0:00

This was a patient that ended up having a right facial nerve palsy,

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but it may have come off as Bell's Palsy.

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Did you guys appreciate the enhancement involving the right facial nerve? Yeah.

0:14

Good, good. So when I look at the internal auditory canal,

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the key thing here is that this segment right here is a distal aspect of the

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canicular segment. And this segment right here is the labyrinthine segment.

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This is the anterior genu. The Gena ganglion is gonna be here,

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and this is the beginning of the tympanic segment of the facial nerve.

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And then when we look at this image right here,

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we can see this diffuse thickening involved the tympanic segment of the facial

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nerve. And then once we go a little bit more inferiorly,

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you can see the enhancement of the right facial nerve compared to the left side.

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So this is this diffuse enhancement of the facial nerve.

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And this would be consistent. So based on this imaging alone,

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this is not quote unquote Bell's palsy. This is facial nerve enhancement.

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Now, Bell's palsy is that if the enhancement actually, um,

1:02

resolves within six weeks to three months, that's classic Bell's palsy.

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If you continue to have a pa facial palsy after three months,

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then you start to have,

1:12

then you have to start worrying about other causes of

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facial nerve enhancement.

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And that could be due to another inflammatory process that involves the ear.

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And if I told you this patient had right ear vesicles,

1:27

then you'd have to consider Ramsay Hunt syndrome.

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Now I think about 30 or 40% of patients that actually are felt to have

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Bell's palsy that don't resolve actually have Ramsay Hunts syndrome.

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But from a pure radiological standpoint,

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we can't really differentiate Ramsay Hunts syndrome for Bell's palsy.

1:45

The other big thing we have to worry about are neoplasms and the sort of,

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the classic thing that we learn about is a tumor involving the parotid gland

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that has retrograde perineural spread along the descending portion of the facial

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nerve. So, you know, I like to do some strange things in my life.

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And so one of the things I love to do is actually, um, read the old literature.

2:07

In fact, you know, I'm giving a talk in India again next week, um,

2:11

on Leonardo da Vinci, uh,

2:13

and making the case that he was his first skull base radiologist.

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And I'm going back and reading his papers that he wrote about 300 years ago.

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It's actually quite fascinating.

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And this was a paper that was actually written in 1821.

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It was written by this person and this person is Charles Bell.

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And so he was actually, uh, a British surgeon, a Scottish surgeon I should say.

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'cause this is the Scottish flag of whom the facial nerve is named after.

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And this beautiful illustration right here on the left hand side is actually

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from his original paper. So this wasn't created by, you know, modern day, uh,

2:46

illustrator. This was actually his paper, uh, for over two, uh, gosh, yeah. Uh,

2:50

over 200 years ago. 250 years ago, I should say 200 years ago. Is that right?

2:54

Yeah, 200 years ago. So, you know, my friend, uh, uh,

2:58

from Singapore Vincent Chong made this great, uh, uh,

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quote that the facial nerve makes. Its hu,

3:04

makes us human because it makes us laugh and it makes us cry.

3:09

So this is an example of what the facial nerve looks like.

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So the facial nerve exits a stylo mastoid frame and as this main trunk,

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and then it has these five primary branches.

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And there are the temporal branch here, the zygomatic branch here,

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the buccal branch here.

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Then you have a marginal mandibular branch and a deep cervical branch.

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And notice how the facial nerve is basically in a plane.

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And because it's in a plane,

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that facial nerve separates the superficial lobe from the deep lobe of the

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parotid gland. So this is an intraoperative view of the facial nerve right here.

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And you can see the various branches. So when we look for the facial nerve,

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the best way to look at it is to find it,

3:51

is that we look at the skull base and we look at the styloid process and the

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mastoid air cells.

3:56

And this arrow points right here at the facial nerve as its exiting the stylo

4:01

mastoid foramen. And we can see it's in the fat. So on the opposite side,

4:05

there's a fat plane surrounding the facial nerve.

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And this is an example of the facial nerve on heavily T two weighted images.

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If you do your imaging just right, sometimes you can actually see that nerve.

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Now, anytime that we have a tumor involving the parotid gland,

4:21

it can extend deeply to involve the facial nerve as it exits the sty

4:26

mastoid fen, and then it can grow retrograde.

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And this is an example here of retrograde peroneal spread, uh,

4:34

of tumor along the facial nerve.

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And this sort of illustrates what we see here on the schematic illustration.

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So when we look at the normal anatomy of the facial nerve, in this case,

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I'll start from the back and go forward. These are the various branches.

4:49

This is the main trunk of the facial nerve here.

4:52

This is the descending portion of the facial nerve. This is the posterior genu.

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This is the typa segment of the facial nerve. There's our anterior genu.

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Here's our geniculate ganglion. This is the labyrinthine segment,

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and this is the canicular segment.

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So this is an example of tumor involved in the descending portion of the facial

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nerve. This is an example of tumor involved in the posterior genu,

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which cor correlates with this schematic illustration here.

5:18

This is an axial image demonstrating retro, uh,

5:21

an abnormal enhancement along the typa segment of the facial nerve.

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And this is an example of tumor growing along the typa

5:30

segment. This is our anterior genu. This is our geniculate ganglion.

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This is the labyrinthine segment which correlates with this area here.

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And there's tumor along the canalicular segment.

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So this is just an example in this case of retrograde perineural spread of tumor

5:46

along the facial nerves. So in the particular case that I showed, um,

5:52

this past week on the facial nerve that was Bell's Palsy,

5:55

that demonstrates a segmental enhancement of the facial nerve.

5:58

And it just leads us into discussion of the normal appearance of the facial

6:01

nerve and the normal anatomy. So any questions with that?

6:06

So for the peral split,

6:09

is there any particular type of tumor or any kind of ancy can spread through the

6:14

facial nerve?

6:15

Yeah, it's a great question. The,

6:16

the most common tumor that you'll see involving the facial nerve is from the

6:20

parotid gland, is gonna be adenoid cystic carcinoma.

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But other tumors that can spread along the facial nerve can be, uh, in the, um,

6:27

would be squamous cell carcinoma. And you can also have lymphomas,

6:31

although lymphoma is very rare in the parid gland.