Unilateral Vestibular Lesions Research Articles

The Relationship between the Subjective Visual Horizontal and Ocular Vestibular Evoked Myogenic Potentials in Acute Vestibular Neuritis.

Vestibular evoked myogenic potentials (VEMPs) and the subjective visual horizontal (SVH) (or vertical [SVV]) have both been considered tests of otolith function: ocular-VEMPs (oVEMPs) utricular function, cervical VEMPs (cVEMPs) saccular function. Some studies have reported association between decreased oVEMPs and SVH, whereas others have not. A retrospective study of test results. A tertiary, neuro-otology clinic, Royal Prince Alfred Hospital, Sydney, Australia. We analyzed results in 130 patients with acute vestibular neuritis tested within 5 days of onset. We sought correlations between the SVH, oVEMPs, and cVEMPs to air-conducted (AC) and bone-conducted (BC) stimulation. The SVH deviated to the side of lesion, in 123 of the 130 AVN patients, by 2.5 to 26.7 degrees. Ninety of the AVN patients (70%) had abnormal oVEMPs to AC, BC or both stimuli, on the AVN side (mean asymmetry ratio ± SD [SE]): (64 ± 45.0% [3.9]). Forty-three of the patients (35%) had impaired cVEMPs to AC, BC or both stimuli, on the AVN side, [22 ± 41.6% (4.1)]. The 90 patients with abnormal oVEMP values also had abnormal SVH. Correlations revealed a significant relationship between SVH offset and oVEMP asymmetry (r = 0.80, p < 0.001) and a weaker relationship between SVH offset and cVEMP asymmetry (r = 0.56, p < 0.001). These results indicate that after an acute unilateral vestibular lesion, before there has been a chance for vestibular compensation to occur, there is a significant correlation between the SVH, and oVEMP results. The relationship between SVH offset and oVEMP amplitude suggests that both tests measure utricular function.

Vertigoheel improves central vestibular compensation after unilateral peripheral vestibulopathy in rats.

The aim of this study was to assess the effect of Vertigoheel on central vestibular compensation and cognitive deficits in rats subjected to peripheral vestibular loss. Young adult male Long Evans rats were subjected to bilateral vestibular insults through irreversible sequential ototoxic destructions of the vestibular sensory organs. Vestibular syndrome characteristics were monitored at several time points over days and weeks following the sequential insults, using a combination of behavioral assessment paradigms allowing appreciation of patterns of change in static and dynamic deficits, together with spatial navigation, learning, and memory processes. Vertigoheel administered intraperitoneally significantly improved maximum body velocity and not moving time relative to its vehicle control on days 2 and 3 and on day 2, respectively, after unilateral vestibular lesion (UVL). It also significantly improved postural control relative to its vehicle 1 day after UVL. Conversely, Vertigoheel did not display any significant effect vs. vehicle on the severity of the syndrome, nor on the time course of other examined parameters, such as distance moved, mean body velocity, meander, and rearing. Spatial cognition testing using Y- and T-maze and eight-radial arm maze did not show any statistically significant difference between Vertigoheel and vehicle groups. However, Vertigoheel potentially enhanced the speed of learning in sham animals. Evaluating Vertigoheel's effect on thigmotaxis during the open-field video tracking test revealed no significant difference between Vertigoheel and its vehicle control groups suggesting that Vertigoheel does not seem to induce sedative or anxiolytic effects that could negatively affect vestibular and memory function. Present observations reveal that Vertigoheel improves central vestibular compensation following the unilateral peripheral vestibular loss as demonstrated by improvement of specific symptoms.

Correlation of SVINT and Sensory Organization Test in Children with Hearing Loss.

