Electrical Vestibular Stimulation in Humans: A Narrative Review

A Randomized, Double Blind, Sham-Controlled Clinical Trial to Evaluate the Efficacy of Electrical Vestibular Nerve Stimulation (VeNS), Compared to a Sham Control for Generalized Anxiety Disorder

Aims and Objectives: It has been hypothesised that vestibular stimulation may have a modulatory effect on anxiety. The aim of this randomised, double blind, sham-controlled trial was to determine the efficacy and safety of a non-invasive electrical vestibular nerve stimulation (VeNS) device as a treatment for anxiety compared to a sham stimulation device. Materials and methods: A total of 60 participants (mean age [SD]: 35.6 [8.1]) with a generalized anxiety disorder assessment (GAD-7) score of ≥10 were randomised to receive either an active VeNS device (n = 34) or a sham control device (n = 26). Both groups were asked to complete 20 stimulation sessions (30 min duration) at a rate of 3-5 sessions per week at a research clinic. The primary outcome was change in GAD-7 score from baseline to the end of study (when each participant finished their 20 stimulation sessions). Secondary outcomes were change in Insomnia Severity Index (ISI), and the Short Form 36 Health Survey (SF-36) scores (8 domains). Results: One participant allocated to the sham group withdrew from the study. The mean (SD) number of weeks it took to complete the 20 stimulation sessions was 5.8. The active group had a statistically greater reduction in GAD-7 score compared to the sham group (-7.4 versus -2.2, P < .001; respectively). A total of 97% (n = 33) of the active group achieved a clinically meaningful reduction (defined as ≥4-point reduction) in GAD-7 from baseline to the follow up visit compared to 24% (n = 6) of the sham group (P < .001). Additionally, the active group showed a significant improvement in ISI (-4.9 versus 2.2, P < .001) and greater improvements on all eight SF36 domains (P < .001) compared with the sham group. There was no device related reported adverse events. Conclusion: Regular non-invasive electrical vestibular nerve stimulation appears to have a clinically meaningful benefit when used as an intervention for Generalized Anxiety Disorder.

Enhancing balance and auditory function in bilateral vestibulopathy through otolithic vestibular stimulation: insights from a pilot study on cochlea-vestibular implant efficacy

Introduction

This study evaluates cochleovestibular implants (CVI) for improving auditory and vestibular function in patients with bilateral vestibulopathy and severe-to-profound hearing loss. CVI uniquely combines auditory and vestibular stimulation, offering a potential solution for dual impairments in hearing and balance.

Methods

Ten patients underwent CVI implantation. Auditory function was assessed with pure-tone audiometry (PTA) and speech recognition at baseline, 3, and 9 months post-implantation. Vestibular function was measured using the Dynamic Gait Index (DGI), Sensory Organization Test (SOT), posturography, and the Dizziness Handicap Inventory (DHI). Placebo-controlled tests verified cochleovestibular stimulation specificity.

Results

Auditory outcomes showed PTA improvements from 78 dB HL preoperatively to 34 dB HL at 3 months and 36 dB HL at 9 months, alongside speech recognition gains. Vestibular improvements included significant DGI (p < 0.05) and SOT score increases (33% to 68%, p < 0.05). DHI scores reflected reduced dizziness-related disability. Residual balance gains after device deactivation suggest neural adaptation, and placebo tests confirmed cochleovestibular stimulation specificity.

Discussion

CVI effectively restores auditory and vestibular function, with improvements in hearing, balance, and quality of life. Neural plasticity likely supports long-term benefits. Future research should refine device design and stimulation protocols to enhance outcomes further.

Stimulation conditions leading to electrical vestibular co-stimulation in cochlear implant users

Objectives

The study objective was to investigate the influence of electrical stimulus properties on cervical and ocular vestibular-evoked myogenic potentials to electrical stimulation by cochlear implants (e-cVEMPs, e-oVEMPs).

Methods

E-VEMPs were recorded in adult Nucleus cochlear implant (CI) patients using electric pulse trains (4 biphasic pulses at 1000 Hz burst rate). Ground path and stimulation electrodes were varied between monopolar stimulation at basal electrode contact E3 (MP1 + 2 E3), monopolar stimulation at apical electrode contact E20 (MP1 + 2 E20), and bipolar transmodiolar stimulation between E3 and E14 (BP E3-E14). The electric pulse train was further varied to 2 pulses at 1000 Hz, 2 pulses at 500 Hz, and a single pulse, in patients with present e-VEMP responses. VEMPs to bone-conducted vibration (BCV) were recorded as reference in all participants.

Results

Measurements were conducted in 30 ears of 27 participants (mean age 49.3 years, SD 12.7 years). E-VEMPs were present in 13 ears (43%). 5 of the 13 cases showed e-VEMPs but no BCV evoked VEMPs. Response numbers increased with increasing stimulation levels. The highest response rate of 40% was obtained for MP1 + 2 E3 stimulation. Stimulus variation did not affect response numbers. E-VEMP amplitudes were comparable to BCV-stimulated VEMPs. Latencies were up to 3.1 ms shorter for electric stimulation. Some patients showed e-VEMP thresholds close to or below the electric hearing threshold level.

Conclusion

The occurrence of e-VEMPs is dependent on current path and stimulation level. Vestibular co-stimulation by the CI is more likely in patients with high stimulation levels and for monopolar stimulation of basal electrode contacts.

Level of Evidence

4.

