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• Transcranial oscillatory currents may stimulate the vestibular cortex in the range of its physiological activity (1 or 2 Hz) • Induced behavioral effects (motion sickness and postural sways) are not due to a peripheral spread of the current towards vestibular receptors. • Motion sickness represents a previously neglected possible side effect of slow-frequency tACS. The vestibular cortex is a multisensory associative region that, in neuroimaging investigations, is activated by slow-frequency (1–2 Hz) galvanic stimulation of peripheral receptors. We aimed to directly activate the vestibular cortex with biophysically modeled transcranial oscillatory current stimulation (tACS) in the same frequency range. Thirty healthy subjects and one rare patient with chronic bilateral vestibular deafferentation underwent, in a randomized, double-blind, controlled trial, to tACS at slow (1 or 2 Hz) or higher (10 Hz) frequency and sham stimulations, over the Parieto-Insular Vestibular Cortex (PIVC), while standing on a stabilometric platform. Subjective symptoms of motion sickness were scored by Simulator Sickness Questionnaire and subjects' postural sways were monitored on the platform. tACS at 1 and 2 Hz induced symptoms of motion sickness, oscillopsia and postural instability, that were supported by posturographic sway recordings. Both 10 Hz-tACS and sham stimulation on the vestibular cortex did not affect vestibular function. As these effects persisted in a rare patient with bilateral peripheral vestibular areflexia documented by the absence of the Vestibular-Ocular Reflex, the possibility of a current spread toward peripheral afferents is unlikely. Conversely, the 10 Hz-tACS significantly reduced his chronic vestibular symptoms in this patient. Weak electrical oscillations in a frequency range corresponding to the physiological cortical activity of the vestibular system may generate motion sickness and postural sways, both in healthy subjects and in the case of bilateral vestibular deafferentation. This should be taken into account as a new side effect of tACS in future studies addressing cognitive functions. Higher frequencies of stimulation applied to the vestibular cortex may represent a new interventional option to reduce motion sickness in different scenarios. [ABSTRACT FROM AUTHOR]

• In unoperated vestibular schwannoma, ipsilesional canals show decreased vestibulo-ocular reflex (VOR) gain and increased saccade amplitude and frequency. • One week after unilateral vestibular deafferentation lesioned canal gains drop by 0.22–0.35 and first saccade frequency and amplitudes increase by 37% and 2.9°. • The video head-impulse test excitation/dis-facilitation VOR asymmetry is less for the intact posterior canal than for the other canals. To examine the vestibulo-ocular reflex (VOR) and compensatory-saccades before and after complete unilateral vestibular deafferentation (UVD). Forty patients were studied before and after surgery for vestibular or facial schwannoma using the video head-impulse test (vHIT) and multivariable regression. 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. 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. Saccade compensation from surgical UVD is near complete by one-week. [ABSTRACT FROM AUTHOR]

• Vestibulo-collic reflex and linear vestibulo-ocular reflex pathways may be affected in the early period of multiple sclerosis. • Linear vestibulo-ocular reflex is more affected than vestibulo-collic reflex in pediatric-onset multiple sclerosis. • Vestibular myogenic potential abnormalities confirm central involvement in pediatric-onset multiple sclerosis. This study aimed to examine the vestibulo-collic reflex (VCR) and linear vestibulo-ocular reflex (lVOR) and their correlation with brain lesions in pediatric-onset multiple sclerosis (POMS). The study group consisted of 17 patients (34 ears) with POMS (mean age 18.73 ± 2.02, mean age at disease onset 14.64 ± 1.36 years), and the control group included 11 age-matched healthy subjects (22 ears). Ocular and cervical Vestibular Evoked Myogenic Potentials (oVEMP and cVEMP) were performed to assess IVOR and VCR pathways. Magnetic Resonance Imaging was evaluated in the study group. In the POMS group, 47.05 % of oVEMPs and 17.64 % of the cVEMPs were abnormal, while all VEMPs were normal in the control group. The oVEMP amplitude was associated with infratentorial lesion volume (r = −0.459, p = 0.01) and total lesion volume of the brainstem and cerebellum (r = −0.450, p = 0.01). The cVEMP asymmetry ratio was correlated with the deep white matter lesion volume (r = 0.683, p < 0.001). The MVEMP scores were found to correlate only with lesion volumes in the cerebellum (r = 0.488, p = 0.04) and infratentorial region (r = 0.573, p = 0.01). Ocular and cervical VEMP abnormalities confirm that lVOR and VCR pathways may be affected in early POMS. Routine use of the VEMP test, especially the oVEMP test is recommended as a useful tool in the follow-up of POMS patients. [ABSTRACT FROM AUTHOR]

• Video Head Impulse tests of the vestibulo-ocular reflex (VOR) provided the best separation of vestibular neuritis (VN) from posterior circulation stroke (PCS). • Refixation saccade-analysis complemented VOR gain measures in differentiating VN from PCS. • Ocular VEMP (oVEMP) asymmetry demonstrated low sensitivity but high specificity as a marker of VN. To separate vestibular neuritis (VN) from posteriorcirculation stroke (PCS) using quantitative tests of canal and otolith function. Video Head-Impulse tests (vHIT) were used to assess all three semicircular canal pairs; vestibulo-ocular reflex (VOR) gain and saccade metrics were examined. Cervical and ocular-Vestibular-Evoked Myogenic Potentials (c- and oVEMP) and Subjective Visual Horizontal (SVH) were used to assess otolith function. For controls (n = 40), PCS (n = 22), and VN (n = 22), mean horizontal-canal VOR-gains were 0.96 ± 0.1, 0.85 ± 0.3 and 0.40 ± 0.2, refixation-saccade prevalence was 71.9 ± 41, 90.7 ± 57, 209.2 ± 62 per 100 impulses and cumulative-saccade amplitudes were 0.9 ± 0.4°, 2.4 ± 2.2°, 8.0 ± 3.5°. Abnormality-rates for cVEMP, oVEMP and SVH were 38%, 9%, 72% for PCS, and 43%, 50%, 91% for VN. A gain ≤0.68, refixation-saccade prevalence of ≥135% and cumulative-saccade amplitudes ≥5.3° separated VN from PCS with sensitivities of 95.5%, 95.5%, and 81.8%, and specificities of 68.2%, 86.4% and 95.5%. VOR-gain and saccade prevalence when combined, separated VN from PCS with a sensitivity and specificity of 90.9%. Abnormal oVEMP asymmetry-ratios were of low sensitivity (50%) but high specificity (90.9%) for separating VN from PCS. vHIT provided the best separation of VN from PCS. VOR-gain, refixation-saccade prevalence and amplitude were effective discriminators of VN from PCS. vHIT and oVEMP could assist early identification of the aetiology of Acute Vestibular Syndrome in the Emergency Room. [ABSTRACT FROM AUTHOR]

