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Nuances of AVM Surgery

Mustafa Baskaya

July 29, 2020


- Hello, ladies and gentlemen, and thank you for joining us for another session of the Virtual Operating Room from The Neurosurgical Atlas. Our guest this evening is Dr. Mustafa Baskaya, from University of Wisconsin. It's truly an honor to have him. He's a superb surgeon and pioneer in microneurosurgery. And tonight he's going to talk to us about the microsurgical treatment of arteriovenous malformations. So tonight I wanna start this discussion, by mentioning some of our conflict of interests, if you may call it that way, that both Mustafa and I are very much in favor of surgical resection of arteriovenous malformations and feel that for grade one through three AVMs, mostly grade one and two obviously, and some of grade three, selectively surgical treatment, in appropriate hands provides a significant advantage over other modalities of therapy. Secondly, both Mustafa and I believe that embolization plays a minor role in overall surgical treatment of arteriovenous malformations. That is not the, I would say the philosophy of every microsurgeon for AVMs, but as he'll talk to you about that, there are only select number of AVMs where you can really reach early on the feeders, like supracrebellar or what we call tentorial surface AVMs, where the draining vein can be very much obstructive in reaching the SCA feeders early on or giant AVMs where gradual decrease in flow can be effective in minimizing what we call edema, or normal pressure breakthrough issues for resection of giant AVMs. He's planning to review all the indications for why embolization plays a minor role, but I want everybody to understand that those are some of the philosophical differences, that both him and I have, that is not typical of other philosophies, among other AVM surgeons. So, with that in mind, I like, Mustafa, to ask you to start your talk and we'll go ahead and continue a dialogue and discuss the pros and cons of every technique. Thank you again.

