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Grand Rounds-Modified (Simplified) Orbitozygomatic Craniotomy and Extradural Clinoidectomy: Nuances

Johnny Delashaw

May 17, 2011


- Hello, ladies and gentlemen. Thank you for joining us for another session of the AANS Operative Grand Rounds. This session will be a discussion regarding the technical nuances for performance of orbitozygomatic craniotomy, or supraorbital osteotomy. We'll briefly discuss extradural clinoidectomy as well. Dr. Johnny Delashaw will be our discussant. There is a series of link below this window which you may use to navigate throughout the session. Thank you. Johnny, thanks for joining us this morning. We know that you have done much work in this area, and therefore we appreciate your expert comments. Let's start with the disclosures, none of which interferes with the presentation today. Let's talk about what we mean when we talk about orbitozygomatic craniotomy. Is it one-piece or two-piece, and how far do we remove the zygoma? For this discussion, based on what I have seen in your writings is, this is mostly what we we're talking when we say pterional craniotomy with a supraorbital osteotomy, and really removing much of the zygoma, at least the temporal piece, is not necessary. Can you tell us what your thoughts are, Johnny?

- Sure, the orbitozygomatic craniotomy, whether you do it in a one-piece fashion or two-piece fashion, really what it is is a frontal and temporal craniotomy that incorporates the supraorbital rim, a portion of the orbital roof, and the superior portion of the zygoma. We used to take out the lower portion of zygoma in addition, but I found that that exposure really offers very little for the middle fossa floor or the anterior fossa floor, or the anterior clinoid paraclinoid region, and so we've stopped doing that, only because it doesn't seem to add a lot more for exposure, provides more cosmetic deformities, and really makes the surgery a little bit more difficult. So, we've gotten rid of the lower zygoma, it just doesn't seem to make that much difference. We concentrate more right along the pterion, taking that supraorbital rim and that portion of the zygoma that's near the pterion, to allow us to get that direction, right along the pterion, down towards the middle fossa floor and the anterior fossa floor in the paraclinoid region.

- Thank you. And if I may ask you to show us on this illustration on the right-hand side, you can see the bone which is removed, but really there is not much done in the lower portion of zygoma, as you mentioned.

- Yes, so if you look here at this terrific diagram here, this cartoon, the far right is a picture of the left side, and some burr-hole's been placed, one in the keyhole region, one in the posterior temporal region, and then there's been a cut made right along the supraorbital nerve to preserve it, and it simply is a frontal temporal craniotomy that incorporates the supraorbital rim right here, and just the upper portion of zygoma. And in this particular diagram, it's showing a one-piece. Here is the bone flap separately, that's been removed from the left side. This is looking from the outside in. If you flip the bone flap over, this is what it looks like on the inside. So this is a one-piece here, in this diagram. But essentially, that's what the orbitozygomatic craniotomy is, what we call the modified orbitozygomatic craniotomy, and it just means that it's not the original one that was described in the literature, which includes the entire zygoma.

- Okay, thank you. And so today for our discussion, we're gonna focus really on orbitozygomatic, the way it's been described by you by one of your articles a few years ago. And it says, supraorbital osteotomy with a pterional craniotomy all in one piece. That's what we wanna really clear for our viewers, because there's much variations of technique. And really doing this one-piece supraorbital osteotomy with a pterional craniotomy gives you all you need. It's very efficient, it doesn't require any of the cosmetic deformity associated with removing the additional piece of the zygoma, and we're gonna therefore focus on that for the rest of our discussion today. So, what is a surgical corridor provided? It really expands the corridor to reach the lesions around the circle of Willis, the orbit, the paraclinoid and parasellar locations, cavernous sinus, especially on a more cranially located basilar apex region. May I ask you, what are your indications for using OZ, or what are the cases you like to use this approach for?

- So, I use it for a lot of different reasons. The tumors that I tend to be involved with is several tumors. Tumors I tend to be involved with are tumors that are around the paraclinoid region. So for example, a pituitary tumor that's extended laterally, that's extremely large that can't be approached transsphenoidally, or really it's only gonna be partially resected transsphenoidally. A meningioma that debulks from sellae which has incorporated the optic nerve and is extending laterally. A craniopharyngioma that's not central, but it's also extending laterally. Sphenoid wing meningiomas is a perfect example of using this type of approach, and other tumors located in that region. Trigeminal schwannomas, we can also use this approach. So there's a number of kinds of tumors right there in that location. Anneurisms, it's very ideal for an ophthalmic artery aneurism, a superior hypophyseal artery aneurism, a giant aneurism involved the internal carotid or the carotid bifurcation, that area of the brain, this is a great approach to get there, to have a less obstructive view. Again, it's still very important to open up the CSF cistern in the Sylvian fissure, and to have as little retraction as possible to expose that artery. But it starts with removal of bone, removal of this orbitozygomatic region to open up the corridor and allow you to see.

- Thank you. So, as you very well mentioned, tumors that have a significant suprasellar extension, where they really look at, you know, sort of cranially-located portions that you need to work with, especially for orbital tumors that are in the posterior 1/3 of the orbital space. Do you use an OZ for such intraorbital tumors, Johnny?

- You know, for the orbital tumors that I get involved in, and those are frequently meningiomas that have extended up through the supraorbital fissure or through the optic foramen, and particularly the supraorbital fissure. Or even those tumors that are schwannomas, or hemangiomas within the orbit, this is a great approach, because it gives the surgeon, the neurosurgeon and possibly the ophthalmologist who is involved, a panoramic view of the orbit. And that panoramic view allows us to pick our direction within the orbit to remove the tumor. If we're interested in optic nerve pathology, we wanna go medial to the levator palpebrae, gives us a direct avenue right to the optic nerve with avoiding the other cranial nerves. Sometimes we have to go lateral in the lateral portion of the orbit, and doing this gives us a panoramic view where any other kind of craniotomy, we have a small view, and it limits our ability to dissect out the orbital contents. So, orbital tumors are terrific this way. That's the way I do all the orbital numbers pretty much, unless it's something very superficial, and then I might do something a little bit more narrow, like what's called a supraorbital craniotomy, which just involves the frontal bone and the orbital rim. But most of the time we use the modified or the zygomatic craniotomy.

- Thank you. That was very helpful. So, this is a picture from one of your papers, which really establish the advantage of removing the supraorbital bar. And here, as you can see, the angle when the bar is now removed, this is the orbit, this is a sagittal view, a sagittal illustration. So if this is orbital context, this is the bar, this is the frontal lobe. This is the view you get really, without removing the orbital bar or the rim, and when you remove that, it really gives you a lot more sort of surgical angle in working more superiorly underneath the frontal lobe. How many percent of your subfrontal approaches would you say you use the OZ for in your practice every year?

- That's a really, really good question. I think one of the things I'd like to comment on before I answer that question is that by removing the orbital rim, it gives you the advantage of looking up. So if you have an operation where you're gonna look right down on the orbit, it may not be nearly as important, but if you're going to look up, which means, you know, a brain retraction, if you wanna reduce that brain retraction and be able to see, taking over a rim really makes a big difference. In fact, in the laboratory, in our skull-based laboratory, we actually measured the difference. And by just taking the rim, we were able to see 30% more area and volume in that location around the paraclinoid region, without brain retraction. So it made a huge difference. Taking the lower zygoma, which we've gotten away from, only gave us about a 10 to 15% difference, so it really wasn't worth it. And it really was 10 to 15% looking down towards the face. So the rim really does cause an obstruction, and I highly recommend it'd be removed for most of these kinds of skull-based operations. As far as what craniotomy I use, I tend to use an OZ craniotomy for frontal, temporal, paraclinoid lesions, almost universally. The only time I use this, what's called the supraorbital craniotomy is when I'm attacking a lesion that's between the two optic nerves. For example, a pituitary tumor that's very large and it's confined just within the optic chiasmal region, which is not extending laterally, or an Acom aneurism. But the OZ craniotomy has become our bread and butter of craniotomy in this stage for small distance.

