0:01

I wanna make one point about the

0:03

benefit of susceptibility-weighted

0:05

imaging as a pulse sequence on an MRI scan.

0:10

Susceptibility-weighted imaging has largely

0:12

replaced gradient echo scan because of its very

0:16

high sensitivity to the presence of blood products.

0:19

This is an MPGR gradient echo scan looking for blood

0:24

products, and only the most observant individual might

0:28

suggest that there's a small area of dark signal on

0:31

this gradient echo scan suggestive of blood product.

0:34

This is the same patient again,

0:36

published in 2005, showing all of these

0:39

little black dots on an SWI sequence.

0:44

So this just highlights for you the

0:46

increased sensitivity for susceptibility,

0:51

deoxyhemoglobin, and hemosiderin

0:54

on SWI sequences, that's far

0:57

superior to gradient echo scans.

1:00

If you don't have the SWI pulse sequences

1:03

as part of your software package or your

1:05

scanner, I highly recommend you purchase it.

1:08

If you do not have it, then the next best

1:11

thing is going to be your gradient echo scan.

1:15

So let's continue with traumatic axonal injury.

1:18

As I mentioned, this is usually a rotational,

1:21

acceleration-deceleration injury. Histopathologically,

1:24

you have those axonal traction balls with

1:27

swelling of the brain and the shearing injury.

1:30

The triad is at the gray-white junction,

1:32

the corpus callosum, often splenium.

1:35

And then the dorsolateral midbrain.

1:37

And this is what is utilized to grade

1:39

the degree of diffuse axonal injury.

1:43

When one has all three of these

1:45

together, it has a very poor prognosis.

1:48

If you also see diffusion-weighted imaging, it

1:51

suggests that the patient has diffuse cytotoxic edema,

1:55

which again implies brain injury that is permanent.

2:00

So look at the gray-white junction, look

2:02

at the splenium, look at the midbrain.

2:05

And look at the residual of the contusional injury.

2:08

It used to be that we had this concept of

2:11

non-hemorrhagic shearing injury. With the

2:16

advent of susceptibility-weighted imaging,

2:18

that concept has really declined because

2:22

with SWI, we see so much more hemorrhage.

2:25

It's pretty rare for you to have a tearing of

2:28

the white matter without some element of petechial

2:31

hemorrhage seen on SWI.

2:33

If you only have gradient echo scans, maybe you're

2:36

seeing white matter regions without the hemorrhage.

2:39

That would be your non-hemorrhagic shearing injury.

2:41

But when you employ SWI sequences, you recognize

2:45

that non-hemorrhagic shearing is pretty uncommon.

Diffuse Axonal Injury

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