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Splitting the Sylvian Fissure: A Necessary Skill to Approach Vascular and Parasellar Lesions

Paul Camarata

May 17, 2021

Transcript

- Ladies and gentlemen, thank you for joining us for another session of the virtual alarm. My name is Aaron Cohen. Our guest today is Dr. Paul Camarata from the University of Kansas. He is a dear friend, amazing surgeon, and he's also the terminal neurosurgery at University of Kansas in addition to being a director at the American Board of Neurological Surgery. He's going to talk to us today about Sylvian fissure split. It technically a very difficult procedure, but, if it's done well, it's an amazing adjunct to approach to any lesion along the parasellar area into a skull base. It is often underestimated. Its difficulties are also underestimated, but it has to be performed atraumatically. I always have been convinced that when my new fellow start working with me, if I ask them to split a fissure for the first five minutes, I have a very clear understanding of what is their technical skills. Just because the Sylvian fissure split is truly one of those work horses of subarachnoids dissection. It really minimizes frontal lobe retraction. It opens a huge corridor to a circular welless and really makes the technique of our most approach to any lesion in the interpeduncular cistern very easy and safe. So, Paul, I cannot thank you enough for your incredible lecture. I'm actually very excited to listen to you. After you're done, I'll show a video and so my thoughts as well. So with that, please go ahead and thank you.

