 So, you see the C shape of the lateral ventricle wrapped around the thalamus and in the central section from the foreman of mandra to the frontal horn to the tip of the ventricle anterior tip of the ventricle is the frontal horn. So, foreman mandra is the margin which separates the frontal horn from the body. The body starts from the frontal horn and ends at the point where see the both the mammillary bodies in the body are joined together by a hippocampal commissure. When they go anteriorly they diverge to form the columns of fornics which form the foreman of mandra. Similarly, when they come posteriorly they diverge to form the crura of the fornics which enters the temporal horn and joins the hippocampus. So, the point where the body of the fornics bifurcates to form the crura is the end of the body. So, the body end starts from the foreman of mandra and ends at the level of the bifurcation of the crura. So, from there to here is the atrium and the trigon of the lateral ventricle. The occipital horn can be variable in dimension it can be a very small projection to occupying most of the occipital lobe. The temporal horn again goes down into the temporal lobe. So, if you see they are not in one straight line the temporal horn diverges laterally again why is that? Why does the temporal horn diverge laterally? Because of the presence of the brainstorm the brainstorm is directly under the body of the ventricle the thalamai because the body wraps around the thalamai the brainstorm is just directly under the thalamus both thalamai. So, this widened area in between in the central incisoral space. So, the tentorium space is divided into anterior tentorium incisoral space, mid incisoral space and posterior incisoral space. The mid incisoral space is the part which contains the brainstorm. So, the temporal lobes wind around the brainstorm and hence create this peculiar shape of the ventricle. Now, if you look at the lateral ventricle from mesially this red fibers fibers of the corpus callosum. So, you see the floor of the frontal horn formed by the rostrum of the corpus callosum. So, this portion is called as the rostrum. So, it forms the floor of the frontal horn the anterior wall of the frontal horn is formed by the genus of the corpus callosum and the part of the body. So, the body of the corpus callosum again forms the roof of the body of the lateral ventricle and then the roof of the trigon and the temporal horn is formed by the tapetum. The tapetum is the fibers which extend laterally and go down covering the atrium and the temporal horn. The spleenium forms two bundles called as forceps major they are thick bundles. Hence you see that in addition to what process said the forceps major is very thick. So, because of that the trigon are widely separated than the frontal horns. The frontal horn the genu forms the forceps minor which are thin connections. So, you see these are the thick fibers of the forceps major which comes from the spleenium and these are the relatively thinner fibers which come from the genu and you have the tapetum which covers the temporal horn laterally and it separates the optic radiation from the wall of the ventricle. So, what is there between the optic radiation and the ventricle is the tapetal fibers. Similarly, as the hippocampus and the fornex and the column of fornex form a C shaped structure the codyte nucleus and the amygdala the tail of the codyte nucleus and the amygdala both the structures are wrapped around the thalamus. So, the hippocampus formation is wrapped around the thalamus medially and the amygdala and the tail of the cadyt nucleus and the codyte nucleus is wrapped around the thalamus laterally. So, you have the hippocampus medially, hippocampus, crura, body of the phonics, columns of phonics and mammillary body, they are wrapped around the thalamine medially and this is lateral. So, the lateral wall of the ventricle, we talked about the anterior wall, the floor. The lateral wall of the frontal horn is formed by the bulge of the caudate nucleus, you saw that in the specimen. So, the lateral wall is formed by the bulge of the caudate nucleus, continuing down as the tail and here the caudate nucleus ends in the amygdala which forms the roof of the temporal horn. So, in the roof of the temporal horn, you have the amygdala and also it projects anteriorly to form part of the anterior wall of the temporal horn. So, the amygdala is continuous with the hippocampus at the tip of the temporal horn. Here you have the amygdala nucleus which continues merges with the hippocampus anteriorly. So, we talked about all this, the forceps major, forceps minor, tappetum, location of the phonics and the hippocampal formation, location of the caudate nucleus and the amygdala. Now, what is the coroidal fissure? Coroidal fissure is a very important structure in neurosurgery where you can reach certain structures which are present medial to the coroidal fissure which otherwise would be difficult to reach with standard neurosurgical operations. You can open the coroidal fissure and reach the structures which are located in the midline location. Of course, there are alternatives. You have the inter hemispheric approaches, but reaching around the brainstem is much more difficult when you do not use