Variance of vestibular-evoked myogenic potentials

Normative and Pathological Ranges of Cervical Vestibular Evoked Myogenic Potentials in Normal Subjects and Patients with Complete Compensated Unilateral Vestibular Loss: A Cross Sectional Study

To know the normative ranges of VEMP response metrics in healthy young adults. To know the pathological cutoff of VEMP metrics in unilateral vestibular loss patients. To compare our VEMP metrics with the normative values of other studies from the western world. Prospective cross-sectional study. Tertiary care audiovestibular laboratory. 30 healthy subjects and 15 cases with a unilateral complete compensated loss. Various VEMP parameters-p1 latency, n1 latency, p1-n1 amplitude and Interaural asymmetry ratio (IAR) were entered into databases and analyzed. We compared our parameters with the most cited scientific data on VEMP available in the PubMed database, and we analyzed the results. 90% of controls and 80% of cases got VEMP responses at 95 dB HL threshold, 500 Hz with subject/patient placed in sitting upright with head turned to opposite side position. The normative data of VEMP response metrics in young adults for p1, n1 latencies, p1-n1 amplitude, and IAR are 13 ± 2 ms, 21 ± 2 ms, 91 ± 33 uV, and 9.25 ± 7.3, respectively. As the VEMP test has 100% sensitivity and 100% (95% CI 87-100%) negative predictive value in detecting the saccular dysfunction, we recommend the VEMP test as a mandatory tool in the vestibular test battery. There is no statistically significant difference in various VEMP parameters between the control and normal sides of the case group.

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 cervical and ocular vestibular-evoked myogenic potential responses between tone burst versus chirp stimulation

PURPOSE

To compare the effectiveness of chirp and tone burst stimuli in oVEMP and cVEMP testing for healthy adults METHODS: This study was conducted in 56 healthy volunteers (112 ears). Ocular and cervical VEMP (oVEMP, cVEMP) tests were performed for each participant using tone burst and chirp stimuli. VEMP response rates, latency of each peak (p1-n1, n1-p1), peak to peak amplitude (p1-n1 amplitude and n1-p1 amplitude), and rectified amplitudes were measured and compared between these two different stimuli.

RESULTS

VEMP response rates with chirp stimuli are higher than the tone burst stimuli for both cVEMP and oVEMP tests (The difference was statistically significant for oVEMP, p = 0.001). Chirp stimuli have higher p1n1 amplitude and rectified amplitude and shorter p1and n1 latency then tone burst stimuli for cVEMP (p = 0.015, p = 0.007, p < 0.001, p < 0.001, respectively). Chirp stimuli also have higher n1p1 amplitude and shorter n1and p1 latency then tone burst stimuli for oVEMP (p = 0.006, p < 0.001, p < 0.001, respectively).

CONCLUSION

The present findings show that the chirp stimulus triggers earlier VEMP responses with higher amplitudes than the tone burst stimulus during cVEMP and oVEMP testing. VEMP response rate with chirp stimulus is also higher than the tone burst. Therefore chirp stimulus can be used in VEMP testing as effectively as, if not more than, tone burst stimulus in clinical practice.

Weak Vestibular Response in Persistent Developmental Stuttering

Vibrational energy created at the larynx during speech will deflect vestibular mechanoreceptors in humans (Todd et al., 2008; Curthoys, 2017; Curthoys et al., 2019). Vestibular-evoked myogenic potential (VEMP), an indirect measure of vestibular function, was assessed in 15 participants who stutter, with a non-stutter control group of 15 participants paired on age and sex. VEMP amplitude was 8.5 dB smaller in the stutter group than the non-stutter group (p = 0.035, 95% CI [−0.9, −16.1], t = −2.1, d = −0.8, conditional R² = 0.88). The finding is subclinical as regards gravitoinertial function, and is interpreted with regard to speech-motor function in stuttering. There is overlap between brain areas receiving vestibular innervation, and brain areas identified as important in studies of persistent developmental stuttering. These include the auditory brainstem, cerebellar vermis, and the temporo-parietal junction. The finding supports the disruptive rhythm hypothesis (Howell et al., 1983; Howell, 2004) in which sensory inputs additional to own speech audition are fluency-enhancing when they coordinate with ongoing speech.

Vestibular-Evoked Cerebral Potentials

The human vestibular cortex has mostly been approached using functional magnetic resonance imaging and positron emission tomography combined with artificial stimulation of the vestibular receptors or nerve. Few studies have used electroencephalography and benefited from its high temporal resolution to describe the spatiotemporal dynamics of vestibular information processing from the first milliseconds following vestibular stimulation. Evoked potentials (EPs) are largely used to describe neural processing of other sensory signals, but they remain poorly developed and standardized in vestibular neuroscience and neuro-otology. Yet, vestibular EPs of brainstem, cerebellar, and cortical origin have been reported as early as the 1960s. This review article summarizes and compares results from studies that have used a large range of vestibular stimulation, including natural vestibular stimulation on rotating chairs and motion platforms, as well as artificial vestibular stimulation (e.g., sounds, impulsive acceleration stimulation, galvanic stimulation). These studies identified vestibular EPs with short latency (<20 ms), middle latency (from 20 to 50 ms), and late latency (>50 ms). Analysis of the generators (source analysis) of these responses offers new insights into the neuroimaging of the vestibular system. Generators were consistently found in the parieto-insular and temporo-parietal junction-the core of the vestibular cortex-as well as in the prefrontal and frontal areas, superior parietal, and temporal areas. We discuss the relevance of vestibular EPs for basic research and clinical neuroscience and highlight their limitations.