- Thank you so much Aaron. It's really an honor to be here and to present Splitting the Sylvian Fissure: A Necessary Skill to Approach Vascular and Parasellar Lesions for all of the reasons that you mentioned. I really hope that by the end of the talk, the viewers will really understand the reason that you need to employ this technique to as many lesions around the skull base, the parasellar areas as you can. I think practice makes perfect, you know, as Malcolm Gladwell say, "You have to practice a technique a number of times before you become proficient and before you master it." I hope you'll understand the forest for the trees. And I thought I would give you just a brief outline of the talk, of the approach. We'll talk about the anatomy, some principles of the approach, the technique, and then give you some examples. And really want to impress on you the wondrous views that you will see, the amazing vistas that you see in the Sylvian fissure. I had a former mentor, Bob Maxwell, who used to say, "I would love to spend a while on the isle of rile." So something we don't hear it spoken of as the isle of rile, the insula anymore. Rile being an expert in anatomist in previous centuries and lecture. And I wanna also highlight the point that I really didn't learn the technical aspects of splitting the fissure really well in residency. I mean, we did it for sort of the obvious lesions, those where it's typically thought to be most clinically useful exploring insular tumors, removing insular tumors, middle cerebral artery aneurysms. And that was really the only time we used it in my training. But there are suprasellar lesions, sub-cortical insular lesions, opercular epilepsy lesions, even olfactory groove meningiomas that we use it for. I learned the technique by watching colleagues of mine, like Dr. Cohen, like Dr. Marcos, like Dr. Sammy and surgeons all over the world who employed this technique and by watching their videos and reading up on it. So, again, a brief outline, we'll talk some historical notes, the anatomy, the principles of the approach, the technique and then I'll give you some examples. So Galen was really the first to describe the cerebral cisterns about the year 200 AD. Galen was a Greek physician. He moved to Rome, actually took care of the Roman gladiators. And it was in those fallen gladiators that he did some anatomical dissections and also in primates. Varoli the first to describe the arachnoid membrane and Vesalius actually named it, Vaselius who you see down here in 1670. Curiously, however, Vaselius did not, he was the father of modern anatomy. He did not recognize that the Sylvian fissure was there. He thought that gyri were basically randomly arranged on the surface of the brain. He's considered the father of modern anatomy. In 1543, he wrote this, "The gyri or convolutions of the brain are found with the same frequency over the whole surface of the brain and I think they could be perfectly compared to the clouds drawn by a school child." Indeed, I mean, you don't see in his diagram here, any Sylvian fissure. All of the gyri looked to be the same. So, he thought they were simply randomly assigned. So, who was it that first discovered the Sylvian fissure? And we were talking about this a little bit before the recording. We'll of course, leave it to the Italians who at least claimed to have discovered BlueJeans, piano, the radio, espresso, newspapers, wine, et cetera. But yes, the Italians also discovered the Sylvian fissure. First identified by Fabrici d'Acquapendente, leaning water is what that means. But Fabrici d'Acquapendente was famous for being really the most authoritative anatomist of the second half of the 16th century. He also was recognized as having exceptional medical talent. He taught, or he actually has patients included, Galileo Galilei, Paolo Sarpi, the Grand Dukes of Tuscany. So he was really a well-recognized physician and anatomist at the time. He wanted to create a grand work, sort of a reference book that was containing more than 300 illustrations painted by hand in natural color that would represent literally every detail of the human body and the anatomy of many animals. He was the Chairman of Anatomy and Surgery at Padova which was a very famous seat at the time, Vaselius also held that seat earlier. And, this was going to be called the Theatrum totius Ani Molly's Fabrica. It was begun in 1591, never completed and never published, and only the colored illustrations remain. And they're currently preserved in the Sun Medical Library of Venice according to his will. Here is one of those plates that was drawn. And you can see anteriorly here to the right of the image, the frontal lobe, you see the cranial nerves coming out here at the bottom, and you see the Sylvian fissure represented right here. But who is it really named after? Well, of course, it's named after Franciscus de le Boë or duBois, which in French means, of the Woods. So, it was a Latinization of his name. So, Sylvius, you can think of the Sylvan woods, the woods, the forest. He was born in Hannover, which in Germany, and many of you will recognize the site of another technically gifted and spectacular neurosurgeon Majid Samii currently there. He moved to Amsterdam, had a lucrative medical practice. He drew and described for the first time, the fissure in the book, "Casp. Bartolini Institutiones Anatomicae." He was from France, eventually moved to Germany. And as I mentioned, became Dutch and here is a slide from that work. And you see the fissure diagrammed here along with the isle of rile, the insula. It says, "F.S, so that is a Franciscus Sylvius. If you examine the indentations represented in that figure, you just saw you'll notice the deep, the brain is divided from one side to the other by the anfractuosa fissura which starts in the front near the ocular roots and their moves backwards above the base of the spinal cord following the temporal bones, dividing into the upper and the lower parts of the brain." And Sylvia's in his Disputationem Medicarum says, "Particularly noticeable is the deep fissure or hiatus, which begins at the roots of the eyes, oculorum radices meaning the optic nerves that runs posteriorly above the temples as far as the roots of the brainstem. Medulla divides the cerebrum into an upper and larger part and a lower smaller parts." So Sylvius was famous for other things. It is known that he described the pulmonary circulation. And at one point in time was speculated that he actually discovered Gin. Turns out that wasn't actually the case. Gin had been around long before that. There are many citations in the literature, but it's kind of a fun fact that you can take with you through your discussions of Franciscus Sylvius. But perhaps it actually was another Italian that described the Sylvian fissure even 150 years before Sylvius. And I would say it might've been Michelangelo Monoroti, another Italian who in the years 1508 to 1512 painted the ceiling of the Sistine chapel in Rome and on the Sistine chapel is this work here, which is typically described as the creation of Adam. But it was discovered actually or postulated even decades ago that this may not actually be the creation of Adam. If you look very closely, Adams eyes are actually already open here. You can see his eyes already open. And indeed, this is a representation of God. God actually he's not even touching Adam yet. So he wouldn't have created him, but perhaps this is God giving Adam knowledge or wisdom or in indeed reason. And I say that because if you look at the silhouette of God here, you can make out God's cincture, the belt around his gown as perhaps being the Sylvian fissure in the sagittal section of the brain. This was pointed out by many before me decades ago. But if you look, and if you're there in Rome, you can actually look directly overhead at this and see a sagittal section of the brain complete with the sash here representing the vertebral artery, the cerebellum in this area, the pituitary stock perhaps, or the brainstem here, the pituitary gland and stock here, even the optic chiasm and the Sylvian fissure. So the first neurosurgeon to popularize really and truly meticulously describe and use the Sylvian fissure is of course, professor M. Gazi Yasargil. And this was an article written by one of his students, his apostles, where he actually described it as you see here, the Yasargil Highway. Essentially everyone that uses this technique can trace back the use of this to professor Yasargil. And I would encourage any of you to try and study and obtain for your own library the micro neurosurgery written by professor Yasargil volumes one, two and three. I believe there's a volume four as well, but in volume one, he describes splitting the Sylvian fissure. This is from his book and you can see the cisterns outlined here beautifully. The cisterns around the optic nerve, the carotid cistern and the olfactory cistern and the Sylvian cistern. Yasargil described the fact that not all Sylvian fissures are the same. So you can see here, his diagram with sort of middle cerebral artery ghosted in deep in the fissure, the temporal lobe here, this would be a right-sided fissure, the frontal lobe here, and the crossing veins. Some fissures are widely open as you see here on the left, others completely stuck together as you see here on the right. And indeed some fissures with the frontal lobe indenting into the temporal lobe here, others with the temporal lobe insinuating itself into the frontal lobe. And that's where splitting the fissure as Dr. Cohen mentioned to you becomes quite difficult, tedious and needs to be meticulous. Yasargil actually said, the principal, this would be really the reason for splitting the fissure could not be more better explained than this from the professor. "The principle would be to... The brain could be completely undisturbed while dissection and clipping of an intracranial aneurysm was carried out. To approach this ideal, a craniotomy must take advantage of those natural planes and spaces, which nature has provided to expose the base of the brain without significant brain retraction." Another disciple of Yasargil, Professor John Fox. And Fox had a book when I was training, now decades ago called "The Pterional Perspective: The Atlas of Neurosurgical Anatomy" which is still available in electronic form. And you could probably purchase copies from used booksellers as well. Just a phenomenal book, both for description of splitting the fissure and for photos of the same. John Fox says, "As we have gained more experience, which I mentioned above, you gotta repeat this and practice it. We have opened the Sylvian fissure more and more." What were his