Complex regional pain syndrome (CRPS) formerly reflex sympathetic dystrophy (RSD), “causalgia”, or reflex neurovascular dystrophy (RND) is an amplified musculoskeletal pain syndrome (AMPS). It is a chronic systemic disease characterized by severe pain, swelling, and changes in the skin. CRPS is expected to worsen over time. It often initially affects an arm or a leg and often spreads throughout the body; 92% of patients state that they have experienced a spread, and 35% of patients report symptoms in their whole body.
Complex Regional Pain Syndrome is a multifactorial disorder with clinical features of neurogenic inflammation (swelling in the central nervous system), nociceptive sensitisation (which causes extreme sensitivity or allodynia), vasomotor dysfunction (blood flow problems which cause swelling and discolouration) and maladaptive neuroplasticity (where the brain changes and adapts with constant pain signals); CRPS is the result of an “aberrant [inappropriate] response to tissue injury”. Treatment is complicated, involving drugs, physical therapy, psychologic treatments, and neuromodulation and is usually unsatisfactory, especially if begun late.