Feasibility of the simultaneous ocular and cervical vestibular-evoked myogenic potentials in unilateral vestibular hypofunction

ObjectiveThis 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.MethodsTwenty 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.ResultsTwenty 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.ConclusionsThe 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.SignificanceSimultaneous 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.     

Acoustic, mechanical and galvanic stimulation modes elicit ocular vestibular-evoked myogenic potentials

ObjectiveThis study compared the characteristic parameters of ocular vestibular-evoked myogenic potentials (oVEMPs) elicited by the air-conducted sound (ACS) and bone-conducted vibration (BCV) stimulation modes as well as the galvanic vestibular stimulation (GVS) mode.DesignFifteen healthy subjects underwent oVEMP tests using ACS (127 dBSPL), BCV (142 dB force level), and GVS (5 mA) modes. The response rate, latencies of nI and pI, nI–pI interval and amplitude were measured for each mode and compared among modes.ResultsAll 15 healthy subjects (30 ears) had 100% response rates in both BCV- and GVS–oVEMPs, exhibiting a response rate significantly higher than 80% in ACS–oVEMPs. The mean nI latency was the shortest in the GVS mode, followed by BCV and then ACS modes. The variation among the latencies of the three modes was significant. Likewise, the mean nI–pI amplitudes in ACS-, BCV- and GVS modes varied significantly. However, the mean nI–pI interval did not differ significantly among the three modes.ConclusionsAmong the ACS (127 dBSPL), BCV (142 dB force level), and GVS (5 mA) modes, the BCV mode yields a 100% response rate and the largest nI–pI amplitude of oVEMPs.SignificanceThe oVEMPs in ACS and GVS modes may help to differentiate the saccular from the retro-saccular lesions. If ACS–oVEMPs are normal, then oVEMPs in BCV and GVS modes can distinguish between utricular and retro-utricular disorders. Restated, oVEMPs in ACS, BCV, and GVS modes may promote the topographical delineation of the lesion site of the otolithic–ocular reflex pathway.     

Selective effects of head posture on ocular vestibular-evoked myogenic potential (oVEMP) by bone-conducted vibration

ObjectiveBy altering head postures from sitting, supine to head hanging, this study investigated the effects of gravitational force on ocular vestibular-evoked myogenic potential (oVEMP) via either air-conducted sound (ACS) or bone-conducted vibration (BCV) stimuli.MethodsTwenty healthy volunteers underwent the oVEMP test via ACS or BCV stimuli with the sitting, supine, and head hanging positions on the same day in a randomized order.ResultsAll subjects had clear BCV oVEMPs in the three head postures. No significant differences existed in terms of mean nI and pI latencies, the nI–pI interval, and asymmetry ratio regardless of various positions. However, the mean nI–pI amplitude with the head hanging position (15.9 ± 6.4 μV) was significantly larger than that with the sitting position (13.8 ± 6.0 μV), but not significantly larger than that with the supine position (14.7 ± 6.1 μV). Nevertheless, such a difference in reflex amplitude does not exist in oVEMPs elicited by ACS stimuli. With the sitting position, mean linear acceleration at the mastoids in response to BCV stimuli was −0.06 ± 0.02, 0.20 ± 0.04 and −0.04 ± 0.02 g along the x-, y-, and z-axis, respectively, which did not differ significantly from those with the head hanging position.ConclusionBy altering head postures from sitting to head hanging, gravitational force can exert a selective effect on the reflex amplitude of oVEMPs elicited by BCV stimuli, but not by ACS stimuli.SignificanceCompared to ACS mode, BCV mode can provoke higher response rate, generate earlier and larger waveforms, and be influenced by both dynamic shearing force and static gravitational force to enlarge the reflex amplitude of oVEMPs.     