- Thank you. This is really an illustration for us just to show that for lesions that are especially up you know, around the third ventricle area, like a large craniopharyngioma with a suprasellar extension, this is really a great approach right in this region, because it really gives you a more from the bottom to top surgical corridor. Let's talk about this meningioma, for example, Johnny, as you can see, it's a medial sphenoid wing meningioma, it's relatively sizeable. Would you say this is a perfect candidate for it, OZ?

- This is the perfect candidate for an orbitozygomatic craniotomy, because it's gonna allow you to get right to the surface of the tumor very early with minimal brain retraction, if any. So you're gonna get right to the tumor, you're gonna get down to the base of the tumor, which remember, in meningiomas, it's very important to get to the base of the tumor because that's where the attachment is, and that's also where it's vascular supply is. And if you can detach it and take care of it's blood supply, what's interesting is as you do that, the tumor becomes softer, and the plane around the brain becomes easier. So what I like to do is I'd like to certainly to debulk the tumor when I have a large tumor like this, but I like to get down to the base as quickly as I can and detach it, as well as devascularize it. And by removing this bowl in this location and getting into its blood supply, which in this particular case would be likely the orbital meningeal artery and possibly the middle meningeal artery which you can get to very easily with an OZ craniotomy, that you'll have devascularized the tumor very early in the surgery. I do wanna make one comment about this particular meningioma, it's very large for the audience, it's not necessarily the ones that we always do, this is an, I like to fish, and this is like a big fish. We keep these, just really a terrific example here. But what I would like to say about this is, this particular one, you need to really concentrate preoperatively and decide whether the orbital roof is involved in the tumor, and how much the orbital roof is involved. But if you have a lot of hyperostosis in the orbital roof, you really wanna do a two-piece orbitozygomatic craniotomy. And the reason why is as we go through this talk today, the one-piece involves cracking the roof of the orbit to remove the bone flap. And if the tumor is attached to the roof of the orbit with a tremendous hyperostosis there, when you do that crack, you could end up taking the tumor with the bone flap and anything that's attached to it, like the optic nerve, and the carotid, and it really will be a bad day for you. A bad day for the patient, a bad day for you. So, we really preoperatively, we wanna look and make sure that the orbital roof is void of tumor, and then go from there.

- Thank you. This is a case that I'm gonna show the surgical video a little bit later. I personally use the OZ relatively selectively, and we're gonna talk more detail about that as we go along, but keep this case in mind as we're gonna come back about how this was done at the end of our discussion. So, let's start our presentation about the nuance of technique and how to do orbitozygomatic craniotomy. This is the incision that I believe most of us are accustomed, or have been accustomed to using and--

- I'd like to make a comment here on the incision. This is the incision I like to use. It's right there at the beginning of the hairline. You wanna get down very low to the orbital rim with your skin exposure, so it's important to get it near the hairline rather than back and having to move more scalp. But what I do wanna emphasize is, this is about the average incision, but if the scalp is a little stiff, make the incision longer. Make it go down farther down the other side. What we will want to do is reflect the scalp without having to really retract very hard on the scalp. We wanna reflect it all the way down to the supraorbital rim. So, this is kind of an average incision, but sometimes we make a longer one if we have a little bit more difficulty in getting the skin to come down up to the supraorbital rim.

- Thank you. And please interrupt me anytime now. I appreciate your comments. And again, this comes all the way to the contralateral . I wanted to make the point to be generous with your scalp incision and stay as close to parentline as possible, because you really don't wanna do all this beautiful bone work and find out your exposure has been compromised because of your scalp incision. Let's go ahead and briefly review this positioning video, for our audience to see how the positioning works here. As you can see this 3D presentation where the pins are placed, and the second pin is behind the ear, and that creates more working distance for the surgeon to be to work and again, you can see the turning of the head that is almost about 30 degrees. Let's go ahead and talk about really, roadmap for the osteotomy, as you can see here, Johnny. And the cut along the orbit is usually, is what people get mostly confused about. And what I have sort of learned to sort of simplify myself, which may be a slight variation of what you do is, the first cut comes all the way to the top of the orbit, as you can see on the left of our illustration, and stops right there and the drill turns around, and the heel comes off and the number, a B1 sort of thins out the orbital rim. The second cuts really goes around the zygomatic arch, the frontal process through the key-hole, and then the last cut is really through the orbital roof, that can be done through an osteotome through the keyhole, or underneath the orbital rim above the orbital contents as we'll show in a second. What variations of technique do you have for this orbital roof osteotomy, Johnny?

- Yeah, so the diagrams again, are terrific.

- Thank you.

- I use a landmark of the supraorbital notch or super orbital foramen, and I like to turn my original bone flap, the frontal portion of it, right up towards that nerve, either right at it, or maybe just slightly lateral to it. If you do that, more times than not, you won't even enter the frontal sinus. Now, we can deal with the frontal sinus, but it makes the surgery a little simpler as far as closure if we're not in the frontal sinus, and really right at the supraorbital notch is about all the portion of the orbital rim you need to remove for most pathology. So that's what I use as a landmark there. As far as the zygoma, I think you have a great diagram there, I go just a little bit below the frontal zygomatic suture, take my side cutting bit, whether that be a silver zero or a C1, whatever that bit is, and cut right through that zygoma protecting orbital contents with a spatula right along the lateral portion of the orbit, and then directly connect it right up to that key-hole burr-hole. And I think once you do that, then remember the orbital roof tends to be quite thin up at the front, and you can take it an osteotome and tap that osteotome on the frontal region, which if I show you right here, for an OZ you tap an osteotome here, and tap an osteotome right at this cut, and weaken do orbital roof so that you'll be able to crack it forward. And remember, I think we're gonna talk about this a little more, there's two weaknesses you have to make. You have to make one along orbital roof, and one along the sphenoid wing.

- Thank you. So, this is a skin incision where you can use a dissector, a flat dissector to protect the superficial temporal artery, and as you get close to the roof of the zygoma, trying to protect again, the superficial temporal artery. This is the scalp flap and exposure of the fat pad and the temporalis muscle. These are very basic techniques, and go all the way until we can feel the frontal process of the zygoma. The next illustration really shows cutting through the fat pad, and protecting the frontal branch of the facial nerve. As you can see, the cut is straight down and never turns more anteriorly to go across the frontal branches of the facial nerve to avoid frontalis palsy. This is an intraoperative picture, again, showing the, it's a left-sided approach. This is temporalis muscle, the scalp flap has been reflected anteriorly. And again, staying below the fat pad and above the temporalis fascia. You may take a piece of the superficial part of the temporalis fascia with you, and that's fine, depending if you're doing the interfascial technique or subfascial technique. But what's most important, that the frontal of branches of the nerve are embedded in the fat pad for the superior fascia of the fat pad. Am I correct, Johnny?

- You are absolutely correct. So, in order to avoid a frontalis palsy, and I think this is important, not only for orbitozygomatic craniotomy, but also important for pterional craniotomy, is in order to avoid that, I think there are two principles here. One, is reduced scalp retraction. So, always make your skin incisions long enough that your not holding too hard on the scalp. I think that's one of the major issues why people get frontalis palsy is rather than cutting it. The second is remember that the facial nerve sits in that fat pad. And what you can do is you can remove the superficial temporalis fascia near the orbital rim and near the zygoma and reflect it forward as shown in this diagram. And if you do that, you're going to avoid injuring that nerve, and that superficial temporalis fascia comes up over the external surface of the zygoma, so it's actually very ideal for exposing the zygoma, and particularly the frontal zygomatic suture. So I think this is a terrific idea to avoid a frontalis palsy. But I cannot overemphasize that small incisions are more likely to cause frontalis palsies than large incisions. So, even though it takes a few more minutes to close the skin, your patient's gonna be much happier with the cosmetic result if you have very little retraction on the scalp.