reasons? Well, Fox says the small vessels are not compressed by the arachnoid bands during retraction if you split the fissure. Less resistance and had hence less brain retractor pressure to retraction of the frontal lobe as Dr. Cohen mentioned at the outset. Traction on one lobe does not pull and injure the other. Fewer bridging veins need to be sacrificed. The olfactory nerve can be preserved and minimal traction on perforating vessels and the aneurysm. Speaking of retraction, there are a number of studies out there that show that retraction can indeed be hazardous to the brain. A certain significant percentage of complications from aneurysm surgery and other surgeries resulting in elevation of the frontal lobe shown that a significant percentage of those complications can be directly linked to retraction. Investigators throughout the decades have applied strain gauges to cerebral retractors in order to quantify the force and the time factors. Here's an elegant study really came out I believe the surgical forum, it's the publication that comes from American College of Surgeons every year from their clinical Congress. And Dr. Jannetta, famous chairman at the University of Pittsburgh, Manuel Dujonny and others here, you see who did this study, where they put strain gauges on the brain to see what kind of retraction pressures were generated. And the average attraction time was 40 minutes. They found in their cases and handheld retraction often exceeded 25 torrs sometimes for greater than 30 minutes. You can see here, this figure here, what happened in one of the canine brain trials, where they were using a retractor to 40 torr for one hour, what happens to the temporal lobe. So retraction, bad. Why split the fissure? Well, you could say, for many people say, why climb Mount Everest? Because it's there. But the real reason is less brain retraction, more brain relaxation and better exposure. Why not to split the fissure? Well, it's time consuming. It adds time to every case, no question about it. No matter how facile or experts you are, it adds time. For instance, to clipping an anterior communicating artery aneurysm, where you might think and many people do. You just elevate the frontal lobe, go down to the ACA and the AECOM. Well, you got to put a retractor in to do it. You split the fissure first and many times, you need really no retraction to get there. So it is time consuming, adds to the case. The risk of pial and microvascular injury is not inconsequential. The embryology, just a real brief slide here about the fissure. It appears to form from a flat depression that's a closed through the convergence of two edges in the fetal brain. At first appears on the lateral aspect of the hemispheres before any of the other folds or fissures are present. And then subsequently there's a gradual confluence of the anterior and poster edges, which closes the depression. So it's actually completely different from the other soul side that occur in the brain and the growth of the gyri where the growth of the Sylvian percolate is inversely correlated with the growth of the Sylvian subarachnoid space. It's directly correlated in all of the other salsa and a growth of Gyri. How far to split the fissure? A diagram here from one of the dissections of Professor Rhoton. Well, I say widely, try and widely split the fissure, but of course it depends on the lesion that you are going to attack. And then some brief anatomical notes about the fissure and how it is divided anteriorly into a stem. And laterally divides into the anterior ascending ramus, the anterior horizontal ramus. Between the two you have the pars triangulararis and then posteriorly, the insulo-opercular part. Not all fissures are the same. Anyone who has a split the fissure will recognize that some fissures are easier to split than others. And indeed some fissures appear to be unable to be split or at the outset look like it's going to be just horrendously difficult because of the application of the frontal and temporal loads so close together. And then once you get through that outer arachnoid, and follow one of the nice little arteries into the fissure then you can see, well, wait a minute, this is easier than it looked at the beginning of the case. We'll show you some examples of that. What tools do you need? Well, the principles of the approach of course, are releasing the frontal and temporal lobes as completely as possible. Dynamic retraction only with the suction plus or minus patties. If you use a suction, it's most helpful to use sort of the Bel tip suction, the atraumatic suction. And then a suction, at least the one I use is the Fukushima section with the pear shaped opening that you can sort of fold your thumb over, to get less or more retraction as you need it. Suction using patties and moist cotton balls at the time to help hold the fissure open. Widely opened the corridor to the parasellar and subfrontal areas and use sharp dissection whenever possible. When I see a resident or trainee trying to do this, the first concept, and the first move is always to use something blunt, like a hook or a Rhoton six or some spatula to probe. When actually really sharp dissection is the best. And Dr. Cohen has described this in his videos and on this very website where you use the scissor with the tips together or something sharp. In general, sharp dissection are always better and even less traumatic. Believe it or not, it's sort of counter-intuitive but less traumatic than sticking a blunt probe into the fissure to try and separate things. And continuing again with principles of the approach, the use of gentle bipolar spreading. Teasing the arachnoid with a jeweler's forceps. Using gentle dynamic retraction, micro scissors, and the arachnoid knife. These are different techniques. You find one works and the other doesn't, you switch to that. Every fissure is different. Every brain is different. You might see that as you're beginning to tease the fissure with your jeweler's forceps, that it doesn't tear very easily. The arachnoid is completely scarred and you have to switch to using scissors. Other times, you'll see the teasing or splitting gently with the bipolar will help. Other times splitting with the bipolar begins to tear the pial. And so you have to sort of know multiple techniques and approaches. And so if one technique isn't working, choose another. Personally, I prefer to start distally to split the fissure. Some people start proximately. I do it distally and go distal to proximal. The downside of that in the event for instance, of a ruptured aneurysm, you're going to be coming perhaps to the aneurysm before you have proximal control. And I would say, as I've gotten more experienced, that's become less and less of an issue. You know where the aneurysm is, you're gonna try and avoid getting anywhere near the dome. You stay away from it, so you can still come lateral to medial. Superficial to deep or deep to superficial. You can see, we'll show you with some of the techniques here that really, once you start your superficial dissection and get into the depth of the fissure, then it becomes a deep to superficial dissection as Dr. Yasargil described. Moist telfa keep the Sylvian vein to the temporal side if it's a normal anatomical Sylvian fissure. Avoid bipolar coagulation if you can at all help it because as most expert micro surgeons will tell you, you kind of fuse the arachnoid at that point in time, and you lose that ability to use the arachnoid as a dissection plane and follow the arteries into the fissure. So where to use it? The obvious place in splitting the Sylvian fissure for MCA aneurysms, for Sylvian AVMs, for insular gliomas. The less apparent places that you can use it are medial spheroid wing meningiomas. You begin to split the fissure for that and the opportunities to split the fissure then become manifold. And as you're doing it, you identify the arteries first. So when you come upon the Sylvia and the medial sphenoid wing meningioma, you're not afraid of knowing where those vessels are, because you've already identified them in splitting the fissure. Olfactory groove or planum meningiomas. Even less of an obvious fissure split. And then for sellar and parasellar lesions. The tools of the trade, the round and sickle knife, the arachnoid knives, bell tip suction and micro scissors. Jeweler's forceps and bipolar. So let's go to some of the videos. And here is the first video. And this is really just describing what Yasargil said. When you peel an orange, okay, this is the concept of splitting the fissure. When you peel an orange, you don't go all along the surface of the orange with your thumb, like this. That's not the way to split an orange out. You don't do that. Because when you do you mastarate the orange. I mean, you essentially ruin it. What you do is you find an area where you can get deep, stick your finger in there deep, and then split it from inside out. Really a nicer description could not have been made. This from the professor himself. Let's go to the next video. All right. This is a video describing an approach I believe to just a couple of aneurysms in a woman with a horrible vascular path. But again, temporal to the right, I believe frontal to the left. We're trying to keep that vein. And you see I'm using a Yasargil knife a round knife and using suction with dynamic retraction. I always usually put a catenoid on each side so that when I put my suction onto the brain, it's not hitting the brain, it's hitting the catenoid. So then you find a vessel and just an artery, not a vein, but an artery. And you follow that artery into the fissure deep, and you follow that artery. And that artery leads you to the open fissure, which you see here. And then you can see you're coming deep to superficial. So this is another, just lifting up the frontal lobe, gently here as well, trying to identify the optic nerve, the carotid artery. Again, protecting the brain with catenoids. I encourage all my residents to do this because I have on countless occasions damaged the pial by bringing a suction or a bipolar into the field and just not paying attention, you hit the brain. So it's a good idea to protect as much of the brain as you possibly. Can you see the optic nerve there coming into view again, with lifting up the frontal lobe and just simply using the bipolar to tease the arachnoid. The carotid artery lateral it there. And then you'll see us gradually teasing the arachnoid here with the bipolar and using the suction. Here again is a bit more of the medial Sylvia dissection. And once you come from lateral to medial, you might encounter a place like Yasargil showed early on where the frontal lobe is absolutely