Grand Rounds-Endoscopic Transnasal Surgery: Personal Perspectives

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- Hello, ladies and gentlemen, and thank you for joining us for another installment of the WNS operative grand rounds. Today, we have a special guest Dr. Dan Kelly from St. John's health center and John Wayne cancer Institute. He's director of the brain tumor and pituitary disorder program there. He's truly a master surgeon, a gifted surgeon that I have seen at work when I was at UCLA. And I'm very appreciative that he's going to share his expertise regarding nuances of technique for minimally invasive skull-based surgery. Dan, thanks again, and please go ahead.

- Thanks very much, Aaron. Pleasure to participate in your series here. So what I thought I would do today is to talk about the applications and some of the technical nuances of a keyhole and endoscopic brain and skull based tumor removal. And I'm really gonna focus on four approaches and where I think these techniques are most applicable, and I'm gonna focus a lot on endoscopy. There's my disclosures with Mizuho. And so what I'd like to do is really focus on the concept of keyhole surgery, which is really the idea of removing tumors through a smaller, more precise openings to minimize collateral damage to the brain scalp and muscle. And we're going to start with the endonasal endoscopic approach, because really that is the approach that has embraced the endoscope more than any other areas of neurosurgery. And I think it's a nice platform for what we can do with this enhanced visualization that we get with the endoscope. And I'm going to talk about the supra-orbital approach. And then I'm going to talk about what we like to refer to as gravity assisted trans-dural approaches and where the utility of the endoscope comes in there. So trans falcine and transtentorial approaches. And what I like to tell patients is that our goal is really to sneak in and sneak out. And to enter and leave unnoticed with as much stealth as possible. And of course not to get caught. And of course, complication avoidance is a big part of all this, and we'll touch on that as well. So these approaches, this concept of keyhole surgery, which has really been around for several decades, I think has come into a new era. A lot of the traditional skull based approaches that we've used, have been augmented or replaced in some instance because of numerous technical advances, which have come together in the last couple of decades. And of course these are all familiar to you. Frameless navigation, tractography, and functional MRI. Our instruments have gotten better and more refined. The ultrasound probe can be very useful for real-time navigation, the doppler probe which I think is really critical, particularly for endonasal endoscopic trans sphenoidal surgery, but also an intracranial surgery. And then finally the endoscope. And I think the endoscope has really helped us revolutionize a number of these techniques. And again, I want to sort of highlight the trans sphenoidal approach because I think it's really where the endoscope has shown its most benefit. And this little cartoon here shows what we're all familiar with, the microscope. It gives us a beautiful up close view, but it does provide somewhat of a tunnel vision, whereas with the endoscope, because the scope itself is taken into the cavity, the operative site, it gives us this more panoramic high resolution view, and we can use angled endoscopes to look around corners. And it's really a different sort of view compared to the microscope. And here's just an example of a pituitary case where you can see the lesion on the MRIs above. And you can see here the view through a speculum and the microscope, somewhat dark, definitely looking very clearly at the, sella here and the bone edges. And here, when we bring the endoscope in the same image, you can see this much more panoramic view. You can see the carotids here, the cavernous carotids, you can see the optical carotid recess is here. You can begin to see the optic canals here. A much different view, much more panoramic, and particularly now with our high definition cameras, the views are just really unparalleled. So there's the microscope and the endoscope. And when we use the endoscope, and not just in endonasal surgery, but intercranialy, there's really several ways to use it. So we can just take a look at the endoscope. Did we miss any tumor that we could have otherwise, we might have otherwise missed with the microscope? Do we do an endoscope assisted removal, or can we do a fully endoscopic removal, which is what many of us have gone to in trans sphenoidal surgery? And there's some good data to really suggest that the endoscope is helping us achieve greater tumor removals. And that's particularly in the trans sphenoidal literature. This is a paper from 2011 from the group in France, looking at non-functional adenomas. And what they showed here, is that when they went from a microscopic cohort where they did consecutively microscopic removals, and then to a fully endoscopic approach, the gross total removal rate went up significantly from 50 to 72%. And this was most important in the larger tumors. So that with bigger tumors, the endoscope allows a greater degree of tumor removal. We also did a study that was published recently looking at 140 patients where we went as far as we could with a operating microscope to remove adenomas. And then we brought the endoscope in. And in this study, 36% of the time, when we brought the endoscope in, we found additional tumor that we could remove. And so this really emphasized the advantage of the endoscope. And this was again, particularly evident with the large tumor. So in tumors that were two centimeters or greater in size, and over half of them, we were able to remove additional tumor. And I think this really drives home the point that the endoscope just provides this visualization, that you're simply not going to get with the tunnel vision of the microscope. And so now I'm going to talk a little bit about the nuances of this endonasal endoscopic approach. Aaron, do you have any questions at this point or should I keep moving?

