Reflex Sympathetic Dystrophy

Reflex sympathetic dystrophy (RSD), currently better named Complex Regional Pain Syndrome (CRPS), is a syndrome (collection of symptoms) that is characterized by burning pain (can vary from mild to severe), stiffness in the affected joints of the extremity, swelling, discoloration, skin changes (thinness, shininess, excessive sweating, hair changes), bone changes (osteoporosis), and extreme sensitivity to light touch. The severity of the symptoms can also vary widely, from just a little vasomotor changes (variation in the color of the skin from moment to moment, due to constriction of blood vessels) to rather disabling pain and almost complete joint stiffness, resulting in a useless hand or foot (the usual affected parts of the body). The rest of this discussion will only deal with CRPS of the hand and upper extremity; since this is the only part of the body I treat and have experience with. The disorder is unique in that it simultaneously affects the nerves, skin, muscles, blood vessels, and bones. One good aspect of CRPS is that the problem is self-limited (will eventually resolve by itself), although treatment can help hasten the resolution and decrease the permanent effects of it (primarily stiffness).

CRPS has been called many things in the past (RSD, casualgia, Sudeck’s atrophy, and shoulder-hand syndrome). Causalgia was first documented in the 19th century by physicians concerned about pain Civil War veterans continued to experience after their wounds from high-velocity impacts such as those from bullets or shrapnel had healed. Doctors often called it "hot pain," after its primary symptom. Complex Regional Pain Syndrome, or CRPS, is a better term because research has shown that it is more complex than just a reflex in the sympathetic nervous system. It is due to a perception of pain and other noxious input to the brain that is sustained long after the initial insult to the body has ceased. Research and clinical evidence indicates that the original injury probably occurs due to an injury to the sympathetic nervous system. (The sympathetic nervous system controls the automatic processes of the body, such as heart rate, blood flow, the stomach and intestines, and sweat glands, among other things.) When the nervous system becomes overactive, burning pain is felt and swelling and warmth are left in the affected arm. If not treated, CRPS can cause stiffness and loss of use of the affected part of the arm.

Figure 1 On the right, the swollen, painful hand of early CRPS with reddened joints.

What causes CRPS?

This is a much more complex question than you may realize, and it is an area of vigorous research that is targeted and supported by the National Institutes of Health. In some cases, the cause of CRPS is unknown. Why any one particular injury will result in CRPS and another similar injury to the same patient did not, is not clear. Why one particular surgery will result in CRPS, when hundreds of seemingly identical surgeries in other patients did not, is unknown. To say that CRPS developed "after" a surgery also does not answer the question of "what caused the CRPS?" "After" does not mean "because of" (for those of you interested in Logic, this is the "post hoc, ergo propter hoc" falacy), nor does it tell us anything of the mechanism of its causation.

Often an injury such as a fracture or a laceration can cause CRPS, or the symptoms may appear after a surgery. The onset of symptoms is not immediate, and may lag about 3 weeks or so from the event that we think probably caused it, so identifying the cause can be difficult to impossible. Other causes include pressure on a nerve, infection, cancer, neck disorders, stroke, or heart attack. We think that the common event in all of these conditions is a painful injury, probably involving a nerve. It is theorized that these damaged nerves send inappropriate signals to the brain, interfering with normal information about sensations, temperature, and blood flow. The incidence of CRPS does not seem to be more common after large injuries, and can follow even relatively minor injuries that do not obviously involve a nerve.

Until recently, doctors thought that CRPS always involved a problem in the sympathetic nervous system (as I noted above, the sympathetic nervous system controls the automatic processes of the body, such as heart rate, blood flow, the stomach and intestines, and sweat glands, among other things.) They also thought that the problem involved a reflex arc, from the injured part to the spine and back to the arm. This is where the term "Reflex Sympathetic Dystrophy" came from. (The "dystrophy" part came from the muscle atrophy that developed in untreated arms.) Research has shown that, while this may explain some cases, it does not explain all, or possibly even most, cases.

If SMP does not explain the pain in most patients with CRPS, what is the cause of the pain? Experts agree that there are problems in the peripheral nervous system (the nerves in the body) and the central nervous system (the brain and spinal cord) of patients with CRPS, but the details are not known. There are other factors that could be involved in the development of CRPS because they directly affect the activity of the nervous system, muscles and bones. Examples of these factors are emotional issues or stress (see section below on personality types) and not using a painful body part. One thing we know for certain: many pathological processes are at work, the condition affects more than one organ system in the extremity, and that pain is the predominant symptom experienced by the patient. This is why the term "Complex Regional Pain Syndrome" is a better name than "Reflex Sympathetic Dystrophy". RSD, however, is such a well-established and widely-used term, it will not disappear from the medical vocabulary.

We now know much more about the sympathetic reflex, and this sort of pain is now called "sympathetically maintained pain", or SMP, and is found in other conditions as well. The only way a doctor can find out if a patient has SMP is to do a sympathetic nerve block. (Sympathetic nerve blocks are injections of a numbing drug, called a local anesthetic, into different sites in the body). A person suffering from CRPS can be said to have SMP only if he or she has good pain relief from a sympathetic block.

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