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Grand Rounds-Resection of Olfactory Groove and Tuberculum Sella Meningiomas

Jon Robertson and William Couldwell

October 16, 2010

Transcript

- Ladies and gentlemen, hello and thanks for joining us. My name is Aaron Cohen, I'm a Neurosurgeon from Goodman Campbell Brain and Spine in India Department of Neurosurgery. I would like to invite you on behalf of the AANS to join us, for the first of an exciting new series of educational forums called AANS Operative Grand Rounds. The goal of the AANS Operative Grand Rounds is to provide, and discuss nuances of technique in a case-based format, to enhance the safety and efficiency of neurosurgical procedures and most importantly, to minimize complications, to improve the care of our patients. The AANS Operative Grand Rounds is a Multimedia Format includes PowerPoint presentations, Editor's surgical videos and other tools that combine information not available elsewhere. With the participation of experts in the field, we'll tackle difficult neurosurgical disorders, that affect the cranium and spine. The unique aspect of the AANS Grand Rounds includes, its ability to showcase surgical video simultaneously, with relevant expert discussions. My goal remains to present, not only glorious and victorious surgical cases, but rather to include the inter-operative misadventures, that lead to difficult moments in surgery when they happen because when we make the correct decision, in difficult moments, we make the biggest difference in the outcome of our patients. Finally, I would sincerely appreciate your feedback on how we can improve the future sessions of the AANS Grand Rounds. This is a learning experience for all of us and your feedback is the only way to satisfy your interest for worthwhile continuing surgical education. Here we start our journey, with the first session of the AANS Operative Grand Rounds, a discussion regarding Surgical Management, of Anterior Skull Base Meningioma. Okay, it's a pleasure for me to introduce Dr. Bill Couldwell from University of Utah and Dr. Jon Robertson, from Semmes Murphey Neurologic and Spine Institute. Gentlemen, thank you for joining us today. Today's presentation now will be a discussion regarding management of Anterior Skull Base Meningioma. We're gonna be discussing the hurdles and pitfalls. This is going to be the disclosure for the involved faculty. Anterior Skull Base Meningiomas, are primarily consist of olfactory groove, and tuberculum sella meningiomas. Although these tours are relatively very, adjacent to each other, they often have very different presentations. More rarely, we have a tumor such as Planum Sphenoidale and Orbital meningioma in the same region. We're gonna start with Olfactory Groove Meningioma technical considerations. As a basic knowledge, these obviously arise from the cribiform plate. They typically reach a giant size, and often presents with very subtle findings, including personality change, or may present with a seizure. Imaging, including an MRI and MRA. will be useful in terms of defining the relationship, of the optic nerve and vessels to the tumor. And if any of the vessels are engulfed in the superior, posterior aspect of the tumor, in a groove behind the tumor. CT will determine the amount of hyperostosis, catheter angiography is not usually necessary, as these tumors vascularity often, originates from the anterior ethmoidal artery, which in turn come from ophthalmic artery. Embolization of the anterior ethmoidal artery will place the ophthalmic artery, and therefore the vision at risk. I'll ask Dr. Jon Robertson if he has any comments, regarding embolization for these tumors?

- I would agree that embolization for these tumors is not necessary, in a majority of cases. Occasionally you'll see a tumor, such as a malignant meningioma, with a vascularity that you might have to consider embolization, but, in general it's not used.

- Bill may I ask about your thoughts?

- Yes, I would agree with Jon, you can actually access the basal attachment of these tumors fairly quickly, and early on in the operation. And so, we've stopped embolizing these tumors completely.

- Okay, and also, I think these tumors are relatively easy to devascularize, once you expose them from the base of the entry fossa, without having too much important structures around them to avoid, unless you go very posterior. Let's start with a case presentation of 55 year-old man, with a progressive history of personality change, who presented with a seizure and no visual change. This is the MRI, at different views of T1 with enhancement, revealing a relatively homogeneous tumor with moderate amount of edema causing significant amount of pressure on bilateral frontal lobes. This angiogram was performed in the outside institution before the patient was transferred, and as you can see, the draping of the frontal polar artery, and some of the vascularity at the base of the tumor. Obviously most of the important vessels, the anterior cervical complex vessels, are pushed more superiorly and posteriorly, and should be avoided during surgery. Preoperative consideration, seizure prophylaxis. If the patient doesn't have a seizure before surgery, often we continue just seven days of prophylaxis, based on the data from post-traumatic seizure information. However, if the patient does have seizure before surgery, we have to discontinue for 7, for 6 to 1 year afterwards. May I ask for comments regarding you guys preferences in that regard?

- I would also see both license I think is very important. And in this case it does appear to be some edema associated with this tumor, and this is the steroids preoperatively, I think it's significant more importantly, in a young individual, as opposed to the older individual, I think steroid preparation preoperatively is very important.

- Okay. Bill, how much time would you leave your patients in a seizure prophylaxis post-operatively?

