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Brainstem Cavernomas: Concepts, Strategies and Technical Tips

Jacques Morcos

August 12, 2020

Transcript

- Welcome ladies and gentlemen for another session of the Virtual Operating Room from the Neurosurgical Atlas. Tonight, our guest is Dr. Jacques Morcos from University of Miami. Jacques is not only a great surgeon, a dear friend, but truly an amazing leader in National Neurosurgery and internationally known for his neurosurgical techniques. Jacques has also been an amazing innovator and a leader in innovative way of neurosurgical education, both in the form of symposia and other virtual forms of teaching resources. Recently, there's a Cerebrovascular and Skull Base University of Miami Symposium has been truly the gold standard for neurosurgical education in the era of COVID. Tonight, he'll talk about management of cavernous malformations around the brainstem. Jacques, I wanna thank you for joining us, we're very excited to see your amazing videos. Please go ahead.

- Thank you, Aaron. It's a fantastic pleasure privilege to join your very popular platform that you've been championing for many years. So if may I have my slides to start it? Thank you. Aaron again, thanks a lot, everybody welcome. It's about 8:06 PM Eastern Standard Time in the US, it's wonderful to see so many people from around the world in this COVID era where we do miss not seeing each other in person, but that's the next best thing. So if would like to know about the educational things we are doing here in University of Miami, feel free to email me and I can give you more details of our website or I'm on Twitter. And I put weekly announcements about the next sessions that we offer on Wednesdays and Thursdays with my partner, Mike Ivan, we do various educational activities for the last several weeks now. So you're welcome to join us with those as well. Today, I thought I'd talk about Brainstem Cavernomas, particularly concepts, strategies, technical tips. And of course, it will be with videos as well. My disclosures are completely irrelevant to the talk. Before I start, it's been very marking week, at least for me personally, I'm originally from Lebanon. And of course, I feel with all my people back home in Lebanon, what happened last Tuesday, if any of you has any affinity to that beautiful country, that's been so masserated with multiple hits and hark have any interest in donating. Please donate to the Red Cross in Lebanon that's the website, any donation that goes through the governments that will disappear, but those donations will be very much used appropriately. As if we're not having enough trouble in the world, you know, with our social wars here in the United States, with all the talks about racisms and so forth, I just felt compelled to write an essay. And those of you who are kind of interested to read, and what would like some positive messaging just was published last week. I encourage you to read it. If you feel with what's going on, at least in the United States, with the social turmoil that we're living. I simply give my own personal perspective as an immigrant neurosurgeon, who just loves the United States and what it should stand for. So I'll move on. So outline of the talk, anatomy of the brainstem, both pure and surgical, surgical principles, goals, strategies and tactics. I will discuss surgical approaches and then I'll go with case examples, both decision-making and technical tips. Some pure anatomy. This is a brainstem, we're all familiar with what it stands for, but we don't often look at this, but we should. Those wonderful cross-sectional anatomical depictions of nuclei and tracts, rostral, caudal in the medulla, the pons, I'll show you middle and caudal pons, a midbrain, rostral and caudal pons. And let's start from the top, Rostral Midbrain to the bottom. Clearly I'm not gonna name every structure, but just to, again, those that may perhaps the younger among you to give you an idea of how complex is this anatomic region is. This is it's jam-packed with important things. So this is a Rostral Midbrain. This is a Caudal Midbrain. And as you're looking at those sections, I want you to think of what surgical avenues you think exists. If you're not familiar with this topic, the so-called safe entry zone. I'm gonna talk about that later on, to the brainstem going around or between those tracts and nuclei. This is the Mid Pons. Luckily, the mid pons has, is much more forgiving because there is less density of really critical things. And it's more forgiving regarding choosing an approach through it. As you can see this, of course, the corticospinal tract, and again, no time to go over details, but this is again, the facial colliculus in the floor of the fourth ventricle. And that's the Rostral Medulla, very busy, except perhaps for the olive and the sulcus here. We'll talk about that later. And this is a Caudal Medulla, of course, this is a pyramid right here in the front. Anatomy surgical now, which I showed you a very brief, pure anatomy. Let's talk about surgical anatomy. We have to thank Albino Bricolo that started that conversation a few decades ago when he published about surgery for brainstem glioma, primarily, and the so-called no fly zone and the so-called safe entry zones. And that has been very, very many variations on the theme, various authors introducing their own twist on it. I'll cover that in a second. I've taken this from a paper by Spetzler and his group, and I will use their specimen and their so-called safe entry zones. And I'm gonna give you my edits and my own personal opinion on it. In the midbrain, certainly that anteromedial zone is safe generally. The intercollicular entry point is safe. The lateral sulcus, mesencephalic sulcus is a wonderful entry point. They've put these as safe zones. I really totally disagree, I've put them in orange. First of all, it's extremely impractical to enter the pons smack dab in the midline behind the basler. And even though an entry between the MLF, frightened left is possible, but in practice that is just too morbid and I would not consider this a safe zone. A safe zone is the supraficial and infrafacial triangle. And certainly in here, that's the best safe zone laterally, the peritrigeminal zone around the trigeminal exit zone in the pons. Medulla, you can certainly go through the olive. You could go through a dorsal midline myelotomy. You can go through the lateral medullary zone right here. I'm tending to forget that you don't see my pointer. So I'm gonna keep this going on, maybe in the red color here. So for a lateral medullary zone here, for example, the green line. So that's a summary of all the so-called safe entry points. You could consider those green arrows you see at the various points in the brainstem. A couple of those actually are from Aaron. These are a summary of surgical approaches. Now you can build around this and we're gonna cover them, but it gives you an idea that there are many, many ways to angle into the brainstem. I think the string of the coming two or three slides are probably the most important part in my opinion of the talk. And I want to spend some time on that before going into case examples. So I'd like to divide it into goals, strategies, and tactics, like many other things. Goals mean conceptual reasoning of what you want to do with this brainstem cavernomas. Strategies is your analytical planning and tactics is really the practical execution of your surgery. So then let's divide those into those three columns. You can see, and I consider that there are four steps. So you end up with four steps that for each, for your goals, for your strategies and for your tactics. And let me get into more specifics. Goals is fairly obvious, how do you get there? How do you find the cavernoma? Leave no trace of you having been there and resect it completely. Those are the four goals we all want with brainstem cavernoma surgery. Strategies that correspond to each are to get there, you need to understand the surface geometry. To find the lesion, you need to understand the depth geometry. To leave no trace of you being there, you need to understand optimum, what I call optimal intra-axial neural path. You need to develop that. And to resect it completely, of course, depends on your surgical skills and your micro application of microsurgical ergonomics. Now, the tactics becomes even more granular. I'm not gonna read the entire slide, but just have an idea, have a look particularly, I'll highlight the lack of static retraction, I very much like dynamic retraction regarding depth geometry, minimal neural distortion, avoidance