Transcranial facial nerve stimulation by magnetic stimulator in normal subjects

Magnetic stimulation provides a new method to stimulate facial nerve transcranially. Stimulation can be directed to the intracranial part of the facial nerve, whereas the conventional electric stimuli are delivered extracranially to a more peripheral part of the nerve. Fourty healthy volunteers were examined to determine the normal responses for transcranial facial nerve stimulation. The center of the inducing coil ring was located so that its center was 3 cm posterior and 6 cm lateral to the vertex. Responses were recorded on the nasolabial fold. Latencies were 4.5 +/- 0.4 ms on both sides, being 1.1 ms longer than those elicited by electric stimulation of the nerve at the stylomastoid foramen. Amplitudes with magnetic stimuli were equal to those obtained with electric stimuli. The transcranial magnetic stimulation seems to be an accurate and promising method to examine the facial nerve.