- We leave them on routinely, for about four weeks. If they haven't presented with a seizure, we try to do a fairly rapid course and discontinue it after four weeks. If they presented with seizure, I usually leave them six months to a year.

- Okay. I have had a significant interest in using a lumbar drain in these tumors for many reasons. We're gonna go into detail about why that's important. I think for a large meningioma having a relaxed brain is so important to expose the tumor, identify the important cerebrovascular structures early on in surgery. If the tumor is medium to small, we put the lumbar drain and we generously, obviously not very generously, but at least drain 20 CC or so, at the time of the dural opening, and whatever needs further to be drained, to achieve the relaxation. If the tumor is very large, like the one you saw, on just on the MRI, a few slides ago, we still do use lumbar drain. However, we do not drain any CSF, until the dura is being opened, to prevent any brain herniation, but we do routinely try to use lumbar drain. What are you guys' comments on that?

- I've used lumbar drains fairly generously over the last 20 years. And it's quite interesting, if you go back historically under the 1970s, in my training and we were trained not to use lumbar drains. That was just absolute no-no. But in my experience over the last 15 to 20 years, I've found lumbar drains very useful. And I would agree with your use of lumbar drains. I'd basically do the same thing, and preoperatively.

- Okay.

- Post-operatively do not, maintain lumbar draining though.

- Okay, thank you. Do you fear with the very giant tumors that there is a risk, before you open the dura there could be herniation?

- I typically did not open the lumbar drain, before I open the dura.

- Okay.

- What I like to do, is particularly a large tumor such as this, if you approach this from an anterior approach subversively, you can actually get into the tumor, and start decompressing the tumor, and if things are tight, you can open the lumbar drain for drainage. It's really a call that you make at the time of surgery, dependent upon how, everything looks, the brain itself, in terms of the tightness, et cetera, vital signs of and what have you.

- Thank you. Bill, may I ask for your comments?

- Yeah. We've basically adopted the same approach as Jon described. We're a little careful with using the lumbar drain in giant tumors like this. And if I am concerned about the risk of herniation, we'll put in external ventricular drain instead. We may leave the lumbar drain in post-operatively if we breached the frontal fossa with of removal tumor. And so we prepare the patient for that, and tell them they may come out with a drain on their back if necessary.

- Okay. I see, you usually know these tumors, unfortunately distorted ventricles, is hard sometimes to get an EVD into the frontal horn. But I see if it is possible it would be very useful. About the craniotomy approach, I would assume most people approach this bifrontally, and this provides a panoramic view. We have approached this pterionally, and have had a very good success, and we'll go through pros and cons of each. The pterional approach is obviously very familiar to us, it avoids the frontal sinus, and post-operatively the potential risks for CSF fistula leak. It is efficient. It prevents the fraction of both frontal lobes. You can importantly identify the optic nerve and carotid artery early into the dissection process and protect them. And it gives you maybe a believable way, to be more aggressive, with the tumor since you know what the important stuff are. It does provide a lateral corridor, which is usually a shortened distance, to the important cerebrovascular structures, in case a vascular injury occurs, and make us maybe more able to protect them, and the early proximal vascular control obviously, would be nice to have, also preservation of the superior sagittal sinus may be important. Although, people mention that the anterior third of the sagittal sinus may be sacrificed. I still have gained significant respect for the veins, no matter where they are. This is a illustration of a right, lateral, frontotemporal craniotomy. This is the frontal lobe. This is the temporal lobe. The Sylvian fissure has been opened, and the tumor, as you can see is located along the dura, of the frontal fossa, and opening the cistern initially, and the anachoroid membranes would allow the identification of the optic nerve, and carotid artery. This way, we'll be able to move across, dissect these important structures early on from tumor, isolate the tumor, and be able to be very aggressive devascularizing it, without worrying about placing these important skull based structures at risk. It is as you can see important to have a very relaxed brain to proceed with this kind of procedure, since if there is a significant amount of edema, and increasing pterional tension, proceeding with this step can be difficult. Often the tumor may fill in this subarachnoid space, around the optical carotid cisterns, and release of CSF may not gain much space, or give us much chance at decreasing intracranial tension. That's another reason for using lumbar drain. This is devascularizing the tumor, along the frontal fossa. I do believe, the better we tend to vascularize the tumor early on, and you can see the inset, the better chance of managing the surgery efficiently, because you will have less blood loss, you'll have a more clearable field to work through, and you can do a more aggressive debulking, and a more aggressive debulking, would allow an easier rolling of the tumor from the subvascular structures. And those are two critical factors, in making the surgery safe, efficient, and in my opinion, for better outcome. This is debulking the tumor. We use micro scissors, we can use a CUSA, or sanopet or other ultrasonic instruments. However, using the CUSA over sanopet close to the capsule the tumor has to be caution or cautiously used, since the sanopet or CUSA may injure the vessels, and cause dissection of the intrusive artery, or the frontopolar artery. We then use a cottonoid to carefully dissect, and wipe the brain away from the tumor, as it's been devascularized. The frontopolar artery, usually will be stretched at this stage, and has to be sharply dissect the way. The frontal temporal approach as you can see does offer you an early identification of the A1, and as you can see, the arachnoid Heubner, and you can use microsurgical techniques, obviously sharp techniques, in order to dissect the tumor away. It is important as you can see in the inset, to carefully identify, if a perforator is truly a perforated to the brain or to the tumor, before it is sacrificed. And as you can see here, in the dissection through the micro scissors, it was clearly demonstrated to be a feeder to the tumor, and could be safely sacrificed. The ones that are going to posteriorly, especially like arachnoid Heubner, have to be carefully protected. Let's talk about the Bifrontal approach. It's a panoramic view of the tumor. It's more space to work through. It does provide a shorter working distance to the tumor. However, as we all know, a wider exposure is not necessarily a replacement for a good microsurgical technique. Jon may I ask you how you approach this tumor?

