Transcutaneous Kilohertz High-Frequency Alternating Current at 10 kHz for Upper-Limb Tremor in People with Parkinson’s Disease: A Double-Blind, Randomized, Crossover Study

<b>Background/Objectives:</b> Preclinical studies have evidenced a peripheral nerve blockade with kilohertz high-frequency alternating current (KHFAC) stimulation. It could have a potential effect on aberrant nerve hyperactivity, such as tremor in people with Parkinson's disease (PwPD). The objective was to investigate the effects of transcutaneous KHFAC at 10 kHz compared with sham intervention on tremor modulation, upper limb motor function, and adverse events in PwPD. <b>Methods:</b> This randomized, double-blind, crossover trial included PwPD, who received transcutaneous KHFAC and sham interventions, within a 48 h washout period. Measurements were taken pre-intervention, during, immediately after, and 10 min post-intervention. The main outcomes were rest, postural, and kinetic tremor acceleration. Secondary outcomes were handgrip strength, nine-hole peg test (NHPT), movement onset time, and adverse events. <b>Results:</b> Sixteen PwPD were analyzed. Kinetic tremor diminished only in active treatment from baseline at post-intervention (-32.3% (SD 63.3); <i>p</i> = 0.03) and 10 min after intervention (-38.9% (SD 60.3); <i>p</i> = 0.03). Active treatment showed a greater reduction in kinetic tremor at post-treatment compared to sham (-58.7% SD 123; <i>p</i> = 0.055) close to reaching statistical significance. Only active intervention diminished movement onset time at post-intervention (-26.9% (SD 28.3); <i>p</i> = 0.04). Active intervention diminished handgrip strength compared to sham intervention during the stimulation (-6.6% (SD 10.0); <i>p</i> = 0.02). No relevant adverse effects were reported. <b>Conclusions:</b> KHFAC stimulation at 10 kHz appeared safe and showed potential benefits for reducing kinetic tremor in PwPD. The transient reduction in grip strength suggested an effect on alpha-motoneurons. However, further studies with larger sample sizes are necessary to confirm these findings.