0:00

As we discuss the extraconal space, it's probably

0:04

appropriate to stop a moment and talk about

0:06

facial fractures that affect the orbits.

0:09

Within the orbits,

0:10

the most common fracture is the orbital floor fracture

0:14

followed by the medial orbital wall or lamina papyracea

0:17

fracture. These are usually due to trauma to the orbit,

0:22

particularly involving things like a fist to the orbit or

0:26

when one falls and hits the side of a curb because of the

0:31

interconal pressure that is transmitted with a punch.

0:35

For example,

0:35

to the orbit usually have the fractures

0:38

explode outward rather than inward.

0:41

And that is a characteristic of blowout

0:44

fractures of the orbit.

0:45

For orbital fracture evaluation, I usually rely on the

0:50

thinnest section images and scroll through the numerous

0:54

images that allow us to identify subtle fractures.

0:59

And this is because some of the areas of the bone that are

1:03

present in the orbit are very thin, and therefore, we want

1:07

to detect subtle abnormalities. We have to make sure,

1:11

however,

1:11

that we do not mistake certain normal areas

1:16

of dehiscence in the bone for fractures.

1:20

For example,

1:21

here we see a small area where there appears to be a

1:25

defect in the bone, and this is actually seen bilaterally.

1:29

This is actually one of the entrance points of the

1:33

anterior ethmoid artery, and you can see

1:36

this as well on the coronal images.

1:39

I'm going to eliminate the cross-referencing for a moment

1:43

and demonstrate this on the coronal scan where you see the

1:47

inward deviation of the bone secondary to the entrance

1:53

site of the anterior ethmoid artery.

1:56

And this also is present for a posterior ethmoid artery

2:00

that we can sometimes see along

2:03

the medial wall of the orbit.

2:06

In this individual, however,

2:08

we are struck by the presence of an extensive amount of

2:12

orbital emphysema that is air within the orbit as well as

2:17

outside the orbit in the tissues around the mandible,

2:21

the masseter muscle,

2:22

as well as the maxillary antrum, and this is

2:26

usually indicative of multiple fractures.

2:28

Let's focus on the orbital fractures.

2:31

However,

2:32

for this patient, we will focus on the coronal imaging

2:36

because this is the best sequence to

2:39

identify orbital floor fractures.

2:42

Here we see that the patient has dramatic depression

2:46

of the orbital floor bilaterally.

2:51

The bone of the orbit which should lie across this A has

2:56

been reflected medially. And now what is seen here is

3:00

herniation into the maxillary

3:01

antrum is fat as well as the inferior rectus muscle.

3:07

We note on the right side that the medial orbital wall has

3:12

also been fractured with fat coursing medially and the

3:17

orbital floor is also depressed with the inferior

3:21

rectus muscle also being reflected downward.

3:24

If we look at this with soft tissue windows, we can see the

3:29

abnormal configuration of the inferior

3:33

rectus muscle bilaterally.

3:37

And if we were to draw in the expected location of the

3:41

orbital floor, we would note that the muscles are herniated

3:46

below the level of the orbital floor

3:49

in what we would term entrapment.

3:51

When those orbital muscles are entrapped, the patient often

3:55

will have restriction of gaze and

3:57

that may lead to diplopia.

3:59

Orbital entrapment syndrome of the muscles is one of the

4:02

indications for prompt surgical correction of

4:05

the fracture on the soft tissue windows.

4:08

We would also look for injury to the

4:11

globe and to the retrobulbar space.

4:14

And as we look at these axial scans, although there is a

4:18

sense of amount of air around the globes, there is no

4:21

injury to the globe and there is no retrobulbar hematoma.

4:26

Retrobulbar hematoma could lead to compression of the

4:29

optic nerve and orbital compartment syndrome where you

4:35

have increased pressure in the orbit such that it

4:39

compresses the vascular supply to the optic nerve leading

4:43

to the potential complication of orbital trauma and

4:45

orbital compartment syndrome which

4:47

is ischemic optic neuropathy.