Unraveling The Mystery Of CRPS
Complex regional pain syndrome (CRPS) has emerged as one of the more controversial topics in podiatry in recent years. Not only are there no clear-cut answers in regard to the etiology of the condition, standard terminology for describing the condition has been equally elusive in the past. With this in mind, expert panelists discuss various issues in diagnosing and treating this condition. Q: We have all heard different terms used for this condition, including reflex sympathetic dystrophy (RSD), complex regional pain syndrome (CRPS), causalgia and Sudek’s Atrophy. What is the current preferred terminology and definition for this complex condition? A: Nearly 80 different terms have been used in the past to describe this condition and this reflects “the lack of understanding of the pathophysiology of the condition,” according to Jeffrey C. Christensen, DPM. Lawrence Fallat, DPM, concurs. He says the different terminology caused so much diagnostic confusion that the International Association for the Study of Pain (IASP) developed standardized definitions. All the panelists agree that the condition is currently referred to as either CRPS type I (CRPS I), which was previously referred to as RSD or sympathetically maintained pain (SMP), or CRPS type II (CRPS II), which was previously called causalgia. Nelson Hendler, MD, MS, says CRPS I involves circumferential pain and the presence of both thermal and mechanical allodynia. Dr. Christensen says CRPS I may have these criteria: 1) the presence of an initiating noxious event or a cause of immobilization; 2) continuing pain, allodynia or hyperalgesia with which the pain is disproportionate to any inciting event; 3) evidence of edema, changes in skin blood flow or abnormal sudomotor activity in the region of pain; and 4) this diagnosis is excluded by the existence of conditions that would otherwise account for the degree of pain and dysfunction. Dr. Christensen says the last three criteria must be satisfied when considering a diagnosis of CRPS I. Dr. Hendler disagrees. Steven Mandel, MD, says some researchers have suggested there may be three “subtypes” of RSD. The first subtype is a limited syndrome with vasomotor signs predominating while the second subtype would be a limited syndrome marked by neuropathic pain and sensory abnormalities. Dr. Mandel says the third subtype would be CRPS, in which one would see motor trophic changes and related diffuse changes with osteopenia on bone scan. Discussing the differences between CRPS I and CRPS II, Dr. Mandel notes that with CRPS I, there is more of an occult lesion and a lesser injury that affects unmyelinated axons. In cases of CRPS II, one is dealing with a major nerve injury that is often caused by motor involvement, according to Dr. Mandel. Dr. Hendler says CRPS II is pain in the distribution of a mixed peripheral nerve that has both thermal and mechanical allodynia, usually with EMG/NCV abnormalities. Dr. Christensen says the following criteria must be satisfied when considering a diagnosis of CRPS II: • continuing pain, allodynia or hyperalgesia after a nerve injury, but not necessarily limited to the distribution of the injured nerve; • evidence of edema, changes in skin blood flow or abnormal sudomotor activity in the region of pain; and • this diagnosis is excluded by the existence of conditions that would otherwise account for the degree of pain and dysfunction. Dr. Hendler disagrees with these criteria, emphasizing that continuing pain, allodynia or hyperalgesia that occurs after a nerve injury must be limited to distribution of the injured nerve in cases of CRPS II. He also maintains that, in these cases, it is not common to see edema, changes in skin blood flow changes or abnormal sudomotor activity in the region of pain. Q: What causes CRPS? A: Drs. Fallat and Hendler agree that the exact mechanism that causes CRPS is unclear. However, Drs. Christensen, Fallat and Hendler say trauma can be a precipitating factor. Dr. Fallat says trauma can cover the full spectrum from gunshot wounds and crush injuries to seemingly minor injuries such as repetitive motion injuries or a sprained ankle. Dr. Christensen says the ankle sprain is the most common cause of CRPS in the foot and ankle. Dr. Hendler says there may be a genetic predisposition to CRPS. Dr. Mandel concurs and notes that some authors have discussed an interaction between trauma severity and genetic factors conferring CRPS. Dr.