Thank you, Casey, for such a kind introduction. And I have a few disclosures, but none of them are going to relate directly to the content I'm going to present to you today. And like Casey said, our purpose for this session is to really give you some practical tips on how to take excellent care of your patients as this multidisciplinary team that's taking care of patients who are critically ill, coming to you from all different kinds of settings, from your EDs, from other hospitals, from the floors. So how do you do this right as multidisciplinary team members? So the purpose of this particular talk is to give you the, for lots of you, it's going to be a refresher, but tips and tools on reading your own CT scans of the head, and a little bit about CT angiograms as well. So let's start with a case. Our patient is a 57-year-old male. He's an unrestrained motor vehicle collision. On arrival, the initial GCS is 9. His pupils are too sluggish. His face appears symmetric. His primary survey, multiple open fractures, posterior scalp laceration, and I'm going to show you his initial head CT. And we don't have another laser pointer, but I'm going to try to point things out to you. But take a look at this video. See if you think this is normal. Is this abnormal? What do you think? All right. So this happens in the middle of the night. The junior radiology resident puts in a preliminary read for you and says the CT head is normal. What do you think? Show of hands if you think the CT head is normal. And a show of hands if you think the CT head is abnormal. So everyone agrees, right? So what is this radiology resident doing? The only thing we didn't have is a cup of coffee. So from an imaging perspective, let's look at a few findings, right? So on CT, when we speak the language of radiology, for CTs, we're going to talk about density. On MRI, I for intensity. So just remember, on MRI, we talk about intensities. On CTs, we talk about density. So we're looking at these hyperdense signals in the subarycnoid space. We're seeing a hyperdense signal outside the skull. And then as we scroll through some of those cuts, some of those axial cuts, we're continuing to see some of that hyperdensity. We're seeing some hyperdensity also in the right frontal region, maybe a little bit in the left frontal region as well, then some in the left parietal region. So what are we seeing? So we're seeing some subarycnoid hemorrhage. We're seeing a scalp contusion and laceration. We're seeing some more contusions in the frontal lobes, and we're seeing more contusions in the parietal region as well. So all of you correctly identified this is abnormal. There's a lot going on. So the most important thing when you're looking at the CT, just like everything else you do in critical care, you've got to be systematic. If there is a prior, compare. Always make sure that you scan your EHR to see, is there a prior CT head that I need to compare this with to understand whether there is truly presence of edema, asymmetry, somebody has a known brain tumor in the past, or they've had a prior stroke. Just pull up your priors, just like you do for your EKGs, just like you do for your chest X-rays. And then be systematic. Whatever approach you adopt, just do it the same way every single time you see a CT head, whether you like to go outside in or inside out. My preference is to go inside out. So I tend to look at the brain parenchyma first, then I look at the ventricular system. I do quickly scroll through to make sure the head is straight in the gantry. And how are we going to know that a patient's head is straight in the gantry if both the eyeballs line up on that same axial cut? Then if you're seeing asymmetry between the right side and the left side, you can say, OK, the head is straight in the gantry. That asymmetry is real. If I'm seeing sulci, gyri obliterated on one side, that asymmetry is real. But if someone's head is tilted, that asymmetry may not be real. So that systematic approach is important. And the more you do it the same way, the better you're going to get at it. So why do we need CTs? For a lot of our critically ill patients, these are much faster exams. So for you to send a critically ill patient down who's perhaps in septic shock on multiple pressers, they're intubated, you've got a portable vent, you really need it. Their pupils are fixed and dilated. You've done your ICP management. For you to send that patient down for a CT scan to be able to identify a massive hemorrhage that's going to be management changing is going to be imperative. And you can't stick that patient in an MRI scanner having them lay flat for 45 minutes or longer. And there's much lesser monitoring in your MRI scanner. So CTs are critical when we're managing these patients who are hemodynamically unstable, who have a lot of things going on, attached to a lot of different machines. Review your images in different planes, not just the axial. Lots of hospitals will give you coronals, but will not give you sagittal. But if your hospital radiology department gives you sagittals, make sure you look at the sagittal, because then you can really see the cerebellar tonsils as well. Are they really, really at risk of impending tonsillar herniation through the foramen magnum or not? Don't forget your bony windows. So once you've looked at the parenchyma, you've looked at your ventricles, you've looked at the deep structures, you looked at the cortex, you've looked at the bone, then your CT imaging review is complete. And always compare priors. So most important learning points for CT, it's fast, but it still needs coordination. So it's multidisciplinary coordination. You may have a transport nurse. You may have a respiratory therapist