Vestibular Neurostimulation for Parkinson's Disease: A Novel Device-Aided Non-Invasive Therapeutic Option

Dopaminergic replacement therapy remains the mainstay of symptomatic treatment for Parkinson's disease (PD), but many unmet needs and gaps remain. Device-based treatments or device-aided non-oral therapies are typically used in the advanced stages of PD, ranging from stereotactic deep brain stimulation to levodopa or apomorphine infusion therapies. But there are concerns associated with these late-stage therapies due to a number of procedural, hardware, or long-term treatment-related side effects of these treatments, and their limited nonmotor benefit in PD. Therefore, there is an urgent unmet need for low-risk adjuvants or standalone therapies which can address the range of burdensome motor and nonmotor symptoms that occur in PD. Recent studies suggest that non-invasive neurostimulation of the vestibular system may be able to address these gaps through the stimulation of the vestibular brainstem sensory network which extensively innervates brain regions, regulating both motor and a range of nonmotor functions. Therapeutic non-invasive vestibular stimulation is a relatively modern concept that may potentially improve a broad range of motor and nonmotor symptoms of PD, even at early stages of the disease. Here, we review previous studies supporting the therapeutic potential of vestibular stimulation for the treatment of PD and discuss ongoing clinical trials and potential areas for future investigations.

Exploring the Potentials of Wearable Technologies in Managing Vestibular Hypofunction

The vestibular system is dedicated to gaze stabilization, postural balance, and spatial orientation; this makes vestibular function crucial for our ability to interact effectively with our environment. Vestibular hypofunction (VH) progresses over time, and it presents differently in its early and advanced stages. In the initial stages of VH, the effects of VH are mitigated using vestibular rehabilitation therapy (VRT), which can be facilitated with the aid of technology. At more advanced stages of VH, novel techniques that use wearable technologies for sensory augmentation and sensory substitution have been applied to manage VH. Despite this, the potential of assistive technologies for VH management remains underexplored over the past decades. Hence, in this review article, we present the state-of-the-art technologies for facilitating early-stage VRT and for managing advanced-stage VH. Also, challenges and strategies on how these technologies can be improved to enable long-term ambulatory and home use are presented.

Stimulation Crosstalk Between Cochlear And Vestibular Spaces During Cochlear Electrical Stimulation

OBJECTIVES

Possible beneficial "crosstalk" during cochlear implant stimulation on otolith end organs has been hypothesized. The aim of this case-control study is to analyze the effect of electrical cochlear stimulation on the vestibule (otolith end-organ), when using a cochleo-vestibular implant, comparing vestibular stimulation (VI) and cochlear stimulation (CI).

METHODS

Four patients with bilateral vestibulopathy were included. A double electrode array research implant was implanted in all cases. Dynamic Gait Index (DGI), VOR gain measured by using vestibular head impulse test (vHIT), acoustic cervical myogenic responses (cVEMP) recordings, and electrical cVEMP were used in all cases. Trans-impedance Matrix (TIM) analysis was used to evaluate the current flow from the cochlea to the vestibule.

RESULTS

While patients did not have any clinical vestibular improvement with the CI stimulation alone, gait metrics of the patients revealed improvement when the vestibular electrode was stimulated. The average improvement in the DGI was 38% when the vestibular implant was activated, returning to the normal range in all cases. Our findings suggest that any current flow from the cochlear space to the otolith organs was insufficient for effective cross-stimulation. The functional results correlated with the data obtained in TIM analysis, confirming that there is no current flow from the cochlea to the vestibule.

CONCLUSION

The only way to produce effective electrical otolith end-organ stimulation, demonstrated with this research implant, is by direct electrical stimulation of the otolith end organs. No effective cross-stimulation was found from cochlear electrode stimulation.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:2349-2355, 2024.

The VertiGO! Trial protocol: A prospective, single-center, patient-blinded study to evaluate efficacy and safety of prolonged daily stimulation with a multichannel vestibulocochlear implant prototype in bilateral vestibulopathy patients

BACKGROUND

A combined vestibular (VI) and cochlear implant (CI) device, also known as the vestibulocochlear implant (VCI), was previously developed to restore both vestibular and auditory function. A new refined prototype is currently being investigated. This prototype allows for concurrent multichannel vestibular and cochlear stimulation. Although recent studies showed that VCI stimulation enables compensatory eye, body and neck movements, the constraints in these acute study designs prevent them from creating more general statements over time. Moreover, the clinical relevance of potential VI and CI interactions is not yet studied. The VertiGO! Trial aims to investigate the safety and efficacy of prolonged daily motion modulated stimulation with a multichannel VCI prototype.

METHODS

A single-center clinical trial will be carried out to evaluate prolonged VCI stimulation, assess general safety and explore interactions between the CI and VI. A single-blind randomized controlled crossover design will be implemented to evaluate the efficacy of three types of stimulation. Furthermore, this study will provide a proof-of-concept for a VI rehabilitation program. A total of minimum eight, with a maximum of 13, participants suffering from bilateral vestibulopathy and severe sensorineural hearing loss in the ear to implant will be included and followed over a five-year period. Efficacy will be evaluated by collecting functional (i.e. image stabilization) and more fundamental (i.e. vestibulo-ocular reflexes, self-motion perception) outcomes. Hearing performance with a VCI and patient-reported outcomes will be included as well.

DISCUSSION

The proposed schedule of fitting, stimulation and outcome testing allows for a comprehensive evaluation of the feasibility and long-term safety of a multichannel VCI prototype. This design will give insights into vestibular and hearing performance during VCI stimulation. Results will also provide insights into the expected daily benefit of prolonged VCI stimulation, paving the way for cost-effectiveness analyses and a more comprehensive clinical implementation of vestibulocochlear stimulation in the future.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04918745. Registered 28 April 2021.

Patient-Reported Outcomes After Vestibular Implantation for Bilateral Vestibular Hypofunction

Importance

Standard-of-care treatment proves inadequate for many patients with bilateral vestibular hypofunction (BVH). Vestibular implantation is an emerging alternative.

Objective

To examine patient-reported outcomes from prosthetic vestibular stimulation.

