COMPLEX REGIONAL PAIN SYNDROME TYPE (REFLEX SYMPATHETIC DYSTROPHY) Current Evidence Complex regional pain syndrome type (CRPS1), formerly known as reflex sympathetic dystrophy (RSD) and also called reflex neurovascular dystrophy (RND) and amplified musculoskeletal pain syndrome (AMPS), is a poorly understood disorder characterized by pain, abnormal sensation, and in some patients circulatory irregularities Over time, disuse and atrophic changes of the extremity may develop Initially thought to be primarily an adult disease, CRPS1 is increasingly being recognized in children There are often delays in diagnosing children with CRPS1 Emergency clinicians can play a valuable role by considering CRPS1 in children with pain and making appropriate referrals for a prompt, definitive diagnosis In most patients symptoms of CRPS1 will eventually resolve, but early treatment may prevent prolonged disability Children with CRPS1 as young as years have been described The average age of children with CRPS1 is approximately 12 years, girls outnumbering boys by as much as 6:1 Most cases in children involve the lower extremity CRPS1 usually follows minor trauma, but some cases develop without an identified precipitant The pathophysiology of CRPS1 is not well understood Early theories suggested abnormal synapses develop between sensory afferent nerves and sympathetic afferents after an injury “Sympathetic” dystrophy is probably a misnomer, and nomenclature has changed because local epinephrine and norepinephrine levels are lower, not higher than normal, and vasodilation, not sympathetic vasoconstriction, may predominate Current theories include regional sensitization of the central and perhaps peripheral nervous system from an initial injury Experimental evidence suggests involvement of glutamate and NMDA (N -methyl-D -aspartic acid) receptors in this process Patients with other dysautonomic conditions, including gastrointestinal dysmotility, migraine, cyclic vomiting, and chronic fatigue, may also have CRPS1