 So, let us come to this part of the anatomy and the interesting thing about this anatomy is this is the anti-clinoid, right? So, this is the anti-clinoid. So, when you are coming by the t-reonal approach, just by drilling this, right, gives you an access to about 8 mm, extra 8 mm of the internal catheter artery and a little bit about 8 mm or 1 of the optic nerve. Just these two things. I have never heard of anybody ever injuring the internal catheter artery by doing an anti-clinoidic to me, never. An aneurysm or rupture I admit, but injuring the internal catheter artery I have never heard of. It has not been published and I will tell you why. There is a little bit of anatomy involved. So, you know, when people say, oh, I am doing an anti-clinoidic to me, there is nothing great about it and that is basically because of the anatomy. You know, the interesting thing is that this anti-clinoid is attached to the rest of the skull with two roots. I will call them roots. One is the anterior root which attaches it to the plenum sonoidal here and there is a posterior root which is also known as the optic strut which attaches it to the point which divides the superior orbital fissure from the optic foramen. You can see that. Now the interesting thing is the internal catheter artery, trace the internal catheter artery in the cavernous sinus and you will realize that the internal catheter artery stops short of the anterior clinoid which means the posterior root and turns backwards at the supraclinoid segment. You understand? So, actually when you are drilling the anterior clinoid, the internal catheter artery has already turned backwards. You get it? So, therefore, it comes like this and it turns back like this. So, when you are drilling coming like this and drilling here, the internal catheter artery is not there. So, actually the internal catheter artery has never been injured by anti-clinoid activity. A dorsally placed aneurysm? Yes, but the internal catheter artery you know. There is a small nuance which you need to know. Now, the next point comes is when you are drilling the anti-clinoid, how do you disconnect it from the rest of the bones? You disconnect it from the rest of the bones. Imagine you are coming from here. One is by going this way, going towards the plenum sonoidal. So, when you go towards the plenum sonoidal, you detach the anterior root. And what is the second way you detach? By drilling the posterior root, working between the optic nerve here and the supraorbital fissure here. How do you drill this? First you decompress the supraorbital fissure exposing the optic nerve. As soon as you do that, you have actually taken care of the anterior root. Is that clear? When the next point you do is go on pouring it out from inside, going on pouring out from inside, what happens is you are actually detaching the posterior root. You get it? Just this small piece of anatomy if you have in your mind, you know, you can easily do this procedure without any problems. I learnt about this was the day when I could do it without any problems. You get it? Now, the other very interesting point is the dural rings. The location of the dural rings appears to be so complicated, but it is actually very, very simple. It is very simple because when you look at the orientation, so it comes from the cavernous sinus like this, turns like this and becomes supraclinoid that everybody knows. And so there is a proximal dural ring here and proximal dural ring here at the cavernous sinus and a distal dural ring here. Let us look at it from the anatomical point of view. So, you have one proximal dural ring coming from here. So, when you the carotid artery comes like this, it passes to the proximal dural ring, turns and becomes supraclinoid here. So, you have a proximal dural ring here and you have a distal dural ring here. So, now this forms the carotid collar which connects the proximal dural ring to the distal dural ring. So, when you drill this, what are you exposing? You are exposing the carotid collar and the paratinoid segment of the internal carotid artery which is in the carotid collar. Now, the third point that I would like to make is very simple points, just very simple points. The third point is very interesting that your actual subarachnoid space starts at the level of the distal dural ring. So, anything that is proximal to the dural ring is extradural. So, the clinoidal segment of the internal carotid artery is actually extradural. It is not intradural. So, if there is an aneurysm of the paracinoid segment which is extradural, it will never cause subarachnoid hemorrhage. So, anything which is in the cavernous anus or in the paracinoid segment and it is not protruding into beyond the distal dural ring will never cause a subarachnoid bleed. These are small points. So, now, this will become very clear when you are actually doing when you are actually doing surgery. So, now, just to take you beyond this. So, just the cavernous anus segment come to the proximal dural ring. This is where the cavernous anus stops. Then, this is the part which is drilled. The clinoidal segment is