Effect of Cochlear Implantation on Air Conduction and Bone Conduction Elicited Vestibular Evoked Myogenic Potentials-A Scoping Review.

Background/Objectives: Cochlear implantation (CI) is an effective intervention for individuals with severe to profound hearing loss; however, it may impact vestibular function due to its proximity to related anatomical structures. Vestibular evoked myogenic potentials (VEMPs) assess the function of the saccule and utricle, critical components of the vestibular system. This review examines CI's impact on air conduction (AC) and bone conduction (BC) VEMP responses. Methods: A scoping review was conducted following PRISMA guidelines, using databases such as Medline, Embase, Cochrane Library, Scopus, and ProQuest Dissertations. Studies reporting on AC and/or BC-VEMP in CI recipients were included. Data extraction focused on VEMP response rates, amplitudes, and latencies pre- and post-CI. Risk of bias/quality assessment was performed using the Newcastle-Ottawa Scale. Results: Out of 961 studies identified, 4 met the inclusion criteria, encompassing a total of 245 CI-implanted ears. Results indicated that AC-VEMP responses were often reduced or absent post-CI, reflecting the influence of surgical changes in the middle ear mechanics rather than otolith dysfunction. In contrast, BC-VEMP responses were more consistently preserved, suggesting that BC stimuli bypass the middle ear and more accurately delineate otolith function. Variations in VEMP outcomes were noted depending on the surgical approach and individual patient factors. Conclusions: CI impacts vestibular function as measured by VEMP, with AC-VEMP showing greater susceptibility to postoperative changes compared to BC-VEMP. The presence of preserved BC-VEMP alongside absent AC-VEMP underscores the need to differentiate between these measures in assessing vestibular function

Bionic Ears & Dizziness: Examining the Impact of Cochlear Implantation on Vestibular Function

Cochlear implantation (CI) is regarded as an effective and life-changing intervention for individuals with bilateral severe to profound hearing loss. The success of CI has seen an expansion of its candidacy criteria in recent times. Vestibular dysfunction and vertigo are known to occur following CI. However, current literature reports wide variability in the prevalence of post-CI vestibular dysfunction with few studies examining all five vestibular end-organs. The primary aim of this thesis is to enhance understanding of post-CI vestibular dysfunction and vertigo using clinical history and a battery of modern audio-vestibular tests: three-dimensional video head impulse testing (3D vHIT), vestibular evoked myogenic potentials (VEMP), home audiometry and home video-oculography (VOG). The use of 3D vHIT and both cervical and ocular VEMPs demonstrate that CI can have impacts on all five vestibular end-organs with lateral canal function most affected. Coupled with findings of stable home audiometry and direction-changing nystagmus on home VOG, these tests reveal post-CI secondary endolymphatic hydrops as the main cause of post-CI episodic spontaneous vertigo. Finally, patients with sudden sensorineural hearing loss (SSNHL) increasingly proceed with CI. Such patients are characterised by relative preservation of utricular and lateral canal function, loss and spontaneous recovery of posterior canal function. There is a trend in evidence gathered thus far, that those with SSNHL have a higher frequency of post-CI vertigo compared to controls. The findings of this thesis establish the unique clinical and vestibular test profile of CI recipients which previously had limited opportunities for characterisation. It highlights an effective method for pre- and post-CI vestibular assessment, demonstrates the clinical utility of novel technologies, and identifies some risk factors and causes of post-CI vertigo that assist counselling and management of this distinct patient group

The role of non-invasive camera technology for gait analysis in patients with vestibular disorders

