Differences in video head impulse test gains from right versus left or outward versus inward head impulses

Vestibular Findings on the Video Head Impulse Test (vHIT) in Pregnancy: A Cross-Sectional Study

Background Functional and anatomic changes occur during pregnancy. Some of these changes are in the auditory and vestibular systems. However, there is a lack of information about the functional changes to critical structures that contribute to balance and proprioception. This study aims to evaluate the functions and shifts to the semicircular canals throughout gestation. Methodology This is a cross-sectional study. A video head impulse test (vHIT) was performed on all healthy pregnant patients with gestational periods ranging from the 20th to 40th weeks who were admitted to a maternal-fetal care unit. Vestibulo-ocular reflex (VOR) gains in the lateral, posterior, and anterior semicircular canals and gains in asymmetry were obtained. Results A significant positive relationship was observed in the right (R = 0.1064; P = 0.0110) and left (R = 0.2993; P = 0.0001) lateral semicircular canals as gestational weeks increased. Lower gains were seen at the start of the second trimester for the lateral canals. No significant gains were seen in the anterior or posterior canals throughout pregnancies until labor. No significant gains in asymmetry were detected. Conclusions Pregnant females may present vestibular changes in the semicircular lateral canals starting from the 20th week of gestation until labor. Increased gains may be associated with volumetric changes probably given by hormonal actions.

Factors affecting variability in vestibulo-ocular reflex gain in the Video Head Impulse Test in individuals without vestibulopathy: A systematic review of literature

Introduction

The purpose of this systematic review was to summarize and synthesize published evidence examining variations in vestibulo-ocular reflex (VOR) gain outcomes for the Video Head Impulse Test (vHIT) in healthy individuals without vestibulopathy in order to describe factors that may influence test outcomes.

Methods

Computerized literature searches were performed from four search engines. The studies were selected based on relevant inclusion and exclusion criteria, and were required to examine VOR gain in healthy adults without vestibulopathy. The studies were screened using Covidence (Cochrane tool) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards (PRISMA-2020).

Results

A total of 404 studies were initially retrieved, of which a total of 32 studies met inclusion criteria. Four major categories were identified which lead to significant variation in VOR gain outcomes: participant-based factors, tester/examiner-based factors, protocol-based factors, and equipment-based factors.

Discussion

Various subcategories are identified within each of these classifications and are discussed, including recommendations for decreasing VOR gain variability in clinical practice.

The Effect of Different Head Movement Paradigms on Vestibulo-Ocular Reflex Gain and Saccadic Eye Responses in the Suppression Head Impulse Test in Healthy Adult Volunteers

Objective: This study aimed to identify differences in vestibulo-ocular reflex gain (VOR gain) and saccadic response in the suppression head impulse paradigm (SHIMP) between predictable and less predictable head movements, in a group of healthy subjects. It was hypothesized that higher prediction could lead to a lower VOR gain, a shorter saccadic latency, and higher grouping of saccades. Methods: Sixty-two healthy subjects were tested using the video head impulse test and SHIMPs in four conditions: active and passive head movements for both inward and outward directions. VOR gain, latency of the first saccade, and the level of saccade grouping (PR-score) were compared among conditions. Inward and active head movements were considered to be more predictable than outward and passive head movements. Results: After validation, results of 57 tested subjects were analyzed. Mean VOR gain was significantly lower for inward passive compared with outward passive head impulses (p < 0.001), and it was higher for active compared with passive head impulses (both inward and outward) (p ≤ 0.024). Mean latency of the first saccade was significantly shorter for inward active compared with inward passive (p ≤ 0.001) and for inward passive compared with outward passive head impulses (p = 0.012). Mean PR-score was only significantly higher in active outward than in active inward head impulses (p = 0.004). Conclusion: For SHIMP, a higher predictability in head movements lowered gain only in passive impulses and shortened latencies of compensatory saccades overall. For active impulses, gain calculation was affected by short-latency compensatory saccades, hindering reliable comparison with gains of passive impulses. Predictability did not substantially influence grouping of compensatory saccades.

Evaluation of Vestibulo-Ocular Reflex (VOR) in Tinnitus Patients with Normal Hearing

OBJECTIVES

This study aimed to evaluate the correlation between tinnitus parameters (duration, severity, reaction, handicap levels) and vestibulo-ocular reflex (VOR) gain values in patients with tinnitus with normal hearing without vertigo or any other complaints and to compare the VOR gains with a healthy group.

MATERIALS AND METHODS

The study group consisted of 30 individuals aged between 18 and 65 years who suffered from tinnitus but not from hearing loss and vertigo. The control group also consisted of 30 individuals who were categorized as healthy adults. The tinnitus handicap inventory, tinnitus reaction questionnaire, and tinnitus handicap questionnaire were applied to each individual in the tinnitus group, and the video head impulse test (VHIT) was conducted in 2 groups.

RESULTS

Statistically, a significant difference was found between the 2 groups in terms of VOR gain values in horizontal and vertical semicircular canal planes (p<0.05). However, there was no statistically significant correlation between tinnitus parameters, age, and VOR gain values in the study group (p>0.05).