- Well, I think this is great. I have nothing to add. I completely agree with you that for micro adenomas, it is much better from micro adenomas. That somewhat, some people may disagree. Before you continue, if I may ask you, for micro adenomas we both agree endoscopy is better. Better visualization, especially with angled scopes, we can see around the corners, in the gutters, get better resections. How about micro adenomas, do you feel endoscopy also makes a difference there?

- So I think it does in my practice, I've converted over several years ago in large part because of collaboration with Aman Kasam and Ricardo Corral, we'd completely converted over. And even for micro adenomas, And I do think for instance, for some micro adenomas such as cushing microadenomas, or prolactinomas that are intolerant to dopamine agonists, there may be some degree of cavernous sinus invasion. And I think you can get a much better view of the medial wall of the cavernous sinus with the endoscope particularly with a 30 degree or a 45 degree scope than you can with the microscope. That said, the literature would suggest that perhaps the outcomes are no better. There was just recently a paper that came out in journal of clinical endocrinology metabolism by John Jane and Ed Oldfield, comparing rates of microscopic versus endoscopic removal of functional adenomas. I believe it was acromegaly, and essentially the results were the same. And so I think with some functional tumors and smaller tumors, the endoscope may not be as beneficial, but I think that time will tell. So it's a work in evolution, I would say. So the endonasal endoscopic approach, I'm sure many of you that practice this are familiar with it. Obviously it's used for the vast majority over 95% of pituitary adenomas, great majority of Rathke's cleft cyst, many craniopharyngiomas, particularly in the retrochiasmal region, which I'll talk about. Clival chordomas, a lot of midline meningiomas are also being accessed this way. Sinonasal carcinomas, particularly olfactory neuroblastomas. Some meckel's cave lesions and some petrous apex lesions. So it is really now our workhorse for, I think, midline skull-based pathology. So the way we do this, this is the room set up here showing you here's our fellow putting on the navigation mask on the patient. We have two monitors, one for the ENT person or the assistant to look at, who's driving in the scope. And the neurosurgeon here, looking at the monitor straight ahead, the bed is angled slightly. And typically we put the patient's head on a horseshoe head holder only for the more extended cases such as a craniopharyngioma or a meningioma will we put the patient in pins. Now we always prep for an abdominal fat graft. So that's our room set up. In terms of the approach, I think initially when people were doing the endonasal endoscopic approach, there was a lot of removal of tissue at the back of the nasal cavity. We've gotten much more selective with this in part from our work with Ricardo Corral and now Chester Griffis. We do what are called bilateral nasoseptal rescue flaps, which is in some ways a misnomer, because it's not a flap, but basically if you're familiar with raising a nasoseptal flap, which is shown here, we only make the initial incision here. And then these, the septal mucosa, is pushed down out of the way. And this preserves the septal artery here so that you don't burn any bridges here. If you need a nasoseptal flap, you can use this. We use this approach for virtually all pituitary adenomas. We only do formal nasoseptal flaps, again on the extended approaches, such as craniopharyngiomas, meningiomas, clival chordoma. So this is our standard approach. Very simple. We really don't take any mucosa. We push what we call the septal olfactory strip up out of the way, reflect it bilaterally so that we hopefully preserve olfaction and we're able to preserve olfaction in about 97% of our patients based on some recent smell data that we have. So in addition to this, then of course, you have to do a generous posterior septectomy outlined here so that you can move both instruments. We always do a bi nostril approach. I think a uni nostril approach for the endoscopic route, is very constricting. I like to say it's like having three chopsticks in a nostril and it's just not enough room. So I think you need both nostrils, posterior septectomy, a posterior ethmoidectomy and then a wide sphenoidotomy that allows you to maneuver. And this just an image here of Dr. Griffis doing that initial approach here. So this is how we are, once we're operating, here's Dr. Griffis looking at his monitor here. I am looking at my monitor. We put the navigation screen right in the middle. And so it's two surgeons, two nostrils, and two high definition monitors. The endoscope typically goes in the top of the right nostril and the two other instruments go one in each nostril. If we use a 30 degree scope or a 45 degree scope, we'll move the endoscope down to the bottom to allow maneuverability of the instruments. So that's our basic setup. It's obviously it's a busy place. It's sort of a concert here, all symphony of the hands working, and you really have to get in sync with your ENT colleague, or if it happens to be another neurosurgeon. So when we do the approach, one of the things that I think is really critical is the attention to the