Post Cochlear Implantation Vertigo: Ictal Nystagmus and Audiovestibular Test Characteristics.

OBJECTIVE: To investigate ictal nystagmus and audiovestibular characteristics in episodic spontaneous vertigo after cochlear implantation (CI). STUDY DESIGN: Retrospective and prospective case series. PATIENTS: Twenty-one CI patients with episodic spontaneous vertigo after implantation were recruited. INTERVENTIONS: Patient-initiated home video-oculography recordings were performed during one or more attacks of vertigo, using miniature portable home video-glasses. To assess canal and otolith function, video head-impulse tests (vHITs) and vestibular-evoked myogenic potential tests were conducted. MAIN OUTCOME MEASURES: Nystagmus slow-phase velocities (SPVs), the presence of horizontal direction-changing nystagmus, and post-CI audiovestibular tests. RESULTS: Main final diagnoses were post-CI secondary endolymphatic hydrops (48%) and exacerbation of existing Ménière's disease (29%). Symptomatic patients demonstrated high-velocity horizontal ictal-nystagmus (SPV, 44.2°/s and 68.2°/s in post-CI secondary endolymphatic hydrop and Ménière's disease). Direction-changing nystagmus was observed in 80 and 75%. Two were diagnosed with presumed autoimmune inner ear disease (SPV, 6.6°/s and 172.9°/s). One patient was diagnosed with probable vestibular migraine (15.1°/s).VHIT gains were 0.80 ± 0.20 (lateral), 0.70 ± 0.17 (anterior), and 0.62 ± 0.27 (posterior) in the implanted ear, with abnormal values in 33, 35, and 35% of each canal. Bone-conducted cervical and ocular vestibular-evoked myogenic potentials were asymmetric in 52 and 29% of patients (all lateralized to the implanted ear) with mean asymmetry ratios of 51.2 and 35.7%. Reversible reduction in vHIT gain was recorded in three acutely symptomatic patients. CONCLUSION: High-velocity, direction-changing nystagmus time-locked with vertigo attacks may be observed in post-CI implant vertigo and may indicate endolymphatic hydrops. Fluctuating vHIT gain may be an additional marker of a recurrent peripheral vestibulopathy.

Subjective visual horizontal correlates better with ocular than with cervical vestibular evoked myogenic potentials.

OBJECTIVE: To examine the relationship between widely used otolith function tests: the Subjective Visual Horizontal (SVH) and Vestibular Evoked Myogenic Potentials (VEMP). METHODS: A retrospective analysis was performed on 301 patients who underwent SVH, ocular and cervical VEMP (oVEMP and cVEMP) tests on the same day. Correlations between the mean SVH tilt and amplitude asymmetry ratios for bone-conducted (BC) oVEMP and air-conducted (AC) cVEMP were examined. Diagnoses included vestibular neuritis, stroke, vestibular migraine, Meniere's disease, sudden sensorineural hearing loss (SSNHL) and vestibular schwannoma. RESULTS: SVH results were concordant with the oVEMP in 64% of cases and the cVEMP in 51%. Across all patients, SVH demonstrated a significant moderate correlation with BC oVEMP amplitude asymmetry ratios (r = 0.55, p < 0.001) and a weak correlation with AC cVEMP amplitude asymmetry ratios (r = 0.35, p < 0.001). A stronger correlation between SVH and oVEMPs was observed in patients with vestibular neuritis (r = 0.67, p < 0.001) and SSNHL (r = 0.76, p = 0.001). CONCLUSIONS: SVH correlates better with oVEMP than cVEMP symmetry. SIGNIFICANCE: This finding reinforces the hypothesis of a common utricular origin for both SVH and oVEMPs which is distinct from the saccular origin of cVEMPs.

Scoping out noisy galvanic vestibular stimulation: a review of the parameters used to improve postural control.

