Complex regional pain syndrome.

Complex regional pain syndrome (CRPS) is characterised by constant regional neuropathic pain that is usually associated with abnormal sensory, autonomic, motor and/or trophic changes. Though it usually develops after trauma to a limb, in CRPS pain is disproportionate in time or intensity to the usual course of pain after injury. There are two subtypes of CRPS: in type I no overt nerve lesion can be identified; in type II definite nerve injury is evident. CRPS has had various names including causalgia, reflex sympathetic dystrophy, Sudeck’s atrophy, algoneurodystrophy, and shoulder-hand syndrome. All those terms were replaced by CRPS after a 1993 conference by the International Association for the Study of Pain (IASP), which aimed at clarifying and providing more uniformity for diagnosis. Only recently has it begun to feature in more general medical textbooks, and most clinicians have not been trained to recognise it. The pathophysiology of CRPS is multifaceted and remains incompletely understood. Several lines of evidence point towards disturbances involving abnormal response to tissue injury, peripheral and central pain sensitisation processes, neurogenic inflammation, endothelial dysfunction, disturbed sympathetic-afferent coupling, hyperalgesic priming, somatosensory cortical reorganisation, genetic predisposition, and even some degree of autoimmunity. Methods