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The limits of stability in patients with unilateral vestibulopathy
Abstract and Figures
Objective: To characterize the stability limits and region in patients with unilateral vestibulopathy according to the side of the lesion and determine if that imposes any bias. To analyze if the stability limits and region depend on the functional deficit as evaluated in the sensory organization test.
Methods: Forty patients with chronic dizziness and without any vertigo spell for least 6 months prior to testing. In all of them, a unilateral vestibulopathy was diagnosed clinically and at vestibular testing. A computerized dynamic posturography system was used to test for the ability of patients and controls to displace their center of pressure (COP) to the corresponding LOS. The area was calculated and compared to other data from vestibular tests.
Results: The area of stability among patients shows a reduction to 35–62% of the expected total. That reduction was not found to be dependent on age.
Conclusion: There is a symmetric reduction in the limits of stability (LOS) in patients with unilateral vestibulopathy who suffer chronic instability. None of the areas measured were correlated with the composite score of the sensory organization test and, as such, must be considered as an adjunct measure to characterize the postural limitations in those patients.
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Supplementary resource (1)
... Nuestro trabajo se diferencia de otros estudios en que no hemos considerado que el paciente tuviera un daño vestibular crónico, sino que no hiciera uso de la información vestibular aunque ya se hubiera recuperado de ese daño. Se ha demostrado que se pueden mejorar los límites de estabilidad en las personas de edad avanzada realizando una adecuada rehabilitación del equilibrio y, por ello, existen protocolos de rehabilitación tanto domiciliarios como asistidos con posturografía dinámica [15], al igual que hay ejercicios de rehabilitación vestibular encaminados a mejorar el uso de la información vestibular de pacientes que no la utilizan de forma adecuada [16]. En términos de salud, los beneficios de la detección de pacientes con alto riesgo de caída son indiscutibles, tanto por el sufrimiento del paciente como por el gasto sanitario secundario a las consecuencias de la caída. ...
Introducción y objetivo: El desarrollo de las plataformas dinamométricas computerizadas ha significado una evolución trascendental en la medición del equilibrio en bipedestación estática. El objetivo principal de nuestro estudio es determinar la relación entre los límites de estabilidad y el tipo de información que utilizan estos pacientes para mantener el equilibrio. Método: Estudio de cohortes retrospectivo de una muestra de 70 pacientes a partir del análisis de los resultados obtenidos en las posturografías dinámicas computerizadas (PDC) realizadas en la Unidad de Otoneurología del Servicio de Otorrinolaringología y Cirugía de Cabeza y Cuello del Complejo Asistencial Universitario de Salamanca. Resultados: No hay ningún tipo de déficit en 28 de los 70 pacientes a los que se realizó una PDC. La media de los límites de estabilidad en los pacientes con un valor compuesto patológico es menor que los pacientes con un compuesto normal, siendo esta relación estadísticamente significativa (p<0,05). Los pacientes con mayor afectación de los límites de estabilidad son aquellos que no hacen un buen uso de la información vestibular y visual. Discusión / Conclusiones: Es importante analizar si el paciente usa correctamente la información vestibular para mantener el equilibrio y de no ser así, promover estrategias de rehabilitación para reducir el riesgo de caídas.
... En todos ellos se ha descrito una reducción del área de estabilidad del 35-62% independientemente de la edad. En los ancianos se producen también alteraciones visuales, propioceptivas, musculoesqueléticas y demencia, que, asociado a la toma de fármacos, reducen aún más ese área y favorecen las caídas [9][10][11][12]. ...
Introducción y objetivos:
La disfunción vestibular periférica implica a los órganos vestibulares o a los nervios vestibulares, produciendo una gran variedad de síntomas y signos clínicos.
Material y métodos:
Revisión narrativa.
Resultados:
El otoneurólogo es el encargado de realizar una evaluación exhaustiva para llegar a identificar el trastorno que presenta el paciente que acude con vértigo o desequilibrio. La clave diagnóstica es la anamnesis profunda completada con un cuidadoso examen otoneurológico. Además, las nuevas tecnologías de estudio que han surgido en este campo permiten un cambio en la definición, caracterización y tratamiento de estas patologías.
Conclusiones:
En la presente revisión narrativa se describirán los dos grandes grupos de deficiencia vestibular periférica: la vestibulopatía unilateral y bilateral.
... The implicit assumption underlying the clinical interest of body sway is that the projection of the body center-of-mass on the standing surface (CoM) is the regulated variable of the postural control system, which can be indirectly accessed by measuring the position of the center-of-pressure (CoP). A number of performance measures of maintenance of this posture, based on the CoP-CoM pair, have been developed which are used in clinical decision making [1] in relation with a number of pathological conditions, such as the following ones: cerebellar ataxia [2][3][4], vestibular dysfunctions [5][6][7], peripheral neuropathy due to diabetes [8][9][10], Alzheimer's disease [11,12], multiple sclerosis [13,14], Parkinson's disease [15,16], traumatic brain injury [17,18], stroke [19,20] and identification of malingerers for forensic medicine [21]. The underlying biomechanical model is a Single Inverted Pendulum (SIP), pivoted around the ankle. ...
