The thoracic outlet is the space between your collarbone (clavicle) and your first rib. This narrow passageway is crowded with blood vessels, muscles, and nerves. If the shoulder muscles in your chest are not strong enough to hold the collarbone in place, it can slip down and forward, putting pressure on the nerves and blood vessels that lie under it. This causes a variety of symptoms which together are known as thoracic outlet syndrome.

The thoracic outlet is the space between your collarbone and first rib.

Cause

Thoracic outlet syndrome can result from injury, disease, or a congenital problem, such as an abnormal first rib. It is more common in women than in men, and poor posture and obesity can aggravate the condition.

Psychological changes are often seen in patients with thoracic outlet syndrome. It is not clear whether these changes are a cause or result of the syndrome.

Symptoms

Symptoms may vary, depending on which nerves or blood vessels are compressed. Symptoms from nerve compression are much more common than symptoms from blood vessel compression.

Pressure on the nerves (brachial plexus) may cause a vague, aching pain in the neck, shoulder, arm, or hand. It may also cause pain, numbness, or tingling on the inside of the forearm and the fourth and fifth fingers of the hand. Weakness may make your hand clumsy.

Pressure on the blood vessels can reduce the flow of blood out of your arm, resulting in swelling and redness of your arm. Less commonly, pressure can reduce the blood flow into your arm and hand, making them feel cool and easily fatigued.

Overhead activities are particularly difficult because they worsen both types of compression.

There may be a depression in your shoulder, or swelling or discoloration in your arm.

Your range of motion may be limited.

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