Microneurosurgical Resection of Midbrain Gliomas

Ugur Ture

August 08, 2022


- Colleagues and friends, thank you for joining us for another session of the Virtual Operating Room. My name is Aaron Cohen, our guest today is Dr. Uğur Türe, from Yeditepe University in Istanbul. Dr. Türe doesn't require an introduction. I really have always referred to him as one of the most prominent knights in microneurosurgery. He has taken the legacy of Professor Yaşargil to a completely higher level. It's truly an honor. Uğur I've always followed your career. I've always considered you one of the best surgeons I've learned from. Your technical skills I think are beyond what I have seen in many, many other neurosurgeons I have witnessed across my career. And so it's truly an honor to have you today with us. You're gonna talk about a very tough topic and that's resection of midbrain gliomas. Very interested to learn how you select these tumors, how you approach them, and what are the obviously benefits we can provide to patients for these tumors that are very controversial to undergo surgery. So thank you again and look forward to watching your webinar. Please go ahead.

- Thank you Dr. Cohen-Gadol or my dear friend Aaron. It's great honor for me to be part of Neurosurgical Atlas. Really I'm very happy to be in this Neurosurgical Atlas program. And I thank you for your kind words. And I choose this topic for today because I think I have enough experience in the midbrain gliomas and I like to share with you this experience. First of all, I like to mention our mentors that they started brainstem surgery. In my knowledge, Dr. Pool from New York was the first neurosurgeon that removed brainstem gliomas in 1968. And then of course the Hoffman, Epstein and Bricolo, especially these are for brainstem gliomas. And Professor Yaşargil also. Interesting the Professor Yaşargil I put in the last, 1994. But he started in 1970s brainstem gliomas and I learned from him. But he published very late. This is the reason that this is his publication date. But otherwise he started very early in the brainstem gliomas. And as you know that brainstem gliomas are very rare, the midbrain gliomas much, much more rare. And it is very difficult to have experience in this topic because it is very rare, and very few people perform this surgery. So it was not possible to see in my residency or something. But I had great opportunity to work with Professor Yaşargil in Zurich, and later in Little Rock and whatever I perform surgery. Most of them is from Professor Yaşargil and I'm very happy that still he is active in Istanbul and we are working together in Istanbul. Midbrain or mesencephalon is the most rostral portion of the brainstem and located between the pons and diencephalon. As you know, there are several nuclei and major white matter tracts in the midbrain. Midbrain, pons and medulla oblongata. Why I choose midbrain gliomas? Because if I put together all brainstem gliomas, it is not homogeneous group because midbrain, pons and medulla oblongata differ among themselves in their macro, micro and functional anatomy, in their pathoclisis, or preferential vulnerability to pathological processes. This term, brought to neurosurgical literature by Professor Yaşargil. This is very important term: pathoclisis. And in their anatomical topographic relations. So they are totally different and different pathoclisis result in a different incidence of tumors and in a different distribution of histio-types in each of these three portions of the brainstem. For example, low grade tumors are more common in midbrain but very, very rare in pons. So different anatomical relations translate into different surgical approaches required to reach each of these three different brainstem segments. Pons glioma poses completely different surgical challenges than a midbrain glioma. So we have to separate. And then also mid brain glioma, in turn poses completely different challenge than midbrain cavernoma. So I do not want to mix them. So this is the reason. And I have now enough cases. I operated 290 brainstem surgery, microsurgical only cases. So I like to separate them. So also the gliomas, I like to separate from carvernomas as you know that the brainstem carvernoma surgery is more common. But brainstem glioma surgery, radical brainstem glioma surgery is less common. So this is the reason that I choose today to talk about only midbrain glioma. So I like to mention a little about my journey in brainstem surgery. I started brainstem surgery very late and I had some difficulties. First of all, I had some difficulties to learn brainstem anatomy because in supratentorial region we learned the anatomy in the atlases, like axial cuts, anterior is anterior, posterior is posterior. And MRI, we can put the MRI together and we can understand this anatomy, and we can learn this anatomy. And in surgical perspective we also look this way except transsphenoidal approach. But in brainstem anatomy, in all of the atlases, the brainstem anatomy is just upside down. This is anterior, this is posterior. First of all, this is against our MRI anatomy. This is totally different perspective than our MRI. 