A review of the geometrical basis and the principles underlying the use and interpretation of the video head impulse test (vHIT) in clinical vestibular testing.

This paper is concerned mainly with the assumptions underpinning the actual testing procedure, measurement, and interpretation of the video head impulse test-vHIT. Other papers have reported in detail the artifacts which can interfere with obtaining accurate eye movement results, but here we focus not on artifacts, but on the basic questions about the assumptions and geometrical considerations by which vHIT works. These matters are crucial in understanding and appropriately interpreting the results obtained, especially as vHIT is now being applied to central disorders. The interpretation of the eye velocity responses relies on thorough knowledge of the factors which can affect the response-for example the orientation of the goggles on the head, the head pitch, and the contribution of vertical canals to the horizontal canal response. We highlight some of these issues and point to future developments and improvements. The paper assumes knowledge of how vHIT testing is conducted.

Exploring assessment of balance using virtual reality in patients at risk of chemotherapy-induced peripheral neuropathy.

BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting toxicity for people treated for cancer. Impaired balance and falls are functional consequences of CIPN. Virtual reality (VR) technology may be able to assess balance and identify patients at risk of falls. AIMS: To assess the impact of potentially neurotoxic chemotherapy on balance using VR, and explore associations between VR balance assessment, falls and CIPN. METHODS: This prospective, repeated measures longitudinal study was conducted at two Australian cancer centres. Eligible participants were commencing adjuvant chemotherapy containing a taxane for breast cancer, or oxaliplatin for colorectal cancer (CRC), per institutional guidelines. Balance assessments using VR were conducted at baseline, end of chemotherapy and 3 and 6 months after completion of chemotherapy. Participants also completed a comprehensive CIPN assessment comprising clinical and patient-reported outcomes, and recorded falls or near falls. RESULTS: Out of 34 participants consented, 24 (71%) had breast cancer and 10 (29%) had CRC. Compared to baseline, balance threshold was reduced in 10/28 (36%) evaluable participants assessed at the end of chemotherapy, and persistent in 7/22 (32%) at 6 months. CIPN was identified in 86% at end of chemotherapy and persisted to 6 months after chemotherapy completion in 73%. Falls or near falls were reported by 12/34 (35%) participants, and were associated with impaired VR balance threshold (P = 0.002). CONCLUSIONS: While VR balance assessment was no better at identifying CIPN than existing measures, it is a potential surrogate method to assess patients at risk of falls from CIPN.

Vestibular semicircular canal function as detected by video Head Impulse Test (vHIT) is essentially unchanged in people with Parkinson's disease compared to healthy controls.

BACKGROUND: Parkinson's disease (PD) is a common multi-system neurodegenerative disorder with possible vestibular system dysfunction, but prior vestibular function test findings are equivocal. OBJECTIVE: To report and compare vestibulo-ocular reflex (VOR) gain as measured by the video head impulse test (vHIT) in participants with PD, including tremor dominant and postural instability/gait dysfunction phenotypes, with healthy controls (HC). METHODS: Forty participants with PD and 40 age- and gender-matched HC had their vestibular function assessed. Lateral and vertical semicircular canal VOR gains were measured with vHIT. VOR canal gains between PD participants and HC were compared with independent samples t-tests. Two distinct PD phenotypes were compared to HC using Tukey's ANOVA. The relationship of VOR gain with PD duration, phenotype, severity and age were investigated using logistic regression. RESULTS: There were no significant differences between groups in vHIT VOR gain for lateral or vertical canals. There was no evidence of an effect of PD severity, phenotype or age on VOR gains in the PD group. CONCLUSION: The impulsive angular VOR pathways are not significantly affected by the pathophysiological changes associated with mild to moderate PD.

A Video Self-Modeling Intervention Using Virtual Reality Plus Physical Practice for Freezing of Gait in Parkinson Disease: Feasibility and Acceptability Study.

