Timothy E. Hullar

Introduction: In the early years following the development of the caloric test, one of the parameters used to quantify vestibular function was nystagmus duration. A common finding in patients with Meniere’s disease (MD) is the presence of unilateral caloric weakness, despite normal results on the video head impulse test (vHIT). It has been proposed that the apparent caloric loss could be due to the creation of local flow facilitated by canal distention. If the nystagmus duration is linked to the hydrostatic effect, one could hypothesize that MD patients would demonstrate shorter slow-phase velocity (SPV) duration. Objective: The aim of the study was to examine SPV and the duration of nystagmus following caloric testing in MD patients. Method: 24 participants (12 controls; 12 MD) were assessed using bithermal, bilateral caloric stimulation. To control for possible side differences, two subgroups were analyzed: MD-ipsilateral (affected ear); MD-contralateral (unaffected ears). Ears in the control group were side matched with ears in the MD groups and the terminology control-ipsilateral or control-contralateral was used to represent this matching. Results: Significant differences were observed for SPV between controls-contralateral and MD-ipsilateral ears (cold: p ≤ 0.001; warm: p = 0.02) and between controls-ipsilateral and MD-ipsilateral ears (cold: p ≤ 0.001; warm: p = 0.04). Significant SPV differences were observed between MD-contralateral and MD-ipsilateral ears (cold: p ≤ 0.001; warm: p = 0.03). However, no differences were found between groups in the duration of nystagmus following cold or warm irrigation (cold: p = 0.2; warm: p = 0.33). Conclusion: Results support previous literature suggesting SPV can be affected in patients with MD even if vHIT gain is normal. However, mechanisms that influence the SPV seem to differ from those for the nystagmus duration. Indeed, nystagmus duration seems to remain unaffected in MD patients with vHIT-caloric dissociation, suggesting that it may be controlled by other factors.

Ototoxic chemicals in the workplace can pose a risk to hearing and balance functions. Our objective was to identify evidence-based practices for occupational health settings in managing ototoxicity. This resulted in the document, Health Management of Workers Exposed to Ototoxic Chemicals, created by the International Ototoxicity Management Group. To develop a practical approach for any workplace, we reviewed a variety of sources and used an international panel of interdisciplinary experts. Evidence included data from experimental, observational, and review studies. Thirty-two subject matter experts were invited to review the document; twenty-two completed the review and unanimously endorsed the ototoxicity management system as proposed. Six key action steps were proposed to: (1) identify workers exposed to ototoxic chemicals, (2) perform auditory and vestibular assessments, (3) follow-up after monitoring health, (4) document worker data, (5) maintain healthy safety culture, and (6) review ototoxicity management approach. These steps focus on the management of workers who are at-risk for workplace ototoxic chemical exposure at any level (with or without concurrent noise exposures). Early identification strategies include self-report questionnaires; auditory testing; vestibular screening; referrals for diagnosis; management of cases; and monitoring of exposure scenarios to prevent further cases.

Maintaining balance involves the combination of sensory signals from the visual, vestibular, proprioceptive, and auditory systems. However, physical and biological constraints ensure that these signals are perceived slightly asynchronously. The brain only recognizes them as simultaneous when they occur within a period of time called the temporal binding window (TBW). Aging can prolong the TBW, leading to temporal uncertainty during multisensory integration. This effect might contribute to imbalance in the elderly but has not been examined with respect to vestibular inputs. Here, we compared the vestibular-related TBW in 13 younger and 12 older subjects undergoing 0.5 Hz sinusoidal rotations about the earth-vertical axis. An alternating dichotic auditory stimulus was presented at the same frequency but with the phase varied to determine the temporal range over which the two stimuli were perceived as simultaneous at least 75% of the time, defined as the TBW. The mean TBW among younger subjects was 286 ms (SEM ± 56 ms) and among older subjects was 560 ms (SEM ± 52 ms). TBW was related to vestibular sensitivity among younger but not older subjects, suggesting that a prolonged TBW could be a mechanism for imbalance in the elderly person independent of changes in peripheral vestibular function.

In Reply We are grateful to have the opportunity to respond to the letter by Cambron et al. With their help, we analyzed an updated 2019 data set using the same techniques we had previously applied to information from 2017 for use in our study.¹ As Cambron et al point out and our data show, the opening of new cochlear implant centers in the interim has allowed veterans in major metropolitan areas such as Indianapolis, Las Vegas, New Orleans, and San Diego, and smaller urban centers such as Eugene, Oregon and Reno, Nevada to gain significantly better access particularly to centers providing audiologic services (Figure). Ongoing apparent disparities elsewhere may paradoxically reflect superior levels of care: outcomes are likely to be better at high-volume centers, which naturally require larger catchment areas. For example, veterans in Arizona are on average distant from care, but the alternative—developing a patchwork of small centers spread throughout the state—would dilute the pool of experienced and highly specialized cochlear implant clinicians. Identify all potential conflicts of interest that might be relevant to your comment. Conflicts of interest comprise financial interests, activities, and relationships within the past 3 years including but not limited to employment, affiliation, grants or funding, consultancies, honoraria or payment, speaker's bureaus, stock ownership or options, expert testimony, royalties, donation of medical equipment, or patents planned, pending, or issued. Err on the side of full disclosure. If you have no conflicts of interest, check "No potential conflicts of interest" in the box below. The information will be posted with your response. Not all submitted comments are published. Please see our commenting policy for details.

