of the cranial nerve behind? And not completely here. And on the top of that, you have a really high, I think, quite high risk of CSF leak between probably 10 and 15% in a case like this. So here, we decided to do use a different strategy, there is a piece of tumors that is very good for endoscopic endonasal approach. This is some space here into the clivus or this piece here into the cavernous sinus here. Oops, I did maybe a mistake. No, I'm sorry. No so there is a piece here into the cavernous sinus, and there is a piece here that is... I'm just changing the color. That is into the clus perfect for endoscopic endonasal approach. But this piece here that is leading the subarachnoid space, or here on the top or here next to the brainstem, we decided to go with a transcranial open approach. So first step up of the surgery here you also see those different compartments of the tumor, cavernous sinus but also in the subarachnoid space, you can see here on those fiesta sequences, that the third nerve is really laminated on the top of this upper part of the tumor on the right side. So first step of the surgery we can go into the video, was to do an endoscopic endonasal approach. The goal was to resect everything that was extradural, we did also one nostril approach, left nostril. So if the goal of the surgery was really to stay extradural, not to open the dura, not to end up into the subarachnoid space because what we wanted to avoid with this double approach strategy, was the risk of CSF leak, also to have a better control of the cranial nerve but what we really wanted to avoid was the risk of CSF leak. So here is the tumor resection into the nose, you see that there is calcification. Chordoma not so difficult tumor to resect on endonasally, when it's a purely extradural, especially here it was very hyper T2. So it was a tumor that could be sack, for the vast majority of it. And then also falls apart of the tumor that was located into the cavernous sinus. The risk was a six nerve because there was a big piece into the left cavernous sinus as you can see, we use monitoring to identify the six nerve. These patient had almost no symptoms, which make it even more important to choose the strategies that have the lowest risk of morbidity. Second step was a combined petrosal approach. We use a new techniques that we are in the process of publishing kind of mini combined petrosal approach we focused it here on mastoidectomy, and the drilling here the mastoid process, I am enroofing the sigmoid sinus. The concept is to transpose sigmoid on transverse sinus. Okay, we are not doing a lateral lab approach. The space given by the drilling of the petrosal bone is not the space we would use to reach the tumor. The space we will use to reach this tumor, is to really create a space, into this fissure between temporal lobe, and the cerebellum, like in transsylvian approach. This is what give us the space to work. So everything is into openings, the dura is on proper way in order to mobilize sigmoid sinus, transverse sinus to have really the space, on the line of sight, to look at these tumors. Here's cutting the tentorium after having a litigated superior petrosal sinus as major as possible to preserve the petrosal vein. And you see that now I have a not very deeper working distance, in fact it's a quite short on working distance but I'm quite happy that I can control the cranial nerve right one after the other. In fact the tumor was quite adherent, to some cranial nerves to the brainstem, and this technique, to peel the arachnoid away from the tumor, it was I think the best way to ensure a good post-operative results with a very low morbidity. The only things that this patient had it was 4th nerve paralysis, she recovered quite rapidly but working on both sinus of the 4th nerve for many hours is a very high risk of having a force. But she recovered quite well after a few weeks or a few months I don't remember, but she definitely recovered from these force. The resection was a complete, and we stopped where we saw the border with the endoscopic endonasal approach. And we waited for about a month between both approach to be sure that we would have a good scar, to finish the resections with a transpetrosal approach, to really identify the limits of the previous endoscopic endonasal approach. At the end, you see the beautiful view of the flow of the ventricals that we just saw, with the body and this shows you how this approach can be nice to reach what's right wall ventricular tumor extending into the 3rd ventricle. Putting fat, closing the middle ear which is the most important, it's to really close the middle ear to avoid a leak. But the leak, with this strategy, I thought was much lower than the risk of leak using purely endoscopic endonasal approach. We can go to the next slide. This was a post-operative MRI showing a complete resection in this patient, next slide. Oh, it's me sorry. I will skip this case because I think I am running a little bit late and I am going to this case here at the level of the craniocervical junction. This chordoma, is located really midline, and this is a perfect case for an endoscopic endonasal approach, because it's midline, and there is almost nothing to do into the nose to reach this tumor. We can work through... Is a both nostril, there is nothing to do with the septum, just to push a little bit inferior turbinates on the side, to create some space, but that's it. We can run the video. A very straightforward case and there is no duped. This is a perfect approach for a case like this. Another option would have been a transcranial approach, posterior lateral, anterior lateral, more interior lateral extremely complex for such an easy case, with endoscopic endonasal techniques. Though here, we are doing a U flap, and once the U flap is done, push down we are quite directly on the tumor. The tumor is resected progressively, there is no critical structure to be afraid of. The only thing