• There is a quantifiable vestibulo-ocular reflex suppression (VORS) measured using video head impulse test devices. • Visually enhanced vestibulo-ocular reflex and VORS test responses depend on head oscillation frequency. • Participant concentration during VORS testing has significant effect VORS magnitude. To investigate the main effects of some testing and analysis variables on clinically quantified visually enhanced vestibulo-ocular reflex (VVOR) and vestibulo-ocular reflex suppression (VORS) results using video head impulse test. This prospective observational clinical study included 19 healthy participants who underwent the VVOR and VORS tests. The effect of demographic variables, head oscillation frequency, rotation direction, visual acuity and analysis time window width and location of the recorded tests on the quantified results of both VVOR and VORS were evaluated. And specifically, for the VORS test the effect of cognitive reinforcement of the participant during testing was evaluated. A statistically significant difference was observed among the VVOR, non-reinforced VORS, and reinforced VORS tests for mean gain values of 0.91 ± 0.09, 0.6 ± 0.15, and 0.57 ± 0.16, respectively (p < 0.001). The optimized linear mixed-effect model showed a significant influence of frequency on the gain values for the reinforced and non-reinforced VORS tests (p = 0.01 and p = 0.004, respectively). Regarding the gain analysis method, statistically significant differences were found according to the short time interval sample location of the records for the initial location of the VVOR test (p < 0.006) and final location of the reinforced VORS test (p < 0.023). Significant differences were observed in the gain values according to VVOR and VORS testing. Head oscillation frequency is a significant factor that affects the gain values, especially in VORS testing. Moreover, in VORS testing, participant concentration has a significant effect on the test for obtaining suppression gain values. When a short time interval sample is considered for VVOR and VORS testing, intermediate time samples appear the most adequate for both tests. The quantified visually enhanced vestibulo-ocular reflex (VVOR) and vestibulo-ocular reflex suppression (VORS) tests have recently been added to the assortment of available clinical vestibular tests. However, despite the clinical validity of these quantified tests that appear to be of increasing clinical interest, the effects of most of the clinical testing methods and mathematical variables are not well defined. In this research we describe what are the main collecting and analysis variables that could influence to the VVOR and VORS tests. Specially for VORS test, participant concentration on test tasks will have positive effect on the measured vestibulo-ocular reflex (VOR) suppression. [ABSTRACT FROM AUTHOR]

• Cervical and ocular vestibular evoked myogenic potentials (cVEMPs, oVEMPs) in almost all cases of vestibular involvement can help both in diagnosis and in prognosis. • More research is needed to understand the applications of both c- and oVEMPs, especially the latter. • A significant percentage of published data have neglected one or more vital VEMP parameters. Cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs respectively) are now used by an increasing number of laboratories to evaluate otolith inner ear function and their pathways through the central nervous system. However, the literature is incomplete or unclear as to what information both c- and oVEMPs can add beyond what a good clinical examination can provide, and what other paramedical tests can provide also, and the present review aims to clarify what is known so far. The following review will describe what is known with regards to both c- and oVEMPs and their use. MEDLINE (accessed by PubMed, years 1994–2018) was searched with the following string: ("vestibular evoked myogenic potentials" [all fields]). Only articles published in English were evaluated. Both c- and oVEMPs are useful not only for confirming the presence of superior semicircular canal dehiscence (SSCD), but also for confirming the presence of acoustic neuromas when MRI is not available, bilateral vestibulopathies, inferior vestibular neuritis and vestibular dysfunction in inherited neuropathies. Further work is required, especially with respect to oVEMPs. The usefulness of both c- and oVEMPs goes beyond the confirmation of SSCDs, and is useful in many clinical cases. [ABSTRACT FROM AUTHOR]

• Repetitive oVEMPs reliably differentiate MG patients from controls. • Inferior oblique muscle recordings at 30 Hz were most sensitive and specific. • At higher repetition rates, the decrement occurred with later stimulus repetitions. To determine the most effective stimulation parameters for the diagnosis of ocular myasthenia gravis (MG) using repetitive ocular vestibular evoked myogenic potentials (oVEMP) for quantification of the extraocular muscle response decrement. Repetitive bone-conducted oVEMPs were elicited in 18 MG patients and 20 healthy subjects. We compared four different stimulus repetition rates (20 Hz, 30 Hz, 40 Hz, 50 Hz) and 100 Hz continuous stimulation, as well as recordings from the inferior oblique muscles and the lateral rectus muscles to determine the most sensitive and specific oVEMP parameters for decrement detection. Repetitive stimulation at all tested repetition rates with recordings from inferior oblique muscles allowed for effective differentiation between MG patients and healthy subjects. Among all repetition rates, 30 Hz showed a trend towards superiority, with a sensitivity of 71% and a specificity of 94% (area under the curve (AUC) 0.88) when using the smaller decrement of the two eyes and −10% as cutoff. Considering the larger decrement for analysis (−9% as cutoff), sensitivity increased to 82%, but specificity decreased to 78% (AUC 0.81). Our study demonstrates, that repetitive oVEMP stimulation elicits a robust decrement in the inferior oblique muscles of MG patients at repetition rates between 20 Hz and 50 Hz, with a probable optimum at 30 Hz. Repetitive inferior oblique oVEMP stimulation with optimal stimulus parameters facilitates early and accurate diagnosis of ocular MG. [ABSTRACT FROM AUTHOR]