Objective: Noisy galvanic vestibular stimulation (nGVS) has been used to facilitate vestibular function and improve gait and balance in people with poor postural control. The aim of this scoping review is to collate, summarize and report on the nGVS parameters that have been used to augment postural control. Method: A systematic scoping review was conducted up to December 2022. Data were extracted and synthesized from 31 eligible studies. Key nGVS parameters were identified, and the importance of these parameters and their influence on postural control evaluated. Results: A range of nGVS parameters have been used to augment postural control, including; noise waveform, amplitude, frequency band, duration of stimulation, method of amplitude optimization, size and composition of electrodes and the electrode skin interface. Conclusion: Systematic evaluation of the individual parameters that can be manipulated in the nGVS waveform identified that a broad array of settings have been utilized in each parameter across the studies. Choices made around the electrode and electrode-skin interface, as well as the amplitude, frequency band, duration and timing of the waveform are likely to influence the efficacy of nGVS. The ability to draw robust conclusions about the selection of optimal nGVS parameters to improve postural control, is hindered by a lack of studies that directly compare parameter settings or consider the variability in individuals' response to nGVS. We propose a guideline for the accurate reporting of nGVS parameters, as a first step toward establishing standardized stimulation protocols.

Patterns of vestibular dysfunction in chronic traumatic brain injury.

Background: Dizziness and imbalance are common following traumatic brain injury (TBI). While these symptoms are often attributed to vestibular dysfunction, the relative contribution of peripheral vs. central mechanisms is unclear. This study investigated the prevalence of semicircular canal and otolith abnormalities in a cohort of patients with chronic TBI and symptoms of dizziness or imbalance. The relationship between vestibular, oculomotor and posturography results was further explored. Methods: Clinical records of patients attending the New Zealand Dizziness and Balance Centre from January 2015 to December 2019 were reviewed for consideration in the study. Inclusion required: an age of 18-80 years, a diagnosed TBI, and vestibular assessment using three-dimensional video head impulses (vHIT), cervical and ocular vestibular-evoked myogenic potentials (c and o VEMPs, respectively) and caloric testing. Severe TBI, pre-existing vestibular diagnoses, and incomplete test results were excluded. Rates of abnormalities were determined for each test and compared with results of oculomotor function testing and postural control, measured using the sensory organization test (SOT). Results: Of 158 reviewed records, 99 patients aged 49 ± 15 years (59 female) fulfilled criteria for inclusion in the study. The median time between the head injury and the clinical assessment was 12 (IQR 6-21) months. Abnormalities involving one or more components of the vestibular labyrinth and/or nerve divisions were identified in 33 of 99 patients (33.3%). The horizontal semicircular canal was most frequently affected (18.2%), followed by the saccule (14.1%), utricle (8.1%), posterior (7.1%) and anterior (2.0%) semicircular canals. Vestibular test abnormalities were associated with skull-base fractures, superior canal dehiscence, and focal ear trauma. Oculomotor dysfunction and postural instability were recorded in 41.1 and 75.5% of patients, respectively. Postural instability correlated with abnormal oculomotor function (p = 0.008) but not peripheral vestibular hypofunction (p = 0.336). Conclusions: Dizziness and/or imbalance in chronic TBI was associated with impaired postural stability for tasks requiring high levels of use of vestibular and visual input for balance. Vestibular hypofunction identified through vHIT, VEMP and caloric testing was recorded but was less common, except when the injury involved a fractured skull-base. There was no specific pattern of end-organ or nerve involvement which characterized this group of patients.

Efficacy of nGVS to improve postural stability in people with bilateral vestibulopathy: A systematic review and meta-analysis.

