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Case: Left MCA Stroke on CTA

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Depending upon your institution, you may

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have a protocol in which a patient gets a

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non-contrast head CT scan for stroke, followed

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by CT angiogram and associated CT perfusion.

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Some programs will just do a non-contrast CT and a

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CTA in order to define the anatomy and to determine

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whether the patient is a candidate for thrombectomy and

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IV thrombolysis. In this case, of the patient

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who had a dense MCA on the non-contrast scan,

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the patient had ordered a CT angiogram to

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follow, and this was done on the same day.

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So what we're seeing is a contrast-enhanced CTA of the

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head and neck, and these are usually done together—both

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the head and the neck together in one bolus of contrast.

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Now, for

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the evaluation of the patient who has a

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stroke, obviously, time is of the essence.

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So for the evaluation forr the CTA, generally, I go

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with the thick section images to start with. So that way,

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I have a sense of what's going on, and I can

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get on the phone with the clinician and say, "Hey,

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there's a definite thrombus here in the internal

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carotid artery or in the middle cerebral artery."

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So that's

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thick section images because

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you can scroll through them faster.

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However, for the detailed anatomy that we

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need to know for the overall report, I will

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then go ahead and look at the thin section

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images as well as the reconstructed images.

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And in most cases, we're talking about

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maximum intensity projection (MIP) images

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of both the neck vessels to look for the

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carotid bifurcation to see how stenotic

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it is, as well as intracranial MIPs.

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As I'm going to scroll through this, you'll

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see that the way I look at a CTA is I look

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at one vessel at a time, going up and down.

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So here we are at the lowest-most portion, and we

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have the aortic arch. I'm going to follow,

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since I saw that the patient had a dense MCA

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on the left side, I'm going to follow the left common

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carotid artery up and down in its entirety, not

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looking at the right and not looking at the vertebral

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artery, just focusing on one blood vessel at a time.

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So here I am, following the left

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common carotid artery upward.

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And we start to see the carotid bifurcation.

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So I'm at the carotid bifurcation, and I have

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to make an assessment of the patient's carotid

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stenosis. In this case, although there is

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calcified plaque that you see as these bright

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little areas around the internal carotid artery,

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remember, the internal carotid artery comes off

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posteriorly in most patients at the bifurcation.

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So there is some atherosclerotic plaque, but I'm not seeing

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high-grade stenosis at all.

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I'm now following the internal carotid

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artery up and following it in its cervical

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portion until it comes to its petrous portion.

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So here we are at the petrous portion.

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Little bit of irregularity in the blood vessel here.

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So there is some atherosclerotic

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soft plaque in the petrous internal

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carotid artery, but not high grade.

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I'm gonna look at this again on the thin sections.

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And then we come to the cavernous

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portion of the internal carotid artery.

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We had seen the calcifications on the non-contrast

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study, and here we see that although there are

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calcifications, we are not seeing a high-grade stenosis.

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I call high-grade stenosis intracranial.

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Anything that's greater than 50%.

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When we're looking at the carotid bifurcation, we're

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usually talking about 70% as high-grade stenosis.

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So we follow the cavernous internal carotid artery,

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and this is the, obviously, the odontoid process right here.

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So we're at the paraclinoid internal carotid artery.

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We're now at the supraclinoid internal carotid artery.

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And as we come to the distal portion of the internal

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carotid artery at the M1-A1 junction, this is A1.

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M1, we're missing M1.

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So as you can see, this blood vessel, as opposed

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to here, where it goes across to the M1 segment,

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on the right side, on the left side, it stops.

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And this is the thrombus right here.

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You're seeing it as absence of contrast.

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Despite that, we do see some

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vessels in the Sylvian fissure.

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Some of them are not filling as well as others,

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because they don't have as good flow.

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Some do have good flow.

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And then as we continue upward in the Sylvian fissure,

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we see more of the middle cerebral artery branches.

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Not quite as abundant as on the

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right side, but they are present.

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And this is likely through

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collateral circulation going upward.

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So I've now evaluated the left side.

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Common carotid artery, no occlusion.

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Carotid bifurcation, no stenosis that

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the interventionalist has to worry about.

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Let's look at the right common carotid artery.

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So we'll do this a little bit more quickly.

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So right common carotid artery coming off

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of the innominate artery, the right common

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carotid artery in the neck cervical portion,

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we come to the right common carotid artery bifurcation.

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There is stenosis here with soft plaque,

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as well as calcified hard plaque.

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But once again, just visually,

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this is not high-grade stenosis.

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I would measure this in its minimum width,

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and then compare it to the normal distal

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internal carotid artery, which is here.

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I would say it's probably gonna end up being

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a 50% stenosis, and then following this up to

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the petrous internal carotid artery, not too

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bad, the cavernous internal carotid artery.

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Calcified atherosclerotic plaque, but no stenosis.

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Here's the M1 segment.

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Here's the A1 segment.

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It looks good.

