Thoracic Outlet Syndrome

Thoracic Outlet Syndrome is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • The symptoms of thoracic outlet syndrome (TOS) are produced by compression of the brachial plexus, subclavian vein, or subclavian artery during their passage from the cervical area toward the axilla and proximal arm.
  • Subdivided into 3 categories depending on the predominant symptoms:
    • Neurogenic thoracic outlet syndrome (NTOS):
      • Comprises 90–98% of adult patients
      • Female > male
      • True (1–3%): Those with objective findings
      • Disputed (90%): Those with no or limited objective findings
    • Venous thoracic outlet syndrome (VTOS):
      • 2–4% of patients
    • Arterial thoracic outlet syndrome (ATOS):
      • Least common, <1%
      • Male = female
  • Vascular manifestations are more common in adolescents, seen in >50% of teens with TOS.
  • Right extremity is more commonly affected.

Etiology

  • Anatomic anomalies:
    • Bony anomalies include cervical rib, 1st thoracic rib, or clavicular abnormalities:
      • Cervical ribs occur in <1% of the population, ∼70% in women, and most are asymptomatic.
      • Less commonly, fracture of the clavicle and trauma to the sternoclavicular and costoclavicular joints
    • Congenital bands or anomalous muscles
    • May play a role in neurologic and venous types but is almost always implicated in arterial type
  • Neurogenic:
    • Often have a history of neck trauma, such as whiplash (hyperextension injuries) or with repetitive motion patterns
  • Venous:
    • May be preceded by excessive activity, especially in adolescent athletes
    • Caused by acute thrombosis of the subclavian vein (also called Paget–Schrötter disease) or by venous impingement
  • Arterial:
    • Often develop spontaneously
    • Unrelated to trauma or work
    • May experience true claudication with overhead exercises
    • Almost always have a complete cervical rib or an anomalous 1st rib
    • Caused by subclavian artery aneurysm or subclavian/axillary artery impingement:
      • Arterial emboli that arise from either mural thrombus in the subclavian artery aneurysm or from thrombus forming distal to subclavian artery stenosis
  • Descent of the shoulder girdle and sagging musculature can also predispose to TOS:
    • Aging
    • Obesity
    • Heavy breasts

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