Objective: Noisy galvanic vestibular stimulation (nGVS) has been used to boost vestibular afferent information to the central nervous system. This has the potential to improve postural control for people for whom vestibular signals are weak, such as in bilateral vestibulopathy (BVP). The aim of this systematic review and meta-analysis is to investigate the evidence for nGVS as a modality to improve postural control in people with BVP. Methods: A comprehensive systematic search was conducted of five databases up to July 2022 to find studies applying nGVS to people with BVP, with the aim of improving postural control. Two independent reviewers screened and identified eligible studies, completed a risk of bias evaluation (Cochrane) and extracted relevant data. The standardized mean difference (SMD) based on Hedges' g was calculated as a measure of effect size for the primary outcome measure that best identified postural control, and a forest plot generated. Results: Seven studies met the eligibility criteria, with five being suitable for meta-analysis. Meta-analysis revealed a moderate effect in favor of nGVS improving postural control during standing and walking [pooled SMD = 0.47 95% CI (0.25, 0.7)]. nGVS-mediated improvements in postural control were most evident in observations of reduced sway velocity when standing on a firm surface with eyes closed, and in the reduced variability of gait parameters, particularly those measuring lateral stability. Conclusions: Coincident nGVS in people with BVP improves postural control during standing and walking. This improvement appears to be context specific, in that vestibular augmentation is most effective in situations where visual inputs are limited, and where reliable context specific proprioceptive cues are available. Further research is warranted investigating additional circumstances in which nGVS improves postural control, including investigating the residual, and sustained effects of nGVS. Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=342147, identifier: 342147.

The human vestibulo-ocular reflex and compensatory saccades in schwannoma patients before and after vestibular nerve section.

OBJECTIVE: To examine the vestibulo-ocular reflex (VOR) and compensatory-saccades before and after complete unilateral vestibular deafferentation (UVD). METHODS: Forty patients were studied before and after surgery for vestibular or facial schwannoma using the video head-impulse test (vHIT) and multivariable regression. RESULTS: Prior to UVD (median(IQR), 14(58.4) days), the average VOR-gain towards the lesioned-ear was lower than in normal for all semicircular canals (lateral, anterior, posterior: 0.69, 0.72, 0.49). One-week after UVD (5(3.0) days) VOR gains were further reduced (0.22, 0.37, 0.27), however, within one-year after UVD (171(125.0) days) the lesioned-ear VOR gains had slightly increased (+0.08, +0.11, +0.03), maximally for the anterior-canal. After UVD, the VOR gain asymmetry (gain towards minus away from intact-ear) was lower for the intact posterior-canal plane (0.56, 0.56, 0.22). For the lesioned canals, the frequency and amplitude of the first compensatory-saccade increased from 61-93% and 1.9-3.6° pre-surgery, to 98-99% and to 3.1-5.9° one-week post-surgery and remained unchanged over one-year; second saccade frequency and amplitude decreased over the same timespan. CONCLUSIONS: After UVD the high-acceleration VOR for the intact posterior-canal plane is more symmetrical than the other canals. First compensatory-saccades adapt within one week and subsequently change only marginally. SIGNIFICANCE: Saccade compensation from surgical UVD is near complete by one-week.

Vestibular function testing in the 21st century: video head impulse test, vestibular evoked myogenic potential, video nystagmography; which tests will provide answers?

PURPOSE OF REVIEW: To most neurologists, assessing the patient with vertigo is an unpleasant and worrisome task. A structured history and focused examination can be complemented by carefully selected laboratory tests, to reach an early and accurate diagnosis. We provide evidence-based recommendations for vestibular test selection. RECENT FINDINGS: The video head impulse test (vHIT), cervical and ocular vestibular evoked myogenic potential (VEMP) and home-video nystagmography are four modern, noninvasive methods of assessing vestibular function, which are equally applicable in the hospital and office-practice. Collectively, they enable assessment of all five vestibular end-organs. The prevalence and patterns of test abnormalities are distinct for each vestibular disorder. We summarize typical abnormalities encountered in four common vestibular syndromes. SUMMARY: In the context of acute vestibular syndrome, an abnormal vHIT with low gain and large amplitude refixation saccades and an asymmetric oVEMP separates innocuous vestibular neuritis from stroke. In episodic spontaneous vertigo, high-velocity ictal nystagmus and asymmetric cVEMP help separate Ménière's disease from vestibular migraine. In chronic imbalance, all three tests help detect unilateral or bilateral vestibular loss as the root cause. Recurrent positional vertigo requires no laboratory test and can be diagnosed and treated at the bedside, guided by video nystagmography.

A Window Into the Whole Story: Temporal Bone Plasmacytoma Presenting With a Mobile Third Window.

