Department of Physical Therapy, Faculty of Social Welfare and Health Sciences, University of Haifa, Haifa, Israel.
Department of Physical Therapy, Steinhardt School of Culture Education and Human Development, New York University, New York, NY, USA.
J Neuroeng Rehabil. 2021 Mar 25;18(1):55. doi: 10.1186/s12984-021-00852-0.
Persistent postural-perceptual dizziness (PPPD) is a condition characterized by chronic subjective dizziness and exacerbated by visual stimuli or upright movement. Typical balance tests do not replicate the environments known to increase symptoms in people with PPPD-crowded places with moving objects. Using a virtual reality system, we quantified dynamic balance in people with PPPD and healthy controls in diverse visual conditions.
Twenty-two individuals with PPPD and 29 controls performed a square-shaped fast walking task (Four-Square Step Test Virtual Reality-FSST-VR) using a head-mounted-display (HTC Vive) under 3 visual conditions (empty train platform; people moving; people and trains moving). Head kinematics was used to measure task duration, movement smoothness and anterior-posterior (AP) and medio-lateral (ML) ranges of movement (ROM). Heart rate (HR) was monitored using a chest-band. Participants also completed a functional mobility test (Timed-Up-and-Go; TUG) and questionnaires measuring anxiety (State-Trait Anxiety Inventory; STAI), balance confidence (Activities-Specific Balance Confidence; ABC), perceived disability (Dizziness Handicap Inventory) and simulator sickness (Simulator Sickness Questionnaire). Main effects of visual load and group and associations between performance, functional and self-reported outcomes were examined.
State anxiety and simulator sickness did not increase following testing. AP-ROM and HR increased with high visual load in both groups (p < 0.05). There were no significant between-group differences in head kinematics. In the high visual load conditions, high trait anxiety and longer TUG duration were moderately associated with reduced AP and ML-ROM in the PPPD group and low ABC and high perceived disability were associated with reduced AP-ROM (|r| = 0.47 to 0.53; p < 0.05). In contrast, in controls high STAI-trait, low ABC and longer TUG duration were associated with increased AP-ROM (|r| = 0.38 to 0.46; p < 0.05) and longer TUG duration was associated with increased ML-ROM (r = 0.53, p < 0.01).
FSST-VR may shed light on movement strategies in PPPD beyond task duration. While no main effect of group was observed, the distinct associations with self-reported and functional outcomes, identified using spatial head kinematics, suggest that some people with PPPD reduce head degrees of freedom when performing a dynamic balance task. This supports a potential link between spatial perception and PPPD symptomatology.
持续性姿势感知性头晕（PPPD）是一种以慢性主观性头晕为特征的疾病，视觉刺激或直立运动可使其加重。典型的平衡测试无法复制已知会增加 PPPD 患者症状的环境——拥挤的地方有移动的物体。我们使用虚拟现实系统，定量评估了 PPPD 患者和健康对照组在不同视觉条件下的动态平衡。
22 名 PPPD 患者和 29 名健康对照者使用头戴式显示器（HTC Vive）在 3 种视觉条件下（空的火车平台、有人移动、人和火车都在移动）进行了一个正方形快速行走任务（四方步测试虚拟现实-FSST-VR）。头部运动学用于测量任务持续时间、运动平稳度以及前后（AP）和左右（ML）运动范围（ROM）。使用胸带监测心率（HR）。参与者还完成了功能性移动测试（计时起立行走测试；TUG）和评估焦虑（状态特质焦虑量表；STAI）、平衡信心（活动特异性平衡信心量表；ABC）、感知障碍（头晕障碍量表）和模拟器疾病（模拟器疾病问卷）的问卷。检查了视觉负荷的主要效果和组间差异，以及性能、功能和自我报告结果之间的关联。
测试后状态焦虑和模拟器疾病并未增加。在两组中，高视觉负荷都会增加 AP-ROM 和 HR（p<0.05）。两组的头部运动学均无显著差异。在高视觉负荷条件下，高特质焦虑和较长的 TUG 持续时间与 PPPD 组的 AP 和 ML-ROM 减小相关，而低 ABC 和高感知障碍与 AP-ROM 减小相关（|r|=0.47 至 0.53；p<0.05）。相比之下，在对照组中，高 STAI-特质、低 ABC 和较长的 TUG 持续时间与 AP-ROM 增加相关（|r|=0.38 至 0.46；p<0.05），而较长的 TUG 持续时间与 ML-ROM 增加相关（r=0.53，p<0.01）。
FSST-VR 可能会揭示 PPPD 患者在动态平衡任务中超越任务持续时间的运动策略。虽然未观察到组间的主要影响，但使用空间头部运动学识别的与自我报告和功能结果的关联表明，一些 PPPD 患者在执行动态平衡任务时会减少头部自由度。这支持了空间感知与 PPPD 症状之间的潜在联系。
