Endoscope-Assisted Skull Base Surgery in the Posterior Fossa

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- 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. Henry Schroeder from Germany. He is truly a gifted surgeon. I have been following his career very closely. I've learned much from him, from his innovative techniques. And this evening, he's going to talk to us about endoscopic assisted posterior fossa surgery. He has beautiful videos, amazing content, and with that in mind, Henry, I wanna thank you for attending and doing this at 2:00 AM in Germany. That tells a lot about your immense sacrifice for neurosurgery and what you have done for all of us. So I'm very excited to learn from you, and please go ahead.

- Good afternoon or good evening, I have to say in Germany or goodnight or hello to everybody. Aaron it's a great pleasure to be invited to your initiative. I really appreciate your efforts in spreading this neurosurgical knowledge via your Neurosurgical Atlas. It's a great pleasure to be here, although the time is not so convenient. And my topic is Endoscope-assisted Skullbase Surgery in the Posterior Fossa. And the posterior cranial fossa is ideal for using an endoscope because you have so many corners where you can look around, you have so many nerves, which have to be crossed and you get the endoscopic visualization gives you a much better view than the microscope. So what is the concept of endoscope-assisted microsurgery? It's very simple, it's just using an endoscope and a microscope together. And you know, the microscope has an advantage if you have superficial structures, you have a big lens, that means you have a good optical resolution, You have to binocular view. However, if you go deep down in the surgical field, and if you have a narrow surgical corridor, you lose a lot of light. The view is very limited. You cannot look around the corner. And that is the disadvantage of the microscope. The cons is that you have a very good optical resolution, because you look directly with our eyes, through the lens system. We have the 3D visualization, but we have poor depth of field and narrow view field, poor illumination in the depth. And that is a time when the endoscope makes sense in my opinion, you brings your eye close to the lesion, you have a wide angle view, perfect illumination, magnification, and you can you use an angulated endoscope, look around the corner and at the skullbase that is so helpful. Of course, we have the cons of 2D visualization. Most of the time, but there's a fish eye effect. This is a distortion of the image and motion parallax, which means that closer objects move more than distant ones. We have this through the 3D impression, even when you use the 2D endoscope. We use 2.7 millimeters endoscopes. You have an angulated ocular to bring the camera out of the way from bimanual dissections. We have different angulated views, 30, 45 and 70. Most of the time I use 30 and 45. And the size of 2.7 millimeters is ideal. So the visualization tool from the carnival is too big in my opinion, to go in between the nerves and the CP angle. That's why I use the smaller ones. Of course, you need curved instruments if you want to remove tumor tissue, which can only be seen with an angulated optics of 45 degree, for example, that's why we designed some angulated instruments. And for me still is the HD camera is the best because you have such a good color fidelity and you have a high resolution. You can even see erythrocytes running through the blood vessel, such a high resolution you can have with an HD camera. Next slide. So sometimes people say there's a controversy between endoscopy and microsurgery, but I say it's not true, it's complimentary. We use the endoscope if we don't see well with the microscope. There are some drawbacks of the endoscope-assisted technique. When we use a microscope and we work in the depths, we have very poor visualization here in the depths. But we always see structures which are in front of us, even if they are not in focus so if I work in the depths, I see when my instruments touching these nerves, these structures. When I use the endoscope, I'm fine, as long as the lens is in front of these important structures. However, if I go deep down and pass these structures, I don't see what is behind. I can see very well on the depths, but I don't see what I'm doing with my instruments to these structures, which are behind the lens. And that is a great danger that you work on the depths and you damage structures deep down in the field. So the video you see, we come with the endoscope, we see a small residual epidermoid here, on the control diameters side of the colliders. We work with a microscope and we see these structures here, not in focus, but I see if I touch them. Now, I changed to the endoscope. I have a perfect visualization and the depths I can dissect this tumor very nicely, but I don't know what are my instruments doing here with the nerves and that's why we have to be careful. Next. Another problem is heat generation. You should never leave the endoscope fixed in front of the cochlear nerve. And if it's there for some minutes and you make dissection without irrigation, because that really can make a thermal damage to the nerve. That you should keep in mind. So many people ask me when you think that the endoscope gives such a nice view, why are you not doing all this procedure from the beginning purely endoscopically? But I think that makes more sense. Video. For example, I have here an epidermoid close to the jugular foramen, and I have to dissect a small perforator. Why should I do this under the endoscope? What