Lea Alhilali, MD Profile picture
Nov 4, 2022 15 tweets 8 min read Read on X
1/Hate it when one radiologist called the stenosis mild, the next one said moderate--but it was unchanged?!

Here’s a #tweetorial of a lumbar grading system that’s easy, reproducible & evidence-based

#medtwitter #spine #neurosurgery #radres #neurorad #meded #FOAMed #FOAMrad Image
2/Lumbar stenosis has always been controversial. In 2012, they tried to survey spine experts to come to a consensus as to what are the most important criteria for canal & foraminal stenosis. And the consensus was…that there was no consensus. So what should you use to call it? Image
3/Well, you don’t want just gestalt it—that is a recipe for inconsistency & disagreement. But you don’t want to measure everything either—measurements are not only cumbersome, they introduce reader variability & absolute measurements don’t mean the same thing in every patient. Image
4/Think of it functionally. Nerves need to fit in their space, like you fit in clothing. Mild stenosis is like comfy clothes—no squeezing. Moderate stenosis clothing isn’t loose, but there isn’t extra room either. Severe stenosis is like too tight jeans, your body gets compressed Image
5/So how do we tell if the nerves have enough room—if the clothing fits loosely, tight, or too tightly? We look at the space around them. For the canal, it is CSF—if there's enough room, extra space will be filled by CSF. For foramina, it is fat—extra room is filled by fat. Image
6/For mild canal stenosis, there is mild attenuation of the CSF space, but there is still plenty of CSF around, just like there is plenty of room in your comfy sweat pants Image
7/For moderate canal stenosis, the canal starts closing in, so there is less CSF around and the nerve roots appear aggregated. It’s like the clothes you wear to the club, there isn’t much room between your skin & the clothing, but you can still fit into them (hopefully) Image
8/Severe canal stenosis is the too tight jeans. The canal doesn’t just hug up to the nerve roots, it compresses them. Like your belly after a big meal trying to get into tight jeans, they get squished and deformed in order to fit, so they can’t be separated from each other. Image
9/This classification isn’t just easy to remember, it’s also evidence based. This is the Lee classification that has excellent reproducibility not just among radiologists, but among everyone. And it does correlate w/increasing symptoms. Image
10/For foraminal narrowing, the nerve inside the foramen has fat around it on four sides that can be attenuated as the space gets tighter. How many sides are attenuated determines how severe the stenosis is. Image
11/Mild stenosis is where you have loss of the fat on 2 sides. So it is still comfy clothing bc the fat is preserved on the other two sides, so you still have lots of space. Image
12/For moderate stenosis, you lose the space on all four sides, but the nerve itself is not compressed or deformed. Like a sleek outfit, it shows your curves, but doesn’t deform them. It’s not a comfy outfit, per se, & I wouldn’t eat a lot while wearing it, but it’s not too small Image
13/For severe stenosis, we are trying to fit into those jeans from high school and it isn’t going well. You are squishing in everything you can to get it to fit. Same with the foramen—the fat isn’t just gone, the nerve is compressed and deformed. Image
14/This is also named the Lee system. It fits well with the Lee classification for canal stenosis. It also is extremely reproducible and correlates with findings at surgery.

So you don’t have to remember a complicated system—just ask yourself, how does the clothing fit? Image
15/So put away your measuring calipers! You can end the inter-observer variability. These systems are easy to remember, make sense, and are based in evidence. As they say, if it fits—wear it! Image

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More from @teachplaygrub

Dec 6
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
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The first two structures encountered are the nasal septum and the inferior turbinate. Image
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Will it go in smoothly or will it be a tight fit? Image
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Dec 2
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
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It also important for understanding dural arteriovenous fistulas as well. Image
Read 17 tweets
Nov 27
1/Controversy in radiology can get tense!

The Mt Fuji sign for tension pnemocephalus is under scrutiny. When should you call it?

A thread about imaging this important neurosurgery complication Image
2/First, let’s clarify about what the Mt Fuji sign actually is

Most are familiar with the fact that large collections of pneumocephalus can compress the frontal lobes—making them look like the slopes of a mountain

But this isn’t actually enough to call Mt Fuji. Image
3/You also need to see frontal lobe separation

This means subdural air tension > the CSF surface tension between the frontal lobes

Water has one of the highest liquid surface tensions—so means pressure is high

This little V is why it looks like Mt Fuji, not any mountain Image
Read 9 tweets
Nov 25
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
Nov 20
1/Time to rupture all your misconceptions about aneurysms!

When you see an aneurysm on imaging, do you know if it’s at high risk of rupture?

This month’s @theAJNR SCANtastic shows you which aneurysms are bursting w/risk!

ajnr.org/content/45/11/…Image
2/Aneurysm rupture is a devastating even, as it results in subarachnoid hemorrhage & complications such as hydrocephalus, vasospasm, infarcts, & death.

Preventing it by treating aneurysms before they rupture is key. But you also don’t want to overtreat. Image
3/To remember what features make an aneurysm more likely to rupture, think what makes that guy at the bar that you angered more likely to rupture & start a fight.

What makes him more likely to rupture are the same things that make aneurysms more likely to rupture Image
Read 19 tweets
Nov 11
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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