Can complex regional pain syndrome be painless?

While spontaneous and stimulus-evoked pain are the hallmarks of complex regional pain syndrome (CRPS), also known as reflex sympathetic dystrophy, autonomic abnormalities, motor dysfunction, and trophic changes in the affected limb are additional clinical characteristics distinguishing this syndrome. Even though the exact underlying mechanisms of the syndrome remain obscure, a recent hypothesis suggests that the abnormal response of neural nociceptive tissue plays a major role in the pathogenesis of CRPS via the mechanism known as 'neurogenic inflammation'. The group of patients presented here exhibited all the clinical characteristics of CRPS but had no pain, thereby indicating that ongoing or evoked pain is not a necessary condition for CRPS to be maintained. We suggest the term complex regional painless syndrome to describe this syndrome.