Predictive Value of Vestibular Evoked Myogenic Potentials in the Diagnosis of Menière's Disease and Vestibular Migraine

OBJECTIVE

To explore the usefulness of vestibular evoked myogenic potentials (VEMPs) in the diagnosis of Menière's disease (MD) and vestibular migraine (VM).

STUDY DESIGN

Retrospective cohort.

SETTING

Multidisciplinary neurotology clinic.

PATIENTS

Definite MD and definite VM patients between January, 2015 and May, 2017, as well as healthy volunteers.

INTERVENTIONS

Cervical and ocular VEMP (cVEMP and oVEMP) testing.

MAIN OUTCOME MEASURES

VEMP response, amplitude, and latency.

RESULTS

Twenty five definite MD, 34 definite VM, and 13 control subjects were analyzed. MD affected ears had significantly lower cVEMP (p = 0.007) and oVEMP (p < 0.001) amplitudes than control ears. VM ears had significantly lower oVEMP (p = 0.001), but not cVEMP (p = 0.198) amplitudes than control ears. MD affected ears, but not VM ears, had significantly more absent cVEMP (25.9% versus 0%, p = 0.005) and oVEMP responses (40.7% versus 0%, p < 0.001) than control ears. oVEMP latency was significantly shorter for both MD affected (p < 0.001) and VM ears (p < 0.001) than control ears. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated using a neurotology clinic MD prevalence of 7.9% in dizzy patients. A present cVEMP or oVEMP both have more than 93% chance of ruling MD out in the tested ear, while a cVEMP amplitude more than 54.9 μV or oVEMP amplitude more than 5.1 μV both have more than 94% of ruling out MD in the tested ear.

CONCLUSIONS

Despite some overlap in VEMP results between MD and VM, when the diagnosis is uncertain between the two disorders due to symptomatic overlap and nonspecific audiometric data, VEMPs can be helpful in guiding treatment toward one disease entity or the other until more evidence points to a definitive diagnosis.

Normalizing cVEMPs: Which Method Is the Most Effective?

OBJECTIVES

To determine the most effective method for normalizing cervical vestibular evoked myogenic potentials (cVEMPs).

DESIGN

cVEMP data from 20 subjects with normal hearing and vestibular function were normalized using 16 combinations of methods, each using one of the 4 modes of electromyogram (EMG) quantification described below. All methods used the peak to peak value of an averaged cVEMP waveform (VEMPpp) and obtained a normalized cVEMP by dividing VEMPpp by a measure of the EMG amplitude. EMG metrics were obtained from the EMG within short- and long-duration time windows. EMG amplitude was quantified by its root-mean-square (RMS) or average full-wave-rectified (RECT) value. The EMG amplitude was used by (a) dividing each individual trace by the EMG of this specific trace, (b) dividing VEMPpp by the average RMS or RECT of the individual trace EMG, (c) dividing the VEMPpp by an EMG metric obtained from the average cVEMP waveform, or (d) dividing the VEMPpp by an EMG metric obtained from an average cVEMP "noise" waveform. Normalization methods were compared by the normalized cVEMP coefficient of variation across subjects and by the area under the curve from a receiver-operating-characteristic analysis. A separate analysis of the effect of EMG-window duration was done.

RESULTS

There were large disparities in the results from different normalization methods. The best methods used EMG metrics from individual-trace EMG measurements, not from part of the average cVEMP waveform. EMG quantification by RMS or RECT produced similar results. For most EMG quantifications, longer window durations were better in producing receiver-operating-characteristic with high areas under the curve. However, even short window durations worked well when the EMG metric was calculated from the average RMS or RECT of the individual-trace EMGs. Calculating the EMG from a long-duration window of a cVEMP "noise" average waveform was almost as good as the individual-trace-EMG methods.

CONCLUSIONS

The best cVEMP normalizations use EMG quantification from individual-trace EMGs. To have the normalized cVEMPs accurately reflect the vestibular activation, a good normalization method needs to be used.

Toward Optimizing VEMP: Calculating VEMP Inhibition Depth With a Generic Template

OBJECTIVES

Cervical vestibular evoked myogenic potentials (cVEMP) indirectly reveal the response of the saccule to acoustic stimuli through the inhibition of sternocleidomastoid muscle electromyographic response. VEMP inhibition depth (VEMPid) is a recently developed metric that estimates the percentage of saccular inhibition. VEMPid provides both normalization and better accuracy at low response levels than amplitude-normalized cVEMPs. Hopefully, VEMPid will aid in the clinical assessment of patients with vestibulopatholgy. To calculate VEMPid a template is needed. In the original method, a subject's own cVEMP was used as the template, but this method can be problematic in patients who do not have robust cVEMP responses. We hypothesize that a "generic" template, created by assembling cVEMPs from healthy subjects, can be used to compute VEMPid, which would facilitate the use of VEMPid in subjects with pathological conditions.

DESIGN

A generic template was created by averaging cVEMP responses from 6 normal subjects. To compare VEMPid calculations using a generic versus a subject-specific template, cVEMPs were obtained in 40 healthy subjects using 500, 750, and 1000 Hz tonebursts at sound levels ranging from 98 to 123 dB peSPL. VEMPids were calculated both with the generic template and with the subject's own template. The ability of both templates to determine whether a cVEMP was present or not was compared with receiver operating characteristic curves.

RESULTS

No significant differences were found between VEMPid calculations using a generic template versus using a subject-specific template for all frequencies and sound levels. Based on the receiver operating characteristic curves, the subject-specific and generic template did an equally good job at determining threshold. Within limits, the shape of the generic template did not affect these results.

