About Complex Region Pain Syndrome

About Complex Region Pain Syndrome 
“The more names the medical profession has for a condition, the less they understand it”
--Charlie April M.D. ISIS Meeting October 2006

Previously called Reflex Sympathetic Dystrophy (RSD), CRPS (called crips) is a subset of neuropathic pain that generalizes from an injury site to affect an entire extremity. It will occasionally ‘spread’ without additional injury to other parts of the body. Statistically it is a rare condition. There are considered to be about 15,000 new cases diagnosed in the United States each year, one new case for every 100,000-300,000 people. Unfortunately, CRPS is like being struck by lightning or bitten by a shark, it doesn’t matter how rare it is if it happens to you.

The condition has never been well understood by clinicians. However, a model is slowly emerging and treatment options are available for the condition.

First, it is important to understand Neuropathic Pain. While all CRPS is neuropathic, not all neuropathic pain is CRPS. Neuropathic pain occurs when nerves are injured, deteriorate, or are compressed. Some common examples are carpal tunnel syndrome, radiculopathy, or diabetic neuropathy. Common features of nerve pain are a reduction in normal ability to feel replaced with burning and shooting pain in the distribution of the affected nerve. These conditions are treated with a variety of medical tools ranging from epidural steroid injections, to physical therapy, to acupuncture and chiropractic, to pharmacologic agents, to decompressive surgeries. The hallmark of neuropathic pain is its clinical pattern of distribution along the zone of the damaged nerve or nerves.

It is also important to be aware of the difference between the inflammation of infection, tissue injury, and arthritis. Each of these conditions is similar but slightly different. The body has a way of using similar mechanisms to solve different problems. Inflammation to combat infection results in the activation of white cells, other components of the immune system and the vascular system. Inflammation to treat injury is a mechanism to clean up a damaged component of the body. In autoimmune inflammation such as rheumatoid arthritis the body actually attacks itself as if it were a foreign object. One of the components of CRPS is an inflammation that is activated by the nervous system that seems to incorporate both normal and pathologic elements of the inflammatory process.

In some fashion the sympathetic nervous system becomes involved (the old name Reflex Sympathetic Dystrophy). The primary role of the sympathetic nervous system is the regulation of blood flow into the extremities and tissues to control heat regulation, excretion of metabolites, and nutrition. In normal tissues it has no role in pain. This seems to change in CRPS with confusing series of changes in the tissues, warm and red, blue and sweaty, and rapid changes back and forth.

Compared to neuropathic pain and injury, which is very common, Complex Regional Pain is very highly unusual. For CRPS to develop linkage to the central nervous system including the brain and the spinal cord relay centers occurs. Peripheral links to the immune system and the endocrine system can occur. Changes in the involved limb take on characteristics seen when the nerve is
severely injured. Burning pain rapidly moves beyond the area of the original injury. Unpredictable changes in limb color, temperature, and sweating occur. ‘Trophic changes’, meaning unexpected swelling, atrophy, and nail bed changes occur.

Diagnosis can be relatively simple when the limb changes are obvious and far more difficult when the changes are more subtle. One of the more common mistakes is for a practioner to classify neuropathic injury as CRPS. Unfortunately there is no gold standard test for the condition. Commonly use studies in Colorado are the three phase bone scan, quantitative Sudomotor reflex testing (QSART), and infrared thermography. Sympathetic blocks are still commonly used for treatment but are not very helpful for the diagnosis. Each of the tests documents a different element of how the nervous system changes. However, the changes seen in each case can occur in other conditions. The International Association for the Study of Pain (the people who named it CRPS) has a set of clinical criteria that form the basis of clinical diagnosis and research protocols.

These include the following:

1. The presence of an initiating noxious event, or a cause of immobilization.
2. Continuing pain, allodynia, or hyperalgesia with which the pain is disproportionate to any inciting event.
3. Evidence at some time of edema, changes in skin blood flow, or abnormal Sudomotor activity in the region of the pain.
4. This diagnosis is excluded by the existence of conditions that would otherwise account for the degree of pain and dysfunction.
5. Criteria 2-4 must be satisfied.

Treatment of the condition has evolved rapidly of the last few years. In reality the treatment is not much different that that used for neuropathic pain. A pyramid of medications including the tricylic antidressants, older and newer anticonvulsants such as carbamazipine and pregabalin, as well as several medications directed toward the NMDA (n-methyl D aspartate) receptor are used. Pain control includes cervical or lumbar blocks, antiinflamatories, opioids, physical therapy, electrical stimulation, topical lidocaine (EMLA or Lidoderm), custom made local anesthetic creams, and even spinal cord stimulation or implantable pumps.

With recent advances in medications many cases of CRPS can be helped. STAR makes every attempt to return patients to work and to living the most normal life possible. Just as in the case of other chronic conditions such as stroke, spinal cord injury, or heart disease much of the treatment is about solving and treating the conditions that can be treated, managing the others and helping a patient come to terms with the condition.

1. CRPS: Current Diagnosis and Therapy / Eds Peter R. Wilson, Michael-Hicks, R. Normal Harden. ISBN 0-931092-55-8, IASP Press, 2005
2. Mechanisms and Mediators of Neuropathic Pain, Malberg & Chaplin, eds., Berkhauser Verlag, Sweden 2002. ISBN 3-7643-6237-5
3. Emerging Strategies for the Treatment of Neuropathic Pain, Campbell, et al eds, IASP Press Seattle 2006 ISBN 0-931092-61-2
4. Hyperalgesia: Molecular Mechanisms and Clinical Implications Brune & Handwerker, eds IASP Press Seattle 2004 ISBN 0-931092-50-7