- Thank you, Aaron. It's my honor to be part of this and thank you for the opportunity. I really appreciate. And like you said, we share a common philosophy, microsurgical philosophy, in many things, including the AVM treatment. And I will just briefly, go to the next. I have no disclosures, other than loving the microneurosurgery. So this is just general information about the AVMs. Annual hemorrhage risk present, most of them, they present with intracranial hemorrhage, epileptic seizures, and as we know, most of them live as potential AVMs. What increases the hemorrhage risk is the recent hemorrhage, less than one year. And if there's any outlet, venous outlet, obstruction, or stenosis in the venous outlet, if you have only one draining vein. And some others are questionable, like associated aneurysm, feeding pedicle aneurysm or intranidal, although I don't bleed intranidal aneurysms, all these AVM vessels, actually, they're aneurysmal dilatation. And history of multiple past hemorrhages, small size is questionable. Again, this is challenged by many studies. And deep location, posterior fossa location and intra and periventtricular location. I believe posterior fossa and periventricular location slightly increases the risk of hemorrhage. What other factors important in the decision-making? And, most important, patients age, patient's general health, neurological status and symptomatology of the patient and recent or past hemorrhages from this AVM, and patient's occupation, hobbies and patient psychological makeup, how the patient is taking this AVM. How seriously they are taking, or sometimes they don't worry, and they don't wanna get any treatment. So these are important points, that you consider treating the AVMs. What kind of options we have? Observation is always the good option. Microsurgical resection, with or without preoperative embolization, as Aaron pointed out, and then I was in the recent webinar, about the importance of the preoperative embolization. I rarely use preoperative embolization and in very very selected cases. And radiosurgery, embolization before radiosurgery, then the radio surgery. And embolization alone as a cure and microsurgical resection after radio surgery. These are all and many other combinations, you can apply in complex AVMs, but great ones and tools usually straightforward and most of the trees, You don't need these combined treatments. Another important things is the location, size, configuration, compact versus diffuse, location and pattern of the arterial supply, presence of the deep perforator supply, location and pattern of the venous drainage, outflow obstruction, whether or not there's outflow obstruction or restenosis, is important in decision-making. And associated aneurysms, evidence of steal and the presence of the fresh or old hemorrhage, hematoma, near the AVM. And then surgeon-related factors and the treating team-related factors are important, too. Surgeon's experience. Does neurosurgeon to have the experience to deal with these AVMs? Availability of embolization and radiosurgery, in the same institution. Familiarity with the surgeon's own results. And if you're doing this, so many of them, but you are having so many complications, maybe you should go back and look what you are doing wrong, and then correct those and is good to check your results, maybe annually, maybe every other year. And what other supporting facilities does surgeon have? Neuro-ICU, neuron acidity, intraoperative angiography, experienced surgical assistance. These are all factors play a very important role in treating these AVMs. I'm gonna skip this, as this is Yarsagil's classification, as something I follow, but you don't have to. So either convexity pallial, central AVMs, limbic AVMs and medio-basal temporal AVMs and the posterior fossa AVMs. What are the fundamental, very simple principles of the microsurgical treatment of the AVMs? It's simple, right? Obvious. Find and coagulate and divide the arterial feeders, eliminate them first. Dissect the nidus circumferentially, in a spiraling fashion. Divide main drainage vein or veins at the end. So these are three most important steps. And it's essential to preserve main venous drainage until the last minute, until you're ready to remove the AVM completely. And the goal, while you are doing, the goal is to not interfere with the normal parenchyma, normal vasculature and normal neural structures. Keep everything clean in your field and do the circumferential dissection, without interrupting the normal vasculature and normal neural structures. I don't like being minimalist in AVM craniotomies. Okay? If you wanna do safe AVM surgery, don't get stuck with that keyhole, minimal invasive, there's no such a thing in AVM surgery. You have to have a very large craniotomy and you have to inspect. In order to inspect all surface anatomy, you have to make a large craniotomy. And that will allow the inspection of the cortical vascular anatomy, sulcal anginal anatomy and then you have a chance to compare and then get in your three-dimensional mind, where are these arteries and the veins, how they compare with your angiogram. And then if you do very small craniotomy, you may not be able to see everything clearly. Also large craniotomy will allow you to do,* if in very large AVMs, you can have transosseous arterial feeders, and then you can control with the large craniotomies. And then just a few millimeter smaller than your craniotomy, you open your dura, and when you're opening the dura, please exercise extreme care, because some of these arteries and the veins, might be stuck to the dura and you don't wanna involve them early, especially that's the draining vein. So you'll have an engorged AVM, right away, when you're trying to stop the bleeding from the superficial drainage vein, when you are reflecting the dura. So first you do, inspect everything and identify potential arterial feeders, on the surface. Then, this is my technique, and I'm gonna show you that. I start dissecting arachnoid around these arteries and veins. And then I open all sulci, around this AVM and then follow feeders to the sulci. And opening this sulci helps relaxing the brain. Also help you to identify the feeders may be diving into that sulcus, and then either feeding the AVM, or sometimes they can be ampersand arteries. So opening this in systematic fashion and it will help you to define the normal anatomy and also define the pathological anatomy, anatomy disturbed by the AVM. Once you identify all these, and you identify the feeders and draining veins, you can start doing this spiraling fashion dissection, as recommended by Professor Yasargil. And only coagulate arteries or veins on the vasculature in a few millimeters in length. Don't be insisting in coagulating long enough. And then you have to irrigating bipolar, or if you don't have an irrigating bipolar, your assistant can irrigate constantly, so your bipolar forceps don't get stuck to the vessel you're coagulating. And then if you encounter the bleeding from the AVM, don't be persisting coagulating in these bleedings. Okay, don't. So you can cause major problems. So just put a little compression on it and wait. It will stop, okay? Don't try to pack the bleeding away from the AVM, on the brain side. That can cause intracerebral hemorrhage or interventricular hemorrhage and suddenly, you have a swollen brain. And this is the case example of showing my general technique in surgical treatment off the AVM. This is a 54-year-old man. Incidentally found AVM. After discussing the pros and cons, we recommended the surgical resection of this AVM, without any preoperative