Evaluation of quantitative head impulse testing using search coils versus video-oculography in older individuals

Frequency dependence of human thresholds: both perceptual and vestibuloocular reflex thresholds

Although perceptual thresholds have been widely studied, vestibuloocular reflex (VOR) thresholds have received less attention, so the relationship between VOR and perceptual thresholds remains unclear. We compared the frequency dependence of human VOR thresholds to human perceptual thresholds for yaw head rotation in both upright ("yaw rotation") and supine ("yaw tilt") positions, using the same human subjects and motion device. VOR thresholds were generally a little smaller than perceptual thresholds. We also found that horizontal VOR thresholds for both yaw rotation about an Earth-vertical axis and yaw tilt (yaw rotation about an Earth-horizontal axis) were relatively constant across four frequencies (0.2, 0.5, 1, and 2 Hz), with little difference between yaw rotation and yaw tilt VOR thresholds. For yaw tilt stimuli, perceptual thresholds were slightly lower at the lowest frequency and nearly constant at all other (higher) frequencies. However, for yaw rotation, perceptual thresholds increased significantly at the lowest frequency (0.2 Hz). We conclude 1) that VOR thresholds were relatively constant across frequency for both yaw rotation and yaw tilt, 2) that the known contributions of velocity storage to the VOR likely yielded these VOR thresholds that were similar for yaw rotation and yaw tilt for all frequencies tested, and 3) that the integration of otolith and horizontal canal signals during yaw tilt when supine contributes to stable perceptual thresholds, especially relative to the low-frequency perceptual thresholds recorded during yaw rotation.NEW & NOTEWORTHY We describe for the first time that human VOR thresholds differ from human forced-choice perceptual thresholds, with the difference especially evident at frequencies below 0.5 Hz. We also report that VOR thresholds are relatively constant across frequency for both yaw rotation and yaw tilt. These findings are consistent with the idea that high-pass filtering in cortical pathways impacts cognitive decision-making.

Video head impulse test in stroke: a review of published studies

Accurate and timely diagnosis of posterior circulation stroke in patients with acute dizziness is a challenge that can lead to misdiagnosis and significant harm. The present review sought to identify and describe published research on the clinical application of vHIT in posterior circulation stroke. vHIT, a portable device, has gained prominence in evaluating peripheral vestibular disorders and offers potential applications in diagnosing neurological disorders, particularly posterior circulation stroke. Several studies have shown that vHIT can differentiate between stroke and vestibular neuritis based on VOR gain values, with high sensitivity and specificity. The manuscript also discusses vHIT's performance in differentiating between types of posterior circulation stroke, such as PICA, AICA, and SCA strokes. While vHIT has demonstrated promise, the review emphasizes the need for further research to validate its use as a tool to rule out stroke in acute dizziness patients in the emergency department. In conclusion, the manuscript underscores the potential of vHIT as a valuable addition to the diagnostic arsenal for acute dizziness, particularly in the context of posterior circulation stroke. It calls for further research and wider adoption of vHIT in clinical settings to improve patient care and reduce unnecessary costs associated with misdiagnoses.

Vestibulo-Ocular Reflex Suppression: Clinical Relevance and Assessment in the Digital Age

Background

Visual acuity and image stability are crucial for daily activities, particularly during head motion. The vestibulo-ocular reflex (VOR) and its suppression (VORS) support stable fixation of objects of interest. The VOR drives a reflexive eye movement to counter retinal slip of a stable target during head motion. In contrast, VORS inhibits this countermovement when the target stimulus is in motion. The VORS allows for object fixation when it aligns with the direction of the head's movement, or when an object within or outside the peripheral vision needs to be focused upon.

Summary

Deficits of the VORS have been linked to age-related diseases such as balance deficits associated with an increased fall risk. Therefore, the accurate assessment of the VORS is of particular clinical relevance. However, current clinical assessment methods for VORS are mainly qualitative and not sufficiently standardised. Recent advances in digital health technology, such as smartphone-based videooculography, offer a promising alternative for assessing VORS in a more accessible, efficient, and quantitative manner. Moreover, integrating mobile eye-tracking technology with virtual reality environments allows for the implementation of controlled VORS assessments with different visual inputs. These assessment approaches allow the extraction of novel parameters with potential pathomechanistic and clinical relevance.

Key Messages

We argue that researchers and clinicians can obtain a more nuanced understanding of this ocular stabilisation reflex and its associated pathologies by harnessing digital health technology for VORS assessment. Further research is warranted to explore the technologies' full potential and utility in clinical practice.

Changes in vestibular-related responses to combined noisy galvanic vestibular stimulation and cerebellar transcranial direct current stimulation

Vestibular nuclei and cerebellar function comprise vestibular neural networks that control vestibular-related responses. However, the vestibular-related responses to simultaneous stimulation of these regions are unclear. This study aimed to examine whether the combination of noisy galvanic vestibular stimulation (nGVS) and cerebellar transcranial direct current stimulation (ctDCS) using a complex transcranial electrical stimulation device alters vestibular-dominant standing stability and vestibulo-ocular reflex (VOR) function. The center of foot pressure (COP) sway and VOR of participants (28 healthy, young adults) were assessed under four conditions of transcranial electrical stimulation using nGVS and ctDCS. The COP was calculated with the participant standing on a soft-foam surface with eyes closed using a force plate to evaluate body sway. VOR measurements were collected via passive head movements and fixation on a target projected onto the front wall using a video head impulse test (vHIT). VOR gain was calculated in six directions using a semicircular canal structure based on the ratio of eye movement to head movement. The nGVS + ctDCS and nGVS + sham ctDCS conditions decreased COP sway compared to the sham nGVS + ctDCS and sham nGVS + sham ctDCS conditions. No significant differences were observed in the main effect of stimulation or the interaction of stimulation and direction on the vHIT parameters. The results of this study suggest that postural stability may be independently affected by nGVS. Our findings contribute to the basic neurological foundation for the clinical application of neurorehabilitation using transcranial electrical stimulation of the vestibular system.

Reduced Vestibulo-Ocular Reflex During Fast Head Rotation in Complete Darkness

The human vestibulo-ocular reflex (VOR) leads to maintenance of the acuity of an image on the retina and contributes to the perception of orientation during high acceleration head movements. Our objective was to determine whether vision affects the horizontal VOR by assessing and comparing the performance at the boundaries of contribution of: (a) unrestricted visual information and (b) no visual information. Understanding how the VOR performs under both lighted and unlighted conditions is of paramount importance to avoiding falls, perhaps particularly among the elderly. We tested 23 participants (M age = 35.3 years, standard error of mean (SEM) = 2.0 years). The participants were tested with the video Head Impulse Test (vHIT), EyeSeeCam from Interacoustics™, which assesses whether VOR is of the expected angular velocity compared to head movement angular velocity. The vHIT tests were performed under two conditions: (a) in a well-lit room and (b) in complete darkness. The VOR was analyzed by evaluating the gain (quotient between eye and head angular velocity) at 40, 60 and 80 ms time stamps after the start of head movement. Additionally, we calculated the approximate linear gain between 0-100 ms through regression. The gain decreased significantly faster across time stamps in complete darkness (p < .001), by 10% in darkness compared with a 2% decrease in light. In complete darkness, the VOR gain gradually declined, reaching a marked reduction at 80 ms by 10% (p < .001), at which the head velocities were 150°/second or faster. The approximate linear gain value was not significantly different in complete darkness and in light. These findings suggest that information from the visual system can modulate the high velocity VOR. Subsequently, fast head turns might cause postural imbalance and momentary disorientation in poor light in people with reduced sensory discrimination or motor control, like the elderly.

Video Head Impulse Test: A Comparison and Analysis of Three Recording Systems

The present study aimed to compare the efficacy and reproducibility of three existing systems in a group of healthy individuals for vHIT. A prospective randomized study was conducted on 12 healthy individuals. The vHIT tests were carried out. The values of the gains for the 3SCCs of each ear were collected using the three devices. The expected average gain of 1 was the gain standard. The statistical significance in the difference in gains were assessed. There is good reproducibility of the results of the vHIT examination. EyeSeeCam appeared to be the worst performing system with a slightly overstated average gain of 1.15. Otometrics has longest average examination time per patient. Synapsis is the system with the best quality/time invested and easiest to access. Video head impulse system depends on the examiner's preference, reproducible and superimposable depending on the examiner and experience.

Head and vestibular kinematics during vertical semicircular canal impulses

BACKGROUND

The video head impulse test (vHIT) is a common assessment of semicircular canal function during high-speed impulses. Reliability of the vHIT for assessing vertical semicircular canals is uncertain. Vertical head impulses require a complex head movement, making it difficult to isolate a single semicircular canal and interpret resulting eye rotations.

OBJECTIVE

The purpose of this study was to provide descriptive head kinematics and vestibular stimuli during vertical plane impulses to ultimately improve impulse delivery and interpretation of vHIT results for vertical semicircular canals.

METHODS

Six participants received right anterior (RA) and left posterior (LP) semicircular canal impulses. Linear displacements, rotational displacements, and rotational velocities of the head were measured. Peak velocities in semicircular canal planes and peak-to-peak gravitoinertial accelerations at the otolith organs were derived from head kinematics.

