The influence of voluntary EMG activity and click intensity on the vestibular click evoked myogenic potential

Head Orientation Modulates Vestibular Cerebellar Evoked Potentials (VsCEPs) and Reflexes Produced by Impulsive Mastoid and Midline Skull Stimulation

The cerebellum plays a critical role in the modulation of vestibular reflexes, dependent on input from proprioceptive afferents. The mechanism of this cerebellar control is not well understood. In a sample of 11 healthy human subjects, we investigated the effects of head orientation on ocular, cervical, postural and cerebellar short latency potentials evoked by impulsive stimuli applied at both mastoids and midline skull sites. Subjects were instructed to lean backwards with the head positioned straight ahead or held rotated in different degrees of yaw towards the right and left sides. Impulsive mastoid stimulation, a potent method of utricular stimulation, produced localised vestibular cerebellar evoked potentials (VsCEPs: P12-N17) which were strongly modulated by head orientation. The response was larger on the side opposite to the direction of head rotation and with stimulation on the side of rotation. In contrast, ocular VEMPs (oVEMPs: n10-p16) were present but showed little change with head posture, while cervical VEMPs (cVEMPs: p15-n23) were larger with the head held rotated away from the side of the recording. Postural effects with lateral vestibular stimulation were strongly modulated by head rotation, with more powerful effects occurring bilaterally with stimulation on the side of rotation. The duration of the postural EMG changes was similar to the post-excitation inhibition of the electrocerebellogram (ECeG), consistent with cerebellar participation. We conclude that head rotation selectively affects evoked vestibular reflexes towards different targets, consistent with their physiological roles. Changes in VsCEPs may contribute to the modulation of postural reflexes by the cerebellum.

Multifrequency Analysis of Masseter Vestibular Evoked Myogenic Potentials in Young Adults

PURPOSE

The purpose of this study was to explore the dynamics of multifrequency tone bursts on the masseter vestibular evoked myogenic potential (mVEMP) parameters. Furthermore, it sought to determine the optimal frequency tuning of mVEMP responses.

METHOD

Twenty young adults with normal hearing sensitivity participated in the study. Bilateral tone burst evoked mVEMPs were obtained using the zygomatic montage at 250-, 500-, 750-, 1000-, 1500-, and 2000-Hz stimulation frequencies. Self-monitoring biofeedback was given during the procedure to confirm the tension of the masseter muscle between 49.9 and 150.6 rms. Furthermore, the electromyography (EMG) scaling was done to avoid any muscle-related irregularities.

RESULTS

Tone burst evoked mVEMPs were found to be 100% present at the stimulation frequencies of 250, 500, 750, and 1000 Hz. There were no ear and gender effects seen for any of the frequencies. Significant shortening of the P1 and N1 latencies with increasing stimulation frequencies was observed. The peak-to-peak amplitude was the highest at 500 Hz and lowest at 2000 Hz tone bursts under both EMG scaled and unscaled conditions.

CONCLUSION

The present revealed higher response rates and larger amplitudes study of mVEMP at lower frequencies, and, therefore, the frequency tuning was seen for the stimulation frequency at 500 Hz.

Effect of Real-Ear Adjusted Stimuli on Vestibular Evoked Myogenic Potential Variability in Children and Young Adults

OBJECTIVES

There is large variability in cervical and ocular vestibular evoked myogenic potential (c- and oVEMP) amplitudes. One potential source of variability is differences in ear canal shape and size. Real ear-to-coupler difference (RECD) values are used to measure the acoustic environment of an individual's ear canal. RECD may be a useful measure to calibrate air conducted VEMP stimuli, which are elicited at high intensities and may put patients at risk of unsafe sound exposure. A recommendation for avoiding unsafe exposure is to use a 125 dB SPL stimulus for individuals with an equivalent ear canal volume (ECV) ≥ 0.9 mL and a 120 dB SPL stimulus for individuals with a smaller ECV. The purpose of this project was to determine if using a stimulus calibrated in the ear using RECD values significantly reduces intra-subject and inter-subject VEMP amplitude variability. We hypothesized that using a RECD-calibrated stimulus would significantly reduce inter-subject amplitude variability but not significantly reduce intra-subject variability. We further hypothesized that an RECD-adjusted VEMP stimulus would better protect against delivering unsafe sound exposure compared to the method of using ECV alone.

DESIGN

Eleven children (4 to 9 years), 10 adolescents (10 to 18 years), and 10 young adults (20 to 40 years) with normal hearing, tympanometry, vestibular and neurological function participated. On all subjects, RECD was measured twice per ear to account for test-retest reliability. cVEMP and oVEMP were then recorded bilaterally with a 500 Hz tone burst at a traditional and an adjusted VEMP intensity level. The traditional intensity level was 125 dB SPL for individuals with ≥ 0.9 mL ECV and 120 dB SPL for individuals with ≤ 0.8 mL ECV. The adjusted intensity level was calculated by subtracting the average 500 Hz RECD measured values from the 500 Hz normative RECD value. This value was applied as a correction factor to a 125 dB SPL stimulus. Peak to peak amplitudes were recorded and used to calculate asymmetry ratios.

RESULTS

Young children had significantly smaller ECVs compared to adolescents and young adults. Young children had larger RECDs; however, this was not significant in post hoc analyses. The method of calibration had no significant effect on intra-subject variability for cVEMP [ F (1, 27)= 0.996, p = 0.327] or oVEMP [ F (1, 25)= 1.679, p = 0.206]. The method of calibration also had no significant effect on inter-subject amplitude variability for cVEMP [ F (1, 120)= 0.721, p = 0.397] or oVEMP [ F (1, 120)= 0.447, p = 0.505]. Both methods of calibration adequately protected against unsafe exposure levels. However, there were subjects with ECVs ≥ 0.9 mL who approached unsafe exposure levels from the ECV-calibrated stimulus, suggesting there may be rare cases in which a 125 dB SPL stimulus is unsafe, even for patients with larger ECVs.

CONCLUSIONS

The calibration method made no significant difference in intra- or inter-subject variability, indicating that the acoustic environment of the outer ear is not significantly contributing to VEMP amplitude variability. The RECD-adjusted stimulus is effective in protecting against unsafe exposure levels for two trials of both c- and oVEMPs. There may be instances where more than two trials of each test are required, which increases the effective stimulation level. Clinicians should be cautious when delivering VEMPs and not unnecessarily expose patients to unsafe levels of sound.