'Cause in the MRI anterior is anterior, posterior, posterior. And also in our surgical approach, most of the midbrain we approach from posterior or lateral. So to understand this anatomy we have to turn it. So this is colliculus, posterior. MRI, colliculus is posterior. Crus cerebri, anterior. But of course we cannot read it now. So I have to sit down in the Photoshop and I correct it myself. So this was my starting, to learn the brainstem anatomy. And I recommend to you to learn this anatomy this way. And then you can have this three dimensional picture in your brain. Another problem is the MRIs. MRI, they looks from below. This is just opposite to our, again, the surgical perspective. So they call that this is left-sided midbrain tumor. No. Now is left-sided midbrain tumor. So it is very simple to turn it. So all over my MRIs left is left, because this is correct atomic and surgical picture. So this is short introduction. And then I had to learn this anatomy, intrinsic anatomy of the brainstem. And I had chance to work it. And I did this 25 years ago. This is the first photograph of medial lemniscus. There were no photograph of medial lemniscus at that time. So I had to touch it. I had to follow the fifth nerve, I had to follow seventh nerve. So this was great experience. I had to dissect the corticospinal tract in the pons and I had to see how it's running. So I enjoy this time in the laboratory and try to learn intrinsic anatomy of the brainstem. And the superior and inferior cerebellar peduncle. And this is middle cerebellar peduncle, lateral lemniscus, so on. So and then the tractography was developed at that time and I was very lucky to work with good neuroradiology team. So in all of my cases, brainstem cases, we performed preoperative and three months postoperative tractography. Medial lemniscus and corticospinal tract, as well as cerebellar peduncles, superior, middle and inferior. So these five main tracts we perform before surgery. And this tractography picture give me some idea to my approach, sometimes very critical. I know tractography is still developing but it is something and I strongly recommend you to work on it. But the tractography, we need to do ourself, not the radiologists because radiologists put many color pictures, billions of information. But we have to choose information for our surgery. So we have to do ourself. And then I like to summarize my philosophy and approaches to midbrain gliomas in this talk. I use seven different approaches. You know, midbrain is very small structure, but whole midbrain is, you know, midbrain is deep structure, so-called. But whole midbrain is open to systems. So somehow to reach this midbrain with using microsurgical anatomical knowledge is easy because it's whole midbrain is in the opened systems, it's in the surface. Another point, the vascularity of the midbrain is not very complex. Simple. Arterial vascularization and the venous, also, system is not very complex. So these things bring together that midbrain surgery could be very successful. Another point is that most of the midbrain gliomas are low grade gliomas, even pilocytic astrocytomas. So these are the points that I like to mention in midbrain gliomas. And I will show you some examples of cases that I used different approaches. And then I will try to explain why I used that approaches. First of all, transsylvian approach, number one. You can reach the crus cerebri in transsylvian approach. This is four-years-old boy, right-sided, midbrain glioma, and it looks like crus cerebri glioma, right-sided. But the patient is not hemiplegic, slight hemiparesis. So the very critical issue is the pyramidal tracts. So and then tumor is going up. And when we performed the tractography, you can see that sensory and motor fibers are deviated and moved medially and posterior. So the anterior approach could be useful for this case. And the tumor looks like in crus cerebri. Interesting. A transsylvian approach. This is after reduction of the tumor, without rigid retraction. And this is the postoperative MRI. I noticed in the surgery that tumor was originating from tegmentum, and separated fibers of the crus cerebri and came to the surface. So this tumor looks like a crus cerebri tumor in the preoperative period. But in the surgery it turned out to be tegmentum tumor. This is important point, in my old series I do not have any crus cerebri glioma. I do not have also thalamopedundular glioma. I think thalamopedundular glioma term is somehow, is not correct. And it is interesting that in Bricolo's series there is no crus cerebri glioma and in Yaşargil's series also there is no crus cerebri glioma. This is important point. And anyway, this is postoperative MRI of this patient. Pilocytic astrocytoma, sensory and motor fibers are almost normal. And this is early postoperative. And now he's big boy and no recurrence or nothing. This is pilocytic astrocytoma. Most of the cases