Grand Rounds-Brain Mapping for Resection of Insular Gliomas: Lessons Learned

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- Hello folks and thank you for joining us today. We're lucky we had to have with us, Dr. Bob Carter, the Chairman of Neurosurgery at UC San Diego. He has extensive experience with treatment of low grade gliomas, and I'm very appreciative for his time to be with us. Both of us have no disclosures or conflict of interests. The discussion today will be for the Neurosurgeon focus on low grade gliomas. The topic is very broad. However, we thought reviewing the techniques of resection of low grade gliomas in the most difficult region in the area of the Insula would be beneficial. Therefore, this session we'll review technical losses for resection of Insular gliomas, both in the dominant and non-dominant hemisphere. Bob, thank you for your time.

- Aaron thank you, and it's a pleasure to be here with you. Obviously, this is an important topic and one of great interest to Neurosurgeons as we've developed better surgical techniques for treating low grade tumors. I want to thank you also for your dedication to putting forth these video learning sessions, which I think are quite valuable.

- Thank you, Bob. Let's go ahead, and once again, there is no disclosures of either of us for this presentation. We're going to talk about Insular Gliomas. I thought we can open up with an illustration that embodies the most important techniques in resection of these tumors, obviously the tumors in a very functional cortex and not only itself can be functional. Also it is bounded by very important neurovascular structures. Medially it is bounded by lateral lenticulostriate arteries, obviously by the MCH superficially, a long M2 branch and a long to perforator that can go to motor cortex. Those can be pretty critical, obviously knowing where to stop medially is important. Obviously the trans insular, I'm sorry, the trans Sylvian route can be very challenging. Can you tell me what are the three pearls that you consider most important on an novice surgeon who wants to approach these challenging tumors?

- I think that's a great question, Aaron, and you know, a couple of things come to mind. One is the wide split of the Sylvian fissure and feeling comfortable with the split to be able to do it technically properly and get the exposure to really see the Insula, to not feel that you're working in a deep dark tunnel, but really have some exposure of the surface of the Insula. Secondly, I think you have to have a navigation system that you really trust. Navigation can be important, especially for the early surgeon who is experiencing for the first few times, the transition from abnormal to normal tissue, and trying to really understand that. So navigation can be quite helpful and having a mechanism either internally or through experience with a given system for accounting for brain shift and the like. Those are two important things. And then finally, I think early on the wisdom to be willing to stop if you're in territory that you're unfamiliar with, there's nothing worse than taking a patient and causing a problem either on a motor deficit, from the lenticulorstriate that was taken in a way that causes deficit, we can get into later in the talk all about mapping brain function, which I think is a really important adjunct as well.

- Thank you.

- One, two factors that I want to discuss with you before we jump in Bob, is that the Transcend Symbian valve does provide a good amount of space to work. However, these tumors often reach a very large size and you may need to do some Cortical resection along the Inferior Gyrus or Superior Temporal gyrus. And obviously on the dominant hemisphere, that can be very functional and eloquent. So I assume that for your left left-sided Insular tumors, you do them awake and the right-sided Insular tumors, you try them sleep as much as possible. Is that correct?

- Yeah, that's a great question. And generally you're correct. On the dominant hemisphere tumors, I would certainly prefer to do them awake. I've migrated over recent years to doing both dominant and dominant hemispheric tumors, generally awake. It's just something I've become more comfortable with in terms of monitoring the patient during the procedure. And as we'll discuss the techniques of the awake craniotomy, I think have gotten again much more readily performed in terms of our anesthetic techniques and how we can bring the patients in and out of cooperation during the surgery. So I would like to say that for me, as many as I can do awake, I would prefer both dominant and non-dominant hemisphere.

- This is very interesting because that's exactly what I have done. We also started more doing awakes on the left versus right. And we found out doing both awake, not only it reinforces the surgeon to the surgeon that the patient is doing okay, therefore continue to be more aggressive. And that's really security blanket really has allowed us to be more aggressive in the non-dominant hemisphere with the resection of these very challenging tumors, where you really, no matter how accurate of navigation you have, it is a very difficult space to work with. It is very disorienting to as many important things around and that security blanket of knowing how good the patient is doing, makes you resect these tumors more aggressively, even in a non-dominant hemisphere. And most importantly, the more awakes you do, the more comfortable your team feels with it. And therefore you feel like you can almost do anything awake and take advantage of that, Continuous Interoperative, neurological monitoring.