In the study of balance and postural control the (Single) Inverted Pendulum model (SIP) has been taken for a long time as an acceptable paradigm, with the implicit assumption that only ankle rotations are relevant for describing and explaining sway movements. However, more recent kinematic analysis of quiet standing revealed that hip motion cannot be neglected at all and that ankle-hip oscillatory patterns are characterized by complex in-phase and anti-phase interactions, suggesting that the SIP model should be substituted by a DIP (Double Inverted Pendulum) model. It was also suggested that DIP control could be characterized as a kind of optimal bi-axial active controller whose goal is minimizing the acceleration of the global CoM (Center of Mass). We propose here an alternative where active feedback control is applied in an intermittent manner only to the ankle joint, whereas the hip joint is stabilized by a passive stiffness mechanism. The active control impulses are delivered to the ankle joint as a function of the delayed state vector (tilt rotation angle + tilt rotational speed) of a Virtual Inverted Pendulum (VIP), namely a pendulum that links the ankle to the CoM, embedded in the real DIP. Simulations of such DIP/VIP model, with the hybrid control mechanism, show that it can reproduce the in-phase/anti-phase interaction patterns of the two joints described by several experimental studies. Moreover, the simulations demonstrate that the DIP/VIP model can also reproduce the measured minimization of the CoM acceleration, as an indirect biomechanical consequence of the dynamic interaction between the active control of the ankle joint and the passive control of the hip joint. We suggest that although the SIP model is literally false, because it ignores the ankle-hip coordination, it is functionally correct and practically acceptable for experimental studies that focus on the postural oscillations of the CoM.
... The moving room paradigm requires an individual to maintain balance within increased oscillations of the visual environment (typically referred to as the "visual cave"). The avoidance task requires dynamic movement outside one's base of support in response to a visual stimulus and reflects a different subdomain of balance [15]. We previously reported the feasibility and reliability of our platform in healthy young adults [16] and preliminary validity in adults with vestibular hypofunction [17]. ...
Background:
Deficits in sensory integration and fear of falling in complex environments contribute to decreased participation of adults with vestibular disorders. With recent advances in virtual reality technology, head-mounted displays are affordable and allow manipulation of the environment to test postural responses to visual changes.
Objectives:
To develop an assessment of static and dynamic balance with the Oculus Rift and (1) to assess test-retest reliability of each scene in adults with and without vestibular hypofunction; (2) to describe changes in directional path and sample entropy in response to changes in visuals and surface and compare between groups; and (3) to evaluate the relation between balance performance and self-reported disability and balance confidence.
Design:
Test-retest, blocked-randomized experimental design.
Setting:
Research laboratory.
Participants:
Twenty-five adults with vestibular hypofunction and 16 age- and sex-matched adults.
Methods:
Participants stood on the floor or stability trainers while wearing the Oculus Rift. For 3 moving "stars" scenes, they stood naturally. For a "park" scene, they were asked to avoid a virtual ball. The protocol was repeated 1-4 weeks later.
Outcome:
Anteroposterior and mediolateral center-of-pressure directional path and sample entropy were derived from a force plate.
Results:
We observed good to excellent reliability in the 2 groups, with most intraclass correlations above 0.8 and only 2 at approximately 0.4. The vestibular group had higher directional path for the stars scenes and lower directional path for the park scene compared with controls, with large variability in the 2 groups. Sample entropy decreased with more challenging environments. In the vestibular group, less balance confidence strongly correlated with more sway for the stars scenes and less sway for the park scene.
Conclusion:
Virtual reality paradigms can shed light on the control mechanism of static and dynamic postural control. Clinical utility and implementation of our portable Oculus Rift assessment should be further studied.
Level of evidence:
II.
Las pérdidas auditivas neurosensoriales severas a profundas en adolescentes pueden ir acompañadas de desórdenes vestibulares desapercibidos que impactan el desarrollo motor desde edades tempranas e influyen en el aprendizaje y el desempeño diario. La identificación temprana y el conocimiento sobre la neuromaduración vestibular pueden generar alternativas para mejorar el rendimiento académico. Objetivos: caracterizar el compromiso vestibular con los resultados de la posturografía en adolescentes con pérdida auditiva severa a profunda. Método: estudio en el paradigma cuantitativo, con técnica descriptiva, buscando posibles relaciones entre las variables estudiadas. Población: 38 adolescentes con pérdida auditiva severa a profunda, divididos en dos subgrupos por rango de edad: de 12 a 15 años y de 16 a 19 años. Resultados: los adolescentes mayores tuvieron un menor movimiento oscilatorio. Los estudiantes con antecedentes del desarrollo tienden a tener un desempeño inferior en la posturografía. En el logro académico, las áreas con mayores dificultades reportadas son pensamiento cuantitativo, lenguaje y comunicación. Discusión: Los antecedentes del desarrollo y la edad son importantes para el desarrollo de habilidades en el balance y el equilibrio. No se registraron relaciones directas entre la posturografía con bajo rendimiento académico. Conclusiones: A pesar de que no se demostró relación directa entre los resultados de la posturografía con los logros académicos, su caracterización sugiere efecto indirecto sobre el pensamiento cuantitativo, el lenguaje y comunicación. La integración de los sistemas sensoriomotores y cognitivos durante el desarrollo son clave para la neuromaduración y el desarrollo de habilidades.
