Noisy galvanic vestibular stimulation induces a sustained improvement in body balance in elderly adults

Abstract

Vestibular dysfunction causes postural instability, which is prevalent in the elderly. We previously showed that an imperceptible level of noisy galvanic vestibular stimulation (nGVS) can improve postural stability in patients with bilateral vestibulopathy during the stimulus, presumably by enhancing vestibular information processing. In this study, we investigated the after-effects of an imperceptible long-duration nGVS on body balance in elderly adults. Thirty elderly participants underwent two nGVS sessions in a randomised order. In Session 1, participants received nGVS for 30 min twice with a 4-h interval. In Session 2, participants received nGVS for 3 h. Two-legged stance tasks were performed with eyes closed while participants stood on a foam rubber surface, with and without nGVS, and parameters related to postural stability were measured using posturography. In both sessions, the postural stability was markedly improved for more than 2 h after the cessation of the stimulus and tended to decrease thereafter. The second stimulation in Session 1 caused a moderate additional improvement in body balance and promoted the sustainability of the improvement. These results suggest that nGVS can lead to a postural stability improvement in elderly adults that lasts for several hours after the cessation of the stimulus, probably via vestibular neuroplasticity.

Finding a Balance: A Systematic Review of the Biomechanical Effects of Vestibular Prostheses on Stability in Humans

“…Electrode size was roughly 2 cm × 2 cm in all studies apart from Keywan et al in which the electrodes were 4 cm × 6.4 cm [27]. Only five trials explicitly stated the use of a portable, battery-powered stimulator [16,25,26,40,42]. The size and weight of the portable stimulator was only mentioned in two studies which both used the same model (112 mm × 67 mm × 28 mm, 200 g) which was worn attached to the waist [25,42].…”

“…The use of zero-mean current noisy galvanic stimulation (nGVS) is not consequently considered more advantageous. Battery-powered portable current stimulators are effective in delivering nGVS to vestibular afferents, demonstrating the potential of nGVS as a prosthetic technique [25]. Modulating anodal and cathodal currents provides a means of modulating the firing rate of vestibular afferents [24].…”

“…A total of 11 studies investigated the use of GVS to modulate vestibular function [16,[25][26][27][28]31,[38][39][40][41][42]. Only five of these were conducted on participants with BVD, with the rest conducted on healthy patients.…”

“…Only five trials explicitly stated the use of a portable, battery-powered stimulator [16,25,26,40,42]. The size and weight of the portable stimulator was only mentioned in two studies which both used the same model (112 mm × 67 mm × 28 mm, 200 g) which was worn attached to the waist [25,42]. Two studies applied constant GVS [26,28].…”

“…This protocol was followed in four proceeding studies. These, unlike the study by Iwasaki et al which had the primary intention of finding the optimal amplitude, went on to use this optimal stimulus intensity as a tool to explore different biomechanical effects of nGVS on balance [16,25,27,42]. The mean amplitude optimal stimulus intensity found for patients with BVD ranged from 454 (±55) to 456 µA (±82).…”