we wanted to preserve was stability, so we looked for those species of tumor, along the odontoid process with a 45 degrees looking down, instead of drilling the odontoid out of C1. This was the goal of the surgery, not to resect the tumor because we thought it would be anyway easy, but the goal was to preserve stability. Next slide. So the limitation of endoscopic endonasal approach, also craniocervical junction, it's deep. And sometimes the lower aspect of the tumor, cannot be reached through the nose. It could be reached through the mouth, but not through the nose. And if the tumor is extensive and you can see on the previous video it was not extensive, but if it's extensive and if you want to go laterally to the combine you need to resect the middle tumor in the same way you actually like part of it at least. You may need to resect your station tube. And if you go laterally as I said in the beginning, you will increase the risk for the differential ICA on the 12th nerve. And if you open the dura, then you increase significantly, the risk of CSF leak, and the problem also with endoscopic endonasal approach when you have a condyle infiltration tumor, at the level of the cranial cervical junction is that you're also creating instabilities that you cannot treat with the approach. So midline is easy, but laterally there is drawbacks, because you have to resect multi-issue, you have also a higher risk with the ICA some critical structure like your 12 and 6 nerves. This is an example of it. You see this big tumor here going in ball condyle, we've also a little bit of extension, reaching here the vertebra artery, it was at the time where we were pushing quite far, our indication from endoscopic endonasal approach. So we did it endoscopic it was a very challenging case, to resect completely this tumor with the need, to really get to this gradual part of this tumor because this is the piece that you really have to resect, if you want to be able to do proper proton beam therapy nasal. This is a video of it, we can run it. So when dealing a case like this to resect inferior turbinate at least on one side, to resect your station tube you just saw it. And then we need to drill the condyle, we need to go very deep drilling the condyle in order to have access to this piece of tumors that is intradural. We were reaching with this case the vertebral artery we could not identify with a doppler. So it's a very extensive approach. We were happy at the end of the case that we had a nice resection of the patient. No big major complication, no issues with under nerve, no vascular injury. But for the patient for this lady the post-operative... Of course we can go to the next slide, Was quite difficult and she remained in the floor, for at least a month with a significant, verofrangella insufficiency, and then she had some morbidity from endonasal approach for a long time. On the top of it, we had to use proton beam therapy because it was a chordoma. And proton beam therapy, make all those symptoms worse. So we thought that, yes the surgery went fine, the approach was nice, but the outcome for the patient was not optimum. And I show you now some cases where I really change my attitude, my strategy, for those complex craniocervical junction tumor because I was not completely satisfied with the outcome. This is a case of a chordoma as a craniocervical junction tumor you see that a similar case than before it's going on both side, big intradural extension here, and it's reaching the jugular foramen, and there is some extension here in front of the anterior arch of C1. So quite complex case. Endoscopic endonasal is an option, but this piece of tumor is definitely here, my fear... Sorry, this piece here intradural is my fear, first because it's intradural with the risk of CSF leak and I need a big opening to have control of it, but also because it seems that there is a tight relationship with the critical structure. I think I switched two slides. So here you can see with gadolinium you have this piece of tumor here is enhancing, and this is weird for a chordoma. Everything was T2 but we've gadolinium you have only this piece that enhanced. And these to me was assigned that it was vascularized by the posterior circulation. And it was making me more afraid of the relationship between this piece of tumor, and the vessels. Not necessarily the baker, but the tiny brunches from the baker. And there is also a piece of tumor here, that these may be infiltratings are being observed brainstem. So put all these together, advantages... Disadvantages of endoscopic endonasal compared with advantages disadvantages, of nasal from cranial open approach I decided to choose the open approach. And what I did is a posterolateral far lateral approach, using a classic corridor with some bending up the condyle, but most of the condyle was already destroyed. With the idea that at the end of the open approach, at the end of what I could resect with the microscope, but I will use the endoscope to reach the PCs of tumors in dark corners with the microscope. And I knew also that I could use not only use zero degree endoscope but 30 degrees, 45 degrees, 70 degrees endoscope, to look on the opposite side. And we have done a multiple study now in the lab to look at how much we could increase the exposure of open approach with the use of endoscopic assistance. So let's run the video. This was a posterolateral transannular approach, you see that there is a fracture of the condyle. I am doing a little bit of mastoidectomy openings with jugular flamen to have control of it. I am using the doppler to identify the jugular bulb, and then through the condyle I am removing the tumor, through the condyle under the microscope. I am draining the clivers controlling also the pelvic cavity space here. All the tumor, into the pelvic cavity space was quite easily controlled with the microscope. Next slide. But the upper part of the tumor if you remember the images, there