Background:
Unilateral vestibular deficits are associated with postural instability and loss of quality of life. Common treatments frequently fail to achieve satisfactory outcomes.
Objective:
To assess the durability of changes in participant-reported disability and objective posturography after computerized vestibular retraining.
Methods:
This was a single-group study. Individuals with persistent symptoms of an objectively determined unilateral vestibular deficit completed questionnaires and posturography assessments before and after twelve sessions of computerized retraining, and 4-6 months and 10-12 months after treatment.
Results:
13 participants completed the post-treatment assessments; 9 completed the follow up. Mean improvements in perceived disability at 4-6 months after retraining were: DHI 14.3 points (95% confidence interval 4.0 to 24.5), ABC scale 14.9 points (4.3 to 25.6), FES-I 11.6 points (-3.2 to 26.5).The SOT composite score increased by 11.4 points (95% CI 1.9 to 20.9; p = 0.0175) immediately after treatment, 8.9 points (-2.9 to 20.7; p = 0.1528) at 4-6 months, and 10.6 points (2.2 to 19.0; p = 0.0162) after 10-12 months. At the 10-12 month time point, the areas of the functional stability region increased significantly for both endpoint excursion (p = 0.0086) and maximum excursion (p = 0.0025).
Conclusion:
Computerized vestibular retraining was associated with improved participant reported disability and objective measures of postural stability.
This cohort study compares dynamic postural stability and risk of falls before and after computerized vestibular training among adults with unilateral vestibular deficits.
Background
Figures and movements in Latin dance are effectively used to provide posture stabilization and balance control. A Computerized Dynamic Posturography can be used to complete a functional evaluation of postural control and stability in static and dynamic conditions, mediated by the interaction between the visual, vestibular, and somatosensory systems.Research Question: According to the results of Computerized Dynamic Posturography, do dancers have better postural control and stability when compared to non-dancers, and can dance activity be recommended for vestibular rehabilitation?
Material and Methods
Our study included 26 professional Latin dancers and 26 non-dancers as a control group whoboth had no problems with their hearing or balance. Pure-tone audiometry and Computerized Dynamic Posturography tests were applied to the participants. The test results for the professional dancers and the control group were compared and evaluated. In statistical analysis, the Mann-Whitney U and Independent Samples T tests were used. A value of p<0.05 was accepted for significance.
Results
According to the results of the Computerized Dynamic Posturography, the dancers generally performed better than the control group. While statistically significant and better performances were observed in dancers in terms of the composite balance, visual and vestibular scores within the scope of the Sensory Organization Test (p<0.05), no statistically significant difference was found for somatosensory and preference scores (p>0.05). Also, significant differences were obtained between the two groups in some subtests of Adaptation, Unilateral Stance and Limits of Stability assessment (p<0.05). No significant difference was observed in Rhythmic Weight Shift results (p>0.05).
Importance
The results of thisresearch demonstrate that balance and posture improve through dance. Therefore, adding appropriate dance activities to vestibular rehabilitation programmes might be helpful
b>Introduction : The ability to Reach quickly to changing external stimuli, to move the body quickly and precisely in any direction and to maintain the centre of gravity above the support base, all contribute to maintaining balance in dynamic conditions. The Limits of Stability Test (LOS) provides information on the state of dynamic equilibrium in a standing position.
Aim : Assessment of dynamic postural control in developmental age.
Material : 127 healthy children (65 girls and 62 boys) aged 6 – 17years.
Methods : All children underwent LOS test (posturograph NeuroCom) with registration of reaction time (RT), movement velocity (MVL), directional control (DCL) , maximum excursion (MXE) and endpoint excursion (EPE).
Results : At the age of 6-7 years, not fully developed jumping strategy and visual feedback mechanism in the control of movement were observed. All tested parameters were significantly worse in children aged 6 – 9 years. After this period, a significant improvement in TR and MVL was observed, with no significant changes in subsequent age groups while significant improvement in MXE up to 12 , EPE and DCL up to 13 years of age was noted. No significant gender differences were fund in the LOS test parameters.
Conclusions : 1 The LOS test showed significantly lower dynamic balance development in children aged 6 – 7 years. 2 The study showed a significant improvement in all parameters of the LOS test up to 13 years of age, which supports the termination of the function at that time.