is the advantage? There is no added advantage in my opinion, I can use it under the microscope in a much better way. I have a three dimensional view. I have the perfect illumination and I also have a very good optical resolution because I look directly through the lens system with my eyes. So for these procedures, I think the microscope is the better tool. Next. However, if I have this case, video please, you see here is a cochlear nerve and there's tumor below in the internal auditory canal, and I have to recheck to get it. I can use a 45 degree endoscope. I look behind the nerve and I can dissect all the tumor out without touching the cochlea nerve in this area. So that is a big advantage of the endoscope. I can look around the corner. I can look into the depths and I can dissect very safely. So next slide. So we have also used 3D endoscopes. We use it for endonasal surgery, but you know, if you work in the nose, especially in the initial phase, you have covering or blood on one lens or the other, and then you always change between 3D view and 2D view back and forth and this really makes your headache. Once you have opened the sinuses, it can be used, but still I'm adapted to the 2D endoscope very well. So I still prefer that. We also test at some of these exocopes. They are very nice for superficial structures, for superficial tumors, for spine surgery but if you have a sophisticated deep seated tumor in the depths, where you want to make vascular surgery, I still prefer the microscope because it still has a better optical quality. So what are the surgical technique? We start on the microsurgical dissection. Then we want to use the endoscope. I use it mostly free hand for inspection. I don't use a microscope to bring the endoscope in, but I use it free hand. I'm looking at the screen of the endoscopic camera and then I go in and I inspect the area. You can also use an instrument in the left-hand, hold the camera and the right and you can dissect. But if I have a prolonged dissection, I like to fix the endoscope with this mechanical holding arm here. And with this endoscope holder, I have both hands free and I can dissect the tumor. And of course you should have the screens in an economic position in front of you. So some examples vestibular schwannomas are a good indication for endoscope assisted, but should you operate all of these tumors? I think usually when you have young people with a tumor, even if it's small and they have good hearing advice for surgery early before they deteriorate. But this was a sports teacher and he asked me if you take this tumor, can I do my exercises on the high bar? And I said, no. I cannot promise that this would be possible. So he refused the surgery and you see, I watched him now for 10 years. The tumor grows only a little bit, and he is still a very good hearing. So there are exceptions. As long as the hearing is very good and there is no history of hearing loss then of course, observation is an initial possibility to follow up the patient. But most of them, you know, request surgery and then you should do it before they deteriorate with hearing. If you have a small tumor like this, and we always try of course, to preserve a very good hearing. We use for these tumors a supine position. The head is a little bit elevated, is rotated 45 degrees to the other side. And then we rotate the whole table to have a good view into the CP angle. Then there is a sigmoid sinus, transfer sinus and then we mark the skin incision. Of course, all the procedures is done under the monitoring of acoustic potential and EMG. And we use a middle retrosigmoid approach for these tumors. And I always want to see the blue of the sigmoid sinus at the beginning of the transfer sinus for vestibular schwannoma. And the craniotomy goes a little bit more in the back to have a tangential view to the fundus. If I have a tumor, which is only extrametal then you don't need to go too far in the back with your craniotomy. What I find very helpful is the suction specular. We place a suction specula in the depths of the field. And then I can work under continuous irrigation. For me, for vestibular schwannoma surgery it's very important that I have the clean surgical field. And always you have some minor bleeding which disturbs the view. And that's why we use continuous irrigation to clear the view. Here's the tip of the suction specular. And here's the tumor so we can irrigate and all the CSF and irrigation fluid goes to the suction spatula, I don't need to use... Video, please. I don't need to use suction, but I have two forceps and I can make a bimanual dissection with traction and counter traction. And all this irrigation fluid goes automatically to the suction spatula. So it gives me a third hand, which I found very useful in vestibular schwannoma surgery. Okay, next. So an example, this was a 28 year old male with a hearing loss on the right ear. And then they found on the left side a vestibular schwannomas. Then he went to several doctors and most of them advised for gamma knife. But if you look to the literature, you see that's a tumor control rate after 15 years is very good, 90%. But the hearing preservation rate after 15 years is only 30%. And that's why I think, especially in young patients, I always advocate for surgery first. The problem is if the tumor is located in the fundus, we need to drill the posterior wall of the internal arterial canal to get access to the tumor. But we cannot draw everything then we open the posterior semicircular canal or the vestibule, and usually the patient is deaf. And that's why I use the endoscope for the last piece, for the last view to