0:01

In addition to the evaluation of the stability of the ligaments

0:05

with atlanto-occipital and atlanto-axial dissociation,

0:11

we obviously want to look at the vertebral bodies themselves.

0:15

This is an example of a Jefferson fracture.

0:19

It's a comminuted fracture,

0:20

actually a burst fracture of the C1 vertebra.

0:24

Sometimes it will just affect the anterior

0:27

arches of the C1 vertebra.

0:29

Sometimes it also affects the posterior arch

0:33

of the C1 vertebra.

0:34

As you can see here,

0:36

we have the right sided posterior arch,

0:38

which is somewhat comminuted,

0:40

as well as the anterior arch of C1.

0:43

Now, this in and of itself, does not necessarily mean it's

0:46

an unstable fracture. If the ligaments are intact,

0:49

it actually may represent a stable fracture.

0:52

These fractures are also nicely demonstrated

0:54

on the coronal reconstruction,

0:56

where we can see the fracture fragment on the left

1:00

side, as well as the comminuted

1:02

fracture fragment on the right side.

1:04

And as we proceed a little bit more posteriorly,

1:07

you can see the additional line of fracture.

1:10

Let's look at this on the sagittal scan.

1:13

And we want to look and make sure that

1:15

the lentilodontoid distance is preserved.

1:19

And this looks perfectly fine, nicely at pose

1:22

there. You can see a fracture fragment on the

1:25

superior arch of the anterior arch of C1.

1:28

Here is the fracture going through both anteriorly

1:32

as well as in the posterior arch,

1:34

representing this somewhat comminuted burst fracture.

1:38

Looks like it's a little bit worse on

1:40

the right side than the left side.

1:43

The orientation of the fracture fragments

1:46

on the coronal image is very important.

1:49

What you see is that there is offset of the lateral mass of

1:53

C1 from the lateral mass of C2 on both sides.

1:59

So this should normally be aligned.

2:01

This is all part of that same mechanism of

2:04

burst where it kind of explodes outward.

2:06

And so these lateral masses are laterally displaced

2:11

in this type of fracture, the Jefferson fracture.

2:15

On the CT scan of the Jefferson fracture,

2:19

we saw that the lateral mass of C1 was displaced laterally

2:24

on both sides compared to the lateral

2:26

mass of the odontoid process.

2:29

That suggests that there probably is ligamentous injury.

2:32

Let's look at the MRI scan on the same patient.

2:35

So this is the T2-weighted scan.

2:38

Here's the STIR images.

2:39

We've talked about how the STIR image is the best

2:42

sequence for looking at ligamentous injury.

2:45

So we will follow the anterior longitudinal ligament upward

2:49

and we see that there does appear to be an intact anterior

2:55

longitudinal ligament as we go up to the clivus.

3:00

There is some prevertebral edema as this bright signal intensity.

3:04

As we follow the posterior longitudinal ligament, we notice

3:09

that we have this disruption of the posterior longitudinal

3:12

ligament as it converts to the tectorial membrane.

3:15

And there we have a discontinuity here.

3:18

So there is ligamentous disruption

3:21

of the tectorial membrane.

3:22

As we go off midline, we see the atlanto-occipital region, on this

3:33

side shows normal distance and just

3:36

very slight high signal intensity.

3:39

The atlantoaxial space is also normal with

3:44

just a little bit of bright signal intensity.

3:47

As we go off posteriorly towards where the fracture has occurred,

3:51

we do see bright signal intensity edema

3:53

in the adjacent soft tissues.

3:55

But note that when we go to the contralateral side, we see

4:00

something different. Here we have brighter signal intensity.

4:03

It's narrower anterior than posteriorly.

4:07

So this kind of triangular look implies that there is

4:11

ligamentous injury extending along the posterior

4:14

margin of the atlantoaxial space,

4:19

and that is asymmetric from the right side to the left side,

4:24

where you see that there's the same distance between the two.

4:28

So there is this little offset.

4:30

And there is likely this ligamentous injury as well as

4:34

the injury that we described to the tectorial membrane.

4:38

We want to look at the spinal laminar line

4:40

and the spinal laminar ligaments,

4:41

which effectively are the ligamentum flavum.

4:44

They look just fine. And there isn't really offset here.

4:48

The atlanto-odontoid space is preserved.

4:53

If we look at the axial scans,

4:55

we will see that bright signal intensity here

5:00

which is largely in the retropharyngeal space,

5:04

more so than the prevertebral space.

5:06

There is a little bit of bright signal intensity

5:08

in the prevertebral space,

5:09

but this is anterior to the longus musculature.

5:15

So here's our longus musculature.

5:17

This is actually in the retropharyngeal space

5:21

rather than the prevertebral space.

5:24

On this MRI scan,

5:26

I want you to pay attention to the flow

5:29

voids of the vertebral arteries.

5:32

Notice that the left vertebral artery shows a normal flow void,

5:37

but the right vertebral artery has

5:40

high signal intensity within it.

5:42

This implies that there may be dissection or thrombosis of the

5:47

right vertebral artery that is associated with the fracture,

5:51

which, as you recall,

5:52

was more on the right side than the left side on the CT scan.

5:57

So there has been compromise of the

6:00

right vertebral artery versus the left vertebral artery.