Thread by @AaronLBerkowitz

Thanks for all the positive feedback on my clinical neuroanatomy of the arm/hand #tweetorial!
Let's finish off the upper extremity with the brachial plexus!

#Neurology #MedEd #MedStudentTwitter

@CPSolvers @Tracey1milligan @MadSattinJ @MedTweetorials @DxRxEdu

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As I wrote, we all probably learned the brachial plexus FIRST in med school, but it's more complicated (and usually less clinically relevant) than knowing the 5 nerves I discussed previously.

So I suggest learn those 5 nerves first, then go back for the plexus!

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Do you REALLY need to memorize the entire brachial plexus...?

Yes, if you're a neurologist...or a med student studying for the step (otherwise, this might be just for fun)!

So let's make it easy...

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...with the Rule of Threes!!

First draw THREE headless/armless stick figures, long bodies, short legs:

Top and bottom: legs to the left
Middle: legs to the right

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Now draw THREE more lines to make another Y that connects Top and Bottom and makes a sideways M

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Now step THREE

Draw THREE more lines:

An X connecting the top 2
+ 1 more line connecting the bottom 2

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Guess what? THREE steps each with THREE components and you have the basic brachial plexus (proximal L/distal R; thumb side top), now just label from Left to Right:

Roots (C5-6-7-8-T1)
Trunks (Upper/middle/lower
Divisions (Ant/post)
Cords (Lateral posterior, medial)
Branches

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You already know the functions of the 5 terminal branches from the last tweetorial!

There you go, Brachial Plexus made simple!
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The next level is for neuro-nerds only...11 more less clinically relevant nerves:

THREE sets of THREE ...+ 2 more.

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Rules of THREES continues

THREE nerves arise from roots:
- Long thoracic (to serratus anterior)
- Nerve to subclavius
- Dorsal scapular (rhomboids)

Lesion of first leads to scapular winging

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THREE nerves arise from posterior cord
- Upper subscapular (subscapularis)
- Lower subscapular (subscapularis/teres major)
- Thoracodorsal (latissimus dorsi)

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THREE nerves from medial cord all with MEDIAL in their names:
- Medial pectoral (pec major/minor)
- Medial brachial cutaneous
- Medial antebrachial cutaneous

Latter 2 sensory nerves to medial arm/forearm...remember where we mentioned these in the last tweetorial...?

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Last 2 break our rule of threes :(

- Lateral pectoral nerve arises from lateral cord (pec major)–there was a medial one so has to be a lateral one

- Suprascapular nerve from upper trunk (supra and infra spinatus)–there was a subscapular so had to have supra

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Of all these 11 gourmet brachial plexus nerves, I've only seen long thoracic affected clinically but rarely...surgical injury and Parsonage-Turner syndrome...how about you #neurotwitter?

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So how do you use this anatomy clinically?

Well if you know the nerves from the last tweetorial, if you see muscles/sensation from more than one nerve affected clinically trace back to the part of the plexus or root(s) that provide a common origin ...

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Helpful? How do you remember the brachial plexus?

Want to see this animated out and narrated? If your school/hospital has AccessNeurology from @mgh_educacion you can watch this and other animations

all figures from amazon.com/Lange-Clinical…

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@threadreaderapp unroll please