Description:With age and impairment due to neurodegenerative processes, the nervous system expresses symptoms of dizziness and imbalance with a dramatic increase in fall risk. While the fall risk of older individuals is well-known, the symptoms for patients with peripheral nervous system (PNS) pathology and central nervous system (CNS) degeneration are less well-known and manifest as vestibulo-ocular and vestibulo-spinal impairment. Emerging research shows a clear dysfunction in vestibular physiology in these populations, which adversely affects gaze and postural control and increases fall risk. This session will discuss the pathophysiology of vestibular function in the context of aging and PNS/CNS damage, critical examination tools, and research-based recommendations to augment vestibular motor learning in these patient populations. The presenters will use case studies to illustrate characteristic deficits in vestibular function and guide clinical decision making regarding examination and treatment. Learning Objectives:1 . Describe the natural aging process as it relates to vestibulo-ocular and vestibulospinal function. 2. Discuss the evidence for vestibular damage within 2 model neurodegenerative diseases. 3. Describe the research evidence for motor learning within the vestibulo-ocular and vestibulospinal pathways in the context of aging and neurodegeneration. 4. Identify crucial examination tools and treatment methods to measure and improve gaze and gait stability in patients with a variety of neurodegenerative diseases.

Ce travail est constitué de trois études en plus de la revue de la littérature sur le système de l'équilibration, sur les troubles de l'équilibre d'origine vestibulaire périphérique et sur les principes de la rééducation. I. Etude normative et de la reproductibilité des tests vestibulo-spinaux et rotatoires Objectif : déterminer pour chaque tranche d'âge les valeurs normatives aux tests vestibulo-spinaux et rotatoires et vérifier l'effet de la latéralité sur les sens de déviation et de rotation ; et l'effet du sens de déplacement sur l'amplitude de l'angle. Méthodologie : 120 sujets âgés de 20 à 79 ans ont effectué les tests vestibulo-spinaux et rotatoires pour rechercher les valeurs normatives et 31 parmi ces derniers ont refait les épreuves pour vérifier la reproductibilité des résultats. Résultats :- Les tests vestibulo-spinaux augmentent avec l'âge. Il n'y a pas d'effet de la latéralité sur le sens de déviation ou de rotation. Le sens de déviation ou de rotation n'a pas d'influence significative sur l'amplitude de l'angle. Dans les tests rotatoires avec ou sans fixation, les durées de stabilisation dans le sens horaire et anti-horaire ne sont pas significativement différentes. Conclusion : - les résultats augmentent avec l'âge. Les thérapeutes doivent en tenir compte lors de l'évaluation. II. Etude normative et de la reproductibilité d'une échelle du handicap lié aux troubles de l'équilibre et aux vertiges (E.H.T.E.V.) Objectif. - Déterminer les scores normatifs, en fonction de l'âge et vérifier l'effet du sexe sur les résultats et la reproductibilité de l'E.H.T.E.V. Méthodologie : - La recherche des scores normatifs et de l'effet du sexe a été faite sur une population de 120 sujets, âgés de 20 à 79 ans, sans troubles d'équilibre. L'étude de la reproductibilité des résultats a été faite sur 47 sujets. Les résultats.- Les scores à l' E.H.T.E.V augmentent avec l'âge. Il n'y a pas d'influence significative du sexe sur les scores et la reproductibilité est importante. Conclusion.- Les scores sont influencés par l'âge et il n'y a pas d'effet du sexe sur les résultats. La reproductibilité est importante. Cependant la traduction de cette échelle de l'anglais en français nécessite la validation et la vérification de la fiabilité. III. Intérêt du traitement par exercice rotatoire chez les patients atteints du syndrome de Ménière Objectif : L'objectif de notre travail consiste à évaluer l'efficacité du traitement des troubles d'équilibre par des exercices rotatoires chez les patients souffrant du syndrome de Ménière unilatéral. Méthodologie : les patients sont soumis à des stimulations rotatoires visant à symétriser et à diminuer la réponse nystagmique post-rotatoire. Pour évaluer l'efficacité de ce traitement, les résultats pré- et post-thérapeutiques aux épreuves vestibulo-spinales et rotatoires ainsi que l'analyse de la perception des vertiges par les sujets ont été utilisés. Résultats : -Les patients ont eu en moyenne 11 séances de fauteuil rotatoire pour être subjectivement améliorés. Les épreuves objectives et subjectives montrent une amélioration significative. Conclusion : L'étude montre une amélioration des paramètres objectifs et subjectifs./ After literature review on equilibrium system and peripheral vestibular disorders, vestibular and rehabilitation techniques, Three studies are described in this work. I. “Normative and reproductibility study investigating static, dynamic and rotational testing in rehabilitation of peripheral vestibular balance disorders”. Objective: To determine for different age group, the normative values of vestibular rotational and vestibulospinal tests; to verify the effect of handedness on the direction of veering or rotation during dynamic testing ; and to verify the effect of the veering or rotation direction on angle's amplitude. Method: One hundred and twenty healthy volunteers aged from 20 to 79 years underwent vestibulospinal tests and rotational tests. Results:Vestibulospinal