 So, basically a third ventricle ostomy is perforating the floor of the third ventricle that is when we are talking about endoscopy, but it also means opening the laminar terminus as you saw some pictures and typically that is done transcranially. The indications most often we do the third ventricle ostomy for aqueductal stenosis. We know that the failure rate for third ventricle ostomy is for children less than six months is close to 100 percent and you have to keep repeating it less than a year it is about 50 percent and so either we resort to a shunt or repeat endoscopies. I have seen some articles where even less than six months they keep trying three four times doing endoscopy. I prefer not to do an endoscopic third ventricle ostomy for anybody less than a year and the anterior fontanelle when it is large it makes it really quite difficult to get a closure and so when you have a large anterior fontanelle again I do not do a third ventricle ostomy. Again post your third ventricle tumours this is really the ideal situation for a third ventricle ostomy to work because it achieves three things you get a CSF diversion you can get CSF for tumour markers and if they are positive you do not need to operate on the tumour you do not need to get a biopsy you could directly give chemotherapy or radiotherapy and you may also if you wanted to get a biopsy it is possible to place a burhole little more anteriorly and obtain a biopsy of the posterior third ventricle tumour. Now infection considering tuberculosis is so common in India it is tempting to do a third ventricle ostomy for TB induced hydrocephalus I have found it on occasion the floor is opaque it is quite vascular you could have troublesome bleeding and so in general we avoided you might get away with it but it is quite troublesome and then we have had a very few cases in which we have had patients with arachnoid cysts supracellarachnoid cysts where you can go in through the foramina manro fenestrate the cyst and then just as a precaution fenestrate the floor of the third ventricle so you can deal with this quite adequately. So these are the general indications now as far as the anatomy I think it is important over here that we understand that if we it is not possible to see anatomy because of distortion it is better not to proceed because from the anatomy that is been shown to you you can cause a lot of harm. So A placement of the burhole accurately identification of the foramina manro the two mammillary bodies the dosim cellae quite often you can actually see the dosim cellae in front of the mammillary bodies and you make the hole behind the dosim cellae in front of the mammillary bodies. The infundibular recess that you will see as I will show you the video a nice red structure and of course the basal artery which you need to be really worried about. Now as far as the burhole is concerned we typically would make the burhole three centimeters of the midline and either on the coronal suture or just a just in front of it. Now you need to change this burhole based of different shape you have a dolico catholic head it is going to be different and so what you was basically you draw a line on the sagittal MR from the joining the foramina manro to the point where you plan to make the hole in the floor and if you extend that to the vertex that is where your burhole should be because you have got a rigid scope and these three points have to be in line for you to be able to do anything of significance and so that is the importance of placement of the burhole. As far as going laterally is concerned if you saw those images which were shown on the specimens as well as some of Dr. Gupta's specimens if you go to lateral to get into the ventricle frontal horn not for third vent crostomies but if you are planning to do other procedures you have run the risk of going right through the caudate nucleus. So just be careful about that when you see these specimens just study the position of the caudate nucleus in relation to the convexity and realize that if you start going later you will go right through the caudate nucleus. Now perforating the floor I have seen people pulling it with forceps I have seen cutting with scissors and they are all successful but I find that the safest is using a Fogati's catheter you put it in twist it a little bit and it is blunt and so it does not really cause much damage you really worried about getting into the basilar artery or even getting into the brainstem. Now the caudary I have seen people use it and it is scary so try and avoid it because what you will find is you put the caudary out there and then you have a pulsating floor and then you want to actually get the caudary to touch it and so you push a little more and then you push it directly on to the basilar artery try and avoid using bipolar caudary. Though the caudary tip is blunt you might want to use that alone without and get that pedal and throw it out of the operating theater so that nobody presses it while using but you could use the caudary tip without using the current. So here is the video we gently clean the whole thing up you can now either make a linear incision or a flap it depends on the thinner the scalp I prefer to make a U-shaped flap because the closure becomes a little easier. How many of you have actually done and a third went lost me then I won't you you've actually seen a third went lost me being done everyone okay then I'm not going to go into how you're going to connect up the endoscope to it at all but basically when you're tapping the ventricle I find that many people when they inexperience they don't really look at the markings and you find that