were species of tumor going up into the petrous apex. How can I reach the petrous apex with posterolateral far lateral approach It's not the same region well I have the endoscope. And the tumor cavity created the road towards the petrous apex. I just have to follow the tumor, we can run the video. And this is what I did. I followed the tumor up to the petrous apex with an endoscope draining the pathological bone, getting to the ICA from below, petrous ICA reaching here suspensory sinus. To achieve a nice resection of this piece of tumor that was into as a petrous apex. We can move to the next slide. This was the MRI showing you as a piece of tumors that was into the petrous apex as we reach putting with an endoscope and the final step of the surgery was in fact to open the dura because that was a big piece intradural. And the big advantage here is that I was controlling the cranial nerve quite well under the microscope, which I think was the safer for those cranial nerves that were a little bit infiltrated as well as a matter of the brainstem. On here, final advantage which is a great advantage I have no fear of CSF leak. I can completely resect the dura that I think is infiltrated. When you go endoscopic endonasal you try to reduce the opening of the dura because the more you open the more you increase the risk of a CSF leak. Here, I have no risk of CSF leak. Very little, if I close is a mastoid process. So I did a complete resection of what I thought was infiltrated and at the end I put the batch that I stage with some fats. Let's go to the next slide. And the final... Again another advantage of it, I finished the surgery with a fixation. So here we have only one endoscopic endonasal if you succeed you still have to go back to the surgery for fixation because this patient has no more condign on one side. We had the little stroke here into the it was completely a symptomatic, but it shows you is that there was some feeders coming from the posterior stipulations. I'm sorry, I don't know where was the images, I think I missed a slide showing images. It was a much bigger tumor, like a board around six centimeter in diameter really center in the craniocervical junction. This teaser another case of similar tumor, big tumor off the craniocervical junction that we operated through posterolateral far lateral approach the same strategy. You see that the patient was positioned at the supine in order to be able to fix at the end of the surgery. I'm sorry, I don't know where was the images, I think I missed a slide showing images. It was a much bigger tumor like a ball around six centimeter in diameter really center in the craniocervical junction. So same strategies that before except that here because the tumor was going lower we had to transpose the and take advantage of the of C1, not only is a condyle in the case before it was not necessary to transpose the because we were going just through condyle on the upper part of the condyle. Here the tumor is going over, so we need to transpose to access to his of C1. You just saw that we switched the microscope to now look really in front of the dura sac. We are draining the condyle to get into the tumor. We are doing also a small suboccipital drilling to expose the . I push the microscope as much as I can to resect everything that seems to at accessible with the microscope. Here I am peeling the tumor from dural SAC. At some point I cannot reach a more diverse for example, or the opposite side, it was a bilateral tumor. So then I put the endoscopy inside, start with a 30 degree, then put 45 degree and then 70 degree. To progressive do exactly the same that we would do through the nose holding the endoscope, holding instrument in my left hand, using the chopsticks technique. And those are instrument with my right hand and in fact I am doing exactly the same through the condyle. That's what I would do through the nostril same technique, except that a case like this the risk of CSF leak is very low. We'll see just after that there was a little bit of infiltration of dura is that we closed fat, but the nasal cavity are not open. And we reach the opposite side, the opposite autologous canal, the opposite endoscopic guidance. So here I thought that posterolateral far lateral approach would give me a much lower risk for this patient, lower risk of CSF leak, lower risk of corneal nerve deficit, with the advantage of a fixation during the same stage of the surgery. I put also a piece of cement between what was remaining of lateral mass of C1 on the mastoidectomy cavity to give a little bit of stability on the right side before fixation. Next slide. Next. sorry. So this here... This type of approach require some preparation because you understand that I am looking at the contralateral ventrolateral from a posterolateral corridor, transcondylar corridor or in front of the dural SAC. I have never seen the ventrolateral with angle of U before. And you know that the trajectory of the ventrolateral the craniocervical junction is complex. And I want to have an idea of what I will look at during my surgery with my endoscope. So this is clearly approach where you need some research in the lab before going for this type of approach, it cannot be only improvisation. So one of our research fellow Arianna Fava did some work in the lab looking at this anatomy in Canterbury specimen. So this is a view of the far lateral posterolateral approach from one side, ventrolateral is transposed. We have 12 nerves here. And then we put the endoscope and we look at the opposite ventrolateral after draining the lateral mass, after draining the odontoid process, after draining the contralateral conduit, contralateral mass of C1, and contralateral mass of C2. In order to put this view of the into my mind and to also find a way to identify safely the contralateral fetal artery. And the way to identify it safely is to drill the transverse process of C1, to get to the transverse forum in of