and rotational tests results increased significantly with age. We determined the normative values for each age group. The effect of handedness on the direction of the veering or rotation was not significant. The effect of the veering or rotation direction (left, right) on angle's amplitude was also not significant. Response time of stabilization for clockwise and counterclockwise rotational chair testing (with and without optic fixation): all differences were not significant. Conclusion : Age is an important factor in result of vestibulospinal and rotational tests. The handedness (left or right) does not influence vestibulospinal results. II. Normative study and reliability of french version of dizziness handicap inventory. Objective: this prospective study is to determine the normality per age group, secondly to assess the effect of sex on the scores and the reproductibility of the "Echelle du Handicap lié aux Troubles de l'Equilibre et aux Vertiges" (E.H.T.E.V) french version of the "Dizziness Handicap Inventory (D.H.I). Subjects and method.- The normative scores and the effect of the sex have been determined through the study of a group of 120 subjects. without any instability disorder. Reproductibility has been assessed on 47 individuals. The results.- The scores of the instability related handicap increase with age. There is no significant influence of sex. The reproductibility coefficient is higher.Conclusion:- The scores of the E.H.T.E.V increase with age. There is no significant influence of sex on scores and the coefficient of the reproductibility is good. But the translation of this handicap scale, need a study of validity and reliability. III. “ Benefit of rotational exercises for patients with Meniere's syndrome”. Objective: To date, the effectiveness of balance rehabilitation for patients with Meniere's syndrome has not been unanimously acknowledged by all physicians and physiotherapists. The purpose of this study is to assess the therapeutic efficacy of rotational exercises in the treatment of disequilibrium for patients with unilateral Meniere's syndrome. Methodology: Rotational stimuli were used to symmetrize and reduce postrotatory nystagmic response. Three reference sources were used to assess the efficacy of this management: vestibulospinal function tests rotational tests and the self-perceived impact of vertigo. Results: Patients required 11 sessions (mean value) to attain subjective improvement. Rotational tests and dynamic tests of the vestibulospinal function improved. Conclusion: The objective and subjective measures of disequilibrium were significantly improved.

Le système vestibulaire et le cortex moteur participent au contrôle de la posture, mais la nature de leurs interactions est peu documentée. Afin de caractériser les interactions vestibulo-corticales qui sous-tendent le contrôle de l’équilibre en position debout, l’activité électromyographique (EMG) du soléaire (SOL), du tibial antérieur (TA) et du péronier long (PERL) de la jambe droite a été enregistrée chez 14 sujets sains. La stimulation galvanique vestibulaire (GVS) a été appliquée avec la cathode derrière l’oreille droite ou gauche à différents intervalles inter-stimulus (ISIs) avant ou après la stimulation magnétique transcrânienne induisant des potentiels moteurs évoqués (MEPs) au niveau des muscles enregistrés. Lorsque que la cathode était à droite, une inhibition des MEPs a été observée au niveau du SOL à un ISI de 40 et 130 ms et une facilitation des MEPS a été observée au niveau TA à un ISI de 110 ms. Lorsque la cathode était à gauche, une facilitation des MEPs a été observée au niveau du SOL, du TA et du PERL à un ISI de 50, -10 et 0 ms respectivement. L’emplacement de ces interactions sur l’axe neural a été estimé en fonction des ISIs et en comparant l’effet de la GVS sur les MEPs à son effet sur l’EMG de base et sur le réflexe-H. Selon ces analyses, les modulations observées peuvent avoir lieu au niveau spinal ou au niveau supraspinal. Ces résultats suggèrent que les commandes de la voie corticospinale peuvent être modulées par le système vestibulaire à différents niveaux de l’axe neuronal. / The vestibular system and the motor cortex are involved in the control of posture but the nature of their interactions is poorly documented. To characterize vestibulo-cortical interactions underlying the control of balance during quiet standing, the electromyographic activity (EMG) of the soleus (SOL), tibialis anterior (TA) and peroneus longus (PERL) of the right leg was recorded in 14 healthy subjects. Bipolar galvanic vestibular stimulation (GVS) was applied with the cathode behind the right or left ear at various inter-stimulus intervals (ISI) before and after transcranial magnetic stimulation eliciting motor evoked potentials (MEP) in the muscles recorded. When the cathode was on the right, MEP in the SOL were inhibited at 40 and 130 ms while MEP were facilitated in TA at 110 ms. When the cathode was on the left, MEP were facilitated in the SOL at 50 ms, in TA at -10 ms and in PERL at 0 ms. The localization of these interactions along the neural axis was estimated according to the ISI and by comparing the effect of the GVS on the MEP to its effect on the background EMG and on the SOL H-reflex. Based on these analyses, the observed modulations of MEP observed could have occurred at spinal or supraspinal level. These results suggest that the corticospinal output may be modulated by the vestibular system at different levels of the neural axis.