Purpose of the study Current balance assessments performed in clinical settings do not provide objective measurements of gait. Further, objective gait analysis typically requires expensive, large and dedicated laboratory facilities. The aim of this pilot study was to develop and assess a low-cost, non-invasive camera technology for gait analysis, to assist the clinical assessment of patients with vestibular disorders. Materials and methods used This is a prospective, case-controlled study that was developed jointly by the local Neurotology Department and the Centre for Sports Engineering Research. Eligible participants were approached and recruited at the local Neurotology Clinic. The gait assessment included two repetitions of a straight 7-metre walk. The gait analysis system, comprised of a camera (P3215-V, Axis Communications, Sweden) and analysis software was installed in an appropriately sized clinic room. Parameters extruded were walking velocity, step velocity, step length, cadence and step count per meter. The effect sizes (ESB) were calculated using the MatLab and were considered large, medium or small if >0.8, 0.5 and 0.2 respectively. This study was granted ethical approval by the Coventry and Warwickshire Research Ethics Committee (15/WM/0448). Results Six patients with vestibular dysfunction (P group) and six age-matched healthy volunteers (V group) were recruited in this study. The average velocity of gait for P group was 1189.1 ± 69.0 mm·s-1 whereas for V group it was 1351.4 ± 179.2 mm·s-1, (ESB: -0.91). The mean step velocities were 1353.1 ± 591.8 mm·s-1 and 1434.0 ± 396.5 mm·s-1 for P and V groups respectively (ESB: -0.20). The average cadence was 2.3 ± 0.9 Hz and 2.0 ± 0.5 Hz for P and V groups respectively (ESB: 0.60). The mean step length was 620.5 ± 150.7 mm for the P group and 728.5 ± 86.0 mm for the V group (ESB = -1.26). The average step count per meter was 1.7 ± 0.3 and 1.4 ± 0.1 for P and V groups respectively (ESB = 3.38). Conclusion This pilot study used a low-cost, non-invasive camera technology to identify changes in gait characteristics. Further, gait measurements were obtained without the application of markers or sensors to patients (i.e. non-invasive), thus allowing current, clinical practice to be supplemented by objective measurement, with minimal procedural impact. Further work needs to be undertaken to refine the device and produce normative data. In the future, similar technologies could be used in the community setting, providing an excellent diagnostic and monitoring tool for balance patients

Role of cVEMP in Management of Balance Disorders

Balance disorders may occur in a multitude of ENT-related diseases, thus making a correct diagnosis is challenging. In the last few decades, there has been a paradigm shift in the diagnostics of balance disorders due to the availability of better objective modalities that allow the assessment of different components of the complex vestibular labyrinth with relative ease. With the advent of vestibular-evoked myogenic potentials (VEMP) since the last few decades, it is possible to test otolith organs in isolation and objectively. This chapter will discuss the procedure, physiological basis, and effectiveness of cervical VEMP in the evaluation of saccular function in patients suffering from balance disorders

Assessment of Utricular Nerve, Hair Cell and Mechanical Function, in vivo.

Vestibular research currently relies on single response measures such as ex vivo hair cell and in vivo single unit recordings. Although these methods allow detailed insight into the response properties of individual vestibular hair cells and neurons, they do not provide a holistic understanding of peripheral vestibular functioning and its relationship to vestibular pathology in a living system. For this to take place, in vivo recordings of peripheral vestibular nerve, hair cell and mechanical function are needed. The previous inability to record vestibular hair cell responses stemmed from a difficulty in accessing the vestibular end-organs and stimulating them in isolation of the cochlea. To circumvent this, we developed a ventral surgical approach, removing the cochlea, to provide full access to the basal surface of the utricular macula. This allowed functional and mechanical utricular hair cell recordings, alongside gross utricular nerve responses. Recordings were performed in anaesthetized guinea pigs using Bone Conducted Vibration (BCV) and Air Conducted Sound (ACS) stimuli, providing a clinical link to vestibular reflex testing. We have thus far performed experiments involving: 1) Selective manipulation of vestibular nerve function, using electrical stimulation of the central vestibular system. 2) Glass micropipette recordings from the basal surface of the macular epithelium, which provided a robust and localized measure of extracellular utricular hair cell function. 3) With the macular exposed, we have measured the dynamic motion of the macula using Laser Doppler Vibrometry, which was recorded alongside the hair cell and nerve response recordings. 4) We have used physiological and pharmacological experimental manipulations to selectively modulate utricular nerve, hair cell or mechanical function, demonstrating the ability to differentially diagnose the basis of peripheral vestibular disorders in the mammalian utricle. These tools allow for a more complete understanding of peripheral vestibular function and a first order perspective into clinical disorders effecting the otoliths

