Grand Rounds-Tackling challenging Cranial Cases: Pearls for Success

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- Hello ladies and gentlemen, and thank you again for joining us. Today we have one of our special guests, Dr. Bill Caldwell, from University of Utah. He's a master surgeon who's going to be sharing with us some of his instructive surgical videos. Each video has a special learning point associated with it and he's gonna share those details with us today. Bill, thanks again for your time and please go ahead.

- Thank you very much, Aaron. It's an honor to be here. As you mentioned, I've chosen these cases. Each one has a couple of nuances and teaching points that I'd like to convey. And so, they run the gamut of a relatively straightforward cases to more complicated cases. And I hope you enjoy.

- Thank you.

- The first case we'll start with is a brainstem tumor in a 68 year old gentleman. And this was taken care of by Clough Shelton, our neurotologist and myself. He presented with a left tongue numbness and left facial numbness, primarily in the V3 distribution and his imaging demonstrated a pons tumor, located between the entry point and exit point of the fifth and the seventh nerve in the pons. And you can see the tumor in this location here. So, we'll perform this in the lateral position and choose a presigmoid transtemporal approach to this, to afford us a complete lateral trajectory to the region of the upper lateral pons. Now, it's important to remember that the area between the fifth and the seventh nerve at the brainstem, is a very forgiving corridor for which to access tumors in cavernous malformation. So, Dr. Shelton now is drilling the temporal bone here, and you can see he's exposing the bone and exposing the dura both in front of and behind the sigmoid sinus. So, after the transtemporal drilling, I'll come in and we'll expose the area of the pons. We'll take away any of the patrols of veins that we need to, but we leave as many as possible. Here, I'm demonstrating the fourth nerve under the edge of the tentorium and their entry zone of the fifth nerve. There's the seventh nerve at the inferior pons. And we'll choose an entry point exactly between five and seven in line with their route entry and exit zone. We open up endo millimeter to into the brainstem and we find this partially cystic tumor. The tumor was very soft and easily dissectable from the tumor cavity. This particular trajectory allows us the best exposure to the entire tumor bed as possible. So you could make a case to come in a retrosigmoid in this approach, but becoming in directly lateral, it gives us a good exposure to view the entire tumor cavity. And so, at the end of the dissection, we can see the entire tumor cavity and then we proceed with closure. It's a simple matter to close. We use fat graft, close the mastoid defect, and then cover it with this plating system. His postdoctoral scan shows excellent resection of the tumor and no increase in his neurological deficit. So, very safe trajectory to approach the tumor.

- Thank you, Bill. My only question would be really what you discussed the use of retrosigmoid or a purely retrosigmoid approach versus a presigmoid. And I agree with you sometimes that very steep angle, very medial toward the brain stem is not easily accessible without and without much cerebellar retraction. So, it is really a very neat approach. It really gives you a beautiful view of the medial aspect that would obviate the need for significant retraction on the cerebral hemisphere. Any other thoughts before we go to the next case?

- No, I think we've covered it. This was a retrolabyrinthine approach. So we really use the presigmoid corridor behind the labyrinth to approach the tumor. So, it gave us a better exposure to the tumor without sacrificing here.

- And this is also a nice approach for cavernomas in that region that often occur where you can sort of go through the brainstem with little consequences. Let's go ahead to your next case, please.

- Okay, the next case demonstrates a 54 year old woman with a visual loss progressive in her left eye. And she has evidence of a schwannoma of the cavernous sinus. Now, because she's got a visual loss in her left eye, we felt it was important to decompress the optic nerve itself. Here's the tumor, well circumscribed and pushing in the optic nerve in this location. So we felt a primary surgical approach was the best option in this case to reduce the pressure on the eye and preserve her vision. So, a standard pterional opening, we either part the hair or shave the strip as in this case and proceed with opening. The bone flap is removed and we drilled the sphenoid ridge down flat. Here's the meaning of the orbital band. So we want to drill this very flat along the base of the skull in this case today. And what we're doing here, is we're early on decompressing the optic nerve. And then we approach the tumor in a extradural fashion. This is V2 in this location here, the tumor you could see inside the Sphenoid sinus there, and we're removing the tumor as our window between V1 and V2 here. We bring the ultrasonic aspirator. We debulk the tumor and then proceed with extra capsular dissection. It's important to keep in mind that the carotid artery and the six nerve is lying just beneath the tumor. We're very careful here. We've dissected off V2 or dissecting it off V1 in this location. And then we will start to remove the capsule in a piecemeal fashion. Ultimately, we reduced the tumor down to its attachment on the medial aspect of the carotid and remove all the tumor extending up into the superior orbital fissure. This is the remaining capsule and we'll sharply dissect this off. This is the origin of the tumor. This is a trigeminal schwannoma, originating between V1 and V2. So now we have to consider closure. We're into the Sphenoid sinus, as I mentioned. So we'll plug that hole with a muscle graft here from the temporalis muscle, fibrin glue, and also close the sphenoid opening on the medial aspect of the optic nerve. And again, place the muscle graft, and then hold it in place with fibrin glue. We entered the frontal sinus with our craniotomy because she had big sinuses and we'll close that with a pair of cranial flap and then a MedPor cranioplasty for cosmesis. This is our postoperative scan, shows complete resection, and she was neurologically stable after the operation.