what I call of cornering. You don't want to be working around the bend of a fiber tract. You certainly want to want to preserve the DV- The Developmental Venous Anomaly, I will come back to this last point. You can see on the slide, I definitely resect the draining vein of the cavernoma not to be confused with the DVA. That is always a little draining vein, if you leave it in my experience, you can have a recurrence. Take the vein, don't sacrifice the DVA. Please make sure you understand what I'm saying, don't confuse, I am not saying take the DVA. I'm saying take the small draining vein that drains into a DVA, if a DVA is present. I avoid piecemeal resection, and I'll show this in some of the examples. The next two slides are very important too, what explains mistakes and suboptimal management results? Of course, you can tell that the slides are a summary of my own mistakes and perhaps mistakes I've seen in others as well, over many years of doing this. And you can have, you can create mistakes in all four levels, those all four steps, but I'm gonna highlight some of the particularly common mistakes you may or may not think about not knowing when not to operate, meaning being inappropriately aggressive with brainstem cavernomas. Other side of the coin, missing the opportunity to operate when you should have. Meaning being inappropriately conservative. The next mistake, anatomy absolutely does not mean pathology. So those safe entry zones are beautiful when they're drawn and colored on slides, like I've shown you, but of course, that's on a normal brainstem. You introduce a cavernoma and not everything changes, but many things changed. So the concept of safe entry zone is almost meaningless when a lesion distorts anatomy. Favorable geometry does not mean favorable physiology. I'm gonna show you a couple of examples in my videos in a minute. But for example, when I was a fellow with Spetzler in the mid '90s, my co-fellow Adam Brown, he's the one who's first author on that famous paper with Spetzler, Adam Brown and Roberts Spetzler discussing the two-point method. You choose a cavernoma, you put the point in the center, you put the point on the surface, you extrapolate the slide. That is your so-called surgical strategy or trajectory. That principle does not apply always, should not apply always. It's very helpful as an initial guide, but please don't apply the two-point method blindly. Avoid the obvious entry point is not always the safest and that it is nowhere truer than in the fourth ventricular floor. And I'll show you examples, a few more mistakes, suboptimal execution of steps one and or two will lead to suboptimal execution of steps three or four. So what I want to say is, if you're a step two and step three results in contradicting choice, contradictory choices of an approach, always favor step three, meaning safety. Other mistakes cavernomas remind are like, I know we them Mulberry, but I think of them as Cauliflower. You see how a Cauliflower looks like? Many protrusions. Cavernomas are like this. It is very easy as you're amputating a cavernoma to miss a protrusion of these cauliflowers. And then that's the cause of residual. So, you know, those little things right there. A small vein draining the cavernoma into a main DVA should be resected, do not resect the DVA. And finally, there is no role for radiosurgery, in my opinion, whatsoever in cavernomas of the brainstem in spite of what might be in the literature. Surgical approaches. You know, you open several papers, it's a traditional thing. You either will see a series of surgical approaches and what entry zones they apply to, or the reverse, a series of anatomical regions of the brainstem and what approaches might be applicable. Again, I'm not gonna read that to you, I'm gonna show you later by examples. You need to look at that from both perspectives to really have a complete appropriate decision-making. Those various approaches, we'll cover some of those in a second. So I do think that Spetzler probably still has a largest series in the literature close to 400 cases, but even in his hands, you can see the morbidity significant, any new deficit, 53% in the top right there. Post-op rehab regenerate about 8% new permanent deficits, about 35%. And those are the hands of a very experienced surgeon and team. Yashar Kalani has looked at a meta analysis of many authors, about 2000 covered enormous from around the literature. I'm not gonna read those numbers, very similar results. So what this tells us is, there is immense room for improvement. Of course, we owe a lot to this man Al Rhoton, and of course, he clarified a lot of our anatomy and as a tribute to this great man, I will use his, some of his dissections to show you the illustrations that I want to show you. So these are some of the approaches, the Pterional/COZ/CO transylvian apply to this region of the midbrain. For example, the transsylvian pretemporal with or without transtentorial approach is good to this lateral view of the midbrain. The anterior transpetrous Kawase, is very good for upper pons, anterolateral upper pons. I love this approach, supracerebellar infratentorial, but particularly, the paramedian variant of it. Not so much the midline because of the peaking tentorium or the extreme lateral, but the paramedian is the most versatile. Just off the midline gets you to the dorsum. The posterior interhemispheric transtentorial is an okay approach. Please don't do it the way at least Rhoton showed that in his anatomy with the patient prone, I like to do it with the way you see it on the right with this, with the gravity helping the right hemisphere, falling away from the faults and do not use self-retaining retractor. You will in use Homonymous hemianopsia, let gravity do the work, then cut the tentorium as needed. Midline suboccipital telovelar, of course excellent for fourth ventricular floor, the retrosigmoid is extremely versatile. The presigmoid subtemporal or posterior petrosal has it's occasional use for brainstem cavernoma for lower pons. The far lateral of course is excellent for medulla and lower third of the pons, particularly laterally and anterolaterally. So the rest of the talk will be case examples. I will apologize from now, I cannot speed up through the videos. This platform does not allow that. So if I see that I'm running out of time, I will move on to the next video. Decision-making technical tips, the way I'm gonna do it, I'm gonna start from the midbrain or rostral and cover. I'll try to cover examples for each region with videos. So let's start with a dorsal approach to the midbrain. This will be a Thalamo-Mesencephalic cavernoma that I did recently, I use the posterior interhemispheric supracollicular transpineal approach. This brief 50 year old female in 2016 had Southern diplopia treated elsewhere with CyberKnife, horrible thing to have done. She worsened, the cavernoma grew, she developed radiation injury due to CyberKnife, she's dysarthric hemiparetic has a Parinaud syndrome and failure of inferior gaze as well. She's now referred to me. Luke, if you don't mind playing the video, I want you during the video to note the vein of rosenthal and the pineal gland entry as a highlight of the video. This is a summary of the history I just told you. And I'll put my pointer to perhaps show as I... Things that like to show you. So the cavernoma of course, is here. You can see it there. So you could certainly consider supracerebellar infratentorial, but look how steep the tentorium is. In as much as the posterior interhemispheric is less preferred because you are dealing with the occipital lobe. In this case, I thought it's a better approach. Yes, you do have to contend with the occasional bridging vein. And when you sacrifice a bridging vein, please notice you put the clip on it far end next to the confluence of veins. Another anatomical fact, of course, there is no self-retaining retraction. It is not straightforward, as you might think to find the straight sinus, the forks and tentorium look like in surgery, it's not like a cadaver. It looks like it's the same layer. It is very easy to injure the straight sinus. So here I am using a navigation and of course, microscopic view to make sure I recognize the straight sinus and then cutting the tentorium with a non-stick bipolar. And then of course, I'm gonna want to see the vein of Galen and Rosenthal. And I like to open the tentorium, not starting from its edge, but starting from its center because you can then lift it with a hook and continue the cut. Aaron, do you have any comments on this approach while we're watching tentorial splitting?

