Introdução: Desde sua primeira descrição na década de 40 o espectro de aplicação da reabilitação vestibular vem crescendo, tornando-se opção de tratamento em disfunções vestibulares periféricas, incluindo as uni e bilaterais, e em doenças do sistema nervoso central. O presente estudo avalia a eficácia de exercícios que estimulam a adaptação do reflexo vestíbulo-ocular em indivíduos com quadro agudo de vertigem. Métodos: neste estudo clínico prospectivo foram avaliados indivíduos aleatoriamente alocados em um grupo de estudo, que realizou exercícios para adaptação do reflexo vestíbulo-ocular, e em um grupo controle, que realizou exercícios placebo. Os critérios de inclusão foram história de pelo menos um episódio de vertigem nos últimos cinco dias, idade acima de 18 anos, e alteração em pelo menos dois dos testes objetivos de equilíbrio (teste de Romberg, teste de Fukuda e \"head-shaking\" nistagmo) e/ou presença de nistagmo espontâneo. Os pacientes de ambos os grupos foram orientados a utilizar dimenidrato na dose máxima de 150 mg ao dia, divididas em três doses, podendo auto-regular a dose conforme a intensidade dos sintomas apresentados. Foram excluídos indivíduos que tivessem utilizado medicação com ação no sistema vestibular nos últimos sete dias, com presença de alterações sugestivas de doença do sistema nervoso central, diagnóstico de vertigem posicional paroxística benigna ou de fístula perilinfática. Os pacientes foram avaliados, no início do estudo e em três visitas subseqüentes, realizadas nos períodos de três a cinco dias, sete a dez dias e dezoito a vinte e um dias após o início da pesquisa. Em todas as visitas a avaliação foi realizada por meio de notas atribuídas à intensidade dos sintomas (escala analógica visual), quantidade de medicação utilizada e resultados dos testes de equilíbrio. Resultados: Foram analisados 87 xxxv indivíduos, 45 no grupo de estudo e 42 no grupo controle. Na avaliação inicial os grupos eram semelhantes do ponto de vista estatístico em relação ao sexo e idade dos pacientes, tempo decorrido entre o início dos sintomas e a primeira avaliação, intensidade dos sintomas e achados de exame físico. O grupo de estudos apresentou intensidade de sintomas inferior ao grupo controle nas segunda e terceira avaliações; na quarta e última avaliação ambos os grupos apresentaram sintomatologia semelhante. A quantidade de medicação utilizada pelos pacientes do grupo de estudos foi inferior à utilizada pelo grupo controle em todos as avaliações realizadas. Não houve diferença entre os grupos em relação ao desaparecimento do nistagmo espontâneo exceto na terceira avaliação. A proporção de pacientes com teste de Romberg alterado foi menor no grupo de estudo quando comparada ao grupo controle nas segunda (tendência à significância estatística) e terceira avaliações, não havendo diferença entre os grupos na última avaliação. Nos testes de Fukuda e de \"head-shaking\" nistagmo não houve diferença entre os grupos em relação à proporção de testes alterados nas primeira e segunda avaliações, entretanto nas terceira e quarta avaliações o grupo de estudos teve menor proporção de testes alterados. Conclusões: O grupo submetido aos exercícios para adaptação do reflexo vestíbulo-ocular obteve melhora clínica mais rápida, fez uso de quantidade menor de dimenidrato e apresentou normalização dos testes clínicos de equilíbrio mais precocemente quando comparado ao grupo controle / Introduction: Since its first description in 1940 decade, the spectrum of use of vestibular rehabilitation has broadened and nowadays comprises unilateral, bilateral and even central vestibular disorders. The objective of this study is to evaluate the effect of exercises for adaptation of the vestibuloocular reflex in patients with acute vertigo. METHODS: Study design: prospective randomized trial, patients blinded to assignment groups. The study population had the following characteristics: = 18 years of age, at least one episode of vertigo in the last five days, negative results in at least two objective vestibular tests and/or presence of spontaneous nystagmus. The exclusion criteria were: use of any medication interfering with the vestibular system in the past seven days, clinical history or physical findings indicative of central nervous system disorders, clinical diagnosis of benign paroxysmal positional vertigo or perilymphatic fistula. Patients were randomly allocated to the intervention and placebo controlled groups. Intervention group performed exercises for adaptation of the vestibulo-ocular reflex; control group performed placebo exercises. Both groups were instructed to use dimenhydrinate and self-adjust the dose according to the intensity of their symptoms (up to 150mg/day). Patients evaluated by the assessment of the intensity of symptoms, by analogue visual scale, neuro-otological examination (presence of spontaneous nystagmus, Romberg test, Fukuda test and head-shaking nystagmus) and need to use the medication. There were three appointments in the follow-up period: three to five days, seven to ten days and eighteen to twenty one days after the initial evaluation. Results: There were 87 patients eligible for the study, 45 in the intervention group and 42 in the control group. At the initial evaluation, there was no statistically significant difference between the intervention and control groups in terms of sex, age, interval from onset of symptoms to inclusion in the study, intensity xxxvii of symptoms and neuro-otological tests results. Intensity of symptoms: the mean of the patients\' analogue visual scale score was similar for the intervention and control groups at the initial evaluation. At the second and third evaluations the mean score of the intervention group was significantly smaller. At the fourth and final evaluation, the groups were similar again. In the intervention group the amount of medication used by patients was always smaller than in the control group. Presence of spontaneous nystagmus was similar in between the groups at all but the third evaluation. As to the Romberg test results, the proportion of patients with a positive test was smaller for the intervention group at the second and third evaluations (borderline significant for the second intervention). At the fourth and final evaluation, the groups were similar again. As to the Fukuda and headshaking nystagmus tests, results were similar, at the third and forth evaluations the intervention group performed better than the control group. Conclusions: Vestibular exercises for adaptation of the vestibulo-ocular reflex have beneficial effects on treatment of patients with acute vertigo. The intervention group recovered faster, used a reduced amount of medication and performed better on balance tests as compared to the control group

