The effects of click and tone-burst stimulus parameters on the vestibular evoked myogenic potential (VEMP)

Vestibular evoked myogenic potentials (VEMP) are short latency electromyograms (EMG) evoked by high-level acoustic stimuli and recorded from surface electrodes over the tonically contracted sternocleidomastoid (SCM) muscle and are presumed to originate in the saccule. The present experiments examined the effects of click and tone-burst level and stimulus frequency on the latency, amplitude, and threshold of the VEMP in subjects with normal hearing sensitivity and no history of vestibular disease. VEMPs were recorded in all subjects using 100 dB nHL click stimuli. Most subjects had VEMPs present at 500, 750, and 1000 Hz, and few subjects had VEMPs present at 2000 Hz. The response amplitude of the VEMP increased with click and tone-burst level, whereas VEMP latency was not influenced by the stimulus level. The largest tone-burst-evoked VEMPs and lowest thresholds were obtained at 500 and 750 Hz. VEMP latency was independent of stimulus frequency when tone-burst duration was held constant.     

Improving vestibular evoked myogenic potential reliability by using a blood pressure manometer

OBJECTIVE/HYPOTHESIS: To improve the reliability of vestibular evoked myogenic potentials (VEMP), we propose a feedback method making use of a readily available blood pressure manometer with inflatable cuff to control the sternocleidomastoid muscle (SCM) contraction. STUDY DESIGN: Prospective study. MATERIALS AND METHODS: The feedback method for SCM contraction consisted of subjects pushing with their jaw against the hand-held inflated cuff to generate a specified cuff pressure. This pressure level was monitored by subject and investigator. First, we tested in a group of healthy subjects whether there was a learning or fatigue effect during four successive SCM contraction runs when making use of the feedback method. Then, we investigated the mean rectified voltage (MRV) values of the SCM. Next, we examined the hypothesis that the MRV values of the SCM contraction measured before and simultaneously with the VEMP test were equal when using this feedback method. Finally, we compared the VEMP amplitude variability in two circumstances: with and without the feedback method. RESULTS: There was no learning or fatigue effect, and the MRV values measured before the VEMP were not significantly different from those measured during the VEMP test. The VEMP amplitude variability was significantly lower when applying the feedback method than when no feedback method was used. CONCLUSION: This feedback method improves significantly the VEMP amplitude reliability.     

Characterization of age-related changes in vestibular evoked myogenic potentials.

A tone-burst stimulation of 500 Hz seems to be clinically most appropriate to elicit vestibular evoked myogenic potentials (VEMPs) because those VEMPs can be recorded at the lowest stimulus intensity possible. However, little is known about gender and age-related changes of the amplitude in tone-burst (500 Hz) evoked VEMPs. The aim of the present paper was therefore to investigate the influence of gender and age on VEMP amplitude in relation to the tonic muscle activity. VEMPs of 64 healthy subjects were recorded ipsilaterally during air- or bone-conducted tone burst stimulation. The EMG of the tonically activated sternocleidomastoid muscle was recorded ipsilaterally with surface electrodes. Averages were taken for P1/N1 amplitudes of male and female volunteers within 3 different age groups. Although the amplitude decreased with increasing age the tonic activity was not significant different between the age groups. Consequently the relation between VEMP amplitude and tonic muscle activity decreased with increasing age. The normative values of the age-dependent relation between VEMP amplitude and tonic muscle activity were described by the 90% confidence interval of the individual values. Normative thresholds were calculated. Normal saccular receptor function could be diagnosed if the VEMP amplitude is above (or equal to) the normative value at a given tonic muscle activity and age. Normative data as described above are required to diagnose isolated saccular defects, which are indicative of a vestibular disorder.     

Aging effect on vestibular evoked myogenic potential.