in midbrain gliomas are pilocytic astrocytoma. This is another case. When I saw this MRI I said, "Okay, this must be crus cerebri glioma." Again, four years-old-boy, right-sided, it's much bigger, but still the thalamus is not involved. Midbrain glioma do not invade the thalamus or do not invade the pons, they just push. But it looks like a crus cerebri glioma. But you see again the sensory and motor fibers now push posteriorly and laterally, so transsylvain approach is suitable. And then after surgery also it turned out to be that this tumor was also from tegmentum. So I do not have crus cerebri tumor. This is tegmentum tumor. Again it is pilocytic astrocytoma. Second one, this is interesting approach: extreme anterior interhemispheric transcallosal approach. Normal transcallosal approach, we open the corpus callosum approximately here, just in the same line with the foramen of Monro. But in this case just between genu and body, I open the corpus callosum. This is the case, suitable case for this approach. You see this is superior aqueduct tumor, true aqueduct tumor. This is interesting entity, true, well circumscribed aqueduct tumor. It causes hydrocephalus and they all low grade. And of course the third ventriculostomy is the one of the option. But when I saw this MRI, I saw that third ventriculostomy could be more difficult than removal of this tumor through the foramen of Monro. But I have to get the correct angle to get this tumor. So this is our reconstruction, 3D reconstruction, before surgery and we have to have correct angle. An extreme anterior transcallosal approach. So the hydrocephalus should be happening, you know, without hydrocephalus we cannot perform this surgery. So the important point is that... This is anterior interhemispheric approach. I always use right-sided craniotomy. I'm a right-handed surgeon. And then always open between two pericallosal arteries. And I use cottonoid for navigation, to choose my entry point of the corpus callosum. You can use navigation, I have navigation, but I enjoy to use this cottonoid. And I just open callosal fibers, separate callosal fibers and go to right lateral ventricle in this case. And then to check inside of the ventricle, I have to check that I am in the correct ventricle. I was expecting right ventricle. And then I can look to foramen of Monro here. If I choose the correct angle, tumor is just front of me. You see, this is posterior commissure and this is tumor in the aqueduct. Without cutting anything except callosal incision. This is right side, anterior septal vein, the foramen of Monro, choroid plexus, and third ventricle, and posterior commissure, and tumor is here. So it is pilocytic astrocytoma, you can tell. And I remove this tumor. I prefer to use two hands instead of endoscopic removal. You can pull it with endoscope but some case can come, some not. And so I prefer to use my both hands with long instruments and to go there and stay there with the longest suction and longest bipolar. And just this is the adhesion of the tumor with the aqueduct tissue and this typical pilocytic astrocytoma. And I didn't edit this part. It took two minutes to just remove the tumor, but I should have correct angle. This is the key. Otherwise I cannot perform this surgery. An enlarged foramen of Monro is enough for me to work. So I don't need to open the foramen of Monro, enlarge the foramen of Monro. And this is after removal of the tumor. And I am checking with the endoscope again that is there any residual tumor. And I have to see that CSF is coming from fourth ventricle. So this opening was enough. So just seven millimeter, but I just separate the fibers. And then this is three months later. You see even if you separate the fibers they come back and it looks like there is two millimeters. Actually I work in seven millimeters but I separate. This is postoperative MRI. Some people was not sure that I maybe doesn't show whole incision but I like to show this. Look at this. This is whole series of the sagittal picture, whole series of sagittal picture. So when you separate the callosal fibers, they may come back, some part at least. I'm a little crazy. I'm exaggerating, I know. But I believe this is less invasive than endoscope, because I just do very small callosal incision. But even in the endoscope you have to pass through the centrum semiovale, which also callosal fibers are there. Anyway, pilocytic astrocytoma. Another case, typical, aqueduct tumor, hydrocephalus. And this is more difficult because there is a interthalamic adhesion but you can go through, underneath the interthalamic adhesion. And you see interthalamic adhesion is intact. And this is the incision and correct angle to remove this tumor. And we published. I have now five cases like this. And all of them are low grade. And we published this. Third one. Third one is the posterior interhemispheric transtentorial approach. This is very suitable case. The tectal tumors are most suitable case for this approach, through posterior interhemispheric, but not cutting the