0:01

I'd like to make a distinction between two

0:03

things that are sometimes associated with the term the

0:07

AOD distraction. And that is the difference between the

0:12

atlanto-occipital distraction or dislocation, or dissociation

0:18

from the atlanto-odontoid distraction or dissociation.

0:22

We really should be using the term atlantoaxial.

0:26

That is the connection between C1 and C2 as

0:30

opposed to the atlanto-occipital,

0:33

which is C2 to the skull base.

0:36

Here on the images, we see a normal

0:41

distance between the occipital condyle and the

0:45

C1 vertebra, the atlanto-occipital relationship is normal.

0:51

However,

0:52

we have widening here of the atlantoaxial space.

0:57

So this is the C1 lateral mass,

1:01

this is the C2 lateral mass, and this is the atlanto-

1:05

axial space that is widened in this individual.

1:09

And on the MRI scan, the atlanto-occipital

1:15

relationship is normal without bright signal,

1:18

but the atlantoaxial connection shows bright

1:23

signal intensity on the STIR image.

1:25

And you can see this on the coronal scan that both

1:28

sides are brightened signal intensity as well as

1:32

widened. So this is the atlantoaxial distraction.

1:39

Here we have the atlanto-odontoid

1:43

or atlantoaxial distraction.

1:46

You see that on the posterior arch of C1 to

1:52

the C2 lateral mass, there is bright signal intensity

1:57

which is seen here. This is the lateral mass of C1.

2:01

This is bright signal intensity between it and the

2:05

C2 vertebra. So this is bright and signal intensity.

2:08

It happens that on this individual, we also see

2:13

bright signal intensity between the occipital

2:17

condyle and the lateral mass of C1.

2:20

So this patient has both atlanto occipital dissociation as

2:26

well as atlantoaxial dissociation, manifest as the

2:31

bright signal intensity in the space between the

2:34

occipital condyle and the C1 and between

2:37

C1 and C2 on the STIR image.

2:40

So again,

2:41

let's just make sure we understand this distinction.

2:44

Atlanto-occipital is between C1

2:48

and the occipital condyles.

2:50

You see this very bright signal intensity between the

2:53

occipital condyles and the C1 with the

2:57

disruption of the ligaments and you can

3:00

see also bright signal intensity in the pre

3:02

vertebral space in this individual, as well as apical

3:06

ligament disruption. Bright signal intensity,

3:10

occipital condyle to C1, contrasted with atlantoaxial

3:16

distraction between C1 and C2,

3:20

between the lateral mass of C1 inferiorly and

3:25

its articulation with the lateral mass of C2.

Atlanto-Odontoid Versus Atlanto-Axial Distractions

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