adjunct. So I will go to the video. Luke, can you help me? Okay, so we opened the dura, but a couple of points, dura was stuck. I brought the microscope. I need to get really low in the subtemporal region. So, I don't wanna rush and cause bleeding from and it's stuck, Dura is stuck to the draining vein, actually. Large draining vein, you see. And once you open that, I'll start defining the anatomy of the AVM. And arteries will look, a little more pinkish and thicker walls and the veins will look more tortuous, and then the thinner walls. I'm talking about the AVM veins. For example, veins here you see, these are normal veins, okay? But this is a dilated vein here, you see. That is the draining vein, so in order to define the anatomy, I'm dissecting the draining vein first. I open the sulcus around it. And now I'm trying to find the main feeders. The ideal situation, after you define all these, going after the superficial and deep drainage, but the main drainage. So that will soften the AVM and facilitate a safer exposure, safer dissection. So I'm going here again. So this is another, that vein was coming, turning around and I'm dissecting these. I suspect this is the arterial feeder here. See this and this one, and then I free them. They are under my control now. And then next I'm going to do other sulcus around the AVM. See, this is gonna be normal vein, and here you see the normal vein's blue and this is I'm not sure, this one is a feeding artery or artery passing by, ampersand artery. And I continue to open and define the pathological anatomy of the AVM. So I'm gonna follow this artery here, and make sure it's passing by. See, it's passing by, but here you can see it's giving the side feeders, so if you don't isolate these side feeders, and if you take, prematurely, some of these feeders, you may be, basically, occluding the normal blood supply to the surrounding normal brain. So don't take any artery early, follow them, make sure they are going to the nidus and take them closest point at the nidus. If you take it early, you might be taking some normal feeders. So you don't know and until you're 100% sure, don't take any arterial feeders. Any question, if you wanna soften the AVM, you can put a temporary clip and then explore. See, this another artery going there. And I am lifting the AVM now, see? And I am pointing with my scissor an occluded thrombose vein. So I'm not satisfied, I keep dissecting, dissecting until, see, as you guys notice, I haven't taken any feeders yet, because I wanna first define. I wanna dissect everything, skeletonize everything. And then you can start taking the side feeders or the main feeders. If you, just suddenly jump, it becomes bloody and you don't define the anatomy, and you are taking maybe very tiny veins, and then AVM becomes engorged, although you are not taking the main draining veins. This gyrus is diseased gyrus, is AVM inside. Once I established that, I am more unlocking all the sulci around the AVM, At the beginning, it it may look like I am spending too much time at this. Why don't I go and start coagulating? But that's lobectomy, that's not the AVM surgery. At the end, you'll make up for the time you think you lost with this dissection. See, that's the main draining vein. So now, I establish draining vein, now I'm going to do superior aspect of the AVM and opening the other sulcus around the AVM. And as you'll notice, as much as possible, sharp dissection. And I don't have dogmas. I don't say, "I always do sharp dissection." "I always do blunt dissection." Anything works. Sometimes sharp, sometimes blunt, sometimes peeling. So whichever one works. So now, this artery looks different, right? This artery here. You'll see the knuckles in it and it looks pathological. That's gonna be the feeding artery. So now I put the temporary clip and I'll dissect them and that will soften the nidus, so I can dissect, safer. You see, another one diving and it's right at the nidus. So you take that and then place the small AVM clips. Sometimes these can serve as a landmark. If you are doing an imaging, intraoperative imaging. So you know where did your AVM clips, and if you see any residual, it can help you to localize the residual. So another small feeder coming from that main artery. I'm diving under the AVM now and you notice that vessel start becoming blue. See? That's a good sign. That means you are doing good. AVM is softer and some parts of the AVM is turning blue. So once I made sure that a feeder was going to the nidus, I am taking them, removing the AVM clips. I'm removing the temporary clips. I'm putting AVM clips or coagulating them. Now, you can do your corticectomy around AVM, because you did all you can. You got the more softer superficial feeders. You got some side feeders, below the AVM, on the inferior aspect of the AVM, and now you can do it. And the key when you are doing this corticectomy and white matter dissection, important thing is keeping all the AVM vessels, that loops, inside your dissection plane. Mild coagulation, not very high intensity coagulation. and keeping them, inside your plane. So all the loops stays inside. All the AVM loops stay inside. And you shouldn't be thinking about anything else, during the surgery. Like any microsurgery we do, this is a sacred time between you and your patient. This is a meditation time. You shouldn't get stressed out. You shouldn't think about... Turn your clock off and do it. See, this is the AVM loop. You'll see, I'll coagulate and keep that loop. Another AVM loop. I'm gonna keep all these inside my dissection plane. See, another one. Coagulate, coagulate. Keep the loops this way. Wherever I am, keep them with the AVM away from the white matter. Another one, so go. So it's making good progress. AVM is turning more and more blue and is becoming softer and deflated. And this is the calcified, perinidal aneurysm. So this vessel, I'm not sure. It can be ampersand. I already took side feeders here, you see here and I'm following it making sure, it's not going to the AVM or it's going to the AVM and seems like it's passing by and I'm going under it. And you'll notice, I'm retracting the AVM, I'm not detecting any brain. And once AVM becomes softer, you can retract the AVM. Don't retract at the very beginning. And last things you do, main draining vein, coagulate, put a good, strong clip there and remove everything. Another trick I learned, from my mentor, Dr. Roberto Heros. After you resect and you're 100% sure. Can we go to the next slide? You raise the blood pressure 15, 20 millimeter mercury more, for 15 to 20 minutes and just observe the resection bed. Any unusual bleeding means very likely you left the residual AVM. And then you inspect and then search for the AVM. And then if you find it, you remove it. So it's very good results. He made excellent results, and I like to keep these patients in the ICU at least three, four days, maintain their blood pressures on the lower side, like 90 to 120, 90 to 130, and then gradually increase every day to avoid those dilated capillaries leaking. So how do we do this? We have to have everything, right? You have to have imaging tools, you have to have the intraoperative angio, the detailed anatomical knowledge, and you need to also know results and the writings of the pioneers in this field, like Yarsargil, Drake, Stein, Heros, Spetzler. And then you have to have a very low M&M, when you are dealing with AVM and your complete obliteration rate, regardless, should be 100%. Complications occur number one, faulty preoperative judgment. If you're operating on AVM that you should not operate, like some grade fours, grade