So, a quick show of hands, how many guys have done a far lateral approach? So, pretty much everybody. It's kind of interesting. Five years ago, asking that question about endoscopic and a nasal, pretty much no hands, and the same way with far laterals. It's really interesting to see how it's spreading across the United States. So what we'll do is we'll finish up the lecture series talking about the far lateral approach to the skull base. And so, with Professor Roten not being here, I just don't think this meeting can occur without showing this slide. So does anybody know, I went by a couple of stations yesterday and tried to get people to dissect this out. Does anybody know what this is? Say it loud. Say it proud. Lymphatic sac. That's right, the lymphatic sac. And so, as we were talking about yesterday, when you have endo-lymphatic sac tumors, they're going to be a little bit inferior and lateral to the IAC, as you can see right here. So, with the far lateral approach, we've had the anterior approaches that we talked about, the anterior lateral, the straight lateral, and then the posterior lateral approaches are also in this mix. And what you found traditionally is that the anterior approaches were a bit suboptimal. I mean, prior to the modern endoscopic era, it was very difficult to get to this area directly through the clivus. You had problems with closure, et cetera, et cetera. As well, with the strict posterior approach, you really had problems with retraction. So these anterior medullary lesion, anterior foramen magnum lesions were optimally approached through this far lateral approach. When you go to these skull base meetings, one of the most difficult things, at least for me, when I started, is it's kind of this word soup thing. I mean, people start with one word, and then they add another word to it, and another word, and finally it gets to be very confusing. With all skull base approaches, I think you guys have understood, you guys understand this after this course, but really they're modifications of the theme. And with the far lateral approach, it's really no different. These are the basic modifications, so when you look at the far lateral approach coming down into this region, you have the retrocondylar approach, no resection of the condyle, sneaking in right behind it. You also have transcondylar, which are partial and complete. So here you can see there's a partial transcondylar resection, here's a complete. Why do we really talk about these two? I mean, what would be a sequela of a total condylectomy? Yeah, spinal instability. So that's why, if you can get in here and do a partial transcondylar, you can hopefully avoid that situation. And then you have the supracondylar approach, hypoglossal schwannomas. This is a great approach for this, lesions that really kind of touch the foramen magnum but don't go below that. The supracondylar approach is really nice, and then the pericondylar, which is out here in that jugular fossa area, that's another modification of the far lateral approach. And so looking at any skull base approach, you really have to hammer home the anatomy. You have to understand the anatomy to really understand how to do these types of procedures. And so here we're going to review the bone, the muscles, the arteries, and the veins. And so looking at the bone, a couple things that you want to understand. You want to understand this occipital condyle. So if everybody kind of starts that PGY-1 year, I bet if I asked you where is the occipital condyle, and this is for demonstration purposes, so don't tell me if I'm wrong, but I would bet you would say it would be in the middle. So most people kind of have that picture of the condyles being in the middle, but really they're in the anterior third of the foramen magnum, as you can see right here. The other thing you need to understand is where the hypoglossal canal is relative to the occipital condyle. So is it in the posterior third? No. Is it in the middle third? Sort of. And it typically starts at the middle third, anterior third junction, and then goes not only laterally, but anteriorly. So you really need to understand that as you drill the condyle. And then the other thing which Dr. Robertson went over is this C1 vertebral body. It's really, really important to understand not only the midline process, but also the tubercle of C1. Really if you think about it, if you stay between those Phil Go posts, you're fine. If you go anterior to it, just anterior to it, I mean, what are you in? A lot of venous bleeding. I mean, it's really, you never want to go past this area because this is a whole other world of anatomy. Now when we first, at least when I first started reading about these approaches, I mean, it was very apparent that everybody wanted to kill you on the muscles. So we're going to continue that tradition right here and go over these three layers. So looking at the superficial musculature, what are the two muscles that we include? Sternocleidomastoid muscle, trapezius, and then you peel those layers back and you have these two muscles that are in that middle layer. What's that muscle? Yeah. Yeah, and so you can see the orientation, the splenius kind of runs from that lateral to medial, very apparent in the operating room, and the semispinalis really runs more vertical. And then the suboccipital triangle, what's this muscle? So if this is C2 here, this is the subocciput right here, mastoid tip right here, what's that muscle? Superior oblique, this muscle, and then that