- I couldn't agree more.

- Thank you. So we're going to review some of the basic details just through these illustrations before jumping into some of the videos open your fissure widely is critical. What we do in these tumors, either dominant and non-dominant in awake condition, is we keep the patients sleepy using Precedex and use this Sylvian dissection when the patient is still asleep and do a very wide exposure superior in Social side, inferior in Social side, recognizing those bounderies are critical. We cannot cheat and just expose the Fissure just so far, half way, because you see the tumor as sort of jumping to removing the tumor, because you really need to define your boundaries. And then you coagulate that superficial perforate is to the Insula. You protect any long perforator M2 branch that goes towards the motor cortex, that's critical. You avoid evolsing any perforator and M2 branches because that puts the M2 branch at risk of thrombosis. We do all of that asleep because that can be painful to the patient due to manipulation of the vessels. So the first part of the surgery is Precedex, patient more sleepy. Transsylvian remove as much of the tumor as you can. And then when you find you can use more and you really need mapping, we awaken the patient, we do cortical mapping of the inferior funnel percula and superior temporal percula. And then you do cortical resection in these gyroid to expand our corridor, can you comment?

- No, I would echo a couple of comments. One is the idea of having the patient be asleep for the initial part of the surgery of course, is quite standard and important part. I might as well jump in and comment. We do one of two things, you may do it slightly differently. When we have the patient initially in position, we will put them in pens asleep, and then we will wake them up to check their comfort level with the general positioning. Then we will go back asleep for the opening of the craniotomy, and as you've said, the exposure of the Fissure, I agree with you completely on that. I think this is also the time for the surgeon to do all the necessary work, to become oriented in the Insula, to again, assess the integrity of the stereotactic navigation and also begin to get a biopsy and some of the early work on the tumor before going to mapping. So, oh, we'd have a very similar approach. And I concur with everything that you've said thus far.

- Obviously after we have coagulated the perforaters to the Insula, which is relatively safe, all the M2 superficial preforators, you can be sometimes have to work between the M2 branches. It's very easy to dissect Temporal Opercula over the Insula versus the frontal Opercula. That's just because more of the large vessels lie over the Inferior part of the Insula and the vessels create that arachnoid space to dissect. But it's very tempting to jump into the tumor without exposing thoroughly the Superior Insular Sulcus and inferior insular Sulcus and define your superior inferior borders. The medial border is defined through the lateral Lenticularstriate arteries. These borders are critical because as you will see, there will be some shifts and the surgeon can get disoriented. Okay. go ahead Bob.

- You know, I'll ask you a question, Aaron, and this is more of a general surgical philosophy on these tumors, but one of the choices a surgeon has to make is really working on these tumors internally and then debulking towards the margin. Or as you said, defining the margin and beginning to really develop that plane early on in the process. I actually agree with you that if one debulks extensively internally, but then does not take the time to define the margin. Generally, you're going to have a subtotal resection or a resection that on the postoperative scan, you may feel like, wow, I could have done a bit more. So I think you're wise to both anteriorly and posteriorly superiorly and inferiorly get some sense of the margin of this tumor as you work and take the time to develop that. Otherwise you will probably have a subtotal resection and one that you might think you could have done more on.

- I want to include that very well as well that these tumors, the surgeon at all times, the more you can appreciate the margins, the better resection you're going to have. The moment you get to the middle of these tumors and your stealth goes, not very accurate. You do have a problem on your hands. A case I was trying to advocate more in terms of the compression is when the Insular tumor is very large and it's beyond the superior inferior sulcus. In that situation unfortunately, there will be no way for you to define the margins until you do more Cortical resection over the frontal or temporal Operculy. But if this is a tumor, that is very well-defined to the Insular. I cannot agree with you, Bob. The key to success is early differentiation of the margins.

- And certainly internally decompressing can help you do that it's a matter of balancing the internal versus the border work.

- And it's important in this illustration to really know where your functional fibers are after you remove the tumor. And this is sort of straitum that has the nutmeg appearance. Everybody talks about. I've done about 40 of these difficult Insular tumors in my career so far, and I still have a hard time defining that nutmeg. I can definitely appreciate the lateral lenticulostraite arteries that you often see here more anteromedial and those define more medial margins. However, the corner radiata is almost superior to you and going medially and the internal capsule, obviously this is three dimensional and you should definitely use subcortical mapping if you feel uncomfortable and you don't know where you are. What other landmarks what you use Bob to find the medial and these functional areas and cerebrovascular structure?