- Thank you. And as you can see again, the nerves come across through the fat pad, or superficial fascia of the fat pad, and enter the scalp, as you can see here. And if you keep the fat pad, its superficial fascia together, as well as maybe even taking the superficial fascia of the temporalis muscle, and reflecting everything anteriorly, there is a fat pad below the superficial fascia of the temporalis more anteriorly, and that's okay to use Bovie there because really the nerve is in the fat pad, and therefore, as you go more inferiorly, we'll see in a second, you're gonna face a fat pad, which is okay to go through more inferiorly. And here is really trying to strip the fat pad and other fascial contents from the frontal process of the zygoma. And there is some fat here, usually, that is okay to play with and it would not have any consequences. Here is that piece of fat that I was talking about more inferiorly. The fat pad has been reflected with the superficial plus fascia and the orbital contents and the periorbita are being dissected off the orbital rim. The next one, we try to release the supraorbital nerve. If there is a foramen, we usually try to take a piece of bone with a drill, with a C1, or a B1 bit. If it is a grove, usually the nerve can be easily untethered and pushed anteriorly. It's important to keep the nerve intact as it will cause some numbness that can be uncomfortable to the patient, and most importantly, it can develop a painful neuroma. So, although it's a sensory nerve, it has to be protected. Reflect the temporalis muscle. As you can see here, a cuff is left, and muscle is reflected sort of anteroposteriorly. Again, the muscle that can be released from the posterior edge of the frontal process of the zygoma. Any nuances here, Johnny?

- So, what you have to remember is, any time you cut the temporalis muscle and reflect it either posteriorly, anteriorly, or inferiorly, when you completely detach the temporalis muscle from the skull, you are going to get some atrophy. And for cosmetic results, just remember that at the end that you may want to augment your area with some bone cement, particularly along the pterion, because that's where it tends to atrophy. So even though you get the bone hooked, the muscle hooked back up to the bone, I usually leave a temporalis cuff, as you're showing here. Even if you do that, it probably will atrophy some, so I tend to augment a little bit of this right in this location here with some kind of bone cement, because you typically get some atrophy at the end. If you do, augment a little. You don't have to get carried away, but if you augment a little bit, you don't have that indentation at the end, at six months after surgery, and the patients look terrific, and then it looks like they've never had surgery. So I tend to augment that a little bit because this temporalis detachment ultimately causes some atrophy.

- Thank you. The first burr-hole, you know, it's a dealer's choice if you want to put it here or further up just below the superior temporal line, and the reason we put it here, because usually we can dissect the dura freely all the way along. If you put one here, usually inferiorly, the temporalis muscle may get on the way of #3 then fail to strip the dura effectively. What is most important is really the key-hole, and it gotta be placed just perfectly right. For a one-piece orbitozygomatic or supraorbital osteotomy, this is the key factor. And not only the location is important, but also the angle of the drill. Here, as you can see, a M3 is being used and an acorn drill bit. And we use the landmark of identifying the frontozygomatic suture right here, staying about four to five millimeters above it, and slide four or five millimeters posterior to it, and then angle the drill 45 degrees to the surface of the temporal bone, and then drill right there. And 95% of the time, we end up exposing the the orbital groove and the frontal dura without difficulty. You don't wanna misjudge the location and end up removing a lot of bone, which can cause cosmetic deformity later. Do you have any pointers for placing the key-hole, Johnny?

- Yes. I totally agree with your description here as far as the key-hole. If you look here, here on this background here, you'd likely get both exposing the periorbital right along near the lateral orbital portion, and you wanna expose the frontal dura. Now, remember though, that as you come and bring the scalp down, the pericranium becomes the periorbita, and you can come down and actually with a feeler, feel where you should put the burr-hole right here as far as getting to the periorbita. I find actually, the most difficult part of making this burr-hole is not so much exposing the orbit, it's exposing the frontal dura. The frontal dura tends to be just a little bit behind you, so it's very easy to put the drill in like this and expose the periorbita, but still not see the frontal dura. And you need to see the frontal dura and the periorbita so you could get this osteotome right between the two and begin that crack, at the weakness of the wall of the roof, so that you can take a one-piece, so the craniotomy. So that's my key, is if you can protect it by bringing down a Penfield #1 kinda know where the periorbita is and begin your key-hole burr-hole here, but remember you still gotta aim back and find that

- Okay. Yeah, I appreciate that. And again, the orbital roof here is in an angle because of the position of the head. Sometimes the residents feel like it should be in this direction, it's actually in that direction. Knowing that direction is very important. And here is an intraoperative image showing the frontozygomatic suture and the burr-hole. And you can see orbital contents, the orbital roof, and the dura sneaking right there. Again, the first cut starts from the first burr-hole all the way, usually medial to the supraorbital nerve. In this way if you already created a cut by releasing the supraorbital nerve in a foramen, you may just go ahead and join there. And that would be the first cut for the craniotomy part of the procedure. The second cut is the temporal osteotomy, which is standard for a pterional craniotomy. As Johnny, you mentioned, then we use a B1 across the pterion to thin the bone there, and then we go ahead and do the first osteotomy for the supraorbital rim and the frontal process of the zygoma. And that's just staying about a centimeter or so below the frontozygomatic suture, and protecting the orbital contents, and then using a B1 and cutting across the bone. And then here is that cut completed, and then we're gonna go ahead and you can do it two ways, use the osteotome, reflect the orbital contents as you just mentioned. It joins that peri, the periorbital contents join the scalp and the galea, almost here, so you can reflect all together and then use an osteotome to cut the orbital roof. And then also use a smaller osteotome through the key-hole, put a couple of patties to protect the dura and the periorbital contents, and direct your osteotome to your, sort of end of your bony cut in the frontal region, you don't want it pointed posteriorly, and that should complete, really, your osteotomy. And as you can see, this is a small osteotome at the top of the picture with two pieces of Cottonoid through the key-hole, and this is the bone we cut. One nuance I would like to mention is that cracking the roof without adequate visualization and doing the two cuts, one from the anterior part and one through the key-hole, it's not a good idea if you do it blindly because sometimes, especially in tumors that thicken the orbital roof, such as a meningioma, if you practice roof blindly without cutting through it effectively by lifting the bone flap, you can crack all the way down to the orbit canal and injure the optic nerve. So it is important to practice patience and cut the orbital roof effectively. Any nuances on these steps, Johnny, please?

- Yes, your description is terrific. The one thing I would like to emphasize is that right along the sphenoid wing, it's very important, I think, to try to make that extremely weak early in your craniotomy. So after you've turned your craniotome, and you're down here on the wing and you're weakening it off with your B1 bit or your Silver Zero bit, whatever kind of drill you're using, at the end what I like to do is take the osteotome right here and just tap it a few times and if you feel it kind of give, that has released the frontotemporal portion of the bone from the sphenoid wing. Now, all you have that's attached to this bone flap is the orbital roof. And once you weaken the orbital roof, with your osteotome, you'll feel the bone flap sort of give way, and then it's very easy to remove the flap and you know you've done it safely. Never, ever try to remove a bone flap forcing it, because if you try to force it, then you haven't weakened the orbital roof, and if you haven't weakened the roof and you try to force it, it could crack it any direction, and the direction it could crack is exactly what you said, right along the sphenoid wing, the lateral sphenoid wing and the anterior clinoid, which would put your optic nerve at risk, your internal carotid at risk. And if you have a tumor in that location, everything could come out in one piece, and it'd be a very, very bad day for the surgeon and the patient. So really, weaken the sphenoid wing and then make sure your orbital roof feels very weak. Don't force it and you'll have a tremendous exposure and begin your surgery in a very good light.

