Formerly called Reflex Sympathetic Dystrophy (RSD), in 1996 scientist made a push to change the name to Complex Regional Pain Syndrome (CRPS). Their hope was to shift the focus away from the sympathetic nervous system (fight or flight system) as the primary cause of this pain syndrome. Because the sympathetic system releases adrenaline, most scientists believed that RSD was caused by high levels of adrenaline. However, in a landmark study, a group of researchers showed that those with RSD had the same level of adrenaline as those without RSD. This really rocked the medical world. This study proved that adrenaline and the sympathetic nervous system are not the primary cause of RSD. Thus, the name was changed to complex regional pain syndrome and “sympathetic” was removed from the name. Even after 12 years since the original description of CRPS, clinicians are still trying to get a handle on how to diagnosis it.
In September, 2008 a group of researchers compared the two different ways to diagnose CRPS. In this study, the two different criteria were found to be very similar. No mater which criteria was used, the clinicians were able to accurately identify who has CRPS. The basic criteria for diagnosing complex regional pain syndrome are as follows:
- Sensory Abnormalities: The presence of pain disproportionate to the initiating event like a joint sprain or an injection. Cold sensitivity is also very common and very specific for CRPS. Allodynia (pain with normally non-painful stimuli like light touch) is usually present. Basically, folks with CRPS experience worsening pain with cold and even clothing touching the region.
- Swelling and Sweating Abnormalities: Swelling in the affected limb is a sign of CRPS. Sometimes, increased sweating in noted also.
- Temperature Abnormalities: Differences in skin color and temperature are often noticed by those with CRPS. At various times, the affected limb will be hot and sometimes it will be cold. Different skin colors like red, blue, and purple are also seen in CRPS.
- Motor and Trophic Abnormalities: Fingernail abnormalities or abnormal hair growth are classified as “trophic” changes. Tremors, loss of fine motor control, and joint stiffness, all constitute the motor control changes found in CRPS.
People with CRPS will usually notice symptoms in all four areas of abnormalities. A clinician will usually see signs in at least two out of the four categories. Because CRPS causes such a wide array of symptoms, CRPS clearly involves multiple systems, not just the sympathetic nervous system. Even though CRPS is usually confined to one limb, pain in the opposite limb (mirror pain) is not uncommon and can add to confusion. But, this “spread” of pain in CRPS is understandable if one considers the brain’s role in constructing the pain experience. The brain connects everything. The brain controls the sympathetic nervous system, the endocrine system, the immune system, and the pain experience. For example, think about phantom limb pain. Where does that pain come from? The limb is gone. The tissue is gone. The tissue is not the issue. The central nervous system (the brain and spinal cord) has taken over and is creating the pain experience. So even though the tissue is gone, the pain is still there. Similarily, amputating the limb does not solve the pain from CRPS either because pain is an output message from the brain.
How is CRPS treated? That is a topic for another discussion. At this point, it is important to understand the complexity of pain as exemplified with CRPS. Hopefully, with some understanding, everyone involved in treating CRPS can move in a positive direction.