- Yeah, that's a great question. So certainly the vessel landmarks I think, are really important and can't be underestimated. And the vessels themselves, as we'll see later in the video are readily identified. One of the things that I think is critical as you begin to work out at these margins and develop your transition between tumor and natural SoCal planes. That process is one that I think comes with some experience and recognizing the border and the transition between the abnormal and the normal. As far as specific landmarks here, I tend to use navigation a fair amount and trust my system. At the same time I know what you're saying. It can be frustrating when navigation seems to be off target, and you're starting to get feedback from the system that you don't completely trust. And in that situation, I won't hesitate as I'm making a transition to a perhaps more normal appearing area, I'll send additional frozen section biopsies. I'll ask my pathologist to give us some feedback. I will obviously use tactile and visual cues in terms of abnormal versus normal tissue. And whenever I'm transitioning to a new plane of tissue, I will double-check where I am on stereotaxi.

- Thank you, great points. One of the technical challenges of this operation is opening the Sylvian fissure. It's definitely a microsurgical procedure and something that people have to be very comfortable with. So I thought we will use a video to show the techniques just before we start doing that, I want to pick a, I want to get a credit to Gazi Yasargil. Also Professor Yasargil who has really defined the idea of inside to outside opening up Sylvian Fissures. I cannot emphasize in this surgery, you really have to be very comfortable with opening the fissure very widely, going from inside to outside is important. We're going to show that on the video momentarily, but the surgeon has to definitely take his time and make sure the Sylvian fissure is carefully opened. So let's go ahead and just review the basic techniques here. I'm sorry for additional a voiceover in the video. This is a left sided Insular Glioma, and you can see the Sylvian fissure. That's relatively easy to identify. We cover both frontal and temporal area. This is the frontal area. This is the temporal area with telfoid to protect it from the intense heat of the microscope. We opened the Fissure distally and use jeweler forceps more superficially anteriorly, because if you fine vein, it's very difficult to disect with a microscissor. Then we go deep in the distal part of the Fissure and then come superficial as you saw the video and then expose the Fissure and M2 branches very widely. So this is the superior socal side. Sulcus inferior Insule sulcus, M2 branches are really skeletonized. We know what every one of these guys are to protect them from the bipolar coagulation. And with surgical manipulation. You can see this is the first step, we're just gonna go deep into the Insular, do the biopsy, remove as much of the tumor as much as we can. Any comments, Bob?

- First of all, I really like the jeweler's forceps technique, I saw that for the first time after being in practice for a little while, and found that it was really quite nice for getting that Fissure open and avoiding tearing veins and causing problems early on. What I call the inside to outside technique, where you go deep and then come superficial as you work at the anterior and posterior aspects of the fissure. That is a really great way to open the Fissure in a vascular way without injuring vessels or tearing small perforating vessels off of M2 branches. Two really important points. As you probably know, in some cases, you may find that a little bit of insufflation of saline through a micro catheter can expand the Fissure a little bit as you go to do that initial opening of the Fissure.

- Thank you, Bob. I think that's a great point about they saline within the Fissure. This is using again, using the tool of forceps, just like Bob emphasized very nicely. And then going from inside to outside, I'm going to hold the video here. We were deep in the Fissure, since we didn't have a good piece of this video, I want to re re review it again, just for our viewers. You see, we have opened up the Fissure deep here, distally, and I'm opening the Fissure from the bottom up. We're not necessarily working from top to bottom. So you find the large M2 branch, and then you follow the M2 branch deep. And then you open superficially that's as Yosh calls it it's like opening an orange. You put your finger within the Fissure and radially, open the Fissure out. It's a lot easier to open an orange that way rather than from outside the orange end to end. And that's such a critical nuance that I never knew until I spent some time with Professor Yasargil. So let's review our first case and a right-sided non-dominant Insular tumor is easier to manage than a dominant on, 42 year old attorney who was noted to have a generalized seizure. So as you can see, this patient has a sizeable, right Insular glioma posteriorly, it's essentially a burst internal capsule and anteriorly. You find yourself very much close to the normal structure within a millimeter of the tumor versus normal brain. Obviously this is typical for Insular tumors to have a very distinct border from Insular to the Insafalic structures and call date. And I guess we can review more of the other slices of the MRI. Most often insular tumors may have frontal or temple extensions, and they reach a relatively large size, and you may have to do a temporal lobectomy besides removing the insular extension on the tumor.