- Thank you. This is the bone flap, this is an intraoperative picture of a bone flap. As you can see, everything is in one piece, the supraorbital roof.

- I'd like to make one comment. So here we see this area right here, and this is the key burr-hole that was made that Dr. Cohen has so eloquently described. Remember, when you put the temporalis muscle back, it's going to atrophy some, and this area here can easily cause an indentation. So, I'd definitely put some kind of titanium burr-hole cover, and then maybe a little cement here just to augment that area and so that if there is some atrophy, we don't get a tremendous indentation at the end of the surgery.

- I think that's a great thought. And that's one of the criticism of the orbitozygomatic craniotomy as in its potential for cosmetic deformity. And as you very well mentioned, Johnny, if you deal with that effectively, then there won't be a problem. It's just a matter of knowing it. We do at times, if we need to remove extra piece as a second piece of orbital roof along the sphenoid wing inferiorly, and that gives you even an extra amount of space to push the orbital contents down with your dural opening in order to get additional surgical corridor space. Do you do that regularly, or no, Johnny?

- So, if it's for an aneurysm, yes. If it's for a tumor, yes. If it's for a tumor in the paraclinoid region, yes. Orbit, yes. In other words, I always do it. So what I do is I take a Penfield #1, I take the cup portion of the Penfield #1, and I separate the dura from the orbital roof, and it comes off very easily. Even in older folks, this area is not as difficult as the dura along the frontal bone itself. I'm able to peel that down, and then I just take a rongeur and bite it off. It comes off very, very easily. And I wanna open up the superior orbital fissure. When you do that, you'll find the orbital meningeal artery right there, and you can bite that all off. So I take all that bone off, preserving the periorbita, down to the superior orbital fissure. Once I'm at the superior orbital fissure, then it really depends upon the pathology of what I'm dealing with, whether I'm taking more bone or not. Whether I'm gonna remove the anterior sphenoid, whether I'm gonna decompress the optic nerve, whether I'm gonna remove more of the lateral orbit to get into the lateral cavernous sinus, or get into the lateral orbit. So it really depends on the pathology, but pretty much I take the roof there off the supraorbital fissure, because there are some bumps and ridges there, and there's no reason to have those in our way. So, that's just kind of a routine for me. You don't need to replace that bone at the end of the surgery. You can put your bone flap back on and you get an excellent cosmetic result, so there's no reason not to that.

- Thank you. And here it is again, the orbit being pushed down and the piece of the bone of the orbital roof being removed, an intraoperative photo. And here is what you get. I mean, a beautiful view the orbital contents you can see here, and the dura, and really, when you opened it, you can remove a little bit of extra bone of the sphenoid wing using a rongeur. And we really start the second part of this talk, which I wanted to discuss with you, the clinoidectomy. We don't do that for every pathology, but I think this extradural clinoidectomy is something I do, versus intradural, and I would like to briefly get your comments in terms of advantages and disadvantages of each. I think the advantage of an extradural clinoidectomy is that you have the dura, it protects the intradural contents and may allow a more thorough bone removal. However, if you have an aneurysm and if there is a rupture because you're manipulating the clinoid extradurally, you may not be able to visualize what's going on very well. The intradural clinoidectomy, it's more efficient, it's more tailored. Since you're intradural, you may find out you never actually need to remove the clinoid, so it may decrease the number of clinoidectomies that you may need to do. And since you see the aneurysm under direct vision, you can protect the aneurysm and make sure there is no injury or a manipulation that places the aneurysm at risk. Reviewing the literature, it's difficult to compare which clinoidectomy is better, intradural or extradural. You do the extradural, I assume, since you write about it, Johnny?

- Yes, so well, I'd like to make a comment about the clinoidectomy as the following. When we started removing the clinoid in a routine fashion for a lot of pathology, we actually began removing it intradurally. And that's years ago. And the reason why was, it was difficult to see the clinoid extradurally because the temporal orbital band prevented us from seeing the anterior clinoid very well, and so it was a very small corridor to try to drill this bone away. So we would do it intradurally. And intradurally is fine. The problem with doing it intradurally is one, you don't have the dura to protect you from the structures of the brain, you've gotta be very careful with your drill bit, no parties in the field, and two is, if you have a tumor, it may obstruct your view of the anterior clinoid and so you've got most of the tumor out. And then that portion of the surgery may not nearly be as important. If you already have the tumor out, you may not need to remove the clinoid. Getting the clinoid out early may help you with devascularizing the tumor. For aneurysms, I would say, it really depends upon how comfortable you are with the approach. You should remove the clinoid in what you think is the most comfortable way for yourself. If you're more comfortable with the contents of the brain and those structures be protected by the dura, then I would do it extradurally. If you like to see all those structures before you remove the anterior clinoid, then I would do it intradurally. Personally, I tend to do almost all of them extradurally. I cut that temporal orbital band, it releases things, I do a cavernous sinus Dolan's dissection just to show the anterior portion of the cavernous sinus, and I'm looking completely at the anterior clinoid in the optic canal. I have lots of room, and I can drill that away having the protection of the dura on the brain and the optic nerve. And I think it's safer, but that's in my hands 'cause I'm used to it. So I don't have any problem either way, but I think once you learn to take that temporal orbital band and do a little anterior cavernous sinus dissection extradurally, you see the clinoid so well, it's hard to go back and take it out intradurally.

- Thank you. It's very well said. Whichever one you're more comfortable with. And then, to remove the clinoid, you can cut this from the temporal dural fold, just through the lateral part of the superior orbital fissure. And I think this is a very important nuance, Johnny, and I'm interested in your opinion, because when you cut that, it really increases your space. If you don't, your retractors on the frontal and temporal dura right around the lateral part of this clinoid will be fighting with each other, you really don't see what's going on, the dura is creating really a big obstacle for you to get there. Am I correct?

- You're absolutely correct. The temporal orbital band of the frontal temporal fold, that band is the dura that goes in and becomes the periorbita, and it goes through the supraorbital fissure. And very superficial is just an orbital meningeal artery and a vein that's gonna be coagulated. If you cut that fold, you go in between the two layers of dura. The outer layer of dura is quite thick and covers the temporal lobe. The thin layer is right along the lateral wall of the cavernous sinus, and you can actually put just a little tension and it peels away. And as it peels away along the middle fossa floor, it peels away right along the lesser wing of sphenoid, and ultimately you see the anterior clinoid and the optic canal. And it's quite quite an amazing corridor. And I think that was a major technical advance in cavernous sinus surgery and extradural clinoidectomy. And you don't have to take, Evandro de Oliveira showed me that one day in a course, a AANS course. He said, "Look at this, Johnny. Watch this." And I was amazed at how much more room I had. And of course, I think Evandro learned that technique from who originated a lot of this cavernous sinus surgery in the 1980s.