muscle. Yeah, so minor typically subocciput to the tubercle of C1, superior oblique here goes from the transfer process of C2 to the subocciput, inferior oblique, same over here, I'm sorry, C1, inferior oblique, C1 tubercle to the splenius process of C2, and posterior major goes from C2 to the subocciput, minor from C1 to the subocciput. And then arteries, I mean vertebral arteries, the obvious one, so you have this V3 segment, there's a vertical segment and a horizontal segment. The other thing really to point out here is that if you want to identify this vertical segment, if you follow C2 out, it's always going to cross over the posterior aspect of the vertebral artery. The other thing is you have this posterior meningeal artery and then this recurrent meningeal artery that you need to be aware of occasionally, you can get in there and get some arterial bleeding and really think that you got in the vertebral and it's just this posterior meningeal artery. And then the other thing I guess to be cautious of is the occasional pica that comes off extra durably. And then veins, I think it's just safe to say there are a bunch of them. There are always people that talk about blood loss on this operation and I really don't think that's a true issue as long as you try to stay out of that venous plexus. I mean if you just dive right into it, I mean, you know, I have no doubt that you'll see a lot of blood, but if you try to stay subperiosteal in your dissections, you can really stay out of this venous bleeding. So let's go through the procedure itself. You start out with positioning, and one of the things that I will say when you start out in your practice, this is probably one of the things that's going to burn you the most often when you first get out there, because you really just take that for granted and all this positioning and how the head's positioned, the head's up to avoid venous bleeding. I mean you're kind of focused on the procedure itself, so this is something that often is overlooked, but I tell you, positioning is so, so important. What we do here is I put them in pins, Dr. Robertson does not use pins. I tend to rotate the head a little bit towards the floor, and you can see here I also flex the head. Some people don't like that because it changes that vertical segment orientation of the vertebral artery, but to me this is a really small window, the shoulder to here, and when you're working in that small space, especially for me on the left side, it's really a tight, tight area, so I try to open it up here, and I have not had any problems with the vertebral artery doing this, but you have to be aware. For those skin incisions, we have this retroauricular C-shaped incision right here. Bernard Georges, when he first wrote about this, he used this kind of more hockey stick incision, and you'll see people do it different ways, but this is the way we do it. So when you take down the muscle, essentially we take the flat forward, the retroauricular C-shaped incision, take it forward to the mastoid tip, which is right here, and then you're looking just straight at the muscle. So you've got trapezius muscle, a little hint of that there, splenius capitis, and here's the sternocleidomastoid muscle. So we're looking at this basically muscle mass here, and moving forward, I've gotten away from this H-shaped, and really just do more of this inferior limb, because after four or five of these, I really kind of looked at that bone as I exposed it right here, and looked at it, and decided that I'd never really done anything with it, so why look at it? So we leave this here, and basically take this down as a muscle mass. Carl and several others have a good experience with more of a minimally invasive far lateral, in which you just go straight down through the muscle, and that's fine, I mean the basic principles of exposure are just the same. And then the initial exposure, so you take down this muscle mass as one, you're not taking them down in individual layers, but you're taking them down as one, and one of the things that really took me a little bit in understanding this is when you read the textbooks, they kind of skip from making the skin incision to taking out the tumor, and it's really difficult for me to understand how the hell that muscle mass came down without getting in the vertebral artery itself. So what I do is I basically palpate that midline tubercle, I mean that's so familiar anatomy, always start in the middle, and then you can palpate the transverse process, and bovie over that transverse process, and you're releasing what muscles off of that. So superior and inferior oblique. So at that point I have a tunnel, and I really just take my finger and run it from that midline all the way out to that other hole, and then just bovie straight down, and so that makes this exposure really a five or ten minute process once you get the muscle down. And then at that point you've got this, the lamina of C1, actually this is C2 right here, this is the residual C1 lamina, but you've got the complete exposure in the vertebral arteries kind of sitting right there, right in front of your face. And then the dural opening, I like to hug the vertebral artery as close as possible, always, always, always remember about closure in skull base cases. So I don't want to be too close to where I don't have a cuff, because that can be problematic. A lot of the earlier case series of far lateral, there were lots of pseudomeningoceles, so you really want to think about closure, and