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Learning About Thoracic Outlet Syndrome (TOS)

Vein, artery, and nerves located inside the thoracic outlet

What is it?

Thoracic outlet syndrome (TOS) is a condition in which the nerves or blood vessels are squeezed tightly in a small space behind the collarbone (clavicle). This space is called the thoracic outlet. TOS can cause pain, numbness, or weakness in your shoulder, arm, or hand. Sometimes it causes swelling.

What are the types of TOS?

There are different types of TOS. The most common type is neurogenic (nerve) TOS. This is caused by nerves that are squeezed in the thoracic outlet. In vascular (blood vessel) TOS, veins or arteries are squeezed.

What causes it?

TOS is caused by a thoracic outlet that's smaller than normal and that squeezes nerves or blood vessels. The smaller outlet may be caused by:

  • Bone structures that aren't normal. There may be an extra rib. Or the shape of the bones may make the thoracic outlet too small.
  • Muscles that are shaped or located so that they make the outlet smaller.
  • Injuries from a mishap or a fall. Injuries can also be from repeated movements, such as from swimming or from pitching a baseball.

What are the symptoms?

Symptoms depend on the type of TOS.

Symptoms of nerve TOS may happen when you move your arms to shoulder level or to other positions that put pressure on the nerves. These symptoms include:

  • Pain, numbness, or tingling in the neck, shoulder, arm, or hand.
  • Weakness in the arm or hand.
  • In some cases, headaches.

Symptoms of vascular (blood vessel) TOS include:

  • Sudden swelling and pain in the arm and shoulder.
  • Pain and fatigue in the lower arm or hand when you hold them over your head.
  • Wounds on the hands and fingers that don't heal.
  • Sudden pain, weakness, numbness, or tingling in the hands.
  • Cold, pale fingers.
  • A bluish skin colour in the arms and hands.

How is it diagnosed?

Your doctor will ask if you have trouble using your hands or arms in activities like driving or washing your hair. You'll be asked about any injuries you've had to your neck or shoulder.

You will have a physical exam. This may include moving your arms and holding them in different positions. Your doctor will check for symptoms and changes in your pulse.

Your doctor may order a chest X-ray. Other imaging tests, such as an MRI, a CT scan, or an ultrasound, may be done.

You may have nerve tests such as an electromyogram (EMG) or a nerve conduction study. They measure electrical signals from nerves to muscles. These tests can tell the doctor if your symptoms are caused by a nerve problem or by the muscle.

Your doctor may also give you a shot to numb a muscle in your neck to see if it makes your symptoms go away.

How is it treated?

The treatment depends on the type of TOS and what's causing it.

If your TOS is caused by squeezed nerves, you will probably have physiotherapy first. The aim is to help relieve your symptoms. It may help you improve your posture, stretch the muscles in the area, and move better. It can also help you reduce the repeated movements that caused the TOS or made it worse. Your doctor may suggest that you lose some weight. It may take some pressure off the nerve.

If your TOS involves blood vessels, you may have medicine or surgery to remove blood clots. You may have a procedure to repair a blood vessel. And you may take blood thinners to help prevent more blood clots.

With either type, you may have surgery to relieve the tightness in the thoracic outlet area.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

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