the trans-coroidal approach. So, where is the coroidal fissure? The coroidal fissure is again a C-shaped structure, so it wraps around the ventricle that means it has to be related to the hippocampal formation or the caudate amygdala formation, which one is it? The hippocampus wraps around the thalamai, so it has a natural cleft with the thalamus and that is filled with tinnia from where the coroid plexus is attached. So, that is defined as the coroid fissure. So, it starts from the foreman of Manro and goes up till the inferior coroidal point which is at the head of the hippocampus. So, again it is a C-shaped structure starting from the foreman of Manro here extending down and inferiorly till the head of the hippocampus. The coroidal fissure allows entry of anti-coroidal artery, lateral posterior coroidal artery which arises from the posterior sabral artery and the medial posterior coroidal arteries do not enter the ventricle through the coroidal fissure. They enter through the quadrilgeminal system into the velum intopostum of the third ventricle, so they enter directly into the roof of the ventricle from here. So, when the PCI circles the brainstem, the lateral posterior coroidal arteries enter the coroidal fissure near the crura of the phonics. The anti-coroidal artery enters at the inferior coroidal point. The medial posterior coroidal arteries enter through the quadrilgeminal system. So, again you can appreciate the shape of the ventricle, the thalamus, the mammillary bodies, columns of the phonics. This is an anterior view again which shows the body of the corpus callosum forming the roof of the body of the lateral ventricle and the tepital fibers forming the roof and the lateral wall of the temporal horn. You already saw the internal capsule and its formation, this is the chordate nucleus thalamus basal ganglia. What is the surgical importance here? When you retract in a transcolosal approach when you retract the ventricle, wall of the ventricle laterally, if you put it at the level of the pharoma of mandro, you retract the genu of the internal capsule because it comes up to the ventricular surface. So, this can result in hemiparosis or hemiplegia. So, one has to be very careful when you retract the lateral wall of the ventricle at the level of pharoma of mandro. You will be little more safer here, little more safer here, but this is a point which you should be aware of when doing a transcolosal surgery. So, this is the inter hemispheric transcolosal. You see the corpus callosum. How do you differentiate the corpus callosum from the cingulate gyrus? One is pericolosal artery. Then what else? It's white in color when compared to the cingulate gyrus which is gray in color. So, you have to be very careful because the cingulate gyrus sometimes can be closely approximated and bilateral cingulate gyrus damage when you are doing a transcolosal approach, what does it give rise to? One is possibly mutism. Second one, it can cause severe emotional disturbances because you destroy part of the limbic system when you do lesioning of both cingulate gyrus. So, this is the opening into the ventricle showing the pharoma of mandro. This is the coroid plexus. Now the coroid plexus is attached by modified pyrometer to both the fornix called as tinnia furnaces and it is attached to the thalamai by again a tinnia called as tinnia thalamai. So, when you want to enlarge the coroid fissure, suppose you have a colloid cyst which does not present itself at the pharoma of mandro. It presents itself behind the pharoma of mandro. Then what do you do? How do you enlarge the coroidal fissure? It is said that unilateral sectioning of fornix does not cause severe memory disturbances but still there is a better option than cutting the fornix. What is that option? It can be subcoroidal or supracoroidal. Which one would you prefer? Subcoroidal has the chance of damaging the thalamastriate vein and the internal cerebral vein. Why is that? Velum intopostum is a double layer, the internal cerebral vein course in between the two layers. Sometimes it can have a cistern which enters from the cordigerminal cistern called as cistern of velum intopostum. There the dissection for an intopornitial approach is very easy. But when there is no cistern, when you do a subcoroidal dissection, you can damage one of the veins. It is better to do it from above and also you can enter the thalamus when you are trying to do that. So, a dissection above the coroidal fissure, above the coroid plexus is better, supracoroidal approach. So, you see the veins, how do you identify you have entered the right or left lateral ventricle? So, you see the coroid plexus which enters into the opposite direction, passes into the opposite direction, you know that you have entered the right or left lateral ventricle based on the direction the coroid plexus takes. Similarly, you look at the thalamastriate vein, the anterior septal vein, thalamastriate vein and the supracoroidal vein. So, the direction these veins take to enter the pharomenophmandral will help you in determining which side of the ventricle you have entered. So, we were talking about the coroidal fissure. Coroidal fissure is a potential cleft between the hippocampal formation and the thalamus. It is covered by the