0:01

Let's look at another example of perineural spread.

0:04

In this case, by a large cell undifferentiated carcinoma

0:08

of the parotid gland.

0:11

This is likely a case of squamous cell carcinoma

0:15

of the parotid gland, which I'll get to

0:17

momentarily that dedifferentiated.

0:21

So here we have the parotid gland,

0:23

which is infiltrated.

0:24

It has both a superficial as well as

0:26

a deep portion that is infiltrated.

0:28

You can see that it extends into the parapharyngeal

0:33

space fat. The normal bright signal intensity here

0:36

has been infiltrated, and as we go up superiorly, you

0:40

can see that there has already been

0:43

a temporal bone resection here.

0:46

But there looks like there's a tumor that's

0:48

going through the stylomastoid foramen.

0:53

Not only that,

0:54

but as we scroll superiorly in the region of the

0:59

expected location of the foramen ovale, you see soft

1:04

tissue present, and here you can see that the foramen

1:08

ovale is infiltrated, and the tumor is

1:11

actually coming along the Meckel's cave.

1:14

So here's our carotid artery,

1:16

here's our lower portion of the Meckel's cave on the

1:20

left side, and here we have the

1:21

tumor extending into the

1:28

trigeminal impression, and from there into the

1:32

cavernous sinus. Oh my goodness, look at this.

1:36

Not only is it growing into the cavernous sinus,

1:37

it's growing posteriorly into the basal cisterns and

1:42

compressing the brainstem as it continues

1:46

to grow along the fifth cranial nerve.

1:50

So I'm going to show you this on the T2-weighted

1:53

scan just to point out that it's going to be

1:56

intermediate to dark in signal intensity and

1:58

not bright and therefore needs biopsy.

2:01

This patient already had the diagnosis of large

2:04

cell undifferentiated carcinoma on the T1

2:08

post-contrast scan. You see the avid enhancement of

2:12

the tissue which has grown through the

2:15

foramen ovale into Meckel's cave,

2:17

into the cavernous sinus, and into the prepontine

2:20

cistern on the right side.

2:22

This little structure here is a vein;

2:24

you can ignore that.

2:26

But I wanted to show this case also in the coronal plane.

2:32

Here we are in the coronal plane, and note the

2:35

marked enlargement of the foramen ovale.

2:38

Here's the normal foramen ovale, and here we

2:41

have the marked enlargement of the foramen ovale.

2:44

We have Meckel's cave on the left side,

2:47

the normal side.

2:48

Here's Meckel's cave on the abnormal side, and

2:52

if we continue into the cavernous sinus,

2:55

here's our normal cavernous sinus region.

2:58

Here's the tumor infiltrating the

3:00

cavernous sinus and actually displacing

3:01

the cavernous carotid artery medially.

3:06

This is pretty gross.

3:08

Involvement of the third division of the fifth

3:10

cranial nerve via the auriculotemporal nerve

3:12

by large cell undifferentiated carcinoma,

3:15

which grew into the basal cisterns.

3:18

Here again, this is just a vein,

3:20

so we can ignore that.

3:21

I thought I saw some involvement of

3:23

the 7th cranial nerve as well, but that's not panning out so

3:28

much on the coronals at all.