Objective: The skull vibration-induced-nystagmus test (SVINT) is a noninvasive and effective screening tool for the function of the otolith and canal structures in children. It can instantaneously assess vestibular asymmetry. This study aimed to analyze the SVINT results of healthy children vs. children with hearing loss (HL) and to correlate it with sensory organization test (SOT) results as a functional balance evaluation tool. Design: This case-controlled study compared the results of SVINT to the results of the SOT of the computerized dynamic posturography (CDP) in a control group of 120 healthy normal-hearing children (i.e., NH group) vs. hearing loss (HL) group of 60 children, including 30 children with hearing aids (HAs) and 30 children with a unilateral cochlear implant (CI). The SVINT results were compared to the caloric test (CaT) and video head impulse test (vHIT) and associated with SOT scores. Results: Thirty-one children in the HL group had normal SVINT and normal SOT results. A total of 21 children in the HL group had SVINT-negative and abnormal results in the SOT (possibly due to bilateral vestibular loss (BVL)). Eight children in the HL group had positive SVINT and abnormal SOT results. However, none of the children had only positive SVINT with normal SOT findings. Moreover, 52% of children had a normal result on both the SOT and CaT, whereas 27% had abnormal results on both tests (17% bilateral weakness and 10% unilateral), and 22% had the only result of the SOT suggesting a functional abnormality. Similarly, when associating the result to vHIT, 51% had normal results on both tests, and 25% had abnormal results (13% bilateral and 12% unilateral weakness). Conclusions: SVINT findings can be correlated with SOT findings in the case of the unilateral vestibular lesion (UVL), which adds a diagnostic value in these pediatric cases but may differ in the case of the bilateral vestibular lesion (BVL). However, SVINT findings need to be cautiously interpreted in light of other test findings such as the SOT, CaT, and vHIT.

Virtual reality for the measurement of SVV and SVH during static head tilt in healthy adults: a novel vestibular test

Background and objective Few previous studies have used virtual-reality (VR) technology to measure subjective visual vertical (SVV) and subjective visual horizontal (SVH) during static head tilt (0°, 30°, 45°, 60° and 90°). We propose a novel vestibular test for measuring the normal range of SVV and SVH during static head tilt in healthy adults. Methods Eighty healthy adults were included in the study. SVV and SVH were calculated in nine head positions. Results With head tilt 90° to the right, SVV skewed to the right, and SVH skewed upward. With head tilt 90° to the left, SVV skewed to the left, and SVH skewed downward. SVV was asymmetrical only at a head tilt of 90°. SVV and SVH were similar at all degrees of head tilt, except for 30° to the right, 45° to the left, and 0°. Conclusions VR measurements showed that SVV and SVH differed at various degrees of static head tilt. The standardized protocol proposed here may be used to establish a reference range for utricle function when evaluating acute, unilateral vestibular lesions.

L-Thyroxine Improves Vestibular Compensation in a Rat Model of Acute Peripheral Vestibulopathy: Cellular and Behavioral Aspects.

Unilateral vestibular lesions induce a vestibular syndrome, which recovers over time due to vestibular compensation. The therapeutic effect of L-Thyroxine (L-T4) on vestibular compensation was investigated by behavioral testing and immunohistochemical analysis in a rat model of unilateral vestibular neurectomy (UVN). We demonstrated that a short-term L-T4 treatment reduced the vestibular syndrome and significantly promoted vestibular compensation. Thyroid hormone receptors (TRα and TRβ) and type II iodothyronine deiodinase (DIO2) were present in the vestibular nuclei (VN), supporting a local action of L-T4. We confirmed the T4-induced metabolic effects by demonstrating an increase in the number of cytochrome oxidase-labeled neurons in the VN three days after the lesion. L-T4 treatment modulated glial reaction by decreasing both microglia and oligodendrocytes in the deafferented VN three days after UVN and increased cell proliferation. Survival of newly generated cells in the deafferented vestibular nuclei was not affected, but microglial rather than neuronal differentiation was favored by L-T4 treatment.

