Thank you so much, it's a huge pleasure to be here talking about abnormal hyperdense and hyperdense findings in emerging HET-CT in pediatric patients. First we're gonna list just the hyperdense and hyperdense findings on HET-CT, and then I'm gonna try to spend some time just focusing on the most common cases that we see in the ED and its mimickers. So here's the list of hyperdense and hyperdense findings that you can see in HET-CT in pediatrics. And I'm gonna concentrate on hemorrhage and thrombosis for the hyperdense findings, and the hyperdense findings I'm gonna concentrate in extra-axial hygromas, PRESS, AJE, and mimickers. Let's go ahead and jump in and talk about hemorrhages. So first we're gonna talk about extra-axial hemorrhages. Our first case here is your classic epidural hematoma, so the biconvex lens that you see that does not cross the suture but can cross the midline, very commonly associated with a fracture, as you can see in this patient. The subdural hematoma is a concave or convex appearance of a hemorrhage in the extra-axial spaces, does not cross the midline but can cross the suture. And here's a superior hemorrhage. I think superior hemorrhage is somewhat of a new concept that we pediatric neuroradiologists look for, and especially in the neonatal period. So this is a type of hemorrhage that we see in the neonatal period, sometimes in early infancy, that because of its location is very peripheral along the brain parenchyma, it can have associated hemorrhage in the extra-axial spaces, as you can see in this patient from the literature, and also can see some edema in the adjacent parenchyma. But it's different from your subarachnoid hemorrhage, where you can see a better distribution of the blood products through the basal cisterns or the south side, as you can see in this patient, that also have a holoprosencephaly. So intraparenchymal hemorrhages. Intraparenchymal hemorrhages, I have here three cases, actually two cases, but three images of a post-traumatic hemorrhage. And when I look for cases of hemorrhage, I look for areas of hemorrhage, like as you can see here, right adjacent to the area of fracture. So a little punctate for side of hemorrhage in the parenchyma. And you can see also a patient, next patient has an area of contra-coup. You can see a hematoma in the occipital region, and then the area of hemorrhage is in the contra-coup region. This patient, as I was scrolling through the images, was very difficult to tell if this was actually partial volume from the anterior skull, or if it was hemorrhage. And you can see here in the coronal image that it clearly show an area of hemorrhage. So here's the point is that we need to look for our coronal and fascia reformats and our 3D reformats in all our patients, especially with history of trauma. Diffused external injury is another cause of intraparenchymal hemorrhage that you see in the trauma scenario. I would say that diffused external injury, the most common scenario, you have a very normal or very underwhelming head CT, but a patient is doing clinically really poorly. So that dissociation of the clinical finding and the imaging finding is very common for diffused external injury. This particular case I'm showing you here, you can see there's some effacement of cerebral cell site, and you see at least two little punctate for side of hemorrhages in the parenchyma. Obviously when we did the SWI, and I'm showing you here the two punctate for sides that we saw on the CT, but if you actually here look at the SWI MRI, you can see multiple other findings, multiple other punctate hemorrhage that you can see in the gray white matter location compatible with diffused external injury. I'd like to show also cavernous malformation as causes of intraparenchymal hemorrhage. I think you see that not infrequently. It can sometimes be difficult, especially if the patient comes with a history of trauma. Here the first example, you can see a very subtle area of increased attenuation within the frontal region, which is a blood produce in the patient with cavernous malformation. I think this is a very common finding that we see for cavernous malformation in CT, so be aware of that, especially if you have a history of trauma, not to be confused with acute parenchymal injury. You can also see cavernous malformation with a combination of hemorrhage and calcification, as you can see here in the second patient, or you can see in the third patient, a large area of hemorrhage, so this patient have cavernous malformation with acute bleeding of that frontal region. This patient here came first to us from an outside institution and the history of probably AVM, and we did look at it carefully. We were able to find other findings, other little areas of cavernous malformation, which is similar to the very first case that I showed, just a very faint area of increased attenuation, so we say this is probably acute hemorrhage in a cavernous malformation. MRI confirmed the multiple cavernous malformation with acute hemorrhage on the frontal region. This is a case of aspergillosis. We can also see a hemorrhage and infectious processes like this patient. Clinical history here is key, and I'm gonna be talking about clinical history being super important throughout this