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Galvanic vestibular stimulation (GVS) helps stabilize subjects when balance and posture are compromised. This work aimed to define the cortical regions that GVS activates in normal subjects. We used functional near-infrared spectroscopy (fNIRS) to test the hypothesis that GVS activates similar cortical areas as a passive movement. We used transcranial current stimulation (cathode in the right mastoid process and anode in the FPz frontopolar point) of bipolar direct current (2 mA), false GVS (sham), vibration (neutral stimulus), and back and forth motion (positive control of vestibular movement) in 18 clinically healthy volunteers. Seventy-two brain scans were performed, applying a crossover-type experimental design. We measured the heart rate, blood pressure, body temperature, head capacitance, and resistance before and after the experiment. The haemodynamic changes of the cerebral cortex were recorded with an arrangement of 26 channels in four regions to perform an ROI-level analysis. The back-and-forth motion produced the most significant oxygenated haemoglobin (HbO2 ) increase. The response was similar for the GVS stimulus on the anterior and posterior parietal and right temporal regions. Sham and vibrational conditions did not produce significant changes ROI-wise. The results indicate that GVS produces a cortical activation coherent with displacement percept.

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OBJECTIVE: Galvanic vestibular stimulation has been evaluated in the context of vestibular rehabilitation. The objective was to identify evidence in the scientific literature about the clinical applications of galvanic vestibular stimulation. METHODS: In this systematic review, the articles describing the applications of galvanic vestibular stimulation were extracted from PubMed, Web of Science, MEDLINE, Scopus, LILACS and SciELO databases. The survey was limited to articles published in English, Portuguese and Spanish. All the articles about the clinical applications of galvanic vestibular stimulation were compiled. Repeated articles in the databases, literature review articles, case reports, letters and editorials were excluded. The descriptors included: galvanic vestibular stimulation, postural balance, central nervous system diseases, vestibular diseases, spinal cord diseases and cognition. RESULTS: The search strategy resulted in the initial selection of 994 articles; the reading of titles and abstracts was accomplished in 470 articles and the complete reading in 23 articles. Clinical applications of galvanic vestibular stimulation included Ménière's disease, vestibular neuritis, bilateral vestibular disorders, vestibular schwannoma, Parkinson's disease, ischemic central lesions, motor myelopathies, anxiety disorders, cognition and memory. CONCLUSION: Galvanic vestibular stimulation has been considered a potentially useful strategy for balance rehabilitation, since it has the effect of stimulating the central connections related to the postural balance, favoring new neuronal synapses that allow the partial or total recovery of postural imbalance.

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INTRODUCTION: Galvanic vestibular evoked myogenic potentials evaluate vestibular nerve responses using electric stimulation by records collected from the sternocleidomastoid muscle. A normal vestibular evoked myogenic potential response consists of the first positive, P1, and negative, N1, peaks. The response can be affected by factors such as age and gender and is also consequential in the diagnosis of pathologies. OBJECTIVES: The present study was performed to obtain normative data on healthy adults, to help in diagnosis by establishing clinical norms as well as to investigate changing test parameters with age in galvanic vestibular evoked myogenic potentials. METHODS: A total of 100 healthy participants were included in the study. Galvanic vestibular evoked myogenic potential (current 3 mA, duration 1 ms) was performed randomly on both ears of each participant. The participants between the ages of 18-65 (mean age 39.7 ±â€¯13.9) were divided into 5 groups according to their ages. Normative data of galvanic vestibular evoked myogenic potentials parameters were calculated in groups and in total, and age-related changes were examined. RESULTS: The galvanic vestibular evoked myogenic potential waveform was elicited from all participants (200 ears). The latency of P1 and N1 was 7.82 ±â€¯3.29 ms and 22.06 ±â€¯3.95 ms, respectively. The P1-N1 amplitude value was 66.64 ±â€¯24.5 µV. The percentage of vestibular asymmetry was 16.29 ±â€¯11.99%. The latencies of P1 and N1 and P1-N1 amplitude values demonstrated significant differences among different age groups (p < 0.01). CONCLUSIONS: The results of this study show that as age increased, latencies were prolonged, and amplitudes gradually decreased. The normative data aids in the diagnosis of retrolabyrinthine lesions and the increase in the clinical use of galvanic vestibular evoked myogenic potentials.

