1/Sometimes the tiniest thing can be the biggest pain—that’s microvascular compression of the trigeminal nerve! But seeing such a tiny finding can be hard!
2/The most important thing to remember is that the nerve is 3D so you have to look for compression in all 3 planes. Let’s start w/the axial plane. On a normal axial, the trigeminal nerves should look like the arms of an alien sticking out of the pons.
3/Compression in the axial plane usually will deviate the nerve laterally—making it so that the Alien looks like he is flexing one of his arms. So if you see the Alien trying to show his guns—that’s microvascular compression!
4/In the sagittal plane, the nerve looks like an elephant’s trunk coming out of the pons. It should have a smooth curve up and over before it enters Meckel’s cave, just like the way an elephant’s trunk curves.
5/If the trunk is flattened, like it’s balancing ball or is curved downwards—that’s microvascular compression in the sagittal plane. If the nerve is pressed downward, you could miss this in the axial plane—bc the movement is parallel to the axial plane. You need a sagittal view
6/In the coronal plane, the nerves look like two gun barrels pointed at you, by a very potty bellied cowboy that is the pons.
7/If the nerves lose their gun barrel shape, and looks more like a boomerang—in any direction—that is microvascular compression. Coronal is usually the most helpful view, bc you can see movement both up and down and left to right.
8/So now you know what the normal trigeminal nerve looks like in all 3 planes—and you can now check for microvascular compression in three dimensions. Remember, images may be 2D, but life—and pathology—are 3D!
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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
Here's a little help on how to do it yourself w/a thread on how to read a head CT!
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!
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
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!
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
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.