RSD: Unraveling the Puzzle of Pain

Three years ago, my 14 year old sister complained of acute pain in her lower jaw. My mother did not make much of the fact that her face was extremely sensitive to the touch and hardly noticed that it was warmer than other parts of her body. She took my sister to the dentist to see if a cavity was the culprit. What else could be causing pain if there had been no injury to her face? After he had carefully examined each of her teeth, our dentist could find no explanation to my sister’s pain. She was therefore referred to a maxillofacial specialist, who suspected a Temporomandibular Joint and Muscle Disorder (TMJ). Psychosomatic explanations took over when the pain kept soaring. Four months later, a pediatric neurologist ruled out a tumor to settle on shingles inside the ear. To the relief of my parents, the pain eventually subsided. However, a few months later the excruciating pain hit my sister all over again, but this time appeared in her leg. No connection was made with the previous incident as there was no reason to even think that there might be a link between pain in the jaws and pain in the leg. My sister started to avoid using her leg and walked barefoot, as the contact of her shoe was uncomfortable. Physicians in the specialized orthopedics department of a leading children’s hospital noticed her limping and extreme sensitivity to touch, and immediately diagnosed her with Reflex Sympathetic Dystrophy (RSD) or Complex Regional Pain Syndrome (CRPS), a “chronic, painful, and progressive neurological condition that affects skin, muscles, joints, and bones (1).

 The chief symptom of CRPS is continuous, intense pain out of proportion with the severity of the injury (if an injury has occurred), which worsens over time. This chronic pain syndrome affects between 200,000 and 1.2 million Americans and is two to three times more frequent in females than males (2). Two types of CRPS have been identified: CRPS Type 1 and CRPS Type 2. Type 1, also referred to as RSD (Reflex Sympathetic Dystrophy), involves cases in which a nerve injury cannot be identified (3). Type 2, commonly known as Causalgia, results from a major nerve injury (3). Like in my sister’s case, the syndrome often goes misdiagnosed for months, sometimes years, as few physicians are trained to recognize symptoms that can mimic other conditions. CRPS occurs mostly in the extremities such as the arms, legs, hands or feet, but the pain can migrate to different body locations, which makes it even more difficult to identify. The pain can spread to an entire limb, even if only a toe or a finger was initially injured. Diagnosis is further complicated by the fact that some people will improve gradually over time without treatment.

Doctors aren’t entirely certain what causes CRPS. Reflex Sympathetic Dystrophy appears to involve a complex interaction between the sensory, motor, autonomic nervous system, and immune system (1). In the case of CPRS Type 2, it was suggested that the brain and the spinal cord’s control over these various processes may be altered after injury. As a result, a malfunction in part of the nervous system causes neurons to misfire, sending repeating pain signals to the brain. This explanation, however, fails to account for the mechanisms triggering pain in CRPS Type 1 without recognizable initial trauma to the body, and also why not every injury will result in the syndrome. Another theory is that post-injury CRPS (CRPS Type 2) is a response from the immune system, which triggers an inflammation in the affected area. CRPS Type 2 would therefore be a disruption of the healing process (4).

Various theories have also been formulated in order to explain the mechanisms underlying the causes of unexplainable chronic pain such as in CPRS Type 1. Doctors have long suspected that CRPS involved some sort of malfunction in the sympathetic nervous system (5). Some of the symptoms associated with CRPS like sweating, severe burning pain, changes in the color and temperature of the skin, changes in skin texture, swelling and sensitivity to the touch could therefore be explained by an anomaly in the set of nerves that control sweating, the size of blood vessels, and other bodily functions (5). However, it is believed that these sympathetic nervous system problems or sympathetically-maintained pain (SMP) only apply to some patients affected with CRPS Type 1 (5). If specialists agree that the peripheral and central nervous systems might be at fault, the exact mechanisms at work are still unclear (5). As Reflex Sympathetic Dystrophy remains a poorly defined syndrome, it is difficult for affected patients, their families, and their doctors to understand and accept that pain can occur spontaneously.             