drilled exposing the clinoidal segment of the internal carotid artery. Then, there is a distal dural ring and then, just beyond the distal dural ring is the ophthalmic artery. So, this is the ophthalmic artery and then comes the paracinoid segment of the internal carotid artery which goes on to the p-com artery. So, the entire segment from the distal proximal dural ring to the p-com artery is the paracinoid segment and we have several aneurysms in this segment. So, this was a very interesting case where there is a bleeding into, I need to publish this. This bleeding was occurring in the subfrontal region. There is a basilar top aneurysm here and this basilar top, look at this. You see this nubbin here. This was protruding beyond the dorsum cellae and it bled like this into the subfrontal area. So, it bled like this. Very interesting case. So, when we did that and then once this was clipped. So, this was clipped and we also noted that there is a ventral wall aneurysm which is just opposite the ophthalmic artery. So, you see here this is the ophthalmic artery. This is a ventral wall aneurysm and this is the clipped basilar top aneurysm. So, now, this is the obitozygometric shortme. This is the frontal lobe. This is the temporal lobe just to take you to the video and we are just concentrating on clenoidal deling and nothing else. So, now, you see the optic nerve and the carotid artery going from the right side. So, you now the important thing is this is the area of the plenum sonoidal. This is the area of the plenoid. So, what is more important? First, I told you drill the plenum sonoidal so that you mobilize the optic nerve. That way, you will take care of the anterior root of the anterior root. So, just and it is a very thin piece of bone. So, with a diamond drill you just drill that. So, you expose the optic nerve. Then, the next part is drilling the clenoid. So, this is where the clenoid is. Another very big advantage is that when you do that then what happens is that. So, now, what is happening? I will just tell you later on that now this is the you see this is the ophthalmic artery going immediately this was the distal dural ring. This was the clenoidal segment and I am just opening and the aneurysm will be just opposite to the ophthalmic artery. So, the aneurysm is here. Yes, the aneurysm is here. So, gradually I am resetting. So, just with a series of examples then you will understand this is intradural drilling. So, I just make sure that it is there and you see that. So, it turns like this and goes into the cavernous sinus. Now, I am trying different types of clips. This clip not working. Obviously, not working. This is absolutely wrong. So, try this this didn't work. So, this is the aneurysm here. Try this clip, you know, fenestrated some way impossible. This is nonsense. You know, you can't you can't be so this didn't work and this is the aneurysm there. So, what do you do? What I did was I opened the cavernous sinus here. So, there is a little bit of bleeding there. Now, so, this creates space there between the at the ventral wall aneurysm and then you have a clip and a little bit of bleeding from the cavernous sinus that you can easily clip with a surgery cell. I am just telling you I will show you more example, but I am just telling you just a little bit that extra 8 millimeters gets you the space to work with aneurysms of this location. Is that clear? So, if you look at the first principle was start with drilling of the optic foramen. Mobilize the optic nerve that is the first principle. The second principle is then you drill the antiretrinoid. Then the last part you just remove it with a piece of biopsy fossil. It will come to that just more details. C4 of thalmigarty that is the next point. C4 of thalmigarty. See what the location of your aneurysm is in relation to the of thalmigarty. And then look for suitable maneuvers to clip the aneurysms whether you want to use a fenestrated clip, angle clip, whatever type you want. This is the way it has to be done. So, let us take a proper example. This is just that was just to show you the operative steps, but now there is a proper example. This is this and came as supracella meningioma, but you see this target sign. This is a target sign and the enhanced images definitely shows you that this is filling with blood, filling with contrast, filling with blood. And the MR of course shows you thrombosis as well as flow voids inside. And this is the medially directed so this is a fairly large and so this is where it is coming out beyond the clinoid, the ICA and then you see this is medially directed and fairly large. When you do an angiogram, what do you see? So, this is posterior and upwards, this is the of thalmigarty and this is the P comarty. So, this is medially directed, chaotic of thalmic aneurysm, this is the PCA and this is. So, when you have an aneurysm like that, what you need is definitely you need to see for the left side, number one. This is a lateral image. So, there is no question of course, but they will often be mirror aneurysms of the opposite side whenever you have an aneurysm like