The Principles of Keyhole Surgery

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- Welcome colleagues and friends. Thank you for joining us for another session of the Virtual Operating Room from the Neurosurgical Atlas. Our guest this evening is Dr. Charles Teo from University of New South Wales, Australia. He is an internationally known neurosurgeon who has truly refined and pioneered keyhole concept in cranial surgery. Charlie, thank you for joining us. We're very much excited to listen to your pearls of technique in keyhole surgery. Please proceed.

- Thanks Aaron, and a great privilege and great honor. And thank you Luke, for giving the AV backup. It's a pleasure that we're all in. I'm sure that it's challenging for all of us. And hello to my friends, and hello to those who I haven't met, but who hopefully I will meet in the future. So I presume Luke, you're gonna put it up for me, and we might get started. So Aaron gave me the task of talking to you about The Keyhole Concept, and presuming that many of you are already qualified neurosurgeons who practice probably keyhole surgery already. And just to give you a few little pearls from my 30 years of practice and 11,000 brain tumors. So it goes like this. I like talking about tailored craniotomies, in other words, personalized craniotomies. And to think of it like, where do I make the entrance and how do I consider the corridor to the target? So a large door like this is totally unnecessary to admit a small person like this. It is cumbersome, time-consuming to construct something like that, associated with a lot of morbidity and some mortality. And what I mean by that is if you see a large tumor like this, but it's not on the surface, then clearly this can be accessed through a small craniotomy. Now that's completely different if it's a large superficial tumor, but a large, deep seated tumor like this, olfactory groove meningioma, that sure, extends down into the middle cranial fossa. It extends into the beyond the tuberculum sellae into the pituitary fossa, but this can be removed totally including those components that are in other foci through a minimally invasive keyhole approach. Why? Because it's deep to the surface and you don't require a large craniotomy to access a tumor like this. And again, you can see how we managed to get into the cribriform fossa through this eyebrow approach. And this is 24 hours, well, 12 hours after surgery and he was discharged 24 hours after surgery because it was done through a minimally invasive keyhole eyebrow craniotomy. There are times like I mentioned, where you need a big door or a big entrance to access large tumors. And this is one such tumor of course, it's a parasagittal meningioma that comes to the surface. And to afford a complete and radical cure of course, one needs to get complete access to the attachment and hence the need to do a large craniotomy. It's still, of course, a keyhole craniotomy 'cause the whole idea of keyhole is that it's a concept, not the size. So the concept is to minimize collateral damage to make the opening as a large as is necessary, but as small as possible to minimize time, blood loss, pain, et cetera. And to, of course, ultimately benefit the patient. So where does one make the entrance when it's a deep seated lesion? And this brings up the concept of the two point rule or the long access of your lesion. I was always taught that the best way to access a glioma like this was through the most superficial part of the tumor. But I think it's pretty easy to see that if we access this tumor through this most superficial portion, it would give you a pretty good visualization of this portion of the tumor, but terrible visualization of this portion of the tumor. In other words, the majority of the tumor. So what I'm saying is that, place a point at the deepest point, place a point along the long axis, take that to the surface. And of course, that's where you need to give you ultimate maximum visualization of the majority of that tumor. Just to give you some examples, how do you access or how do you determine the long axis? Look at all three planes, the axial, coronal and sagittal planes, and figure out which is the long axis. Now, if you look at this plane here, there's the deepest, darkest point. There's the superficial point. And if you draw a line to the surface, you have to go through the optic radiation, you probably have to go through eye and that is not palatable. Whereas the long axis in the cranial plane, again, there's a deepest, darkest point, and there's the most superficial point. And it takes you to the other side. Again, really not the best access. You could of course go this way, but again, that will take you through probably optic fibers. Now look at this. If you looked at all three axes, then you would see that on the sagittal plane, the deepest point is here, the long access is there. Take that trajectory to the surface and it takes you through a very, very accessible corridor called the superior parietal lobule. We access that through a small craniotomy, 'cause of course the lesion is deep to the surface. We can go further down through the sulcus. And really the only breach of normal tissue is this small two or three millimeters normal tissue in this area right here. Then of course it's imperative to position the patient so that you're always operating along the perpendicular plane. And what I mean by that is, if you are operating a non-perpendicular to the floor, then of course the brain is gonna collapse into your corridor, you'll have to put a self-retaining retractor in there, that'll clutter your small craniotomy, and the whole thing will be made more complicated. So position the patient using frame less two guidance so that you're operating in the perpendicular plane in all three axes. And again, we're doing that here, where you're working at the long axis, we're now positioning the patient so that the brain doesn't fall into our corridor. This is the patient's previous biopsy at another hospital. The incision you see is much longer than our incision here, which will afford a complete resection. Luke, if you can stop playing this video, that'd be nice. I'd like to show this video for two reasons. One, because it shows that this can be done through a minimal access keyhole craniotomy about the size of about two centimeters in diameter. And there's a lot of pressure on people these days to operate using these corridors or tubes, tubular retractors or tubular access ports. I'm very much against them; and this video shows clearly why I'm against them. It is imperative to use the natural elasticity and mobility of the brain to access the corners or the difficult access portions of this tumor. And I think you'll see from this video that I'm constantly moving the brain around using the natural movement of the brain to access these more difficult areas of this tumor. Remember, it's not just a pure; maximally utilize the mobility of the brain. So you'll see from this video, just in a short video that I'm constantly moving the brain around, I'm moving my light source around. I'm triangulating my instruments so that I keep that corridor open. And you really don't need a retractor to get you access. Again, look at that; it's three point triangulation using bipolar and sucker to keep that corridor open. And we all know that self retaining retractors have been shown to cause micro influx underneath them, that's been well shown by studies. And again, you can try and avoid all those potential damage to the brain by not using retractors and not using tubular access ports. And how do you do that? It's all about planning, figuring out their trajectory, figuring out the long axis and positioning the patient upfront so that you don't have to use a retractor, so the brain doesn't fall into your corridor. I think that's enough Luke, we can go on to the next slide. And you can see a complete resection, and a good outcome, no neurological deficits. The next concept is how does one determine the corridor through which one operates? Now, I would contend to you that navigating one's way through that crowded corridor would not be attractive. And what I mean by that is that it'd be a whole lot less cumbersome and safer to navigate a clean corridor like this. So let's take a difficult tumor like a petroclival meningioma. We all know there's many different ways to skin a cat, and this patient for example, had multiple comorbidities. She was elderly, we didn't want to have her in ICU for any period of time. We wanted to minimize collateral damage and get her out of hospital quickly. How do we do that? Well, the whole intention of the operation was to decompress her brainstem and not to necessarily get a complete resection of the cavernous sinus portion. So what are the trajectories? There's one deep point, there's a superficial point. So surely one of the approaches is through the CP angle, retro-sigmoid type approach. But I'm sure you can appreciate that if we do a retro-sigmoid approach as this we have to cut through scalp initially, then of course goes through the bone of the calvarium, then of course the dura. Then you'll have these impediments in your corridor such as the superior petrosal vein, cranial nerves. You'll have to retract cerebellum and then eventually you get to the tumor. Let me suggest this. Look at the long axis now; deepest portion, most superficial portion. And what about an endonasal trans-clival approach to this tumor? What are our hurdles to get through this access? And I think you'll see that really, once you get through nose, there's mucosa, there's the bone of the clivus, there's dura, and then your tumor. There are no cranial nerves in your way, there are no major neurovascular