CONCLUSIONS

A generic template can be used instead of a subject-specific template to calculate VEMPid. Compared with cVEMP normalized by electromyographic amplitudes, VEMPid is advantageous because it averages zero when there is no sound stimulus and it allows the accumulating VEMPid value to be shown during data acquisition as a guide to deciding when enough data has been collected.

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.

Cervical Vestibular Evoked Myogenic Potentials (cVEMPs) Evoked by Air-Conducted Stimuli in Patients with Functional Neck Dissection

OBJECTIVE

Cervical vestibular-evoked myogenic potentials (cVEMPs) are short-latency vestibulocollic reflexes. The damage on any point of the vestibulocollic reflex pathway could affect the cVEMPs. Whether neck dissection has an effect on the sacculocollic pathway, and consequently on cVEMPs, remains unexplored. The aim of this study was to evaluate the cVEMP findings in patients with functional neck dissection without vestibular symptoms.

PATIENTS AND METHODS

This cross-sectional study design, 20 patients who had undergone unilateral neck dissection with sparing of the accessory nerve, SCM and internal jugular vein, were included. The response rates (%), cVEMPs parameters such as the prestimulus background EMG [Root mean square (RMS)] activity (μV), P13 and N23 peak latencies (ms), interpeak (N23-P13) interval (ms), scale and non-scale interpeak (N23-P13) amplitudes (μV) were compared between the groups. Amplitude asymmetry ratio (AAR) was calculated.

RESULTS

Twenty patients (14 males and 6 females), age was between 38 and 79 years were included in the study. All of the patients had clear cVEMPs on the NOS, whereas 18/20 (90%) patients had on the NDS. P13 and N23 peak latency of the NDS were found to be significantly longer than the NOS (P = 0.01). There was no significant difference in N23-P13 interpeak interval between two sides (P > 0.05). There was a negative correlation between P13 peak latency and post-operative time (P = 0.042; R = ‑0.484). Scale and non-scale N23-P13 interpeak amplitudes of the NDS were found to be significantly lower than the NOS (P = 0.03). Mean AAR was found as 0.28 ± 0.16 (0.08-0.76). Seven patients (35%) had abnormal amplitude asymmetry. RMS values, were statistically and significantly lower in NDS compared to NOS (P = 0.01). However, no correlation was observed between the RMS values and peak latency and peak amplitude values (P > 0.05).

CONCLUSIONS

cVEMP testing is an easy-to-apply, non-invasive, painless, and recordable test that can be used for evaluations of SAN and SCM function for patients undergoing neck dissection. After neck dissection, VEMP abnormalities can be detected. However, further studies are needed to indicate whether these abnormalities originate within the vestibular system and are due to pathologies originating from the SANs and SCMs. In addition, preoperative and postoperative studies are needed to better guide the clinical application of cVEMP testing.

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.

Aging and wave-component latency delays in oVEMP and cVEMP: a systematic review with meta-analysis

INTRODUCTION

The natural aging process may result in morphological changes in the vestibular system and in the afferent neural pathway, including loss of hair cells, decreased numbers of vestibular nerve cells, and loss of neurons in the vestibular nucleus. Thus, with advancing age, there should be a decrease in amplitudes and an increase in latencies of the vestibular evoked myogenic potentials, especially the prolongation of p13 latency. Moreover, many investigations have found no significant differences in latencies with advancing age.

OBJECTIVE

To determine if there are significant differences in the latencies of cervical and ocular evoked myogenic potentials between elderly and adult patients.

METHODS

This is a systematic review with meta-analysis of observational studies, comparing the differences of these parameters between elderly and young adults, without language or date restrictions, in the following databases: Pubmed, ScienceDirect, SCOPUS, Web of Science, SciELO and LILACS, in addition to the gray literature databases: OpenGrey.eu and DissOnline, as well as Research Gate.

RESULTS

The n1 oVEMP latencies had a mean delay in the elderly of 2.32ms with 95% CI of 0.55-4.10ms. The overall effect test showed p=0.01, disclosing that such difference was significant. The heterogeneity found was I²=96% (p<0.001). Evaluation of p1 latency was not possible due to the low number of articles selected for this condition. cVEMP analysis was performed in 13 articles. For the p13 component, the mean latency delay in the elderly was 1.34ms with 95% CI of 0.56-2.11ms. The overall effect test showed a p<0.001, with heterogeneity value I²=92% (p<0.001). For the n23 component, the mean latency delay for the elderly was 2.82ms with 95% CI of 0.33-5.30ms. The overall effect test showed p=0.03. The heterogeneity found was I²=99% (p<0.001).

CONCLUSION

The latency of oVEMP n1 wave component and latencies of cVEMP p13 and n23 wave components are longer in the elderly aged >60 years than in young adults.

Normal Values for Cervical Vestibular-Evoked Myogenic Potentials

OBJECTIVES

To assess the variability of normal values for cervical vestibular-evoked myogenic potentials (cVEMP) testing and to provide guidance regarding which parameters should be reported for clinical practice.

STUDY DESIGN

Forty-eight normal subjects with no history of hearing loss or vestibular symptoms underwent cVEMP testing. Measurement parameters were tabulated and compared to other sets of cVEMP normal values in the literature. The literature was reviewed to assess the clinical significance of abnormal cVEMP results. The distributions of threshold and symmetry ratios for normal subjects were compared to the distributions of 90 patients who underwent cVEMP testing.

SETTING

Tertiary academic center.