C1, and to do the same as the level of the transverse process of C2 to get to the transverse foramen of C2. Follows a bone, follows a consent was bone to find fixed zone of the . This is another case of craniocervical junction chordoma here a big tumor also with intradural extension relationships that I felt would be difficult here with artery. It's not going very high up into the clivers but it has some tight relationship with the vessel on cranial nerve. You have also an extension here into the condign significant one, so this patient will at some point need some fixation. Here I decided not to do posterolateral far lateral approach but to do anterolateral lateral approach to the craniocervical junction going from one site to the other. Because of the speeds of tumor that was going into the condyle and it was more into one side to the other access than anterior, posterior axis for the tumor. So anterolateral corridor using also the endoscope if needed to check the corner with the microscope. So this is the position of the patient incision of the anterolateral approaching in front of the sternocleidomastoid region detachment here of the gastric mysel, because we need to have control of the jugular foramen in the case like this, because the tumor was going next to the jugular foramen. This is transverse process of C1. Here we detached superior inferior lateral rectus muscle and the muscle. And then we open transfers foramen of C1 and we transpose here the we expose the lateral mass of C1. We expose the condyle and we go through that and we a fantastic freeway to the opposite side. Because there was some infiltration, or at least it was in contact with the jugular foramen majorly I wanted to have control of the jugular foramen to really get to the being comfortable, close to the jugular foramen, to go high up. After tumor resection extra dura I needed to have control of the subarachnoid space so we opened the dura behind the sigmoid sinus to resect the piece of tumors that was intradural. You'll see that it was a multiple bowl tumor, not very infiltrative to the nerve but multiple ball surroundings as a vessel in between lower cranial nerve. So I was happy to have this microscopic view. Then I put the endoscope at the end to make sure that they have achieved a complete resection. And I find out that there is this little ball of tumor, just medial to the jugular foramen on the opposite side. And I'm not sure I would have seen it if I would have gone endoscopically endonasally. What I am sure off, if that through the nose, I would have 10-15% risk of CSF leak in a patient lenses. So here we can resect against the dura as we want. We have no fear of CSF leak is the only thing we need to do is to close properly the middle ear. And at the end we put this piece of cement here to create stability between what was remaining of lateral mass of C1 under the mastoid cavity. Next. And this is a CT scan post-op, which this piece cement. The goal of this was to create some stability, to put the collar, to have proton beam therapy and to fix after a proton beam therapy, because metallic outwear make it difficult to plan proton beam therapy. This is a very interesting case of a jugular foramen tumor, but not only this tumor is going from the cavernous sinus to the CP angle here to as a jugular foramen and down into the neck. So it's a very extensive approach, extensive tumor about a 10 centimeter height. So what is the approach in a case like this that give you the possibility to resect most of the tumor. This patient was operated before you can see here is that little bit of temporal lobe is missing and they just took some tumor into the petrous apex, that's it. So they kept the tumor into two parts sinus and the rest of the tumor behind specialties, a piece into the jugular foramen. So here, what we decided to do is an approach to the jugular foramen. And with the idea is that maybe we could do more with the help of an endoscope. So here is the opening up the jugular foramen, with the approach exposing the lower cranial nerve here just at the exit of the jugular foramen. And here, I find out something that I did not expect, but I should have expected it because it was very hyped about T2. So tumor was extremely soft without calcification. So instead of doing the big opening between the lower cranial nerve dissecting the lower cranial nerves, I just puts the endoscope in between the cranial nerve with very limited many predation on a sec, most of the tumor from below. And once everything into the neck, everything into the jugular foramen was suck with the endoscope from below. I went into the corridor to get into the petrosal bags into the clivus. On here also, once I was limited with my microscope, I put the endoscopy inside and I removed the tumor that was extradural at the level of the CP angle in fact it was not intradural. Here I am looking at the middle ear opening from below quite amazing view . The only piece of tumor I was not able to resect which is corridor discovery is the part of the tumor into the cavernous sinus. Impossible to reach the cavernous sinus through an corridor, even with an endoscope. At least I could not do it. Next slide. So here we need a second surgery. This is to show you a different direction we used with the microscope, with the under scope. And at the end we did just an endoscopic endonasal approach to remove these final piece of tumor here on the right side, that was located into the cavernous sinus. Quite easy approach to do because the tumor was very soft. So we did a very simple approach to as a pituitary, just like a pituitary adenoma and we opened laterally and we went into cavernous sinus to set the tumor. It was very easy to just like it was done into the neck. I will now finish with two cranial cases, and chordoma This was a very interesting case, a big tumor in the region of the endo petroclival region. The radiologist we are telling is that most likely it would be a