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Diffuse Axonal Injury

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0:00

This was a passenger,

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an eleven-year-old passenger in a motor vehicle collision.

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The CT scan

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shows a relatively small collection

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over the left parietal region

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that has a lentiform shape to it,

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and there is associated some subarachnoid hemorrhage,

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but it looks like a relatively small area of injury.

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We want to look at the bone windows to see

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whether there is a fracture.

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And indeed,

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one can see that the inner table of the calvarium

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is fractured in this individual.

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So this was the coup side of the injury.

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And the patient has a small epidural

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collection associated with it,

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likely from a small tear of a middle

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meningeal peripheral branch.

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Just to be sure,

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we would look at the thin-section images.

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These are the 1 mm thick sections.

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The disadvantage of looking at the thin-section images is

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that they do get more noisy

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since it is a 1 mm thick section.

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Nonetheless,

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although we can see some of the subarachnoid hemorrhage,

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we are still seeing a relatively small

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extra-axial collection here.

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We can measure this and 5 millimeter

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extra-axial collection,

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likely an epidural hematoma from a peripheral

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middle meningeal injury from the fracture.

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So call into the clinicians and say,

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I see a minor injury with a small incomplete fracture,

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small epidural hematoma measuring 5 mm by 2 cm by 1cm,

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a little bit of subarachnoid hemorrhage.

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And they respond to you,

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"Oh, the patient's doing really well."

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The patient is doing very poorly and

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has alteration of consciousness.

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So, the patient will likely get serial scanning.

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And you're kind of unimpressed with the degree of

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the pathology, even on the thin-section images.

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At this juncture,

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if there is a discordance between the neurologic

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examination and the CT scan,

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generally, the clinicians will repeat the

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scanning at the six-hour mark with CT.

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However,

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particularly in children where they don't want to do

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serial CT scanning,

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they may proceed to get an MRI scan.

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Let's see what happens to this individual.

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Okay.

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So, this is the same patient with the six-hour scan.

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And as we look at the patient study,

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we see that this epidural hematoma has increased in size,

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and there continues to be subarachnoid hemorrhage.

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Remember to look contrecoup.

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So, we saw that there was a fracture in the left parietal

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region and the epidural hematoma.

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As we look contrecoup,

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we're not seeing very much in the right hemisphere.

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And the clinician say the patient's doing very poorly.

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So, they may scan again at 6 hours

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or depending upon the width of this collection,

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they may intervene.

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Let's measure it.

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Epidural hematoma,

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measuring 2.2 cm.

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That's an indication for surgery.

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As you recall,

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the epidural hematoma

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indication was 15 mm width

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or 30 CCs of volume.

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In this case, they decided to wait

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and the next scan we get is an MRI scan.

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On the MRI scan,

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I'm going to show you the FLAIR scan first.

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So, this is a FLAIR scan.

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Dark CSF,

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dark white matter,

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higher-intensity gray matter.

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And you can see the collection of blood,

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as well as what looks like an underlying

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hematoma in the brain or contusion

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and likely the subarachnoid hemorrhage.

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There really isn't much in the way of midline shift.

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You probably want to look at the

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T1-weighted scan, as well.

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And it shows the mixed signal intensity blood products.

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And this is both dark on T1 as well

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as areas of high signal on T1.

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And by virtue of the fact it was dark on T2,

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we know that this is deoxyhemoglobin.

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You see that there are some blood products in the

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subarachnoid space, as well.

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Other than that, not too bad.

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If we look at the diffusion-weighted scans,

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we just see a little bit of cytotoxic

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edema in the area of the hematoma.

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We have a T2-weighted scan, as well.

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Again, dark signal intensity on T2-weighted scan,

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lentiform shape,

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likely representing acute epidural hematoma.

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Parenchymal hematoma with edema.

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Otherwise, looking pretty good.

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So, you dictate epidural hematoma with

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mild contusion in the posterior,

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left frontal, lobe and parietal lobe,

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with associated subarachnoid hemorrhage,

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22 mm in thickness, no midline shift.

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What did you forget to do?

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Well, I've told you before

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that the best sequence for detection

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of blood is susceptibility-weighted scan.

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This is the SWI scan,

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the susceptibility-weighted scan of the exact same patient.

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You'll note the very dark signal of the extra-axial collection.

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However, in addition, look for black dots.

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Here are black dots of deoxyhemoglobin in the subcortical

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white matter in the area adjacent to that contusion.

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But you can see that these little black

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dots are really all over the place.

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Here at the gray-white junction.

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Here in the right frontal lobe.

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These black dots are not veins.

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How do we know that they're not veins?

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These are the veins here.

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The veins usually are branching and they usually

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go from smaller to larger as they go centrally.

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Here's a hemorrhage in the splenium

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of the corpus callosum.

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Here is hemorrhage

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in the subcortical white matter of the parietal lobe,

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as well as

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the more posterior parietal lobe.

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And as we look further inferiorly,

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look at the frontal lobes.

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Lots and lots of these black dots all over the place.

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This is our gyrus rectus region.

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And there's blood products along the posterior gyrus rectus.

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Here we have the temporal region on the left side.

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Look at right along the gray-white matter interface.

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All of these areas of dark dots.

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These are all areas of shearing injury, hemorrhagic,

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shearing injury from diffuse axonal injury,

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in a rotational acceleration deceleration injury.

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There's even hemorrhage in the cerebellum.

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None of this is apparent on the T2-weighted scan,

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nor on the FLAIR scan,

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nor for that matter,

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on the accompanying CT scan from the same day.

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This is the power of MRI, in particular

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with susceptibility-weighted scanning.

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In a patient who has discordance between the imaging

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findings on CT and the neurologic deficits,

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one should definitely recommend susceptibility-weighted

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MRI scan in the setting of potential

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diffuse axonal injury.

Report

Description

Faculty

David M Yousem, MD, MBA

Professor of Radiology, Vice Chairman and Associate Dean

Johns Hopkins University

Tags

Vascular Imaging

Vascular

Trauma

Neuroradiology

MRI

Interventional

Emergency

CT

Brain

Bone & Soft Tissues

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