Multifrequency Narrowband Chirp Evoked Cervical Vestibular Myogenic Potentials: Evaluation of Responses in Normal-Hearing Young Adults

Purpose:

The study aimed to explore the various parameters of multifrequency narrowband Claus Elberling chirp (NB CE-chirp) evoked cervical vestibular evoked myogenic potentials (cVEMPs) in normal-hearing healthy young adults. The study also attempted to define the optimal frequency tuning characteristic of NB CE-chirp evoked cVEMPs.

Method:

cVEMP was performed on 26 young healthy adults using four different NB CE-chirps centered at 500, 1000, 2000, and 4000 Hz. The neck torsion method was applied for electrode placement. To have the acute recording, visual feedback of sternocleidomastoid muscle contraction was provided, and electromyography (EMG) scaling was done.

Results:

cVEMPs were present for 100% across all frequencies except at 4000 Hz. Amplitudes between each pair of frequencies were significantly different for EMG scaled and unscaled conditions. Frequency tuning was observed at 500 Hz regardless of scaling done. Positive peak 1 of cVEMP (P1) latencies showed no differences between frequencies while both negative peak 1 of cVEMP and the complex of positive peak 1 and negative peak 1 of cVEMP (P1N1) interpeak latency values decreased with increasing frequency. Interaural amplitude asymmetry ratio showed no difference between scaled and unscaled amplitudes. Intraclass correlation revealed a range of test–retest reliability across frequencies. EMG unscaled amplitude were having relatively lower test–retest reliability consistently across frequencies

Conclusions:

Differences in amplitudes between frequencies with a maximum at 500 Hz can be attributed to the low frequency centered saccular response. No differences in P1 were observed. Yet, N1 latency and P1N1 interpeak latency difference gradually shortened with the decrement in the stimulus duration as the stimulation frequency increased. The lower reliability of EMG unscaled amplitude across frequencies supports the need to use EMG scaling to avoid confounding variables related to muscle contraction.

Comparison of the Effects of Matching and Normalization on the Cervical Vestibular Evoked Myogenic Potential

HYPOTHESIS

We compared two means of mitigating the effect of sternocleidomastoid (SCM) contraction strength on the cervical vestibular evoked myogenic potential (cVEMP): contraction matching and amplitude normalization.

BACKGROUND

SCM muscle contraction strength affects the amplitude of the cVEMP which can impact measures of inter-side asymmetry and diagnostic outcomes.

METHODS

In 19 normal subjects, we investigated the effect of muscle contraction variation within a cVEMP recording. We then compared cVEMP recordings on the right and left sides with matched and unmatched muscle contraction strength using raw amplitudes and amplitude ratios (i.e., normalized amplitudes).

RESULTS

Contraction variability had significant effects on small sections of a cVEMP recording, but there was no significant effect on overall cVEMP amplitude, suggesting that the cVEMP is relatively unaffected by variable effort during a recording. Matching the contraction across the two sides (d = 0.53, p = 0.016) and amplitude normalization (d = 0.43, p = 0.004) both significantly reduced inter-side asymmetry, but normalization had no additional benefit once the sides were matched (interaction effect, p = 0.019). cVEMPs recorded with matched contractions had the smallest range of asymmetry values.

CONCLUSION

The study shows that controlling the background contraction during a cVEMP recording, either by using similar contractions for each trial or by normalizing the amplitude, reduces cVEMP asymmetry and can prevent incorrect results in the minority of subjects who make asymmetric muscle contractions.

Relationship Between Galvanic Vestibular-evoked Myogenic Potentials and the Prognosis of Unilateral Severe to Profound Idiopathic Sudden Sensorineural Hearing Loss With Vertigo

OBJECTIVE

Idiopathic sudden sensorineural hearing loss (ISSNHL) may not only impair cochlear function but also damage vestibular structures, including the saccule, utricle, semicircular canals, and vestibular afferents. Poor recovery often occurs in patient with serious ISSNHL and accompanying vertigo. To define the severity of the disease and to predict prognosis, galvanic vestibular-evoked myogenic potentials (VEMPs) are added to the inner ear test battery.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Thirty patients with unilateral severe to profound ISSNHL and accompanying vertigo were enrolled in this retrospective study.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURES

All subjects underwent pure tone audiometry, cervical and ocular VEMPs, and caloric tests before the initiation of treatment. The treatment outcome, rates of abnormal responses in the tests, and the characteristic parameters of VEMPs such as latencies and amplitudes, were analyzed.

RESULTS

In affected ears, the rates of abnormal acoustic cVEMPs, vibratory oVEMPs, galvanic cVEMPs, and galvanic oVEMPs were 60, 47, 37, and 20%, respectively. The improvement in the hearing of the affected ear was specified as good recovery or poor recovery. The normal galvanic VEMP group had a significant higher rate of good recovery than abnormal galvanic VEMP group (87% versus 27%; p = 0.003).

CONCLUSIONS

Patients with unilateral severe to profound ISSNHL and accompanying vertigo who have normal galvanic VEMPs have a higher likelihood of hearing recovery than those who have abnormal galvanic VEMPs.

Effects of Tonic Muscle Activation on Amplitude-Modulated Cervical Vestibular Evoked Myogenic Potentials (AMcVEMPs) in Young Females: Preliminary Findings

Cervical vestibular evoked myogenic potentials (cVEMPs) are usually elicited by transient tonebursts, but when elicited by amplitude-modulated (AM) tones, they can provide new information about cVEMPs. Previous reports of cVEMPs elicited by AM tones, or AMcVEMPs, have not systematically examined the effects of tonic EMG activation on their response properties. Fourteen young, healthy female adults (ages 20-24) with clinically normal audiograms participated in this study. AMcVEMPs were elicited with bone-conducted 500 Hz tones amplitude modulated at a rate of 37 Hz and recorded for five different EMG targets ranging from 0 to 90 μV. Amplitude increased linearly as tonic EMG activation increased. Signal-to-noise ratio (SNR) was minimal at 0 μV, but robust and with equivalent values from 30 to 90 μV; phase coherence and EMG-corrected amplitude had findings similar to SNR across EMG target levels. Interaural asymmetry ratios for SNR and phase coherence were substantially lower than those for raw or corrected amplitude. AMcVEMP amplitude scaled with tonic EMG activation similar to transient cVEMPs. Signal-to-noise ratio, phase coherence, and EMG-corrected amplitude plateaued across a range of EMG values, suggesting that these properties of the response reach their maximum values at relatively low levels of EMG activation and that higher levels of EMG activation are not necessary to record robust AMcVEMPs.