Objective It has long been suggested that antivertiginous medications exert their symptomatic effect through inhibition of the vestibulo-ocular reflex (VOR). We tested this hypothesis by directly measuring the VOR after administration of three agents from different substance classes: an antihistamine, a benzodiazepine and a calcium channel antagonist. Methods The gain and the variability of the high velocity VOR was assessed using video head impulses (vHIT) under the following conditions: baseline, after dimenhydrinate, after diazepam and after cinnarizine. Results We found that all three medications did not change any VOR gain or variability parameter: At 60 ms, the gain was 0.95 at baseline, 0.99 under dimenhydrinate, 0.99 under diazepam and 0.96 under cinnarizine. The gain variability across repetitive head impulses remained also uninfluenced. Conclusions The human high frequency VOR remains robust to pharmacological perturbations at common clinical doses and the assumption that symptomatic vertigo relief is achieved merely through impairment of the VOR requires re-examination. Significance Alternative mechanisms of pharmacological action might be operant, such as the modulation of vestibulo-cortical pathways, a differential effect on the low frequency VOR and an altered sensitivity to drugs in acute unilateral vestibulopathy. [ABSTRACT FROM AUTHOR]

Objective The staging system of Meniere’s disease utilizes audiograms to probe cochlear dysfunction. We explored the addition of galvanic vestibular-evoked myogenic potentials (VEMP) to further explore vestibular function. Methods Seventy patients with unilateral Meniere’s disease were enrolled in this study. Within 2 weeks of diagnosis, all subjects underwent pure tone audiometry, cervical and ocular VEMP, and caloric test. The prevalence of abnormal tests and the VEMP characteristic parameters such as latencies and amplitudes were analyzed. Results In affected ears, the abnormal rate of acoustic cVEMPs, galvanic cVEMPs, vibratory oVEMPs and galvanic oVEMPs was 37%, 17%, 20%, and 9%, respectively. No significant differences existed in VEMP latencies and amplitudes between affected ears and unaffected ears. Conclusions The impairment of otolithic organs was found to be more than that of vestibular afferents. The deterioration of the saccule was more than that of the utricle, whereas retrolabyrinthine degeneration of sacculo-collic reflex and vestibulo-ocular reflex was similar. Significance This study is the first to use an electrophysiological test to evaluate the retrolabyrinthine function of patients with unilateral Meniere’s disease. [ABSTRACT FROM AUTHOR]

Objective This study investigated the effect of betel nut chewing on the otolithic reflex system. Methods Seventeen healthy volunteers without any experience of chewing betel nut (fresh chewers) and 17 habitual chewers underwent vital sign measurements, ocular vestibular-evoked myogenic potential (oVEMP), and cervical VEMP (cVEMP) tests prior to the study. Each subject then chewed two pieces of betel nut for 2 min (dosing). The same paradigm was repeated immediately, 10 min, and 20 min after chewing. On a different day, 10 fresh chewers masticated chewing gum as control. Results Fresh chewers exhibited significantly decreased response rates of oVEMP (53%) and cVEMP (71%) after dosing compared with those from the predosing period. These abnormal VEMPs returned to normal 20 min after dosing. In contrast, 100% response rates of oVEMP and cVEMP were observed before and after masticating chewing gum. In habitual chewers, the response rates of oVEMP and cVEMP were 32% and 29%, respectively, 20 min after dosing. Conclusion Chewing betel nuts induced a transient loss of the otolithic reflexes in fresh chewers but may cause permanent loss in habitual chewers. Significance Chewing betel nuts can cause a loss of otholitic reflex function. This creates a risk for disturbed balance and malfunction, for instance, during driving. [ABSTRACT FROM AUTHOR]

Several types of acoustic stimulation (i.e. tone bursts or clicks), bone-conducted vibration, forehead taps, and galvanic stimulation elicit myogenic potentials. These can be recorded in cervical and ocular muscles, the so called vestibular evoked myogenic potentials (VEMPs). The cervical VEMP (cVEMP) resembles the vestibulo-collic reflex and the responses can be recorded from the ipsilateral sternocleidomastoid muscle. The ocular VEMP resembles the vestibulo-ocular reflex and can be recorded from extra-ocular muscles by a surface electrode beneath the contralateral infraorbital margin. Initially, the literature concerning VEMPs was limited to peripheral vestibular disorders, however, the field of VEMP testing is rapidly expanding, with an increasing focus on central neurological disorders. The current literature concerning VEMP abnormalities in central neurological disorders is critically reviewed, especially regarding the methodological aspects in relation to quality as well as the clinical interpretation of the VEMP results. Suggestions for further research are proposed as well as some clinically useful indications. [ABSTRACT FROM AUTHOR]

Objective To study brainstem function in Parkinson’s Disease (PD) at different stages, through a battery of vestibular-evoked myogenic potentials (VEMPs) and compare the results with scores on clinical scales assessing the presence of symptoms linked to brainstem involvement. Methods Cervical, masseter and ocular VEMPs were recorded in patients with early PD ( n = 14, disease duration 1.42 ± 0.7 years), advanced PD ( n = 19, disease duration 7.26 ± 2.9 years) and in 27 age-matched controls. In PD, the following clinical scales were administered: Mini-BESTest, REM sleep Behavior Disorder Screening Questionnaire (RBD-SQ), PD Sleep Scale, Epworth Sleepiness Scale and Geriatric Depression Scale. Results Rate of VEMPs alterations was higher ( p < 0.001) in PD than controls, but similar within PD groups. However, early and advanced PD showed a different pattern of abnormalities ( p = 0.02), being latency delay prevalent in the former and absence in the latter. VEMP impairment correlated directly with RBD-SQ scores in both PD cohorts and inversely with Mini-BESTest scores in advanced PD. Conclusions VEMPs displayed progressive severity of alterations at different stages of PD, with remarkable correlations with presence of postural instability and RBD. Significance The combined use of VEMPs may provide interesting insights into the pathophysiological mechanisms of PD at the earliest and prodromal stage of the disease. [ABSTRACT FROM AUTHOR]

