Gaze stabilization during dynamic posturography in normal and vestibulopathic humans.

Effects of vestibular and cerebellar deficits on gaze and torso stability during ambulation

Selective Engagement of Plasticity Mechanisms for Motor Memory Storage

Vestibular neuritis is often mimicked by stroke (pseudoneuritis). Vestibular eye movements help discriminate the two conditions. We report vestibulo-ocular reflex (VOR) gain measures in neuritis and stroke presenting acute vestibular syndrome (AVS). Prospective cross-sectional study of AVS (acute continuous vertigo/dizziness lasting >24 h) at two academic centers. We measured horizontal head impulse test (HIT) VOR gains in 26 AVS patients using a video HIT device (ICS Impulse). All patients were assessed within 1 week of symptom onset. Diagnoses were confirmed by clinical examinations, brain magnetic resonance imaging with diffusion-weighted images, and follow-up. Brainstem and cerebellar strokes were classified by vascular territory-posterior inferior cerebellar artery (PICA) or anterior inferior cerebellar artery (AICA). Diagnoses were vestibular neuritis (n = 16) and posterior fossa stroke (PICA, n = 7; AICA, n = 3). Mean HIT VOR gains (ipsilesional [standard error of the mean], contralesional [standard error of the mean]) were as follows: vestibular neuritis (0.52 [0.04], 0.87 [0.04]); PICA stroke (0.94 [0.04], 0.93 [0.04]); AICA stroke (0.84 [0.10], 0.74 [0.10]). VOR gains were asymmetric in neuritis (unilateral vestibulopathy) and symmetric in PICA stroke (bilaterally normal VOR), whereas gains in AICA stroke were heterogeneous (asymmetric, bilaterally low, or normal). In vestibular neuritis, borderline gains ranged from 0.62 to 0.73. Twenty patients (12 neuritis, six PICA strokes, two AICA strokes) had at least five interpretable HIT trials (for both ears), allowing an appropriate classification based on mean VOR gains per ear. Classifying AVS patients with bilateral VOR mean gains of 0.70 or more as suspected strokes yielded a total diagnostic accuracy of 90%, with stroke sensitivity of 88% and specificity of 92%. Video HIT VOR gains differ between peripheral and central causes of AVS. PICA strokes were readily separated from neuritis using gain measures, but AICA strokes were at risk of being misclassified based on VOR gain alone.

Effects of heel height and high-heel experience on foot stability during quiet standing

Objective:To investigate interrelationships in parameters between caloric test and video head impulse test（vHIT） in the common peripheral vertigo diseases and healthy people, and to conduct correlation and difference analysis between the results in two tests, so as to evaluate the clinical diagnosis value of peripheral vertigo. Methods:The caloric test and vHIT were fulfilled in 68 patients with vertigo and 17 healthy volunteers. The diagnosis was done according to history inquiring, otology and audiology examination and vestibular tests. The vestibulo-ocular reflex（VOR） gain and gain asymmetry（GA） of a vHIT as well as unilateral weakness（UW） and the sum of the slow-phase velocities（SPVs） of warm and cold irrigation of the same side were compared. A cutoff value of VOR gain of a vHIT was also calculated using a receiver-operating characteristic curve. Results:In all ears（n=170）, there was significant correlation in ipsilateral SPVs and VOR gain（r=0.568, P<0.0001）; In all ears（n=34） of 17 healthy volunteers, there was no correlation in ipsilateral SPVs and VOR gain（r=-0.05, P=0.778）; In all affected ears（n=76）, there was statistically positive correlation in ipsilateral SPVs and VOR gain（r=0.571, P<0.0001）; In all the unaffected ears（n=94）, there was positive correlation in ipsilateral SPVs and VOR gain（r=0.286, P=0.005）. In 60 patients with unilateral vestibular disease（n=60）, there was statistically significant negative correlation between the VOR gain of affected ears and UW（r=-0.513, P<0.0001）; there was statistically significant positive correlation between GA of a vHIT and UW（r=0.713, P<0.0001）. There was a statistically significant negative correlation between the VOR gain of affected ears and UW in the fluctuating vertigo group（r=-0.516, P=0.002） as well as a positive correlation between GA and UW（r=0.529, P=0.001）; In the non-fluctuating vertigo group, there was a statistically significant negative correlation between the VOR gain of affected ears and UW（r=-0.428, P=0.029）; there was a positive correlation between GA of a vHIT and UW（r=0.743, P<0.0001）. In the vestibular neuropathy group, there was a negative correlation between the VOR gain of affected ears and UW（r=-0.462, P=0.030）; there was a statistically significant positive correlation between GA of a vHIT and UW（r=0.757, P<0.0001）. There was a negative correlation between the VOR gain of affected ears and UW in the vestibular peripheral disease group（r=-0.516, P=0.002） as well as a statistically significant positive correlation between GA and UW（r=0.529, P=0.001）. The mean value of UW（65.5%） was higher in the overt saccade group than that in the normal VOR group, there was statistically significant difference（P=0.006）. According to the UW damage degree grading, there was statistically significant difference in abnormal educe rates（χ²=17.76, P<0.05）. Based on the gold standard of caloric response, a cutoff value of 0.865 was determined; the parameters of the two tests were dissociated in 28.3%. Conclusion:There was a statistically significant correlation in parameters between vHIT and caloric test. The patients of overt saccade always accompany with the high UW, which could indicate that the vestibular function severely damaged. vHIT and caloric test can be complementary tools for the comprehensive evaluation of patients' vestibule function, on account of dissociation between the results of vHIT and caloric test and general result of consistent check.