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Stable walking relies critically on motor responses to signals of head motion provided by the vestibular system, which are phase-dependent and modulated differently within each muscle. It is unclear, however, whether these vestibular contributions also vary according to the stability of the walking task. Here we investigate how vestibular signals influence muscles relevant for gait stability (medial gastrocnemius, gluteus medius and erector spinae)-as well as their net effect on ground reaction forces-while humans walked normally, with mediolateral stabilization, wide and narrow steps. We estimated local dynamic stability of trunk kinematics together with coherence of electrical vestibular stimulation (EVS) with muscle activity and mediolateral ground reaction forces. Walking with external stabilization increased local dynamic stability and decreased coherence between EVS and all muscles/forces compared to normal walking. Wide-base walking also decreased vestibulomotor coherence, though local dynamic stability did not differ. Conversely, narrow-base walking increased local dynamic stability, but produced muscle-specific increases and decreases in coherence that resulted in a net increase in vestibulomotor coherence with ground reaction forces. Overall, our results show that while vestibular contributions may vary with gait stability, they more critically depend on the stabilization demands (i.e. control effort) needed to maintain a stable walking pattern.

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OBJECTIVE: To analyze the results of the subjective visual vertical test using the "bucket method" in patients with chronic suppurative otitis media (CSOM). STUDY DESIGN: Cross-sectional, controlled study. SETTING: Outpatient otology clinic in a tertiary care hospital. SUBJECTS AND METHODS: Patients had CSOM, defined as the presence of chronic infection or inflammation of the middle ear cleft, associated with a perforation of the tympanic membrane, frequent or intractable middle ear suppuration, with or without cholesteatoma. Controls were selected using a nonprobability, purposive sampling method. We excluded patients with neurologic or metabolic diseases, cognitive deficits, otosclerosis, vestibular migraine, Ménière's disease, past use of ototoxic medication, or head and neck cancer. The volunteers were subjected to the subjective visual vertical test using the "bucket method." The results obtained in our study and control groups were analyzed using nonparametric tests. RESULTS: Our study comprised 51 patients with CSOM and 50 controls. In the CSOM group, we observed that 72.5% of the patients had vestibular symptoms in the past year, and 70.5% had abnormalities identified in at least 1 vestibular function test. The subjective visual vertical test revealed that patients with CSOM (with and without cholesteatoma) had significantly higher deviations of the true vertical as compared with controls (CSOM, 3.66°; controls, 0.76°; P < .001). CONCLUSION: Our results revealed that CSOM was associated with high rates of vestibular symptoms, abnormal vestibular function tests, and abnormal subjective vertical visual results.

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RESUMEN El sistema vestibular tiene un rol fundamental en funciones sensorio-motoras, control del equilibrio y estabilidad de la mirada. En las últimas décadas un amplio número de trabajos ha descrito la importancia de las aferencias vestibulares en el funcionamiento de diversas áreas del cerebro relacionadas con funciones cognitivas tales como la atención, memoria, navegación y otras habilidades visuo-espaciales. Estudios en pacientes con vestibulopatía han demostrado que estos individuos presentan disminución de su rendimiento en algunas pruebas neuropsicológicas; y, a su vez, que personas con patología cognitiva como deterioro cognitivo leve y demencia por enfermedad de Alzheimer tienen mayor probabilidad de presentar pruebas vestibulares alteradas. Esta revisión se enfoca en el papel que cumple el sistema vestibular y su asociación con habilidades cognitivas; basándose en estudios básicos y clínicos que describen una red vestibular cerebral y que han llevado a proponer modelos teóricos que relacionan la función vestibular con la cognición.

