超越VOR增益：功能性头脉冲试验作为多感觉整合与凝视稳定性的探针

文献信息

中文摘要

功能性头脉冲试验（fHIT）测量个体在高加速度被动头脉冲期间能够看到的内容，量化正确识别短暂闪现视标的百分比，而非从眼动速度运动学推断凝视稳定性。本文追溯了fHIT的技术演变，从其动态视力测试的概念起源到其标准化方案（在峰值头加速度时呈现80毫秒，按1,000-7,000°/s²分箱），并利用临床数据提出功能性前庭评估的新概念框架。积累的证据揭示了视频头脉冲试验（vHIT）运动学增益与fHIT功能表现之间的显著分离，证明现实世界前庭损伤中的临床瓶颈常常是在视觉和认知需求下实时整合多感觉信号的中枢能力。在外周前庭病变中，fHIT表明功能性视觉完全依赖于80毫秒视标呈现窗口内隐蔽性扫视的精确时间聚集。在前庭性偏头痛中，fHIT在视动冲突下可能揭示运动学测试完全遗漏的中枢感觉重加权失败（感觉错配）。在老年人中，fHIT表现——不同于vHIT增益——与Tinetti平衡评分相关，预测跌倒风险的比值比为3.9，而双任务研究证实同时进行的认知负荷选择性降低fHIT准确性。基于这些趋同的分离，我们提出一个新的三级功能框架，将凝视稳定性组织为外周反射机制、扫视替代和中枢感觉门控。该模型确立fHIT可以通过在不可预测的被动扰动期间同时挑战凝视稳定性、视觉辨别、注意力分配和短期记忆编码，直接探测更高层次的中枢整合环路。这一理论转变将异常功能表现与正常运动学增益并存重新定义为不是悖论，而是中枢处理或认知资源分配/注意力缺陷的指标，为定制高级前庭康复提供了新蓝图。

英文摘要

The functional head impulse test (fHIT) measures what individuals can see during high-acceleration passive head impulses, quantifying the percentage of correctly identified briefly flashed optotypes rather than inferring gaze stabilization from kinematic eye velocity. This paper traces the technological evolution of fHIT from its conceptual origins in dynamic visual acuity testing to its standardized protocol (80-ms presentation at peak head acceleration binned across 1,000-7,000°/s2) and leverages clinical data to propose a new conceptual framework for functional vestibular assessment. Accumulated evidence reveals a stark dissociation between video head impulse test (vHIT) kinematic gain and fHIT functional performance, proving that the clinical bottleneck in real-world vestibular impairment is frequently the central capacity to integrate multisensory signals under visual and cognitive demands in real time. In peripheral vestibulopathies, fHIT demonstrates that functional vision depends entirely on the precise temporal clustering of covert saccades within the 80-ms optotype presentation window. In vestibular migraine, fHIT under optokinetic conflict could unmask central sensory re-weighting failures (sensory mismatch) completely missed by kinematic testing. In older people, fHIT performance-unlike vHIT gain-correlates with Tinetti Balance Scores, predicting fall risk with an odds ratio of 3.9, while dual-task studies confirm that concurrent cognitive load selectively degrades fHIT accuracy. Based on these converging dissociations, we propose a novel three-level functional framework that organizes gaze stabilization into peripheral reflex mechanics, saccadic substitution, and central sensory gating. This model establishes that the fHIT could directly probe the higher-level central integrative loop by simultaneously challenging gaze stabilization, visual discrimination, attentional allocation, and short-term memory encoding during unpredictable passive perturbations. This theoretical shift reframes abnormal functional performance alongside normal kinematic gain not as a paradox, but as an indicator of central processing or cognitive resource allocation/attention deficits, providing a new blueprint for tailoring advanced vestibular rehabilitation.