Vestibular Evoked Myogenic Potentials Are Abnormal in Idiopathic REM Sleep Behavior Disorder

Cervical and Masseter Vestibular Evoked Myogenic Potentials in Diabetes Mellitus Type 2

PURPOSE

Diabetes affects the peripheral auditory and vestibular systems. Research suggests that both cervical vestibular evoked myogenic potentials (cVEMP) and ocular VEMP (oVEMP) are affected in individuals with diabetes. Masseter VEMP (mVEMP) is a new tool that assesses the vestibulomasseteric reflex pathways. The study aimed to characterize the cVEMP and mVEMP latency and amplitude parameters in diabetes mellitus type 2.

METHOD

The study included 21 participants with type 2 diabetes mellitus and 21 age- and gender-matched participants without diabetes aged 48-68 years. mVEMP and cVEMP were recorded using 500 Hz tone burst stimuli, presented at an intensity of 125 dB peSPL for both the groups.

RESULTS

The study suggests significantly prolonged P13 (p = .00) and P11 latencies (p = .00) in participants with diabetes (M for p11 = 15.81, M for p13 = 15.39) compared to participants without diabetes (M for p11 = 13.12, M for p13 = 14.19) for both cVEMP and mVEMP, respectively. No significant differences were observed in N23 (p = .4) and N21 latencies (p = .18) between the diabetes (M for N21 = 22.62, M for N23 = 22.61) and nondiabetes groups (M for N21 = 22.21, M for N23 = 22.40). Additionally, a significant reduction in cVEMP amplitude (P13-N23) was noted in the diabetes group (M for P13-N23 = 0.71, p = .00) than the nondiabetes group (M = 1.44), while mVEMP amplitudes (P11-N21) remained similar across groups (M for P11-N21 for diabetes = 0.72, (M for P11-N21 for nondiabetes = 0.77, p = .44). There were no significant correlations between the duration of diabetes and VEMP parameters, nor between cVEMP and mVEMP responses in either group.

CONCLUSIONS

The findings revealed notable differences in cVEMP and mVEMP findings in diabetes individuals. These results suggest that diabetes may lead to neural and labyrinthine impairments. The degree of vestibular impairment varies and affects different reflex pathways. Even though mVEMP has a similar saccular origin as cVEMP, the results between the two do not correlate with each other.

Multisensory mechanisms of gait and balance in Parkinson's disease: an integrative review

Understanding the neural underpinning of human gait and balance is one of the most pertinent challenges for 21st-century translational neuroscience due to the profound impact that falls and mobility disturbances have on our aging population. Posture and gait control does not happen automatically, as previously believed, but rather requires continuous involvement of central nervous mechanisms. To effectively exert control over the body, the brain must integrate multiple streams of sensory information, including visual, vestibular, and somatosensory signals. The mechanisms which underpin the integration of these multisensory signals are the principal topic of the present work. Existing multisensory integration theories focus on how failure of cognitive processes thought to be involved in multisensory integration leads to falls in older adults. Insufficient emphasis, however, has been placed on specific contributions of individual sensory modalities to multisensory integration processes and cross-modal interactions that occur between the sensory modalities in relation to gait and balance. In the present work, we review the contributions of somatosensory, visual, and vestibular modalities, along with their multisensory intersections to gait and balance in older adults and patients with Parkinson's disease. We also review evidence of vestibular contributions to multisensory temporal binding windows, previously shown to be highly pertinent to fall risk in older adults. Lastly, we relate multisensory vestibular mechanisms to potential neural substrates, both at the level of neurobiology (concerning positron emission tomography imaging) and at the level of electrophysiology (concerning electroencephalography). We hope that this integrative review, drawing influence across multiple subdisciplines of neuroscience, paves the way for novel research directions and therapeutic neuromodulatory approaches, to improve the lives of older adults and patients with neurodegenerative diseases.