- Thank you Bill. I have a question, obviously the best quarter between V1 and V2, if the tumor is attached to V1 or V2 and they still have some good sensation in that area or the corresponding region of the face, I assume you're gonna lead a piece of the tumor on the nerve to avoid disturbing numbness?

- Yes, it's like doing a hearing preservation in an acoustic tumor. We go under high magnification, use fine micro dissectors and try to remove all the tumor off the origin. And if you take your time, you'll be able to differentiate tumor from normal nerve. But you wanna be very careful with the first division because you don't wanna incur any corneal numbness, which could in a dry climate, like in Utah, is a real problem for ultimately keratitis and a possible blindness. So, I'm very careful with the first division, but we'll spend the time and try to dissect all the tumor off of V1 and V2 that we can and try to remove it easily. And, it's amazing if you take your time, you'll be able to get it off in most cases.

- And do this procedure have any double vision after surgery, or it was only temporary?

- She had temporary double vision for a few weeks and it got better.

- Thank you. Let's go ahead to your next case, please.

- The next case is a ruptured basilar aneurysm in a 48 year old woman, and on her preoperative workup, she had another aneurysm in the anterior circulation. So, we'll do a combined approach here. And I really wanna emphasize the importance of the subtemporal approach in this basilar aneurysm treatment. So, this was a small aneurysm and our endovascular people felt that there was nothing that they would do in this case easily. You'll see it's small aneurysm, is not amenable to coiling. We did talk about the option of stenting, but we felt it was probably in her best interest to go ahead and just clip the aneurysm. And, the patient is placed in the lateral position here. And to do this combined pterional, subtemporal approach, we'll make a little more generous flap, and you can see a frontal temporal flap, extending a little posteriorly, and we wanna center our subtemporal approach on the root of this zygoma. So, ventricular ostium is placed to help in brain relaxation during the case. And we're coming in subtemporally. Here's the tentorial edge, gives us a direct quick approach to the basilar artery. In this case, we've got lots of room to place a temporary below the superior cerebellar takeoff. The third nerve is the key to the approach because that guides you to between the superior cerebellar and the posterior cerebral. Here's the region of the bifurcation. And we're now dissecting out the region of the neck of the aneurysm. Now, as I said, this was a very broad based small aneurysm. And, so the beauty of the subtemporal approach is it gives you this lateral trajectory and you're able to dissect off the perforators off of the upper basilar and behind the aneurysm. This is why I prefer this approach if I can use it for these aneurysms. Here's the aneurysm, inter-operative bleeding. So I go ahead and clinically place a clip. Now, this is an important point because I've placed a clip and you'd say, well, the aneurysm is taken care of, but I think I can clip it better because the neck of the aneurysm comes down further. So, what I'll do is we'll dissect it out further, take off that clip and place a fenestrated clip from laterally, and it's easy to place it, watch the perforators in the backside, place the fenestrated clip. And I'm much more convinced that I've better clip this aneurysm completely. Take off the temporary, ICG angiography. And you can see the basilar is wide open the ipsilateral P1, contralateral P1 and superior cerebellar. All vessels are open, monitoring stable. So, we'll go after the small little entry communicating aneurysm. At this point, it's a simple operation now to go over, reach over pterionally, and then place a clip on the small unruptured and to your communicating aneurysm. Closure, MedPor cranioplasty for cosmesis and for temporal wasting.

- Thank you.

- That concludes this.