RESULTS

The largest rotational velocities occurred in the target semicircular canal plane, with non-negligible velocities occurring in non-target planes. Larger vertical displacements and accelerations occurred on the right side of the head compared to the left for RA and LP impulses.

CONCLUSIONS

These results provide a foundation for designing protocols to optimize stimulation applied to a singular vertical semicircular canal and for interpreting results from the vHIT for vertical semicircular canals.

VOR gain of lateral semicircular canal using video head impulse test in acute unilateral vestibular hypofunction: A systematic review

Introduction

Acute unilateral vestibular hypofunction is characterized by sudden onset of vertigo or dizziness, vomiting/nausea, gait instability, and nystagmus. This is commonly described as an acute vestibular syndrome and usually attributed to vestibular neuritis; however, up to 25% of acute vestibular syndrome is caused by a stroke of posterior circulations. The video head impulse test is a recent tool in the vestibular test battery that assesses the vestibule-ocular reflex by measuring the VOR gain and recording overt and covert saccades, these findings have been found to be helpful in the diagnosis of various vestibular disorders.

Method

A literature search was conducted in databases, including PubMed Central, PubMed, and Web of Science. All the articles that define video head impulse test (vHIT), acute vestibular hypofunction, and vestibular neuritis were considered for the preliminary search. No limits were placed on the date of publication. The searches were limited to studies with full-text availability, published in English, and including human subjects. Search words such as "head impulse test," "video head impulse test," "vestibular ocular reflex," "acute vestibular syndrome," "acute vestibular hypofunction," "vestibular neuritis," and "vHIT in central vestibular disorders" were entered into different databases in different combinations using boolean operators such as AND, OR, and NOT.

Results

Searches across different databases, including Web of Science, PubMed Central, and PubMed, resulted in a total of 1,790 articles. Title screening was done for all the articles. Out of the 1,790 articles, we found that 245 articles were related to vestibular hypofunction i.e., 1,545 articles were removed at this stage. A further 56 duplicate articles were removed. This led to a final screening of 189 articles. The exclusion criteria included unavailability of full text, studies reported in languages other than English, case reports, reviews, and articles including participants having other comorbid conditions. This final screening led to 133 articles being excluded, which led to the full-text screening of 56 articles. After screening the full-text articles as per the eligibility criteria, 21 articles were found to be eligible for the systematic review. Among the remaining studies, six articles were excluded due to different specific reasons. A total of 15 articles were included in this systematic review. The mean VOR gain for the patients with vestibular neuritis was 0.48 ± 0.14 for the ipsilesional ear, whereas the mean VOR gain was > 0.80 in the contralesional ear for all the patients with acute vestibular neuritis. In patients with PICA lesions, the VOR gain for the ipsilesional ear was 0.90 (range 0.87-0.94) and for the contralesional ear was 0.88 (range 0.84-0.93). In patients with AICA lesions, the mean VOR gain was variable. Based on the above mean VOR gain findings, the authors propose the following adjective description scale of VOR of the lateral canal using vHIT: normal VOR gain above 0.80, mild VOR gain loss for 0.70-0.79, moderate loss for 0.69-0.4, severe loss for 0.39-0.2, and profound loss for < 0.2.

The Effect of Somatosensorial System on Vestibular System

The aim of this study was to investigate the effects of the somatosensory system on the vestibular system and the interconnected ways they work together to maintain balance. The study was conducted on 54 individuals (27 females and 27 males), aged between 18-25 years. vHIT as well as cVEMP tests were used to evaluate the participants. Tests were carried out while sitting, standing on firm surface and standing on foam respectively. According to the posterior vHIT results, there was a significant difference between VOR gains obtained while sitting and standing on firm surface in right side as well as on the left side (p < 0,01). Moreover, when VOR gains in standing on firm and standing on foam results were compared to each other, statistical significance was found right and left posterior canals (p < 0,05). Concerning the results obtained from VEMP, a statistically significant difference was seen in the comparison of P1-N1 amplitudes of the right side on firm surface and standing on foam (p < 0,01). When the inputs from somatosensorial system are disturbed, the parts of the vestibular system that are primarily affected are the posterior SSC, saccule and inferior vestibular nerve. This can be interpreted as the inferior vestibular nerve being more affected than the superior vestibular nerve when posture is disturbed due to somatosensory cues being unavailable or unstable.

[Gain characteristics of three pairs of semicircular canals in video head impulse paradigm test and suppression head impulse paradigm test in healthy young Chinese population]

Objective:To summarize gain characteristics of three pairs of semicircular canals in head impulse paradigm （HIMP） and suppression head impulse paradigm （SHIMP） in healthy young Chinese population. Methods:HIMP and SHIMP tests were performed on 40 healthy young volunteers enrolled as study group, by using EyeseeCam examiantion system （Interacoustics，Denmark）. The elicitation rates and gain values of the two saccades were recorded, and the gain values were compared and analyzed. Results:The results of 40 healthy young people were as follows: in HIMP, the instantaneous gain at 60 ms of the horizontal semicircular canals were 1.11±0.07 on the left side and 1.08±0.07 on the right side; the regression gain of the horizontal semicircular canals were 1.09±0.06 on the left side and 1.10±0.06 on the right side; the regression gain of the vertical semicircular canals were 1.08±0.12 on the right anterior, 1.07±0.11 on the left posterior, 1.41±0.16 on the right posterior and 1.42±0.16 on the left anterior. So in HIMP, no significant difference could be found between left and right side in both horizontal and vertical semicircular canal conjugate plane regarding regression gain （P>0.05）, except that 60 ms instantaneous gain on the left horizontal semicircular canals was slightly higher than that on the right side （P<0.05）.The instantaneous gain values of the horizontal semicircular canal at 60 ms in SHIMP were 1.08±0.08 on the left side and 1.06±0.07 on the right side; the regression gain in horizontal semicircular canals were 1.06±0.07 on the left side and 1.07±0.06 on the right side, respectively; the regression gains of vertical semicircular canal were 1.06±0.13, 1.08±0.16, 1.49±0.16, 1.39±0.15, on the right anterior, left posterior, right posterior, and left anterior side. So in SHIMP, no significant difference could be found in 60 ms instantaneous gain in horizontal conjugate plane, regression gain in horizontal conjugate plane and regression gain in right anterior left posterior conjugate plane （P>0.05）, while the regression gain of the left anterior right posterior conjugate plane in the right was found slightly higher than that of the left （P<0.05）.Both 60 ms instantaneous gain and regression gain in horizontal conjugate plane in HIMP were slightly higher than that of SHIMP （P<0.05）, while no significant difference could be found in vertical conjugate planes （P>0.05）. In both HIMP and SHIMP tests, gains of the left anterior right posterior conjugate plane was slightly higher than that of both horizontal plane and the right anterior left posterior conjugate plane （P<0.05）, while no significant difference could be found in gains between horizontal and the right anterior left posterior conjugate plane （P>0.05）. Conclusion:Gain values of HIMP and SHIMP were slightly different among different semicircular canals conjugate planes.It is suggested that each examination center should establish normal values for their own and make correction regularly.

Vestibular therapy to reduce falls in people with Alzheimer's disease: study protocol for a pilot randomized controlled trial

BACKGROUND

Falls are highly common in patients with Alzheimer's disease (AD); around two-thirds of AD patients fall annually. Fall events are major drivers of injury, early institutionalization, and shorter survival. Balance and mobility impairment are among the most important fall risk factors in AD patients. Vestibular therapy (VT) is an effective rehabilitation intervention in improving balance and fall risk through vestibular function, but not often used in AD. We want to evaluate the feasibility of using VT to reduce falls and improve balance function in patients with AD and drive use of an existing, potentially beneficial therapy in a patient population whose high level of vestibular deficits is currently unaddressed.

METHODS

The proposed pilot clinical trial will be a parallel-group randomized controlled trial. Patients with a diagnosis of mild-moderate AD, age ≥ 60, and the presence of a caregiver will be recruited from the Johns Hopkins Memory and Alzheimer's Treatment Center. Eligible patients will be offered vestibular testing. Patients with vestibular loss will be offered participation in the VT trial. One-hundred AD patients with vestibular loss will be enrolled and randomized 1:1 into the control and intervention arms of the trial. All patients will undergo baseline balance and cognitive assessment, followed by 8 weeks of active control therapy or VT, consisting of ~25-min office sessions with a vestibular therapist. Patients will be tracked for falls and undergo follow-up balance and cognitive assessment at 8 and 52 weeks (1 year) to assess the potential short-term and longer-term effects, respectively, of VT on balance and cognition. The main outcomes of this trial are falls, balance (using the Berg Balance Scale and the Timed Up and Go test), and cognition (using the clock drawing test, the Card Rotations test, the Money Road Map test, and the triangle completion task).

DISCUSSION

As the population ages and the number of individuals with AD in the US grows to a projected 14 million in 2050, managing falls in AD will continue to grow as a critical public health concern; this trial assesses feasibility of a potential solution.

TRIAL REGISTRATION

ClinicalTrial.Gov identifier - NCT03799991 . Registered 01 August 2019.

