Thoracic outlet syndrome

Thoracic outlet syndrome is a condition that occurs when nerves or blood vessels become compressed between your collarbone and first rib, leading to pain, numbness or swelling in the shoulder, arm and hand. It can affect the nerves, veins or arteries in this area, and symptoms can range from mild discomfort to more serious circulation problems. With an accurate diagnosis and the right care team, most people find relief and return to their normal activities.

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A medical illustration that details the blood flow of a shoulder.

Anatomy of the thoracic outlet

The thoracic outlet is the narrow space between your collarbone and your first rib, near the top of your chest. Important nerves and blood vessels, including veins and arteries that carry blood to and from your arm, pass through this tight passageway on their way from your chest to your shoulder and arm.

When this space becomes too narrow or is affected by extra tissue, injury or repetitive motion, it can put pressure on the nerves or blood vessels traveling through it. Depending on which structures are compressed, thoracic outlet syndrome may affect nerve function, vein circulation or artery blood flow, which is why symptoms can vary from person to person.

Overview

Symptoms

Symptoms of thoracic outlet syndrome depend on whether the compression affects the nerves, veins or arteries in the thoracic outlet. Common signs include:

Pain, aching or tightness in the neck, shoulder or arm
Numbness or tingling in the arm, hand or fingers
Weakness or fatigue in the hand or arm
Swelling or heaviness in the arm, which may point to vein involvement
Coldness, paleness or a weak pulse in the arm or hand, which may point to artery involvement
Discoloration of the arm or fingers

Symptoms can develop gradually or appear suddenly, and they may worsen with activities that involve raising the arms overhead or repetitive shoulder movement.

Causes

Thoracic outlet syndrome develops when the space between the collarbone and first rib narrows enough to compress nearby nerves or blood vessels. Common causes include:

An extra rib present at birth, known as a cervical rib
Poor posture that narrows the space over time
Repetitive overhead arm movements common in certain sports or jobs
Injury to the collarbone, first rib or surrounding area
Muscle enlargement or tightness near the thoracic outlet

In some cases, no single clear cause can be identified.

Risk factors

Certain factors can increase your likelihood of developing thoracic outlet syndrome, though having one or more of these doesn't mean you'll develop this condition:

Participating in sports that involve repetitive overhead arm motion, such as swimming, volleyball or baseball
Jobs that require frequent overhead reaching or repetitive shoulder movement
A history of neck or collarbone injury
Being born with an extra cervical rib
Poor posture, which can narrow the thoracic outlet over time

Knowing your risk factors can help you and your care team make informed decisions about prevention and treatment.

Diagnosis

Diagnosing thoracic outlet syndrome typically starts with a discussion of your symptoms and a physical exam, including tests that check how your symptoms respond to specific arm and shoulder positions. Because thoracic outlet syndrome can affect nerves, veins or arteries, your care team may use imaging or other tests to confirm the diagnosis and identify which structures are involved. Common tests include:

Ultrasound, which can check blood flow through the veins and arteries near the thoracic outlet
CT or MRI scans, which provide detailed images of the bones, muscles and blood vessels in the area
Nerve conduction studies, which measure how well nerves are transmitting signals
X-rays, which can help identify an extra rib or other bone-related causes

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