Stimulation from Cochlear Implant Electrodes Assists with Recovery from Asymmetric Perceptual Tilt: Evidence from the Subjective Visual Vertical Test

Vestibular end organ impairment is highly prevalent in children who have sensorineural hearing loss (SNHL) rehabilitated with cochlear implants (CIs). As a result, spatial perception is likely to be impacted in this population. Of particular interest is the perception of visual vertical because it reflects a perceptual tilt in the roll axis and is sensitive to an imbalance in otolith function. The objectives of the present study were thus to identify abnormalities in perception of the vertical plane in children with SNHL and determine whether such abnormalities could be resolved with stimulation from the CI. Participants included 53 children (15.2 ± 4.0 years of age) with SNHL and vestibular loss, confirmed with vestibular evoked myogenic potential (VEMP) testing. Testing protocol was validated in a sample of nine young adults with normal hearing (28.8 ± 7.7 years). Perception of visual vertical was assessed using the static Subjective Visual Vertical (SVV) test performed with and without stimulation in the participants with cochleovestibular loss. Trains of electrical pulses were delivered by an electrode in the left and/or right ear. Asymmetric spatial orientation deficits were found in nearly half of the participants with CIs (24/53 [45%]). The abnormal perception in this cohort was exacerbated by visual tilts in the direction of their deficit. Electric pulse trains delivered using the CI shifted this abnormal perception towards center (i.e., normal; p = 0.007). Importantly, this benefit was realized regardless of which ear was stimulated. These results suggest a role for CI stimulation beyond the auditory system, in particular, for improving vestibular/balance function

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 Meniere'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

Evaluation of central and peripheral vestibular patients with the video-head impulse test