Exploration of sleep quality and rest-activity rhythms characteristics in Bilateral Vestibulopathy patients

Sleep and circadian timing systems are constantly regulated by both photic and non-photic signals. Connections between the vestibular nuclei and the biological clock raise the question of the effect of peripheral vestibular loss on daily rhythms, such as the sleep-wake cycle and circadian rhythm. To answer this question, we compared the sleep and rest-activity rhythm parameters of 15 patients with bilateral vestibulopathy (BVP) to those of 15 healthy controls. Sleep and rest-activity cycle were recorded by a device coupling actimetry with the heart rate and actigraphy at home over 7 days. Subjective sleep quality was assessed by the Pittsburgh Sleep Quality Index (PSQI). Sleep efficiency and subjective sleep quality were significantly reduced, and sleep fragmentation was increased in BVP patients compared to controls. BVP patients displayed a damped amplitude of the rest-activity rhythm and higher sleep fragmentation, reflected by a higher nocturnal activity compared to controls. These results suggest that both rest-activity and sleep cycles are impaired in BVP patients compared to healthy controls. BVP patients seem to have greater difficulty maintaining good sleep at night compared to controls. BVP pathology appears to affect the sleep-wake cycle and disturb the circadian rhythm synchronization. Nevertheless, these results need further investigation to be confirmed, particularly with larger sample sizes.

Assessment of Sacculocollic and Vestibulomasseteric Reflex Pathways in Individuals With Migraine and Vestibular Migraine

PURPOSE

The study's objective was to evaluate the functioning of sacculocollic and vestibulomasseteric reflex pathways in individuals with vestibular migraine and migraine.

METHOD

Seventy-five participants aged 18-50 years were selected for the study. Participants were divided into three groups. Group 1 consisted of 25 healthy individuals, Group 2 consisted of 25 migraine individuals, and Group 3 consisted of 25 individuals with vestibular migraine. Cervical vestibular-evoked myogenic potential (cVEMP) and masseter vestibular-evoked myogenic potential (mVEMP) were recorded using a 500-Hz tone burst stimulus presented at 125 dB peSPL for all participants.

RESULTS

The cVEMP test results showed a delayed p13 and n23 latency for both migraine and vestibular migraine individuals when compared to healthy individuals. Also, the amplitude of the p13-n23 peak was reduced compared to healthy individuals in both migraine and vestibular migraine. Similarly, the mVEMP test results showed a delayed p11 and n21 latency for both migraine and vestibular migraine individuals. No difference was observed in the amplitude of the p11-n21 peak complex between the three groups. Spearman's rho correlation revealed no significant (p > .05) correlation between cervical and masseter VEMP latency and amplitude parameters between healthy, migraine, and vestibular migraine individuals.

CONCLUSIONS

The results of the study are suggestive of the pathology of the sacullocollic and vestibulomasseteric reflex pathways in individuals with migraine and vestibular migraine. Individuals with migraine and vestibular migraine should undergo a detailed vestibular evaluation.

Is the Otolithic Function Affected in Patients with Obstructive Sleep Apnea Syndrome?

BACKGROUND

 While cardiovascular and neurological diseases induced by obstructive sleep apnea syndrome (OSAS) hypoxia are well established, the association between neuro-otological diseases and OSAS is not entirely understood. Vestibular and audiological tests have been used to evaluate the degeneration of neurons in the brainstem caused by recurrent hypoxia.

PURPOSE

 Evaluation of the vestibular-evoked myogenic potential (VEMP) test findings applied to detect the possible influence on the vestibular reflex arc due to hypoxia in patients diagnosed with OSAS using Activity-Specific Balance Confidence (ABC) and Berg Balance Scale (BBS) scales determination of scores.

RESEARCH DESIGN

 This was a cross-sectional study.

STUDY SAMPLE

 Participants aged 18 to 60 who underwent polysomnography due to snoring/sleep apnea were divided into an OSAS, and a control group of subjects were also included. Each group consisted of 20 participants.

DATA COLLECTION AND ANALYSIS

 All participants were evaluated with cervical VEMP (cVEMP) and ocular VEMP (oVEMP) tests. The groups were compared regarding variables such as the rate of oVEMP and cVEMP waves obtained, the interval between the waves, and the latency and amplitude. Also, BBS and ABC scales were applied to all participants.

RESULTS

 The cVEMP (50%) and oVEMP (45%) response rates and amplitudes were significantly lower in the OSAS group. No significant difference was found between the groups when comparing other VEMP parameters. However, a statistically significant decrease was observed in the ABC and BBS scores in the OSAS group.