bundles in your way, and there's no brain to retract on your way. So let's go to video 22, please, Luke. This is an extended endonasal trans-clival approach to a petroclival meningioma. And why did I choose this? Because of the corridor. The long access took me to either retro-sig, or trans-clival transnasal. And you can see here that this is the top, this is the bottom, this is the right paraclival carotid. We're now skeletonizing the right paraclival carotid to retract the paraclival carotid to get to the apex of the petrous bone to access this tumor. So we've got carotid pushed out of the way. We've got the bottom of the dorsum sellae right here, sorry, pituitary fossa right here. We've done a claviculectomy, and now we're drilling out the petrous apex, and look at the access. It's perfect, beautiful access. There are no cranial nerves in your way. Basal artery can be dissected laterally, sorry, medially; and the paraclival carotid can be retracted laterally. We opened the dura, we've debunked the tumor and we're now achieving a complete and radical resection of a petroclival meningioma without any impediments in our corridor. And you'll see here, pons decompressed, basal and trunk, third cranial nerve, sixth cranial nerve being dissected away from the tumor; two handed surgery, excellent visualization and reaching all the way out by retracting the paraclival carotid laterally. And at the end, a complete resection. Thanks, Luke, if you can go on the next slide. And here's the pre-op, post-op showing fat graft complete tumor resection. We didn't touch the cavernous sinus portion. Six weeks, post-op. Six years post-op, a small recurrence here, but this has been stable for about 10 years now. I haven't had to re operate and she's clinically very well. Straight after to surgery she had a six nerve palsy that improved by six weeks. And at six years she's neurologically intact, no brainstem compression, and she was out of hospital within 48 hours of surgery. So let's go through some work horses for the keyhole cranial neurosurgeon. We're gonna be talking about keyhole calvarial openings, we'll talk about the keyhole eyebrow approach to the paracell and suli region. The S.C.I.T approach or the supracerebellar infratentorial keyhole approach. The mini pterional approach to insular lesions or middle cranial fossa lesions. And of course the work horse to the posterior fossa, the keyhole retro-sigmoid approach. I don't have much time, so if you don't mind, we'll just try and rush through all of these and I'll show you just some nice clinical examples. This is a patient who had a multifocal GBM. You can clearly see the superficial one on the left side and the deep thalamic one on the right side. He was code inoperable, they tried to take out the superficial one at another place. And then because it was multifocal they were gonna send him home to die. So how do we approach them? We approach them simply because we can access these through a minimally invasive keyhole approach. The superficial one, you'll note, actually requires a larger craniotomy than the deep and large thalamic one, which needs a burr hole type craniotomy. So on the right side for the deep thalamic tumor, a very small burr hole type approach. And for the a left-sided superficial one, a much larger craniotomy. Again, they're both keyhole craniotomies, because they both fulfill the philosophy of keyhole concept. But of course, this one came to the surface and to achieve a complete radical resection of the surface one, we needed a larger craniotomy. This video, we might rush through this one. Luke, just start it and I'll give some narration. So this is our approach to the deep seated thalamic one on the patient's right side; and it's standard microsurgical technique. Opening up fissures and sulci to get as close to the tumor as possible. And then of course, again, this whole concept of operating without any sort of retraction, because we've positioned the patient perfectly so that the brain doesn't fall in. And again, that's all about preoperative planning and positioning that's incredibly important so you don't have to use retractors to maintain your corridor. And again, it's standard microsurgical technique. Why don't you rush it forward a little bit there, Luke, if you don't mind. And at the end you can see; maybe just a little bit more. Again, I will contend that that opening is smaller than any opening you could use with a tubular retractor. It's about the size of, I guess, a small penny. And then of course, this is the one on the dominant side where we had to expose. And you can see why we had to expose a much larger craniotomy to get the complete resection of this, that is more superficial GBM. Okay, that's enough for the video. Thanks, Luke. And this is pre-op and post-op, you can see now I can take control now. Here's the approach. Small craniotomy, trans-sulcal, transsylvian; only a small breach in the normal brain to get to the thalamus. And again, I think you can say a complete resection, minimally invasive, no footprints, and a complete resection also of the superficial one; and a very good clinical outcome. No neurological deficits after surgery. Five days after surgery. You can show just quickly that video, Luke. That's him doing weights, showing that his strength is normal; five days after that surgery. Okay, next. Here's a deep seated butterfly glioma of the rostrum of the corpus callosum. Again, look at the long axis, check out the long axis. Where does it take you to the surface? Is that a non eloquent area? Is the corridor a uncluttered corridor? And if so, that's your approach. Complete resection, minimally invasive. Again, we followed the long axis to the surface. It went through the brain, so we didn't have to compromise. And again, a good clinical outcome with a very small butt hole type incision. Here's another corpus callosum butterfly glioma, this time of the splenium. This is where you're gonna need some angled views. And again, a complete resection. How have we done it? We've done it through a keyhole craniotomy on the non-dominant side. Again, nice and low so that we get underneath the optic radiation. So the only thing you have to worry about here, this is the sigmoid transverse junction. And you know that the vein of Labbe attaches here. If you can avoid the vein of Labbe with preoperative planning, then try and make your craniotomy above or below or away from the vein of Labbe so you don't compromise it. It's a nice slow process through basically the posterior part of the inferior temporal gyrus which will hopefully preserve the optic radiation for these butterfly gliomas. Let's go to the eyebrow approach. It's a bit of a workhorse; everyone knows it now. It's been popularized for many decades now, mostly by Axel Perneczky, but by others as well. And it gives you excellent exposure to the clinoid; the tuberculum sellae, the sellae, para sellae, super sellae, infer sellae, middle cranial fossa to about the mid-level of the cavernous sinus; posterior fossa to about the upper third of the clivus. Brainstem, mostly midbrain, some upper pons, several peduncles, prepontine cistern, and contralateral clinoid, contralateral plenum, and contralateral para sellae. It doesn't give you good access to olfactory groove or fossa because it is remember, an antero lateral approach. In other words, you've got to look over the roof or the hill of the orbit. But here's a really nice example of a midbrain glioma. Someone tried the biopsies, it took them 12 hours, coded inoperable, sent the patient for radiotherapy. You can play this video, thanks, Luke. Thankfully, the patient came to us for a second opinion. A very difficult area to access, but I think you'll see that the sub frontal eyebrow approach is a perfect approach to get to this tumor. Now it doesn't give you good access to the superior portions. And again, I wanna use this video to demonstrate a few things. The first is that the eyebrow approach, the incision is within the eye brow itself, the hair bearing area. The craniotomy is a small craniotomy based on the keyhole. The pericardial flap is reflected anteriorly and the scalp is stretched up superiorly. The inner table of the calvarium is drilled off to give you a more direct approach to the skull base, and it gives you another half a centimeter of exposure. And then this is a sort of view you're gonna get of the optico-carotid window, the posterior clinoid, the third nerve, and the brainstem back here. This is the approach we took for this particular tumor. You can see that we are operating through all the different windows. There's the optico-carotid window, here's the bifurcation, M1, A1. We just mobilizing above the carotid. And then look how dark it gets through the optico-carotid window. It's very difficult to get light through that very cluttered corridor. And this is where the endoscope becomes an invaluable tool when you're practicing keyhole craniotomies. So we take out as much tumor as we safely take out using standard microsurgical technique. And once it gets a bit too dark we put the endoscope in, and this is the view you're gonna get. Now a lot of people think the endoscopic view is not as good as the microscopic view. I would contend that it's actually even better. And what I mean by that is that the light source is taken to the target so illumination is better, magnification is better, and angle view is better. So we're looking upwards now. Here's what we saw with the microscope, normal brainstem, and look what we can see with the endoscope by looking upwards. We can see the subtalar motion. So he's the interface clearly defined by the endoscopic view. Normal brainstem, discolored pinky-purplish shimmer. And I did this about 20 