CONCLUSION

Considering the lower VOR gain values of the study group than the control group, these patients may need to be followed up for vestibular dysfunction associated with tinnitus, which can be a symptom of peripheral vestibular disorder. Moreover, this study will contribute to the literature because we determined a high-frequency component of VOR by VHIT, which was used to evaluate the relationship between tinnitus parameters and peripheral vestibular function.

Effect of different head impulse procedures on vestibulo-ocular reflex gain

OBJECTIVE

to study the effects on vestibulo-ocular reflex (VOR) gain using both video head impulse test (vHIT) and Suppression Head impulse test (SHIMP) either using the outward or the inwards head impulse.

METHODS

Twenty healthy subjects were enrolled in the study. They were examined using otometric vHIT and SHIMP test lateral plane using the lateral outwards head impulse ten impulses for each side and the inwards head impulse ten impulses for each side. The VOR gain resulting from the outwards versus inwards head impulse during the vHIT and SHIMP were statistically compared.

RESULTS

Twenty healthy subjects, 10 Males and 10 females with a mean age 35±11.7. Paired t- test showed no statistical significance difference in the mean VOR gain of right lateral semicircular canal (1.1±.12) using outwards versus (1.03 ± .22) inwards head impulses, nor for the left lateral semicircular canal mean VOR gain (1.1 ± .22) using outwards head impulse (1.1 ± .3) for inwards head impulse in vHIT. Paired t- test showed no statistical significance difference in the mean VOR gain of right lateral semicircular canal (0.96 ± 0.2)using outwards versus (1.04 ± 0.2) inwards head impulses, nor for the left lateral semicircular canal mean VOR gain (0.98 ± 0.25) using outwards head impulse (1.1 ± 0.28) for inwards head impulse in SHIMP test. No statistical significant difference was found between the VOR gain resulting from the right versus the left semicircular canal.

CONCLUSION

The starting head position does not affect the VOR gain using both vHIT and SHIMP tests.

Unstable Gaze in Functional Dizziness: A Contribution to Understanding the Pathophysiology of Functional Disorders

Objective: We are still lacking a pathophysiological mechanism for functional disorders explaining the emergence and manifestation of characteristic, severely impairing bodily symptoms like chest pain or dizziness. A recent hypothesis based on the predictive coding theory of brain function suggests that in functional disorders, internal expectations do not match the actual sensory body states, leading to perceptual dysregulation and symptom perception. To test this hypothesis, we investigated the account of internal expectations and sensory input on gaze stabilization, a physiologically relevant parameter of gaze shifts, in functional dizziness.

Methods: We assessed gaze stabilization in eight functional dizziness patients and 11 healthy controls during two distinct epochs of large gaze shifts: during a counter-rotation epoch (CR epoch), where the brain can use internal models, motor planning, and resulting internal expectations to achieve internally driven gaze stabilization; and during an oscillation epoch (OSC epoch), where, due to terminated motor planning, no movement expectations are present, and gaze is stabilized by sensory input alone.

Results: Gaze stabilization differed between functional patients and healthy controls only when internal movement expectations were involved [F(1,17) = 14.63, p = 0.001, and partial η² = 0.463]: functional dizziness patients showed reduced gaze stabilization during the CR (p = 0.036) but not OSC epoch (p = 0.26).

Conclusion: While sensory-driven gaze stabilization is intact, there are marked, well-measurable deficits in internally-driven gaze stabilization in functional dizziness pointing at internal expectations that do not match actual body states. This experimental evidence supports the perceptual dysregulation hypothesis of functional disorders and is an important step toward understanding the underlying pathophysiology.

Comparison of three video head impulse test systems for the diagnosis of bilateral vestibulopathy

INTRODUCTION

A horizontal vestibulo-ocular reflex gain (VOR gain) of < 0.6, measured by the video head impulse test (VHIT), is one of the diagnostic criteria for bilateral vestibulopathy (BV) according to the Báràny Society. Several VHIT systems are commercially available, each with different techniques of tracking head and eye movements and different methods of gain calculation. This study compared three different VHIT systems in patients diagnosed with BV.

METHODS

This study comprised 46 BV patients (diagnosed according to the Báràny criteria), tested with three commercial VHIT systems (Interacoustics, Otometrics and Synapsys) in random order. Main outcome parameter was VOR gain as calculated by the system, and the agreement on BV diagnosis (VOR gain < 0.6) between the VHIT systems. Peak head velocities, the order effect and covert saccades were analysed separately, to determine whether these parameters could have influenced differences in outcome between VHIT systems.

RESULTS

VOR gain in the Synapsys system differed significantly from VOR gain in the other two systems [F(1.256, 33.916) = 35.681, p < 0.000]. The VHIT systems agreed in 83% of the patients on the BV diagnosis. Peak head velocities, the order effect and covert saccades were not likely to have influenced the above mentioned results.

CONCLUSION

To conclude, using different VHIT systems in the same BV patient can lead to clinically significant differences in VOR gain, when using a cut-off value of 0.6. This might hinder proper diagnosis of BV patients. It would, therefore, be preferred that VHIT systems are standardised regarding eye and head tracking methods, and VOR gain calculation algorithms. Until then, it is advised to not only take the VOR gain in consideration when assessing a VHIT trial, but also look at the raw traces and the compensatory saccades.