The Cause of CRPS
The cause, if indeed there is only one, for complex regional pain syndrome (CRPS) is unknown. Most physicians, researchers, and CRPS attorneys expect that there are a variety of causes which result in the same battery of symptoms. Apart from the clear sign of improper nervous system function and skin and muscle tissue damage, however, the precise mechanisms by which CRPS develops are still unknown.
The disorder most typically develops after a person has suffered an injury, usually to the hand, foot, arm, or leg. In persons afflicted with causalgia, the sustained injury usually involves direct nerve damage. Whether the injury itself is relatively minor or rather serious does not appear to have any real bearing on whether CRPS will develop. If the injury begins to heal, but the pain, swelling, and redness remain long after they should have dissipated, the injured person has likely developed reflex sympathetic dystrophy (RSD) or causalgia.
Commonly seen abnormalities in sufferers of CRPS include thinly myelinated or unmyelinated nerve fibers in the affected area and the dilation of blood vessels. This dilation also allows for fluid to leak into the surrounding skin, contributing to the red and swollen appearance. However, the extent to which these abnormalities are causes or effects of CRPS is unknown.
Some researchers suggest that the pain may be caused by pain receptors in the affected areas becoming responsive to nervous system messengers. These messengers, known as catecholamines, include epinephrine, norepinephrine, and dopamine. Commonly used in preparing the body for danger (epinephrine is often referred to as adrenaline), these chemicals may be produced by the central nervous system as a response to injury.
If the pain receptors in the injured area become responsive to these neurotransmitters, a vicious cycle might be started. The pain would cause the release of catecholamines, which would then cause more pain, prompting the body to send out more of the neurotransmitters in an attempt to prepare itself for a fight or flight response. However, this theory has not yet been proven, and more research is required to determine its legitimacy.
Another hypothesis regarding CRPS is that it is caused by a disruption in the healing process. This seems to be a likely factor for CRPS, considering that the symptoms are similar to those expected by a wound that has not yet healed. The redness, soreness, and swelling could be caused by an overactive immune response. This is more likely in cases of RSD or causalgia brought on by serious injury.
Another aspect of CRPS that has been noted is its similarity to other chronic pain disorders such as fibromyalgia. Some have even suggested that many cases of CRPS are simply a misdiagnosis of fibromyalgia. The similarities include comparable reactions to specific brachial pressure points in individuals diagnosed with both disorders.
Parallels between CRPS and multiple sclerosis have also been inspirational for researchers, prompting studies to see if treatments for MS might be effective in CRPS patients. Because both disorders affect the central nervous system sensitivity and glial activation, researchers tested a low dose glial attenuator on CRPS sufferers, noting some favorable results. Treating CRPS patients with known treatments of similar disorders may be the next step in determining the causes of RSD and causalgia.