Lea Alhilali, MD Profile picture
Sep 19, 2022 19 tweets 7 min read Read on X
1/Need help reading spine imaging? I’ve got your back!
A #tweetorial about the ABCs of reading spine MRs & CTs.
#medtwitter #FOAMed #FOAMrad #medstudenttwitter #medstudent #neurorad #radres #neurosurgery #spine #orthopedics @medtweetorials @stefantigges Image
2/A is for alignment. Normal spinal alignment is perfectly in balance, resulting in the minimal energy needed for erect posture. Even subtle changes in alignment need compensatory changes to maintain posture, resulting in more work/energy expenditure & pain. Image
3/The goals for alignment on imaging: (1) look for unstable injuries & (2) look for 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
4/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
5/Assess the ligaments w/the bones. Unlike long bones, ligaments in the spine cover along the bones like saran wrap. Anterior longitudinal along the vertebral body front, posterior longitudinal along the vertebral body & posterior ligamentous complex along posterior elements Image
6/On CT, you can infer ligamentous injury from the alignment—if the space is too wide, the ligament can’t be intact. On MR you can see edema in the ligament (suspect ligamentous injury) or focal disruption (see the ligamentous injury) Image
7/C is for canal on CT & cord on MRI. On CT, look at canal contents for any large masses or collections that could compromise the canal. You won’t see it all, but you have to try. On MR, assessing the canal is easy. You can also see the cord itself to check for edema/injury Image
8/D is for discs or degenerative findings. Normal discs should look like a kidney on its side, with a little indentation in the middle just like the renal hilum. Any change to this reniform shape means that there is a disc bulge. Image
9/Normal discs also have a very distinctive appearance on sagittal imaging. You should see a T2 bright disc with a dark nucleus pulposus center. It looks like the cross section of a jelly filled donut Image
10/If you lose that jelly filled donut appearance, and the discs look flatter or darker without a definable center—more like flat pancakes than jelly donuts—then the disc is degenerated. Image
11/Several things can happen to a degenerated disc. First, you can get a bulge. I think of a bulge like gaining weight—you slowly get fatter & loosen your belt. For a disc, the annulus degenerates, gets looser & the disc gets a pot belly—so you lose the renal hilum indentation. Image
12/Next you can get a protrusion. If a bulge is loosening your belt (i.e., the annulus is more lax but still intact), a protrusion is like a hernia. The annulus suddenly tears and disc herniates out. This means it is more focal and can happen more acutely. Image
13/Next is an extrusion. Extrusion is when herniated disc become like toothpaste. B/c it’s squishy like toothpaste, an extrusion can move up or down away from the parent disc. Extrusion base can be smaller than the rest of it bc it can squish through small holes like toothpaste Image
14/Finally is a free fragment. This is when a piece of the extrusion breaks off from the rest of the disc—like when you break off some toothpaste onto your toothbrush. You can see this on imaging bc the fragment is usually a different signal than the parent disc—much T2 brighter Image
15/Besides the disc, you should also look at the facet joints. A normal facet joint looks like a hamburger. When the facet starts to look more like a mushroom than a hamburger, with overhanging osteophytes, that’s when I call it degenerated Image
16/In the c-spine, there are also uncovertebral joints. These are at the lateral vertebral body. Normally they should be smooth. On coronal images, they look like little devil horns. When they start to get osteophytes & look more like moose antlers, then they are degenerated. Image
17/So every spine dictation becomes formulaic, like a mad libs fill in the blank. Go through your ABCs and look for abnormalities in each. When you get to the D, if the study was done for degenerative changes, you should evaluate each level individually. Image
18/At each level, it is also a fill in the blank formulaic dictation. You should assess disc, facets, & possibly uncovertebral joints, looking for the signs we have talked about that show they are degenerated. Then you should say what they are doing to the canal & neural foramina Image
19/So now you know how to approach spine imaging studies in a systematic way—so that your dictations will have all the necessary elements to strike that perfect balance between enough detail and enough brevity. I told you I had your back! Image

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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
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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
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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
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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
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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
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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

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