Phase-specific Deep Brain Stimulation revisited: effects of stimulation on postural and kinetic tremor

Abstract

AbstractBackgroundIn Essential tremor (ET), involuntary shaking of the upper limbs during isometric muscle contraction closely reflects the patterns of neural activity measured in the thalamus - a key element of the tremorgenic circuit. Phase-specific deep brain stimulation (DBS) builds upon this observation while using accelerometery of the trembling limb to trigger repetitive electrical perturbations to the thalamus and surrounding areas at a specific time within the tremor cycle. This closed-loop strategy has been shown to induce clinically significant postural tremor relief while delivering less than half the energy of conventional DBS.ObjectiveThe main aim of the study was to evaluate treatment efficacy across different contexts and movement states.MethodsWe used accelerometery and a digitizing tablet to record the peripheral tremor dynamics of 4 DBS implanted ET patients while alternating stimulation strategies (no stimulation, continuous open-loop and phase-specific) and movement states (intermittent posture holding and spiral drawing).ResultsIn addition to observing a suppressive effect of phase-specific DBS on both postural and kinetic tremor, our results reinforce the key role of phase-specificity to achieve tremor control in postural motor states and highlight the difficulty of quantifying phase-dependent effects during continuous movement. Moreover, this study supports the hypothesis that ET patients with more stable tremor characteristics benefit the most from phase-specific DBS.ConclusionsBy creating a better understanding of the dynamic relationship between central and peripheral tremor activity, this study provides important insights for the development of effective patient and context-specific therapeutic approaches for ET.