CONCLUSION

 The identification of VEMP alterations in the OSAS group is a clear indication that the vestibular reflex pathways may be adversely affected by hypoxia. Personal rehabilitation programs can be created by evaluating activities of daily living with the ABC and static and dynamic balances with BBS in patients with OSAS.

Masseter and cervical vestibular evoked myogenic potentials in individuals with auditory neuropathy

OBJECTIVE

This study aimed to explore the functional integrity of vestibulo-masseteric and sacculo-collic reflex pathways in individuals with Auditory Neuropathy (AN). The study also aimed at finding the correlation between mVEMP and cVEMP response parameters for AN and healthy individuals.

DESIGN

Standard group comparison research design.

STUDY SAMPLE

Individuals with AN (n = 20); age-gender matched healthy individuals (n = 20) were recruited. Each participant underwent routine audiological evaluation; mVEMP and cVEMP testing. mVEMP and cVEMP were recorded using 500 Hz tone burst stimulus for all the participants.

RESULTS

Most of the AN individuals had no mVEMP (ipsilateral & contralateral - 60%; bilateral - 50%) and cVEMP (60%) responses. There was no significant association (p > 0.05) between the duration of AN with mVEMP and cVEMP findings. However, a significant correlation (p < 0.05) was found for EMG rectified amplitude of mVEMP and cVEMP in AN.

CONCLUSION

The results of this study suggested an impaired function of the vestibulomassteric and sacculocollic reflex pathways in individuals with AN. Vestibular evaluation should be included as a part of the regular test battery for individuals with AN.

Evaluation of Masseteric Vestibular Evoked Myogenic Potentials in Patients With Migraine

PURPOSE

Masseter vestibular evoked myogenic potentials (mVEMP) involve the connection between the vestibular complex and trigeminal nerve nuclei. Given the theory that migraine is caused by increased activation of the trigeminal nerve, it is believed that mVEMP responses may have influenced in migraine patients.

METHOD

The study included 20 individuals with migraine and 20 healthy controls. Latency, amplitude, and interaural amplitude asymmetry ratio of mVEMP responses recorded in migraine patients were compared with control group.

RESULTS

Considering the mVEMP normalization study conducted by Başöz et al. (2021) in a similar age group and in the same clinic, latency prolongation and amplitude decrease were observed in subjects with migraines. Migraine is considered a central pathology, as shown in the cervical and ocular VEMP (cVEMP/oVEMP) literature. No difference was observed in the interaural amplitude asymmetry ratio, which is important in peripheral pathologies. Additionally, when the number of pathological ears was examined in order to understand the total exposure, it was observed that the number of pathological ears was significantly higher in the migraine group.

CONCLUSION

In future studies, using mVEMP together with cVEMP and oVEMP tests, which allow evaluation of otolith organs and vestibular nuclei, will be valuable in determining the lesion location.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.25607901.

Masseter Vestibular-Evoked Myogenic Potential Result of Possible Meniere's Patients

BACKGROUND

 The masseter vestibular-evoked myogenic potential (mVEMP) test evaluates the vestibulomasseteric reflex neural pathway between the sound-stimulated saccule hair cells and the motor neurons of the trigeminal nerve.

PURPOSE

 This study aims to investigate the contribution of mVEMP to the conclusive diagnosis of recurrent vestibulopathy patients that were diagnosed with Possible Meniere's disease.

METHODS

 The study includes 20 healthy individuals aged 18 to 40 years and 20 patients that were diagnosed with Possible Meniere's disease according to the American Academy of Otorhinolaryngology and Head and Neck Surgery (AAO-HNS, 1995) Guidelines for the Definition of Meniere's Disease. In addition to the AAO-HNS, 1995 criteria, the presence of aural signs on the affected side was questioned according to the Meniere's criteria updated in 2015. mVEMP records were obtained by using surface electrodes placed on masseter muscles. Latency and amplitude values and asymmetry ratios of mVEMP waves were used for statistical analysis.

