Masseter Vestibular evoked myogenic potentials: A new tool to assess the vestibulomasseteric reflex pathway

Purpose: This review article provides the readers with an in-depth insight in understanding and interpreting various research literatures on the masseter vestibular evoked myogenic potentials(mVEMP). The article also reviews the contemporary researches involving the clinical applications of the mVEMP. Conclusions: Masseter VEMP is an evolving yet clinically promising neuro-otology test tool that has recently gained more research interest and is considered an additional tool to diagnose various vestibular disorders. Masseter VEMP assesses the functional integrity of the acoustic-masseteric and vestibulo-masseteric reflex pathways. The mVEMP could be used as a complementary test to evaluate the same peripheral generator as the cervical VEMP but a different central pathway i.e., vestibulo-trigeminal pathway. Various research studies that have experimented on parameters such as the effect of different electrode montages(zygomatic vs mandibular configurations), stimulation rates, filter settings and stimuli used to evoke mVEMP have been discussed in this article that could assist in the optimization of a comprehensive clinical protocol. The latency and the amplitude of mVEMP waveforms serve as significant parameters in differentiating normals from those of the clinical populations. Along with the cVEMPs and oVEMPs, mVEMP might help diagnose brainstem lesions in REM Sleep behaviour disorders, Multiple Sclerosis and Parkinson's disease. However, further studies are required to probe in this area of research.

Evaluation of ocular and cervical vestibular evoked myogenic potentials in a conductive hearing loss model

Objective: To investigate the effects of conductive hearing loss(CHL) on vestibular evoked myogenic potentials(VEMPs) using a simulated CHL model, and to provide the basis for future studies.Methods: Twenty-one healthy subjects were recruited in this study. We measured ocular VEMPs(o VEMPs) and cervical VEMPs(c VEMPs) in these subjects by air-conduction sound(ACS) stimulation. CHL was simulated later by blocking the right external auditory canal with a soundproof earplug to evaluate its impacts on VEMPs. Subjects' responses before simulated CHL served as the control, and were compared to their responses following simulated CHL.Results: o VEMPs following simulated CHL showed decreased response rate, elevated thresholds, attenuated amplitudes and prolonged N1 latencies compared with those before simulated CHL, and the differences were statistically significant. Similarly, c VEMPs following simulated CHL also showed decreased response rate, elevated thresholds and attenuated amplitudes, with prolonged P1 latencies compared with those before simulated CHL, although only differences in response rate, threshold and amplitude were significant.Conclusions: Conductive hearing loss affects the response rate and other response parameters in o VEMPs and c VEMPs.

The effect of EMG magnitude on the masseter vestibular evoked myogenic potential(mVEMP)

Introduction:The masseter vestibular evoked myogenic potential(mVEMP)is a bilaterally generated,electromyographically(EMG)-mediated response innervated by the trigeminal nerve.The purpose of the present investigation was to 1)determine whether subjects could accurately achieve and maintain a range of EMG target levels,2)to examine the effects of varied EMG levels on the latencies and amplitudes of the mVEMP,and 3)to investigate the degree of side-to-side asymmetry and any effects of EMG activation.Methods:Subjects were nine neurologically and otologically normal young adults.A high-intensity tone burst was presented monaurally while subjects were seated upright and asked to match a range of EMG target levels by clenching their teeth.Recordings were made from the ipsilateral and contralateral masseter muscles referenced to the ear being monaurally stimulated.Results:We found that the tonic EMG target had no effect on mVEMP latency.Additionally,although mVEMP amplitudes“scaled”to the EMG target,there was a tendency for the subjects’EMG level to“undershoot”the EMG target levels greater than 50 mV.While some individuals did generate differences in EMG activation between sides,there were no significant differences on average EMG activation between sides.Further,while average corrected amplitude asymmetry was similar across EMG targets,some individuals demonstrated large,corrected amplitude asymmetry ratios.Conclusions:The results of this investigation suggest that,as with cVEMP recordings,the underlying EMG activation may vary between subjects and could impact mVEMP amplitudes,yet could be mitigated by amplitude correction techniques.Further it is important to be aware that even young normal subjects have difficulty maintaining large,tonic EMG activity during the mVEMP recording.

Vestibular function for children with insulin dependent diabetes using cervical vestibular evoked myogenic potentials testing

BACKGROUND Healthy vestibular system adjusts balance during static and dynamic conditions.This is important for normal development(standing up and walking).Vestipulopathies(central and peripheral)are common complications of diabetes in adult population.Related studies are scare in children with type 1 diabetes(T1D).AIM To assess saccular function of otolith organ in children with T1D and predictors for its dysfunction.METHODS Cervical vestibular evoked myogenic potential(cVEMP)was used for objective evaluation.RESULTS The study included 40 patients(boys=15;girls=25).Patients had mean age of 13.63±1.50 years,duration of diabetes of 5.62±2.80 years,frequent attacks of diabetic ketoacidosis(55%)and hypoglycemia(30%),hyperlipidemia(20%),hypertension(12.5%)and peripheral neuropathy(40%).Dizziness was found in 10%.Compared to healthy children(n=25),patients had prolonged cVEMP P1 and N1 latencies and reduced P1-N1 amplitude.Bilateral cVEMP abnormalities were found in 60%(vs 25%for unilateral abnormalities).Higher frequencies and severe vestibulopathies were found with chronic diabetes of>5 years,hemoglobin A1c values>7%,frequent diabetic ketoacidosis and hypoglycemic attacks and presence of dizziness.Regression analyses showed that predictors for prolonged P1 latencies and reduced P1-N1 amplitudes were only chronic diabetes(>5 years){odds ratio(OR)=2.80[95%confidence interval(CI):1.80–5.33],P=0.01;OR=3.42(95%CI:2.82–6.81)}and its severity(hemoglobin A1c>7%)[OR=3.05(95%CI:2.55–6.82),P=0.01;OR=4.20(95%CI:3.55–8.50),P=0.001].CONCLUSION Dysfunction or injury of the saccular macula and its pathways is prevalent in children with T1D.Optimum glycemic control is important to prevent diabetes related vestipulopathies.