Clinical characteristics of patients with dizziness/vertigo showing a dissociation between caloric and video head impulse test results

OBJECTIVE

To explore the clinical characteristics of patients with dizziness/vertigo who showed a dissociation between the results of the caloric test and video head impulse test (vHIT).

METHODS

A total of 327 patients who complained of dizziness/vertigo were continuously included. All patients underwent both the horizontal vHIT (h-vHIT) and caloric tests. Of the 327 patients, 69 patients showed a dissociation between the results of the two tests, 4 patients were excluded because the interval between the two tests exceeded 7 days. Finally, 65 patients were included in the analysis.

RESULTS

Among the 65 patients, 55 (84.6%) patients showed a positive caloric test (+) with a negative h-vHIT (-), and 10 (15.4%) patients showed a negative caloric test (-) with a positive h-vHIT (+). Peripheral and central lesions were identified in 50 (90.9%) and 5 (9.1%) patients, respectively, in the caloric test (+)/h-vHIT (-) group; and central lesions were found in 6 (60%) patients in caloric test (-)/h-vHIT (+) group. The etiologies were unilateral peripheral vestibular dysfunction (n = 25), Meniere's disease (MD, n = 10), sudden hearing loss with vertigo (SHLV, n = 7), benign paroxysmal positional vertigo (n = 5), vestibular neuritis (n = 2), autoimmune inner ear disease (n = 1), vestibular migraine (VM, n = 3), multiple sclerosis (n = 1), and multiple system atrophy (n = 1) in the caloric test (+)/h-vHIT (-) group, which were SHLV (n = 3), MD (n = 1), VM (n = 1), episodic ataxia type 2 (n = 1), cerebellopontine angle tumor (N = 1), Parkinson's disease (n = 1), Persistent postural perceptual dizziness (n = 1), and posterior circulation ischemia (n = 1) in the caloric test (-)/h-vHIT (+) group.

CONCLUSION

Dissociation between the results of caloric test and h-vHIT is not uncommon. A positive caloric test with a negative h-vHIT occurred more frequently, and these patients mostly had peripheral vestibular lesions; while a negative caloric test with a positive h-vHIT was unusual, these patients had both peripheral and central lesions.

An innovative eye-tracker: Main features and demonstrative tests

We present a set of results obtained with an innovative eye-tracker based on magnetic dipole localization by means of an array of magnetoresistive sensors. The system tracks both head and eye movements with a high rate (100-200 Sa/s) and in real time. A simple setup is arranged to simulate head and eye motions and to test the tracker performance under realistic conditions. Multimedia material is provided to substantiate and exemplify the results. A comparison with other available technologies for eye-tracking is drawn, discussing advantages (e.g., precision) and disadvantages (e.g., invasivity) of the diverse approaches, with the presented method standing out for low cost, robustness, and relatively low invasivity.

Vestibulo-Ocular Reflex Is Modulated by Noisy Galvanic Vestibular Stimulation

We investigated whether noisy galvanic vestibular stimulation (nGVS) modulates the vestibulo-ocular reflex (VOR) and whether this effect is correlated with the effect of nGVS on body sway. Thirty healthy young adults participated. The video head impulse test (vHIT) was used to estimate the ratio of eye motion velocity/head motion velocity to VOR-gain. The gain 60 ms after the start of head motion (VOR-gain-60 ms) and regression slope (RS) (i.e., gain in eye and head motion; VOR-gain-RS) were calculated. The total path length of the foot center of pressure (COP-TL) during upright standing was calculated to estimate body sway. Noisy Galvanic Vestibular Stimulation at 0.2, 0.6, 1.2 mA, or sham stimulation (direct current: 0 mA) was delivered to the bilateral mastoid process in random order during vHIT and COP measurements. Application of nGVS at 0.2 mA significantly reduced VOR-gain-RS, while application of nGVS at 0.6 mA significantly increased COP-TL. Vestibulo-ocular reflex-gain-60 ms differed significantly between 0.2 and 1.2 mA. There was no significant correlation between COP-TL and VOR-related parameters. These findings suggest that nGVS at 0.2 mA inhibits the VOR, while nGVS at 0.6 mA increases body sway during upright standing, although there may be no relationship between the respective effects in healthy individuals.

Enhanced Eye Velocity With Backup Saccades in vHIT Tests of a Menière Disease Patient: A Case Report

Reduced eye velocity and overt or covert compensatory saccades during horizontal head impulse testing are the signs of reduced vestibular function. However, here we report the unusual case of a patient who had enhanced eye velocity during horizontal head impulses followed by a corrective saccade. We term this saccade a "backup saccade" because it acts to compensate for the gaze position error caused by the enhanced velocity (and enhanced VOR gain) and acts to return gaze directly to the fixation target as shown by eye position records. We distinguish backup saccades from overt or covert compensatory saccades or the anticompensatory quick eye movement (ACQEM) of Heuberger et al. (1) ACQEMs are anticompensatory in that they are in the same direction as head velocity and so, act to take gaze off the target and thus require later compensatory (overt) saccades to return gaze to the target. Neither of these responses were found in this patient. The patient here was diagnosed with unilateral definite Meniere's disease (MD) on the right and had enhanced VOR (gain of 1.17) for rightward head impulses followed by backup saccades. For leftwards head impulses eye velocity and VOR gain were in the normal range (VOR gain of 0.89). As further confirmation, testing with 1.84 Hz horizontal sinusoidal head movements in the visual-vestibular (VVOR) paradigm also showed these backup saccades for rightwards head turns but normal slow phase eye velocity responses without backup saccades for leftwards had turns. This evidence shows that backup saccades can be observed in some MD patients who show enhanced eye velocity responses during vHIT and that these backup saccades act to correct for gaze position error caused by the enhanced eye velocity during the head impulse and so have a compensatory effect on gaze stabilization.

Video Head Impulse Test in Darkness, Without Visual Fixation: A Study on Healthy Subjects

OBJECTIVE

The head impulse test (HIT) is triggered by the vestibulo-ocular reflex (VOR), complemented by the optokinetic and pursuit systems. This study aimed to evaluate the possibility of individualizing the VOR contribution to the HIT.

DESIGN

Thirty-six healthy individuals (19 males, 17 females; age 21-64 years, mean 39 years) underwent horizontal video HIT (vHIT). This was first conducted in darkness, without visual fixation, and then visually tracked.

RESULTS

Seventy percent of the impulses delivered ocular responses opposite to the direction of the head, matching its velocity to a point where quick anticompensatory eye movements (SQEM) stopped the response (SQEM mean latency 58.21 ms, interquartile range 50-67 ms). Of these, 75% recaptured the head velocity after culmination. Thirty percent of the responses completed a bell-shaped curve. The completed bell-shaped curve gains and instantaneous gains (at 40, 60, and 80 ms) before SQEM were equivalent for both paradigms. Females completed more bell-shaped traces (42%) than males (15%); p = 0.01. The SQEM latency was longer (62.81 versus 55.71 ms, p < 0.01), and the time to recapture the bell-shaped curve was shorter (77.51 versus 92.52 ms, p < 0.01) in females than in males. The gains were comparable between sexes in both paradigms.

CONCLUSIONS

The VOR effect can be localized in the first 70 ms of the vHIT response. In addition, other influences may take place in estimating the vHIT responses. The study of these influences might provide useful information that can be applied to patient management.

Age adjusted normative data for Video Head Impulse Test in healthy subjects

PURPOSE

This study aims to assess the effect of age in vestibulo-ocular reflex (VOR) gain measured by Video Head Impulse Test (VHIT) and to present normative data of VOR gain, median gain at 40, 60, 80 and 0-100 ms, and gain asymmetry according to decades of life in healthy subjects.

MATERIAL AND METHODS

A total of 132 subjects with no previous history of vestibular disorders were enrolled to assess VOR gain by employing VHIT. The test was performed in the X-axis evaluating both horizontal semicircular canals (HSC). The same right-handed operator performed the test in all subjects.

RESULTS

The mean VOR gain was higher in the right ear (0.99 ± 0.09) compared to the left ear (0.97 ± 0.08) (p = 0.001). Median gain at 60 ms was 0.92 ± 0.12 in the right HSC and 0.93 ± 0.10 for the left HSC, without significant difference (p = 0.94). A significant decrease of VOR gain occurred with increasing age in the right ear (r = -0.21, p = 0.01). Median gain at 60 ms decreased significantly as age increased in both HSC (right r = -0.17, p = 0.04; left r = -0.23, p = 0.006). No significant differences in VOR gain values were observed when the sample was stratified by age according to the analysis of variance.

CONCLUSIONS

A slight but significant decrease in VOR function was observed as age increased for gain and median gain at 60 ms. Larger studies, including patients with central and peripheral vestibular disorders, are needed to assess the clinical implication of this effect when evaluating patients with vestibular disorders.

