Good morning, and congratulations for sticking it out for the last session of the Congress, saving the best for the last, so let's get some windows into the brain. So I'm going to talk to you about neuromonitoring, specifically the CT scanner's role. And some of this is just going to be a quick refresher, and perhaps will also remind you of those times where you were trying to find your radiologist, and you couldn't, and you really wanted to get that answer. So we'll talk about some key findings on CT. I'm an Associate Professor of Neurology and Neurosurgery at Mount Sinai. So let's start with a case. Our patient is a 57-year-old male, unrestrained, motor vehicular, gets in this motor vehicular accident, and his initial Glasgow coma scale is 9, opens his eyes to pain, he's moaning, he's localizing to pain, pupils are 2, sluggishly reactive, face appears more or less symmetric, primary survey negative for fractures, and this is his initial HCT. So we'll fly by this, see if you can identify any abnormalities. And we'll do it one more time. All right, so how many of you were able to identify any abnormalities there? With a show of hands? Awesome, half of you. Okay, great. And now we're going to go ahead and test whether you got that right or not. So let's call your radiologist, make sure that you can confirm what you read. Was that right or not? But they're not answering their phone. Somebody puts in a preliminary read that radiology resident is saying this is normal. How many of you think the CT head was normal? Nobody, right? There were abnormalities. So this junior radiology resident is obviously wrong, and they used some template. So on that CT head video, there were some abnormalities, and we'll just walk through each of these. So what are we seeing up here? And feel free to shout out any answers before we click through. We'll try to make this interactive, but we didn't want to put in too many polls, otherwise it would go on for much longer. But you're seeing some subaryknoid hemorrhage. Anybody for what we're seeing up here? Maybe some contusions. Here's a scalp contusion laceration, and some more contusions, and some more contusions, right? So that was not normal. So from a self-learning perspective, what I might suggest is some format resources. These are easily available. They are free. Some of them are peer-reviewed. Some of them are not peer-reviewed. But I'll just share that I like to incorporate a lot of these when I'm teaching neuroimaging, because we have learners who are coming with a different background, a different knowledge level. But you also want to spark that interest, so people can use this at the bedside, particularly when they're encountering, if you're working in a mixed medical-surgical ICU, you may not always have patients who you're getting neuroimaging on. So here's a good review, great for anatomy, learning neuroradiology. I'm going to show you some slides from there. That's great for anatomy, too. Radiopaedia, I think that's a good source for cases. And then if you really wanted to learn about vascular imaging, neurovascular imaging, I think neuroangio.org is a pretty good source. So how do you even begin to read a CT head? Well, for this audience, you just want to be systematic, just like you do for a chest X-ray, for EKG, for body CTs. Just be systematic. Compare prior images if they're available. Come up with your own approach. Do you like the outside-in approach or inside-out? I tend to read my CT heads inside-out. I will look at the parenchyma. Then I look at the ventricles. Then I look at the bony windows. I'm going to look at, you know, is there anything abnormal even outside within the soft tissues, et cetera. So just coming up with your own approach. Do it the same way every single time, and you're not going to miss anything. Also, compare. Compare to prior images. So another key thing about CT heads, I would say that axial, coronal, sagittal, not a lot of centers are going to have sagittal CT heads. We happen to be at a center that has sagittal CT head, but axial and coronal. So make it a habit at least to review your images in different planes. Don't forget the bony window. We tend to forget that, not just for patients who come in with this history of traumatic brain injury, but just make it a habit. If you look at the parenchymal window, then look at your bony window. So key learning points for CT before we go into some imaging. CT is fast. Minimal downtime in the scanner. Yes, there's exposure to radiation. If you're thinking stroke, I'll just make a plug for time is brain. Get that CTA head and neck at the same time. Get your vessel imaging and your parenchymal imaging at the same time so you don't have to move your patient back and forth from the scanner back to the ICU room. Oops, we forgot to get vessel imaging, or maybe now we need to get vessel imaging. So take that pause and determine what is the full breadth of imaging you need so your patient doesn't have to move back and forth and you're minimizing time and upholding time is brain. How many nephrologists or nephrology critical care folks in the room? Okay, so I'm not offending anybody when I say neuron before nephron, but make sure that at our institution we bypassed getting creatinine before giving somebody CT angiogram because we want to uphold time is brain. Posterior fossa, so CT head is wonderful for a lot of great things but not super for the posterior fossa, but if you are at a center that does the sagittal plane, it's worthwhile taking a look at that. Always review your own images, but do check if your radiology friends agree with what you saw. And vice versa, you have the luxury of having the patient in front of you. Our radiology friends don't. You may pick up things that they didn't, so have them attend their