going down. You may send your trainee down, your fellow or your resident, depending upon how sick your patient is. If stroke is on your differential list, any acute focal neurological deficit where there may be an underlying vascular etiology, stroke has to be on your differential list. And if stroke is on your differential list, you have to make sure that you also add vessel imaging. So before you send your patient down, they're sick, you don't want them going back and forth. OK, now I got the CT. They come back up to the room. I'm going to send them down for a CT angiogram. That's not how we're going to do it. We get our CT. We're going to get that CT angiogram head and neck. If we're thinking that there's going to be cerebral sinus venous thrombosis, we'll get that CT venogram. So take 30 seconds to think about what is on your differential list for a patient's acute focal neurological deficit or unexplained coma, and order the complete set of imaging, including your vessel imaging, at the same time. How many nephrologists in the room? All right, awesome. So neuron before nephron, right? I say this all the time, but often for our stroke paradigm, we're not waiting for the creatinine, right? So make sure that your radiology teams are in agreement. We're not going to wait for the creatinine, because the risk benefit, the benefit of getting this diagnostic imaging far outweighs the risk to the kidneys. And there's plenty of literature that tells us the anticipated trajectory of contrast associated nephropathy, if you believe in that entity like I do. But nevertheless, you're not going to wait for that creatinine. CTs are not great for the posterior fossa. But if you try that sagittal plane, you can get some idea about what's going on in the posterior fossa. You have the luxury of seeing the patient in front of you. The radiologist does not. So your eyes on that CT are going to be so much more valuable, and making sure that you review your own images and then compare your read with the radiologist's read. And if they miss something, let them know. And if they report something, you're going to go back and say, hey, this is not what I was expecting, but it makes sense. And then you'll also know what are your incident lomas, things that you found, but you don't necessarily need to act upon. We're going to do a quick refresh of normal anatomy, because I know this room loves neuroanatomy. No, I'm kidding. It's hard. Neuroanatomy is hard. And no matter how many times we review it, there are certain things that, as intensivists, we must know on CT scan. So I'm just going to show you some classic cuts. So this is an axial CT head, left side, right side. That Mickey Mouse-like structure is our midbrain. The little button-like nose is a cerebral aqueduct. We also end up seeing the circular villus. And depending upon how old your patient is, you may end up seeing some calcifications, and you may end up visualizing some of your blood vessels. So if somebody has, say, new onset right hemiparesis, you may end up seeing that hyperdense left MCA sign. So this is a good place to begin to look for your circular villus. As you scroll one slice up, again, you get a better picture of that midbrain. You can see your circular villus in that supracellar cistern. Cisterns are additional CSF fill spaces. The ventricles are the largest CSF fill spaces, but there are other spaces in the brain that also have CSF. It's important to know about some of these cisterns, because when we're suspecting impending herniation, we're going to see cisternal effacement. So remember this quadrigeminal cistern around that Mickey Mouse-like structure. Back here is our right occipital lobe and left occipital lobe. We're seeing our temporal lobes up here. More normal anatomy, the lateral ventricles. The lateral ventricles have three horns, the frontal horn, the temporal horn, the occipital horn. So depending upon which lobe that horn is sitting in, it's named based on which lobe that horn is sitting in. So very easy to remember. Three horns for the lateral ventricle, frontal horn, temporal horn, occipital horn. When we talk about gravite differentiation, are you really seeing that differentiation in the densities of your gray matter and white matter? When there's going to be evolving injury or cerebral edema, we say that there's loss of gravite differentiation. And that's one of the places where you're going to look for it. So that's why that symmetry is your patient's head straight in the gantry before you comment on whether there's loss of gravite differentiation. Another classic cut, looking at the level of the basal ganglia. This is the head of the caudate. So we talk about the basal ganglia. You've got the thalamus. And in between the thalamus, there's this hypodense structure, which is an inverted L-shaped structure. That's your internal capsule. So the internal capsule, your basal ganglia, and thalamus. That's another classic cut that you should know how to read. Now let's do some pathology. So first up, CT in traumatic brain injury. So up here, we're seeing this hyperdensity. It's holohemispheric. It's not respecting different sutures. It's just holohemispheric. There's a big midline shift. Can everybody appreciate sulci gyri here on the right side? You see sulci gyri? Not really, right? So there is cerebral edema there. But how about sulci gyri on the left side? We're not even seeing it there. So there's this midline shift. There's impending herniation. This patient is probably going to have a pupil that's either asymmetric, or their pupil is going to be fixed and dilated. You're thinking about intubating them, calling neurosurgery, giving them hyperosmotic sedation, et cetera, right? And again, acute