Objective: In this study, we investigate the effect of VIM-DBS on speech in ET patients. We compare how uni- vs. bilateral DBS contributes to the severity of stimulation induced dysarthria (SID) by means of acoustic measures, and investigate if these measures co-vary with measures of perceived tempo and intelligibility.

Background: VIM-DBS is an effective treatment to suppress medically resistant ET. However, SID is a common side effect of thalamic stimulation. In recent studies, data from oral diadochokinesis (DDK) tasks indicated that acoustic parameters are affected by VIM-DBS. However, the following questions remained unaddressed so far: a) Do acoustic measures indicate whether SID occurs, and if so, is it more pronounced under bilat. DBS compared to unilat. DBS? And b) Do DDK measures co-vary with perceptual measures of impairment in running speech? The present study aims to answer these questions by comparing acoustic DDK measures under uni- and bilateral DBS with intelligibility and perceived tempo ratings performed by naive listeners of running speech from a reading task.

Methods: 16 German ET patients were recorded acoustically with DBS-off, unilat.-right-DBS-on, unilat.-left-DBS-on and bilat.-DBS-on. Speech materials consisted of an oral DDK task /kakaka/. To capture the extent of speech impairment, we measured syllable durations and intensity ratio. Furthermore, patients read a standard text at a comfortable speech rate. Single phrases out of this text were rated by 20 naive listeners on a five-point scale for perceived speech tempo and intelligibility.

Results: We found significant effects of DBS on both acoustic measures as well as on perceived speech tempo and intelligibility ratings (bilat. DBS > unilat. DBS). Relating the acoustic parameters of the DDK task to the perceptual ratings of the reading task, there is a significant linear relationship between syllable durations and perceived speech tempo, and between syllable durations and perceived intelligibility. There was no linear relationship between intensity ratio and perception results.

Conclusions: Our data suggest that acoustic parameters reflect more severe SID in bilateral compared to unilateral DBS. Furthermore, DDK measures such as syllable durations predict listeners’ perception of speech impairment in patients with ET.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-effect-of-uni-and-bilateral-thalamic-deep-brain-stimulation-on-speech-in-patients-with-essential-tremor-acoustics-and-intelligibility/