DIAGNOSTICS AND DIAGNOSTIC CRITERIA

The nature of, diagnostic criteria for, and even the naming of CRPS have been controversial.¹⁹ See Figure 3 for the IASP Diagnostic Criteria.²⁰ Taking into consideration the controversy in nomenclature, the Special Interest Group “Pain and the Sympathetic Nervous System” of the International Association for the Study of Pain (IASP) at a workshop in Orlando in 1993 came up with the new name after “extensive grappling.”²¹ Robert A. Boas describes the terminology, “The umbrella term for all disorders falling within the domain of causalgia and reflex sympathetic dystrophy was now designated as a complex regional pain syndrome (CRPS). Complex describes the varied and dynamic nature of the clinical presentation within a single person over time, and among persons with seemingly similar disorders. It also included the features of inflammation, autonomic, cutaneous, motor, and dystrophic changes, which distinguish this from other forms of neuropathic pain. Regional – as in the wider distribution of symptoms and findings beyond the area of the original lesion—is a hallmark of these disorders. Such symptoms and signs usually affect the distal part of a limb but occasionally can involve discrete regions or spread to other body areas. Pain is the sine qua non for the CRPS syndrome—pain that is disproportionate to the inciting event. This is not just burning pain, but includes spontaneous pain and thermal or mechanically induced allodynia. Syndrome – the constellation of symptoms and signs of CRPS represents a series of correlated events that are sufficient to be designated as a distinctive entity, even though we are not sure what constitutes each of these events, or which are essential, nor the nature of the pathological changes that ensue.”²²

There are three classifications of this syndrome. CRPS type I usually occurs after an illness or injury that did not directly damage the nerves in an affected limb or region of the body. It was previously termed reflex sympathetic dystrophy (RSD), but the current research suggests multiple causes rather than the sympathetic nervous system as the culprit. Complex regional pain syndrome type II, formerly known as causalgia, has been commonly distinguished by evidence of neuronal damage. However, recent studies suggest that there may not be a clear distinction between the syndromes.²³ CRPS III was created for the difficult cases that contained pain and sensory changes, with either motor or tissue changes, but did not comply fully with the more classical forms.^{24, 25}

The diagnostic criteria are not yet optimized or even standardized in the literature, and there is reportedly no noticeable difference since the introduction of the criteria.^26-28 Although the criteria are an important step in the right direction, they lack specificity, which makes it difficult to determine new treatment approaches targeted at particular pain mechanisms.^{29, 30} There are several other clinical criteria, including Bruehl’s or Veldman’s clinical criteria, however the IASP criteria are cited more widely in the literature and treatment trials.³¹ Stages of progression of CRPS have also been set forth, however an eight year study of 829 subjects failed to identify these stages.³² A second IASP conference in 2000 also rejected the concept of staging.³³

HOW COMMON IS CRPS?

There are only a few published epidemiological studies regarding the incidence of CRPS in the general population. The most recent studies by M. de Mos began in 1992 with ongoing data collection utilizing electronic patient records.³⁴ The first of two de Mos studies included 600,000 patients throughout the Netherlands from1996-2005.³⁵ The conclusion of the study was an incidence rate of CRPS at 26.2 new cases per 100,000 annually.³⁶ Applying the results from the de Mos study to the U.S. census bureau population estimates of 299,665,000; one would expect over 50,000 new cases of CRPS-I annually.³⁷ Most of these patients are at an economically productive age, but CRPS seriously limits their ability to work. The Reflex Sympathetic Dystrophy Foundation conducted a study of 1,348 CRPS patients and found that work was seen to increase pain in 79% of the cases, 38% were unemployed, 17.4% worked full time, 8% part time, and 21% worked at one time but had to stop because of CRPS.³⁸

In another study from 2006 of 168 patients, 28% were officially disabled because of CRPS, and the cost of physical therapy for a year per patient was estimated at $6,000.³⁹ The costs for physical therapy alone for the officially disabled percentage (28-38%) of 50,000 new cases annually calculates to 84-114 million dollars per year. This does not take into account the cost of therapy for those who are not considered officially disabled, or the surgery, or the pain medications, etc. It is clear that CRPS is a disabling disease and has a severe impact physically, vocationally, and economically. Michael Rowbotham, MD comments, “Overall, the present situation is most unfortunate, considering the very high burden of suffering, lost productivity, and a cost of treatment that may exceed $100,000 (per patient).”⁴⁰