- No, I think this is an excellent approach. I would have most likely chosen the supracerebellar approach, I just have had a lot of luck with it, and I'm not saying it would have been an easy approach. It just appeared to me that it may be the least invasive approach and most direct, but again, I could have had some challenges with the superior portion of the tumor and a very steep aspect of the tentorium. So that's something that always is a challenge to think about, but I just love that permedian supracebral approach is so flexible.

- I love it. And I'm showing this because it's an unusual use of it for me. So you can see here a vein of Rosenthal you can see vein of Galen, and of course the limitation of this approach is that you are going to work between the veins, but now here is the pineal gland. And of course in an adult is not. And with the use of navigation, it appeared to me, I see, I wanted to avoid the tectorial plate, tectorial plate, oops is right, get the color again, tectorial plate is right here. So pineal gland is completely non-eloquent, and that's what I'm doing here, going through it. And you will see that the trajectory, if you think of the sagittal I showed you was exactly in my line of sight as you will see in a second. And we're gonna get into a hematoma. I am not even touching the colliculi the superior or inferior colliculi and working below galen, medial to rosenthal and I'm in hematoma. And I'm using the beauty of this gliotic plane to get through and cut it and get the cavernoma out.

- It's definitely a very nice approach. I have to tell you, it's you're directly on it with minimal invasion of the neural structure. So it is truly a very beautiful anatomy and you're preserving most of the functions. So I think this is an excellent route.

