technique to identify reduced bone mineral density in crps. additionally, this method promises to quantify the bone architecture in the periphery of affected limbs. 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 patient's 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. classification type i, formerly known as reflex sympathetic dystrophy (rsd), sudeck's atrophy, or algoneurodystrophy, does not exhibit demonstrable nerve lesions. as the vast majority of patients diagnosed with crps have this type, it is most commonly referred to in medical literature as type i. type ii, formerly known as causalgia, has evidence of obvious nerve damage. despite evidence of nerve injury, the cause or the mechanisms of crps type ii are as unknown, as the mechanisms of type i. patients are frequently classified into two groups based upon temperature: "warm" or "hot" crps in one group and "cold" crps in the other group. the majority of patients (about 70%) have the "hot" type, which is said to be an acute form of crps. cold crps is said to be indicative of a more chronic crps and is associated with poorer mcgill pain questionnaire scores, increased central nervous system involvement, and a higher prevalence of dystonia. prognosis is not favourable for cold crps patients; longitudinal studies suggest these patients have "poorer clinical pain outcomes and show persistent signs of central sensitisation correlating with disease progression". prevention vitamin c supplementation may be useful in prevention of the syndrome following fracture of the forearm, foot, or ankle. treatment treatment of crps often involves a number of modalities. therapy physical and occupational therapy have low-quality evidence to support their use. physical therapy interventions may include transcutaneous electrical nerve stimulation, progressive weight bearing, graded tactile desensitization, massage, and contrast bath therapy. in a retrospective cohort (unblinded, non-randomised and with intention-to-treat) of fifty patients diagnosed with crps, the subjective pain and body perception scores of patients decreased after engagement with a two-week multidisciplinary rehabilitation programme. the authors call for randomised controlled trials to probe the true value of multidisciplinary programs for crps patients. mirror box therapy mirror box therapy uses a mirror box, or a stand-alone mirror, to create a reflection of the normal limb such that the patient thinks they are looking at the affected limb. movement of this reflected normal limb is then performed so that it looks to the patient as though they are performing movement with the affected limb. mirror box therapy appears to be beneficial at least in early crps. however, beneficial effects of mirror therapy in the long term is still unproven. graded motor imagery graded motor imagery appears to be useful for people with crps-1. graded motor imagery is a sequential process that consists of (a) laterality reconstruction, (b) motor imagery, and (c) mirror therapy. transcutaneous electrical nerve stimulation (tens) transcutaneous electrical nerve stimulation (tens) is a therapy that uses low-voltage electrical signals to provide pain relief through electrodes that are placed on the surface of the skin. evidence supports its use in treating pain and edema associated with crps, but it does not seem to increase functional ability in crps patients. medications tentative evidence supports the use of bisphosphonates, calcitonin, and ketamine. nerve blocks with guanethidine appear to be harmful. evidence for sympathetic nerve blocks generally is insufficient to support their use. intramuscular botulinum injections may benefit people with symptoms localized to one extremity. ketamine ketamine, a dissociative anesthetic, appears promising as a treatment for crps. it may be used in low doses if other treatments have not worked. no benefit on either function or depression, however, has been seen. bisphosphonate treatment as of 2013, high-quality evidence supports the use of bisphosphonates (either orally or via iv infusion) in the treatment of crps. bisphosphonates inhibit osteoclasts: cells involved in the resorption of bone. bone remodeling (via osteoclast activity in resorption of bone) is thought to sometimes be hyperactive in crps. it is hypothesized that bone resorption causes acidification of the intercellular milieu which, in turn, activates nerves involved in nociception that densely innervate bone and causes pain. therefore, inhibiting bone resorption and remodeling is thought to help with regard to crps pain. crps involving high levels of bone resorption, as seen on bone scan, is more likely to respond to bisphosphonate therapy. opioids opioids such as oxycodone, morphine, hydrocodone, and fentanyl have a controversial place in treatment of crps. these drugs must be prescribed and monitored under close supervision of a physician as they can quickly to physical dependence and addiction. to date far, no long-term studies of oral opioid use in treating neuropathic pain, including crps, have been performed. the consensus among experts is that opioids should not be a first-line therapy and should be considered only after all other modalities (e.g., non-opioid