the fundus in these small tumors. This one example you see here is the vestibular nerves. Here is a tumor. So the media part of the tumor is dissected on the microscopic view. The media part can be excised, but then you see it is a blind dissection. If I follow the tumor in the area of the fundus, and that's why I now take a 30 degree endoscope, I fix it with a mechanical holding arm so I'll have both hands free and I can look into the internal auditory canal and I can dissect the tumor on a direct visualization to preserve the vestibular nerve and the facial nerve. I think for this step of the procedure, the endoscope is extremely helpful because you see very well. And now I have a 45 degree endoscope to make sure that there is no tumor left. Next. And you see the amount of drilling. So we looked into this area with a 45 and 30 degree endoscope. And I could preserve a good hearing, which in my opinion is more reliable in the long term than after radiation, because we have seen many patients which deteriorate over three to five after gamma knife. What is the strategy in large schwannomas? Initially, I also placed the patients through pine and dissect it, but you have always some bleeding and you need a suction and you have not in the same extra medic dissection what I want to have with two forceps. Next. That's why I use since more than 10 years the hemisitting position. The legs are elevated so that the blood is not run away. They have a good blood pressure. They head is turn to the same side and we have always an anal esophageal echo for the detection of her embolism or skin incision. The disadvantage is that we need always cerebellar retraction, which is not required in the supine position. And we have the risk of pneumocephalus especially after prolonged procedures. And if the patient has already dilated ventricles, and there is a risk of air embolism. But these two are potential risks but they are not very frequent. And it's not too inconvenient for the surgeon because you have a hand rest here. You can put your hands here and you have a good manual dissection. One example, this is a young girl, 11 years old, she came in November last year to us with balance problems and headache. And she has this large vestibular schwannoma. She has still sound good hearing on the right ear. Hemisitting position, skin incision, craniotomy. And then we start with the surgery. The first step is opening of the internal auditory canal. I always try to unroof the canal 180 degrees to release the pressure. Then we have stimulation probe, we are looking for the facial nerve. Sometimes, although it's rare, it can be on the dorsal surface. Then you opens the tumor capsule and we take some specimens biopsies. Then we have vigorously debarking of the tumor with auto aspiration. And now you see the big advantage of the hemisitting position for forceps or dissect. I retract the tumor and then I can dissect the continuous irrigation. Identification of the facial nerve is the internal auditory canal with the simulation probe. Dissection of the tumor from the canal. And then again, you see here dissection of the cochlear nerve from the tumor under constant irrigation. And this keeps the view very precise and I always have a good view and I see very well the plane for dissection. This is only because we have this constant irrigation. Then again, debarking of the tumor and step-by-step mobilization of the tumor with a bimanual technique. Traction and counter traction just with two forceps. And here you see the facial nerve is coming now. Careful dissection, no stretching of the nerve. This is a facial nerve running here. Careful dissection, no stretching of the nerve, just perpendicular dissection. The right angle to the only to the cross of the fibers to avoid any problems. You know the tumor is always sticky to the facial nerve at the entrance into the internal auditory canal. But with this constant irrigation and counter traction technique, we could dissect the tumor completely from the nerve. So the last piece and we could stimulate the facial nerve. And then the endoscope is very helpful to look into the internal auditory canal to see open air cells and also to see small remnants, which were hidden behind the bone, which could not be seen with a microscope. And then we put some muscle and fix it the fibrin glue to avoid CSF leakage. Next. So post-op MRI, one day and you see she has slight facial palsy, but not much and this resolved after a few weeks. And we could also preserve useful hearing although the tumor was very large. The hemisitting position, I think is a very ideal for these larger tumors because you always have a nice plane for dissection. So should you always aim for gross total resection? This is a surgery I did more than 15 years ago, was a large tumor. And I was taught that vestibular schwannomas have to be removed completely doesn't matter what is with the facial nerve. She is after 10 years now, she has no recurrence, but you see, she has disfiguring facial palsy, and this should not be our aim in my opinion. This is a nice girl. Came to me with this tumor and she was told at another institution that she has to accept the facial palsy. She will have it definitely. And then we said, we can try to white this. Again, the hemisitting position. Opening of the internal auditory canal with a drill. Dissection of the tumor from the internal arterial canal and then debarking of the tumor with ultrasonic aspiration. And again, is it the by manual technique. You see the tumor was very vascular where it was always some bleeding. But because of this irrigation, I had always my plane. I could dissect