A 63-year-old man presented with imbalance when coughing due to a respiratory tract infection. He had a history of multiple myeloma with a plasmacytoma of the left temporal bone. Examination revealed a positive leftward head impulse test, no spontaneous nystagmus, left-beating positional nystagmus, and left-beating Valsalva-induced nystagmus. Videonystagmography, audiology, and comprehensive vestibular function tests revealed a subtotal left peripheral audio-vestibular loss. Temporal bone computed tomography showed an unchanged bony erosion of the left labyrinth from 2 years prior. Vertigo subsided after treatment of the respiratory tract infection. Although no tumor progression was evident, coughing had triggered a preexisting third mobile window to declare itself. Laryngoscope, 131:E966-E969, 2021.

Bone-Conducted oVEMP Latency Delays Assist in the Differential Diagnosis of Large Air-Conducted oVEMP Amplitudes.

Background: A sensitive test for Superior Semicircular Canal Dehiscence (SCD) is the air-conducted, ocular vestibular evoked myogenic potential (AC oVEMP). However, not all patients with large AC oVEMPs have SCD. This retrospective study sought to identify alternate diagnoses also producing enlarged AC oVEMPs and investigated bone-conducted (BC) oVEMP outcome measures that would help differentiate between these, and cases of SCD. Methods: We reviewed the clinical records and BC oVEMP results of 65 patients (86 ears) presenting with dizziness or balance problems who underwent CT imaging to investigate enlarged 105 dB nHL click AC oVEMP amplitudes. All patients were tested with BC oVEMPs using two different stimuli (1 ms square-wave pulse and 8 ms 125 Hz sine wave). Logistic regression and odds ratios were used to determine the efficacy of BC oVEMP amplitudes and latencies in differentiating between enlarged AC oVEMP amplitudes due to dehiscence from those with an alternate diagnosis. Results: Fifty-three ears (61.6%) with enlarged AC oVEMP amplitudes were identified as having frank dehiscence on imaging; 33 (38.4%) had alternate diagnoses that included thinning of the bone covering (near dehiscence, n = 13), vestibular migraine (n = 12 ears of 10 patients), enlarged vestibular aqueduct syndrome (n = 2) and other causes of recurrent episodic vertigo (n = 6). BC oVEMP amplitudes of dehiscent and non-dehiscent ears were not significantly different (p > 0.05); distributions of both groups overlapped with the range of healthy controls. There were significant differences in BC oVEMP latencies between dehiscent and non-dehiscent ears for both stimuli (p < 0.001). A prolonged n1 125 Hz latency (>11.5 ms) was the best predictor of dehiscence (odd ratio = 27.8; 95% CI:7.0-111.4); abnormal n1 latencies were identified in 79.2% of ears with dehiscence compared with 9.1% of ears without dehiscence. Conclusions: A two-step protocol of click AC oVEMP amplitudes and 125 Hz BC oVEMP latency measures optimizes the specificity of VEMP testing in SCD.

The neuro-otology of Susac syndrome.

OBJECTIVE: We characterised the clinical and neuro-otological characteristics of patients with Susac syndrome. METHODS: The medical records of 30 patients with Susac syndrome were reviewed for details of their clinical presentation and course, neuro-otological symptoms, investigation results including audiology and vestibular function tests, treatment and outcomes. RESULTS: Our findings demonstrate that 29 of our 30 patients with Susac syndrome developed neuro-otological symptoms such as hearing loss, disequilibrium, tinnitus or vertigo during their disease course. Hearing loss was the most common neuro-otological symptom occurring in 93% of patients. A rising configuration of low-frequency greater than the high-frequency sensorineural hearing loss was the most characteristic finding on audiological testing (37% of reviewed audiograms). Disproportionately poor speech discrimination was identified in 20% of cases, and one case demonstrated a retrocochlear pattern on electrophysiological testing. Four patients required hearing aids and a further two patients required a cochlear implant due to severe hearing loss. Two out of two treated patients had improvements in hearing after the prompt administration of corticosteroids, indicating the potential for recoverable hearing loss if relapses are treated early. Effects on vestibular function were variable in ten patients who were tested, with most showing preservation of function despite significant hearing loss. CONCLUSIONS: Neuro-otological symptoms in Susac syndrome are almost universal. In the correct clinical context, a rising configuration of low to high-frequency sensorineural hearing loss should prompt consideration of Susac syndrome. Treatment of inner ear symptoms in Susac syndrome requires further research as early immunotherapy may be beneficial.

