Complex regional pain syndrome

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By Steven H Horowitz MD

Complex regional pain syndrome is also known as Causalgia, Reflex sympathetic dystrophy. -ed.

In this clinical article, Dr. Steven Horowitz of the University of Vermont and Massachusetts General Hospital discusses complex regional pain syndrome (CRPS), a consensus-defined clinical neuropathic pain syndrome with an illustrious history and fascinating ever-elucidating pathophysiology. CRPS presents with pain, hyperalgesia, and allodynia as well as motor, vasomotor, sudomotor, and trophic changes, most often induced by trauma or immobilization. It is likely that peripheral nerve injury produces neuroinflammation peripherally, and centrally in the dorsal horn, thalamus, and elsewhere, resulting in peripheral and central sensitization, enhancement of symptomatology, and spread to other anatomical areas. Multiple cortical changes have been demonstrated on fMRI when symptoms are most manifest, which seem to return to normal with clinical improvement. Treatment is based on restoration of limb function and relief of pain and other symptoms.

Key points

  • Complex regional pain syndrome (CRPS) is a consensus-defined clinically diagnosed pain syndrome with hyperalgesia, allodynia, vasomotor, sudomotor, motor, and trophic symptoms and signs initiated by trauma and/or immobilization.
  • There is no “gold-standard” diagnostic test; the diagnosis remains “clinical” at present.
  • The pathophysiology, although incompletely understood, involves neuroinflammation and neuromodulation at multiple peripheral and central nervous system levels.
  • Treatment is directed toward restoration of limb function. There are no FDA-approved medications. Therapies of proven value in other neuropathic pain states are of some benefit in CRPS.