carotids. You have to think carotid, as doctor Los likes to say, always think carotid when you're at the CELA. carotid artery injury, in my opinion is extremely avoidable. And we found that the doppler ultrasound is in fact more reliable than navigation, because it's real time. And whether you use navigation, and the doppler, I think the Doppler's always helpful to identify the carotids prior to the dural opening. Other thing that's really important is, if you really don't know where the carotids are, and you're worried about them, you're probably going to do a conservative opening that limits your exposure and may result in a optimal tumor removal. And this takes 30 seconds. It's very helpful. And I think it gives you the confidence to do a wide opening It gives you the confidence to do a wide dural opening and to get an adequate exposure out to the edges of the cavernous sinuses bilaterally. I will also say that we use the Doppler routinely for all of our other intercranial cases in which there's vascular encasement. So I'm going to just show you a couple examples here. So this is a typical macroadenoma here, not very complicated, sort of a bread and butter case, just to show you how the endoscopic approach works. The normal gland here is pushed up. It's very thinned out. You can see there's a little bit more gland off to the left Aaron, why don't you go ahead and roll that video. And so here, we're showing the dural opening after a wide cellar opening, I generally like to do a U shaped opening and then flap the dura upward. And always being cognizant when you're opening the dura, not to open into the tumor or the gland, we really like to visualize the gland early on to protect it. And you can see here, we're lifting the gland up here. This is a crescent of gland, which is probably viable, but these very thin remnants we cut away so that we don't put undue traction on the gland. So this then gives us a larger window to go in and take the tumor out. We like to utilize the concept of the pseudo capsule, which Ed Oldfield has written about extensively, which is a rim of compressed normal pituitary gland, which surrounds every adenomas. So in this particular case, the tumor has a very nice pseudo capsule, and you can see as we're manipulating the tumor away from the gland, the gland is progressively getting thicker and more hyperemic. And the gland is definitely getting happier here. And we liked that, and you can just do this sort of two handed technique. And notice the very close following of the endoscope, really giving you that really nice view. And now we're looking near the top. The gland is being more mobilized here. We can start to see more gland up here. We're using a 30 degree endoscope now, and Dr. Griffis is following me in here and we're peeling the tumor with its pseudo capsule predominantly intact, away from the gland. Now, obviously it doesn't always work this way every time. And a lot of these tumors fall apart and they have to be taken out in a piecemeal fashion. But if you can do this sort of pseudo capsular removal, you're almost assured of a gross total tumor removal. And so that's again, I think the advantage of the endoscope here. So again, we're looking with the 30 degree endoscope. Could you get this view with the microscope? For the most part, yes, but I think it gives you these views along the cavernous sinus in the super sella space that you're probably not going to get with the microscope. And so again, very helpful views here. We're looking way off to the, there we were looking off to the left cavernous sinus with a 45 degree scope. Here's the reconstruction. There was really no significant CSF leak here, but with a large dead space like this, we generally like to put a back graft in to fill the dead space. As an insurance against a postoperative CSF leak. The dura gets flat down. And then in all cases we cover the sella with a layer of collagen sponge, such as deurogen. We use hela stat, which is cheaper. And then we put a buttress in here. And this is in the intrasellar, extra dural space. No nasal packing. In this case, we put some additional fat in the sella here and then another layer of collagen and then some tissue glue to hold that in. And that's really the closure. As I said, we don't use packing, only in cases where we have very little bone will we put a nasal pack in for several days to act as a soft buttress. So there's the postop day one scan. This is a fat suppressed T1 weighted image. You can see the gland enhancing nicely. You can see the infundibulum, and this patient's gone on to do very well. So that's a straightforward pituitary adenoma. But what about more complex things such as craniopharyngiomas and tuberculum sella meningiomas. These are now in many instances accessible through the endonasal endoscopic approach, and there's been a lot of people doing this and writing about it. And I think if you're going to tackle these kinds of cases, it really should be done with a team approach. It should be done fully endoscopically. And you really have to think about the closure, about the nasal septal flap, which has been popularized by doctors Corral and Kasam. And I would, strongly recommend that before undertaking these, you really consider the skull-based closure issues. So let me just show you a couple examples of craniopharyngiomata. I won't talk about meningeomas, I'll