BACKGROUND: Despite optimal medical and surgical intervention, freezing of gait commonly occurs in people with Parkinson disease. Action observation via video self-modeling, combined with physical practice, has potential as a noninvasive intervention to reduce freezing of gait. OBJECTIVE: The aim of this study is to determine the feasibility and acceptability of a home-based, personalized video self-modeling intervention delivered via a virtual reality head-mounted display (HMD) to reduce freezing of gait in people with Parkinson disease. The secondary aim is to investigate the potential effect of this intervention on freezing of gait, mobility, and anxiety. METHODS: The study was a single-group pre-post mixed methods pilot trial for which 10 participants with Parkinson disease and freezing of gait were recruited. A physiotherapist assessed the participants in their homes to identify person-specific triggers of freezing and developed individualized movement strategies to overcome freezing of gait. 180° videos of the participants successfully performing their movement strategies were created. Participants watched their videos using a virtual reality HMD, followed by physical practice of their strategies in their own homes over a 6-week intervention period. The primary outcome measures included the feasibility and acceptability of the intervention. Secondary outcome measures included freezing of gait physical tests and questionnaires, including the Timed Up and Go Test, 10-meter walk test, Goal Attainment Scale, and Parkinson Anxiety Scale. RESULTS: The recruitment rate was 24% (10/42), and the retention rate was 90% (9/10). Adherence to the intervention was high, with participants completing a mean of 84% (SD 49%) for the prescribed video viewing and a mean of 100% (SD 56%) for the prescribed physical practice. One participant used the virtual reality HMD for 1 week and completed the rest of the intervention using a flat-screen device because of a gradual worsening of his motion sickness. No other adverse events occurred during the intervention or assessment. Most of the participants found using the HMD to view their videos interesting and enjoyable and would choose to use this intervention to manage their freezing of gait in the future. Five themes were constructed from the interview data: reflections when seeing myself, my experience of using the virtual reality system, the role of the virtual reality system in supporting my learning, developing a deeper understanding of how to manage my freezing of gait, and the impact of the intervention on my daily activities. Overall, there were minimal changes to the freezing of gait, mobility, or anxiety measures from baseline to postintervention, although there was substantial variability between participants. The intervention showed potential in reducing anxiety in participants with high levels of anxiety. CONCLUSIONS: Video self-modeling using an immersive virtual reality HMD plus physical practice of personalized movement strategies is a feasible and acceptable method of addressing freezing of gait in people with Parkinson disease.

Suppression head impulse test paradigm (SHIMP) characteristics in people with Parkinson's disease compared to healthy controls.

The suppression head impulse test paradigm (SHIMP) is a newly described indicator of vestibular function which yields two measures: vestibulo-ocular reflex (VOR) gain and a saccadic response. It is an alternative and complementary test to the head impulse test paradigm (HIMP). Parkinson's disease (PD) has known saccadic and central vestibular pathway dysfunction. This paper is the first description of SHIMP VOR gain and saccade characteristic in this population. This prospective observational study measured the SHIMP VOR gain and saccade characteristics in 39 participants with idiopathic PD and compared this to 40 healthy controls (HC). The effect of group, demographic variables and SHIMP characteristics were evaluated. SHIMP VOR gains were not significantly different between groups (p = 0.10). Compared to HC, the PD group mean SHIMP peak saccade velocity was significantly reduced by an average of 77.07°/sec (p < 0.001), and SHIMP saccade response latency was longer, with an average delay of 23.5 ms (p = 0.003). SHIMP saccade peak velocity was also associated with both head impulse velocity (p = 0.002) and SHIMP VOR gain (p = 0.004) variables, but there was no significant influence of these variables when SHIMP saccade peak velocity was considered as a predictor of PD (p = 0.52-0.91). VOR gains were unaffected by PD. PD-specific saccadic dysfunction, namely reduced peak saccade velocities and prolonged response latencies, were observed in the SHIMP-induced saccade responses. VOR gain using slow phase eye velocity is preferred as the indicator of vestibular function in the SHIMPs paradigm as non-vestibular factors affected saccade peak velocity.

Video-head impulse test in superior canal dehiscence.

