0:00

As I mentioned,

0:02

the secondary complications of traumatic brain injury are

0:06

more likely to cause permanent damage

0:09

than those of the primary injury.

0:11

So far, we've looked at some of the vascular complications,

0:14

secondary complications of traumatic brain injury,

0:17

demonstrating dissections, occluded vessels,

0:21

as well as pseudo aneurysms,

0:23

with the potential for embolic infarcts,

0:26

secondary to the pseudo aneurysm.

0:28

Now, I'd like to talk to you a little bit about herniations.

0:32

Again,

0:32

this is usually not what is occurring at the initial time of

0:36

the insult with the traumatic event is usually something

0:42

that we see over the course of time with

0:45

delay after the initial event.

0:48

The different types of hernia depend upon where the

0:53

patient's lesion is and these lesions that I refer to may

0:56

be interparenchymal. That is a hematoma or contusion.

1:00

Or they may be extra-axial.

1:02

That is a subdural hematoma or an epidural hematoma.

1:05

Both of them can cause enough mass effect that leads to

1:09

herniation. Now, when we refer to the right left shift,

1:15

that can occur with an extra-axial collection.

1:19

In this case, an isodense subdural hematoma,

1:23

we usually refer to the degree of displacement

1:27

from the midline of the septum pellucidum.

1:30

However,

1:32

simple displacement from the midline does not necessarily

1:36

lead to or qualify for subfalcine herniation.

1:41

By subfalcine herniation,

1:43

we mean that the patient has brain tissue which

1:48

is crossing over from, in this case,

1:52

the right side to the left side under the falx cerebri.

1:56

And this is the free edge of the falx cerebri.

1:59

So why?

1:59

While normally we can have a degree of midline shift without

2:04

brain tissue herniating over when we see the brain tissue

2:08

actually crossing from right to left, in this instance,

2:11

that's where we refer to the term subfalcine herniation.

2:15

So although midline shift is concurrent

2:19

with subfalcine herniation,

2:21

it does not complete the qualifications

2:26

for subfalcine herniation.

2:27

Subfalcine herniation is usually due to mass

2:31

effect in the superior portion of the brain,

2:34

not the inferior portion of the brain,

2:36

and in the supratentorial portion of the brain,

2:39

certainly not the infratentorial posterior fossa

2:42

of the brain. In a similar fashion,

2:44

we have a degree of uncal herniation.

2:48

By uncal herniation,

2:50

we mean that the medial temporal lobe

2:55

extends into the cistern and will.

2:59

Will lead to effacement of the cisterns

3:03

around the brain stem.

3:05

So that would be uncal herniation when that uncus or when

3:10

the amygdala or when the medial temporal lobe

3:13

then crosses downward the tentorial edge.

3:17

And you see brain tissue below the tentorial edge,

3:22

for example, in a coronal image,

3:24

then we would say that the patient had transtentorial uncal

3:29

herniation or transtentorial temporal lobe herniation

3:32

or transtentorial herniation. So again,

3:35

this is a degree midline shift to subfalcine

3:38

herniation uncal deviation,

3:41

uncal herniation to transtentorial herniation as it goes

3:45

downward. These are, again, supratentorial herniations.

3:50

When we refer to cerebellar herniations,

3:53

we're obviously talking about the posterior fossa.

3:56

And again, this may be both an intraparenchymal.

3:59

Hemorrhage or it may be extra-axial as in an

4:04

epidural hematoma or a subdural hematoma.

4:07

So again,

4:08

posterior fossa for upward and downward

4:12

cerebellar herniation.

4:14

A lesion in the central aspect of the cerebellum may lead

4:18

to this cerebellar tissue herniating upwards through the

4:22

tentorial incisura the opening of the tentorium superiorly

4:26

in that place it will compress the midbrain and efface

4:30

the perimesencephalic cisterns. At the same time,

4:34

1 may have downward cerebellar herniation what

4:38

we usually refer to as tonsillar herniation.

4:41

And that's when the tonsils are seen at the foramen magnum

4:45

herniating downward through the foramen magnum.

4:49

This then causes compression on the cervical medullary

4:52

junction and the medulla and can lead

4:55

to cardiorespiratory arrest.