Complex regional pain syndrome

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Complex regional pain syndrome (CRPS) is an umbrella term for two disorders, reflex sympathetic dystrophy (RSD) and causalgia, characterised by pain and skin changes following nerve injury. The term CRPS was formally adapted during the meeting of the International Association for the Study of Pain (IASP) in 1993. It is a syndrome rather than a disease, and we may hope for further enlightenment on the mechanisms involved.

Contents

Classification

LogoKeyPointsBox.pngOsteopaenic changes on bone scan are regarded as a strong indication of the diagnosis

The IASP divide the conditions into RSD and Causalgia, and offer standardised criteria of presentation and findings

  • CRPS Type 1 ( RSD)
    • Follows an initiating noxious event
    • Spontaneous pain or allodynia/hyperalgesia beyond territory of one nerve also disproportionate to initiating event
    • Evidence of oedema/skin blood flow abnormality or sudomotor activity
    • Other conditions excluded
  • CRPS Type 2 ( Causalgia)
    • Follows nerve injury but otherwise similar to Type 1
    • Is more regionally confined about a joint or or area
    • Spontaneous pain or allodynia is limited to area involved. It may spread but not in a dermatomal or peripheral nerve distribution.
    • Disproportionate intermittent variable oedema, blood flow, temperature change or sudomotor activity are present about the area involved.
LogoKeyPointsBox.pngthe psychosocial model is important

Diagnostic Criteria

LogoKeyPointsBox.pngDiagnostic criteria
0-3 criteria : Not RSD
3-5 criteria : Possible RSD
6+ criteria : Definite RSD
  • Presentation
    • Burning pain
    • Allodynia
    • Temperature or colour changes
    • Oedema
    • Skin, hair or nail growth changes
  • Investigation
    • Thermometry or thermography
    • Bone x-ray
    • 3-phase bone scan
    • Quantitative sweat test
    • Quantitative tests of cold and touch sensation
    • Response to sympathetic blockade

Treatment

Progression and course

LogoKeyPointsBox.pngThree Phases
  • inflammatory phase
  • contracture with less inflammation
  • spontaneous regression hopefully complete
Taking several years

Classically the syndrome progresses through 3 phases to eventual resolution, however not everyone goes through all three phases. It is believed early and aggressive treatment may alleviate the progression.

A further strain or insult to the affected area is followed by reactivation which is of considerable significance if the condition has been related to work. It has been suggested that repeated small insults beforehand prime the autonomic nervous system to react abnormally thus later producing the syndrome in response to major insult.

References

Stanton-Hicks M et al. Reflex sympathetic dystrophy: changing concepts and taxonomy. (1995) Pain 63:127-33. PMID 8577483.

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