Bone-conducted vestibular and stretch reflexes in human neck muscles.

In normal humans, tapping the forehead produces a neck muscle reflex that is used clinically to test vestibular function, the cervical vestibular evoked myogenic potential (cVEMP). As stretch receptors can also be activated by skull taps, we investigated the origin of the early and late peaks of the bone-conducted cVEMP. In twelve normal participants, we differentially stimulated the vestibular and neck stretch receptors by applying vibration to the forehead (activating both vestibular and stretch receptors) and to the sternum (activating mainly stretch receptors). Patients with bilateral vestibulopathy (BVP; n = 26) and unilateral vestibular loss (uVL; n = 17) were also investigated for comparison. Comparison of peaks in normal subjects suggested that the early peaks were vestibular-dependent, while the later peaks had mixed vestibular and stretch input. The late peaks were present but small (1.1 amplitude ratio) in patients with BVP and absent VEMPs, confirming that they do not strictly depend on vestibular function, and largest in age-matched controls (1.5 amplitude ratio, p = 0.049), suggesting that there is an additional vestibular reflex at this latency (approx. 30 ms). Patients with uVL had larger late peaks on the affected than the normal side (1.4 vs 1.0 amplitude ratio, p = 0.034). The results suggest that the early responses in SCM to skull vibration in humans are vestibular-dependent, while there is a late stretch reflex bilaterally and a late vestibular reflex in the contralateral muscle.

Head impulse compensatory saccades: Visual dependence is most evident in bilateral vestibular loss.

The normal vestibulo-ocular reflex (VOR) generates almost perfectly compensatory smooth eye movements during a 'head-impulse' rotation. An imperfect VOR gain provokes additional compensatory saccades to re-acquire an earth-fixed target. In the present study, we investigated vestibular and visual contributions on saccade production. Eye position and velocity during horizontal and vertical canal-plane head-impulses were recorded in the light and dark from 16 controls, 22 subjects after complete surgical unilateral vestibular deafferentation (UVD), eight subjects with idiopathic bilateral vestibular loss (BVL), and one subject after complete bilateral vestibular deafferentation (BVD). When impulses were delivered in the horizontal-canal plane, in complete darkness compared with light, first saccade frequency mean(SEM) reduced from 96.6(1.3)-62.3(8.9) % in BVL but only 98.3(0.6)-92.0(2.3) % in UVD; saccade amplitudes reduced from 7.0(0.5)-3.6(0.4) ° in BVL but were unchanged 6.2(0.3)-5.5(0.6) ° in UVD. In the dark, saccade latencies were prolonged in lesioned ears, from 168(8.4)-240(24.5) ms in BVL and 177(5.2)-196(5.7) ms in UVD; saccades became less clustered. In BVD, saccades were not completely abolished in the dark, but their amplitudes decreased from 7.3-3.0 ° and latencies became more variable. For unlesioned ears (controls and unlesioned ears of UVD), saccade frequency also reduced in the dark, but their small amplitudes slightly increased, while latency and clustering remained unchanged. First and second saccade frequencies were 75.3(4.5) % and 20.3(4.1) %; without visual fixation they dropped to 32.2(5.0) % and 3.8(1.2) %. The VOR gain was affected by vision only in unlesioned ears of UVD; gains for the horizontal-plane rose slightly, and the vertical-planes reduced slightly. All head-impulse compensatory saccades have a visual contribution, the magnitude of which depends on the symmetry of vestibular-function and saccade latency: BVL is more profoundly affected by vision than UVD, and second saccades more than first saccades. Saccades after UVD are probably triggered by contralateral vestibular function.

Vestibular-Evoked Myogenic Potential Testing in Vestibular Localization and Diagnosis.