RESULTS

 Asymmetry ratios were 15.9 ± 9.7% for the control group and 60.61 ± 45.52 for the experimental group; this difference was statistically significant (p < 0.05). The absolute latency and amplitude results were not statistically different between groups (p > 0.05).

CONCLUSION

 As Murofushi et al. (2001) stated in the literature, cervical vestibular-evoked myogenic potential (VEMP)/ocular VEMP latencies were not affected in peripheral pathologies, and in our study, no difference was observed between the groups in mVEMP latencies. The findings of our study showed that asymmetry ratio and absence of waves should be used in the clinical evaluation of Possible Meniere's disease. We conclude that mVEMP can be used to determine the lateralization of vestibular disorders and to support the presence of a vestibular pathology. mVEMP can contribute to the vestibular test battery.

Clinical neurophysiology of REM parasomnias: Diagnostic aspects and insights into pathophysiology

Parasomnias are due to a transient unstable state dissociation during entry into sleep, within sleep, or during arousal from sleep, and manifest with abnormal sleep related behaviors, perceptions, emotions, dreams, and autonomic nervous system activity. Rapid eye movement (REM) parasomnias include REM sleep behavior disorder (RBD), isolated recurrent sleep paralysis and nightmare disorder. Neurophysiology is key for diagnosing these disorders and provides insights into their pathophysiology. RBD is very well characterized from a neurophysiological point of view, also thank to the fact that polysomnography is needed for the diagnosis. Diagnostic criteria are provided by the American Academy of Sleep Medicine and video-polysomnography guidelines for the diagnosis by the International REM Sleep Behavior Disorder Study Group. Differences between the two sets of criteria are presented and discussed. Availability of polysomnography in RBD provides data on sleep electroencephalography (EEG), electrooculography (EOG) and electromyography (EMG). Sleep EEG in RBD shows e.g. changes in delta and theta power, in sleep spindles and K complexes. EMG during REM sleep is essential for RBD diagnosis and is an important neurodegeneration biomarker. RBD patients present alterations also in wake EEG, autonomic function, evoked potentials, and transcranial magnetic stimulation. Clinical neurophysiological data on recurrent isolated sleep paralysis and nightmare disorder are scant. The few available data provide insights into the pathophysiology of these disorders, demonstrating a state dissociation in recurrent isolated sleep paralysis and suggesting alterations in sleep macro- and microstructure as well as autonomic changes in nightmare disorder.

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.

Multifrequency Analysis of Masseter Vestibular Evoked Myogenic Potentials in Young Adults

PURPOSE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Characteristics of ipsilateral, contralateral and bilateral masseter vestibular-evoked myogenic potential in healthy adults

OBJECTIVE

This study aimed to characterise the ipsilateral, contralateral and bilateral masseter vestibular-evoked myogenic potential using clicks and 500 Hz tone burst stimuli in healthy adults.

METHOD

Masseter vestibular-evoked myogenic potential was recorded from 20 healthy participants aged 19-28 years (11 males and 9 females). Masseter vestibular-evoked myogenic potential was recorded using 500 Hz tone burst and click stimuli in ipsilateral, contralateral and bilateral modes.

RESULTS

A statistically significant difference was observed between ipsilateral and contralateral stimulation for p11 latency, n21 latency and p11-n21 amplitude for both click and 500 Hz tone burst stimuli. The amplitude of the p11-n21 complex was higher for ipsilateral, contralateral and bilateral stimulations for 500 Hz tone burst than for click stimulus.

CONCLUSION

This study showed a significant difference for p11-n21 amplitude between click and 500 Hz tone burst evoked masseter vestibular-evoked myogenic potential. In addition, bilateral stimulation elicited a larger response than ipsilateral and contralateral stimulation.

Changes in sleep performance and chronotype behaviour after vestibular rehabilitation in unilateral vestibular hypofunction

OBJECTIVE

This study aimed to investigate changes in sleep parameters and self-perceived sleep quality in unilateral vestibular hypofunction participants after vestibular rehabilitation.

METHOD

Forty-six unilateral vestibular hypofunction participants (before and after vestibular rehabilitation) along with a control group of 60 healthy patients underwent otoneurological examination, a one-week actigraphy sleep analysis and a series of self-report and performance measures.