ABSTRACT The vestibular system is widely known for its role in sensory-motor functions, balance control and gaze stability. In recent decades, several research articles have described the importance of vestibular afferents in the functioning of brain areas related to cognitive skills such as attention, spatial memory, spatial navigation and other visuospatial abilities. Studies involving subjects with vestibulopathy reveal that these individuals show decreased performance on neuropsychological tests; and that patients with neurocognitive pathologies, such as mild cognitive impairment and dementia due to Alzheimer's disease, have a greater probability of producing diminished or absent responses in clinical vestibular electrophysiological tests. This literature review focuses on the role played by the vestibular system and its association with cognitive abilities. The review incorporates a description of basic and clinical research that describe the cortical vestibular network and emerging theoretical models linking vestibular function to cognition.

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Abstract Introduction: People with vestibular loss present a deficit in the vestibular system, which is primarily responsible for promoting postural control, gaze stabilization, and spatial orientation while the head moves. There is no effective treatment for a bilateral loss of vestibular function. Recently, a vestibular implant was developed for people with bilateral loss of vestibular function to improve this function and, consequently, the quality of life of these patients. Objective: To identify in the scientific literature evidence that vestibular implants in people with vestibular deficit improves vestibular function. Methods: One hundred and forty six articles were found from five databases and 323 articles from the gray literature mentioning the relationship between vestibular implant and vestibular function in humans. The PICOS strategy (Population, Intervention, Comparison and Outcome) was used to define the eligibility criteria. The studies that met the inclusion criteria for this second step were included in a qualitative synthesis, and each type of study was analyzed according to the bias risk assessment of the Joanna Briggs Institute through the critical assessment checklist Joanna Briggs institute for quasi-experimental studies and the Joanna Briggs institute critical assessment checklist for case reports. Results: Of the 21 articles included in reading the full text, 10 studies were selected for the qualitative analysis in the present systematic review. All ten articles analyzed through the critical assessment checklist Joanna Briggs institute showed a low risk of bias. The total number of samples in the evaluated articles was 18 patients with vestibular implants. Conclusions: Taken together, these findings support the feasibility of vestibular implant for restoration of the vestibulo-ocular reflex in a broad frequency range and illustrate new challenges for the development of this technology.

Resumo Introdução: Pessoas com perda vestibular apresentam um déficit no sistema vestibular, o qual é o principal responsável pelo controle postural, pela estabilização do olhar e orientação espacial enquanto a cabeça se movimenta. Não há tratamento efetivo para uma perda vestibular bilateral. Recentemente, foi desenvolvido um implante vestibular para pessoas com perda vestibular bilateral para melhorar essa função e, consequentemente, a qualidade de vida desses pacientes. Objetivo: Identificar na literatura científica evidências de que o implante vestibular melhora a função vestibular de pessoas com déficit vestibular. Método: Cento e quarenta e seis artigos foram encontrados em cinco bases de dados e 323 arti-gos da literatura cinzenta, mencionando a relação entre implante vestibular e função vestibular em humanos. A estratégia PICOS (População, Intervenção, Comparação e Desfechos) foi uti-lizada para definir os critérios de elegibilidade. Os estudos que preencheram os critérios de inclusão para esta segunda etapa foram incluídos em uma síntese qualitativa, e cada tipo de estudo foi analisado de acordo com a avaliação de risco de viés do Joanna Briggs Institute através da critical appraisal checklist for quasi-experimental studies e da critical appraisa lchecklist for case reports. Resultados: Dos 21 artigos incluídos cujos textos completos foram lidos, 10 foram selecionados para a análise qualitativa na presente revisão sistemática. Todos os dez artigos analisados ??através da critical appraisal checklist mostraram um baixo risco de viés. O número total de amostras nos artigos avaliados foi de 18 pacientes com implantes vestibulares. Conclusões: Em conjunto, esses achados apoiam a viabilidade do implante vestibular para a restauração do reflexo vestíbulo-ocular em uma ampla faixa de frequências e ilustram novos desafios para o desenvolvimento desta tecnologia.