talk. Here in this case, patient with ALL, immunosuppressed with that one hemorrhagic lesion, but as you look through the images, you found other lesions as well, so multiple hemorrhagic lesions in a patient immunosuppressed. Think about fungus infection. The last patient here with the intraparenchymal hemorrhage, this is the most classic non-traumatic intraparenchymal hemorrhage that we see in the ED scenarios, a patient that comes with loss of consciousness, of altered mental status, and you see a large area of hemorrhage in the parenchyma. Always comes the question, is this an AVM, is it tumors, a cavernous malformation? By far, the most common cause for hemorrhage to look like that is AVM, which was confirmed in the DSA in this patient. I always like to talk about occult hemorrhage, especially when teaching the residents and fellows, because those areas that I'm gonna show here are areas that we can easily miss hemorrhage in a head CT, especially if you're rushing through a pile of a lot of cases. So the area that I go back and look for specific areas of hemorrhage that can be missed is the hyperparathyme, the tentorium, the vertex, and I'm gonna stop a little in the vertex a little bit. This is an area that we see very frequently, especially with child abuse, and if you don't look for your coronal, you're gonna miss those little tiny punctate foci of hemorrhage, so go back and look again at your sagittal and coronal. Interpeduncular scissor, if you don't look at it, you're gonna miss. Onto your brainstem, same thing, and it's very common to see hemorrhages there, especially if you have an MVA accident, so go back to the area. Go back, actually look at all your head CTs from now on in the area, because you have to start getting used to how a hemorrhage looks like that, and it's abnormal, and what is artifact in the location. Very common to have heart beating artifact there. So you can see here I'm pointing the same hemorrhage in the axial and the sagittal view, because again, I use my reconstructions in all my trauma cases, and I specifically look at that location in the sagittal reconstruction. Other two areas that you have to look for, especially in the trauma scenarios, the middle fossa and the tear fossa, and why is that? Because when you have a trauma, your brain parenchyma and your skull travel and stop in different speeds, and that's an area that you can have friction, and it's common to have hemorrhage as well. So a little bit of mimickers. Actually, this is truly not a mimicker, because you do have bleed there, right? So for the birth-related subdural hemorrhages. But what I put here as a mimicker, because it's a finding that we have to not confuse for an important pathological finding. So let's say you have a neonate that come to do a head CT for some reason, seizure, et cetera, and you see a little bit of hemorrhage along the posterior aspect of the brain, and also tentorial and posterior fossa. This small amount of blood product is normal in the neonatal period, and it's birth-related, and we should not confuse that for a subdural hemorrhage that can be pathological. And especially when you're talking about potential child abuse, you have to be very careful not to over-call this. So in my reports, I say birth-related blood products, and I kind of try to minimize and not say the word subdural, because that can unleash a whole child abuse that maybe is not necessarily in this case. Other mimickers for extra-axial hemorrhage, or bacterial meningitis, can have very dense appearance on CT, as you can see here in this patient, also post-consciously demonstrated in Paima. I think most of the time, we don't fall for that, just because the clinical history is so characteristic. So again, clinical history, super important. And if you don't get a good clinical history, pick up the phone and call and talk to the ED. Other mimicker that actually I fall for that when I was a trainee is the pseudo-subarachnoid hemorrhage. So when you have a lot of cerebral edema, like such in this case, you see the first image, and there's no cerebral cell site at the level of the vertex. You should always see some cell site there. And you can see in the last image that you see the cerebellar tonsils are herniated. And in the two images in the middle, there's no cerebral cell site appearance at all, so diffuse effacement compatible in diffuse cerebral edema. And if you look at this image here, you have increased attenuation within the basal cisterns, and this is a pseudo-subarachnoid hemorrhage that you can see in patients with significant cerebral edema. Other mimickers are metastatic neuroblastoma. It's a classic one. You can also have leukemia and LCH that can present with lesions that are actually soft tissue masses adjacent to the cranium. And those can be, if the patient comes with a history of trauma, sometimes this patient don't have a history of neuroblastoma. You're gonna be the very first one making this diagnosis. Patients come with a history of trauma, and you see this finding. In this particular case, I'm showing here an image post-conscious, but sometimes you can see this in pre-conscious imaging, and they are hyperdense as well in the pre-conscious. So here, if the clinical history is not helpful, you can use