RESULTS

Upper limits of 42% symmetry ratio and the range of 65 to 95 dB HL for threshold were established for our center.The quartile coefficients of dispersion were much less than 1.0 for all cVEMP parameters in the literature, suggesting that the variability in normal ranges across the literature is small. The distributions for threshold and symmetry ratio were similar between normal and patient groups. There is a lack of information in the literature regarding the impairment of function resulting from various degrees of abnormality of VEMP results.

CONCLUSIONS

Normal values for cVEMP parameters are statistically consistent in the literature. The clinical significance of abnormal values has not been validated. For clinical purposes, cVEMP "thresholds" should be reported. Reporting of other parameters is optional.

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.

Input-output functions of vestibular afferent responses to air-conducted clicks in rats

Sound-evoked vestibular myogenic potentials recorded from the sternocleidomastoid muscles (the cervical vestibular-evoked myogenic potential or cVEMP) and the extraocular muscles (the ocular VEMP or oVEMP) have proven useful in clinical assessment of vestibular function. VEMPs are commonly interpreted as a test of saccular function, based on neurophysiological evidence showing activation of saccular afferents by intense acoustic click stimuli. However, recent neurophysiological studies suggest that the clicks used in clinical VEMP tests activate vestibular end organs other than the saccule. To provide the neural basis for interpreting clinical VEMP testing results, the present study examined the extent to which air-conducted clicks differentially activate the various vestibular end organs at several intensities and durations in Sprague-Dawley rats. Single unit recordings were made from 562 vestibular afferents that innervated the otoliths [inferior branch otolith (IO) and superior branch otolith (SO)], the anterior canal (AC), the horizontal canal (HC), and the posterior canal (PC). Clicks higher than 60 dB SL (re-auditory brainstem response threshold) activated both semicircular canal and otolith organ afferents. Clicks at or below 60 dB SL, however, activated only otolith organ afferents. Longer duration clicks evoked larger responses in AC, HC, and SO afferents, but not in IO afferents. Intra-axonal recording and labeling confirmed that sound sensitive vestibular afferents innervated the horizontal and anterior canal cristae as well as the saccular and utricular maculae. Interestingly, all sound sensitive afferents are calyx-bearing fibers. These results demonstrate stimulus-dependent acoustic activation of both semicircular canals and otolith organs, and suggest that sound activation of vestibular end organs other than the saccule should not be ruled out when designing and interpreting clinical VEMP tests.

International guidelines for the clinical application of cervical vestibular evoked myogenic potentials: an expert consensus report

BACKGROUND

Cervical vestibular evoked myogenic potentials (cVEMPs) are electromyogram responses evoked by high-level acoustic stimuli recorded from the tonically contracting sternocleidomastoid (SCM) muscle, and have been accepted as a measure of saccular and inferior vestibular nerve function. As more laboratories are publishing cVEMP data, there is a wider range of recording methods and interpretation, which may be confusing and limit comparisons across laboratories.

OBJECTIVE

To recommend minimum requirements and guidelines for the recording and interpretation of cVEMPs in the clinic and for diagnostic purposes.

MATERIAL AND METHODS

We have avoided proposing a single methodology, as clinical use of cVEMPs is evolving and questions still exist about its underlying physiology and its measurement. The development of guidelines by a panel of international experts may provide direction for accurate recording and interpretation.

RESULTS

cVEMPs can be evoked using air-conducted (AC) sound or bone conducted (BC) vibration. The technical demands of galvanic stimulation have limited its application. For AC stimulation, the most effective frequencies are between 400 and 800 Hz below safe peak intensity levels (e.g. 140 dB peak SPL). The highpass filter should be between 5 and 30 Hz, the lowpass filter between 1000 and 3000 Hz, and the amplifier gain between 2500 and 5000. The number of sweeps averaged should be between 100 and 250 per run. Raw amplitude correction by the level of background SCM activity narrows the range of normal values. There are few publications in children with consistent results.

CONCLUSION

The present recommendations outline basic terminology and standard methods. Because research is ongoing, new methodologies may be included in future guidelines.

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.

Normative data for vestibular evoked myogenic potential in different age groups among a heterogeneous Indian population

To establish normative data of vestibular evoked myogenic potential in different age groups among a heterogeneous Indian population. Prospective study design using a sample of convenience. Eighty five normal controls ranging between the ages 7 and 71 years were asked to provide a written signed consent for the study. Demographic characteristics of the patients were summarized using descriptive statistical methods using SPSS-17 analysing software. The outcome variable (VEMP recording) was expressed in percentiles as function of age. In all patients the stimulus which gave the best response was 95 dB (97.7 %) and 100 dB (95 %). The mean of wave latencies (p1 & n1) for 95-VEMP were, 11.2 ± 3.2 and 17.3 ± 4.7 ms on the right and 11.0 ± 2.8 and 17.0 ± 4.2 ms on the left respectively. The amplitude was 45.1 ± 54 mV on right and 46.9 ± 61.6 mV on the left. The mean of latency difference was 0.87 ms. The VEMP is a relatively simple test. The VEMP response rate was maximum in the younger age group; the optimum intensity was 95 dB. The asymmetry ratio interpretation should be done according to the age specific values.

Role of cervical vestibular evoked myogenic potential response in identifying vestibular dysfunction

Objectives:

To analyse cervical vestibular evoked myogenic potential response parameters in normal volunteers and vertiginous patients.

Subjects and methods:

A prospective study of 50 normal subjects and 50 patients with vertigo was conducted at Chiang Mai University Hospital, Thailand. Cervical vestibular evoked myogenic potential responses were measured using air-conducted, 500-Hz, tone-burst stimuli with subjects in a sitting position with their head turned toward the contralateral shoulder.