fives and some grade fours. And if you abuse embolization and if you really need the embolization and you are not using embolization or incorrect spatial conceptualization of the AVM. Underestimation of that particular patient's co-morbidities and inappropriate surgical planning and wrong surgical timing. All these causes the complications. You don't wanna do too wide margins, especially in the eloquent area AVMs. And intra-parenchymal or intraventricular hemorrhage, means you did not recognize the bleed, either you packed away from the AVM and bleeding continued and suddenly, you start noticing the swollen brain, or early occlusion of the venous drainage, occlusion of normal vein drainage, retraction damage, parenchymal damage from the bleeding. These are all intraoperative complications and factors that cause the complications. Postoperatively, I like to do always intraoperative angio. If I am quite suspicious about the residual AVM, I'll do without closing the head and we have a hybrid OR, and actually I'm talking you guys from one of our hybrid ORs right now, because I just finished a surgery. Or if you're confident, close the head, but before you take the pins out, do the intraop angio in the OR, or you don't have any intraop angio, take the patient to angio suite as early as you can and make sure there's no residual AVM. And then other things are seizures, retrograde venous thrombosis, retrograde arterial thrombosis, and people also experienced the vasospasm. And Yarsargil calls this shocked brain. I don't know what that means, but that means, for whatever region you are operating, seizing the functions of that region. This is another one of the recent cases, anterior cingulate AVM. I'll show you, you'll see is in these interhemispheric AVMs colossal or cingulate AVMs. I don't like having the superficial drainage. Superficial drainage makes surgeon's life more difficult. So I'll prefer having the deep drainage, which is against the Spetzler-Martin grading. So in this one, we decide to... So the position is important in these. You can do neutral position. Neutral position is good anatomical orientation, but in my opinion, in most of the AVMs, it can cause interhemispheric bisection. It limits your one hand, either left or right hand. And then if you use the ipsilateral side down, that helps with the gravity. That side of the brain can fall. You can use two different corridors, contralateral or ipsilateral, that depends on, but I don't recommend doing the contralateral transfalcine approaches until you really gain experience. And maybe it's good to have both sides exposed. So anterior and middle interhemispheric approach, most of the time I'll use neutral position in very, very anterior, in the middle And some anterior, around the corner suture and middle anterior, I like to use ipsilateral side down. I don't wanna retract the motor area or supplemental motor area. For posterior interhemispheric, all depends on the patient and AVM and patient body habitudes semi-sitting, spine ipsilateral side down, spine contralateral side down, spine with head neutral. I use all these and I don't have any algorithm, about the positioning, I change my patient's positioning according to that particular AVM or patient. And this is the case. Luke, if we can go to the video. So in this one, anterior interhemispheric, neutral position. We know that main feeders are from the anterior side lodges. I don't wanna spend any time. First, I wanna get close to the main feeders. In terms for fissure dissection, and here you see the falx here, and this is medial frontal right hemisphere and thick arachnoid. So you need to dissect all that, in order to get the early feeders. Feeders may come from the MCA, superficially, in some large interhemispheric cingulate AVMs, which is rare. But in this particular case, all feeders will be from the anterior cerebral and its branches. So that's what I'm doing. I'm just going for interhemispheric fissure dissection, Interhemispheric fissure and Sylvian fissure dissection is two workhorse of the microneurosurgery. You have to be very, very efficient and good in dissecting Sylvian fissure and the interhemispheric fissure. You can practice these in the cadavers and don't just jump and go do difficult cases and get into trouble. So this is one of the feeders on to cerebral arteries. So I'm following it here. I'm going to follow. And before, I won't do anything, see? I have to see both perichondorsal arteries. I'm mobilizing. And one of them is quite otosclerotic here and is quite relaxed, nice brain. Getting fissure early also have helps you to relax the brain, too. So now I'm getting the feeders. Now I'm gonna follow them and I'm gonna dissect even more posteriorly. Now I feel more confident, because I have some early proximal control. See here, I'm getting deeper and deeper. I am basically unlocking the AVM and moving this way. Moving laterally. So once I got all these feeders, it's gonna to be all safe and good I wish I could do a little bit fast forwarding, Luke. Can we do it, can we try? Here now, once I establish, so I'm following, this superficial one now. So this vessel here, you see, I'm not sure that's going directly to the AVM, but giving side feeders. So I'm taking those side feeders, one by one, until I'm sure either is passing by, or directly going to the nidus. If it is directly going to the nidus, I'm gonna take it at the closest point it's entering to nidus. If it is not, just leave it alone, because it's going to be supplying to the normal brain. See, it is small feeders and you see AVM is easily... I can manipulate AVM easily now, because I took the main feeder. See, once I am sure that that wasn't a side feeder, I took that part. And I'm now unlocking the anterior part of the AVM and I'm performing this sulcal dissection. Okay See, now we got a whole perichondorsal under our control, and no problems at all. So now I'm going to start the corticectomy and everything is defined and superficial drainage is all, away from me on the posterior aspect. Like I said, I don't like having the superficial draining veins in this interhemispheric exposure. It really limits your hands. But, you know, that's not the end of the day. We can still do dissection safely. See, those are the loops, keeping the loops inside. You'll see that the large perinidal aneurysms, in this case, they're all now thrombose and no fluid, because no flow in it. Because we... See this? We cut the flow. There's another loop. I'm keeping the loop on the AVM side here. All keeping, keeping the AVM side. And there's a gliotic plane in most of time in these AVMs. They can sometimes due to the microhemorrhages in the past. So I'm taking one by one. Patiently, not rushing, You never rushing in microneurosurgery. Now taking all large arterial feeders, deep feeders. Sorry, if you guys hear any voice, this is natural in the OR, operating room and one of the hybrid ORs. If you're hearing the voices, that's because there's so many surgeries going next doors and on the other doors and other ORs. So I'm retracting the AVM and elevating. See? And then getting that part. All these things take time and you cut, skeletonize, cut, skeletonize and eventually, it come out in one piece nicely. This patient did very well and again, a complete resection. Postoperative angiogram shows it is all ampersand artery. You see tiny, tiny feeders going and some of them has AVM clips. And you see superficial drainage pre-op and post-op. And another anterior cingulate AVM, A very large one. I'll skip the video of this. So same principle. Noting this is a quite large AVM. And the left side--