Acute unilateral vestibular lesion induced by SARS-CoV-2 infection

SARS-CoV-2 infection has a wide range of symptoms, with a series of ENT manifestations reported in the pandemic years, some of them being considered specific for the infec­tion, such the loss of smell or taste. Dizziness and postural in­sta­bi­li­ty are common symptoms in COVID-19 patients and are nonspecific, but the onset of the disease with acute uni­la­te­ral peripheral vestibular syndrome, without any other symp­toms, is not very frequent. We report two cases of SARS-CoV-2 infection with acute unilateral peripheral vestibular syndrome onset.

Inertial Measurement of Head Tilt in Rodents: Principles and Applications to Vestibular Research.

Inertial sensors are increasingly used in rodent research, in particular for estimating head orientation relative to gravity, or head tilt. Despite this growing interest, the accuracy of tilt estimates computed from rodent head inertial data has never been assessed. Using readily available inertial measurement units mounted onto the head of freely moving rats, we benchmarked a set of tilt estimation methods against concurrent 3D optical motion capture. We show that, while low-pass filtered head acceleration signals only provided reliable tilt estimates in static conditions, sensor calibration combined with an appropriate choice of orientation filter and parameters could yield average tilt estimation errors below during movement. We then illustrate an application of inertial head tilt measurements in a preclinical rat model of unilateral vestibular lesion and propose a set of metrics describing the severity of associated postural and motor symptoms and the time course of recovery. We conclude that headborne inertial sensors are an attractive tool for quantitative rodent behavioral analysis in general and for the study of vestibulo-postural functions in particular.

Posturography with head movements in the assessment of balance in chronic unilateral vestibular lesions

The aim of our study was to validate the method of head-shake static posturography (HS-posturography) in healthy individuals and to establish the value of this novel method in the diagnostics of patients with unilateral vestibular lesion (UV). The study included 202 participants divided into two groups, one consisting of 133 patients with canal paresis CP > 19% and one of 69 healthy subjects. Participant was tested according to the standard protocol of static posturography (SP), and with head movements of 0.3 Hz (HS 40), 0.6 Hz (HS 70) in random order controlled by a metronome. HS-posturography revealed a similar repeatability and internal consistency as the standard posturography. In patients with UV, 4th condition revealed higher sensitivity (74%) and specificity (71%) in HS 40 than in the standard posturography (67%, 65% respectively) and HS 70 (54%, 70% respectively). Static posturography and HS- posturography revealed a high reliability of the testing method. The head movements added to static posturography improve the sensitivity and specificity of the method in group with vestibular impairment. The most important test for that purpose seems to be the one on unstable surface with the eyes closed, with low frequency of head movements.

Different time course of compensation of subjective visual vertical and ocular torsion after acute unilateral vestibular lesion

PurposeTime course of the recovery of otolithic dis-function caused by superior vestibular neuritis has been examined in fifteen patients.MethodsThe subjective visual vertical (SVV) and the ocular cyclotorsion (OT) have been measured four times after the acute episode up to 1 yearResultsIn most of the patients the SVV tilt returned to control values within few months (3–6 months) after the acute episode, while OT remained out of normal range in almost all patients a year later.ConclusionThe abnormal OT observed after 1 year from the acute episode of vestibular neuritis, suggests that the otolithic receptors remained altered for several months and the OT may be a good indicator of the entity of the residual peripheral otolithic lesion. Moreover, the dissociation between the SVV tilt recovery and that of OT supports the issue that the two signs of the otolithic disfunction are only partially linked each other with centrally or peripherally distinct re-balancing circuits.