Vestibular schwannoma surgery causes in majority of patients the unilateral peripheral or combined vestibular lesion due to surgical interruption of both branches of vestibular nerve. It manifests postoperatively with postural instability, vertigo, oscilopsia and even with vegetative symptoms. Central compensation, in which cerebellum plays dominant role, influences duration of the symptoms. Factors affecting compensation may be divided into several groups (general health status of a patient, the tumor itself, actual state of function of vestibular system, external factors induced by a therapeutist). Therapeutic aim is to induce compensatory mechanisms as soon as possible and to reduce overall duration of the compensation. The aim of this study is to consider predictive factors influencing central vestibular compensation and to influence the vestibular compensation itself. Early operated vestibular rehabilitation is a basic procedure. It leads to faster recovery in majority of patients. Even with maximal effort the full compensation is not always achieved. It results in permanent deficit of vestibular function manifested with postural instability. However in some patients it is difficult to achieve full compensation despite maximum effort of a physiotherapeutist and that results in permanent...

published_or_final_version / Physiology / Master / Master of Philosophy

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

Some patients suffer hearing loss in the early postoperative period following vestibular schwannoma (VS) excision despite having intact hearing immediately after surgery. As this phenomenon has rarely been documented or described, the putative mechanism remains vague. The objective of the current study was to document the patterns of change in behavioural and electrophysiological responses in patients following VS surgery to better describe the phenomenon of delayed hearing loss. In particular, we aimed to determine whether the impairment that eventually leads to delayed hearing loss is neural or cochlear in origin. Auditory function was monitored in six adult patients who underwent surgery at Christchurch Public Hospital for excision of unilateral vestibular schwannoma through the retrosigmoid approach. Patients were assessed pre- and postoperatively by puretone audiometry, speech audiometry, tympanometry, distortion product otoacoustic emissions (DPOAEs), and auditory brainstem response (ABR). When measurable hearing was demonstrated postoperatively, pure-tone audiometry, speech audiometry and ABR were assessed at 24 hour intervals following surgery. Transtympanic electrocochleography (ECochG) was carried out if wave I of the ABR was lost during the postoperative period. Postoperative monitoring revealed that 4 patients suffered permanent anacusis and the remaining 2 patients had permanent hearing preservation. There were no patients who experienced delayed hearing loss in the early postoperative period. A phenomenon similar to delayed hearing loss was observed in case 2 who demonstrated loss of ABR wave I on the 7th postoperative day. Postoperative ECochG recorded in this case showed an enhanced negative SP on the operated side. The findings of this study are discussed in detail with particular reference to the underlying pathophysiology.