Objective We investigated the effect of alcohol on the cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs). As alcohol produces gaze-evoked nystagmus (GEN), we also tested the effect of nystagmus independent of alcohol by recording oVEMPs during optokinetic stimulation (OKS). Methods The effect of alcohol was tested in 14 subjects over multiple rounds of alcohol consumption up to a maximum breath alcohol concentration (BrAC) of 1.5‰ (mean 0.97‰). The effect of OKS was tested in 11 subjects at 5, 10 and 15deg/sec. Results oVEMP amplitude decreased from baseline to the highest BrAC level by 27% (range 5-50%, P<0.001), but there was no significant effect on oVEMP latency or cVEMP amplitude or latency. There was a significant negative effect of OKS on oVEMP amplitude (16%, P=0.006). Conclusions We found a selective effect of alcohol on oVEMP amplitude, but no effect on the cVEMP. Vertical nystagmus elicited by OKS reduced oVEMP amplitude. Significance Alcohol selectively affects oVEMP amplitude. Despite the effects of alcohol and nystagmus, both reflexes were reliably recorded in all subjects and conditions. An absent response in a patient affected by alcohol or nystagmus indicates a vestibular deficit. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The ocular vestibular evoked myogenic potential (oVEMP) is a vestibular reflex recorded from the inferior oblique (IO) muscles, which increases in amplitude during eye elevation. We investigated whether this effect of gaze elevation could be explained by movement of the IO closer to the recording electrode. Methods: We compared oVEMPs recorded with different gaze elevations to those recorded with constant gaze position but electrodes placed at increasing distance from the eyes. oVEMPs were recorded in ten healthy subjects using bursts of skull vibration. Results: oVEMP amplitude decreased more with decreasing gaze elevation (9μV from 24° up to neutral) than with increasing electrode distance (2.7μV from baseline to 6.4mm; P <0.005). The oVEMP recorded with gaze 24° down had delayed latency (by 4.5ms). Conclusion: The effect of gaze elevation on the oVEMP cannot be explained by changes in position of the muscle alone and is likely mainly due to increased tonic contraction of the IO muscle in up-gaze. The oVEMP recorded in down-gaze (when the IO is inactivated, but the IR activated) likely originates in the adjacent IR muscle. Significance: Our results suggest that oVEMP amplitudes in extraocular muscles scale in response to changing tonic muscle activity. [Copyright &y& Elsevier]

Abstract: Objective: This study utilized bone-conducted vibration (BCV) stimuli for eliciting ocular vestibular-evoked myogenic potentials (oVEMPs) to assess the vestibulo-ocular reflex (VOR) system in healthy children and adults. Methods: Fifteen healthy children aged 3–14years and 18 healthy adults aged 24–28years underwent oVEMP testing. Structural factors such as body weight, body height and body mass index were measured for each healthy subject. Results: All healthy children and adults presented clear oVEMPs, bilaterally. The characteristic parameters (latencies and amplitude) of oVEMPs did not significantly differ between children and adults. The mean interaural (y-axis) acceleration magnitudes for eliciting oVEMPs were 0.37±0.12g for children and 0.41±0.20g for adults, a non-significant difference. As stimulation intensity increased stepwise, interaural acceleration magnitude increased correspondingly, leading to early nI latency and large nI–pI amplitude of oVEMPs. However, no structural factor was statistically correlated with interaural acceleration magnitude. Conclusion: When children aged >3years, the simple and quick oVEMP test via BCV stimulation can be used for investigating the integrity of the VOR system, with the characteristic parameters (latencies and amplitude) unaffected by structural factors. Significance: Establishing the norm of oVEMP is essential for diagnosing VOR deficit in children aged >3years. [Copyright &y& Elsevier]

Abstract: Objective: To deduce the connectivity underlying ocular vestibular evoked myogenic potentials (OVEMPs) recorded from two sites and produced by lateral transmastoid stimulation in patients with unilateral vestibular dysfunction. Methods: OVEMPs were recorded using lateral impulsive stimuli delivered by a hand-held minishaker placed at the mastoid. Twelve patients were tested using the typical OVEMP recording montage placed inferior to the eyes. In a subset of 6 patients, recordings were also made using a lateral electrode montage. The majority of patients were tested following surgery for inner ear disease. Patient responses were compared to those in normal subjects under similar recording conditions. Results: For the inferior montage, regardless of which mastoid was stimulated, deficits were observed only from the eye opposite the affected ear. In contrast, OVEMPs recorded using the lateral electrode montage showed changes on both sides. Conclusions: OVEMPs produced using lateral transmastoid stimulation and recorded from beneath the eyes are generated by a crossed vestibulo-ocular pathway while the projections underlying the lateral responses are likely to be bilateral. Significance: The vestibular-ocular connectivity underlying the OVEMPs recorded from inferior and lateral recording sites differs. For clinical use, the inferior recording site is the simplest to interpret. [Copyright &y& Elsevier]

Abstract: Objective: To define the ocular and cervical vestibular evoked myogenic potential (oVEMP and cVEMP) profile in Ménière’s Disease (MD), we studied air-conducted (AC) sound and bone-conducted vibration (BCV)-evoked responses in 77 patients and 35 controls. Methods: oVEMPs were recorded from unrectified infra-orbital surface electromyography (EMG) during upward gaze. cVEMPs were recorded from rectified and unrectified sternocleidomastoid EMG during head elevation against gravity. Responses to AC clicks delivered via headphones and BC forehead taps delivered with a mini-shaker (bone-conduction vibrator) and a triggered tendon-hammer were recorded. Results: In clinically definite unilateral MD (n =60), the prevalence of unilateral VEMP abnormalities was 50.0%, 10.2% and 11.9% for click, minitap and tendon-hammer evoked oVEMPs, 40.0%, 22.8% and 10.7% for click, minitap and tendon-hammer evoked cVEMPs. The most commonly observed profile was abnormality to AC stimulation alone (33.3%), followed by abnormalities to both AC and BCV stimuli (26.7%). Isolated abnormalities to BCV stimuli were rare (5%) and limited to the minitap cVEMP. The prevalence of abnormalities for each of the AC VEMPs was significantly higher than for any one BCV VEMP. For click cVEMP, click oVEMP and minitap cVEMP, average Reflex Asymmetry Ratios (AR) were significantly higher in MD compared with controls. Test results for AC cVEMP, AC oVEMP, minitap cVEMP and caloric asymmetry were significantly correlated with hearing loss. Conclusions: Predominance of abnormalities in oVEMP and cVEMP responses to AC sound is characteristic of MD and indicative of saccular involvement. Significance: This pattern of VEMP abnormalities may enable separation of Ménière’s disease from other peripheral vestibulopathies. [Copyright &y& Elsevier]

