Thoracic outlet syndrome (TOS) is a term used to describe a group of disorders that occur when there is compression, injury, or irritation of the nerves and/or blood vessels (arteries and veins) in the lower neck and upper chest area.

The thoracic outlet is the space between your collarbone (clavicle) and your first rib. This narrow passageway is crowded with blood vessels, nerves and muscles.

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 There are a number of types of thoracic outlet syndrome, including

  • Neurogenic (neurological) thoracic outlet syndrome. This form of thoracic outlet syndrome is characterised by compression of the brachial plexus. The brachial plexus is a network of nerves that come from your spinal cord and control muscle movements and sensation in your shoulder, arm and hand. In the majority of thoracic outlet syndrome cases, the symptoms are neurogenic.
  • Vascular thoracic outlet syndrome. This type of thoracic outlet syndrome occurs when one or more of the veins (venous thoracic outlet syndrome) or arteries (arterial thoracic outlet syndrome) under the collarbone (clavicle) are compressed.
  • Nonspecific-type thoracic outlet syndrome. This type is also called disputed thoracic outlet syndrome. Some doctors don't believe it exists, while others say it's a common disorder. People with nonspecific-type thoracic outlet syndrome have chronic pain in the area of the thoracic outlet that worsens with activity, but a specific cause of the pain can't be determined.

Symptoms
The symptoms that you experience as a result of thoracic outlet syndrome will depend on whether the nerves or the blood vessels are affected.

Compressed nerves can cause

  • Muscle wasting in the fleshy base of your thumb (Gilliatt-Sumner hand)
  • Numbness or tingling in your arm or fingers
  • Pain or aches in your neck, shoulder or hand
  • Weakening grip

Compressed blood vessels can cause

  • Discolouration of your hand (bluish colour)
  • Arm pain and swelling, possibly due to blood clots
  • Blood clot in veins or arteries in the upper area of your body
  • Lack of colour (pallor) in one or more of your fingers or your entire hand
  • Weak or no pulse in the affected arm
  • Cold fingers, hands or arms
  • Arm fatigue with activity
  • Numbness or tingling in your fingers

Causes

What Causes Thoracic Outlet Syndrome?
The cause of this compression isn’t always known. However, it may develop as a result of the following conditions:

An Extra Rib: Some people are born with an extra rib above their first rib. This reduces the size of their thoracic outlet and compresses nerves and blood vessels.

Poor Posture and Obesity: People who don’t stand up straight or who have excess abdominal fat may have increased pressure on their joints. This can cause a narrowing of the thoracic outlet.

Injury: Car accidents and other traumatic injuries can compress the thoracic outlet as well as the vessels and nerves in this area.

Overuse of the Shoulders and Arms: Repetitive activities, such as working at a computer or lifting heavy objects above the head, can cause damage to the tissues in the thoracic outlet. Over time, the size of the thoracic outlet may shrink, placing pressure on the vessels and nerves.

Treatment
The goal of treatment for thoracic outlet syndrome is to ease symptoms and pain. The specific type of treatment used may vary depending on the cause and severity of the condition.

Conservative treatment
Physical therapy. If you have neurogenic thoracic outlet syndrome, physical therapy is the first line of treatment. You'll learn how to do exercises that strengthen and stretch your shoulder muscles to open the thoracic outlet, improve your range of motion and improve your posture. These exercises, done over time, may take the pressure off your blood vessels and nerves in the thoracic outlet.

Medications. Your doctor may prescribe anti-inflammatory medications, pain medications or muscle relaxants to decrease inflammation, reduce pain and encourage muscle relaxation.

Clot-dissolving medications. If you have venous or arterial thoracic outlet syndrome and have blood clots, your doctor may administer clot-dissolving medications (thrombolytics) into your veins or arteries to dissolve blood clots. After you're given thrombolytics, your doctor may prescribe medications to prevent blood clots (anticoagulants).

Surgical treatment
Surgery is recommended if other treatment hasn't been effective, if you're experiencing ongoing symptoms or if you have progressive neurological problems.