A dissertation on a study presented to the Discipline of Speech Pathology and Audiology , School of Human and Community Development , Faculty of Humanities , University of the Witwatersrand , In fulfilment of the requirements for the degree M.A. Audiology , March 2017 / In health care, there appears to be greater consideration for the biopsychosocial model of disability and viewing disability in terms of functional health. Recently, the effect of impairment on the significant other’s (SO’s) quality of life (QOL) has been explored. In audiology, there appear to be very few published studies in this area, particularly related to vestibular disorders. The purpose of this study was to investigate the experiences of vestibular disorders on the SO’s QOL. A qualitative research design was employed, including 11 interviews and two focus groups. Participants were SO’s of individuals with chronic vestibular disorders, and were recruited from a private audiology practice in Gauteng through purposive sampling strategies. Data were analysed using thematic analysis. Eight primary themes emerged in the data analysis: social implications, financial implications, searching for a diagnosis, emotional effects, changes in family dynamics, support systems, comparison-oriented coping mechanisms, and referrals for psychological services. Findings suggested that SO’s experienced third-party vestibular disability; however, having the appropriate support systems, including family and friends, was pertinent. It was also indicated that the relationship with the audiologist was essential in providing better understanding of the condition and prognosis thereof, resulting in less frustration and improved adaptation to the reported changes. A key finding was the lack of referral for psychological or counselling services. These findings suggest the need to account for third-party vestibular disability in clinical, theoretical, and academic settings, and they call for the inclusion of third-party disability in policy-making. / MT 2018

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 151-183).

In rats, the subnuclei of the inferior olive (IO) and thalamus exist topographic spatial representation to sinusoidal horizontal linear translations along either the antero-posterior or interaural direction. To examine the effect of GABAergic neurotransmission within the vestibular nucleus on the establishment of gravity-related topographic spatial representation in relay station of the central vestibular pathway, GABAA receptor antagonist bicuculline was used to chronically perturb GABA transmission within the vestibular nucleus of postnatal rats. Implantation of bicuculline-loaded or saline-loaded Elvax slice onto the dorsal surface of vestibular nucleus was performed in P1 rats which were allowed to recover into adulthood. Fos protein expression was used as an indicator to identify central neurons responsive to horizontal linear accelerations. In stationary or labyrinthectomized rats, Fos-immunoreactive (ir) neurons were either absent or sporadically scattered throughout the IO and thalamic subnuclei, indicating that the Fos expression in these neural area was otolithic in origin. In the saline control group, Fos expression induced by horizontal antero-posterior linear acceleration was observed in both the IO and thalamus. Responsive IO subnuclei include β subnucleus of IO and dorsomedial cell column while those in the thalamus include central medial nucleus, paracentral nucleus, mediodorsal nucleus, central lateral nucleus, zona incerta and subparafascicular nucleus of thalamus. For-ir neurons responsive to horizontal interaural linear acceleration were found in those IO subnuclei and thalamic subnuclei. When compared with the saline-treated group, the number of Fos-ir IO neurons responsive to horizontal linear acceleration was significantly lower in adult rats perturbed with bicuculline at P1. Besides, the pattern of Fos expression in both the IO and thalamus was altered in adult rats pretreated with bicuculline. In the utricle-related thalamic subnuclei, the postnatal time when Fos-ir neurons were found triggered by otolithic stimulation was delayed and the number of these Fos-ir neurons was fewer in the bicuculline-treated group than those in the saline-treated group. To investigate whether there exists a critical period for postnatal establishment of topographic spatial representation in the IO and thalamus, implantation of bicuculline-loaded Elvax slice onto the vestibular nucleus was carried out in P14 rats. The topographic spatial representation in IO and thalamus of those rats were unchanged as compared with adult rats pretreated with saline at P14. These results indicate that the GABAergic neuronal circuit in the vestibular nucleus plays an important role in postnatal establishment of topographic spatial representation in the central vestibular system. Most importantly, we documented the occurrence of a postnatal critical period (between P1 and P14) during which GABAergic transmission regulated the formation of a gravity-related spatial framework in the brain. / published_or_final_version / Physiology / Master / Master of Philosophy