RESULTS

After vestibular rehabilitation, unilateral vestibular hypofunction participants showed a significant score decrease in the Pittsburgh Sleep Quality Index, a self-rated reliable questionnaire depicting sleep quality during the last month, as well as a reduction in sleep onset latency and an increase in total sleep time, indicating an objective improvement in sleep quality as measured by actigraphy analysis. However, after vestibular rehabilitation, unilateral vestibular hypofunction participants still showed statistically significant differences with respect to the control group in both self-rated and objective measurements of sleep quality.

CONCLUSION

Vestibular rehabilitation may impact on sleep performance and chronotype behaviour, possibly by opposing long-term structural changes along neural pathways entangled in sleep activity because of the deafferentation of the vestibular nuclei.

Exploring the Relationship between Masseter and Cervical Vestibular-Evoked Myogenic Potentials in Young Adults with Hearing Thresholds Less Than or Equal to 15 dB HL

BACKGROUND

 Cervical vestibular-evoked myogenic potentials (cVEMPs) and masseter vestibular-evoked myogenic potentials (mVEMPs) are considered to have a common saccular origin. While a few studies have examined both vestibular-evoked myogenic potentials (VEMPs) in individuals with brainstem disorders as part of a test battery, the relation between these two potentials has rarely been the subject of discussion.

PURPOSE

 The present study explored the relation between mVEMPs and cVEMPs using electromyography (EMG)-scaled parameters in normal-hearing young adults.

RESEARCH DESIGN

 Within-subject study design.

STUDY SAMPLE

 Twenty young adults between 18 and 39 years of age (11 males, 9 females) participated in the study.

DATA COLLECTION AND ANALYSIS

 cVEMP and mVEMP were performed on all the participants at 95 dBnHL with 500 Hz tone burst stimuli. Various VEMP parameters were evaluated including P13 and N23 peak latencies, the amplitude of the P13-N23 complex, and the Interaural Amplitude Asymmetry Ratio in EMG-scaled and unscaled conditions.

RESULTS

 All participants exhibited a 100% response rate for cVEMP and mVEMP responses. There were no significant ears and gender effect for both cVEMP and mVEMP. No correlation was found between cVEMP and mVEMP. There was no significant difference found between P1 and N1 latency values of cVEMP and mVEMP; however, a significant variation was observed for peak-to-peak amplitude both in EMG-scaled and unscaled conditions between cVEMP and mVEMP.

CONCLUSIONS

 Minimal to no association between any parameters of cVEMPs and mVEMPs suggests no significant relationship between these two VEMPs.

Considering REM Sleep Behavior Disorder in the Management of Parkinson's Disease

Rapid eye movement (REM) sleep behavior disorder (RBD) is the result of the loss of physiological inhibition of muscle tone during REM sleep, characterized by dream-enacting behavior and widely recognized as a prodromal manifestation of alpha-synucleinopathies. Indeed, patients with isolated RBD (iRBD) have an extremely high estimated risk to develop a neurodegenerative disease after a long follow up. Nevertheless, in comparison with PD patients without RBD (PDnoRBD), the occurrence of RBD in the context of PD (PDRBD) seems to identify a unique, more malignant phenotype, characterized by a more severe burden of disease in terms of both motor and non-motor symptoms and increased risk for cognitive decline. However, while some medications (eg, melatonin, clonazepam, etc.) and non-pharmacological options have been found to have some therapeutic benefits on RBD there is no available treatment able to modify the disease course or, at least, slow down the neurodegenerative process underlying phenoconversion. In this scenario, the long prodromal phase may allow an early therapeutic window and, therefore, the identification of multimodal biomarkers of disease onset and progression is becoming increasingly crucial. To date, several clinical (motor, cognitive, olfactory, visual, and autonomic features) neurophysiological, neuroimaging, biological (biofluids or tissue biopsy), and genetic biomarkers have been identified and proposed, also in combination, as possible diagnostic or prognostic markers, along with a potential role for some of them as outcome measures and index of treatment response. In this review, we provide an insight into the present knowledge on both existing and future biomarkers of iRBD and highlight the difference with PDRBD and PDnoRBD, including currently available treatment options.