Design, Setting, and Participants

The Multichannel Vestibular Implant (MVI) Early Feasibility Study is an ongoing prospective, nonrandomized, single-group, single-center cohort study conducted at Johns Hopkins Hospital that has been active since 2016 in which participants serve as their own controls. The study includes adults with severe or profound adult-onset BVH for at least 1 year and inadequate compensation despite standard-of-care treatment. As of March 2023, 12 candidates completed the eligibility screening process.

Intervention

The MVI system electrically stimulates semicircular canal branches of the vestibular nerve to convey head rotation.

Main Outcomes and Measures

Patient-reported outcome instruments assessing dizziness (Dizziness Handicap Inventory [DHI]) and vestibular-related disability (Vestibular Disorders-Activities of Daily Living [VADL]). Health-related quality of life (HRQOL) assessed using the Short Form-36 Utility (SF36U) and Health Utilities Index Mark 3 (HUI3), from which quality-adjusted life-years were computed.

Results

Ten individuals (5 female [50%]; mean [SD] age, 58.5 [5.0] years; range, 51-66 years) underwent unilateral implantation. A control group of 10 trial applicants (5 female [50%]; mean [SD] age, 55.1 [8.5] years; range, 42-73 years) completed 6-month follow-up surveys after the initial application. After 0.5 years of continuous MVI use, a pooled mean (95% CI) of within-participant changes showed improvements in dizziness (DHI, -36; 95% CI, -55 to -18), vestibular disability (VADL, -1.7; 95% CI, -2.6 to -0.7), and HRQOL by SF36U (0.12; 95% CI, 0.07-0.17) but not HUI3 (0.02; 95% CI, -0.22 to 0.27). Improvements exceeded minimally important differences in the direction of benefit (exceeding 18, 0.65, and 0.03, respectively, for DHI, VADL, and SF36U). The control group reported no mean change in dizziness (DHI, -4; 95% CI, -10 to 2), vestibular disability (VADL, 0.1; 95% CI, -0.9 to 1.1) or HRQOL per SF36U (0; 95% CI, -0.06 to 0.05) but an increase in HRQOL per HUI3 (0.10; 95% CI, 0.04-0.16). Lifetime HRQOL gain for MVI users was estimated to be 1.7 quality-adjusted life-years (95% CI, 0.6-2.8) using SF36U and 1.4 (95% CI, -1.2 to 4.0) using HUI3.

Conclusions and Relevance

This cohort study found that vestibular implant recipients report vestibular symptom improvements not reported by a control group. These patient-reported benefits support the use of vestibular implantation as a treatment for bilateral vestibular hypofunction.

Electrical stimulation of the peripheral and central vestibular system

PURPOSE OF REVIEW

Electrical stimulation of the peripheral and central vestibular system using noninvasive (galvanic vestibular stimulation, GVS) or invasive (intracranial electrical brain stimulation, iEBS) approaches have a long history of use in studying self-motion perception and balance control. The aim of this review is to summarize recent electrophysiological studies of the effects of GVS, and functional mapping of the central vestibular system using iEBS in awake patients.

RECENT FINDINGS

The use of GVS has become increasingly common in the assessment and treatment of a wide range of clinical disorders including vestibulopathy and Parkinson's disease. The results of recent single unit recording studies have provided new insight into the neural mechanisms underlying GVS-evoked improvements in perceptual and motor responses. Furthermore, the application of iEBS in patients with epilepsy or during awake brain surgery has provided causal evidence of vestibular information processing in mostly the middle cingulate cortex, posterior insula, inferior parietal lobule, amygdala, precuneus, and superior temporal gyrus.

SUMMARY

Recent studies have established that GVS evokes robust and parallel activation of both canal and otolith afferents that is significantly different from that evoked by natural head motion stimulation. Furthermore, there is evidence that GVS can induce beneficial neural plasticity in the central pathways of patients with vestibular loss. In addition, iEBS studies highlighted an underestimated contribution of areas in the medial part of the cerebral hemispheres to the cortical vestibular network.

[Electrical vestibular stimulation as a tool for treatment of bilateral vestibular loss. Literature review]

The review of the literature on RSCI and PubMed databases presents methods of electrical vestibular stimulation to improve vestibular function in patients with bilateral vestibulopathy. The variants of stimulation of peripheral vestibular structures, such as vestibular implantation, noise galvanic vestibular stimulation are described. The perspectives of development of this direction, advantages of application of electrical stimulation in the future, as well as current limitations that do not currently allow to use these methods in clinical practice are shown.

[Rehabilitation in bilateral vestibulopathy: trends and perspectives]

A review of the literature on rehabilitation methods for bilateral vestibulopathy is presented using RSCI, Scopus and PubMed databases. The principles and effectiveness of physical vestibular rehabilitation, vestibular implants, galvanic vestibular stimulation, and biofeedback-based sensory substitution and augmentation systems are described. The advantages and disadvantages of each method and perspectives for their improvement are presented.

The Need for Vestibular Implants in a Tertiary Referral Ear, Nose, and Throat Center and Its Relation to Hearing Status

BACKGROUND

Patients with bilateral vestibulopathy (BVP) are at increased risk of falling and have poor quality of life. Several research groups are currently developing and investigating vestibular implants to treat BVP. The goal was to identify how many patients can be considered eligible for vestibular implantation.

METHODS

The objective vestibular implantation criteria for research were applied to the results of the caloric irrigation test, the sinusoidal harmonic acceleration test, the video head impulse test, and the cervical and ocular vestibular evoked myogenic potential tests.

RESULTS

Vestibular implant eligibility was situated between 3.6% and 15.7% (semicircular canal implant: 3.6%; otolith implant: 15.7%; combined implant: 4.8%). Only 16 out of the 29 patients (55%) eligible for a vestibular implant had bilateral severe-to-profound hearing loss. The remaining 45% (13/29) thus have better hearing in at least 1 ear.