I actually have gone in about 7 to 8 centimeters so be very careful about keeping a finger at least on what distance you're going in okay. Once you fix on the scope I've got two videos over here I just wanted to show you the single chip camera this is the single chip camera I don't know how we could see it in the olden days but this is such a poor sort of image okay with the high definition you see it's so much better and here you need to identify which ventricle you're in let someone else tap the ventricle for you because you'll be amazed particularly when you have large ventricles and a thin septum you go in there and you angle it immediately you may go right through the septum and you're in the left lateral ventricle so you are in the right ventricle when the right thalamus trite is to the right of the coroid plexus okay so that's how you know where you are so if you see the thalamus trite vein to the left of the coroid plexus you know you're in the left lateral ventricle and that makes a difference in which way you're going to angle it at this point again have a look at the size of the foramina manro don't try and force the endoscope through a small foramin the column of the phonics and that's the anterior nucleus of the thalamus on the posterior border of the foramina manro now when you find that your burhole is placed wrong either to anterior to posterior and let's say you find that this is perfect you can see the mammillary bodies and therefore your endoscope is going to be going right to the area that you're interested in without damaging this but if you find that it is located there and you start moving the scope to look at it you're going to damage the foramina manro and so if you find that you are able to get the forgatti's catheter reasonably well without putting too much of traction on it continue but if you find that it's not just take it out and make another burhole or extend the burhole posteriorly you'll find that actually it's much safer so that's the septal vein and thalamus tight vein and the corioplexus now the side pot has an irrigation system you cannot underuse irrigation just keep irrigating in fact at this point you may get a little bit of venous bleeding which fogs up the whole place and makes it a little murky just get warm cell line and irrigate and you'll find that actually it clears on you need to have a little patience during this time don't hurry up the whole procedure and don't abandon it with the irrigation it will slowly clear up and only if you can see continue so there you see the two mammillary bodies and that's the error the interest in that's the third nerve coming off on each side now the importance of locating the mammillary bodies is that you will know where you are in relation to the midline and the third nerves are very close so if you are off the midline you could cause a third nerve palsy be careful about this that's the region of the basilar artery now this is the Dorsum cell A and the Dorsum cell A is a beautiful structure to use if you find that this whole floor is flapping around too much the best way to do it's to get right on to the Dorsum cell A because that's a rigid structure and when you get on to it you can then slide down the clivers and then open up the arachnoid there so that's if you do see it and it's close by it's a useful thing to use now in this patient it appears that there is already a hole there but actually these two were just areas where the arachnoid was a little thin it wasn't complete and so we've gone in with the Fogati there and do mild twisting movements be a little careful because some vessels can tear off at this point and then the whole thing is how do you enlarge it and it's by inflation of this bulb sometimes what happens is that if you're very careful you could inflate the bulb and bring the arachnoid back up away from the basilar artery and then try opening the bulb because if you have the floor right down and you open the bulb out there and up pushing you could actually push on to the the brainstem and you could widen this quite effectively now at this point using a pair of scissors if you're if you're careful now there you it's also important to go with your endoscope through that hole and have a look to make sure that the second membrane the membrane lilyquist is also open now at the end of this once you've made the third one close to me and you've you've come out I usually you have a large opening in the dura through a bow hole what we've been doing is putting in a small piece of gel foam and covering the entire thing with bone wax and then closing the wound in in layers now the questions that arise here if you do have troublesome bleeding I'm not talking about the basilar artery if it's basilar artery then you've got to probably pack up and go home but oozing if there is any oozing continue to irrigate be patient and if you are certain that it is stopped you can then come out but if you're fine that it is still bleeding keep an external ventricular drain drain do not hesitate to that it's not much of a problem if you find that the opposite on the preoperative MRI you have a situation where the opposite foramana manroh is not big like for example in a post infectious state or a post haemorrhagic state or a tumor that is blocked off both foramana manroh you could do a septas to me and then shunt the patient so when I find that when junior people go into theater with the aim of doing a ventricular to me they have to do the ventricular to me and come out that is not the case because you have the option of doing a shunt so if you find that it's not safe you can't see anatomy distorted get out of there okay