BACKGROUND: Superior Canal Dehiscence is classically diagnosed with typical abnormalities on Vestibular Evoked Myogenic Potentials (VEMPs) and Computed Tomography (CT) scans. AIM: This paper discusses the utility of the video Head Impulse Test (vHIT) in SCD. METHODS: Data from 11 ears (8 patients) with SCD were retrospectively reviewed. Results from vHIT, VEMPs and CT and when possible, MRI scans were correlated. An audit of 300 vHIT from patients undergoing routine testing for any neurotological complaint was also conducted to look at the incidence of isolated abnormal superior canal function. RESULTS: 82% of patients (9 ears) with SCD showed abnormal vHIT (reduced gain and catch-up saccades) isolated to the affected superior semicircular canal. CONCLUSION: Correlation of the CT and VEMPs are important in forming a diagnosis of SCD. However, if isolated superior canal vHIT abnormalities are demonstrated, it is suggestive of SCD and such patients should be referred for further investigations.

Static and dynamic otolith reflex function in people with Parkinson's disease.

PURPOSE: Parkinson's disease (PD) is a neurodegenerative disorder with possible vestibular system dysfunction. This study reports the transient and sustained functions of the otoliths and their reflex pathways in PD compared to healthy controls (HC) and determines if otolith function relates to previous fall history. METHODS: Forty participants with PD and 40 HC had their otolith function assessed. Transient saccular and utricular-mediated reflexes were assessed by cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs, respectively) elicited by air-conducted stimulus (clicks) and bone-conducted vibration (light tendon hammer taps). Static otolith function was assessed by the Curator Subjective Visual Vertical (SVV) test. RESULTS: Compared to HC, the PD group had significantly more absent cVEMP responses to both clicks (47.5% vs. 30%, respectively, p = 0.03) and taps (21.8% vs. 5%, respectively, p = 0.002). Only the PD group had bilaterally absent tap cVEMPs, this was related to previous falls history (p < 0. 001). In both groups, click oVEMPs were predominantly absent, and tap oVEMPs were predominantly present. The PD group had smaller tap oVEMP amplitudes (p = 0.03) and recorded more abnormal SVV responses (p = 0.01) and greater error on SVV compared to HC, p < 0.001. SVV had no relationship with VEMP responses (p = 0.14). CONCLUSIONS: PD impacts on cVEMP reflex pathways but not tap oVEMP reflex pathways. Bone-conducted otolith stimuli (taps) are more robust than air-conducted sound stimuli (clicks) for both o and cVEMPs. A lack of association between SVV and VEMP responses suggest that static and dynamic otolith functions are differentially affected in PD.

Law and (rec)order: Updating memory for criminal events with body-worn cameras.

Body-worn video is increasingly relied upon in the criminal justice system, however it is unclear how viewing chest-mounted video may affect a police officer's statement about an event. In the present study, we asked whether reviewing footage from an experienced event could shape an individual's statement, and if so, whether reporting before reviewing may preserve an officer's original experience. Student participants (n = 97) were equipped with chest-mounted cameras as they viewed a simulated theft in virtual reality. One week later, half of the participants recalled the event in an initial statement while the other half did not. Participants then viewed either their body-worn video or a control video. Finally, participants provided their statement (no initial statement condition) or were given the opportunity to amend their original account (initial statement condition). Results revealed that viewing body-worn video enhanced the completeness and accuracy of individuals' free recall statements. However, whilst reviewing footage enabled individuals to exclude errors they had written in their initial statements, they also excluded true details that were uncorroborated by the camera footage (i.e., details which individuals experienced, but that their camera did not record). Such camera conformity is discussed in light of the debate on when an officer should access their body-worn video during an investigation and the influence of post-event information on memory.

The Potential Benefits of Personalized 360 Video Experiences on Affect: A Proof-of-Concept Study.

Despite the importance of healthy affect to improving hospital outcomes, effective means of promoting healthy affect have yet to be elucidated. One unexplored solution lies with virtual reality (VR) technologies. The present study sought to investigate whether personalized VR interventions could improve affect levels in a university sample (n = 33) and one hospitalized patient depending upon one's baseline affective profile. Positive and Negative Affect Schedule scores were compared before and after witnessing important life events/environments in VR and interview responses were analyzed. Within the university student sample, those with high affective profiles produced significantly greater post/pre negative affect (NA) score decreases than self-fulfilling and low affective profiles. The patient experienced a 10-point increase in positive affect and a 7-point decrease in NA. Overall, the current study tended to demonstrate the acceptability and efficacy of personalized VR experiences in promoting healthy affect.

