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Complex Regional Pain Syndrome

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Other Names

  • Reflex dystrophy syndrome
  • Causalgia
  • Reflex Sympathetic Dystrophy (RSD)
  • Algodystrophy
  • Complex Regional Pain Syndrome (CRPS)


  • This page refers to Complex Regional Pain Syndrome (CRPS), an umbrella term describing excess and prolonged pain and inflammation that follows an injury to the extremities


  • Very controversial disease
  • Ambroise Paré, the father of modern surgery, was the first to describe a disorder that could resemble current CRPS [1]
    • Successfully treated a severe and persistent pain syndrome in French King Charles IX of Valois after a limb phlebotomy
  • First written description was made by Denmark, a British surgeon that used to work at the Royal Navy Hospital in Hampshire in 1812 [1]


  • Incidence between 5.5 - 26.2 cases per 100,000 people per year from two major studies [2]
    • Variation likely present due to use of different diagnostic criteria
    • Budapest Criteria have only been accepted and validated for the past decade (see below)


  • General
    • May be secondary to trauma, stroke, or heart attack
    • Pain is usually out of proportion (soft stimuli like touch will be painful)
    • Occurs acutely in ~7% of patients who have limb fractures or limb surgeries [3]
    • Many cases resolve within the first year [3]
    • May have genetic and psychological contributions
    • Diagnosis of exclusion


  • CRPS-I (previously known as RSD)
    • Historically diagnosed when there was uncertainty about the exact nerve injured [4]
    • Nerve injuries in CRPS I are thought to be more subtle
  • CRPS-II (previously known as causalgia) was diagnosed [4]
    • Labeled once the culprit nerve was identified
    • Nerve injuries in CRPS II are more debilitating and cause weakness and muscle shrinkage
  • Clinically, these are indistinguishable and follow a regional distribution instead of a dermatomal distribution
  • Can also be classified as “warm” CRPS where inflammatory characteristics are dominant or “cold” CRPS where autonomic characteristics are dominant [3]


  • Most cases (>90%) are caused by improper function of the peripheral C-fiber nerve (unmyelinated afferent nerve fibers found in the somatic sensory system) [4]
  • It is unclear why certain people develop CRPS, while others who have had similar trauma do not
  • Can be caused by
    • Fractures
      • In large multicenter prospective study found that 48.5% of patients developed CRPS following a single fracture of the ankle, wrist, scaphoid, or the fifth metatarsal [5]
    • Surgery
    • Sprains and strains
    • Burns
    • Lacerations
    • Limb immobilization (from casting)
    • Penetrating injury
  • Other considerations
    • Fractures:
    • Hypotheses that CRPS is related to hormonal changes in the postmenopausal period remains unproven (need citation)
    • Anecdotal reports that long-term administration of phynotoin and isonizaixd drugs increases the risk of RSD [6]

Risk Factors

  • Demographic
    • Female gender (up to twice as common) [6]
  • Iatrogenic
    • Inadequate anesthesia during fracture reductions [6]

Differential Diagnosis

Clinical Features

  • History
    • Continuous burning or throbbing pain usually in the extremities
    • Disproportionate hyperalgesia
    • Allodynia
    • Swelling
    • Skin changes including erythema, mottling, and "shiny" appearance to skin
    • Loss of function
  • Physical Exam
  • Special Tests


  • No specific test available to diagnose CRPS
  • Diagnosis is made through a thorough history, physical examination, and review of symptoms

Diagnostic Criteria

  • Budapest criteria is associated with improved diagnostic consistency between clinicians compared to IASA criteria [7]
  • Requires presence of both signs of symptoms of CRPS to make the diagnosis
  • The following criteria must be met:
    • Continuing disproportionate pain to any inciting event
    • No other diagnosis can better explain signs and symptoms
    • At least one symptom in all four of the following categories:
      • Sensory: reports of hyperesthesia and/or allodynia
      • Vasomotor: temperature asymmetric and/or skin color changes/asymmetry
      • Sudomotor/edema: edema and/or sweating changes/asymmetry
      • Motor/trophic: decreased range of motion and/or motor dysfunction and/or trophic changes (hair, nail skin)
    • At least one sign at the time of evaluation in two or more of the following categories:
      • Sensory: evidence of hyperalgesia and/or allodynia
      • Vasomotor: evidence of temperature asymmetry (> 1 °C) and/or skin color changes/asymmetry
      • Sudomotor/edema: evidence of edema and/or sweating changes/asymmetry
      • Motor/trophic: evidence of decreased range of motion and/or motor dysfunction and/or trophic changes


