Axillary nerve

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The axillary nerve is one of five terminal branches of the brachial plexus, supplying motor and sensory branches to the shoulder.

Summary

  • origin: posterior cord of the brachial plexus
  • course: passes out of axilla through the quadrangular space to the upper arm
  • major branches: superior lateral cutaneous nerve of the arm
  • motor supply: deltoid and teres minor muscles
  • sensory supply: skin overlying deltoid muscle

Gross anatomy

Origin

The axillary nerve is one of two terminal branches of the posterior cord of the brachial plexus. It receives contributions from C5-6 nerve roots.

Course

Lying posteriorly to the axillary artery in the axilla, it passes inferiorly to the shoulder joint, exiting the axilla through the quadrangular space, with the posterior circumflex humeral artery, to supply the deltoid muscle and a small patch of overlying skin.

Branches and supply
  • muscular branches: deltoid and teres minor muscles
  • articular branches to the glenohumeral joint
  • superior lateral cutaneous nerve of the arm: skin overlying the deltoid muscle

Variants

Some known more common variants include that the nerve:

  • may only have C5 fibers
  • may supply subscapularis
  • branches to the long head of the triceps 
  • branches to the infraspinatus 
  • may supply teres major