 Okay good morning. So now we start client edctomy. The main exercise today will be in skull-based surgery about the bone drilling. So high-speed drilling of bone in depth in neurosurgery is commonly required in of enteric linoid process like in dole length approach, Petrus pyramid in Kavasi's approach, mastoid in trans-petrosal approach and the lateral margin of rim of foreman magnum. This is in far lateral approach. So the aim of drilling is to convert a thick bone into thin bone and then dissect this residue with micro detectors and which is thin egg shell or with 1 millimeter up cut curation punch. Now this is the intradural drilling. The steps are that after bipolar coagulation of the dura. Dura is cut over the optic canal and the clientoid and is reflected down. I will later on show you the video about this. Now drilling starts from the optic nerve area and proceeds laterally over the clientoid. Now basically clientoid is attached by two bases. One is with the plenum and other is with the optic strut. Now while coring the enteric linoid it is the optic strut which is curved. Now in order to make high speed drilling always sit comfortably. Take one loop of the tubings in around your wrist so that if somebody pulls it it is not immediately pulled out from there. Hold it like a pen. Now your hypotherm should rest on the skull or the craniotomy site and this elbow should rest on the operating chair arm so that you are very comfortable there. And action you use is light painting breast action and then side to side or two and fro movements are used for the drilling. Now angled handpiece is used for drilling in the depth. For superficial you can use a straight handpiece. Now do not or never press on the bone or against the bone. Now drill in pulses in between keep irrigating remove the dust with the suction so your field is clear. Now bleeding from the bone is best controlled by either bone wax or by dry drilling with a diamond burr. What happens when diamond burr drills the small bone pieces they get into the crevices and then bleeding stops there. If you put saline it will be washed away so bleeding will not stop. Now cutting is done with the side of the burr rather than the tip because if you see the drill tip cutting tip the saws are on the side not on the tip so the cutting is done by the side. Now make sure that there is no cotton patty or surgy cell near the area to be drilled. However in certain cases if there is some bleeding you can keep gel foam. Gel foam never comes in the drill bit but surgy cell or patty will come in the drill bit and everything will be spoiled and operation is finished. So make sure that there is no cotton patty or surgy cell near the area of drilling. Now huge diamond burrs in low speed to drill the bone over the vital areas like carotid or optic nerve in slow speed. When you see in the microscope bring the drill tip so that you can see the tip now. Now make it on so now it is working and then take it to the target where you want to drill and give those light brush action movements there. Now remove the drill only when it has completely stopped. Otherwise it may endure the structures on the way while coming out. Now this is the extradural drilling you see after frontotemporal chromatomy this area is being dissected in the supiavital fissure region. Now I am trying to separate the endosteal and periosteal layers of the dura in the skull base. Now you see we got the plane and now this periosteal dura is being separated from there and in some patients in this area if you do not dissect it you may not be able to see the clinoid. So you have to reflect this dura the both layers of the dura. Now you can see the part of this and this is being drilled and now this is the meningo orbital band. A fibrous band is there sometimes a small twig of artery, meningo orbital artery may be there. So that should be coagulated cut and now if you reflect the dura the entry clinoid process you will be able to see very clearly and now after thinning it with the 1 millimeter of cut punch, kerosene punch it is drilled and now you see this hole like a canine teeth this entry clinoid has come out. But usually this is not the best here because you should not remove this large piece of entry clinoid it should have been small it should have been drilled further and what was the problem is that it was the premature disconnection from the strut. So the large piece remained. So the best thing is that strut should be drilled in the end so that you have a small piece and that should be drilled. And now you saw that the endosteal layer of the dura was peeled off and now you see in the cavernous sinus this giant pituitary tumor which is already started flowing after opening the dura. Now there is again another small video of extra dura drilling. This is the lesser wing of a spinured medial part which is being drilled after reflecting the dura and now this dura is being separated from this if there is any vascularity then you can coagulate it cut and then separate it from the bone. So this earlier I was doing intradural but now in most of the cases I do extra drill drilling. And now you see this is the entry clinoid you can see this strut and now the center of this should be drilled and cold. So this is the center of this again further dura dissection extra dura dissection and you further define the margins of the clinoid and then this thinned out bone is removed with the up cut further drilling. And now you see this is disconnected now you see bleeding from cavernous sinus and now once it is disconnected now you it is held with forceps and then you can remove it and this is this small piece. So it should come like this not a large piece or large chunk and this cavernous sinus bleeding can easily be controlled by surgery. Now this is the example of intradural drilling this was one para clinoid hypofysyl aneurysm supia hypofysyl aneurysm this is the sylvan fissure which is being split now you see ICA and its bifurcation. This is the third nerve that is the tentorial margin now this is the dura intradural this dura is after coagulation it is cut with the knife and it is reflected down and this covers the optic nerve and carotid. So this I told you that earlier I was doing intradural but so this is why it is a very old video but now we do all extra drills only in most of the cases. Now this drilling starts at the optic nerve area and then you proceed laterally and now you will see that after doing this when you cut this dura in the base and you open both the rings carotid rings and then you get say about 3 millimeter of a space of internal carotid and in this case already the ICA have been dissected in the neck. Now this is the thick arachnoid and dura which is being cut and now you can see part of the aneurysm and this lady presented with the loss of field of vision in this eye. So now the distal clip has been applied at the just before the ICA bifurcation and there is control in the neck. So this is the suction decompression method now the aneurysm is being aspirated now you see it has collapsed and now you put the clip and then it is being dissected there again just to see that nothing comes in the tips of the clip and such aneurysms they usually do not get obliterated by one clip. So you have to use one more or a booster clip in these cases. So another clip was applied and now after this the aneurysm was dissected from the optic nerve and post-op her vision improved and this is the pre-op and this is the post-op. Now the model trees of learning this bone drilling is in continuing medical education programs like you practice in the laboratory temporal bone dissection attending the skull-based surgery fellowships education seminars lectures conferences watching operative videos of the experts if you watch again and again you will learn the tricks how to do this. Now attending the courses and workshops which is live and cadaveric thank you very much.