CONCLUSION

Vestibular implant eligibility in an ear, nose, and throat department was situated between 3.6% and 15.7%, depending on the type of implant that was considered. In addition, the data showed that 45% of the eligible patients had normal-to-moderate hearing in at least 1 ear. In other words, only recruiting patients with (bilateral) severe-to-profound hearing loss for vestibular implantation leads to the systematic exclusion of about half of the candidates. Structure-preserving surgical techniques are thus a major future challenge in the field of vestibular implantation.

Physical Body Orientation Impacts Virtual Navigation Experience and Performance

Most human navigation studies in MRI rely on virtual navigation. However, the necessary supine position in MRI makes it fundamentally different from daily ecological navigation. Nonetheless, until now, no study has assessed whether differences in physical body orientation (BO) affect participants' experienced BO during virtual navigation. Here, combining an immersive virtual reality navigation task with subjective BO measures and implicit behavioral measures, we demonstrate that physical BO (either standing or supine) modulates experienced BO. Also, we show that standing upright BO is preferred during spatial navigation: participants were more likely to experience a standing BO and were better at spatial navigation when standing upright. Importantly, we report that showing a supine virtual agent reduces the conflict between the preferred BO and physical supine BO. Our study provides critical, but missing, information regarding experienced BO during virtual navigation, which should be considered cautiously when designing navigation studies, especially in MRI.

[Recent progress in vestibular prosthesis]

Bilateral vestibulopathy（BVP） is one of the common diseases in the vestibular nervous system, with an incidence rate of about 4%-7% in the population, which can lead to a variety of body dysfunctions. At present, there are two main treatment methods for BVP. One is vestibular rehabilitation. However, only part of BVP patients can finally benefit from vestibular rehabilitation, and most patients will remain with permanent vestibular dysfunction. Benefiting from the maturity of cochlear implant technology, European and American countries took the lead in the development of vestibular prosthesis（VP） technology to restore the vestibular function in patients with BVP. This review will focus on the development history, principles, future applications and the related research progress of VP in China.

How a Subclinical Unilateral Vestibular Signal Improves Binocular Vision

The present study aimed to determine if an infra-liminal asymmetric vestibular signal could account for some of the visual complaints commonly encountered in chronic vestibular patients. We used infra-liminal galvanic vestibular stimulation (GVS) to investigate its potential effects on visuo-oculomotor behavior. A total of 78 healthy volunteers, 34 aged from 20 to 25 years old and 44 aged from 40 to 60 years old, were included in a crossover study to assess the impact of infra-liminal stimulation on convergence, divergence, proximal convergence point, and stereopsis. Under GVS stimulation, a repeated measures ANOVA showed a significant variation in near convergence (p < 0.001), far convergence (p < 0.001), and far divergence (p = 0.052). We also observed an unexpected effect of instantaneous blocking of the retest effect on the far divergence measurement. Further investigations are necessary to establish causal relationships, but GVS could be considered a behavioral modulator in non-pharmacological vestibular therapies.

Binocular 3-D otolith-ocular reflexes: responses of chinchillas to natural and prosthetic stimulation after ototoxic injury and vestibular implantation

The otolith end organs inform the brain about gravitational and linear accelerations, driving the otolith-ocular reflex (OOR) to stabilize the eyes during translational motion (e.g., moving forward without rotating) and head tilt with respect to gravity. We previously characterized OOR responses of normal chinchillas to whole body tilt and translation and to prosthetic electrical stimulation targeting the utricle and saccule via electrodes implanted in otherwise normal ears. Here we extend that work to examine OOR responses to tilt and translation stimuli after unilateral intratympanic gentamicin injection and to natural/mechanical and prosthetic/electrical stimulation delivered separately or in combination to animals with bilateral vestibular hypofunction after right ear intratympanic gentamicin injection followed by surgical disruption of the left labyrinth at the time of electrode implantation. Unilateral intratympanic gentamicin injection decreased natural OOR response magnitude to about half of normal, without markedly changing OOR response direction or symmetry. Subsequent surgical disruption of the contralateral labyrinth at the time of electrode implantation surgery further decreased OOR magnitude during natural stimulation, consistent with bimodal-bilateral otolith end organ hypofunction (ototoxic on the right ear, surgical on the left ear). Delivery of pulse frequency- or pulse amplitude-modulated prosthetic/electrical stimulation targeting the left utricle and saccule in phase with whole body tilt and translation motion stimuli yielded responses closer to normal than the deficient OOR responses of those same animals in response to head tilt and translation alone.NEW & NOTEWORTHY Previous studies to expand the scope of prosthetic stimulation of the otolith end organs showed that selective stimulation of the utricle and saccule is possible. This article further defines those possibilities by characterizing a diseased animal model and subsequently studying its responses to electrical stimulation alone and in combination with mechanical motion. We show that we can partially restore responses to tilt and translation in animals with unilateral gentamicin ototoxic injury and contralateral surgical disruption.

VESTIBULAR IMPLANT STIMULATION PAUSE DETECTION THRESHOLDS: IMPLICATIONS FOR DESIGN OF BATTERY DEPLETION ALERTS

Vestibular implants (VI) modulate the rate and amplitude of charge-balanced current pulses to encode head angular velocity or acceleration. When the battery of a VI becomes depleted, stimulation interruptions can cause vertigo. To avoid this, VIs can use alert signals such as vibration and beeping to remind the user to replace the battery. However, in distracting and noisy environments typical of activities of daily life, some patients may fail to hear or feel those alerts, so a physiological signal can be used as an alternate channel for signaling battery depletion. Pauses in the stimulation waveform can be delivered for this purpose, with the length of the pause long enough to be detected reliably by the patient but not so long as to induce dizziness or a vertigo attack. As a guide for the design of a physiologic battery depletion alert system, this study reports the ability of nine long-term, continuous VI users to detect stimulation pauses of various durations. We also show the effect of distraction on patients' detection thresholds and response latencies for detected events.