schwannoma. We had the multiple discussion about hypostasis, but at the end, I thought yes this is most likely a schwannoma. This patient had a acute angle cephalus and she had a shunt in another institution. She had very limited other raised intracranial pressure that were straightened with the shunt. She had some intermittent diplopia. What kind of approach can you use for a tumor like this? Transsylvian is possible because you see that here is your tumor could be arranged between frontal lobe temporal lobe exposing the supraclinoid carotid. But I thought that the tumor would be beyond, would be beyond the carotid defecation, would be beyond the perforators of the carotid artery. And you see that it's going quite up pushing up the anterior perforating substance. So here, after thinking quite a lot of the best approach I choose the right arrow. On the right arrow in fact is a posterior petrosal approach and you sees a nice window and large windows that you have if you come from behind. And if you come from behind you have a very nice control of those perforators that are pushed anteriorly, but also those push anteriorly because you're coming from behind. Let's look at video. So here is a video of it with posterior petrosectonomy approach same than before draining here as a mastery process, shavings the it's much easier to do a combined petrosal in a tumor, which is not the petroclival meningioma because the bone is now balanced the dura is normal in fact in my experience it's just like doing an FTOZ transsylvian approach. It's a posterior FTOZ and transsylvian approach in my opinion it's the same. Everything is based on dura opening. Dura opening must allow you to freeze a sigmoid sinus on transverse sinus to mobilize it posteriory. This was beautiful, which shown for a very long time by a lefty . It's based on the transposition of the sinuses, these posterior petrosal approach. Here is a section of the dentalium after getting superior petrosal sinus. You see that I am going quite far above the transverse sinus, why? Because I want to freeze the transverse sinus to be able to transpose so transverse sinus to create the space between temporal lobe and cerebellum. So here is a ligation of the superior petrosal sinus with two stitches trying to ligate in front of the drainage points of the superior petrosal vein. It's not always possible but tumor like this it's most often possible to catch a sinus anteriorly. You need to look a little bit behind the superior semicircular canal. It's not always easy to catch dura below the super petrosal sinus on beyond superior semi circular canal. But it's nice if you can present it. You see the vein here, the vein is right there. So you have to do it on under microscopic guidance to keep the vein intact. And then I get into the tumor you see that I have a large corridor, but this large corridor is not given by the draining of the bone. So this white corridor is given because I can open the space between cerebellum and temporal lobe. And I can open the space because I have transposed sigmoid sinus on transverse Sinus. The reception was not very difficult because the tumor was quite soft, but again I was happy to have all those cranial nerve under control. My fear on what I say to this patient is that I think it's a third nerve on the risk of having a postoperative third is extremely high. I try to find third, but there was no way I could find third. I even at some point I thought that what I was looking at which was in fact a pituitary stack was what third, but at the end I realized that a third was lost. I didn't saw it. The only thing I saw with the endoscope is that I left a remnant of tumor at the level of the oculomotor foramen. and this side the third was either very thin around the tumor and I cannot find it or either inside the tumor. What this was a pituitary sack completely pushed on the other side on the anterior. And you see that this corridor was very nice because there was nothing between me on the tumor. Everything was on the other side. At the enclosure proceed with bone wax on middle ear, piece of pericranium and also fat into the cavity. Next slide. We had to to see that in fact it was not the schwannoma. It was a neurofibroma and it could be an explanation for having not seen the third nerve, because in neurofibroma in fact the fibers of the nerve from which the tumor originated inside the tumor. And she had obviously a complete therapy postoperatively on the about one year after the surgery, we are starting to try to rehabilitate his eye. I will finish with a last a case. I'm not gonna show this meningioma because I'm a little bit running late. I'm showing this nice case because to show you that skull based surgery is not only for tumors. Under surgical strategy choice of approach is also a questions that sometimes you need to ask yourself for vascular lesions, such as these giant . This patient 30 year old was complaining of headache, quite strong headache that started quite suddenly. It was not a subarachnoid hemorrhage, but he had a student left eye blindness. He was blind on the left eye with a right quadranopsia temporal superior on the right side. And he had this giant of the ICA. We had a long discussion with our endovascular colleagues that are extremely strong. And you know that in France there is a real strengths with endovascular treatment for vascular lesions, but we were... What we were afraid of with this patient is to create blindness complete blindness. I was afraid we first this right optic nerve and we wanted to preserve it absolutely. So we thought that these analyses more using a flow diverter would be a significant risk either to occlude the ophthalmic artery or to have a gross of the higher pressure on mass effect on the chiasm on blindness. So we decided in these games to do a transcranial, to do a surgery, transcranial approach . I decided to do on FTOZ because I consider that it was just like a suprasellar tumor