years ago so I didn't have hybrid instruments. I'd use a hybrid instrument today. I'd use a sucker bipolar so that I could be a two hand surgeon. In those days, I just, unfortunately could be a one-handed surgeon. I'm holding the endoscope with one hand and sucking with the other hand. And thankfully, this tumor was a very suckable tumor. And again, look at the fantastic visualization you get of the interface right here between normal brain and tumor using endoscopic visualization and illumination. This turned out to be a JPA. The closure is important. We did it all through an eyebrow. She'd been on steroids before by the other surgeon who'd done a biopsy, but we managed to get a complete resection. Again, no footprints, complete resection, including the superior portion; and we did that through endoscopic assisted surgery. This is years later, no recurrence. And you can go to the next slide. Thanks, Luke. And again, this is her almost 20 years later. She's no longer a child, in fact, she's having children and no recurrence. A lot of people say, "Well, Charlie, you might be able to do pretty low vascular tumors like that. But what if you get really vascular tumors? What have you hit the carotid? It's a small access, are you gonna be able to control bleeding with two suckers, a drill, et cetera, et cetera?" The answer is absolutely yes. Remember the whole cavity becomes cavernous. Once you let off CSF, the brain retracts, you take away a bit of tumor. So it's not so much the entrance that's important, it's the corridor and the room that you're creating. And this is one such case of an atypical recurrent post radiotherapy meningioma, where I put a hole in the carotid. I think you can see why. The carotid and all it's branches are within this tumor. And yet we still managed to achieve a complete and radical resection. I managed to repair the carotid artery, a good outcome. This was his biopsy. You can see the biopsy that he had at some other place. They did a standard sort of pterional approach. And this is the approach we did for a complete resection, just an eyebrow approach for a gross total resection of a pretty nasty meningioma. This slide is a bit busy, but I just wanted to show you that the cosmetic. A lot of people say the eyebrow is not good because of the cosmetic outcome. But the cosmetic outcome's very good. So much so that I have a little contest with my fellows. I always get them to try and pick the side on which I've operated and they can't pick it. Even if you look into the eyebrow itself, you cannot see the incision. So the cosmetic result is very, very good. This is a video showing the exact technique of an eyebrow incision. I'll only show that if time permits, then we'll get Aaron's permission to just show that later, if time permits. Let's now go to the S.C.I.T approach. It's one of my favorite approaches 'cause they do a lot of pineal or posterior third ventricular tumors. And it's very minimally invasive, gives you beautiful access. You don't have to open up the basal systems. It's just one of my most favored approaches. How do I position the patient? I used to do them prone, then I did them a lateral keto, and now I do them supine, with just a head turn. So this is supine, head turned, in pins. Slight flection, but not too much flection to give them obstruction of the jugular. Mark out the sigmoid transverse sinuses. And the incision is a paramedian incision, about two finger breadths away from the midline. And why are we making a paramedian? This is a slide. And this is why. if the pineal gland, the head of the camel, then the superior vermis is gonna get in our way if we stand directly behind, in other words, a midline approach, we're gonna have to push down the hump or look around the hump. It's very simple, just go to the side. Paramedian approach, you bypass the superior vermis and you can see the head. Hence the paramedian approach to the midline. Show the video, please Luke. So here we have our straight incision. We have blue lined the transverse sinus. We are now opening the dura in a triangular fashion and reflecting it superiorly against the transverse sinus. Midline is over here, where's midline? Midline is over here, and this is the cerebellum. The first thing you should note is that the cerebellum doesn't come bulging out. And the reason being is 'cause your craniotomy and your dural opening are so small that you don't have brain herniating out of the durotomy. And that's good because it gives you time to relax, make the conditions more ideal, get the anesthetist to drop the CO2 a little bit, position the patient a little bit more head up. And then as soon as you start retracting the cerebellum, the CSF starts coming out. And that gives you a little bit more time, a bit more relaxation. And then of course, the first thing you're gonna see is the opacity of the cisterns. This is where you'd be very careful because you can't see the large veins beyond this opaque arachnoid. So what you've gotta do is presume that there's a large vein behind every little bit of arachnoid, take your time, and you've got plenty of time because the CSF is coming out, brain's are getting more and more relaxed. You're becoming more comfortable. And then of course you can open those cisterns as widely as you like to relax the brain and get good access to this pineal tumor. This pineal tumor happened to be a mixed germ cell tumor with a very tough pterotermic component, very fibrous, very cartilaginous. So we take out the inferior portion using standard microsurgical technique. And Luke, if you could just fast forward this a little bit please. And what you're gonna send me doing now is taking out the other portion using. We went a bit too far. Sorry, Luke, we went a bit too far forward. I just wanted to show the endoscope in there. Maybe halfway between the stab and where you went then, and you might be able to say the endoscope going in. Just go a little bit forward now. And just leave it there, slip up at the endoscoping now, I think I do. So notice there are no fixed retractors on the cerebellum. We've taken out what we can see with a microscope, and now I'm gonna put the endoscope in and you'll see that I've left quite a significant firm portion attached to the bottom of the vein of Galen. And difficult to appreciate with the microscope, incredibly easy to appreciate with the endoscope. So hopefully I'll show you that now. Maybe just go forward just a little bit, Luke. Yep, here we go. Now the endoscope is looking up and you'll see that I've left this very tough portion up here, this is the back of the third ventricle. The vein of Galen's up here. This is the basal vein of Rosenthal right here. And look at this, this is a portion of tumor that was invisible to the microscope and clearly seen with the endoscope. And now we carefully pull that down. Of course, not pulling down vein of Galen and we managed to achieve a complete resection. Okay, Luke, that's enough. Now let's go to the next slide. And there's pre-op scan, post-op; pre-op and post-op. Again, no footprints, no damage to the cerebellum because it's a paramedian approach. And a lot of people go in through a S.C.I.T approach, super cerebellar, infratentorial, transtentorial approach to a supratentorial meningioma of the facts. The point I'd like to make here, little pearl and precaution is that; do not obstruct your view by making a limited opening of the tent. I was taught by previous mentor that you had to make a very limited opening in the tent. If you made a big opening, the brain will herniate into the posterior fossa. There is literature in the olden days saying that you should try and limit your transtentorial approach, but that is absolutely not the case. I make a huge opening in the tent, when I do these lesions, I've done it for many years. I've done many cases. I've never had the occipital lobe herniate into the fossa. It is not a problem, just take my word for it. So feel free to make that opening in the tent as wide as you like. I make the opening way back here at the level of the, almost all of the transverse sinus and open the tent widely to take out these supratentorial lesions. And there is the wide opening of the tent to give you good access. Again, pre-op and post-op showing. That's nice Aaron, thank you. So the opening of the tent is way back here so that it doesn't act as a hurdle to your approach. And again, this is a T2. I wanted to show you the T2 to show there's no footprints on the cerebellum and no footprints on the occipital lobe, pre and post-op again, pristine. Why? Because you get excellent access just by letting out CSF and the whole brain falls down and you don't have to use any sort of fixed retraction. And you don't have to show this video to Luke, but this is me just testing her visual fields to make sure there's no a visual field defect. The next approach is the mini pterional. This is something that's very dear to my heart because I was always taught to make these incisions, the pterion incisions as close to the tragus as possible. In fact, one attending told me to make the incision right next to the tragus which makes the closure very difficult; and I don't know. We were taught that because we were worried about damaging the facial nerve. But if you look at the literature on the anatomy of the facial nerve, it's pretty clear what it says. If you draw a line between the tragus and the outer canthus and figure out the halfway point, we called this the 50 yard line. Then if you draw that point, then the majority of the fibers, frontalis fibers from the facial nerve run in front of that 50 yard line. So what it says is that you don't have to make your incision way back near the tragus, you can bring your incision forward