Clinical Findings in a Pati ent with Large B-Cell Lymphoma andNeuroniti s: A Case Study

BACKGROUND

 Given the multifaceted nature of the balance system, an interdisciplinary approach to patient care is imperative. For surgical patients with complex medical histories, comprehensive vestibular evaluations provide information on baseline vestibular function and identify possible surgical risks and outcomes. This case study follows a patient diagnosed with probable right vestibular neuronitis immediately preceding surgical resection of a left brainstem lesion, later diagnosed as a B cell lymphoma (BCL) and provides details regarding pre- and postsurgical outcomes.

PURPOSE

 This case study expands on the importance of the inclusion of vestibular audiologists on the interdisciplinary team for related surgical procedures to provide insight into possible surgical risks and subsequent effects on patients' postsurgical quality of life.

RESEARCH DESIGN

 Case report.

STUDY SAMPLE

 A 68-year-old female patient evaluated within the Henry Ford Health System for management of diffuse large BCL.

DATA COLLECTION

 Standard neuro-otology, neuro-surgical, audiological, and vestibular evaluations were conducted to evaluate the patient's complex symptomology.

RESULTS

 This case report outlines a patient hospitalized for a left brainstem mass, later diagnosed as an aggressive form of lymphoma, with a concurrent episode of vestibular neuronitis on the contralesional side. Functional outcomes are discussed following surgical intervention to remove the mass. Postsurgical vestibular testing revealed a bilateral vestibular hypofunction.

CONCLUSIONS

 Vestibular audiology plays an essential role in the multidisciplinary team for complex dizzy patients with related surgical procedures, as this subset of the field can offer critical insight into postsurgical recommendations and patient expectations.

[Bilateral peripheral vestibulopathy]

Bilateral vestibulopathy is a relatively widespread and at the same time rarely diagnosed cause of chronic postural instability. Numerous toxic factors, dysmetabolic, autoimmune and neurodegenerative processes can lead to this condition. The main clinical manifestations of bilateral vestibulopathy are balance disorders and visual disturbances (oscillopsia), which can significantly increase the risks of falls in such patients. In addition, cognitive and affective disorders, which also reduce the quality of life in patients with bilateral vestibulopathy, have been described and actively studied in recent years. The diagnosis of bilateral vestibulopathy is based on the results of a clinical neurovestibular study, including a dynamic visual acuity test and a Halmagyi test. A video head impulse test, a bithermal caloric test and a sinusoidal rotation test are used as instrumental methods confirming the dysfunction of the peripheral vestibular system. However, they are still not widespread in neurological practice. Treatment of bilateral vestibulopathy is reduced to vestibular rehabilitation. Encouraging results have been obtained in a number of studies using galvanic vestibular stimulation and the use of vestibular implants. In addition, cognitive rehabilitation methods are currently being developed, which presumably can also improve compensation for bilateral vestibular loss.

Evaluation and management of paediatric vertigo

PURPOSE OF REVIEW

This review summarizes the most current information on cause, evaluation and treatment of dizziness in children.

RECENT FINDINGS

There has been an increased understanding of the multifactorial cause of dizziness in the paediatric population. Quantitative vestibular testing is increasingly used and valuable as a diagnostic adjunct. Vestibular rehabilitation, migraine hygiene, psychological therapies, pharmaceuticals and/or surgery can be used as well tolerated and effective treatments for vertigo in children and adolescents when tailored to cause.

SUMMARY

Paediatric vertigo can be effectively evaluated through careful history taking and physical examination along with adjunctive tests, such as vestibular testing and audiometry, when appropriate. Options for treatment of vestibular disorders in children and adolescents have greatly expanded in recent years allowing for the effective management of nearly all cases of paediatric vertigo, though a multimodal and/or multidisciplinary approach is often needed.

Advancements in inner ear development, regeneration, and repair through otic organoids

The vertebrate inner ear contains a diversity of unique cell types arranged in a particularly complex 3D cytoarchitecture. Both of these features are integral to the proper development, function, and maintenance of hearing and balance. Since the elucidation of the timing and delivery of signaling molecules to produce inner ear sensory cells, supporting cells, and neurons from human induced pluripotent stem cells, we have entered a revolution using organ-like 'otic organoid' cultures to explore inner ear specific genetic programs, developmental rules, and potential therapeutics. This review aims to highlight a selection of reviews and primary research papers from the past two years of particular merit that use otic organoids to investigate the broadly defined topics of cell reprogramming, regeneration, and repair.

Control of Disabling Vertigo in Ménière's Disease Following Cochlear Implantation without Labyrinthectomy

BACKGROUND

The placement of a cochlear implant (CI) can restore auditory function in the case of profound cochlear deafness, which may be due to Ménière's disease (MD) or be associated with symptoms related to endolymphatic hydrops. The usual treatment of disabling vertigo in MD is based on vestibular deafferentation by labyrinth ablation. The aim of the present study was to retrospectively evaluate the efficacy of the CI in the control of disabling vestibular manifestations in the case of MD unresponsive to medical treatments.

METHODS

A case series of five MD patients with disabling vestibular manifestations associated with profound hearing loss was included. A complete audio-vestibular evaluation was performed after CI positioning.

RESULTS

All patients reported clinical benefits after implant positioning: no vestibular crisis was reported after the surgery. The vHIT and the caloric test showed a normal function or a mild vestibular hypofunction. The auditory performances were comparable to those in the general implanted population. All patients reported subjective tinnitus reduction.

CONCLUSIONS

To date, very few studies have reported vestibular outcomes in hydropic pathology on the implanted side; our results are encouraging. We can therefore confirm the efficacy and safety of the CI as a unique treatment for hearing loss, dizziness, and tinnitus in case of disabling cochlear hydrops, especially in those patients where the history of the disease requires preservation of the vestibular function.

