The nerve roots of the lower cervical spinal cord split and merge several times before supplying the arm and hand.
The brachial plexus lies over the first rib and behind the clavicle. It is intimately related to the subclavian/brachial artery and passes between the scalene muscles of the neck.
The plexus is divided into roots, trunks, divisions, cords and terminal branches. By looking at the anatomical distribution of pain or dysfunction, it is possible to determine the location of a brachial plexus lesion.
Brachial plexopathy can occur during delivery with or without shoulder dystocia, and from thoracic outlet syndrome.