read as well. So let's review normal anatomy and a few things to keep in mind. So this is a classic cut at the level of the midbrain. This Mickey Mouse-like structure, so if you can imagine this as the ears and the little nose, so that's our midbrain. Now there are CSF spaces in addition to the ventricles. You don't need to know the names of every single CSF space, but I'll point out a couple of important things. These are called the cisterns, and these cisterns are right around the midbrain. You've got this quadrigeminal cistern and the ambient cistern, so keep that in mind. Occipital lobe, don't worry about the interpeduncular cistern right now, but what I would suggest for the quadrigeminal and the ambient cistern, this is an important area when we're talking about effacement, cisternal effacement when there's mass effect, impending herniation. That's a good area to evaluate. Before you interpret any asymmetry on your CT head, make sure that the patient's head is straight in the gantry. One quick rule for that, go down to the eyeballs, see where the eyeballs are. Are they aligned or not? Because if the head is tilted, you may falsely interpret an asymmetry when there is no asymmetry. So that's one important cistern to keep in mind for cisternal effacement. The other cistern, this interpeduncular as well as this supracellar cistern, important to keep in mind when you're looking for subarachnoid hemorrhage, aneurysmal subarachnoid hemorrhage, because as you well remember, very aneurysms, circular willis, that's where the circular willis is sitting. So that's another important cistern to keep in mind. And you begin to see some of these blood vessels. This is not a contrasted CT, but despite that, because of calcium deposition in blood vessels, or if there is a hyperacute clot, you may end up seeing those blood vessels around the same area. A little more about the normal anatomy, then taking a look at, we spoke about cisterns, CSF-filled spaces, then what about our ventricles? So looking at the ventricles for any abnormalities, any effacement, any enlargement. We're talking about too little or too much CSF, that's another important area to look at. And this gray-white junction, what is the gray-white junction doing? Is the white matter appearing more hypodense? On CT, we always talk about density. On MRI, we talk about intensity. So on CT, is this white matter appearing more hypodense than it needs to? Are you able to see that differentiation between gray matter and white matter or not? Or is there effacement? More about the normal anatomy, we spoke about the cistern, we looked at some blood vessels. Here's a very classic axial cut of the CT head, basal ganglia and thalamus. Here, you see this hypodense structure. This is the inverted L, your internal capsule. You have the anterior limb, the genu, the posterior limb, the thalamus, basal ganglia. You don't have to remember the names of all the basal ganglia, etc., as long as you know the thalamus, basal ganglia, internal capsule. That would be good enough. So now let's look at more abnormalities on our CTs after doing that review of normal anatomy. So when you see this hyperdense structure, hyperdense with maybe some hypodensity as well, this is acute, mostly acute blood. It's not respecting any sutural boundaries. It's sort of hollow hemispheric. That should give you a clue. This is a subdural hematoma. It's acute because of the density of that blood. Here's the same CT head. As we're scrolling down, you see some more acute subdural. Here, is this an acute subdural? Does this look like an acute subdural to you? No, this is an acute epidural hematoma. So this is not an acute subdural hematoma. This is an acute subdural hematoma. Here you're beginning to see some contusions. So what are the key differences? This is something that will show up on your critical care boards, difference between subdural hematoma, epidural hematoma. So length shape, doesn't cross suture lines. Epidural hematoma crosses suture lines, crescent-shaped. Sulcide gyri, so typically you're going to see, so on the extreme right-hand side of the screen, we're seeing sulcide gyri filled with CSF. Here when you compare, this patient's, I'm just showing you one slice, but the eyeballs are aligned. So any asymmetry that we see, like I reminded you previously, this is going to be abnormal. So when you compare the left to the right, you're not seeing as many sulcide gyri. So what is this? Similarly here, we don't see any CSF-filled sulcide gyri spaces, right? It's all looking like finger-like projections. So what are we looking at? So here we're looking at global cerebral edema. Global cerebral edema almost appears as if fingers are hugging the brain, so you don't really see any CSF in between the sulcide. So that's global cerebral edema. And here, this is called effacement of the sulcide gyri. Effacement, and we know that it is only in one hemisphere, not in both hemispheres, because we have the luxury of comparing the two sides. What about chronic subdural hematoma? I showed you acute subdural hematoma, chronic, looking at the density. So subacute to chronic subdural hematomas will appear more hypodense as compared to the rest of the brain. There's some mass effect. You're seeing effacement of the lateral ventricle because you're not seeing that lateral ventricle well enough. And then this patient undergoes a procedure called SEPs, which is a portal evacuation device for subdural hematoma. SEPs can be done at the bedside. So this patient underwent a SEPs evacuation. Despite that SEPs evacuation, you see a little bit of hypodense material that's accumulating. There's a little bit of acute subdural hematoma that's accumulated after the SEPs. And here's reaccumulation of that subdural hematoma. Some normal cisternal