8 Chronic Pain Conditions and Their Diagnostic Criteria

2. Complex Regional Pain Syndrome - When Pain Becomes Disproportionate

Complex Regional Pain Syndrome (CRPS) represents one of the most severe and debilitating chronic pain conditions, characterized by intense burning pain, swelling, and changes in skin color and temperature that are disproportionate to the inciting event or injury. The International Association for the Study of Pain (IASP) established the current diagnostic criteria, which distinguish between CRPS Type I (formerly known as reflex sympathetic dystrophy) and CRPS Type II (formerly causalgia), with the primary difference being the presence or absence of confirmed nerve injury. The diagnostic criteria require continuous pain that is disproportionate to the inciting event, along with evidence of edema, changes in skin blood flow or abnormal sudomotor activity, and decreased range of motion or motor dysfunction. Patients must also display at least one symptom in three of four categories: sensory (hyperalgesia or allodynia), vasomotor (temperature asymmetry or skin color changes), sudomotor/edema (edema or sweating changes), and motor/trophic (decreased range of motion, motor dysfunction, or trophic changes). The condition typically develops following trauma, surgery, or immobilization, with early diagnosis being crucial as the syndrome can progress through distinct stages, from acute inflammatory phase to chronic atrophic phase. Advanced diagnostic tools such as bone scintigraphy, quantitative sensory testing, and autonomic function tests may support the diagnosis, though the clinical presentation remains the cornerstone of CRPS identification.