Key words: CRPS, incidence, review.

Complex regional pain syndrome, CRPS, occurs with severe disabling pain, usually in the leg or hand, coupled with changes in pain perception, hyperesthesia and allodynia. There is as well, edema, changes in the color of the skin, trophic changes, and dystonia. The pain syndrome is often triggered by minor trauma. The pain perception is severe and out of context with the initial trauma.

The syndrome is rare, occurring in a population-based study in the United States, with an incidence of only 5.5 per hundred thousand people per year. The incidence in Iceland, from the National Register of Diseases from the Directorate of Health, was 1.3 per annum, per hundred thousand people.

The exact etiology of the disease is unknown. It is presumed that inflammation is the cause, often resulting from an autoimmune reaction. The term pain sensitization is also used to describe the pain mechanism, both in peripheral nerves and in the central nervous system. There are changes and displacement of the area of the neocortex that is coupled with pain perception. The criteria of the International Association for the Study of Pain (IASP) were the basis for the diagnosis.

Interdisciplinary team management according to the biopsychosocial model is thought to be the preferred treatment approach. The members of the team are occupational therapists, physiotherapists, social workers, psychologists, nurses, and medical doctors, augmented by other disciplines as needed. One treatment option is mirror therapy, where the diseased extremity is held behind a mirror during the training and the patient observes movements of the healthy extremity. Initially treatment is aimed at treating the inflammation, often with NSAID drugs, or with steroids. Medical treatments are the same as apply for the treatment of neural pain, with drugs such as Gabapentin, or anti depressive agents as duloxetine or imipramine. There is an indication to use bisphosphonates such as alendronate, especially if there is osteoporosis.

It is assumed that the function of the NMDA receptor has changed in the central nervous system and treatment with intravenous ketamine, is an option. Spinal cord stimulation of the dorsal horns of the spine has been effective as well.

In majority of cases the syndrome resolves in the first two years, but for the rest the prognosis is dire, symptoms getting worse and persisting for years and even decades.