Objective: To compare the benefits and risks of staged bilateral versus unilateral VIM DBS using the largest ET DBS clinical trial dataset available to date.

Background: Despite over 30 years of clinical experience, high-quality studies on the efficacy of bilateral versus unilateral deep brain stimulation (DBS) of the ventral intermediate (VIM) nucleus of the thalamus for medically refractory essential tremor (ET) remain limited.

Method: Participants from the US St. Jude/Abbott pivotal ET DBS trial who underwent staged – bilateral VIM implantation constituted the primary cohort in this sub-analysis. Their assessments “on” DBS at six months after second-side VIM DBS implantation were compared to the assessments six months after unilateral implantation. Two control cohorts of participants with unilateral implantation only were also used for between-group comparisons.

Results: The primary cohort consisted of n=38 ET patients (22M/16F; age of 65.3 ± 9.5 years) (Table 1). The second side VIM-DBS resulted in a 29.6% additional improvement in the total motor CRST score (p <0.001) compared to unilateral VIM-DBS, with a 64.1% CRST improvement in the contralateral limbs (p <0.001). Added improvement was observed in the axial tremor score (21.4%, p=0.005), and CRST part B (24.8%, p<0.001) score (Table 2). Rate of adverse events was slightly higher after bilateral stimulation.

Conclusion: In the largest ET DBS study to date, staged bilateral VIM DBS is a highly effective treatment for ET with bilateral implantation resulting in greater reduction in total motor tremor scores when compared to unilateral stimulation alone.

References: 1. Bhatia KP, Bain P, Bajaj N et al. Consensus statement on the classification of tremors. from the task force on tremor of the International Parkinson and Movement Disorder Society. Mov Disord 2018; 33(1):75-87.
2. Wong JK, Hess CW, Almeida L, Middlebrooks EH, Christou EA, Patrick EE, Shukla AW, Foote KD, and Okun MS. Deep brain stimulation in essential tremor: targets, technology, and a comprehensive review of clinical outcomes. Expert Review of Neurotherapeutics 2020; 20(4): 319-331.
3. Ferreira JJ, Mestre TA, Lyons KE, et al. MDS evidence-based review of treatments for essential tremor. Mov Disord 2019; 34(7): 950-955

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MDS Abstracts - https://www.mdsabstracts.org/abstract/benefits-and-risks-of-staged-bilateral-versus-unilateral-vim-dbs-for-essential-tremor/