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INTRODUCTION: People with vestibular loss present a deficit in the vestibular system, which is primarily responsible for promoting postural control, gaze stabilization, and spatial orientation while the head moves. There is no effective treatment for a bilateral loss of vestibular function. Recently, a vestibular implant was developed for people with bilateral loss of vestibular function to improve this function and, consequently, the quality of life of these patients. OBJECTIVE: To identify in the scientific literature evidence that vestibular implants in people with vestibular deficit improves vestibular function. METHODS: One hundred and forty six articles were found from five databases and 323 articles from the gray literature mentioning the relationship between vestibular implant and vestibular function in humans. The PICOS strategy (Population, Intervention, Comparison and Outcome) was used to define the eligibility criteria. The studies that met the inclusion criteria for this second step were included in a qualitative synthesis, and each type of study was analyzed according to the bias risk assessment of the Joanna Briggs Institute through the critical assessment checklist Joanna Briggs institute for quasi-experimental studies and the Joanna Briggs institute critical assessment checklist for case reports. RESULTS: Of the 21 articles included in reading the full text, 10 studies were selected for the qualitative analysis in the present systematic review. All ten articles analyzed through the critical assessment checklist Joanna Briggs institute showed a low risk of bias. The total number of samples in the evaluated articles was 18 patients with vestibular implants. CONCLUSIONS: Taken together, these findings support the feasibility of vestibular implant for restoration of the vestibulo-ocular reflex in a broad frequency range and illustrate new challenges for the development of this technology.

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OBJECTIVES: CANVAS is an acronym for cerebellar ataxia, neuropathy and vestibular areflexia syndrome. Limited autopsy data has suggested that CANVAS is caused by a focal dorsal root ganglionopathy that damages Scarpa's (vestibular) ganglion, but spares the Spiral (hearing) ganglion. If the vestibular areflexia of CANVAS is in fact due to ganglionopathy, then there should be global reduction of all vestibular responses. MATERIALS AND METHODS: With this hypothesis in mind, a retrospective review of 5 subjects who met the clinical criteria for CANVAS was performed. Recent advances in vestibular testing have made it possible to quantify responses from all 5 vestibular end organs in the inner ear. Results of the Video head impulse test (VHIT), video oculography, caloric test and vestibular evoked myogenic potential (VEMP) were examined to determine if all 5 end organs are nonfunctional in CANVAS. RESULTS: Severe reduction of function of the six semicircular canals and ocular VEMPs were observed. Only the cervical VEMPs were present and reproducible, consistent with either partial sparing of the inferior vestibular ganglia, specific embryologic resistance of the saccule to the degeneration or a mechanism for cervical VEMPs that does not require an intact vestibular ganglion. CONCLUSION: Our results suggest that Scarpa´s ganglia dysfunction could be the mechanism for loss of semicircular canal and utricular function in CANVAS patients, but the preservation of the cervical VEMP response is unexplained.

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Cerebellar ataxias are a clinically heterogeneous group of neurological disorders. Besides the cerebellum, several forms of hereditary ataxias or non-genetic ataxias also affect other areas of the brain. Some forms of cerebellar ataxias may have cochlear and vestibular involvement and may present with deafness and symptoms or signs of vestibulopathy (dizziness, nystagmus and diplopia). Recognizing otoneurological symptoms in patients with cerebellar ataxias is mandatory, since these signs may guide a specific diagnosis, and clinicians may provide a suitable therapeutic approach. In this review, we describe and discuss the most common forms of cerebellar ataxias associated with deafness and vestibulopathy.

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