ノイズ前庭電気刺激

抄録

　Bilateral vestibulopathy (BVP) is a chronic vestibular syndrome characterized by persistent unsteadiness when walking or standing, particularly in the dark and/or on uneven ground. In BVP, the function of the peripheral vestibular system is bilaterally impaired or absent. For patients with BVP who do not show much improvement in postural stability after vestibular rehabilitation, development of novel treatments is expected. Noisy galvanic vestibular stimulation (nGVS) is a procedure in which an electrical current is applied as a zero-mean current noise to the vestibular system through electrodes placed over the bilateral mastoid processes. In healthy subjects and patients with BVP, the application of imperceptible optimal-level nGVS improved the stability of the standing posture and gait performance. On the other hand, further increase of the nGVS intensity degraded the stability of the standing posture. The proposed mechanism behind these effects is stochastic resonance, in which the existence of an optimal amount of noise can enhance subthreshold signals in a non-linear system. It has also been reported that nGVS has a post-stimulation ameliorating effect on postural stability in healthy adults and BVP patients, even after cessation of the stimulus. The ameliorating effect of nGVS on the posture varies among subjects. We reported that the ameliorating effect of nGVS on postural stability was greater in subjects who had greater instability to begin with, both during application of the stimulus and after cessation of the stimulus. Subjects with a lower dependence on vestibular inputs show greater ameliorating effects of nGVS. nGVS is considered to be one of the promising candidates for novel treatment of refractory postural instability in patients with vestibulopathy, and further clinical studies are needed to increase the evidence level of its therapeutic effects. In addition, the development of basic research on the mechanism underlying the effect of nGVS on the postural control system is also desired.