Objective: To assess speech outcomes in Parkinson’s disease (PD) patients following unilateral MR-guided focused ultrasound (MRgFUS) targeting the subthalamic nucleus (STN) and ventral intermediate nucleus (VIM) of the thalamus using quantitative acoustic analysis.

Background: MRgFUS targeting the VIM improves tremor in PD, whereas STN lesions improve tremor, rigidity, and bradykinesia. Dysarthria, usually mild and transient, is a frequent clinically observed adverse event. However, quantitative acoustic measures that may detect specific treatment-related speech changes remain unexplored.

Method: In this prospective study, 15 PD patients underwent STN MRgFUS (9 left, 6 right) and 9 underwent VIM MRgFUS (8 left, 1 right). Twenty-one healthy controls were studied to provide reference baseline speech metrics.

Speech recordings were obtained using a standardized microphone setup and computer-based acoustic analysis before treatment and at follow-up (3 months for STN, 6 months for VIM). Tasks included sustained phonation, diadochokinetic (DDK) repetition, text reading, and spontaneous monologue. Paired t-tests assessed within-group changes. Target comparisons of change between baseline and follow-up were evaluated using ANCOVA adjusting for age and sex.

Results: Speech remained largely stable following STN MRgFUS, with a significant improvement in loudness modulation (stdPWR, p=0.044) during reading. In contrast, VIM MRgFUS was associated with worsening acoustic features, including reduced pitch variability (F0sd, p=0.013) and loudness modulation (stdPWR, p=0.042) during reading. [figure1]

Comparisons between changes in STN- and VIM-treated patients demonstrated a lower syllable repetition rate (DDKR, p=0.041) during DDK tasks, as well as decreased loudness modulation (stdPWR, p=0.030) and pitch variability (F0sd, p=0.049) during reading in patients treated with VIM MRgFUS. [figure2]

Conclusion: Speech outcomes after MRgFUS lesions in PD differ according to the target. STN MRgFUS appears largely speech-neutral, with a slight improvement in loudness modulation possibly related to reduced rigidity and improved respiratory-laryngeal motor control. Conversely, VIM MRgFUS may be associated with increased hypokinetic speech features in this cohort. This may be potentially influenced by the predominance of procedures in the left hemisphere.

Progression Analysis PD STN and VIM

Between-group comparison PD VIM and STN

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MDS Abstracts - https://www.mdsabstracts.org/abstract/quantitative-changes-in-speech-after-focused-ultrasound-subthalamotomy-and-thalamotomy-in-parkinsons-disease/