it very easily and also much faster than with the supine position. And he has the facial nerve was very sticky. And then in the monitoring we had this reaction that we really disturbed the nerve too much. And then we stopped and left a very small layer of tumor. We left a very small layer of tumor here at the fundus. Next. And you see there's a residual tumor and it's very stable. Now seven years after surgery, no problem. And she has a good function like she wants to have it. So another example, huge tumor, 30 year old male, the 10 years good function. And you don't even see that as a tumor remnant, but I know that I left a small layer of the capsule attached to the nerve. And if I would take that he would have a palsy, for sure. Now this is a very ugly tumor, very sticky to the structures. Multicystic young lady, we removed it hemisitting position and after surgery, she's doing fine. And we just watch the small remnants. So in my opinion, when we have larger tumors and we see during dissections that we have the trends of the facial nerve, which predict a very bad outcome for the facial nerves then we should stop and leave a small layer of the capsule. Very small layer, just a millimeter or two. Then we have a very good outcome. You see, after six months from 16 patients, we have only one grade post Brockman and grade two, all other are one. That should be our aim. What happens with the tumor remnant? That I don't know because the follow-up time is not too long. So far we had just one case who required radiation later on. So another good indication for endoscope assistance, epidermoids. This was a lady. She had two surgeries before resulting in hearing loss after the first surgery. And she came again with a second recurrent tumor here indentation the midbrain. And again, they come from this approach. It's hard to sit down with a microscope to this area in the cerebellar peduncle and that's why they have the problem with prostate resection. So we make a superior retrosigmoid approach. And you see here's all this tumor. And my first question was, where is the trochlear nerve? Because it's somewhere under the 10, but I don't know did the tumor dislocated, is it above or below? So the third degree endoscope was extremely helpful in this case for the identification of the trochlear nerve. And you see, the tumor displaced the trochlear nerve downwards to the brainstem. So it's not up, it's down. So now I know where it's running and I can make it really a rapid decompression and dissectional the upper part of the tumor because there's no risk that I damaged this trochlear nerve. And all this is done under the microscope. There's still no need in my opinion, to use the endoscope in this phase of the surgery. So we dissect down and we found in the posture part and the dorsal part the trochlear nerve, and then we dissect. Although this was a recurrent case, in this case, I was very lucky to find a good plane and with bimanual dissection I could dissect the whole tumor including the capsule from the brainstem. Usually in recurrent cases, this is not possible because the capsule is very sticky. Then it's still advised to force total resection, but here it was possible. Now we see, we use a 45 degree endoscope, the curved dissector to remove the tumor, which is indentating cerebellar peduncle. And this is very, very helpful to have the 45 degree endoscope. Otherwise you cannot see it. Now for suction, and I have my accurate suction and here is the residual tumor deep down indentating the cerebellar peduncle. But on the scopic view, we really could totally remove this tumor. Next. And you see post-op, tumor is taken. Also the indentation is not longer apparent. Another example is a 55 year old female. She presented this facial numbness and has this non enhancing lesion. It is in the Meckel's cave, dilating it, and just also part compressing the brainstem. According to the intensities, there's a little bit hyper intensity in the T1. So it should be not an epidermoid but a dermoid. And we always discuss this case in our endoscopy courses. And many people say, yes, we make a caversial approach. We make a combined approach. For me, I think it should be simple, we just make a retrosigmoid approach to exist part of the tumor with a microscope, and then we use a 45 degree endoscope to look into Meckel's cave. So we open up the arachnoid. This is the fissure surface, the tentorial surface. You see there are some hairs inside. Sometimes you can find teeth dissected away. Try to find the plane here to the facial nerve, which is running here. This is the trochlear nerve running here. And this is now the trigeminal nerve. The trigeminal nerve is very this and very sticky, especially when it goes into the Meckel's cave. And so I did not dissect this nerve because this would destroys the nerve. So here I left a capsule, which was very attached to the nerve. So here we have to blind curataj with a microscope. That's not good. That's why we switched now over to a 45 degree endoscope. And you look, you see how nicely we can look into is this dilated Meckel's cave. And we can dissect the tumor with instrument on a direct visualization from that area to have gross total evacuation. Of course, there is some tumor capsule attached to the nerve, but as I said, it is very adherent. And if you try to dissect it from this area, you really will destroy the nerve. Next. This is the result. You see it is a total evacuation and she is fine and her problems disappeared. This is a lady with progressive gait and balance problems and dysesthesia in the left arm. And you see she has a foramen magnum meningioma. It does extend