Preserving upright stance requires central integration of the sensory systems and appropriate motor output from the neuromuscular system to keep the centre of pressure (COP) within the base of support. Unilateral peripheral vestibular disorder (UPVD) causes diminished stance stability. The aim of this study was to determine the limits of stability and to examine the contribution of multiple sensory systems to upright standing in UPVD patients and healthy subjects. We hypothesized that closure of the eyes and Achilles tendon vibration during upright stance will augment the postural sway in UPVD patients more than in healthy subjects. Seventeen UPVD patients and 17 healthy subjects performed six tasks on a force plate: forwards and backwards leaning, to determine limits of stability, and upright standing with and without Achilles tendon vibration, each with eyes open and closed (with blackout glasses). The COP displacement of the patients was significantly greater in the vibration tasks than the controls and came closer to the posterior base of support boundary than the controls in all tasks. Achilles tendon vibration led to a distinctly more backward sway in both subject groups. Five of the patients could not complete the eyes closed with vibration task. Due to the greater reduction in stance stability when the proprioceptive, compared with the visual, sensory system was disturbed, we suggest that proprioception may be more important for maintaining upright stance than vision. UPVD patients, in particular, showed more difficulty in controlling postural stability in the posterior direction with visual and proprioceptive sensory disturbance.
Why vestibular compensation (VC) after an acute unilateral vestibular loss is the neuro-otologist's best friend is the question at the heart of this paper. The different plasticity mechanisms underlying VC are first reviewed, and the authors present thereafter the dual concept of vestibulo-centric versus distributed learning processes to explain the compensation of deficits resulting from the static versus dynamic vestibular imbalance. The main challenges for the plastic events occurring in the vestibular nuclei (VN) during a post-lesion critical period are neural protection, structural reorganization and rebalance of VN activity on both sides. Data from animal models show that modulation of the ipsilesional VN activity by the contralateral drive substitutes for the normal push-pull mechanism. On the other hand, sensory and behavioural substitutions are the main mechanisms implicated in the recovery of the dynamic functions. These newly elaborated sensorimotor reorganizations are vicarious idiosyncratic strategies implicating the VN and multisensory brain regions. Imaging studies in unilateral vestibular loss patients show the implication of a large neuronal network (VN, commissural pathways, vestibulo-cerebellum, thalamus, temporoparietal cortex, hippocampus, somatosensory and visual cortical areas). Changes in gray matter volume in these multisensory brain regions are structural changes supporting the sensory substitution mechanisms of VC. Finally, the authors summarize the two ways to improve VC in humans (neuropharmacology and vestibular rehabilitation therapy), and they conclude that VC would follow a "top-down" strategy in patients with acute vestibular lesions. Future challenges to understand VC are proposed.
Background:
An acute unilateral peripheral vestibular loss (aUVL) initially causes severe gaze and balance control problems. However, vestibulo-ocular reflexes (VOR) and balance control are nearly normal 3 months later as a result of peripheral recovery and/or central compensation. As pre-existing vestibular sensory loss is assumed to be greater in the healthy elderly, this study investigated whether improvements in VOR and balance function over time after aUVL are different for the elderly than for the young.
Methods:
Thirty aUVL patients divided into three age-groups were studied (8 age range 23-35, 10 with range 43-58, and 12 with range 60-74 years). To measure VOR function eye movements were recorded during caloric irrigation, rotating chair (ROT), and head impulse tests. Balance control during stance and gait was recorded as lower trunk angular velocity in the pitch and roll planes. Measurements were taken at deficit onset, and 3, 6, and 13 weeks later.
Results:
There was one difference in VOR improvements over time between the age-groups: Low acceleration ROT responses were less at onset in the elderly group. Deficit side VOR responses and asymmetries in each group improved to within ranges of healthy controls at 13 weeks. Trunk sway of the elderly was greater for stance and gait at onset when compared to healthy age-matched controls and the young and greater than that of the young and controls during gait tasks at 13 weeks. The sway of the young was not different from controls at either time point. Balance control for the elderly improved slower than for the young.
Conclusion:
These results indicate that VOR improvement after an aUVL does not differ with age, except for low accelerations. Recovery rates are different between age-groups for balance control tests. Balance control in the elderly is more abnormal at aUVL onset for stance and gait tasks with the gait abnormalities remaining after 13 weeks. Thus, we conclude that balance control in the elderly is more affected by the UVL than for the young, and the young overcome balance deficits more rapidly. These differences with age should be taken into account when planning rehabilitation.
Background
Limits of stability, defined as the ability to maintain the center of gravity within the boundary of the base of support, is critically important for older adults in performing their activities of daily living. However, few exercise programs specifically tailored to enhance limits of stability exist. The primary purpose of this study was to determine whether a therapeutically designed intervention, Tai Ji Quan: Moving for Better Balance (TJQMBB), could improve limits of stability in older adults. A secondary purpose was to examine concomitant change in limits of stability and physical performance as a result of the intervention.
