GLOSSOPHARYNGEAL EVOKED-POTENTIALS IN NORMAL SUBJECTS FOLLOWING MECHANICAL STIMULATION OF THE ANTERIOR FAUCIAL PILLAR

The anterior faucial pillar, which is innervated by the glossopharynge al nerve, is thought to be important in eliciting the pharyngeal swall ow in awake humans. Glossopharyngeal evoked potentials (GPEP), elicite d by mechanically stimulating this structure, were recorded from 30 no rmal adults using standard averaging techniques and a recording montag e of 16 scalp electrodes. Ten of the subjects experienced a desire to swallow in response to stimulation. Repeatable responses were recorded from all 30 subjects. The GPEPs recorded from the posterior scalp wer e W-shaped and consisted of P1, N1, P2, N2 and P3 peaks. Mean latencie s of P1, N1 and P2 were 11, 16 and 22 msec, respectively, for both lef t and right pillar stimulation. In contrast, latencies of N2 and P3 va ried significantly between left and right pillar stimulation. Mean lat encies of N2 and P3 were 27 and 34 msec for left, and 29 and 35 msec f or right pillar stimulation. Topographical maps acquired at peak laten cies for P1, N1 and P2 revealed consistent asymmetrical voltage distri butions between the two hemispheres; the largest responses were record ed from the hemisphere ipsilateral to the side of stimulation. The sca lp topography of N2 and P3 varied between male and female subjects as well as between left and right pillar stimulation. These findings supp ort the hypothesis that mechanical stimulation to the anterior faucial pillar alone can elicit repeatable responses from the central nervous system. The integration of this subcortical/cortical activity with th at of the medullary swallowing center may play an important role in el iciting the pharyngeal swallow.