to the level of the 50 yard line, which is basically the hairline and you can safely avoid in the majority of cases, damage to the frontalis branch of the facial nerve. So the no go zone is in front of the 50 yard line, but anything behind the 50 yard line is clearly accessible. And what that means is that if you wanna try and get to the pterion, then of course your incision doesn't have to be as long if you can bring it forwards. And that's what I've now done now. I make my mini pterionals very, very close to the hairline so that I avoid the larger incision. I use this approach for insular gliomas. I use frame less two guidance to give me the location of the Sylvian fissure. I do a transsylvian approach. I don't do a trans-opucular, transcortical approach, I think that's unnecessary if you use the endoscope. I'm sure you all know that many advocates of insular glioma surgery recommend going through the operculum. The reason why is they wanna to get to these deep portions of the tumor. And the reason I need to do a trans opercular approach is 'cause I'm not familiar with endoscopic surgery. If you have deep crevices of these insular glioma. Again, just show some of this video if you like Luke, but we might rush through it to the endoscopic portion. Can you believe while I'm giving the talk, the gardener's outside using one of those leaf blowers. Terrible. I hope you can hear it, but it's incredibly annoying for me. So this is a right side insular glioma. Patient's been biopsied elsewhere. This goes through the temporal stem into the temporal lobes. So just to show you what we're doing here. This is the right side so this is the temporal lobe. We've opened the Sylvian fissure. It is a bulging tumor of the insular, so we just now are gonna do a temporal lobectomy. Here's the insular, these are the candelabra branches of the MCA that need to be preserved. And this is the bulging insular, and these are the MCA branches. So first thing is we wanna do a temporal lobectomy because the temporal lobe is mostly effected by tumor. I want you to advance it a bit, Luke, go to about a quarter of the way. We've done that temporal lobectomy. Again, here's insular, we're just completing the temporal lobectomy. Go on a little bit further, Luke. Okay, what am I doing here? This is again, just completing the temporal lobectomy. Kept going a little bit further, maybe go to about halfway. This is again using standard microsurgical technique. Now here's the bulging insular tumor. We have to operate through the windows, of course, between the branches of the MCA. And now we're entering the tumor through the expanded insula now, preserving those branches, operating through these windows. Next, go to about three quarters of the way along. And of course, this is the most medial portion, we are identifying the lenticulostriate arteries and lenticulostriate veins. This is the technique I'll use for gliomas; basically nice fat bipolars, which dissipates the heat of the bipolars, melts the tumor, chars normal brain, not that it burns normal brain where it chars, but will always just melt tumor. There it is melting tumor. So it's bipolar, sucker, bipolar, sucker. Okay, just go close to the end, see the finished product. And again, here we are operating. Through the windows, the section of the MCA branches, no infarction. And again, pre-op, post-op showing that we got into all those deep areas. And day two discharge home with no neurological deficits. The next approach I'm gonna show you is the standard retro-sigmoid approach. Now I don't know about you but I was taught the standard retro-sigmoid it gives you great access to the CP angle, great access to the posterior fossa. But I was taught to make this big C shaped incision, like this at the back here and reflect everything forward, including the ear. I think we'll talk that because we couldn't make any sort of horizontal incision, even though that gave us the best access to the CP angle, because that would devascularize scalp. But with a small craniotomy and small incision, what you can do is you can make your incision in line with the angle of view. And what that means is that if you make your incision like this and put self retaining retractors in like this, then the self retaining retractors arm won't get in your way. If you make an incision like this and the self retaining retractor is like this, and you're looking like this, and of course the arm of the self retaining retractor is gonna get in the field of view, interrupt your field of view. And when that happens, of course, you've gotta make your incision bigger. So if you can use your frame less guidance to give you the trajectory, the angle of site, and by that, you can then make your incision in line with the angle of sight, put your self retaining retractor in, they're not gonna get in your way, and you're gonna get this perfect trajectory or perfect corridor to the CP angle. So what I'm gonna show you now is the keyhole retro-sigmoid approach. This is a small vestibular schwannoma, but the video really is a nice demonstration. Show this video, would you please, Luke, of this approach. So it's a left vestibular schwannoma. Look at this incision. So the incision is in line with your angle that the arms of your retractor don't get in your way. And this dural opening is reflected against the sigmoid sinus; transverse sinus is up here. We don't have to do a supracerebral approach. If I'm doing a genetic procedure, of course, I opened the dura against the transverse sinus as well. But this is a pre-cerebella approach. So I've only opened the dura and reflected against the sigmoid sinus. Here is your small meningoma. And again, what I wanna demonstrate here is that a lot of people say, "Oh my God, it's just such a small opening. What if I need to use a drill? What if I need to get two suckers in there?" Trust me, there's no problem with that. You can get as many instruments. It's not a problem because the brain relaxes and it becomes very cavernous and spacious. So this is just me creating the dural flap. And here we go, look, here's the drill in the posterior fossa, drilling out the meatus. And I think you can appreciate that there's absolutely no problem with visualization, even though the opening is the size of your thumbnail, and the dural opening is about half the size of that. And you can still get instruments in there; there's no problem in getting drills and suckers in there. Just fast-forward it a little bit, please Luke. And now we've just drilled out the meatus, we're doing standard microsurgical technique, finding the apex of this lesion, pulling the lesion down, saving the cranial nerves. Go fast-forward to please Luke. And fast forward again. And now the whole glioma is out. Fast-forward it again. Now we're gonna put the endoscope in to make sure we've got a complete resection and of course look for any holes in the porous. There's a hole that you wouldn't have seen with the microscope, but you can clearly see with the endoscope. This is where people get CSF leaks from a drilling out the porous. So we put the scope into every case to make sure that we don't leave a CSF fistula. Okay, next, just go to the next slide. Thanks, Luke. And he's the post-op scan showing basically a complete resection, and a hearing preserved and facial preserved. Some people say, "Look, what about large tumors? The worst thing about large tumors is you've got a lot of pressure in the posterior fossa and isn't everything gonna bulge out?" Absolutely not. These small openings do not allow the cerebellum to bulge out. So you don't have to make your opening down to the basal cisterns. You don't have to open the cisterna magna. You've got plenty of time. So what you do is you do your small incision, small cranial opening, small dural opening. And yeah, sure, things are tight in there, but it gives you lots of time to hyperventilate, position the patient, score the pia, allow some CSF out, get into some CSF spaces, and you won't get that panicky feeling as a brain turning, heading out, because it just won't do that. So I do all my large CP angle tumor, eight symmetric acoustic neuromas all through the small incision. And there's never a problem. It's great for any retro-sigmoid, sorry, any CPA pathology, such as this large ependymoma that's crossing the midline and circling the basal artery. Complete resection, all done through a small retro sigmoid mini craniotomy. This looked like a DMG, diffuse midline DIPG type tumor, but it wasn't. I think you can see that it was actually a ventrally exophytic focal brainstem glioma with the pons pushed superiorly. Again, did this all through a mini retro-sig; complete resection. You can see here, mini retro-sig and a good outcome. So we've run out of time so I'd like to say basically that, you have to rethink your approach to cranial surgery. Many of us were taught about the standard openings, where you do a standard COZ, or a standard bi coronal or a standard retro-sig. And I think that was reasonable in the olden days 'cause they didn't have good anesthetic agents, the brain would really swell out. You didn't have single shafted instruments. You didn't have hemostatic agents. So, there was this real need, I think, to make a big opening, if for no other reason, than to decompress the intracranial contents. But with good anesthetic agents, good visualization, good preoperative planning, long axis thinking, single shafted instruments, no need for brain retraction; you don't need to do those big standard openings anymore. It's all about tailored openings, using your preoperative guidance, preoperative imaging, good anesthesia, good conditions; and you can minimize morbidity and minimize collateral damage. And that's it, Aaron.