Ocular vestibular evoked myogenic potential (VEMP) reveals mesencephalic HTLV-1-associated neurological disease

Purpose

Vestibular Myogenic Evoked Potential (VEMP) evaluates vestibulo-ocular and vestibulo-collic reflexes involved in the function of the otolithic organs and their afferent pathways. We compared the results of cervical and ocular VEMP in HTLV-1 associated myelopathy (HAM) and HTLV-1-asymptomatic infection.

Participants and methods

This cross-sectional study included 52 HTLV-1-infected individuals (26 HAM and 26 asymptomatic carriers) and 26 seronegative controls. The groups were similar regarding age and gender. Participants underwent simultaneous ocular and cervical VEMP. The stimulus to generate VEMP was a low-frequency tone burst sound tone burst, with an intensity of 120 decibels normalized hearing level, bandpass filter from 10 to 1,500 Hertz (Hz), with 100 stimuli at 500 Hz and 50 milliseconds recording time. The latencies of the electrophysiological waves P13 and N23 for cervical VEMP and N10 and P15 waves for ocular VEMP were compared among the groups. The absence or delay of the electrophysiological waves were considered abnormal results.

Results

Ocular VEMP was similar among the groups for N10 (p = 0.375) and different for P15 (p≤0.001). Cervical VEMP was different for P13 (p = 0.001) and N23 (p = 0.003). About ocular VEMP, in the HTLV-1-asymptomatic group, normal waves were found in 23(88.5%) individuals; in HAM group, normal waves were found in 7(26.9%). About cervical VEMP, 18(69.2%) asymptomatic carriers presented normal waves and only 3(11.5%) patients with HAM presented normal waves. Abnormalities in both VEMPs were found in 1(3.8%) asymptomatic carrier and in 16(61.5%) patients with HAM.

Conclusion

Neurological impairment in HAM was not restricted to the spinal cord. The mesencephalic connections, tested by ocular VEMP, have been also altered. Damage of the oculomotor system, responsible for eye stabilization during head and body movements, may explain why dizziness is such a frequent complaint in HAM.

Investigating short latency subcortical vestibular projections in humans: what have we learned?

Vestibular evoked myogenic potentials (VEMPs) are now widely used for the noninvasive assessment of vestibular function and diagnosis in humans. This review focuses on the origin, properties, and mechanisms of cervical VEMPs and ocular VEMPs; how these reflexes relate to reports of vestibular projections to brain stem and cervical targets; and the physiological role of (otolithic) cervical and ocular reflexes. The evidence suggests that both VEMPs are likely to represent the effects of excitation of irregularly firing otolith afferents. While the air-conducted cervical VEMP appears to mainly arise from excitation of saccular receptors, the ocular VEMP evoked by bone-conducted stimulation, including impulsive bone-conducted stimuli, mainly arises from utricular afferents. The surface responses are generated by brief changes in motor unit firing. The effects that have been demonstrated are likely to represent otolith-dependent vestibulocollic and vestibulo-ocular reflexes, both linear and torsional. These observations add to previous reports of short latency otolith projections to the target muscles in the neck (sternocleidomastoid and splenius) and extraocular muscles (the inferior oblique). New insights have been provided by the investigation and application of these techniques.

Cervical Vestibular Evoked Myogenic Potentials in Menière's Disease: A Comparison of Response Metrics

OBJECTIVE

The cervical vestibular evoked myogenic potential (cVEMP) has been used to evaluate patients with Menière's disease (MD). Studied cVEMP metrics include: amplitude, threshold, frequency tuning, and interaural asymmetry ratio (IAR). However, few studies compared these metrics in the same set of MD patients, and methodological differences prevent such a comparison across studies. This study investigates the value of different cVEMP metrics in distinguishing one set of MD patients from age-matched controls.

STUDY DESIGN

Prospective study.

SETTING

Tertiary care center.

PATIENTS

Thirty patients with definite unilateral MD and 23 age-matched controls were prospectively included. All underwent cVEMP testing at 500, 750, 1000, and 2000 Hz on each side. Ears were separated into three groups: affected MD, unaffected MD, and control.

MAIN OUTCOME MEASURES

Sound level functions were obtained at each frequency, and normalized peak-to-peak amplitude (VEMPn), VEMP inhibition depth (VEMPid), threshold, frequency-tuning ratio, and IAR were calculated. For all metrics, the differentiation between MD and control ears was compared using receiver operating characteristic (ROC) curves.

RESULTS

500 Hz cVEMP threshold, VEMPn, and VEMPid were similarly good at distinguishing affected MD ears from healthy ears, with ROC area under the curves (AUCs) of more than 0.828 and optimal sensitivities and specificities of at least 80 and 70%. Combinations of these three metrics yielded slightly larger AUCs (>0.880). Tuning ratios and IAR were less effective in separating healthy from affected ears with AUCs ranging from 0.529 to 0.720.

CONCLUSION

The cVEMP metrics most useful in distinguishing MD patients from healthy controls are threshold, VEMPn, and VEMPid, using 500 Hz stimuli.

Vestibular evoked myogenic potentials in practice: Methods, pitfalls and clinical applications

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Vestibular evoked myogenic potentials (VEMPs) are used to test the otolith organs in patients with vertigo and imbalance.

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This review discusses the optimal procedures for recording VEMPs and the pitfalls commonly encountered by clinicians.

•

Better understanding of VEMP methodology should lead to improved quality of recordings.

Vestibular evoked myogenic potentials (VEMPs) are a useful and increasingly popular component of the neuro-otology test battery. These otolith-dependent reflexes are produced by stimulating the ears with air-conducted sound or skull vibration and recorded from surface electrodes placed over the neck (cervical VEMPs) and eye muscles (ocular VEMPs). VEMP abnormalities have been reported in various diseases of the ear and vestibular system, and VEMPs have a clear role in the diagnosis of superior semicircular canal dehiscence. However there is significant variability in the methods used to stimulate the otoliths and record the reflexes. This review discusses VEMP methodology and provides a detailed theoretical background for the techniques that are typically used. The review also outlines the common pitfalls in VEMP recording and the clinical applications of VEMPs.