The intrinsic plasticity of medial vestibular nucleus neurons during vestibular compensation\u2014a systematic review and meta-analysis

BackgroundVestibular compensation is a homeostatic process that occurs in the central nervous system in response to peripheral vestibular dysfunction. Experimental studies in rodent models have suggested that unilateral peripheral vestibular lesions are correlated with an increase in the intrinsic excitability of central vestibular neurons. This process may be dependent on the intrinsic properties of the neurons themselves. We aimed to conduct a systematic review of the literature to survey the evidence for changes in intrinsic plasticity observed during the acute phase of vestibular compensation.MethodsWe systematically reviewed the literature regarding the electrophysiological effect of experimentally induced unilateral vestibular deafferentation (UVD) on the intrinsic membrane properties of medial vestibular nucleus neurons in animal models. We developed tools to assess the methodological quality (precision, validity and bias) of studies that met pre-determined inclusion and exclusion criteria. We extracted numerical data and performed a meta-analysis of specific quantitative data pooled from these studies.ResultsWe identified 17 studies that satisfied the inclusion criteria. There is moderate quality evidence to suggest a statistically significant increase in the intrinsic excitability of medial vestibular nucleus neurons following unilateral vestibular deafferentation. Specifically, the spontaneous discharge rate increases by 4 spikes/s on average and the sensitivity to current stimuli increases.ConclusionUsing this novel approach, we demonstrate that the methodology of systematic review and meta-analysis is a useful tool in the summation of data across experimental animal studies with similar aims.

Quantitative Evaluation of a New Posturo-Locomotor Phenotype in a Rodent Model of Acute Unilateral Vestibulopathy.

Vestibular pathologies are difficult to diagnose. Existing devices make it possible to quantify and follow the evolution of posturo-locomotor symptoms following vestibular loss in static conditions. However, today, there are no diagnostic tools allowing the quantitative and spontaneous analysis of these symptoms in dynamic situations. With this in mind, we used an open-field video tracking test aiming at identifying specific posturo-locomotor markers in a rodent model of vestibular pathology. Using Ethovision XT 14 software (Noldus), we identified and quantified several behavioral parameters typical of unilateral vestibular lesions in a rat model of vestibular pathology. The unilateral vestibular neurectomy (UVN) rat model reproduces the symptoms of acute unilateral peripheral vestibulopathy in humans. Our data show deficits in locomotion velocity, distance traveled and animal mobility in the first day after the injury. We also highlighted alterations in several parameters, such as head and body acceleration, locomotor pattern, and position of the body, as well as “circling” behavior after vestibular loss. Here, we provide an enriched posturo-locomotor phenotype specific to full and irreversible unilateral vestibular loss. This test helps to strengthen the quantitative evaluation of vestibular disorders in unilateral vestibular lesion rat model. It may also be useful for testing pharmacological compounds promoting the restoration of balance. Transfer of these novel evaluation parameters to human pathology may improve the diagnosis of acute unilateral vestibulopathies and could better follow the evolution of the symptoms upon pharmacological and physical rehabilitation.

Identification of New Biomarkers of Posturo-Locomotor Instability in a Rodent Model of Vestibular Pathology.

The vestibular system plays a crucial role in maintaining postural balance. Unilateral vestibular lesions result in a typical syndrome characterized by postural imbalance, altered locomotor patterns and gaze stabilization, as well as cognitive and neurovegetative disorders. One of the main difficulties encountered in the development of new anti-vertigo drugs is the lack of sensitivity in the evaluation of this syndrome. Qualitative assessments of the vestibular syndrome have been developed, but methods of conducting quantitative evaluations are critically lacking. Recently, assessments with a dynamic weight-bearing device (DWB®, Bioseb) revealed postural alterations in rats subjected to unilateral vestibular neurectomy (UVN). Our team is evaluating a new version of this device capable of quantifying additional parameters of postural and locomotor equilibrium. The objective of this study was to use this device to assess these new posturo-locomotor parameters in a rat model of a vestibular pathology. The biomarkers measured by this device are as follows: the barycenter, the support surface and the weight distribution of the rats when they were moving or stationary. Before UVN, the rats showed a symmetric distribution of their weight along the lateral axis. In the acute phase after UVN on the left side, the rats distributed more weight on the right side than on the left side and then distributed more weight on the left side. These results corroborate those presented in our previous study. The support surface of the rats increased between 1 day and 30 days after UVN, and the barycenter distribution reflected the weight distribution. In addition, our results show smaller changes in the weight distributions when the animals are moving compared with when they are stationary in the acute phase after UVN. This study provides new information on the static and dynamic postural balance patterns observed after unilateral vestibular loss in rats. These data are relevant because they objectively quantify the posturo-locomotor component of vestibular syndrome as well as the compensatory strategies used after vestibular loss. These results may guide the development of rehabilitation protocols for vestibular patients and the validation of pharmacological compounds favoring the restoration of equilibrium.

