Complex Regional Pain Syndrome

Complex Regional Pain Syndrome (CRPS) is a neuropathic pain disorder characterized by ongoing pain disproportionate to the degree of tissue injury and persists beyond the usual expected time for tissue healing. Pain is accompanied by sensory, motor, and autonomic abnormalities. Such abnormalities include allodynia, hyperalgesia, sudomotor and vasomotor abnormalities, and trophic changes. Pain does not follow a particular dermatome or myotome but is rather regional. This disabling condition often develops after a trauma, fracture, or surgery. But some spontaneous cases have also been reported.

In the 16th century, Ambroise Paré reported cases with CRPS like symptoms for the first time which developed after phlebotomy. In 1864, Silas Mitchell noted this syndrome after gunshot wounds. He used the term ‘causalgia’ to describe this syndrome in 1872. James A. Evans coined the term ‘reflex sympathetic dystrophy’ to describe a similar condition where he suspected sympathetically mediated pain in 1946. Finally, in 1994, the International Association for the Study of Pain (IASP) named this condition ‘Complex Regional Pain Syndrome’ and proposed a diagnostic criterion. Due to low specificity, a widely accepted revised criterion was proposed in 2010 and is commonly referred to as the "Budapest Criteria."

CRPS has two subtypes: type I, formerly known as reflex sympathetic dystrophy, and type II, formerly known as causalgia. Type I occurs in the absence of nerve trauma, while type II occurs in the setting of known nerve trauma. Clinically they are indistinguishable and follow a regional rather than a dermatomal or peripheral nerve distribution and favor the distal extremities, though spread outside of the initially affected area commonly occurs to the proximal or contralateral limb. CRPS is further subdivided into "warm" versus "cold," and sympathetically-maintained (SMP) versus sympathetically-independent (SIP), which may affect prognosis and treatment options.

CRPS not only impacts function, sleep, and activities of daily living but also takes a significant mental and psychosocial toll on the patient. Its diverse spectrum of clinical presentation and lack of any clearly defined pathophysiology poses a challenge for optimal management of this disorder.