- Very nice lecture, very illuminating. We sincerely appreciate Charlie, obviously huge experience. This is obviously a steep learning curve and requires someone to go slowly and make their exposures narrower and narrower rather than just going from one traditional exposure they have been taught all their residency to an extremely tiny one. I have a few questions for you. Number one is what are the pitfalls as you have seen in young neurosurgeons attempting keyhole surgery?

- Well, I think that philosophy differs a little bit here, Aaron, because I don't think you need to go big necessarily to start off with. I think if you're taught the principles from a very early age and a very early stage in your career, then there is never a reason to make a craniotomy bigger than you have to make it. Now, remember it is a philosophy, not a size. So if you try and do something through an eyebrow, for example, and just say, "Oh my God, that didn't work. I did a subtotal resection or I couldn't clip that aneurysm." Then, clearly that's not an appropriate craniotomy; that's an inappropriately small craniotomy. And a keyhole craniotomy would have been something by which you could have done a proper clipping or proper tumor resection. So Axel Perneczky, a great man, when he was invited to give a plenary session talk at the CNC in one of his final years, rather than show off all the cases that he did, he would concentrate on talking about the concept of keyhole surgery, not the size. Where if you do a small craniotomy and don't achieve the goal of your surgery, then that's wrong, that's wrong in anyone's books. So, if you don't have the technology, if you don't have the skills, if you don't have the anatomical knowledge to achieve your goals for a small craniotomy, then a keyhole craniotomy for you is a big one. It's still a keyhole, it's still doing it through the smallest craniotomy possible, even though it might be bigger than someone else's.