Methods
A single-group design was used in which 145 community-dwelling older adults (average age: 75 years) were enrolled in TJQMBB classes, participating twice weekly for 48 weeks. Primary outcome measures were three indicators of limits of stability (LOS) (endpoint excursion, movement velocity, and directional control), with secondary measures of physical performance being Timed Up and Go and 50-foot speed walk (in seconds), which were assessed at baseline, 24 weeks, and 48 weeks. Changes in the repeated measures of outcome variables were analyzed via latent curve analysis.
Results
At 48 weeks, a significant rate of change (improvement) over time was observed in the three limits of stability indicators (endpoint execution: 8.30% LOS, P<0.001; movement velocity: 0.86 degrees/second, P<0.001; directional control: 6.79% of 100, P<0.001); all reached a threshold of real change as judged by the minimal detectable change values. Improvements in the three limits of stability measures were concomitantly correlated with improved (reduced times) performance scores in the Timed Up and Go (−0.30, −0.45, and −0.55, respectively) and 50-foot walk (−0.33, −0.49, and −0.41, respectively).
Conclusion
In this single-group study, community-dwelling older adults trained through TJQMBB significantly improved their limits of stability, providing preliminary support for the use of TJQMBB as a therapeutic modality for enhancing functional activities in older adults.
Posture control is based on central integration of multisensory inputs, and on internal representation of body orientation in space. This multisensory feedback regulates posture control and continuously updates the internal model of body’s position which in turn forwards motor commands adapted to the environmental context and constraints. The peripheral localization of the vestibular system, close to the cochlea, makes vestibular damage possible following cochlear implant (CI) surgery. Impaired vestibular function in CI patients, if any, may have a strong impact on posture stability. The simple postural task of quiet standing is generally paired with cognitive activity in most day life conditions, leading therefore to competition for attentional resources in dual-tasking, and increased risk of fall particularly in patients with impaired vestibular function. This study was aimed at evaluating the effects of post-lingual cochlear implantation on posture control in adult deaf patients. Possible impairment of vestibular function was assessed by comparing the postural performance of patients to that of age-matched healthy subjects during a simple postural task performed in static and dynamic conditions, and during dual-tasking with a visual or auditory memory task. Postural tests were done in eyes open (EO) and eyes closed (EC) conditions, with the cochlear implant activated (ON) or not (OFF). Results showed that the CI patients significantly reduced limits of stability and increased postural instability in static conditions. In dynamic conditions, they spent considerably more energy to maintain equilibrium, and their head was stabilized neither in space nor on trunk while the controls showed a whole body rigidification strategy. Hearing (prosthesis on) as well as dual-tasking did not really improve the dynamic postural performance of the CI patients. We conclude that CI patients become strongly visual dependent mainly in challenging postural conditions.
Objective:
To examine the effects of repetitive volitional and compensatory step training with preparatory signals on the limits of stability, postural and gait skills, and spatiotemporal gait characteristics in patients with Parkinson's disease with no falls during the previous 12 months.
Design:
Randomized clinical trial with assessor blinded to group assignment.
Subjects:
Twenty-eight patients with Parkinson's disease with no falls during the previous 12 months.
Methods:
Eligible patients were randomly assigned to an experimental group, which undertook repetitive step training with preparatory visual cues, or a control group, which undertook lower limb strength training for 4 weeks. Outcome measures included limits of stability test, postural and gait sub-scores from Unified Parkinson's Disease Rating Scale motor score (UPDRS-PG), and spatiotemporal gait characteristics. All tests were conducted before and after training at patients' peak medication cycle.
Results:
The experimental group showed significant improvements in reaction time, movement velocity, and endpoint excursion of limits of stability, as well as UPDRS-PG score and stride length (p < 0.05), compared with the control group. Both groups significantly increased gait velocity (p < 0.05).
Conclusion:
Repetitive step training with preparatory cues can enhance limits of stability, postural and gait skills and spatiotemporal gait characteristics in patients with Parkinson's disease with no falls during the previous 12 months.
Acknowledgement of the age effects on postural control and balance is essential to differentiate between physiological changes and actual pathological alterations of the elderly. The aim of this study is to establish the age-related postural changes recorded by the Computerized Dynamic Posturography.
70 healthy individuals (35 males and 35 females) with an average age of 44.9 years, evenly distributed in seven age groups. We carried out a Sensory Organization Test and Limits of Stability with the Neurocom Smart Balance Master(®) posturography platform. Statistical analysis was undertaken using ANOVA (p<0.05).
Increased age-related balance percentage for Condition 4 (p=0.022), reduced usage rate of ankle-strategy for Conditions 3 (p=0.027) and 4 (p=0.05) for the higher age groups were reported. Regarding limits of stability, the following were the results: age-related differences at an early stage, reaction time from 40 to 49 years, velocity of movement, excursion and directional control from 50 to 59 years.