INTRODUCTION: La stimulation vestibulaire galvanique (GVS) est utilisée pour évaluer l’intégrité du système vestibulaire et améliorer notre compréhension des mécanismes de l‘équilibre. Néanmoins les réponses évoquées montrent une grande variabilité interindividuelle ce qui rend la compréhension du rôle du système vestibulaire difficile. OBJECTIF: Développer un protocole d’évaluation d’un seuil vestibulaire objectif spécifique à la personne. MÉTHODES: Dix-huit sujets sains droitiers se tenaient debout sur une plate-forme de force, les yeux fermés, la tête vers l’avant. L’accélération de la tête était enregistrée lorsque la GVS (durée: 200 ms) était appliquée à des intensités de 1 à 4,5mA. Des courbes de recrutement ont été générées afin de déterminer le seuil objectif (T). Puis, les participants ont été stimulés à différentes intensités relatives au seuil (0,5T; 0,75T; 1T et 1,5T). L’aire de l’ellipse de confiance (AE) à 95%, la vitesse de déplacement du centre de pression (CoP) et l’activité électromyographique du soléaire (SOL) ont été mesurées. RÉSULTATS: 1) Un seuil objectif a été déterminé pour chaque sujet basé sur l’accélération de la tête. 2) L’aire de l’ellipse, pendant la stimulation, corrélait avec l’intensité de stimulation (r=0,95; p=0,03). 3) L’amplitude de la 1ère phase du patron triphasique de la vitesse de déplacement du CoP corrélait aussi avec l’intensité de stimulation (r=0,98; 0,04). 4) En plus, l’amplitude de la réponse musculaire à moyenne latence induite par la GVS sur le SOL montrait une corrélation significative avec l’intensité de stimulation (r=0,7; p=0,045). DISCUSSION: Un seuil objectif vestibulaire peut être identifié par un accéléromètre. Les réponses vestibulaires mesurées par l’AE et le CoP sont proportionnelles aux intensités de stimulation relatives au seuil objectif déterminé. / INTRODUCTION: Galvanic vestibular stimulation (GVS) is used to assess the integrity of the vestibular system and to improve our understanding of the mechanisms of balance. However, the GVS-induced responses show great inter-individual variability, which makes it difficult to understand the contribution of the vestibular system in maintaining balance. OBJECTIVE: To develop a protocol identifying an objective vestibular threshold for GVS in order to limit this variability observed on GVS-induced responses. METHODS: Eighteen healthy right-handed subjects stood on a force platform, eyes closed, head forward. The head acceleration was recorded when the GVS (duration: 200 ms) was applied at intensities varying between 1 and 4.5mA. Recruitment curves were reconstructed to determine the objective threshold (T). Then, the participants were stimulated at different intensities relative to threshold (0.5T; 0.75T; 1T and 1.5T). The 95% confidence ellipse area, the velocity of the center of pressure (CoP) displacement and the electromyographic activity of the soleus muscle (SOL) were measured. RESULTS: 1) An objective threshold was determined for each subject based on the acceleration of the head. 2) The area of the ellipse, during stimulation, correlated with the stimulation intensity (r = 0.95; p = 0.03). 3) The amplitude of the 1st peak of the three-phase CoP velocity pattern also correlated with the stimulation intensity (r = 0.98; 0.04). 4) In addition, the amplitude of the medium latency response induced by the GVS on the SOL showed a significant correlation with the stimulation intensity (r = 0.7; p = 0.045). DISCUSSION: An objective vestibular threshold can be identified by an accelerometer. The vestibular responses measured by the ellipse area and the CoP are proportional to the stimulation intensities relative to the determined objective threshold.

The thesis deals with the issues of balance disorders in patients after vestibular schwannoma surgery. The aim of this thesis is to evaluate the effect of targeted rehabilitation with biofeedback on balance disorders and subjective visual vertical compensation. During the period of one year, a group of 20 vestibular schwannoma patients were examined and treated in University Hospital Motol. The compensation of vestbuloocular refex was assessed by a tilt of subjective visual vertical. The level of vestibulospinal compensation was determined according to score of the Activities-Specific Balance Confidence Scale. Patients were examined before the surgery, after the surgery and after the rehabilitation. The Homebalance system, developed by Support center for application outputs and spin-off companies at the 1st Faculty of Medicine, Charles University in Prague, branch office in Kladno, was used for the therapy with visual biofeedback. Another aim of this thesis was to monitor the effect of vestibular prehabituation with ototoxic gentamicin application two months before surgery. The statistical analysis of data proved in the case of subjective visual vertical tilt a significant increase of deviation after surgery and a decrease after rehabilitation. According to the ABC questionnaire the confidence of...

