0:01

The MRI protocol for evaluation of the

0:04

patient for head trauma should include T2

0:08

weighted FLAIR imaging, diffusion-weighted

0:11

imaging, and susceptibility-weighted imaging.

0:13

This is a study that there's very little

0:15

role for post-contrast imaging.

0:18

And this was a great example of

0:23

the benefit of MRI for diffuse axonal injury,

0:28

a rotational acceleration-deceleration injury.

0:32

In this case, what we see is a hematoma over

0:36

the right parietal-occipital region, and this is

0:40

likely where there was the original contact injury,

0:44

the so-called coup injury on this FLAIR scan.

0:47

However, we notice that the suppression

0:51

of the cerebrospinal fluid to make

0:53

the CSF dark on FLAIR is not present.

0:57

It's bright CSF.

0:59

That means there's abnormality in

1:01

the CSF and in the trauma setting.

1:03

This is going to be subarachnoid hemorrhage.

1:06

So the patient has bilateral subarachnoid

1:09

hemorrhage over the upper convexity.

1:12

Not only that, but we see that there is abnormal

1:14

signal intensity in the splenium of the corpus

1:17

callosum, manifested as this bright signal intensity.

1:21

It's not only affecting the splenium, it's going

1:23

anteriorly to affect actually the septum pellucidum.

1:27

And here we are at the top of the corpus callosum as

1:30

well, where we see the bright signal intensity.

1:33

So this in and of itself would suggest that

1:36

This is a pretty gross traumatic injury.

1:38

You notice also that the patient has

1:41

high signal intensity in the occipital

1:43

horns of the lateral ventricles.

1:46

The normal frontal horns have dark signal intensity.

1:49

Why is this bright in the occipital horns?

1:51

This is blood layering in the occipital horns of the

1:56

lateral ventricles.

1:58

As you go further inferiorly, you notice

2:00

that the posterior aspect of the midbrain

2:04

shows high signal intensity, maybe worse

2:06

on the left side than the right side.

2:09

And there is spillover into the cerebellar folia,

2:15

where there is bright signal intensity in the

2:18

subarachnoid space of the upper vermian structure.

2:21

So there's hemorrhage also in the posterior fossa,

2:24

as well as injury to the midbrain and pons junction.

2:30

Now let's look at the patient's gradient

2:33

echo scan for hemorrhagic products.

2:37

So normally, we would recommend going

2:39

with susceptibility-weighted imaging.

2:41

If your MRI scanner does not have SWI pulse sequences,

2:47

the next best thing is to go with a low flip angle

2:50

gradient echo scan. Here on this gradient echo scan,

2:54

what we see is an area of dark signal intensity

2:58

crossing into the left side of the midbrain,

3:01

identifying hemorrhagic products in the

3:03

midbrain, associated with that amount of edema.

3:08

As we go further inferiorly, we see blood products,

3:10

also the dark signal intensity in the subarachnoid

3:14

space of the vermis, and then going further.

3:18

Superiorly, blood products layering in the

3:20

occipital horns of the lateral ventricles.

3:23

And then here we have this very black area, this

3:26

dark area in the corpus callosum, the junction

3:29

between the splenium and the septum pellucidum, which is seen

3:33

here, the posterior septum pellucidum, and corresponding

3:37

just to the right of midline, more hemorrhagic

3:40

products in the top of the corpus callosum.

3:43

And...

3:44

Farther superiorly, at the gray-

3:47

white junction, on this gradient echo

3:50

scan, more areas of hemorrhage.

3:53

So this is grade three diffuse axonal injury.

3:57

Why grade three?

3:58

Grade one—

3:59

we have the foci at the gray-white junction

4:03

for shearing injuries at the fixation point

4:07

of the gray matter to the white matter.

4:11

We have the involvement of the corpus callosum,

4:13

identifying it as grade two hemorrhage and injury, and

4:20

the presence of brainstem edema and hemorrhage is the

4:27

criterion for grade three diffuse axonal injury—

4:31

the worst grade.

4:32

So this patient has a very poor prognosis.

4:35

When you just look at the brain, it doesn't

4:37

look... you know, there's no midline shift.

4:38

The ventricles look pretty good.

4:40

The parenchyma doesn't look all

4:42

that horrible on the FLAIR scan.

4:44

But when you combine that with the gradient

4:47

echo scan for blood products, you see that the

4:49

patient actually has a fairly severe diffuse

4:53

axonal injury, grade three, and therefore

4:56

a very poor prognosis.

4:58

This patient has additional pulse sequences.

5:00

The diffusion-weighted scan, as I mentioned previously,

5:04

is useful for the identification of whether or

5:06

not the patient has cytotoxic edema secondary

5:11

to glutamatergic outpouring of neurotransmitters

5:16

that can lead to a diffuse cerebral edema pattern.

5:19

In this case, all we're seeing is the cytotoxic

5:22

edema associated with the shearing injuries,

5:25

rather than the diffuse involvement

5:28

of the brain. The patient had an MRA.

5:33

The MRA is not useful.

5:34

It's not part of our traditional trauma

5:37

protocol. I think it was done because they were

5:41

unsure whether the patient's hemorrhage in the brain

5:44

was secondary to a vascular etiology versus trauma.

5:48

Uh, you might think, "Oh, how

5:49

that... that's pretty obvious."

5:51

But unfortunately, a lot of times what happens is

5:54

that the patient gets in a motor vehicle accident

5:56

and is unconscious, and the clinicians will say,

5:59

"Well, did the patient have an aneurysm that bled,

6:05

which led to loss of control of the motor—"

6:09

"—the car, which led to a motor vehicle collision,

6:13

as opposed to just a motor vehicle collision?"

6:16

And that sequence is, uh, sometimes

6:20

obscured when the patient is unconscious

6:22

and can't give you a clinical history.

6:25

So when they see subarachnoid hemorrhage,

6:28

we would say as radiologists, "Well, it's

6:29

most likely secondary to the trauma."

6:32

But they sometimes ask the question, "Well, could the

6:34

patient have had an aneurysm that bled, which led

6:37

to them being unconscious and crashing their car?"

6:40

So that's why sometimes you will see an MRA

6:43

or a CTA, uh, performed even in the setting of

6:46

trauma. In this case, that, uh, MRA was normal.