The Contributions of Vestibular Evoked Myogenic Potentials and Acoustic Vestibular Stimulation to Our Understanding of the Vestibular System

Vestibular-evoked myogenic potentials (VEMPs) are short-latency muscle reflexes typically recorded from the neck or eye muscles with surface electrodes. They are used clinically to assess otolith function, but are also interesting as they can provide information about the vestibular system and its activation by sound and vibration. Since the introduction of VEMPs more than 25 years ago, VEMPs have inspired animal and human research on the effects of acoustic vestibular stimulation on the vestibular organs, their projections and the postural muscles involved in vestibular reflexes. Using a combination of recording techniques, including single motor unit recordings, VEMP studies have enhanced our understanding of the excitability changes underlying the sound-evoked vestibulo-collic and vestibulo-ocular reflexes. Studies in patients with diseases of the vestibular system, such as superior canal dehiscence and Meniere's disease, have shown how acoustic vestibular stimulation is affected by physical changes in the vestibule, and how sound-evoked reflexes can detect these changes and their resolution in clinical contexts. This review outlines the advances in our understanding of the vestibular system that have occurred following the renewed interest in sound and vibration as a result of the VEMP.

Vestibular-Evoked Myogenic Potentials in Bilateral Vestibulopathy

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

Toward Optimizing Vestibular Evoked Myogenic Potentials: Normalization Reduces the Need for Strong Neck Muscle Contraction

BACKGROUND

The cervical vestibular evoked myogenic potential (cVEMP) represents an inhibitory reflex of the saccule measured in the ipsilateral sternocleidomastoid muscle (SCM) in response to acoustic or vibrational stimulation. Since the cVEMP is a modulation of SCM electromyographic (EMG) activity, cVEMP amplitude is proportional to muscle EMG amplitude. We sought to evaluate muscle contraction influences on cVEMP peak-to-peak amplitudes (VEMPpp), normalized cVEMP amplitudes (VEMPn), and inhibition depth (VEMPid).

METHODS

cVEMPs at 500 Hz were measured in 25 healthy subjects for 3 SCM EMG contraction ranges: 45-65, 65-105, and 105-500 μV root mean square (r.m.s.). For each range, we measured cVEMP sound level functions (93-123 dB peSPL) and sound off, meaning that muscle contraction was measured without acoustic stimulation. The effect of muscle contraction amplitude on VEMPpp, VEMPn, and VEMPid and the ability to distinguish cVEMP presence/absence were evaluated.

RESULTS

VEMPpp amplitudes were significantly greater at higher muscle contractions. In contrast, VEMPn and VEMPid showed no significant effect of muscle contraction. Cohen's d indicated that for all 3 cVEMP metrics contraction amplitude variations produced little change in the ability to distinguish cVEMP presence/absence. VEMPid more clearly indicated saccular output because when no acoustic stimulus was presented the saccular inhibition estimated by VEMPid was zero, unlike those by VEMPpp and VEMPn.

CONCLUSION

Muscle contraction amplitude strongly affects VEMPpp amplitude, but contractions 45-300 μV r.m.s. produce stable VEMPn and VEMPid values. Clinically, there may be no need for subjects to exert high contraction effort. This is especially beneficial in patients for whom maintaining high SCM contraction amplitudes is challenging.

Experimental study of brachial plexus and vessel compression: evaluation of combined central and peripheral electrodiagnostic approach

Introduction

We sought to investigate the reliability of a new electrodiagnostic method for identifying Electrodiagnosis of Brachial Plexus & Vessel Compression Syndrome (BPVCS) in rats that involves the application of transcranial electrical stimulation motor evoked potentials (TES-MEPs) combined with peripheral nerve stimulation compound muscle action potentials (PNS-CMAPs).

Results

The latencies of the TES-MEP and PNS-CMAP were initially elongated in the 8-week group. The amplitudes of TES-MEP and PNS-CMAP were initially attenuated in the 16-week group. The isolateral amplitude ratio of the TES-MEP to the PNS-CMAP was apparently decreased, and spontaneous activities emerged at 16 weeks postoperatively.

Materials and Methods

Superior and inferior trunk models of BPVCS were created in 72 male Sprague Dawley (SD) rats that were divided into six experimental groups. The latencies, amplitudes and isolateral amplitude ratios of the TES-MEPs and PNS-CMAPs were recorded at different postoperative intervals.

Conclusions

Electrophysiological and histological examinations of the rats’ compressed brachial plexus nerves were utilized to establish preliminary electrodiagnostic criteria for BPVCS.

What vestibular tests to choose in symptomatic patients after a cochlear implant? A systematic review and meta-analysis

Vestibular function after cochlear implantation is difficult to understand, as subjective vestibular symptoms seem uncorrelated with the results of objective tests. Consequently, clinicians may struggle to decide what assessments to perform for a symptomatic patient. We used a systematic review and meta-analysis approach to enlighten this point. After a study inclusion process, results were classified into four different groups for each test in each study: (1) 'true positive' if the test showed impairment from pre-operative to post-operative in symptomatic patients; (2) 'false positive' if the test showed impairment from pre-operative to post-operative in asymptomatic patients; (3) 'true negative' if the test showed no impairment in asymptomatic patients; and (4) 'false negative' if the test showed no impairment in symptomatic patients. From these groups, sensitivities and specificities of each test were calculated in a meta-analysis. After reviewing more than 3000 references, 16 studies were included, representing 957 patients. The meta-analysis revealed a sensitivity of 0.21 (CI 95 % 0.08-0.40) for the caloric tests, of 0.32 (CI 95 % 0.15-0.54) for the cervical vestibular evoked myogenic potentials (c-VEMP), and of 0.5 (CI 95 % 0.07-0.93) for the head impulse tests. The analysis of prevalence revealed that c-VEMPs were the most often impaired, and the HIT the most often conserved. Our review and meta-analysis revealed that no vestibular test is sensitive enough to be recommended as a single test. Ideally, all the five vestibular sensors should be tested. In clinical practice, we suggest a case-to-case strategy according to patient's symptoms and their suspected origin.

