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At least 1,009 records · Page 56Linked to original sources
PubMed2003

Postural stability in the elderly during sensory perturbations and dual tasking: the influence of refractive blur.

PURPOSE: To determine the influence of refractive blur on postural stability during somatosensory and vestibular system perturbation and dual tasking. METHODS: Fifteen healthy, elderly subjects (mean age, 71 +/- 5 years), who had no history of falls and had normal vision, were recruited. Postural stability during standing was assessed using a force platform, and was determined as the root mean square (RMS) of the center of pressure (COP) signal in the anterior-posterior (A-P) and medial-lateral directions collected over a 30-second period. Data were collected under normal standing conditions and with somatosensory and vestibular system perturbations. Measurements were repeated with an additional physical and/or cognitive task. Postural stability was measured under conditions of binocular refractive blur of 0, 1, 2, 4, and 8 D and with eyes closed. The data were analyzed with a population-averaged linear model. RESULTS: The greatest increases in postural instability were due to disruptions of the somatosensory and vestibular systems. Increasing refractive blur caused increasing postural instability, and its effect was greater when the input from the other sensory systems was disrupted. Performing an additional cognitive and physical task increased A-P RMS COP further. All these detrimental effects on postural stability were cumulative. CONCLUSIONS: The findings highlight the multifactorial nature of postural stability and indicate why the elderly, many of whom have poor vision and musculoskeletal and central nervous system degeneration, are at greater risk of falling. The findings also highlight that standing instability in both normal and perturbed conditions was significantly increased with refractive blur. Correcting visual impairment caused by uncorrected refractive error could be a useful intervention strategy to help prevent falls and fall-related injuries in the elderly.

Aged↗
PubMed2003

Postural stability changes in the elderly with cataract simulation and refractive blur.

PURPOSE: To determine the influence of cataractous and refractive blur on postural stability and limb-load asymmetry (LLA) and to establish how postural stability changes with the spatial frequency and contrast of the visual stimulus. METHODS: Thirteen elderly subjects (mean age, 70.76 +/- 4.14 [SD] years) with no history of falls and normal vision were recruited. Postural stability was determined as the root mean square [RMS] of the center of pressure (COP) signal in the anterior-posterior (A-P) and medial-lateral directions and LLA was determined as the ratio of the average body weight placed on the more-loaded limb to the less-loaded limb, recorded during a 30-second period. Data were collected under normal standing conditions and with somatosensory system input disrupted. Measurements were repeated with four visual targets with high (8 cyc/deg) or low (2 cyc/deg) spatial frequency and high (Weber contrast, approximately 95%) or low (Weber contrast, approximately 25%) contrast. Postural stability was measured under conditions of binocular refractive blur of 0, 1, 2, 4, and 8 D and with cataract simulation. The data were analyzed in a population-averaged linear model. RESULTS: The cataract simulation caused significant increases in postural instability equivalent to that caused by 8-D blur conditions, and its effect was greater when the input from the somatosensory system was disrupted. High spatial frequency targets increased postural instability. Refractive blur, cataract simulation, or eye closure had no effect on LLA. CONCLUSIONS: Findings indicate that cataractous and refractive blur increase postural instability, and show why the elderly, many of whom have poor vision along with musculoskeletal and central nervous system degeneration, are at greater risk of falling. Findings also highlight that changes in contrast sensitivity rather than resolution changes are responsible for increasing postural instability. Providing low spatial frequency information in certain environments may be useful in maintaining postural stability. Correcting visual impairment caused by uncorrected refractive error and cataracts could be a useful intervention strategy to help prevent falls and fall-related injuries in the elderly.

Aged↗
PubMed2005

The effect of cataract surgery on postural control.

PURPOSE: Falls are a significant cause of morbidity in the elderly. Because decreased vision is known to be a significant risk factor for falling in this age group, we sought to examine the effect of the removal of cataract, a major cause of visual handicap, on postural stability. METHODS: Postural stability was measured in 23 patients who underwent cataract surgery, before and 1 to 4 months after surgery. Stability indices included Stability Effect, Fourier Spectrum of Postural Sway, and Synchronizations, and, based on these measurements, Falling Index, which had been shown in earlier studies to predict the risk of falling. RESULTS: Visual acuity in the surgical eye significantly improved in all patients after surgery (P < 0.01) and did not change in the fellow eye. Stability improved in most patients (19/23) and Fourier Spectrum of Postural Sway improved in the high-frequency bands (above 0.5 Hz), when viewing with the surgical eye, but not when viewing with the nonsurgical eye (P < 0.05). By Falling Index, before surgery, 12 of 23 patients were at high risk of falling, and only six were at low risk. After surgery, 16 of 23 were at low risk and only three remained at high risk (chi(2) test, P < 0.008). CONCLUSIONS: Cataract surgery significantly improves postural stability. Considering the high cost of treating fall-related injuries in the elderly, the findings may imply that cataract surgery is cost effective in this regard.