Abstract: Objective: We compared vibration-induced ocular vestibular evoked myogenic potentials (OVEMPs) with the visual vertical during whole-body roll tilt and eccentric rotation in healthy subjects and patients with unilateral vestibular loss, to determine which test was most sensitive in discriminating impaired utricle function. Methods: OVEMPs and the visual vertical were measured in 11 patients and 11 healthy subjects. Visual vertical was measured during roll tilts between −9.6° and 9.6°, and during rotation at 400°/s with the head upright and the vertical rotation axis located between ±3.5cm from the head center. Results: OVEMPs in patients were strikingly asymmetric, whereas they were approximately symmetric in healthy subjects. Patients showed impaired visual vertical gain during eccentric rotation and increased errors for both roll tilt and eccentric rotation tests. OVEMPs were superior at discriminating between patients and healthy subjects, although eccentric rotation performed nearly as well. Conclusions: OVEMPs provide a powerful test for discriminating between healthy subjects and patients with chronic unilateral vestibular loss, and testing the visual vertical testing during eccentric rotation was superior to testing during whole-body roll tilt. Significance: OVEMPs are easier to administer, less demanding on patients, and in general are more effective at identifying chronic unilateral vestibular loss than visual vertical measurements. [ABSTRACT FROM AUTHOR]

Abstract: Since the first description of sound-evoked short-latency myogenic reflexes recorded from neck muscles, vestibular evoked myogenic potentials (VEMPs) have become an important part of the neuro-otological test battery. VEMPs provide a means of assessing otolith function: stimulation of the vestibular system with air-conducted sound activates predominantly saccular afferents, while bone-conducted vibration activates a combination of saccular and utricular afferents. The conventional method for recording the VEMP involves measuring electromyographic (EMG) activity from surface electrodes placed over the tonically-activated sternocleidomastoid (SCM) muscles. The “cervical VEMP” (cVEMP) is thus a manifestation of the vestibulo-collic reflex. However, recent research has shown that VEMPs can also be recorded from the extraocular muscles using surface electrodes placed near the eyes. These “ocular VEMPs” (oVEMPs) are a manifestation of the vestibulo-ocular reflex. Here we describe the historical development and neurophysiological properties of the cVEMP and oVEMP and provide recommendations for recording both reflexes. While the cVEMP has documented diagnostic utility in many disorders affecting vestibular function, relatively little is known as yet about the clinical value of the oVEMP. We therefore outline the known cVEMP and oVEMP characteristics in common central and peripheral disorders encountered in neuro-otology clinics. [Copyright &y& Elsevier]

Abstract: Objective: To better characterize both ocular and cervical vestibular evoked myogenic potentials (VEMP) responses at different frequencies of sound in 20 normal subjects. Methods: Cervical and ocular VEMPs were recorded. The intensities of sound stimulation decreased from the maximal intensity, until no responses were evoked. Thresholds, amplitudes, latencies and interaural amplitude difference ratio (IADR) at the maximal stimulation were calculated. Results: Both tests showed the similar frequency tuning, with the lowest threshold and highest amplitude for 500-Hz tone-burst stimuli. Sound stimulation at 500Hz showed the response rates of 100% in both tests. Cervical VEMPs showed higher incidence than ocular VEMPs. Ocular VEMP thresholds were significantly higher than those of cervical VEMP. Cervical VEMP amplitudes were significantly higher than ocular VEMP amplitudes. IADRs of ocular and cervical VEMPs did not differ significantly. Conclusions: Ocular VEMP showed the similar frequency tuning to cervical VEMP. Cervical VEMP responses showed higher incidence, lower thresholds and larger amplitudes than ocular VEMP. Significance: Cervical VEMP is a more reliable measure than ocular VEMP, though the results of both tests will be complementary. Five hundred Hertz is the optimal frequency to use. [Copyright &y& Elsevier]

Abstract: Objective: This study compared the results of combined and individual ocular vestibular-evoked myogenic potential (oVEMP) and cervical VEMP (cVEMP) tests in healthy subjects and patients with unilateral vestibular hypofunction to confirm the effectiveness of the combined oVEMP and cVEMP test. Methods: Twenty healthy volunteers and 12 patients with unilateral vestibular hypofunction underwent individual oVEMP and cVEMP tests in a random order, and combined oVEMP and cVEMP test on another day. Results: Twenty healthy subjects had 100% response rates for oVEMPs and cVEMPs in both individual and combined stimulation modes. Significant positive correlations exist between individual and combined oVEMPs/cVEMPs in terms of latencies and amplitudes. In 12 patients with unilateral vestibular hypofunction, differences in abnormal percentages of oVEMPs or cVEMPs were non-significant. Additionally, the characteristic parameters of oVEMP/cVEMP among ears of healthy subjects, good and pathological ears of patients with unilateral vestibular hypofunction did not differ significantly, regardless of whether the individual or combined mode was used. Conclusions: The combined oVEMP and cVEMP test generates similar information to that obtained by individual mode, regardless of whether subjects are healthy or have unilateral vestibular hypofunction. Significance: Simultaneous oVEMP and cVEMP tests may be a convenient screening tool for assessing crossed vestibulo-ocular reflex and ipsilateral sacculo-collic reflex, which definitely shortens the diagnostic test time. Thus, it may favor the large diffusion of these techniques. [Copyright &y& Elsevier]

Abstract: Objective: To assess the effects of vertical and horizontal gaze, head rotation, body position, and vision on the ocular vestibular evoked myogenic potential (OVEMP) produced by air-conducted (AC) sound. Methods: Ten normal subjects were stimulated by 500Hz 2ms AC tone bursts at 136–142dB peak SPL. OVEMPs were recorded from electrodes placed beneath the eyes. Angles of vertical gaze ranged from maximal downward to upward gaze in increments of 5–10°. Horizontal gaze was measured during elevation and ranged from 20° adduction to 20° abduction. Results: Increasing vertical gaze increased OVEMP amplitude, especially for the contralateral eye (neutral vs maximal upward gaze; contra: 1.0 vs 2.6μV; ipsi: 0.8 vs 0.9μV; P <0.001). OVEMPs from the contralateral eye peaked significantly earlier in the upward gaze positions (contra: 9.2ms; ipsi: 10.4ms; P <0.001), but peaked later during downward gaze (contra: 14.2ms; ipsi: 11.4ms; P =0.014). There were small effects of horizontal gaze and supine body position, but no effects of head rotation or vision. Conclusions: OVEMP amplitudes are strongly modulated by gaze position. Truncal position also affects OVEMP amplitude. Significance: This study quantifies the effect of gaze on the OVEMP and demonstrates the importance of controlling for gaze in clinical and experimental studies. [Copyright &y& Elsevier]