Dizziness and vertigo are highly prevalent symptoms that accompany a wide variety of conditions including peripheral vestibular dysfunction, central (vestibular) lesions and somatoform disorders. A correct diagnosis is the prerequisite for successful treatment, which should be directed towards the underlying pathophysiology. Neurophysiological methods that test the integrity of the peripheral and central vestibular system circuitry are essential to make an accurate diagnosis in clinical practice. Currently, that assessment is achieved primarily through eye movement analysis in response to semicircular canal stimulation, namely through caloric stimulation and head impulses. The quantification of the vestibulo-ocular reflex (VOR) dynamic parameters and the characterization of quick eye movements (QEM) triggered with head impulses can now be non-invasively and easily assessed with the video headimpulse test (vHIT). This provided a unique opportunity to carry out neurophysiological studies on the oculomotor responses generated by head impulses in humans. Our aim was to determine if the involvement of central vestibular pathways caused differential disturbances in VOR dynamic changes when explored with the vHIT, which could contribute not only to the differential diagnosis of patients but also to the understanding of VOR control mechanisms. We explored normal subjects and patients diagnosed with acute vestibular syndrome with spontaneous nystagmus of peripheral and central origin and hereditary neurodegenerative disorders. Looking for a simple sign of peripheral disease with the vHIT we noticed anti-compensatory eye movements (AQEM) in patients with peripheral aetiologies of spontaneous nystagmus (SN). In the first study we looked for the accuracy of AQEM to differentiate central from peripheral origins of SN. We recorded the eye movements in response to horizontal head impulses in a group of 43 consecutive patients with acute vestibular syndrome (12 with central, 31 with peripheral disorders), 5 patients after acute vestibular neurectomy (positive controls) and 39 healthy subjects (negative controls). AQEM were defined as quick eye movements (peak velocity above 50°/s) in the direction of the head movement. All patients with peripheral disorders and positive controls had AQEM (latency 231±53ms, amplitude 3.4±1.4º, velocity 166±55º/s) when their head was moved to the opposite side of the lesion. Central patients did not have AQEM. AQEM occurrence rate was higher in peripheral patients with contralesional (74±4%, mean±SD) in comparison to ipsilesional (1±4%) impulses (p<0.001). Overall diagnostic accuracy for differentiating central from peripheral patients was 96% (95% CI for AUC ROC curve: 0.90 to 1.0) for VOR gain and 100% (95% CI: 1.0 to 1.0) for AQEM occurrence rate. These results suggest that AQEM are a sign of vestibular imbalance in a peripheral deficit and should be added to VOR gain analysis in acute vestibular syndrome patients. In the second study on acute vestibular syndrome we reported on a patient with benign paroxysmal positional vertigo (BPPV) and spontaneous nystagmus due to otoconia causing a plug in the horizontal semicircular canal. The video head-impulse test revealed an eye velocity saturation with ipsilesional head impulses that normalized after liberatory maneuvers, documenting for the first time a reversible deficiency of the cupularendolymph high-frequency system dynamics. Furthermore cervical and ocular vestibular myogenic potentials were absent during stimulation of the affected side before the liberatory maneuvers, but normalized within 30 to 80 days. These observations challenge the common belief that VEMPs are evoked by otolith stimulation only, as the assumption of a reversible canal dysfunction by a plug offers a more plausible explanation for all effects. Finally, we reported on a patient presenting with a one-year history of progressive unsteadiness, particularly when in darkness. The video-Head Impulse Test (vHIT)1 (Figure 1 B) revealed a significantly reduced vestibuloocular reflex (VOR) gain in both horizontal (0.38±0.07 and 0.29±0.05) and posterior canals (0.49±0.05 and 0.38±0.06) with covert and overt corrective saccades, but normal VOR responses in both anterior canals (0.89±0.08 and 1.04±0.15), for right and left impulses, respectively. No plausible combination of end-organ lesion should be responsible for these observations. A brain MRI disclosed a left inferior cerebellar peduncle lesion suggestive of a glioma. To the best of our knowledge, this is the first report where three-dimensional vHIT, by means of peripheral-unlikely combinations of VOR lesion, has shown to be of topodiagnostic value. In the second set of studies we explored patients diagnosed with hereditary neurodegenerative disorders with and without vestibular system involvement. In the first study we explored 18 genetically confirmed Huntington’s disease patients (44.7±8.1 years; male=9). VOR latency, VOR gain and QEM characteristics were not different from controls (p>0.11 for all comparisons), suggesting that VOR is preserved at physiological frequency domains in these patients, even in more advanced stages of the disease. In the final study we explored 23 patients with a clinical and genetically confirmed diagnosis of spinocerebellar ataxia (SCA) type 3 (n=15), type 2 (n=4) and type 1 (n=4]), and 9 patients with early onset Friedreich’s ataxia (FA). VOR latency was higher in FA (p<0.001) and SCA3 (p=0.02) as compared to controls, discriminating FA from other ataxic patients with an overall diagnostic accuracy of 88%. VORr, VOR40 and VOR60 were significantly lower in FA and SCA3 (p<0.01). VOR80 was only