Lea Alhilali, MD Profile picture
Aug 11, 2022 • 6 tweets • 4 min read • Read on X
1/"You can put this diagnosis in the differential as many times as you want in your life, but you will only be right once," I told my fellow.
A🧵about a dx you hear about but are rarely lucky enough to see #medtwitter #FOAMed #FOAMrad #medstudent #neurorad #radres #neurosurgery Image
2/Pt had a calcified lesion in the posterior fossa found incidentally on a trauma CT, that was now enlarging. It had very coarse, stippled appearing calcifications, like grains of sand or dirt Image
3/It also had very jagged, irregular margins, almost as if the grains of calcium had just been piled up together haphazardly Image
4/On MRI, it was very T2 dark (from the calcs) & demonstrated mild enhancement. It was extraaxial, but didn't appear to arise from the meninges. Rather, it was in the lateral cerebellomedullary cistern, where CN 9-11 arise. Image
5/So went back to the CT--left SCM & trapezius atrophy but no cord palsy! This means it's a CN11 lesion--not just affecting it from mass effect, then it would affect 10 also. Calcified schwannomas are rare. CN11 schwannomas are rare. Calcified CN11 schwannomas likely don't exist Image
6/Googling "calcified lesion CN11" gave us CAPNON--a rare, non-neoplastic, reactive process. It affects CNs & when it does, usually 11.We were right! So I've had my 1 time to be right about this. If you haven't, now you know what to look for to make this dx a feather in your CAP! Image

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More from @teachplaygrub

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
Nov 8
1/Raise your hand if you’re confused by the BRACHIAL PLEXUS!

I could never seem to remember or understand it—but now I do & I’ll show you how!

A thread so you will never fear brachial plexus anatomy again! Image
2/Everyone has a mnemonic to remember brachial plexus anatomy.

I’m a radiologist, so I remember one about Rad Techs.

But just remembering the names & their order isn’t enough.

That is just the starting point--let’s really understand it Image
3/From the mnemonic, we start with the roots—the cervical nerve roots.

I remember which roots make up the brachial plexus by remembering that it supplies the hand.

You have 5 fingers on your hand so we start with C5 & we take 5 nerve roots (C5-T1). Image
Read 20 tweets
Nov 6
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
Oct 29
1/To call it or not to call it? That is the question!

Feeling wacky & wobbly when it comes to normal pressure hydrocephalus?

Don’t want to overcall it, but don’t want to miss it either!

Check out the latest in NPH w/this month’s @theAJNR SCANtastic!

ajnr.org/content/45/10/…Image
2/NPH was first described in 1965—but, of the original 6 pts, 4 were found to have underlying causes for hydrocephalus.

This begs the question—when do you stop looking & call it idiopathic? When do you suggest it on imaging? Image
3/There’s an iNPH Radscale, which scores 7 different imaging features.

Score above 8 is very sensitive for iNPH.

But who’s going to take out calipers & evaluate SEVEN different imaging findings on every dementia MR?

Also this scale doesn’t predict who will respond to shunting Image
Read 14 tweets
Oct 18
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

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