- I think that's an extremely important point. The concept, not the size of the exposure, which you have very clearly emphasized. How I look at keyhole surgery, which I very often use, like you mentioned, is that I say, what is most important in surgery is operative angles, not operative space. In other words, you don't have to have a lot of space to get this surgery done. You just have to have enough and efficient operative angles. If you do the angles right, you can achieve a lot more via a very spacious operative, let's say area. What are your thoughts about that comment, Charlie?

- That's where we agree 100%. And that's what I was trying to underscore, the importance of preoperative assessment, to pick the right angle. I'm not an aneurysm surgeon, but you are, and I'm sure you appreciate that sometimes a direct approach in an aneurysm can be done through a small craniotomy, but to put the clip on, you need to come from a completely different angle, which means that your craniotomy has to be twice or three times bigger than just visualizing the aneurysm. So that's the importance of that preoperative planning thing. Perneczky talked about doing aneurysms through an eyebrow approach. And he wrote a series of, I think something like 150 cases, or maybe even more. Anyway the bottom line was, I went and heard one of his talks, and he made a very special point about saying that the angle to place the clip is extremely important and that's why his initial craniotomies were quite big when he did aneurysms. He managed to minimize them and make them smaller by using an applicator that he developed that had angled sort of articulations on it. But again, it's all about having the instrumentation and having the technology. If you don't have those articulated aneurysm clip holders, and of course, you're gonna have to use different angles to get to your aneurysm, which means that you have to make your craniotomy much bigger.