OBJECTIVE: Vestibular evoked myogenic potential (VEMP) is applied to explore the integrity of sacculocollic reflex. Although tests to evaluate vestibular-ocular reflex pathway have shown that vestibular function is adversely affected by aging, VEMP, in this study, is used as a novel test to define how aging influences sacculocollic reflex pathway. STUDY DESIGN: Prospective study. SETTING: Academic tertiary referral center. SUBJECTS: Eighty normal subjects, equally divided into four groups according to their age, were enrolled to this study. Group I included patients aged <20 years, Group II patient ages ranged from 21 to 40 years, Group III patients were 41 to 60 years, and Group IV included patients older than 60 years. INTERVENTIONS: Recordings of VEMP responses. MAIN OUTCOME MEASURES: The response rate and parameters of VEMP, including p13 latency, n23 latency, amplitude, and interaural difference ratio. RESULTS: The VEMP response rates from Groups I to IV was 98%, 98%, 90%, and 60%, respectively, disclosing a significant difference only between Group IV and other groups (p < 0.05). The amplitude was negatively correlated with age in contrast to the n23 latency, correlating positively with age; both reached a significant difference (p < 0.05). Although the p13 latency had a trend to prolong as age increased, no significant correlation existed (p < 0.06). Moreover, the interaural difference ratio was also not significantly correlated with age. CONCLUSIONS: As age increased over 60 years, the VEMP response rate decreased dramatically. While age increased, the VEMP amplitude decreased in comparison to n23 latency prolonged. These findings might suggest that aging could deteriorate the saccular and corresponding neural functions. When interpreting the VEMP parameters, it should be kept in mind that aging could affect VEMP responses. Based on this study, we suggest establishing different reference values according to different age groups when evaluating VEMP response in patients with vestibular diseases.     

The effect of sternocleidomastoid electrode location on vestibular evoked myogenic potential

OBJECTIVE: The purpose of this study was to investigate the effect of a sternocleidomastoid (SCM) electrode array on the vestibular evoked myogenic potential (VEMP) and the most optimal recording site for clinical use. METHODS: Fifteen normal adults (10 men and 5 women, aged 18 to 38 years) were tested. We placed electrodes at four different locations over the SCM muscle: the upper part of the SCM muscle at the level of mandibular angle, the middle part of the muscle, and immediately above sternal and clavicular origins of the SCM muscle. Sound evoked myogenic potentials in response to monoaurally delivered short tone-bursts (500 Hz at 95 dBnHL, rise/fall time=1 ms and plateau=2 ms) were recorded with surface electrodes over the isometrically contracting SCM muscle. RESULTS: On the clavicle, the upper and middle parts of SCM from all subjects, air-conducted short tone burst evoked biphasic responses (p13-n23). VEMPs recorded at the upper part of the muscle showed the largest amplitude, followed by that at the middle part. However, the latency of the first peaks (p13-n23) was not constant in the upper part. Recording from the middle part of SCM muscle were more consistent. CONCLUSION: Our findings suggest that the middle part of the SCM muscle is the optimal location for recording vestibular evoked myogenic potential.     

Does the method of sternocleidomastoid muscle activation affect the vestibular evoked myogenic potential response?

The objective of this study was to assess the effects of different methods of sternocleidomastoid muscle (SCM) activation on vestibular evoked myogenic potentials (VEMP). Forty normal volunteers were tested using three different methods of SCM activation: sitting with the head turned away from the test ear (SIT), supine with the head held straight up (SHU), and supine with the head held up and turned away from the test ear (SHT). Dependent measures were latency, and amplitude. Head and body position significantly affected the amplitude of the VEMP, but had no significant effect on latency. Testing subjects in the supine position with the head up and turned toward the non-test ear yielded the most robust amplitude response and sternocleidomastoid EMG activity. When amplitude measures where corrected according to tonic electromyographic (EMG) activity no significant difference was noted between the three different test positions. The increased amplitude in the supine with head turned position can be directly attributed to increased tonic SCM EMG activity.     

