Complex regional pain syndrome type 1

Complex regional pain syndrome type 1 (CRPS type 1), formerly known as reflex sympathetic dystrophy (RSD) or Sudeck's atrophy, is a chronic pain condition that typically develops after an injury, surgery, stroke, or immobilization of a limb. It is characterized by pain that is disproportionate in severity and duration to the initial triggering event. CRPS type 1 differs from type 2 (causalgia) in that it occurs without a confirmed nerve injury. The condition primarily affects the extremities — most commonly the arms, hands, legs, or feet — and involves dysfunction of the peripheral and central nervous systems, as well as the autonomic nervous system. Key clinical features include intense, continuous burning or throbbing pain in the affected limb, along with changes in skin color and temperature, abnormal sweating, edema (swelling), and heightened sensitivity to touch or cold (allodynia and hyperalgesia). Over time, patients may develop trophic changes such as altered hair and nail growth, skin atrophy, joint stiffness, decreased range of motion, and muscle weakness or wasting. The condition can spread from the initially affected area to other parts of the body. Motor disturbances including tremor, dystonia, and difficulty initiating movement may also occur. The exact pathophysiology of CRPS type 1 remains incompletely understood but is thought to involve neurogenic inflammation, altered sympathetic nervous system function, central sensitization, and possible autoimmune mechanisms. Treatment is multidisciplinary and typically includes physical and occupational therapy, pharmacological management (such as nonsteroidal anti-inflammatory drugs, corticosteroids, anticonvulsants like gabapentin, bisphosphonates, and sometimes low-dose naltrexone), psychological support, and interventional procedures such as sympathetic nerve blocks, spinal cord stimulation, or intrathecal drug delivery in refractory cases. Early diagnosis and prompt initiation of rehabilitation are critical for improving outcomes, as delayed treatment is associated with poorer prognosis.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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