- This is an example of a quite a large tumor. And the real challenge in this particular case, is to reduce the volume before you retract the brain, before you put any retractor on the brain at all. So what I like to do is to do a sub frontal approach, a bifrontal craniotomy as you see in these illustrations, I take this down as low as I can, to where I work right on the floor anteriorly, and then stay extradural, extradural. That's the key, not opening the dura, as you see in this illustration. But to stay extradural, and to go right along the, take the crista galli down with a drill, a high speed drill, go right along the olfactory groove, and take your vessels along the cribriform plate olfactory groove area, and very aggressively devascularize the tumors, you'd go posteriorly, identifying your anatomy specifically, once you get to the planum, feel it out and you know exactly where you are, in relationship to the, fmordal vessels which should be just lateral to the clamps saggital sinus area, and take the move out. But the concept is to stay extradurally to devascularize, remove what bone you need to do this. Then to open up the dura, get into the tumor itself, and to debulk the tumor. And again, not putting a retractor on the brain at all at this point, open up the dura only to expose tumor, so that you can get to it and reduce the volume. Once you've got significant reduction of volume, then you can open your dura. If you do it this way, you will really minimize any retraction on the brain. In regard to getting exposure posteriorly, in relationship to the vessels, the optic nerve, and what have you. Once you've taken out 75% of this tumor, from an anterior midline approach, you can very easily go posteriorly identifying, your medial sphenoid wing, phlanoid area, so that you don't feel directly into the tumor and pull the tumor that's spilling over the Tuberculum Sella region, but then take a more lateral approach, on either side, working in and identifying the tumor as it's related to the parotid optic nerve and et cetera. But I think the key in this case, is that minimal brain retraction. And as far as the sagittal sinus itself, it's really not an issue, if you really subfrontal, if you stay extradural in your tumor removal initially, you know, you doing it's very minimal disruption and that's answer is sagittal sinus, because you're just not working in that area. What you see on this illustration, is really the standard, on large craniotomy bone flap, with really you're retracting on both cerebral hemispheres. You get great exposure of the tumor, but it's the retraction injury potential retraction, to the frontal lobes, I think, is a real issue in these cases. And so therefore you try to, in all cases try to retract on the frontal lobe.

- Okay, thank you very much. Bill, any thoughts?

- Yeah, I mean, I would mirror a lot of the things that Jon has mentioned. I think the advantage of a bifrontal approach, with a big tumor like this is it gives you an opportunity to do a good devascularization, of the whole base of the tumor from both sides and coming down. The disadvantage, as you mentioned in your PowerPoint, was that you don't have early access to the vessels. So you have to use other clues to find those and such as following along the spinoid ridge medially, to the region of the clanoid. So you know where the carotid and you know where the optic nerves are. Smaller tumors I prefer to do, from a unilateral approach, but these big tumors, I think that there's a lot of advantages, opening up wide and coming in bilaterally and devascularizing the tumor at the base. That is the first early step.

- Okay.

- That makes the rest of the dissection much easier.

- Thank you.

- There's one other comment that I think should be made about these large tumors. Is always considered, some of these tumors can extend through the cribriform plate into the nasal area. And that's something that you must consider. And certainly a bifrontal approach, where you can do an actual, a midline removal of the cribriform plate, and go into the nasal cavity is something to be considered but, always keep that in mind, particularly when you're dealing with these very large tumors.