Age-Related Changes in the Cochlea and Vestibule: Shared Patterns and Processes

Both age-related hearing loss (ARHL) and age-related loss in vestibular function (ARVL) are prevalent conditions with deleterious consequences on the health and quality of life. Age-related changes in the inner ear are key contributors to both conditions. The auditory and vestibular systems rely on a shared sensory organ - the inner ear - and, like other sensory organs, the inner ear is susceptible to the effects of aging. Despite involvement of the same sensory structure, ARHL and ARVL are often considered separately. Insight essential for the development of improved diagnostics and treatments for both ARHL and ARVL can be gained by careful examination of their shared and unique pathophysiology in the auditory and vestibular end organs of the inner ear. To this end, this review begins by comparing the prevalence patterns of ARHL and ARVL. Next, the normal and age-related changes in the structure and function of the auditory and vestibular end organs are compared. Then, the contributions of various molecular mechanisms, notably inflammaging, oxidative stress, and genetic factors, are evaluated as possible common culprits that interrelate pathophysiology in the cochlea and vestibular end organs as part of ARHL and ARVL. A careful comparison of these changes reveals that the patterns of pathophysiology show similarities but also differences both between the cochlea and vestibular end organs and among the vestibular end organs. Future progress will depend on the development and application of new research strategies and the integrated investigation of ARHL and ARVL using both clinical and animal models.

How Good Are We in Evaluating a Bedside Head Impulse Test?

OBJECTIVES

Clinicians performing a horizontal head impulse test (HIT) are looking for a corrective saccade. The detection of such saccades is a challenge. The aim of this study is to assess an expert's likelihood of detecting corrective saccades in subjects with vestibular hypofunction.

DESIGN

In a prospective cohort observational study at a tertiary referral hospital, we assessed 365 horizontal HITs performed clinically by an expert neurootologist from a convenience sample of seven patients with unilateral or bilateral deficient vestibulo-ocular reflex (VOR). All HITs were recorded simultaneously by video-oculography, as a gold standard. We evaluated saccades latency and amplitude, head velocity, and gain.

RESULTS

Saccade amplitude was statistically the most significant parameter for saccade detection (p < 0.001).The probability of saccade detection was eight times higher for HIT toward the pathological side (p = 0.029). In addition, an increase in saccade amplitude resulted in an increased probability of detection (odds ratio [OR] 1.77 [1.31 to 2.40] per degree, p < 0.001). The sensitivity to detect a saccade amplitude of 1 degree was 92.9% and specificity 79%. Saccade latency and VOR gain did not significantly influence the probability of the physician identifying a saccade (OR 1.02 [0.94 to 1.11] per 10-msec latency and OR 0.84 [0.60 to 1.17] per 0.1 VOR gain increase).

CONCLUSIONS

The saccade amplitude is the most important factor for accurate saccade detection in clinically performed head impulse tests. Contrary to current knowledge, saccade latency and VOR gain play a minor role in saccade detection.

Acute vestibular syndrome: is skew deviation a central sign?

Objective

Skew deviation results from a dysfunction of the graviceptive pathways in patients with an acute vestibular syndrome (AVS) leading to vertical diplopia due to vertical ocular misalignment. It is considered as a central sign, however, the prevalence of skew and the accuracy of its test is not well known .

Methods

We performed a prospective study from February 2015 until September 2020 of all patients presenting at our emergency department (ED) with signs of AVS. All patients underwent clinical HINTS and video test of skew (vTS) followed by a delayed MRI, which served as a gold standard for vestibular stroke confirmation.

Results

We assessed 58 healthy subjects, 53 acute unilateral vestibulopathy patients (AUVP) and 24 stroke patients. Skew deviation prevalence was 24% in AUVP and 29% in strokes. For a positive clinical test of skew, the cut-off of vertical misalignment was 3 deg with a very low sensitivity of 15% and specificity of 98.2%. The sensitivity of vTS was 29.2% with a specificity of 75.5%.

Conclusions

Contrary to prior knowledge, skew deviation proved to be more prevalent in patients with AVS and occurred in every forth patient with AUVP. Large skew deviations (> 3.3 deg), were pointing toward a central lesion. Clinical and video test of skew offered little additional diagnostic value compared to other diagnostic tests such as the head impulse test and nystagmus test. Video test of skew could aid to quantify skew in the ED setting in which neurotological expertise is not always readily available.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10692-6.

Is regression gain or instantaneous gain the most reliable and reproducible gain value when performing video head impulse testing of the lateral semicircular canals?

BACKGROUND

Several different video Head Impulse Test (vHIT) systems exist. The function of each individual semicircular canal (SCC) may be determined by performing this test. All vHIT systems provide information about the function of the vestibular ocular reflex by means of two modalities: SACCADES and GAIN. However, different gain calculation methods exist.

OBJECTIVE

Primary endpoint:•Is instantaneous gain or regression gain the most reproducible and reliable gain value when performing vHIT with testing of the lateral SCCs?Secondary endpoints:•Comparison of each of the instantaneous gain values at 40, 60, and 80ms with the regression gain.•Examination of any intra- and inter examiner variability.•Mean instantaneous gain values, and at different velocities, compared with regression gain values of the lateral SCCs.

METHODS

60 subjects between 18-65 years were included. All patients filled out the Dizziness Handicap Inventory (DHI) questionnaire and underwent four separate vHIT tests, two by an experienced neurotologist and two by an inexperienced examiner.

RESULTS/CONCLUSIONS

240 datasets were obtained, displaying both regression and instantaneous gain values. Regression gain was more reproducible than instantaneous gain. The experienced examiner provided the most reproducible results.When comparing instantaneous gain, we found the gain at 40 ms to be the least reproducible. There was no significant difference between 60 ms and 80 ms.For both examiners no significant intra examiner variability was found.

Clinical Implication of Corrective Saccades in the Video Head Impulse Test for the Diagnosis of Posterior Inferior Cerebellar Artery Infarction

Objective: In the present study, we characterized the vestibulo-ocular reflex (VOR) gain and properties of corrective saccades (CS) in patients with posterior inferior cerebellar artery (PICA) stroke and determined the best parameter to differentiate PICA stroke from benign peripheral vestibular neuritis (VN). In particular, we studied CS amplitude and asymmetry in video head impulse tests (vHITs) to discriminate these two less-studied disease conditions. Methods: The vHITs were performed within 1 week from symptom onset in patients with PICA stroke (n = 17), patients with VN (n = 17), and healthy subjects (HS, n = 17). Results: PICA stroke patients had bilaterally reduced VOR gains in the horizontal semicircular canal (HC) and the posterior semicircular canal (PC) compared with HSs. When compared with VN patients, PICA stroke patients showed preserved gains in the HC and anterior semicircular canal (AC) bilaterally (i.e., symmetric VOR gain). Similar to VOR gain, smaller but bilaterally symmetric CS in the HC and AC were observed in PICA stroke patients compared with VN patients; the mean amplitude of CS for the ipsilesional HC was reduced (p < 0.001, Mann-Whitney U-test), but the mean amplitude of CS for the contralesional HC was increased (p < 0.03, Mann-Whitney U-test) in PICA stroke compared with VN. The receiver operating characteristic (ROC) curve showed that CS amplitude asymmetry (CSs) and VOR gain asymmetry (Gs) of HC are excellent parameters to distinguish PICA stroke from VN. Conclusion: In the current study, we quantitatively investigated the VOR gain and CS using vHITs for three semicircular canals in PICA stroke and VN patients. In addition to VOR gain, quantitative assessments of CS using vHITs can provide sensitive and objective parameters to distinguish between peripheral and central vestibulopathies.

Quantifying a Learning Curve for Video Head Impulse Test: Pitfalls and Pearls

Objective: The video head impulse test (vHIT) is nowadays a fast and objective method to measure vestibular function. However, its usability is controversial and often considered as a test performed by experts only. We sought to study the learning curve of novices and to document all possible mistakes and pitfalls in the process of learning.

Methods: In a prospective cohort observational study, we included 10 novices. We tested their ability to perform correctly horizontal head impulses recorded with vHIT. We assessed vHITs in 10 sessions with 20 impulses per session giving a video instruction after the first session (S1) and individual feedback from an expert for session 2 (S2) up to session 10 (S10). We compared VOR gain, the HIT acceptance rate by the device algorithm, mean head velocity, acceleration, excursion, and overshoot between sessions.

Results: A satisfying number of accepted HITs (80%) was reached after an experience of 160 vHITs. Mean head velocity between sessions was always in accepted limits. Head acceleration was too low at the beginning (S1) but improved significantly after the video instruction (p = 0.001). Mean head excursion and overshoot showed a significant improvement after 200 head impulses (p < 0.001 each).

Conclusions: We showed that novices can learn to perform head impulses invHIT very fast provided that they receive instructions and feedback from an experienced examiner. Video instructions alone were not sufficient. The most common pitfall was a low head acceleration.

Pre-ataxic Changes of Clinical Scales and Eye Movement in Machado-Joseph Disease: BIGPRO Study

BACKGROUND

The pathological burden of spinocerebellar ataxia type 3, also known as Machado-Joseph disease (SCA3/MJD), accumulates before the beginning of symptoms. Our study aims at validating biomarkers for disease progression since pre-ataxic periods. We report on baseline findings of clinical scales and oculomotor neurophysiology.

