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Genesis Chiropractic Spine & Sports Center      













Thoracic Outlet Syndrome

General Information

Description:

  • Constellation of signs/symptoms attributable to compression of the nerves/vessels of the upper extremity as they pass above the first rib and behind the clavicle (thoracic outlet)
    • Symptoms most commonly associated with elevation of the arm/repetitive motion
    • Clinical findings variable due to different structures that may be compressed and sites within the thoracic outlet at which compression can occur

Also called:

  • TOS
  • Scalenus anticus syndrome
  • Venous form (VTOS) referred to as
    • Effort thrombosis
    • Paget-Schroetter disease

Types:

  • Neurogenic (NTOS) > 90%)
  • Arterial (ATOS) < 1%)
  • Venous (VTOS) ~ 3%)
  • Mixed arterial/neurogenic

Who is most affected:

  • Neurogenic: women
  • Venous: men
  • Arterial: equal gender distribution
  • Unusual in pediatric population

Incidence/Prevalence:

  • Common

 

Causes and Risk Factors

Causes:

  • Anatomical
    • Congenital anomaly (bony or soft tissue) - case reports
      • Neurogenic thoracic outlet syndrome in a competitive swimmer due to compression from a fibrous band on the lower brachial plexus trunk can be found at Arq Neuropsiquiatr 2007 Dec;65(4B):1245 
      • Thoracic outlet syndrome due to cervical rib fracture after a fall in a 9-year-old child can be found in Pediatr Neurosurg 2007;43(4):293
      • Thoracic outlet syndrome due to nonunion of the first rib can be found at Arch Orthop Trauma Surg 2008 Jan;128(1):33
    • Trauma
  • Functional
    • Postural alterations
    • Psychological factors

Pathogenesis:

  • Positional compression of neurovascular bundle at thoracic outlet resulting
    • From both acquired extrinsic factors and congenital anatomic predisposition
    • In any of
      • Compression/irritation of brachial plexus roots
      • Compression/kinking of subclavian artery (at crossing of first rib)
      • Compression of subclavian vein (costoclavicular space)
  • 3 potential sites of neurovascular compression are the interscalene triangle (most important space/medial compartment), costoclavicular space (intermediate compartment) and retropectoralis minor space (most lateral compartment)
    • Costoclavicular space has been implicated as most frequent site of arterial compression (interscalene triangle second)
    • Neurologic compression appears to occur with equal frequency in the costoclavicular space and interscalene triangle
  • Review of histopathological findings in 2 cadavers with cervical ribs and brachial plexus compression can be found at J Neurosurg Spine 2008 Apr;8(4):347

Likely risk factors:

  • Cervical ribs (congenital/anomalous)
    • incidence approximately 1% in general population
    • 50% bilateral
    • Often associated with arterial thoracic outlet syndrome
  • Trauma, especially automobile accidents
  • Repetitive motion/stress
  • Occupational factors (poor posture/prolonged computer use)

 

Complications and Associated Conditions

Complications:

  • Post-stenotic dilatation of subclavian artery (arterial thoracic outlet syndrome) resulting in
    • Aneurysm formation
    • Potential for thromboembolism to affected upper extremity
  • Subclavian vein thrombosis (Paget-Schroetter syndrome)
  • Progressive motor deficits, especially of thenar muscles (neurogenic thoracic outlet syndrome)
  • Vascular complications reported to be more common in adolescents with thoracic outlet syndrome than adults (J Pediatr Surg 2008 Jun;43(6):1089)

Associated conditions:

  • Trauma
  • Carpal tunnel syndrome
  • Hypercoagulable state (venous thoracic outlet syndrome)