Lea Alhilali, MD Profile picture
Feb 1, 2023 15 tweets 8 min read Read on X
1/If all you know is: To Zanzibar By Motor Car—then you don’t even know half of facial nerve anatomy—literally!

Here’s a #tweetorial on the facial nerve anatomy you don’t know!

#medtwitter #neurotwitter #neurorad #radres #meded #FOAMed #neurosurgery #neurology #radtwitter
2/On coronal MRI sequences, the brainstem in the region of the facial nerve looks like a bodybuilder.

But it looks like one of those body builders who concentrates only on upper body workouts, so they are huge up top (the pons) & but have chicken legs (the medulla)
3/Facial nerve comes out in this region from between the pons & medulla.

It looks like a weightlifting belt, coming out from the waist between the giant pons upper body & the medulla chicken legs
4/Intracranial segments of the facial nerve follow the stages of life.

To begin, you are born. So is the facial nerve.

It leaves the pons at the root exit point—just as you exit your mother’s womb at birth
5/Next is the attached segment. This is the next stage of life

Just like after birth, you are very attached to your mother in childhood, so too is the facial nerve “attached” to the pons after its birth, like a little kid

It runs closely along the pons undersurface at first
6/Next stage of life is when you must finally leave the safety of clinging to your parents

So too must the facial nerve leave the undersurface of the pons. This is called the root detachment point

You can remember this b/c most teenagers are very cool & “detached” at this age
7/Next is stage of life is transitional.

After leaving for college, you’re not quite independent—you still go home & do your laundry & beg for money! So it’s a “transitional zone” for you

Same for facial nerve—initially it’s “transitional” between central & peripheral myelin
8/Finally is the cisternal segment. This is the stage of life when you’re finally mature & go out on your own

Same for the facial nerve. It’s left the central myelin of its pontine mama behind & is now fully peripheral myelin. It’s ready to go out & meet CN VIII in the IAC
9/The full course of the facial nerve is best seen on coronal images

On the axial images, you can see the portions after it has left the pons (root detachment point, transitional zone & cisternal segment)

You can’t see more proximally b/c this is covered by the pons on axials
10/It’s important to know this anatomy so you can look for compression of the facial nerve in this region.

Most often it’s compression from a vessel (microvascular compression).

Microvascular compression can lead to hemifacial spasm
11/This is most common in the transitional zone b/c central myelin is vulnerable & here central myelin is out in the cistern

It’s like how kids are most likely to get into trouble in the college years—b/c you’re still a kid, but now exposed to more temptations/real world danger
12/You can see compression of the transitional zone on the axial images b/c the transitional zone is after the nerve has left from under the pons

So always look for vessels compressing the nerve right next to pons—like bad influences bringing you trouble during the college years
13/Besides the college years, the next most common time to get into trouble is your childhood. Same w/the facial nerve

Next most common place for microvascular compression is the attached segment. Even though its under the roof of its pontine mama, it can still get punched
14/But you can’t see this area on axial images b/c it’s hidden under the pons!

Most common cause of a failed decompression is that transitional zone compression is relieved but attached segment compression is missed

So always check coronals for attached segment compression!
15/So now you know the intracranial facial nerve by remembering how its segments follow the stages of life—& you know where to look for compression by remembering which stages of life are vulnerable to trouble

Hopefully this will keep you out of trouble w/facial nerve anatomy!

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Lea Alhilali, MD

Lea Alhilali, MD Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @teachplaygrub

Aug 1
1/They say form follows function!

Brain MRI anatomy is best understood in terms of both form & function.

Here’s a short thread to help you to remember important functional brain anatomy--so you truly can clinically correlate! Image
2/Let’s start at the top. At the vertex is the superior frontal gyrus. This is easy to remember, bc it’s at the top—and being at the top is superior. It’s like the superior king at the top of the vertex. Image
3/It is also easy to recognize on imaging. It looks like a big thumb pointing straight up out of the brain. I always look for that thumbs up when I am looking for the superior frontal gyrus (SFG) Image
Read 12 tweets
Jul 29
1/Talk about bad blood!

Do you know when a hematoma is going to expand?

Read on for month’s @theAJNR SCANtastic on all you need to know about imaging intracranial hemorrhage!

ajnr.org/content/46/7/1…Image
@TheAJNR 2/Everyone knows about the spot sign for intracranial hemorrhage

It’s when arterial contrast is seen within a hematoma on CTA, indicating active
extravasation of contrast into the hematoma.

But what if you want to know before the CTA? Image
@TheAJNR 3/Turns out there are non-contrast head CT signs that a hematoma may expand that perform similarly to the spot sign—and together can be very accurate.

How can you remember what they are? Image
Read 9 tweets
Jul 25
1/Time to go with the flow!

Hoping no one notices you don’t know the anatomy of internal carotid (ICA)?

Do you say “carotid siphon” & hope no one asks for more detail?

Here’s a thread to help you siphon off some information about ICA anatomy! Image
2/ICA is like a staircase—winding up through important anatomic regions like a staircase winding up to each floor Lobby is the neck.

First floor is skullbase/carotid canal. Next it stops at the cavernous sinus, before finally reaching the rooftop balcony of the intradural space.Image
3/ICA is divided into numbered segments based on landmarks that denote transitions on its way up the floors.

C1 is in the lobby or neck.

You can remember this b/c the number 1 looks elongated & straight like a neck. Image
Read 10 tweets
Jul 23
1/My hardest thread yet! Are you up for the challenge?

How stroke perfusion imaging works!

Ever wonder why it’s Tmax & not Tmin?

Do you not question & let RAPID read the perfusion for you? Not anymore! Image
2/Perfusion imaging is based on one principle: When you inject CT or MR intravenous contrast, the contrast flows w/blood & so contrast can be a surrogate marker for blood.

This is key, b/c we can track contrast—it changes CT density or MR signal so we can see where it goes. Image
3/So if we can track how contrast gets to the tissue (by changes in CT density or MR signal), then we can approximate how BLOOD is getting to the tissue.

And how much blood is getting to the tissue is what perfusion imaging is all about. Image
Read 18 tweets
Jul 21
1/Do you know all the aspects of, well, ASPECTS?

Many know the anterior circulation stroke scoring system—but posterior circulation (pc) ASPECTS is often left behind

25% of infarcts are posterior circulation

Do you know pc-ASPECTS?!

Here’s how to remember pc-ASPECTS! Image
2/Many know anterior circulation ASPECTS.

It uses a 10-point scoring system to semi-quantitation the amount of the MCA territory infarcted on non-contrast head CT

If you need a review: here’s my thread on ASPECTS: Image
3/But it’s only useful for the anterior circulation.

Posterior circulation accounts for ~25% of infarcts.

Even w/recanalization, many of these pts do poorly bc of the extent of already infarcted tissue.

So there’s a need to quantitate the amount of infarcted tissue in these ptsImage
Read 12 tweets
Jul 2
1/The medulla is anything but DULL!

Does seeing an infarct in the medulla cause your heart to skip a beat?

Does medullary anatomy send you into respiratory arrest?

Never fear, here is a thread on the major medullary syndromes! Image
2/The medulla is like a toll road.

Everything going down into the cord must pass through the medulla & everything from the cord going back up to the brain must too.

That’s a lot of tracts for a very small territory. Luckily you don’t need to know every tract Image
3/Medulla has 4 main vascular territories, spread out like a fan: anteromedial, anterolateral, lateral, and posterior.

You don’t need to remember their names, just the territory they cover—and I’ll show you how Image
Read 18 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Don't want to be a Premium member but still want to support us?

Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!

Ethereum

0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy

Bitcoin

3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us!

:(