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!
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
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).
4/Next in the mnemonic are the Trunks.
Bc Trunks starts w/T, I can remember how they are named.
T is Top to bottom.
Trunks are named top to bottom: Superior, Middle, and Inferior.
But how to remember which nerve roots combine to give you which trunks?
5/Pairing of the nerve roots into the trunks is like pairing off at a dance when there is an odd number.
Everyone immediately turns to the person next to them & the person in the middle is left out.
For the roots, C7 is in the middle & has to go it alone as the middle trunk
6/Next in the mnemonic are the Divisions
Divisions do what their name implies—they divide the trunks.
Each trunk is split or DIVIDED into an anterior & posterior division.
Divisions will look like scissors coming off the trunks, helping you to remember they are splitting
7/This division results in a fundamental change in the nerves—anterior divisions will supply flexors & posterior divisions will supply the extensors.
It's an important dividing line. Like rabid soccer fans, once they've chosen a team, they will never mix w/fans of the other team
8/After the split of the divisions, the nerves come back together as the cords.
It is kind of like doing jumping jacks—they open up and then close back up again.
I remember that they come back together as the Cords bc Cords and Combine both start with C
9/It’s like a toll road
The road widens to let more cars get to the toll booths. Once they have paid the toll, road narrows again
This is what happens w/the divisions—but instead of paying a toll, they are organizing into flexor & extensor groups & coming back together again.
10/But it’s more like going through a worm hole than toll booth
When you go through a wormhole, you are fundamentally changed when you come out the other side (or so I read on the internet)
Once cords emerge from divisions, they’re either team flexor or extensor & can’t go back
11/So when they form the cords, anterior divisions (team flexor) will only combine w/other anterior divisions that innervate flexors.
Similarly, posterior divisions (team extensor) will only combine with other posterior divisions (extensor group).
12/Divisions combine to form 2 ant. cords & 1 post. cord. Why the inequality?
Well, the fundamental purpose of the arm is to flex (pick up things), unlike the leg (which is to extend/stand up).
So bc it’s more important to flex, remember 2 cords to flexors & 1 to extensors
13/All post divisions go to the 1 post cord. How do you remember which ant divisions go into which cord?
Remember, divisions come from the sup, middle, & inf trunks. Superior or even middle class don’t combine w/inferior things. So sup & mid combine. Poor inferior is left alone
14/Names of the cords are based on their relationship to the axillary artery.
Posterior cord (extensors) is posterior to it. The flexor cord made of the superior & middle divisions is lateral. Flexor cord made from the lonely inferior division is medial
15/But this is hard to remember.
So I remember that the flexor cord made from the poor inf division is looked down upon, so it is given the worst seat—at the armpit.
In anatomic positioning, closest to the armpit is medial, so it's the medial cord.
16/Now the final division into branches. Remember posterior cord only supplies extensors & is the only extensor cord. So when it branches, it needs to innervate extensors all along the arm (elbow, forearm, hand). So it gives off axillary to the upper arm & radial to the lower arm
17/Now the branches of the flexor cords. As expected from their names, MEDIAL cord gives a branch for flexors/sensation to MEDIAL forearm/hand (in anatomic position = PINKY side, so ulnar nerve), & LATERAL cord gives a branch for motor/sensation to LAT. forearm (musculocutaneous)
18/Usually superior/middle class look down on inferiors (why inf division travels alone as medial cord). But eventually the rich will have, ahem, liaisons w/inferiors. So it is w/cords. High-class lateral cord finally mingles w/low-class armpit medial cord, making median nerve
19/Now move beyond mneumonics. Remember, brachial plexus splits & recombines like jumping jacks w/a very palindromic 5-3-6-3-5 pattern. The names tell you if they are splitting or combining (Trunk=Together, Division=Divide, Cord=Combine, Branch=break)
20/Now all you need is to recall 1 fact @ each stage
Trunk: C7 left out
Div: Ant flexors don’t mix w/post extensors
Cord: Sup/mid class don’t mix w/inferiors
Br: Each cord gives a branch to region its name describes (post, med, lat) &rich give in to inferiors to form median nerve
21/Now you understand the anatomy of the brachial plexus.
Hopefully, the next time someone has a question about brachial plexus anatomy, you will be the first to raise your hand and BRACH it down for them!
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If you don’t know the time of stroke onset, are you able to deduce it from imaging?
Here’s a thread to help you date a stroke on MRI!
2/Strokes evolve, or grow old, the same way people evolve or grow old.
The appearance of stroke on imaging mirrors the life stages of a person—you just have to change days for a stroke into years for a person
So 15 day old stroke has features of a 15 year old person, etc.
3/Initially (less than 4-6 hrs), the only finding is restriction (brightness) on diffusion imaging (DWI).
You can remember this bc in the first few months, a baby does nothing but be swaddled or restricted. So early/newly born stroke is like a baby, only restricted
1/”I LOVE spinal cord syndromes!” is a phrase that has NEVER, EVER been said by anyone.
Do you become paralyzed when you see cord signal abnormality?
Never fear—here is a thread on all the incomplete spinal cord syndromes to get you moving again!
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1/Do you get a Broca’s aphasia trying remember the location of Broca's area?
Does trying to remember inferior frontal gyrus anatomy leave you speechless?
Don't be at a loss for words when it comes to Broca's area
Here’s a 🧵to help you remember the anatomy of this key region!
2/Anatomy of the inferior frontal gyrus (IFG) is best seen on the sagittal images, where it looks like the McDonald’s arches.
So, to find this area on MR, I open the sagittal images & scroll until I see the arches. When it comes to this method of finding the IFG, i’m lovin it.
3/Inferior frontal gyrus also looks like a sideways 3, if you prefer. This 3 is helpful bc the inferior frontal gyrus has 3 parts—called pars
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