Motor dysfunction and reflex sympathetic dystrophy. Bilateral motor denervation in an experimental model.

Reflex sympathetic dystrophy (RSD) is a neuropathic pain condition most often occurring in relation to trauma to, or surgery on, an extremity. It is characterized among other things by motor disturbances such as joint stiffness and tremor. Signs and symptoms can be induced in a rat model through chronic constriction of a sciatic nerve (CCI-model). In this study the CCI-model was used to evaluate the extent of bilateral peripheral motor nerve-fiber involvement in relation to ligature localization. In 12 Lewis rats, the common sciatic nerve was loosely ligated with four chromic catgut ligatures at the midthigh level just proximal to the right sciatic trifurcation. Acetylcholinesterase (CE) histochemistry of sciatic (distal and proximal to ligation) and corresponding contralateral nerve biopsy specimens was performed at 21 days after ligation. An additional 12 rats were sham-operated and served as controls. As compared to sham-operated controls or contralateral nonligated sciatic nerves, CE histochemistry after 21 days revealed a marked decrease of CE-positive fibers in cross-sections taken from distal and proximal sciatic nerve biopsies ipsilateral to the ligatures. In addition, as compared to sham-operated controls, there was a decrease of CE-positive fibers in cross-sections taken from contralateral nonligated sciatic nerves. The present findings indicate profound motor denervation, distal as well as proximal to the ligatures. Motor denervation also affected the contralateral nonligated sciatic nerve. The evident usefulness of the CCI-model for the study of RSD places the present results in line with the concept of central nervous system involvement in the pathophysiology of RSD.