前庭诱发的肌源性电位临床应用

前庭诱发的肌源性电位（Vestibular evoked myogenic potentials，VEMP）可用于评价球囊功能及其对称性。本文总结VEMP在神经耳科学中的应用情况。首先建立VEMP的临床适用的检查方法，这些方法包括：刺激声的选择、刺激强度及给声方式，建立VEMP在振幅、阈值、潜伏期和耳间潜伏期的正常值。临床上常用于：梅尼埃病和迟发性膜迷路积水、前庭神经炎、听神经瘤、前半规管裂综合征和听神经病的诊断定位。VEMP的振幅变化较大．潜伏期的变化较大，而阈值较稳定。梅尼埃病和迟发性膜迷路积水、前庭神经炎、听神经瘤可以出现振幅的异常或引不出；梅尼埃病、迟发性膜迷路积水和听神经瘤可见振幅和潜伏期异常。听神经瘤还可见耳间潜伏期延长。听神经病主要表现为振幅的异常，振幅减低或引不出。VEMP是一种稳定的肌源性电位，双侧声刺激较为适宜。VEMP的阈值检查主要用于压力或声音敏感性眩晕；耳间潜伏期的异常主要见于桥一小脑角占位病变：振幅和潜伏期的异常一般没有特异性．可见于累及前庭下神经的病变。     

Symmetry measures of vestibular evoked myogenic potentials using objective detection criteria.

Vestibular evoked myogenic potentials (VEMP) has been put forward as a test to evaluate the symmetry of saccular function. In the present study, the symmetry of VEMP was evaluated in 23 healthy subjects using automatic analysis. In response to binaural clicks with a stimulus repetition rate of 4/s all subjects revealed significant VEMP on both sides. The ipsilateral response to monaural clicks was similar to the response to binaural clicks. Although there were large interindividual variations in amplitude, there were only small variations in latency. VEMP measurements were also assessed using different stimulus rates. At the higher stimulus rates there was a decrease in the VEMP amplitude but there were only small changes in the latency. These findings might suggest that amplitude measures are more likely than latency measures to reveal small vestibular lesions.     

Variance of vestibular-evoked myogenic potentials

OBJECTIVES/HYPOTHESIS: Vestibular-evoked myogenic potential (VEMP) has been thought to originate from sacculus. The variance of this potential and the effectiveness of the adjustments of pInII amplitudes using average muscle tonus of ipsilateral sternocleidomastoid muscle were evaluated. In addition, clinical application of VEMP was examined in patients with acoustic tumors (ATs) and vestibular neurolabyrinthitis (VNL). STUDY DESIGN: Prospective evaluation of the VEMP in 18 normal volunteers and 6 patients. METHODS: Variance and left-right difference of each parameter, including pI latency, nII latency, pInII amplitude, and threshold, was analyzed. Input-output function of pInII amplitude was evaluated. Average muscle tonus was calculated in 20 ears and applied for adjustment of pInII amplitude. Sensitivity of each parameter of VEMP was examined in 3 patients with ATs and 3 patients with VNL. RESULTS: VEMP was present in all 36 ears of 18 control subjects. Thresholds of VEMP for normal subjects were 80 to 95 dB normal hearing level (nHL). The muscle tonus affected pInII amplitude significantly; however, no statistically significant improvement was observed in test-retest investigation after adjustment using muscle tonus. The threshold of the affected side was elevated compared with the non-affected side in all patients with ATs, whereas 2 of 3 patients showed normal pInII-ratio. One patient with VNL presented normal VEMP, whereas 2 patients presented no VEMP to the highest stimulus intensity. CONCLUSIONS: Interaural difference of thresholds might be the most useful parameters. Adjustment using average muscle tonus is not necessary when the subject is able to get sufficient muscle tonus.     

