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Thoracic Outlet Syndrome



The thoracic outlet is a narrow passage located inside the body between the neck and the shoulder. Nerves, arteries and veins pass through the thoracic outlet – specifically the nerves in the brachial plexus, the subclavian artery and the subclavian vein.

Thoracic outlet syndrome describes where either the blood vessels (vascular thoracic outlet syndrome) or the nerves (neurological thoracic outlet syndrome) become injured, entrapped or compressed in the thoracic outlet.

By far the most common of these is neurological thoracic outlet syndrome. The condition (sometimes simply referred to as 'TOS') affects around 1% of the population, with women over twice as likely to develop it than men. It is unusual for the condition to develop under the age of 20 or over the age of 50.


The primary cause of the condition is injury or compression of the blood vessels and/or nerves in the thoracic outlet. This can be caused by the following…

  • Congenital anatomical differences – a small number of people have an extra rib or particularly tight fibrous connective tissue in the area of the thoracic outlet which can place pressure on the nerves or blood vessels.
  • Overuse of the arms and/or shoulders - this is relatively common where heavy loads are frequently carried on the shoulders, or in jobs which require very repetitive movements of the arms (e.g. stocking shelves, typing on a computer) or in certain sports, for example swimming, volleyball, golf and weightlifting.
  • Injury to the neck (especially whiplash in car accidents, but also consistently carrying around heavy bags or backpacks).
  • Bad posture.
  • Obesity.
  • Pregnancy – joints and ligaments naturally loosen during pregnancy.


Most symptoms of the condition affect the neck, the arms and hands and the shoulders and sometimes the chest and upper back. Symptoms can be divided into those that occur in both type of the condition, and those that only occur with vascular thoracic outlet syndrome.

Common symptoms include…

  • Pain in the arm – this can be in the form of an ache or a stabbing or burning pain.
  • Pain that worsens as the arm is lifted or during repetitive arm movements or when turning the head or neck.
  • Weakness, or a tingling or numbing of the arm or hand.
  • Loss of dexterity in the hand.
  • Dizziness and headaches (rare).

Symptoms of vascular thoracic outlet syndrome may also include…

  • Swelling of the arm / hand.
  • Skin discolouration on the arm – either a bluish colour or paleness of the skin.
  • One hand noticeably cooler than the other.
  • Arterial pulse either absent or decreased on the affected side.
  • Visual problems (rare).

Tests / Diagnosis

A doctor will first review medical history and current symptoms and then conduct a physical examination to check for any of the symptoms listed above.

You may be asked to move your arms, shoulders or neck into different positions to determine if any pain or other symptoms occur (this is called 'provocation testing').

In order to confirm a diagnosis your doctor may recommend imaging tests such as x-rays, ultrasound or CT or MRI scans.

To check the blood vessels, either an angiography, arteriography or venography may be recommended. Finally, a nerve conduction study may be recommended if there is the possibility of any nerve damage.