- Yeah. Particularly when the tentorium is steep, in spite of the fact that we're talking about, like you, I do it paramedial to use the flatness of the tentorium, Luke, do you think you could take us to the end of this video if possible, or Aaron? Yeah, Aaron, remove this. Okay. And oh, it restarted it, I guess. Yeah. Oh no, that's the end, I'm sorry. So here is the end. Thank you very much. So that's a nice resection of course, hemosiderin ring you can see, patient did not turn a hair. It's a good angle in this trajectory. Right here, like that. Okay. May I have the slides again? Thank you. Next example is a lateral midbrain entry. I'm gonna show you a superior cerebellar peduncle cavernoma that has failed, and this is a very teaching case. It has failed a telovelar approach done elsewhere. So I selected, you'll see why what we were talking about, supracerebellar infratentorial, but in this case, extreme lateral, not paramedian. I like to do these in the concorde position. So let's go over the case. She's 28, had an hemorrhage in July 2019, fourth nerve palsy left hemiparesis you will see in a second elsewhere, a telovelar approach was done. They had interoperative difficulty visualizing the lesion. Partial resection was done, a DVA was in their way. She actually made a very good recovery from that partial resection and then the lesion grow. So this was her origin of hemorrhage, this is the cavernoma at the time, I would not have chosen the telovelar, it's too high. It's traversing, many things and as you will see, perhaps later, there is a DVA right behind it. Here is a DVA totally in the way, not totally in the way, but partially in the way. There is the angiogram showing the DVA very nicely. And that's post-op elsewhere, partial resection. Patient was not hurt, she improved. And I saw her many months later. And then, so what choice of approach? Clearly, at least in my mind, look at this top right image, clearly to me, this is the right approach like that, correct? You're using the flatness of the tentorium as Aaron was just pointing earlier in general, and that's what I did in this case, as this is again, the same angle you can see in the accent. Luke, would you mind playing the video? So the video then if a resection of a Pontomesencephalic residual cavernoma that had a telovelar approach, that's again, her history, which we covered. It's a very good approach for this type of lesion. You can see it reaching the tentorium surface. Tentorial surface of the cerebellum, it's a natural way to go. Unlike the case that I showed you before, the angle here is very favorable. I don't use a sitting position. I use concorde, meaning to me, I know Aaron does it differently. Aaron gave us a beautiful presentation last week in our symposium here and discussed his approach to various lesions, Aaron likes the three quarter prone position. I like the just pure concorde. The patient is prone, but the bed is angled this way. And of course, the thinner of the neck is the easier it is. You must get CSF out. I usually get it the top of the cisterna magna without taking the craniotomy that low, you can very simply get it from there. No self-retaining retraction, look at the fourth nerve. You may have just had the glimpse of the fourth nerve a minute ago, a second ago. And of course, the superior cerebellar artery and the cavernoma is straight looking at me and I'm making no special effort to retract. It's of course, dynamic retraction. I, again, non-stick bipolar to shrink the cavernoma, give yourself a little extra room to navigate it, because again, my principle is to try to keep it as one piece, as much as possible. Remember, it's a cauliflower, by the way, here is the fourth nerve and the SCA. And again, you have to move, at least the SCA around the fourth nerve will be pushed up. So it's a cauliflower. If you start chopping a cauliflower in multiple little pieces, it'll be very hard to collect all of them. So I do as much as I can of circum dissection of the lesion, I shouldn't get some, identify the gliotic plane and then we're gonna work on it. Aaron, why don't you make comments while we're watching?

- You know, this is a beautiful approach, I just want everybody to appreciate how low this lesion on the posterior midbrain is. And it's coming into the pontine borders and you still can very nicely approach it without really much retraction of the cerebellum. The key factor here that you are so beautifully describing is that we're using dynamic retraction. In fact, you had exposed so much more at the tip of the suction, compared to using a face refractor blade that is much wider and requires a lot more retraction to both provide that much exposure at the very point of this suction, which is much more targeted. So by using that very tiny suction and retracting less, you can actually see a lot more at the exact point that you're operating. That's such an important role that I don't think people as much appreciate. Number two, is that the wings of the cerebellum, just like you were showing, are so much more moving in fairly, that is allowing you to see so far inferior to the fourth nerve. It is truly impressive that you are working, and the fourth nerve is actually the top of your exposure, which tells you that how much exposure.

- Yeah. I mean, I don't know if you noticed, I actually, you can use different suckers, for example, the more tapered Fukushima suction, but I like these, even though they're fatter at the tip because they're blunt, you see how I use them as a relative by sectors. You can lose it. The Fukushima suckers are wonderful, different purpose, sharper, more tapered. I used to use this, I'm using navigation here. And I can't remember if this video or others, of course, you can use assisted endoscope. You can now put an endoscope if you don't have enough of a view and look around, I don't think in this video, SCA of course, preserved hanging in mid air. The fourth nerve is out of my view and we're done. Cerebellum is in great shape. Please notice the dural opening should not be very big, if you make it very big, that cerebellum might herniate out of the wound. You don't want that. And very nice, obviously both Aaron and I love this approach. Here is a resection hemosiderin ring tells you, you've done a good job, clearly the correct approach in this case, not the telovelar. And I think I will show you the intact DV. Yeah, I did give her a trenchant fourth nerve palsy again, and it disappeared again after very few, very short weeks. I don't remember how many weeks.

- This is beautiful work, really truly amazing work, Jacques. Is a very difficult case, beautiful approach. You can really appreciate that bimanual dissection. In other words, it's a suction, it's not just sitting there sucking fluid, it is the dissector. Both hands are coordinating like a choreographically French dance, if you may call it. And they all work together do all that, all the time, doing things to do a work of actually two or three, dissectors at the same time. And obviously, as I can appreciate you using the mouse switch and the mouse switch is so critical to keep the image in focus.