- So, as you very well mentioned, Johnny, after the dural fold was cut, we reflected the dura off of the middle fossa. We're gonna see that in our video shortly. And then, here is not more space and you start drilling the lateral part of the clinoid, and the nerve is just usually in the superior 1/3 part of the clinoid, and when you use the drill, you have to be very careful not to injure the nerve. Ample amount of irrigation should be used. And eventually, the clinoid has to be hollowed out very effectively, and the surgeon has to be very patient in this juncture. often the surgeon really starts using this dissector and pushes, and shrugs on things, and the clinoid is not coming off and people get frustrated. I think the key is to drill and hollow out the clinoid. This way it gets disconnected from the optic strut. Be very careful in manipulating the lateral edge of the optic nerve. Make sure it's thoroughly decompressed along its roots with a micro curette. Rather, not use the drill directly on the nerve, just thin the bone over it and then use a curette to deliver the shell of the bone. And then ultimately, if this is hollowed out effectively, it actually comes out easily. Usually there's some bleeding from cavernous sinus, but that's managed very well with Gelfoam powder soaked in thrombin. Any thoughts there, Johnny?

- Yes, so when you remove the anterior clinoid, in the end, it's going to be attached to the optic strut. As you skeletonize the anterior clinoid, pay attention to direction of the optic strut, weaken it, and then you'll be able to essentially crack the anterior clinoid away from the important contents of the optic nerve and the carotid, and be able to pull it out as like a little tube. Now remember, because you're gonna have to wiggle this a little bit to get it out, usually, it's really important that you decompress the optic nerve. So take a diamond bit drill as shown, was shown on the previous diagram, lots of irrigation, and eggshell out the optic canal inferiorly, there's the diamond bit here. Eggshell it out, and use the curette as Dr. Cohen has mentioned, and decompress that optic nerve so that when you begin to remove the anterior clinoid and you move it a little bit, the optic nerve is already depressed and there's less likelihood of injury in the optic nerve as you remove the clinoid because it decompressed. It's also gonna be very helpful to you later on, because when you open up the dura, particularly if you're dealing with something in the paraclinoid region, you now can open up the falciform layer, which is the big dura over the optic nerve, and actually open up the optic nerve sheath a little bit, 'cause the bone's been removed, and it's gonna open up the avenue, the corridor, for the of paraclinoid region even more. So, decompress the optic nerve, skeletonize the anterior clinoid, and weaken it, and as it weakens, we develop an extra plane around the important structures that should come up very easily. And the bleeding that Aaron has mentioned, it's just really not a problem. Some kind of anticoagulant materials, Surgicel, Gelfoam, all those things will stop the bleeding very quickly. Just a little pressure, a little bit of time. Don't get nervous, it's gonna be the sort of venous oozing, and it stops very easily and you're on your way to opening a dura and attacking the pathology as necessary.

- Thank you. And as you can see here, is after the clinoid is removed, we're just shadowing in the carotid artery through the dura here. And as you can see, the carotid artery is awfully close to that clinoid process. And we usually just see the dura in this region, but it's important to realize how close that is, and any aggressive manipulation could place the carotid artery at risk. And here, more bony removal. If you would like to sort of remove the bone along the posterior part of the orbit. And after you removed all this bone, this is the orbital contents and periorbita, it really creates an amazing corridor and you can open the dura.

- Back, Aaron, to that operative photograph. Can you imagine here, when I do surgery with the ophthalmologists and they get a picture of this, this panoramic view of the orbit, they're ecstatic because they don't get this, and they usually do a lot of orbitotomies, they don't get to see such a huge view to attack an orbital tumor. And so, for the surgeons who do this operation, if they use an ophthalmologist to use orbital tumors, they'll ask you time and time again to help them, because the exposure here just to the whole orbital contents is so tremendous, it makes surgery in the orbit much easier. And this is without even dealing with the brain at all.

- Thank you. And here is the opening of the dura, and even without much retraction, you can look through the optic nerve and carotid artery. One important nuance is to put your sutures as much close to the brain as you can, and push the orbital contents with your sutures in order to create an extra corridor. If you don't effectively use those sutures to push the orbital contents down, you're gonna be sacrificing all the extra space you created with your bony work. So, I just wanna make sure our viewers are aware of the fact that really placing these staying sutures are important. Any thoughts there, Johnny?

- I think that's terrific. I love your diagram.

- Thank you. And here is some of your illustrations from the papers and Journal of Surgery, which really has beautifully illustrated this orbitozygomatic craniotomy. Those papers really have been a great guide for me, and this is some of the, you know, bony removal, anatomy of the clinoid, and really optic strut. I think it was a great point that you mentioned, as you can see right here, the anterior clinoid and optic strut. Any thoughts in these pictures you would like to share with us, Johnny?

- Well, you know, here's the optic canal right here, and here's the anterior clinoid. And again, you wanna skeletonize it out, but it's this optic strut right here that you're gonna need to weaken it. Just take your time, be sure to decompress the orbit, actually the optic nerve laterally, and this optic strut will weaken and then it'll also give way. But that's where your connection is gonna be, the ultimate connection is gonna be to loosen that anterior clinoid and the optic strut. I recommend to those people who are novices at this removal of a clinoidectomy to really just take a skull and look at it, and identify that structure so you can know where the optic strut is. The optic strut is the area that ultimately has to be weakened to remove the anterior clinoid.

- Thank you. Let's go ahead and have a look at our surgical videos. Well, Johnny, this is a video of doing the osteotomies on a skull without the soft tissues. I thought this would help our viewers just to get an idea how orbitozygomatic craniotomy works without a lot of the distraction of the soft tissues. Obviously, this is a left-sided approach, and the initial burr-hole is placed at the key-hole. The osteotomies are clearly defined with the hash markings. As you can see, in the key-hole there is a bar, and the space for the dural contents and the frontal dura. The first bone we cut of the craniotomy extends all the way to the orbital rim. Go ahead please, Johnny.

- [Johnny] Yes, you know, what I would emphasize in this is that Aaron here is showing two burr-holes. The key burr-hole is right here, the one that he's described here that gets us to the orbit and into the frontal region. But again, for an older patient, you may want to make additional burr-holes, maybe down the temporal region, maybe down the frontal region, to try to maintain dural integrity. It's going to make the surgery easier for you in the end. But in a younger person, a couple of burr-holes is all that's necessary. So again, you have to tailor your craniotomy to the problem. Here he is showing the weakness of the sphenoid wing here. He's drilling out this area to weaken this right here, the orbital roof and rim, and he's weakened this off. He's also cut the zygoma here, right here, and he's getting this all weak. Again, you'd be protecting the orbital contents with some kind of spatula as we did this. And then we want to use hopefully an osteotome and weaken this area. Weaken this area right here, and this area right here, and the osteotome can be used by tapping it here and here, or if you can, you can move the orbital contents down and actually, though they cut the roof of the orbit with an osteotome. So he's got one here, he's gonna tap it to weaken this roof. You can actually see him, he's tapping it now, and you can also see that it's starting to give way. And you really want it to feel it give away before you pull the bone flap out, because otherwise, again, you might have something attached to it. And he's done a great job here. Look at this great view here, looking right down into the orbit. The superior orbital fissure is gonna be down here and we can remove all this bone safely with a rongeur right here, and just take this all the way right out to the temporal orbital band. He's cutting it here with a saw, but again, I typically use a rongeur. The rongeur is very quick, it's safe, and there's really nothing there that you need to worry about as far as contents. Just stay on the periorbital side, and you'll be able to remove all that additional bone and provide excellent exposure for the pathology you're trying to attack.

- [Aaron] Thank you. This is a second video of ours. If you can also give your expert opinion as you very well did. This is showing the approach for a left, large size sphenoid wing meningioma in a young woman, and I really tried to do a video recording of the placement of the head clamp and all the other details. As you can see, we placed one of the pins behind the ear on the left side, and I'll let you comment. Go ahead, Johnny, please.

