Updated: 11/5/2019

Thoracic Outlet Syndrome (TOS)

Review Topic
  • A 25-year-old woman with no history of trauma presents with right arm pain. She reports that her right arm is easily fatigable, especially after she cooks. She is a chef and denies any history of smoking, hyperlipidemia, or peripheral artery disease. On physical exam, her right upper extremity is pale and cool to the touch. Her distal right radial pulse is diminished compared to her left. Radiography reveals a cervical rib.
  • Clinical definition
    • syndrome resulting from compression/obstruction of the lower trunk of the brachial plexus and subclavian vessels as it passes through the thoracic outlet 
      • the thoracic outlet is above the first rib and behind the clavicle
      • classified into three types
        • neurogenic (compression of brachial plexus)
        • arterial (obstruction in arteries)
        • venous (obstruction in veins)
  • Epidemiology
    • demographics
      • adults
  • Etiology
    • bony
      • cervical rib 
        • an extra rib arising from 7th cervical vertebra
      • rudimentary first rib
    • soft tissue
      • fibrous band from the first rib to the tip of C7 transverse process
      • hypertrophy of nearby muscles (e.g., sternocleidomastoid or scalene muscle)
        • more commonly in weightlifters or athletes
      • Pancoast tumor causing compression
      • cysts
    • trauma
  • Pathogenesis
    • compression of brachial plexus can cause neuropathies
    • compression of subclavian vein or artery can cause pain and edema
  • Symptoms
    • neurogenic
      • difficulty grasping or gripping
      • numbness and tingling in ulnar distribution
      • pain or weakness with elevation or repetitive use of the affected arm
    • arterial
      • claudication
      • diffuse arm and hand pain
      • fatigue and ache, especially after exertion of muscle
    • venous
      • upper extremity swelling
      • diffuse arm or hand pain
  • Physical exam
    • careful neurovascular exam should be performed
    • neurogenic
      • atrophy of intrinsic hand muscles
      • decreased sensation in ulnar nerve distribution
      • reproducible pain with elevation of arms
    • arterial
      • pallor and cool upper extremities
      • weak or absent radial or ulnar pulse
      • may have decreased blood pressure in the affected arm
    • venous
      • edema
      • cyanosis of upper extremity
      • distended veins
  • Radiographs
    • indication
      • may reveal bony abnormalities
    • findings
      • cervical or rudimentary first rib
      • Pancoast tumor
  • Magnetic resonance imaging (MRI)
    • indication
      • may reveal soft tissue abnormalities
  • Ultrasound
    • indication
      • if vascular TOS is suspected
    • finding
      • vascular compression
  • Angiography
    • indication
      • if vascular TOS is suspected but ultrasound is unrevealing or further clarification is needed
    • finding
      • compression
  • Making the diagnosis
    • most cases are clinically diagnosed
  • Other causes of vascular compromise, such as emboli
    • distinguishing factor
      • pain worsened with exertion of the affected muscle and relieved with rest
  • Conservative
    • physical therapy
      • indication
        • for all patients
  • Medical
    • nonsteroidal anti-inflammatory drugs (NSAIDs)
      • indication
        • pain management
    • anticoagulation       
      • indication
        • patients with suspected thrombosis causing compression
  • Operative
    • surgical decompression
      • indications
        • patients with fibrous band
        • patients with cervical rib
        • pain refractory to conservative management
  • Aneurysm formation (post-stenotic)
  • Thromboembolism

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