that. So, you need to look at this and of course, you need to look at balloon test occlusion and cross flow and there is a good cross flow at least on the ICA. So, at least that is very heartening that we can at least have a good. So, even if we if it ruptures we need to actually clip we can actually do it. And then we have a this PCA it is not filling up so well. So, cross flow from the PCA is not very good from the vertebro basilar system I mean. So, now again the same thing. So, this is frontal this is temporal magic it is working. So, and then the the sylvanes fissure. So, you open the sylvanes fissure and do a wide sylvanes dissection because it helps you in subfrontal retraction because it helps to and then you come to the optic nerve and the carotid artery. So, once you reach there then good drain a lot of CSF just make sure that you have your orientation and so this is the distal ICA and then I need to know where the PCOM arteries in relation to the entire thing and also the ophthalmic artery. So, this is the distal ICA and this is where the aneurysm is. So, so now I am looking for the PCOM. So, now there is this large PCOM which you saw on the angiogram which you see that this is here and that is the third nerve going into the cavernous sinus here. So, so this is the third nerve this is the PCOM and this is the optic nerve and the. So, what was the first principle? Mobilization of optic nerve. So, first is not though go directly. So, so you have this. So, always open the dura and this dura acts as a protection you know it acts as a protection. So, when you are drilling this will protect the optic nerve from actually getting the vibrations very important. So, then the first thing is you know just this small mobilization of the optic nerve really helps and I will tell you how it will help. So, just do this. So, what I did was just to you know demonstrate. So, this is where the aneurysm is right and you cannot actually see anything beyond that. So, just trying to make sure that everything is this is the and this is where the cavernous sinus is going to be right. So, now what I am trying to do is can I mobilize this optic nerve and reach proximal to the aneurysm without drilling that is the question that is the hypothesis. So, now I try to mobilize the optic nerve not possible it is not possible to reach there you hear it it is not possible because you are not drilled I am just trying to see if I can see the ophthalmic artery without cutting. So, obviously it is not possible. So, then the next thing is to just drill just drill the optic and this is the falciform ligament here which we will cut. So, once you do that so, this is very simple there is nothing to it except that you have to be use a diamond drill and just make sure that you actually mobilize this and this is the falciform ligament. So, now this is the area of the clenoid. So, we have actually cut the falciform ligament here just mobilize only from here to here, but you will imagine you will understand how much of mobilization you get. Now, what are we drilling the anti-clenoid process coring it inside from inside and then once you core it out from inside the it is very simple matter to just drill it and it becomes mobile and then you can just remove it. So, once you remove this then what do you see below that you see the carotid callers. So, once so, this is where the cavernous sinus is this is removed and this is the distilled ural ring this is the carotid collar and the internal character artery is shifting turning like this and going into the cavernous sinus. Now, I just open the falciform ligament the junction of the carotid collar with the falciform ligament. So, you cut it together and actually it appears very complicated but it is a very there is a lot of dissecting plane there. So, it is just simple to do it just simple to do it. So, then it is not difficult at all you just lift it up there is a space there you just put your disector there and you can do it it is not difficult at all. So, you just this. So, all you have done is mobilize from here to here and mobilize from here to here that is all you have done nothing more to it and this is the cavernous sinus. Now, when you mobilize see you can get mobilization you can see the the proxy. So, so you can actually yeah. So, you can see the ophthalmic artery there and you can see proximal to the aneurysm yeah. So, just by doing that 8 millimeters what have you got you have been. So, see you can insinuate your disector proximal to the aneurysm there right you can see the distal tip there and just that small drilling helps you. So, much yeah and now it is a very simple matter this is the proximal part that is the that is the proximal part this is the distal part always with these aneurysm where you do not have adequate control never take the neck just take just put your apply a clip a little distal. So, that number one the vessel does not kink and you still have the neck in in case the aneurysm bleeds this is a double clip technique never take the neck always go remain a little distal right and then you put in a second clip which takes