significantly lower than controls in SCA3 (p<0.01), discriminating these from other ataxic patients with an overall diagnostic accuracy of 78%. Covert saccades were only triggered in SCA3 but with low occurrence rate and peak velocity (11.1±28.5% and 77.50±15.30°/s) whereas overt saccades were present in all groups. VORr gain showed a negative correlation with disease severity evaluated with SARA (Spearman r=-0.46, p=0.01). vHIT provides phenotypic information that differentiates the most common autosomal ataxias and can serve as a strategy to orient genetic diagnosis. A correlation between VOR and SARA raises the possibility of using VOR gain as a neurophysiologic biomarker for disease severity. Altogether these results supply relevant data in distinguishing peripheral and central nervous system (CNS) vestibular deficits, particularly acute deficits in emergency situation, as acute CNS vertigo can be life-threatening (stroke) and require immediate medical action. We first demonstrated that not only VOR instantaneous gain analysis has topodiagnostic value but also the analysis of gain dynamic changes, as these can point to individual aetiologies, e.g. a SCC plug. Secondly we demonstrated that quick eye movements also supply topodiagnostic cues, and should have their latency, peak velocity, direction and occurrence rate analysed. At a neurophysiological level, the oculomotor responses generated by head impulses also provide an understanding of both the biomechanical cupular-endolymph dynamics, the VOR dynamic control processes taking place and the modulation of vestibular spontaneous nystagmus with head impulsesA vertigem e a tontura são sintomas muito prevalentes que acompanham uma grande variedade de patologias, nomeadamente as vestibulopatias periféricas, centrais e as perturbações somatoformes. Um diagnóstico correcto é o pré-requisito para um tratamento eficaz, o qual deverá ser dirigido à patofisiologia de base. Os métodos neurofisiológicos que testam a integridade dos circuitos do sistema vestibular central e periférico são essenciais para alcançar um diagnóstico preciso na prática clínica. Actualmente, essa avaliação é realizada principalmente pela análise dos movimentos oculares originados pela estimulação dos canais semicirculares, nomeadamente a estimulação calórica e os impulsos cefálicos. A quantificação do parâmetros dinâmicos do reflexo vestíbulo-oculomotor (VOR) bem como a caracterização dos movimentos oculares rápidos (QEM, Quick Eye Movements) desencadeados com os impulsos cefálicos podem agora ser avaliados de forma fácil e nãoinvasiva com o vídeo Head Impulse Test (vHIT). Tal proporciona a oportunidade única de promover estudos neurofisiológicos das respostas oculomotoras desencadeadas pelos impulsos cefálicos em humanos. Acelerações horizontais da cabeça geram, na obscuridade, movimentos oculares conjugados lentos e compensatórios na direção oposta, sendo este reflexo denominado VOR. O principal objetivo deste reflexo é a manutenção de visão nítida e clara por estabilização da imagem na retina, principalmente durante os movimentos rápidos da cabeça. O Head Impulse Test (HIT)1 ou teste de impulsão cefálica é um teste clínico ativo em que este VOR angular é testado a alta frequência. O clínico, ao colocar-se de frente para o doente, aplica movimentos de frequência e direção imprevisíveis segundo o plano horizontal, de baixa amplitude (10-25º), alta aceleração (3.000-6.000º/s2) e velocidade (150-300º/s), enquanto o doente é instruído a manter a fixação num ponto. Se o VOR estiver intacto, o doente será capaz de manter a fixação, não se observando qualquer movimento rápido do olho, denominando-se o HIT de normal ou negativo. Pelo contrário, se o VOR não for compensatório, o olho acompanhará a cabeça durante a rotação impulsiva pelo que no final do impulso será necessário realizar uma sacada de refixação para recolocar o alvo 1 Halmagyi GM, Curthoys IS, Cremer PD, et al. The human horizontal vestibulo-ocular reflex in response to high-acceleration stimulation before and after unilateral vestibular neurectomy. Exp Brain Res. 1990;81(3):479–90. na fóvea, denominando-se o HIT de positivo ou patológico. Dado que não é possível ao olho humano detectar o movimento de fase lenta do VOR durante este impulso, a presença de uma sacada compensatória no final de um HIT clínico é entendida como um sinal indireto de uma fase lenta não compensatória. Enquanto o HIT unicamente permite a identificação da presença de sacadas após o impulso cefálico, o vídeo HIT (vHIT)2 possibilita não só a identificação e a quantificação da fase lenta do VOR, como também das fases rápidas geradas durante e após o impulso cefálico. Indivíduos saudáveis geram fases lentas compensatórias de baixa latência (7-10 ms), gerando fases rápidas ocasionais após os impulsos. Pelo contrário, doentes com lesão vestibular unilateral (UVL) desencadeiam fases lentas com latência aumentada, nãocompensatórias durante impulsos ipsilesionais , assim como movimentos oculares rápidos durante ou após os mesmos. Estes movimentos rápidos são conhecidos como sacadas covert se desencadeadas durante o impulso cefálico, dado a sua observação não ser possível a olho nu, ou como sacadas overt se desencadeadas após o impulso cefálico. Dado que estas fases rápidas apresentam o mesmo sentido da fase lenta deficitária, diminuindo o erro ocular, são consideradas sacadas compensatórias. Os doentes UVL agudos também podem gerar fases lentas não compensatórias durante os impulsos contralesionais, resultado da lesão da via inibitória ipsilesional, bem como gerar fases rápidas. A quantificação do HIT por vídeo-oculografia permite aumentar substancialmente a sensibilidade e