- I was here for a second Aaron a couple of thoughts. One is that as you can see posteriorly here, this is going to be a very challenging area of the tumor to get to in terms of angles and trajectory, as you come through the Fissure. And similarly, this portion that's high riding will also be up and away from you as you work in a surgery. And these are the two most common areas where we might see more substantial residuals in a resection like this. As you mentioned, the temporal extension, we'll be able to deal with it quite readily, the frontal extension in it. And so far as it relates to these vessels, that will be another again, a challenging area in that deeper aspect. Now one of the things I think is really nice to do in the preoperative planning stages is try to anticipate the problem areas before you get to them. And I know that as I've seen in this resection that you've done, you obviously did that.

- So let's go ahead, go to the surgical video of this case. And I would definitely would like to ask your opinion, Bob, how you would have done this different, like this video has been obtained with the permission of the patient. We use regional scalp anesthesia with super orbital and supra trochlear nerve. As you can see here, this would allow a more comfortable, pain control for the patient. And really patient comfort is number one in an awake craniotomy. We'd placed a skull clamp up into position along the square temple line contra-laterally and behind the ear because often there's a large scalp flap that's necessary in these cases. And you really want to get pins out of your way. We have a nurse always working with a patient using ice chips and keeping the mouth and the lips relatively moist. A large craniotomy, the video has been the speed of the, which has been increased just so we can do the temporal lobectomy quickly. You can see the superior temporal gyrus has been resected. Sylvian fissure is apparent, and we're really starting with the right sided temporal lobectomy to create that corridor. We use a florascene and for some of our tumors, obviously this is a low grade tumor and did not enhance with fluorescence to guide the section, temporal lobectomy has been completed, a medial resection of the structures will be done next until the third nerve is apparent along the midline tentorium.

- Aaron, may I ask you, do you supplement with your local anesthetic along the incision line, or do you simply use the regional block?

- Excellent question Bob, we use the injection about just anterior to the ear above the eyebrow and behind the ear. And then what we'll go ahead and do we place the patient in pins with all this, the anesthetic injected at the pin sites and also doing injection and incision. So we'll do whatever we can to make that patient comfortable. It's been my experience Bob, that the patients would help you about four or five hours awake. After that it doesn't matter how great and tolerant they are, they just won't be able to do it. Is this your experience or not?

- Yeah, I think that's actually a great point. And in fact, I would say four to five hours are the best patients with the most cooperativity may have some patients who can really only handle two or three hours. And for that reason, I like to make sure that I'm always, involved with every aspect of this early surgery to facilitate the opening, moving things along quickly. Because as you know, the time is limited that you're going to have the patient who is able to cooperate with you and you want to make sure that's used in the most wise fashion possible very good point.

- I think efficiency is critical. That's why doing insular tumors is so challenging because if you're not very efficient with opening the Fissure and that, that is not an easy task to open the Fissure very widely. If that's taking you a long time and you are not even to the tumor and you haven't done a mapping part. So it really is a combination of surgeons that have to be very fast in microsurgery mapping and tumor resection at the same time. Or how else do you do you're awake, craniotomy? So you saw how we placed the opinions. Do you do regional anesthesia? Do you do anything else to make sure the patient comfortable?

- Yeah, that's a great question. So our anesthesiologists have pushed us to be stronger advocates for regional anesthetic, and it's worked extremely well for the last two to three years, we've really done that on every case.

- Going back to this video, I think you saw that we did a temporal lobectomy, and now we are really working between channels between the M2 branches that we are skeletonizing. May I ask you, Bob, would you have done the temporal lobectomy the way we did it and then work between channels between MCA branches or would you use another technique?

- In fact, as you know, on the preoperative MRI, you can actually typically predict which channels are going to be available to you. And you can ensure that with your navigation, you're starting in the channels that you want to be in, for us as you know, it's exposure. So it's going to typically be the widest channels or the largest openings that we're going to work in and whatever triangles or openings are available to us. I think importantly, what can seem a daunting task at the beginning, because at the beginning, there may not be much room. There may be vessels crisscrossing, but as you start to get in and decompress and then begin to develop these openings often you'll get a sense that there's more working room than you initially thought was possible.

