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Thoracic Outlet Syndromes (TOS)


Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Reviewed/Revised Apr 2022 | Modified Sep 2022
Topic Resources

Thoracic outlet syndromes are a group of disorders caused by pressure on nerves, arteries, or large veins as they pass between the neck and chest. When pressure is put on the nerves, pain and pins-and-needles sensations (paresthesias) occur in the hand, neck, shoulder, and arm. When pressure is put on arteries, the arms become pale and cool. When pressure is put on veins, the arms swell, and the overlying skin may look bluish.

  • 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.

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:

  • An extra little rib in the neck (cervical rib) that puts pressure on an artery

  • An abnormal rib in the chest

  • A badly healed fracture of the collarbone

Thoracic outlet syndromes are more common among women and usually develop between the ages of 35 and 55.

Symptoms of Thoracic Outlet Syndromes

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), blood flow to the arm is decreased, and it 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. Rarely, the pressure is severe enough to cause Raynaud syndrome Raynaud Syndrome Raynaud syndrome, a functional peripheral arterial disease, is a condition in which small arteries (arterioles), usually in the fingers or toes, narrow (constrict) more tightly than normal in... read more Raynaud Syndrome , in which the fingers become pale or blue and often numb when exposed to cold.

Diagnosis of Thoracic Outlet Syndromes

  • A doctor's evaluation

  • Usually nerve conduction studies and electromyography

  • Usually magnetic resonance imaging

  • X-ray of the neck

  • Sometimes angiography

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:

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 Angiography Angiography is a type of medical imaging that uses x-rays and a contrast agent to produce images of blood vessels. In angiography, x-rays are used to produce detailed images of blood vessels... read more 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.

Treatment of Thoracic Outlet Syndromes

  • Physical therapy and exercise

  • Sometimes nonsteroidal anti-inflammatory drugs and antidepressants

  • Sometimes surgery

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.

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