other findings. So when I'm looking for a patient with trauma, which was the case in this patient here, I look for where is the soft tissue hematoma? What is underneath the soft tissue hematoma? Do you have a fracture or not? And that's the case when I stop in this case here and actually can see that the bone was moth-eaten. Unfortunately, I don't have the image here for you guys, but it's very important when you look for a soft tissue lesion like this to look at the bone underneath. If you have an abnormal bone that doesn't look like a fracture or post-traumatic, think about metastatic neuroblastoma. Okay, I'm gonna briefly talk about thrombosis. So if you see a hyperdensity in the head CT in the area of a sinus, and if it is focal, more likely to be thrombosis. In this case here, you can actually see the thrombosis confirmed in the post-conscious imaging. But also, you can see increased attenuation throughout the dural sinuses in this patient here. And here, the clinical history is very important. So this patient did not have a contrast in hands. That was my first idea. Well, this is post-contrast. No, this was not post-contrast. So this is actually all dense sinus. And it was throughout, actually, the dural venous sinuses in the entire head CT. This patient was a patient with ALL that was treated with asperginase, which is known to have hypercoagulation. So clinical history, again, very important. We'll be able to put all the pieces together. This is venous thrombosis. When I have a question, I also use the attenuation. I put the Hounsford units. If it is above 70, then I feel more comfortable that this is truly, indeed, venous thrombosis. One mimicker to be aware is the physiologic neonatal polycythemia. So you can have increased density throughout the venous sinuses. As you see here, this is a neonate, and we were able to, with the clinical history, knowing this was a neonate, to know that this was neonatal polycythemia. You can always look on your medical record and confirm that that's the case. Let's move on and talk about the hypodense abnormalities now. So extra-axial hygromas is the first thing I like to talk about it. And I think extra-axial hygromas versus benign enlarged extra-axial space of infancy, it's something that is very, very difficult to see on CT. So that's why I like to spend some time here. When I was a pediatric radiology fellow, I remember here, especially rotating an ultrasound, if you see vessels crossing through enlarged extra-axial spaces, those are subarachnoid. Therefore, this is benign enlarged of extra-axial space of infancy. I don't know if you guys hear that, but I was very happy with that and continue my fellowship and working 99.9% of the time. And then until it didn't. So then I was very confused when I see a vessel and I was for sure I knew there was a collection there, there was no normal. So I went and look and study, as we always do, we are trainees, and then here we look at it. And we see that most of the cortical veins, you can see in this drawing here, are actually located underneath the arachnoid. However, you have the bridging veins, the cortical meningeal veins or bridging veins, actually have to cross the arachnoid, have to cross the dura to dump into the superior sagittal sinus, which is a dural sinus, an envelope by dura. So if you can imagine if you have a collection between the dura that is uplifted there and the arachnoid, you're gonna have those bridging veins crossing through. So don't be fooled. So in this patient here, you see vessels crossing through. Those are the bridging veins. You do have, indeed, bilateral subdural collections. They are hypodense and similar to CSF. And if you look at it, most of the vessels are, indeed, located in the subarachnoid space, the cortical veins, and they are pushed inward. So this is a little bit more difficult case that I tried to apply all of my knowledge, and I keep looking at it, and I say, okay, I see some cortical veins. They appear displaced. I scroll up and down. They're always displaced. They never touch the inner table. So that's a good sign for me that maybe there's a collection there. Look on the other side, same thing. Maybe there's a collection there, but very hard. And I think sometimes, if you can't tell, it's nothing wrong with us saying it's either one or the other. In this particular case, I go up also and look that there is a thrombose-bridging vein in the vertex. So here, I'm thinking, there's something there. Let's do an MRI. So in the MRI, we were able to confirm that there was, indeed, bilateral subdural collections, and then you can see here also the thrombose-bridging veins superiorly. So, in summary, how do I do to differentiate benign enlargement of extraocular space of infancy and low attenuation collection CT that can be very difficult? I use subtle difference in attenuation. I think this is mostly what we do, right? We try to see if it is a little increase in attenuation compared to CSF, then you know you have some bleeding there or proteinaceous contents. I try to use mass effect in the south side as well. This is a great one. If you do see that, it's very likely to be a pathological collection. But think about if you have a patient that have prominent subarachnoid spaces, and the