Capturing acute vertigo: A vestibular event monitor.

OBJECTIVE: To facilitate the diagnosis of vestibular disorders by patient-initiated capture of ictal nystagmus. METHODS: Adults from an Australian neurology outpatient clinic reporting recurrent vertigo were recruited prospectively and taught to self-record spontaneous and positional nystagmus at home while symptomatic, using miniature video-oculography goggles. Consenting patients with ictal videorecordings and a final unblinded clinical diagnosis of Ménière disease (MD), vestibular migraine (VM), or benign paroxysmal positional vertigo (BPPV) were included. RESULTS: Ictal eye videos of 117 patients were analyzed. Of 43 patients with MD, 40 showed high-velocity spontaneous horizontal nystagmus (median slow-phase velocity [SPV] 39.7°/s; 21 showed horizontal nystagmus reversing direction within 12 hours [24 on separate days]). In 44 of 67 patients with VM, spontaneous horizontal (n = 28, 4.9°/s), upbeating (n = 6, 15.5°/s), or downbeating nystagmus (n = 10, 5.1°/s) was observed; 16 showed positional nystagmus only, and 7 had no nystagmus. Spontaneous horizontal nystagmus with SPV >12.05°/s had a sensitivity and specificity of 95.3% and 82.1% for MD (95% confidence interval [CI] 0.84-0.99, 0.71-0.90). Nystagmus direction change within 12 hours was highly specific (95.7%) for MD (95% CI 0.85-0.99). Spontaneous vertical nystagmus was highly specific (93.0%) for VM (95% CI 0.81-0.99). In the 7 patients with BPPV, spontaneous nystagmus was absent or <3°/s. Lying affected-ear down, patients with BPPV demonstrated paroxysmal positional nystagmus. Median time for peak SPV to halve (T50) was 19.0 seconds. Patients with VM and patients with MD demonstrated persistent positional nystagmus (median T50; 93.1 seconds, 213.2 seconds). T50s <47.3 seconds had a sensitivity and specificity of 100% and 77.8% for BPPV (95% CI 0.54-1.00, 0.64-0.88). CONCLUSION: Patient-initiated vestibular event monitoring is feasible and could facilitate rapid and accurate diagnosis of episodic vestibular disorders.

Long-duration spaceflight adversely affects post-landing operator proficiency.

Performance of astronaut pilots during space shuttle landing was degraded after a few weeks of microgravity exposure, and longer-term exposure has the potential to impact operator proficiency during critical landing and post-landing operations for exploration-class missions. Full-motion simulations of operationally-relevant tasks were utilized to assess the impact of long-duration spaceflight on operator proficiency in a group of 8 astronauts assigned to the International Space Station, as well as a battery of cognitive/sensorimotor tests to determine the underlying cause of any post-flight performance decrements. A ground control group (N = 12) and a sleep restriction cohort (N = 9) were also tested to control for non-spaceflight factors such as lack of practice between pre- and post-flight testing and fatigue. On the day of return after 6 months aboard the space station, astronauts exhibited significant deficits in manual dexterity, dual-tasking and motion perception, and a striking degradation in the ability to operate a vehicle. These deficits were not primarily due to fatigue; performance on the same tasks was unaffected after a 30-h period of sleep restriction. Astronauts experienced a general post-flight malaise in motor function and motion perception, and a lack of cognitive reserve apparent only when faced with dual tasks, which had recovered to baseline by four days after landing.

Virtual Reality for Teletherapy: Avatars May Combine the Benefits of Face-to-Face Communication with the Anonymity of Online Text-Based Communication.

