Chang Tzu-Pu, Schubert Michael C
Department of Neurology/Neuro-medical, Scientific Center, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan (T.-P.C.); Department of Neurology, School of Medicine, Tzu Chi University, Hualien, Taiwan (T.-P.C.); Laboratory of Vestibular NeuroAdaptation, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland (M.C.S.); and Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, Maryland (M.C.S.).
J Neurol Phys Ther. 2021 Jan;45(1):3-11. doi: 10.1097/NPT.0000000000000335.
Convergence of the eyes during head rotation increases the gain (eye velocity/head velocity) of the vestibulo-ocular reflex (VOR). We sought to know whether convergence would increase the VOR gain (mean + SD) in unilateral vestibular hypofunction (UVH).
Vestibulo-ocular reflex gain during ipsi- and contralesional horizontal head rotation at near (15 cm) and far (150 cm) targets was measured in 22 subjects with UVH and 12 healthy controls. Retinal slip was estimated (retinal slip index [RSI]) as the difference between ideal VOR gain (no retinal slip) and the actual VOR gain.
Convergence did not significantly enhance VOR gain for ipsilesional rotation (mean difference, 0.04; 95% confidence interval [CI], -0.01 to 0.09), near viewing (0.77 ± 0.34) versus far viewing (0.72 ± 0.29), yet the VOR gain during contralesional rotation was greater for near viewing (1.20 ± 0.23) than for far viewing (0.97 ± 0.21; mean difference, 0.23; 95% CI, 0.13-0.32). In the 36% of subjects with recovery of their ipsilesional VOR gain, the vergence effect trended to recover (far VOR gain: 1.06 ± 0.17 vs near VOR gain 1.16 ± 0.21; mean difference, 0.10; 95% CI, -0.02 to 0.22). Ipsilesional head rotation induced greater retinal slip for near (RSI = 0.90 ± 0.34) targets than for far targets (RSI = 0.35 ± 0.29; mean difference, 0.56; 95% CI, 0.51-0.61).
The convergence-mediated VOR gain enhancement is preserved during contralesional but impaired during ipsilesional head rotation. Recovery of ipsilesional passive VOR gain does not equate to restored convergence enhancement, although it did increase ∼10%. These data suggest head motion viewing near targets will increase retinal slip, which warrants consideration as a gaze stability exercise for subjects with UVH.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A325).
头部旋转时双眼会聚可增加前庭眼反射（VOR）的增益（眼速度/头速度）。我们试图了解在单侧前庭功能减退（UVH）时，会聚是否会增加VOR增益（均值±标准差）。
对22例UVH患者和12名健康对照者，在近（15 cm）、远（150 cm）目标下测量患侧和健侧水平头旋转时的前庭眼反射增益。通过理想VOR增益（无视网膜滑动）与实际VOR增益的差值估算视网膜滑动（视网膜滑动指数[RSI]）。
会聚并未显著提高患侧旋转的VOR增益（平均差值为0.04；95%置信区间[CI]，-0.01至0.09），近视力（0.77±0.34）与远视力（0.72±0.29）相比，但健侧旋转时近视力的VOR增益（1.20±0.23）大于远视力（0.97±0.21；平均差值为0.23；95% CI，0.13 - 0.32）。在患侧VOR增益恢复的36%的受试者中，会聚效应有恢复趋势（远VOR增益：1.06±0.17 vs近VOR增益1.16±0.21；平均差值为0.10；95% CI，-0.02至0.22）。患侧头部旋转在近目标（RSI = 0.90±0.34）时比远目标（RSI = 0.35±0.29）引起更大的视网膜滑动（平均差值为0.56；95% CI，0.51 - 0.61）。
会聚介导的VOR增益增强在健侧头部旋转时得以保留，但在患侧头部旋转时受损。患侧被动VOR增益的恢复并不等同于会聚增强的恢复，尽管其确实增加了约10%。这些数据表明，头部向近目标运动将增加视网膜滑动，这对于UVH患者作为一种注视稳定训练值得考虑。视频摘要可获取作者更多见解（见视频，补充数字内容1，可在：http://links.lww.com/JNPT/A325获取）。
