Sound-evoked myogenic potentials on the sternocleidomastoid muscle in monkeys

CONCLUSION: We recorded sound-evoked myogenic potentials of the sternocleidomastoid (SCM) muscle using awake monkeys. The characteristics of these potentials are similar to those of vestibular evoked myogenic potentials (VEMPs) in humans, suggesting that the sound-evoked myogenic potentials of the SCM muscle in monkeys may be utilized as an animal model of VEMPs. OBJECTIVE: The pathway of the VEMPs remains uncertain as no animal model has yet been used to record sound-evoked myogenic potentials in the SCM muscle. Therefore, the present study aimed to establish an animal model of VEMPs using macaque monkeys. MATERIALS AND METHODS: Four macaque monkeys were used. A pair of electrodes was attached on the SCM muscle ipsilateral side to the intense sound stimulation. RESULTS: The sound-evoked myogenic potentials of the SCM muscle exhibited a biphasic waveform. When a click at 125 dBSPL was applied, the peak latency of the first positive wave was 12.5 ms and was not delayed when the stimulating sound intensity was reduced. The thresholds of the myogenic potentials were 103 dBSPL, which were 43 dB higher than those of the auditory brainstem response (ABR). When a short tone burst was applied, the reactive optimal frequency of the myogenic potentials was relatively low (500-1000 Hz).     

Acoustic Clicks Activate both the Canal and Otolith Vestibulo-Ocular Reflex Pathways in Behaving Monkeys

Acoustic activation of the vestibular system has been well documented in humans and animal models. In the past decade, sound-evoked myogenic potentials in the sternocleidomastoid muscle (cVEMP) and the extraocular muscles (oVEMP) have been extensively studied, and their potentials as new tests for vestibular function have been widely recognized. However, the extent to which sound activates the otolith and canal pathways remains controversial. In the present study, we examined this issue in a recently developed nonhuman primate model of acoustic activation of the vestibular system, i.e., sound-evoked vestibulo-ocular reflexes (VOR) in behaving monkeys. To determine whether the canal and otolith VOR pathways are activated by sound, we analyzed abducens neurons' responses to clicks that were delivered into either ear. The main finding was that clicks evoked short-latency excitatory responses in abducens neurons on both sides. The latencies of the two responses, however, were different. The mean latency of the contralateral and ipsilateral abducens neurons was 2.44 ± 0.4 and 1.65 ± 0.28 ms, respectively. A further analysis of the excitatory latencies, in combination with the known canal and otolith VOR pathways, suggests that the excitatory responses of the contralateral abducens neurons were mediated by the contralateral disynaptic VOR pathways that connect the lateral canal to the contralateral abducens neurons, and the excitatory responses of the ipsilateral abducens neurons were mediated by the ipsilateral monosynaptic VOR pathways that connect the utricle to the ipsilateral abducens neurons. These results provide new insights into the understanding of the neural basis for sound-evoked vestibular responses, which is essential for developing new tests for both canal and otolith functions in humans.     

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.     

Vestibular evoked myogenic potentials induced by intraoperative electrical stimulation of the human inferior vestibular nerve

Vestibular evoked myogenic potentials (VEMPs) can be recorded from sternocleidomastoid muscle (SCM) in clinical practice. The aim of the present study was to investigate VEMPs upon direct electrical stimulation of the human inferior vestibular nerve to evidence the vestibulocollic reflex arch and their saccular origin, respectively. Seven subjects were stimulated at the inferior (IVN) and superior (SVN) vestibular nerve. The EMG signals of the SCM were recorded. These recordings were compared to air- and bone-conduction evoked VEMPs with respect to latency and shape. All subjects showed normal VEMPs upon acoustic stimulation with a latency of 12.8+/-1.4 ms for P13, and 22.7+/-2.0 ms for the N23 pre-operatively. Upon direct electrical stimulation of the IVN, the mean latency of the positive peak was 9.1+/-2.2 and 13.2+/-2.3 ms for the negative one. No contralateral SCM response was found. Electrical stimulation of the SVN did not result in any EMG response of the SCM. The study shows experimental evidence of the vestibulocollic reflex by direct electrical stimulation of the human IVN for the first time. The method can be utilized to map VIIIth nerve subdivisions and to intraoperatively monitor IVN integrity in a real-time mode.     

