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

Apr 25
1/Radiologist not answering the phone?

Just want a quick read on that stat head CT?

Here's a little help on how to do it yourself w/a thread on how to read a head CT! Image
2/In bread & butter neuroimaging—CT is the bread—maybe a little bland, not super exciting—but necessary & you can get a lot of nutrition out of it

MRI is like the butter—everyone loves it, it makes everything better, & it packs a lot of calories. Today, we start w/the bread! Image
3/The most important thing to look for on a head CT is blood.

Blood is Bright on a head CT—both start w/B.

Blood is bright bc for all it’s Nobel prizes, all CT is is a density measurement—and blood is denser (thicker) than water & denser things are brighter on CT Image
Read 20 tweets
Apr 23
1/Time to FESS up! Do you understand functional endoscopic sinus surgery (FESS)?

If you read sinus CTs, you better know what the surgeon is doing or you won’t know what you’re doing!

Here’s a thread to make sure you always make the important findings! Image
2/The first step is to insert the endoscope into the nasal cavity.

The first two structures encountered are the nasal septum and the inferior turbinate. Image
3/So on every sinus CT you read, the first question is whether there is enough room to insert the scope.

Will it go in smoothly or will it be a tight fit? Image
Read 19 tweets
Apr 21
1/Ready for a throw down?

MMA fights get a lot of attention, but MMA (middle meningeal art) & dural blood supply doesn’t get the attention it deserves.

A thread on dural vascular anatomy! Image
2/Everyone knows about the blood supply to the brain.

Circle of Willis anatomy is king and loved by everyone, while the vascular anatomy of the blood supply to the dura is the poor, wicked step child of vascular anatomy that is often forgotten Image
3/But dural vascular anatomy & supply are important, especially now that MMA embolizations are commonly for chronic recurrent subdurals.

It also important for understanding dural arteriovenous fistulas as well. Image
Read 17 tweets
Apr 16
1/ Need a global perspective on dementia?

Do you know the global cortical atrophy (GCA) score for evaluating dementia patients—or are you still gestalting volume loss???

Don’t estimate when you can calculate!

Here’s a thread of what you need to know about the GCA score! Image
2/The global cortical atrophy score calculates cortical volume loss on a scale of 0-3 in 13 different regions & ventricular dilatation

Gyri shrink down w/atrophy, the same way your cheeks shrink down with aging! Image
3/Gyri look like lips with around a mouth of sulcal space.

Without volume loss, the gyri look like big fat pursed model lips

But w/volume loss they open up like the scream w/thinning of the lips Image
Read 9 tweets
Apr 14
1/Wish that your knowledge of autoimmune encephalitis was automatic?

Do you feel in limbo about limbic encephalitis?

Do you know the patterns?

Read on for what you need to know in this month's @RadioGraphics review!



@cookyscan1 @RadG_Editor doi.org/10.1148/rg.240…Image
@RadioGraphics @cookyscan1 @RadG_Editor 2/Two pearls:
(1) Most common pattern is limbic encephalitis
(2) Small cell can cause any autoimmune pattern.

You can remember the causes by the demographic:
Young man: testicular
Older: Small cell
Woman with psychiatric symptoms (limbic): breast Image
@RadioGraphics @cookyscan1 @RadG_Editor 3/Limbic encephalitis is the most common pattern

But it has many, many different causes

Remember--limbic involvement is shaped like a question mark!

So for limbic encephalitis, the cause remains a question bc differential is so broad

Must question & clinically correlate! Image
Read 8 tweets
Apr 2
1/One important aspect to stroke care is well, ASPECTS.

It’s a simple score system—but it’s important to understand all aspects!

Read on for the latest research on ASPECTS in this month’s @theAJNR SCANtastic!

ajnr.org/content/46/3/5…Image
2/ASPECTS stands for “Alberta Stroke Program Early CT Score.”

It’s meant to replace gestalt-ing what percent of the MCA territory is infarcted.

Instead, it uses a 10-pt score to semi-quantitate the infarcted tissue in the MCA territory on non-contrast head CT Image
3/You can think of it as a score card for the MCA.

For each region of MCA territory NOT infarcted, the pt gets one point—for a highest score of 10, and lowest score of 0 Image
Read 18 tweets

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