Swallowing and upper esophageal sphincter contraction with transcranial magnetic-induced electrical stimulation

This study in three dogs explores the effect of magnetically induced electrical stimulation of the brain to induce swallowing and produce contraction of the upper esophageal sphincter (UES). Single stimuli were delivered at intervals from 15 s to 3 min. Studies were performed with and without perfusion of fluid into the pharynx and upper esophagus. Results showed that magnetic stimulation produced a twitch contraction of the UES when stimulus intensity was above a threshold that varied between 14 and 20% of the stimulator output. Increasing stimulus intensity progressively increased twitch amplitude. Magnetic stimulation also induced swallowing, above a stimulus threshold similar to that for induction of the UES twitch contraction. Fluid perfusion augmented the ability of the magnetic stimulus to induce swallowing. We concluded that a magnetically induced single electrical stimulus of the cerebral cortex produces UES contraction and induces swallowing. The effect on swallowing is facilitated by sensory stimulation of the pharynx. This technique holds the potential for further study of 1) motor and sensory neural mechanisms involved in the control of swallowing and 2) the assessment and management of oropharyngeal dysphagia in humans.