everybody welcome back i hope you're all doing well today we're going to be looking at the anatomy of the basal ganglia so let's start by having a look at this t1 weighted mri sequence and before we get into the anatomy let's just orientate ourselves in this image see where we are which axial slice we're at so you can see we're at the level of the lateral ventricles here coming into the third ventricle via the interventricular foramen we can see our internal capsule here the white matter tracks coming from the cerebrum down into the spinal cord and our external capsule here and that internal capsule is separating our chordate nucleus from our lentiform nucleus here our putamen and our globus pallidus and we can see our thalamia lying on either side of that third ventricle here we can see that this is the anterior portion of the scan with our frontal sinus and this will be posterior so let's start by looking at the head of the chordate or the chordate nucleus now it's more accurate to call these basal nuclei because you can see they're gray matter they're the same as the gray matter they're not white matter and they lie within the cns a ganglion text technically lies outside of the central nervous system and a gray matter bundle within the central nervous system should be called a nuclei so let's try and call them basal nuclei if we go inferiorly in this image we can see that we lose the lateral ventricles but we can still see the head of the chordate and the head of the chordate rises now superiorly and indents that lateral ventricle like this so they lie lateral to the lateral ventricles as we come more superiorly we can see now the chordate starts heading posteriorly this is what's now called the body of the chordate so we can see it running laterally to those lateral ventricles here's our septum pollution separating our lateral ventricles and here we can see the body of the chordate running posteriorly it's quite difficult to see the tail but the tail is a small piece of chordate that now follows those lateral ventricles all the way down as we come down here to down the temporal horns and it comes right to the end of the temporal horns so they start quite bulky anteriorly the caudate nuclei the head of the nuclei and they thin out as they come into the body and they get even thinner as they come to the tail down towards the temporal horns of our ventricles so let's go back to our starting image we can see the putamen or putamen putamen here separated from our caudate nucleus by the anterior limb of that internal capsule and together the chordate with the putamen is what's known as the neostriatum or the corpus stratum otherwise known as the dorsal striatum and they act as a functional unit here and if we go inferiorly again we can see that the putamen starts off pretty much adjacent to the head of the chordate and as we come up superiorly the entertainment stays out here it's bordered by the external capsule and the globus pallidus and it ending up there so it's just this wedge-shaped gray matter nuclei here now internally or medially to that putamen is our globus pallidus and together these are known uh often as a lentiform nucleus and that's just describing its shape got a convex surface on either side a lens shape they don't necessarily act as much as a functional unit like the chordate and the putamen does and that lensiform nucleus is just describing its shape and the globus pallidus is separated into the globus pallidus externa and the globus pallidus in turn and we'll see that better on our coronal views and again that is separated from the chordate by this anterior limb of the internal capsule and from the thalamus by the posterior limb of the internal capsule okay so then we're going to head our way down towards the brain stem so we've covered the chordate the putamen and the globus pallidus the next two nuclei are the subthalamic nuclei and the substantia it's those five areas that make up our basal nuclei in the brain so a good trick here is to get to the third ventricle and scroll down until you see this posterior portion of the midbrain come out that's how we know we're at the most superior portion of the midbrain and t1 is not actually a great slice to look at we're going to go to a t2 weighted scan let's look at our axial t2 here i'm going to come up to that same level of the third ventricle here you can see this is t2 weighted now our gray matter is lighter than our white matter and we've got bright csf as well you can see our chordate our putamen and our globus pallidus clove as well as a bit darker here as we scroll down we will see the start the superior aspect of the midbrain we scroll down one more there we go is our superior colliculi sitting there i'm going to scroll one more slice actually down and now we are into the midbrain we know we're at the level of the superior colliculi because our red nuclei which are lying anterior to this are only at the level of the superior colliculi if we were to go further down our red nuclei like we look here disappear and we've got our inferior colliculi this is a really important region of the brain because not only is it asked a lot in exams but also clinically we've got our we've got many subarachnoid cisterns the midbrain itself is quite a complex structure and so it's an important place to know our anatomy quite well here so posterior to the midbrain this is our quadrigeminal cistone that lies behind our superior and inferior colliculi then anteriorly these two large protrusions from our midbrain are our cerebral peduncles so