Improvement of postural stability in patients with bilateral vestibulopathy by using noisy galvanic vestibular stimulation

Abstract

The peripheral vestibular organs sense angular and linear accelerations of the head, and help to maintain gaze and posture during head movements through the vestibuloocular and vestibulo-spinal reflexes. Bilateral vestibular dysfunction causes persistent imbalance and oscillopsia while moving the body or the head, and so far no effective treatments have been found for this condition except vestibular rehabilitation. We used noisy galvanic vestibular stimulation (noisy GVS), which was delivered as zero-mean current noise, of an imperceptible amplitude to improve postural performance in patients with bilateral vestibular dysfunction. We demonstrated that the application of noisy GVS for 30 sec significantly improved postural performance as measured by stabilometry in patients with bilateral vestibulopathy. We then examined the effect of noisy GVS on locomotion, and showed that it significantly increased the gait velocity and stride length, but significantly decreased the stride time in patients with vestibulopathy. Furthermore, to examine the effect of noisy GVS on vestibular function, we examined the effects of noisy GVS on ocular vestibular evoked myogenic potentials (oVEMP) in response to bone-conducted vibration (BCV). The noisy GVS increased the amplitude of oVEMP responses without affecting the latencies of oVEMP responses, suggesting that noisy GVS improves static and dynamic postural stability by enhancing the function of the vestibular afferents. Finally, we tested the long-term effects of noisy GVS on postural stability in elderly adults, and showed that noisy GVS can lead to a postural stability improvement that lasts for several hours after the cessation of the stimulus, probably via neuroplasticity. This newly discovered effect could contribute to an increase in the application of noisy GVS in appropriate patients.