[Reflex sympathetic dystrophy: still a poorly defined entity].

The reflex sympathetic dystrophy (algodystrophy) constitutes a large nosological field of which the main characteristics are the appearance of algic and vasomotor symptoms at a segmental level of a limb, in consequence to diverse pathologies (trauma, cardiovascular disease, etc.). The widely accepted theory of a dysregulation of the sympathetic nervous system is nowadays counter-balanced by recent work highlighting the preponderant role of polymodal afferent nerves in the pathophysiology of this disease. The diagnosis, being above-all clinical, is marked by two distinct phases appearing in a variable chronology; a warm phase associating fluctionating pain, stiffness and vasomotor symptoms, and then a cold phase characterized by fibrosis, leading to disabling trophic symptoms. Spontaneous recovery is usual and can be delayed by up to two years, however irreversible sequelae can occur. Paraclinical investigations are necessary to confirm the diagnosis: absence of a biological inflammatory syndrome, early hyperfixation on bone scintography or an abnormality in the MRI signal in the sub-chondral zones. The X-ray shows late local demineralization that is often non-homogenous. The treatment is poorly codified. First-line treatment in France, other than antalgics, often rests on the calcitonins. Intravenous diphosphonates are proposed by some in case of treatment failure. Regional venous blocks are sometimes performed in resistant and disabling forms. Rehabilitation and psychological support have a primordial place throughout the evolution of the illness.