Complex regional pain syndrome (CRPS) is a mystery. Every year 15,000 people in the United States are affected. After trauma of some kind to the arm or leg, pain and other symptoms persist long after healing has taken place. There are many theories to explain what went wrong but no known causes. In this study scientists find evidence to support the idea of nerve damage as a possible mechanism.
Skin biopsies were taken from 18 adults with CRPS-I. CRPS-I is one of two types of CRPS. In this type patients don't have a known nerve injury. Skin biopsy is a sensitive test of small nerve fiber damage. Researchers counted the number of neurites (nerve endings). The loss of neurites may cause pain by triggering an overresponse on the part of the rest of the neurons still left.
Seven control subjects were also biopsied. The control group had similar symptoms from traumatic injury or knee osteoarthritis but they didn't have CRPS. The scientists wanted to see if neurite losses occur with trauma of any kind.
The results showed a decrease in the number of neurites for the CRPS group only. About 25 percent of the neurites were missing. The overall number of neurites was different from person to person but each subject had the same number from site to site tested.
The authors say the small size of this study limits their conclusions. Using neurite counts from skin biopsies may not be accurate since there was such a difference in the number of neurites from patient to patient. They conclude that skin biopsy is not a good way to diagnose nerve damage in cases of CRPS.
Anne Louise Oaklander, et al. Evidence of Focal Small-Fiber Axonal Degeneration in Complex Regional Pain Syndrome-I (Reflex Sympathetic Dystrophy). In Pain. February 2006. Vol. 120. No. 3. Pp. 235-243.'