pushing the chiasm very high up. So I decided to do FTOZ. I decided to do clinoidectomy optic nerve compression, incision of the... I forgot the name. Of this dura just in front of the obviously optic nerve. Falciform ligament and on the also to have control of the carotid proximal to the analysis either at clinoid segment or petrous segment. And this is a surgery. I decided also to do a bypass because strategy was a trapping of the analysis to do a bypass. A patient had a balloon test occlusion. We knew that the delay was around 1.5 seconds. And it was a little bit too short to take the risk. And again we didn't want it to do a complete occlusion of this analysis to avoid sacrifice of the ophthalmic artery. So FTOZ mobilization of the dump bodies classic 1B the FTOZ this is a technique I am doing. We did a long time ago at work with disease from Pittsburgh, and the one piece FTOZ I am using this technique. And here is a Makati Keyhole exposing frontal dura on the periorbital. It's again a quite nice technique, you have a fantastic access to the junction between the orbit and cavernous sinus. Here we are pealing from the cavernous sinus to increase the exposure of the clinoid process. Clinoidectomy here on the optic nerve and roofing here this is optic nerve. This is here the draining of the final piece of the clinoid to expose here the clinoid segment of the carotid artery. This is the removal of the glenoid process I try to increase the exposure of the clinoid segment of the ICA, but I understand here that that will not be able to put the clip here because it's very dilated here. And resists in fact started before that and put clippings this area will be extremely difficult. So now I am doing the transsylvian exposure of the resist opening the arachnoid exposing here the optic nerve you can see here how has your optic nerve is compressed by is a fancy form ligament. This is here the distal aspect of resist, trying to find carotid artery on the because I will put a clip here. And the most important here before manipulating more is to open the falciform ligament you sees a compression of the optic nerve at this level and this is why I didn't want it to risk and increasing size of the analysis because it would maybe kill what was remaining of the optic nerve. Here is a bypass with a superior temporal artery classic technique of bypass to provide some more flow before the sacrifice of carotid artery. Once the bypass is done the objective is to traps the analysis and to put clip approximal to the analysis and put the clip distant to it. Keeping a little bit of flow into the resentment for the artery and this was a goal a flow coming artery but also flow coming also through the anastomosis between external carotid artery, internal carotid artery with ophthalmic artery. So here I am trying to have access to the petrous segment of the ICA. This is like triangle. I am exposing the carotid artery to put the clip on it in order to have this proximal clipping of the . I do the same after at the level of the sylvian fissure to the analysis after having controls at the bypass and the flow with the bypass is nice. Here I control anterior corridor and just proximity to it I put the clip. And this was the end of the surgery, didn't do anything on the shrink in the next few months after the surgery. We can move to the next slide. So a good example of first skull-based technique for to treat the vascular lesions you see is a post-op the is notified but you still have a little bit of flow dedicated to the ophthalamic artery. The fission of this patient definitely increase of the right side. He did not recover on the left side, because most likely it was a . Okay this is a case of olfactory groove, meningioma. 60 years old women almost a rapid decrease of vision on severe frontal syndrome, what would you do in a case like this? It's definitely a tumor is that for most of us needs emergency surgery, at least a rapid surgery because of decreased vision. In fact this patient was taking a progestative treatment which was acetate. You don't have it in the US but you have progestative treatment. We stubs this drug on this tumor shrink completely. And she did not require surgery and symptoms, improved rapidly. We published this case together with some others . This is to tell you that again I started my presentation with that first questions that we need to ask ourselves before to decide surgery is, is there any options? And sometimes yes, there is other options which is definitely better for the patient. My conclusion skull base surgeon of the future. We have I think, two road in front of us. We can be either master of a technique, master of an approach endoscopic endonasal for some of us. Transcranial for others. Keyhole for other or we can be experts in skull-based disease, understanding the disease, understanding when surgeries is need on mastering all type of technique and approach in order to choose the best approach for a specific patient. I think this is the future of skull base surgery. But what will be scared by surgery tomorrow is decided now and for the young people starting skull base surgery I think you really need training in all type of approach understanding the disease because this will give you the best tools to treat your patient. Technique is nice, we can run this video. Endoscopy is nice, microscopy is nice, but it will move to the next step. One day, we will not use the endoscope like we are using it today. And if we learn only a technique we are fixed to a tool when this tool is over then it's over also for you. So I think we have to focus on mastering the approach, mastering the technique but also the technique understandings of disease on maybe that in this video this is what we will have in our hands in the future, and the future may come more rapidly and what we think. Thank you very much. I think I was a little bit too long, but sorry for that. Thanks to my team, I have a great team with me.