- Okay. And that's a great point. So if there is truly nasal involvement, which can be definitely the bifrontal approach, is the preferred approach, an anterior approach would be almost prohibited. And again, this is just another view from Dr. Jon, regarding management of perforators, as we discussed, much respect should be paid to the perforators from AECOM complex, and the patient should exercise patience at this juncture. There are other approaches like a subfrontal approach for the medium to small size tumors, that may spare the olfactory nerve, or avoid bifrontal retraction, Endoscopic transnasal approach is definitely a new one, recently has been advanced, and it's minimally invasive. It doesn't require a craniotomy. However, it does limit the ability for microsurgery and microdissection, and be able to micro surgically dissect the tumor from the vasculature, from arteries, and optic nerve can be, very limiting, and just pulling on the tumor can place perforators at risk, and there is also a chance for CSF but definitely for smaller tumors can be a good consideration. Let's talk about positioning and placement for the surgery. We have this 3D model, that I'm gonna show how the patient is positioned, in this position. This is usually the position we place the patient in, with the pinions placed, the malar eminence is on the highest point, and the pinions are placed behind the ear, on the ipsilateral side and the superior temporal line onto contralateral side. I'm gonna turn the model a little bit here, you can see that one of the pinion is behind the ear, this prevents from the arms and the bulky features, of the pinion to be outside of the working zone, of the surgeon or the operator, as you can see here, the pin is totally behind the ear, and it's just above the mastoid groove. And then the other two pins are placed behind the hair line on the superior mass, at the superior temporal line, and prevents placement of the pins into the muscle, or the temporal bone, which may be thick. And again, this is the frontal position of the surgery, with the working corridor along this line. This is typically the position we have used for frontal temporal. This may be one that can be used for a frontotemporal approach, or a more extended temporal approach, or extended frontal temporal approach, I'm sorry, this can be used for a frontal temporal approach, that is extended or bifrontal approach. That's how the pins are placed. For the MRI we showed you because of the size of the tumor, we did a more extended frontal temporary approach, as you can see, the bone removal, is flat to the frontal fossa, as very well mentioned by Dr. Robertson and the bone removal is just lateral to the superior sagittal sinus, the pterion has been thrown away. The 4 D's of meningioma surgery, often they're discussed by Al-Mefty is to dedress the tumor, devascularize the tumor, debulk the tumor, and dissect the tumor micro surgically. Those are the steps, that at least in my mind is reasonable to follow. However, staying extraduraly and decompressing the tumor, definitely can be of great help, in terms of avoiding counter refraction early on. I think obtaining early brain relaxation, to make these maneuvers more feasible, is one of the most critical part of the meningioma surgery along the skull base. Adequate bone work, if you take records of skull-based approach, head elevation, mannitol, lasix and lumbar drain most importantly, I don't think anything really helps more than CSF drainage and that should be kept in mind. Again, this is the tumor we just discussed, and let's go back to the surgical video, and discuss some of the aspects of intraoperative findings and how we can make the surgery safer. In order to make you guys very familiar, this is a left sided frontotemporal craniotomy. The suction apparatus, the cottonoid. This is the left frontal lobe, left temporal lobe, small amount of fissure has been opened more medially and laterally but just along the anterium of the fissure. And this is this, you know, when you can see the optic nerve has been exposed early on and identified a piece of cottonoid maybe placed, for the surgeon to be oriented, as we zoom out in a second to see the tumor. Again, the left frontal lobe, this tumor was approached from the left side since we felt the tumor was more leaning toward the left side, also due to the fact that I am personally left-handed surgeon. we do try to approach too much from the right side, to prevent injury to the dominant hemisphere. As you can see, adequate brain relaxation has really allowed artery retraction, without significant retraction, clear exposure of the tumor, and it would allow very aggressive devascularization. This step was performed initially, as we approached, since when we lifted up the frontal lobe we did have some bleeding along the base of the tumor. Tumor is then highly debulked, Jon may I ask for any comments?

- I think it's going well, I think what you're doing is basically, the critical thing is just to debulk the tumor, once you devascularize it, that's gonna give you the, adequate space to then to continue with the section, but this looks like a very manageable tumor.

- Bill, any thoughts?

- Yeah, I agree. This looks like a very favorable one, fairly, not very vascular, and it's got a good capsule, and, you're able to devascularize it early like this. I make a point when I teach the residents and fellows, to try and make sure you leave the capsule interface, and not remove too much of the capsule early on, so that you can actually bring the capsule in, and dissect it off the brain. And so I'm a big advocate of not too much cautery around the outside of the capsule, so that you can use microsurgical technique and find a re-acclimate dissection, of the capsule off brain.

- Correct. And as you can see this the stage where the debulking has been performed, the cottonoid has been used, to wipe the brain gently away from the tumor. I think that's a great point. What you mentioned that keeping the capsule intact, using it as a handle, as you can see here, usually there's so much space created by the tumor that the fellow or the resident can help you as a third hand with bipolaring, or hemostasis during the surgery. Further debulking has been completed, at this juncture some of the vessels have come into view, obviously any coagulation has to be carefully done. And first the field should be clear, to make sure no important vessel has been sacrificed. Any thoughts, how to avoid and protect these vessels?

- Just have to be extremely careful, one of the things you've got to be, particularly as you get this tumor debulked is not to aggressively pull off the tumor.

- Right, and I think right now, maybe-

- So many times what happens with a big tumor like this, you know, things get going and you've been working for awhile, and towards the end of the dissection, which is the most critical, you know, you've been in there for several hours and you may be a little bit fatigued, and you'll tend to get in a hurry. So you almost have to stop and remind yourself, that this is, the real critical part, trying to this last portion where you're trying to dissect any vessels off of the tumor capsule. As you just have to go very slow and tend to always bipolar on the capsule, pulling the capsule towards you.

- Sure.