- Thank you Bill, great case. May I ask what are you indications to use a pterional approach for a basilar tip aneurysm?

- Sure. So, if the basilar aneurysm is plus or minus within one centimeter of the posterior clinoid, I'll come in subtemporal only. So very high riding basilar apex aneurysms, I'll come in pterional only, and then look up and sometimes do an OZ and look up to get the basilar aneurysm. And also ones that are easier and pointing forward, I will often do those if I'm doing a multiple aneurysm case and I'm not worried about the posterior or the perforators on the backside of the aneurysm, or they're easy to dissect off, then we'll just clip it pterional only. But, if the aneurysm is posterior pointing, and if the aneurysm apex or the basilar apex is at plus or minus one centimeter from the posterior clinoid, I'd like to come in subtemporal only, just for the reasons that I demonstrated here in this case. Because I think I can clip the aneurysm better coming in laterally.

- The challenges with a subtemporal approach that we all know is aneurysm is larger. Typically, you don't have a good view of the contralateral P1, that's the blind spot. Otherwise, it gives you a better view in every respect compared to a pterional approach. Can you tell us how you deal with that for a larger basilar aneurism approach through the subtemporal route?

- Sure. I think there are two disadvantages with the subtemporal approach. Well, firstly, it's a narrow corridor and you don't see as well as you mentioned. And secondly, you have to deal with a third nerve. Now you may have to deal with third nerve coming in pterional only as well, but you almost always have to deal with the third nerve in your way or move it out of the way. It's rare in this particular case that we didn't barely touch the third nerve. But, what you do is I come in, I try to identify in a larger aneurysm where you can't see the contralateral P1. I come in, I place the clip and I go ahead and place the first clip as best I can and then take a look. Once you have the aneurysm clipped, it reduces the neck of the aneurysm, and you can usually look around and see the P1 on the other side. And you can usually see it well enough to do in ICG angiography. In some cases, I used to in the past, I used to do inter-operative angiography, always on the basilars, just for that reason to make sure that I left the P1 open on the other side. But with ICG, you can usually look across by the time you get the aneurysm clipped and get it narrowed enough to be able to see that. But I agree with you, that is one disadvantage from coming in subtemporal only, but you get such a superior view along the backside, especially, on the larger aneurysms to be able to dissect off those perforators all the way across. That's why I prefer.

- So if I correctly understand, for larger aneurysms where you can see the contralateral P1 as well, you may use a tentative clip, clip it, get the whole structure decompress, and then maybe then you use your fenestrated clip when you can see the other side better and sort of finished your clip construction.

- Correct. We place a primary clip in the best possible location judging by, you know, we usually can usually see the superior cerebellar and then get the first clip on and then take it from there.

- Thank you. Let's go ahead to the next case please.

- The next case is a microvascular decompression, and this is a fairly straightforward case that's routine, but I just wanted to show the technique that I've used over the years. It's been very effective and I really wanna credit Taka Fukushima who taught me this technique. And I really think he's a master at this. This is a 63 year old woman with left sided tick. And if you see that she looks like she's got conflict here, vascular conflict with fifth nerve root entry zone. And we'll do, this in the lateral position. And usually use a very small S shaped incision. It's centered over the asterion. And, we'll do a small opening, just blow this asterion and then creep up to the junction of the sinuses. And, this is usually easy to place and it can be done through a very small opening. So, here we are coming in. Here's the petrotentorial junction, petrosal vein. And again, we try to preserve the petrosal vein if we can. If it's in the way, then we'll have to take it. So, here's the fifth nerve at the root entry zone, opening up the arachnoid, draining the CSF. Very little retraction is needed. If the hole is well-placed, you're right there and there's our offending artery, branch of the superior cerebellar, and we'll loosen off the arachnoid. Now the key here, is to loosen up the artery and its investment of arachnoids over a distance to be able to transpose the artery, not just interpose Teflon between the artery and the nerve. We're going to remove the artery from its conflict with the nerve completely. So, we place a sling around the artery and its branch, and we're gonna tack it up to the tentorium here. This is a Teflon sling, and we'll put another sling around. So, two slings. Now, I've developed this technique. I've used because I've had a couple of the slings not be able to stay. And so actually, I tack it down with a micro suture. It's a 7-O prolene in this case and some fibrin glue and that holds the artery completely away and we can close it with merely a bone flap or with a small, a burnable cover to cover the entire opening.