Identification and new methods for quantifying new biomarkers of posturo-locomotor instability in a rodent model of acute peripheral vestibulopathy

Introduction Unilateral vestibular lesion results in a typical syndrome characterized by postural imbalance, alteration of locomotion and gaze stabilization as well as cognitive and neurovegetative disorders. One of the main difficulties encountered in the development of new anti-vertigo drugs is the lack of sensitivity in the evaluation of this syndrome. The use of a dynamic weight-bearing device has revealed postural alterations in rats with unilateral vestibular neurectomy (UVN) on the left side (Tighilet et al., 2017). With a new version of this device, we can quantify additional parameters of postural and locomotor equilibrium. The objective of this study is to use this device to set new parameters on our rat model of vestibular pathology. Material and methods We extracted different biomarkers from this device: the support surface, the weight distribution of rats when they are static or dynamic, and the successive positions of rat's barycenter. Results Before UVN, rats show a symmetric distribution of their weight along the lateral axis. In the acute phase after UVN, rats distribute more weight on the right when they are static and then they put more weight on the left side. After UVN, the support surface of the rats increases, and the barycenter distribution show a higher dispersion. Discussion/conclusion This study provides new information on the postural balance pattern observed after vestibular loss in rats. These data show a new way of quantifying the postural deficit associated with vestibular damage and the compensatory strategies adopted. These results could guide us on the validation of pharmacological compounds favoring the balance recovery.

Vestibular disorders in roll plane from brainstem to cortex

The aim is to review current knowledge of the perception of verticality, its normal function and disorders. This is based on an integrative graviceptive input from the vertical semicircular canals and the otolith organs. The focus is particularly on human psychophysics, neurophysiological and imaging data on vestibular disorders in the roll plane. The signs and symptoms are head tilt, vertical divergence of the eyes (skew deviation), ocular torsion, and tilts of subjective visual vertical (SVV) adjustments, all of which represent the so-called ocular tilt reaction (OTR). Furthermore, these signs will be related to mathematical modeling of specific vestibular cell functions for orientation in space in rodents and in patients. Pathological tilts of the SVV in the roll plane are most sensitive and frequent clinical vestibular signs of unilateral lesions extending from the labyrinths via the brainstem and thalamus to the parieto-insular vestibular cortex [[1]Brandt T. Dieterich M. The dizzy patient: Don’t forget disorders of the central vestibular system.Nat. Rev. Neurol. 2017 Jun; 13: 352-362https://doi.org/10.1038/nrneurol.2017.58Google Scholar]. Due to crossings of ascending graviceptive fibers, peripheral vestibular and pontomedullary lesions cause ipsilateral tilts of the SVV; ponto-mesencephalic lesions cause contralateral tilts. In contrast, SVV tilts, which are measured in unilateral vestibular lesions at thalamic and cortical levels, have two different characteristic features: (i) they may be ipsi- or contralateral, and (ii) they are smaller than those found in lower brainstem or peripheral lesions. Motor signs such as head tilt and body lateropulsion, i.e. components of OTR, are typical for vestibular lesions of the peripheral vestibular organ and the pontomedullary brainstem (vestibular nucleus). They are less frequent in midbrain lesions (interstitial nucleus of Cajal) and rare in cortical lesions. Vestibular function in the roll plane and its disorders can be mathematically modeled by an attractor model of the function of angular head velocity cells and head direction cells [[2]Glasauer S. Dieterich M. Brandt T. Neuronal network-based mathematical modelling of perceived verticality in acute unilateral vestibular lesions: from nerve to thalamus and cortex.J. Neurol. 2018 May 29; https://doi.org/10.1007/s00415-018-8909-5Google Scholar]. Conclusion: Clinical determinations of the SVV are easy and reliable. They indicate acute unilateral vestibular dysfunctions, the causative lesion of which extends from labyrinth to cortex. Together with additional ocular motor or brainstem signs they allow precise topographical diagnosis of side and level.