Case Report: Galvanic Vestibular Stimulation in the Chronic Spinal Cord Injury Patient

The traumatic spinal cord injury can generate sequels with high clinical severity and dysfunction and limitations of irreversible character. Current studies seek to reverse the sequelae and gain functionality in these individuals. Galvanic vestibular stimulation (GVS) has shown to be beneficial in spinal cord function as an evaluation correlated to functionality and for stimulation with physiological and functional characteristics in disease and healthy people. The present study observed the effects of Noise Galvanic Vestibular Stimulation in a patient with chronic spinal cord injury with tetraplegia on postural and trunk control. The evaluations were the Functional Independence Measure (FIM), the American Spinal Injury Association (ASIA) evaluation, and the Clinical Posturography, using force platform to assess postural balance, in the sitting position, through Sensory Organization and Functional Reach Tests. Ten sessions of Noise Galvanic Vestibular Stimulation associated with customized vestibular and neurofunctional rehabilitation were performed. The effects observed were increments in all assessments and tests that include modifications in functional independence, motor and sensory levels, change in disability grade from A (complete) to C (incomplete), and improvements in postural balance and trunk control. The phenomenon of stochastic resonance has shown benefits in postural control in people without vestibular lesions and we could observe some of these phenomena in our patients. We emphasize the need for evaluation with larger populations to observe the phenomena and effects in this group of patients and potential benefits and limitations.

Electrical vestibular nerve stimulation (VeNS): a follow-up safety assessment of long-term usage

OBJECTIVES

This retrospective, open-label study was undertaken to assess the safety of repeated, long-term electrical vestibular nerve stimulation (VeNS). The primary outcome for this study was assessment of hearing function as reported by formal audiometry testing.

METHODS

Assessments were conducted on n=25 long-term users of daily 1.5 mA VeNS. Skin inspection of the mastoid area, otoscope examination of the inner ear, and formal audiometry testing was conducted on n=18 users. All participants completed a survey-based assessment to determine usage of the device, adverse events, and long-term outcomes.

RESULTS

Mean duration of use was 22 months, with approximately 80% of users reporting 1 h of daily, or 1 h of regular (2-3 times per week) VeNS usage. No adverse events were reported. There were no significant findings during examination of the mastoid areas, ear canal, or tympanic membranes. There were no significant findings reported from the formal audiogram assessments.

CONCLUSIONS

This appears to be the first study to provide formal assessment to show that repeated, long-term VeNS usage has not generated any significant side effects or adverse events. Results from this study further support previous literature that electrical vestibular stimulation is both safe and well-tolerated.

Motor Responses of Lumbar Erector Spinae Induced by Electrical Vestibular Stimulation in Seated Participants

Introduction: The study of motor responses induced by electrical vestibular stimulation (EVS) may help clarify the role of the vestibular system in postural control. Although back muscles have an important role in postural control, their EVS-induced motor responses were rarely studied. Moreover, the effects of EVS parameters, head position, and vision on EVS-induced back muscles responses remain little explored. Objectives: To explore the effects of EVS parameters, head position, and vision on lumbar erector spinae muscles EVS-induced responses. Design: Exploratory, cross-sectional study. Materials and Methods: Ten healthy participants were recruited. Three head positions (right, left and no head rotation), 4 intensities (2, 3, 4, 5 mA), and 4 EVS durations (5, 20, 100, 200 ms) were tested in sitting position with eyes open or closed. EVS usually induced a body sway toward the anode (placed on the right mastoid). EMG activity of the right lumbar erector spinae was recorded. Variables of interest were amplitude, occurrence, and latency of the EVS-induced modulation of the EMG activity. Results: The short-latency response was inhibitory and the medium-latency response was excitatory. Increased EVS current intensity augmented the occurrence and the amplitude of the short- and medium-latency responses (more inhibition and more excitation, respectively). EVS duration influenced the medium-latency response differently depending on the position of the head. Right head rotation produced larger responses amplitude and occurrence than left head rotation. Opposite head rotation (left vs. right) did not induce a reversal of the short- and medium-latency responses (i.e., the inhibition did not become an excitation), as typically reported in lower legs muscles. The eyes open condition did not modulate muscle responses. Conclusion: Modulation of EVS parameters (current intensity and duration of EVS) affects the amplitude and occurrence of the lumbar erector spinae responses. In contrast, vision did not influence the responses, suggesting its minimal contribution to vestibulomotor control in sitting. The lack of response reversal in sagittal plane may reflect the biomechanical role of lumbar erector spinae to fine-tune the lumbar lordosis during the induced body sway. This hypothesis remains to be further tested.

Selective optogenetic stimulation of glutamatergic, but not GABAergic, vestibular nuclei neurons induces immediate and reversible postural imbalance in mice

Glutamatergic and GABAergic neurons represent the neural components of the medial vestibular nuclei. We assessed the functional role of glutamatergic and GABAergic neuronal pathways arising from the vestibular nuclei (VN) in the maintenance of gait and balance by optogenetically stimulating the VN in VGluT2-cre and GAD2-cre mice. We demonstrate that glutamatergic, but not GABAergic VN neuronal subpopulation is responsible for immediate and strong posturo-locomotor deficits, comparable to unilateral vestibular deafferentation models. During optogenetic stimulation, the support surface dramatically increased in VN^VGluT2+ mice, and rapidly fell back to baseline after stimulation, whilst it remained unchanged during similar stimulation of VN^GAD2+ mice. This effect persisted when vestibular tactilo kinesthesic plantar inputs were removed. Posturo-locomotor alterations evoked in VN^VGluT2+ animals were still present immediately after stimulation, while they disappeared 1 h later. Overall, these results indicate a fundamental role for VN^VGluT2+ neurons in balance and posturo-locomotor functions, but not for VN^GAD2+ neurons, in this specific context. This new optogenetic approach will be useful to characterize the role of the different VN neuronal populations involved in vestibular physiology and pathophysiology.