- [Johnny] You know, on this movie here, Dr. Cohen's showing how he likes to position the Mayfield headrest. He's putting a pin behind the ear so that, he's going to do a surgery on the left side, so that there is nothing really in his way as far as the Mayfield headrest on the left side where he's going to concentrate on, and therefore he's put a couple of pins up along the region in the right frontal region. Now me, I actually do it a little bit differently. There are many ways to do this. I put all my pins behind both ears. And by doing that, it gives me a little bit more freedom as far as how long the skin incision is. But you need to be a little bit careful when you do that, because when you put it behind the ears, you don't get that tremendous fixation that you will get by having something in front of the ears and something behind the ears. But again, I think if you're careful you can do that and have pretty good access. But see here, Dr. Cohen's patient, he's got that pin way behind the ear, and it's gonna give him a lot of freedom to dissect here without having anything in his way back here, it's gonna allow him to rest his hands here, and it's really a nice way to pin a patient to get the exposure he needs right at the OZ region in the pterion. And there he is, he's draped out the area that he's going to operate on, and now he's putting Raney clips on, and he's gonna come down, I think, and show you the superficial temporalis fascia, and how he peeled that scalp down down to the supraorbital rim. He's right now cutting the scalp again, he's staying between the galea and the temporal muscle, and he's gonna work on trying to preserve that superficial temporal artery in case he needs it for some other reasons. Obviously if you take that artery, it's going to affect your ability to do a bypass. We don't do bypasses that often. It's nice to always preserve things that you can and not get in the world if you get into it, that's usually not what this approach is for, this approach is really for exposing something right along the paraclinoid region. So here he is, he's dissecting out, trying to stay right on top of the temporalis fascia, and he's gonna cut down all the way down to do the root of the zygoma. He's coming here, and you're exposing the superficial temporalis fascia. He's pushing the pericranium down with the scalp. He's ultimately gonna show the supraorbital rim. As we've shown you in the diagram, he's coagulating right along the zygoma. He's got that fat pad exposed, he wants to protect the frontalis nerve and peel that back and find the zygoma, the frontozygomatic suture, and the supraorbital rim. How am I doing, Dr. Cohen?

- [Aaron] Oh, thank you so much. I appreciate all these details. That really helps me as well. And as you very well said, Johnny, reflecting that scalp effectively is so important here, and you've gotta be generous with your scalp incision. You cannot shortcut yourself right at this juncture because the scalp is not folding on itself and giving you the extra space. As you very elegantly mentioned, it's important to keep the fat pad intact in one layer, and you can Bovie underneath it generously, as you can see in the fat over the temporalis muscle. And here again, reflecting that scalp flat around the orbital roof and orbital rim. I'm sorry, and the zygomatic frontal process. Go ahead please, Johnny.

- [Johnny] Yeah, so great exposure here. He's going to reflect the scalp. But notice how the scalp has very little tension on it, and it's already at the supraorbital rim. So he's made a long enough incision that he's gonna be able to make his cuts and really not stress the frontalis nerve. He's coming down here now, and he's looking for the supraorbital notch or foramen. I think he's found it, it's right near his retractor there, and he's gonna come down and expose it. I don't know if this turns out to be a notch or a foramen, it's about 50/50. It's so much nicer when it's a notch, 'cause the superior orb just falls down from the periorbita. But it's not a big deal if it isn't, you can just take a little drill and weaken the bone around it, and the little bone will go down with the periorbita, and you can preserve that nerve.

- [Aaron] Feel free to use your arrow if you like to point at things, Johnny, please.

- [Johnny] So that's what we're talking about right here. Now he's cutting the temporalis muscle, and he's gonna peel that down, and he's gonna get this full bony exposure to allow him to begin his orbitozygomatic bone flap.

- [Aaron] Do you reflect the muscle any differently, Johnny?

- [Johnny] You know, I don't have a total standard way, it depends upon where I'm trying to visualize. Sometimes when I don't need as much exposure as possible, I'll cut the temporalis muscle down near the scalp incision to reflect it forward. It protects the frontalis nerve even more. Sometimes I cut it just exactly like you're doing, and reflect it inferiorly or even posteriorly. So I just, I really, the temporalis muscle, it depends on what I'm trying to accomplish. What is the pathology I'm trying to accomplish? So I don't have one particular way. I would say most commonly I do exactly what you do, I detach it here and reflect it inferiorly.

- [Aaron] And here is cutting the bone off of the orbital rim. And here is trying to thin out the bone that you use the osteotome with on the pterion, and here is the cut through the frontal zygomatic process, making sure all the bony cuts are detached and completed, and here he's using a small osteotome through the key-hole. And you'll see the bone give away, as John, you mentioned in a second.

- [Johnny] So, he's just gently tapping. Remember, the roof of the orbit in the proximal portion is quite thin. There it gives way, and sometimes when you do this, some of the periorbita comes with the bone flap and you see periorbital fat, and I think you can see a little bit there. Not the worry, it doesn't cause any problems. There's quite a bit of fat around the orbit. The fat can be a little bit cumbersome sometimes in your visualization, but when you open the dura and you put those sutures in that Aaron's shown you, that'll push everything down and you get a great exposure. So, if you do take a little bit of periorbita, it's really not a big deal. It's nice if you keep it intact, as it keeps the contents a little bit working fine, particularly when you're trying to do an extradural anterior clinoidectomy. But again, when you take the bone flap off, if you get a little periorbita fat kind of oozing out, not to worry, the major contents of the orbit are deep to that, and it's very unlikely that you're gonna cause any kind of injury to the orbital contents.

- [Aaron] Thank you. As you saw a few seconds ago, the frontal sinus, which is right here was violated here, and I removed all the mucosa with a pituitary rongeur, and then placed pieces of temporalis muscle patches in there to avoid post-operative rhinorrhea. You can see those sutures we talked about very close to the brain to push the orbital contents inferiorly, and really that gives you a gorgeous panoramic view of the suprasellar, or I'm sorry, the optical carotid cistern as the Sylvian fissure open. Let's go towards our last surgical video, if you don't mind, and that video is really under microscope performing the procedure, again, the entire procedure, this time maybe having a better view of how things work. Here again, is a left-sided approach. The scalp flap is made. Johnny, go ahead, please, if you have any other thoughts.

- [Johnny] So, it's exactly right, the cap's made, you wanna be in front of the tragus. Remember, you wanna be within a centimeter of the tragus, and you come down and you make that incision all the way to the temporal areas of root of the zygoma. In this case, he's doing a nice, sharp dissection, showing you the superficial temporalis fascia. This is a cadaver.

- Yes.

- [Johnny] The cadavers are stiffer, but again, I can't overstate, he's made a nice incision so that he doesn't have a lot of retraction here. He is now I'm taking a joker here and he's finding the supraorbital rim. Remember the pericranium, which he's got here with the galea, becomes the periorbita, it's all one continuous layer. He's now cutting the, making that incision in the superficial temporalis fascia, and he's gonna reflect the fat pad over to expose the zygoma, just like we showed you before. In the operating room, he cut through this and then he was using a Bovie. Obviously he doesn't need the Bovie here because it does not have any blood loss, this cadaver, but again, you can use a Bovie if you're deep to the fat pad as you reflect this forward, you're going to be able to expose the zygoma and the frontozygomatic suture, which is where you wanna go. Here he is, here he's doing that, he's cutting it right here. This is the zygoma right here, and the frontozygomatic suture. And look how nice that peels away, it's a periorbita dissection. We got a great exposure here of the lateral orbital area, and then he's gonna ultimately separate this temporalis muscle and reflect it down. He's actually coming down to the malar eminence. Here he's got just a tremendous exposure here in this cadaver. He needs a little temporalis cuff here so that he gets sew the temporal back up at the end of the procedure, and then he's gonna do a supraorbital dissection once he detaches it from this region, and peel this muscle down to get it completely out of the way of where he's going to concentrate operating, which is right here in this location and moving down towards the paraclinoid region. So, this is a great dissection showing the approach. It's preparation to make your burr-hole, and soon your bone flap.