talk about cranios. One of the things about the majority of cranios, which I think lends itself to an endonasal endoscopic approach. And of course the transplant route has been used for many years. I think Marty Weiss was one of the first to write about it Ed Lows, Ed Oldfield, using these extended approaches. And the thing about craniopharyngiomas is they, the majority of them tend to be retrochiasmal in location. So here's the optic chiasm. The tumor is growing above the gland and behind the chiasm. And that location really lends itself well to this endonasal endoscopic approach, which of course is over the gland and under the chiasm and allows us to go straight back without any of the need for brain retraction. And really a nice way to take out these retrochiasmal craniopharyngiomas that said, as we all know, these are extremely formidable tumors. They can be very tough, very stuck, and you have to think about a number of things, to stay out of trouble. Now, this is a video. This is a patient from about eight years ago, and this was an endoscope assisted removal that I did. And I just want to make the point here. You can see how much better the images have gotten, but you'll see the endoscope pass under the chiasm here, right here and into the retrochiasmal space. And you can see that the third ventricle here, and you can see that there was some tumor that was embedded in the hypothalamus, which we elected to leave behind. It was partially calcified. And I thought it was a better part of valor to leave that behind. this patient then went on to get a SRT. And he's now about eight years out and he's tumor free, as far as we know. We've tried to get him to come in for an MRI and he will not. But he's doing quite well. Here is his postoperative MRI at eight months. And you can see that the smaller we left in the hypothalamus is behaving. This was after also he had had stereotactic radiotherapy He was a young teenager at the time, he's now in his twenties and doing well, he's on full hormone replacement therapy. And again, with cranio, I think it really emphasizes the need for a multidisciplinary team approach, not only with ENT, but obviously with the endocrinology, radiation oncology, et cetera. So what are the key operative issues when you're considering an endonasal endoscopic approach? I think you need to raise a nasoseptal flap and consider performing a reverse flap, which Ricardo Corral has described, which is a way to preserve the septum, it's wrapping the contralateral side mucosa around the harvested side to protect the septum. It's a beautiful way to do that. You need to think about exposing the planum and the circular sinus. You're going to be working under the chiasm and you need to treat it very carefully. Sharp dissection is critical. So the use of sharp dissection is critical to avoid traction on critical blood vessels. Considering critical blood vessels, the superior hypophyseal arteries are essential for the irrigation to the gland, but also to the chiasm. And so that's a key part of the procedure. And then of course, identifying the infundibulum and then knowing when to stop. With hypothalamic and vascular adhesions, you can certainly go too far in these. These have been well-documented in the literature of some of the potential complications you can get with over aggressive resection of craniopharyngiomas. The multilayered closure with the nasoseptal flap. The exit strategy is critical to avoiding postoperative CSF leak. And as you know now, with the extended approaches, with the nasoseptal flap, the CSF leak rate, which used to be as high as 20, 30% in many series, is now down closer to around 5%. And hopefully it will continue to go lower as we all get better at performing these complex closures. So here's what the superior hypophyseal look like after removing say a small tuberculum meningioma such as this. The arachnoid plane is protected here. It looks very nice and clean, but that is not what you get with a craniopharyngioma because of where they arise along the infundibulum, they often engulf the infundibulum, as well as get very stuck to the undersurface of the chiasm, or to the top of the chiasm in some instances, and the superior hypophyseal vessels, as shown here, can be engulfed. And you have to make a decision in each case based on the patient's preoperative hormonal status, how aggressive you're going to be. Are you going to try and preserve the stock and pituitary gland function and potentially settle for a subtotal removal? Or are you gonna really try and go for a more complete removal? In many instances, if not most, patients come with panhypopituitarism and often have diabetes insipidus already, and it can be... I think it allows you to be a little bit more aggressive in trying to get a complete removal. And obviously the first time is the best time of the craniopharyngioma. Here's just another picture of a different cranio. There's the optic chiasm, our instruments here in the superior hypophyseal arteries, being stretched by a nodular tumor, which ultimately was dissected free in a way, and these were preserved. So I think this is really key for the visual outcomes and the end gland function. So let me show you an example. This is a typical retro-chiasmal craniopharyngioma, in a 52 year old man with a couple of years of cold intolerance, weight gain, the typical symptoms