Accidental Falls↗
PubMedDate not supplied

The relationship between lower extremity functional strength and severity of peripheral arterial disease.

The purposes of this study were to (1) determine if peripheral arterial disease (PAD) severity is related to deficits in lower extremity functional strength, (2) identify covariates that might affect the relationship between lower extremity functional strength and severity of PAD, and (3) determine if the relationship between lower extremity functional strength and severity of PAD still persists after statistically controlling for significant covariates. A total of 144 patients were grouped into tertiles according to disease severity. Patients having an ankle-brachial index (ABI) of 0.76 to 0.90 were classified as having mild PAD (high ABI group), 0.51 to 0.75 classified as having moderate PAD (moderate ABI group), and 0.36 to 0.50 as having severe PAD (low ABI group). Lower extremity functional strength was assessed using the chair-stand test where the time to complete 5 consecutive stand-to-sit transfers was recorded. Patients were also characterized on ambulatory function and clinical characteristics. The moderate ABI group took significantly (p < 0.05) less time (13.49 +/- 0.49 s) to complete the chair-stand test than the low ABI group (15.86 +/- 0.63 s). Both daily physical activity level and total 6-minute walk distance were identified as significant covariates (p < 0.05) of lower extremity functional strength. After controlling for daily physical activity level and total 6-minute walk distance, no significant differences (p > 0.05) in the time to complete the chair-stand test existed between the ABI groups. These findings indicate that the greater impairment in lower extremity functional strength in patients with severe PAD is explained by their lower physical activity level and poorer overall walking ability.

Aged↗
PubMedDate not supplied

Computerized screening of the human vestibulospinal system.

The vestibular nerve projects rostrally via the ascending medial longitudinal fasiculus (MLF) to eventually supply the ocular muscles and also projects caudally via the descending MLF to eventually supply the spinal and limb musculature. Electronystagmographic techniques are designed to evaluate only portions of the vestibulo-ocular and oculomotor systems. Vestibular lesions affecting only the caudal vestibular nerve distributions or lesions affecting both neural distributions, therefore, cannot be objectively assessed except for the vestibulo-ocular component. A promising recording technique for the evaluation of the vestibulospinal system has been developed and tested in the Raymond E. Jordan Human Vestibular Systems Laboratory. A comparison of two data analysis techniques in normal subjects, unilateral vestibular lesion patients and patients with unilateral lesions of the cerebellar hemispheres have provided pilot data which indicate that the vestibulospinal stability test technique holds considerable promise for both research and clinical evaluation of the human vestibulospinal system.

Adult↗
PubMedDate not supplied

Reference values for serial vestibular testing.

This study defines the normal limits of day-to-day variation in vestibular function. A short-acting caloric test was used and nystagmus intensity was measured by means of an interactive computerized technique. Data were analyzed from 30 normal subjects tested on three successive days and from ten of these subjects who were also tested on 11 additional occasions. Individual caloric test scores generally remained between 55% and 170% of their initial value; narrower ranges resulted when scores were averaged together. There was very little habituation of caloric responses. The upper normal limits of test-retest variation in scores for right-left difference and directional preponderance of caloric responses were 24% and 22%, respectively.

Caloric Tests↗
PubMed1989

Vestibulospinal findings in two syndromes with spontaneous vertigo attacks.

The influence of vestibular dysfunction upon the vestibulospinal reflex (VSR) in two common peripheral syndromes was investigated by two types of posturographic examination: "static" posturography, recording and analyzing the postural sway in stance, and "kinetic" posturography, recording the stepping in place test. The influence of the dysfunction was examined outside the attacks, ie, between attacks and not during or immediately after an attack, in patients with Meniere's disease and in others with a sudden vestibular loss syndrome, "neuronitis." However, in both syndromes the influence of the dysfunction was obvious only in some patients; this indicates that central adaptation intervened in the other patients. In this way, central compensation related to the VSR was assessed and compared with compensation for the vestibulo-ocular reflex assessed by the rotation tests. Discordance was shown in a number of cases, ie, a number of cases showed compensation for one reflex, but not for the other. Comparison of the results of both posturographic methods also showed discordance. Normal performance in the walking test could not always be correlated with normal performance in the standing test and vice versa.

Humans↗
PubMed1991

Orthostatic postural control in vestibular neuritis: a stabilometric analysis.