Cervical vestibular evoked myogenic potentials in children

Introduction

Cervical vestibular evoked myogenic potential is a test used in neurotological examination. It verifies the integrity of vestibular function through a muscular response evoked by an acoustic stimulation which activates the saccular macula. Normal standards in adults have been established, however, there are few published data on the normal responses in children.

Objective

To establish normal standards for vestibular myogenic responses in children without neurotological complaints.

Methods

This study's design is a cohort with cross-sectional analysis. The sample consisted of 30 subjects, 15 females (50%) and 15 males (50%).

Results

The age of the subjects ranged between 8 and 13 years, with a mean of 10.2 (± 1.7). P1 peak showed an average latency of 17.26 (± 1.78) ms and a mean amplitude of 49.34 (± 23.07) μV, and the N2 peak showed an average latency of 24.78 (± 2.18) ms and mean amplitude of 66.23 (± 36.18) μV. P1–N2 mean amplitude was 115.6 (± 55.7) μV. There were no statistically significant differences when comparing by gender or by laterality.

Conclusion

We established normal values of cervical myogenic vestibular responses in children between 8 and 13 years without neurotological complaints.

Repeatability of sound-evoked triceps myogenic potentials

OBJECTIVE

To investigate the repeatability of sound-evoked vestibular evoked myogenic potentials recorded from the triceps (tVEMPs) with and without visual feedback.

DESIGN

tVEMP responses to 95 dB nHL 500-Hz tone bursts were recorded in a longitudinal, repeated measures study where P1 and N1 latencies and amplitudes were measured on three separate occasions from the same individuals. Analysis of variance, intra-class correlations, and limits of repeatability analyses were used to assess tVEMP repeatability and effects of visual feedback.

STUDY SAMPLE

Fifteen participants (nine women) aged between 18 and 41 years took part.

RESULTS

Response rates of 63% and 68% were obtained for tVEMPs with eyes open and closed, respectively. When present, tVEMP latencies and amplitudes exhibited fair to good repeatability. Repeatability of tVEMP latencies and amplitudes measured using Bland-Altman methods was poorer with eyes closed.

CONCLUSIONS

Sound-evoked tVEMP response rates are too low to support their clinical utility at the moment. tVEMP response rate may be improved by refining the balance task to include a force related target. Better tVEMP repeatability with eyes open supports the hypothesis that the response is modulated by visual feedback, and is consistent with studies reporting triceps responses to galvanic stimulation.

Asymmetries in vestibular evoked myogenic potentials in chronic stroke survivors with spastic hypertonia: evidence for a vestibulospinal role

OBJECTIVE

Indirect evidence suggests that lateralized changes in motoneuron behavior post-stroke are potentially due to a depolarizing supraspinal drive to the motoneuron pool, but the pathways responsible are unknown. In this study, we assessed vestibular evoked myogenic potentials (VEMPs) in the neck muscles of hemispheric stroke survivors with contralesional spasticity to quantify the relative levels of vestibular drive to the spastic-paretic and contralateral motoneuron pools.

METHODS

VEMPs were recorded from each sternocleidomastoid muscle in chronic stroke survivors. Side-to-side differences in cVEMP amplitude were calculated and expressed as an asymmetry ratio, a proxy for the relative amount of vestibular drive to each side.

RESULTS

Spastic-paretic VEMPs were larger than contralateral VEMPs in 13/16 subjects. There was a strong positive relationship between the degree of asymmetry and the severity of spasticity in this subset of subjects. Remaining subjects had larger contralateral responses.

CONCLUSION

Vestibular drive to cervical motoneurons is asymmetric in spastic stroke survivors, supporting our hypothesis that there is an imbalance in descending vestibular drive to motoneuron pools post-stroke. We speculate this imbalance is a consequence of the unilateral disruption of inhibitory corticobulbar projections to the vestibular nuclei.

SIGNIFICANCE

This study sheds new light on the underlying mechanisms of post-stroke spasticity.

Capacity of rectified vestibular evoked myogenic potential in correcting asymmetric muscle contraction power

Objectives

Rectified vestibular evoked myogenic potential (rVEMP) is new method that simultaneously measures the muscle contraction power during VEMP recordings. Although there are a few studies that have evaluated the effect of the rVEMP, there is no study that has evaluated the capacity of rVEMP during asymmetrical muscle contraction.

Methods

Thirty VEMP measurements were performed among 20 normal subjects (mean age, 28.2±2.1 years; male, 16). VEMP was measured in the supine position. The head was turned to the right side by 0°, 15°, 30°, and 45° and the VEMPs were recorded in each position. The interaural amplitude difference (IAD) ratio was calculated by the conventional non-rectified VEMP (nVEMP) and rVEMP.

Results

The nVEMP IAD increased significantly according to increasing neck rotation. The IAD in rVEMP was almost similar from 0° to 30°. However, the IAD was significantly larger than the other positions when the neck was rotated 45°. When IAD during 0° was set as a standard, the IAD of the rVEMP was significantly smaller that the nVEMP only during the 30°rotaion.

Conclusion

Rectified VEMP is capable of correcting asymmetrical muscle contraction power. In contrast, it cannot correct the asymmetry if muscle contraction power asymmetry is 44.8% or larger. Also, it is not necessary if muscle contraction power asymmetry is 22.5% or smaller.

Differing response properties of cervical and ocular vestibular evoked myogenic potentials evoked by air-conducted stimulation

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cVEMPs and oVEMPS were recorded simultaneously from 15 healthy volunteers and 1 patient with superior canal dehiscence (SCD) using air conducted (AC) sound over a 30 dB range.

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The SCD patient had larger amplitude responses at all intensities except for the cVEMP at the loudest intensity.

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Whilst the cVEMP p13/n23 response was well fitted by a power law relationship the oVEMP n10/p16 response showed a change in gradient for the louder intensities and this may relate to differences in the pathways responsible.

Objective

To determine the amplitude changes of vestibular evoked myogenic potentials (VEMPs) recorded simultaneously from the neck (cVEMPs) and eyes (oVEMPs) in response to 500 Hz, 2 ms air-conducted sound pips over a 30 dB range.