 I couldn’t help wondering whether class discussions on corollary discharge signals could possibly throw some light on the pain experienced in Reflex Sympathetic Dystrophy. Individuals affected with phantom limb report feeling as though their missing limb is still attached to their body. In normal circumstances, the nervous system would keep a record of sensory inputs from the arm and corollary discharge signals. In the case of individuals with amputated limbs, however, all sensory input is lost while corollary discharge signals still remain intact. Corollary discharge signals literally create expectations for sensory inputs in the nervous system. Without any input signals to interpret, though, conflicting corollary discharge signals are emitted. Pain ensues, as a way for an area in the nervous system to inform another region that something is incorrect and needs to be addressed. Patients often describe the pain as a burning sensation, which sometimes also includes coldness, tingling, or tightness (6). Occasionally, the pain can be made worse by stress, anxiety, or weather changes. My sister has suffered from several episodes of RSD and doctors suspected that the pain was triggered by changes in the weather. Whenever it was very hot, for instance, she often felt a burning sensation and tightness in the affected area similar to the one mentioned by individuals with phantom limb. This observation leads me to speculate whether Type 1 Reflex Sympathetic Dystrophy could be caused by a conflict between corollary discharge signals and sensory input signals. The resulting response from the nervous system would be some degree of pain. The remaining issue though is the fact that my sister experienced pain without losing any limbs or experiencing any trauma. Could the spontaneous outbursts of the syndrome have been a response of her nervous system to previous injuries sustained by her body? Could the pain have resulted from the discordance between movement and motor intent?

In all probability, CRPS does not have a single cause, but is rather the result of multiple causes that produce similar symptoms (4). Whatever the explanations for type 1 CRPS may be, it is essential to the emotional and physical wellbeing of affected individuals that physicians, friends, and family members be of constant support, and trust that their pain is real so as to prevent the development of physiological problems (2). The syndrome can progress to the point where changes in the skin and bone are no longer reversible, resulting in motor disability. While no single treatment can cure CRPS Type 1 as the prognosis varies from person to person, individuals affected with this neurological syndrome often find that their pain lessens with aggressive therapies. Each patient will respond differently to a particular therapy, so it is a matter of finding the treatment that works best for the individual. While spontaneous remission from symptoms occurs in certain people, others can have unremitting pain and crippling, irreversible changes in spite of treatment. It is often best for patients to meet with pain specialists in order to find the most productive ways to manage their pain. Drug therapies, sympathetic blocks, acupuncture, and physical therapy are sometimes an option (5). In my sister’s case, a hospitalization mobilized a team of physiotherapists, psychologists, and orthopedic doctors who helped her re-train her brain into moving her affected leg through the pain. Some doctors believe that early treatment is helpful in limiting the disorder, but this belief has not yet been supported by evidence from clinical studies. More research is needed to understand the causes of CRPS, how it progresses, and the role of early treatment (4).

Works Cited

(1). “Reflex Sympathetic Dystrophy.” Neurology Channel. 17 April, 2008. http://www.neurologychannel.com/rsd/index.shtml 

(2). “About CRPS> Fact and Fiction.” Reflex Sympathetic Dystrophy Syndrome Association. 17 April, 2008. http://www.rsds.org/2/fact_fiction/index.html

(3). “What is CRPS?” Reflex Sympathetic Dystrophy Syndrome Association. 17 April, 2008. http://www.rsds.org/2/what_is_rsd_crps/index.html

(4). “Complex Regional Pain Syndrome Fact Sheet.” National Institute of Neurological Disorders and Strokes. 17 April, 2008. http://www.ninds.nih.gov/disorders/reflex_sympathetic_dystrophy

(5). “Complex Regional Pain Syndrome.” StopPain.org. 19 April, 2008. http://www.stoppain.org/pain_medicine/content/chronicpain/crps.asp

(6). Ramachandran, Vilayanur., Stuart M. Anstis. “The perception of Apparent Motion.” Scientific American. Vol. 254. No.6. June, 1986. 22 April, 2008. http://psy.ucsd.edu/chip/pdf/Percpt_Apprnt_Mot_Sci_Am.pdf