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 cannot flex, Arm medially rotated, Forearm pronated, ‘waiter’s tip’ or more commonly known as 'policeman position ' 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 and the nerve to subclavius which supplies the subclavius muscle.

The musculocutaneous and median nerves derive largely from this trunk.