Upper Trunk

The upper trunk (or superior trunk) is a trunk of the brachial plexus which derives from the C5 and C6 roots.

Damage to the upper trunk causes: Arm hangs by side, Elbow can’t flex, Arm medially rotated, Forearm pronated, ‘waiter’s tip’, Loss of sensation over deltoid (C5) and lateral upper limb (C6).

The suprascapular nerve (C5,C6) arises from the upper trunk of the brachial plexus beneath the fascial floor of the posterior triangle, before it passes beneath the transverse scapular ligament and round the lateral border of the scapular spine.

The musculocutaneous and median nerves derive largely from this trunk.

Nerves of upper limbs (primarily): the brachial plexus (C5–T1) (TA A14.2.03, GA 9.930)
Supraclavicular
  • root (dorsal scapular, long thoracic)
  • upper trunk (suprascapular, to the subclavius)
Infraclavicular
lateral cord
  • lateral pectoral
  • musculocutaneous (lateral cutaneous of forearm)
  • median/lateral root: anterior interosseous
  • palmar
  • recurrent
  • common palmar digital (proper palmar digital)
medial cord
  • medial pectoral
  • cutaneous: medial cutaneous of forearm
  • medial cutaneous of arm
  • ulnar: muscular
  • palmar
  • dorsal (dorsal digital nerves)
  • superficial (common palmar digital, proper palmar digital)
  • deep
  • median/medial root: see above
posterior cord
  • subscapular (upper, lower)
  • thoracodorsal
  • axillary (superior lateral cutaneous of arm)
  • radial: muscular
  • cutaneous (posterior of arm, inferior lateral of arm, posterior of forearm)
  • superficial (dorsal digital nerves)
  • deep (posterior interosseous)
Other
  • cutaneous innervation of the upper limbs

M: PNS

anat (h/r/t/c/b/l/s/a)/phys (r)/devp/prot/nttr/nttm/ntrp

noco/auto/cong/tumr, sysi/epon, injr

proc, drug (N1B)

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