- [Aaron] I think doing this approach at least once or twice it's never been, if it's not been done by a resident before on a cadaver would be so helpful. It is a nice approach if it's, you know, used for appropriate lesions. Here, again, I'm trying to use the frontozygomatic suture, and then showing how the burr-hole should be placed somewhere here. The angle of the drill is very important. You don't wanna go straight down like that. You wanna go from an angle, and then place it just above this suture, and you'll find yourself perfectly where you need to be to expose both the frontal dura along the frontal fossa, as well as the periorbita. You see periorbita there, you see the frontal dura, you see the orbital rim, and you may have to use a Kerrison here just to remove the shell of the bone as the orbital roof joins the lateral frontal bone, and this way defines your orbital rim very effectively, and that's the final product. Here as you well mentioned, Johnny, in a cadaver, or in older individuals in the operating room, you wanna put additional burr-holes. Here we placed two other burr-holes besides the keyhole. Go ahead, please.

- [Johnny] Yeah, so it's important that you try not to violate the dura. If you do, it's certainly correctable, as we all know, but trying to stay extradurally to do your removal of the orbital roof, it just makes the surgery a lot more pleasant and easier, and also makes closure a lot easier if you could not violate the dura. So, I don't hesitate to make extra burr-holes when necessary. Probably not necessary in younger individuals, but in older individuals, it is necessary, and in cadavers it's very necessary because the dura is so thinned out, particularly right where Dr. Cohen is drilling right now. So he's gonna come up here, and sometimes you can't get any farther. You stop. And that's okay. Then just come around, finish the rest of the flap, and then we can take a side cutting bit it cut through that even more. He is gonna come here and he's gonna try to get to that rim, but I'm not sure he's gonna quite get there. But you can thin that out with it with a B1 or Silver Zero bit. A B1 bit, thin it out and finish the craniotomy that way, 'cause sometimes that area right there is quite thick. I think he's, I think Dr. Cohen, are you, I think you're gonna give up and try to thin that out with a--

- [Aaron] Yes.

- Is that correct?

- Yeah. You know, I turned the heel around, that creates a little bit of extra space, and I pulled my drill just out rather than backing it off, and that extra space, as you can see right there, it leaves me with an extra viewing corridor to cut that rim. So if you come all the way with your foot point, turn it around, it removes a little bit of extra bone. Cosmetically it's not been an issue for me, but again, you know, I can't say that the patients haven't felt a little bit of space there, but usually they have not been uncomfortable with that. But that creates that extra space for you to use the C1 or a B1 bit to cut the orbital rim.

- [Johnny] I like that approach. I'm gonna try it out in the operating room.

- [Aaron] And here is really trying to cut that orbital frontal process, and trying to connect all the lines together. Go ahead, please.

- Yeah, so again, he's cutting the zygoma just below the frontozygomatic suture and trying to connect this area here to the orbital frontal burr-hole, the key-hole burr-hole. And again, it's important to know, once all this is done, you wanna make sure you weaken the sphenoid wing, and then weaken the orbital roof. And what he's doing right now, is he's pulled the orbital contents down, and he's doing a very safe approach here where he's tapping along the orbital roof to weaken it. And look how it just gave way. It just gives way there, and you're off to the races to take the bone flap off. He's managed to take this bone flap off, he's got the periorbita here completely intact, he's got the dura intact, he's an amazing cadaver surgeon. 'Cause I can tell you, sometimes the dura is connected to the bone and it can be very difficult to open. He's got a great dissection here. He's now peeling down the dura along the temporal lobe, he's gonna come off and ultimately find the temporal orbital band. You can remove all this bone right here, just very, very safely with a rongeur, you don't need anything special here, just bite, bite, bite, bite, bite. He's gonna bite this bone off here too. But once you start to feel it get tight in the frontal region, you're getting near the optic canal, and at that point in time you really need to step back the one with the microscope and use a drill, because you don't wanna damage the optic nerve.

- [Aaron] Correct.

- [Johnny] Here it exposes this area here, he's right along the temporal orbital band, he's taken off some more bone right around here and around the temporal orbital band.

- [Aaron] Right, I think that you can see the optic nerve right there. I'm sorry, the video is a little bit washed out. You can see the clinoid was drilled all the way and was ultimately removed. And then here it is really removing additional piece of the orbital roof. For further details of surgical videos of clinoidectomy, we ask our viewers to also go to another session with Dr. Delashaw on a middle sphenoid wing meningioma resection where we talk about further details and surgical videos. And here is the are being pushed out inferiorly and a beautiful view of the optic nerve and carotid artery. Well, let's go ahead and go back to our slides for a second and finish our discussion. And another video that I wanted to show very briefly, not to make this discussion long, is how can we maximize subfrontal exposure through the pterional exposure, and not necessarily use OZ all the time, by in selected cases. And what I have done is I use OZ selectively, Johnny, but for other cases for paraclinoid region masses, and a lot of the sphenoid wing meningiomas, what I do is I do the incision as always, this is the right-sided approach, we use that single burr-hole to do a usual pterional craniotomy, and I reflect the dura, and I use a B1 bit and really drill down the roof of the orbit. And do a generous resection of the sphenoid wing laterally, and I drill this all the way down until we essentially get, leave a thin shell of bone over the periorbita. And if in this location you get into the periorbita, that is okay. And as you can see here, this is how the drill is used parallel to the roof of the orbit, drilling that bone as much as possible, protecting the dura with a #3 Penfield as somebody's using suction for you, and ultimately, you know, doing the slight opening of the fissure along anterior limb. This is a frontal lobe, temporal lobe gentle elevation by the retractor over the frontal lobe. And here's that first case we talked about. A 75 year-old male with a progressive history of confusion and speech difficulty. And that MRI I just showed you. And this is an older gentleman, 75 years-old, probably the brain has a little bit more slack, also first of all defining the cerebrovascular structures relative to the tumor, again, showing the incision in this case, and with one of the pins behind the ear. And let's go ahead and briefly review the surgical video in this case, Johnny, if you don't mind, because I would really like to know what your thoughts are in terms of doing this case, not necessarily using the orbitozygomatic craniotomy.

- [Johnny] Well, I think in this particular case, an OZ craniotomy would be ideal, but a pterional craniotomy would work extremely well. You have somebody who is older, who has some brain atrophy, not gonna have to use a lot of brain retraction, the tumor actually has retracted the brain for you, because you're right at the base the skull, so I think it's dealer's choice here. And it depends upon you'd like to do. And doing a pterional flap and kind of drilling down along the floor, and taking the piece that you wanna expose, and the dura there you wanna devascularize things. I think it's a very valid way to do this operation. It's a little simpler and maybe a little bit quicker, but remember, the basic skull-based technique here is to devascularize the tumor early. So, what Dr. Cohen's doing here is he's exposing the floor of the bone flap here, the roof of the orbit, and he's gonna devascularize the tumor before we even gets started. So again, I think this is a very valid approach. When I do these pterional craniotomies and I wanna come down down here like this, I expose the frontal dura, I expose the roof of the orbit, and I just take a diamond bit drill and drill right down to the periorbita, and then I just bite all that bone off. So it's very similar, the only difference is I haven't taken the orbital rim off. For a tumor like this, you don't really necessarily need to get the orbital rim, because the is right there in front of you. For a tumor located really right at the clinoid, you might wanna take that orbital roof off to reduce your brain retraction and have a better visualization deep in the head. Here, this tumor is gonna be right on the other side of the dura, and I think this is a great approach, to do a pterional craniotomy, to devascularize the tumor along the skull base in the temporal and frontal regions as is being shown here.