stuck like glue to the temporal lobe or vice versa. And you just can't get it separate. By then, you've got enough CSF out that you can come sub frontally, as you saw me doing a moment ago. So work from proximal to distal. And then there's a place here in between where you will then come to meet. And the fissure can be widely open. You can see the horrible atheroma in that poor woman's arteries there. But it was a very nice explanation or very nice exposition of essentially the entire vascular tree. Okay, on the next one, this was a... I'm trying to remember. I believe this was a carotid aneurysm as well. And again, this is sort of the proximal fissure where you see, I can't tell right there exactly where the fissure even is. And so I knew where it was posteriorly, but I moved anteriorly. You can see where we're coming anterior. And you notice the use of sharp to suction rather than sticking a Penfield or a Rhoton six or some other blunt instrument in there. Using the micro scissors on high magnification. Using the mouse switch or the foot pedal to move your microscope around so you don't have to keep pulling your hands in and out of the scope. Many micro surgeons use the mouthpiece. I personally use the foot pedal, but basically same thing. It wastes so much time pulling your hands in and out. You lose the beautiful retraction you have here from the suction and you have to go back in and find it every time you move the scope. It's great to get used to one of those techniques where you actually use a foot pedal or the mouthpiece to gently move the scope. Here you see me following a vessel again, and you see the fissure is still stuck superficially. So I'm deep. I go deep and then spread it deeply so that then you can see where it needs to be cut superficially. So very commonly you'll encounter that as you are splitting the deep fissure, you get a lot of space down there, and then you can see where it needs to be cut superficially and gently teased apart. So you can see if you look behind where my a jeweler's forceps are there, the fissure is very deeply split deep. But it's still together here, superficial. So this is kind of like the deep to superficial concept, the sticking your finger deep into an orange, and then doing this superficial peeling and the suction later on. So again, follow the arteries. The arteries will lead you to the Sylvian fissure. Once again, we're down at the base of the brain that's the frontal floor. And you see the olfactory nerve there and the optic nerve to the right. Again, sharp dissection with micro scissors. I don't use a lot of mannitol or CSF drainage typically because I am always worried or concerned that I'm gonna be draining so much spinal fluid out. The fissure will be bereft of CSF. It behooves you in most cases like this, if you really don't need to, you don't have an acute subarachnoids hemorrhage or a very swollen brain to avoid external CSF drainage if you can at all help it. That was just a sort of a fissure split for approximal ICA aneurysm. The next case I believe is a craniopharyngioma perhaps, let's see what the... Oh no, this is a middle cerebral artery aneurysm that was coiled at another institution when it presented with a sub arachnoid hemorrhage. Was actually a very reasonable coiling. This is again, sort of a view from the inside showing you at the top left of your screen there what the aneurysm looks like. I think if I had seen this, I probably would not have opted for coiling as the original therapy, but this is what happened a year later. The aneurysm as you can see regrew quite a bit at the base with the coils protruding out. And so again, in a delayed fashion, when this was discovered a year and a half later, we began here for splitting the fissures superficially. And again, this is the typical reason for splitting the fissure for dealing with a middle cerebral artery aneurysm. So we're splitting the fissure, you see the large Sylvian vein there on the right, trying to keep that to the temporal side. Again, using different techniques here with the small bipolar gently spreading. When you have one instrument in your hand, I was always taught, use that instrument to the utmost. Use it every way that you can until you don't need that instrument anymore. Every change of instrument is wasted time, wasted movement. So again, just sort of protecting the brain with my catenoids using the bipolar. If the fissure doesn't split nicely with the bipolar, you use a different technique. This was finally when we had gotten to the aneurysm, you see the brain, the Sylvian fissure split very nicely. And this aneurysm just, the miserable coiled aneurysm that we've had to deal with on occasion pulling out the dull scissors that we use just for that. And here the final clip application after literally spending 45 minutes removing coils under occasional temporary occlusion until the aneurysm began to bleed. And the final clip application, you see the fissure widely spread , no retractors needed. And the clip applied to the aneurysm preserving the MCA branches. At the end of the case you'll see I've got the fissure really protected in a number of areas with various catenoids again. For the explicit reasoning of reason of keeping me or my trainees from hitting the edge of the brain by an inadvertent suction or instrument. I think we have maybe one or two more videos. This next one is I believe the craniopharyngiomata. One of probably the less obvious if you think, why the heck would you split the fissure for that? I mean, that's just a sub frontal craniotomy, pterional craniotomy. Put a retractor under the frontal lobe, you lift it up puncture the assists, take out as much tumor. You see, it's a very, very calcified lesion. But this is the view you get from a widely split fissure of that craniopharyngioma. You see the anterior cerebral artery right there going from right to left. The middle cerebral coming out towards us and going off to the right. And this is sort of the exposure between the optic nerves. You see the calcified craniopharyngioma there as I push on it with the suction, it deforms the optic nerve. So it's like, you don't wanna really take much more of that out for fear. But see the fissure split starting quite far lateral lined with catenoids, temporal lobe to your right, frontal lobe to the left, and just really a magnificent view of the parasellar area from a widely split fissure, without having to stick a big retract. You see the MCA coming right out there into the Sylvian fissure completely exposed. So it does require more time, no question about it. In the slide on why not to split the fissure, it's gonna take an extra 30 minutes to do this, to get your way down to the aneurysm. But it's indeed much, much less atraumatic. And then maybe I think we have one more video. This is a video using the technique in an olfactory groove meningioma. Another one of those things where shoot, why the heck would you split the Sylvian fissure for an olfactory groove meningioma. That is a sub frontal or interhemispheric approach. You don't need to split the fissure. Well, Majid Samii and others have written about this and you see how the tumor extends back over the plainim. And they wrote about how the results in taking the tumor out via a tyrannical approach like this were better, no question about it. And I have completely switched. And in my cases to remove olfactory groove meningiomas through the pterional approach for the reasons mentioned. You get early exposure of the vessels, the aitus behind the tumor. The downside is, your optic nerves come in towards the end, but you can also see them with a widely split fissure early on. This is not the most appropriately centered video, but you can see again, or you will see as we remove the catenoids and zoom out. Again, the wide wide exposure by splitting the Sylvian fissure. Literally there's the optic nerve down there without using any retraction to lift the frontal lobe. And I had resected many, many olfactory groove meningiomas via a sub frontal approach or interhemispheric approach and was really disheartened by the fact that even when I didn't use retractors the frontal lobes looked like they were really beaten. And after switching to this technique, I found that the recovery has been better. The damage and trauma to the frontal lobes is really almost negligible. And you simply de-bulk the tumor from the inside again, using a lateral sub frontal approach. And I think that is it for the videos. And the technical pearls that I just wanted to leave you with are begin where the frontal and temporal lobes are in apposition. If you can begin at all where the frontal and temporal lobes where there's transparent arachnoid. So some of the cases you saw there was no transparent arachnoid, you just sort of had to find the Sylvian vein, just go a little bit on top of it. Stay on the frontal side of the Sylvian veins if you at all, possibly can. Once you enter the cistern, go deep, just as we demonstrated, go deep as professor Yasargil says and gently spread the lips of the fissure from inside out applying pressure on both sides to the walls. And the goal would be to keep the pials surfaces intact. And that is, if you start and where I and others at times have gone wrong, or when you begin to get pial violations. And again, the more you use the technique, the more versatile you'll become with it. Any tumor that I see that is around the sphenoid ridge and the greater ring of the sphenoid parasellar, I will routinely split the fissure. Again, I began doing this really after residency, as I watched my colleagues and saw people like Dr. Cohen, showing these marvelous videos with the fissure split. And so actually going ahead and doing that where it may not be the first thought that enters your head, but where it can help you. I'm not saying to do something unnecessary, but to get practice at doing it. I think that's the very, very important thing. And then to use your arteries as a guide to the fissure. Find that artery, however, small it may be that is coming out of the fissure and simply follow it down. It will lead you to larger and larger arteries, and then eventually to the major M two branches. So in conclusion, splitting the Sylvian fissure is a useful skill in approaching diverse pathologies in the fissure, parasellar, and sub frontal areas and minimizing retraction. The technique is best employed as I mentioned, using sharp dissection and gentle pressure on the walls of the fissure. Use an inside-out technique, start distal, go proximal. That would be my preference. Keep the pial surfaces intact is the goal and again, use the arteries as a guide to the fissure. All right, thank you, Aaron.