METHODS

Ataxic (Scale for the Assessment and Rating of Ataxia > 2.5) and at 50% risk subjects were included. The latter were subdivided into noncarriers, pre-ataxic carriers near (PAN), or pre-ataxic carriers far from (PAFF) ataxia onset (AO), with 4 years from the predicted age at onset being the cutoff. The subjects were assessed by Neurological Examination Score for Spinocerebellar Ataxia (NESSCA), International Cooperative Ataxia Rating Scale (ICARS), Inventory of Non-Ataxic Signs (INAScount), Composite Cerebellar Functions Score and SCA Functional Index, and video-oculography, including the regression slope of vestibulo-ocular reflex gain (VORr), main sequence of volitional and reflexive vertical saccades, slow-phase velocity of central and gaze-evoked (SPV-GE) nystagmus, and vertical pursuit gain. Correction for multiple comparisons was performed; the threshold for statistical significance was P < 0.05.

RESULTS

A total of 35 ataxic, 14 PAN, 24 PAFF, and 22 noncarriers were included. All variables showed significant differences between groups and correlated to time to onset or time after onset, among all 73 SCA3/MJD carriers; none significantly changed with age in controls. NESSCA, ICARS, INAScount, VORr, main sequence of volitional saccades, and SPV-GE not only distinguished PAN from controls but also correlated with time left to AO.

CONCLUSIONS

Clinical scales and video-oculography variables were already altered in pre-ataxic SCA3/MJD carriers and worsened with time. NESSCA, ICARS, INAScount, VORr, main sequence of vertical volitional saccades, and SPV-GE are good candidates to measure preclinical changes in SCA3/MJD. © 2021 International Parkinson and Movement Disorder Society.

Qualitative and quantitative assessment of magnetic vestibular stimulation in humans

The sensation of phantom motion or exhibition of bodily sway is often reported in the proximity of an MR scanner. It is proposed that the magnetic field stimulates the vestibular system. There are a number of possible mechanisms responsible, and the relative contributions of susceptibility on the otolithic receptors and the Lorentz force on the cupulae have not yet been explored. This exploratory study aims to investigate the impact of being in the proximity of a 7.0 T MR scanner.The modified clinical test of sensory interaction on balance (mCTSIB) was used to qualitatively ascertain whether or not healthy control subjects who passed the mCTSIB in normal conditions 1) experienced subjective sensations of dizziness, vertigo or of leaning or shifting in gravity when in the magnetic field and 2) exhibited visibly increased bodily sway whilst in the magnetic field compared to outside the magnetic field. Condition IV of the mCTSIB was video recorded outside and inside the magnetic field, providing a semi-quantitative measure of sway.For condition IV of the mCTSIB (visual and proprioceptive cues compromised), all seven locations/orientations around the scanner yielded significantly more sway than at baseline (p < 0.01 FDR). A Student's t-test comparing the RMS velocity of a motion marker on the upper arm during mCTSIB condition IV showed a significant increase in the amount of motion exhibited in the field (T = 2.59; d.f. = 9; p = 0.029) compared to outside the field.This initial study using qualitative measures of sway demonstrates that there is evidence for MR-naïve individuals exhibiting greater sway while performing the mCTSIB in the magnetic field compared to outside the field. Directional polarity of sway was not significant. Future studies of vestibular stimulation by magnetic fields would benefit from the development of a sensitive, objective measure of balance function, which can be performed inside a magnetic field.

VOR gain calculation methods in video head impulse recordings

BACKGROUND: International consensus on best practices for calculating and reporting vestibular function is lacking. Quantitative vestibulo-ocular reflex (VOR) gain using a video head impulse test (HIT) device can be calculated by various methods. OBJECTIVE: To compare different gain calculation methods and to analyze interactions between artifacts and calculation methods. METHODS: We analyzed 1300 horizontal HIT traces from 26 patients with acute vestibular syndrome and calculated the ratio between eye and head velocity at specific time points (40 ms, 60 ms) after HIT onset (‘velocity gain’), ratio of velocity slopes (‘regression gain’), and ratio of area under the curves after de-saccading (‘position gain’). RESULTS: There was no mean difference between gain at 60 ms and position gain, both showing a significant correlation (r2 = 0.77, p < 0.001) for artifact-free recordings. All artifacts reduced high, normal-range gains modestly (range –0.06 to –0.11). The impact on abnormal, low gains was variable (depending on the artifact type) compared to artifact-free recordings. CONCLUSIONS: There is no clear superiority of a single gain calculation method for video HIT testing. Artifacts cause small but significant reductions of measured VOR gains in HITs with higher, normal-range gains, regardless of calculation method. Artifacts in abnormal HITs with low gain increased measurement noise. A larger number of HITs should be performed to confirm abnormal results, regardless of calculation method.

Are gain values significantly altered by manual data selection when performing the video Head Impulse Test (v-HIT) on all six semicircular canals with two different v-HIT systems

BACKGROUND

It has not yet been tested whether averaged gain values and the presence of pathological saccades are significantly altered by manual data selection or if data selection only done by the incorporated software detection algorithms provides a reliable data set following v-HIT testing.

OBJECTIVE

The primary endpoint was to evaluate whether the averaged gain values of all six SCCs are significantly altered by manual data selection with two different v-HIT systems.

METHOD

120 subjects with previously neither vestibular nor neurological disorders underwent four separate tests of all six SCCs with either EyeSeeCam® or ICS Impulse®. All v-HIT test reports underwent manual data selection by an experienced ENT Specialist with deletion of any noise and/or artifacts. Generalized estimating equations were used to compare averaged gain values based on unsorted data with averaged gain values based on the sorted data.

RESULTS

EyeSeeCam®: Horizontal SCCs: The estimate and the p-value (shown in parenthesis) for the right lateral SCC and the left lateral SCC were 0.00004 (0.95) and 0.00087 (0.70) respectively. Vertical SCCs: The estimate varied from -0.00858 to 0.00634 with p-values ranging from 0.31 to 0.78. ICS Impulse®: Horizontal SCCs: The estimate and the p-value for the right lateral SCC and the left lateral SCC were 0.00159 (0.18) and 0.00071 (0.38) respectively. Vertical SCCs: The estimate varied from 0.00217 to 0.01357 with p-values ranging from 0.00 to 0.17. Based upon the averaged gain value from the individual SCC being tested, 148 tests before and 127 after manual data selection were considered pathological.

CONCLUSION

None of the two v-HIT systems revealed any clinically important effects of manual data selection. However, 21 fewer tests were considered pathological after manual data selection.

Nightly Hypoxia Does Not Seem to Lead to Otolith Dysfunction in Patients With Obstructive Sleep Apnea

OBJECTIVES

Obstructive sleep apnea (OSA) is a common sleep disorder, which is associated with recurrent oxygen desaturation during sleep. It has already been shown that nocturnal hypoxia may lead to cochlear dysfunction in patients with OSA. Less is known whether hypoxia during sleep also impacts vestibular function in those patients. Thus, the aim of the presented study was to assess a potential vestibulotoxic effect of nightly desaturations with hypoxia in patients with OSA by investigating a possible correlation between respiratory parameters and vestibular function tests.

METHODS

A total of 56 patients were included in the study and underwent a fully attended cardiorespiratory polysomnography (PSG). Vestibular function was assessed using video head impulse test to evaluate horizontal semicircular canal function and cervical vestibular evoked myogenic potentials (cVEMPs) and ocular vestibular evoked myogenic potentials (oVEMPs) to measure otolith function. Descriptive data analysis was conducted and correlation analysis between selected PSG parameters and the results of vestibular testing was performed using Kendall τ coefficient.

RESULTS

A significant correlation between vestibular function and respiratory polysomnographic parameters could not be demonstrated in the study (P > .05) but cVEMP and oVEMP results showed a trend toward a correlation with oxygen desaturation indices and apnea-hypopnea index. Additionally, otolith hypofunction was more prevalent in patients with hypertension as well as OSA.

CONCLUSION

The results of our study show that there is no significant correlation between vestibular function and sleep apnea parameters, although otolith dysfunction might be more prevalent in patients with OSA and hypertension.

Veterans with dizziness recruit compensatory saccades in each semicircular canal plane although VOR gain is normal

BACKGROUND

Exposure to brain injury via blast or blunt mechanisms disrupts multiple sensorimotor systems simultaneously. Large numbers of US Gulf War era and Operation Iraqi/Enduring Freedom veterans with traumatic brain injury (TBI) are suffering the symptom of dizziness - presumed due to "Multi-Sensory Impairment", a clinical pattern of damage to the auditory, visual and vestibular sensorimotor systems.

OBJECTIVE

To describe the oculomotor response to rapid head rotation in a population of veterans with dizziness. We also describe the reliability of using the video head impulse test (vHIT) in a veteran population.

METHODS

We used the vHIT to evaluate the vestibular-ocular reflex (VOR) gain and presence of compensatory saccades (CS) in each semicircular canal of 81 veterans (31% TBI) with dizziness. Data was collected using the ICS Otometric™ vHIT. Data was processed using both the Otometric™ software and custom software written in MATLAB™. This data was evaluated through Kruskal-Wallis rank-sum test and analysis of regression.