Effect of the novel histamine H4 receptor antagonist SENS-111 on spontaneous nystagmus in a rat model of acute unilateral vestibular loss.

Histamine H4 receptors are expressed in the peripheral vestibular system, and their selective inhibition improves vertigo symptoms in rats with unilateral vestibular lesions. The effects of SENS-111, a selective oral H4 receptor antagonist with high affinity to both animal and human receptors, on vertigo symptoms was evaluated in a translational in vivo model of unilateral vestibular loss. Pharmacokinetics of SENS-111 in rats was determined to aid dose selection for efficacy testing. Vestibular lesions were induced in rats by unilateral transtympanic injection of kainic acid. The effect of SENS-111 (10 or 20mg·kg-1 ) on spontaneous nystagmus was evaluated compared with placebo vehicle using video-nystagmography, and the effective dose was compared with those of similar drugs used clinically, as single agents or combined with SENS-111. Doses were selected for plasma exposure were consistent with published phase 1 results from healthy volunteers. SENS-111 of 10mg·kg-1 gave a 21-22% reduction in nystagmus at 1hr post-administration, whereas a loss of efficacy was seen with 20mg·kg-1 . Compared with SENS-111, meclizine and methylprednisolone had minimal effects on nystagmus as single agents, and meclizine abolished the effect of SENS-111 when combined with SENS-111. All evaluated drugs were well tolerated. The exposure-efficacy relationship for improved spontaneous nystagmus seen with SENS-111 in this in vivo model is consistent with phase 1 clinical results and provides preclinical support for pharmacokinetic/pharmacodynamic modelling and selection of effective clinical drug concentrations. This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc.

Skull vibration induced nystagmus in patients with superior semicircular canal dehiscence

ObjectiveTo establish optimum stimulus frequency and location of bone conducted vibration provoking a skull vibration induced nystagmus (SVIN) in superior semi-circular canal dehiscences. MethodsSVIN 3D components in 40 patients with semi-circular canal dehiscence (27 unilateral and 13 bilateral) were compared with a group of 18 patients with severe unilateral vestibular loss and a control group of 11 volunteers. ResultsIn unilateral semi-circular canal dehiscences, SVIN torsional and horizontal components observed on vertex location in 88% beat toward the lesion side in 95%, and can be obtained up to 800Hz (around 500Hz being optimal). SVIN slow-phase-velocity was significantly higher on vertex stimulation at 100 and 300Hz (P=0.04) than on mastoids. SVIN vertical component is more often upbeating than downbeating. A SVIN was significantly more often observed in unilateral than bilateral semi-circular-canal dehiscences (P=0.009) and with a higher slow phase velocity (P=0.008). In severe unilateral vestibular lesions the optimal frequency was 100Hz and SVIN beat toward the intact side. The mastoid stimulation was significantly more efficient than vertex stimulation at 60 and 100Hz (P<0.01). ConclusionSVIN reveals instantaneously in unilateral semi-circular canal dehiscences a characteristic nystagmus beating, for the torsional and horizontal components, toward the lesion side and with a greater sensitivity toward high frequencies on vertex stimulation. SVIN three components analysis suggests a stimulation of both superior semi-circular canal and utricle. SVIN acts as a vestibular Weber test, assessing a vestibular asymmetrical function and is a useful indicator for unilateral semi-circular canal dehiscence.

Perception of Verticality and Vestibular Disorders of Balance and Falls.

