Relationship Between Short-Term Postural Responses to Noisy Galvanic Vestibular Stimulation at Varying Current...

For patients with peripheral vestibulopathy, the optimal intensity of noisy galvanic vestibular stimulation (nGVS) for improving postural stability can vary from day to day, yet frequent measurement is clinically challenging. This study aimed to investigate the relationship between the short-term effects of nGVS at various current intensities on postural stability and the prolonged effects of nGVS applied at the optimal intensity on different days. Specifically, we sought to identify which short-term nGVS intensities were effective in patients who showed improvement with prolonged nGVS.

This trial registration was registered on August 10, 2018, (number: jRCT1080224083). Patients with peripheral vestibulopathy underwent closed-eye center-of-pressure (COP) measurements for 30 seconds without nGVS and with nGVS at 100-2000 μA to determine the optimal intensity (defined as the current yielding the greatest velocity improvement). Prolonged nGVS was then applied at this optimal intensity. Patients demonstrating at least a 10% improvement in mean velocity change during three hours of stimulation compared with placebo were classified as the "improvement" group, while others formed the "no-improvement" group. The percent change in COP velocity from baseline (no nGVS) at each intensity was compared between groups.

The improvement group (n = 9) demonstrated significantly greater reductions in COP velocity than the no-improvement group (n = 30) at 100 μA and 1700 μA (p < 0.05). Additionally, compared with the no-improvement group, the improvement group exhibited enhanced responsiveness across a broader range of short-term nGVS current intensities.

In patients with peripheral vestibulopathy, the beneficial effect of prolonged nGVS on standing postural control is closely related to short-term responsiveness to nGVS across a wide range of current intensities. In particular, when the optimal stimulation intensity lies between 100 and 1700 μA, this relationship appears strongest.