Reviewed by Brian R. Robinson, MD
Thoracic outlet syndrome (TOS) is a compression of the blood vessels or nerves located in the thoracic area of the body, which is the area behind the collar bone. TOS is a cumulative trauma or repetitive stress disorder that can be aggravated by repetitive motion, such as typing on a keyboard, assembly line work or stocking shelves overhead.
TOS develops when a neurovascular bundle (a tight network of nerves and veins) in the chest suffers an abnormal compression or, in the case of repetitive stress injuries, a series of abnormal compressions, by bone, muscle, or connective tissue in the area.
TOS is usually caused by hyperextension neck injuries, such as whiplash or repetitive stress that exert pressure against the blood supply or nerves leading to the arms. In a small percentage of cases, TOS results from an extra rib in the neck, called a cervical rib. People with cervical ribs are ten times more likely to suffer from TOS than people without them.