Objective: To review current knowledge of the perception of verticality, its normal function and disorders. This is based on an integrative graviceptive input from the vertical semicircular canals and the otolith organs.Methods: The special focus is on human psychophysics, neurophysiological and imaging data on the adjustments of subjective visual vertical (SVV) and the subjective postural vertical. Furthermore, examples of mathematical modeling of specific vestibular cell functions for orientation in space in rodents and in patients are briefly presented.Results: Pathological tilts of the SVV in the roll plane are most sensitive and frequent clinical vestibular signs of unilateral lesions extending from the labyrinths via the brainstem and thalamus to the parieto-insular vestibular cortex. Due to crossings of ascending graviceptive fibers, peripheral vestibular and pontomedullary lesions cause ipsilateral tilts of the SVV; ponto-mesencephalic lesions cause contralateral tilts. In contrast, SVV tilts, which are measured in unilateral vestibular lesions at thalamic and cortical levels, have two different characteristic features: (i) they may be ipsi- or contralateral, and (ii) they are smaller than those found in lower brainstem or peripheral lesions. Motor signs such as head tilt and body lateropulsion, components of ocular tilt reaction, are typical for vestibular lesions of the peripheral vestibular organ and the pontomedullary brainstem (vestibular nucleus). They are less frequent in midbrain lesions (interstitial nucleus of Cajal) and rare in cortical lesions. Isolated body lateropulsion is chiefly found in caudal lateral medullary brainstem lesions. Vestibular function in the roll plane and its disorders can be mathematically modeled by an attractor model of angular head velocity cell and head direction cell function. Disorders manifesting with misperception of the body vertical are the pusher syndrome, the progressive supranuclear palsy, or the normal pressure hydrocephalus; they may affect roll and/or pitch plane.Conclusion: Clinical determinations of the SVV are easy and reliable. They indicate acute unilateral vestibular dysfunctions, the causative lesion of which extends from labyrinth to cortex. They allow precise topographical diagnosis of side and level in unilateral brainstem or peripheral vestibular disorders. SVV tilts may coincide with or differ from the perception of body vertical, e.g., in isolated body lateropulsion.

Computational neurology of gravity perception involving semicircular canal dysfunction in unilateral vestibular lesions.

Unilateral peripheral vestibular lesions not only lead to vertigo, nystagmus and imbalance, but also to a bias in the perception of verticality, which can be measured as tilt of the subjective visual vertical (SVV). Previously, this tilt has been assumed to be caused by a residual otolith bias, for example, because unequal numbers of active haircells on both sides of the utricular striola might result in an imbalance of the firing rates of central otolith neurons. Here we propose that a tilt of the subjective visual vertical might as well be caused by a vertical semicircular canal bias in the roll axis after unilateral peripheral lesions. The canal bias, acting similar to angular velocity stimuli, influences the SVV via the central gravity estimator, which under normal circumstances resolves a perceptual tilt-translation ambiguity. To illustrate our hypothesis, we compare model predictions to data on SVV measurements in patients with unilateral vestibular lesions while being tilted or being rotated eccentrically. We further embed the model of peripheral processing in a neural network that implements the idiotropic bias and represents the direction of gravity as population code in a three dimensional spherical topography.

Histamine H1 Receptor Contributes to Vestibular Compensation.