collection is very small, there's not enough mass effect. So it's not always present. Displaced cortical vein sign, I use that one. I can see it. Nowadays, our technique is becoming lower and lower, and it's becoming really hard to see those cortical veins being displaced inward or touching the inner table. But try to look for that. Sometimes, we can still see it. So I try to use all those different findings, and if I don't know, I just tell them I'm not sure. Here's two different cases. And you can see the first case here. You have flattening of the south side. So that's a great sign. So I'm already thinking that this is probably abnormal. I can see that the displaced cortical veins, and again, I scroll up and down to make sure they're always in, and they never touch the inner table. And we'll confirm it later on in MRI. This was low attenuation subdural collections. Here, the second case, we can see that the south side is not flattened. And you can see the cortical veins are touching the inner table. So the displaced cortical vein sign is great when you see it, but to me, I actually use the one they are not displaced even more. So I know that this is benign lodge of extra axis space of infancy because the cortical veins are actually touching the inner table. So let's move on and talk about hypodense abnormalities, PRESS. So PRESS, very briefly, you guys all know posterior reversal encephalopathy. It's not always posterior, for most of the time, it's located in the posterior aspect of parietal and occipital regions. You see vasogenic edema in the subcortical white matter. Usually, the clinical history have increased blood hypertension in patients that have either immunosuppressive pediatric patients or have kidney disease. They present with seizures, headaches, and visual loss. And we were able to confirm the findings here on MRI. But I think the CT was pretty characteristic. One thing I'd like to point out with PRESS is not always, again, they are posterior. So you can actually see throughout the brain. And you can also see in the posterior fossa. So don't be dissuaded that it is PRESS if you don't see it in the classic location. Use the clinical history, again, super important. The other thing with PRESS is sometimes you can have hemorrhage. So if you see hemorrhage as well, don't think it's not PRESS because of hemorrhage. Okay, the last thing we're gonna talk about is AJE stroke and mimickers. So this is the first case that we have of the patient that was found down in the pool. You can see loss of gray-white matter differentiation throughout. And I think one thing that we tend to underlook is the deep gray-white. In this case here, you do not delineate your basal ganglia really well. So this is compatible with diffuse hypoxic chemical insult in a patient that was found in a pool. And I say in a patient that was found in a pool because, again, clinical history is super important. There are other findings that can give you, other clinical histories that can give you a similar appearance. This is just to compare with a normal patient. You can see the gray-white matter differentiation both peripherally and in the basal ganglia are really well-defined. And this will be a late finding of hypoxic chemical insult where your hypodensity is seen throughout. And you almost see like another reversal pattern of what the gray matter looks, decrease in attenuation. The white matter is increasing attenuation. So very significant, profound hypoxic chemical insult. The stroke, we do see in kids. It's fortunately less often than in adults. But it's important for us to know the subtle findings that you can see in the very early hours of a stroke. So in this particular patient, between 12 and 24 hours after the symptoms, you can see a hyperdense MCA sign. You can see a symmetric cell sign. And you can also see the insular ribbon sign where you lost a gray-white matter differentiation. So all those same findings you can see in adults. You can see in pediatrics. Be aware, you can see stroke in pediatrics. Other findings that you can see on the head CT when it's a little bit later on in the process and then it's a little bit easier for us to see on CT is a decreased gray-white matter differentiation and hyperdensity. If you use the 40-40 window, that becomes more obvious. So always use that window. You can also see strokes after trauma. So you can actually have a subfalse herniation. Subfalse herniation is gonna compress your ACA in the contralateral side. And you can have later on a stroke there. So be aware of that finding as well. Let's talk very briefly about some mimickers of hypoxic chemical insult and stroke. So this is a patient that came with a history of being sick for a few days, come to the ED with loss of consciousness. We can do a CT here. And we see the bilateral symmetric decreased attenuation of the thalamus. You do an MRI and you can see the same finding. The thalami is also a little bit swelled up. And you can see there was also some punctate areas of hemorrhage. This was confirmed to be acute necrotizing encephalopathy, an entity that we as pediatric neuroradiologists are more and more aware. And we should put in our differential diagnosis for bilateral symmetric thalamic involvement. Another patient that have