Methods

Fifteen healthy volunteers (mean age 29, range 18–57 years old) and one patient with unilateral superior canal dehiscence (SCD) were studied. The stimulus was reduced in increments to 105 dB pSPL for the normals (81 dB pSPL for the SCD patient). A statistical criterion was used to detect responses.

Results

Ipsilateral (i-p13/n23) and contralateral (c-n12/p24/n30) peaks for the cVEMP montage and contralateral (c-n10/p16/n21) and ipsilateral (i-n13) peaks for the oVEMP montage were present for the baseline intensity. For the lowest intensity, 6/15 subjects had responses for the i-p13 cVEMP potential and 4/15 had c-n10 oVEMP responses. The SCD patient showed larger responses for nearly all intensities. The cVEMP potentials were generally well fitted by a power law relationship, but the oVEMP c-n10, p16 and n21 potentials showed a significant increase in gradient for the higher intensities.

Conclusion

Most oVEMP and cVEMP responses follow a power law relationship but crossed oVEMP responses showed a change in gradient above a threshold.

Significance

The pattern of response to AC stimulation may be a property of the pathways underlying the potentials.

Frequency tuning of the cervical vestibular-evoked myogenic potential (cVEMP) recorded from multiple sites along the sternocleidomastoid muscle in normal human subjects

Frequency tuning of tone burst-evoked myogenic potentials recorded from the sternocleidomastoid muscle (cervical VEMP or cVEMP) is used clinically to assess vestibular function. Understanding the characteristics of cVEMP is important for improving the specificity of cVEMP testing in diagnosing vestibular deficits. In the present study, we analyzed the frequency tuning properties of the cVEMPs by constructing detailed tuning curves and examining their morphology and dependence on SCM tonic level, sound intensity, and recording site along the SCM. Here we report two main findings. First, by employing nine tone frequencies between 125 and 4,000 Hz, some tuning curves exhibited two distinct peaks, which cannot be modeled by a single mass spring system as previously suggested. Instead, the observed tuning is better modeled as linear summation of two mass spring systems, with resonance frequencies at ~300 and ~1,000 Hz. Peak frequency of cVEMP tuning curves was not affected by SCM tonic level, sound intensity, and location of recording site on the SCM. However, sharpness of cVEMP tuning was increased at lower sound intensities. Second, polarity of cVEMP responses recorded from the lower quarter of the SCM was reversed as compared to that at the two upper sites. While more studies are needed, these results suggest that cVEMP tuning is mediated through multiple generators with different resonance frequencies. Future studies are needed to explore implications of these results on development of selective VEMP tests and determine the nature of polarity inversion at the lower quarter of SCM.

Why do oVEMPs become larger when you look up? Explaining the effect of gaze elevation on the ocular vestibular evoked myogenic potential

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 (9 μV from 24° up to neutral) than with increasing electrode distance (2.7 μV from baseline to 6.4 mm; P<0.005). The oVEMP recorded with gaze 24° down had delayed latency (by 4.5 ms).

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.

Vestibular-evoked myogenic potentials eliciting: an overview

Recently, the favoured approach for unilateral testing of saccular function is the recently developed method of vestibular-evoked myogenic potentials (VEMPs). VEMP testing is a reliable technique, since it selectively stimulates and investigates each lateral canal in isolation from the other, providing information for the assessment of otolith function and inferior vestibular nerve integrity. The aim of this study was to provide a current review of the different methods used to record VEMPs. We noticed discrepancies in relation to the ways used to record the VEMPs in relation to the following factors: types of stimuli used (clicks or tone bursts) and body muscles tested, patient position at the time of recording, response, type of phone used and way of stimulus presentation (mono or binaural, ipsi or contralateral) and others. As a conclusion, despite the numerous studies in the field, there is no consensus in the literature as to the best recording method for VEMPs. However, the new ocular VEMPs in response to bone conducted vibration seem to be of clinical importance for the evaluation of utricular function. Further research is needed to support its clinical usefulness.

Vestibular evoked myogenic potentials: past, present and future

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.

Sound evoked triceps myogenic potentials

OBJECTIVE

To determine if a sound evoked myogenic potential could be obtained from the triceps with the recording and stimulus parameters routinely used to obtain a vestibular evoked myogenic potential (VEMP) from the sternocleidomastoid.

STUDY DESIGN

Prospective study of myogenic potentials recorded from the triceps in healthy subjects. We used a monaural acoustic stimulus and measured the unrectified myogenic potential using surface electromyography electrodes, using response-triggered averaging, on the triceps of 18 subjects.

SETTING

University-affiliated otoneurology clinic.

PATIENTS

Eighteen healthy adult volunteers (11 women and 7 men), age ranging between 27 and 36 years.

MAIN OUTCOME MEASURES

Latencies and amplitudes of the first two waves of the evoked response.

RESULTS

: The P1 latency was 36.83 +/- 8.42 ms (range, 26.34-57.99 ms; 95% confidence interval [CI], 33.53-40.14 ms), the N1 latency was 43.74 +/- 8.80 ms (range, 34.67-66.32 ms; 95% CI, 40.29-47.19 ms), the P1-N1 interlatency was 6.90 +/- 1.23 ms (range, 5.21-9.79 ms; 95% CI, 6.42-7.39 ms), and the P1-N1 interamplitude was 93.23 +/- 51.25 microV (range, 16.33-206.62 microV; 95% CI, 73.14-113.32 V).

CONCLUSION

A monaural sound stimulus elicits a robust and reproducible surface myogenic potential in triceps muscles.

Properties of binaural vestibular evoked myogenic potentials elicited with air-conducted and bone-conducted tone bursts

The purpose of this investigation was to compare the effects of monaural and binaural stimulation on unilaterally-measured vestibular evoked myogenic potential (VEMP) magnitude and latency. The subjects were eighteen normal-hearing adults with no history of vestibular disease. Monaural VEMPs were acquired with air-conducted (AC) and bone-conducted (BC) 500 Hz tone bursts presented at 95 dB nHL and 70 dB nHL, respectively. These stimuli were simultaneously paired with 95 dB nHL contralateral tone bursts at 250, 500, 750, or 1000 Hz during acquisition of binaural VEMPs. Results indicated that AC-VEMP relative magnitudes decreased in each of the binaural conditions compared to the monaural condition. However, no changes in relative magnitude between conditions occurred for BC-VEMPs. Similar latencies were observed for monaural and binaural VEMPs. Differences in bilateral interaction seen between the AC-VEMP and BC-VEMP conditions are consistent with modification of sound transmission through the ear during presentations of binaural sound.

