BACKGROUND: Complex regional pain syndrome (CRPS) is a chronic pain disorder characterized by disproportionate pain and autonomic disturbances, and its management remains challenging. Opioid therapy is controversial because analgesic responses vary considerably among patients.

CASE REPORT: A 52-year-old woman developed CRPS type 1 after a crush injury to her right foot. She presented with severe persistent pain, allodynia, edema, and gait disturbance. A fentanyl infusion test (100 μg over 30 minutes) was performed to assess opioid responsiveness. Her Numeric Rating Scale score decreased from 8 to 3, indicating opioid-sensitive pain. Based on this response, tramadol therapy was initiated in combination with rehabilitation. The patient subsequently showed progressive pain relief and functional recovery, and tramadol was successfully tapered over 11 months.

CONCLUSIONS: Our case suggests that a fentanyl infusion test may help identify opioid-responsive patients with CRPS and guide individualized analgesic therapy while avoiding unnecessary opioid use.

KEYWORDS: Complex regional pain syndrome, fentanyl infusion test, opioid responsiveness, rehabilitation