- Right, okay. Luke, may I have the slide please? Thank you. So there is this post-op again, please remember this trajectory and this approach. Look at the DVA intact. Post-op I don't think I ever actually saw it. I don't remember, but it wasn't in my way at all. Okay. Onto the Pons. I am gonna show you a lateral entry to the pons. So this is gonna be, please remember, by the way, interject here, the simpler, the approach, the better it is. We are all, not all, those of us who are like me and like Aaron, both cerebrovascular and skull based surgeons doesn't mean we're gonna enjoy using the largest, most complex skull-based approach, we could apply to a cavernoma, no. if a simple approach does it, that's what you want to use. And this next case is a great example. I'm gonna use a subtemporal approach to adapt to come to a ponto-mesencephalic cavernoma during pregnancy and I'll show you briefly her story. She came from another country, she's had a cavernoma. This is her third pregnancy, they thought it was inoperable. They loaded her with steroids during her pregnancy, gave her incredibly severe exogenous cushing syndrome. She was 23 weeks pregnant became with myopathic, you'll see her picture in a second, came to be hemiparetic two over five wheelchair bound, severe cushionoid and the third nerve palsy. Look at the acne of the steroids. Look, she's sitting in a wheelchair she's 23 weeks pregnant and here is her cavernoma. So this is a very good case too, again discuss, as I will discuss later on a similar issue, Well, first of all, clearly it is operable. As a matter of fact, the larger the cavernoma, the more operable it is. Give me a cavernoma like this any day versus a five millimeter cavernoma buried in the middle of the pons. This cavernoma gives you access to itself. Now you might say, okay, how do we get to this one? You might say, let's go telovelar, but I would say telovelar is not a good idea. She has normal facial nerve. You you're gonna go through here? No. Not a good choice. That is brain with facial colliculus, the obvious choice is this. I mean, it's on the surface lateral surface. This is a very forgiving entry point. The lateral mesencephalic sulcus, pure simple subtemporal approach, even though the cavernoma is huge and daunting and so forth, the approach doesn't have to be as complex as a cavernoma. So that's what I chose. So not telovelar, but subtemporal. and this is a fetal heart rate monitoring the baby. Didn't turn a hair, simple approach and resected it. And I think I skipped the video because it's too long, but that's a post-op very simple approach. She improved actually immediately. And I forgot to put her picture two months later. Of course, her cushing syndrome disappeared. This is her actually post-op day one. It's okay, we can skip the video, but I'm showing you that her hemiparesis was actually already better on post-op day one. Her eye movements were fine and so forth, you can take my word for it. I'm gonna show you another subtemporal, but one transtentorial approach to a pontomesencepalic cavernoma. Luke, would you mind playing the video? This video was narrated, but we, and I thank my former fellow, when he was my fellow two years ago, Georgio Zenonos for having put this video together at the time, 27 year old female, progressive left sided weakness, numbness, diplopia, difficulty speaking. You can see hemiparesis, only one out of five left upper extremity, two out of five, left lower extremity, left body anesthesia pain temperature, touch left, facial hemianesthesia. Dysarthric, the video is playing, isn't it? I guess it's not frozen, is it? No. Yeah, here we go. Here's a cavernoma. Again, clearly you would choose a subtemporal approach. But in this case, I used transtentorial. You will see because it's hidden under the tentorium here. It has the solid component is below the tentorium. The hematoma component is above, so just simply split the tentorium. Now this is very nice, cadaveric montage that again, Georgio did the work to put this together. When you hear him narrating it, you will understand that we're thinking about the anatomy of the tracts, corticospinal tract, the frontopontine fibers, the temporopontine fibers, how you analyze your entry point. You have to of course, sit down and say, well, what tracts are in my way, but please, please, please remember, this is pure anatomy. This is only the starting point, you have to think of the lesion, super impose it, understand how it distorted this anatomy, use DTI imaging if necessary, to see where all these tracts have gone and then choose your approach appropriately. Perhaps we can skip. If you don't mind, if it's easy to skip, I don't need to show you another subtemporal. Could we skip to the end of the video? Perhaps it can show you the post-op MRI and if it doesn't, it's okay.

- Jacques, may ask there's a question about neuromonitoring intraoperatively. What cases do you monitor intraoperatively which select cases and what do you monitor? Would you please tell us.

- Sure. Well, I mean, most as a general answer, most brainstem, if you want them, play the video as I'm talking, might as well, most brainstem cavernomas you're gonna monitor somatosensory evoked potential motor evoked potential, you're gonna monitor three, four, and six cranial nerve. If you're near those areas, you're gonna monitor, you know, appropriate segments of the brainstem, the cranial nerves, but almost always the long tracts, SSEP, MEP, brainstem evoked potential, those are a given. You know, very important in addition to navigation.

- I really liked the fact that you try to avoid the floor of the fourth ventricle in most of these cases. Go ahead please.