人类声诱发短潜伏期负电位的研究

目的在极重度感音性聋耳的ABR检测中发现一个位于3～4ms潜伏期的"V"字形负向波形,称声诱发短潜伏期负电位(Acoustically Evoked Short Latency Negative Response,ASNR)。本研究通过大宗病例调查和临床实验来探讨ASNR的特点和起源。方法回顾性调查并分析3104例ABR检测结果,以详尽了解ASNR的出现率和特性。对20名双耳极重度感音性耳聋患者(6～62岁)和12名健康人(23～30岁)进行了ABR和前庭诱发肌源性电位(VEMP)测试。患者组包括了16名人工耳蜗植入术后的患者,植入耳在裸耳状态时可提供无功能耳蜗模型。结果判读侧重于:人工耳蜗植入耳能否诱发ASNR,以及对比在极重度感音性聋耳中ASNR组和非ASNR组的VEMP出现率及反应阈值。结果ASNR仅出现于极重度感音性聋耳,并且对强声刺激(80～120dBnHL)有依赖性。在653例极重度感音性聋患者(981耳)的ABR波形中,有80例(12.3%)117耳(11.9%)出现了ASNR。ASNR有良好的重复性,可排除伪迹干扰的可能性。ASNR具有神经电位的特征,表现在随着声刺激的增强,其潜伏期缩短而振幅增大。ASNR与ABR的波形完全不一样,无法将其解释为传统听觉神经通路产生的电位。临床实验中,3个人工耳蜗植入耳能诱发出ASNR,说明ASNR的发生与耳蜗无关。所有9个ASNR耳都诱发出VEMP,且阈值与正常对照组无统计学差异(P>0.05),提示ASNR耳具有正常的球囊功能。在非ASNR组中,三分之二没有引出VEMP,而另外三分之一虽然可以诱发出VEMP,但阈值明显较正常对照组高(P<0.01),分别提示球囊功能丧失或低下。此外,有一外半规管麻痹耳诱发出了ASNR和VEMP。结论ASNR并非伪迹,而是一种依赖强声刺激,且只出现于极重度感音性聋耳的神经电位。ASNR的出现完全依赖于正常的球囊功能,而不依赖于残余听力或者半规管功能。据此认为ASNR起源感觉器官为球囊,根据其潜伏期推测电位源自前庭神经核。     

听力正常儿童骨导前庭诱发肌源性电位正常值的建立

目的 记录听力正常儿童骨导前庭诱发肌源性电位(BC-VEMP)特征,为临床儿童前庭功能评估提供参考。 方法 选择31名(62耳)4~12岁听力正常儿童,按照年龄进行分组,4~5岁组11人(22耳),6~12岁组20人(40耳),行BC-VEMP测试。将60 dB nHL作为起始刺激强度,记录骨导刺激时颈性VEMP(cVEMP )、眼性VEMP(oVEMP)的N1潜伏期、P1潜伏期、N1-P1波间期、N1-P1波幅、波幅不对称比以及阈值。使用SPSS软件进行统计学分析。 结果 4~12岁听力正常儿童BC-VEMPs引出率为100%。4~5岁组与6~12岁组相比,BC-cVEMP的P1、N1潜伏期、P1-N1波间期、P1-N1波幅、阈值、波幅不对称比均无统计学差异(P>0.05)。两组间BC-oVEMP的N1、P1潜伏期、N1-P1波间期、N1-P1波幅、阈值、波幅不对称比均无统计学差异(P>0.05)。 结论 BC-VEMPs是一种可行的前庭功能辅助性检査手段,不同年龄段儿童BC-VEMPs正常值的建立,可为儿童前庭功能的评估提供参考。     

不同刺激模式前庭诱发肌源性电位的反应特性

目的 前庭诱发的肌源性电位(vestibular evoked myogenic potential,VEMP)可用于评价球囊功能及其对称性,比较3种刺激模式VEMP的振幅与潜伏期,希望得出适合临床应用的方法。方法 测量21名健康成人3种刺激模式(双侧短声、1侧短声和1侧短声对侧白噪声)的VEMP的潜伏期、振幅,计算出3种情况下的振幅及潜伏期的均值、双侧振幅比值、双侧振幅不对称性。结果 3种刺激模式刺激侧振幅与潜伏期无明显差异,但1侧短声刺激对侧振幅低于刺激侧,潜伏期比刺激侧长2-3 ms。双侧短声刺激p13波和n23波出现率为100％,1侧短声对侧白噪声刺激p13和n23出现率最低,无特别应用的意义。3种刺激方式VEMPs振幅变化较大。结论 VEMP是一种稳定的肌源性电位,双侧短声刺激和1侧短声刺激都不失为较好的刺激方法,双侧给声对双侧听力正常者较为适宜。应用双侧VEMP的振幅比值和对称性,判断双侧球囊的功能。     

