 So mid-sagittal brain anatomy, because when we are knowing what the normal anatomy is and then when we know what the variant anatomical structures are, then only we can confidently identify the various pathologies. So let's go through the basic anatomy and we have divided into short 15-15 minutes talk. So the first is sagittal midline of the brain. So this is one of the most important sectional planes in neuroimaging and I am sure all of us will agree to this. A good working knowledge of the normal uranatomy of the sagittal brain is essential for identifying subtle abnormalities that can manifest in various ways clinically. Because of this fact, there are various articles which you search on the net like this one, 25 diagnoses on midline image of the brain from fetus to child to adult. So even a single image can give you various diagnosis if you know the anatomy well. So this is how a midline sagittal T1 weighted image look like. All of us have always seen this kind of a structural image whenever we go to learn anatomy and this is the midline structure. We can see the corpus callosum well, we can see the midbrain, pons and the medulla. We can see the pituitary gland, the infundibular stalk. So overall any guesses how many structures can we actually identify on this midline sagittal section of the brain. So if you again go and look for the articles on the anatomy of mid sagittal brain, you will find that as much as 87 structures small and big can be identified on a midline sagittal brain image. And we will also see some clinical application of these variant anatomies. So as I told you lot of structures can be identified on the midline plane but let's see few important ones. So I have just tried and marked a few of them. So let's go through these. So this is corpus callosum, all of us already understand that and here we know that this is the posterior part of the corpus callosum which we call as the splenium of corpus callosum and the anterior part of corpus callosum which we call as the genu of corpus callosum. The part which is before the genu that is going little downwards accordingly is the rostrum of corpus callosum. This is the body of corpus callosum and the part with this little thinned out is the isthymus of corpus callosum. So we see a lot of pathological identities like corpus callosum, lipomas, urgenesis of corpus callosum or partial urgenesis of corpus callosum when we identify and try to identify the complete normal corpus callosum structures. Just a size the corpus callosum here what we are able to see is a gyrus. So this is known as the singulate gyrus. So this one is the singulate gyrus. Another thing which is important here is when you see posteriorly, so we are going to see the ventricles and various CSF pathways in details. But here what you are seeing is the quadrigeminal plate system. So this is sometimes confusing that we call it a quadrigeminal plate, quadrigeminal plate systems, tectum, tegmentum, so we are going to see that. So here you see this is the area of the pineal gland, this is the quadrigeminal plate and the system which is behind the quadrigeminal plate is the quadrigeminal plate system. This we all know is the fourth ventricle and here the structure which is marked just ventral to the midbrain is the mammillary body. So it can be seen continuing here. Again midline sag we have few zoomed out images also and there we will see the pituitary and the infundibular stalks in detail. But here you can identify cellar, the pituitary gland, posterior pituitary bright spot which should always be identified on your T1 weighted images and the optic plasma. This marked as number 18 over here is your plenum sphinoidal. So you have many a times meningiomas which are broad based towards the plenum sphinoidal. So this is that area and this is your sphinoid sinus. All of us know that this is the pons and this is how a normal structure of midbrain pons and medulla looks like. So lot of time when we have hypoplasias we can have disproportionate size of the pons midbrain and the rest of the brain stem. So we should always make a point to see whether the normal proportions of midbrain and pons are maintained. We are also going to see the importance of midbrain to pons area ratios in subsequent slides. Two another important points here are the oscis landmarks. So the number marked as 26 over here which you can see is the baseon here at the end of the clivus and posteriorly corresponding as marked 27 is the opistion. So these baseon and opistion they mark the boundaries of the furamen magnum. So whenever we have to comment upon inferior cerebellar, tonsillar, herniations or ectopias or for that matter over basilar invaginations we have to understand the importance of this boundary markings. So these are the landmark points which are the baseon and the opistion. So these were the structures which we revised. Going ahead this is another zoomed in image where you can clearly identify the pituitary gland in the cellar, the pituitary posterior bright spot on T1 which should be placed along the posterior aspect of the pituitary gland. So if you don't see it then also it's abnormal and it can be seen in cases of diabetes, insipidus, sometimes it can be a topically placed which is another important pathology. This is the optic chiasma over here and if you see the structure of the corpus