Impact of deep brain stimulation surgery on speech and swallowing in patients with essential tremor

Purpose: The ventral intermediate nucleus (VIM) of the thalamus is the typical target of deep brain stimulation (DBS) for controlling tremor in essential tremor (ET). It remains unclear whether the outcomes are significantly different on speech and/or swallowing functions. This study was to compare speech and swallowing outcomes in patients with ET without VIM DBS, and those with unilateral/bilateral VIM DBS.Methods: We conducted a retrospective review of 133 patients with the diagnosis of ET. We analyzed the clinical speech and swallowing evaluations, and compared outcomes across four ‘DBS disposition’ groupings: no DBS, left, right, or bilateral VIM DBS.Results: Speech function was worse in bilateral group versus no DBS and unilateral groups. Orofacial (p=0.000), rate (p=0.001), and prosody (p=0.003) were significantly different between groups. No DBS and unilateral groups demonstrated either no dysarthria or mild hyperkinetic dysarthria versus exhibiting higher rates of dysarthria including an ataxic component in bilateral group. Bilateral group showed more impaired swallowing severity versus no DBS and unilateral groups, however, these differences were not statistically significant.Conclusions: The results demonstrated speech and swallowing changes in the ET patient population after VIM DBS. This data provides support for further study in order to better understand the speech and/or swallowing changes that may occur with VIM DBS.