Complex Regional Pain Syndrome

Definition/diagnostic criteria Complex regional pain syndrome (CRPS) is a chronic pain condition typically affecting a limb after injury or surgery. The diagnostic criteria classify CRPS into two types: CRPS-I (without nerve injury) and CRPS-II (with nerve injury). Diagnosis is primarily clinical, based on patient history and symptoms. Diagnostic features include continuing pain disproportionate to any inciting event, with sensory, motor, autonomic, skin and bone abnormalities.

Epidemiology CRPS is relatively rare, with an estimated incidence in the UK of around 26.2 per 100,000 person-years. It is more common in females, with a female-to-male ratio of 3.4:1. The peak age of onset is between 50 and 70 years.

Diagnosis
Clinical features: Patients typically present with severe, persistent pain that is often described as burning, stabbing or throbbing. Swelling, changes in skin temperature and colour, abnormal sweating and range-of-motion limitations are common. There may also be trophic changes such as hair and nail growth abnormalities.

Investigations: Diagnostic tests are mostly used to exclude other conditions. Typical abnormalities in CRPS include abnormal skin temperature asymmetry, altered autonomic activity and osteoporotic changes on X-ray. Triple-phase bone scintigraphy can be supportive but is not definitive for CRPS.

Treatment Treatment is multidisciplinary and patient centred, focusing on pain management, physical rehabilitation and psychological support.

• Pharmacological treatment: Options include oral analgesics like paracetamol and NSAIDs. For neuropathic pain, first-line treatments are amitriptyline, gabapentin or pregabalin. Opioids are not recommended for long-term use due to the lack of evidence for effectiveness and risk of dependence.
• Physical and occupational therapy: Rehabilitation aims to restore function and reduce pain. Graded motor imagery and mirror therapy can be particularly effective.
• Psychological interventions: Cognitive behavioural therapy (CBT) can be beneficial for managing chronic pain and the associated psychological impact.
• Interventional treatments: Sympathetic nerve blocks may be considered, although evidence for their long-term effectiveness is limited.

Prognosis The prognosis of CRPS is variable. Early diagnosis and intervention can improve outcomes, with some patients achieving significant pain reduction and functional improvement. However, for others, the condition can become chronic and disabling. The risk of spread to other limbs and the development of long-term physical and psychological complications are concerns.