- Do you agree with me, Charlie, that many neurosurgeons use these larger exposure because it gives them this false sense of confidence that through bigger exposures, you actually have more safety when in fact that's not the case?

- So it's a whole concept of bigger is better that we were taught as residents, that we're taught by our forefathers. And you can't blame them because I actually, given that I'm over 60 years of age, I started off in that era, Aaron, with no propofol, volatile anesthetic agents like Halothane and Infloran. And I can tell you now it was scary. Virtually every craniotomy we did, the brain would come bulging out. And I understood then the importance of bigger is better. The bigger the craniotomy, the more chance you've got of decompressing the brain, releasing CSF, getting rid of ICP before you attacked your deep-seated tumor. I understood it. But I think you would concede that with propofol... We rarely see that now. Mostly we see good conditions when we open up and talk about how times have changed. So to those surgeons who say bigger is better, I understand it, but believe me times have changed. Preoperative imaging has changed. Instrumentation has changed and aesthetic conditions have changed. Hemostatic agents have changed, bipolars. When I started neurosurgery we didn't even have bipolars. So, it's a completely different game now.

- I agree. May I please ask you, when you work on these deep keyhole areas, the lighting is a challenge which endoscope can concur very nicely. The other challenge is when you're using the microscope, it's very difficult to keep in focused because the depth of the operative field is very long. Do you use the mouth switch in order to be more efficient so you don't have to every time adjust handles and keep the image in focus? What kind of techniques do you use to keep the image in focus in deep operative corridors using the microscope, Charlie?

- Yeah, that's a good question. I was taught using the mouthpiece and I liked it actually. And then of course, as you know, I trained with Yasargil, who uses the mouthpiece, and he made Diane cut the little hole in his mouth so he could stick it. But now look, I am so happy with the way that I picked his trajectory upfront now, that I don't move the microscope as much as I used to. So I haven't used the mouthpiece for the last 15, 20 years now. And I get rid of the auto focusing, of course, and I only use the manual focusing, and I always have an assistant as well and that helps. And my assistant's always a fellow who's a fully qualified neurosurgeon. So it's the assistant who does the zooming and I don't have to use the foot pedal. He does it all for me. And I must say that I'm still very efficient using it that way. If I didn't have an assistant, if I didn't have such good preoperative planning, I think the mouthpiece is a very important and good tool.