- You're welcome, beautiful lecture. Elegant work, Paul. I really enjoyed it. I wanna emphasize one more time, it's really underestimated. How difficult split fissures had. It's really also estimated how important it is. I think if you don't use the mouth switch or the foot pedal, the Sylvian fissure split will become very difficult. And it becomes arduous and people give it up. You have to make the microscope part of your face. And to do that, you'll have to use either one of those things. I remember out putting with Yasargil about 16 years ago, and he was still using that 1951 original microscope. Yes. And you have the red circle in his operating room where you can step out of it at any moment. And he was operating and just in the middle of doing a sub frontal IVM, he turned to me and said that you have to create a microscope that becomes like a loop where you can just fix it on your face. And I think that's what's something we're challenged with to this date. Luke, let's go ahead and start my slides. I'm just gonna echo some of the very valuable thought processes you brought up that are so important. And that's really atraumatic Sylvian fissure. You can see that on the left lower image, this is after an MC clipping. You can see a more definition on the right with a perforator in the finished ration. And you have to make it look that almost you are not there. You're almost like this thief in the night. You just come in and go. You make it absolutely atraumatic. The brain floats on water and CSF because it shouldn't even touch anything in regular conditions, letting alone being retracted with a fixed retractor. I think those are ideas that are really important. You brought up this nice video of the anatomy, which I don't think is that important as long as you understand that you really have to follow the arteries as a roadmap. During your guide, the arteries are absolutely critical. They pulsate, they create those exaggerated CSF space is around them. And they will create because of their pulsation, those exaggerated CSF way of CSF pathways, are your absolute highways. Your sugar highways, or comarata highways, to the critical parts of the brain at the base of skull. I wanted to briefly show the star. It's the Sylvian point where it's the most widest area of the fissure laterally. That is your start, just look at the fissure. And it's almost impossible to know how difficult or easy fissure is by just looking superficially because superficially, most of them look difficult, but that's because where they come closest to apposition. But the moment you start opening them, you'll see they can become very easy. So that's something that you wanna remember. So I wanted to review again, the most common mistakes that fellows make. Most of them start from here. And as you know, there's different cross-sections across the fissure. Here you can see one of our illustrations from the neurosurgical Atlas. Here's plane A, section B and the section C. You can see section A is where the temporal polarity is. And that's where the frontal and temporal lobes really stick together. This is a tough location. Again, you're gonna have a tough location posteriorly along the posterior Sylvian fissure, which really tight. Between the two, you're gonna have that Sylvian point where things are wider. And that's, embryologically because of the formation of that C in the brain. And also because there's so many more vessels that are larger in this region, obviously to create that pulsatile motion to create a generous Sylvian cistern. So you start from section B, you can start section A or C because you're really gonna injure the cortex. You start there, you get underneath. You find the arteries that going deep to superficial and let the arteries guide you. If you don't have arteries, you're gonna destroy the pial. There's just no way around it. If you're now using mouth switch, if you do it using foot pedal, you have to come in and out so many times because you're as high magnification and the depth, even in a very little change in depth, it goes out of focus and it really frustrates the surgeon. And that's why people just give it up. Say, I don't wanna split the fissure. And so when you start here, you have to remember, and again, we're starting right there. We're starting right there. We start down here. Many people just wanna continue as if this is the pathway. When in fact you have to direct your attention this way, I can't emphasize that more. This redirection as you're operating is so important otherwise you're gonna get lost in the Sylvian-

