How are complex regional pain syndrome (CRPS) type I and type II defined?

Updated: Jun 20, 2018
  • Author: Gaurav Gupta, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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In 1994, a consensus group of pain medicine experts gathered by the International Association for the Study of Pain (IASP) agreed on diagnostic criteria for reflex sympathetic dystrophy (RSD) and causalgia, and renamed them complex regional pain syndrome (CRPS) types I and II, respectively. These designations were determined by the type of inciting event, rather than by any differences in clinical presentation or pathophysiology. Many experts felt that the IASP diagnostic criteria were ambiguous; however, these criteria were developed as just a starting point, and the IASP fully intended to validate them through clinical research studies. [1]

CRPS type I requirements feature causation by an initiating noxious event, such as a crush or soft tissue injury; or by immobilization, such as a tight cast or frozen shoulder. CRPS type II is characterized by the presence of a defined nerve injury. Both types demonstrate continuing pain, allodynia, or hyperalgesia that is usually disproportionate to the inciting event. At some point during the syndrome's development, both show evidence of edema, changes in skin blood flow revealed by color changes and skin temperature changes greater than 1.1°C from the homologous body part, or abnormal sudomotor activity in the painful region. Both types require the exclusion of any other condition that might account for the degree of pain and dysfunction seen. [2]

The 1994 IASP criteria have proven to be extremely sensitive (ie, they rarely miss a true case of CRPS). However, since their inception, the 1994 taxonomy has been criticized by experts on clinical criteria validation and specialists in pain medicine on the grounds that the criteria are insufficiently specific (ie, use of the criteria results in overdiagnosis of CRPS). A small single center validation study demonstrated empirically that the 1994 CRPS criteria did indeed cause overdiagnosis of the syndrome. [2]

In response to such concerns, investigators used factor analysis to categorize 123 patients with CRPS into 4 statistically distinct subgroups. [3] This resulted in modified diagnostic criteria felt to be valuable for further validation studies. [3, 4]

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