An Overview of Complex Regional Pain Syndrome (CRPS)
Complex Regional Pain Syndrome (CRPS), which was initially named causalgia, was originally recognized during the Civil War by Silas Mitchell, a wartime surgeon. This doctor combined the Greek words for cause (causa) and for pain (algia) to obtain this descriptive term. RSD, or reflex sympathetic dystrophy, was the other common term that was used until just recently.
CRPS is a chronic disorder characterized by severe pain, swelling of the limb or involved region (shoulder or hip) and changes in the texture of the skin. CRPS may initially affect a portion of an arm or leg and spread throughout the limb.
The causes of Complex Regional Pain Syndrome are not fully understood but the underlying disorder is thought to be some type of nerve disruption. CRPS is typically brought on by an injury to the limb such as a burn, bruise, sprain, cut, fracture or surgery of the limb. There are 10% of patients who have no inciting injury.
CRPS symptoms are noted by chronic, excessive pain (called allodynia and hyperalgesia) and changes to the limb including skin turgor (thickness). Other signs include skin color change (red or blue depending upon the length of time this disorder is present), temperature change (hot or cold depending upon the stage) and swelling of the involved part.
Complex Regional Pain Syndrome is not a psychological problem. It is not “in your head.” However, reactive depression (see website) can develop with this disorder due to the chronic nature of this pain.
There are two types of CRPS; CRPS I and CRPS II. Since they are so similar, no differences will be noted here. The treatment is the same in either case.
CRPS symptoms in patients vary in intensity and duration. Many studies of this disorder demonstrate that most cases are mild and many patients recover with time. There are more severe cases where the patient may not recover. Some do have long-term disability.
Why Does CRPS Occur?
The origin of CRPS is theorized but still not fully understood. To know what changes could happen to induce Complex Regional Pain Syndrome, knowledge of the nervous system is necessary.
There are two different types of nervous systems in the body. The more primitive one is the autonomic nervous system. The somatic nervous system (soma means body) is the other type.
These two systems have different responsibilities. The autonomic nervous system is the “housekeeping” system. The somatic nervous system is the conscious system. This somatic system is the one that delivers signals to and from the brain that we can “feel” and control. Motion of our body occurs through this somatic system.
The autonomic system plays a major role in CRPS.
The Autonomic System
The autonomic system consists of two parts, the sympathetic nervous system and the parasympathetic system. You might remember the sympathetic system from high school as the “fight or flight” system. When a human is in danger, the heart pumps harder, the muscles engorge, adrenaline pumps into the bloodstream and vision becomes sharper. This is a direct result of stimulation of the sympathetic system.
The parasympathetic system is the system of maintenance of body functions. Digestion, relaxation and even sex are controlled by the parasympathetic system.
These two systems are generally in balance and both are needed to keep the body functioning. We have always thought these systems direct signals only one way (efferent). That is, they only send signals one way from the brain to the body but not the other way around (the body to the brain). We have found no sympathetic “sensory nerves”.
The sympathetic system is intimately connected to the arteries. Arteries obviously carry blood from the heart to the extremities. Veins of course carry blood back to the heart. Arteries have thick, muscular walls whereas veins have paper-thin walls. The arteries can contract since they are muscular lined. This contraction, which narrows these vessels, is controlled by the sympathetic nervous system.
This vessel wall contraction is important for survival. If we are out in a very cold environment, the blood vessels of the skin will contract to reduce blood flow and preserve heat. If we are engaged in strenuous physical exercise, the blood vessels open to allow more oxygen into the muscles to keep them functioning at a high level. If we lose too much blood, the vessel walls will contract to prevent shock from developing.
Sweating is also under control of the sympathetic nervous system. Sweat glands are directly wired to produce sweat under the influence of the sympathetic nervous system and adrenaline. Sweat occurs to allow cooling from evaporation to prevent the core from overheating.
Contraction of the blood vessels as stated before will restrict the blood flow. Since blood flow brings heated blood from the core to the extremities, contraction of these vessels will allow the extremity to become cooler. What is counterintuitive is that the loss of sympathetic nerve supply (called loss of sympathetic tone) will warm this extremity, as there is no restriction of the warm blood flow.
CRPS has an initial warm stage and then only later does the extremity become cold. This warming is thought to be due to the initial loss of the sympathetic nerve supply to the injured part. This loss means the arteries will initially dilate and bring more warmth to the extremity.
Later in CRPS, the artery muscle cells “miss” the sympathetic nerve supply and up-regulate to become more sensitive to circulating catecholamines (adrenalin) in the blood. This adrenalin will cause these more sensitive cells to contract. This contraction slows blood flow, which causes the “coldness” of the involved extremity..