RESULTS

Veterans with dizziness recruit CS in all semicircular canal planes even though their VOR gain is normal. The vHIT is a reliable clinical test to quantify the metrics of the VOR and CS in veterans.

CONCLUSION

Veterans with dizziness symptoms use compensatory saccades in all planes of semicircular canal rotation, despite having normal peripheral VOR gain during rapid head rotation. The video head impulse test is a stable measure of vestibular slow phase and metrics of compensatory saccades in veterans with dizziness.

Improved Oculomotor Physiology and Behavior After Unilateral Incremental Adaptation Training in a Person With Chronic Vestibular Hypofunction: A Case Report

BACKGROUND AND PURPOSE

Traditional vestibular rehabilitation therapies are effective in reducing vestibular hypofunction symptoms, but changes to the vestibulo-ocular reflex (VOR) are minimal. This controlled case report describes an increase in VOR after 6 months of incremental VOR adaptation (IVA) training in a person with chronic unilateral vestibular hypofunction.

CASE DESCRIPTION

The participant was a 58-year-old female with a confirmed (Neurologist P.D.C.) left vestibular lesion stable for 2 years prior to entering a clinical trial examining the effects of daily IVA training. She was evaluated monthly for self-reported symptoms (dizziness handicap inventory), VOR function (video head impulse test), and VOR behavior (Dynamic Visual Acuity test). Intervention consisted of 6 months of 15 minutes per day unassisted training using the IVA training regime with a device developed in our laboratory. The take-home device enables the VOR response to gradually normalize on the ipsilesional side via visual-vestibular mismatch training. The intervention was followed by a 6-month wash-out and 3-month control period. The control condition used the same training device set to function like standard VOR training indistinguishable to the participant.

OUTCOMES

After the intervention, ipsilesional VOR function improved substantially. The VOR adapted both via a 52% increase in slow-phase response and via 43% earlier onset compensatory saccades for passive head movements. In addition, the participant reported fewer symptoms and increased participation in sports and daily activities.

DISCUSSION

Here, a participant with chronic vestibular hypofunction showing improved oculomotor performance atypical for traditional vestibular rehabilitation therapies, subsequent to using the newly developed IVA technique, is presented. It is the first time to our knowledge an improvement of this magnitude has been demonstrated as well as sustained over an extended period of time.

Comparison of Video Head Impulse Test (vHIT) Gains Between Two Commercially Available Devices and by Different Gain Analytical Methods

OBJECTIVES

To evaluate whether video head impulse test (vHIT) gains are dependent on the measuring device and method of analysis.

STUDY DESIGN

Prospective study.

METHODS

vHIT was performed in 25 healthy subjects using two devices simultaneously. vHIT gains were compared between these instruments and using five different methods of comparing position and velocity gains during head movement intervals.

RESULTS

The two devices produced different vHIT gain results with the same method of analysis. There were also significant differences in the vHIT gains measured using different analytical methods. The gain analytic method that compares the areas under the velocity curve (AUC) of the head and eye movements during head movements showed lower vHIT gains than a method that compared the peak velocities of the head and eye movements. The former method produced the vHIT gain with the smallest standard deviation among the five procedures tested in this study.

CONCLUSION

vHIT gains differ in normal subjects depending on the device and method of analysis used, suggesting that it is advisable for each device to have its own normal values. Gain calculations that compare the AUC of the head and eye movements during the head movements show the smallest variance.

Intra- and Interexaminer Variability of Two Separate Video Head Impulse Test Systems Assessing All Six Semicircular Canals

OBJECTIVE

To evaluate intra- and interexaminer variability of the video Head Impulse Test (v-HIT) when assessing all six semicircular canals (SCCs) of two separate v-HIT systems.

STUDY DESIGN

Prospective study.

SETTING

Department of Otolaryngology, Head and Neck Surgery, Aalborg University Hospital, Denmark.

PATIENTS

One hundred twenty healthy subjects.

INTERVENTION

Four separate tests of all six SCCs with either system A or system B. Two examiners tested all subjects twice. Pretest randomization included type of v-HIT system, order of paired SCC testing, as well as initial examiner.

MAIN OUTCOME MEASURE

Gain values and the presence of pathological saccades were registered. Ninety-five percent limits of agreement (LOAs) were calculated for both intra- and interexaminer variability. Adding or subtracting the value from the mean difference achieves the upper and lower bound LOA. Ninety-five percent of the differences lie within these limits.

RESULTS

Interexaminer reliability: System A: LOAs between 0.13 and 0.24 for the horizontal SCCs and between 0.42 and 0.74 for the vertical SCCs. System B: LOAs between 0.09 and 0.13 for the horizontal SCCs and between 0.13 and 0.20 for the vertical SCCs. Intraexaminer reliability: System A: LOAs were 0.19 and 0.14 for the horizontal SCCs and varied from 0.43 to 0.53 for the vertical SCCs. System B: LOAs were 0.14 for the horizontal SCCs and varied from 0.13 to 0.22 for the vertical SCCs.

CONCLUSION

Horizontal SCC testing: both v-HIT systems displayed good intra- and interexaminer variability. Vertical SCC testing: System B displayed good intra- and interexaminer variability whereas the opposite was true with system A.

Failure on the Foam Eyes Closed Test of Standing Balance Associated With Reduced Semicircular Canal Function in Healthy Older Adults

OBJECTIVES

Standing on foam with eyes closed (FOEC) has been characterized as a measure of vestibular function; however, the relative contribution of vestibular function and proprioceptive function to the FOEC test has not been well described. In this study, the authors investigate the relationship between peripheral sensory systems (vestibular and proprioception) and performance on the FOEC test in a cohort of healthy adults.

DESIGN

A total of 563 community-dwelling healthy adults (mean age, 72.7 [SD, 12.6] years; range, 27 to 93 years) participating in the Baltimore Longitudinal Study of Aging were tested. Proprioceptive threshold (PROP) was evaluated with passive motion detection at the right ankle. Vestibulo-ocular reflex (VOR) gain was measured using video head impulses. Otolith function was measured with cervical and ocular vestibular-evoked myogenic potentials. Participants stood on FOEC for 40 sec while wearing BalanSens (BioSensics, LLC, Watertown, MA) to quantify center of mass sway area. A mixed-model multiple logistic regression was used to examine the odds of passing the FOEC test based on PROP, VOR, cervical vestibular-evoked myogenic potential, and ocular vestibular-evoked myogenic potential function in a multisensory model while controlling for age and gender.

RESULTS

The odds of passing the FOEC test decreased by 15% (p < 0.001) for each year of increasing age and by 8% with every 0.1 reduction in VOR gain (p = 0.025). Neither PROP nor otolith function was significantly associated with passing the FOEC test.

CONCLUSIONS

Failure to maintain balance during FOEC may serve as a proxy for rotational vestibular contributions to postural control. Semicircular canals are more sensitive to low-frequency motion than otoliths that may explain these relationships because standing sway is dominated by lower frequencies. Lower VOR gain and increased age independently decreased the odds of passing the test.

State biomarkers for Machado Joseph disease: Validation, feasibility and responsiveness to change

Machado-Joseph disease (SCA3/MJD) is the most common spinocerebellar ataxia worldwide, and particularly so in Southern Brazil. Due to an expanded polyglutamine at ataxin-3, SCA3/MJD presents a relentless course with no current disease modifying treatment. Clinical scales used to measure SCA3/MJD progression present moderate effect sizes, a major drawback for their use as main outcomes in clinical trials, given the rarity and slow progression of the disease. This limitation might be overcome by finding good surrogate markers. We present here a review of studies on peripheral and neurophysiological markers in SCA3/MJD that can be candidates for state biomarkers. Data on markers already studied were summarized, giving emphasis on validation against clinical scale, and responsiveness to change. While some biological fluid compounds and neurophysiological parameters showed poor responsiveness, others seemed to be good candidates. Some potential candidates that are waiting for responsiveness studies were serum levels of neuron specific enolase, vestibulo-ocular reflex and video-oculography. Candidates evaluated by RNA and microRNA expression levels need further studies to improve their measurements. Data on peripheral levels of Beclin-1 and DNAJB1 are promising but still incipient. We conclude that several potential candidates should follow onto validating studies for surrogate state biomarkers of SCA3/MJD.