subdural hematoma. We're also seeing some hyperdensity layering around the cerebellum, but where the folds of the dura are, called the fox of the cerebellum, or the tentorium, the tent of the cerebellum, these are not usually surgically evacuated. You just kind of wait for them to get resolved. But this, definitely, you've got to think about calling your neurosurgery friends as you're actively resuscitating this patient. Here's a nice acute epidural hematoma. We've all seen this on our boards, epidural hematomas versus subdural hematomas. What are the differences? And arterial bleeding versus venous bleeding. So rupture of those veins that are in the cerebral sinus venuses, that's going to give you your subdural hematoma. Here we see a contusion in the right parietal temporal region, and there's some hypodensity around the contusion, that's cerebral edema around the contusion. Another quick reminder, just a comparison between epidural and subdural. Epidural hematomas are going to be lens shaped. They're going to respect your sutures. As compared to your subdural hematomas, they're going to cross suture lines, they're going to be crescent shaped. So sulci gyri spoke to you about this effacement. And just for comparison, I did put up a normal CT head as well, and you can see this. You can see global cerebral edema, it's finger-like projections hugging the brain. And then when you look at this asymmetry, this patient probably has an evolving right MC territory stroke, and you can't see any sulci gyri in the right frontal parietal region as compared to your normal CT head. How about a chronic subdural hematoma? So depending upon the density of blood, as blood and blood products are going to get resolved, you're going to see changes in the density. Some of your patients with repeated falls, or who are on anticoagulation, or that ECMO patient who suddenly has developed left hemiparesis, and they're more somnolent. When you scan their head, you find this. So anticoagulation-related bleeds will have different layers in them. I'll show you some CTs. This is a patient who's fallen a few times, and they've got a little membrane in their subdural hematoma. They undergo a bedside procedure called a SEPs to evacuate the subdural hematoma. Unfortunately, a few days later, they get this reaccumulation. So now you know how to recognize epidural hematomas, subdural hematomas, contusions. You've seen midline shifts. You've seen effacement of sulci gyri, global cerebral edema. Cisterns, like I told you, they are CSFL spaces. They're much smaller than our ventricles. You don't need to know the names of all the cisterns. Just a few of them, particularly the supracellar cistern, where your circular villus will sit. Your quadrigeminal cistern, where a patient who has impending uncle herniation, you'll see cisternal effacement. So when you're using that language, cisternal effacement, it means that you're getting, and I'll show you a scan, that your cisterns are becoming obliterated. You're not being able to see, for example, this nice smiley face. You begin to see a frown developing in your cisterns, and that's suggestive of impending herniation. So what about hydrocephalus? So what happens in hydrocephalus, depending upon whether it's obstructive or non-obstructive, obstructive somewhere in the ventricular system, there is an obstruction. It could be at different levels, or it could be non-obstructive. But the anatomy of your ventricles is going to change. Typically, you're not supposed to see the temporal horns. They're very small. They're slit-like. But when they're not slit-like and they're so obvious, it should alert you that there may be some underlying hydrocephalus. The frontal horn anatomy on that scan that I showed you looked very different, right, as compared to a normal head CT. So that should also alert you. If your third ventricle appears rounded off, that should alert you that there may be underlying hydrocephalus. If there's a lot of atrophy on the scan, then it could be hydrocephalus ex vacuo. But if you're seeing blood in the ventricles at any level, it could be the lateral ventricle, could be the third, could be the fourth, you're seeing a component of obstructive hydrocephalus. I told you about the hyperdense MCA sign. This is not a contrasted CT angiogram. This is a non-contrast CT head, and we're seeing a dense MCA sign. Just a quick reminder of what your clinical syndromes may look like, depending upon where the clot is. When you're seeing these patients with emergent large vessel occlusion, if the patient has a clot in their MCA superior division, so just to orient you, this is your internal carotid artery, branches into the anterior cerebral artery, middle cerebral artery. In most patients, you see a bifurcation of that middle cerebral artery. Some patients can have a trifurcation of that middle cerebral artery. But depending upon where the clot is, your clinical syndrome is going to look different. And back here is our basilar artery. And we know that patients with basilar artery clots will also slip into a coma. It's very hard to distinguish between a hemorrhagic stroke and an ischemic stroke just on the basis of somebody's clinical symptoms. It's as good as flipping a coin. So if stroke is on your differential, which it better be for anybody who has vascular risk factors, which is practically everyone in our ICUs, particularly adult ICUs, we've got to think about, do we need vessel imaging, CT angiogram, head and neck? It's going to be helpful both in ischemic stroke and hemorrhagic stroke. In the interest of time, I won't go over the ASPECT score. But remember, on the non-contrast CT head, depending upon how many areas are affected, the best score is 10. It