Neurophysiological Aspects of REM Sleep Behavior Disorder (RBD): A Narrative Review

REM sleep without atonia (RSWA) is the polysomnographic (PSG) hallmark of rapid eye movement (REM) sleep behavior disorder (RBD), a feature essential for the diagnosis of this condition. Several additional neurophysiological aspects of this complex disorder have also recently been investigated in depth, which constitute the focus of this narrative review, together with RSWA. First, we describe the complex neural network underlying REM sleep and its muscle atonia, focusing on the disordered mechanisms leading to RSWA. RSWA is then described in terms of its polysomnographic features, and the methods (visual and automatic) currently available for its scoring and quantification are exposed and discussed. Subsequently, more recent and advanced neurophysiological features of RBD are described, such as electroencephalography during wakefulness and sleep, transcranial magnetic stimulation, and vestibular evoked myogenic potentials. The role of the assessment of neurophysiological features in the study of RBD is then carefully discussed, highlighting their usefulness and sensitivity in detecting neurodegeneration in the early or prodromal stages of RBD, as well as their relationship with other proposed biomarkers for the diagnosis, prognosis, and monitoring of this condition. Finally, a future research agenda is proposed to help clarify the many still unclear aspects of RBD.

Neurophysiological Aspects of REM Sleep Behavior Disorder (RBD): A Narrative Review

REM sleep without atonia (RSWA) is the polysomnographic (PSG) hallmark of rapid eye movement (REM) sleep behavior disorder (RBD), a feature essential for the diagnosis of this condition. Several additional neurophysiological aspects of this complex disorder have also recently been investigated in depth, which constitute the focus of this narrative review, together with RSWA. First, we describe the complex neural network underlying REM sleep and its muscle atonia, focusing on the disordered mechanisms leading to RSWA. RSWA is then described in terms of its polysomnographic features, and the methods (visual and automatic) currently available for its scoring and quantification are exposed and discussed. Subsequently, more recent and advanced neurophysiological features of RBD are described, such as electroencephalography during wakefulness and sleep, transcranial magnetic stimulation, and vestibular evoked myogenic potentials. The role of the assessment of neurophysiological features in the study of RBD is then carefully discussed, highlighting their usefulness and sensitivity in detecting neurodegeneration in the early or prodromal stages of RBD, as well as their relationship with other proposed biomarkers for the diagnosis, prognosis, and monitoring of this condition. Finally, a future research agenda is proposed to help clarify the many still unclear aspects of RBD.

Cervical vestibular-evoked myogenic potentials in patients with essential tremor

Although different neuroanatomical structures and pathways are emphasized as possible explanations for essential tremor (ET), there is still an ongoing debate. This study aimed to assess the role of brainstem and reflex pathways with cervical vestibular-evoked myogenic potentials (VEMP) in patients with ET. This prospective study included 34 patients with ET and 25 healthy controls. Cervical VEMP was performed in both groups and latencies, inter-peak latency intervals, peak-to-peak amplitudes and asymmetry ratios were recorded. There was statistically no significant difference between the groups in terms of age (38.9 ± 14.9 years vs. 38.9 ± 14.9 years, p = 0.673) and gender (female to male ratio: 14/11 vs. 20/14, p = 0.828). Right N1 latency and right N1-P1 interval were significantly longer in the patient group (p < 0.05). There was a significant positive correlation between the duration of disease and the right N1-P1 interval (p < 0.05). There was no significant difference between the patient and control groups in terms of bilateral P1 latency, left N1 latency, left N1-P1 interval, and bilateral N1 and P1 amplitudes (p˃0.05). Cervical VEMP may reveal the involvement of brainstem and associated reflex pathways in ET.

Sleep Performance and Chronotype Behavior in Unilateral Vestibular Hypofunction

OBJECTIVE

To evaluate sleep behavior and its relation to otoneurological parameters in a group of patients with chronic unilateral vestibular hypofunction (UVH) without self-reported sleep disturbances when compared with healthy subjects serving as a control group (CG).