and signs of hypopituitarism. And then he had six months of progressive visual loss and ultimately went on to develop diabetes insipidus. It's a complex tumor, you can see this large CSF pocket above the diaphragma sella here in the tumor, extending back toward the hypothalamus here. And you can see on these coronal images. But reaching quite far back, almost three and a half centimeters back toward the third ventricle. This is showing the initial exposure here and very rapidly going to the tumor removal. And you can see that the tumor is extending well behind the chiasm here. Here we're cutting the infundibulum in this case because the patient had panhypopituitarism. And then it's a matter of just internally debulking the tumor and really peeling it away very carefully using microdissection techniques, peeling it away from the arachnoid and gently pulling in that pseudo capsule. Very critical to keep your eye on the superior hypophyseal vessels and protect them. Here you can see a large piece of the tumor coming out. And then in the end, you typically get this view of the third ventricle here. And what we thought was a gross total removal. Here's the reconstruction with a harvested bone graph. We always put fat into the resection area, the bone graph followed by collagen and the nasoseptal flap. And then this is a way that Dr. Griffis' device of placing a soft buttress with the merocel tampons, right up to the, right up to the reconstruction. We put one in each nostril, we leave those in for about for four or five days and then take them out. So here's the immediate postoperative scan. And we always do this from the recovery room. We like to see what reconstruction looks like. You can actually see the merocel tampons here. You can see the bone, you can see some fat in the super sella space here, and you have a baseline on the amount of intracranial layer and that's really important. Obviously, if the patient can leak, sometimes they don't obviously leak, but they can suck in air. We did not use a lumbar drain on this particular patient And we use those sparingly. So here's the postop day one MRI again, showing the fat graft in position, the merocel in position. And you can see this is post gadolinium and here is a fat suppressed post gadolinium coronal image. And the patients now more than a year out and has what appears to be a gross total tumor removal. He's on full hormone replacement therapy and doing well with recovery of his vision by the way. Now, this is another patient with a recurrent craniopharyngioma who had had a prior craniotomy elsewhere, she was pan hypo pitch. She had a preexisting cranial nerve III palsy She had not had radiation, had a subtotal removal, and this tumor came back over the course of about 18 months. And you can see it extends down into the sella here, but it's pushing up on the chiasm, particularly on the right side and we'll show the video here. So in this case, same approach, this was a virgin approach. You can see that the dura's open here. We have, often we put collagen or a surge foam here as we're opening, because you get this bleeding from the circular sinus. In this case, we were pretty good. You can see the gland there again. This patient has panhypopituitarism. We were really hoping here to decompress the cyst and then go on and treat the patient with radiation. You can see the optic chiasm here. You can see the superior hypophyseal, and particularly with a redo on someone who's had a craniotomy, one has to be extremely careful with the dissection because of the additional scar tissue. Again, using sharp dissection. Now you can start to see the pulsations. You can see the optic chiasm here, and you can see this tumor that extended down into the sella here, and here we're opening posteriorly and really down into membrane posterially trying to get some of this capsule. We really got more than we thought we would. And you can see here in a moment, with the 30 degree endoscope you can get this beautiful view down into the posterior fossa. Here we're just taking the last bit of safely removable tumor and leaving a little bit adherent to the undersurface of the chiasm. So here you can see into the third ventricle, beautiful view of the third ventricle, very pristine in this particular case, there was no adhesions there. And then when you come in with the 30 degree scope angled down, you can see a beautiful view of the basilar apex, and the third nerves, and leaving a little bit of nodule of tumor there, that was just too stuck that we thought was a better, again, to leave behind. Again, this is a redo. The patient's going to have radiation. So here's our closure with fat going in, and then some collagen going into the defect, followed by bone here, a bony harvest that we took from the posterior nasal septum, and then the nasoseptal flap going into position here. And again, this multilayered closure, again, in this case, we did not use a lumbar drain, additional fat as a buttress and a tissue glue. And then the merocel tampons going in to hold everything into position for four or five days. Okay. So, and there's her postop scan. You can see the fat graft again. You can see the merocel and the nasoseptal flap enhancing nicely. And really a pretty good resection. And this lady will go on to get stereotactic radiotherapy.

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