Functional Head Impulse Test in Professional Athletes: Sport-Specific Normative Values and Implication for Sport-Related Concussion

Dizziness, slow visual tracking, or blurred vision following active head (or body) movements are among the most common symptoms reported following sport-related concussion, often related to concurrent dysfunctions of the vestibular system. In some cases, symptoms persist even if bedside and auxiliary standard vestibular tests are unremarkable. New functional tests have been developed in recent years to objectify neurological alterations that are not captured by standard tests. The functional head impulse test (fHIT) requires the patient to recognize an optotype that is briefly flashed during head rotations with various angular accelerations (2,001–6,000 deg/s²) and assesses the proportion if correct answers (pca). 268 active professional athletes (23.70 ± 5.32y) from six different sports were tested using fHIT. Pca were analyzed both pooling head acceleration in the range of 2,001–6,000 deg/s² and computing a single pca value for each 1,000 deg/s² bin in the range 2,001–8,000 deg/s². No significant difference (p = 0.159) was found between responses to head impulses in the plane of horizontal (pca: 0.977) and vertical semicircular canals (pca: 0.97). The sport practiced had a major effect on the outcome of the fHIT. Handball players achieved a better performance (p < 0.001) than the whole athlete group, irrespective of the direction of head impulses. The pca achieved by athletes practicing snowboard, bob and skeleton were instead significantly below those of the whole athlete group (p < 0.001) but only when vertical head impulses were tested. Overall, pca declined with increasing head acceleration. The decline was particularly evident in the range not included in the standard fHIT exam, i.e., 6,001–8,000 deg/s² for horizontal and 5,001–8,000 deg/s² for vertical head impulses. When vertical head impulses were tested, athletes practicing snowboard, bob and skeleton (non-ball sports) showed, beside the lower overall pca, also a steeper decline as a function of vertical head acceleration. The findings suggest that: (1) functional VOR testing can help understanding sport-specific VOR requirements; (2) the fHIT is able to detect and objectify subtle, sport-specific changes of functional VOR performance; (3) if sport-specific normative values are used, the fHIT test procedure needs to be optimized, starting from the highest acceleration to minimize the number of head impulses.

Increased Prevalence of Vestibular Loss in Mild Cognitive Impairment and Alzheimer's Disease

BACKGROUND/AIMS

Recent evidence has shown that Alzheimer's Disease (AD) patients have reduced vestibular function relative to healthy controls. In this study, we evaluated whether patients with Mild Cognitive Impairment (MCI) also have reduced vestibular function relative to controls, and compared the level of vestibular impairment between MCI and AD patients.

METHODS

Vestibular physiologic function was assessed in 77 patients (26 MCI, 51 AD) and 295 matched controls using 3 clinical vestibular tests. The association between vestibular loss and cognitive impairment was evaluated using conditional logistic regression models.

RESULTS

Individuals with vestibular impairment had a 3 to 4-fold increased odds of being in the MCI vs. control group (p-values < 0.05). MCI patients had a level of vestibular impairment that was intermediate between controls and AD.

CONCLUSION

These findings suggest a dose-response relationship between vestibular loss and cognitive status, and support the hypothesis that vestibular loss contributes to cognitive decline.

Changes of video head impulse test results in lateral semicircular canal plane by different peak head velocities in patients with vestibular neuritis

BACKGROUND

The peak head velocity influences on the video head impulse test (vHIT) results, but it has been not known how much the difference is.

AIMS

To evaluate the clinical evidence for the superiority of high-velocity compared to low-velocity vHIT.

MATERIAL AND METHODS

vHIT was performed in 30 patients with vestibular neuritis using two peak head velocities (mean 80 vs. 240°/s). vHIT gains and parameters of corrective saccades (CSs) were compared. A vHIT gain of ≤0.8 or a peak CS velocity of ≥100°/s was considered pathologic.

RESULTS

The vHIT gains were significantly lower (mean 0.5 vs. 0.6), and GA was larger (35 vs. 25%) at high-velocity vHIT, compared to low-velocity vHIT. CSs were significantly more frequent (100 vs. 80%) and peak CS velocities were larger (252 vs. 112°/s) at high-velocity vHIT. The abnormal rates based on vHIT gains were higher (90% vs. 73%) and CSs occurred more frequently (100% vs. 80%) at high-velocity vHIT. The abnormal rates based on the peak CS velocity were significantly higher at high-velocity vHIT (100% vs. 57%).

CONCLUSION

High-velocity vHIT is superior to low-velocity vHIT with a difference of 17-20% based on pathologic vHIT gains and presence of CSs.

Usability of the Video Head Impulse Test: Lessons From the Population-Based Prospective KORA Study

Objective: The video head impulse test (vHIT) has become a common examination in the work-up for dizziness and vertigo. However, recent studies suggest a number of pitfalls, which seem to reduce vHIT usability. Within the framework of a population-based prospective study with naïve examiners, we investigated the relevance of previously described technical mistakes in vHIT testing, and the effect of experience and training.

Methods: Data originates from the KORA (Cooperative Health Research in the Region of Augsburg) FF4 study, the second follow-up of the KORA S4 population-based health survey. 681 participants were selected in a case-control design. Three examiners without any prior experience were trained in video head impulse testing. VHIT quality was assessed weekly by an experienced neuro-otologist. Restrictive mistakes (insufficient technical quality restricting interpretation) were noted. Based on these results, examiners received further individual training.

Results: Twenty-two of the 681 vHITs (3.2%) were not interpretable due to restrictive mistakes. Restrictive mistakes could be grouped into four categories: slippage, i.e., goggle movement relative to the head (63.6%), calibration problems (18.2%), noise (13.6%), and low velocity of the head impulse (4.6%). The overall rate of restrictive mistakes decreased significantly during the study (12% / examiner within the first 25 tested participants and 2.1% during the rest of the examinations, p < 0.0001).

Conclusion: Few categories suffice to explain restrictive mistakes in vHIT testing. With slippage being most important, trainers should emphasize the importance of tight goggles. Experience and training seem to be effective in improving vHIT quality, leading to high usability.

Differences in head impulse test results due to analysis techniques

BACKGROUND

Different analysis techniques are used to define vestibulo-ocular reflex (VOR) gain between eye and head angular velocity during the video head impulse test (vHIT). Comparisons would aid selection of gain techniques best related to head impulse characteristics and promote standardisation.

OBJECTIVE

Compare and contrast known methods of calculating vHIT VOR gain.

METHODS

We examined lateral canal vHIT responses recorded from 20 patients twice within 13 weeks of acute unilateral peripheral vestibular deficit onset. Ten patients were tested with an ICS Impulse system (GN Otometrics) and 10 with an EyeSeeCam (ESC) system (Interacoustics). Mean gain and variance were computed with area, average sample gain, and regression techniques over specific head angular velocity (HV) and acceleration (HA) intervals.

RESULTS

Results for the same gain technique were not different between measurement systems. Area and average sample gain yielded equally lower variances than regression techniques. Gains computed over the whole impulse duration were larger than those computed for increasing HV. Gain over decreasing HV was associated with larger variances. Gains computed around peak HV were smaller than those computed around peak HA. The median gain over 50-70 ms was not different from gain around peak HV. However, depending on technique used, the gain over increasing HV was different from gain around peak HA. Conversion equations between gains obtained with standard ICS and ESC methods were computed. For low gains, the conversion was dominated by a constant that needed to be added to ESC gains to equal ICS gains.

CONCLUSIONS

We recommend manufacturers standardize vHIT gain calculations using 2 techniques: area gain around peak HA and peak HV.

Video Head Impulse Test for Early Diagnosis of Vestibular Neuritis Among Acute Vertigo

BACKGROUND

This study assesses the value of the video head impulse test (vHIT) for early diagnosis of vestibular neuritis (VN) among acute vertigo.

METHODS

Thirty-three cases of vestibular neuritis (VN), 96 patients with other acute vertigo (AV), and 50 cases of normal controls used vHIT to quantitatively test a pair of horizontal vestibulo-ocular reflection (VOR) gains, two pairs of vertical VOR gains, and the corresponding three pairs of VOR gain asymmetry. The peculiarity of VOR gains in VN and the differences between VN and other AV, normal controls by vHIT, were collected and analyzed.

RESULTS

There were statistically significant differences in the three pairs of VOR gains asymmetry between VN and other AV, and normal controls (P<0.01). The sensitivity was 87.9% and specificity was 94.3% in differentiating VN from normal and other acute vertigo by vHIT.

CONCLUSIONS

This study shows vHIT has advantages in the diagnosis of VN in acute vertigo with good sensitivity and specificity and indicates a widespread clinical application.

Diagnostic Value of Gains and Corrective Saccades in Video Head Impulse Test in Vestibular Neuritis

Objectives We investigated changes in video head impulse test (vHIT) gains and corrective saccades (CSs) at the acute and follow-up stages of vestibular neuritis to assess the diagnostic value of vHIT. Study Design Case series with chart review. Setting Tertiary medical center. Subjects and Methods Sixty-three patients with vestibular neuritis who underwent vHIT at an initial presentation and an approximately 1-month follow-up were included. vHIT gains, gain asymmetry (GA), peak velocities of CS, and interaural difference of CS (CSD) were analyzed. Results Mean vHIT gains increased significantly from the acute stage to the follow-up exam. The mean GA, peak velocities of CS, and CSD had decreased significantly at the follow-up. The incidence of CSs was also significantly decreased at the follow-up. The abnormal rate (87%) considering both gain and CS value was significantly higher than that (62%) considering vHIT gain only at the follow-up, although the abnormal rates did not differ at the acute stage (97% vs 87%). Conclusion The abnormal rates based on both vHIT gains and CS measurements are similar at the acute stage of VN but are considerably higher at the follow-up stage compared with the abnormal rates based on vHIT gains alone. It is thus advisable to check both CS and vHIT gain while performing vHIT to detect vestibular hypofunction.