  • Nerve conduction studies may be used to reveal some CRPS-associated nerve injury [4]


  • Ultrasound may be used to identify underlying nerve injury


  • May reveal underlying nerve damage

Nuclear Medicine

  • Triple phase bone scan with contrast
    • Can show CRPS-associated excess bone resorption
    • May aid in localization


  • No current classification system exists




  • Indications
    • Unknown
  • Technique
    • Spinal cord stimulation

Rehab and Return to Play


  • Needs to be updated

Return to Play/ Work

  • Needs to be updated

Complications and Prognosis


  • 70% of patients improve within the first year [2]
    • Improvements were usually seen in the function of the extremity
    • Visible symptoms like edema and skin color changes usually improve
    • 25% of these patients fulfilled the Budapest Criteria and only 5% were without complaints
    • Patients that report higher levels of anxiety and pain-related fear at the beginning of therapy have worse long term outcomes after a year


  • Chronic pain
    • Some patients may progress to severe pain with sympathetic dysfunction that will require regional anesthetic blockade to participate in physical therapy [8]
  • Pleiotropic effects involving most organ systems [9]:
    • Cardiovascular: increased heart rate, decreased heart rate variability, and atypical chest pain
    • Respiratory: shortness of breath and dystonia of chest wall muscles
    • Musculoskeletal: weakness, muscle atrophy, bone lakes due to osteoclastic activation, and bone marrow edema
    • Endocrine: stress, impaired hypothalamo-pituitary adrenal axis leading to tertiary adrenal insufficiency
    • Dermatologic: Erythema, mottling, “ligature sign,” livedo reicularis, and cyanosis
    • Urologic: Urinary frequency, urgency, and incontinence
    • Gastrointestinal system: constipation, nausea, vomiting, intermittent diarrhea, dysphagia, and indigestion

See Also


  1. 1.0 1.1 Iolascon, G., de Sire, A., Moretti, A., & Gimigliano, F. (2015). Complex regional pain syndrome (CRPS) type I: historical perspective and critical issues. Clinical cases in mineral and bone metabolism : the official journal of the Italian Society of Osteoporosis, Mineral Metabolism, and Skeletal Diseases, 12(Suppl 1), 4–10. https://doi.org/10.11138/ccmbm/2015.12.3s.004
  2. 2.0 2.1 Bruehl, S. (2015). Complex regional pain syndrome. BMJ. https://doi.org/10.1136/bmj.h2730
  3. 3.0 3.1 3.2 Bruehl, S. (2015). Complex regional pain syndrome. BMJ. https://doi.org/10.1136/bmj.h2730
  4. 4.0 4.1 4.2 4.3 U.S. Department of Health and Human Services. (n.d.). Complex regional pain syndrome fact sheet. National Institute of Neurological Disorders and Stroke. Retrieved June 19, 2022, from https://www.ninds.nih.gov/health-information/patient-caregiver-education/fact-sheets/complex-regional-pain-syndrome-fact-sheet
  5. Dey S, Guthmiller KB, Varacallo M. Complex Regional Pain Syndrome. [Updated 2022 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430719/
  6. 6.0 6.1 6.2 ZYLUK, A. N. D. R. Z. E. J. (2004). Complex regional pain syndrome type I. Risk factors, prevention and risk of recurrence. Journal of Hand Surgery, 29(4), 334–337. https://doi.org/10.1016/j.jhsb.2004.01.003
  7. Goebel A, Bisla J, Carganillo R, et al. A randomised placebo-controlled Phase III multicentre trial: low-dose intravenous immunoglobulin treatment for long-standing complex regional pain syndrome (LIPS trial). Southampton (UK): NIHR Journals Library; 2017 Nov. (Efficacy and Mechanism Evaluation, No. 4.5.) Appendix 3, Research diagnostic criteria (the ‘Budapest Criteria’) for complex regional pain syndrome. Available from: https://www.ncbi.nlm.nih.gov/books/NBK464482/
  8. Rho, R. H., Brewer, R. P., Lamer, T. J., & Wilson, P. R. (2002). Complex regional pain syndrome. Mayo Clinic Proceedings, 77(2), 174–180. https://doi.org/10.4065/77.2.174
  9. Schwartzman, R. J. (2012). Systemic complications of complex regional pain syndrome. Neuroscience and Medicine, 03(03), 225–242. https://doi.org/10.4236/nm.2012.33027
Created by:
John Kiel on 14 June 2019 08:25:15
Last edited:
29 June 2022 18:26:42