splenium. I never cut the splenium. Just posterior interhemispheric, cutting the tentorium in the tectal tumors. Superior cerebellar. Interesting point, I never have case, you know the superior cerebellar peduncle is almost half of the midbrain, is the cross of the superior cerebellar peduncle, or superior cerebellar peduncle is the big part of the tegmentum and none of the cases superior cerebellar peduncle was involved with the tumor, always pushed by the tumor. This is interesting point. And I use posterior interhemispheric approach in lateral, oblique or, now because of intraoperative MRI, I use prone-oblique position position. Just, this craniotomy, the tumor was in the left side and so the left side is vent down. So without retraction, using the gravity we can reach the tumor. And on the last four and five years I am using the intraoperative MRI routinely. So it helped me a lot. But I like to mention that ultrasonography is one of my favorite also. And also I think that it is not fair to compare intraoperative MRI and intraoperative ultrasound because they are different. First of all, the intraoperative ultrasonography is excellent for navigation and you can use 10 times in the surgery but the MRI you can use one or maximum two times. So it looks like we should not compare them. Anyway, but it's nice to see that intraoperative MRI show us some more information. So my radical resection of course is much higher with using intraoperative MRI. And so I told you it's not fair to compare them. One of them may be car, one of them like airplane. And so they are different. And this is three months postoperative MRI. Looks like radical resection and opening the aqueduct. Very important point, the aqueduct. We have to manage postoperative CSF problems. We have to prepare ourself and patient for CSF problems. So we have to open this aqueduct. And you see superior cerebellar peduncle is almost normal. And pilocytic astrocytoma. Another case, again, tectal tumor push tegmentum, but still tectal tumor. Right side and similar case. And superior cerebellar peduncle never invaded by tumor. And this is postoperative MRI and superior cerebellar peduncle is intact also. And then pilocytic. Another case it looks like whole midbrain this tumor, but you see thalamus is not involved, pons is not involved but just pushed. And same approach. And sensory and motor fibers are still intact and they never invaded also by tumor. And this is postoperative MRI. And also it was a pilocytic astrocytoma. And the sensory and motor fibers and superior cerebellar peduncle is intact. She had a third nerve palsy and it recovered a lot. But still this, she has some mydriasis here. Pilocytic astrocytoma. Again. Another point is the most of the tectal tumors, it looks like whole tectum is tumor. It's turned out to be originating from one colliculus. First of all, you have to understand left or right colliculus and then you have to understand superior or inferior colliculus. And this is superior cerebellar peduncle, always intact. And this is postoperative. You see this is left-sided superior colliculus tumor. The other colliculus are totally intact. And again superior cerebellar peduncle postoperative. Pilocytic astrocytoma. Fourth approach is paramedian supracerebellar-transtentorial approach. One of my favorite approach. Fourth, paramedian supracerebellar-transtentorial. Which cases suitable? The best cases are tegmentum tumors. This is right-sided tegmentum tumors. Typical pilocytic astrocytoma. And, you know, the tumor extend up and down, but don't invade. And there are some cystic component. This is also typical pilocytic astrocytoma. And you see lateral side is free. And so paramedian supracerebellar approach, transtentorial, is the best to reach this tumor and remove this tumor. And superior cerebellar peduncle also moved backward. And so approximately, you know, the lateral mesencephalic sulcus is the general approach, but in this case I will approach through the tumor. And one point I like to mention, there are many surgeons that they prefer subtemporal approach for midbrain tumors or cavernomas. But whatever you do it, you have to retract the temporal lobe with this. Even if you can drill this part, but still. And I do not use subtemporal approach for midbrain. I can reach the same area using supracerebellar-transtentorial approach. When you release the CSF from cisterna magna and the cerebellum, with the gravity, cerebellum went down and we can reach this same region. Of course, in both approach we have to cut the tentorium. So I use supracerebellar-transtentorial approach in the midbrain, not subtemporal. And I preferred to use semi-sitting position. But now with the intraoperative MRI I have to modify a little. So this, also if the patient has a cardiac sepal defect, I don't use the semi-sitting position. In this case I used, in lateral position, paramedian supracerebellar approach. And you see, in five minutes I am there. Right-sided, this is tentorium, this is cerebellum, this is fourth nerve, the tentorium. You know