Self-disclosure is an essential component of social communication that has been associated with trust, liking, and ultimately strong relationships. As technology continues to develop, so do the number of methods to create and maintain relationships. While speaking face-to-face (FtF) remains the primary way to communicate, computer-mediated communication has become more common, meaning that research into self-disclosure has expanded to new domains, including virtual reality (VR). This study compared self-disclosure between three conversation contexts: FtF, online text-based (OTB) communication, or VR. Zero-contact dyads comprised female university students who completed 20-minute conversations guided by one of two discussion prompts: the closeness-generating or small talk procedure. These prompts were designed to either increase or not increase self-disclosure. These conversations were recorded and coded for the frequency of total, factual, cognitive, and emotional self-disclosures as objective measures. Participants' perceptions of personal and partner's self-disclosures were also assessed by questionnaires as perceived measures. FtF and VR conditions exceeded OTB communication in perceived and objective measures of self-disclosure. Although no significant differences emerged between FtF and VR conditions for factual or perceived self-disclosure, participants in the FtF condition had more total, cognitive, and emotional self-disclosures than VR conditions. Implications for communication and teletherapy are discussed. The present study offers preliminary evidence that VR could potentially rival FtF as a communication medium and be as effective in facilitating self-disclosure. Findings offer a starting point for research on social applications of VR.

µVEMP: A Portable Interface to Record Vestibular Evoked Myogenic Potentials (VEMPs) With a Smart Phone or Tablet.

Background: Cervical VEMPs and ocular VEMPs are tests for evaluating otolith function in clinical practice. We developed a simple, portable and affordable device to record VEMP responses on patients, named µVEMP. Our aim was to validate and field test the new µVEMP device. Methods: We recorded cervical VEMPs and ocular VEMPs in response to bone conducted vibration using taps tendon hammer to the forehead (Fz) and to air conducted sounds using clicks. We simultaneously recorded VEMP responses (same subject, same electrode, same stimuli) in three healthy volunteers (2 females, age range: 29-57 years) with the µVEMP device and with a standard research grade commercial (CED) system used in clinics. We also used the µVEMP device to record VEMP responses from six patients (6 females, age mean±SD: 50.3 ± 20.8 years) with classical peripheral audio-vestibular diseases (unilateral vestibular neuritis, unilateral neurectomy, bilateral vestibular loss, unilateral superior canal dehiscence, unilateral otosclerosis). Results: The first part of this paper compared the devices using simultaneous recordings. The average of the concordance correlation coefficient was rc = 0.997 ± 0.003 showing a strong similarity between the measures. VEMP responses recorded with the µVEMP device on patients with audio-vestibular diseases were similar to those typically found in the literature. Conclusions: We developed, validated and field tested a new device to record ocular and cervical VEMPs in response to sound and vibration.This new device is portable (powered by a phone or tablet) with pocket-size dimensions (105 × 66 × 27 mm) and light weight (150 g). Although further studies and normative data are required, our µVEMP device is simpler (easier to use) and potentially more accessible than standard, commercially available equipment.

Imbalance: Objective measures versus subjective self-report in clinical practice.

BACKGROUND: Dizziness and imbalance are very common complaints in clinical practice. One of the challenges is to evaluate the 'real' risk of falls. Two tools are available: the patient's self-report and the measure of the patient's balance. We evaluated the relationship between these methods using the Dizziness Handicap Inventory (DHI) and measures of balance while visual inputs are perturbed with Virtual Reality (VR). METHODS: 90 consecutive patients underwent the DHI questionnaire and the balance test. The DHI questionnaire was used to measure the subject's perception of handicap associated with dizziness. The balance test measured the postural sway in several visual conditions: eyes open, eyes closed, and with an unpredictable visual perturbation using VR at several amplitudes of movement. RESULTS: No correlation was found between the DHI score and the balance measurement. The visual perturbations allow us to characterize patients into three groups: one group with a high DHI score who did not fall on the balance test (5.5%), one group with a low DHI score who failed eyes closed on a compliant surface (9.0%), and one group of the remaining patients (85.5%). The correlation between the DHI score and the balance performance became significant on the remaining group of patients. CONCLUSION: Both subjective self-report and objective measure are important to characterize a patient. The use of VR visual perturbations allowed us to define three important groups of patients. VR visual perturbations provided additional information that helps explain the lack of correlation between DHI and objective test results.