more to the left side. So the approach should be far lateral from the left side. You see spinal accessory nerve here C2 fibrous C1. And then we start with a microscope to dissect the tumor, debug it and dissect it. But you see, there is a blind corner. I cannot look completely to the front of the foramen magnum from this area. That's why I switched now again to a 30 degree endoscope, fix it on a mechanical holding arm. And then we can dissect this tumor pod, which is sticky to the ventral dura. I took the inner layer of the dura with the tumor out. And then finally we have coagulation of superior layer of the dura. And the front inspection shows the gross total resection of the tumor, the vestibular artery and here's the brainstem. Next. So when we make the far lateral approach, and now I just go to the end of the contre and then I look, then takes the endoscope to look to this blind corner. So we just finish here with our drilling and then I use the endoscope to look into the blind corner. I think it's very helpful for this procedure to have a good overview. And this up to three years, no recurrence. And she's really doing fine. Jugular tubercle meningioma the same. If you want to look down to the hypoglossal canal here, it's a problem because the jugular tubercle is in your way. You see with a microscope, I cannot see behind this jugular tubercle but with an endoscope, I have a good view to the hypoglossal canal and I can dissect the tumor here on a direct visualization. This was an 18 year old female. She had multiple problems. Dizziness, ataxia, headache, facial palsy, double vision, hemiparesis. And she presented with this cavernoma in the parnten area, really a big one. And what is the best approach? I think a lateral approach is always preferable to a posterior approach. So we can retrosig and went to the middle cerebellar peduncle. Of course, on the monitoring. And you see this is aids nerve. This is the dilated pontine surface. Then we open up the ponter cerebella that fissure, dissect that to the middle cerebellar peduncle. And the under navigational guidance, we go through the tissue. It's long, but we can find it with the navigation and we dissect. And again, when people say, why are you not using the endoscope? If I put my endoscope here in front, I don't see. Because the opening and the brainstem is very small and the endoscope will only obstruct my ability to manipulate in the depths. So is a microsurgical resection of the tumor. And then finally we use the endoscope to check the cavity. That is very helpful because we can use a sucker to displace a tissue and make sure everything is removed. You see, this is your trigeminal nerve. And this is its nerve, trigeminal nerve here. Also for cavernoma, the endoscope can be quite useful. And she is doing fine. Two years after surgery, she's still doing good. And I met her on a petrol station in the south of Germany while she was on the way for a skiing vacation, which seems to be a good sign for balance and neurological function. This was a strange case. This was a 20 year old male. He came with sudden ear pain, tinnitus and hearing loss. And then he was treated with medication for the hearing loss. And then he developed also a facial palsy. And then neurologist, they show the case to me. And here is a lesion in the internal auditory canal. There is dilation. And contrast enhancement, but not the whole lesion. So initially we saw that looks like a vestibular schwannoma. This was also that but it's not very typical. So we said, okay, we have to go in and look what it is. So we see here the ICA running into the internal arial canal. So we open the internal auditory canal, we cut the intrameatal dura, and then we dissect the vestibular nerve. The vestibular nerves are not working anyway. So we can also cut it to get access to the lesion. But what is it? So we cut the vestibular nerve. And then we dissect it. This was a rare case for thrombosis. I get aneurism purely intrameatal. So we dissected a way. You see here is the facial nerve. See really compressed. Suppose you obviously come because of the thrombosis of this aneurysm. So there was some residual flow. That's why we make an opening of the aneurism and then enter a teractomy. We removed the clot from the vessels and we place a temporary clip. Then an approximate part where the different parts are also some back bleeding and replace the clip too. And I was thinking, should we simply close the ICA? Or is it an important vessel? So I was not sure because in the pre-op angiography we saw a little bit of delayed filling. So it was not complete occluded by the ICA so that's why we opted for the reconstruction. And we made an end-to-end anastomosis of the ICA. So first we suture the frontal wall of the ICA and then the posterior wall. Of course, you may argue this was not be necessary because it's not a major vessel. It's a small vessel, it's the ICA. ICA as a dominant one, but you never know. That's why I thought might be better we reconstruct the vessel. Then after finishing all the lines we removed the distal clip first then removed the proximal clip. And then we had a good flow with the microvascular doppler. And then we had the angiography. Okay, next. And his facial palsy improved, but the deafness remained and you see here's the anastomosis. But maybe it would not be necessary. So for aneurysm clipping in the posteial cranium Fossa the use of endoscopes is all very helpful. This was in a lady with an unsteady gait, dizziness and balance problems. And you see there is edema in the brainstem from a PICA aneurism pointing to the brainstem, very unusual. And our intervention has