also bilateral symmetric hypotenuation in the basal ganglia, but also very significant hypotenuation in the cerebellum. And this was drug abuse. So we are seeing that in pediatrics. We're seeing that obviously in the teenager period with opioid use, it's very frequent. Another one, I think you all look at this and say, this is not a stroke, this is herpes encephalitis, and that's what it was. But I think it's important for us to know that when you look at an area of hypodensity, especially if it is located at the level of the temporal pole, to think of other, and especially herpes encephalitis, such important diagnosis to make early on. So there's obviously not everything that is decreased in attenuation in the basal ganglia, HIE. So you have to know the clinical history. And I'm not gonna stop talking about that. You have to know your clinical history. You have to call your clinician. You have to look at your medical record. You can have metabolic processes. You can have intoxication, osmotic myelinosis, barencephalitis, again, acute necrotized encephalopathy, and hypoglycemia. And one thing that I forgot to put here, also you can have venous thrombosis presented with bilateral symmetric involvement of the thalamus. So some take-home points for the hypertensive findings on CT in pediatric patients. Clinical history, again, I'm going to be talking about that. Look at the status of coronary reconstructions. They are super important, especially in the post-traumatic scenario. Look for other lesions. If you had other lesions that looked like cavernous malformation, if you had other lesions that looked infectious, that's going to be very important in a differential diagnosis. And if you're specifically looking for enthalposis, remember to use your house and units. I think I feel very helpful for me. And also remember, if it is a neonatal period, this could be a neonatal polycythemia. For the hypertensive findings, again, clinical history. And hygroma versus benign and large backtracks in spaces of infancy. Use your attenuation, effacement of the cerebral cell site, and displaced or not displaced cortical vein sign. For PRESS, remember, clinical history is key. And also, you can have PRESS that is not only located posteriorly, it can be everywhere. It can be in the posterior fossa, and it can also have hemorrhage. For hypoxia, ischemic insults, stroke, and mimickers, remember the early findings of stroke. Use your 40-40 window. Look at the deep gray-white. Don't neglect that. And also know your differential diagnosis of bilateral basal ganglia hypodensities. Thank you so much. I'm David Murski from the Children's Hospital of Colorado, and I'm gonna be speaking to you today on pediatric demyelinating diseases. Only disclosure is that tomorrow is National Giving Day, so I encourage you all to donate to a good cause. Acquired demyelinating syndromes represent a wide range of CNS conditions, causing damage to the myelin sheath, resulting in inflammation and axonal loss. Unfortunately, the incidence in children is not insignificant, occurring in nearly one per 100,000 per year. Of those, the majority are gonna be, at least 20%, are gonna be multiple sclerosis, which is similar to what we see in the adult patient population, being that multiple sclerosis is the most common demyelinating syndrome. Historically, these were classified by monophasic or relapsing course. Over the last two decades, we've seen, due to the recognition of circulating antibodies towards CNS antigens, specifically Aquaporin-4 and MOG, it's led to a shift in diagnosis. But because of the paucity of biomarkers and overlap in presentations, which makes distinction of these diseases difficult at presentation, there's still a heavy reliance on MR imaging to satisfy not only criteria for diagnosis, but also therapy. So in a child that comes in with their first acute demyelinating attack, they can be classified as a clinically isolated syndrome, either monofocal or polyfocal, with or without ADEM-type features, a small percentage of which are gonna be diagnosed with neuromyelitis optica spectrum. But up to 50% of these patients may progress to relapsing demyelinating syndrome, including multiple sclerosis, MOG, NMO, and then antibody-negative RDS. For the purpose of this talk, we're gonna focus on these three entities. So let's begin with pediatric onset multiple sclerosis. This is the most common immune-mediated demyelinating disorder of the CNS, both in adults and in pediatrics. Typical onset is young adulthood. It's a rare disease in the pediatric population, with only 5% of patients reporting onset under 18. And just like in the adult population, there's an increased prevalence within girls versus boys. As for the pathophysiology, it's related to a dysregulated immune system leading to CNS injury, and there's good evidence to support that there's both genetic susceptibility as well as environmental triggers at play. Specific to genetic susceptibility, if you look at the lifetime risk of a first-degree relative of multiple sclerosis patients, it's as high as 5%. And in addition, there's been certain immunologic human leukocyte antigen genes that have been shown to be associated with an increased risk for the development of MS, specifically DR-15. As