- Beautiful presentation, really amazing technique, Sebastien I really enjoyed it. I enjoyed the videos, I enjoyed the techniques. Very well done, I loved your philosophy so I think everything all together is quite excellent. Now I wanted to ask you a question, Sebastien, number one is you sometimes use just one for your endoscopic approaches and I find that to be very limiting. The movement of instruments can be very much conflicted in each other and sorting and everything else. How do you feel about using a uni nasal approach for resection of complex skull based tumors?

- Well, you're raised the point in fact. And I have been using at the beginning of my endoscopic practice, a binostrill approach. Someone was holding the scope or we were using endoscope holder. But we moved to this one nostril chopsticks technique. This is the name we gave to us this technique because it's really holding the endoscope on with those fingers, manipulating a section. And the section is very specific. It's not a straight section it's a my label on rotative section, which means when I do that with my fingers, the tip of the section is doing that. And with this technique, I am not using any strengths in fact to hold my endoscope. The endoscope is just like this, I'm not closing my hand to hold the endoscope, I don't need it. Because in the nose a space is extremely limited and the endoscope is supported by the under nozzle structures. So it's based on first not using any strengths to manipulate and hold your instruments. Secondly, the more narrow is a space the best it is, because your endoscope your section can only go in one place. If you have a big space, first you have to use your muscle to hold the endoscope because if you don't do it it's gonna fall. Here with my technique, it cannot fall because it's supported by as inferior . And secondly, if you use strings then it's more difficult to precisely mobilize your instruments. So this is a key of this technique. There more... The less is a corridor the easiest it is. Because everything can only go in one direction, but obviously you need ongoing instruments, you need my label section. My section sometimes I bend it like this, like a hook to look behind the carotid artery as you saw it in some video. With 30... With 45 degrees, 70 degrees go up I use the endoscope from storage, which is nice but you have to work with it because the quality of the image is not good enough but you need really ongoing endoscope on good instruments. And this is key, and there is no swerved conflict. I have zero swerved conflict. I had swerved conflict when someone was holding the skull. If someone holds as skull I'm sure you feel the same thing. If you need to do some delicate work with your two hands the endoscope needs to go back. Because if it stayed at the tip of your instruments you have swerved conflict. So you ask the guy to move back. But if he move back with the 2D view of the endoscope you increase the risk of doing a mistake with the guaranteed with the vessel because you lose the 3D, you lose a 3rd dimensions that you have only if you really have seen endoscope on the tip of your instruments.