Comparison of head rotation versus head elevation methods for vestibular evoked myogenic potentials by using logon stimulus

OBJECTIVES

To compare vestibular evoked myogenic potentials (VEMP) between two different methods, head rotation (HR) with unilateral recording and head elevation (HE) with bilateral simultaneous recording.

SUBJECTS AND METHODS

Twenty-eight healthy children (56 ears) were involved in the study. The subjects were tested in two different positions: head rotation (HR) method and head elevation (HE) method. Right- and left-side recordings were made separately in HR method and simultaneously in HE method. Logon type stimulus with 120dB Hl intensity was used to trigger VEMPs in both methods.

RESULTS

The response rate was 80.4% for HR method and 89.3% for HE method (p>0.05). There was no significant difference between the two groups with respect to P1 latency, N1 latency, and P1-N1 interval. The mean P1-N1 amplitude of HE method was higher than HR method (p<0.05). There were very strong positive correlations between two methods regarding N1 latency and P1-N1 interval (r: 0.849 and 0.841, respectively).

CONCLUSION

Bilateral simultaneous VEMP recording in head elevation position by using logon stimulus is a practical way to evaluate vestibulocollic reflex in children and it gives superior results than unilateral recording with head rotation position.

Potencial evocado miogênico vestibular (Vemp): avaliação das respostas em indivíduos normais

TEMA: o Potencial Evocado Miogênico Vestibular (Vemp) é formado por respostas miogênicas ativadas por estimulação sonora de alta intensidade. Essas respostas são registradas por eletromiografia de superfície sobre a musculatura cervical na presença de contração muscular, ativando a mácula, o nervo vestibular inferior e as vias vestíbulo-espinhais descendentes. OBJETIVO: descrever as respostas evocadas do Vemp em uma população normal. MÉTODO: selecionaram-se 30 sujeitos adultos, sendo 13 homens e 17 mulheres, sem queixas otoneurológicas. Utilizou-se 200 estímulos tone burst com freqüência de 1Hz e intensidade de 118dB Na, filtro passa-banda de 10Hz a 1500Hz. Os traçados obtidos foram analisados em relação ao primeiro potencial bifásico composto por P13 e N23. RESULTADOS: não houve diferença estatisticamente significativa entre o lado da estimulação em relação a latência e amplitude, porém foi encontrada diferença estatisticamente significativa em relação à amplitude do potencial entre os sexos. CONCLUSÃO: Vemp demonstrou ser uma ferramenta confiável na avaliação da função vestibular.

The Usefulness of Rectified VEMP

Objectives

For a reliable interpretation of left-right difference in Vestibular evoked myogenic potential (VEMP), the amount of sternocleidomastoid muscle (SCM) contraction has to be considered. Therefore, we can ensure that a difference in amplitude between the right and left VEMPs on a patient is due to vestibular abnormality, not due to individual differences of tonic muscle activity, fatigue or improper position. We used rectification to normalize electromyograph (EMG) based on pre-stimulus EMG activity. This study was designed to evaluate and compare the effect of rectification in two conventional ways of SCM contraction.

Methods

Twenty-two normal subjects were included. Two methods were employed for SCM contraction in a subject. First, subjects were made to lie flat on their back, lifting the head off the table and turning to the opposite side. Secondly, subjects push with their jaw against the hand-held inflated cuff to generate cuff pressure of 40 mmHg. From the VEMP graphs, amplitude parameters and inter-aural difference ratio (IADR) were analyzed before and after EMG rectification.

Results

Before the rectification, the average IADR of the first method was not statistically different from that of the second method. The average IADRs from each method decreased in a rectified response, showing significant reduction in asymmetry ratio. The lowest average IADR could be obtained with the combination of both the first method and rectification.

Conclusion

Rectified data show more reliable IADR and may help diagnose some vestibular disorders according to amplitude-associated parameters. The usage of rectification can be maximized with the proper SCM contraction method.

Vestibular evoked myogenic potential: recording methods in humans and guinea pigs

The vestibular evoked myogenic potential (VEMP) is a clinical test that assess the vestibular function by means of an inhibitory vestibulo-neck reflex, recorded in body muscles in response to high intensity acoustic stimuli.

AIM

To check and analyze the different methods used to record VEMPs in humans and in guinea pigs.

MATERIALS AND METHODS

We researched the following databases: MEDLINE, LILACS, SCIELO and COCHRANE.

RESULTS

we noticed discrepancies in relation to the ways used to record the vestibular evoked myogenic potentials in relation to the following factors: patient position at the time of recording, type of sound stimulus used (clicks or tone bursts), parameters for stimuli mediation (intensity, frequency, duration of presentation, filters, response amplification gain and windows for stimulus recording), type of phone used and way of stimulus presentation (mono or binaural, ipsi or contralateral).

CONCLUSION

There is no consensus in the literature as to the best recording method for vestibular evoked myogenic potentials. We need more specific studies in order to compare these recordings and establish a standard model to use it in the clinical practice.

Vestibular-evoked myogenic potential (VEMP) to evaluate cervical myelopathy in human T-cell lymphotropic virus type I infection

STUDY DESIGN

Cross-seccional analysis.

OBJECTIVE

To define the clinical usefulness of vestibular-evoked myogenic potential (VEMP) in detecting cervical medullar involvement related to human T-cell lymphotropic virus type 1 (HTLV-1) associated myelopathy/tropical spastic paraparesis (HAM/TSP).

SUMMARY OF BACKGROUND DATA

VEMP is generated by acoustic or galvanic stimuli, passing through the vestibulo-spinal motor tract, the spinal nerves and recorded by means of surface electrodes on the sternocleidomastoid muscle. HAM/TSP is a progressive inflammatory myelopathy with predominant lesions at the thoracic spinal cord level, although the cervical spine can be affected. VEMP may be of value to investigate cervical myelopathy.

METHODS

Seventy-two individuals were evaluated of whom 30 HTLV-1 were seronegative and 42 HTLV-1 seropositive (22 asymptomatic, 10 with complaints of walking difficulty without definite HAM/TSP and 10 with definite HAM/TSP). VEMP was recorded using monaural delivered short tone burst (linear rise-fall 1 millisecond, plateau 2 milliseconds, 1 KHz) 118 dB NA, stimulation rate of 5 Hz, analysis time of 60 milliseconds, 200 stimuli, band pass filtered between 10 and 1.500 Hz.