Results:

The mean ± standard deviation age and male:female ratio in the normal (44.0 ± 9.3 years; 12:38) and vertigo groups (44.7 ± 9.8 years; 17:33) were not significantly different. The prevalence of absent responses in the normal (14 per cent) and vertigo ears (46 per cent) differed significantly (p < 0.0001). Other cervical vestibular evoked myogenic potential parameters (i.e. response threshold, P1 and N1 latency, P1–N1 interlatency and interamplitude, inter-ear difference in P1 threshold, and asymmetry ratio) showed no inter-group differences.

Conclusion:

The absence of a cervical vestibular evoked myogenic potential response is useful in the identification of vestibular dysfunction. However, patients should undergo a comprehensive battery of other vestibular tests to supplement their cervical vestibular evoked myogenic potential response findings.

Cervical vestibular-evoked myogenic potentials: norms and protocols

Vestibular-evoked myogenic potential (VEMP) testing is a vestibular function test used for evaluating saccular and inferior vestibular nerve function. Parameters of VEMP testing include VEMP threshold, latencies of p1 and n1, and p1-n1 interamplitude. Less commonly used parameters were p1-n1 interlatency, interaural difference of p1 and n1 latency, and interaural amplitude difference (IAD) ratio. This paper recommends using air-conducted 500 Hz tone burst auditory stimulation presented monoaurally via an inserted ear phone while the subject is turning his head to the contralateral side in the sitting position and recording the responses from the ipsilateral sternocleidomastoid muscle. Normative values of VEMP responses in 50 normal audiovestibular volunteers were presented. VEMP testing protocols and normative values in other literature were reviewed and compared. The study is beneficial to clinicians as a reference guide to set up VEMP testing and interpretation of the VEMP responses.

Age-related changes in vestibular evoked myogenic potentials using a modified blood pressure manometer feedback method

PURPOSE

To collect age-specific vestibular evoked myogenic potential (VEMP) data and to characterize age-related differences in VEMP parameters using a modified blood pressure manometer (BPM) method of sternocleidomastoid (SCM) muscle monitoring.

METHODS

VEMPs were recorded on healthy adults ranging in age from 23 to 84 years with no history of dizziness, neuromuscular pathologies, or cervical complaints. Participants were assigned to 3 groups using a nonprobability static group assignment based on their age. VEMP P1 and N1 latency, threshold, peak-to-peak amplitude, and interamplitude difference (IAD) ratios were obtained at 130 dB SPL.

RESULTS

Statistical differences were detected in peak-to-peak mean amplitude and threshold measures among groups. Post hoc analysis revealed that differences shown were between the young group and both older groups. No significant differences were noted in P1 and N1 latencies or IAD ratios.

CONCLUSIONS

This study confirmed a significant decline in VEMP amplitude and increase in VEMP thresholds in healthy older persons. Normative age-related data may be necessary to properly interpret VEMP recordings in a clinical setting when evaluating aging populations. The BPM method utilized for controlling SCM muscle may be a valuable alternative to control SCM muscle contraction when electromyography equipment is not available.

Test-retest reliability and age-related characteristics of the ocular and cervical vestibular evoked myogenic potential tests

OBJECTIVE

To determine the test-retest reliability and age-related trends of the cervical and ocular vestibular evoked myogenic potential (cVEMP and oVEMP, respectively) responses to air-conducted sound and bone-conducted vibration stimulation.

STUDY DESIGN

Prospective study.

SETTING

Tertiary referral center.

PATIENTS

Fifty-three healthy adults with no hearing or vestibular deficits.

INTERVENTION(S)

All subjects underwent cVEMP and oVEMP testing in response to sounds (0.1-ms clicks and 500-Hz tone bursts) and vibration (midline forehead taps at the hairline, Fz, with a reflex hammer and a Brüel & Kjaer Mini-Shaker Type 4810). Twelve subjects underwent an additional testing session that was conducted at a mean of 10 weeks after the first one.

MAIN OUTCOME MEASURE(S)

Test-retest reliability for VEMP response parameters (latency, peak-to-peak amplitude, and asymmetry ratio) were assessed using the intraclass correlation coefficient (ICC).

RESULTS

: oVEMP amplitudes had excellent test-retest reliability (ICC > 0.75) for all 4 stimuli; cVEMP amplitudes had excellent reliability for hammer taps and fair-to-good reliability for other stimuli. oVEMP asymmetry ratios had excellent reliability for clicks and fair-to-good reliability (ICC = 0.4-0.75) for other stimuli; cVEMP asymmetry ratios had fair-to-good reliability for clicks and hammer taps. Older subjects (>50 years old) were found to have significantly decreased cVEMP amplitudes in response to clicks, tones, and taps with a Mini-Shaker and significantly decreased oVEMP amplitudes in response to clicks, tones, and taps with a reflex hammer. No age-related changes were found for latencies or asymmetry ratios.

CONCLUSION

Overall, oVEMP response parameters demonstrated better test-retest reliability than cVEMP response parameters, but oVEMPs and cVEMPs had similar age-related changes.

Vestibular evoked myogenic potentials: review

Background:

Disorders of balance often pose a diagnostic conundrum for clinicians, and a multitude of investigations have emerged over the years. Vestibular evoked myogenic potential testing is a diagnostic tool which can be used to assess vestibular function. Over recent years, extensive study has begun to establish a broader clinical role for vestibular evoked myogenic potential testing.

Objectives:

To provide an overview of vestibular evoked myogenic potential testing, and to present the evidence for its clinical application.

Review type:

Structured literature search according to evidence-based medicine guidelines, performed between November 2008 and April 2009. No restrictions were applied to the dates searched.