Abstract: Objective: This study compared ocular vestibular-evoked myogenic potentials (oVEMPs) in children and adults using air conducted sound stimulation to determine when oVEMP characteristic parameters in children reach adult levels. The relationships between oVEMP characteristics and structural factors were also investigated. Methods: In total, 15 healthy children (aged 3–13years) and 15 healthy adults (aged 24–33years) underwent a combined oVEMP and cVEMP test under 105dBnHL acoustic stimulation. Results: Mean nI latency, pI latency, nI–pI interval and amplitude of oVEMPs of children did not differ significantly from those of adults. In contrast to oVEMPs, a significant difference in p13 cVEMP latency existed between children and adults. Correlating the structural factors with the characteristic parameters of oVEMPs did not show significant relationship. However, p13 and n23 latencies of cVEMPs in children were significantly related to the age, head girth, body height and body weight. Conclusions: The non-invasive oVEMP test can quantitatively measure the vestibulo-ocular reflex (VOR) system, which has similar characteristic parameters in children aged >3years and adults. For children aged <3years, modified methodologies for testing oVEMPs are warranted. Significance: The oVEMP test may serve as an effective diagnostic tool for evaluating the integrity of the VOR system for those >3years old. [Copyright &y& Elsevier]

Abstract: Objective: The n10 component (n10) of the ocular vestibular evoked myogenic potential (oVEMP) to brief bone conducted vibration (BCV) of the forehead at Fz is probably caused by the vibration selectively activating vestibular otolithic receptors. If the n10 is due primarily to utricular activation then diseases which affect only the superior division of the vestibular nerve (SVN) should reduce or eliminate n10. Methods: The n10 component of the oVEMP was measured in 13 patients with unilateral SVN but with inferior vestibular nerve function preserved. Results: We compared the n10 to BCV of these 13 SVN patients to previously published data for healthy subjects and patients after complete unilateral vestibular loss. We found that in 12 out of the 13 patients with SVN, n10 was markedly reduced or absent under the contralesional eye. Conclusion: Since all utricular afferents course in the superior vestibular nerve and in 12/13 of these patients the n10 was reduced we conclude that the n10 component of the oVEMP to BCV is probably mediated by the superior vestibular nerve and probably due to activation of mainly utricular receptors. Significance: The n10 appears to be a simple new test of superior vestibular nerve and probably mainly utricular function. [Copyright &y& Elsevier]

Abstract: Objectives: Cervical vestibular evoked myogenic potentials (cVEMPs) have been found to be useful for clinical testing of vestibular function. Recently, investigators showed that short-latency, initially negative surface EMG potentials can be recorded around the extraocular muscles (oVEMPs) in response to air-conducted sound (ACS), bone-conducted vibration (BCV), and head taps. Although these evoked potentials, which are located around the eyes, most likely originate primarily from the otolith-ocular pathway, the possibility of contamination by other nerve activities cannot be completely eliminated. The purpose of the present study was to clarify the origin of oVEMPs by examining these possibilities using clinical findings. Methods: Twelve healthy subjects and 15 patients were enrolled. Of the 15 patients, 3 patients had undergone exenteration of the unilateral intraorbital contents, one had undergone exenteration of the right eyeball with preservation of extraocular muscles, 5 had facial palsy, and 6 had profound hearing loss. ACS and/or BCV were used in these subjects. Results: Exenteration of the unilateral intraorbital contents resulted in absence of myogenic potentials on the affected side. On the other hand, exenteration of the eyeball with preservation of extraocular muscles did not have a major impact on the responses. There were no significant differences in the waveforms between healthy subjects and patients with facial palsy or profound hearing loss. Conclusions: The results suggested that short-latency, initially negative evoked potentials recorded below the eyes are not affected by cochlear or facial nerve activities and are dependent on the presence of extraocular muscles. Significance: This study provides the evidence that oVEMPs originate from exraocular muscles activated through the vestibulo-ocular pathway. [Copyright &y& Elsevier]

Abstract: Objective: Synchronous extraocular muscle activity can be recorded from around the eyes at the beginning of a vestibular-evoked eye movement (ocular vestibular evoked myogenic potentials, OVEMPs). As galvanic vestibular stimulation (GVS) evokes the vestibulo-ocular reflex, we wished to investigate GVS-evoked OVEMPs. Methods: We stimulated 10 normals and 6 patients with unilateral vestibular loss (uVL) with bi/unipolar 4mA, 2ms current steps at the mastoid. OVEMPs were recorded from electrodes placed superior and inferior to the eyes. Results: OVEMPs were present beneath both eyes in all normal subjects: an initial positivity ipsilateral to the cathodal electrode (peak latency 9.9ms, amplitude 1.3μV) and an initial negativity contralateral to the cathode (8.8ms, 2.4μV). In the patients, stimulation of the affected side produced little or no response. Stimulation of the intact side produced only contralateral responses. Conclusions: The infra-orbital response is likely produced primarily by the inferior obliques, producing conjugate torsion away from the cathode. The projection to the ipsilateral eye depends upon normal vestibular function on the contralateral side. Significance: OVEMPs can be evoked by GVS. While bilateral effects are obtained with unilateral stimulation in normals, the primary vestibular pathway to the inferior oblique in humans is crossed. [Copyright &y& Elsevier]

