Field Distribution of Compound Muscle Action Potentials of the Calf Muscles in Rabbits

Abstract

The purpose of this study is to verify that compound muscle action potentials (CMAPs) generated a stationary potential and to examine extension of the CMAPs away from the stimulated muscle. A referential derivation and/or bipolar derivation to record the stationary potentials were carried out following tibial nerve stimulation at the popliteal fossa in 10 rabbits. After recording a bipolar and/or referential derivation, wave changes were monitored before and after severing the tibial nerve. The change of the wave by compressing or direct electrical stimulation to the calf muscle was also monitored. In referential derivatives, the stationary waves were observed on top of the skull in all the rabbits examined with the peak latency of the potentials from 3.78 msec to 5.04 msec. In bipolar derivations, the upper limits of the stationary waves recorded were the trunks. The peak latencies were from 2.35 msec to 5.46 msec with an average of 4.12 msec. By analyzing the results from severing the tibial nerves, compressing the calf muscles, and direct electrical stimulation of the calf muscle, the origin of these stationary potentials was determined to be CMAPs of the calf muscles. These findings suggest contamination of the stationary potentials originated by CMAPs for recording of any evoked potentials when motor nerves are stimulated.