Vestibular compensation is responsible for the spontaneous recovery of postural, locomotor, and oculomotor dysfunctions in patients with peripheral vestibular lesion or posterior circulation stroke. Mechanism investigation of vestibular compensation is of great importance in both facilitating recovery of vestibular function and understanding the postlesion functional plasticity in the adult CNS. Here, we report that postsynaptic histamine H1 receptor contributes greatly to facilitating vestibular compensation. The expression of H1 receptor is restrictedly increased in the ipsilesional rather than contralesional GABAergic projection neurons in the medial vestibular nucleus (MVN), one of the most important centers for vestibular compensation, in unilateral labyrinthectomized male rats. Furthermore, H1 receptor mediates an asymmetric excitation of the commissural GABAergic but not glutamatergic neurons in the ipsilesional MVN, which may help to rebalance bilateral vestibular systems and promote vestibular compensation. Selective blockage of H1 receptor in the MVN significantly retards the recovery of both static and dynamic vestibular symptoms following unilateral labyrinthectomy, and remarkably attenuates the facilitation of betahistine, whose effect has traditionally been attributed to its antagonistic action on the presynaptic H3 receptor, on vestibular compensation. These results reveal a previously unknown role for histamine H1 receptor in vestibular compensation and amelioration of vestibular motor deficits, as well as an involvement of H1 receptor in potential therapeutic effects of betahistine. The findings provide not only a new insight into the postlesion neuronal circuit plasticity and functional recovery in the CNS, but also a novel potential therapeutic target for vestibular disorders.SIGNIFICANCE STATEMENT Vestibular disorders manifest postural imbalance, nystagmus, and vertigo. Vestibular compensation is critical for facilitating recovery from vestibular disorders, and of great importance in understanding the postlesion functional plasticity in the adult CNS. Here, we show that postsynaptic H1 receptor in the medial vestibular nucleus (MVN) contributes greatly to the recovery of both static and dynamic symptoms following unilateral vestibular lesion. H1 receptor selectively mediates the asymmetric activation of commissural inhibitory system in the ipsilesional MVN and actively promotes vestibular compensation. The findings provide not only a new insight into the postlesion neuronal circuit plasticity and functional recovery of CNS, but also a novel potential therapeutic target for promoting vestibular compensation and ameliorating vestibular disorders.

Effectiveness of Customised Vestibular Rehabilitation Therapy in Unilateral and Bilateral Vestibular Lesion Patients

International Journal of Medicine and Public Health,2018,8,3,104-107.DOI:10.5530/ijmedph.2018.3.22Published:October 2018Type:Original ArticleEffectiveness of Customised Vestibular Rehabilitation Therapy in Unilateral and Bilateral Vestibular Lesion PatientsAggarwal Amita, and Patel Nishi Aggarwal Amita*, Patel Nishi Physiotherapy, Dr. DY. Patil College of Physiotherapy, Maharashtra- 411018, INDIA. Abstract:Introduction: Vestibular dysfunction is either unilateral or bilateral. These depict similar signs and symptoms. Here patient primarily complains of head movement induced dizziness and imbalance. The present study compared the customized vestibular rehabilitation therapy (VRT) in unilateral and bilateral vestibular lesion patients. Method: The subjects were assigned into two groups by purposive sampling (n=10 each). Group A was Unilateral and group B was Bilateral Vestibular Lesion. Both were given customized vestibular rehabilitation therapy. The twelve days protocol included gaze stability (two mins), dizziness (thirty secs hold, three repetitions) and balance improvement progression exercises (five repetitions each) with thirty secs rest interval in between. Student t test was used for analysis. Patients were evaluated for dizziness and risk of fall using Dizziness Handicap Inventory (DHI) and Fall Efficacy Scale (FES). For the assessment of balance, Tandem Walk, Limit of Stability and Clinical Test of Sensory Interaction on Balance (CTSIB) sub-parameters were evaluated using Balance Master. Result: The vestibular rehabilitation therapy was effective for functional domain of dizziness and FES in both unilateral and bilateral lesion patients. In unilateral lesion patients even physical domain of dizziness, reaction time (RT), end point excursion (EPE) and directional velocity (DCL), sub-parameters of limit of stability and step width, speed, end sway sub-parameters of tandem gait also improved. In bilateral vestibular lesion, only the sway velocity in CTSIB showed improvement. Conclusion: Customized Vestibular Rehabilitation Therapy was effective in improving dizziness and risk of fall greater than balance in unilateral and bilateral vestibular lesion patients. Keywords:Balance Master, Dizziness Handicap Inventory, Fall Efficacy Scale, Vestibular DysfunctionView:PDF (184.42 KB)