the cistern in between is known as the interpeduncular cystone the interpeduncular cistern and the quadrigeminal system are connected by what's called the ambient system i i feel like a lot of people struggle with the ambient cistern and it's it's quite simple like ambient temperature the surrounding temperature it's the same here the ambient system is the system that's surrounding the midbrain there anteriorly we can see our mammillary bodies which are the inferior border there of the hypothalamus and uh anteriorly to those millery bodies we can see our optic chiasm here okay so let's get back to the basal nuclei the subthalamic nuclei are quite difficult uh to see on the scan and i'm going to show you some later here but we if we scroll upwards and see where our thalamia are sitting as then we go down the image just before the midbrain starts we have two nuclei sitting just below the thalamus a little bit anterior and they are what's known as our subthalamic nuclei the subthalamic nuclei lie slightly anterior to these red nuclei and slightly superior that's also another way to remember where they are not well seen on this image now we can see our red nuclei and anteriorly to that these dark patches here are our dopamine rich dopamine containing substantia niagara fibers they're paired nuclei one on either side and they separate our red nuclei from our cerebral peduncles now there's another uh waiting that we can do to see the substantiation diagram more clearly and that's what's known as a susceptibility weighted imaging or swi and that sequence is really sensitive to local magnetic changes so we can see blood vessels really well because about the oxyhemoglobin or hemoglobin in the blood and we can see our substantia really well from that dopamine that's within those axons again come to the third ventricle scroll down we can see our superior colliculi we can see the red nuclei really well and anteriorly to that we can see now the superior portion of our substantia as we scroll down further we're going to get into the bulk of the substantia we can see if we convince ourselves that there's a little split between this posterior limb of the substantia and there should be a slight gap there that's what's known as a swallow tail gap and you lose that in um diseases such as parkinson's it's not well seen here you can see again here we can convince ourselves that there's just a little swallow tail there and as we go down we should lose our red nuclei but still keep our substantia and these now we know are our inferior colliculi okay perfect so let's now go on to a ct scan just to see what it looks like it's quite different on a ct scan but obviously the locations are all the same so here we have a ct scan i'll get us back to our point where we are have our lateral ventricles and our third ventricle we can see now that our basal nuclei are lighter than the white matter coming through and again we can follow the head of the chordate the body and down to the tail now you can see that the ventricles are a bit bigger on this image we can see that we've got our temporal horns as well as quite big occipital horns our lateral ventricles give off this occipital horn as well as coming down to temporal horns we can see our lentiform nucleus here and it's just really important when you're looking at a ct scan of often a screening scan when someone presents with a focal neurological deficit if we lose this gray gray white matter differentiation that's an early sign of a potential infarct and this chordate head is actually supplied by the anterior circulation the a1 or a2 branch of the anterior cerebral artery so it's a common place that we could see lots of gray white matter differentiation perhaps before we see it at the level of the cortex and then going down into the brainstem again it's a bit more difficult now to see the substantia niagara it's not actually a great test to be looking at the midbrain here that much better on mri and then just lastly i want to show you a case where a patient has a disease where the globus pallidus and the um subthalamic nuclei as well as a bit of the substantia actually light up on t1 weighted image so we can see here our chordate our putamen and then our globus pallidus is bright on t1 coming down into the midbrain we can see our red nuclei here and we've got this bright uh substantial regions and if i go to our sagittal view this will hopefully give you a better idea of where the subthalamic nuclei are here we are at the midline you can see the nose we're cutting them the brain stem perfectly in half we can see the cerebral aqueduct coming down with our superior and inferior colliculi so you can see the level we were at earlier mammillary bodies quadrigeminal cystone interpeduncular system and our ambient cistern that tectum of the mid-range and i'll take mentum here and what we can see is if i go slightly laterally i can see our thalami here and this bright t1 in our in our globus pallidus coming down underneath there's our thalamus and here's our subthalamic nuclei sitting there often very difficult to see on scans but here in this disease we can see that it's bright on t1 coming down then into our substantia so i hope that's helped i hope you even gained some knowledge when you either in a clinical setting or you having an exam we've just orientated ourselves here we hopefully can pick out the basal ganglia we've got a better 3d understanding of where they lie within the brain so i hope you've enjoyed it and i'll see you all in the next anatomy video goodbye everybody