- Its not perpendicular.

- Exactly, well said, Paul. Please feel free to comment anytime you wish. You have to change your pathway. This is so important. It is amazing how such a simple concept is really, really not appreciated. So you have to redirect and find M2. Then moment you find M2s, it's fun. It really is a lot of fun, because the planes just fall away. You can see this gorgeous corridor opening in front of you. And just that brilliant prestigious anatomy of the fissure is just enjoyable to dissect. Obviously you start here and then move in and out inside to out to go to this region or go to this region. So this oblique trajectory is really most commonly lost. And people just enter here. I've seen people get lost here and they feel like, oh, I can't, where's the fissure? So just please keep that in mind. Do you have any other thoughts here Paul?

- No, this is a really excellent slide because when you talk about going distal to proximal, you don't start at the most distal location of the fissure. You're actually somewhere between and then you can move back if you need to something and the distal fissure insula, but then you would go forward to go anterior. But yeah, and I also can't stress enough, the fact that what you said about the microscope as an extension of your eyes. Dr. Heroes taught me microsurgery and you would just see him moving the scope all over the place with the foot pedal, et cetera. And in this case, I mean, when you're splitting the fissure, you said there's so many times you're going in and out of focus, deep proximal. If you're taking your hands out every single time, it's gonna become very tedious.