in doing that I always leave a little cuff. But I do try to hug the sigmoid sinus and jugular bulb area as close as possible. I try to hug the vertebral artery as close as possible, because as we were talking about in the lab, skull base is all about trajectory. I mean it's not about 360 exposure, it's about trajectory, and I really want to be at this level right here. And then dural closure, these close very nicely primarily, typically at the junction between the posterior fossa and the cervical spine, it's a little tight in that region, and so don't hesitate to take a pericranial graft and sew it in place. But this is very commonly what it looks like. Here's the condyle right here, suboccipit right here, and the cervical spine stuff right here. So as far as bony exposure, one of the things that did not go over, you essentially want to take off the lamina, the hemilamina of C1. If you need that C2, take that as well. But you want to hug that sigmoid sinus and jugular bulb in your exposure. And once you're finished, I mean it looks somewhat like a comma, in that you've got this wide exposure here, and then it tailors down to this tail right here. And then muscle closure, it's just taking that muscle mass back up and sewing it in place. So you can see here, here's pre-op, here's post-op, real nice cosmesis. You can see here on the MRI, the muscles come back right where you left them. And then the skin incision, we carry it into a preexisting skin crease right here and here. So no comment about the faces, but I think the skin incision looks okay. And then this is a video to kind of tie it all together, and you can see the park bench position right here. Tape the shoulder down, all pressure points padded appropriately. Carl knows Wayne Ham, I mean there's not one thing on this, one piece of skin on this patient's body that doesn't have padding on it. Retro-auricular C-shaped incision, the skin flap is rotated anteriorly, so sternocleidomastoid muscle right there, splenius capitis right here. This is the muscle mass up in here that we don't take down. And then once we've taken the muscle mass down inferiorly, this is the transverse process of C1 right here. This is the tubercle of C1 back here. And then let's just connect the dots, and you can see right here, this is just taking that tunnel that we've made and removing the muscle mass from that fat that always overlies the suboccipital triangle region. And so once that muscle is taken down, it's easy, it's a nice exposure. Here's the hemilamina of C1 right here. This is the sulcus arteriosus of the vertebral artery right here, and you can see here we're just kind of pushing it up to further define that region. And so now you have the vertebral artery as it comes in. You know the vertebral artery always follows the condyle, so if you can think about the condyle, just think about how it's oriented, the vertebral artery's wrapping right around it. So if I have the vertebral artery as it pierces the dura right here, I know that's exactly where I need to be. And so we've taken off the suboccipital here, taken off the hemilamina of C1. We always like to irrigate with a little bit of blood, and then I'll move things forward just a little bit. This is just drilling over the, drilling just up to the tubercle. I really do a lot of retrocondylar approaches using the far lateral approach for things like chordomas and malignancies. I will do more of the transcondylar approaches, but because Bonine pathology typically displaces the neurovasculature away from the operative field, you don't really have to take the condyle out. I mean the tumor's done the dissection for you. So moving this forward a little bit, you can see here's the opening. So we open it right behind the vertebral artery right here, and you get a little CSF. And then once you get it open, your trajectory is right in line with the tumor. So a little variation that I do want to talk about, you won't really see this in a lot of these cases, but this worked out really nicely for this case, is that this dentate ligament, occasionally in situations where the pathology has not displaced everything, you can take the dentate ligament and really roll the cervical cord out of the way. Of course, you won't want to place too much traction, but you can take a suture and just tie it through that dentate ligament and roll the cord back, and you can see this is an AVM in that region, and it really creates nice exposure. So lots of little modifications that you can do to enhance your exposure with this far lateral approach. So moving on to pathology, I mean one of the things that is obvious in this course is everybody teaches the approaches, but you got to really know when to apply it. And I think meningioma is probably the most common tumor that we use the far lateral approach in. And so this is a lady that's got a classic foramen magnum meningioma. Very typical far lateral approach, retrocondylar variation. You can see here, open the dura right behind the vertebral artery as it goes into the dura. The dural opening is very straightforward, linear. And then you got the tumor exposed here, and there's that dentate ligament again that we're dealing with. One of the things that you'll see as well, you'll see the C2 and C1 nerve roots. I freely take C1. What does C1 innervate? Dr. Robertson just said that we're, talked about a certain muscle, the rectus capitis lateralis. So you can take the C1 nerve root freely. C2 I take freely as well, and I really don't worry about that