Lea Alhilali, MD Profile picture
Jan 23, 2023 10 tweets 6 min read Read on X
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 #tweetorial to help you w/ICA #anatomy!

#medtwitter #meded #neurotwitter #neurorad #radres #FOAMed 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
4/C2 is the petrous or horizontal segment. This is where the ICA gets to the next floor, the skullbase

I remember this b/c the ICA makes a curve forward here, like a swan’s neck--and number 2 has a forward, swan like curve that looks just like the curve of the petrous segment Image
5/C3 is the lacerum segment—from above foramen lacerum to petrolingual ligament.

It’s easy to remember b/c lacerum comes from the latin word for torn (b/c foramen lacerum is irregular like a tear or laceration)

Number 3 zig zags like a laceration or torn edge, so C3 = lacerum Image
6/C4 is the cavernous segment

Cavernous segment has the anterior genu. Here, the ICA makes a curve back, so it looks like a knee (genu is latin for knee)

You can remember C4 is cavernous bc the number 4 has a curve back like the anterior genu of the cavernous ICA, like a knee Image
7/C5 is the clinoid segment—at the ant. clinoid process

Clinoid process gets its name from its sloped shape. It’s from the same latin root as recline (CLIN)

And we all take a break (take five some might say😉) by sitting back or reclining

Take FIVE & reCLINE. C5 is CLINoid Image
8/C6 is the ophthalmic segment.

I remember this b/c the circle of the number 6 looks like eyes and its curve looks like eyebrows.

So 6 is an eye = ophthalmic Image
9/C7 is the communicating or terminal segment

You can remember this bc the number 7 looks like the ICA ending & giving off the PCOMM

The number 7 has the shape of a turn off right before the road ends—& the ICA gives off the PCOMM in its C7 segment right before terminating Image
10/Now you can remember all the segments of the ICA!

Hopefully this will help you to be precise in your localization and siphon away the term “carotid siphon”!! Image

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More from @teachplaygrub

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
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You don’t need to remember their names, just the territory they cover—and I’ll show you how Image
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1/Time is brain! But what time is it?

If you don’t know the time of stroke onset, are you able to deduce it from imaging?

Here’s a thread to help you date a stroke on MRI! Image
2/Strokes evolve, or grow old, the same way people evolve or grow old.

The appearance of stroke on imaging mirrors the life stages of a person—you just have to change days for a stroke into years for a person

So 15 day old stroke has features of a 15 year old person, etc. Image
3/Initially (less than 4-6 hrs), the only finding is restriction (brightness) on diffusion imaging (DWI).

You can remember this bc in the first few months, a baby does nothing but be swaddled or restricted. So early/newly born stroke is like a baby, only restricted Image
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Jun 27
1/”I LOVE spinal cord syndromes!” is a phrase that has NEVER, EVER been said by anyone.

Do you become paralyzed when you see cord signal abnormality?

Never fear—here is a thread on all the incomplete spinal cord syndromes to get you moving again! Image
2/Spinal cord anatomy can be complex. On imaging, we can see the ant & post nerve roots. We can also see the gray & white matter. Hidden w/in the white matter, however, are numerous efferent & afferent tracts—enough to make your head spin. Image
3/Lucky for you, for the incomplete cord syndromes, all you need to know is gray matter & 3 main tracts. Anterolaterally, spinothalamic tract (pain & temp). Posteriorly, dorsal columns (vibration, proprioception, & light touch), & next to it, corticospinal tracts—providing motor Image
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Jun 23
1/Do you get a Broca’s aphasia trying remember the location of Broca's area?

Does trying to remember inferior frontal gyrus anatomy leave you speechless?

Don't be at a loss for words when it comes to Broca's area

Here’s a 🧵to help you remember the anatomy of this key region! Image
2/Anatomy of the inferior frontal gyrus (IFG) is best seen on the sagittal images, where it looks like the McDonald’s arches.

So, to find this area on MR, I open the sagittal images & scroll until I see the arches. When it comes to this method of finding the IFG, i’m lovin it. Image
3/Inferior frontal gyrus also looks like a sideways 3, if you prefer. This 3 is helpful bc the inferior frontal gyrus has 3 parts—called pars Image
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Jun 19
1/Feeling intoxicated trying to remember all the findings in alcohol use disorder?!

Here’s something to put you in high spirits!

This month’s @Radiographics has the important neuroimaging findings alcohol use disorder!



@cookyscan1 @RadG_editor #RGphx pubs.rsna.org/doi/10.1148/rg…Image
2/There’s an easy rhyme to help you remember the important neuroimaging findings of alcohol use disorder

“Basal ganglia is white...”

Get intrinsic T1 shortening in the BG that makes it look white as a ghost! Image
3/Next “...Cortex is bright”

Acute hyperammonemic encephalopathy cause cortical restricted diffusion, especially the insula, so that it looks as bright as a light bulb! Image
Read 8 tweets
Jun 9
1/Need help reading spine imaging? I’ve got your back!

It’s as easy as ABC!

A thread about an easy mnemonic you can use on every single spine study you see to increase your speed & make sure you never miss a thing! Image
2/A is for alignment

Look for:
(1) Unstable injuries

(2) Malalignment that causes early degenerative change. Abnormal motion causes spinal elements to abnormally move against each other, like grinding teeth wears down teeth—this wears down the spine Image
3/B is for bones.

On CT, the most important thing to look for w/bones is fractures. You may see focal bony lesions, but you may not

On MR, it is the opposite—you can see marrow lesions easily but you may or may not see edema associated w/fractures if the fracture is subtle Image
Read 11 tweets

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