Thoracic outlet syndrome

Also called TOS

Thoracic outlet syndrome is when nerves or blood vessels in the lower neck and upper chest (the thoracic outlet) are squeezed. This can cause pain, numbness, tingling or weakness in the arm and hand, or swelling and colour changes if a blood vessel is affected. It can be caused by posture, repetitive overhead movements, an injury or an extra rib.

Last updated Nov 9, 2026

What it is

Most people improve with physiotherapy, posture changes and painkillers.

If symptoms are severe or a blood vessel is affected, surgery to make more space may be offered.

Common signs

  • Pain in the neck, shoulder or arm
  • Numbness or tingling in the arm or fingers
  • A weak grip
  • Swelling or a blue colour in the arm
  • A cold hand

How it is usually diagnosed

  • Examination
  • X-rays to look for an extra rib
  • Nerve conduction studies
  • Ultrasound or other scans of blood vessels

Records worth keeping

Keeping these together makes each appointment easier, especially when you see a new doctor:

  • X-ray and scan reports
  • Nerve conduction results
  • Physiotherapy plans
  • Vascular or neurology letters

Questions to ask your doctor

  • Is a nerve or blood vessel being squeezed?
  • Which exercises will help?
  • Would surgery be worth considering?

When to get help right away

Call 112 or go to the nearest emergency department if you have:

  • Sudden swelling, pain and blue colour in an arm, or a cold, pale hand: call 112

This page is general information. It is not a diagnosis and does not replace a doctor who knows your history. Medfold keeps your records organised; it does not interpret them.

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