coroid plexus. It can be open to access lesions in a transventricular approach to lesions surrounding the brain stem. And it is separated from a white matter stem from the ventricle. Internal to the insula you have all the layers of the basal ganglia, the external capsule, the clostrum, the extreme capsule and then you have the insula. It is important to recognize this anatomy of extreme capsule because when you are doing an insulctomy for seizures for example, this extreme capsule and clostrum help you in avoiding damage to the basal ganglia. So, you see the shape of the coroidal fissure is again C-shaped, surrounds the thalamus, has coroid plexus outlining it from the inferior coroidal point to the pharomenophmandral. The lateral wall, the medial wall of the trigon and the occipital horn has two prominences. One is called as calcaravis, this is the superior prominence. The inferior prominence is called as the bulb of the corpus callosum. So, the bulb of the corpus callosum is formed by the forceps major, the indentation of the forceps major on the medial wall of the occipital horn and trigon. The calcaravis is formed by the deep indentation of the calcarine sulcus. So, the calcarine sulcus intends deep into the trigon to produce the calcaravis. Similarly, lateral to the hippocampus, you have one deep prominence. You have a prominence in the temporal horn which extends up to the trigon. What is that called? It is called as collateral eminence in the temporal horn and it is called as collateral trigon in the trigon. It is formed by the deep indentation of the collateral sulcus which separates the parahippocampal gyrus from the occipital temporal gyrus. So, these are all the important landmarks when you want to do a sub-temporal approach to the amygdala and hippocampus. You follow the collateral sulcus into the ventricle and enter the temporal horn sub-temporally. So, we talked about the opening of the coroid fissure. You see the fornix is elevated to enter the vellum interpostum. The internal sabral vein is seen. These are the two internal sabral veins. So, you are going supra-coroidal sub-phornitial to enter into the vellum interpostum. The two internal sabral veins, the masa intermedia of the third ventricle, the aqueduct. What is the shape of the normal aqueduct? It is triangular in shape. The base is towards the pineal and the apex is towards the anterior third ventricle. What is the normal shape of the foramen of mandro? It is a crescent, always a normal foramen of mandro is always a crescent. You get a rounder shape only in hydrocephalus. So, this is the anti-coroid fissure dissection, sub-phornitial supra-coroidal. This is the coroid plexus lift attached. This was a tumor arising in the thalamus. So, to reach it, we do what is called as inter-phornitial approach. In inter-phornitial approach, you have to cut the corpus callosum from the foramen of mandro up to the spleenium and then split the fornices to reach into the third ventricle. We already talked about the boundaries of the ventricle. Now, coming to the third ventricular floor, from anterior to posterior, you have the lamina terminalis. Behind the lamina terminalis is the anterior commissure. The anterior commissure is not exactly in the floor of the third ventricle, it is in the anterior wall. So, the anterior wall is formed by the lamina terminalis which extends from the upper surface, upper mid-surface of the chiasm to the rostrum of the corpus callosum. So, because it is attached to the upper surface of the chiasm, there is a recess which is called as optic recess, supra-optic recess. So, you see the anterior commissure. This is the chiasmatic recess. It is the posterior border of the chiasm. From here, the optic tracts go laterally around the borders of the third ventricle. So, initially, they form the lateral wall of the third ventricle and then you have the infundibular recess which is the recess which extends into the pituitary stalk and it is surrounded by an eminence which is called as tubar scenario or median eminence. And behind that is an area which is relatively devoid of neural tissue. So that is the site where we do a third ventricle ostomy. In front of the mammillary bodies and behind the tubar scenario, you have a relatively thin area devoid of neural tissue which can be perforated to do a third ventricle ostomy. Behind the mammillary bodies, you have the upper surface of the brainstem which forms midbrain which forms the floor of the third ventricle and then you have the aqueduct. So, you see the columns of phonics which go behind the anti-comissure and you have the laminar terminalis below which forms the anti-wall of the third ventricle, chiasmatic recess, chiasm, infundibular recess, mammillary bodies. So, the chorite plexus is attached to the upper surface. It forms the roof of the third ventricle. The vellum interpostum, the bottom layer forms the roof of the third ventricle. It is attached to the thalamus on thin line which is called as stria medullaris thalamai. The stria medullaris thalamai extends from the pharomendophan row to the habanula. So, I will show that habanula in the next one. This is the masa intermedia and this is the sulcus which separates the thalamus from the hypothalamus. So, you have the hypothalamus