- Thank you, Bill. We may ask how often you use this technique versus the simple Teflon in place.

- So, if we can transpose the artery, I prefer to transpose the artery. That includes for hemifacial spasm, geniculate neuralgia or trigeminal neuralgia. The reason for that, is because I believe that it gives the best chance of completely reducing the conflict and reducing numbness down the line as well. But in some cases, as you know, ectatic basilar artery, a large vestibular artery in case it was lower cranial nerve conflict, it may be impossible to completely transpose the artery. So in those cases, I'll use a Teflon interposition buttress. But in cases that we can move the artery like this one, I think that's a good example of how we like to leave it. And then we look around after we've removed the artery, you wanna look around and make sure there's no other small artery or vein as well. But in this case, it was completely free after removing of the artery.

- Do you believe that veins can come here and cause neurovascular conflict?

- I do, in big veins, but I must admit in those cases that I've explored them and I've found veins, I'm never as confident that it'll be the same outcome as in a case such as this.

- Okay, so if you don't find anything, do you pinched the nerves like Fukushima describes with your bipolars?

- Yeah. So, he's actually described that as he massages the nerve with his bipolars. And that actually is very effective at breaking the pain cycle early on, whether it induces longterm control from that, that's completely unknown in my mind. But, I don't hesitate to massage the nerve at the end of the case to try and break the pain cycle and leave them with some temporary numbness. But as you know, it gets better, fairly uniformly.

- If you have a vein and it's causing maybe some neurovascular conflict, do you still pinch the nerve or not.

- I do, I do. In fact, in this case I didn't massage the nerve at all because it's pretty convincing in this particular case that I've removed the offending vessel. But if it's a iffy case with a vein, I'll take the vein and massage the nerve, yes.

- So you avoid massaging only if there is a very obvious arterial vascular conflict?

- Correct.

- Thank you. Let's go ahead to your next case, please.

- Okay, the next one is a complicated middle cerebral artery aneurysm on the left side in a young woman. And this is an interesting case because I think it questions the origin and the genesis of these types of aneurysms. But, this is a 36 year old woman, 37, I'm sorry, presented with headaches and she had this aneurysm. Now, the interesting thing here is that this aneurysm, she had an MRI eight years prior that did not show an aneurysm. So, this is an incidental aneurysm, but it's definitely grown. And, when we did an angiogram on it, it looked as if there was a vessel coming out of the dome of the aneurysm. So you wonder if this is a dysplastic artery. So we felt this was not amenable to endovascular treatment. So we'll do a left sided frontal temporal approach, left optic nerve here and dissect the fissure and follow the middle cerebral to its branch point and one here. And we'll expose the region of the aneurysm. Here's our aneurysm, careful microdissection. And you can see this aneurysm is incorporating two or three different branches here. Here's this distal branch coming out of the dome of the aneurysm. So we felt what our plan is here is, we'll revascularize this distal branch and then clip the rest of the aneurysm. So, we harvested superficial temporal artery. This case, patient has heparin in eyes at this point, we fish mouth the end of the artery, bevel it, and then proceed with the bypass. So, we'll isolate this distal branch, coming off the aneurysm, performing arteriotomy, place a little bit of methylene blue to visualize the artery better and proceed with our anastomosis. Now, I personally prefer to do this with interrupted sutures that's so I can place each suture under direct vision, and we're not dependent on one or two knots up for the entire bypass. So, we'll then verify that the bypass is open with ICG, which it is in this case. And then proceed now with taking this branch down from the artery. You see, I've clipped it here so that we maintained a flow into the other branch coming off the aneurysm. Now, we disconnected the branch. We revascularize, we'll dissect out the remaining part of the aneurysm now. Now, we use this slightly curved sigidi clip, to reconstitute the artery, preserved these two branches, and we'll go ahead and place another clip to take care of that dog here and intraoperative ICG looks perfect here, and this is our post-op scan. And you can see the bypass is open and the middle cerebral is opening in this other branches. Here's our bypass. She did very well neurologically. So I think this case emphasizes, Aaron, that in some cases, you know, you have to use different techniques to deal with these complicated aneurysms. It was not amenable to an avascular therapy, and we had to revascularize the vessel in this case and clip this complicated middle cero blinders.

