What Causes Thoracic Outlet Syndrome?

Compression may arise from a person's anatomy, an injury, repetitive arm activity, or changes in posture and surrounding muscles. More than one factor can contribute.

The thoracic outlet contains the brachial plexus, which carries nerve signals to the arm, and major blood vessels serving the arm. An extra rib above the first rib, an unusually shaped first rib, or a tight fibrous band can reduce the available space.

A collarbone injury, scar tissue, repetitive overhead movement, heavy shoulder loading, or enlarged neck and chest muscles may further narrow the passage. A slumped shoulder position can also increase strain in the area, although posture alone does not establish the diagnosis.

When nerves are affected, thoracic outlet syndrome can present with arm or hand tingling, numbness, pain, weakness, or early fatigue. Blood-vessel compression may instead cause swelling, colour change, coolness, heaviness, or a weaker pulse in the affected arm.

Notice which positions or tasks bring symptoms on, whether the whole arm or particular fingers are involved, and whether there is swelling or colour change. Avoid repeatedly forcing an activity that produces worsening numbness, weakness, or vascular symptoms.

A clinician may examine neck, shoulder and arm movement, sensation, strength, pulses and symptom-provoking positions. Depending on the findings, imaging or nerve and blood-flow tests may help identify the structure being compressed and exclude other causes.

For nerve-related compression, physiotherapy may address shoulder mechanics, breathing pattern, mobility, strength and activity modification. Postural work should be tailored to the individual rather than reduced to simply pulling the shoulders back.

Arrange a clinical assessment for persistent or recurring arm numbness, tingling, pain, weakness, swelling, or colour change, especially when overhead activity reliably triggers it. These symptoms can have several causes, so examination matters.

Seek urgent medical care if an arm suddenly becomes swollen, blue or unusually pale, cold, severely painful, or weak, or if you cannot feel a pulse. Sudden chest pain, shortness of breath, coughing blood, fainting, or new one-sided weakness also requires emergency assessment.

Ask which structure appears compressed, whether your symptoms suggest nerve or blood-vessel involvement, and what other neck, shoulder, nerve, or circulation problems need consideration. You can also ask which movements to modify, what examination or testing would change management, and whether a physiotherapy assessment fits your situation.