- I tend to minimize the amount of cottonoids that I put on the brain. You can sometimes just pack one cottonoid after another and before you know it, you've got a lot of cottonoids stuck in that. Sometimes that can traumatize that frontal lobe. So again, let the tumor come to you, and it will come to you with general traction, and not pulling the capsule as you deliver it, like you're doing there, watching for those vessels, but trying to avoid as much as you can, any trauma to the adjacent frontal lobe, because a tumor like this, the displaced frontal lobe is basically very sick brain.

- You can see the optic nerve here, there. I'm sorry Jon, the optic nerve is right under the suction, just to orient. And I'm gonna just make one comment. I'm sorry to interrupt you, Jon, you can see, we tried, this is the most posterior part of the tumor Jon, and we do use micro forceps to grab the anachroids, and take it away from the tumor especially, when we get to any important parts, where there are important cerebrovascular structures, this tumor is rolling nicely as you can see, you should be careful with rolling too aggressively and pulling the tumor, as very well mentioned by Dr. Robertson. But this is again the area of the hypothalamus, I think you see one of the, A1's coming to view more posteriorly. We very much avoid aggressive bipolaring in this region, and use only gentle irrigation with suction at a distance from the areas where the perforators are connected, since even bipolaring rather haphazardly in this area can dissect and injure vessels. I'm sorry, Jon go ahead.

- A caution about placing cottonoid, when you're working around and if it's a real tight area that you're working in, sometimes if you're not paying attention, you'll push a cottonoid in, and you push it against the optic nerve, you've got a cottonoid that really is, you really shouldn't manipulate or put any anything at all on the optic nerve, if you can avoid it. So you wanna see the optic nerve, but if you gonna put something on it, put a piece of gel form or Surgicel.

- Correct.

- Not a cottonoid against it.

- Yes. And as you can see, try to maybe use the arachnoid membranes and take advantage of them or what they call exploit them by grabbing it with the micro forceps and letting the tumor roll away, grab the arachnoid, and sort of dissect away, the important optic nerve, and some of the other structures right into that cutting with micro scissors, where it will be difficult to see the tip of the scissors, in very tight areas.

- Could you comment on, when you have the situation where for instance, the frontalpolar branch, major branch, is actually encased by the tumor.

- Right.

- It's within the tumor, how do you manage that?

- We're gonna go over to that with our last case where something will happen in the OR, and I would appreciate your comments there. This is the secondary tumor, as you can see from the optic nerve, carefully the arachnoid membranes have been grabbed with a very fine forceps and they are carefully preserved. This is another case, just showing how this is a right frontotemporal craniotomy for the same size tumor. And you can see how early the devascularization was possible. And you will see the high vascularity of anterior ethmoidal arteries, coming off just the backside of the crista galli. And I think after a second or so, after a few seconds, you will see the crista galli is gonna come to view, and you will orient yourself as you can see right there. So this is a good way to know how far you're devascularizing, because, how far am I? Am I all the way out to the other side, to devascularize if I'm coming from the lateral approach? And that may be helpful in terms of orienting the surgeon along the base of the frontal lobe. I'm sorry, go ahead.

- No, I just wanted to follow up on, your microsurgical techniques. So we like to use high magnification, and dissect the tumor away from the brain, not the brain away from the tumor, and use the debulking of the tumor, to develop your arachnoid planes. And then exploit those arachnoid planes and only divide what you can see. And so we don't like to do blunt dissection and especially around the posterior part of the tumor. So I would agree with the way that you were doing, the last case.

- Right.

- Nicely demonstrated where you devascularized the tumor early on, and that's the key initial step.

