Thoracic outlet syndrome overview

How thoracic outlet syndrome develops

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.

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Common causes of thoracic outlet syndrome

What can compress nerves or blood vessels in the thoracic outlet?

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
  • Injury to the neck
  • Bad posture
  • Obesity
  • Pregnancy

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Thoracic outlet syndrome symptoms

How thoracic outlet syndrome can affect the upper body

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 types of the condition, and those that only occur with vascular thoracic outlet syndrome.

Common symptoms include:

Arm pain

Pain may feel aching, stabbing or burning.

Pain with movement

Pain may worsen when lifting the arm, repeating arm movements or turning the head or neck.

Weakness, tingling or numbness

Altered sensation or weakness may affect the arm or hand.

Loss of dexterity

Fine hand movements may become more difficult.

Dizziness or headaches

These symptoms may occur rarely.

Arm or hand swelling

Swelling may develop on the affected side.

Skin discolouration

The affected arm may appear bluish or unusually pale.

Cooler hand temperature

One hand may feel noticeably cooler than the other.

Reduced pulse

The arterial pulse may be weaker or absent on the affected side.

Visual problems

Visual symptoms may occur rarely.

Thoracic outlet syndrome tests and diagnosis

How thoracic outlet syndrome is assessed

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.

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