- Very well said. One of the areas that's critical is when this M2 branches come M3 and enter the frontal lobe, they tether you. So you really can't lift up this bank of brain anymore to undermine or remove tumor because these M2 branches are like ropes tethering you down. And that's when you really need to awaken the patient and map that face area in the non-dominant hemisphere maybe. This patient is awake, so you don't need to phase reversal. In that case, you just use cortical stimulation. The patient is awake. We usually start at two to three milli amps and use anatomical landmarks based on stealth to find where motor cortex is, map the face area. And when you know where the face is, let's say in this scenario, then you can do cortical resection here and be able to mobilize this cortex and undermine it. Any other technical nuances here for that section technique?

- Well, we might want to interject at some point here, Aaron, cause I think it is an important point. The sizes of suckers, the types of suckers and the adjunctive aspiration devices that might be used. So for example, I feel comfortable using suckers generally in the 16 or what we call the, in our institution, the safe suckers, which are the suckers with a small aspiration near the tip, which decreases the amount of force from the suction. I've also not hesitated to use the sauna pet device with a very low setting. And one of the tips that I find very good for this type of surgery is the painter tip named after one of the partners in your group. Troy painter, that tip when at a very low setting is very nice for dealing with very from tumor tissue. So I think you have to adjust your aspiration device according to the firmness of the tumor. However, you do have to be very cautious about high suction settings and of course, very high aspiration settings, because there's nothing worse than dragging in a vessel that you don't want to be in your aspiration device. I think that's a part that's a little bit of an art form. As you begin to work with these tumors, may I ask you what type of suction or aspiration devices have you used?

- Thank you, Bob. We use Rotan seven. I assume that refers to the diameter of the suction. We set it as a lower setting. I think 120 millimeter mercury. If I have the unit right and I have avoided using the sonapad, just because I have had a one NCA injury using that. I think the other issue is in my hands, that bipolar, when I bipolar and coagulate, I emulsify a tumor and did normal brain emulsifies to bipolar coagulation differently than the brain. And I feel very comfortable with that technique of emulsifying using bipolar versus Sonopec. Using Sonopec, but I just don't have that. I can appreciate the difference between the tumor and normal brain, does that make sense to my hands?

- One of the things I will suggest you want to give it a try is that if you do use that painter tip, I use a sideways aspiration technique. It provides a very similar effect to the bipolar emulsification. I think you're absolutely correct. If you try to use a Sonopec with direct straight on aspiration is it can be rather uncontrolled, but the painter tip can be quite nice in this regard. I also agree with you I'm right handed. So I typically will hold the bipolar in my right hand and between the tips emulsify the tissue and aspirate away the abnormal, I think that's a very good technique.

- Thank you, let's go ahead and continue with the video here. I think we can see that we have created those channels between the M2 branches. So well mentioned by Bob here. And some of the perforators to the tempo were coagulated and cut as the temporal lobe was removed anyways. And you can see how emulsifying the tumor between the bipolar blades and removing that. We use a combination of multiple bipolars ISO cooled silver glides, depending how fine we'd have to be working. So as you can see, I exhausted the resection through the channels were not doing cortical mapping for, as you can see the face just now twitching here and then use some subcortical mapping just to make sure we don't irritate the fibers from the face. As the face area was mapped. Then we stay about a centimeter anterior to the face mapped. And now I can mobilize the bank of tissue and be able to remove tumor just in these unreachable areas. Bob, you mentioned that it's important, useful, or some to make sure we haven't caused any stroke, because if you have caused any stroke by manipulating thevessels, you would know because of the breakdown in the blood-brain barrier, here's those lateral lenticularstriate arteries. I can't emphasize how important that is for people to recognize where these are and know that this is the most medial extent of resection. If there is some bleeding at the bed of the resection, please be patient do not aggressively, coagualate just irrigate, maybe a little bit of Surgicel and eventually that will stop Aggressive, coagulation will injure the fibers, the small perforators, and can be very troublesome.

- One question for you, Aaron, which is, tell me a little bit about your monitoring team in terms of monitoring facial function and or in the case of a speech mapping situation, who is at the helm of below the drapes, interacting with the patients on your team.

