Motor nerve conduction analysis of double crush syndrome in a rabbit model

Abstract.

 The double crush syndrome was proposed by Upton and McComas in 1973, but there are still many unclear points regarding its mechanism. We propose a model that enables electrophysiological study of the same nerve from the same individual over time. We employed 29 rabbits and used their sciatic nerves. (Four rabbits died from infection, and in nine rabbits we could not record the M-wave because the electrodes were off during the course of the study.) Sixteen rabbits were grouped into six experimental groups and one control group. Bipolar stimulus electrodes were buried at three locations in their sciatic nerves. The two areas between the proximal and intermediate electrodes and between the intermediate and distal electrodes were defined as the “nerve proximal part” and “nerve distal part,” respectively. An electrical stimulus was applied via each electrode, and the muscle action potential (M-wave) was recorded from the gastrocnemius. A narrow tube was inserted in the nerve proximal part and a wide tube in the nerve distal part. A decrease in the motor nerve conduction velocity (MCV) was observed in the nerve proximal part (narrow tube) followed by a decrease in MCV in the nerve distal part (wide tube). A wide tube was then inserted in the nerve proximal part and a narrow tube in the nerve distal part. A decrease in MCV was observed in the nerve distal part (narrow tube) followed by a decrease in MCV in the nerve proximal part (wide tube). We believe that these results are important findings in regard to the double crush syndrome (DCS) hypothesis and the reversed DCS hypothesis.