said, no, we cannot cause us because there is an acute angle of the PICA arising from the vertebral artery. And if we occlude this aneurysm here, because of this accurate angle, we will have an occlusion of the aneurysm. And then we said, okay, we make the surgery. We used a retrosigmoid inferior approach. This is a lower clear nerve group, nine and 10. This is nine. This is 10. And now I could not see the aneurysm. So I need to use a 45 degree endoscope to have an idea about the aneurysm. We see the vestibular artery coming here. Here is origin of PICA. This is all aneurism. And yeah, I want to see where are the perforators. And you see the small perforators are running here in the back. So I have an anatomical understanding of the situation. And then I tried to clip the aneurysm on the endoscopic view. But if the endoscope was in, I had no place for my dissection and also no place for the clip appliers, that's why I switched back to the microscope. I dissect the neck, which was very sticky to the brainstem. And then I clipped the aneurysm, neck on a microscopic view. But it was clearly blind because I could not see here very well. But what is in the tip of my endoscope. It's very dangerous that we have a perforator inside, which we cannot see. But you see with a microscope, I could not observe the position of the clipboard. With a 45 degree endoscope, I can go in. I see the clip tip has rolled here, but the perforator, which runs here is not in the clip. And this gives you the safety that you can terminate the surgery with a good clipping of the aneurysm. Next. And you see post-op, the aneurysm is completely occluded. So for aneurysm surgery, it's very nice, especially in the posterior cranial fossa. Good indication also is microvascular decompression. We use the endoscope a lot of that trigeminal neuralgia first. We approach it as it's not correct. It's a superior retrosigmoid approach is just in the knee from the transverse sinus to the sigmoid sinus. Here is the small opening. So I want to see the temporaila surface and the pitra surface and especially useful is the endoscope. If we have a very prominent suprameatal tubercle like here so we cannot look to the Meckel's cave. And we don't see if there are some venous compression distally. And you see with the 45 endoscope we see here, when running and then taking the trigeminal nerve, which runs here. So endoscope very helpful to look behind the suprameatal tubercle. So our technique usually is an SCA transposition. You see here, this is a trigeminal nerve. Here is a loop of the SCA, there is a petrous vein. We never takes the petrous veins. We tried to preserve it always only in the case it is compressing the trigeminal nerve and it is a branch we can think about it, but never takes a petrous vein because you think it's safe. So with endoscope we get an inspections and we make an arachnoid dissection. It's very important that we follow the SCA far distally dorsally because when you make a transposition, you have this access length of the SCA and you have to put it somewhere in the kicking of the vessels. That's why we need to dissect all the way on the surface of the dorsal surface of the cerebellum in the positive direction. You see is the SCA coming here. So we have mobilized the vessel. Then I placed one teflon in front just to keep the vessel there. And then we make this transpositions. It brings a whole vessel under this tent, under the surface of the tent in the posterior direction. Then I use the sling. I use a teflon sling to keep it in this position, I think is the best way to decompress the trigeminal nerve is if nothing is in contact to the nerve. It's not always possible, but if the SCA is probably usually it is possible, and I always place a sling and I take an aneurysm clip to fix it in this position. Is best as a suture, initially I took sutures, but sometimes you have to re tighten it. Then it's much easier with the aneurysm clip and the endoscopic inspection shows the trigeminal nerve is completely free. No contact between nerve and vessel and no contact to the teflon, which also might be an irritation for the nerve. So is that for me, is the ideal transposition and decompression. Of course, you have to make sure that the vessels are not compressed. That's why we use usually Doppler to check. So sometimes the transposition is impossible. What we are doing then, you see this as a 71 year old male. Yes, since two years, trigeminal neuralgia on the left side and you see here, this is a mega brassalla artery. And if you look in, you see, here this is it's nerve. This is a very stretched abducens nerve. And this is the trigeminal nerve. So trigeminal nerve is here, abducens nerve. And this is ICA running here. So what can we do in this case? There's no space, no place to make a sling. So just what we do is we decompress this end of the root entry zone. We replace a lot of teflon. There is still a compression here. So I thought this will not be a successful surgery. I was afraid, but I contact him. Next. And he is now over eight years after surgery is completely pain-free and needs no medication. So rhizotomy is an indication, especially in patients when we have no compression and the patient has multiple sclerosis. What we do then is we go in with the hook, especially if it's a lower third, it's a very nice surgery. Sometimes we have to take some middle third. We try to avoid to take two thirds of the nerve, because this can make really this a seizure in the face. If you take just one third like here, then sometimes they even don't feel hyper seizure in the face. And they ask me always, no doctor, you took the wrong