- Yes, you may have seen here. I really went through the effort of saving the bridging vein, vein of Labbe, of course, sometimes you have to take a couple of bridging veins in subtemporal approach. Would you mind giving, okay, and here is post-op MRI, a good resection nor residual, or as you know, it's always hard to see on post-op day one MRI, but you can tell when you put side by side with the pre-op. May I have my slides, please? Thank you. So let's give you an example of Caudal Pons coming from the side where I'm using a Kawase approach. I love the Kawase approach. I mean, I'm not suggesting it's a simple approach, it's a wonderful approach for many, many things, where it has its limitation. For many years, I followed kind of my own classification and I would say, this is what I call the second quarter of the clivus, from the top down the second quarter, meaning it corresponds to the anterolateral pons and the midbrain, and that's where the fifth nerve, the fourth nerve are smack dab center. So let's play that video, Luke, if you don't mind. So I'm gonna show a right side that Kawase approach in this patient who has familial cavernomas, I've operated on her several times, I've operated on her sister several times. I will show you the natural history of her cavernoma, notice the tiny cavernoma in the pons, how it's gonna grow over time. This small thing will blossom into this, just few months later, and then into this, and then gradually reaching the surface of the pons, we will use DTI to see, to help me decide. And here is DTI, it's telling me the cortical spinal tract is not in the way of the lateral entry, which is why I chose lateral entry through the Kawase. I had to do drill Kawase because it is low, low in the pons. Now the lower limit of the Kawase approach is seventh and eighth nerve. Do not attempt to risk, in my opinion, do attempt to resect, a brainstem lesion or an extra-axial lesion, like a meningioma of that petroclival region through a Kawase approach, if it goes caudal to the seventh and eighth nerve, you will put those nerves at risk and that's not the appropriate approach, you might as well use a petrosal posterior approach. So we are, I may not want to spend the whole video showing you a Kawase, but I took the middle meningeal artery. You have to of course, do extra dural work, here is greater superficial petrosal nerve. Let me use my, well, I missed it, but the greater superficial petrosal nerve was here, This is a petrous carotid artery. Now here in a Kawase, you have to put self-retaining retractor. You have to wedge it on the petrous ridge. I love this drill, this drill is covered all the way to the tip. It is curved and I like to use diamond. So I use it for most skull-based drilling. I am drilling the Kawase area as long as you're preserving the basal turn of the cochlea, which would be approximately right here at the angle between IAC and GSPN. And of course, as long as you avoid horizontal petrous carotid, everything else is fair game to drill. The internal auditory canal will make, as you know, bisect the 120 degree angle. IAC is here, GSPN is here. I'm sorry. RQ with eminence is here, GSPN is here, basal turn of cochlea is here, the lay of the IEC would be right here. And that angle is approximately 60 degree on each side. So once you've done the bony drilling, then you cut the dura. It is hard to explain in words how to cut the dura. If I had more time, I would spend more time, but I really want to cover more cases, but there are three cuts of dura you must make. Temporal lobe. I mean, dura on the convexity of the temporal lobe, the tentorium and the presigmoid dura. These three pieces of dura, meet at the superior petrosal sinus. So you have to cut the superior petrosal sinus. And now, I am looking smack dab into the lateral pons. The trajectory is right there. And of course, we're already in hematoma, I mean, in cavernoma hematoma. And then, as we all say, once you're in the hematoma and the cavernoma, the technique is the same everywhere. And here is a cavernoma coming up. It is really in this case, I cannot think of a better angle of view than doing this. By the way, once you open the dura, do not keep yourself retaining retractor, remove it. You have to have a lumbar drain. Only use the self-retaining retractor to do the extra dural work. Then the lumbar drain will take care of the intradural work and we're putting fat graft here. Aaron, you have comments to make on the Kawase approach?

- Yeah, there is a cup- No, this is beautiful work. There is a couple of questions, number one, do you use lumbar drain? I do use it very liberally, very liberally. Somebody is asking how do you achieve brain relaxation? Even in my paramedian super several approaches, I use lumbar drain liberally. Number two, there is a question is, do you use a way, craniotomy for resection of cavernoma as close to the eloquent cortex.

- Not in the brainstem, but-

- Right, in a cortex, they're asking.

- Very rarely. I've done it a few times, as you know, cavernoma is not a glioma. The decision will not be how much do I leave behind? Should I leave some glioma? It's like AVMs in cavernoma, either you remove it or you don't remove it at all. And with DTI, you can tell pretty much pre-op whether a cavernoma is resectable or not. But if you have any doubt, absolutely do it awake, speech area, motor area, and this woman again, improved. This is I think post-op day one or two, and this is her few weeks later. Very well tolerated approach. Luke, may I have my slides? Okay. Lateral pons, another case of course, pons is the most common region. Far lateral approach, hopefully most of you are familiar with the far lateral approach. Luke, could you play the video? Again, this was edited at the time by Georgio Zenonos, my former fellow with Samir Sur, my chief resident and other helpers. 31 year old man, he loves playing soccer. He had right arm weakness and the left sixth nerve palsy. Here is your lesion. I want you to think about how would you do it, I think the approach is fairly obvious here. It's on the surface of the lower pons. Notice the DVA, I think your choice is between retrosigmoid or far lateral. And you will see in a second in the anatomical montage that we put together, why far lateral makes more sense? So here is your pons, here are your fibers, your tracts, and so forth. The only, so from a conceptual point of view, I'm gonna speak ahead of the video. I'll let the video keep going. The far lateral approach allows you a caudocranial trajectory from below up that the retrosigmoid approach does not allow you to do. And that's the main difference. The second difference of course is a wider approach. So you do DTI, you analyze the fiber tracts, you overlay the lesion. And here, I think you're gonna see in a second, the overlay of the cavernoma and comparing a retrosigmoid angle versus a far lateral angle. These are not my dissections. Again, these are from Georgio and his colleagues from previous dissections, beautiful dissections. Here is the entry of the peritrigeminal entry zone. I want you to think of this arrow coming from below, and I want you to think with this arrow coming straight laterally. So here is retrosigmoid coming from laterally, but the access of the cavernoma was, you remember was oblique and not oblique, cranial caudal. That's why I chose the far lateral. I'm not saying the retrosigmoid wouldn't have done it, but I think the angle of view this way is better. This arrow, the way this arrow is pointing is what the far lateral will give you. And I think you'll appreciate it in the video. I still do my far lateral approach as hockey stick, you can certainly do with paramedian, you can do lazy-S there are many ways to do it. I think anatomically, this does not split the muscles because you go between in the median raphe, you leave a cuff on the superior nuchal line and all of that gets attached at the end. I certainly hope most of you are familiar with the far lateral approach. It's like pterional approach for the posterior fossa. Of course, you have to drill it thoroughly, the juxtacondylar bone, not the condyle. The myth, not the myth, the misunderstanding that the far lateral approach means transcondylar is wrong. You are not entering the condyle. In most cases, you are going up to the condyle. And when you do that, then that trajectory makes it so flat, that angle is so flat, AICA, lower cranial nerves. You can see the dura is completely flushed with the bone. Look, I'm already, I've done almost no dissection, and I am looking right there at the cavernoma. So I'm gonna be between six nerve medial to me, seventh nerve lateral to me, pontomedullary sulcus caudal to me. And if you play the video, I think you will see the six nerve. I'm gonna clear these red arrows. I don't know if it has frozen or not, but there is six nerves, you saw it? Just right there. So we're between, this is a infra vagal trigone, use every triangle of arachnoid that you can free up. Now, putting this retractor is very different from putting a retractor on the temporal lobe. This retractor is placed after you've done your arachnoid dissection to improve the lighting. That retraction is very well tolerated. It is cranial nerve six, you see? It stretched on the cavernoma. You can see the vertebral artery, the AICA I'm using navigation to reassure myself and then, you know, the rest straightforward enter. There you go, you see you spread your bipolar, some hematoma expresses itself and then work between those triangles of nerves. And I think the angle that the far lateral is giving me in this particular case is an anterior look to the cavernoma, the retrosigmoid, you would have done what I showed you in my slide earlier, cornering, it would have given you cornering, you would have had this pushing I'm doing right now, I would have done a lot more pushing on the brainstem, have I'd done retrosigmoid.