below this sulcus which is this area and above that is the thalamus. So, the approaches to the ventricle, you have an occipital approach to the trigone. You have an inter hemispheric approach which is called as Poppen's approach which approaches the pineal region which is supratentorial approach. The same approach to the pineal region from below is called as supracerabular approach of cross. So, these are the two approaches to the pineal gland. The posterior transcautical approach through the superior parietal lobule again can reach the ventricle. So, you have to go through the superior parietal lobule. On the left side it is very critical because you can injure language areas if you go down below the superior parietal lobule. Then you have the anterior transcautical and anterior inter hemispheric approach. Of the two, the anterior transcautical approach has a slight tendency to produce seizures in the postoperative period when compared to a transcolosal approach whereas a transcolosal approach has its disadvantages of producing hemispheric disconnection. So, disconnection syndrome but in the normal clinical situation you do not have much of disconnection when you do a very limited collosal sectioning. And then sub temporal approach for the temporal horn, posterior fronter temporal approach you can after splitting the sillion fissure you can reach the temporal horn area and the inter pedicular area. So, you see the foreman of manrood this right side because the coroid plexus is entering the foreman manrood to the left. You see the thalamus right wing on the right side. You see the coroid plexus going back around the thalamus anteriorly is the caudate nucleus which forms this is the caudate nucleus which forms the lateral wall of the ventricle. This is the floor of the frontal horn formed by the rostrum of the corpus callosum. So, this is the thalamus behind the thalamus tritwain is the groove which separates the caudate and the thalamus. And you see the turning of the corpus this coroid plexus into the temporal horn posteriorly. Above that is the septum pellucitum. The septum pellucitum is broader anteriorly very narrow posteriorly. So, through the foreman of manrood you see the optic infundibular recess which is always red in color. And this is the space in front of the mammillary bodies do not use a sharp instrument in performing this fenestration because any branch of the basilar artery or perforator if it is cut by a sharp instrument it produces hemorrhage which can be troublesome. So, always use bipolar coagulation to make a fenestration and then use a fagartica theta to dilate. You have a dilator forceps also for doing an ETB, but you have to be little careful in that because it is a very firm instrument and using a balloon is much more gentle in this area. So, always inflate and deflate the balloon gently, do a trial inflation outside in the third ventricle and then usually 1 to less than 1 ml is required. What is the most important step here is it the perforation of the floor or what is the most important step? So, the second membrane that is the lilyquist membrane that is the most important step that has to be opened for a third ventricle ostomy to work lilyquist membrane extends from the dorsum cell layer to the mammillary bodies. So, it forms a veil across the intrepid and killer fossa. So, you see the basilar artery when you open the lilyquist membrane and you see the branches of the basilar artery. So, this was a thalamic mass which is being biopsied. The important step of doing an intraventricular biopsies is you push the biopsied to reach a few millimeters below the surface and then take a biopsied. Why is that? The tissue pressure helps in producing hemostasis. The other way is to continue irrigation till the bleeding stops. You have to be patient. If you produce bleeding by doing a biopsie on a tumor, the best way to obtain hemostasis is continuously irrigate till the bleeding stops. So, any troublesome bleeding which happens eventually will stop if you do enough irrigation. See, the with continuous irrigation the bleeding is coming down. So, the bleeding has stopped. So, this is a pineal mass again endoscopic third ventricle ostomy and biopsie of the pineal mass was done. Entering the Faraman of Mandro and this is after the third ventricle ostomy. The positioning of a burhole, when you want to reach a pineal region and do a third ventricle ostomy, what is the ideal position for a third ventricle ostomy burhole? So, usually the coronal suture is the landmark which we use for a third ventricle ostomy. Put the burhole at the coronal suture or 1 or 2 centimeters in front of it to have a direct view into the third ventricle and see the floor. If you want to see the pineal region, where is the location of the burhole you have to put? So, it usually means 4 to 5 centimeters in front of the coronal suture. So, either you may require a two burhole or you need a compromise around 3 centimeters in front of the coronal suture to do both the third ventricle ostomy and the biopsie of the pineal gland. So, this is the tumor which is seen bulging from the posterior third ventricle towards the mid and anterior third ventricle you see the mass here. The same technique is used, where you punch the forceps into