- Excellent question Bob, about who the patient in non dominant cortex, we just use visual inspection because they're awake. We don't want to put Eng reads our needles into their subcutaneous space. So we have a speech pathologist who is excellent, Theresa, who is available for all our mappings and also monitors any movement in the arms legs or say, or face or changes to speech. And for the dominant cortex, we use Theresa as well, she's a speech pathologist. And we use naming for a receptive language and we just use counting numbers for motor speech. Any introduction with either one with stimulation obviously would be counted as a region that has to be spared. My question for you is this Bob, do you use the same technique? Number one, and what are the other nuances you try to recruit in terms of mapping more and receptive language?

- Yeah, that's a great question. And I think any number of surgeons will tell you that they have a very slight variation on how they initiate the mapping and how they do it in a systematic way. You've probably heard many of those surgeons discuss those techniques. For us, we have a wonderful, what I call intra-operative neurologist, Dr. Jeff Gertrude comes to each of these surgeries and we also have a speech pathology, sorry, a neuropsychologist Dr. Mark Norman, who attends these surgeries and Dr. Norman will typically have seen the patient's pre-op and then does an intra-operative evaluation with a variety of, as you've said, naming tasks and or motor tasks in terms of counting or expressive tasks that are defined. We typically initiate as you described, based on anatomy, possibly within integration of our magnetoencephalography from the pre-operative evaluation, that's where we'll start. And then we'll look for a positive loss of expressive speech as we stimulate, as we define cortical areas for potential entry. Once we've got that positive control, we will then consider eligible cortex areas, where we obviously don't see any signal loss in terms of after discharges and monitoring for after discharges, that's done by, our inter-operative neurology team. And then if we see that, of course, irrigation with ice cold saline is undertaken.

- That's my next point, if you detect a seizure first, you use ice cold saline as described by Berger and Sartorius, and then if that's uneffective, which is rarely possible, then you use a sort of a short acting like a versed. Am I correct? So this is the pre-op MRI and the post-op MRI. And by focusing on those lateral lenticulostriate arteries you really can get pretty flush. We destroyed them without necessarily causing an injury. This is the blind spot you talked about, and you may say, well, maybe there is a little bit of tumor left and I won't disagree with you, but this is really a tough area to resect. The rest of the tumor.

- And I have to say Aaron and compliments to you on this particular procedure. Clearly this was a really excellent with resection of a very large tumor. I think one of the things that you spoke about, which is having a certain patience as you're dealing with these tumors and working away, the surgeries can be longer. They may be somewhat tedious, but at the same time, if you continue to work and define those margins, you can get a result like this. And your team is to be congratulated on this particular case, again, a wonderful, wonderful intersection.

- Thank you, Bob. I appreciate the compliment. Here is again to other slices showing the extent of resection going all the way up. So in the non-dominant hemisphere, we can be pretty aggressive. We can do pretty well unfortunately in the dominant hemisphere sometimes that cannot be always the case before we go next. This is again in a non-dominant hemisphere. Do you think achieving such results in a dominant hemisphere is as possible Bob?

- No, I think with the awake technique, you can come quite close, but I will say Aaron, that one of the things that I have found even with the awake technique and the dominant hemisphere is you will frequently have situations where the patient may begin to falter. And there's a question that comes up. Is this an early sign of speech hesitancy or expressive hesitancy? Is this a fatigue factor? Is this a later anesthetic effect? And all of those issues speak to the need to be relatively expeditious as you're proceeding along. And then also begin to have some confidence in the way you actually interpret the messages that are coming back from your monitoring team. Let me give you an example. If you're working on a dominant hemisphere, insular tumor, and you know that you've localized at the cortex and you have a sense of where white matter fibers are for expressive speech, that may be a portion of the tumor that you want to tackle last or near the end. And the reason I say that is sometimes I've seen surgeons go into those areas and then find themselves hesitating to do more because the patient is exhibiting some potential complication of surgery and then a large amount of tumor that was eminently resectable is left behind. That's my particular approach. I don't know how you approach it. Others might have a different philosophy, but for me, as a, as I try to plan the surgery, I try to make sure that I get all the easy and readily doable parts done before actually dealing with the more challenging marginal resection near functional cortex.