The human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) is a worldwide pandemic that affects the lives of millions of people across all ages. Its devastating effects are far-reaching and affect all aspects of an individual’s daily life. HIV/AIDS is responsible for widespread clinical manifestations involving the head and neck. Disorders of the auditory and vestibular systems are often associated with HIV/AIDS, however the extent and nature of these vestibular manifestations is still largely unknown. The main aim of this research study was to investigate vestibular functioning and pathology in adults with HIV/AIDS. This was achieved through three main research steps: a systematic literature review of the body of peer-reviewed literature on HIV/AIDS related vestibular manifestations and pathology, a description and comparison of vestibular involvement in adults with and without HIV/AIDS and an investigation to determine if HIV/AIDS influence the vestibulocollic reflex (VCR) pathways. For the first study a systematic literature review related to vestibular findings in individuals with HIV infection and AIDS was conducted. A varied search strategy was used across several electronic databases to identify relevant peer-reviewed reports in English. Several databases (Medline, Scopus and PubMed) and search strategies were employed. Where abstracts were not available, the full paper was reviewed, and excluded if not directly relevant to the study’s aims. Articles were reviewed for any HIV/AIDS associated vestibular symptoms and pathologies reported. For the second and third study, a cross-sectional, quasi-experimental comparative research design was employed. A convenience sampling method was used to recruit subjects. The sample consisted of 53 adults (29 male, 24 female, aged 23-49 years, mean = 38.5, SD = 4.4) infected with HIV, compared to a control group of 38 HIV negative adults (18 male, 20 female, aged 20-49 years, mean = 36.9, SD = 8.2). A structured interview probed the subjective perception of vestibular complaints and symptoms. Medical records were reviewed for cluster of differentiation 4+ (CD4+) cell counts and the use of antiretroviral (ARV) medication. An otologic assessment and a comprehensive vestibular assessment (bedside assessments, vestibular evoked myogenic potentials, ocular motor and positional tests and bithermal caloric irrigation) were conducted on all subjects. The systematic literature review identified 442 records, reduced to 210 after excluding duplicates, reviews, editorials, notes, letters and short surveys. These were reviewed for relevance to the scope of the study. There were only 13 reports investigating vestibular functioning and pathology in individuals affected by HIV/AIDS. This condition can affect both the peripheral and central vestibular system, irrespective of age and viral disease stage. Post-mortem studies suggest direct involvement of the entire vestibular system, while opportunistic infections such as oto- and neurosyphilis and encephalitis cause secondary vestibular dysfunction resulting in vertigo, dizziness and imbalance. The second study showed an overall vestibular involvement in 79.2% of subjects with HIV in all categories of disease progression, compared to 18.4% in those without HIV. Vestibular involvement increased from 18.9% in the Centers for Disease Control and Prevention (CDC) category 1 to 30.2% in category 2. Vestibular involvement was 30.1% in category 3. There was vestibular involvement in 35.9% of symptomatic HIV positive subjects and 41.5% in asymptomatic HIV positive subjects. Individuals with HIV were 16.6 times more likely to develop vestibular involvement during their lifetime, than among individuals without this disease. Vestibular involvement may occur despite being asymptomatic. The third study showed that abnormal cervical vestibular evoked myogenic potentials and caloric results were significantly higher in the HIV positive group (p=.001), with an odds ratio of 10.2. Vestibulocollic reflex and vestibulo-ocular reflex involvement increased with progression of the disease. There were more abnormal test results in subjects using ARV therapies (66.7%) compared to those not using ARV therapies (63.6%), but this difference was not statistically significant. Vestibular involvement was significantly more common in subjects with HIV than among those without this disease. This disease and its associated risk profile include direct effects of the virus on the vestibular system as demonstrated by postmortem studies. Opportunistic infections may compromise the functioning of the sensory and neural structures of hearing and the vestibular system indirectly, causing vertigo, dizziness or disequilibrium. Ototoxicity may also be related to vestibular dysfunction, due to the ototoxic nature of certain ARV medications. HIV/AIDS influence not only the vestibulo-ocular reflex, but also the vestibulocollic reflex pathways. Primary health care providers could screen HIV positive patients to ascertain if there are symptoms of vestibular involvement. If there are any, then they may consider further vestibular assessments and subsequent vestibular rehabilitation therapy, to minimize functional limitations of quality of life. / Thesis (DPhil)--University of Pretoria, 2014. / lk2014 / Speech-Language Pathology and Audiology / DPhil / Unrestricted