Effects of selective cochlear toxicity and vestibular deafferentation on vestibular evoked myogenic potentials in guinea pigs

CONCLUSION: The findings suggest that sound-evoked myogenic potentials on the guinea pig sternocleidomastoid muscle (SM) originate from the vestibular end organ and not from the cochlea of the inner ear. OBJECTIVE: Studies in animals of the sound evoked vestibular myogenic potentials on the SM should aid in elucidating the pathway of the vestibular-evoked myogenic potential (VEMP). However, details of the pathway of the VEMP remain to be elucidated. This study aimed to clarify aspects of this pathway. MATERIALS AND METHODS: In the present study, short latency biphasic myogenic potentials on the SM in guinea pigs were induced by an intense brief sound. RESULTS: The thresholds of the potentials were 67 dB SPL above those of the auditory brainstem response (ABR). The potentials were eliminated by a vestibular deafferentation, but were observed after selective cochlea toxicity using an amikacin injection.     

A study on vestibular-evoked myogenic potentials via galvanic vestibular stimulation in normal people

Objectives

The aim of our study is to examine vestibular-evoked myogenic potentials (VEMPs) elicited by the galvanic vestibular stimulation in the sternocleidomastoid muscle (SCM) in healthy subjects for clinical applications of auditory neuropathy or vestibular neuropathy in the future.

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.     

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.     

Comparison of tone burst and tapping evocation of myogenic potentials in patients with chronic otitis media

OBJECTIVE: Vestibular evoked myogenic potential (VEMP) has recently been broadly studied in cochleo-vestibular disorders to elucidate its mechanism. Because it is evoked by loud sound stimulation, impairment of the sound transmission through the middle ear may affect VEMP results. This study aims to compare the response rate of VEMPs using the tone burst method and the tapping method in patients with chronic otitis media (COM). DESIGN: Fourteen patients (22 ears) with conductive hearing loss due to COM were subjected to VEMP tests using both the tone burst method and the tapping method. Each ear was stimulated by a short-tone burst (95 dB nHL, 500 Hz), followed by tapping on the forehead with a tendon hammer, 200 times at a frequency of 5 Hz. RESULTS: Thirteen (59%) of the 22 ears showed positive VEMPs using the tone burst method, whereas 20 ears (91%) displayed positive VEMPs by the tapping method (p < 0.05). The latencies of wave p13 and n23, and the amplitude p13-n23 using the tone burst method were 13.4 +/- 4.1 msec, 20.5 +/- 4.6 msec, and 77.2 +/- 17.2 microV, respectively. These results do not significantly differ from those obtained using the tapping method. In ears with perforated eardrums (N = 11), five ears (45%) displayed positive VEMPs by the tone burst method; compared with nine ears (82%) with positive VEMPs using the tapping method, representing a nonsignificant difference. In ears with healed eardrums (N = 11), eight ears exhibited positive VEMPs by tone burst, with a mean air-bone gap of 25.6 +/- 15.2 dB at 500 Hz, in contrast to a gap of 30.0 +/- 22.9 dB in three ears without VEMPs, indicating no significant difference. CONCLUSIONS: When stimulating sound is attenuated by middle ear pathology, VEMPs are expected to be poorly elicited. Under such conditions, myogenic potentials may be evoked with the tapping method to elicit the absent VEMPs that result from middle ear or inner ear pathology.     

Laterality of vestibular evoked myogenic potentials

To clarify the laterality of acoustically evoked vestibulocollic reflexes with a short latency (vestibular evoked myogenic potentials, VEMPs). responses on the bilateral sternocleidomastoid muscles (SCMs) to unilateral acoustic stimulation were studied. Twenty-one healthy volunteers were enrolled. Surface electrodes were placed on the upper half of each SCM (active) and on the lateral end of the upper sternum (reference). Clicks and 500-Hz tone-bursts (95dB nHL) were used. All subjects showed positive-negative biphasic responses on the ipsilateral SCM by clicks and tone-bursts. Click-stimulation of 41 of the 42 ears did not evoke any response on the contralateral SCM. However, in one ear, positive-negative biphasic responses were evoked on the contralateral SCM. Recordings on the contralateral SCM by tone-bursts showed no response in 32 ears, small positive-negative biphasic responses in four ears, and small negative-positive biphasic responses in six ears. These findings show that VEMPs are ipsilateral-dominant, basically consistent with the hypothesis that they are of saccular origin.     

Laterality of vestibular evoked myogenic potentials

To clarify the laterality of acoustically evoked vestibulocollic reflexes with a short latency (vestibular evoked myogenic potentials, VEMPs), responses on the bilateral sternocleidomastoid muscles (SCMs) to unilateral acoustic stimulation were studied. Twenty-one healthy volunteers were enrolled. Surface electrodes were placed on the upper half of each SCM (active) and on the lateral end of the upper sternum (reference). Clicks and 500-Hz tone-bursts (95 dB nHL) were used. All subjects showed positive-negative biphasic responses on the ipsilateral SCM by clicks and tone-bursts. Click-stimulation of 41 of the 42 ears did not evoke any response on the contralateral SCM. However, in one ear, positive-negative biphasic responses were evoked on the contralateral SCM. Recordings on the contralateral SCM by tonebursts showed no response in 32 ears, small positive-nega-tive biphasic responses in four ears, and small negative-positive biphasic responses in six ears. These findings show that VEMPs are ipsilateral-dominant, basically consistent with the hypothesis that they are of saccular origin.     