- And again with us, okay-- The patient did very well, postoperatively and the same principle. In this one, you'll see, this is the early case. I thought embolization will be helpful. This is like when I first came here and we embolized, but I had a extreme difficulty, during the interhemispheric exposure. Then I, after this case and some other cases, I use embolization as appropriative adjunct. I realize, embolization is not helping me, it's causing more problem. Why do we do embolization? Because we want to reduce the surgical morbidity mortality, right? But embolization has its own complication rates. And it varies from 2% to 15% in some series and most of them very serious hemorrhage cases. So this patient, luckily didn't experience any problem, but embolization didn't help me here and actually obstructed my dissection, during the early exposure of interhemispheric fissure. Eventually, she did very well. And this is another case. Grade four AVM is in the right, under the motor cortex and the posterior cingulate area. Again, one of the early cases. I thought maybe embolization, helps me, if I embolized the most deepest part of the AVM. And I, at the end I don't get tired and I will embolize it. And that's how I learned from my mentors, but at surgery, embolization wasn't helpful at all. And I'll also, when I cut the... Can we go to the next? Yeah. When I cut one of the arteries, embolize with the Onyx, it was still bleeding. And you'll see, in some parts of this video, I already exposed those arteries, which were embolized by Onyx. So what was the point if I'm going to expose anyway? So we call it surgical embolization. We can watch some of this. So see, I'm... His motor cortex is right there, spatial the leg area anterior to the AVM.* So you need to be very careful. Actually we can, skip this video. He woke up with the mild, lower extremity weakness, improving over 48 hours. And he did excellent recovery. And this AVM was called inoperable by some neurosurgeons in very reputable centers. So it wasn't inoperable. And this is another AVM. Dominant hemispheric temporal perisylvian AVM. Again, the reason I'm showing you, this whole MCA is ampersand artery. This is like a one by one. You need to skeletonize M1, M2, M3 and make sure you take only the vessels going to the nidus. You need to be very familiar with the variations of anatomy, normal anatomy and pathological anatomy, created by the AVM. And this just shows you how we skeletonize, with excellent results. And this is a speech area AVM. Wernicke recently did it, and same principles, complete microsurgical case. Luke, can we see the video? So this is, again, you will have many, many ampersand arteries here. This is perisylvian area and Wernicke area. So you need to spend time to dissect the anatomy and bring the anatomy to you, okay, so it's not going to show up right away. The AVM is not going to show up. You need to define those. That's a draining vein, going to the vein of love there. We found out that, and then now I'm going to find the nidus and dissect the gyrus around the nidus so I minimize the cortical damage, because we know that this is a superior temporal gyrus AVM, and this is perceptive speech right next to the AVM. So same principles again, like I showed you before. small ampersand arteries taken by AVM clip, then coagulation and then follow. I will follow this branch here. I'll take the side feeders, if it is passing by. If it is not, then you go into the nidus. You take anything you can use ICG green, Micro-Doppler, any adjunct to facilitate the safe resection is good. I don't have any objection for that. Again, large cortical artery, giving the side feeders taken one by one. So we can stop here actually. And rest of the AVM resection is okay. Again, he woke up with the mild speech deficits and all of them improve to the perfect normal speech, in one week. And this is like hippocampal AVM. Middle-aged female patient presented with the new-onset seizures and actually she was in subclinical status and we stopped that. And when we woke her up, we found this AVM. This is the AVM. I did it in the frontotemporal approach and subtemporal trans fusiform gyrus. So again, nice rejection, no cortical entry, because I came stop subtemporal here. And she did very well. She has been seizure-free since the AVM, last one and a half year. And this is another dramatic case. I use the embolization because of the high shunt. And this is an elderly gentleman, who was considered inoperable. Again, many surgeons, many reputable centers. Fixed peripheral visual loss and slow, but progressive cognitive decline. If you look at these previous MRIs, this T2 changes were less and it's getting more and more, probably due to the high shunting from the direct AV fistula. We thought, maybe I thought actually, maybe occluding that may help me at the surgery, but in reality, it did not. And why? Because, right after the embolization, this gigantic varix start thrombosing and it's surgery. I had to go under this to get these main PCA feeders. So made my job much easier. I had to retract that giant thrombose varix, and then add probably another two, three hours to the surgery. The preoperative embolization was completely unnecessary in this case. I did it, but you can watch this in the neurosurgical focus. This entire video. He did very well. His visual deficits remain unchanged, but his cognitive deficits improved significantly. Another AVM, I'm gonna skip this. Interhemispheric approach ipsilateral side down. And then emergency AVMs. Sometimes you don't have time to evaluate these spatial. This is a patient with known AVM and the seizure disorder. And they have been sitting on this AVM for several years, just treating his seizures. And when he came to us, he was comatose GCS three and replace two ventriculostomies, and he was hand eating. So I took him to do angio and then the surgery, right away. So first I opened the lateral ventricle, go through the superior frontal gyrus, went into the lateral ventricle, suctioned a lot from the lateral ventricle. And then I went to resect the AVM. This was an inferior temporal fusiform gyrus AVM. And then that helped me to get to the temporal hole. I clean all the blood from the temporal hole and stop at that time and remove the AVM. This is immediate post-op CAT scan. You see, this is almost three weeks CAT scan and post-op two months. Here his MRC was two and one year, MRC was one and he's living independently. Sometimes you can do emergency AVM surgeries, if the AVM is not very big, right adjacent to the hematoma and you're gonna remove the hematoma, or AVM is in your way. AVM is between you and the hematoma and it's small. So swollen brain or other things won't matter. You can remove the AVM quickly, get the hematoma out and save the patient's life. And this is another emergency case. We did a large case and we took her to the surgery right away and evacuate the hematoma. She was completely hemiplegic and start improving after surgery right away, because AVM was small and I was there to drain the clot. So in my opinion, grade five and some grade four AVMs, should be treated conservatively. There are certain cases you may need to operate and in those cases, the preoperative embolization might be helpful. That's the only time I will use preoperative embolization. And if there's another particular reason. Preoperative embolization should reduce the risk of overall treatment plan. It should be guided and individualized, according to that patient's needs. Now you don't need to do every time. And indications for curative or palliative or preradiosurgery embolization are limited. Radiosurgery has a role in certain AVM, especially the small AVMs, and that AVMs surgery will carry high risk. We already talk about this. And most important thing is going to the lab, studying the anatomy, studying all these microsurgical techniques in cadaveric heads, brains, and in animal surgeries. Doing as many as microdissection you can do. And if you do it, you'll have wonderful results. And watch many, many AVMs videos. Watch. And thanks to Dr. Aaron Cohen-Gadol He put this Neurosurgical Atlas for you guys. I still watch his surgeries. I go to surgical, neurosurgical. I get email prompts. I've watched because you learn every time. When you've watched these other people surgeries, you realize, "Wow, I wasn't doing like this." "Maybe next time I should try this." And you'll watch and watch and watch and watch, you learn more and more, so then became versatile. But lab is everything. You have to go to the lab. This is our lab. As Confucius said, "I hear, I forget. I see, I remember I do, I understand." Read, listen, watch, dissect.

