Thread by @theneurolander

Brachial plexus!!!

“Erb-Duchenne palsy, Erb-Charcot paralysis, Erb's point, Erb-Westphal symptom, Erb's spot”

German neurologist Wilhelm Heinrich Erb (1840–1921)

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Components

“Ready To Drink Cold Beer”

Root (5): C5-T1
Trunk (3): upper, middle, lower
Division (6): anterior & posterior from each of the trunks
Cord (3): lateral, posterior, medial
Branch (5)

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How are roots formed?

“formed by the anterior (ventral) rami of C5 to T1 spinal nerves”

Extent
- interscalene triangle (bounded by anterior scalene and middle scalene)

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How do roots mix to form trunks?

C5 + C6 = upper trunk
- Erb’s point: confluence of C5&C6 at upper trunk

C7 = middle trunk

C8 + T1 = lower trunk

Extent
- interscalene triangle to supraclavicular space of posterior triangle

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How do trunks divide to form divisions?

Each trunk splits into anterior and posterior divisions just behind and above the clavicle

Extent
- around and within cervico-axillary canal or apex of axilla

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How do divisions form cords?

Post divisions of all 3 trunks= posterior cord (C5-T1)
Ant divisions of upper&middle trunks= lateral cord (C5-C7)
Ant division of lower trunks= medial cord (C8-T1)

*cords are named according to their relation to the 2nd part of axillary artery

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How do branches arise from brachial plexus?

from cords and from divisions

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How to draw a simple brachial plexus?

1st: roots
2nd: 3 letter Y’s
3rd: 2 letter E’s
4th: 1 letter X

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5th: rule of 3
a. 3 nerves from roots
b. 2 (exception) from trunk
c. 3 from each cord

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Nerves from brachial plexus

Root, trunk, cord, and terminal branches

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Root branches

“PLeaseD”

Phrenic (C3-C5)
Long thoracic nerve (C5-C7)
Dorsal scapular nerve (C4-C5)

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Trunk branches

Subclavius (C5-C6)
Suprascapular (C5-C6)

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Cord branches

Lateral cord – Look Miss Look
Medial cord – M4U
Posterior cord – ULTRA

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Lateral cord branches

“Look Miss Look”

Lateral pectoral nerve (C5-C7)
Musculocutaneous nerve (C5-C7)
Lateral root of median nerve (C5-C7)

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Medial cord branches

“M4U”

Medial Pectoral (C8-T1)
Medial cutaneous nerve of arm (C8-T1)
Medial cutaneous nerve of forearm (C8-T1)
Median root of median (C8-T1)
Ulnar (C7-T1)

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Posterior cord branches

“ULTRA”

Upper Subscapular (C5-C6)
Lower Subscapular (C5-C6)
Thoracodorsal nerve (C6-C8)
Radial (C5-T1)
Axillary (C5-C6)

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Terminal branches

“3 musketeers assassinated 5 rats, 5 mice and 2 unicorns!”

3 musketeers: Musculocutaneous nerve(C5, C6, C7)
Assasinated: Axillary nerve(C5-C6)
5 rats: Radial nere(C5, C6, C7, C8, T1)
5 mice: Median nerve(C5, C6, C7, C8, T1)
2 unicorns: Ulnar nerve(C8, T1)

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Summary – mnemonic

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Summary – table

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Conditions

a. Erb & Klumpke palsy
b. Thoracic outlet syndrome
c. Winged scapula

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Erb & Klumpke palsy

Erb – upper trunk
vs
Klumpke – lower trunk

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Thoracic outlet syndrome

Compression of lower trunk (same as Klumpke) & subclavian vessels

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Winged scapula

Medial scapular winging
- long thoracic nerve dysfunction
- serratus anterior muscle weakness

Lateral scapular winging
- spinal accessory nerve dysfunction
- trapezius muscle weakness

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Have a great day!

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