Vestibular Evoked Myogenic Potentials in Patients with Spinocerebellar Degeneration

To estimate vestibulo-collic reflexes in patients with spinocerebellar degeneration (SCD), vestibular evoked myogenic potentials (VEMPs) were recorded in 16 patients with SCD and in 9 normal subjects. The patients with SCD were classified into three groups: those with olivo-ponto-cerebellar ataxia (OPCA; n=10); those with cortical cerebellar atrophy (CCA; n=3); and those with Machado-Joseph disease (MJD; n=3). While all of the patients with OPCA and CCA showed biphasic responses (p13-n23), 2 of the 3 patients with MJD showed abnormal VEMPs bilaterally. Three sides in these 2 patients showed an absence of VEMPs, and one side showed a remarkably delayed p13. These two patients showed little response in caloric tests. These results suggest that the vestibulo-collic reflex as well as the vestibulo-ocular reflex could be damaged in MJD patients but preserved in OPCA and CCA patients.     

The relationship between hearing loss and vestibular dysfunction in patients with sudden sensorineural hearing loss

Objective: To investigate the relationship between hearing loss and vestibular dysfunction in patients with sudden sensorineural hearing loss (SSHL).

Methods: Clinical data including the symptom of vertigo of 149 SSHL patients were investigated retrospectively. Pure tone audiometry, ocular vestibular-evoked myogenic potential (oVEMP) and cervical vestibular-evoked myogenic potential (cVEMP) evoked by air-conducted sound (ACS), and caloric test were employed for cochlear and vestibular function assessment. The relationship between hearing level and vestibular dysfunction was analyzed.

Results: The pure tone averages (PTAs) (mean?±?SD) of SSHL patients with and without vertigo were 88.81?±?21.74 dB HL and 72.49?±?21.88 dB HL (Z?=??4.411, p?=?0.000), respectively. The PTAs of SSHL patients with abnormal and normal caloric test were 84.71?±?22.54 dB HL and 70.41?±?24.07 dB HL (t?=??2.665, p?=?0.009), respectively. Conversely, vertigo and abnormal caloric results also happened more frequently in patients with profound hearing loss. However, no consistent tendency could be found among vestibular evoked myogenic potentials (VEMPs) responses or hearing loss.

Conclusions: SSHL patients with vertigo or abnormal caloric test displayed worse hearing loss; and vice versa, vertigo and abnormal caloric results happened more frequently in SSHL patients with profound hearing loss.     

The otolithic organ as a receptor of vestibular hearing revealed by vestibular-evoked myogenic potentials in patients with inner ear anomalies

The human vestibule has preserved an ancestral sound sensitivity and it has been suggested that a reflex could originate from this property underlying cervical muscle micro-contractions secondary to strong acoustic stimulation. Previous studies have established that an early component of loud sound-evoked myogenic potentials from the sternocleidomastoid muscle originate in the vestibule. This is based on findings that the response can still be obtained from patients with complete loss of cochlear and vestibular (semi-circular canal) function. Our data confirm, in a more direct way, a saccular origin of this short-latency acoustic response and verifies that a saccular acoustic response persists in the human ear. The contribution of this response to the perception of loud sounds is discussed. It is concluded that vestibular response to sound might be used to assist in the rehabilitation of deafness.     

Vestibular evoked myogenic potentials in patients with bilateral profound hearing loss

We report vestibular evoked myogenic potentials (VEMPs) in 3 patients with bilateral profound hearing loss in order to confirm that they are not of cochlear origin. All of the 3 patients (31-year-old man, 67-year-old man and 47-year-old woman) had bilateral profound hearing loss. They were diagnosed as having congenital hearing loss, bilateral Ménière's disease and inner ear syphilis. Their pure-tone hearing ranged from 81 dB HL to nearly total hearing loss. Stimulation by click (95 dB nHL) evoked biphasic myogenic responses (p13-n23) on the sternocleidomastoid muscle ipsilateral to the stimulated ear. The ear in which the stimulation did not evoke biphasic myogenic responses did not have a caloric response either. These results suggested that VEMPs are not likely of cochlear origin but of vestibular origin.     

