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• 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]

• 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]

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: Spatial orientation and navigation depends on information from the vestibular system. Previous work suggested impaired spatial navigation in patients with bilateral vestibular failure (BVF). The aim of this study was to investigate event-related brain activity by functional magnetic resonance imaging (fMRI) during spatial navigation and visual memory tasks in BVF patients. Methods: Twenty-three BVF patients and healthy age- and gender matched control subjects performed learning sessions of spatial navigation by watching short films taking them through various streets from a driver’s perspective along a route to the Cathedral of Cologne using virtual reality videos (adopted and modified from Google Earth®). In the scanner, participants were asked to respond to questions testing for visual memory or spatial navigation while they viewed short video clips. From a similar but not identical perspective depicted video frames of routes were displayed which they had previously seen or which were completely novel to them. Results: Compared with controls, posterior cerebellar activity in BVF patients was higher during spatial navigation than during visual memory tasks, in the absence of performance differences. This cerebellar activity correlated with disease duration. Conclusions: Cerebellar activity during spatial navigation in BVF patients may reflect increased non-vestibular efforts to counteract the development of spatial navigation deficits in BVF. Conceivably, cerebellar activity indicates a change in navigational strategy of BVF patients, i.e. from a more allocentric, landmark or place-based strategy (hippocampus) to a more sequence-based strategy. This interpretation would be in accord with recent evidence for a cerebellar role in sequence-based navigation. [ABSTRACT FROM AUTHOR]

Objective To measure changes in amplitudes of vestibular evoked myogenic potentials (VEMPs) elicited from neck, upper and lower limb muscles during a quiet standing task with increased postural threat achieved by manipulating surface height. Methods: Twenty eight subjects were tested while standing on a platform raised to 0.8 m and 3.2 m from the ground. Surface electromyography was recorded from the ipsilateral sternocleidomastoid (SCM), biceps brachii (BB), flexor carpi radialis (FCR), soleus (SOL) and medial gastrocnemius (MG) muscles. Stimulation was with air-conducted short tone bursts (4 ms). After controlling for background muscle activity, VEMP amplitudes were compared between heights and correlated with changes in state anxiety, fear and arousal. Results: VEMP amplitude significantly increased in SCM (9%) and SOL (12.7%) with increased surface height ( p < 0.05). These modest increases in SCM VEMP amplitude were significantly correlated with anxiety ( Rho = 0.57, p = 0.004) and confidence ( Rho = −0.38, p = 0.047) and those for SOL were significantly correlated with anxiety ( Rho = 0.33, p = 0.049) and fear ( Rho = 0.36, p = 0.037). Conclusion: Postural threat significantly increased vestibulospinal reflex (VSR) gains. Results demonstrate that VEMPs can be used to test different VSR pathways simultaneously during stance. Since fear and anxiety are prevalent with vestibular disorders, they should be considered as potential contributing factors for clinical vestibular outcome measures. [ABSTRACT FROM AUTHOR]

Objectives Although the caloric test, rotational test, and posturography have been used to investigate balance function conventionally, and they are older than tests of otolithic organs, yet it seems that most clinicians are less familiar with the development of otolithic (saccular and utricular) function in children. This study reviewed the electrophysiological testing used to assess the functional development of the otolithic system in growing children. Methods Based on the literature, studies of cervical vestibular-evoked myogenic potential (cVEMP) and ocular VEMP (oVEMP) tests in children ranging from newborns, small children to adolescents were reviewed. Papers concerning foam posturography in children were also included. Results The cVEMPs can be elicited in newborns at day 5, whereas the oVEMPs are absent in neonatal period. When children grow to 2 years old, the oVEMPs can be induced with eyes closed condition, while the oVEMPs with eyes up condition can be elicited in children aged >3 years old, with the characteristic parameters similar to adult levels. In contrast with cVEMPs, it is until the neck length >15.3 cm (aldolesence), one need not account for neck length in evaluating cVEMP latency. Additionally, foam posturography indicated by the Romberg quotient of the sway velocity/area on foam pad is considered to reflect the otolithic function, which reached adult levels when the children at 12 years old. Conclusions For the functional development of the otolithic system in growing children to approach adult levels, the earliest occurrence is the oVEMP test, followed by the foam posturography, and cVEMP test. [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]

Highlights: [•] BPF of 1–1000Hz showed larger oVEMP amplitude than BPF of 10–1000Hz and BPF of 100–1000Hz. [•] BPF of 1–1000Hz did not significantly differ in oVEMPs from BPF of 1–500Hz and BPF of 1–2000Hz. [•] The optimal BPF setting for acoustic stimuli in recording oVEMP is suggested between 1 and 1000Hz. [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: Recently, ocular vestibular evoked myogenic potentials (oVEMPs) have been described and added to the neuro-otologic test battery as a new measure for the vestibulo-ocular reflex. oVEMPs represent extraocular muscle activity in response to otolith stimulation e.g. by air-conducted sound or bone-conducted vibration. In response to vestibular stimulation, electromyographic activity of the extraocular muscles can be recorded by means of surface electrodes placed beneath the contralateral eye. oVEMPs are likely to reflect predominantly utricular function, while the widely established cervical vestibular evoked myogenic potentials (cVEMPs) assess saccular function. Thus, measuring oVEMPs and cVEMPs in addition to caloric and head impulse testing provides further evaluation of the vestibular system and enables quick and cost-effective assessment of otolith function. This review summarizes the neurophysiological properties of oVEMPs, gives recommendations for recording conditions and discusses oVEMP alterations in various disorders of the vestibular system. With increasing insight into oVEMP characteristics in vestibular disorders, e.g. Menière''s disease and superior semicircular canal dehiscence syndrome, oVEMPs are becoming a promising new diagnostic tool for evaluating utricular function. [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: 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: This study utilized a combined ocular vestibular-evoked myogenic potential (oVEMP) and cervical VEMP (cVEMP) test in children with benign paroxysmal vertigo (BPV) to investigate whether the upper or lower brainstem is more frequently affected in BPV children. Methods: Fifteen BPV children aged 4–14 years, and 15 age- and sex-matched healthy children were enrolled. All subjects underwent pure tone audiometry, stabilometry, and a combined oVEMP and cVEMP test using acoustic stimulation. Results: All BPV patients displayed normal hearing and clear oVEMPs. However, 11 (73%) of 15 BPV patients had delayed cVEMPs, showing significant difference when compared with 100% normal cVEMPs in healthy children. The sway path and sway area in stabilometry were significantly different between BPV and healthy children, regardless of whether their eyes were open or closed. However, neither the sway path nor sway area correlated significantly with cVEMP results. Conclusion: Normal oVEMPs in BPV children indicate an intact vestibulo-ocular reflex pathway, which travels through the upper brainstem. In contrast, delayed cVEMPs in BPV children reflect a retrolabyrinthine lesion along the sacculo-collic reflex pathway, which descends via the lower brainstem. Hence, the lower brainstem is more frequently affected than the upper brainstem in children with BPV. [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]