What is Thoracic Outlet Syndrome?

Thoracic outlet syndrome is caused by compression of the artery, vein or nerve in the thoracic outlet (the area just above the collar bone, between the neck and the chest.) Sometimes the compression is caused by an anomalous (extra) rib or abnormal bony anatomy after a clavicle (collar bone) fracture or shoulder surgery, or sometimes it is caused by enlargement of the scalene muscles of the neck. Many people with TOS have a history of whiplash trauma (motor vehicle accident, fall or assault) or repetitive activity of the arms (word processing, filing, lifting).

Symptoms are dependent on which structure (artery, vein or nerve) is compromised.

Neurogenic (nerve related) TOS is the most common (over 90% of patients) and is often the most difficult to diagnose and treat effectively. Patients may have burning pain in the shoulder and chest wall area and/or shooting pain (a “pins and needles” sensation) in the arm from the compression of the nerves of the brachial plexus. Pain can severely limit the movement of the arm. Hand weakness can also develop over time.

Venous (vein related) TOS involves compression of the subclavian vein draining the arm. It can produce arm swelling, fullness in the armpit and engorgement or prominence of the superficial veins of the chest and shoulder region. Sometimes compression can cause venous thrombosis (blood clot in the vein) which leads to permanent venous damage.

Arterial (artery related) TOS is the least common type of TOS and involves compression of the subclavian artery which supplies blood to the arm. Subclavian artery compression can result in arm pain or weakness with the use of the arm. Less commonly, it produces subclavian artery aneurysms and emboli (blockage of small arteries in the hand from a blood clot that breaks loose from the aneurysm). Patients may develop numb, cool or blue fingertips.

How is Thoracic Outlet Syndrome Diagnosed?

TOS is often suggested by symptoms and physical examination. X-rays can identify an anomalous rib or bony abnormality which may predispose to TOS. Nerve testing is sometimes performed to assess for nerve damage. Venous TOS is diagnosed by CT or conventional positional venogram. During this exam, contrast is injected through an intravenous line in the arm while the arm is moved above the head to maximize compression on the vein. Arterial TOS is diagnosed by CT angiography or MR angiography, which can delineate subclavian artery aneurysm, stenosis or occlusion.

How is Thoracic Outlet Syndrome Treated?

The cornerstone of treatment for neurogenic TOS is specific physical therapy beginning with breathing exercises and attention to posture. Improving work place ergonomics and avoidance of injury is critical. Surgery may be indicated in severe refractory cases and involve removal of enlarged scalene (neck) muscles, scar tissue around the nerves, and any bony abnormalities. Although in carefully selected patients the initial surgical outcome is excellent, symptoms return within a year in as many as 25% of patients, presumably because of scarring around the nerves.

Arterial and venous TOS are usually treated with surgery, which involves removing the scalene muscles and first rib. Often angiographic techniques are employed in conjunction with surgery to dissolve blood clots or to angioplasty the involved vein or artery. Prognosis is good in most cases, if the problem is identified and treated early.