- Beautiful work, Mustafa. You know, I've always been a huge fan of the work you have done. Truly one of the best microsurgeons of our time, The passion you have, the passion you have for microsurgery. The clean work that you do, is exemplary and truly a role model for all of us. I want it to bring up some of the questions that people chatted, and they can please go ahead and add their questions right now. The first one is, do you believe in an awake craniotomy for an AVM, no matter where the AVM is, Mustafa?

- I haven't done any awake craniotomy, but you may have a certain, I mean, you may have a case that you may, but you are doing awake craniotomy for mapping purposes. You open the head, you map the area. It's positive. Are you going to close? I don't know. So I thought about in a couple of cases and I offered them a surgery and maybe awake craniotomy with mapping, but I explained the problems with that too. And then both patients, chose radiosurgery. But I think you can find the role and I'm not opposed to doing it.

- Okay, I agree with you. I think a awake AVM surgery has a very small role, because it's first of all, very uncomfortable to the patient. Touching all those vessels that are very well innervated, is very challenging. You can get into bleeding that is gonna be very difficult to control. I think most of the time AVMs move the function. You may actually map and get some disruption of function, but in fact, when you remove the AVM, as long as you stay very close to the nidus, you're gonna be very safe. So I think those are important considerations, that I completely agree with you. The second question I had for you, Mustafa. What are the pitfalls in AVM surgery, you have seen younger surgeons do? What are the things, if let's say going back 20 years from now, 10 years from now, you had known. How would you have done AVM surgery differently?