Differences in Vestibular-Evoked Myogenic Potential Responses by Using Cochlear Implant and Otolith Organ Direct Stimulation

Objective: Several studies have demonstrated the possibility to obtain vestibular potentials elicited with electrical stimulation from cochlear and vestibular implants. The objective of this study is to analyze the vestibular-evoked myogenic potentials (VEMPs) obtained from patients implanted with cochlear and vestibulo-cochlear implant. Material and Methods: We compared two groups: in the first group, four cochlear implant (CI) recipients with present acoustic cVEMPs before CI surgery were included. In the second group, three patients with bilaterally absent cVEMPs and bilateral vestibular dysfunction were selected. The latter group received a unilateral cochleo-vestibular implant. We analyze the electrically elicited cVEMPs in all patients after stimulation with cochlear and vestibular electrode array stimulation. Results: We present the results obtained post-operatively in both groups. All patients (100%) with direct electrical vestibular stimulation via the vestibular electrode array had present cVEMPs. The P1 and N1 latencies were 11.33-13.6 ms and 18.3-21 ms, respectively. In CI patients, electrical cVEMPs were present only in one of the four subjects (25%) with cochlear implant ("cross") stimulation, and P1 and N1 latencies were 9.67 and 16.33, respectively. In these patients, the responses present shorter latencies than those observed acoustically. Conclusions: Electrically evoked cVEMPs can be present after cochlear and vestibular stimulation and suggest stimulation of vestibular elements, although clinical effect must be further studied.

Rare Disorders of the Vestibular Labyrinth: of Zebras, Chameleons and Wolves in Sheep's Clothing

The differential diagnosis of vertigo syndromes is a challenging issue, as many - and in particular - rare disorders of the vestibular labyrinth can hide behind the very common symptoms of "vertigo" and "dizziness". The following article presents an overview of those rare disorders of the balance organ that are of special interest for the otorhinolaryngologist dealing with vertigo disorders. For a better orientation, these disorders are categorized as acute (AVS), episodic (EVS) and chronic vestibular syndromes (CVS) according to their clinical presentation. The main focus lies on EVS sorted by their duration and the presence/absence of triggering factors (seconds, no triggers: vestibular paroxysmia, Tumarkin attacks; seconds, sound and pressure induced: "third window" syndromes; seconds to minutes, positional: rare variants and differential diagnoses of benign paroxysmal positional vertigo; hours to days, spontaneous: intralabyrinthine schwannomas, endolymphatic sac tumors, autoimmune disorders of the inner ear). Furthermore, rare causes of AVS (inferior vestibular neuritis, otolith organ specific dysfunction, vascular labyrinthine disorders, acute bilateral vestibulopathy) and CVS (chronic bilateral vestibulopathy) are covered. In each case, special emphasis is laid on the decisive diagnostic test for the identification of the rare disease and "red flags" for potentially dangerous disorders (e. g. labyrinthine infarction/hemorrhage). Thus, this chapter may serve as a clinical companion for the otorhinolaryngologist aiding in the efficient diagnosis and treatment of rare disorders of the vestibular labyrinth.

No Impact of Stochastic Galvanic Vestibular Stimulation on Arterial Pressure and Heart Rate Variability in the Elderly Population

Objective

Noisy galvanic vestibular stimulation (nGVS) is often used to improve postural stability in disorders, such as neurorehabilitation montage. For the safe use of nGVS, we investigated whether arterial pressure (AP) and heart rate vary during static supine and slow whole-body tilt with random nGVS (0.4 mA, 0.1–640 Hz, gaussian distribution) in a healthy elderly population.

Methods

This study was conducted with a double-blind, sham-controlled, cross-over design. Seventeen healthy older adults were recruited. They were asked to maintain a static supine position on a bed for 10 min, and the bed was tilted up (TU) to 70 degrees within 30 s. After maintaining this position for 3 min, the bed was passively tilted down (TD) within 30 s. Real-nGVS or sham-nGVS was applied from 4 to 15 min. The time course of mean arterial pressure (MAP) and RR interval variability (RRIV) were analyzed to estimate the autonomic nervous activity.

Result

nGVS and/or time, including pre-/post-event (nGVS-start, TU, and TD), had no impact on MAP and RRIV-related parameters. Further, there was no evidence supporting the argument that nGVS induces pain, vertigo/dizziness, and uncomfortable feeling.

Conclusion

nGVS may not affect the AP and RRIV during static position and whole-body tilting or cause pain, vertigo/dizziness, and discomfort in the elderly.

Posture, Gait, Quality of Life, and Hearing with a Vestibular Implant

BACKGROUND

Bilateral vestibular hypofunction is associated with chronic disequilibrium, postural instability, and unsteady gait owing to failure of vestibular reflexes that stabilize the eyes, head, and body. A vestibular implant may be effective in alleviating symptoms.

METHODS

Persons who had had ototoxic (7 participants) or idiopathic (1 participant) bilateral vestibular hypofunction for 2 to 23 years underwent unilateral implantation of a prosthesis that electrically stimulates the three semicircular canal branches of the vestibular nerve. Clinical outcomes included the score on the Bruininks-Oseretsky Test of Motor Proficiency balance subtest (range, 0 to 36, with higher scores indicating better balance), time to failure on the modified Romberg test (range, 0 to 30 seconds), score on the Dynamic Gait Index (range, 0 to 24, with higher scores indicating better gait performance), time needed to complete the Timed Up and Go test, gait speed, pure-tone auditory detection thresholds, speech discrimination scores, and quality of life. We compared participants' results at baseline (before implantation) with those at 6 months (8 participants) and at 1 year (6 participants) with the device set in its usual treatment mode (varying stimulus pulse rate and amplitude to represent rotational head motion) and in a placebo mode (holding pulse rate and amplitude constant).

