Overview

Thoracic outlet syndrome (TOS) is a group of conditions caused by compression of the nerves or blood vessels as they pass from the neck and upper chest to the arm, through a narrow space called the thoracic outlet. The brachial plexus — the bundle of nerves to the arm — is most often involved, in what is called neurogenic TOS.

The diagnosis is debated because symptoms are vague and overlap with other conditions. It is a clinical diagnosis made after other causes, such as a pinched nerve in the neck, have been considered.

Typical Pattern

Numbness, tingling or pain in the arm and hand, often without a clear nerve-root pattern
Symptoms that come on with arms overhead, reaching, carrying, or sustained postures like screen work
Vague ache or heaviness in the shoulder, neck or arm
Weakness or clumsiness in the hand in more advanced cases
Less commonly, the blood-vessel forms: a cold, pale or blue hand (arterial) or swelling and heaviness of the arm (venous)

Symptoms are often made worse by activities that narrow the outlet — arms raised, shoulders pulled down and back, or carrying a heavy bag on the shoulder.

Why It Develops

The thoracic outlet space can be narrowed by:

Muscle tightness or development around the neck and shoulders (scalene and pectoral muscles)
Poor postural habits — rounded shoulders and a forward head, especially with prolonged sitting
Repetitive overhead or carrying activities
An extra cervical rib (an anatomical variation present from birth) in some people
Previous injury to the neck or collarbone area

In many cases the compression is dynamic — it happens in certain positions rather than all the time.

How It Is Diagnosed

There is no single perfect test. A clinician typically:

Takes a history of position-related arm and hand symptoms
Examines the neck, shoulder and upper back, and checks the pulse and symptoms in positions that narrow the outlet
Considers whether the pattern fits the neck (nerve root), the shoulder or the thoracic outlet
May order nerve conduction studies or imaging (ultrasound, MRI or vascular studies) when the picture is unclear or a blood-vessel form is suspected

TOS is often a diagnosis of exclusion, and it can coexist with neck and shoulder problems.

Treatment

Conservative care is the first line, and most people improve:

Education about postures and activities that provoke symptoms
Avoiding or modifying triggers — prolonged arms-overhead work, heavy bag carrying, sustained rounded-shoulder postures
Exercises to strengthen and control the muscles around the neck and shoulder blades, and to improve posture
Graduated return to sport and work

Injections or surgery are reserved for specific situations — for example a true vascular form, or neurogenic TOS that persists despite a thorough conservative program. Surgery is uncommon.

When to Get Assessed

Arrange an assessment if arm or hand symptoms persist, are worsening, or keep returning with activity. Seek urgent care if the arm becomes suddenly cold, pale, blue, swollen or very painful, or if there is sudden weakness — those patterns need prompt evaluation.

Cervical radiculopathy — the main condition TOS is compared with
Neck pain
Neck muscles anatomy
Cervical spine anatomy
Thoracic outlet anatomy
Chin tucks exercise

References

StatPearls. "Thoracic Outlet Syndrome." https://pubmed.ncbi.nlm.nih.gov/32491382/

This information is for education only and is not a medical diagnosis. InjuryAtlas does not replace an assessment by a qualified health professional. If you have severe pain, visible deformity, numbness, loss of function, or symptoms that are getting worse, seek medical care promptly.

Thoracic Outlet Syndrome