is the Alberta stroke early CT score. It can help identify which patients will benefit from thrombectomy. However, in 2023, there were several RCTs that showed us that even if there are lots of hypodensities and the ASPECTs is low, or also called as large core infarction, those patients will also benefit from thrombectomy. The risk of hemorrhagic transformation may be a little bit higher. So maybe it's good to know what ASPECTs is. But the relevance of that ASPECTs, because we're also going to send large core infarction patients for thrombectomy, you as intensivists don't necessarily need to expend more energy in trying to understand the ASPECTs score. But you should just know it is a CT-based score. Looking at pre- and post-intervention cerebral angiography for that patient with that hyperdense MCA sign that I showed you, there's a cutoff. We're really not seeing any vessels. Your post-intervention, and I've just labeled the blood vessels for you, you see good recanalization in the MCA territory. Moving forward to basilar stroke, here is a hyperdense basilar sign, similar to what we saw in that hyperdense MCA sign. Stroke, as it evolves over days to weeks to months, is going to begin to look different on your CTs. And later on, you're going to see encephalomalacia, or atrophy at the site where there was a stroke. And that space is going to get filled with CSF. Here's an example of a low-bar ICH patient. I'm showing you the CT here. There's a big midline shift. There's an EVD catheter-related hyperdensity hemicranial flap. And this is just their MRI from post-stroke day three. Remember, imaging for neuroemergencies is like your EKG for a STEMI. You've got to know how to review these images, compare your read with a radiologist's read, and ask yourself, before sending that patient down, do I need vessel imaging? Here's another example of an evolving cerebellar stroke. Think of that patient with that basilar clot I showed you. We're also seeing signs of hydrocephalus. Third ventricle is rounded off. Temporal horns are more obvious. Frontal horns are also rounded off. Here's a suboccipital crani that saved this patient's life. I'm going to wrap up with parenchymal hematoma. Different types, depending upon your patient's story and what they're coming in with, is there any underlying coagulopathy? Is there a history of underlying cancer? Do they have history of hypertension? Are they on antiplatelets, anticoagulants? Are they a liver patient? Are they on mechanical circulatory support? And you're using a heptandrip. It could be ECMO. It could be VADs. It doesn't matter what it is. You've just got to know your context to understand how to interpret the potential underlying etiology for blood on the scan. If there is a history of trauma, the obvious differential, yes, it could be trauma. But if your patient also has all these other things, including they're on a DOAC or they're on warfarin, and they had the hemorrhage and then fell, you may see both, right? So you've got to keep an open mind when you're thinking about what to expect on the scan so you can think of the underlying etiology. A lot of the initial management is going to look similar. So here's a hemorrhagic contusion, like some of the contusions we saw. Here's a patient with thrombocytopenia. We're seeing hypodensities, but also different ages of blood. That's classic for a patient who has an underlying coagulopathy. Loss of edema out of proportion to how much blood you're seeing, that should tell you that there might be an underlying tumor there. And patients with high blood pressure, I'll show you some classic scans. This will show up on the boards as well. Your thalamus, cerebellum, pons, basal ganglia, classic locations for hypotensive hemorrhages. And about 20% or so of these hemorrhages will be low bar as well, but 80% tend to be deep. ABC upon 2 is a classic way of calculating the volume of your intracerebral hemorrhage. This comes from a very old paper. When you think about these primary ICHs being like an ellipsoid, so ABC upon 2, A is the widest diameter, B is perpendicular to that widest diameter, C is the total number of slices. But remember that when this formula was derived, the CT slice thickness was 10 millimeters. Now most of our CT slice thicknesses tend to be 5 millimeters. So divide the number of slices by 2, and then plug it into the formula. Hematomas can expand early, so you've got to be aggressive, particularly in the first three hours. How do you identify who is at risk of hematoma expansion? There are lots of different signs. But just like everywhere else in the body where you look for contrast extravasation to identify whether somebody is bleeding actively, same thing here. The CT angiogram-based CT spot sign tells you the hematoma could expand. This is a classic star-shaped subarachnoid hemorrhage that you get in the supracellar cistern, because those very aneurysms are going to be at the level of the circular willis. So like we said, that's supracellar cistern. That's another reason why you should know that cistern. Here's another patient with subarachnoid hemorrhage, aneurysmal, just given the pattern of bleeding. You're seeing blood also in the sylvian fissures, and these are bilateral EVD tips. For improving your own ability to read more CTs, I've just put together some phone resources. They're free. But you can test yourself out. They have a lot of good videos. And I did borrow some of the materials from there. But you can continue your own learning, and now you should feel like experts in reading your own head CTs. Thank you so much. Thank you.

critical care

CT scans

traumatic brain injuries

interprofessional coordination

emergency management

neuroimagery learning