Before diagnosing complex regional pain syndrome (CRPS), a physician will review the patient’s medical history and should perform physical examination. In many cases, CRPS can be traced back to a specific accident, illness or injury. The physician will look for changes in the texture and color of skin and problems with range of motion of one or more joints. Blood tests may be performed to rule out other conditions, such as arthritis.

CRPS is a clinical diagnosis, and there are no tests specific and sensitive for it. But other tests that may be performed include:

• Bone scan. A type of radionuclide imaging. This nuclear medicine test highlights features of the bones when viewed with a special camera. Bone scans can reveal small fractures and increased circulation to the joints in areas affected by CRPS.
  
  
• Sympathetic nervous system tests. A group of procedures that help reveal disturbances in the sympathetic nervous system by measuring skin temperature and blood flow or the amount of sweat in affected and unaffected limbs. If comparisons between the two limbs show dissimilarity, it may indicate CRPS. Sympathetic nerve blocks can also be used to determine whether or not a person is suffering a CRPS problem that involves the sympathetic nervous system. If the block reduces pain, the sympathetic nervous system may be the source of some of the signs and symptoms of CRPS.
  
  
• MRI (magnetic resonance imaging). A noninvasive or minimally invasive imaging test involving powerful magnets. An MRI may show tissue changes such as wasting of muscle or skin caused by CRPS.
  
  
• X-ray. A painless test in which an image is created of part of the body by using low doses of electromagnetic radiation that are reflected on film or fluorescent screens. Though they are usually not a diagnostic test for CRPS, x-rays can detect a loss of minerals from the bones, which may indicate later stages of the disorder.