- I agree with you, Paul. If you use the mouse switch, and if you're comfortable with microsurgery two handed surgery, not that the suction is just sitting there uselessly, but if you use it as a gentle dynamic retractor, and if you use the bipolar, specific bipolars that works both as a spreader, single this sector, when it's closed and by just that gentle avulsion action, you're open to find arachnoid bands. Again, a bipolar would become a three instrument spreader when it's closed as straight to sector number six, and number three, you will use it as grabbing those arachnids and gently avulsion them. You can eventually using the mouth switch and three instrument at the same time, which are not exchanging whatsoever. I bet you can change split the fissure under 20 minutes, even under the most difficult circumstances. And that's a video we're gonna reveal momentarily. So now that we are gonna... This is sort of a very minimal section for a pectoral aneurism, where you really don't do much. But most often we need to split it up a little bit more. And I'll briefly review that Paul, as well. I can emphasize the idea of this orange that you mentioned. If you try to hold an orange and open it, you can't, you have to get inside it from the top and then get the slices out. And that's such a critical function that is often very difficult to understand. And as you can see here again, coming inside, and then going outside here, just keep that in mind. And remember, and I usually dissect the superficial thick membrane of where the veins are via jeweler forceps. I use two jeweler forceps and just avulse the membrane. And it takes you under 30 seconds. The work that will take almost 15 minutes to use the micro scissors because a gentle avulsion allows the veins to dissect the membrane, atraumatically for you and let the veins fall away rather than just often when you try to do them with micro scissors, you actually injure so many of the veins that you quite coagulate all the superficial veins. Because the veins are so adhered here into the superficial arachnoid. They're so encased in it. So you really need a function where you do gentle evulsion let the planes that are there open by themselves, rather than you forcing the plane using a micro scissor. So let's go ahead Luke can bring the video, which we did last part here and I appreciate that. So this is again splitting fissure inside to outside small MCA. It was in the image of which we showed. And again, focusing on the idea of efficiency, not sitting there for 45 minutes, proving to everyone that you can do this. You really have to have three elements in Sylvian fissure. You have to be meticulous, atraumatic, which are both one and then efficient. In other words, if you say, okay, I can do an amazing Sylvian fissure and it takes you 45 minutes to do it, I think you'll find out that that's just not practical to do that. So this is a 34 year old female with an unruptured right-sided aneurysm, small one where I'll do a treatment because she had a history of suffering from another aneurysm. And that was the reason we did that. And here's the aneurysm you can see here. Here's the positioning, you put a single pin like the ashraveil. And here's the exposure. You can see the fissure. This looks like an easy fissure, but in fact, when you get into it Paul, you find that it's more difficult. I use that round knife, you showed that very well. And I open up the membranes and then I use the fine jeweler forceps. And you can see here so beautifully, really opens up for you and so efficient and lets the veins to really remain intact. Remember that vein who was crossing it just really open itself up. And I don't use the coagulation whatsoever. Why? Because I think that injures the pial surfaces, if the pial surface is oozing, I just put a piece off a cotton ball there and give it a couple of minutes or just irrigate. You can see how the jeweler forceps just opens up the hole expressway to the insula and parasellar areas. And again, there's a little bit of bleeding, but either somebody gently uses the suction for me. In fact, this is actually one of my residents working. And here you can see that atraumatic just gentle motion of the arachnoid bend. If you really want to do the same centimeter, it would take so long more using the micro scissors and the vein would be gone by then anyways. So using that by hand it, which again, requires that a mouse switch to be able to open the superficial arachnoid membranes that are thick. And they're in fact, the most difficult. After that's done, then I just go very deep, just go as deep as you can and you find an artery and then come to outside. And that's so critically important. After that, it's gonna be really micro scissors because micro scissors can become scissors straight re sectors and gentle retractors all three. Every instrument is Sylvia lab, I just keep the suction, which is metal, which is very soft as a surface. And I go deep. And I just, as you can see, I remain in focus, no matter how deep I'm going. And then I'll use the gentle spreader action of the bipolar forceps as I move anteriorly. So this was a fissure that appeared apparently relatively straightforward, but you can see it's very adherent. And I just parked that suction like a gentle, fixed retractor for a little bit while I'm doing the dissection. And as you can see, it's just such a beautiful, pristine anatomy that is so enjoyable to start the case with. Because see the suction gets parked. It's not just moving, hitting the pial causing an injury. It gets parked, I'm very efficient, action is completed. Then it moves to the next step. And I think that's the critical part that I've had a very hard time Paul to teach people that the suction has to sit there gently, not necessarily move and bang up the pial at all times to really define what is the important functional dynamic retraction as so many people talk about. After you get along the anterior part of the fissure, again, inside to outside and so easy to split the fissure and tear or allow what we call the sphenoidal segment of the fissure. Paul, do you have any other comments?