Recent advances in head impulse test findings in central vestibular disorders

The head impulse test (HIT) is used to evaluate the vestibulo-ocular reflex (VOR) during a high-velocity head rotation. Corrective catch-up saccades that occur during or after the HITs usually indicate peripheral vestibular hypofunction, whereas in acute vestibular syndrome, normal clinical (bedside) HITs should prompt a search for a central lesion. However, recent quantitative studies that evaluated HITs using magnetic search coils or video-based techniques have demonstrated that specific patterns of HIT abnormalities are associated with central vestibular disorders. While normal clinical HITs are typical of central lesions, discrepancies have been observed between clinical and quantitative HITs. The horizontal head impulse VOR gains can be significantly reduced unilaterally or bilaterally (positive HITs) in lesions involving the vestibular nucleus, nucleus prepositus hypoglossi, or flocculus. In diffuse cerebellar lesions, the VOR gain during horizontal head impulses may increase (hyperactive) with corrective saccades directed the opposite way. The presence of cross-coupled vertical corrective saccades during horizontal HITs is also suggestive of diffuse cerebellar lesions. Lesions involving the vestibular nucleus, medial longitudinal fasciculus, and cerebellum may show decreased or increased gains of the VOR during vertical HITs. Defining the differences in patterns observed during abnormal HITs may help practitioners localize the responsible lesions in both central and peripheral vestibulopathy.

Vestibular Impairment in Dementia

OBJECTIVE

Recent studies suggest an association between vestibular and cognitive function. The goal of the study was to investigate whether vestibular function was impaired in individuals with mild cognitive impairment (MCI) and Alzheimer's disease (AD) compared with cognitively normal individuals.

STUDY DESIGN

Cross-sectional study.

SETTING

Outpatient memory clinic and longitudinal observational study unit.

PATIENTS

Older individuals ≥55 years with MCI or AD. Age, sex, and education-matched normal controls were drawn from the Baltimore Longitudinal Study of Aging (BLSA).

INTERVENTION

Saccular and utricular function was assessed with cervical and ocular vestibular-evoked myogenic potentials (c- and oVEMPs) respectively, and horizontal semicircular canal function was assessed with video head impulse testing.

MAIN OUTCOME MEASURES

Presence or absence of VEMP responses, VEMP amplitude, and vestibular ocular reflex (VOR) gain were measured.

RESULTS

Forty-seven individuals with cognitive impairment (MCI N = 15 and AD N = 32) underwent testing and were matched with 94 controls. In adjusted analyses, bilaterally absent cVEMPs were associated with an over three-fold odds of AD (OR 3.42, 95% CI 1.33-8.91, p = 0.011). One microvolt increases in both cVEMP and oVEMP amplitudes were associated with decreased odds of AD (OR 0.28, 95% CI 0.09-0.93, p = 0.038 and OR 0.92, 95% CI 0.85-0.99, p = 0.036, respectively). There was no significant difference in VOR gain between the groups.

CONCLUSIONS

These findings confirm and extend emerging evidence of an association between vestibular dysfunction and cognitive impairment. Further investigation is needed to determine the causal direction for the link between peripheral vestibular loss and cognitive impairment.

Stability of the aVOR to Repeat Head Impulse Testing

OBJECTIVE

The angular vestibulo-ocular reflex (aVOR) is known to be influenced by factors such as arousal and cognition during traditional vestibular function testing. However, the inherent variability of the aVOR to head impulse testing has not been explicitly examined. The purpose of this study was to determine the variability of the aVOR to active and passive head impulses using the gold standard scleral search coil method to record head and eye rotation.

STUDY DESIGN

Descriptive.

SETTING

Tertiary referral center.

PATIENTS

Twenty six healthy control subjects agreed to active and passive horizontal head impulse testing on at least two separate sessions from two unique institutions. An additional 27 individuals with cochlear implantation (CI) underwent passive horizontal and vertical semicircular canal plane head impulse testing. Test sessions were separated from 3 to 210 days in the normal subjects and from 49 to 537 days in the subjects with CI.

MAIN OUTCOME MEASURE(S)

Reliability of the angular VOR gain (eye velocity/head velocity) over time.

RESULTS

In the healthy control subjects, there was no difference in aVOR gain between right and left ears, between session one and session two, or between active (self-generated, 0.99 ± 0.08) or passive (imposed, 1.0 ± 0.08) head impulses. In the patients, we also found the aVOR gain very stable over time. However, the aVOR gains of the patients were different across the semicircular canal planes tested (p < 0.001) with the four vertical semicircular canals having lower aVOR gains than the two horizontal canals.

CONCLUSIONS

Our data suggest the aVOR gain is quite stable when tested across unique days in healthy controls and patients with auditory-only inner ear pathology.

Eye Control Deficits Coupled to Hand Control Deficits: Eye-Hand Incoordination in Chronic Cerebral Injury

It is widely accepted that cerebral pathology can impair ocular motor and manual motor control. This is true in indolent and chronic processes, such as neurodegeneration and in acute processes such as stroke or those secondary to neurotrauma. More recently, it has been suggested that disruptions in these control systems are useful markers for prognostication and longitudinal monitoring. The utility of examining the relationship or the coupling between these systems has yet to be determined. We measured eye and hand-movement control in chronic, middle cerebral artery stroke, relative to healthy controls, in saccade-to-reach paradigms to assess eye-hand coordination. Primary saccades were initiated significantly earlier by stroke participants relative to control participants. However, despite these extremely early initial saccades to the target, reaches were nevertheless initiated at approximately the same time as those of control participants. Control participants minimized the time period between primary saccade onset and reach initiation, demonstrating temporal coupling between eye and hand. In about 90% of all trials, control participants produced no secondary, or corrective, saccades, instead maintaining fixation in the terminal position of the primary saccade until the end of the reach. In contrast, participants with stroke increased the time period between primary saccade onset and reach initiation. During this temporal decoupling, multiple saccades were produced in about 50% of the trials with stroke participants making between one and five additional saccades. Reaches made by participants with stroke were both longer in duration and less accurate. In addition to these increases in spatial reach errors, there were significant increases in saccade endpoint errors. Overall, the magnitude of the endpoint errors for reaches and saccades were correlated across participants. These findings suggest that in individuals with otherwise intact visual function, the spatial and temporal relationships between the eye and hand are disrupted poststroke, and may need to be specifically targeted during neurorehabilitation. Eye-hand coupling may be a useful biomarker in individuals with cerebral pathology in the setting of neurovascular, neurotraumatic, and neurodegenerative pathology.

Loss of Peripheral Sensory Function Explains Much of the Increase in Postural Sway in Healthy Older Adults

Postural sway increases with age and peripheral sensory disease. Whether, peripheral sensory function is related to postural sway independent of age in healthy adults is unclear. Here, we investigated the relationship between tests of visual function (VISFIELD), vestibular function (CANAL or OTOLITH), proprioceptive function (PROP), and age, with center of mass sway area (COM) measured with eyes open then closed on firm and then a foam surface. A cross-sectional sample of 366 community dwelling healthy adults from the Baltimore Longitudinal Study of Aging was tested. Multiple linear regressions examined the association between COM and VISFIELD, PROP, CANAL, and OTOLITH separately and in multi-sensory models controlling for age and gender. PROP dominated sensory prediction of sway across most balance conditions (β's = 0.09–0.19, p's < 0.001), except on foam eyes closed where CANAL function loss was the only significant sensory predictor of sway (β = 2.12, p < 0.016). Age was not a consistent predictor of sway. This suggests loss of peripheral sensory function explains much of the age-associated increase in sway.

The Video Head Impulse Test

In 1988, we introduced impulsive testing of semicircular canal (SCC) function measured with scleral search coils and showed that it could accurately and reliably detect impaired function even of a single lateral canal. Later we showed that it was also possible to test individual vertical canal function in peripheral and also in central vestibular disorders and proposed a physiological mechanism for why this might be so. For the next 20 years, between 1988 and 2008, impulsive testing of individual SCC function could only be accurately done by a few aficionados with the time and money to support scleral search-coil systems—an expensive, complicated and cumbersome, semi-invasive technique that never made the transition from the research lab to the dizzy clinic. Then, in 2009 and 2013, we introduced a video method of testing function of each of the six canals individually. Since 2009, the method has been taken up by most dizzy clinics around the world, with now close to 100 refereed articles in PubMed. In many dizzy clinics around the world, video Head Impulse Testing has supplanted caloric testing as the initial and in some cases the final test of choice in patients with suspected vestibular disorders. Here, we consider seven current, interesting, and controversial aspects of video Head Impulse Testing: (1) introduction to the test; (2) the progress from the head impulse protocol (HIMPs) to the new variant—suppression head impulse protocol (SHIMPs); (3) the physiological basis for head impulse testing; (4) practical aspects and potential pitfalls of video head impulse testing; (5) problems of vestibulo-ocular reflex gain calculations; (6) head impulse testing in central vestibular disorders; and (7) to stay right up-to-date—new clinical disease patterns emerging from video head impulse testing. With thanks and appreciation we dedicate this article to our friend, colleague, and mentor, Dr Bernard Cohen of Mount Sinai Medical School, New York, who since his first article 55 years ago on compensatory eye movements induced by vertical SCC stimulation has become one of the giants of the vestibular world.