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, specifically in the area superior to the 1st rib and posterior to the clavicle.
• Three forms of thoracic outlet syndrome (TOS) have been described: neurogenic (nTOS), venous (vTOS), and arterial (aTOS).
• Synonym(s): scalenus anticus syndrome; cervical rib syndrome; costoclavicular syndrome

Pregnancy Considerations
Generalized tissue fluid accumulations and postural changes may aggravate symptoms.

Epidemiology

• There are no universal diagnostic criteria to accurately determine epidemiology.
• Estimated 3 to 80 cases per 1,000 people (1)
• nTOS
  • Approximately 95% of all TOS cases
  • Predominant in 20- to 50-year-old females
• vTOS
  • Approximately 4% of all TOS cases
  • Predominant in 20- to 35-year-old physically active males
• aTOS
  • Approximately 1% of all TOS cases
  • No gender preference
  • Typically seen in young adults and associated with congenital anomalies

Etiology and Pathophysiology

• TOS primarily impacts 3 anatomic spaces within the thoracic outlet:
  • Scalene triangle
    • Bordered by the anterior scalene, middle scalene and 1st rib
    • Contains trunks of the brachial plexus and subclavian artery
  • Costoclavicular space
    • Bordered by the clavicle, 1st rib and upper portion of the scapula
    • Contains divisions of the brachial plexus, subclavian artery and vein
  • Subcoracoid space
    • Bordered by the pectoralis muscle, 2nd to 4th ribs, and coracoid process
    • Contains cords of the brachial plexus, axillary artery and vein
• 70% of cases are soft tissue in nature, causing compression of neurovascular structures (local tumor, muscle hypertrophy, variant anatomy). The remainder are bony in nature (cervical rib, malunion) (1).
• Cases are also divided into traumatic and non-traumatic etiologies. Trauma is most common, particularly for nTOS.
• Prolonged or repetitive motion of the shoulder in abduction or extension can provoke symptoms

Risk Factors

• Trauma, especially to the shoulder girdle
• Presence of a cervical rib
• Posttraumatic, exostosis of clavicle or 1st rib, postural abnormalities (e.g., drooping of shoulders, scoliosis), body building with increased muscular bulk in thoracic outlet area, rapid weight loss with vigorous physical exertion and/or exercise, pendulous breasts
• Occupational exposure via repetitive activity: computer users; musicians; repetitive work involving shoulders, arms, hands
• Young, thin females with long necks and drooping shoulders

General Prevention

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

Commonly Associated Conditions

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