there are arteries from the superior cerebellar artery to tentorium. We have to be careful. And then I coagulate the tentorium and I'll just cut the tentorium perpendicular to the midbrain. Of course we have to careful with the fourth nerve. But when you cut the tentorium, you have a great space and you see tumor in the surface. Just under the pia, this is the tumor. So I cut the pia, again parallel to fiber system. And this is typical pilocytic. We have to take some samples for frozen section and then we can use CUSA to debulk the tumor. And then this the cystic parts, you can see. And then, after removal of tumor, I'm checking with endoscope. I love to use endoscope in every case. You see, there is a residue in the upper part that I couldn't see in the microscope. And then there is a residue in the lower part, also I couldn't see with the microscope. So the beauty of endoscope. So I really enjoy to use it for help to microsurgery. And then the rest of them I remove with the microscope. I am still more comfortable with the microscope. And I am checking again. This is the lower part, residual tumor. Also the lateral part. And then I am checking with the endoscope and now it looks okay. So this was pilocytic astrocytoma and this is postoperative. This is typical tegmentum pilocytic astrocytoma, right side. Yeah. And the postoperative sensory and motor fibers are intact. And superior cerebellar peduncle also. Pilocytic astrocytoma. Another case, very typical. This is left-sided now, cystic component, pilocytic astrocytoma tegmentum tumor. You see, again superior cerebellar peduncle is intact and the sensory and motor fibers. Same approach from left side. This is almost normal. Pilocytic astrocytoma. Fifth one: perimedian supracerebellar infratentorial approach. Which I use this approach for pineal tumors. Why I call perimedian? Because I use midline incision and I just go lateral. So number five, number five is the midline incision, but I never go midline because there are veins always in the midline. So I do not coagulate them, I don't want to coagulate them. And also in the midline there is a deep steep angle that, especially in Turkish people, you cannot reach the pineal. So we have to go a little off line, which I learned this from Professor Yaşargil, he always used this approach for pineal. So for the tectum tumors you can use this approach also. And this is typical tectal tumor. The patient had a hydrocephalus and she had a shunt in another institution. And you see, it looks like whole tectum is tumor, but if you pay attention, this is inferior, left-sided, inferior colliculus tumor, left-sided inferior colliculus tumor. And the cerebellar peduncle also pushed laterally and posterior. So this is the perimedian approach. Midline incision, but go one side. So this is another advantage why I use midline, because if there is a veins, because sometimes you can see paramedian tentorial veins, some of them can be very big. So if you cannot deal with it, you can use this. In pineal, in most of the cases, you can use right or left side. So this is also another advantage of this incision. So this is perimedian. It means midline incision, but I always go off line to the tectum. You see this is the semi-sitting position, with the gravity I don't retract anything. This is tentorial vein, it's hanging. And tumor you can see here, without microscope even. And this is after resection. Of course, we have to preserve collicular artery. And this is after resection. And you can see that tumor was in one colliculus, inferior colliculus. And cerebellar peduncle is intact. And pilocytic. Another case, tectal glioma. You know, also one point that I don't immediately operate every tectal glioma. This is also I like to mention. You know, if there is no effect or... This patient has just tremor, an incidental finding and this hydrocephalus is not active. So I said okay, let's wait. But you see, tectal tumors also can grow. And also the contrast enhancement changed and hydrocephalus has grown more now, so this is time to remove. Same approach. Again, the superior cerebellar peduncle is important. And this is postoperative. Again from one colliculus and pilocytic. Sixth one. I performed this approach in one case. Why I did, I will show you. Exactly the same but contralateral. Supracerebellar infratentorial but contralateral. So I go to the left side to the right colliculus. Why? This is the case. This is three times operated in another institution. Right side third nerve palsy and left sided hemiparesis. It looks like everywhere is tumor but still this is a tegmentum tumor. Tegmentum tumor, separate the crus cerebri fibers and come to anterior. Also has a cystic portion and opened the collicular surface also. So, and then it goes down to the almost foramen Magendie, cystic part. So how can I approach this? But this is also not thalamopeduncular tumor, this is tegmentum tumor. It's in the tegmentum. Thalamus pushed upper, pons pushed downward. But if I come from transsylvian, I cannot reach the inferior part. So