- Yeah, I can't include that better. That you've got to start doing a temporal lobectomy, do the frontal part and leave the medial and posterior aspects last. I think that's, that's a big, important nuance, obviously with the permission of the patient. This is on the third postoperative day and, you can really do pretty good resections with these. If you stick with the concepts of microsurgery mapping and being efficient in surgery. This is a 25 year old female with focal motor seizures. You can see this is a left sided tumor Bob, and this is relatively diffuse. I would like to comment on what you think about this tumor momentarily. It was a very small area of enhancement. This was an actual biopsy at an outside institution, determined to be inoperable. She was neurologically intact. Beside's almost every hour having the motor speech arrests and that biopsy diagnosis was consistent with an algo grade two, even though there was some area of enhancement and the surgeon felt that they took a piece of the enhancing area through Stratec biopsy. Looking at these films, is this an algolesion? This is an epilepsy surgery procedure versus an oncological procedure. How would you approach? And this is a really a high functioning patient.

- Yeah, that's a great question. And clearly dominant hemisphere. So for me, and in our center, this would start with, again, the preoperative evaluation. I've been at two institutions during my career and my prior institution we tended to functional MRI and my current institution, I've migrated to my needle encephalography just because again, that's available. And we find that it's an excellent technique for mapping both speech and motor areas. So that would be the first step in terms of trying to define trajectories and proximity to speech areas. I do feel like this is a tumor that you can do quite a lot of resection on. And so you have to determine in your own mind ahead of time, can I get to a percentage of resection that is going to make a substantial difference for this patient? And as you know, in high-grade gliomas such as glioblastoma, there's some definition in larger studies of that if we can get approximately three quarters of the tumor out, we can actually improve survival. Now this is actually low grade glioma, and I think the same oncological principles of cytoreduction apply here. If we can get a substantial resection, we can facilitate long-term control of the tumor. This is an algo grade two. So we're also going to want to know a 1P19Q status, and eventually other molecular markers will probably increasingly play a role in determining what we understand about responsiveness of these tumors chemotherapy, which of course is an important part of the conversation for resection. As far as biopsy goes, of course, I would be hesitant to perform a stereotactic biopsy in this region generally. I think you do risk vascular injury, which can turn a very simple biopsy into a substantial problem. That being said, my preference would be to combine the biopsy with the resective procedure, using the same principles that we've described. Now, if we look at the challenging parts of this tumor, I think we have a large portion of a tumor here. That's going to be quite resectable. We'll, need to map motor cortex in this region, as it descends inferiorly. here we're going to, again on the deeper side, this posterior medial aspect will be a bit of a challenge for us. And then also, because it's an awake speech case, it will be hard to determine at what point we might feel like we're hesitating after we've resected this tumor in terms of leaving some behind. So I wouldn't be surprised if there was residual tumor at the end of this resection, but I would feel it was definitely warranted to go in and try to remove as much as possible.

- I completely agree, and that's exactly what we did. So I'm going to just, we get this go over through the steps. We did discuss them on the previous video. So I'll make this very brief since you very eloquently, really reviewed the basic concepts that you know, about 50% of the patients with low grade gliomas are still alive at 10 years. And there is plenty of data, although not class one evidence that surgical treatment and cytoreductive surgery is very helpful. And because of that data, we'll see radiation therapy becoming more and more, a second have a low would call level treatment option and surgery is becoming again more and more respected as the first line of therapy. So how to do this case, I think the function of insula, which were this tumor is pretty well known. I'm going to briefly start off, skip those as they're easily known to most of our colleagues when you do use functional MRI. So I know you guys use magnetoencephalography, which is also a great way to do it. We use finger tapping to know where the motor cortex is. Obviously that's not very necessary because that is easily found during mapping naming is important because obviously it's along the superior temporal line. You want to know where that's located if you have to do any resection, naming can be difficult to really accurately determine using functional MRI. But here you can see some signal along the posterior aspect of the tumor and on the posterior temporal lobe, more generation is critical because this tumor has a funnel extension, and you definitely have to preserve that piece of cortex. And as expected is just above that tumor. DTI, more and more, it's playing a role in these tumors. This is a tumor that has been, sort of has pushed away that fibers rather than infiltrating the fibers you can see on this 3D reconstruction where the tumor is in blue and the other fibers are in khaki colors. I have seen diffuse insular tumors that they have infiltrated as a internal capsule. And that's one way for us to select our preoperatively candidates not to be a surgical candidate, do you use DTI Bob?

