Current state of knowledge
The syndrome continues to perplex, fascinate, and frustrate clinicians and researchers alike. Although very sensitive, the 1994 criteria lacked specificity and led to over diagnosis of CRPS type 1.1 Given the high false-positive rate of IASP criteria, a combination of symptoms and signs were proposed by Harden and Bruehl2 to increase discrimination between CRPS and non-CRPS patients.
These criteria were published in an IASP-sanctioned book but are not formally adopted yet. The new criteria proposed that the patient must not only have pain disproportionate to the inciting event but also report 1 symptom in 3 of 4 categories (sensory, vasomotor, sudomotor/edema, and motor/trophic) and display at least 1 sign in 2 or more of the above 4 categories. These criteria cluster categories of signs and symptoms that have been proved meaningful by research introduce a separate category of motor problems (paired with trophic changes). The accompanying Table (see below) has been created on the basis of these criteria and is currently in use by our own pain program, the Comprehensive Pain Program of Toronto Western Hospital.
However, we caution that the current proposed criteria as well as the 1994 IASP classification have great difficulty accounting for patients who present with large areas of hypoesthesia instead of hyperesthesia (personal communication with Norman Harden, coauthor of the Harden and Bruehl criteria). Such hypoesthesia is not rare and seems to be a central phenomenon but is poorly understood.3
At present, CRPS type 1 is considered to be a multifactorial regional syndrome.4 It affects both the peripheral nervous system and CNS and additionally has musculoskeletal, endocrinological, and vascular ramifications.
The incidence of CRPS type 1 in the general population is reported by Sandroni and associates5 to be 5.46 persons/100,000 with period prevalence (1989-1999) of 20.57/100,000. Women are affected 4 times more often than men. Approximately three-fourths of CRPS type 1 cases in the community resolve spontaneously, while pain clinics address refractory CRPS. In another study, however, the incidence was recorded to be 4 times higher than the one reported by Sandroni and colleagues.6