Vestibular evoked myogenic potentials in young children: test parameters and normative data

OBJECTIVE: The vestibular evoked myogenic potential (VEMP) is a test of the vestibulocollic reflex that has been extensively studied in adults. Much is known about the normal values in adults as well as their changes with age. In children, the expected test values and their possible changes in development have not yet been described nor has the feasibility of reliable testing in this group. The aim of this prospective study is to accumulate normative data and to verify the viability of testing in young children. The study focused on optimal test parameters, reproducibility, and subject compliance in a pediatric population. METHODS: Thirty normal-hearing children (60 ears) ages 3 to 11 completed VEMP testing and audiograms for analysis. VEMP testing was performed with alternating clicks at three intensities (80-, 85-, and 90-dB normalized hearing level) using averaged, unrectified electromyograms recorded by surface electrode on the sternocleidomastoid muscle ipsilateral to the stimulus. VEMP latencies, amplitude, compliance, and length of testing were recorded for each patient, as well as their feedback on the testing session. The subjects were divided into four age groups for analysis. RESULTS: All but one of the subjects attempting VEMP testing was able to finish. Of 30 children completing VEMP tests, bilateral reflexes were recorded for all subjects with symmetric responses in 28 of 30 subjects (93%). The mean peak latencies (+/- standard deviation [SD]) of pI and nII were 11.3 msec (1.3 ms) and 17.6 msec (1.4 ms), respectively. The mean pI-nII amplitude (+/- SD) was 122 muV (68 muV). There was a significantly shorter nII mean peak latency of group I (ages 3-5) left ear in comparison to other groups, with an absolute shorter mean latency nII in the right ear of group I (not significant). Average test time was 15 minutes with two researchers testing, and subjects were highly compliant. CONCLUSIONS: VEMP is a well-tolerated test for screening vestibular function in young children, performed with minimal test time and reproducible results. Mean latencies in this study suggested a shorter initial negative peak (nII) than in adult studies, consistent with prolongation seen in previous research on the effects of age. Ninety-decibel normalized hearing level clicks were adequate for uniform response rates. Expected latency and amplitude values in single-channel VEMP-unrectified electromyograms were established. This is the first study describing expected latencies and optimal testing parameters in children.     

Response characteristics of vestibular evoked myogenic potentials recorded over splenius capitis in young adults and adolescents

Background and objectivesExamine vestibular evoked myogenic potential (VEMP) responses recorded from surface electrodes over Splenius Capitis (SPC) in a seated position. Specific aims: (1) validate response characteristics of VEMP recordings from surface electrodes over Sternocleidomastoid (SCM) and over SCP and (2) assess age effects on responses in adolescents and young adults.Materials and methodsSimultaneous surface VEMP was recorded bilaterally from electrodes placed over the dorsal neck musculature at a location known from previous work to record from SPC in 15 healthy participants during trials with head rotation toward and away from the stimulated ear. VEMP was also recorded from electrodes over SCM, ipsilateral to the stimulus ear, in the same participants in a supine, head lift/turn position.ResultsResponse amplitudes significantly increased with contraction strength and decreased with age. Participants were able to maintain sufficient contraction strength (amplitude) with head rotation to reliably measure over SPC. Normalized response amplitudes measured from electrodes over contralateral SPC were largest with head rotation contralateral to the stimulus ear. Normalized amplitudes and peak latencies were comparable to the same measures from SCM obtained in supine, head lift/turn position.ConclusionsOtolith generated myogenic responses can be recorded seated from electrodes over the dorsal neck with head rotation contralateral to the stimulus ear. In this position, contralateral recordings are consistent with responses known from previous work to arise from SPC; ipsilateral recordings may include crosstalk from activated muscles nearby, including ipsilateral SCM. Overall, techniques targeting contralateral SPC during contralateral head turn may provide additional methods of recording VEMPs.     