Inhibitory synaptic transmission within the vestibular circuits plays an essential regulatory role in coordinating vestibular functions. The maturation profile of γ- aminobutyric acid (GABA) synapses in the vestibular system remains unknown. To address this, we first used double immunohistochemistry to document the postnatal expression profile of GABAA receptors in canal-related and saccule-related vestibular nuclear neurons of rats. The proportion of Fos / GABAA receptors α1 subunit doublelabeled neurons progressively increased with age. Whole-cell patch-clamp experiments on brainstem slice preparations were also employed to characterize the developmental properties of these synapses within the medial vestibular nucleus. The frequency of GABAA receptor-mediated miniature inhibitory postsynaptic currents (IPSC) progressively increased during the first two postnatal weeks and reached a plateau thereafter. This is in agreement with an increase in sensitivity to GABAA receptor α1 subunit agonist zolpidem during the same period. The rise time and decay time however decreased by 2-fold. These results suggest that change in the composition of GABAA receptor occurs during the functional maturation of medial vestibular neurons. To further investigate whether GABA receptors contribute to synaptic plasticity in the developing vestibular nucleus, two stimulus protocols were used. Repetitive depolarizing pulses induced long-lasting decrease in the frequency of GABAA receptormediated spontaneous IPSCs between P3 and P7. The probability of inducing such frequency decline of sIPSCs decreased after the first postnatal week. High frequency stimulation on the other hand, induced long-term depression (LTD) of GABAA receptormediated evoked IPSCs between P3 and P5. The probability of inducing LTD decreased after P14. These results indicate that LTD at GABAergic synapses could be easily induced in developing medial vestibular neurons before maturation of GABAergic synaptic transmission. To examine if GABAergic transmission within the vestibular nucleus is crucial for establishment of gravity-related spatial organization, an intervention approach was adopted to perturb GABAergic transmission within the postnatal vestibular nucleus. A slice of Elvax loaded with either GABAA receptor agonist muscimol or antagonist bicuculline was inserted into the fourth ventricle and covered the bilateral vestibular nuclei at different ages. Expression of Fos protein in functionally activated neurons was used to demarcate the topographic spatial map in the inferior olive. The spatial map in subnuclei IOβ and DMCC was disturbed in each adult rat that was implanted with bicuculline- or muscimol-loaded Elvax at P1. However, no change was observed in adult rats that were pretreated with bicuculline or muscimol at P14 or P21. Vestibularrelated behavior tests were also performed. The acquisition of negative geotaxis, an otolith-related orientation reflex, was delayed in postnatal rats pretreated with bicuculline but was advanced in those rats pretreated with muscimol. Furthermore, the acquisition of motor learning, evaluated by rotarod test, was impaired in adult rats treated with bicuculline or muscimol. Taken together, our results indicated that maturation of GABAergic transmission within the vestibular nucleus play important roles in development of spatial recognition and vestibular-related behavior. / published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

The human vestibular system is responsible for maintaining balance and orientation, and stabilizing gaze during head motion. Head motion is sensed by vestibular sensors and encoded via the firing rate of vestibular neurons. Vestibular disorders can result in dizziness, imbalance, and disequilibrium. Currently there are no therapeutic options for individuals suffering from bilateral vestibular dysfunction. A potential solution is a vestibular prosthesis (VP). This device serves to replace peripheral vestibular organs by sensing angular motion, detected by semicircular canals (SCCs), and linear head motion, detected by the otolith organs, and selectively stimulating the corresponding vestibular afferents. An ideal VP will not only mimic the patient-dependent vestibular neural dynamics, but also consume low power. In this study, three energy-efficient ways to implement the motion encoding function required in a vestibular prosthesis are presented. Both analog and digital signal processing techniques to implement the vestibular signal processing functions are investigated.