METHODS

Fifty-one patients affected by UVH underwent a retrospective clinical and instrumental otoneurological examination, a 1-week actigraphy sleep analysis, and a series of self-report and performance measures (SRM/PM). A CG of 60 gender- and age-matched healthy subjects was also enrolled. A between-group analysis of variance was performed for each variable, while correlation analysis was performed in UVH patients between otoneurological, SRM/PM, and actigraphy measure scores.

RESULTS

When compared with CG subjects, UVH patients were found to be spending less time sleeping and taking more time to go from being fully awake to asleep, based on actigraphy-based sleep analysis. Also, SRM/PM depicted UVH patients to have poor sleep quality and to be more prone to an evening-type behavior. Correlations were found between vestibular-related functionality indexes and subjective sleep quality, as well as between longer disease duration and reduced sleep time.

CONCLUSION

For the first time, a multiparametric sleep analysis was performed on a large population-based sample of chronic UVH patients. While a different pattern in sleep behavior was found, the cause is still unclear. Further research is needed to expand the extent of knowledge about sleep disruption in vestibular disorders.

LEVEL OF EVIDENCE

Level 3 Laryngoscope, 2021.

Distinct Vestibular Evoked Myogenic Potentials in Patients With Parkinson Disease and Progressive Supranuclear Palsy

Background: Early brainstem neurodegeneration is common in Parkinson's disease (PD) and progressive supranuclear palsy (PSP). While previous work showed abnormalities in vestibular evoked myogenic potentials (VEMPs) in patients with either disorder as compared to healthy humans, it remains unclear whether ocular and cervical VEMPs differ between PD and PSP patients.

Methods: We prospectively included 12 PD and 11 PSP patients, performed ocular and cervical VEMPs, and calculated specific VEMP scores (0 = normal, 12 = most pathological) based on latencies, amplitude, and absent responses. In addition, we assessed disease duration, presence of imbalance, motor asymmetry, and motor disability using the Movement Disorder Society Unified Parkinson's Disease Rating Scale, part III (MDS-UPDRS III). Moreover, we ascertained various sleep parameters by video-polysomnography.

Results: PSP and PD patients had similar oVEMP scores (6 [3–6] vs. 3 [1.3–6], p = 0.06), but PSP patients had higher cVEMP scores (3 [0–6] vs. 0 [0–2.8], p = 0.03) and total VEMP scores (9 [5–12] vs. 4 [2–7.5], p = 0.01). Moreover, total VEMP scores >10 were only observed in PSP patients (45%, p = 0.01). MDS-UPDRS III correlated with cVEMP scores (rho = 0.77, p = 0.01) in PSP, but not in PD. In PD, but not in PSP, polysomnographic markers of disturbed sleep, including decreased rapid eye movement sleep, showed significant correlations with VEMP scores.

Conclusions: Our findings suggest that central vestibular pathways are more severely damaged in PSP than in PD, as indicated by higher cervical and total VEMP scores in PSP than PD in a between-groups analysis. Meaningful correlations between VEMPs and motor and non-motor symptoms further encourage its use in neurodegenerative Parkinsonian syndromes.

REM Sleep without atonia correlates with abnormal vestibular-evoked myogenic potentials in isolated REM sleep behavior disorder

STUDY OBJECTIVES

The neurophysiological hallmark of REM sleep behavior disorder (RBD) is loss of atonia during REM sleep. Indeed, signs and symptoms of neurodegeneration can occur after years, even decades, from its beginning. This study aimed to measure neurophysiological alterations of the brainstem that potentially correlate with the severity of atonia loss, and determining whether a prodromal neurodegenerative disorder underlines this condition when it occurs as an isolated condition (iRBD).

METHODS

Subjects with iRBD and matched healthy controls were recruited. The study included the recording of one-night polysomnography, vestibular-evoked myogenic potentials (VEMPs), and a [123I]-FP-CIT dopamine transporter (DAT) scan. The quantification of REM sleep without atonia (RSWA) was made according to two previously published manual methods and one automated method.

RESULTS

The rate of alteration of VEMPs and VEMP score were significantly higher in iRBD patients than controls. Moreover, VEMP score was negatively correlated with the automated REM atonia index; a marginal statistical significance was also reached for the positive correlation with the visual tonic electromyographic parameter, while the other correlations, including that with DAT-scan score were not statistically significant.

