0:00

This is a diagram of the progression of disease

0:03

when one has an axonal shearing injury.

0:07

The image on the far left is a normal example of the white

0:13

matter tract with the foot processes on the cellular body in

0:18

the normal state.

0:20

However, when one has a shearing injury,

0:23

you can see that there is disruption of that white matter.

0:27

And not only that,

0:28

you start to have that outpouring of the neurotransmitter

0:32

that I mentioned, which is usually represented by glutamate.

0:37

Initially, one might just have the white matter injury.

0:40

However,

0:41

over the course of time when there is a diffuse process,

0:45

you start to have all of these glutamate injuries affecting

0:51

the cellular body itself.

0:52

And this is, as I said,

0:54

cytotoxic when one has excessive glutamate.

0:58

in the subarachnoid space.

0:59

So the ultimate endpoint is cellular death by

1:05

the outpouring of glutamate.

1:07

As I mentioned,

1:09

the use of susceptibility weight imaging

1:12

for diffuse axonal injury is critical.

1:16

There was the concept in the past about an entity known as

1:21

non-hemorrhagic shearing injury, and that was because we did

1:26

not have that acute sensitivity to blood products by SWI.

1:31

So this is a gradient echo scan,

1:34

and you may detect some

1:38

high signal intensity in the white matter.

1:40

of this gradient echo scan,

1:42

but you certainly wouldn't suggest that the patient has

1:45

had a hemorrhagic injury.

1:46

This is the same patient.

1:48

And again, this is from 2005 when SWI first came out.

1:53

And you'll notice now that there are

1:55

multiple areas of hemorrhage.

1:57

So the concept of non-hemorrhagic shearing injury has been

2:02

rebuffed by the advent of utilization of susceptibility

2:07

weighted imaging in the brain tissue.

2:08

So at these gray-white junctions,

2:11

you have hemorrhagic injury to the brain.

2:13

This is demonstrated also diagrammatically by the cellular

2:17

bodies and the white matter tracks here,

2:19

and by the presence of all of these little

2:22

injuries to the white matter.

2:24

And then there is often dying back of various amounts of the

2:28

cells who have had their white matter tracks sheared off.

2:33

So when we talk about diffuse axonal injury,

2:36

or traumatic axonal injury, or shearing injuries,

2:40

or acceleration deceleration rotational injury,

2:43

what we have is this shear strain deformation that tears the

2:46

white matter and usually results in what's

2:49

called axonal traction balls,

2:51

where the cellular cells will swell up and ultimately die.

2:56

And the location that we usually look for these

2:59

are at these three critical regions.

3:02

The gray-white matter junction,

3:05

and that's usually in the high frontal and parietal region,

3:08

the corpus callosum,

3:10

and particularly in the splenium of the corpus callosum,

3:13

where the only indicator may be a small amount of

3:16

intraventricular hemorrhage.

3:17

And as I said,

3:19

along the dorsolateral midbrain where it approaches

3:24

and bangs up against the tentorial edge.

3:29

This is a very poor prognostic finding to

3:33

have any of these findings in the brain.

3:37

This is a fast spin echo T2-weighted scan and a gradient

3:42

echo scan in a patient who had diffuse axonal injury.

3:46

You can see that the patient has areas of hemorrhage

3:49

that are evident on the fast spin echo scan,

3:52

but much more demonstration of blood

3:55

products on the gradient echo scan.

3:57

This patient demonstrates two out of the three zones of

4:01

hemorrhagic diffuse axonal injury, in that you have it

4:05

at the gray-white junction of the frontal lobes,

4:07

as well as portions of the parietal lobe,

4:10

as well as an injury to the splenium of the corpus callosum.

4:14

The third location where one would have

4:19

an injury would be in the midbrain.

4:22

And as you recall,

4:23

the posterior portion of the midbrain,

4:26

as it hits the tentorial edge,

4:29

is the final and third location for

4:32

classic diffuse axonal injury to the brain.