Bone-conducted evoked myogenic potentials from the sternocleidomastoid muscle

The aim of this study was to show that bone-conducted clicks and short tone bursts (STBs) can evoke myogenic potentials from the sternocleidomastoid muscle (SCM) and that these responses are of vestibular origin. Evoked potential responses to bone-conducted auditory stimuli were recorded from the SCMs of 20 normal volunteers and from 12 patients with well-defined lesions of the middle or inner ear or the VIIIth cranial nerve. The subjects, who had various labyrinthine and retro-labyrinthine pathologies, included five patients with bilateral profound conductive hearing loss, two with bilateral acoustic neuroma post-total neurectomy and five with bilateral sensorineural hearing loss. Air- and bone-conducted evoked myogenic potentials in response to clicks and STBs were recorded with surface electrodes over each SCM of each subject. In normal subjects, bone- and air-conducted clicks and STBs evoked biphasic responses from the SCM ipsilateral to the stimulated ear. The bone-conducted clicks evoked short-latency vestibular-evoked myogenic potential (VEMP) responses only in young subjects or in subjects with conductive hearing loss. STBs evoked VEMPs with higher amplitude and better waveform morphology than clicks with the same acoustic intensity. Patients with total VIIIth cranial nerve neurectomy showed no responses to air- or bone-conducted click or STB stimuli. Clear VEMP responses were evoked from patients with conductive or sensorineural hearing loss. It is concluded that loud auditory stimuli delivered by bone- as well as air conduction can evoke myogenic potentials from the SCM. These responses seem to be of vestibular origin.     

Bone-Conducted Evoked Myogenic Potentials from the Sternocleidomastoid Muscle

The aim of this study was to show that bone-conducted clicks and short tone bursts (STBs) can evoke myogenic potentials from the sternocleidomastoid muscle (SCM) and that these responses are of vestibular origin. Evoked potential responses to bone-conducted auditory stimuli were recorded from the SCMs of 20 normal volunteers and from 12 patients with well-defined lesions of the middle or inner ear or the VIIIth cranial nerve. The subjects, who had various labyrinthine and retro-labyrinthine pathologies, included five patients with bilateral profound conductive hearing loss, two with bilateral acoustic neuroma post-total neurectomy and five with bilateral sensorineural hearing loss. Air- and bone-conducted evoked myogenic potentials in response to clicks and STBs were recorded with surface electrodes over each SCM of each subject. In normal subjects, bone- and air-conducted clicks and STBs evoked biphasic responses from the SCM ipsilateral to the stimulated ear. The bone-conducted clicks evoked short-latency vestibular-evoked myogenic potential (VEMP) responses only in young subjects or in subjects with conductive hearing loss. STBs evoked VEMPs with higher amplitude and better waveform morphology than clicks with the same acoustic intensity. Patients with total VIIIth cranial nerve neurectomy showed no responses to air- or bone-conducted click or STB stimuli. Clear VEMP responses were evoked from patients with conductive or sensorineural hearing loss. It is concluded that loud auditory stimuli delivered by bone- as well as air conduction can evoke myogenic potentials from the SCM. These responses seem to be of vestibular origin     

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.     