Age only affects the balance rate under more complex sensory conditions. For healthy people, ankle strategy is more frequently used than hip strategy; however, the use of hip strategy increases under more difficult sensory conditions. Limits of stability get worse with age, namely after the age of 40-50 years.
Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
To analyze vestibulo-ocular responses using the video head impulse test in the yaw axis.
Prospective.
Tertiary and university hospital.
Two hundred twelve healthy subjects with no history of vestibular or neurologic impairment.
Video head impulse test in the lateral semicircular canal plane.
Vestibulo-ocular reflex (VOR) gain and appearance of refixation saccades (RSs) considering sex, age, and head impulse velocity and direction.
Mean gain was 1.06 ± 0.07, and there were no differences between sexes. For all the impulses (n = 9,654; 4,947 rightward and 4,707 leftward), VOR gain decreased as head impulse velocity increased. When gain was evaluated by age and head velocity, it was steady until age 70 years for higher-velocity impulses and until age 90 years for lower-velocity head impulses. RSs were detected in 52 subjects, occurring after impulses to both sides of the head in 22 of these subjects. The number of subjects with RSs was significantly higher after age 71 years, and velocity was correlated, not with age, but with head impulse velocity.
VOR gain was stable until age 90 years and thereafter dropped. However, this decrease occurred progressively in younger subjects as head impulse velocity increased, with VOR gain for faster head impulses decreasing significantly in subjects older than 70 years. This finding, in addition to the appearance of RSs, can be explained by the effect of aging on the deterioration of the vestibular system in the semicircular canals.
The purpose of this study was to evaluate if the intensity of recurrent chronic pain would modify postural performance in reaching the functional limits of stability (LOS) in chronic low back pain (CLBP) patients.
Three groups of subjects were investigated. Healthy persons comprised the asymptomatic group (n = 32) while CLBP patients (n = 36) were divided into 2 subgroups, according to the reported intensity of resting pain on a numerical rating scale: patients with low (LP) and high pain (HP) levels. The maximal displacement of the center of pressure (COP) indexing the LOS magnitude and the COP mean velocity indexing the performance in reaching LOS were calculated on a Kistler force plate during forward and backward voluntary body lean with eyes open (EO) or closed (EC).
The forward LOS was lower in both the LP (P < .01) and HP (P < .01) subgroups than in the asymptomatic under EO and EC conditions, while no differences between the LP and HP groups were found. The backward LOS was lower in the HP group than in asymptomatic but only with EC (P = .01). Eye closure caused an increase in forward (P = .02) and backward (P = .001) COP velocity in the LP group and forward COP velocity in the asymptomatic (P = .04) only. With EC, the only intergroup difference was lower forward COP velocity in the HP than LP group (P = .04).
Subjects with CLBP had reduced forward LOS regardless the pain level. However, the higher level of pain was associated with slower execution of voluntary leaning tasks, with EC only.
Patients with unilateral vestibular lesions have a set of deficits requiring compensation based on the inherent plasticity of the central nervous system. In the 1940s, it was reported that patients with unilateral vestibular dysfunctions who exercised recovered faster than those who did not. The present prospective, randomized investigation aimed to assess the role of a computerized posturography-assisted early vestibular rehabilitation protocol combined with a home-based exercise program in the treatment of patients with unilateral peripheral vestibular disorders occurring 2 weeks previously. Fifteen patients were randomly assigned to a 5-week posturography-assisted vestibular rehabilitation protocol and a home-based exercise program (Group A), while 15 simply awaited spontaneous compensation (Group B). All patients underwent computerized posturography approximately 2 weeks after their vestibular disorder was diagnosed and again after 6 weeks. Ten healthy volunteers were also studied (Group C). After rehabilitation, Group A patients improved significantly in most sensory measures [modified clinical test of sensory organization and balance (mCTSIB)] and motor parameters [limits of stability (LOS)] by comparison with preliminary outcomes, and there were no significant differences in sensory (mCTSIB) and motor (LOS) findings between Group A and the healthy volunteers. At the same time point, several motor (LOS) parameters were still altered in Group B by comparison with the healthy volunteers. These preliminary outcomes support the hypothesis that the compensation achievable after 6 weeks with a customized program of posturography-assisted vestibular rehabilitation and home-based exercises is superior to the results of physiological spontaneous compensation.
Accelerometry (ACC) shows promise as an easily implemented clinical measure of balance. The purpose of the study was to estimate test-retest reliability of ACC measures and determine the relationship between ACC measured at the pelvis and underfoot center of pressure (COP) measures during sensory organization test (SOT) conditions. Eighty-one subjects were recruited from the community with no known orthopedic or vestibular deficits (19-85 years). Subjects completed three consecutive, ninety second trials for each of the six SOT conditions, while wearing the accelerometer. ACC and COP time series were described by calculating the normalized path length, root mean square (RMS), and peak-to-peak values. The test-retest reliability of the three measures within each SOT condition was estimated over three trials using the intraclass correlation coefficient. ACC and COP test-retest reliability were similar, ranging from 0.63 to 0.80 using ACC and 0.42 to 0.81 using COP for the measure of normalized path length. Linear regression between ACC and COP measures showed significant correlation under almost every SOT condition using both single and average measures across trials. The degree of association between COP and ACC was equivalent when using the first trial or the 3-trial average, suggesting that one trial may be sufficient. The use of accelerometry may have value in estimating balance function and minimizing clinical evaluation time.