Posturographic data for 182 vestibular neuritis patients were recorded on a static posturographic platform (stabilometry) with the patients' eyes both open and closed. Three of the parameters studied are presented here: mean position of the center of pressure, area of the statokinesigram, and Romberg's quotient. Vestibular neuritis modifies the performance of the fine-postural system in unpredictable ways, varying with the subject. It may disturb either the mean position of the center of pressure or the integration of visual input. Sixty of the patients in this study did not use visual input to stabilize their position in relation to their surroundings. The value of stabilometry as a method for observing the integration of visual input in the control of orthostatic posture is discussed.

Adult↗
PubMed1991

Tullio phenomenon and postural stability: experimental study in normal subjects and patients with vertigo.

The effect of low-frequency sound (LFS) on postural stability was studied in 55 healthy volunteers and in 152 patients with vertigo due to different types of inner ear disease. The sound pressure levels ranged from 130 to 132 dB and were given at frequencies of 25, 50, and 63 Hz. The duration of each stimulation lasted 30 seconds. The postural responses were measured with a force platform. The LFS stimulation improved the postural stability of the healthy subjects through the alerting response. We did not observe any difference in the body sway according to whether the LFS was delivered with monaural or binaural stimulation. Twenty-six percent of the patients with Meniere's disease, 40% with chronic otitis media with vertigo, and 26% with vertigo of peripheral origin experienced significant postural instability at least at two of the three test frequencies during stimulation with LFS. The results demonstrate that in subjects with different types of inner ear disease the vestibular system starts to respond to LFS. The activation of vestibulospinal responses by LFS seems to be an expression of the Tullio phenomenon.

Acoustic Stimulation↗
PubMed1993

Postural control in young and elderly adults when stance is challenged: clinical versus laboratory measurements.

The use of dynamic posturography (EquiTest) for the characterization of postural control biomechanics would be aided by specific knowledge of what the measured data imply about body segment movements. To investigate this issue, the biomechanics of a group of 15 healthy elderly subjects were compared to those of healthy young subjects by using both dynamic posturography and a laboratory movement and force measuring system. The results from EquiTest were analyzed by 1) routine clinical interpretation of data and 2) a clinical research interpretation by subjecting the EquiTest parameters to additional statistical comparison of mean performance of the young and elderly groups. The young-elderly differences from the 2 EquiTest analyses were then compared to the young-elderly differences derived from the laboratory protocol. The routine clinical interpretation of EquiTest data identified the same increases in sway shown by the laboratory study, but did not reveal the more subtle differences indicated by the laboratory study. When the EquiTest data were subjected to additional statistical analysis, the characterization of difference between young and elderly subjects was the same as that of the laboratory study, with the exception of issues of head versus trunk movement, a measure not made by EquiTest. This essential similarity in the characterization of elderly compared to young subjects by both systems suggests 1) that EquiTest is able to detect subtle differences in biomechanics of postural control between young and elderly healthy adult groups and 2) that implied movements of center of gravity, trunk versus lower limbs, and strength of reaction measures are consistently detected by both EquiTest and the laboratory kinematics and dynamics measurement systems.

Adolescent↗
PubMed1995

Vestibular and sensory interaction deficits assessed by dynamic platform posturography in patients with multiple sclerosis.

Vestibular impairments have not been routinely identified in patients with multiple sclerosis (MS), because of the confounding effects of deficits in other neural systems. In this study, 35 patients with MS were evaluated by means of a systematic alteration of the sensory environment (dynamic posturography) in order to identify those patients who became unstable when vestibular inputs were needed to maintain stance. Subjects were assigned to either a high-function (HF) or a low-function (LF) group on the basis of a functional status assessment score obtained prior to the posturography test. For the HF group, 30% (7/23) had abnormal posturography scores. Of those subjects, 3 had a vestibular dysfunction pattern or a somatosensory-vestibular impairment. In contrast, 58% of the LF group (7/12) had abnormal posturography scores. Nearly all of these LF patients (6/7) had a vestibular dysfunction pattern or a combined visual-vestibular or somatosensory-vestibular impairment. Posturography might serve as one method to evaluate the functional consequences of a vestibular deficit in patients with MS.

Adult↗
PubMed1992

Equilibrium.

Explore the source record for details and available documents.

Humans↗
PubMed1993

Oscillopsia in patients with loss of vestibular function.