the depth of the tumor at least for a few millimeters and take a biopsie from there and then irrigate irrigate irrigate till the bleeding stops. This is third ventricle ostomy being done for adult aqueductal stenosis who had shunt done a few years before presentation presented with shunt malfunction. When you enter the ventricle you can see the shunt tube is blocked by it being buried in the substance of the brain and also plugged by the coroid plexus. So, you see the coroid plexus is there posteriorly, here is the coroid plexus underneath and anteriorly it is buried into the substance of the brain. So, the problem is when you pull out a shunt tube like this it causes massive intraventricular hemorrhage. So, you have to be very careful in pulling out a tube which is not functioning and which has been in place for many years. So, now through a perforation in the septum palusidum I have entered the opposite ventricle I could not make out the pharoma of manro on this side because of the positioning of the shunt tube and the additions then entered through the left for a manro into the third ventricle this patient presented with shunt malfunction. So, he had this hemorrhages in the upper mid-drain these are the mammillary bodies and the site is not very transparent. So, it becomes difficult when you have a lesion like this which is not very transparent you have to be careful the opening has to be made gently with a bipolar coagulation and gradual widening of the opening with Fogarty and you have to be very careful not to use any sharp instruments here and not to pull on these structures using the forceps. So, you see the second membrane there as soon as the opening through the floor of the third ventricle is made even that was very tough to open with coagulation with repeated coagulation I had to use the balloon repeatedly to widen it finally manage to widen it sometimes you can get tissues which are very tough in chronic hydrocephalus. So, you see the opening which is gradually widened it did not happen in the first or second instance of balloon dilatation it required repeated attempts to get a and then the second membrane was also present which was quite below the basilar artery arising this is the Dorsum cellar so, arising and attaching itself to the basilar artery. So, just to ensure that the ETB works I had to perforate that membrane of arachnoid also and postoperatively CSF flow studies will show the CSF flowing across the third ventricle again many of you will be faced with this situation of childhood aqueductal stenosis with the hydrocephalus if the child is less than one year old the chances of ETB not working is high especially if the child is less than six months of age if you do an ETB the chances of success is less than 20 percent or 10 percent so, that is a problem in but this is a slightly older child this is about four or five years old child which shows this hydrocephalus see this child had a very thin membrane which was floating like this and it was difficult to open but once it was opened the whole pre-pontine system is laid open this is the third now this is the sixth now the basilar artery bifurcation perforators arising from this is the third now of the right side third now of the left side sixth now this is the clivus dorsum cellar but with the scope I was using the lota scope so it was difficult to position it here to open that this is the membrane huge diaphanous membrane which was covering the entire floor of the third ventricle this is the post I come sure I think whereas in another child with aqueductal stenosis the space was very narrow the approach is standard pre-coronal burhole three to four centimeters away from the midline in front of the coronal suture and you see but here the problem is you see the basilar artery touching the floor of the third ventricle and this is the dorsum cellar optic recess so the space between the dorsum cellar and the basilar artery which is coming up to the floor of the third ventricle is very small so that makes it tricky again so in the previous case you saw the space was very wide open in this case the space is very narrow but to avoid complications especially in damaging the basilar artery the technique is standard bipolar coagulation use Fogati to enlarge the opening again it required multiple attempts because this strands of arachnoid below the floor of the third ventricle was very thick and opening that with the balloon was more and more difficult required multiple attempts to open it cautiously and when you open the balloon you can also tear a perforator if it is very close to the basilar artery by opening a balloon on very near the basilar artery you can tear a perforator from the basilar artery to without using a sharp instrument so just to complete the story this child went home and I did it from the right side but the child developed a subdural later on which became infected and this child came from a different city required a craniotomy to drain this subdural and then came for follow-up where the subdural's fortunately resolved and the CSF flow studies showing that the third ventricle ostomy is working this child had a large head so the child is doing relatively well at this stage the third ventricle ostomy seems to be functioning thank you