413-414 - Brachial plexus Flashcards
Put the following in order from proximal to distal: cords, divisions, roots, branches, trunks
Roots, trunks, divisions, cords, branches
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What nerve injury causes Erb palsy?
Traction or tear of upper trunk: C5-C6 roots
“Erb-er” trunk
What can cause Erb’s palsy in infants? In adults?
lateral traction on neck during delivery; trauma
What muscles and related deficits are involved in Erb’s palsy?
- Deltoid, supraspinatus → can’t abduct (arm hangs by side)
- Infraspinatus → can’t laterally rotate (arm hangs medially rotated)
- Biceps brachii → can’t flex or supinate (arm extended and pronated)
What nerve injury causes Klumpke palsy?
traction or tear of lower trunk: C8-T1 root
How can infants get Klumpke palsy? Adults?
upward force on arm during delivery; trauma (eg. grabbing a tree branch to break a fall)
What muscles are affected in Klumpke palsy?
Intrinsic hand muscles:
- lumbricals
- interossei
- thenar
- hypothenar
How does Klumpke palsy present? Why?
Total claw hand; lumbricals normally flex MCP joints and extend DIP and PIP → MCP is extended and DIP/PIP are flexed
What nerve injury leads to thoracic outlet syndrome?
Compression of lower trunk [of the brachial plexus] and subclavian vessels
What spinal roots make up the upper, middle and lower trunks of the brachial plexus?
C5 & C6 => upper
C7 => middle
C8 & T1 => lower
What trunks make up the lateral cord of the brachial plexus?
upper & middle
What trunks make up the posterior cord of the brachial plexus?
upper, middle, and lower
What trunks make up the medial cord of the brachial plexus?
the lower trunk only
What nerves arise from the posterior cord of the brachial plexus? Do they lead to flexors or extensors?
axillary and radial
both → extensors
Which cords give rise to the musculocutaneous nerve?
lateral cord
Where does the long thoracic n. arise from?
C5, C6, C7 roots