Nerves and blood vessels may be squeezed as they go through the tight passageway from the neck to the chest.
Pain and a pins-and-needles sensation may begin in the neck and shoulder, then extend down the arm.
Various diagnostic tests are done to look for possible causes, but no test can confirm the diagnosis.
Physical therapy, exercise, and pain relievers usually help relieve symptoms, but sometimes surgery is needed.
(See also Overview of the Peripheral Nervous System.)
The thoracic outlet is the passageway between the neck and the chest for major blood vessels and for many nerves as they pass into the arm. Because this passageway is very crowded, blood vessels or nerves to the arm may be squeezed between structures (such as a rib, the collarbone, or an overlying muscle), resulting in problems. Nonetheless, the exact cause of thoracic outlet disorders is often unclear.
Very rarely, the cause is a clear-cut anatomic abnormality, such as the following:
Thoracic outlet syndromes are more common among women and usually develop between the ages of 35 and 55.
If pressure is put on the nerves, thoracic outlet syndrome causes pain and pins-and-needles sensations that usually begin in the neck or shoulder, then spread along the inner surface of the arm into the hand.
If pressure is put on one of the subclavian arteries (located under the collarbone), the arm becomes pale and cool.
If pressure is put on the veins, the hand, arm, and shoulder on the affected side may swell, or the overlying skin may look bluish (a condition called cyanosis) because blood flow is impaired, resulting in an inadequate oxygen supply. Rarely, the pressure is severe enough to cause Raynaud syndrome, in which the fingers become pale or blue and often numb when exposed to cold.
Doctors base the diagnosis of a thoracic outlet syndrome on symptoms and results of a physical examination and several diagnostic tests. However, none of these tests can definitively confirm or rule out the diagnosis of thoracic outlet syndrome.
The following tests are usually done:
Nerve conduction studies and electromyography may detect abnormalities characteristic of thoracic outlet syndrome.
Magnetic resonance imaging (MRI) is done to look for anatomic abnormalities.
Through a stethoscope placed on the collar bone or near the top of the armpit, doctors may hear sounds indicating abnormal blood flow (bruits) in an artery that is being squeezed by nearby structures. Or doctors may take an x-ray of the neck to look for an extra rib in the part of the spine that runs through the neck.
Angiography of the arteries in the arm (brachial arteries) may be done to detect abnormal blood flow. In this test, x-rays are taken after a substance that is visible on x-rays (radiopaque contrast agent) is injected into the bloodstream.
For most people with symptoms of thoracic outlet syndrome, physical therapy and exercise result in improvement. Nonsteroidal anti-inflammatory drugs (NSAIDs) and antidepressants given in low doses may also help.
Surgery may be needed if an anatomic abnormality or pressure on large blood vessels is confirmed or if symptoms continue to progress. However, because a definitive diagnosis is difficult to make and because symptoms often persist after surgery, doctors usually consult an experienced specialist, who can help determine whether surgery is needed.