Vestibular-evoked myogenic potentials recorded from miniature pigs and rats

Objective:To report vestibular evoked myogenic potentials from different recording sites(neck extensor or masseter muscles) in miniature pigs and rats.Methods:Potentials were recorded using 1000 Hz tone bursts from the neck extensor muscle or masseter muscle in normal adult Bama miniature pigs and rats anesthetized with 3%pentobarbital sodium and Sumianxin Ⅱ.Results:At 80 dB SPL,the first positive wave(P wave) of VEMPs was recognizable in 58%of rats with a latency of 6.45±0.23 ms and an amplitude of 1.45±0.49 μV when recorded from the neck extensor muscle,and in 50%of rats with a latency of 6.38±0.34 ms and an amplitude of 1.57±0.35 μV when recorded from the masseter muscle.In miniature pigs,at the same stimulus intensity,P wave was recognizable in 58%of the animals with a latency of 7.65±0.64 ms and an amplitude of 1.66±0.34 μV when recorded from the neck extensor muscle,and in 50%of the animals with a latency of 7.65±0.64 ms and an amplitude of 0.31±0.28 μV when recorded from the masseter muscle.Conclusion:VEMP can be induced from both neck extensor and masseter muscles in the miniature pig and rat.For a given species,the site of recording affects P wave induction rate and amplitude but not latency.Consistency and repeatability analysis suggests that the masseter muscle is a better recording site in miniature pigs while the cervical extensor is a better recording site in rats.For a given recording site,both latency and amplitude of the P wave are slightly greater in miniature pigs than in rats.

Vestibular-evoked myogenic potentials in miniature pigs

Objective:To report detection of vestibular-evoked myogenic potentials (VEMPs) in the miniature pig. Methods:Potentials evoked by 1000 Hz tone bursts were recorded from neck extensor muscles and the masseter muscles in normal adult Bama miniature pigs anesthetized with 3%pentobarbital sodium and Carbachol II. Results:The latency of the first positive wave P from neck extensor muscles was 7.65 ± 0.64 ms, with an amplitude of 1.66 ± 0.34 uv and a rate of successful induction of 75%at 80 dB SPL. The latency of potentials evoked from the masseter muscles was 7.60 ± 0.78 ms, with an amplitude of 1.31 ± 0.28 uv and a rate successful induction of 66%at 80 dB SPL. Conclusion:The latencies and thresholds of VEMPs recorded from the neck extensor muscle and the masseter muscle appear to be comparable in normal adult Bama miniature pigs, although the amplitude recorded from the neck extensor muscle seems to be higher than that from the masseter muscle. However, because of their usually relatively superficial and easily accessible location, as well as their large volume and strong contractions, masseter muscles may be better target muscles for recording myogenic potentials.

Inferior vestibular neuritis in a fighter pilot:A case report

Pilot spatial disorientation is a leading factor contributing to many fatal flying accidents. Spatial orientation is the product of integrative inputs from the proprioceptive, vestibular, and visual systems. Vestibular neuritis (VN) can lead to sudden pilot incapacitation in flight. VN is commonly diagnosed by demonstration of unilateral vestibular failure, as unilateral loss of caloric response. As this test reflects the function of the superior part of the vestibular nerve only, cases of pure inferior nerve neuritis will be lost. This paper describes a fighter pilot with symptoms suggestive of VN but with normal caloric test results. Further test showed unilateral loss of vestibular evoked myogenic potential. We believe that the pilot suffered from pure inferior nerve vestibular neuritis. VEMP plays a major role in the diagnosis of inferior nerve vestibular neuritis in pilots. Aeromedical concerns are also discussed.

Transmastoid Approach for Resurfacing the Superior Semicircular Canal Dehiscence with a Dumpling Structure

Background： Superior semicircular canal dehiscence （SSCD） is gradually recognized by otologists in recent years. The patients with SSCD have a syndrome comprising a series of vestibular symptoms and hearing function disorders which can be cured by the operation. In this study, we evaluated the characteristics of patients with SSCD and determined the effectiveness of treating this syndrome by resurfacing the canal via the transmastoid approach using a dumpling structure. Methods： Patients with SSCD, confirmed by high-resolution computed tomography and hospitalized at Beijing Tongren Hospital between November 2009 and October 2012, were included in the study. All of the patients underwent the unilateral transmastoid approach for resurfacing the canal, and received regular follow-up after surgery. Data from preoperative medical records and postoperative follow-up were comparatively analyzed to evaluate the effect of surgery. Results： In total, 10 patients and 13 ears （three left ears, four right ears, three bilateral ears） were evaluated in the study, which included 7 men and 3 women. Different symptoms and distinctive manifestations of vestibular evoked myogenic potential were found in these patients. Alter surgery, 4 patients had complete resolution, 5 had partial resolution, and 1 patient, with bilateral SSCD, had aggravation. None of the patients suffered from serious complications such as sensorineural hearing loss, facial paralysis, cerebrospinal fluid leakage, or intracranial hypertension. Conclusions： In patients with unilateral SSCD, resurfacing the canal via the transmastoid approach using a dumpling structure is an effective and sate technique. However, more consideration is needed for patients with bilateral SSCD.