Abstract: Objective: This study compared the ocular vestibular-evoked myogenic potentials (oVEMPs) that are elicited (recorded) in response to monaural and separately, simultaneous binaural acoustic stimulations. The optimal stimulation mode for oVEMPs was also determined. Methods: Twenty healthy volunteers (14 men and 6 women, aged from 22 to 33years, mean 28years) without any previous ear disorders were enrolled in this study. Each subject underwent oVEMP testing using monaural acoustic stimulation (Mon-oVEMP) with different stimulus intensities, and with bilateral recording. On another day, the same volunteers underwent oVEMP testing using simultaneous binaural acoustic stimulation and bilateral recording (Bin-oVEMP). Results: With 95dB nHL tone burst stimulation, the biphasic nI–pI waveforms were recorded with maximal amplitudes from the electrodes located below the eyes contralateral to the side of acoustic stimulation while the subject was gazing upward. Significant correlations were identified between Mon-oVEMPs and Bin-oVEMPs with respect to threshold, latencies and amplitude. However, no significant difference existed between Mon-oVEMPs and Bin-oVEMPs in terms of the response rate, threshold, latency or amplitude. Conclusions: The Bin-oVEMP test yields the same information as the Mon-oVEMP test, but the duration of recording in the former is shorter than the latter. Significance: The Bin-oVEMP test may be a more convenient screening tool for evaluating the crossed vestibulo-ocular reflex. [Copyright &y& Elsevier]

Abstract: Objective: Sound and vibration evoke a short-latency eye movement or “sound-evoked vestibulo-ocular reflex” (VOR) and an infraorbital surface potential: the “ocular vestibular-evoked myogenic potential” (OVEMP). We examined their relationship by measuring the modulation of both responses by gaze and stimulus parameters. Methods: In seven subjects with superior semicircular-canal dehiscence (SCD) and six controls, the sound-evoked VOR was measured in 3D using scleral search coils. OVEMPs were recorded simultaneously, using surface electromyography. Results: Eye movement onset (11.6±0.8ms) coincided with the OVEMP peak (12.1±0.35ms). OVEMP and VOR magnitudes were 5–15 times larger in SCD compared with controls. OVEMP amplitudes were maximal on upgaze and abolished on downgaze; VOR magnitudes were unaffected. When stimulus type was changed from sound to vibration, OVEMP and VOR changed concordantly: increasing in controls and decreasing in SCD. OVEMP and VOR tuned to identical stimulus frequencies. OVEMP and VOR magnitudes on upgaze were significantly correlated (R =0.83–0.97). Conclusion: Selective decrease of the OVEMP upon downgaze is consistent with relaxation or retraction of the inferior oblique muscles. The temporal relationship of OVEMP and VOR and their identical modulation by external factors confirms a common origin. Significance: Sound-evoked OVEMP and VOR represent the electrical and mechanical correlates of the same vestibulo-ocular response. [Copyright &y& Elsevier]

Abstract: Objective: Patients with superior canal dehiscence (SCD) typically have enhanced sound-evoked vestibular reflexes, such as vestibulo-collic and vestibulo-ocular reflexes. We wished to investigate whether sound-evoked lower limb EMG responses and postural sway are also enhanced in this condition. Methods: Eight patients with CT confirmed SCD (11 affected ears) and 8 age-matched normal controls participated. Three sound-evoked responses were measured; vestibulo-collic reflexes (i.e. vestibular-evoked myogenic potentials, VEMPs), lower limb vestibulo-spinal reflexes and body sway (centre of pressure in mm). Sound stimuli were 500Hz air-conducted tone bursts of varying lengths (VEMPs: 2ms; vestibulo-spinal: 20ms; sway: 1s and 200ms) set at fixed levels above each subject’s VEMP threshold. Results: SCD patients had very large VEMP and vestibulo-spinal responses following high intensity stimulation, but at the matched intensity of 15dB above threshold amplitudes were similar in both SCD patients and controls. The amplitude of both responses increased linearly with increasing stimulus intensity in both groups. Large (∼20mm), stereotyped sway responses were present in only one (atypical) patient with high intensity stimulation. Small (∼2mm) sway responses were present in the remaining patients, and began immediately following the vestibulo-spinal responses. Conclusions: Despite the presence of large vestibular reflexes, there is usually very little body sway in response to loud sounds in SCD patients. Significance: Large short-latency vestibulo-spinal reflexes in SCD do not necessarily evoke large sway responses. [Copyright &y& Elsevier]

Abstract: A dysfunction of the vestibular system is commonly characterized by a combination of phenomena involving perceptual, ocular motor, postural, and autonomic manifestations: vertigo/dizziness, nystagmus, ataxia, and nausea. These 4 manifestations correlate with different aspects of vestibular function and emanate from different sites within the central nervous system. The diagnosis of vestibular syndromes always requires interdisciplinary thinking. A detailed history allows early differentiation into 9 categories that serve as a practical guide for differential diagnosis: (1) dizziness and lightheadedness; (2) single or recurrent attacks of vertigo; (3) sustained vertigo; (4) positional/positioning vertigo; (5) oscillopsia; (6) vertigo associated with auditory dysfunction; (7) vertigo associated with brainstem or cerebellar symptoms; (8) vertigo associated with headache; and (9) dizziness or to-and-fro vertigo with postural imbalance. A careful and systematic neuro-ophthalmological and neuro-otological examination is also mandatory, especially to differentiate between central and peripheral vestibular disorders. Important signs are nystagmus, ocular tilt reaction, other central or peripheral ocular motor dysfunctions, or a unilateral or bilateral peripheral vestibular deficit. This deficit can be easily detected by the head-impulse test, the most relevant bedside test for the vestibulo-ocular reflex. Laboratory examinations are used to measure eye movements, to test semicircular canal, otolith, and spatial perceptional function and to determine postural control. It must, however, be kept in mind that all signs and ocular motor and vestibular findings have to be interpreted within the context of the patient''s history and a complete neurological examination. [Copyright &y& Elsevier]