- Thank you. This is a postop MRI reveal, adequate resection of the tumor, with no significant complicating features. So we'll proceed with discussion regarding management of Tuberculum Sella Meningioma, They are also in a similar category as olfactory groove. Although they have very different presentations. There were about 5 to 10% of intracranial meningiomas, they typically present with Chiasmal syndrome, unilateral optic atrophy, and normal sella. The key about normal sella is important, as this is a key differentiating factor, of a Tuberculum Sella Meningioma for somewhat unusual looking prolactinoma or intra-sellar tumor, which will cause expansion of the Sella. Again, Normal Sella and a dural tail, is key to differentiate a prolactinoma or a intra-sellar tumor, such as a pituitary tumor. Obviously we do not like to offer surgery for prolactinoma, if it can be treated medically. Endocrine and ophthalmological work-up is very important, as CT scan will assess hyperostosis and MRA we'll assess any chance of aneurysm or arterial narrowing. The approach is usually from the side of the worst vision, as some manipulation of the ipsilateral optic nerve is necessary for gross total resection of the tumor. Invades both optic canals, and therefore both canal should be decompressed adequately, and that's mandatory, to achieve decompression of the nerve thoroughly. Displaces the optic nerves laterally, pituitary stalk posteriorly, respects the Liliequist membrane. And it's been at least some people's experience, that no matter how wide of exposure you do on this side of the optic nerve, there is potentially some postoperative deterioration of the vision, especially if the vision is extremely poor on the ipsilateral side and the nerve is already very badly injured. We do not recommend sacrificing any non-functional optic nerve, since rare reports of non-functional object nerves recovery has been documented. Let's go ahead and start with our case. A 57-year-old female with a two year history of progressive visual loss. Unfortunately, most of these patients, at least by the time they present, they have severe visual loss at least in one eye. And this was her MRI, again showing a relatively homogeneous ANSI lesion in the para sella or anteroseptal region. As you can see, one of the key factors is a dural tail, in this tumor that centered over the tuberculum sella, fostering the diagnosis of Tuberculum Sella Meningioma. These tumors as you can see don't often reach as giant of a size as olfactory groove meningiomas, since they cause a displacement and compression of the optic nerves early due to the location. And therefore the decreasing vision is alarming sign for the patient to see a doctor. Steroids and anticonvulsants as discussed previously for the case of olfactory groove meningiomas. Lumbar drain is critical to be able to achieve brains decompression. The tumor often fills the optics, cross optical carotid cisterns, and prevents adequate egress of CSF early on during the operation. Therefore, the surgeons always have a backup plan regarding obtaining CSF. For large tumors, we do open this lumbar drain after the dura has been opened to prevent their herniation. We'll proceed with our video of the MRI we just reviewed. This is a right frontotemporal craniotomy. temporalis muscle, right frontal lobe, Sylvian fissure, temporal lobe, a gentle amount of retraction has been placed on the basal posterior frontal lobe, just along the sphenoid wing and along the anterior lymphoid Sylvian fissure. Using microsurgical techniques, the fissure is opened, and the important M1 and M2 vessels are protected. As you can see, the craniotomy is very flat to the roof of the frontal lobe. Jon may I ask for your comments at this point?

- The approach of this tumor pterional approach, which is not my preferred approach, but I think it's key and watching this now did you, take down the scene with away. Did you drill this down, extraduraly?

- I think that's a great point. As you can see, the sphenoid is somewhat hampering our view. So I agree with you in that case, I shouldn't have drilled down, the sphenoid wing more aggressive, that would have given us.

- If you're approaching this internal approach. I think taking a sphenoid away now, open it up to the spirominal fissure, and possibly taking down the cannula and all of those things are very important, in approaching a tumor.

- Right but I have included some illustrations in that regard because I think that's a very good way to do it as well. And the viewer should definitely understand the nuances of such technique. As you can see, the sibling fissure has been opened, and a bridging then will be coagulated, to provide a more easy elevation over the frontal lobe without significant retraction. Bill may I ask for your comments?

- Yeah, I think that, actually I would have done is the same way as you did, and you need to open up the fissure widely here, get this signoid ridge down as Jon mentioned. And really get that frontal lobe, and temporal lobe separated. So you can elevate the frontal lobe, and quickly identify where the optic nerve is, in relationship to the tumor, because it could be displaced, as you know, laterally and posteriorly with this. And you wanna make sure exactly where the nerve is early in the dissection.

- Correct. And you can see the M1 branch right there. I think the M2 branches are sort of draped over it. Go ahead, Bill.

- Oh, I think you're doing a great job here. And now you look like you're trying to identify where the tumor is attached just medial to the clanoid there.

- Correct, that's the optic nerve coming into view. That's the carotid artery right there, and that's the tumor, and it allows early identification of the two structures. As you can see again, this is a little bit more frontal lateral view. This is the optic nerve, carotid artery, we stay into midline that's key and the tumor is devascularized and debulked from the Tuberculum Sella. Again, aggressive debulking, and early devascularization is key while the optic nerve is carefully protected laterally with a ridge of the tumor always.

- One comment is that you've gotta be very careful where you put your frontal lobe retractor.

- Correct, the nerve can display laterally, and the tip of the retractor can be very close proximity to the nerve there. So you've got to really be cognizant of where the nerve is when you're retracting the frontal lobe.

- Thank you. And this is the optic nerve, a decompression was performed with pituitary lonjuras to grab some of the heart of the tumor. At this juncture, we start micro surgically to identify the edges of the nerve, against the tumor, as you can see, the right's optic nerve does very much stand out as displayed open by the tumor, that is located right there. And we tried to do the best we can, to dissect it away from the tumor without injuring it. First creating a plane, and then using micro scissors to dissect the nerve away.

- Aaron, one thing that I like to do at this juncture is try to get some early decompression, of the ipsilateral optic nerve, and try to get some of the tumor out. Not maybe directly underneath the nerve, but make sure it's decompressed early, so that any shift to the brain does not exacerbate the tension on the nerve.

