Last reviewed: 20 Dec 2021
Last updated: 17 Dec 2019



History and exam

Key diagnostic factors

  • presence of risk factors
  • chronic pain
  • limb pain with radiation
  • allodynia and hyperalgesia
  • body scheme changes
  • oedema
  • trophic skin and nail changes
  • erythema or bluish appearance
  • local sweating changes or sweating asymmetry
  • muscle weakness

Other diagnostic factors

  • tremors
  • dystonic posturing
  • contractures
  • sensory loss in glove and stocking distribution
  • local changes in hair growth
  • skin bullae

Risk factors

  • trauma
  • immobilisation
  • female sex
  • other inciting event

Diagnostic investigations

Investigations to consider

  • electromyogram
  • nerve conduction studies with surface electrodes
  • punch skin biopsy
  • radiograph of affected limb
  • bone scintigraphy with technetium 99m
  • dual-energy x-ray absorptiometry (DXA)
  • quantitative CT scan
  • MRI testing
  • vascular studies
  • sympathetic nerve blocks
  • intravenous regional anaesthetic blocks

Emerging tests

  • quantitative sensory testing
  • thermography
  • laser Doppler flowmetry
  • sweat (sudomotor) tests

Treatment algorithm



Nicholas Shenker, BM BCh, MA, PhD, FRCP

Consultant in Rheumatology

Cambridge University Hospitals NHS Foundation Trust

Addenbrooke's Hospital




NS is medical adviser to Cambridge Nutraceuticals with stock options. He has received consultancy fees from Roche to provide unrestricted sponsored educational meetings, and grants from Versus Arthritis, the National Institute for Health Research Clinical Research Network, and the Medical Research Council. NS is an author of references cited in this topic.

Gaurav Chhabra, MBBS, FRCA, FFPMRCA

Consultant in Pain Medicine and Anaesthesia

North Bristol NHS Trust




GC has been sponsored by Medtronic, Boston Scientific, Abbott, Nevro, Stimwave, and Polar Medical for attending various conferences and cadaveric workshops relevant to pain medicine and neuromodulation. GC is an associate examiner for the European Society of Regional Anaesthesia & Pain Therapy European Diploma of Pain Medicine exam and is also the regional advisor for pain medicine for the South West Severn deanery.


Dr Nicholas Shenker and Dr Gaurav Chhabra would like to gratefully acknowledge Dr Steven H. Horowitz, a previous contributor to this topic.


SHH declares that he has no competing interests.

Peer reviewers

Andre Tomasino, MD

Department of Neurological Surgery

Weill Cornell Medical College

New York-Presbyterian Hospital

New York



AT declares that he has no competing interests.

Ari Weinreb, MD, PhD

Associate Chief of Rheumatology

VA Greater Los Angeles Healthcare System

Associate Professor of Medicine

David Geffen School of Medicine


Los Angeles



AW declares that he has no competing interests.

Jonathan Berman, MBBS

Consultant in Pain Management and Anaesthesia

Pain Management Department

Royal National Orthopaedic Hospital NHS Trust




JB has been reimbursed by Pfizer for lectures given at Pfizer-sponsored meetings and courses.

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