Thoracic Outlet Syndrome

Description

• 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

Epidemiology

• 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