RESULTS

The median scores at baseline and at 6 months on the Bruininks-Oseretsky test were 17.5 and 21.0, respectively (median within-participant difference, 5.5 points; 95% confidence interval [CI], 0 to 10.0); the median times on the modified Romberg test were 3.6 seconds and 8.3 seconds (difference, 5.1; 95% CI, 1.5 to 27.6); the median scores on the Dynamic Gait Index were 12.5 and 22.5 (difference, 10.5 points; 95% CI, 1.5 to 12.0); the median times on the Timed Up and Go test were 11.0 seconds and 8.7 seconds (difference, 2.3; 95% CI, -1.7 to 5.0); and the median speeds on the gait-speed test were 1.03 m per second and 1.10 m per second (difference, 0.13; 95% CI, -0.25 to 0.30). Placebo-mode testing confirmed that improvements were due to treatment-mode stimulation. Among the 6 participants who were also assessed at 1 year, the median within-participant changes from baseline to 1 year were generally consistent with results at 6 months. Implantation caused ipsilateral hearing loss, with the air-conducted pure-tone average detection threshold at 6 months increasing by 3 to 16 dB in 5 participants and by 74 to 104 dB in 3 participants. Changes in participant-reported disability and quality of life paralleled changes in posture and gait.

CONCLUSIONS

Six months and 1 year after unilateral implantation of a vestibular prosthesis for bilateral vestibular hypofunction, measures of posture, gait, and quality of life were generally in the direction of improvement from baseline, but hearing was reduced in the ear with the implant in all but 1 participant. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT02725463.).

The potential of noisy galvanic vestibular stimulation for optimizing and assisting human performance

Noisy galvanic vestibular stimulation (nGVS) is an emerging non-invasive brain stimulation technique. It involves applying alternating currents of different frequencies and amplitudes presented in a random, or noisy, manner through electrodes on the mastoid bones behind the ears. Because it directly activates vestibular hair cells and afferents and has an indirect effect on a variety of brain regions, it has the potential to impact many different functions. The objective of this review is twofold: (1) to review how nGVS affects motor, sensory, and cognitive performance in healthy adults; and (2) to discuss potential clinical applications of nGVS. First, we introduce the technique. We then describe the regions receiving and processing vestibular information. Next, we discuss the effects of nGVS on motor, sensory, and cognitive function in healthy adults. Subsequently, we outline its potential clinical applications. Finally, we highlight other electrical stimulation technologies and discuss why nGVS offers an alternative or complementary approach. Overall, nGVS appears promising for optimizing human performance and as an assistive technology, though further research is required.

Vestibular Implant Imaging

Analogous to hearing restoration via cochlear implants, vestibular function could be restored via vestibular implants that electrically stimulate vestibular nerve branches to encode head motion. This study presents the technical feasibility and first imaging results of CT for vestibular implants in 8 participants of the first-in-human Multichannel Vestibular Implant Early Feasibility Study. Imaging characteristics of 8 participants (3 men, 5 women; median age, 59.5 years; range, 51-66 years) implanted with a Multichannel Vestibular Implant System who underwent a postimplantation multislice CT (n = 2) or flat panel CT (n = 6) are reported. The device comprises 9 platinum electrodes inserted into the ampullae of the 3 semicircular canals and 1 reference electrode inserted in the common crus. Electrode insertion site, positions, length and angle of insertion, and number of artifacts were assessed. Individual electrode contacts were barely discernible in the 2 participants imaged using multislice CT. Electrode and osseous structures were detectable but blurred so that only 12 of the 18 stimulating electrode contacts could be individually identified. Flat panel CT could identify all 10 electrode contacts in all 6 participants. The median reference electrode insertion depth angle was 9° (range, -57.5° to 45°), and the median reference electrode insertion length was 42 mm (range, -21-66 mm). Flat panel CT of vestibular implants produces higher-resolution images with fewer artifacts than multidetector row CT, allowing visualization of individual electrode contacts and quantification of their locations relative to vestibular semicircular canals and ampullae. As multichannel vestibular implant imaging improves, so will our understanding of the relationship between electrode placement and vestibular performance.

Bilateral vestibulopathy: beyond imbalance and oscillopsia

Objective

To optimize the current diagnostic and treatment procedures for patients with bilateral vestibulopathy (BV), this study aimed to determine the complete spectrum of symptoms associated with BV.

Method

A prospective mixed-method study design was used. Qualitative data were collected by performing semi-structured interviews about symptoms, context, and behavior. The interviews were recorded and transcribed until no new information was obtained. Transcriptions were analyzed in consensus by two independent researchers. In comparison to the qualitative results, quantitative data were collected using the Dizziness Handicap Inventory (DHI), Hospital Anxiety and Depression Scale (HADS) and a health-related quality of life questionnaire (EQ-5D-5L).

Results

Eighteen interviews were transcribed. Reported symptoms were divided into fourteen physical symptoms, four cognitive symptoms, and six emotions. Symptoms increased in many situations, such as darkness (100%), uneven ground (61%), cycling (94%) or driving a car (56%). These symptoms associated with BV often resulted in behavioral changes: activities were performed more slowly, with greater attention, or were avoided. The DHI showed a mean score of severe handicap (54.67). The HADS questionnaire showed on average normal results (anxiety = 7.67, depression = 6.22). The EQ-5D-5L demonstrated a mean index value of 0.680, which is lower compared to the Dutch age-adjusted reference 0.839 (60–70 years).

Conclusion

BV frequently leads to physical, cognitive, and emotional complaints, which often results in a diminished quality of life. Importantly, this wide range of symptoms is currently underrated in literature and should be taken into consideration during the development of candidacy criteria and/or outcome measures for therapeutic interventions such as the vestibular implant.

Electronic supplementary material

The online version of this article (10.1007/s00415-020-10243-5) contains supplementary material, which is available to authorized users.