Promontory electrical stimulation to elicit vestibular evoked myogenic potentials (VEMPs)

Conclusion: Vestibular evoked myogenic potentials (VEMPs) provoked electrically at the promontory provide a feasible method to record vestibular responses in awake patients. Objectives: Electrically evoked VEMP testing has been performed by galvanic stimulation at the mastoid so far. The present study examined an electrical stimulation mode close to the otolith organs at the promontory. Methods: Fourteen cochlear implant candidates who were planned for clinical routine promontory stimulation testing (PST) to assess auditory nerve function underwent promontory VEMP testing. After testing the cochlear nerve function during PST promontory cervical VEMPs (p-c-VEMPs) and promontory ocular VEMPs (p-o-VEMPs) were recorded during subsequent transtympanic electrical stimulation at the promontory. Results: Promontory VEMP testing was well tolerated by the patients. Mean latencies for p-c-VEMPs were 10.30 ± 2.23 ms (p1) and 17.86 ± 3.83 ms (n1). Mean latencies for p-o-VEMPs were 7.64 ± 1.24 ms (n1) and 11.2 ± 1.81 ms (p1). The stimulation threshold level was measured at 0.15 ± 0.07 mA for p-c-VEMPs and at 0.19 ± 0.11 mA for p-o-VEMPs. The discomfort level was found to be at 0.78 ± 0.29 mA for p-c-VEMPs and at 0.69 ± 0.25 mA for p-oVEMPs. Mean p1-n1 amplitude in p-c-VEMPs was 124.78 ± 56.55 µV and p-o-VEMPs showed a mean n1-p1 amplitude of 30.94 ± 18.98 µV.     

End-point indicators of low-dose intra-tympanic gentamicin in management of Ménière’s disease

Conclusions: One-shot, low-dose intra-tympanic gentamicin (ITG) treatment was effective and safe for Ménière’s disease (MD) patients. Head thrust test (HTT) and vestibular evoked myogenic potentials (VEMPs) test could be used as endpoint indicators for vertigo control in MD patients.

Objectives: The present study is to explore end-point indicators of ITG injection in MD.

Methods: Patients with MD were reviewed from June 2012 to March 2014. Single-shot ITG at a concentration of 30?mg/ml was administered to patients. The sensitivity and specificity of HTT and VEMPs for vertigo control were measured.

Results: All 37 patients with a median follow-up of 26 months were included. Of those 37 patients, 24 patients (64.9%) obtained class A vertigo control and seven patients (18.9%) obtained class B vertigo control. Only six patients had class C control (16.2%). The sensitivity and specificity of HTT for vertigo control were 74.2% and 50.0%. Meanwhile, the sensitivity and specificity of VEMPs threshold were 83.9% and 33.3%. When combined HTT and VEMPs, sensitivity and specificity were 93.5% and 66.7%. Based on the four-tone average thresholds at 0.5, 1, 2, 3?kHz, 78.4% patients had no significant change in PTA and 16.2% patients experienced significant improvement.     

Posturography frequency analysis of sound-evoked body sway in normal subjects

Sound-evoked activation of the vestibular system has been suggested for a long time, and myogenic potentials have been recorded at the level of different muscular groups while a high intensity sound was applied. The aim of this study was to analyse sound-evoked postural responses in normal subjects and to correlate them with the activation of the vestibular system. Body sway was measured by posturography and elaborated through spectral frequency analysis in 40 healthy volunteers in the basal condition and after applying a sound stimulus monoaurally. Spectral frequency analysis results showed a significant increase, in presence of stimulus, of body sway at low and middle frequencies only on the lateral plane and in the closed-eyes condition. As it seems that these frequency ranges are mainly under vestibular control, our results suggest that sound activates specifically the vestibular system, and posturography during sound stimulation represents an alternative approach to assess vestibular function.     

Evaluation of vestibular evoked myogenic potentials

In previous studies, electromyographic potentials, recorded in response to auditory clicks, have been attributed to stimulation of the otolith (saccule) and have been termed vestibular evoked myogenic potentials (VEMPs). In this study, we assessed the VEMPs in subjects with normal auditory brainstem evoked responses, with no history of vestibular symptoms or neck and other skeletal muscle abnormalities. To this effect, 32 subjects (64 ears), after ethics committee approval, were exposed to 75, 150, and 300 clicks at 100 dB, and the responses were averaged. Electromyographic activity was recorded by applying surface electrodes over the sternocleiodomastoid muscle under the following three conditions: no muscle contraction/no clicks, muscle contraction/no clicks, and muscle contraction/clicks. Our findings suggest that electromyographic responses have to be obtained, during muscle contraction, first without and then with clicks. Our data also suggest that comparison of these two recordings is necessary for meaningful results.