- A question that came up is when would you approach through the floor of the fourth ventricle? And I wanna emphasize this point, Jacques, if that's okay with you, if there is any neural tissue still intact over the cavernoma on the floor of the fourth ventricle, use the retrosigmoid approach. In fact, I may go through more normal tissue of the middle cerebellar peduncle and save a little bit of neural tissue at the floor of the fourth ventricle, because it's so critical at the floor of the forth and the middle cerebellar peduncle is so giving. Do you agree with me on that?

- Completely I agree, and I believe, well I'm I see it's already nine o'clock, but the next case, I believe is exactly that it talks about what I labeled it, the path less traveled. And actually we sent something for publication. Exactly the point you just made, how about we stop this video, and I like to really show what you just said. The post-op MRI showed complete resection. Let me see, that we see is this. Yeah, let's skip this one. No, I'm gonna skip it. Can you give me the slides again. Again, far lateral on this case. Same case, another case. Very similar, did beautiful. I'm skipping it, far lateral approach. Very handy approach. But I do want to say, let me skip those. Let me see, to remind myself, ah, yes, this is the case. So again, to go briefly, this case was operated elsewhere, when the cavernoma was like this, through the floor of the fourth ventricle, not a good thing to do. The patient had a very bad facial nerve palsy. Don't do that, you see how much brain tissue there is, right there. Sorry, it takes me a while to bring the pointer, but you cannot. This is unforgiving brain, you cannot go through this brain to remove a cavernoma like this. She indeed had the rough course, here is a cavernoma pre-op elsewhere. Post-op, there was a residual cavernoma. She made a partial recovery and this, she's 27. And she comes to me. Oh, she gets a cyberknife or gamma knife, I can't remember. She comes to me now with this cavernoma. So that's exactly the point that Aaron was talking about. So let's spend a second here. You don't want to do this again, she still has a facial palsy, but it's partial. I'm not gonna put her through another year of recovering her facial palsy. I'm gonna come this way, go through more brain tissue. The so-called path less traveled rather than applying the two-point method I was talking about earlier. So this is a detailed analysis of her slices for me to understand. And I did a far lateral approach. I'm gonna skip the video. Please notice the DVA in her, went through all this. I don't have time for the video, I'm just gonna skip it. And this is what I did. Excellent approach for this. It's counter-intuitive, you are attempted to go through floor of the the fourth ventricle, please don't. Go through this very forgiving, look at my path. Look how I saved the DVA, it's a perfect approach for this. And maybe I can show, well, maybe I can show one fourth ventricular example and stop is to this approach.

- Take your time, Jacques. Take your time, Jacques. We're doing great. The cases are amazing. Everybody's staying around, we have great audience. Let's see the video, it's enjoyable.

- Thank you. The quality of this video may not be as good as the others, it's a bit older video, but I believe it's the one where I map the facial colliculus so here, see, it was speaking through the fourth of the fourth floor of the fourth ventricle. This one is in too much brain tissue to go through from laterally, particularly when it's speaking like this. If you're gonna go through the floor of the fourth ventricle, you'd better know exactly where the facial colliculus is. And I will show you in the video, how you use the Nim Stimulator to map the facial colliculus right here. And remember, hemosiderin reaching the surface doesn't mean the lesion reaches the surface. We will not see the lesion when I entered the floor of the fourth ventricle. With the telovelar, I believe my fellow is assisting my fellow doing a lot of this approach. Here we are doing, I believe the mapping in a second, by the way, when you do telovelar, you really have to cut. Again, like Sylvian fissure splitting, you have to cut that inferior medullary velum, gets you all the way up, and sometimes you have to put a self-retaining retractor holding the tonsil from medially, the uvula up? Can you guess already the yellowish discoloration, right here? Oops. Sorry, it's in black, but right here, but the lesion doesn't reach the surface. So you have to map, you put your retractor, I don't know where to enter. So I'm gonna take my nim stimulator and I'm marking with a pen or whatever the ink, where it stimulated. So I stimulate your mapping, like you map the cortex and I'm gonna end up with a circle approximately like this of a no fly zone. So the infrafacial entry would have been here. The supraficial entry would have been here. I mean, the video is moving, but you know what I mean. Assuming what I'm shading is the facial, no fly zone colliculus area. In this case, we are going to use a superficial triangle, not the infrafacial triangle, because with navigation, it showed me that that's where most of the cavernoma is, but it's still not easy. I did give the patient temporary facial palsy. It was at least a grade four because of my traction on this structure. So in as much as I hate the approach, sometimes you really have to use it. When it's that far into the floor. See what I'm doing here? I'm mapping with my Nim, where the facial colliculus is going and so forth. Aaron, I don't really want to waste more time. I think showing the resection there, we can go to the end of it and I could perhaps go to...