nerve. But nevertheless, they are pain-free in the majority of cases. Next. So venous sacrifice for me is a major problem in trigeminal neuralgia. You see here is a vein running in this direction, petrosal vein. This is the trigeminal nerve. And you see this is severe indentation of the trigeminal nerve, which runs here by this vein. So we take a 30 degree endoscope to look behind this suprameatal tubercle. Then we can coagulate this vessel and you see it's a severe indentation. We have a lot of patients which have not approximate compression like we should have it according to the textbook, but we have the distal compression close to the entry into the Meckel's cave and this is the origin of the pain. Next. One case you see here is a small vein visible, what should we do? Trigeminal nerve here and this is a vein. So it looks pretty the same, like the previous case. So we coagulate it. And then the patient did not very well. She has severe headaches. She had balance problems and you see there's already swelling invisible on the first day after surgery and this becomes worse. And I was very afraid that she will bleed because of the venous congestion, which we caused by a venous sacrifice. So it's not always safe to take a vein especially if the vein is very thick, we should be very careful. This is another patient, also a vein very close to the nerve. And we look in, you see, this is it's nerve. First nerve, and you see here, there is this big vein. Can we take it? It looks the same like in this lady where we have this disaster. But here we look, what is the vascular anatomy? And you see there a two draining points of the veins. One is here with a irregular superior petrosal vein. And this vein is draining into the meckel's cave. The sinus close to the Meckel's cave. And you see this the same vein. So it's the same vein has two cranaj points. And that's why we can make the sacrifice because the blood will run with this collateral to the superior petrous simus. So in this case, we can create coagulate it and we can be pretty sure that this will not harm the patient. But if you don't see that there are collateral of the vein. You see this as a collateral here running in this area. And this site launch, we have coagulated and released trigeminal nerve. And he's doing very well, has no pain and no problems with venous congestion. So if you have collaterals, I think it's safe to do it. If you don't have it, I don't do it anymore. Next. Another patient, you see it's a very tight on time cistern, very tight. We go in. We have fear prominent suprameatal tubercle. With the endoscope we can look behind. See, this is a trigeminal nerve and you see two big veins running here and here is the SCA. So we have to drill the tubercle and then we dissect an endoscopic view because we cannot look with a microscope here into the depths. But the SCA is not a problem. The problem is really the indentation of the nerve again, by this vein. But this vein we cannot coagulate. So we have to dissect it from the surface of the brainstem. Then we put some teflon in to keep it away from the nerve. And again, I try to put the teflon away from the nerve. Best is to have no contact between the nerve and any Teflon. That is the best, in my opinion. It's not always possible but if we try, we see here is still a contact. So we shrink a little bit with bipolar, but not too much, just a little bit to one thrombosis. And then we place another piece of teflon here to keep the vein away from the nerve. Next. So another very good indication. This is my last example is a hemifacial spasm. And hemifacial spasm as the value of the endoscope is even more important than intrameningeal. We have an inferior to rectosigmoid approach. We have, again, the 45 degree rotation of the head, and then the whole table. We use a straight incision and we perform a lower retrosigmoid craniotomy. We always record lateral spreads. And then ideally they go away showing that you have a good decompression. The small approach because you don't need much space. Some people always stop to use an endoscope from the beginning, but sometimes you have such a small space. If I bring my endoscope in, I cannot move my instruments. So that's why I start always with a microscope. We look with a microscope in, it's not very well seen what is here and that is a big time for the endoscope. With a 45 degree endoscope, you see very nice. The ICA comes as a common trunk from the bezella which runs here. And then it gives rise to the ICA and to the PICA. And this is the facial nerve. So it gives you a clear overview over the anatomy, much better than with this tangential view of the microscope. And here again, you see this intermediate nerve, just the facial nerve, and here is the ICA loop causing the compression. Then we switch back to the microscope. I put some Teflon in. And then again, we check the anatomy with the endoscope, common trunk, ICA common truck, ICA running here and PICA running here. So you can inspect a hole somewhere ignites space, and you can really make sure that you do not overlook. Position of the Teflon again, I try to white to area where there was a compression. I put my Teflon far away. So that's a nerve which was damaged by the Vesicle loop is almost completely free. That is the best. The video starts with the dissection of the arachnoid over the lower cranial nerve pool. It's an infra flopula approach to avoid a retraction to the cochlear nerve, which runs here, the noise nerve. There's the facial nerve, this is its nerve. And you see this loop of the vertebral artery compressing here's the facial nerve, severe compression. So I place some