The effect of alcohol on cervical and ocular vestibular evoked myogenic potentials in healthy volunteers

ObjectiveWe 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).MethodsThe 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 15 deg/sec.ResultsoVEMP 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).ConclusionsWe found a selective effect of alcohol on oVEMP amplitude, but no effect on the cVEMP. Vertical nystagmus elicited by OKS reduced oVEMP amplitude.SignificanceAlcohol 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.     

Vestibular dysfunction in patients with auditory neuropathy detected by vestibular evoked myogenic potentials

ObjectivesThis study aimed to determine vestibular involvement in patients with auditory neuropathy (AN) using ocular vestibular evoked myogenic potential (oVEMP), cervical vestibular evoked myogenic potential (cVEMP), caloric tests, video Head Impulse Tests (vHIT), and Suppression Head Impulse Paradigm (SHIMP) tests.MethodsTwenty-two patients with AN (study group) and 50 age-and-gender-matched healthy subjects (control group) were enrolled. All patients underwent air-conducted sound oVEMP and cVEMP tests. In the study group, 20 patients underwent a caloric test, 10 patients underwent a video Head Impulse Test (vHIT), and nine patients underwent the Suppression Head Impulse Paradigm (SHIMP) test.ResultsSignificant differences in VEMP abnormalities were found between the two groups. Most AN patients showed no VEMP response, while only a few patients showed VEMP responses with normal parameters. Some AN patients presented abnormal VEMP parameters, including thresholds, latencies, and amplitudes. The abnormal rate (including no response and abnormal parameters) was 91% in the cVEMP test and 86% in the oVEMP test. No significant difference was found between oVEMP and cVEMP abnormalities. AN patients exhibited a 70% abnormal rate in the caloric test. Most AN patients showed normal VOR gains. Most patients showed no overt corrective saccades in vHIT, and exhibited normal anticompensatory saccades in the SHIMP test.ConclusionMany AN patients experience vestibular dysfunction, which may be detected by using a vestibular functional test battery.SignificanceVEMP abnormalities might reflect the status and degree of vestibular involvement in AN.     

The n10 component of the ocular vestibular-evoked myogenic potential (oVEMP) is distinct from the R1 component of the blink reflex

ObjectiveBone-conducted vibration (BCV) in the midline at the hairline (Fz), results in short latency potentials recorded by surface electrodes beneath the eyes – the ocular vestibular-evoked myogenic potential (oVEMP). The early negative component of the oVEMP, n10, is due to vestibular stimulation, however it is similar to the early R1 component of the blink reflex. Here we seek to dissociate n10 from R1.MethodsSurface potentials were recorded from the infraorbital electromyogram of 10 healthy subjects, 6 patients with bilateral vestibular loss, 2 with unilateral vestibular loss, 4 with facial palsy and 3 with facial and vestibular nerve lesions on the same side. BCV was delivered at Fz, the inion, the glabella or the supraorbital ridge using a tendon hammer or a bone-conduction vibrator.ResultsOnset latencies of the n10 evoked by taps at Fz or inion were significantly shorter than the R1 components of blink responses to supraorbital and glabellar stimuli. Upward gaze increased the amplitude of n10 but not R1. The n10 was absent bilaterally in patients with bilateral vestibular loss and beneath the contralesional eye in patients with unilateral vestibular loss, but in both these groups of patients R1 was preserved. In severe facial palsy the R1 component was absent or delayed and attenuated ipsilesionally, but n10 was preserved bilaterally. In subjects with unilateral facial and vestibular nerve lesions (Herpes Zoster of the facial and vestibulocochlear nerves) the dissociation was complete – the ipsilesional R1 was absent or attenuated whereas the ipsilesional n10 was preserved.Conclusionsn10 is distinguished from R1 by its earlier onset, laterality, modulation by gaze position and dissociation in patient groups.SignificanceThe n10 component evoked by BCV at Fz is not the R1 component of the blink reflex.     

Effect of betel nut chewing on the otolithic reflex system

Objective

This study investigated the effect of betel nut chewing on the otolithic reflex system.