0:01

As I mentioned in the introduction to trauma, there

0:05

are the primary injuries to the brain associated with

0:08

trauma, and then there are the secondary injuries.

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The secondary injuries usually occur in delayed

0:14

fashion after the initial injury, and yet, these

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secondary injuries may be the injuries that lead to the

0:23

greatest deficits of the patient and/or their death.

0:27

So after the injury, the brain will respond in its

0:31

stereotypical fashion as it leads to brain swelling.

0:34

When the brain swells, it leads to

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increased intracranial pressure.

0:38

When you have increased intracranial pressure,

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you have the possibility of herniation,

0:43

you have the possibility of development of

0:45

hydrocephalus, you have the possibility of

0:48

compression of structures at the foramen magnum,

0:52

which may lead to cardiopulmonary arrest.

0:56

As I mentioned also, when you have trauma that

0:58

has fractures associated with it, you may have CSF

1:02

leakage and communication with the paranasal sinuses,

1:07

the outside world, or the mastoid air cells,

1:10

which can lead to the presence of meningitis.

1:13

Meningitis, that infection, can lead to great

1:17

deficits and, in the worst-case scenario, can lead to

1:21

meningoencephalitis, where you have brain infection,

1:24

brain abscess, all associated as a secondary phenomenon

1:30

after the initial trauma.

1:33

The herniations that we're most concerned with are

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listed here: subfalcine, uncal, transtentorial,

1:39

upward and downward cerebellar, and tonsillar herniation.

1:42

Subfalcine herniation is when the brain herniates

1:46

under the, usually the anterior border of the falx.

1:50

And that right-to-left shift, as you see in this patient

1:54

who has an isodense subdural hematoma, can lead to

1:58

entrapment of portions of the brain, usually the

2:01

cingulum at the junction here, or it can lead to

2:05

compression of anterior cerebral artery branches, with

2:09

a secondary phenomenon of a stroke involving the ACA.

2:15

Uncal herniation is usually when the temporal

2:19

lobe, the medial temporal lobe, herniates medially.

2:23

If it then goes downward, we would

2:27

call that transtentorial herniation.

2:30

So uncal herniation is a deviation medial to

2:33

lateral, and transtentorial herniation is a downward

2:37

herniation of the medial temporal lobes.

2:39

At this point, it's usually compressing the brainstem.

2:43

And it may actually pick off

2:45

some of the blood vessels, including

2:47

that of the posterior cerebral artery.

2:49

So here we have a demonstration of an

2:51

epidural hematoma, which is causing both left-

2:54

to-right shift with subfalcine herniation.

2:57

Here's our cingulum herniating subfalcine.

3:01

Here is our uncus herniating medially and then downward.

3:07

And then you can have herniations

3:08

through fracture sites.

3:10

Here, you have the brain herniating outward.

3:12

And this is a more dramatic

3:14

example of transtentorial herniation.

3:17

Herniation.

3:18

Notice that in the posterior fossa, we have downward

3:23

herniation of the tonsil, left side and right side.

3:30

When you have mass effect in the central aspect of the

3:35

cerebellum or the superior aspect of the cerebellum, you

3:39

may actually see upward herniation of the cerebellum.

3:42

That's the least common of all the herniations.

3:47

So here is a diagram from our textbook, *Neuroradiology,

3:51

The Requisites*, showing upward herniation of the

3:54

cerebellum above the tentorium, where it may compress

3:59

the midbrain and lead to obstruction of the aqueduct.

4:03

Here is the downward tonsillar herniation.

4:08

And here is the transtentorial

4:10

herniation of the temporal lobe.

4:13

Here is the subfalcine herniation of the cingulum

4:17

and the medial aspect of the frontal lobe.

4:20

When these things occur, as I said, you may get

4:23

secondary strokes due to compression of the anterior

4:28

cerebral arteries or the posterior cerebral arteries.

4:32

Which is seen in this patient who had traumatic

4:34

temporal lobe involvement with secondary posterior

4:39

cerebral artery infarction from the herniation medially.

4:44

This is another example of a

4:45

patient's status post trauma.

4:47

And what you see is a stroke, as evidenced on

4:51

the diffusion-weighted scan and the ADC map,

4:55

in the medial parietal lobes because of compression of

5:01

the posterior cerebral artery, leading to involvement

5:05

and infarction of the medial parietal lobes.