Name a hallmark feature of complex regional pain syndrome after injury?

• A. Allodynia with edema and autonomic changes
• B. Joint effusion without sensory changes
• C. Pure motor weakness with normal sensation
• D. Fever without pain

Answer: (A)

Complex regional pain syndrome after injury is defined by sensory and autonomic changes that accompany disproportionate pain. Allodynia, where non-painful stimuli trigger pain, often pairs with edema from vasomotor instability and autonomic signs such as altered sweating and skin temperature or color. This combination—pain amplified by normal touch, plus swelling and autonomic dysregulation—best represents the hallmark pattern seen after injury.

The other scenarios don’t fit because they lack this combination of sensory disturbance and autonomic/vascular changes: a joint effusion without sensory changes misses the neuropathic component; pure motor weakness with normal sensation lacks the sensory and autonomic signs; fever without pain doesn’t reflect the spontaneous, localized autonomic and sensory dysregulation typical of CRPS.