1. Measurements of human upright body movements in three dimensions have been made on thirty-five male subjects attempting to stand still with various stance widths and with eyes closed or open. Body motion was inferred from movements of eight markers fixed to specific sites on the body from the shoulders to the ankles. Motion of these markers was recorded together with motion of the point of application of the resultant of the ground reaction forces (centre of pressure). 2. The speed of the body (average from eight sites) was increased by closing the eyes or narrowing the stance width and there was an interaction between these two factors such that vision reduced body speed more effectively when the feet were closer together. Similar relationships were found for components of velocity both in the frontal and sagittal planes although stance width exerted a much greater influence on the lateral velocity component. 3. Fluctuations in position of the body were also increased by eye closure or narrowing of stance width. Again, the effect of stance width was more potent for lateral than for anteroposterior movements. In contrast to the velocity measurements, there was no interaction between vision and stance width. 4. There was a progressive increase in the amplitude of position and velocity fluctuations from markers placed higher on the body. The fluctuations in the position of the centre of pressure were similar in magnitude to those of the markers placed near the hip. The fluctuations in velocity of centre of pressure, however, were greater than of any site on the body. 5. Analysis of the amplitude of angular motion between adjacent straight line segments joining the markers suggests that the inverted pendulum model of body sway is incomplete. Motion about the ankle joint was dominant only for lateral movement in the frontal plane with narrow stance widths (< 8 cm). For all other conditions most angular motion occurred between the trunk and leg. 6. The large reduction in lateral body motion with increasing stance width was mainly due to a disproportionate reduction in the angular motion about the ankles and feet. A mathematical model of the skeletal structure has been constructed which offers some explanation for this specific reduction in joint motion.(ABSTRACT TRUNCATED AT 400 WORDS)
We measured variability of foot placement during gait to test whether lateral balance must be actively controlled against dynamic instability. The hypothesis was developed using a simple dynamical model that can walk down a slight incline with a periodic gait resembling that of humans. This gait is entirely passive except that it requires active control for a single unstable mode, confined mainly to lateral motion. An especially efficient means of controlling this instability is to adjust lateral foot placement. We hypothesized that similar active feedback control is performed by humans, with fore-aft dynamics stabilized either passively or by very low-level control. The model predicts that uncertainty within the active feedback loop should result in variability in foot placement that is larger laterally than fore-aft. In addition, loss of sensory information such as by closing the eyes should result in larger increases in lateral variability. The control model also predicts a slight coupling between step width and length. We tested 15 young normal human subjects and found that lateral variability was 79% larger than fore-aft variability with eyes open, and a larger increase in lateral variability (53% vs. 21%) with eyes closed, consistent with the model's predictions. We also found that the coupling between lateral and fore-aft foot placements was consistent with a value of 0.13 predicted by the control model. Our results imply that humans may harness passive dynamic properties of the limbs in the sagittal plane, but must provide significant active control in order to stabilize lateral motion.
Gait initiation is a transient procedure between orthostatic posture and steady-state locomotion and includes anticipatory anteroposterior (AP) and lateral movements. Commands for this task are located in some levels of brain stem, which modulates activity of central pattern generator in the spinal cord. The purpose of this work was to explore the role of the vestibular system in this voluntary stepping.
Six patients with chronic bilateral vestibular loss (BVL) were measured by means of a large force plate (70 cm x 120 cm ) and the displacement of the center of pressure (COP) during gait initiation was calculated. Measurement parameters comprised maximum distance (MD), velocity (MV) in the AP and lateral direction as well as for pre-, first- and second-step stages, and the angle of the COP trajectory.
For all stages, BVL patients registered lower values for both MD and MV in the AP direction than did normal subjects. In the lateral direction, however, neither MD nor MV in BVL patients showed any difference from those of normals. The step angle of the COP trajectory was obviously reduced.
These results suggest that in the AP direction, the vestibulospinal pathway can influence the locomotor related neural circuits, including the central pattern generator and supraspinal levels, by means of modifying the velocity and step length in order to stabilize the trunk. On the other hand, the control mechanism in the lateral direction may be different from that in the AP direction.
The stability limits of erect stance are described as a geometrical structure in a movement space. Mechanical properties and response latency, a neural property, are determining factors for the stability limits. Standing stability limits of adults and young children are compared, and a simple scheme is suggested by means of which infants can discover the stability limits as they learn to stand. The mechanics of different standing movements are discussed because their spatial temporal properties relate directly to their different stability limits. The combination of the stability limits for different movements gives a total set of stability limits, a different structure for adults than for children.