- That was deep, Aaron. I haven't had any personal problems, because I spent so many years in training. I learned from probably others mistakes, but what I see in the young junior faculty and the problems with the fellows or when I was in training. Problems caused during the surgery. If you intervene, the normal venous drainage, or a VM drainage, too early, and thinking you are doing a nice dissection, but you are taking those normal veins, or you are taking the main draining vein of AVM too early. That's the most common mistake and most disastrous mistake, you can make. And then my own personal disasters in AVM surgery, actually the ones I didn't operate, believe or not. I have one patient, they were not feeling comfortable with surgery, back-and-forth, surgery, surgery versus radiosurgery. It was not very big AVM, but deep cingulate AVM, almost in the near posterior cingulate area. And I, instead of insisting in the surgical treatment, patient had a venous outflow stenosis. I insisted at the beginning, since I didn't feel the enthusiasm from the patient and the family, I backed off. I let them decide and they decide to go ahead with the radiosurgery. Six months, no, almost one year after the radiosurgery, patient came with a huge hemorrhage. So I should have be more insisting, to tell the patient, "Surgery is the right treatment for you, not the radiosurgery." because that latest period is... It's something in radiosurgery. So that was one mistake I noticed. Another mistake I noticed, by one of our, I mean, one of the junior faculty I observe, think sometimes you can mix the AVMs, with the dural AV fistula. You think you are treating a dural AV fistula, but in reality, it's AVM or other way around. That may cause disasters.

- Sure. Sure. Two things, I believe in removing AVM in the acute period. In other words, if a patient comes in with a hemorrhage, as long as the patient is neurologically doing okay, there is not too much brain edema and midline shift and brain doesn't look angry on the scans. I take them next day, remove the clod, remove the AVM. It has a huge advantage from a delayed fascia demo surgeons belief, because you take the clot, most of them get better and also they don't recover from the hemorrhage and then you hit them again with a surgery. They recover from both at the same time. Do you agree with that, Mustafa?

- I agree, I agree. If it is AVM is not very complex or sometimes also, Aaron, those hemorrhage guides you to the AVM, and helps you in dissecting the AVM. And if that hemorrhage, if you wait too long, it can scar down. May become a fibrotic scar around the AVM and it will make your surgery more difficult. If you can and if you think it's safe, I advocate early AVM surgery.

