Effect of thalamic deep brain stimulation on swallowing in patients with essential tremor.

Objective: Deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) is a mainstay treatment for severe and drug-refractory essential tremor (ET). Although stimulation-induced dysarthria has been extensively described, possible impairment of swallowing has not been systematically investigated yet. Methods: Twelve patients with ET and bilateral VIM-DBS with self-reported dysphagia after VIM-DBS were included. Swallowing function was assessed clinically and using by flexible endoscopic evaluation of swallowing in the stim-ON and in the stim-OFF condition. Presence, severity, and improvement of dysphagia were recorded. Results: During stim-ON, the presence of dysphagia could be objectified in all patients, 42% showing mild, 42% moderate, and 16 % severe dysphagia. During stim-OFF, all patients experienced a statistically significant improvement of swallowing function. Interpretation: VIM-DBS may have an impact on swallowing physiology in ET-patients. Further studies to elucidate the prevalence and underlying pathophysiological mechanisms are warranted.