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
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
3/It also had very jagged, irregular margins, almost as if the grains of calcium had just been piled up together haphazardly
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.
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
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!
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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.
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
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!
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
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
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!
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 memorize
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
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.
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
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.