Diagnostic value of prolonged latencies in the vestibular evoked myogenic potential

BACKGROUND: As a parameter for the evaluation of the vestibular evoked myogenic potential (VEMP), amplitude has been used clinically. However, the significance of latency has not been considered. OBJECTIVE: To clarify the diagnostic value of latencies of the VEMP. DESIGN: We reviewed records of the VEMP of patients with various diseases and compared them with records of healthy volunteers. SETTING: Data were collected from patients in an outpatient clinic of a tertiary care center and healthy volunteers. SUBJECTS: Clinical records of 134 patients (61 men and 73 women, aged 20-75 years) were reviewed. Diagnoses were Meniere disease in 43 patients, acoustic neuroma in 62 patients, vestibular neuritis in 23 patients, and multiple sclerosis in 6 patients. Also, 18 healthy volunteers (13 men and 5 women, aged 25-38 years) were enrolled. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURES: Click-evoked myogenic potentials were recorded with surface electrodes over each sternocleidomastoid muscle. Latencies and amplitudes of responses were measured. RESULTS: Vestibular evoked myogenic potentials were absent or decreased in 51% of patients with Meniere disease (n = 22), 39% with vestibular neuritis (n = 9), 77% with acoustic neuroma (n = 48), and 25% with multiple sclerosis (3 of 12 sides of 6 patients). Concerning latency, patients with Meniere disease or vestibular neuritis hardly showed any latency prolongation. Four patients with acoustic neuroma showed prolonged p13; all had large tumors. All patients with multiple sclerosis showed prolonged p13. CONCLUSION: Prolonged latencies of the VEMP suggest lesions in the retrolabyrinthine, especially in the vestibulospinal tract.     

An acoustically evoked short latency negative response in profound hearing loss infants

OBJECTIVE: A large negative deflection with a 3-4 ms latency within the auditory brainstem response has been reported in some profound hearing loss ears under intense stimuli in adult subjects. The wave has been termed the N3 potential or acoustically evoked short latency negative response and it is assumed to be a vestibular-evoked potential. The purpose of the current study was to investigate the relationship between the vestibular-evoked myogenic potentials and the acoustically evoked short latency negative response in infants with a functionless cochlea and normal or impaired semicircular canal. METHODS: Seventeen 3 months old infants with profound bilateral sensorineural hearing loss had acoustically evoked short latency negative responses and vestibular-evoked myogenic potentials recorded and caloric tests performed. RESULTS: No spontaneous symptoms of vestibular dysfunction were found in the examined infants. ASNR with medium latency 3.3 ms and threshold value 80-90 dB normal hearing level was elicited from 10 ears. VEMPs were present in 12 ears. ASNRs and VEMPs were absent in two ears with normal response to caloric stimulation. No response to caloric stimulation was elicited from other two ears with normal saccular function. For the ears with absence of ASNR, four had normal VEMP and the rest were considered to have saccular afunction. Significant correlation was found between the presence of ASNRs and VEMPs. CONCLUSION: Acoustically evoked short latency negative responses could be a valuable tool for assessing vestibular function in infants with profound sensorineural hearing loss.     

不同刺激模式前庭诱发肌源性电位的反应特性

目的前庭诱发的肌源性电位(vestibular evoked myogenic potential，VEMP)可用于评价球囊功能及其对称性，比较3种刺激模式VEMP的振幅与潜伏期，希望得出适合临床应用的方法。方法测量21名健康成人3种刺激模式(双侧短声、1侧短声和1侧短声对侧白噪声)的VEMP的潜伏期、振幅，计算出3种情况下的振幅及潜伏期的均值、双侧振幅比值、双侧振幅不对称性。结果3种刺激模式刺激侧振幅与潜伏期无明显差异，但1侧短声刺激对侧振幅低于刺激侧，潜伏期比刺激侧长2～3ms。双侧短声刺激p13波和n23波出现率为100％，1侧短声对侧白噪声刺激p13和n23出现率最低，无特别应用的意义。3种刺激方式VEMPs振幅变化较大。结论VEMP是一种稳定的肌源性电位，双侧短声刺激和1侧短声刺激都不失为较好的刺激方法，双侧给声对双侧听力正常者较为适宜。应用双侧VEMP的振幅比值和对称性，判断双侧球囊的功能。