- Okay. What are the features that make you embolize an AVM, Mustafa?

- Only AVM nowadays I will embolize, is grade four or grade five AVM, is huge AVM and a desperate case. Most of the grade fives, we don't treat, most of the time, but you can find a grade five and it's desperate case. You need to treat, young patient and then, embolization may make surgeries a option. And those cases, grade fours and fives, I will embolized and the remove the rest of it. And embolizing part of the AVM is gonna be more problematic for the patient's functional outcome.

- Do you believe in normal pressure breakthrough?

- I tell you truth. I haven't seen any. I don't know. It's described, but I haven't seen it. And if you can overcome with the good resection and keeping the blood pressure low in high-flow AVMS longer than usual. Like instead of four, five days, you can keep the patient in seven, 10 days with low blood pressure. Once you pass the seven day seven, 10 day, everything will be fine.

- Well, there are a number of other questions, but I think these were the major ones. Mustafa, I wanna, again, thank you for joining us, this evening. Really showing you an amazing microsurgical techniques and such a critical part of AVM surgery. On a personal note, there's one other question that's actually from Pablo, very interesting is, "What's the timetable from embolization to resection." Do you embolize the day before and then resect, or do you give it more time, Mustafa?

- Depends on the reason you are embolizing. If you're embolizing to avoid so-called normal perfusion breakthrough, high-flow large AVM, then you may need to do stage embolization. That's advocated by Spetzler and Dr. Heros. So you do stage embolization and maybe last stage embolization. You do your surgery right after the last embolization. The example I gave, that direct AV shunt, I took that patient right off to the embolization, because it was thrombosing. I worry about the retrograde thrombose, thrombosing the normal veins. So depends on what purpose, but personally, if I embolize, I will embolize and the next day. I'll operate.

- Okay. Well, you know, on a personal note, I think AVM surgery selects the best of microneurosurgeons. AVM surgery is just a different beast. It's a freak of nature. Its is the only operation that it starts the most beautiful and often ends in the more ugliest scene in intracranial surgery. There's not only a technical expertise, that's record, but efficiency and time, because there are times in AVM surgery that you have to land the plane as I call it. And unless you go through storm, you're never gonna land the plane. And it starts just like when you get off and get in the air at cruising altitude, there's some bleeding initially, then as you start resecting things were clean and dry. And then when the last stage you have to get into some storm and bleeding before you remove the AVM. I do believe there is actually, a phenomenon of a too clean of an operative field, at the very end of the AVM resection. Essentially, you have to fight through some controlled bleeding and not uncontrolled bleeding, to remove the AVM. I can assure you that some of my operative fields, look dirtier than yours, but probably my operative times are less. And again, that's a philosophy. How much clean versus how much extra time you want to spend. There is no doubt with extra time, you can be more careful. You can protect the feeders more. And those are the advantages and disadvantages. Everyone develops as they become more experienced, in AVM surgery. But no question, AVM surgery is beautiful. It's my most beautiful operation, because it truly lets you choose and demonstrate your technical expertise. And for that reason, I'm truly privileged to be operating on AVMs in general, Do you have any closing statements or philosophies you want to share with us, Mustafa?

- Like you said, Aaron, you know, doesn't matter. Everybody has their own technique, their own style. The outcome will talk. You have to no mortality and minimal morbidity, when you do the AVM surgery. And the AVM is the ultimate level of microneurosurgery. AVM surgery is a beautiful, but right here. And like Aaron said, you start with the simple things, but eventually, you gonna have issues. Once you know how to go through that, how to go fly through the storm, you'll do fine. And then I emphasize microsurgical training. Whatever you do, you do microsurgery. You want to start for young guys, AVM surgery. First start the cortical GBM glioblastoma case and operate GBM like you're operating AVM. Then the rest will come.

- I agree.

- And Aaron, thank you very much. What you do is precious. And I admire you. You are spreading all these philosophy, microneurosurgery or neurosurgical. I know personally, you know, from the meetings you used to go out. And I remember you saying, "I need to finish my Atlas." you know, and you did it beautifully. You did beautiful. You sacrifice a lot, but people will gain and they are gaining from this. Thank you very much.

- You're welcome. With that, I wish everyone around the globe, who joined us this evening, morning, during the night. I know many of you guys are actually joining us during the night from the Far East and part of the Middle East. I want to thank you again for joining us. Next week, we'll have the next session of Virtual Operating Room, which we'll like to have all of you with us again. Have a great day and take care.

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