Introduction Downbeat nystagmus (DBN) is the most common form of acquired fixation nystagmus. Patients typically suffer from oscillopsia and postural instability. Postural symptoms are known to improve during walking, in particular at fast speeds ( Schniepp et al., 2014 ); however, it is unknown whether locomotion also influences ocular motor symptoms in these patients. We thus investigated the frequency and timing of DBN occurrence during standing and walking at different speeds in patients with DBN. Methods Eye movements of DBN patients with clear central-gaze nystagmus were recorded using video-oculography during standing as well as treadmill walking at individual slow, preferred and fast speeds. Subjects were instructed to fixate on a target straight in front of them at 2 m distance. We analyzed the frequency and timing of occurrence of compensatory quick-phases (downbeats) throughout the gait cycle as well as the angular and linear components of the vestibulo-ocular-reflex (VOR) to assess general gaze stabilization performance during walking in these patients. Results were compared to healthy controls. Results Compared to rest, slow walking significantly lowered the frequency of DBN occurrence in all patients. With increasing walking speed, DBN frequency was further reduced and in some subjects even fully suppressed during fast walking. In addition, DBN events predominantly occurred at the start of the swing phase, indicating that DBN occurrence is phase-coupled to distinct periods of the gait cycle. Whereas angular VOR gains of patients during walking were comparable to those of healthy subjects, linear VOR components were found to be significantly decreased. Conclusion DBN ocular-motor symptoms improve during walking, in particular at fast speeds, indicating a speed-dependent re-weighting of the involved vestibulo-cerebellar pathways during locomotion. In addition, compensatory quick-phase eye movements (downbeats) most frequently occur during distinct phases of the gait cycle, suggesting that a phase-coupled locomotor feedback such as spinal motor efference copies influences the brain networks associated with downbeat nystagmus. Notable deficits in compensating linear head motion during walking indicate impairments in pathways processing otolithic inputs, despite an intact integration of vestibular cues from the semicircular canals ( Glasauer et al., 2004 ). [ABSTRACT FROM AUTHOR]

Aim To investigate the natural course of progression of ocular motor signs in patients with progressive supranuclear palsy (PSP). Methods 114 patients with a possible or probable PSP following NINDS-SPSP criteria seen at the Department of Neurology and the German Center for Vertigo and Balance Disorders (LMU, Munich) were included in this retrospective study. All patients underwent a structured neuro-ophthalmological testing by a orthoptist at initial diagnostic evaluation, 35 patients several times during their course of disease. The following ocular motor signs were extracted from the charts: Saccadic slowing (with normal range of movement) and saccadic paresis (loss of saccade initiation or severe saccadic hypometria) in vertical and horizontal direction, range of up- and downward as well as horizontal ocular motility during smooth pursuit in mm, presence of square wave jerks, function of the vestibulo-ocular reflex on head impulse testing. Clinical ocular motor signs were analysed in all patients in relation to the duration of disease at the time of examination (based on the medical history of the first sign indicative for PSP) or longitudinally during the course of disease in a subgroup of 35 patients. Results In the whole group of PSP patients saccadic abnormalities showed the following distribution over time: at 1 year of disease duration 10% showed only saccadic slowing on upgaze, 40% on up- and downgaze, 21% saccadic paresis on upgaze and 29% complete vertical saccade paresis; at 2 years the proportion of vertical saccade paresis was 32%, at 3 years 65% and at 4 years 82%. Progression of horizontal saccade paresis was slower (year 1: 6%, year 2: 9%, year 3: 21%, year 4: 41%). The subgroup of patients with longitudinal follow up showed a similar tendency. Ocular motility in this group decrease by a mean of 1.5 mm/a on upgaze, 1.6 mm/a on downgaze and 1.4 mm/a on horizontal gaze. The degree of motility loss on up- and downgaze over time showed a good correlation (R2 = 0.71). Conclusion Ocular motor examination can be used as a robust marker of disease progression. Variability between patients however is considerable. Prospective clinical and apparative quantification of ocular motor markers in well-characterized cohorts of PSP patients is needed. [ABSTRACT FROM AUTHOR]

Introduction Patients with bilateral vestibular dysfunction cannot fully compensate passive head rotations with eye movements, and therefore experience oscillopsia, making everyday activities, such as walking or driving harder to undertake. Their dynamic vision during passive head movements depends on their residual vestibulo-ocular reflex (VOR) function and on re-fixation saccades. The Head Impulse Testing Device – Functional Test (HITD-FT) is a recently proposed and innovative technique for assessing dynamic vision during passive high-acceleration head rotations, mimicking natural everyday movements. Goals To validate the HITD-FT as a tool to assess the performance of the vestibulo-ocular reflex (VOR) and the effect of re-fixation saccades on the overall dynamic visual function in opioid-induced bilateral vestibular dysfunction. Materials and methods The opioid remifentanil was continuously administrated in 14 healthy men (median age 26 years, range 21–31) in order to reversibly induce a bilateral vestibular impairment. Each subject was tested with the HITD-FT before and during opioid administration. In each test, passive, unpredictable, high-acceleration (2000–7000°/s 2 ) and small amplitude (10–20°) the ects-FT score mirrorice comched 300°/srdmic visual function matters. Unctionality, i.e. disturbing oscillopsia lity to com head rotations where applied while subjects fixated a visual stimulus. The visual stimulus consisted of a standard Landolt ring and appeared on a screen 80 ± 2 ms after head acceleration reached 300°/s 2 . Subjects were asked to identify the orientation of the ring and the provided answers were analyzed together with eye and head movements recorded with EyeSeeCam system. Results Before opioid application, VOR and dynamic reading performances were intact (head-impulse gain: 0.87 ± 0.08, mean ± SD; HITD-FT rate of correct answers: 90 ± 9%). The opioid administration induced impairment in the VOR function (head-impulse gain 0.63 ± 0.19) and in dynamic reading (HITD-FT 26 ± 15%) in 12/14 subjects. HITD-FT scores correlated with head-impulse gain impairment ( R = 0.63, p = 0.03) and with gain difference (before/during opioid R = −0.64, p = 0.02). One subject had non-pathological head-impulse gain (0.82 ± 0.03) and high HITD-FT score (92%). One subject could read (93%) despite a low head-impulse gain (0.59 ± 0.03) performing re-fixation saccades. Summary Our study suggests that the recently proposed HITD-FT is an appropriate method to document the combined effect of VOR performance and re-fixation saccades in vestibular dysfunction. Testing dynamic vision with head movement characteristics closely related to subjects’ daily activities makes the HITD-FT a suitable tool for assessing overall dynamic visual performance, e.g., to monitor progress during vestibular rehabilitation. [ABSTRACT FROM AUTHOR]