Effects of transcutaneous vagus nerve stimulation on anxiety and balance under space constraints in Parkinson's disease with anxiety syndrome: A preliminary study

BackgroundImpaired balance and anxiety are critical motor and non-motor symptoms in Parkinson's disease. Space constraints could heighten anxiety and compromise balance, particularly in anxious individuals. Transcutaneous vagus nerve stimulation (tVNS) has potential for modulating anxiety and motor control, but its effects under space constraints in people with Parkinson's disease (PwPD) remain unclear.ObjectiveWe aimed to investigate the benefits of tVNS on anxiety and dynamic balance under space constraints in anxious PwPD.MethodsSixteen anxious PwPD completed a randomized cross-over trial involving active and sham tVNS sessions. Participants conducted mediolateral weight-shifting by coupling the weight-bearing of their more-affected lower extremity to a sinusoidal target in non-constraint, low-constraint, and high-constraint conditions. Weight-shifting tracking error and amplitude, physiological anxiety, and subjective anxiety were assessed.ResultsUnder space constraints, tracking error was reduced (low-constraint: p = 0.002; high-constraint: p = 0.001) and weight-shifting amplitudes toward the more-affected side (low-constraint: p < 0.001; high-constraint: p = 0.015) and less-affected side (low-constraint: p < 0.001; high-constraint: p = 0.015) were larger in active tVNS session compared with sham tVNS session. Relative to sham tVNS, active tVNS led to a lower normalized skin conductance level (physiological anxiety) in the low-constraint (p = 0.012) and high-constraint (p < 0.001) conditions. Neither weight-shifting performance nor anxiety levels were affected by tVNS in the non-constraint condition.ConclusionsThis study provides preliminary evidence that tVNS has the potential to improve weight-shifting control and modulate anxiety under space-constraint conditions in anxious PwPD. These findings suggest that tVNS may be a promising non-invasive intervention for space-related balance deficits in this population.Trial registrationClinicalTrials.gov, Balance Exercise and Vagus Nerve Stimulation on Weight-shifting Control and Ambulation in Parkinson Disease and Anxiety, https://clinicaltrials.gov/ct2/show/NCT06476912, NCT06476912.