I decided to go. And then, also important point that if I go the same, there is an intact, very thin crus cerebri fibers if I go through the same side. So I decided to go contralateral. This is the reason. So the same approach, perimedian supracerebellar but not going through here because I have better angle from other side. And this is the only case that I use contralateral supracerebellar. This is end of surgery. I go through the inferior colliculus because tumor was in the surface, right sided. And I am within the midbrain. And this is basilar artery. This is basilar cerebral. Superior cerebellar artery. And I left a little piece of tumor in the basilar artery because the tumor was firm and I should increase the power of CUSA, which could be disaster with the perforators of the basilar artery. So I left some piece of tumor in the tip of basilar artery using this approach. You see, I come from here. You see, normal crus cerebri here. So I have better angle here. And I left a little piece here in the tip of the basilar artery, here. And I'm very lucky that this tumor is still staying in the same size more than 10 years without any additional treatment. No Gamma Knife. So this was prior, 2010. And her third nerve is improved, 2015. And now, she's now 17 or something and the the same residual tumor is staying there. In the last approach is the seven. Number seven is the uvulotonsillary fissure approach. This is again, well circumscribed aqueduct tumor, but it's in the inferior part of the aqueduct, so I cannot come from here. So if the tumor in the inferior side of the aqueduct, I use uvulotonsillary fissure approach. What is uvulotonsillary fissure approach? Yaşargil used this approach more than 40 years. Between uvula and tonsil, he separate. Now you can call it as also the telovelar approach. But Yaşargil was using this approach for 40 years, no, almost 50 years. Yeah. Without vermis cutting just go to fourth ventricle. You can reach the aqueduct very well, especially in semi-sitting position. It's just there. And so this is the angle of approach and this is inferior aqueduct tumor. Again, pilocytic astrocytoma. I'd like to share this case with you. This is again, tectal tumor. Now I have intraoperative MRI because of this reason. Most of the cases, you know, supracerebellar is my favorite, but I have to use semi-sitting position. But for intraoperative MRI I cannot use it. So I use posterior interhemispheric approach. So if the tumor is not hidden underneath the splenium, I prefer this approach. So this tumor is suitable for supracerebellar approach and posterior interhemispheric approach. You can use both approaches for this case. But because of intraoperative MRI, I prefer posterior interhemispheric approach. This way, right side down, go there. And I couldn't remove. It was like a chewing gum. and even the CUSA was not also working well. And it was attached to the Galen and internal cerebral vein. And from this approach I had difficulty to manipulate and if some bleeding happened, it could be disaster. And believe it or not, I stopped surgery. So I have monitoring, I have intraoperative MRI, I have whatever, everything, but still I couldn't do it, because it was not suitable for posterior interhemispheric approach. But I didn't know because I couldn't know that the tissue, how tissue is firm. Is it suckable or not? So I left the tumor and I stopped surgery. And then I talked with the family and I asked the patient also, that they should allow me to do re-operation. So five days later I perform supracerebellar infratentorial approach in semi-sitting position and I remove it. So this was important case for my education also. You know, you may have everything, but it doesn't matter. Microsurgery is microsurgery, and you have to choose correct approach for each case. The approach was correct. I used that approach for such a tumors, in many case I was successful. But in that case, no. Because of the tumor tissue was totally different and it was not possible to manipulate the Galenic and internal cerebral vein. But in semi-sitting position, I was able to separate with my both hands. So supracerebellar approach is somehow, I love it. This is the one of the reason, but in many cases you can use other approach. But anyway, this is the case that I learned a lot. So it was pilocytic astrocytoma. It's all I'd like to share. Complication. I have one major complication. Typical tectal glioma with hydrocephalus. So in this case, posterior interhemispheric is more suitable because if the tumor goes more down, posterior interhemispheric is more suitable. If the tumor goes more up supracerebellar is more suitable. This case you can use both approaches. But posterior interhemispheric is suitable, so I used posterior interhemispheric approach for this tumor. And it was very nice surgery, believe or not, but she did not wake up. I did not have a MRI, intraoperative MRI at that time and I performed CT scan, nothing. Next day, did not wake up. Next day no, no, no. And we performed MRI. Believe or