for environmental triggers, both vitamin D insufficiency and Epstein-Barr virus have been shown to be associated. We're all familiar with the diagnostic criteria for multiple sclerosis, the McDonald's criteria, but the one thing that I wanna point out is that in 2017, there was an update that placed more emphasis on imaging in terms of satisfying both dissemination in space and time. So for space, in a patient with a clinically isolated syndrome or a typical MS attack, if they have an MRI with one or more T2 hyperintense lesion that's characteristic of multiple sclerosis in at least two typical regions of the CNS, be it periventricular, cortical or juxtacortical, infratentorial, or spinal cord, this would qualify as dissemination in space. For dissemination in time, same thing. In a patient with CIS or a typical MS attack, on imaging, MRI of the brain or spine, if the patient has presence of an enhancing and non-enhancing lesion or a new lesion on follow-up MRI, this will satisfy dissemination in time. So let's take a look at some of these lesions and see how they look. Periventricular lesions are the most common finding that we see in multiple sclerosis as high as 86%. And what we're looking for are ovoid, well-demarcated lesions that are perpendicular to the close oceptal margin or periventricular region, also called Dawson's fingers. And what we're seeing on imaging relates to perivenous inflammation seen on pathology. Juxtacortical lesions are common. These are lesions abiding the cortex. And it can be a challenge sometimes distinguishing between intracortical, leucocortical, a mixed white matter, gray matter picture. But as far as the guidelines are concerned, the recommendation is to include all four in the same group for dissemination in space. Posterior fossil lesions in pediatric onset multiple sclerosis are quite common, occurring 25% more frequent than adult onset MS. And brain stem lesions are present in up to 61%. Not uncommon to see middle cerebellar peduncle lesions in this diagnosis. Tumor-affective lesions in pediatric onset multiple sclerosis are rare, but they do occur. And they're large, usually single, have mass effect and edema, commonly supertentorial. The important thing just to note is that they show similar MRI features and clinical evolution to the standard lesions. As far as contrast enhancement, pediatric onset multiple sclerosis is much more inflammatory than adult. And up to 70% will have enhancing lesions on their baseline MRI. Enhancement may be punctate, nodular, linear, or an incomplete ring, as you can see in this case, that it looks like a horseshoe type of appearance, very characteristic of multiple sclerosis and can help you in discriminating from demyelinating plaque versus a tumor. In addition, you can sometimes see leptomeningeal enhancement on delayed post-contrast flare MRI, which is a marker for cortical demyelination. But probably the most important brain finding to mention when it comes to multiple sclerosis is that of black holes. These are non-enhancing T1 hypo-intense lesions that indicate chronicity and are the result of either severe demyelination or axonal loss. So in a child with an acute CNS demyelination, presence of one or more black hole at baseline is the single strongest predictor of multiple sclerosis. Spinal cord involvement is not uncommon and oftentimes may be clinically silent. What we're looking for are short T2 hyper-intense lesions, classically less than two vertebral body segments in length. When we look at the axial cross-sectional area of the lesion, we can see that it's more asymmetric, posterolateral often involvement, and cervical segment is most commonly affected. Optic neuritis is common in multiple sclerosis, typically unilateral, short segment involvement, less contrast enhancement than say MOG, and may or may not have restricted diffusion. What about the prognosis for multiple sclerosis? Well, greater than 98% of pediatric onset MS will have relapsing remitting course. And compared with adults, they're gonna have more relapses in the first four years and a larger number and volume of new lesions on MRI. But despite having this highly active inflammatory disease, recovery from each of these episodes is often remarkable and rarely do you see permanent disability in childhood. But the truth is, since these patients start at a much younger age, accumulating disease, they reach similar levels of impairment 10 years earlier than their adult counterparts. Let's move on to myelin oligodendrocyte glycoprotein antibody-associated disease, also known as MOG. This is also an inflammatory disorder of the central nervous system characterized by immune-mediated demyelination that targets the eyes, the spine, and the brain. It's a fairly young diagnosis, only discovered in 2007, and as such, the insolence and prevalence are largely unknown. In the published literature, children account for up to half of reported cases with a median age of onset 20 to 30 years. It's associated with various clinical phenotypes, and as such, it was long misdiagnosed. But recently, it's become a distinct entity on account of specific characteristics such as young age of onset, optic neuritis, and generally, a good outcome. In contrast to multiple sclerosis, MOG tends