Thoracic Outlet Syndrome



  • This syndrome consists of a constellation of symptoms that affect the head, neck, shoulders, and upper extremities caused by compression of the neurovascular structures (brachial plexus and subclavian vessels) at the thoracic outlet.
  • Three forms of thoracic outlet syndrome (TOS) have been described:
    • Neurogenic (nTOS)
    • Venous (vTOS)
    • Arterial (aTOS)
  • Synonym(s): scalenus anticus syndrome; cervical rib syndrome; costoclavicular syndrome; first rib syndrome


  • There are no universal diagnostic criteria to accurately determine epidemiology.
  • nTOS
    • Approximately 90–95% of all TOS cases (1)
    • Predominant in 20- to 50-year-old females
  • vTOS
    • Approximately 5–10% of all TOS cases (1)
    • Predominant in 20- to 35-year-old physically active males
  • aTOS
    • Approximately 1% of all TOS cases (1)
    • No gender preference

Etiology and Pathophysiology

  • TOS primarily impacts three anatomic spaces within the thoracic outlet (1):
    • Scalene triangle
      • Bordered by the anterior scalene, middle scalene, and first rib
      • Contains trunks of the brachial plexus and subclavian artery
    • Costoclavicular space
      • Bordered by the clavicle, first rib, and upper portion of the scapula
      • Contains divisions of the brachial plexus, subclavian artery, and subclavian vein
    • Subcoracoid space
      • Bordered by the pectoralis muscle, 2nd to 4th ribs and coracoid process
      • Contains cords of the brachial plexus
  • Proposed etiologies include (1):
    • Congenital: cervical rib, first rib
    • Traumatic: motor vehicle accidents
    • Functional: overuse activity of the upper extremity, particularly shoulder abduction/extension

Risk Factors

  • Trauma to the shoulder girdle
  • Presence of a cervical rib (1% of population)
  • Exostosis of clavicle or 1st rib
  • Postural abnormalities (e.g., drooping of shoulders, scoliosis)
  • Occupational exposure via repetitive activity (e.g., computer users, musicians, overhead athletes, repetitive upper body work)

General Prevention

Consider workplace evaluation for proper occupational ergonomics, including proper posture.

Commonly Associated Conditions

  • Paget–von Schrötter syndrome: effort thrombosis of subclavian vein
  • Gilliatt-Sumner hand: neurogenic atrophy of abductor pollicis brevis
  • Pancoast tumor

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