not, bilateral pericallosal artery infraction, which I couldn't understand. It could be azygos. Otherwise, how it can happen? I don't know. And we perform angiography. No azygos, but whole pericallosal bilateral, of course anterior part. And she never wake up. And it was diffuse midline glioma. And she passed away almost two years after that surgery. Still I don't understand. You know, we have to learn something from our complication. This case I couldn't learn even. Another point that, you know, diffuse periaqueductal tumors. Diffuse periaqueductal tumors are another entity. These are not tectal tumors. You see, 360 degree, surrounding the aqueduct, is tumor. And these are not suitable for surgical resection in my opinion. And the best way, wait and see, mostly benign, and just perform third ventriculostomy, endoscopic . I have now five cases like this. One of them start to grow and then I did operation, but otherwise I am following others. Did I perform every case? No, I have now 55 midbrain glioma surgery, microsurgical. I have also five endoscopic third ventriculostomy. This is another story. But 55 microsurgical midbrain glioma. But I have 25 cases that I didn't operate. Why? Because of like this, something like that. If the tumor in the pons, midbrain, thalamus, globus pallidus, this is not suitable for surgery. Or if the tumor is in the pons and midbrain and everywhere. So I don't perform surgery. And also I have some cases that tectal glioma, a small one, no problem, so I am just following them. So 25 cases I did not operate because the multifocal glioblastoma or midbrain or very benign some lesion. I like to share at end of my top this case. This is 2010, three years old, very nice girl. And somehow incidental. I think she just went down and they performed CT. And anyway, incidental finding. This one, left-sided, typical pilocytic tegmentum tumor. Pilocytic astrocytoma, left side. Three years old, but incidental finding. What you can do. Well I can remove this, it's nice case for removal, but I don't like the jump immediately any patient. Because also the family was in shock, you know? So I said, okay, let's wait. And then three months later, six months later, whatever. And nothing changed. Nothing changed. You see, well it looks like... Five years later it start to shrink. It start to shrink. Five years later. And she's growing. And 10 years later. You see, 2010, 2015, 2019. I was almost planning to do surgery with this case. I don't know what is this, but this is also interesting experience for me. I'm very glad that I didn't touch this tumor, this case. I don't know it's tumor. I don't know what is this. Now I have 55, but this is for my publication, I prepared this. And mostly pediatric cases. And it is very nice that all of them almost pilocytic. And I do not have crus cerebri tumor, 20 of them tegmentum, none of them invade the superior cerebellar peduncle. So it must be, it is coming from some corner in the tegmentum. And seven of them aqueduct tumor, six of them are true aqueduct, well circumscribed tumor, but one of them is diffuse periaqueductal tumor, which start to grow. Then I did surgery. And 23 of them are tectum tumors. And I use seven approaches. And now, I mostly use posterior interhemispheric transtentorial. One of the reason is it's suitable for intraoperative MRI. And I use less perimedian supracerebellar because of, again, intraoperative MRI problem. But I like both approaches. And most of them are pilocytic or low grade, but there is high grade tumor those, I have six cases that, diffuse midline glioma or glioblastoma in the midbrain. Which is, generally in the literature they say all of them are benign, but it is not like this in my case series. I use, macroscopic total 70%. Near-total, this is looks like a total, to be honest with you. And this sub-total lesions, mostly before the intraoperative MRI, so I couldn't separate the tissue, I couldn't be more aggressive. So, but this is today my result. No perioperative mortality. But one, that I showed you, major surgical morbidity. And most of the cases, 96, are same or better than preoperative. This is better than my cavernoma series. Interesting. So it is really very rewarding surgery, the midbrain glioma surgery. And there is only one patient, slightly worse three months after surgery. I performed some of the cases, I performed two, three operations because of the residual tumor or recurrent tumor or hydrocephalus. Hydrocephalus is very important. And three patients died due to recurrent tumor, high grade tumors during the follow-up period. So microsurgical removal of midbrain gliomas is feasible with good resection and clinical results and provided adequate microsurgical technique and, of course, anesthesiologic management, correct preoperative understanding of tumor exact topographic origin, I think this is the most critical issue, and the growth pattern of the tumor. So these elements determine surgical indication and dictates the appropriate surgical approach. I like to show this slide that, you know, last