Conclusion:

The benefits of vestibular evoked myogenic potential testing have already been established as regards the diagnosis and monitoring of several clinical conditions. Researchers continue to delve deeper into potential new clinical applications, with early results suggesting promising future developments.

Acoustically evoked, short latency negative response in children with sensorineural hearing loss

Introduction:

The auditory brainstem response consists of fast and slow waves. The acoustically evoked, short latency negative response is a large, negative deflection with a latency of 3 milliseconds which has been reported in patients with profound hearing loss. It may be of vestibular, particularly saccular, origin, as is the vestibular evoked myogenic potential.

Purpose:

To assess the presence of acoustically evoked, short latency negative responses in children with severe to profound sensorineural hearing loss.

Materials and methods:

Twenty-three children (46 ears) with sensorineural hearing loss underwent audiological evaluation and auditory brainstem response, vestibular evoked myogenic potential and caloric testing.

Results:

An acoustically evoked, short latency negative response was present in 30.43 per cent of ears and absent in 69.57 per cent. Vestibular evoked myogenic potentials were recorded in all ears in the former group, but in only 53.13 per cent in the latter group. Caloric testing was normal in 82.6 per cent of the total ears tested.

Conclusion:

The presence of an acoustically evoked, short latency negative response is dependent not on residual hearing but on normal saccular function. This response can be measured in patients who cannot contract their neck muscles.

Influence of blood pressure manometer feedback on the parameters of the vestibular evoked myogenic potential test

OBJECTIVES

The objective of this study was to evaluate the merits of a blood pressure (BP) manometry feedback method for measurement of vestibular evoked myogenic potentials.

METHODS

Sixty ears of 30 normal volunteers were prospectively investigated. The vestibular evoked myogenic potentials were recorded under 3 different conditions: in the feedback-negative (FB-) condition, ie, in a sitting position without feedback; in the feedback-positive (FB+) condition, ie, in a sitting position with self-monitored BP feedback (using a BP cuff); and in a supine condition, ie, in a supine position without feedback. The interaural amplitude difference (IAD) ratios and interaural latency differences were analyzed.

RESULTS

The mean IAD ratio was smaller in the FB+ condition than in the FB- and supine conditions, but the difference was without statistical significance. The upper limits of the normal range of the IAD ratios were 39.5%, 18.3%, and 25.9% for the FB-, FB+, and supine conditions, respectively. The interaural latency difference of p13 was significantly smaller in the supine condition than in the FB- and FB+ conditions.

CONCLUSIONS

Although the reduction of the mean IAD ratio did not reach statistical significance by feedback monitoring in our study, feedback using a BP manometer may have some clinical significance, in that a more stable IAD ratio may be obtained with a narrower normal range and a smaller variation.

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 potentials in patients with benign paroxysmal positional vertigo involving each semicircular canal

PURPOSE

We have investigated vestibular evoked myogenic potentials (VEMPs) as a function of age and the involvement of each of the 3 semicircular canals in patients with benign paroxysmal positional vertigo (BPPV).

MATERIALS AND METHODS

We performed prospective assessment from January 2005 to September 2006. Vestibular evoked myogenic potential was measured in 53 patients with BPPV and 84 healthy subjects, with the latter subdivided by patient age.

RESULTS

The subgroup of healthy subjects older than 60 years showed significantly more prolonged p13 and n23 latencies and lower amplitude than the other 2 subgroups. Of the 53 patients with BPPV, 13 (24.5%) showed abnormal VEMP responses on the affected side when compared with their age-related control subgroup. There was no correlation between VEMP findings and the affected semicircular canal.

CONCLUSION

Patients with BPPV may show abnormal VEMP findings, irrespective of the involved semicircular canal, and age was associated with VEMP results suggesting degeneration of the maculae of the saccule.

Vestibular evoked myogenic potentials of undiagnosed dizziness

OBJECTIVE

Recording of vestibular evoked myogenic potentials (VEMP) can facilitate the evaluation of otolith function. The dizziness caused by otolith lesions is not completely understood. To clarify which symptoms of dizziness originate from the otolith organs, we examined the relationship between symptoms and VEMP results in patients with undiagnosed dizziness.

METHODS

The subjects were 18 patients with undiagnosed dizziness aged less than 40 years who underwent VEMP examination. The VEMP results were evaluated using the interaural ratio of p13-n23 amplitude.

RESULTS

Abnormal VEMP results were obtained in five of seven patients who experienced a sensation of falling (p=0.013), in none of the three patients who experienced a swaying sensation (p>0.05), and in one of eight patients who experienced a floating sensation (p>0.05). Five of six patients with abnormal VEMP results complained of disequilibrium lasting a few seconds.

CONCLUSIONS

Dizziness with a sensation of falling lasting for a few seconds was related to abnormal VEMP results, suggesting that it resulted from saccular dysfunction. VEMP examination may be considered a useful modality in the diagnosis of dizziness of unknown origin.

Vestibular system in infants after systemic aminoglycoside therapy

OBJECTIVES

The ototoxic action of systemic therapy with aminoglycoside antibiotics leading to the loss of inner ear hair cells is well recognized. The mitochondria-mediated pathway of apoptosis may play a role in inducing the apoptosis of vestibular hair cells due to aminoglycoside toxicity. Aminoglycosides are, nevertheless, routinely used for treatment of vital infections in neonatologic departments. Although there is a strong supposition that aminoglycosides can influence the vestibular function in infants, the routine examination of the infants' inner ear does not include vestibular tests. The purpose of the present study was to evaluate vestibular function in a group of infants prior to and after administration of systemic aminoglycosides, using caloric tests and vestibular-evoked myogenic potentials (VEMPs).

