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What is thoracic outlet syndrome?

Thoracic outlet syndrome (TOS) is the compression of nerves and blood vessels in the upper chest that travel to the arms through a passage called the thoracic outlet. This often results in neck pain, shoulder pain, and arm pain. Thoracic outlet syndrome affects people of all ages and genders. The condition is common among athletes who participate in sports that require repetitive motions of the arm and shoulder. This includes swimmers, rowers, baseball players, and volleyball players.

Some types of TOS can be treated with physical therapy and medication. Some patients with severe or persistent symptoms may need surgery to reopen the thoracic outlet.


Types of thoracic outlet syndrome

Neurogenic (neurological) thoracic outlet syndrome

Neurogenic TOS is characterized by compression of the brachial plexus, a network of nerves that run from your spinal cord to your upper limbs and control muscle movements and sensation in your shoulders, arms, and hands. Neurogenic TOS can result in tingling, weakness, and even mild skin color changes when you raise your arms overhead. This is the most common type of TOS in adults.

Venous thoracic outlet syndrome

Venous TOS happens when the vein that drains blood from the arm, the subclavian vein, is compressed as it travels under the collarbone and through the thoracic outlet. This can cause swelling, redness, or make your arm feel heavy when you use it or raise it overhead. In extreme cases, venous TOS can cause clotting of the vein, resulting in significant swelling and persistent pain. This situation is called effort thrombosis, or Paget-Schroetter disease. This type of TOS often affects children.

Arterial thoracic outlet syndrome

Arterial TOS occurs when the muscles and bones surrounding the thoracic outlet rub against (impinge) the subclavian artery, the artery that supplies blood to the arm. This can result in loss of blood flow to the arm and make your arm feel cold and painful. Often this is temporary, happening only when your arm is raised. However, severe or long-term arterial TOS can damage the artery, cause clotting, and require emergency medical attention. The most rare form, arterial TOS, requires surgery to decompress the thoracic outlet.

How serious is thoracic outlet syndrome?

With proper treatment, TOS is manageable condition. Although many cases of thoracic outlet syndrome are not preventable, the condition is treatable. Treatment is important to prevent serious complications.

If left untreated, TOS can cause complications, such as:

  • permanent nerve damage and other neurological complications
  • permanent arm swelling and pain, especially in patients with venous TOS
  • blood clots
  • pulmonary embolism, a life-threatening condition in which a blood clot travels to the lungs
  • gangrene, the death of tissue often caused by a loss of blood flow

TOS | Symptoms & Causes

What are the symptoms of thoracic outlet syndrome?

Symptoms of thoracic outlet syndrome include:

  • neck pain
  • shoulder pain
  • arm pain
  • numbness and tingling of the fingers
  • impaired circulation to the extremities causing discoloration, swelling, or pain

How can I reduce the symptoms?

If you have TOS, you should avoid holding your arms out or overhead for long periods. Avoid sleeping with your affected arm extended behind your head. You should also avoid repetitive motions with your arms, including lifting heavy objects repeatedly. Take rest periods at work and throughout the day to minimize fatigue.

What causes thoracic outlet syndrome?

It is not always possible to know what caused thoracic outlet syndrome. Any condition that results in enlargement or movement of the muscle, bone, and other tissues near the thoracic outlet can cause thoracic outlet syndrome.

Causes may include:

  • muscle enlargement, such as from weight lifting
  • repetitive use, such as in baseball and rowing
  • injury
  • an extra rib
  • weight gain

TOS | Diagnosis & Treatments

How is thoracic outlet syndrome diagnosed?

Proper diagnosis is the most important step in treating thoracic outlet syndrome. Your doctor will perform a complete physical exam and review the results of previous diagnostic tests.

Your doctor may recommend a thorough evaluation by a skilled neurologist to rule out cervical spine disease and other neurological conditions with similar symptoms.

Additional tests that help diagnose thoracic outlet syndrome include:

How is thoracic outlet syndrome treated?

Most cases of neurogenic thoracic outlet syndrome can be treated with physical therapy and medication. Severe cases may require surgery.

Physical therapy

Physical therapy includes a variety of exercises that effectively stretch open the tissues of the thoracic outlet. These are done with and without weights to pull the outlet into a "relaxed" open position. Physical therapy may be done before surgery, as in the case of neurogenic TOS, or may be prescribed after surgery to help you regain strength and stability.


Your doctor might prescribe medications such as an anti-inflammatory medications (ibuprofen, Advil) or muscle relaxants to help relieve your symptoms. Cortisone injected into a joint or muscle can help lower inflammation and provide relief. If you have venous or arterial TOS, your doctor may prescribe blood thinners to prevent or treat blood clots.


Although neurogenic TOS can often be treated with exercise and physical therapy, you may need surgery if your symptoms continue despite these treatments. The primary goal of surgery is to remove the source of compression on the nerves that supply the arm, forearm, and hand. This is typically accomplished by removing the first rib, anterior scalene muscle, and any additional abnormal muscles or fibrous bands. If there is an extra rib causing compression, it should also be removed.

Most patients with venous or arterial TOS will need surgical treatment. Surgery for venous and arterial TOS is very effective when performed before blood clots have a chance to form. If you have venous TOS and a blood clot has already formed, you will need emergency treatment to dissolve the clot and thin the blood. Surgery will reduce your risk of another clot or the return of symptoms.

How we care for thoracic outlet syndrome

Our goal in the Thoracic Outlet Syndrome Program at Boston Children’s Hospital is to return our patients to full function. This requires varying levels of intervention, depending on your particular circumstances, and ranges from physical therapy to interventional radiologic techniques to surgery, or often a combination of all three.

TOS | Programs & Services