a especificidade do HIT na avaliação do VOR sem as dificuldades técnicas dos coils, de difícil utilização na prática clínica. As novas câmaras digitais apresentam características de peso, forma, resolução espacial e de taxa de amostragem que permitem a sua utilização na prática clínica na quantificação do HIT com boas taxas de correlação com o coil . O registo dos perfis de velocidades ocular e cefálica durante o impulso cefálico permite o cálculo do ganho do VOR, definido como o ratio entre estas velocidades. Esse ratio pode ser calculado em momentos específicos, como p.ex. a 40, 60 e 80 ms após inicio do impulso (ganho instantâneo) ou como resultante de regressão linear (ganho por regressão). Enquanto que o último 2 Bartl K, Lehnen N, Kohlbecher S, Schneider E. Head Impulse Testing Using Videooculography. Ann N Y Acad Sci. 2009;1164(1):331–3.parece ser o valor mais robusto, o primeiro permite a avaliação variação dinâmica do ganho do VOR durante o impulso. Para o cálculo do VOR contribui a sua latência, de tal forma que se esta fosse zero deveríamos ter valores de ganho de 1.0 . Dada a existência de uma latência e, portanto, de uma discrepância entre as curvas de velocidades cefálica e ocular, os valores de normalização que obtivemos no nosso laboratório são ligeiramente inferiores (0.95±0.09). Calculando os limites de normalidade do ganho de VOR, obtivemos valores de 0.77 a 1.13. A avaliação do ganho de VOR permite por último o cálculo da assimetria interaural, que apresenta nas nossas séries, valores de normalidade muito baixos (<6.97%), quando comparados com os valores de normalidade para as provas calóricas (<25%). Os QEM são identificados como picos de aceleração bidirecionais e são classificados de acordo com o sentido relativo à fase lenta, a latência (ms), o pico de velocidade (º/s) e a taxa de ocorrência (%, taxa de impulsos que geram esses QEM). Os QEM podem apresentar o sentido da fase lenta do VOR deficitário e contribuir para a diminuição do erro ocular, sendo consideradas sacadas de correção ou sacadas catch-up, em analogia com os QEM da perseguição sacádica. Nas situações em que o ganho do VOR apresenta valores superiores à normalidade (situação observada em doentes com algumas patologias centrais) podem assumir o sentido contrário ao da fase lenta do VOR e ser igualmente classificadas como sacadas de correção uma vez que trazem a retina de regresso ao alvo. Nos indivíduos normais por nós estudados as sacadas overt apresentam valores de velocidade e de taxa de ocorrência relativamente baixos, enquanto as sacadas covert são inexistentes. Assim, a existência de uma lesão vestibular aguda (UVL) é verificável através do vHIT pela presença de uma fase lenta não compensatória durante os impulsos ipsilesionais. O cálculo do ganho do VOR e do índice de assimetria, permitem quantificar o grau da lesão. Nas fase aguda da lesão, o erro ocular resultante de um menor ganho de VOR é mais elevado, pelo que são identificadas sacadas compensatórias mais frequentes, com maior velocidade de pico e maior amplitude, tanto durante como após o impulso ipsilesional. Pelo contrário, durante a recuperação da fase lenta verifica-se o aumento progressivo da latência e diminuição da taxa de ocorrência destas sacadas. A maior parte dos doentes com síndrome vestibular agudo3 , definido como vertigem espontânea com nistagmo espontâneo, náuseas, vómitos e 3 Hotson JR, Baloh RW. Acute vestibular syndrome. N Engl J Med. 1998;339(10):680–5. desequilíbrio, resultam de lesão vestibular unilateral aguda. No entanto, a identificação no serviço de urgência daqueles que resultam de lesões do sistema nervoso central (CNS) e potencialmente em maior risco constitui um desafio. Como a análise isolada do tipo de nistagmo espontâneo não é suficiente para diferenciar os doentes com patologia periférica daqueles com patologia do sistema nervosa central, desenvolveram-se para este efeito algumas provas clínicas. Uma das mais importantes é o HIT. A ausência de sacada de refixação durante os impulsos ipsilesionais em doentes com nistagmo espontâneo e sem evidência de outros sinais e sintomas neurológicos, parece ser o que melhor prevê isoladamente a existência disfunção do CNS como causa do síndrome vestibular agudo4. A presença de nistagmo espontâneo constitui no entanto uma dificuldade adicional dado que as fases rápidas do nistagmo e a sacadas overt apresentam a mesma direção, ambas fazem o reset da fixação ocular e partilham propriedades cinemáticas. A realização de provas adicionais tais como o alinhamento ocular vertical (vertical skew) e sentido do nistagmo na levo e dextroversão aumentam o valor diagnóstico do HIT, mas requerem aptidões e competências habitualmente não disponíveis no serviço de urgência. Dado que o vHIT permite a quantificação das respostas oculomotoras aos estímulos impulsivos e apresenta uma curva de aprendizagem rápida na execução da prova, procurámos realizar um conjunto de experiências com o objetivo de determinar se o envolvimento de vias vestibulares centrais causam alterações do VOR dinâmico objectiváveis com o vHIT. Colocámos como hipótese que tais alterações poderiam ser não só traduzidas num algoritmo para topodiagnóstico clínico mas também contribuir para a compreensão dos mecanismos neurofisiológicos de controlo do VOR impulsivo. Para tal estudámos indivíduos saudáveis, doentes com UVL e nistagmo espontâneo de origem periférica e central e doentes com diagnósticos específicos de doença neurodegenerativa hereditária, com e sem envolvimento das vias vestibulares centrais. Nos próximos parágrafos são sumariamente descritos os fundamentos, objectivos, métodos, resultados e conclusões das experiências realizadas.