Objectives: Vestibular reflexes have traditionally formed the cornerstone of vestibular evaluation, but perceptual tests have recently gained attention for use in research studies and potential clinical applications. However, the unknown reliability of perceptual thresholds limits their current importance. This is addressed here by establishing the test-retest reliability of vestibular perceptual testing. Design: Perceptual detection thresholds to earth-vertical, yaw-axis rotations were collected in 15 young healthy people. Participants were tested at two time intervals (baseline, 5 to 14 days later) using an adaptive psychophysical procedure. Results: Thresholds to 1 Hz rotations ranged from 0.69 to 2.99°/s (mean: 1.49°/s; SD: 0.63). They demonstrated an excellent intraclass correlation (0.92; 95% confidence interval: 0.77 to 0.97) with a minimum detectable difference of 0.45°/s. Conclusions: The excellent test-retest reliability of perceptual vestibular testing supports its use as a research tool and motivates further exploration for its use as a novel clinical technique.

Recent evidence has shown that auditory information may be used to improve postural stability, spatial orientation, navigation, and gait, suggesting an auditory component of self-motion perception. To determine how auditory and other sensory cues integrate for self-motion perception, we measured motion perception during yaw rotations of the body and the auditory environment. Psychophysical thresholds in humans were measured over a range of frequencies (0.1–1.0 Hz) during self-rotation without spatial auditory stimuli, rotation of a sound source around a stationary listener, and self-rotation in the presence of an earth-fixed sound source. Unisensory perceptual thresholds and the combined multisensory thresholds were found to be frequency dependent. Auditory thresholds were better at lower frequencies, and vestibular thresholds were better at higher frequencies. Expressed in terms of peak angular velocity, multisensory vestibular and auditory thresholds ranged from 0.39°/s at 0.1 Hz to 0.95°/s at 1.0 Hz and were significantly better over low frequencies than either the auditory-only (0.54°/s to 2.42°/s at 0.1 and 1.0 Hz, respectively) or vestibular-only (2.00°/s to 0.75°/s at 0.1 and 1.0 Hz, respectively) unisensory conditions. Monaurally presented auditory cues were less effective than binaural cues in lowering multisensory thresholds. Frequency-independent thresholds were derived, assuming that vestibular thresholds depended on a weighted combination of velocity and acceleration cues, whereas auditory thresholds depended on displacement and velocity cues. These results elucidate fundamental mechanisms for the contribution of audition to balance and help explain previous findings, indicating its significance in tasks requiring self-orientation. NEW & NOTEWORTHY Auditory information can be integrated with visual, proprioceptive, and vestibular signals to improve balance, orientation, and gait, but this process is poorly understood. Here, we show that auditory cues significantly improve sensitivity to self-motion perception below 0.5 Hz, whereas vestibular cues contribute more at higher frequencies. Motion thresholds are determined by a weighted combination of displacement, velocity, and acceleration information. These findings may help understand and treat imbalance, particularly in people with sensory deficits.

The Veterans Health Administration (VHA) hospital system provides US veterans with access to both primary and specialty health care. It provides more than 1000 community-based outpatient clinics,¹ whereas specialized care is concentrated in larger VHA facilities typically located in major cities, thereby simplifying access to tertiary care in the most densely populated areas. Larger urban VHA facilities are also often affiliated with major academic centers that provide specialist faculty, sometimes via a shared appointment. The relatively small number of tertiary care facilities, however, risks an uneven availability of specialized services and poorer care overall.

Objectives: We sought to compare balance outcomes according to treatment modality of vestibular schwannoma (VS) via a meta‐analysis that divided measuring tools of balance outcomes into three categories based on type.Methods: A comprehensive review of the literature from January 1966 to September 2017 was performed, looking for studies about long‐term balance outcomes after microsurgery (MS), radiotherapy (RT), or observation for VS. A comprehensive meta‐analysis was used to analyze effect sizes, explore possible causes of heterogeneity, and check publication bias with a funnel plot and Egger's regression.Results: Among 633 references, 34 were included in the meta‐analysis. Perceived dizziness improvement rate was significantly higher in the MS group than in the RT group (odds ratio [OR]: 1.61; 95% confidence interval [CI]: 1.08 to 2.40; P < .05, I² = 4.18], but no significant difference was observed between the two groups with regard to validated dizziness questionnaire score (standardized mean difference: 0.04; 95% CI: −0.36 to 0.44; P = .84, I² = 69.61) or dizziness or disequilibrium‐related symptom incidence rate (OR: 0.91; 95% CI: 0.50 to 1.68; P = .77, I² = 0). In a subanalysis conducted within the groups after intervention, the MS group demonstrated a lower vertigo incidence rate (P < .001), and the RT group experienced a significant reduction in validated dizziness questionnaire score (P < .05).Conclusions: Our results indicate that MS should be considered at least equal to RT in regard to resolving long‐term dizziness and improving balance outcomes. Furthermore, well‐designed studies are necessary to predict balance outcomes after VS treatment and to choose from among possible treatment options.Level of Evidence: 2a Laryngoscope, 130:178–189, 2020