anatomy. You can keep this handy to go over your cisternal anatomy. Hydrocephalus. Look at the temple horns. These are supposed to appear really small, slit-like, but they're enlarged. You look at the frontal horns. In the previous CT heads, I showed you the frontal horns here. They're rounded out. They're rounded out. They're enlarged. Here, this is indicative of the presence of hydrocephalus. Now, whether it's obstructive or not, the ventricular system communicates with each other. But if there is an obstruction, whether it's blood, whether it's a mass, you'll see it at the level of one of these ventricles. So obstructive versus non-obstructive, you may get some sense after you look at the entire ventricular system. The third ventricle should appear oblong or ovoid. It shouldn't appear rounded off. So this is hydrocephalus. And what is this again over here? Contusions. So again, a reminder of the frontal contusions that we saw previously. From TBI, we'll take a look at the CT head in acute ischemic stroke. Normal CT head. Is there anything abnormal on this CT head? How many of you think there's something abnormal here? Show of hands. Awesome. So what are we seeing? A hyperacute clot in the right MCA. So that's the dense MCA sign. We won't be going into CT angiograms, but this is where the cutoff was. On the conventional angiogram, you can see pre-intervention, there are no blood vessels. Out here, post-intervention, it fills up nicely because that clot has been suctioned out. Like I was telling you, there are format resources as well as lots of universities that also put up their de-identified case files depending upon your learning style you could use. Either, this is from University of Rochester, you can see the evolution of stroke. Within 24 hours, you begin to see some effacement of sulci gyri. There's hypodensity, evolution, and further evolution with some encephalomalacia that's three months out from that acute ischemic stroke. So recap of the signs of cerebral edema and raised ICP. Global cerebral edema. Here's a frontal contusion. Effacement of the temporal horn, but the temporal horn on the left side is increasing in size, so telling you that there is some evolving hydrocephalus. Hydrocephalus, this is obstructive hydrocephalus with blood in the third ventricle. Acute subdural hematoma. Mass effect, midline shift. Effacement of the sulci gyri. So these are all the different signs that should tell you that there is raised intracranial pressure cerebral edema. Here's an example of an evolving stroke. Again, compression of the fourth ventricle. There's something that's been done over here. Surgical decompression, so suboccipital crani. It's a life-saving surgery preventing further mass effect on the brain stem. So there's a good surgical evacuation. And we'll move on to ICH. Just a quick recap of different types of ICHs. I've been showing you contusions in those patients with traumatic brain injury, somebody who has low platelets. You can see that there are some different densities of blood. When you begin to see different densities of blood, no matter where the hematoma is within the parenchyma, outside the brain, you've got to think about an underlying coagulopathy, either a thrombocytopenia or the patient may be on warfarin, for example. So you begin to see different ages of blood within the same hematoma, intraparenchymal or extraaxial. There's a lot of edema. This edema appears out of proportion to that hemorrhage that you're seeing. That should alert you, when you're seeing more edema as expected, that should alert you that perhaps there's an underlying tumor underneath all of this. And this is a classic ICH, basal ganglia ICH related to high blood pressure. Example of a low-bar ICH. I showed you decompressive suboccipital craniectomy. Here's a decompressive hemicranie. This you can keep handy if you want to understand how large the patient's ICH is. This can also be plugged into an ICH score just to show you that, yes, there is a way to quantify the hematoma. A is the largest diameter, B is perpendicular to A, and C is the total number of slices. But be mindful, know that when the original formula was derived, the slices were 10 millimeters in thickness and now they're only five millimeters in thickness. So the total number of slices do need to be divided by two before you plug into the formula. Classic locations. This will also show up on your boards. Classic locations. Thalamus, cerebellum, pons, basal ganglia. That was hematoma expansion. And I want to show you a spot sign. Just like you see this anywhere else in the body, contrast extravasation will look like this. And we'll wrap up with subaryknoid hemorrhage. I showed you the cisterns. Hyperdense material in the cisterns should alert you, based on the patient's clinical story, whether there's underlying trauma or whether there is worse headache of someone's life, that there might be an underlying aneurysm. For that hydrocephalus to relieve that hydrocephalus, bilateral EVDs were placed. So that's the tip of the EVD. So here's a recap of everything that we went over. CT had normal anatomy. We saw some signs of raised ICP hydrocephalus. We looked at TBI, contusions, subdural hematoma, epidural hematoma, acute ischemic stroke, that dense MCA sign, evolving stroke over different time periods. We looked at ICH and we wrapped up with subaryknoid hemorrhage. So that's your window into the world. Now, if your radiologist doesn't answer the phone in a timely fashion, your patient in a coma who you just intubated and sent down for that STAT head CT, you should be able to interpret your own head CT, but make sure you get that radiologist to also agree with you. Thank you.

CT scanner

neuromonitoring

traumatic brain injury

CT scan findings

systematic approach