The supraclavicular nerves arise from the ventral rami of C3 and C4 as a common trunk at the posterior border of the sternocleidomastoid muscle.  The nerves descend deep to platysma and the deep cervical fascia and divide into medial, intermediate and lateral branches.  These branches diverge and pierce the deep fascia just above the clavicle.  Occasionally some branches may pass through the clavicle prior to piercing the deep fascia.

Supply
The medial branch supplies the skin over the manubrium as far as the midline, as well as the sternoclavicular joint.  The intermediate and lateral branches supply skin and fascia related to corresponding thirds of the clavicle, as far as the sternal angle and second rib.  The lateral branch supplies skin over the upper and posterior aspects of the shoulder, as well as the acromioclavicular joint.