Strabismus Measurements with Novel Video Goggles.

PURPOSE: To assess the validity of a novel, simplified, noninvasive test for strabismus using video goggles. DESIGN: Cross-sectional method comparison study in which the new test, the strabismus video goggles, is compared with the existing reference standard, the Hess screen test. PARTICIPANTS: We studied 41 adult and child patients aged ≥6 years with ocular misalignment owing to congenital or acquired paralytic or comitant strabismus and 17 healthy volunteers. METHODS: All participants were tested with binocular infrared video goggles with built-in laser target projection and liquid crystal display shutters for alternate occlusion of the eyes and the conventional Hess screen test. In both tests, ocular deviations were measured on a 9-point target grid located at 0±15° horizontal and vertical eccentricity. MAIN OUTCOME MEASURES: Horizontal and vertical ocular deviations at 9 different gaze positions of each eye were measured by the strabismus video goggles and the Hess screen test. Agreement was quantified as the intraclass correlation coefficient. Secondary outcomes were the utility of the goggles in patients with visual suppression and in children. RESULTS: There was good agreement between the strabismus video goggles and the Hess screen test in the measurements of horizontal and vertical deviation (intraclass correlation coefficient horizontal 0.83, 95% confidence interval [0.77, 0.88], vertical 0.76, 95% confidence interval [0.68, 0.82]). Both methods reproduced the characteristic strabismus patterns in the 9-point grid. In contrast to Hess screen testing, strabismus video goggle measurements were even possible in patients with comitant strabismus and visual suppression. CONCLUSIONS: The new device is simple and is fast and accurate in measuring ocular deviations, and the results are closely correlated with those obtained using the conventional Hess screen test. It can even be used in patients with visual suppression who are not suitable for the Hess screen test. The device can be applied in children as young as 6 years of age.

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.

Sustained and Transient Vestibular Systems: A Physiological Basis for Interpreting Vestibular Function.

Otolithic afferents with regular resting discharge respond to gravity or low-frequency linear accelerations, and we term these the static or sustained otolithic system. However, in the otolithic sense organs, there is anatomical differentiation across the maculae and corresponding physiological differentiation. A specialized band of receptors called the striola consists of mainly type I receptors whose hair bundles are weakly tethered to the overlying otolithic membrane. The afferent neurons, which form calyx synapses on type I striolar receptors, have irregular resting discharge and have low thresholds to high frequency (e.g., 500 Hz) bone-conducted vibration and air-conducted sound. High-frequency sound and vibration likely causes fluid displacement which deflects the weakly tethered hair bundles of the very fast type I receptors. Irregular vestibular afferents show phase locking, similar to cochlear afferents, up to stimulus frequencies of kilohertz. We term these irregular afferents the transient system signaling dynamic otolithic stimulation. A 500-Hz vibration preferentially activates the otolith irregular afferents, since regular afferents are not activated at intensities used in clinical testing, whereas irregular afferents have low thresholds. We show how this sustained and transient distinction applies at the vestibular nuclei. The two systems have differential responses to vibration and sound, to ototoxic antibiotics, to galvanic stimulation, and to natural linear acceleration, and such differential sensitivity allows probing of the two systems. A 500-Hz vibration that selectively activates irregular otolithic afferents results in stimulus-locked eye movements in animals and humans. The preparatory myogenic potentials for these eye movements are measured in the new clinical test of otolith function-ocular vestibular-evoked myogenic potentials. We suggest 500-Hz vibration may identify the contribution of the transient system to vestibular controlled responses, such as vestibulo-ocular, vestibulo-spinal, and vestibulo-sympathetic responses. The prospect of particular treatments targeting one or the other of the transient or sustained systems is now being realized in the clinic by the use of intratympanic gentamicin which preferentially attacks type I receptors. We suggest that it is valuable to view vestibular responses by this sustained-transient distinction.

Balance in Virtual Reality: Effect of Age and Bilateral Vestibular Loss.