- [Aaron] Right, and as you can see, Johnny, he's drilling this orbital roof very effectively. If you sort of do a pseudo-OZ, you're only not removing the bone, by you're really spend a good amount of time drilling that orbital roof from it's lateral aspect, and making sure the inner aspect of the skull bone is very flat with the orbital roof. It's critical to create that flat trajectory straight to the tumor. And as you can see here, this is a piece of the lateral part of the clinoid, and it's been further drilled away and bone wax is used, obviously to avoid any postoperative rhinorrhea.

- [Johnny] I'd like to make one comment here for the viewer. When you're drilling bone along this area, and it's involving a meningioma, and you start to experience some bleeding of the bone because it's a vascular tumor, the diamond bit drill can be very, very helpful to you. The diamond drill heats up a little bit. You don't want it to get too hot and injure vital neural structures, but it can heat up for you and actually act like a Bovie or a bipolar, and decrease the bleeding within the bone. So, when you're drilling this location, and particularly you're having some bleeding, the diamond bit drill can be extremely helpful to you. I typically use a coarse diamond rather than a fine diamond, to take the bone away a little faster, but it does heat up, and it helps coagulate this area, bone wax, this is also helpful, but the diamond drill can really slow down the bleeding for you.

- [Aaron] Thank you. I think that's an important point. And again, you can see the extra bone that's being removed, both on the temporal side and the frontal sides, and this really creates a flat trajectory all the way to the orbital roof. And here's the final product, Johnny, of removing as much or close to the orbital roof to sort of get as close as possible to OZ, but not necessarily do the whole thing. Here's the tumor being exposed after dura is open and sutures are placed close to that brain, as you very well mentioned. This tumor is gonna come at you right when you open the dura. The classic techniques of meningioma surgeries devascularize early to decrease blood loss and keep the section plane cleaner later, and that's what we're doing. So, would you have used OZ in this situation, or would you have gone with this approach, Johnny?

- You know, it's kinda like, I think either approach is fine. I probably would have used the OZ, because I'm very comfortable with it and my residents are very comfortable with it, and we'd probably use OZ. I think this is terrific, going this way. I think you're gonna have an easier closure, and you're gonna have to deal less with cosmetic problems. I think this is terrific.

- [Aaron] Well, thank you. And, you know, just to show the intradural work here, as you can see, this is an older gentleman, the brain is more giving, and we sometimes use the Bovie loops and they do work effectively as long as you're not deep in the brain and not close to the cerebrovascular structures. Again, trying to devascularize that tumor along the frontal fossa is a key factor. And here is the tumor being dissected away from the frontal lobe. For the sake of time, Johnny, I'm just gonna go ahead and briefly mention the details. Again, the tumor being dissected off of the frontal lobe here, the planes are tried to, kept intact. This tumor did cause intracerebral edema, as you can see the planes are not as clear. Placing a Cottonoid usually seems to work very well to wipe the brain away from the tumor and keep the planes recognizable. Again, aggressive debulking here. Often these meningiomas have little islands that are very easily suckable with a bipolar suction and avoid ultrasonic aspirator is possible when you get deep into tumor because of the risk of injury to cerebrovascular structures. And again, if you can move around different areas of the tumor and do that, remove the tumor effectively and debulk it with a suction and you know, bipolar, that's probably the safest way to go. Again, this is the edge of the tumor being reflected off the frontal lobe, and again, the dura is being gradually more cauterized in the roots of the tumor. As we know, meningiomas are like a mushroom, they have a root that doesn't extend all the way along their fundus necessarily, and here he's really staying along the sphenoid wing and trying to devascularize the tumor, always having in mind how medial are you, because you don't wanna get too medial with your bipolar caught along the root, as you can see here, and cause injury more medially without knowing. Here the tumor is being elevated and the optic nerve, here we go, is being identified early on before your devascularization and tumor dissection is carried all the way medially, because now you know where the optic nerve and carotid artery are, now you can be more aggressive to devascularize the tumor laterally, knowing that you're not gonna blindly end up on the top of the optic nerve with your bipolar and injure the nerve. Any other nuances here, Johnny?

- [Johnny] No, not at all. This looks terrific. What I would say is for the tumors that are a little bit more medial, I would recommend, if it is more medial, that you split the Sylvian fissure.

- [Aaron] Yes.

- [Johnny] Right in the middle of the sellar, to try to go underneath the tumor. Again, with these large tumors, you're still gonna have to debulk it so you can get around it, but you definitely want to find the optic nerve and you wanna find the middle cerebral artery and the carotid artery, to prevent damage. Once you see where those are, you can be very aggressive along the attachment, and give the attachment a release, and your tumor really will almost fall out, at least with the component around the frontotemporal region, and then you can concentrate all your time on where the tumor is attached, and determine how aggressive you wanna be on that final 10% of the tumor, whether you want to leave little bits, because the person's old, it's probably not worth the morbidity, or whether they wanna be extremely aggressive and remove all the bone contents and try to get a complete gross total resection.

- [Aaron] Thank you. And here is the last pieces of the tumor being moved anteriorly. Again, this tumor was not very adherent to the MCA complex, and that's why we were able to deliver it in a much bigger piece. And that obviously makes the surgery efficient, but you don't want to sacrifice speed for injury to neurovascular structures.

- [Johnny] And I think, you know, if you remember on the MRI, this is more of a lateral sphenoid wing meningioma.

- [Aaron] Correct.

- [Johnny] And from that you can see that the MCA was aways away from the tumor, but look how he's devascularized the tumor. He's got a really good devascularized, and then all of a sudden this tumor just wants to come out. It's very amazing that once you get the blood supply of the tumor, the planes between the frontal lobe and the temporal lobe become even more dramatic.

- Right. And then that big piece comes off, the surgery is carried out a lot more efficiently rather than not devascularize early and then keep on dropping into bleeding at every step and slowing down your surgery. And here is, as you can see, it's the attachment in the mid portion of the sphenoid wing, Johnny, and he's sort of using curettes to remove additional bone off of the dura. This gentleman was 75 years old, we did not get aggressive further. And as you can see, the anatomy of the optic nerve and carotid artery, that the arachnoid planes were left intact, which is very important in a meningioma surgery to keep the arachnoid membranes over the cerebrovascular structures the way they are. And so, I think the last few slides, we're just gonna, and this is a postoperative MRI showing adequate resection. And the pearls and pitfalls that you know, full OZ is really not necessarily these day. You don't have to remove orbitozygomatic arch, just what we discussed today in terms of the frontal process and dura of the supraorbital is adequate. And make your scalp incision generously to prevent frontalis palsy, protect the supraorbital nerve, and manage the frontal sinus violation effectively. Minimize bone loss around the key-hole, do not fracture orbital roof blindly, and protect the orbital contents. And really, cutting the frontotemporal dural fold facilitates extradural clinoidectomy, irrigate and protect the optic nerve from the drill during your clinoidectomy and do not drill close to the nerve. And carotid artery is really closer than you think during clinoid removal. And exercise patience with hollowing out the clinoid, and wax well as a CSF leak postoperatively can be really a spoiler. And Johnny, I would really like to thank you for your expert opinion, really an amazing discussion from your side to create really a forum to get our viewers a great sense of how this procedure is performed. I really thank you again.

- [Johnny] Dr. Cohen, it's a pleasure. I am always impressed with how much work you've done to teach the community of neurosurgeons, and how great your diagrams are, and your surgeries. And I appreciate you inviting me today for this topic that really has the passion for me in neurosurgery. Thank you again for having me be involved.

- [Aaron] Thank you, Johnny.

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