two decades, we have many important new tools development in the surgical field and they all very nice and I have all of them. But none of them is the key for success of surgery, in my opinion. Professor Yaşargil did not have any of them. He had only CUSA and he did not have any of them. And I am still trying to have his good result like him, you know, so we are very lucky that we have all this and I'm very happy that I am using, but we should not trust any of them. We need to have all information together from each of them and we should use all of them and put together in our brain. And then also understanding of surgical neuroanatomy, surgical indication. This is important. Surgical indication. I have to choose correct case for my level. You know, I should check: what can I do? This is my surgical indication. 10 years ago it was different. Today it is different. Five years later I hope it will be different. So we have to choose surgical indication for ourself and also it depends on our environment, our ability, our technical technology and our team. So there are many factors. So this was the reason that I started brainstem surgery very late. And then correct surgical approach is key. Of course, microsurgical technique also key. But as I show you, in previous case I had everything but I couldn't remove the tumor because it was wrong surgical approach. Of course this was not my work alone. I am working with great team and Professor Yaşargil with us. I am still learning from him every day and I am very happy to discuss the cases with him. And I'm very happy when he's in the operating theater and observing me and discussing cases and I'm very thankful to him. And also I like to thank Dr. Carlo Serra that he put together all this database and he did a great job with this work. And at last, I'd like to mention that next year, please note that 2023, in August we have a 3rd Rhoton Society Meeting, we have a Future of Microneurosurgery meeting and we have a Semi-sitting Position in Neurosurgery meeting together. And I look forward to see you in Istanbul next August. Thank you for your attention.

- Very enjoyable or really fun to watch. Great tour of surgery within the midbrain. And really, the approaches are so well described. I wanna emphasize a few things that you mentioned. Number one, that, you know, most of the tumors are originating from tegmentum. They're mostly pilocytic and they're slow growing. And even a sub-total safe resection does a pretty nice job. And these tumors can remain quiet for many years after a sub-total resection and drainage of the cyst. So you gotta put safety on the first priority, just like you showed in that tumor that was carpeting the perforators of the basilar, the recurrent tumor. I think that was an excellent approach. And also number two is that anytime you can avoid the subtemporal approach, it's great. The advantages of the supracerebellar is immense. The, you know, paramedian, the perimedian and the for lateral supracerebellar provide a beautiful panoramic view of the mid to posterior midbrain. And therefore I use those exclusively. The past 10 years I have hardly ever used the subtemporal approach. The amount of tension you put the temporal lobe is really significant and can be very morbid. And you really can't know who's gonna do okay, who's not gonna do okay. But the majority of people do well with a paramedian supracerebellar approach. The last thing I wanna mention is that I've also given up on the posterior interhemispheric transtentorial approach. I have hardly ever used it. I have completely changed to the paramedian supracerebellar approach because I think the wings of the cerebellum provides you a more inferior trajectory. So you don't need that steep superior to inferior trajectory that the posterior interhemispheric transtentorial approach provides for you. I think really any pineal tumor, any posterior midbrain diencephalic tumor, even most of the posterolateral ones, can be very effectively removed via the paramedian supracerebellar approach. I haven't even done, I'll say a midline supracerebellar approach the past few years because of the flexibility of the paramedian approach. Part of the problem is that in neurosurgery we get so lost in the approach that we never focus about what to do when we're there. And if you really choose just very select approaches and get very good at it, that are very efficient, your outcomes actually can be tremendously improved because you're really focusing on tumor removal when you are there rather than how to get there. So these are a few things I wanted to emphasize and congratulate you really on your incredible microsurgical career, Uğur.

- Thank you. Thank you very much. I hope you enjoy. It's very important for me your comments. Thank you. Thank you, Aaron.

- You're welcome. Thank you again Uğur and we look forward to having you with us in the near future.

- Thank you. Have a nice evening or have a nice day. Bye-bye.

- Thank you. Bye.

- Bye-bye.

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