METHODS

VEMPs and auditory brainstem responses were recorded and caloric stimulation was performed in 68 infants aged 2.5-3.5 months: 40 healthy controls and 28 infants after therapy with amikacin, 15mg/(kgday) in three doses. The therapy duration varied from 10 to 14 days. In 18 infants antibiotic therapy was administered for a respiratory infection, and in 10 for sepsis. Infants with other risk factors of inner ear damage and treated with more than one ototoxic drug were excluded from the study. The tests were performed on the day of admission to hospital and repeated on the day of discharge.

RESULTS

The results of all tests were normal on admission. On the day of discharge, no reaction to caloric stimulation was elicited in six patients and no VEMPs were recorded in four subjects. Hearing thresholds were normal in all the individuals during both examinations.

CONCLUSIONS

The vestibular organ in infants after systemic therapy with amikacin may be damaged more frequently than the cochlear organ. The horizontal canal is more vulnerable to aminoglycosides, as compared to the saccule. The vestibular organ should be routinely examined in infants after systemic treatment with aminoglycosides.

Vestibular-evoked myogenic potentials

PURPOSE OF REVIEW

This article reviews the literature on vestibular-evoked myogenic potential testing, a short latency electromyogram evoked by high acoustic stimuli and recorded via surface electrodes over the sternocleidomastoid muscle. Applications and refinements of this technique are described for different pathologies and in adults and children.

RECENT FINDINGS

Various techniques for electrode placement have been described to elicit a vestibular-evoked myogenic potential response, which has been clinically investigated in normal individuals, under pathological conditions, and in adult and pediatric patients. As vestibular-evoked myogenic potential amplitude is linearly related to the level of background activity of the sternocleidomstoid muscle, maintaining steady contraction of the muscle can be challenging in some patients.

SUMMARY

Vestibular-evoked myogenic potential testing may provide additional information about the vestibular system and allow site of lesion testing (e.g. saccule and inferior vestibular nerve) in patients of all ages. Its role has yet to be defined in the diagnosis and treatment of common vestibular disorders, including Meniere's disease, vestibular neuronitis, labyrinthitis, and other diseases. Further research is needed to support its clinical usefulness in patients with balance disorders, to optimize patient selection, and to establish its cost effectiveness.

Vestibular-evoked myogenic potentials and caloric stimulation in infants with congenital cytomegalovirus infection

BACKGROUND

The influence of congenital cytomegalovirus infection on cochlear function has been well recognised; however, its impact on the vestibular system in infants has not been examined. The purpose of the present study was to evaluate vestibular function in a group of infants, using caloric stimulation tests and vestibular-evoked myogenic potential measurements.

MATERIALS AND METHODS

Vestibular-evoked myogenic potentials and auditory brainstem responses were recorded and caloric stimulation was performed in 66 infants aged three months, comprising 40 healthy controls and 26 infants with congenital cytomegalovirus infection.

RESULTS

No reaction to caloric stimulation was elicited from 16 examined ears, no vestibular-evoked myogenic potentials were recorded from 12 ears, and profound sensorineural hearing loss was diagnosed in eight ears. Pathological results were observed predominantly in infants with symptoms of intrauterine congenital cytomegalovirus infection present at birth.

CONCLUSIONS

In infants with clinical symptoms of congenital CMV infection present at birth, abnormal vestibular test results occurred more frequently than abnormal auditory brainstem response results. Vestibular organs should be routinely examined in individuals with congenital cytomegalovirus infection.

Clinical value of tone burst vestibular evoked myogenic potentials at threshold in acute and stable Ménière's disease

Introduction:

The objectives of this preliminary, prospective, cohort study were to ascertain the characteristics of vestibular evoked myogenic potentials at threshold levels in two groups of Ménière's disease patients – acute and stable – and to identify whether vestibular evoked myogenic potentials can provide any specific, objective information to distinguish acute from stable Ménière's disease.

Subjects and methods:

The study was based at a tertiary neuro-otology centre. Twenty adult patients who fulfilled the American Academy of Otolaryngology–Head and Neck Surgery1 criteria for Ménière's disease were divided into two groups: 11 patients with acute Ménière's disease and nine patients with stable Ménière's disease. Eighteen healthy adult volunteers served as controls. All subjects underwent vestibular evoked myogenic potential testing with ipsilateral, short tone burst stimuli at 500 Hz, as well as pure tone audiometry. The patients also underwent caloric testing.

Results:

Vestibular evoked myogenic potentials were present in all controls, and were present in 65 per cent of patients but absent in 35 per cent. The mean absolute threshold (Tvestibular evoked myogenic potential) ± standard deviation in normal controls was 116 ± 7.7 dBSPL; this did not differ statistically from that in patients, nor did it differ between acute and stable Ménière's disease. The p13/n23 latencies at the threshold levels in the normal, acute and stable groups (mean ± standard deviation) were respectively: 15 ± 2.2 ms/23.0 ± 2.5 ms; 15.7 ± 0.9 ms/23.7 ± 0.9 ms; and 15.3 ± 2.0 ms/24.2 ± 1.9 ms. The mean interaural amplitude difference ratio (IAD) ± standard deviation was significantly higher in the stable group compared with the acute group (0.54 ± 0.33 vs −0.15 ± 0.22; p = 0.007) and with the controls (0.54 ± 0.33 vs 0.1 ± 0.22; p = 0.05).

Conclusions:

The parameter that best differentiated acute from stable Ménière's disease at threshold was the interaural amplitude difference ratio. Therefore, this parameter may be used to monitor the clinical course of Ménière's disease.

