0:01

I'd like to use this case to demonstrate the facial

0:05

nerve as it courses through the parotid gland.

0:09

So this was a patient who had a Bell's palsy

0:13

who had a left-sided facial paralysis.

0:16

And on this image, you see that we are looking at

0:19

T1-weighted fat-suppressed post-gadolinium

0:23

enhanced scans.

0:24

So T1-weighted CSF is dark, fat-suppressed,

0:29

dark fat. Post-gadolinium-enhanced scan,

0:32

you can see the cavernous sinus

0:34

here in portions of the dura.

0:36

But what we also see is the facial nerve, and we see

0:39

the labyrinthine portion as well as the tympanic

0:43

portion of the facial nerve enhancing.

0:46

This then would probably be the area of the geniculate

0:48

ganglion with the greater superficial

0:51

petrosal nerve coming off of it.

0:54

Again, I'm showing you the enhancement of the

0:57

facial nerve in its labyrinthine and tympanic portion

1:00

with the greater superficial petrosal nerve

1:02

coming off anteriorly.

1:04

As we follow the facial nerve down, we have the

1:07

tympanic portion, which is showing enhancement here.

1:13

This is the horizontal or tympanic

1:16

portion of the facial nerve.

1:19

And then scrolling more inferiorly, we have the

1:23

intramastoid descending portion of the facial nerve.

1:28

And you notice that the nerve on the left abnormal

1:32

side is larger than the nerve on the right side.

1:36

Now,

1:37

the mastoid portion of the facial nerve may or may

1:42

not show enhancement normally. In this case,

1:44

the pathology is that the nerve is enlarged and

1:48

enhancing, as well as the fact that the

1:50

labyrinthine portion enhanced.

1:53

So if we continue to scroll downward,

1:56

we come to the stylomastoid foramen, and here we are

2:02

at the inferior portion of the mastoid bone.

2:04

We got a little bit of the styloid process

2:08

identified.

2:09

And then, this is the facial nerve coming

2:12

out into the parotid gland.

2:14

Now,

2:17

the intraparotid portion of the facial nerve

2:19

should not enhance. As you're going to see

2:22

as I scroll, the facial nerve remains enhancing.

2:26

If we look at the contralateral side, we don't see

2:28

anything analogous enhancing in the parotid gland.

2:32

So based on this, we can identify the superficial

2:36

and deep portions of the parotid gland.

2:38

On this pulse sequence, you see that the parotid

2:41

tissue is dark, probably because it has

2:44

some fatty infiltration to it.

2:46

And this portion of the parotid gland would

2:49

be termed the superficial portion.

2:55

This portion, which goes more medially, would be

3:00

considered the deep portion.

3:02

And we see that both on the right side, as well

3:06

as the left side. Now, on the right side,

3:09

we don't have an enhancing facial nerve to

3:12

identify the different lobes. Again,

3:17

we might say the word lobes, but we mean portions.

3:20

So if you follow the facial nerve forward,

3:23

you can see that it innervates the parotid gland.

3:27

Normally on the side, for example,

3:30

that is not pathologic,

3:32

we don't see the facial nerve.

3:34

And what we see, as far as these little interstices

3:37

here or branching structures, actually represent

3:41

either veins or the ductal system.

3:47

So this was a nice example of pathology in a patient

3:50

who had facial nerve enhancement, allowing us

3:54

to be able to see the superficial and deep portions.

3:58

Again, notice that the facial nerve has an intimate

4:01

relationship with the retromandibular vein.

17:31

the deep portion.