Institute of Psychology II, University of Luebeck, Lübeck, Germany.
Department of Neurology, University Medical Center Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany.
J Neurol. 2019 May;266(5):1236-1249. doi: 10.1007/s00415-019-09255-7. Epub 2019 Feb 26.
Over the past years galvanic vestibular stimulation (GVS) has been increasingly applied to stimulate the vestibular system in health and disease, but not in patients with persistent postural-perceptual dizziness (PPPD) yet. We functionally tested motion perception thresholds and postural responses to imperceptible noisy (nGVS) and perceptible bimastoidal GVS intensities in patients with PPPD with normal vestibulo-ocular reflexes. We hypothesized that GVS destabilizes PPPD patients under simple postural conditions stronger compared to healthy controls. They were compared to healthy subjects under several conditions each with the eyes open and closed: baseline with firm platform support, standing on foam and cognitive demand (count backward). Low and high GVS intensities (range 0.8-2.8 mA) were applied according to the individual thresholds and compared with no GVS. PPPD patients showed a reduced perception threshold to GVS compared to healthy control subjects. Median postural sway speed increased with stimulus intensity and on eye closure, but there was no group difference, irrespective of the experimental condition. Romberg's ratio was consistently lower during nGVS than in all other conditions. Group-related dissociable effects were found with the eyes closed in (i) the baseline condition in which high GVS elicited higher postural sway of PPPD patients and (ii) in the foam condition, with better postural stability of PPPD patients during perceptible GVS. Group and condition differences of postural control were neither related to anxiety nor depression scores. GVS may be helpful to identify thresholds of vestibular perception and to modulate vestibulo-spinal reflexes in PPPD, with dissociable effects with respect to perceptible and imperceptible stimuli. The sway increase in the baseline of PPPD may be related to an earlier transition from open- to closed-loop mode of postural control. In contrast, the smaller sway of PPPD in the foam condition under visual deprivation is in line with the known balance improvement under more demanding postural challenges in PPPD. It is associated with a prolonged transition from open- to closed-loop postural feedback control. It could also reflect a shift of intersensory weighting with a smaller dependence on proprioceptive feedback control in PPPD patients under complex tasks. In summary, GVS discloses differences between simple and complex balance tasks in PPPD.
在过去的几年里，电刺激前庭（GVS）已被越来越多地应用于健康和疾病中的前庭系统刺激，但尚未用于持续性姿势感知性头晕（PPPD）患者。我们在具有正常眼震反射的 PPPD 患者中对运动感知阈值和姿势反应进行了功能性测试，以测试不可察觉的噪声（nGVS）和可察觉的双耳 GVS 强度。我们假设 GVS 在简单姿势条件下比健康对照组更能使 PPPD 患者不稳定。他们在几种情况下与健康受试者进行了比较，每种情况都睁眼和闭眼：基线时使用坚固的平台支撑，站在泡沫上和认知需求（倒数）。根据个体阈值，施加低（0.8-2.8 mA）和高（2.8-4.5 mA）GVS 强度，并与无 GVS 进行比较。与健康对照组相比，PPPD 患者的 GVS 感知阈值降低。随着刺激强度的增加和闭眼，姿势摆动速度的中位数增加，但无论实验条件如何，均无组间差异。与其他所有条件相比，nGVS 时 Romberg 比值始终较低。在闭眼时，发现与组相关的可分离效应（i）在基线条件下，高 GVS 会引起 PPPD 患者更高的姿势摆动，以及（ii）在泡沫条件下，可察觉的 GVS 可使 PPPD 患者的姿势稳定性更好。姿势控制的组间和条件差异既与焦虑评分也与抑郁评分无关。GVS 可能有助于识别前庭感知的阈值，并调节 PPPD 中的前庭-脊髓反射，对可察觉和不可察觉的刺激具有可分离的作用。PPPD 的基线中姿势摆动的增加可能与从开环到闭环姿势控制模式的较早转换有关。相比之下，在视觉剥夺下的泡沫条件下，PPPD 的摆动较小与 PPPD 中更具挑战性的姿势挑战下平衡改善的已知情况一致。这与从开环到闭环姿势反馈控制的过渡延长有关。它还可能反映了在复杂任务下 PPPD 患者中感觉间权重的变化，对本体感觉反馈控制的依赖性较小。总之，GVS 揭示了 PPPD 中简单和复杂平衡任务之间的差异。
