The impact on Parkinson’s disease of electrical parameter settings in STN stimulation

TLDR

Deep brain stimulation for Parkinson’s disease benefits from adjustable electrical settings that can be tuned to maximize therapeutic effects while minimizing side effects, though the underlying mechanisms remain speculative. The study aimed to determine how changes in electrical parameters affect Parkinson’s motor symptoms. Twelve patients with chronic bilateral STN DBS were studied under double‑blind randomized conditions, testing up to 26 combinations of voltage, frequency, and pulse width on tremor, bradykinesia, and rigidity using both constant‑energy and variable‑energy paradigms. Higher voltages (≥3 V) and frequencies (≥130 Hz) produced the greatest improvement in tremor, bradykinesia, and rigidity, with the combination of maximum voltage and narrowest pulse width being most effective, while a 5 Hz setting worsened akinesia, confirming that high frequency and voltage are key to optimal STN stimulation.

Abstract

<b><i>Background: </i></b> The main advantage of deep brain stimulation (DBS) in the treatment of PD is that the electrical settings can be adjusted to optimize benefits and minimize adverse effects. The main objective of this study was to discover how varying these electrical parameters impacted on parkinsonian motor signs. <b><i>Methods: </i></b> Twelve patients with PD with chronic bilateral subthalamic nucleus (STN) stimulation were selected. The authors evaluated the effects of a variation in the voltages, frequencies, and pulse widths on tremor, bradykinesia, and rigidity using two different paradigms: one in which the total electrical energy delivered was held constant, and one in which this was varied. Up to 26 parameter conditions were tested under double blind randomized conditions. <b><i>Results: </i></b> Voltages ≥3 V and frequencies ≥130 Hz led to the greatest improvement in all three parkinsonian signs. A rate of 5 Hz significantly worsened akinesia. The combination of the highest voltage with the narrowest pulse width was most effective. <b><i>Conclusions: </i></b> This study confirms that the most beneficial effects induced by STN stimulation are obtained at high frequencies and that voltage is the most critical factor to obtain adequate alteration in STN activity. The mechanisms by which STN DBS improves parkinsonism remain speculative.