Objective: To investigate the effects of unilateral thalamic deep brain stimulation (DBS) on walking in persons with medication-refractory essential tremor (ET).
Methods: We performed laboratory-based gait analyses on 24 persons with medication-refractory ET before and after unilateral thalamic DBS implantation. Normal and tandem walking parameters were analysed across sessions (PRE-DBS/DBS OFF/DBS ON) by repeated measures analyses of variance. Pearson's correlations assessed whether changes in walking after DBS were global (ie, related across gait parameters). Baseline characteristics, lead locations and stimulation parameters were analysed as possible contributors to gait effects.
Results: DBS minimally affected gait at the cohort level. However, 25% of participants experienced clinically meaningful gait worsening. Walking speed decreased by >30% in two participants and by >10% in four others. Decreased walking speed correlated with increased gait variability, indicating global gait worsening in affected participants. The worsening persisted even after the stimulation was turned off. Participants with worse baseline tandem walking performance may be more likely to experience post-DBS gait worsening; the percentage of tandem missteps at baseline was nearly three times higher and tandem walking speeds were approximately 30% slower in participants who experienced gait worsening. However, these differences in tandem walking in persons with gait worsening as compared with those without worsening were not statistically significant. Lead locations and stimulation parameters were similar in participants with and without gait worsening.
Conclusion: Global gait worsening occurred in 25% of participants with unilateral DBS for medication-refractory ET. The effect was present on and off stimulation, likely indicating a microlesion effect.
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