0:00

This is a patient who presented with recurrent

0:04

squamous cell carcinoma of the skin.

0:07

As we scroll the images on the T1-weighted scans, we

0:11

see the abnormality in the soft tissue anterior

0:16

to the maxillary antrum on the left side.

0:19

This is coursing towards the nasal area as well.

0:25

And this is demonstrated nicely outlined by the

0:28

subcutaneous fat as it courses to the nasal ala.

0:32

Now, one might ask, well,

0:34

what does this have to do with the orbit?

0:36

So as we continue to scroll this

0:39

case further superiorly,

0:42

we come to the location of the junction of

0:45

the orbit with the maxillary antrum.

0:48

And we see that there continues to be soft tissue

0:50

present in the skin as well as extending to the

0:55

anterior border of the maxillary antrum on the T1,

0:59

and T2-weighted images on the postgadolinium fat-suppressed scan.

1:04

This enhancement can be seen extending to the

1:09

orbital floor at the junction

1:12

with the maxillary antrum.

1:14

What I'd like to do is to demonstrate this on the T1-weighted

1:17

scans involving the axial

1:21

and coronal plane. On the axial scan,

1:25

as we get to the edge of the orbit,

1:28

we notice contrast enhancement at the orbital floor

1:33

junction with the left maxillary antrum.

1:38

And this is seen

1:41

in an elliptical fashion at the orbit

1:45

maxillary antrum junction.

1:47

I'm going to just zoom in on the abnormality on the

1:52

coronal image and move the section just a little

1:56

bit better into our field of view.

1:58

What we see here

2:00

is at the orbital floor junction with the maxillary

2:04

antrum an area of contrast enhancement

2:07

which is not the extraocular muscle.

2:11

Here is the inferior oblique

2:15

joining with the inferior rectus muscle, the medial

2:18

rectus muscle, and these all will show contrast

2:21

enhancement. Superior rectus muscle here.

2:23

What we are seeing here, however,

2:25

is something below the muscle at the orbital floor

2:30

and this represents the infraorbital nerve.

2:35

The infraorbital nerve runs in the infraorbital

2:39

foramen and this is located

2:42

within the orbital floor.

2:44

It's an area that we look at particularly with

2:46

regard to orbital floor fractures to determine whether

2:50

or not that fragment is involved.

2:52

The reason why it's important is that if that

2:54

fragment is involved, it usually leads

2:57

to paresthesias or hypoesthesia.

3:00

Within the infraorbital nerve sensory distribution

3:03

which is along the upper cheek and malar region.

3:08

So if we contrast this with the contralateral side,

3:12

normally the infraorbital nerve does

3:15

not show contrast enhancement.

3:17

What we are seeing here is perineural spread of

3:22

squamous cell carcinoma of the skin along the

3:25

infraorbital nerve into the orbit.

3:28

Skin cancers can do this.

3:31

Neurotropic melanoma is one of the skin cancers which

3:35

also has a predilection for perineural spread.

3:37

However, because squamous cell carcinoma is so much more

3:41

common than melanoma in this location,

3:44

it is the most common skin cancer to cause perineural spread.

3:49

Basal cell carcinoma also can cause perineural

3:53

spread from skin cancer.

3:56

This is the least likely between squamous cell neurotropic melanoma

4:00

and basal cell carcinoma.

4:02

We'll talk about perineural spread also when we're

4:06

dealing with minor salivary gland tumors,

4:09

such as adenoid cystic carcinoma.

4:11

Adenoid cystic carcinoma is the tumor that has the

4:15

greatest predilection for perineural spread,

4:18

being present in greater than 60% of cases.