There is a lack of comparative studies examining changes in vestibulo-ocular reflex (VOR) gain with head velocity in the video head impulse test (vHIT) of patients with vestibular neuritis (VN). Thus, the purpose of present study was to identify the effect of head impulse velocity on the gain of the VOR during the vHIT in patients with VN. Head impulse velocities ranging from 100%-200°/s [158.08 ± 23.00°/s in the horizontal canal (HC), 124.88 ± 14.80°/s in the anterior canal (AC), and 122.92 ± 14.26°/s in the posterior canal (PC) were used during vHIT trials of 32 patients with VN. Differences in VOR gain on the ipsilesional and contralesional sides according to head velocity were analyzed. The mean VOR gains in ipsilesional side were decreased to 0.47 in the HC and 0.56 in the AC, leading to marked asymmetry compared to the contralesional side; PC gain was relatively preserved at 0.82 in the ipsilesional side. The mean head impulse velocity applied during vHIT trials in each semicircular canal plane did not differ bilaterally. On the contralesional side, VOR gain was negatively correlated with head impulse velocity (R2=0.25, P=.004 in HC; R2=0.17, P=.021 in AC; R2=0.24, P=.005 in PC), while VOR gain on the ipsilesional sides of the HC and AC was not. Head impulse velocity may have a differential impact on VOR gain, depending on the degree of deficit. Increasing head velocity in vHIT may be considered to identify subtle deficits on the contralesional side of patients with VN.

To identify differences in the vestibulo-ocular reflex (VOR) gain value and the peak saccade velocity in the suppression video head impulse test paradigms according to the age of the subject and the direction of the impulse. Retrospective chart analysis. Tertiary referral hospital. Between October 2017 and May 2019, we enrolled subjects who had previous histories of dizziness but no dizziness over the last 1 month. We conducted cervical vestibular-evoked myogenic potential and caloric tests, as well as video head impulse tests. We excluded the subjects who had abnormal cervical vestibular-evoked myogenic potential results (asymmetry ratio of greater than 30%) and abnormal caloric test results (caloric paresis of greater than 25%). We included 647 subjects aged 10 to 87 years. The mean VOR gain and peak saccade velocity were maintained in subjects less than 70 years old (VOR gain, 0.991 ± 0.08, peak saccade velocity, 348.47 ± 142.32). However, the decreases in VOR gain and peak saccade velocity were significant in subjects over 70 years old (VOR gain, 0.928 ± 0.09, peak saccade velocity, 315.51 ± 0.09; p < 0.001). The mean VOR gain of the rightward impulse (1.00 ± 0.09) was higher than the leftward impulse (0.96 ± 0.08, p < 0.001). Both the VOR gain and peak saccade velocity of suppression video head impulse test paradigms declined with increasing age over 70 years. In addition, the VOR gain of the rightward impulse was higher than the leftward impulse in the right-eye recordings.

Vestibulo-ocular reflex in eccentric rotation in squirrel monkeys

Advancing age is associated with more impaired mediolateral balance control after step down task

