Which sign is most characteristic of complex regional pain syndrome?

• A. Fever and tachycardia only
• B. Exaggerated pain with vasomotor changes
• C. Weakness and numbness only
• D. Pain relief with movement

Answer: (B)

CRPS presents with ongoing, intense limb pain that is out of proportion to any injury, along with autonomic (vasomotor) changes in the affected area. The most characteristic sign is an exaggerated pain response paired with vasomotor instability, which leads to differences in skin color and temperature (such as red to pale or warm to cool skin) and abnormal sweating. This combination reflects dysfunction in the sympathetic control of blood flow and sweat glands in the involved limb. Other features like edema, trophic changes, or motor symptoms can occur, but the hallmark is the disproportionate pain with vasomotor changes. Fever and tachycardia are systemic and not central to CRPS; weakness and numbness can appear but don’t define the condition; pain that improves with movement is not typical.