Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is a neuropathic pain disorder characterized by persistent pain that is disproportionate to the severity of the tissue injury and continues beyond the usual expected period of tissue healing. The pain is accompanied by sensory, motor, and autonomic abnormalities. Such abnormalities include allodynia, hyperalgesia, sudomotor and vasomotor abnormalities, and trophic changes. The pain is regional and does not follow a specific dermatome or myotome pattern. This disabling condition often develops after a trauma, fracture, or surgery. Some spontaneous cases have also been reported. In the 16th century, Ambroise Paré first reported cases with symptoms similar to CRPS, which developed after phlebotomy. In 1864, Silas Mitchell observed this syndrome after gunshot wounds. He used the term to describe this syndrome in 1872. James A. Evans coined the term  in 1946 to describe a similar condition, in which he suspected that sympathetically mediated pain was involved. Finally, in 1994, the International Association for the Study of Pain (IASP) named this condition  and proposed diagnostic criteria. Due to low specificity, a widely accepted revised set of criteria was proposed in 2010 and is commonly referred to as the . CRPS is classified into 2 subtypes—type 1, previously referred to as reflex sympathetic dystrophy, and type 2, formerly called causalgia. Type 1 arises without nerve trauma, whereas type 2 follows a known nerve injury. These conditions present with indistinguishable clinical features, typically affecting a regional area rather than following a dermatomal or peripheral nerve distribution. Symptoms typically involve the distal extremities but may extend proximally or to the contralateral limb. CRPS can also be categorized as warm or cold and may be sympathetically maintained or independent—classifications that influence prognosis and treatment strategies. In addition to impairing function, sleep, and activities of daily living, CRPS imposes a substantial psychological and psychosocial burden. The condition's variable clinical spectrum and poorly defined pathophysiology complicate management.