to be monophasic over a relapsing course. Characteristic features are gonna be optic neuritis, ADEM presentation, or transverse myelitis. Presentation will vary amongst age, so younger children will tend to have an ADEM, more common presentation, whereas older children can have optic neuritis and or transverse myelitis. The attacks will develop over several days and may plateau with variable recovery over weeks to months. The important thing to note is that these may be preceded by an infection or a vaccination. As for the pathophysiology of MOG, MOG is a transmembrane protein located on the surface of the oligodendrocytes and myelin sheets. While the function is not totally understood, it's thought that it may play a role in cell, maybe a cell adhesion molecule, regulate microtubule stability, modulate myelin immune interactions. And so what you see in the MOG-associated disorders is that you have an antibody targeting these proteins, causing damage to the oligodendrocytes as well as to the myelin sheath, ultimately resulting in perivenous and confluent demyelination. Diagnostic criteria is quite simple. Presence of antibodies in either optic neuritis, transverse myelitis, ADEM, or one of the other classic syndromes associated with MOG. Optic neuritis is the most common manifestation in MOG-associated disorders and more commonly bilateral as compared to multiple sclerosis. In addition, long segment involvement is also very common. The one distinguishing thing to point out is that it tends to prefer to involve the anterior segments of the optic nerves rather than the posterior segments. So there's oftentimes sparing of the chiasm and retrochiasmatic structures. One other specific finding that's seen in MOG-associated disorders as it pertains to optic neuritis is that you can have enhancement of the perioptic nerve sheath as well as surrounding orbital fat, highly specific for MOG as opposed to multiple sclerosis or NMO. Spinal involvement's common, occurring in up to one-third of patients. And just like in MS, they may have mild symptoms despite extensive spinal cord lesions. Now in contrast to MS where we saw short lesions, less than two segments, typically these are longitudinally extensive transverse myelitis of greater than three vertebral body segments. When we look at the cross-section of the cord at the site of a lesion, the T2 is typically confined to the central gray matter giving you that H sign or butterfly sign. And also another specific finding for MOG is that there's a common involvement of the conus medullaris. Brain involvement is common. What we're looking for are large, ill-defined lesions of the white matter and gray matter. Deep gray structure can be involved. And when these lesions get large enough, they may converge into a leukodystrophy-like pattern. Enhancement's gonna be less well-defined compared with multiple sclerosis as you can see in this case with these patchy, fluffy areas of enhancement. And posterior fossil lesions are quite common. Similar to multiple sclerosis including brain stem as well as cerebellar peduncles. But the one distinction between MOG and multiple sclerosis is that the lesions tend to be larger, more ill-defined whereas in multiple sclerosis, they're more smaller and well-defined lesions. These can show substantial resolution during follow-up imaging. One newly recognized feature of MOG-associated disorders is that of cerebral cortical encephalitis which goes by the acronym FLAMES. Clinically, these patients present with seizures, aphasia, stroke-like episodes, headaches and fever and the majority of which are gonna be unilateral and accompanied radiologically by cortical swelling as well as leptomeningeal enhancement as you can see in this case. As for prognosis, these children do better than NMO and MS so long-term disability rates are lower. It's not associated with a primary or secondary progressive course and mortality is low in this diagnosis. Lastly, we'll talk about neuromyelitis and optica spectrum disorders. Also known as Devix disease, this is an inflammatory set of disorders of the CNS that's due to severe immune-mediated demyelination and axonal damage, predominantly targeting the optic nerves and the spinal cord. This is a rare diagnosis, oops, sorry. This is a rare diagnosis and amongst all comers, pediatric onset only represents 3% to 5% of NMO and similar to multiple sclerosis, there is a high prevalence among females as compared to males. As the pathophysiology, you have IgG autoantibodies against the aquaporin-4 water protein channels. These proteins are abundant in the astrocytic processes at the blood-brain barrier and they help facilitate water movement across cell membranes in response to osmotic gradients. So in the context of NMO spectrum disorders, you have antibodies that are targeting these proteins, causing damage to the astrocytes. Ultimately, this leads up to demyelination and inflammation resulting in astrocyte death, axonal loss, perivascular lymphocytic infiltration and vascular proliferation. So whereas MOG can be thought of as an oligodendrocytopathy, we think of NMO spectrum disorders as an astrocytopathy. The aquaporin-4 channels are highly expressed in and around the periventricular region as well as the diencephalic