Differential Effects of High and Low Frequency Subthalamic Nucleus Deep Brain Stimulation on Force Steadiness in Patients with Parkinson’s Disease: An Exploratory Study

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an established therapy for patients with Parkinson’s disease (PD). However, the frequency-dependent impact on force steadiness remains largely unknown. This explorative study investigated how stimulation frequency and disease severity influence force steadiness during precision pinch.

Force steadiness was assessed during a precision pinch task in patients with Parkinson’s disease implanted with STN DBS. Ten individuals performed a force tracking task at 10% and 20% of maximal voluntary contraction (MVC) under four stimulation conditions: (a) 130 Hz, (b) 50 Hz, (c) STN DBS “OFF”, and (d) 130 Hz. Force steadiness was quantified as the coefficient of variation (CoV) of force.

Patients with Parkinson’s disease with higher scores (UPDRS-III > 25) showed significantly greater force CoV compared with the subgroup with UPDRS-III ≤ 25 at both contraction levels (10% MVC: U = 2, p = 0.038, Cliff’s δ = 0.83; 20% MVC: U = 1, p = 0.019, Cliff’s δ = 0.92). Within the more impaired subgroup (UPDRS-III > 25), Friedman tests revealed significant STN DBS effects at both contraction levels (10% MVC: χ²(3) = 8.00, p = 0.046; 20% MVC: χ²(3) = 8.00, p = 0.046). Post hoc multiple comparisons with Bonferroni correction indicated that 130 Hz stimulation significantly reduced CoV relative to DBS “OFF” (p = 0.044).

In this exploratory study no differential effects were observed in less severely affected patients with Parkinson’s disease between high and low frequency stimulation parameters with respect to force steadiness. Tailoring STN DBS protocols according to individual motor performance characteristics may improve motor pinch performance in patients with Parkinson’s disease relevant for daily critical execution. As a result of selection and analysis bias, further randomized controlled studies are warranted assessing additional STN-DBS parameters and targeting different muscles.