at all if need be. And then pica aneurysm is also very, very common, a great exposure for this area. You can see here, here's the aneurysm, very straightforward clip, and then ICG filling of the pica there. Vagal cranial nerve schwannomas, I mean these are things that are often gammonite, but occasionally surgery is undertaken. You can see very nice exposure of the entire tumor. Here's the seventh, eighth nerve complex. This is nine, so this was a vagal schwannoma. So this patient underwent a subtotal resection with gammonite, because she had intact vagal function. She's done very well. She's about eight years out on that. And C1 schwannoma is very, very uncommon, but far lateral approach is a very nice exposure. You can see this is really a midline lesion, and so coming from this far lateral approach, see the tumor, here's the condyle essentially here. So the tumor's done all your dissection for you, all you gotta do is get there. Once you get there, you can enfold it, enfold it, enfold it, and then get the whole tumor out. C2 schwannomas, I mean sometimes you hear people give these videos and talks about marked spinal cord compression, and I see videos like this, and all the people here know that's really not a lot of compression. I mean you can follow this if need be, but I like to scare people when they have tumors and let them think they're gonna die. So they went ahead with surgery, and it was very straightforward, of course. Neuroteric cysts, not an uncommon pathology when you talk about frame and magnum lesions. And once again, benign tumors, all you really gotta do is get there. This is the condyle here, it's been drilled down flush with the condyle, vertebral artery right here, this is the arachnoid, here's C2, and you can see here, here's a little branch coming superiorly, likely part of the accessory nerve. C1 and the accessory nerve about 20% of the time will have a common junction, it's really important to know that because occasionally you'll get confused that it's going out the C1 frame and then take that nerve and it might be the accessory nerve, so it's a really good picture of that connection right through there. But here, all you gotta do is get the window and you're fine. Chordomas, I think everybody will agree that you need everything in the kitchen sink as far as approaches to deal with chordomas. This was approached through a far lateral primary bone pathology, occasionally you'll get this, this ended up being a plasma cytoma, but far lateral gave a nice approach to that. This is kind of that variation, that supracondylar approach for a dermoid, and I won't really go through all this video, but once again, getting the far lateral exposure, you can see here, very, very little retraction. This is the 9th and 10th nerve complex, 11 coming up from below right here, and here's the dermoid right here. A little FYI on dermoids, don't let the material touch anything, I mean it's extremely caustic, so once I even hit that dermoid cyst right here, the facial nerve of course is right here, but all of a sudden the nerve monitoring just went off for about 10 minutes, so about 20 minutes later of irrigation it calmed down, but be very wary of dermoid cysts, do not let the cyst contents spill out. Melanocytoma, another lesion that can be in the frame of the magnum, not common, looks like a meningioma, but it's black, benign. Synovial cysts, this is one of Dr. Robertson's cases, but preoperatively really wasn't known what this was, far lateral approach here, you can see opening that, you're actually going extradural there, this is inside the dura, and it was just synovial cyst contents. This is that AVM that we saw, nice exposure here, resection of the AVM, very, very little retraction, here's the dentate ligament, and it's moved over there. And then congenital lesions, we've kind of had a run of these recently, but occasionally you get somebody that comes into your office that has these congenital lesions that they've been living with for a long time, you can see pretty decent compression of the magnum, and what you can do with a far lateral approach, you can easily get in here in a nice fashion, but I will caution you, don't ever, ever, ever take one of these out without fusing them. I thought that you could get this thing out, and I showed it to Menezes, and he was very adamant that you never take these out without fusing them, so we did an occipital-cervical fusion on that person. And then we've had a couple of dura laevi fistulas, this is really extradural here, really nice when you get in here, you don't really have any bleeding as long as you stay outside of the dura laevi fistula. Here's just basically cauterization of the fistula itself. What you're trying to do here, just like an AVM, is resect the mass, and this is what we're doing here. With fistulas, you want to take the vein last, just like with AVMs. So all this stuff is really busy, but you want to take out the mass and then place one clip across the vein as the fistula empties into it, and then that collapses everything. And so far lateral approach is an excellent approach for lesions that involve that anterior lateral part of the foramen magnum, also the hypoglossal foramen and perijegular fossa. And as you can see, it's really applicable in a variety of pathologies. Like this entire weekend, anatomy is the absolute key when you talk about skull base approaches. Thank you.

far lateral approach

skull base

surgical technique

pathologies

dural arteriovenous fistula

anatomy