- That's a great question and DTI we do use it. We are just now coming to the juncture of integrating it into the operating room environment at our facility. I feel like it is a valuable tool to visualize what we know is happening. We certainly know that those fiber tracks typically are in direct proximity to the tumor, to the extent that we are able to interpret infiltration versus compression and movement of the fiber tracks away. I still believe that we're somewhat in the infancy of, really using DTI in this role. I think it's going to be increasingly used, however, and I'm certainly an advocate of more information.

- Okay. I agree with you. It is in its infancy and you can use it as one element in your big decision-making process. It's definitely not the only one, because again, it's a threshold study. You can threshold your MRI. You can have your technician threshold, your signals and sort of get what you want to see. But that doesn't mean that's the reality. This is really basics. And this is on the left side. You can see that insulor can be wildly open, but you cannot forget the motor speech. You cannot forget, the Wernicke's area often in women, especially can extend much anterior along the superior temporal gyrus, and so if you, most of the time can remove all the tumor you have to map here. You have to be able to map here and then be able to see how much of the superior temporal gyrus you can resect, how much of the third temporal gyrus you can resect. To open additional corridors to remove the tumor along its so superior and inferior poles. So Bob, as you can see in this picture, we did this do this case, opening the Fissure wildly, the tumor was almost protruding through the Fissure. And then this is really a postop MRI, relatively good resection and anteriorly and more inferiorally. And then more superiorly you can say maybe it was a little bit to my left and that's again, the area where the speech area is overhanging the tumor and can be very difficult to undermine. I guess, the ultimate philosophy in resection of these tumors that they are complex and non-operative approach is not unreasonable, but the patient should be evaluated by a team that has extensive experience with the resection of these challenging tumors. Using microsurgical techniques and mapping techniques really more than 90% of the section is more often than not possible. And really the complication avoidance really relates to appreciation of the pathal anatomy relative to neuro normal neurovascular anatomy. And I'm going to review the last few bullet points that the surgeon should appreciate during resection of the tumor. We talked about why Sylvian fissure section exposure of MCA widely section along the superior and inferior pre-insularsulci. You're vascularization of the tumor, coagulating the short insular perforating branches and resection of the tumor while paying special attention to the deep margins, especially to the lateral lenticulorstriate perforators. M2 branches can be very much embedded. And within the Insular tumor, have to be carefully protected. The M2 perforating branches have to be coagulated and cut, and their avulsion can cause significant injury to the important M2 branches. The lateral lenticulorstraite arteries are critical and injury would cause Hemiplegia, corona radiata and motor fibers are very sensitive to aggressive coagulation and long perforating arteries toward the motor cortex have to carefully be protected. Again you can see here, the ICA M1, these lateral lenticulostriate arteries that go to the striatum. Postoperative care is relatively easy on some patients may have seizures. They have temporary worsening of their language and sometimes weakness, but as long as they wake up from surgery, well they tend to recover just fine. The increased frequency of seizures and some temporary deficits. If developed a day after surgery is not necessarily a long-term disabling. Any other thoughts you would like to add Bob, before we close the session?

- The concept that you may have a temporary worsening of neurological function is certainly common in the, in the swelling phase, following surgery. I tend to agree with you. I often will counsel patients that if we've had a good exam throughout the procedure and at the conclusion of the procedure, I feel that they're going to come back to that exam typically. And so I'm less worried about that. Even though there may be a temporary increase in their deficit related to the actual post-operative, from the surgery itself. The insular tumor and the associated procedures to do a really good job on the resection of an insular tumor. This is best done in the context of a broad team-based approach for awake craniotomy in general, and to be familiar with that. So you don't want to have as your first awake craniotomy, a complex insular tumor, you definitely want to make sure that you've got those processes in place that you have that dedicated team that can give you a very good anesthetic technique. There's nothing more frustrating than getting well into a complex tumor, and then finding that the patient is no longer able to cooperate or the patient is no longer able to participate in the necessary functional testing. And so I want to emphasize again, put into place the team, get the experience with the team and then move on to these tumors as you've done that.

- Bob we'd like to really thank you for joining us for you really great experience, really an amazing dialogue that you created. And I personally enjoyed your comments, thanks again.

- Aaron thanks it was a pleasure to be here and a pleasure to work with you. Again, my congratulations to you as you've developed these visual learning techniques it's really important for us in neurosurgery.

- Thank you Bob.

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