Contrary to standard teaching, many patients with bilateral vestibular loss clearly deny oscillopsia or imbalance in darkness. In an attempt to characterize these patients within the larger population of all patients with bilateral vestibular loss, the rotation and posturography test results of 22 patients with bilateral vestibular loss were reviewed. In addition, dynamic visual acuity was assessed with an eye chart test. There was a poor relationship between oscillopsia and dynamic visual acuity or rotation testing. There were three patterns of response on rotation testing, and loss of high-frequency gain was seen in as many patients who reported oscillopsia as did not. There were some patients with normal gain values at all frequencies tested who reported oscillopsia. It may be that the change in the VOR, rather than the absolute VOR loss, is responsible for the production of oscillopsia. On the basis of this and other studies, treatment strategies for patients with bilateral vestibular loss are suggested.

Adolescent↗
PubMed1994

Sensory interaction posturography in patients with peripheral vestibular disorders.

The results of posturography, using all sensory inputs, are compared with recordings when one or more of the sensory inputs are altered by the test conditions. This gives an idea of the sensory interaction in central compensation in the vestibulospinal reflex. Positive and negative effects could be observed in patients with peripheral vestibular disorders.

Female↗
PubMed2003

A hypothesis: self-propulsion in a wheelchair early after stroke might not be harmful.

BACKGROUND: There is often strong clinical resistance to patients self-propelling a wheelchair post stroke as this is believed to produce immediate increases in abnormal posture and movement. Research to support this viewpoint is limited. OBJECTIVE: To begin investigation of the immediate effects of self-propulsion on symmetrical sitting. DESIGN: Replicated single-case studies ABABA. SETTING: Movement analysis laboratory. SUBJECTS: Four patients, a maximum of eight weeks post stroke and six age-matched healthy volunteers. INTERVENTIONS: Subjects sat in the wheelchair during the A phases and self-propelled forwards during the B phases. The Manchester Active Position Seat (consists of 68 force transducers which transmit data at 10 Hz) measured the magnitude of peak force and the position of peak force on both sides of the seat. The mean symmetry index and standard deviation for each study phase were calculated and graphed for each subject. Interpretation was by visual inspection. RESULTS: Only one stroke patient and one volunteer increased asymmetry of magnitude of peak force following the two periods of self-propulsion. Only one of the stroke patients increased asymmetry of position of peak force following self-propulsion compared with three of the healthy volunteers. CONCLUSIONS: These results raise the hypothesis that self-propulsion early post stroke might not produce immediate detrimental effects on seated symmetry.

Aged↗
PubMed2007

The ability of the Biodex Stability System to distinguish level of function in subjects with a second-degree ankle sprain.

OBJECTIVE: To assess the capacity of the Biodex Stability System using a one-leg stance protocol to differentiate between injured and non-injured limbs and between level of disabilities. DESIGN: Cross-sectional study. SETTING: Military and civilian clinic. SUBJECTS: Thirty-four individuals with a second-degree lateral ankle sprain and 36 healthy subjects. METHODS AND MEASURES: Subjects were tested on the Stability System 30 days after injury using a one-leg stance protocol in the dynamic limit-of-stability mode. All subjects also filled out a disability questionnaire (Lower Extremity Functional Scale). The groups were compared based on the overall dynamic limit-of-stability score and its relationship with the score on the disability questionnaire was also examined. RESULTS: The overall dynamic limit-of-stability scores (subjects with a lateral ankle sprain: 13.0% (5.5)-26.0% (9.2); healthy subjects: 16.9% (7.9)-27.9% (9.6)) clustered in the lower end of the theoretical range of 0-100%. Statistically significant differences in the overall dynamic limit-of-stability scores were found between the injured and non-injured limbs but group differences were small and clinically not relevant. No significant relationships were found between the overall dynamic limit-of-stability scores and the Lower Extremity Functional Scale scores (58.2 (11.8)) of the subjects with a lateral ankle sprain. CONCLUSIONS: The one-leg stance protocol carried out in the dynamic limit-of-stability mode is very challenging and offers a very limited capacity to differentiate between injured and non-injured limbs. The main outcome of the Stability System does not appear to be a good indicator of the functional capacity of people with a lateral ankle sprain.

Adult↗
PubMedDate not supplied

A stabilometric technique for evaluation of lower limb instabilities.

Stabilometry is a technique designed to register postural equilibrium control. This investigation used a computerized strain gauge force plate to measure sway movements in the frontal plane with the patient standing on one leg. Fifty-five young healthy individuals were studied as a reference group and to determine the reproducibility of the method. The clinical population consisted of 14 patients with unilateral injuries to the lateral ligaments of the ankle. These were measured, both with and without an ankle brace. The different parameters used to describe the body sway could well discriminate between the injured and the uninjured leg. When the brace was used the effect was obvious and none of the parameters showed any significant difference compared to the uninjured leg.

Adolescent↗