BACKGROUND: Quantitative balance measurement is used in clinical practice to prevent falls. The conditions of the test were limited to eyes open, eyes closed, and sway-referenced vision. We developed a new visual perturbation to challenge balance using virtual reality (VR), measuring postural stability by a Wii Balance Board (WBB). METHODS: In this study, we recorded balance performance of 116 healthy subjects and of 10 bilateral vestibular loss patients using VR to assess the effect of age and the effect of total loss of vestibular function. We used several conditions: eyes open (normal visual inputs), eyes closed (no visual inputs), stable visual world (vision referenced), and perturbed visual world (visual perturbation) at different amplitudes of perturbation. Balance under these visual conditions was assessed on the WBB (stable support surface) and on the WBB plus foam rubber (unstable support surface). RESULTS: In healthy subjects, we found that the percentage of falls increased with age and with the amplitude of perturbation for both conditions: WBB or WBB + foam. Moreover, we can define a threshold for falls in each age group as the amplitude of perturbation which induced falls. For bilateral vestibular loss patients, on the WBB + foam, all of them failed with eyes closed and with perturbed visual world even at the minimal amplitude of perturbation. Finally, we observed that stable visual world induced fewer falls than eyes closed whatever the subject's group (healthy or bilateral vestibular loss) and whatever the age decade. CONCLUSION: VR allowed us to develop a useful new tool with a wide range of visual perturbations. Rather than only two levels of visual condition (eyes open and eyes closed), the VR stimulus can be continuously adjusted to produce a visual perturbation powerful enough to induce falls even in young healthy subjects and which has allowed us to determine a threshold for falls.

A new saccadic indicator of peripheral vestibular function based on the video head impulse test.

OBJECTIVE: While compensatory saccades indicate vestibular loss in the conventional head impulse test paradigm (HIMP), in which the participant fixates an earth-fixed target, we investigated a complementary suppression head impulse paradigm (SHIMP), in which the participant is fixating a head-fixed target to elicit anticompensatory saccades as a sign of vestibular function. METHODS: HIMP and SHIMP eye movement responses were measured with the horizontal video head impulse test in patients with unilateral vestibular loss, patients with bilateral vestibular loss, and in healthy controls. RESULTS: Vestibulo-ocular reflex gains showed close correlation (R(2) = 0.97) with slightly lower SHIMP than HIMP gains (mean gain difference 0.06 ± 0.05 SD, p < 0.001). However, the 2 paradigms produced complementary catch-up saccade patterns: HIMP elicited compensatory saccades in patients but rarely in controls, whereas SHIMP elicited large anticompensatory saccades in controls, but smaller or no saccades in bilateral vestibular loss. Unilateral vestibular loss produced covert saccades in HIMP, but later and smaller saccades in SHIMP toward the affected side. Cumulative HIMP and SHIMP saccade amplitude differentiated patients from controls with high sensitivity and specificity. CONCLUSIONS: While compensatory saccades indicate vestibular loss in conventional HIMP, anticompensatory saccades in SHIMP using a head-fixed target indicate vestibular function. SHIMP saccades usually appear later than HIMP saccades, therefore being more salient to the naked eye and facilitating vestibulo-ocular reflex gain measurements. The new paradigm is intuitive and easy to explain to patients, and the SHIMP results complement those from the standard video head impulse test. CLASSIFICATION OF EVIDENCE: This case-control study provides Class III evidence that SHIMP accurately identifies patients with unilateral or bilateral vestibulopathies.

Proposed diagnostic criteria for cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS).

PURPOSE OF REVIEW: Diagnosis of ataxic disorders is an important clinical challenge upon which prognostication, management, patient solace, and, above all, the hope of future treatment all rely. Heritable diseases and the possibility of affected offspring carry the added burden of portending adverse health, social and financial ramifications. RECENT FINDINGS: Cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS) is an inherited multisystem ataxia compromising cerebellar, vestibular, and sensory function. It is not uncommon, but despite early attempts the genetic defect is yet to be identified. As the search for the causative gene continues, we have found it useful to further define this syndrome in terms of its likely phenotype. SUMMARY: We propose staged diagnostic criteria based on the identified pathology in CANVAS. We envisage that these criteria will aid the clinician in diagnosing CANVAS and the researcher in further elucidating this complex disorder.