Thoracic Outlet Syndrome (TOS) Evaluation

What is thoracic outlet syndrome (TOS)?

Your thoracic outlet is a small space just behind and below your collarbone. The blood vessels and nerves that serve your arm are located in this space. Thoracic outlet syndrome (TOS) is the presence of hand and arm symptoms due to pressure against the nerves or blood vessels in the thoracic outlet area.

There are three types of TOS. The type depends on which structure is compressed — nerve, vein, or artery. Ninety-five percent of cases of TOS are due to compression of the nerves to the arm (called neurogenic TOS). Three to four percent are due to obstruction or clotting of the main vein to the arm, the subclavian vein, a condition called venous TOS. The third type, arterial TOS, is the rarest type, occurring in one percent of cases, and it is due to disease in the artery leading to the arm, the subclavian artery. Almost all cases of arterial TOS are associated with an extra rib (cervical rib) or an abnormal first rib.

What are the symptoms of TOS?

The common symptoms depend on which structure is being compressed. In neurogenic TOS, the symptoms are pain, numbness, tingling, and/or weakness in the arm and hand. Also common is a tired feeling in your arm, which is made worse by working with your arms raised over your head. Neck pain and headaches in the back of your head are also frequent symptoms. Another common occurrence is pain that starts in your shoulder and runs down your arm, as well as pain in your fingertips. Unfortunately, the symptoms of neurogenic TOS can be vague and non-specific. Venous TOS is distinguished by swelling in your entire arm, plus pain and dark discoloration. Arterial TOS presents with pain, coldness, and a pale discoloration of the hand. Cramps occur when using the arm for activity.

Neurogenic TOS is most often the result of neck trauma such as a whiplash injury. Slipping and falling on floors or ice, or repetitive stress from working on assembly lines or keyboards are the next most common causes. The symptoms are due to scar tissue formation in neck muscles (called scalene muscles).
Venous TOS is commonly due to strenuous use of the arm and shoulder. Its underlying cause is congenital narrowing of the space through which the major arm vein (subclavian vein) passes from the shoulder area into the heart.

Arterial TOS is caused by a narrowing in the main artery to the arm (subclavian artery) which invariably is secondary to a congenital extra rib (cervical rib) which lies at the base of the neck, just above the highest rib in your chest, or it can be secondary to an abnormal first rib. Once the artery has been narrowed, one of two things will happen. The artery may enlarge, forming an aneurysm just beyond the narrowing, and a clot will form in the wall of the aneurysm; or the artery may remain narrowed and a clot will form inside the artery just beyond the narrowing. The danger of the clot is that pieces of it will break off (called emboli) and travel down the arm to block the circulation to your hand. When this occurs, the hand becomes cold, numb, painful, and discolored and you are in danger of losing your hand completely. Treatment to restore circulation is essential.

What can I expect during the exam?

A complete examination takes approximately 30 minutes. Pressure cuffs may be placed on your arms, wrists and fingers to determine any underlying arterial blockages. The technologist will place small sensors on the fingertips and ask you to perform different maneuvers with your arms. Waveforms will be recorded for the doctor to evaluate.

Patient Instructions

Please call us with any questions or to schedule an appointment for a Fort Myers thoracic outlet syndrome test: (239) 694-8346