To determine the effect of vestibular rehabilitation on reduction of fall risk in individuals with unilateral vestibular hypofunction and to identify those factors that predict fall risk reduction.
Retrospective chart review.
Tertiary referral center.
Forty-seven patients with unilateral vestibular hypofunction, aged 28 to 86 years, who were at risk for falls on initial assessment.
All patients underwent vestibular rehabilitation including adaptation exercises, designed to improve gaze stability, and gait and balance exercises.
Fall risk (Dynamic Gait Index), visual acuity during head movements (Dynamic Visual Acuity), and subjective complaints were measured initially, at 2-week intervals, and at completion of physical therapy.
As a group, the patients had significantly reduced risk for falls (p <0.001) after rehabilitation. Time from onset of symptoms did not affect the efficacy of vestibular rehabilitation. Both older (> or = 65 yr) and younger (< 65 yr) adults showed significant reductions in fall risk with vestibular rehabilitation (p <0.001). However, a significantly greater proportion (Chi2= 0.016) of older adults remained at risk for falls at discharge compared with young adults (45% versus 11%). Initial Dynamic Gait Index and Dynamic Visual Acuity scores predicted fall risk reduction in patients with unilateral vestibular hypofunction. A model was developed using initial Dynamic Gait Index and Dynamic Visual Acuity scores to predict fall risk reduction.
Vestibular rehabilitation is effective in significantly reducing fall risk in individuals with unilateral vestibular deficit. The model predicts fall risk reduction with good sensitivity (77%) and specificity (90%).
The postural instability of patients with vestibular loss (11 with bilateral and 101 with unilateral vestibular loss) at different times following the lesion was investigated by means of posturography and compared to healthy subjects. In addition, subjects submitted to galvanic vestibular stimulation were also studied to compare their postural performances with those of patients with complete unilateral vestibular lesion. The platform consisted of a static computerized force platform, on which a seesaw platform could be placed to test the subjects in dynamic conditions. The displacement of the center of foot pressure was measured under different conditions: subjects standing on the fixed platform, eyes open and eyes closed and subjects standing on the seesaw platform, eyes open and eyes closed. In the last condition, balance was tested in the subject's pitch plane by allowing the platform to rotate forwards and backwards only and in the patient's roll plane by allowing the platform to rotate to the left and to the right. The results showed that in static conditions, only bilateral vestibular loss patients had abnormal values compared to controls. In contrast, in dynamic eyes-closed conditions, both bilateral and unilateral patients could be differentiated from controls. Bilateral patients were unable to stand up without falling in both pitch and roll planes. Unilateral patients fell in the first week following the lesion and exhibited increased postural oscillations in both planes from the 2-week up to the 1-year postlesion stage. In addition and more importantly, they fell more often or had higher sway in the roll than in the pitch plane. Therefore, this study suggests that dynamic posturography on a seesaw platform could be a valuable tool for clinical diagnosis and quantitative analysis of imbalance in patients suffering from a unilateral vestibular loss up to 1 year after the lesion.
We present here the results of a short-term prospective study on a group of 37 patients with persistent unsteadiness. The treatment of these patients was customized according to the results of the Sensory Organization Test carried out using computerized dynamic posturography. A 5-week period of instrumental rehabilitation was established involving visual biofeedback-based computerized balance intervention that manipulated the individuals' capacities, the goals of the tasks and the environmental context. Exercises were performed twice weekly. This adaptation of the treatment was based on the hypothesis that it would reduce the level of disability and handicap associated with the unsteadiness suffered by these patients. Of the patients, 73% improved their status according to the DHI results. Furthermore, in the group of patients that showed an improvement in the DHI, their SOT composite score increased significantly, their reaction time reduced and their sway velocity, endpoint excursion, maximum excursion and directional control all increased. However, for those patients who did not experience a significant improvement or who recorded an increase in the total DHI score, the modifications in the SOT and LOS tests were not significant.
Functional stability limits (FSLs) are the percentage of the base of support that individuals are willing to extend their centre of pressure. The objective of this study was to provide construct validation of FSLs as a measure of balance by comparing FSLs across ages and with clinical balance measures. A total of 52 participants volunteered. FSLs significantly decreased with age (p < 0.004). Correlations between FSLs and age (-0.56 < R < -0.73), multi-directional reach test (0.35 < R < 0.75) and anteroposterior and mediolateral centre of pressure excursions during static stance (-0.29 < R < -0.72) were generally moderate to good. Cronbach's alpha (0.75) indicated that these measures were internally consistent, i.e. measuring similar aspects of the balance construct. FSLs appear to be valid indicators of balance ability. They may be used in posture prediction models to determine when a step is required when reaching or lifting objects and in biomechanical models as a means of incorporating stability constraints.