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I look in the Sylvian fissure,

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and the branches look fine.

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Then I go down and look at the next set of

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vessels, which are the vertebral arteries.

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And once again, the way I would evaluate

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this is just one vessel at a time.

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So here we have the origin of the left vertebral artery.

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That's the V1 segment.

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This brightness here

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is some venous contamination.

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We follow the left vertebral artery in its vertebral

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segment, which is called the V2 segment.

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We follow that up, up, up.

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Here's where it exits the vertebral segment.

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So this is what's known as the V3

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segment, outside the vertebral segment, but

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before it enters the intracranial segment.

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And as it enters the dura, this is the V

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4 segment, and there are no stenoses.

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Let's go back down and find the right

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vertebral artery and follow it from below.

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So here is the origin of the right vertebral

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artery. Calcified plaque here, narrowed.

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Here it comes off.

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This is your right vertebral

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artery that we're following.

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Now entering the V2 segment, we

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follow the V2 segment all the way up.

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A little bit of venous, right?

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Contrast here.

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Here's still the vessel.

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Here's the vessel coming out.

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This is the V3 segment with a little

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bit of calcified plaque right here.

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Intracranial segment, V4 segment, which

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looks fine, and it joins the basilar artery.

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So at this point, I've looked at

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all of the four major vessels.

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I now have to look at the intracranial vasculature.

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And for that, although I would look on the thin

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section images, we're gonna go to the MIPs.

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I like the coronal MIP the most.

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This is the coronal maximum

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intensity projection (MIP) image.

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And we are looking at the intracranial circulation.

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So that's why we're seeing the brain.

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And as we come from anterior to posterior,

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we see the anterior cerebral arteries.

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So this is the right internal carotid artery coming

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to the A1 segment and the M1 segment. These are

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the middle cerebral artery branches, and we're gonna

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see the connections with the anterior cerebral artery

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branches on the left side internal carotid artery.

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This is the A1 segment.

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Now, I see a high-grade stenosis

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of the left A1 segment origin.

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It should be connecting to this blood vessel like this.

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And there's a stenosis here.

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Might even be a thrombus here.

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The M1 segment is completely gone.

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So here's our M1 on the right.

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The M1 on the left is missing, and yet we still

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do see middle cerebral artery branches, presumably

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coming from either posterior cerebral artery

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collaterals or anterior cerebral artery collaterals.

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So the new finding is—ah, there also is a

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proximal left A1 segment thrombus or

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stenosis here. Thrombus.

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If we see the cut within the blood vessel,

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stenosis, if we see that the vessel is

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narrowed, and then as we continue further

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posteriorly, we come to the basilar artery.

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So here's our basilar artery with the posterior

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cerebral and superior cerebellar branches.

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Here are the two vertebral arteries

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coming together to form the basilar artery.

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So this is the

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V4 segment of the left and V4

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segment of the right vertebral arteries.

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And obviously, we would also look

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at all the other projections.

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So here is the occluded left middle

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cerebral artery that we described before.

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And you may also see this in the sagittal projection.

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So coming from the left side, we're seeing the

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relative paucity of branches in the Sylvian fissure,

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as compared to the right side,

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where you see more of these loops.

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So there are some vessels that were missing

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within the Sylvian fissure, likely from

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a clotted vessel or diminished flow.

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Here are the anterior cerebral arteries.

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Here's your basilar artery coming in,

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your posterior cerebral arteries.

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A lot of these vessels are showing atherosclerotic

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disease, as shown by irregularity to their contour.

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Here's another little area of stenosis here.

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In this posterior cerebral artery.

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So what I'm not doing right now is showing

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you the thin-section images, but you

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would go through them and verify that.

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The one thing that I get to with the thin-section

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images is that you would be able to see more clearly

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that, uh, left A1 segment stenosis and/or clot.

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If you were looking at the thin-section images.

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That's the type of thing that might not be

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identified on the thick sections because it was

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a small segment of the left A1, and so let me

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just try to scroll quickly up to that level again,

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following the internal carotid artery, giving

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them a sense of the degree of stenosis of the

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left internal carotid artery at the bifurcation.

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So I would measure that and use the NASCET criteria.

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That is, the narrowest part of the

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internal carotid artery to a normal part.

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We had worried a little bit about

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the petrous internal carotid artery.

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There is irregularity here and soft plaque in the petrous

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left internal carotid artery, but not high-grade stenosis.

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This is the internal carotid artery coming to

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the occluded M1 segment and looking for the...

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A1 segment.

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Here's the A1, and it's right here.

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It looks like I see a small low-density

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area, which could be a clot right at the

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A1 origin as opposed to stenosis.

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It's a clot that is spanning both the

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proximal A1 as well as the M1 segment.

Report

Faculty

David M Yousem, MD, MBA

Professor of Radiology, Vice Chairman and Associate Dean

Johns Hopkins University

Tags

Vascular

Neuroradiology

Emergency

CTA

Brain

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