The complex regional pain syndrome (CRPS) has been known by a variety of names over the years, including: reflex sympathetic dystrophy, causalgia, Sudeck atrophy, and algodystrophy. It is a painful condition involving a limb, and usually occurs after some sort of trauma; but there may or may not be evidence of injury to a major nerve. It may have concomitant skin change, sweating irregularity, and motor function defects, but the chief complaint when a patient presents to his or her caregiver is the severe pain.
Many different treatments have been used over the years, with varying results. Unfortunately, if a patient does not improve within 6 months, CRPS often results in an adverse impact on the life of the sufferer, affecting psychological health and gainful employment. Researchers still do not know the cause of CRPS. One theory is that there is immune activation in the affected limb, blood and cerebrospinal fluid of CRPS patients. A recent article published in "Annals of Internal Medicine" shows the results of a study whereby researchers attempted to treat the chronic pain of CRPS by modulating the immune system with intravenous immunoglobulin (IVIG). It was a small study, but there were reductions in pain among the study participants.
Because late CRPS pain is often refractory to treatment, many feel that this condition is sustained by so-called neuroplasticity mechanisms. These mechanisms are theorized to occur at the level of both the spinal cord and the brain, representing maladaptive neuronal memory; pain persists despite no or minimal need for a noxious stimulant to cause that pain. The fact that CRPS appears to respond to IVIG suggests that immunity plays a role in sustaining chronic pain, perhaps through both central and peripheral neuroimmune activation; IVIG would appear to reduce such activation.
Autoimmunity may also play a role in CRPS. Perhaps those patients who develop CRPS after a trauma may be susceptible due to autoantibodies; IVIG has the ability to neutralize these harmful antibodies. Another study actually did find that patients with chronic CRPS had a higher incidence of immune disorders compared to those patients whose CRPS was short-lived.
While the study of IVIG for CRPS discussed above is a small one, it does give one more facet to chronic pain, that multifaceted scourge which impacts the daily lives of so many. It reminds us that chronic pain involves so many alterations in the body and mind: there are changes in sensory processing, the onset of fear and depression from the reality of and prospect for continued, chronic pain, and the consequent hopelessness resultant from loss of employment and the impact on personal relationships.
The definitive study on IVIG for the chronic pain of CRPS has yet to be done. It will be expensive and long and involve multiple institutions. If such a study does confirm the utility of IVIG in CRPS, it could prompt the treatment of other causes of pain through the manipulation of the immune system. Wouldn't that be interesting?