medications, physical therapy, and procedures) have been trialed. spinal cord stimulators spinal cord stimulation appears to be an effective therapy in the management of patients with crps type i (level a evidence) and type ii (level d evidence). although they improve patient pain and quality of life, evidence is unclear regarding effects on mental health and general functioning. dorsal root ganglion stimulation is a type of neurostimulation that is effective in the management of focal neuropathic pain. the fda approved its use in february 2016. the accurate study demonstrated superiority of dorsal root ganglion stimulation over spinal (dorsal column) stimulation in the management of crps and causalgia. sympathectomy surgical, chemical, or radiofrequency sympathectomy—interruption of the affected portion of the sympathetic nervous system—can be used as a last resort in patients with impending tissue loss, edema, recurrent infection, or ischemic necrosis. however, little evidence supports these permanent interventions to alter the pain symptoms of the affected patients, and in addition to the normal risks of surgery, such as bleeding and infection, sympathectomy has several specific risks, such as adverse changes in how nerves function. amputation no randomized study in medical literature has studied the response with amputation of patients who have failed the above-mentioned therapies and who continue to be miserable. nonetheless, on average, about half of the patients will have resolution of their pain, while half will develop phantom limb pain and/or pain at the amputation site. 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. it affects both men and women; however, crps is three times more frequent in females than males. crps affects both adults and children, and the number of reported crps cases among adolescents and young adults has been increasing, with a recent observational study finding an incidence of 1.16/100,000 among children in scotland. history the condition currently known as crps was originally described by ambroise paré. he successfully treated a severe and persistent pain syndrome that occurred to the french king charles ix of valois after a limb phlebotomy . during the american civil war silas weir mitchell, is sometimes also credited with inventing the name "causalgia". however, this term was actually coined by mitchell's friend robley dunglison from the greek words for heat and for pain. contrary to what is commonly accepted, it emerges that these causalgias were certainly major by the importance of the vasomotor and sudomotor symptoms but stemmed from minor neurological lesions. in the 1940s, the term reflex sympathetic dystrophy came into use to describe this condition, based on the theory that sympathetic hyperactivity was involved in the pathophysiology. in 1959, noordenbos observed in causalgia patients that "the damage of the nerve is always partial." misuse of the terms, as well as doubts about the underlying pathophysiology, led to calls for better nomenclature. in 1993, a special consensus workshop held in orlando, florida, provided the umbrella term "complex regional pain syndrome", with causalgia and rsd as subtypes. research the national institute of neurological disorders and stroke (ninds), a part of the national institutes of health, supports and conducts research on the brain and central nervous system, including research relevant to rsds, through grants to major medical institutions across the country. ninds-supported scientists are working to develop effective treatments for neurological conditions and ultimately, to find ways of preventing them. investigators are studying new approaches to treat crps and intervene more aggressively after traumatic injury to lower the patient's chances of developing the disorder. in addition, ninds-supported scientists are studying how signals of the sympathetic nervous system cause pain in crps patients. using a technique called microneurography, these investigators are able to record and measure neural activity in single nerve fibers of affected patients. by testing various hypotheses, these researchers hope to discover the unique mechanism that causes the spontaneous pain of crps, and that discovery may lead to new ways of blocking pain. other studies to overcome chronic pain syndromes are discussed in the pamphlet "chronic pain: hope through research", published by the ninds. research into treating the condition with mirror visual feedback is being undertaken at the royal national hospital for rheumatic disease in bath. patients are taught how to desensitize in the most effective way, then progress to using mirrors to rewrite the faulty signals in the brain that appear responsible for this condition. however, while crps can go into remission, the chance of it reoccurring is significant. the netherlands has the most comprehensive program of research into crps, as part of a multimillion-euro initiative called trend. german and australian research teams are also pursuing better understanding and treatments for crps. in other animal species crps has also been described in non-human animals, such as cattle. notable cases paula abdul, singer, actor, tv personality jill kinmont boothe, us ski slalom champion