RESULTS

VEMP was normal in the seronegative group (30 controls). In the seropositive, abnormal VEMP was seen in 11 of 22 (50%) of the HTLV-1 asymptomatic carriers, in 7 of 10 (70%) of those with complaints of walking difficulty and in 8 of 10 (80%) of the HAM/TSP patients. In this last group, the pattern of response was different. No VEMP response was more frequent when compared with the HTLV-1 asymptomatic group (2-tailed P-value = 0.001).

CONCLUSION

VEMP may possibly be useful to identify patients with cervical myelopathy and to distinguish variable degrees of functional damage. Minor injury would be related to latency prolongation and major injury to no potential-evoked response.

Vestibular evoked myogenic potentials evoked by multichannel cochlear implant - influence of C levels

CONCLUSIONS

This study showed that vestibular evoked myogenic potentials (VEMPs) evoked by cochlear implant (CI), could be related to the comfortable level (C level), particularly in the channels that are closer to the apical turn of the cochlea.

OBJECTIVE

The purpose of this study was to investigate the correlation between VEMPs and C level of each channel.

SUBJECTS AND METHODS

We investigated 24 children who underwent cochlear implantation. VEMPs were recorded from the operated ears with the CI switched 'off' or 'on'. To investigate the correlation between VEMPs and C level, we selected 13 patients with Nucleus 24 (SPrint), and divided them into group A (normal VEMPs) and B (absence of VEMPs). In these children, all the 22 electrodes were active, and were mapped in the same frequency range for each channel.

RESULTS

Twenty children (83%) showed no VEMPs with the CI 'off'. Among them, 10 elicited VEMPs with the CI 'on', but the other 10 did not. In all channels, the mean C levels of CI were higher in group A than in group B. The p values in channels 1-12 were >0.10, in channels 13-16 were 0.06-0.09, and in channels 17-22 were 0.05-0.06, which were lower but not statistically significant.

The effects of logon versus click on vestibular evoked myogenic potentials

CONCLUSION

Logon is superior to click to trigger larger and more consistent vestibular evoked myogenic potentials (VEMPs).

OBJECTIVES

To record and compare the parameters of VEMPs evoked by bone- and air-conducted logon (l-VEMPs) and click (c-VEMPs).

SUBJECTS AND METHODS

Air- and bone-conducted l-VEMPs and c-VEMPs were recorded in 28 normal ears with an Amplaid MK12 (Amplaid, Milan) equipment.

RESULTS

VEMPs response rate was 100% with both air-conducted logon and click, while l-VEMPs showed a higher response rate (79%) in comparison with c-VEMPs (21%) with bone-conducted stimuli. A significant (p<0.05) increase of P1, N1 and P1-N1 amplitude and augmented P1 and N1 latencies were noticed in l-VEMPs with respect to c-VEMPs.

Vestibular evoked myogenic potentials: optimal stimulation and clinical application

By easily stimulating the ear with loud sound and recording on tonically contracted neck muscles, vestibular evoked myogenic potential (VEMP) test can reflect inner ear function other than the cochlea and semicircular canal. This expands the test battery for clinicians to explore saccular disease, adding a potential usefulness to the sacculo-collic reflex. The ideal stimulation mode for VEMPs is as follows: 95 dB tone bursts, frequency 500 Hz, stimulation repetition rate 5 Hz, rise/fall time 1 ms, plateau 2 ms, binaural stimulation with bilateral recordings. Animal model using guinea pigs has been established, which sets the stage for useful future studies investigating VEMPs in guinea pigs that would appear to resemble human VEMP responses. Clinically, VEMP test has been widely used in central and peripheral vestibular disorders.

Comparison of the Head Elevation Versus Rotation Methods in Eliciting Vestibular Evoked Myogenic Potentials

OBJECTIVES

Because active and tonic sternocleidomastoid (SCM) muscle contraction is essential for recording the vestibular evoked myogenic potential (VEMP), false-negative VEMPs are sometimes encountered in those who cannot sustain SCM muscle contraction by head elevation. Hence, the goal of this study was to investigate whether the effortless head rotation method can replace the head elevation method in eliciting VEMP responses.

DESIGN

Twenty healthy volunteers underwent VEMP testing, using monaural tone burst stimulation. First, the subject was instructed to keep the head elevated in the pitch plane for recording, followed by rotating the head sideways toward one shoulder as head down in the yaw plane for another recording (elevation-rotation sequence). On the next day, VEMP testing was performed in reverse order (rotation-elevation sequence). Twelve patients with cochleo-vestibular disorders were also enrolled in this study and underwent VEMP testing, using the two methods in random order.

RESULTS

In the elevation-rotation sequence for subjects without cochleo-vestibular disorders, the response rate for the elevation method (100%) was significantly higher than the response rate for the rotation method (70%). In contrast, no significant difference existed in the response rate between the two methods in the rotation-elevation sequence (85% versus 88%). Comparison of the response rates for the initial elevation (100%) and initial rotation methods (85%) revealed a significantly lower response rate for the initial rotation method. Mean latencies of the onset waveform and peaks p13 and n23 showed significant differences between the two methods when using the elevation-rotation sequence but no differences on the rotation-elevation sequence. Furthermore, the rotation method displayed significantly smaller amplitude than the elevation method when using the elevation-rotation sequence but no significant difference in amplitude between the two methods when applying rotation-elevation sequence. In 12 patients with cochleo-vestibular disorders, the response rates for the elevation method (67%) and rotation method (58%) were significantly reduced compared with the rates for subjects without cochleo-vestibular pathology. However, when either the elevation or the rotation method response was considered, VEMPs were present in 11 (92%) of the 12 patients with cochleo-vestibular disorders.

CONCLUSIONS

The head rotation method may serve as an alternative for eliciting VEMPs in those who cannot sustain SCM muscle contraction by head elevation. However, the lower response rate with smaller amplitude prevents the use of the head rotation method as an initial screening test for VEMPs. We therefore recommend that when VEMP responses cannot be elicited by the head elevation method, the head rotation method should be utilized to reduce false-negative results.