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

Mar 21
1/Don't fall for the siren song of calling all bright round objects at foramen of Monro colloid cysts.

Like a true siren song, this may be a TRAP!

If you hear the call of colloid—read this first!

Here's a thread about lesions here that can trap you--& how you can avoid them! Image
2/Here are 3 lesions, all round and bright and in the region of the foramen of Monro.

Can you tell from the images which is a colloid cyst and which may be something else?

Choose which one or ones you think are a colloid cyst! Image
3/In this case it was A!

B was a tortuous basilar

C was a cavernoma of the chiasm/hypothalamus that had bled and projected into the third ventricle. Image
Read 12 tweets
Mar 16
1/Remembering spinal fracture classifications is back breaking work!

A thread to review the scoring system for thoracic & lumbar fractures—“TLICS” to the cool kids! Image
2/TLICS scores a fx on (1) morphology & (2) posterior ligamentous complex injury

Let's start w/morphology

TLICS scores severity like the steps to make & eat a pizza:

Mild compression (kneading), strong compression (rolling), rotation (tossing), & distraction (tearing in) Image
3/At the most mild, w/only mild axial loading, you get the simplest fx, a compression fx—like a simple long bone fx--worth 1 pt.

This is like when you just start to kneading the dough. There's pressure, but not as much as with a rolling pin! Image
Read 13 tweets
Mar 14
1/The 90s called & wants its carotid imaging back!

It’s been 30 years--why are you still just quoting NASCET?

Do you feel vulnerable when it comes to identifying plaque vulnerability?

Here’s a thread to help you identify high risk plaques with carotid plaque imaging Image
2/Everyone knows the NASCET criteria:

If the patient is symptomatic & the greatest stenosis from the plaque is >70% of the diameter of normal distal lumen, patient will likely benefit from carotid endarterectomy.

But that doesn’t mean the remaining patients are just fine! Image
3/Yes, carotid plaques resulting in high grade stenosis are high risk.

But assuming that stenosis is the only mechanism by which a carotid plaque is high risk is like assuming that the only way to kill someone is by strangulation. Image
Read 25 tweets
Mar 12
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
Mar 10
1/I always say you can tell a bad read on a spine MR if it doesn’t talk about lateral recesses.

What will I think when I see your read? Do you rate lateral recess stenosis?

Here’s a thread on lateral recess anatomy & a grading system for lateral recess stenosis Image
2/First anatomy.

Thecal sac is like a highway, carrying the nerve roots down the lumbar spine.

Lateral recess is part of the lateral lumbar canal, which is essentially the exit for spinal nerve roots to get off the thecal sac highway & head out into the rest of the body Image
3/Exits have 3 main parts.

First is the deceleration lane, where the car slows down as it starts the process of exiting.

Then there is the off ramp itself, and this leads into the service road which takes the car to the roads that it needs to get to its destination Image
Read 21 tweets
Mar 3
1/Does PTERYGOPALATINE FOSSA anatomy feel as confusing as its spelling?

Does it seem to have as many openings as letters in its name?

Are you pterrified of the pterygopalatine fossa (PPF)?

Let this thread on PPF anatomy help you out. Image
2/The PPF is a crossroads between the skullbase & the extracranial head and neck

There are 4 main regions that meet here:

(1) Skullbase itself posteriorly, (2) nasal cavity medially, (3) infratemporal fossa laterally, and (4) orbit anteriorly. Image
3/At its most basic, you can think of the PPF as a room with 4 doors opening to each of these regions: one posteriorly to the skullbase, one medially to the nasal cavity, one laterally to the infratemporal fossa, and one anteriorly to the orbit 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!

:(