Vestibular-evoked myogenic potentials (VEMPs) are short-latency, otolith-dependent reflexes recorded from the neck and eye muscles. They are widely used in neuro-otology clinics as tests of otolith function. Cervical VEMPs are recorded from the neck muscles and reflect predominantly saccular function, while ocular VEMPs are reflexes of the extraocular muscles and reflect utricular function. They have an important role in the diagnosis of superior canal dehiscence syndrome and provide complementary information about otolith function that is useful in the diagnosis of other vestibular disorders. Like other evoked potentials, they can provide important localizing information about lesions that may occur along the VEMP pathway. This review will describe the VEMP abnormalities seen in common disorders of the vestibular system and its pathways.

Evidence of a Vestibular Origin for Crossed-Sternocleidomastoid Muscle Responses to Air-Conducted Sound.

OBJECTIVES: Small, excitatory surface potentials can sometimes be recorded from the contralateral sternocleidomastoid muscle (SCM) following monaural acoustic stimulation. Little is known about the physiological properties of these crossed reflexes. In this study, we sought the properties of crossed SCM responses and through comparison with other cochlear and vestibular myogenic potentials, their likely receptor origin. DESIGN: Surface potentials were recorded from the ipsilateral and contralateral SCM and postauricular (PAM) muscles of 11 healthy volunteers, 4 patients with superior canal dehiscence and 1 with profound hearing loss. Air-conducted clicks of 105 dB nHL and tone bursts (250 to 4000 Hz) of 100 dB nHL were presented monaurally through TDH 49 headphones during head elevation. Click-evoked responses were recorded under two conditions of gaze in random order: gaze straight ahead and rotated hard toward the contralateral recording electrodes. Amplitudes (corrected and uncorrected) and latencies for crossed SCM responses were compared with vestibular (ipsilateral SCM) and cochlear (PAM) responses between groups and across the different recording conditions. RESULTS: Surface waveforms were biphasic; positive-negative for the ipsilateral SCM, and negative-positive for the contralateral SCM and PAM. There were significant differences in the amplitudes and latencies (p = 0.004) for click responses of healthy controls across recording sites. PAM responses had the largest mean-corrected amplitudes (2.3 ± 2.8) and longest latencies (13.0 ± 1.2 msec), compared with ipsilateral (1.6 ± 0.5; 12.0 ± 0.7 msec) and contralateral (0.8 ± 0.3; 10.4 ± 1.0 msec) SCM responses. Uncorrected amplitudes and muscle activation for PAM increased by 104.4% and 46.8% with lateral gaze respectively, whereas SCM responses were not significantly affected. Click responses of patients with superior canal dehiscence followed a similar latency, amplitude, and gaze modulation trend as controls. SCM responses were preserved in the patient with profound hearing loss, yet all PAM were absent. There were significant differences in the frequency tuning of the three reflexes (p < 0.001). Tuning curves of healthy controls were flat for PAM and down sloping for ipsilateral and contralateral SCM responses. For superior canal dehiscence, they were rising for PAM and slightly down sloping for SCM responses. CONCLUSIONS: Properties of crossed SCM responses were similar, though not identical, to those of ipsilateral SCM responses and are likely to be predominantly vestibular in origin. They are unlikely to represent volume conduction from the PAM as they were unaffected by lateral gaze, were shorter in latency, and had different tuning properties. The influence of crossed vestibulo-collic pathways should be considered when interpreting cervical vestibular-evoked myogenic potentials recorded under conditions of binaural stimulation.

The human vestibulo-ocular reflex and saccades: normal subjects and the effect of age.