- I think that's a great point. And you will see in a second, we'll do that. I should probably open the foramen before dissecting, but at this juncture, we're just dissecting. And in a second, we'll cut the falciform ligament to untether the nerve, which is critical in terms of manipulating. Here is you're using a curved Carla knife, opening the falciform ligament, the nerve is there. I think Dr. Robertson does that earlier in the operation, which has some advantages in terms of protecting the nerve potentially further the carotid artery, the optic nerve, opening the falciform ligament again, and sometimes a drill maybe necessary or a sanopet. Sometime anchor turret may be useful. I do try the anchor turret first, as you will see in a second, because the heat of the drill may be problematic. Here is a turret removing additional portion, of the bone over the optic nerve. We try to avoid bipolars and use irrigation. You can see the edge of the nerve into the foramen, and a portion of the tumor going into the foramen, after the nerve has been further untethered, we'll be more aggressive with handling the nerve away from the tumor, which unfortunately at this juncture looks very much adherant to the ipsilateral optic nerve. After the nerve has been decompressed ipsilaterally, this is the contralateral optic nerve. We remove more of a tumor and use the optic chiasm, to find a contralateral optic nerve, and using microsurgical techniques, under high magnification, although there seems to be no plane, between that contralateral optic nerve and the tumor. We have been able to use the microsurgical techniques to create that plane. Again, this is a contralateral optic nerve ipsilateral optic nerve from the right side of the view, dissecting the tumor carefully, from the contralateral optic nerve. Go ahead, Bill.

- Yeah, I would agree with this dissection, and the key here is to identify the contralateral optic nerve, which is a little more difficult coming in from the opposite side. And so there's a couple of tricks that I use. I come around front and I come around back, but if you can follow the tumor around the back of the chiasm and then keep dissecting it, towards the other optic nerve that can help you.

- And as you can see in a second, we'll be removing the tumor from the contralateral optic nerve, through the foramen using the pituitary lonjura. Removal of the tumor inside is very important, as the risk of postoperative delayed deterioration of vision could be attributed due to expansion of the tumor, and necrosis of the tumor inside the foramen dalas left. This is at the end of the operation, as you can see, why did fissure exposure as commented by Dr. Couldwell, the ipsilateral optic nerve, contralateral optic nerve, the cavity left by the tumor, and the dural opening and the flat trajectory, I do believe as Dr. Robertson, very appropriately mentioned, that we should have removed this sphenoid more aggressively, the dura then is further coagulated, or the bone is drilled away, to prevent the risk of recurrence.

- There's just one or two take away comments. As you noticed throughout this procedure, if you'd come in along the pterional approach, your constantly working over the optic nerve on that side, and whether you like it or not, your suction is laying on top of that optic nerve. Each time you're working across the midline, you're touching the optic nerve. Any manipulation of an optic nerve, that's already been stretched, and it's already pathologic in terms of obviously from clinical standpoint, visual impairment, you're just having a higher risk of potentially damaging the optic nerve. So whether you're working above the optic nerve, or working between the optic nerve and the carotid artery, in some circumstances to mobilize that tumor from that from the ipsilateral side as you're working initially, this is a major issue in regard to how to approach this, that begs for you to consider, removing the anti caratonoid, opening up the optic canal, opening up the periorbital to try to mobilize, the optic nerve or give it some at least additional room, to move as you manipulate that tumor away. The other comment about this is that none of these cases, can you tell from the scans on the front end, whether or not this tumor is involving the optic canal proximal portion of the optic canal, tumor can extend into the optic canal, of most concern is that when it encases the hypothalamic artery and when you're trying to mobilize that tumor that's hidden beneath that optic nerve, on the ipsilateral side, it's not as bad on the contralateral side, but on the ipsilateral side, it can become a real problem. And particularly, if you by chance get into the ophthalmic artery, which may be adjacent to the tumor. So there's a number of pitfalls here, that really concern, at least concerned me, in regard to approaching these specifically from one angle, if you will, from a purely novel approach.

- Okay.

- That I've gone to exclusively like Dr. Robertson has said to taking the clinoid off on the ipsilateral side, opening the canal widely right up to the orbit, and then also reaching cross-court, and drilling the top of the canal on the other side, just because it gives the the nerve more room down the line. If there's any recurrence, then you're not gonna have visual loss.

- Okay. And this is a illustration depicting the fact that the tumor was devascularized, debulked, and then used chiasm carefully, to find the contralateral optic nerve, as it may be difficult to do that anteriorly at times. This is I think the approach Dr. Robertson is mentioning, if I'm correct Jon, and more extensive osteotomy along the roof of the orbit, remove all the clinoid, generous decompression of the optic nerve and carotid artery, generous opening of the thalumus ligament. May, I ask you for some comments Jon?

