The purpose of this study is to evaluate waves of antidromically evoked facial nerve response on normal guinea pigs. The facial nerve was stimulated at the stylomastoid foramen, and the action potentials were lead from the geniculate ganglion (an active electrode) and scalp (a reference electrode). To reduce the artifact, the polarity of the stimulation was alternated. All of the waves 1.5 msec after the stimulation disappeared after using a musle relaxant or transecting the facial nerve just distal to the stimulating site. Thereafter only a triphasic wave remained. The latency of the triphasic wave changed by shifting the stimulating electrode to the peripheral branch. This study revealed that the waveforms consist of two components, an initial triphasic antidromically evoked facial nerve response, followed by EMG.