Vestibular evoked myogenic potentials

PURPOSE OF REVIEW

Vestibular evoked myogenic potential testing is the only clinically feasible way to measure function of the saccule. Interest in this test has exploded in recent years because of its potential utility in diagnosing third-window disorders and in diagnosing and monitoring Ménière's disease.

RECENT FINDINGS

Recent literature on vestibular evoked myogenic potential covers a wide range of topics. Review articles, method articles and many case reports and uncontrolled case series are seeking new applications for vestibular evoked myogenic potential in diagnosis and monitoring of neurotologic disease, and in shedding light on inner ear diseases by mapping anatomic sites of involvement. The most informative work is still in the areas of superior semicircular canal dehiscence and in Ménière's disease. Also, many aspects of vestibular evoked myogenic potential and its use have not yet been adequately studied or described.

SUMMARY

Vestibular evoked myogenic potential is a new test of saccular and inferior vestibular nerve integrity. It holds great promise for diagnosing and monitoring Ménière's disease and some other neurotologic disorders. It is still an evolving field, however. The methods, equipment, and applications for vestibular evoked myogenic potential testing are not yet standardized. It is not yet time for this test to be widely applied, but that time is not far off.

Validity of a new feedback method for the VEMP test

CONCLUSIONS

We used a feedback method, based on a blood pressure manometer with inflatable cuff, to control the sternocleidomastoid muscle (SCM) contraction. To obtain comparable left-right VEMP responses, it is necessary (1) to determine which cuff pressures on both sides yield identical mean rectified voltage (MRV) values of the SCM contraction and (2) to apply these cuff pressures during the VEMP test.

OBJECTIVE

To investigate the effect of the SCM muscle contraction variability on the VEMP variables when applying the feedback method.

MATERIALS AND METHODS

Subjects pushed with their jaw against the hand-held inflated cuff to generate cuff pressures of subsequently 30, 40 and 50 mmHg during a MRV and VEMP measurement.

RESULTS

When analyzing the relationship between the applied cuff pressures and the MRV values/VEMP amplitudes, we showed that (1) there was a linear relationship, (2) there was no side effect and (3) there was an interaction effect between 'side' and 'subject'. There was neither a side effect, nor an effect of the applied cuff pressure when considering the p13 latencies. As for the n23 values, there was no side effect but there was a significant difference when comparing the n23 latencies at cuff pressures of 30 vs 40 mmHg/50 mmHg.

Diagnostic value of vestibular evoked myogenic potentials in cerebellar and lower-brainstem strokes

BACKGROUND

Vestibular evoked myogenic potentials (VEMPs) provide assessment of vestibular function. They consist in picking up compound muscle action potentials in the sternocleidomastoid (SCM) muscles in response to auditory stimulation of the vestibulum. VEMP testing has found application mainly in peripheral vestibular disorders, whereas reports about VEMPs in central vestibular lesions are rather scarce.

AIMS OF THE STUDY

Based on the physiological connections between the cerebellum and the vestibular nuclei, we investigated the influence on VEMPs of cerebellar and lower-brainstem strokes. We examined whether or not this method may be suitable as a clinical tool for the evaluation of the extent of cerebellar strokes.

PATIENTS AND METHODS

Nineteen patients with cerebellar ischemic stroke and 15 patients with lower-brainstem ischemic stroke (11 in the pons, four in the medulla) were included. The latencies and amplitudes of P13 and N23 in both groups of patients were compared with those obtained in a control group of 53 normal individuals.

RESULTS

VEMP responses were obtained in all patients and controls. At the group level, mean peak latencies and amplitudes, and the number of subjects with significantly deviant values did not differ between patients and controls. There were no latency or amplitude differences ipsilaterally or contralaterally to the lesion. At the individual level, there was no correlation between laterality of lesion and that of P13 or N23 abnormalities in patients with cerebellar strokes; however, there were two patients (one pontine, one medullar stroke) who presented P13 and N23 latency abnormalities ipsilaterally to the lesion.

CONCLUSION

Cerebellar strokes do not influence VEMPs. Moreover, despite previous reports, we were unable to find at a group level any statistically significant VEMP changes in patients with lower-brainstem strokes as compared with controls. Therefore, VEMPs do not appear a suitable tool for assessment of brainstem integrity in patients with posterior fossa strokes. However, they could constitute a sensitive method for documentation of involvement of the central vestibular pathways in patients with brainstem stroke.

Vestibulär evozierte myogene Potenziale

The recording of vestibular evoked myogenic potentials is a relatively new neuro-otologic method which gives specific information about the function of the sacculus and the inferior vestibular nerve on each side separately. The main indications for this method are vestibular schwannoma and fistula of the labyrinth, involvement of the sacculus or the inferior vestibular nerve in Menière's disease and vestibular neuritis, vertigo of unknown etiology, and forensic questions.

Saccular damage in patients with high-frequency sensorineural hearing loss

Subjects with high frequency sensorineural hearing loss (HF-SNHL) without retrocochlear pathology are those group which certainly encountered inner ear damaging factors. This study was designed to evaluate the effects of cochlear damaging factors on the sacculocollic pathway. Fifty patients (76 ears) with varying degrees of HF-SNHL but without clinical manifestations of vestibular pathology tested for vestibular evoked myogenic potentials (VEMP). The results were compared with those of 18-healthy referents (32 ears) examined in the same way. Subjects with HF-SNHL greater than 40 dB HL showed significantly more saccular deterioration, estimated as negative VEMP responses than did the referents. This suggests subclinical disturbances of the vestibular system especially of the saccule in these patients. The underlying mechanism may be simultaneous damage to both the cochlea and saccule by the same factors.