This method is still under experimental development. Electrodiagnostic testing
Electromyography (EMG) and nerve conduction studies (NCS) are important ancillary tests in CRPS because they are among the most reliable methods of detecting nerve injury. They can be used as one of the primary methods to distinguish between CRPS types I and II, which differ based on evidence of actual nerve damage. EMG and NCS are also among the best tests for ruling in or out alternative diagnoses. CRPS is a "diagnosis of exclusion", which requires that no other diagnosis can explain the patients symptoms. This is very important to emphasise because patients otherwise can be given a wrong diagnosis of CRPS when they actually have a treatable condition that better accounts for their symptoms. An example is severe carpal tunnel syndrome (CTS), which can often present in a very similar way to CRPS. Unlike CRPS, CTS can often be corrected with surgery to alleviate the pain and avoid permanent nerve damage and malformation.Both EMG and NCS involve some measure of discomfort. EMG involves the use of a tiny needle inserted into specific muscles to test the associated muscle and nerve function. Both EMG and NCS involve very mild shocks that in normal patients are comparable to a rubber band snapping on the skin. Although these tests can be very useful in CRPS, thorough informed consent must be obtained prior to the procedure, particularly in patients experiencing severe allodynia. In spite of the utility of the test, these patients may wish to decline the procedure to avoid discomfort.
As in any other chronic pain syndrome, the brain likely becomes chronically stimulated with pain, and late amputation may not work as well as it might be expected. In a survey of 15 patients with CRPS type 1, 11 responded that their lives were better after amputation. Since this is the ultimate treatment of a painful extremity, it should be left as a last resort. Prognosis
The prognosis in CRPS is improved with early and aggressive treatment; with the risk of chronic, debilitating pain being reduced with the early treatment. If treatment is delayed, however, the disorder can quickly spread to the entire limb, and changes in bone, nerve, and muscle may become irreversible. The prognosis is worse with the chronic "cold" form of CRPS and with CRPS affecting the upper extremities. Disuse of the limb after an injury or psychological distress related to an injury are also associated with a poorer prognosis in CRPS. Some cases of CRPS may resolve spontaneously (with 74% of patients undergoing complete resolution of symptoms (often spontaneously) in a population based study in Minnesota), but others may develop chronic pain for many years. Once one is diagnosed with CRPS, should it go into remission, the likelihood of it resurfacing after going into remission is significant. Taking precautions and seeking immediate treatment upon any injury is important. Epidemiology
CRPS can occur at any age, with the average age at diagnosis being 42.