Here we characterize in 80 normal subjects (16-84 yr (means ± SD, 47 ± 19 yr) the vestibulo-ocular reflex (VOR) and saccades in response to three-dimensional head impulses with a monocular video head impulse test (vHIT) of the right eye. Impulses toward the right lateral, right anterior, and left posterior canals (means: 0.98, 0.91, 0.79) had slightly higher mean gains compared with their counterparts (0.95, 0.86, 0.76). In the older age group (>60 yr), gains of the left posterior canal dropped 0.09 and left anterior canals rose 0.09 resulting in symmetry. All canal gains reduced with increasing head velocity (0.02-0.13 per 100°/s). Comparison of lateral canal gains calculated using five published algorithms yielded lower values (~0.80) when a narrow detection window was used. Low-amplitude refixation saccades (amplitude: 1.11 ± 0.98°, peak velocity: 63.9 ± 34.0°/s at 262.0 ± 93.9 ms) were observed among all age groups (frequency: 40.2 ± 23.4%), increasing in amplitude, peak velocity, and frequency in older subjects. Impulses toward anterior canals showed the least frequent saccades and lateral and posterior canals were similar, but lateral canal impulses showed the smallest saccades and the posterior canal showed the largest saccades. Saccade peak-velocity approximate amplitude "main sequence" slope was steeper for the horizontal canals compared with the vertical planes (60 vs. <40°/s per 1°). In summary, we found small but significant asymmetries in monocular vHIT gain that changed with age. Healthy subjects commonly have minuscule refixation saccades that are moderately to strongly correlated with vHIT gain. NEW & NOTEWORTHY Gaze fixation is normally stabilized during rapid "head-impulse" movements by the bisynaptic vestibulo-ocular reflex (VOR), but earlier studies of normal subjects also report small amplitude saccades. We found that with increased age of the subject the vertical VOR became more variable, while in all semicircular canal directions the saccade frequency, amplitude, and peak velocity increased. We also found that the VOR gain algorithm significantly influences values.

Video Head Impulse Testing.

The bedside head impulse, first described nearly 20 years ago, is the single most useful clinical test of the human vestibulo-ocular reflex (VOR). The video head impulse test (vHIT), its laboratory counterpart, now enables the objective assessment of the VOR. We examine how the vHIT can be utilized in three common clinical scenarios: the acute vestibular syndrome, recurrent spontaneous vertigo, and chronic imbalance. Combined with vestibular evoked myogenic potentials (VEMPs), vHIT enables assessment of all five vestibular end-organs by a clinician within the clinic itself.

Otolith Function Testing.

Two technically simple tests, vestibular evoked myogenic potential (VEMP) and subjective visual vertical/horizontal (SVV/H) test, have the potential to transform otolith function testing from the research laboratory to the outpatient clinic. Cervical- and ocular-VEMPs are short latency surface potentials produced through the activation of saccular and utricular afferents by sound and vibration. They are tests of dynamic otolith function. The SVV/H test in peripheral lesions probes static asymmetries in utricular function and represents a perceptual error in perceived gravitational vertical/horizontal. VEMPs and SVV/H enable the characterization of patterns and severity of otolith dysfunction in common vestibular disorders. Combined with tests of semicircular canal function, they provide a useful tool for eliciting diagnostic profiles in vestibular neuritis and Ménière's disease. VEMPs are valuable in the pre-surgical confirmation of superior semicircular canal dehiscence and in some cases, may alert the clinician to the presence of a vestibular schwannoma in patients with symmetrical hearing.

Vestibular-Evoked Myogenic Potentials in Bilateral Vestibulopathy.

Bilateral vestibulopathy (BVP) is a chronic condition in which patients have a reduction or absence of vestibular function in both ears. BVP is characterized by bilateral reduction of horizontal canal responses; however, there is increasing evidence that otolith function can also be affected. Cervical and ocular vestibular-evoked myogenic potentials (cVEMPs/oVEMPs) are relatively new tests of otolith function that can be used to test the saccule and utricle of both ears independently. Studies to date show that cVEMPs and oVEMPs are often small or absent in BVP but are in the normal range in a significant proportion of patients. The variability in otolith function is partly due to the heterogeneous nature of BVP but is also due to false negative and positive responses that occur because of the large range of normal VEMP amplitudes. Due to their variability, VEMPs are not part of the diagnosis of BVP; however, they are helpful complementary tests that can provide information about the extent of disease within the labyrinth. This article is a review of the use of VEMPs in BVP, summarizing the available data on VEMP abnormalities in patients and discussing the limitations of VEMPs in diagnosing bilateral loss of otolith function.