callosum like the rostrum genu of corpus callosum it can be traced again ahead and this part the thin T1 hyper intense line which we can see is the lamina rostralis. This one continues again into the lamina terminalis which is continuing into the optic chiasma. Here which you can see a well defined avoid cut section of a structure. So this structure which has been marked as 46 is the anterior commissure, this one. So these are all the commissural fibres which you are seeing over here and the one which has been marked as the 47 number this one is the furnitial body that is continuing below vertically as the furnitial column. So this is all the commissural fibres which you can trace on midline. Another important point here so you see the 58 number marked is a CSF intensity area a linear band like CSF intensity track which is the aqueduct. So one which is posteriorly seen here is your cortegeminal plate. So this one a bump seen here is the superior colliculus the other second bump is the inferior colliculus and when you trace it above this is the pineal gland area. So when you know the normal thing you can easily identify a lot of abnormalities. So this is again a T2 weighted fiesta image midline sag and this makes you identify the CSF pathways very easily. So here you see the aqueduct and then you can identify if there are presence of any aqueductal region weps or not. Here this is the fourth ventricle the mammillary body. We are also going to see the importance of the distance between the inferior margin of the mammillary body and the superior margin of the pons. This one as mark 62 is the pre-pontine systems. These systems are important because when you are identifying subarachnoid hemorrhages or when you are identifying leptomeningal enhancement or cisternal enhancement in cases of meningitis you need to mention where all the enhancement or subarachnoid hemorrhages present. Here you can see it in the region of the pineal gland there is a cyst like structure which is present. So this is about the CSF spaces we are going to see in details in the next talk as well. So just if you even search for a midline sagittal anatomy image on MR you are going to find a lot of them and all of them will have many labelling on them because as we saw we can identify more than 80 structures in the midline. So let's see the important vascular markings which we can identify. So here you can see the confluence and that is the tocula herofilae the ones which is looking dark the flow void. Here we can see another linear flow void which is the straight sinus this one. This vascular structure which is seen as a hypo intense band is the vein of gallin. So when you see pediatric age group vein of gallin malformation this is where you are looking at. This is your internal cerebral vein which is important when you are identifying cases of ICV thrombosis. So few more images and little bit of revision. So the one which is marked here is the area of great cerebral vein of gallin. So just along this plenium of corpus callosum going ahead is the area of internal cerebral vein and then is the thalamus triad veins. So this is a reno post contrast image which is showing the same clearly. What is important is on your routine T2 weighted images whenever you see loss of low world along this plane you have to increase your rate of suspicion for thrombosis in these sagittal venous sinuses. At the same time we can identify these cisterns. So here the one which is marked as A is the cistern of lamina terminalis. So as we know that this rostrum is going to continue into lamina terminalis so this is the cistern of lamina terminalis. This is the optic chisma so this is the chismatic cistern. Here C so that is the cistern which is just ventral to the midbrain and that is called as the inter peduncular cistern. Here you have the area of the ambient cistern. As I already mentioned the one which is posterior to the quadrature manual plate here E is the quadrature manual cistern. The one which you see here is the cerebellum pontine cistern so that will be better seen on your axial images pre-pontine cistern and you have this one which is your cistern of magna. So all these spaces are important specifically in subaripnoid hemorrhages or meningeal abnormalities. Another image focusing on the CSF pathways so here you see the number 3 is marked area of the cerebral aqueduct. This image I have just taken to show you the tegmentum and the tectum. So sometime there is confusion in that so the one which is posterior is the tectum also called as the quadrature manual plate. The one which is the ventral part that is the midbrain margin that is the tegmentum in between the two is your aqueduct which is a narrow CSF pathway as such anatomically. So any pathology which is going to be present in this area will compress this aqueduct and create hydrocephalus in the upstream CSF channels. So this we already saw so number 1 here is the interventricular foramen of Monroe. So you see your colloid cyst somewhere here. And number 2 marked here is the posterior floor of the third ventricle. 