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Medically Reviewed By:

2026-05-01

  • Condition
  • Severity: Urgent

Thoracic Outlet Syndrome

Also Known As: TOS
Thoracic outlet syndrome (TOS) is a group of conditions caused by compression of the nerves, arteries, or veins that pass through the thoracic outlet — the narrow space between the collarbone, first rib, and surrounding muscles where blood vessels and nerves travel from the neck into the arm. TOS causes arm pain, numbness, tingling, weakness, and vascular symptoms ranging from arm swelling and discoloration to dangerous blood clots and arterial aneurysms.


Types of Thoracic Outlet Syndrome

Neurogenic TOS (nTOS) accounts for approximately 95% of all TOS cases and results from brachial plexus nerve compression. Venous TOS (vTOS) involves subclavian vein compression and is the cause of Paget-Schroetter syndrome (effort thrombosis). Arterial TOS (aTOS) is the least common but most dangerous form, caused by subclavian artery compression that can lead to arterial aneurysm, thrombosis, and distal embolization.

What Causes Thoracic Outlet Syndrome?

TOS results from anatomical abnormalities that narrow the thoracic outlet, including cervical ribs (extra ribs arising from the seventh cervical vertebra, present in 0.5–1% of the population), tight or hypertrophied scalene muscles, abnormal fibromuscular bands, prior clavicle fractures with malunion, and postural changes from repetitive overhead work or prolonged forward head posture.

Thoracic Outlet Syndrome Symptoms

Neurogenic TOS presents with pain, numbness, tingling, and weakness in the arm, hand, and fingers — often worse with overhead activities or carrying objects. Venous TOS causes arm swelling, bluish discoloration, and effort-related pain. Arterial TOS may cause cold hands, color changes with arm elevation, digital ulcers, or sudden arterial clotting.

TOS Diagnosis

Accurate TOS diagnosis requires a careful clinical history, physical examination including provocative maneuvers, and targeted imaging. Nerve conduction studies and electromyography (EMG) evaluate neurogenic TOS. CT angiography or MRI angiography is used for vascular TOS. Chest X-ray identifies cervical ribs or structural abnormalities.

TOS Treatment: Arterial & Venous TOS Decompression

Vascular TOS (both arterial and venous) requires surgical decompression of the thoracic outlet, typically via first rib resection through a transaxillary or supraclavicular approach. Removing the first rib and releasing any fibromuscular bands relieves compression and eliminates the mechanical cause of the disease. Venous TOS may require additional venous stenting or venoplasty after decompression. Arterial TOS may require repair of arterial aneurysm or bypass of a diseased subclavian artery.

SYMPTOMS

  • Arm, hand, and finger pain, numbness, or tingling (neurogenic TOS)
  • Weakness in the hand or grip
  • Arm swelling, bluish discoloration, and effort-related pain (venous TOS)
  • Cold hand, color changes with arm elevation, or digital ulcers (arterial TOS)
  • Symptoms worse with overhead activities or carrying objects

DIAGNOSIS METHODS

  • Clinical Examination and Provocative Maneuvers +

    Adson's test, Wright's maneuver, and Roos test assess for arterial, venous, or neurogenic compression patterns.

  • Nerve Conduction Studies / EMG +

    Evaluate neurogenic TOS — identifies brachial plexus dysfunction.

  • CT Angiography or MRI Angiography +

    Used for vascular TOS to define subclavian artery or vein compression and plan surgical approach.

  • Chest X-ray +

    Identifies cervical ribs or structural thoracic abnormalities.

TREATMENTS

RELATED CONDITIONS

FREQUENTLY ASKED QUESTIONS

  • How is TOS different from carpal tunnel syndrome? +

    Both cause hand numbness and tingling, but carpal tunnel syndrome results from median nerve compression at the wrist. TOS involves compression at the thoracic outlet — the base of the neck and upper chest — and typically affects all fingers rather than just the thumb and first two fingers.

  • Is TOS surgery risky? +

    TOS decompression surgery is a technically demanding procedure that requires a highly experienced vascular surgeon. In skilled hands, outcomes are excellent — the vast majority of patients with vascular TOS experience complete resolution of their vascular symptoms after surgery.

  • Can TOS be treated without surgery? +

    Neurogenic TOS often improves with physical therapy, postural correction, and activity modification. Vascular TOS (venous or arterial) causing active clotting or limb-threatening symptoms requires surgical decompression. Conservative management of vascular TOS is generally not appropriate.