- Yes this is the approach is actually not an extensive approach. I mean, typically this is a orbital craniotomy. You'd call it an orbital frontal, or orbital frontal temporal. It depends on how large you wanna make it, but, mine is typically taking the lateral orbital rim, it's lateral to the superorbital nerve, taking the lateral rim and the anterior third of the orbital roof, along with a small portion of the frontal bone, it extends just immediately close to the sphenoid wing laterally. So it's a small orbital frontal craniotomy to work alone along the orbital roof, but you're not only working along the orbital roof, but you can swing a bit loudly, and come along the sphenoid wing. Most people are unfamiliar with taking the sphenoid wing down along the frontal fossa floor as opposed to starting out loudly on the sphenoid wing, but through that same approach, you can take down the sphenoid wing, you can open up the superior orbital fissure. You can clearly identify the interface between the anterior aspect of the catheter size and the superior orbital fissure, take down the anterior clinoid, open up the optic canal, both the roof and the lateral wall of the optic canal. All of this can be done extraduraly before we were actually approach the tumor. It's key that if you do this approach and I found it extremely valuable, it's an extradural approach. The dura is only opened immediately over the tuberculum sella. And I usually open up the dura from a transverse fashion from one medial sphenoid wing to the opposite, extended as needed to expose, but your retractor is placed along the extradural space, if you will of the frontal lobe that you retracted on. Normal retraction, small exposure, and you're able to approach the pathology, both from an anterior approach, to debulk it, which allows you to mobilize it before you look at it from a lateral approach if you're having difficulty mobilizing it from the optic nerve or the carotid artery. But allowing two different views will prohibit you in situations where a tumor is not just a straightforward tumor that is tumor involvement the optic canal. In case of the optomic artery, the tumor is inherent to either the chiasm or to either optic nerve. having that additional exposure is extremely valuable in dealing with these tumors 'cause not all of these tumors are nice soft circ-able tumors. You'll get into some tumors that are a fibroblastic meningiomas, and they can be very difficult to deal with if you don't have the right exposure, because you just can't mobilize the tumor, it becomes very difficult.

- Okay, thank you. And again, this is maybe a extra space would let you work on more avenues underneath the optic curve as well as over it. Maybe this way you would decrease the amount of manipulation placed over the optic nerve. This is a postoperative MRI of this patient, revealing adequate decompression and removal of the tumor. This is a pre-operative MRI showing the tumor, growing into the sella. And this is post operative MRI review post total removal. And this is a flare image to show that careful dissection of the fissure will prevent any injury to the frontal temporal lobe. And in this case none was visualized. So what are the technical nuances? So I think what's most important that we all agree is preserving function is most important than approach craniotomy or the postop MRI. If the tumor is too adherant to the optic nerve, just leave some of it there as long as the optic nerve is well decompressed. Decrease blood loss early with devascularization. Devascularization and generous debulking for efficiency of the section, and rolling the tumor cannot be adequately emphasized. If you do not debulk the tumor adequately, it's gonna be difficult to roll it. You're gonna start pulling, and before you know it, you may have something in your sucker that you did not wanna see. Meticulous handing of adjacent structures obviously critical micro forceps to dissect the arachnoid membranes, and sharply dissection to handle the vessels. Use the arachnoid membranes, they are your friend, irrigation rather than aggressive suction around the peripheries is the key, veins I don't think get enough credit. First time is the best time for a gross total resection, and study preoperative images to localize the cerebral vascular structures beforehand is critical. And always look for displaced structures for meningioma surgery. It is just 5,000 times to say there it was, and be wrong, but it's definitely not acceptable even once, to say there it was, and be right. Pterional approach may offer you all need. However, skull based approaches may offer advantages based on individual case. Decreased intracranial tension is key. Devascularize early, identify critical structures, use the pedicle, it's a pedicle, these tumors are a mushroom, focus on the pedicle to devascularize, keep the field dry to protect the important structures. Generous debulking, midline position should be maintained to prevent injury to optic nerve and other subvascular structures. Despite adherence of the nerve, the plane can be found under high magnification if patience is exercised. Protect the blood supply from the chiasm, which comes from inferior and superior aspect of the anterior superiority complex. This section should come inside the chiasm to identify the hidden contralateral optic nerve. Obviously that has to be protected. Leave the tumor on to the perforators if necessary. Anterior choroidal artery, Artery Of Heubner, those are not forgiving. And if the tumor has to be left, leave it there. I do believe life runs through those arteries. Untethering the optic nerve for its mobilization is key. Use bipolar and scissors on the tumor capsule, do not be aggressive with using ultrasonic aspirators, which will cut through the vessels. A-Comm stretched and displaced, be very watchful for them along the posterior superior aspect of the tumor. No vessel along the posterior superior aspect of the tumor should be taken unless carefully inspected to make sure it's not going to the brain. Tumor feeders from the ACA complex may be very easily mistaken for perforators when there is bleeding and there's tumor adherence. I'll like to ask both of you guys for any closing remarks, Jon and Bill, please.

- I think all of the cases, that have been presented are very good cases. All the technical points that were mentioned are very appropriate.

- Thank you, Bill.

- So I think that you really outlined some of the highlights of meningioma surgery I mean, I think exposure is critical, the approaches, and we've talked about the different approaches, the dissection techniques, emphasizing the arachnoid dissection, fine microsurgical technique, sharp dissection. I wanna congratulate you Aaron, I thought this was a great session.

- Okay, I appreciate that. Well, I wanna thank both Dr. Robertson and Couldwell, both experts, and really people who have done a lot of these more than most people, and their expert opinion has been crucial in making this session successful. Thank you so much.

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