(53) Theta-Burst DBS Reduced Tremor in Participants with Parkinson’s Disease but Not Essential Tremor.

Introduction: Deep brain stimulation (DBS) of either the subthalamic nucleus (STN), globus pallidus internus, or ventral intermediate nucleus of the thalamus (VIM) is a proven strategy to mitigate tremor in Parkinson’s Disease (PD) and Essential Tremor (ET). However, continuous high frequency DBS can produce side effects. Recent studies of theta-burst (bursts of high frequency pulses applied at 4-8 Hz) transcranial magnetic stimulation suggested that theta patterns attenuate tremor with fewer side effects.

Methods: All procedures were approved by the Duke University Health System IRB and all participants provided written informed consent. We compared the effect of theta-burst DBS to high frequency DBS, 4.5 Hz DBS, and no DBS on log-transformed tremor power (LTP) in participants with PD and ET during intraoperative experiments. We measured local field potentials and LTP during each trial.

Results: 12 participants (8 with ET, 4 with PD) received theta-burst DBS. Repeated measures ANOVA with factors of participant, disease, and DBS pattern revealed a trend of DBS pattern on LTP (p = 0.0751). There was a significant interaction between disease and DBS pattern (p = 0.02515). Detailed hypothesis testing revealed no difference in LTP between the ET and PD cohorts with DBS off (p = 0.3975). The application of high frequency and theta-burst DBS reduced LTP in the PD cohort (mean difference ± SD: 1.154 ± 0.500 and 1.665 ± 0.500 au, p = 0.0283 and 0.0025, respectively). Indeed, theta-burst but not high frequency DBS reduced LTP to a greater extent than 4.5 Hz DBS in the PD cohort (p = 0.0261 and 0.1795, respectively). Conversely, there was no significant effect of DBS pattern among the ET cohort. High frequency DBS did not reduce LTP compared to DBS off (p = 0.7133). In the ET cohort, theta-burst DBS numerically (but not significantly) increased LTP power compared to DBS off (0.333 ± 0.336 au, p = 0.3699). LTP was significantly larger for the ET cohort than the PD cohort during theta-burst DBS (1.440 ± 0.678 au, p = 0.0456).

Conclusion: Theta-burst DBS reduced tremor within a PD cohort but not for an ET cohort. However, due to limitations of intraoperative setting, we did not observe a decrease in tremor with high frequency DBS within the ET cohort. Larger cohorts and extra-operative testing are required before evaluating the long-term effects of theta-burst DBS.