it. So, that you are absolutely sure that there is no kinking of the vessel and other thing is you can put both of them and then the next point is what is the next point whenever you are doing aneurysm surgery after you think you have clipped the other thing is. So, perforator of course, with such a giant aneurysm you cannot and you do not want to mobilize it to actually injure perforate, but you puncture it and see. So, what you do is you puncture it and you see if it is working it is not working right that is the other thing. So, you puncture of course, it was working luckily for me this time and so this was now this was basically you know I have lots and lots of videos of climidal segment aneurysm, but you know sometimes they will be on both sides. So, they will be like ballooning on both sides there you will have to have penetrated clips you have to reconstruct the vessel. So, there I have several of them, but I mean this was luckily going towards the cellar. So, this is a superior hyperfisal artery aneurysm. So, it was possible to do it, but the point here is not the surgery for aneurysm. It is basically trying to tell you that anterior clenoderma you just know these three principles. First cut the anterior root, mobilize the optic nerve that is the first way do not directly go to the anterior aneurysm. The second is core out the anterior aneurysm. You are actually going to the posterior strut. The third point of anatomy is that there the internal catheter artery is actually turning backwards proximal to that. So, that when you are drilling the posterior strut you are actually not in contact with the internal catheter artery. Now, what happens is that you have another a meningioma like this. Now, of course, you do not want to remove it totally because it is all involved in perforators and everything and you know. So, obviously, it will be a sub-total approach, but here the issue is you do not see any anatomy and you need to know where the internal catheter artery is. So, here an extradural drilling gets you to the internal catheter artery and you see middle cerebral artery when you are opening the selenium fissure. You see internal catheter artery extradurally and then you can actually know the level at which all the vessels are. That is a very, very useful technique. So, what you do is so, this is so, you have the globe here the frontal and the temporal regions and then you have this and you core it out as you do and then once you core it out from inside and remove then what happens is that you can actually get the extradural portion of the vessel. And the other very interesting manoeuvre which you can do to get to that is on the temporal side the temporal dura if you just dissect it off from the cavernous sinus dura right. Give an incision just see the V1 and V2 nerve roots see the you have the superior orbital fissure here just give an incision sharp incision dissect off the temporal dura from the cavernous sinus dura as soon as you do that the anterior anti-clinoid you can get very well I mean you know you can actually see it very well and you can actually see so that nothing comes in your this dura doesn't come you know it doesn't fall inside right. And of course, then while you are doing drilling you must make sure that it's not completely pneumatized. So, when would you go intradural it's very logical it's very logical if it's an aneurysm which is pointing dorsally you don't want it to bleed when the dura is closed. So, you will go intradural see the aneurysm grow proximal and distilled to it and dissect it. The second point is if you actually want limited drilling you see the only thing is that there is an aneurysm you want to see the proximal control you want to mobilize the optic nerve you can just do an intradural drilling when do you do an extradural drilling it is if there is a supracellar para cavernous lesion where you want to see the internal catheter artery to see the level of the internal catheter artery to see the level of the middle cerebral artery. So, you know what level there is an up to that level you can resect the meningioma or any tumor with impunity or beyond that you have to be careful right that's the other thing. The advantages of extradural drilling is that you know you are away from all anatomical structures and from cotton pledgets and all that and brain is protective and the other advantages that the bone dust and blood does not enter into the suprachnoid spaces but the disadvantage is that if an aneurysm you use an extradural drilling then which type of aneurysm can you use an extradural drilling in? Supposing I say you can use extradural drilling in some aneurysms also which one would you not like to use extradural drilling in? Which aneurysm will you say? So, if it is a dorsally placed aneurysm which you which which drilling will you adopt? Intradural because dorsal means it's right below the optic strut there if you don't see it you are in trouble right, but if it is a aneurysm pointing medially aneurysm pointing posteriorly no problem you can still use an extradural drilling is that clear to you? Thank you.