AXILLARY NERVE C5/C6

 

axillary nerve

ORIGIN

  • posterior cordof brachial plexus
  • formed from posterior divisionof upper trunk

COURSE

  • it passesbeneath the shoulder joint through the quadrangular space with the posterior circumflex humeral artery
  • it then wraps around the surgical neck of the humerus

SENSORY SUPPLY

  • the “sergeant’s patch”of skin over the lower part of deltoid muscle

MOTOR SUPPLY

  • shoulder muscles
    • deltoid– abducts, flexes and extends shoulder
    • teres minor– externally rotates shoulder, forms part of rotator cuff which stabilises shoulder joint

COMMON INJURIES

  • fractureof surgical neck of humerus
  • stab woundsto posterior shoulder
  • anterior shoulder dislocation
  • pressureof crutches on armpits (“crutch palsy”)

CLINICAL FEATURES OF AXILLARY NERVE PALSY

  • SENSORY LOSS
    • numbness over “sergeant’s patch”
  • MOTOR DEFICIT
    • paralysis of deltoid– very weak shoulder abduction from 15-90°; weak shoulder flexion and extension
    • paralysis of teres minor– weak shoulder external rotation
  • DEFORMITY
    • wastingof deltoid muscle, making the bones of the shoulder joint very prominent and obvious
    • shoulder may appear adducted and internally rotated

Reference:

http://www.cram.com/flashcards/upper-extremity-special-tests-1246316

 

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