Nerve · Neck

Brachial plexus

Plexus brachialis

The brachial plexus is the switchboard of the arm: five spinal nerves from the lower neck are rewired through trunks, divisions and cords into the named nerves that run down the limb. Every muscle and every patch of skin below the shoulder is supplied through it. It leaves the neck through a tight corridor — between the scalene muscles, then under the collarbone and behind pectoralis minor — travelling with the subclavian artery. Because that corridor is narrow and moves with the arm and the breath, it is the classic site where the whole plexus can be compressed, producing aching, heaviness, tingling and clumsiness through the arm rather than one clean nerve pattern.