- Cut it.

- And here you can see so atraumatic the pial surfaces are. And then you, obviously it is from a retraction because of the oblique surface to the aneurysm there. And that's what you have to really cannot put a forceful retractor here the aneurysm is pointing down. And you can see the pial membranes or so protected. Here's the clip. But the critical part is that choreographically beautifully like an Italian music apro of the movement. There is no break dance movement. There's no violent movement. There's no non deliberate movement. There's no wasted movements. Because every movement, no matter what injures brain. And therefore we have to remember to keep that idea of the phenomenon. And here is the final product that surgery is really a very effective final performance of a dance. Choreographically, beautifully planned not necessarily a practice. And so for Sylvia fissure section to be done, one has to practice it so many times that when you do it really, it just comes to you so fluidly. And just like a piano player when you're in front of 3000 people, they're not gonna be practicing their performance. It is the final performance. Every note has to transition to the next one. And I do believe that neural surgeons have the hardest time with this transition. Luke, can we go to the... Yeah, thank you. And as neurosurgeons Paul, that philosophically we'd have the hardest time making that transitional movement from one dance move to the next. And the brain is our partner and we have to let the brain tell us how we dance. We don't tell the brain how to dance. They guide us, they direct us. And for us to be able to really have those gentle movements that are so every moment is perfectly 100% efficient in completing a task, that art of science of understanding every fine move and the most amount we can get out of that is really what I have tried to learn. The science of operative movements. What I really have to learn after editing 15,000 hours of operation in the Neurosurgical Atlas. And I can tell you that the residency doesn't teach you much. I can tell you that it might teach you some obviously principals, even at the beginning of your practice, it's so difficult to know what you're doing. As you get two or three years through the practice and you get your own videos. And I remember I was five years through a practice. Everybody's thought I was a great surgeon. I thought, I'm walking on water, I'll get my surgical videos. I started recording, I look at the video after the emotional intensity of not being in surgery. And I would just look at it and I would feel like I'm the absolute worst surgeon possible. Just so humiliating. So many inefficient movements. And with time I decreased the time from doing an IVD for MI fissure spasm to two hours to an hour, 45 minutes, an hour, half an hour. And right now I can say, I can easily do one in 40 minutes. I think that's the kind of operative technique that we have to focus on. And nobody can tell you that Paul. Nobody's gonna sit down with you and tell you that. And this is the problem with neurosurgical ego is that you become so entrenched. It's a self fulfilling prophecy in surgery. Your residents can't tell you you're not doing well. You yourself feel like I'm a neurosurgeon, I must be perfect. And then at that point, there's no self-learning, there's no self-reflection. And that's really the biggest trap that the moment you feel like you know everything, the moment you feel like you don't have to learn more. I always say, that's the only you must retire. Unless you continue self-reflection, continue watching your videos, just like a football game. Just like Tom Brady or anybody who is good watches their video many, many times no matter how good they are and they try to do a better next time. Any thoughts you have about those comments?

- Well, I think that's an incredibly prescient. As you did as well after, I continued after my residency and fellowship observing, going to meetings, traveling. I mean, I've been all over the country with either patients of mine or simply calling a colleague and say, hey, I wanna learn how you do that. Going down to Little Rock, going to Phoenix, going wherever and always learning. And loved your analogy, your vision of a musician performing. When you're splitting the fissure especially, you can't just go at it by road every way. You have to do what the brain gives you, what the individual fissure gives you. And if something's not working, you kind of move very slowly on the wave to another fluid movement. So I thought that was a beautiful concept. But I would just encourage self-reflection, again, like you say, like professional athletes do reviewing the films after you've done something. There's nothing more instructive and sometimes humiliating than like you say, taking a look at those operative videos. I'd encourage those who are novel and new at learning this technique to do that sort of reflection really on a regular basis.

- Yeah, very beautifully said. And I do believe residency gives you certain tools, but the most 90% of your learning occurs when you start your practice. When you build a practice, which takes a few years, and now you have your taste is coming in. And now that's the time when the real learning occurs. That's commitment to surgical excellence, that's self reflection. And really that's the time where you really gonna prove if you are really a surgeon that can do this right or you're a surgeon that just gonna be static, be stagnant and not necessarily advance the outcomes. It's really up to us. It's not up to our residency. It's not up to our patients. It's not the legal aspects of medicine. It is us as neurosurgeons that we need to prove that in addition, it is the captain who really gets the ship to the shore under turbulent conditions and a difficult case. Otherwise, any of us can do great in a very simple, easy case. So some personal reflections on, I think some surgery. I wanna thank you, Paul, for truly being a dear friend, such a practical surgeon, superb technician. An honor to have you today and look forward to having you with us again.

- It was an honor to be here, Aaron, thank you, my friend. I really appreciate it. And thanks for the invitation.

- You're welcome.

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