CONCLUSIONS

Brainstem neurophysiology in iRBD can be assessed by VEMPs and their alterations may possibly indicate an early expression of the neurodegenerative process underlying this disorder at the brainstem level, which awaits future longitudinal confirmation. The correlation between RSWA and VEMP alteration might also represent a prodromal aspect anticipating the possible evolution from iRBD to neurodegeneration, whereas DAT-scan abnormalities might represent a later step in this evolution.

The vestibulo-masseteric reflex and the acoustic-masseteric reflex: a reliability and responsiveness study in healthy subjects

The vestibulo-masseteric reflex (VMR or p11 wave), the acoustic-masseteric reflex (AMR or p1/n21 wave) and the mixed vestibulo-cochlear p11/n21 potential are responses of masseter muscles to sound that can be employed to evaluate brainstem function. This study was aimed at establishing the test-retest reliability and responsiveness of these reflex parameters according to the type of electrode configuration. Twenty-two healthy volunteers (M:F = 11:11; mean age 25.3 ± 5.2 years) participated in two testing sessions separated by one week. Zygomatic and mandibular montages were compared following unilateral and bilateral stimulations. For reliability purposes, intraclass correlation coefficient (ICC), coefficient of variation of the method error (CVME) and standard error of measurement (SEM) were calculated. The minimal detectable difference (MDD) was also determined as a measure of responsiveness. Both VMR (p11 wave) and AMR could be consistently evoked from test to retest, although the frequency rate was significantly higher (all p values ≤ 0.009) with zygomatic (VMR: 97.7-100%; AMR: 86.9-97.6%) than mandibular montage (VMR: 84.7-89.8%; AMR: 65.0-67.8%), with no significant differences between unilateral and bilateral stimulations. Good-to-excellent reliability and responsiveness (high ICC, low CV_ME, SEM and MDD scores) were detected for corrected amplitudes and peak latencies for all reflex responses, whereas raw amplitudes were associated to poor reliability. The reliability of the zygomatic montage proved superior to the mandibular montage for all reflex responses. Given their high test-retest consistency and capability to study different features of the reflex arch, both peak latencies and corrected amplitudes should be reported and considered in the interpretation of reflex testing results.

Enhancing research quality of studies on VEMPs in central neurological disorders: a scoping review

Common pitfalls in vestibular-evoked myogenic potential (VEMP) recording methods have been extensively outlined by several reviews. Conversely, the robustness of research methodology employed for the design and conduct of VEMP studies has never been appraised. To fill this void, we conducted a scoping review to map and evaluate the overall quality of the existing literature on VEMPs in central neurological disorders. Five databases were searched from inception to October 2018 for case-control studies on multiple sclerosis (MS), cerebellar and/or brainstem strokes, Parkinson's disease (PD), migraine, and tumors of the cerebellopontine angle. Study quality was assessed using the Agency for Healthcare Research and Quality criteria (AHRQ). The 11-criteria AHRQ scoring system revealed that PD studies achieved a score of 5/11, migraine and cerebellar and/or brainstem stroke a score of 4/11, MS and tumors of the cerebellopontine angle a score of 3/11. Age was found to be one of the main sources of case-control imbalance: compared with controls, cases were significantly older with a 3.6-yr difference in MS studies, 6 yr in PD, up to 12 yr in stroke and tumors. Regardless of pathological condition, case-control groups were found unmatched also by gender. Post hoc power calculations revealed that 53% of the studies achieved the minimum statistical power of 80%. This scoping review revealed low research quality across the literature on VEMPs in central neurological disorders. Scoping lines are provided on actions to be undertaken in future studies to establish a common methodological platform and enhance the quality of research in this field.NEW & NOTEWORTHY Robust methodology is a prerequisite for any type of research, particularly for observational designs such as those employed in vestibular-evoked myogenic potential (VEMP) research. On these premises, this scoping review provides methodological guidelines to improve validity, accuracy and consistency of clinical outcomes from VEMP studies involving central nervous system disorders. In fact, the high risk for bias that is inherent to poor methodology threatens the validity of the findings of works that are technically sound but methodologically flawed.