areas, also in the optic nerves and the spinal cord and this is going to make sense when we look at the areas of involvement on imaging. One specific area to mention are the circumventricular organs. These are highly vascular structures located around the third and fourth ventricles and characterized by a lack of blood-brain barrier. They play a specialized role in balancing CNS and peripheral blood flow and they have a very high expression rate of aquaporin-4 channels. We're gonna pay close attention to area post-treatment which we'll touch upon shortly. Diagnostic criteria, if you have the antibodies, then you only need to have one of the following, say optic neuritis, transverse myelitis, area post-treatment syndrome or one of the other classic syndromes. If you don't have the antibodies or the unknown antibody status, then you need two or more core clinical characteristics and typical MRI features. Optic neuritis is the most common finding in these patients and in 75% of children, it's their first symptom. Just like in MOG, it's often bilateral and just like in MOG, it's long segment involvement but the difference here is that NMO will go back and oftentimes can involve the chiasm and retrochiasmatic structures whereas MOG tends to spare those regions. This is an example of bilateral involvement and then here you have an example of unilateral involvement extending back to the optic chiasm. Spinal involvement is also common, occurring as high as 1 3rd as initial presentation and similar to MOG, we're thinking longitudinally extensive transverse myelitis, so greater than three vertebral body segments. They can show patchy enhancement and similar to MOG, there is a central gray matter predominance but what we can see here is that these lesions are a little bit more ill-defined and tend to bleed out into the white matter of the spinal cord and so they tend to have greater than half cross-sectional involvement of the spinal cord. These patients suffer severely with clinical deficits from these lesions. So detection of a longitudinally extensive transverse myelitis with corresponding clinical correlate is the most specific neuroimaging characteristic of NMO spectrum disorders. Brain involvement is gonna be more common in children occurring in up to 1 3rd of patients and so they're gonna be in areas that are highly expressing aquaporin-4, so we mentioned the periventricular regions, diencephalic structures such as the hypothalamus, thalamic involvement, you can even have the surface of the brain stem such as the midbrain here being slightly coated. When these lesions get large enough and they extend out into the white matter, they can have a cloud-like pattern of enhancement as you can see in this case here. Now we mentioned areopostrema before when we were talking about the specific areas of high expression of aquaporin-4 and areopostrema syndrome is one of the core clinical presentations of NMO spectrum disorder. Areopostrema are paired structures located on the medial poster-inferior surface, the medulla oblongata, plays a role in vomiting, thirst, hunger and blood pressure control, so no surprise when you have a demyelinating plaque there, these patients will present with hiccups, nausea or uncontrolled vomiting. Here's an example of a sagittal flare showing a fairly well demarcated lesion in the region of the area of areopostrema and sometimes these lesions can actually get mass-like in appearance and can be somewhat difficult to differentiate between a tumor. Prognosis is poor for these patients, specifically patients that have relapsing disease and relapsing disease is quite common in pediatrics. They suffer stepwise deterioration due to visual, motor, sensory and bladder deficits from recurrent attacks and thus initiation of long-term relapse-preventing treatments after the first episode is mandatory. So in conclusion, acquired demyelinating syndromes represent a wide range of CNS conditions causing damage to the myelin sheath. Recognition of circulating antibodies towards CNS antigens has led to a shift in the diagnosis and because there is a paucity of biomarkers and overlap in presentations, it makes distinction of these diseases difficult and thus a heavy reliance on MRI to help you with your diagnosis and therapy optimization. So for take-home points, brain imaging for multiple sclerosis, think small ovoid lesions, periventricular, Dawson's finger, posterior fossa. MOG, think large, ill-defined lesions, gray and white matter, deep gray structures as well as posterior fossa. NMO, periventricular, diencephalic, areopostrema. Optic nerve involvement for multiple sclerosis is gonna be short, discrete lesions, typically unilateral. You're gonna have long segment lesions and bilateral involvement for both MOG and NMO. However, MOG tends to spare the chiasm and retrochiasmatic structures where NMO will often extend back. And then lastly, spinal imaging where you have short segment lesions in multiple sclerosis, typically off-lateral, posterolateral in the cord. MOG and NMO tend to involve the central gray matter with NMO bleeding out into that white matter surrounding it.

pediatric neuroradiology

head CT scans

hemorrhages

Posterior Reversible Encephalopathy Syndrome

demyelinating diseases

MRI

diagnosis