Modulating autonomic nervous system activity with transcutaneous auricular vagus nerve stimulation in Parkinson's...

Cardiovascular dysautonomia is a debilitating non-motor symptom of Parkinson's disease (PD) that limits exercise capacity and neurorehabilitation outcomes. Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging non-invasive neuromodulatory therapy that modulates cardiovascular activity and could potentially serve as an adjunct to exercise, yet its physiological effects on cardiovascular function in PD remains unexplored.

This proof-of-concept, sham-controlled crossover pilot study (N = 8) investigated the acute effects of taVNS on cardiovascular autonomic activity in idiopathic PD.

Participants underwent active taVNS (30 Hz, 250 μs, 0.1-4 mA) or sham stimulation (0 mA) during a 15-min resting phase, immediately followed by the Ewing Battery of cardiovascular reflexes. Acute autonomic shifts were phenotyped using continuous heart rate variability (HRV) monitoring.

This proof-of-concept protocol was feasible, as all participants completed the randomized crossover stimulation visits and autonomic reflex testing without adverse events. Baseline autonomic burden (COMPASS-31) was associated with the magnitude of heart rate response to active stimulation. Immediately following stimulation and during the deep breathing challenge, active taVNS was associated with directionally consistent changes in vagally mediated HRV metrics including RMSSD, pNN50, and HF power, relative to sham.

Continuous HRV monitoring and autonomic reflex testing appears feasible for characterizing acute autonomic responses to taVNS in PD. Active stimulation was associated with directional changes in vagally mediated HRV metrics during the post-stimulation period and during deep breathing, supporting the biological plausibility of acute autonomic modulation. These preliminary findings justify larger, adequately powered studies designed to determine whether taVNS can reliably modulate cardiovascular autonomic regulation and inform rehabilitation optimization in PD.