"Virtual" lesioning of the human oropharyngeal motor cortex: a videofluoroscopic study.

OBJECTIVE

To use focal cortical inhibition and create a "virtual" lesion in the oropharyngeal motor cortex in healthy subjects to determine whether this provokes swallowing dysfunction.

DESIGN

Intervention study: before and after cortical stimulation.

SETTING

Tertiary care center.

PARTICIPANTS

Healthy adult volunteers (N=9; age range, 21-44y) participated in the study.

INTERVENTIONS: Active or sham 1-Hz repetitive transcranial magnetic stimulation (rTMS) over the cortical sites in each hemisphere evoking the largest mylohyoid motor-evoked potentials (mMEPs) to single pulse transcranial magnetic stimulation.

MAIN OUTCOME MEASURES: Videofluoroscopic assessment was performed before and 5, 30, and 60 minutes after rTMS.

RESULTS

The motor threshold was 83%±10% for the hemisphere with the larger mMEP (dominant) and 92%±9% for the hemisphere with the smaller mMEP (nondominant). When rTMS was performed over the dominant hemisphere, there was a decrease in oral transit time (P=.05), an increase in swallow reaction time (P=.0001), but no change of pharyngeal transit time or laryngeal closure duration. When rTMS was performed on the nondominant hemisphere, there was also a decrease in oral transit time (P=.05), but no change in any of the other swallowing measures. Neither active intervention produced any signs of aspiration or penetration. Sham stimulation had no effect.

CONCLUSIONS

Inhibiting the human oropharyngeal motor cortex using rTMS transiently modifies swallowing behavior in a way reminiscent to that seen in stroke patients.