Teflon initially far in front of the facial nerve. The first Teflon always goes between the vestibular artery and the brainstem in front. You see here's severe annotation of the facial nerve here. And then again, I take a Teflon loop. Around the vestibular nerve, you must be very careful that you do not overlook any perforators and make an incision of the dura in between the jugular foramen and the internal auditory canal. And it takes a Teflon loop and I fix it. And again, the clip is very helpful because I can re tighten it if it's not tight enough. So sometimes we make a pure endoscopic decompression. Look it's not running out, this is running. Now you see here, there's a PICA loop going far up into the brainstem. If you come from here to look and you come from here and to look inside, it's very difficult to see this PICA loop, which goes up very, very much up into the brainstem. Next. So I use a microscope for inspection. But I could not see the exit point of the PICA from vertebral artery. I try to retract the cerebellum a little bit, but then the potentials went down. So I use the 45 degree endoscope, to see the vertebral line here. And you see here is your origin of the PICA going here into the brainstem. So this is severe indentation. So I had to use a 45 degree endoscope because I couldn't see it and was curved dissector. I could mobilize the loop out of the brainstem. Under the microscope, it was not possible because I really couldn't see it. It was so familiarly and when I rechecked the cerebellum, I had a problem with the acoustic nerve potentially. Next. This is interesting is the last case is an arachnoid band. This was a patient with 20 years history of hemifacial spasm. And you see in the tough, there is no vessel, nothing. And you see the facial nerve, which runs here is a little bit more anterior dislocated compared to the other side. This is the facial nerve here and here's the facial nerve on this side. So this was strange. And when we looked in, we see really a strangulation of the facial nerve. This is the facial nerve, this is the vestibular cochlea nerve. And here you see, there is a really like in strangulation and there's no compression of the facial nerve in the approximate area where we usually have the compression and hemifacial spasm. And here is like a small neural tissue band, which fixed the nerve in front, very strange. It's clearly a malformation, which he has from the beginning. And then we just opened this arachnoid. So we cut this strangulation, it's all arachnoid and then we open also the pentolinium with a diamond knife to get it released. Next. And the specimen really disappeared the next day. This is another case. Again, you see here strangulation with these arachnoid bands. And we also simply cut these bands and he was doing fine. So we had a lot of cases with these arachnoid bands just in two of them and only a venous compression just in one. So it's very rare, seems to be very, very rare. Most frequently we have the PICA. And what are prognostic factors? We found that prognostic factors, a good outcome is this approximal indentation of PICA. All these patients went very well. Sometimes it took more than five to six months after they became spasm free, but all improved very much. What is a bad prognostic factor was a periphery grooving. Yeah, it's very thin. It's just paper thin. These patients had persistent spasms sometimes many years also after surgery. So seems to be really a structural damage in the nerve, which prevents a good outcome. So this was my series of endoscope assist microsurgery in more than a thousand cases. Most of the microvascular decompression, but also tumor cases. I hope I could convince you to use the endoscope ends up procedures. It's very helpful to see into blind corners, which cannot be seen with a microscope. Thank you for attention, and always invite you to our course, which we do hopefully next year in Greifswald. And I hope to see you soon physically face to face. Thank you for your attention.

- Henry spectacular work, really enjoyable. I'll tell you it's true, beautiful, clean, precise, gentle microsurgery. I absolutely admire your technique, especially the technique of bimanual dissection using fine forceps. It is the most atraumatic way to handle cranial nerves and it really provides better results. There's no question about the sitting position. It provides a flow of fluid and blood, with irrigation out of the field and allows better management of the cranial nerves. Obviously endoscope expands our operative corridor and the videos just show tremendous experience that is very obvious, very enjoyable to watch. And it's quite impressive. I'm gonna go ahead and ask if anybody has any questions, they're welcome to post if they're interested. Otherwise, I think the entire session we had over 215 people watching. Really a demonstration of your expertise from all over the world, Henry. And so I think everybody's just being thankful and really appreciate all of your time, especially 20:00 AM in the morning in Germany. That means a lot. So I wanna again, I appreciate your time, your effort and hope that we can invite you again next time for another session, Henry.

- Yeah, it would be my great pleasure. Thanks for the kind invitation. It's really very much fun to be here and an honor also.

- It's an honor, honor is ours. Have a great morning.

- Yeah, you too, thank you. Thank you everybody for watching. I hope to see you soon physically. We have to meet again and have a good beer not just electronically.

- We sure hope so. Henry, thanks a million again.

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