- I agree. I do believe that keyhole surgery is such an important part of neurosurgery. It is really thriving to accomplish more with less. Now, when I say with less, it doesn't mean a smaller exposure, is I think as surgeons become more skilled, they can do more through smaller operative corridors. So truly a keyhole surgery is a sign of technical efficiency and maturity. Don't you agree?

- I do. The bottom line is I do, but I would like to say upfront that I once had a surgeon come in and I was doing a retro-sig for a small opening, and he goes, "Charlie, I know you can do it, but it makes it so much more difficult for you." And he didn't realize how silly he sounded, because, the point I'd like to make is this is difficult. It's challenging, you're getting out of your comfort zone. You do need technical prowess. You do need new skills and it is difficult for the surgeon, no doubt about it. If for no other reason that you're getting out of your comfort zone, but are we in it to make our lives better or are we in it to make our patients' lives better? And that's why when you reflect on his statement, it's a ridiculous statement. I mean, at the time it sounded, "Oh, that's right. Why would I make life more difficult for myself? I could do a much bigger opening, it would make it a little bit easier." But we're not in it to make it easier for us. The patient does benefit from it. I didn't show you the slide, but there's a slide. We get assessed by the Australian hospital credentialing group. And what they do is I look at your length of stay of a standard craniotomy. And the length of stay for a standard craniotomy in every other institution, major teaching hospitals in Australia was seven to 10 days after standard craniotomy. Ours was 1.2 days. So, do I think I'm that better a surgeon? No. Do I think operating on pathology that's less risky? No, in fact, I operate on really risky stuff. It's the fact that these people do recover well. If you don't use a retractor, the brain recovers better. If you don't make a big incision, then there's not as much pain. If you don't lose as much blood, you don't feel as bad after surgery. If you can cut down the opening in the closing times, then you reduce the operation by a half an hour to an hour. And so all that adds up, and what it adds up to is a patient that feels better, looks better and is better after surgery and can get home a whole lot more quickly. So we published our results from many retro-sigmoid craniotomies, 890 mini retro-sigmoid craniotomies, with only two post-operative complications from the approach, I mean. So two CSF leaks where I actually didn't use the endoscope. So the point is this, that patients do benefit from these minimally invasive approaches with less collateral damage, as long as you're still achieving the goal of the surgery. Don't do it just because it looks good and the patients feel better if you leave half the tumor behind, or if you don't get a proper clip on the aneurysm. You've got to still achieve the goal of surgery, but if you can do it through a smaller opening with less collateral damage, that's a whole lot better than a bigger opening with more collateral damage.

- Which very well summarizes your impression in this statement that it's not about how you get there, it's about what to do where you're there. I think that's the statement you were trying to make. Somebody among the audience was curious. What's your feelings about using a lumbar drain? Often, it provides a much easier pathway to the cisterns and it's just makes the surgery a lot quicker, I believe.

- With all honesty, three times in 30 years. So I guess my philosophy is trying not to use a lumber drain if you can help it. If you have to, fine. And when do you have to? Essentially, you will know. I mean, if you can't get access to a major CSF volume within minutes of opening the dura, then you need a lumbar drain. So that olfactory groove meningioma that I did through the eyebrow, the first case I showed, that patient had a lumbar drain, because I knew that I wasn't gonna get to any CSF spaces until the end of the tumor. But in most cases you can get to a CSF space. And so if a lumbar drain had no complications, of course I'd use it. I mean, why wouldn't you? It just makes life easier. But we all know of all the complications of lumbar drainage. And so if you can minimize complication right, then do so without a lumbar drain. And you just have to trust me on this one. When you open the dura this much, the size of a thumbnail, versus this, that brain does not herniate out; it just doesn't do it. Surface tension keeps it in there. So what it does do is it allows you to sit back like this. What's the CO2, get the CO2 down. Not good enough, elevate the head of the patient. Not good enough, elevate more. And it gives you all this time to relax, take a few deep breaths. The brain's not herniating out. Yasargil told me sine you opened the dura, you score the pia, and that let's CSF drip, and sure it might take you about three or four extra minutes, but by the time you get everything set up, the brain is relaxed and pulsating and you can start getting access to your tumor or to a larger CSF space.

- No, I agree with you completely. So with that in mind, I wanna thank you very much, Charlie. We had a huge audience, over 315 people were with us the entire time, over 500 people at some point were with us during this lecture. It obviously shows the importance of your work. And we will definitely be interested in having you with us in the near future; maybe emphasizing each of the corridors more in detail. So this is maybe an overview lecture. And in subsequent lectures, we can go through each corridors individually and explore them in detail and be able to enjoy your immense experience and learn from your legacy. So with that, and everybody who's been here with us this evening, thank you again.

- Pleasure, thanks, Aaron. Bye, everyone.

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