3 we already know is the aqueduct and number 4 is the median aperture of magenta. So here we are seeing few more structures. So all of these are like revision to each other. So just you can take it as a quick brush up for your anatomical knowledge. So your tectum, tegmentum and this is the portion of your body of phoenix and this is the lamina terminalis. Few examples of important pathologies which we can identify. So one is your ectopic pituitary posterior pituitary bright spot is ectopically present and MRI is the only modality which can adequately identify this particular entity. So height even signal 3 to 8 millimeter tissue nodule at median eminence most commonly seen in the floor of the third ventricle. So lot of time this is related to pituitary dwarfism. Another thing this is very commonly seen variant cordigeminal plate lipoma or even hyper intense area which is seen along the posterior margins of the cordigeminal plate. Sometime on your swan images it will also show blooming due to chemical shift artifact and that can mimic that some calcification or some hemorrhage is present but actually it is just a fat containing lipoma. This image is a sagittal T2 which you can acquire in your patients when you are suspecting normal pressure hydrocephalus whenever there is disproportionate dilatation of your ventricles as compared to the atrophy and then you see a significant flow void in the area of cerebral aqueduct as we all know that wherever there is a flowing signal like in blood vessels on MRI we are going to receive a flow void a signal void area. So when there is a hyper dynamic CSF flow allow across the aqueduct you get this kind of flow void and when the flow void is reaching almost up to the floor of the fourth ventricle you can call it as a significant flow void that means there is a hyper dynamic flow across the aqueduct and that is towards a suggestion towards a shunt responsive normal pressure hydrocephalus which you can take forward with your CSF flow analysis study. So again you will plan your CSF flow studies perpendicular to this aqueduct. This is an example of a aqueduct region web. So this is a Fiesta 3D sequence thin images which have been obtained and you can see in the midline there is a hypo intense thin web which can be easily identified. So in cases of aqueduct and stenosis earlier it was used to be kind of idiopathic but now we know that most of the time we find some short webs or hypo intense areas. Next important thing in here as a measurement perspective is your midbrain to Pons area ratios which you can measure like this how it has been marked and the importance of this is in cases of your Parkinson plus syndrome. So all of us know that in progressive supranuclear palsy there is going to be midbrain atrophy. So therefore this area ratio will be reduced. So midbrain to Pons area ratio is important in these scenarios if it is less than 0.24 this is most of the time seen with progressive supranuclear palsy and you see flattening of the upper margin of the midbrain which normally should be convex and that is called as the hummingbird sign. So these are the three kind of generic classification convex upper margin, linear upper margin and as it atrophies more there will be concavity of the upper margin of the midbrain. Then coming next to cerebellar tonsillar ectopia. So what we have to see is this particular line that is called as the macrae line this is the easiest of all. So the one which is connecting the baseon is and the opistion. So when the cerebellar tonsils they herniate below this line of macrae that time you have to call it as cerebellar tonsillar herniation or ectopia. What is basilar invagination that is seen with the help of tip of odontoid. So that is normally about 5 millimeters below this line and basilar invagination is diagnosed when the tip is going above this particular landmark. So all of us have seen many cases of cerebellar tonsillar ectopias we know they are associated with chiari malformations. So this is the plane which will help us identify the inferior cerebellar tonsillar herniation. So this is how you can measure the amount of the cerebellar tonsillar herniation. This is a typical example of anal chiari malformation. Another place where you get these kind of sagging is the intracranial hypotension which could be spontaneous which could be secondary intracranial hypotension along with multiple features which you know about it. The ones which can be identified on your midline sag are a bulky convex margin pituitary gland then there will be reduction in the distance between the mammillary body and the pons. So that is the mammillopontine distance and also there will be sagging with inferior cerebellar tonsillar herniation. So this is the distance we were talking about so you measure it between the mammillary body and the upper margin of the pons. If it is below 5.5 that is suggestive of intracranial hypotension. Another thing which you can measure is the pontomizancephalic angle. You can see how it is measured on this image and normal value is around 65 plus minus 10. Value less than 10 is like you can understand it is like suggestive of sagging. So it is again another ancillary finding in cases of intracranial hypotension. So to conclude it was a short talk on the midline sagittal brain anatomy and just to emphasize the fact that for all the resident this is one of the most important sections of your brain MRI so you should always try and identify the important landmark points as already mentioned we can identify as many as 87 of them. So this was a quick revision thank you all for your patient listening.