Objective: To assess speech outcomes in patients with essential tremor (ET) following unilateral and bilateral MR-guided focused ultrasound (MRgFUS) thalamotomy targeting the ventral intermediate nucleus (VIM) using quantitative acoustic analysis.

Background: Unilateral MRgFUS thalamotomy targeting medication-refractory tremor has been shown to be an effective treatment for patients with ET. Given the bilateral nature of ET, contralateral interventions are increasingly being considered, raising concerns about potential effects on speech function. In this context, objective acoustic speech measures may provide sensitive markers for detecting subtle treatment-related speech changes.

Method: In this prospective study, 19 ET patients treated with unilateral thalamotomy (15 left, 4 right) and 9 ET patients treated with bilateral thalamotomy (all right-sided) were included. Twenty-one healthy controls were included to provide reference baseline speech metrics.

Speech recordings were obtained at baseline and at 6-month follow-up using a standardized microphone setup and computer-based acoustic analysis. Tasks included sustained phonation, diadochokinetic (DDK) syllable repetition, text reading, and spontaneous monologue. Paired t-tests were used to assess within-group changes.

Results: Following unilateral thalamotomy, significant reductions were observed in pitch variability (F0sd, p=0.030) during phonation tasks and diadochokinetic irregularity (DDKI, p=0.031) during DDK tasks, as well as increased loudness modulation (stdPWR, p=0.012) during the reading task [figure1]. In contrast, bilateral thalamotomy demonstrated no significant overall changes in acoustic speech parameters across tasks.

Conclusion: Unilateral and bilateral thalamotomy are associated with different speech outcomes. Unilateral thalamotomy may improve tremor-related speech instability and articulatory timing, whereas bilateral treatment appears largely speech-neutral in this cohort, suggesting preservation of speech function after the second treatment. However, these findings should be interpreted considering that all bilateral procedures in this cohort were performed on the right hemisphere, whereas left-sided VIM ablations involve the language-dominant hemisphere and could therefore carry a higher theoretical risk of speech-related changes.

Progression Analysis ET Unilateral

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MDS Abstracts - https://www.mdsabstracts.org/abstract/quantitative-changes-in-speech-after-unilateral-and-bilateral-vim-mrgfus-thalamotomy-in-essential-tremor/