Rotational vestibular function declines with age resulting in saccades as a compensatory mechanism to improve impaired gaze stability. Small reductions in rotational vestibulo-ocular reflex (VOR) gain that would be considered clinically normal have been associated with compensatory saccades. We evaluated whether compensatory saccade characteristics varied as a function of age, independent of semicircular canal function as quantified by VOR gain. Horizontal VOR gain was measured in 243 participants age 27-93 from the Baltimore Longitudinal Study of Aging using video head impulse testing. Latency and amplitude of the first saccade (either covert - occurring during head impulse, or overt - occurring following head impulse) were measured for head impulses with compensatory saccades (n = 2230 head impulses). The relationship between age and saccade latency, as well as the relationship between age and saccade amplitude, were evaluated using regression analyses adjusting for VOR gain, gender, and race. Older adults (mean age 75.9) made significantly larger compensatory saccades relative to younger adults (mean age 45.0). In analyses adjusted for VOR gain, there was a significant association between age and amplitude of the first compensatory covert saccade (β = 0.015, p = 0.008). In analyses adjusted for VOR gain, there was a significant association between age and amplitude of the first compensatory overt saccade (β = 0.02, p < 0.001). Compensatory saccade latencies did not vary significantly by age. We observed that aging increases the compensatory catch-up saccade amplitude in healthy adults after controlling for VOR gain. Size of compensatory saccades may be useful in addition to VOR gain for characterizing vestibular function in aging adults.

Purpose The aim of the present study was to assess the vestibuloocular reflex (VOR) gain function and VOR gain asymmetry during the various phases of the menstrual cycle in young healthy female participants. The study also aimed to characterize the presence or absence of corrective saccades during the various phases of the menstrual cycle. Method Twenty-nine young healthy females participated in the study. The video head impulse test (vHIT) was performed in lateral, left anterior right posterior, and right anterior left posterior plane during the various phases of the menstrual cycle to see the changes in VOR gain function and VOR gain asymmetry ratio changes. Results A repeated measure analysis of variance test did not show any significant main effect for the VOR gain function and VOR gain asymmetry ratio in various phases of the menstrual cycle in all the participants. The result suggested no changes in VOR gain function and VOR asymmetry ratio in healthy females during the menstrual cycle. Also, there was an absence of saccades in the entire participants group during the various phases of the menstrual cycle. Conclusions As the VOR gain function does not change during the various phases of the menstrual cycle in young healthy females, there is no need to consider the various phases of the menstrual cycle while testing any female participant during the vHIT test.

Vestibular Migraine (VM) is the most common cause of non-positional episodic vestibular symptoms. Patients with VM commonly report increased motion sensitivity, suggesting that vestibular responses to head movement may identify changes specific to VM patients. Here we explore whether the vestibulo-ocular reflex (VOR) gain alters in response to a clinical “headshake” maneuver in patients with VM. Thirty patients with VM in the inter-ictal phase, 16 patients with Benign Positional Paroxysmal Vertigo (BPPV) and 15 healthy controls were recruited. Patients responded to the question “Do you feel sick reading in the passenger seat of a car?” and completed a validated motion sickness questionnaire as a measure of motion sensitivity. Lateral canal vHIT testing was performed before and after headshaking; the change in VOR gain was calculated as the primary outcome. Baseline VOR gain was within normal limits across all participants. There was no significant change in VOR gain after headshaking in any group (p = 0.264). Patients were 4.3 times more likely to be in the VM group than in the BPPV group if they reported nausea when reading in the passenger seat of a car. We postulate that a headshake stimulus may be insufficient to disrupt cortical interactions and induce a change in VOR gain. Alternatively, changes in VOR gain may only be apparent in the acute phase of VM. Reading in the passenger seat of a car was considered uncomfortable in all VM patients suggesting that this specific question may be useful for the diagnosis of VM.

Postural stability control performance assessment is necessary in providing important information for individuals who are at risk of falling or who have balance impairment. Instrumented assessment is suggested as a valid and reliable test, but the cost and the difficulty of setup are significant limitations. The aim of this cross-sectional (test-retest reliability) study was to develop and determine the reliability of a low-cost posturography for assessing postural stability control performance during standing. The low-cost posturography was developed with four load cells and an acrylic platform. The center of pressure (COP) displacement and velocity were analyzed using written software. Test-retest reliability was performed with six different standing postural stability tests in twenty healthy volunteers on two different days. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), coefficient of variation (CV), and Bland–Altman plot and limits of agreements (LOA) were used for analyses. The low-cost posturography was accurate (ICC = 0.99, p < 0.001; SEM = 0.003 cm) when compared to the true with calculated X and Y coordinates, with a moderate to excellent test-retest reliability for both COP displacement (ICCs ranged 0.62–0.91, p < 0.05; SEMs ranged 17.92–25.77%) and COP velocity (ICCs ranged 0.62–0.91, p < 0.05; SEMs ranged 18.09–27.69%) in all standing postural stability tests. Bland–Altman plots and LOAs suggested good agreement of tested parameters from the developed low-cost posturography between different days. In conclusion, the developed low-cost posturography had adequate reliability for assessing COP displacement and velocity during standing postural control stability performance tests.

Laboratory-based measurement of standing balance in individuals with knee osteoarthritis: A systematic review

Flexibility of vestibulo-ocular reflex adaptation to modified visual input in human