Vestibular assessment in children with sensorineural hearing loss: diagnostic accuracy and proposal for a diagnostic algorithm

IntroductionVestibular assessment in children with sensorineural hearing loss (SNHL) is critical for early vestibular rehabilitation therapy to promote (motor) development or guide decision making towards cochlear implantation (timing of surgery and laterality). It can be challenging from a clinical viewpoint to decide which vestibular tests should be performed for a pediatric patient. The aim of this study was to evaluate the diagnostic accuracy of several clinically available vestibular tests in children with SNHL, and to provide recommendations for the implementation of vestibular testing of children in clinical practice, to screen for vestibular hypofunction (VH).MethodsA two-center retrospective chart review was conducted. Eighty-six patients between the age of 0 and 18 years were included in this study with SNHL. Vestibular tests included video headimpulse test (VHIT), caloric test (performed at the age of four or higher), rotatory chair and cervical vestibular evoked myogenic potential (cVEMP). A combination of the clinical assessment and (combinations of) vestibular test outcomes determined the diagnosis. The diagnostic quality of tests and combination of tests was assessed by diagnostic accuracy, sensitivity and specificity.ResultsVH was diagnosed in 44% of the patients. The VHIT and caloric test showed the highest diagnostic accuracy compared to the rotatory chair and cVEMP. All combinations of VHIT, caloric test and cVEMP showed improvement of the diagnostic accuracy compared to the respective tests when performed singularly. All combinations of tests showed a relatively similar diagnostic accuracy, with the VHIT combined with the caloric test scoring the highest. Adding a third test did not substantially improve the diagnostic accuracy.DiscussionVestibular testing is feasible and VH is highly prevalent in children with SNHL. A proposed diagnostic algorithm recommends starting with VHIT, followed by cVEMP for children under the age of four, and caloric testing for older children if VH is not confirmed with the first test. Performing a third test is redundant as the diagnostic accuracy does not improve substantially. However, challenges remain, including the lack of a gold standard and the subjective nature of the diagnosis, highlighting the need for standardized testing and increased understanding of VH in this population