Lea Alhilali, MD Profile picture
Dec 7, 2022 18 tweets 9 min read Read on X
1/Have disagreements between radiologists on the degree of cervical canal stenosis become a pain in the neck?!
Here’s a #tweetorial on cervical stenosis grading that’s easy, reproducible & evidence based
#medtwitter #spine #neurosurgery #radres #neurorad #meded #FOAMed #FOAMrad Image
2/In the lumbar spine, it is all about the degree of canal narrowing & room for nerve roots. In the cervical spine, we have another factor to think about—the cord. Cord integrity is key. No matter the degree of stenosis, if the cord isn’t happy, the patient won’t be either Image
3/Cord flattening, even w/o canal stenosis, can cause myelopathy. No one is quite sure why. Some say it’s b/c mass effect on static imaging may be much worse in dynamic positions, some say it’s repetitive microtrauma, & some say micro-ischemia from compression of perforators Image
4/Let’s start w/canal stenosis. Measurements have been proposed (<10mm), but this is cumbersome & introduces reader variability. Think functionally. Cord swims in CSF, like a fish in water. Like a fish, it needs room to swim. How much room is in the fish bowl determines stenosis Image
5/Mild stenosis is when your fish bowl decorations take up 1 side of the bowl. Not great, but fish can still swim. Moderate means your decorations take up both sides—swimming is really affected. Severe means you went all out w/decorations & there isn’t any more room for the fish Image
6/The sides of the fish bowl are the ventral & dorsal CSF. So mild canal stenosis is when either the ventral or dorsal CSF is effaced, but the other side of the fish bowl is still empty. Not ideal, but the fish can still swim Image
7/For moderate canal stenosis, both sides of the fish bowl have been filled. So both the ventral and dorsal CSF have been effaced. Now the room to swim has been notably limited Image
8/Finally, in severe canal stenosis, the bowl is completely filled and no CSF is seen. There is no room for the fish in this scenario. Similarly, there is no room for the cord and it is compressed. Not only is there no swimming, the fish has been crushed. Image
9/This classification is to all other classifications like a goldfish is to all other pets—super easy & simple. It’s also evidence based. It's the Muhle classification. It has excellent reproducibility. It hasn’t been correlated w/pain, but it's been correlated w/SSEP & outcomes Image
10/But canal stenosis isn’t enough. Cord flattening can cause myelopathy regardless of degree canal stenosis. It’s like being punched in the face—no matter how far away the hit comes from, it still hurts. Cord flattening is like being punched—it hurts even in mild stenosis Image
11/Think of the canal like a parking space. Even if no one encroaches on your space, if someone opens their door & dings your car, your car is still damaged and you are still mad. Your parking space may still be wide open, but you still have a nick in your door. Image
12/Cord flattening has 3 degrees. Either it’s not there, there, or so bad it causes cord damage. Think of it like a fight. Cord deformity w/o signal is like someone pushing you to start a fight---you can still walk away. Cord deformity w/signal is a punch to the face—it’s on! Image
13/Here are examples:

Cord deformity w/o signal (Grade 2, someone pushing and trying to start something)

Deformity w/cord signal (Grade 3, fight has already started & the cord already has a black eye!) Image
14/Remember, this is independent of the degree of canal stenosis. You can have cord deformity and signal even in lesser degrees of canal stenosis. Remember--cord flattening can cause cord damage regardless of the degree of canal stenosis. Image
15/This is the Kang system, and it was created to bring the idea of cord flattening into the rating of cervical spine stenosis, since flattening/deformity contribute to myelopathy regardless of stenosis. Image
16/Why don’t we just use the Kang & forget Muhle? Well, the problem w/Kang is that if there’s no cord signal, many degrees of canal stenosis are equal. Here, both mild stenosis w/flattening & severe stenosis w/flattening are equal in Kang, but clearly one is much more at risk Image
17/So we use both. For every level, we rate the degree of canal stenosis according to Muhle & the degree of cord flattening according to Kang. Remember—there is no perfect classification system. Sometimes you need combine. Image
18/So remember both canal and cord matter in the cervical region! Degree of stenosis is important, but even w/o it, cord flattening can have you swimming w/the fishes. So hopefully, you will take to these rating systems like a fish to water! Image

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More from @teachplaygrub

May 6
1/Have disagreements between radiologists on the degree of cervical canal stenosis become a pain in the neck?

Worried about sticking your neck out & calling severe cervical stenosis?

This month’s @theAJNR SCANtastic has the latest about Cspine MRI!

ajnr.org/content/46/4/7…Image
@TheAJNR 2/In the lumbar spine, it is all about the degree of canal narrowing & room for nerve roots.

In the cervical spine, we have another factor to think about—the cord.

Cord integrity is key. No matter the degree of stenosis, if the cord isn’t happy, the patient won’t be either Image
@TheAJNR 3/Cord flattening, even w/o canal stenosis, can cause myelopathy.

No one is quite sure why.

Some say it’s b/c mass effect on static imaging may be much worse dynamically, some say repetitive microtrauma, & some say micro-ischemia from compression of perforators Image
Read 16 tweets
May 2
1/Do radiologists sound like they are speaking a different language when they talk about MRI?

T1 shortening what? T2 prolongation who?

Here’s a translation w/an introductory thread to MRI. Image
2/Let’s start w/T1—it is #1 after all! T1 is for anatomy

Since it’s anatomic, brain structures will reflect the same color as real life

So gray matter is gray on T1 & white matter is white on T1

So if you see an image where gray is gray & white is white—you know it’s a T1 Image
3/T1 is also for contrast

Contrast material helps us to see masses

Contrast can’t get into normal brain & spine bc of the blood brain barrier—but masses don’t have a blood brain barrier, so when you give contrast, masses will take it up & light up, making them easier to see. Image
Read 20 tweets
Apr 28
1/Asking “How old are you?” can be dicey—both in real life & on MRI! Do you know how to tell the age of blood on MRI?

Here’s a thread on how to date blood on MRI so that the next time you see a hemorrhage, your guess on when it happened will always be in the right vein! Image
2/If you ask someone how to date blood on MRI, they’ll spit out a crazy mnemonic about babies that tells you what signal blood should be on T1 & T2 imaging by age.

But mnemonics are crutch—they help you memorize, but not understand. If you understand, you don’t need to memorizeImage
3/If you look at the mnemonic, you will notice one thing—the T1 signal is all you need to tell if blood is acute, subacute or chronic.

T2 signal will tell if it is early or late in each of those time periods—but that type of detail isn’t needed in real life

So let’s look at T1Image
Read 20 tweets
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

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