TOS stands for Thoracic Outlet Syndrome. The thoracic outlet is the hollow space between your neck and shoulder on each side, above the collar bone. Three vital structures pass through the thoracic outlet on each side: an artery, a vein, and a nerve plexus. If compression of one or more of these structures causes symptoms, thoracic outlet syndrome is present.
Compression may be caused by abnormal fibrous bands or muscles, or an extra rib, present from birth. Alternately, acquired abnormalities, such as muscle enlargement or injury, or a fractured bone, may cause compression. In addition, patients may develop abnormal movement of the arms and shoulders from work, injury, or athletics. Abnormal shoulder movement may cause compression when using the arms for typical activities, when using a computer, or during athletic activity.
Doctors define three types of thoracic outlet syndrome, based on the primary structure being compressed:
Venous TOS-compression of the subclavian vein
Arterial TOS-compression of the subclavian artery
Neurogenic TOS-compression of the brachial plexus
Symptoms of TOS are different in each type of TOS. Patients with venous TOS suffer swelling of the arm from decreased blood flow returning to the heart. Patients with arterial TOS suffer loss of blood flow to all or part of the arm. Patients with neurogenic TOS suffer a broad range of sensory and motor disturbances of the affected arm and hand
Thoracic outlet syndrome occurs in women more than men, usually between the ages of 20 to 40. We currently recognize an increased risk of developing thoracic outlet syndrome in the following situations:
Neck injuries resulting from motor vehicle accidents
Work environments with repetitive stress injures
Overhead athletic activities
Recently, thoracic outlet syndrome has been diagnosed in a number of elite athletes, including NBA basketball players and MLB pitchers.