Thoracic Outlet Syndrome is actually a group of distinct disorders all of which involve compression at the superior thoracic outlet. This has an undesirable effect on the brachial plexus nerves that pass through the arms from the neck. It can also affect the Subclavian Artery and Vein which pass between the chest and upper extremities. In layman’s terms, Thoracic Outlet Syndrome affects the area between the collarbone and the first rib. Symptoms include pain in the shoulders and neck along with numbness in the fingers.