- That's okay. Let me ask you a couple of question, let the video run. It's very informative because I liked the way you're holding the tissues. I assume you make a vertical incision, is that correct?

- I did. Yes. You can see it, it's vertical parallel.

- How are you holding on to the tissue, edges of the brainstem? You're putting some tags on it because they usually get into your suction.

- I usually use Surgicel, not, I don't know if this case or not, but I like to use Surgicel or soft cotton. I skipped a video where I use free cotton, not with that thread marker. Soft cotton on the tip of the suction, holding the brainstem edges. That's what I normally do, Aaron.

- What about, this is another question while we're watching this video. When did you use a presigmoid approach for a cavernoma, Jacques?

- Large ones that are what I call the third quarter behind the third qua- meaning the lower pons below seven and eight, and it needs to be large and it needs to, for whatever reason, I need the lateral angle to it that a far lateral or retrosigmoid will not achieve. So that's why it's very rare to use for a cavernoma.

- So there's a question asked, and I know the answer, but I'm gonna ask anyways, Abdul is asking, what are the disadvantages of SRS for cavernomas?

- Well, it doesn't work. You mean stereotactic radio surgery work, my colleagues in spite of all the thick one, that's got a long discussion, but in spite of all the papers, you know, it's a denominator effect that is in the bu- I refer you to a beautiful paper many years ago by Fred Barker, talking about temporal clustering. When a cavernoma bleeds and rebleeds, it tends to occur in clusters. So you cannot take credit for the gamma knife, if you gamma knife somebody and the rebleed rate gets slower, it was gonna get lower anyway, because that's the natural history. Our colleagues in Sweden, the neurosurgeons in Sweden, where Leksell was tell you that it does not work for brainstem cavernomas. I've shown you just today, at least three cases where I had to operate, and I have many more of failed cavernoma gamma knife on cavernoma, not only failed, but radiation necrosis, or radiation side effects around it. If you cannot operate on a cavernoma watch it, let it grow, let it reach the surface, let it rebleed a number of times until you think, you can operate on it, then operate on it.

- Luke, let's go ahead and exit the slides. You know, when we talk about the management of these lesions, really getting there is very difficult and how you handle the surrounding neural structures that are normal. When you get there, resection of cavernoma, it's not that difficult if you have fair amount of experience. It really pushes the limits of a surgeon to operate in a very deep, lonely hole be able to be ambidextrous and be able to really manage the tissues, and handle them very carefully. So cavernomas truly are, in my opinion, some of the most beautiful lesions we tackle. Before we close, I wanted to ask you a question that it's been sorta something in my mind to ask for a long time. I know we're gonna have a session in about a month with Dr. Herro Spetzler and Al Mefti about the makings of a great neurosurgeon. Before we close tonight, I wanna ask you personally, Jacques. What is the making? What is the anatomy of a master neurosurgeon in your mind?

- Well, I mean, these are very tough questions because you suddenly put me in the class of those people, you just mentioned, but, well, I'm gonna plug, put a plug if you don't mind to the beautiful podcast that Mike Wang and John Paul Caulkan have been doing, and have interviewed many people out there. Well, they interviewed me, and that was the title of the podcast, the Anatomy of a Neurosurgeon go listen to it, but don't just listen to mine. Listen, there are fantastic ones. Those brilliant idea, my partner, Mike Wang had to do to get to the depths, you know, and some you talk about technique, but technique goes so far, that is that second layer. I'm gonna answer you very briefly. I don't want to keep people too long here, but you know, the qualities I'm gonna give you, it's dedication, it's passion, you have to be modest to recognize your limitations, learn from your mistakes and never forget them. And then recycle this over and over again, and be open-minded, you see dogma gets in the way. Be open-minded, age should not be a hurdle to learning new things. I'm not gonna keep talking, Aaron. This conversation can go on for a long time. I'm gonna shut up.

- Oh, that's okay. You know, we're gonna talk a lot more in a month. And so I want to, again, thank you very much, you know, Jacques you're truly has been a role model for so many neurosurgeons, rightfully so. You have done so much, you have been a great leader. You have been multidimensional. You have been so much more than a master surgeon, and I wanna congratulate you on your immense leadership, friendship, collegial personality you have, and you have been such a great mentor for so many young neurosurgeons. So with that in mind, I wanna ask all of you to join us next week, Monday night, again, eight Eastern time. Our speaker would be Dr. Rick Boop, a very dear friend as well, just like Jacques. Who'll be talking about management of extremely difficult lesions, which will be Thalamopeduncular gliomas and their resection strategies. With that in mind, I wanna wish all of you guys, a great morning, afternoon, or evening, wherever you are around the globe and wish your families happiness and health. Again, Jacques, thank you.

- Thank you so much. Goodnight or goodbye everybody. Thank you, Aaron.

- Thank you.

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