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..
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The CRPS “Mis-direction” of Nerve Signals
Complex Regional Pain Syndrome is thought be related to a miscommunication between the sympathetic nerve fibers and local pain nerve fibers. Pain fibers, like sympathetic fibers follow blood vessels. It turns out that sympathetic nervous system fibers and pain fibers are both unmyelinated (not wrapped by myelin) small diameter fibers. This makes them somewhat compatible to cross-connect.
What might happen in CRPS is that there is an accidental connection between the pain fibers and the sympathetic fibers. In turn, there is a disconnection between the sympathetics and the blood vessels.
If this abnormal connection occurs, it fits with the symptoms. The sympathetic fibers will send a signal and the message never gets to the muscular wall of the artery. Instead, the abnormal connection to the pain nerves inadvertently reroutes a pain signal to the brain. Since the sympathetic signal never gets to the extremity, the blood vessels cannot contract and the extremity initially becomes warm and swollen.
Symptoms of Complex Regional Pain Syndrome
The overlying factor in CRPS is pain avoidance behavior patterns. The extremity is so unreasonably painful that the patient will avoid any contact with this area. This leads to disuse atrophy and the old saying “if you don’t use it, you lose it” is never truer than with this disorder. Disuse is suspected to cause a significant portion of the symptoms. The stages in CRPS generally have to do with the length of presence of this disorder.
Stage one occurs initially after the injury. This stage is noted by severe burning pain, swelling of the skin, stiffness of the involved joint and reduced range of motion. The skin turns reddened and swelling occurs. Some patients may note increased sweating of the involved part (hyperhidrosis).
Allodynia is typical in this stage. This is pain occurrence upon normal stimuli. A light touch will burn. If the patient is caught early in this stage, a physical therapist with experience in treating CRPS can be very helpful.
Stage two can be noted by more intense pain. The joint becomes more swollen and hair growth diminishes. The nails become atrophic (thickened and brittle). Disuse of the extremity occurs due to pain and osteoporosis (loss of bone mass) occurs. This is due to Wolfe’s law, which states that bone that is unloaded will lose bone stock. The arm notes disuse atrophy, as muscles are not used.
Stage three is the end stage for Complex Regional Pain Syndrome. The muscles have not been used so the arm is atrophic. The joint involved will become contracted and useless. The pain causes the individual to ignore the extremity. Disuse osteoporosis is severe. Skin is shiny and smooth.
The goal is to avoid this stage by aggressive PT prior to onset of stage 3.
Diagnosis of CRPS
There is no single diagnostic test for CRPS. Diagnosis is a compilation of different findings based upon a thorough history, physical examination and possible imaging findings. The diagnostician needs to rule out other potential pain generators before the diagnosis of CRPS is considered. That is, a diagnosis of CRPS is a diagnosis of exclusion.
Treatment of Complex Regional Pain Syndrome
The mainstay for treatment is early occupational and physical therapy. Desensitizing the involved area is paramount. There are modalities that can be used including direct stimulation of the area, electrical stimulation, contrast baths, medications and even implantable stimulators and pumps.
For additional information on Complex Regional Pain Syndrome (CRPS), please contact the office of Dr. Donald Corenman, spine specialist and neck doctor offering diagnostic and surgical second opinions to patients in the USA and around the world.