- Understood the advantage over a uni nostril approach is less trauma to any close up for you. Is that correct?

- Yes because the first I resect a less and less the meter job on the nostril I am working. Again because the more I resect, the more I need strengths, the more I need strengths, the less precise I am. And secondly the other nostril is intact. So the patient post-op, he breathe like when you do a treat area the normal waves a microscope, like we were doing it before. So the morbidity for the patient is is very limited. And with this technique of stitching the mucosa I sometimes avoid a nasal septal flap. Nasal septal flap is washing nose in my practice for three months.

- I see, okay. Well, I think that I really liked your technique of using endoscope maximizing that and extending the reach of the skull base approaches. I think that's an excellent approach that many of us should use more and more because it's not about what kind of skull based surgeon you are, it's by using everything available and letting the pathology dictate the approach, I think that that's extremely important. The last instrument you showed with the arms and the camera, is that mark available in the more kids right now or where did you-

- No, no, I don't think it is. I think it's the last model of the robots, the da Vinci robots. And it's very big in fact. It looks small but the tube is more than one centimeter I think. So it's not for us yet. But it will come at some point. At some point, I'm sure we will not using these endoscope big camera holding it so this was a conclusion for me. We should not stack to a technique based on a tool because when these tool move to the next generation, then we need to learn again. So we need to develop skills, skills that we can use in all type of approach and adapt ourselves to the technologies that is coming very fast, new tools, new microscope, new visualization equipment.

- I agree, this was a beautiful lecture, beautiful technique. I learned some, I really enjoyed it. I wanna thank you again Sebastien, for being with us and look forward to having you with us in the future as well.

- I have a favor to ask you.

- Sure.

- And I want you to keep it in the video.

- Yes.

- I want you to say the name of my hospital when last time.

- Okay no problem. If you're asking me to do that, let me try and see how about Lariboisiere?

- No Lariboisiere

- How about that? Lariboisiere.

- Lariboisiere, you did it very good before.

- Okay, how about that? Let me try one last time. Lariboisiere.

- It's better.

- Let me try one last time.

- Lariboisiere.

- I'm gonna try one last time. Lariboisiere. I'm going to try one very last time. Lariboisiere. Lariboisiere.

- That's it, perfect.

- Thank you for helping -

- It was a great session, thank you very much for inviting me. It was a real pleasure. Thanks also beyond your fantastic organizations that you have created.

- Thank you.

- Thank you very much.

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