- Thanks Bill, great case. A couple of points I just have learned along the years, as well as using end to side bypasses a lot easier than end to end. And I think that's what you did here, which really creates a lot more ease of technique that I'm trying to do end to end here. The other is use of that band-aided clip that you use, really increases that vision of the surgeon around the clip rather than the straight clip. So, otherwise, I think it's a spectacular job, so.

- Yeah, the other point, the reason I left and I revascularized and decide as well on that, is that, and it probably wasn't evident from the video, but there was an early bifurcation of that branch. And I revascularized one of the branches while I left the other branch open during the bypass. Okay, so there was immediate branch 0.2 branches. I left one of them open and one bypass of the other ones. So I didn't cut off circulation to the entire artery.

- Thank you. Let's go ahead and get your last case, please.

- My last case is a complicated skull-based meningioma, occurring in a young man, a 20 year old man with a meningioma that extended both intraorbitally and intracranially. And I'm doing this with our oral surgeon, Goopy Patel here in Utah. And this is a 20 year old man with this problem with proptosis and this skull-based meningioma here, and there's a small isthmus connecting to this intraorbital component, which was significant. And he had proptosis as you can see. And he's got new sinus in this case from the tumor and the follow sinus is very large and also compressing his orbit. So, we'll perform a transcranial orbital tummy, coming your right side, open up the dura over the right frontal lobe and lagging the anterior superior sagittal sinus, and come now trans bessel. Now, we've identified the tumor at the base of the skull, and this is a meningioma that's being removed. And now, we'll start to concentrate on the orbital part of their section, remove the dura over the orbit and proceed with orbital drilling. Now, we're gonna completely decompress the orbit in this case. This is this isthmus area that I was referring to, where the tumor was extending from the orbit to the anterior skull base. Here's the orbit. Now, we'll remove all the bone. Here's the tumor extending transcranial to the orbit. We'll completely remove all the bone of the orbit. And this is where the tumor's invading into the orbit here immediately. So, the tumor extends anteriorly, just out to the region of the medial campus area. And so this is Dr. Patel now dissecting the anterior part of the tumor. So, we'll remove the anterior part of the tumor through this orbital incision and the posterior part of the tumor transcranially. Specimen and close up the orbital approach. Now, we'll come back in transcranially. Here's the posterior aspect of the tumor. It's attached to the superior oblique muscle. So, we'll remove that with this attachment and then proceed with removing rest of the tumor at the base of the skull. So this is a young man and we're being very aggressive at removing all the tumor with normal margins. We'll proceed with primary dura closure, the AlloDerm graft in this case, vascularized pair of cranial flap to place underneath the frontal lobe and over the orbit. We put another piece of AlloDerm over the orbit and then suture down our pair of cranial flap. Bone flap is replaced, and here's this postoperative scan, which shows good reduction of his orbit and his glow. In this case, you can see where all the tumor was removed from the post-op scan.

- Thank you Bill. Our first question is, I see that you did not reconstruct the roof of your orbit with a solid material. And what are the risk of endophthalmitis without construction of the roof?

- So, that's an excellent question. So, we've looked at our results of our patients with meningioma, that presenting with proptosis, and we have a large series of patients. And, when people come in with meningiomas producing proptosis, I've come to the conclusion that I need to do a very adequate decompression because the cases where we haven't done an adequate decompression or reconstructed, either with titanium mesh or MedPor the orbit, we haven't had the globe completely reduced. And so, my current practice is to completely decompress and not formally reconstruct the orbit if the patient has a meningioma producing overrule proptosis, and I haven't noticed any prop, any enophthalmos pulsating enophthalmos in that group at all. They tend to have some pulsations early on after surgery, and then the orbit contents scar down and the, you know, the pulsations have gone away and we haven't had any enophthalmos at all. So, I have seen enophthalmos several times, but it's not in cases with oral and tumor involvement, involving the oval contents.

- And in this case, because the tumor was not going to the multiple strip part of the orbit next to the end of conal area, you didn't need to go to a client or evict to me or of decompress take note, is that correct?

- Correct. And as you know, I like to really decompress the optic nerve in the region of the cone and the optic canal in those patients with tumor involving the, anywhere near the optic nerve, back at that area. In this particular case, it was just medial and superior orbital involvement. And we were able to remove the tumor completely. Now, the patient did have a superior oblique palsy post-operatively as expected because the tumor was invading that muscle, but.

- Okay, Bill, thanks for sharing with us some of your pearls of techniques and we really enjoyed.

- It's an honor, thank you very much.

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