Assessment of the risk of fall, related to visual stimulation, in patients with central vestibular disorders

Study on the Difference of Human Body Balance Stability Regulation Characteristics by Time-Frequency and Time-Domain Data Processing Methods

This paper aims to investigate the differences in standing balance control ability between freestyle skiing aerials athletes and ordinary graduate students by means of wavelet transform (WT) and the overall stability index (OSI) and to discover the characteristics of the postural control ability of dissimilar subjects and appropriate methods to assess the postural control ability of the human body.

RESEARCH METHODS

In all, 16 subjects were tested, including 8 from the Chinese national team who had won the world championships of freestyle skiing aerials, with 10+ years of training (age: 23 ± 23.1 years, Height: 176 ± 2.1 cm, and weight: 69 ± 3.5 kg), and 8 ordinary graduate students of Shenyang Institute of Physical Education (age: 22.6 ± 4.6 years, Height: 179 ± 3.3 cm, and weight: 73 ± 4.1 kg). When performing the tasks, the research subjects were required to stand on the steady support surface (with eyes closed and legs closed) for 30 s in each testing. The displacement data of the anteroposterior (AP) direction and the mediolateral (ML) direction of their centre of pressure (COP) were recorded. Then, WT and OSI were calculated. Two dissimilar methods were compared to analyse the characteristics of balance ability.

RESULTS

(1) The athletes' WT values in the AP direction and the ML direction were concentrated in the interval of 22~30 s and 0-8 s, respectively, while the ordinary graduate students' WT values in the AP direction and the ML direction were concentrated in the interval of 10~25 s and 0-7 s, respectively; (2) the WT values of the regular graduate students in the AP direction and the ML direction were higher than those of the athletes (p < 0.01); and (3) the OSI value in the AP direction of the athletes was higher than of the ordinary graduate students, while the OSI value in the ML direction of the athletes was lower than that of regular graduate students.

CONCLUSION

Compared to the OSI, WT can analyse the characteristics of balance control ability more effectively. The COP displacement frequencies of the athletes and ordinary graduate students were concentrated in the low-frequency bands. The athletes had superior adjustment ability in an imbalanced state and could adjust to the best position without effort. In addition, the athletes had a stronger adaptive ability. In comparison, the ordinary graduate students had comparatively poor adaptive ability and weak adjustment ability in the imbalanced state, so it was difficult for them to attain the best angle after adjustment.

Individuals with cerebral palsy show altered responses to visual perturbations during walking

Individuals with cerebral palsy (CP) have deficits in processing of somatosensory and proprioceptive information. To compensate for these deficits, they tend to rely on vision over proprioception in single plane upper and lower limb movements and in standing. It is not known whether this also applies to walking, an activity where the threat to balance is higher. Through this study, we used visual perturbations to understand how individuals with and without CP integrate visual input for walking balance control. Additionally, we probed the balance mechanisms driving the responses to the visual perturbations. More specifically, we investigated differences in the use of ankle roll response i.e., the use of ankle inversion, and the foot placement response, i.e., stepping in the direction of perceived fall. Thirty-four participants (17 CP, 17 age-and sex-matched typically developing controls or TD) were recruited. Participants walked on a self-paced treadmill in a virtual reality environment. Intermittently, the virtual scene was rotated in the frontal plane to induce the sensation of a sideways fall. Our results showed that compared to their TD peers, the overall body sway in response to the visual perturbations was magnified and delayed in CP group, implying that they were more affected by changes in visual cues and relied more so on visual information for walking balance control. Also, the CP group showed a lack of ankle response, through a significantly reduced ankle inversion on the affected side compared to the TD group. The CP group showed a higher foot placement response compared to the TD group immediately following the visual perturbations. Thus, individuals with CP showed a dominant proximal foot placement strategy and diminished ankle roll response, suggestive of a reliance on proximal over distal control of walking balance in individuals with CP.

A quantitative analysis of postural control in elderly patients with vestibular disorders using visual stimulation by virtual reality

Introduction

Postural instability is one the most common disabling features in vestibular disorders.

Objective

This study aimed to analyze the limit of stability and the influence of manipulation of visual, somatosensorial and visual–vestibular information on postural control in older adults with vestibular disorder, with and without a history of falls.

Methods

Cross-sectional study. Participants – 76 elderly patients with vestibular disorder (G1, without falls; G2, with falls) and 41 healthy elderly subjects (control group; CG). Using posturography, analyzed were limit of stability area, body center of pressure, and velocity of oscillation in the standing position in 10 conditions, including open/closed eyes, unstable surface with eyes closed, saccadic and optokinetic stimuli, and visual–vestibular interaction.

Results

Limit of stability area in CG was better compared with G1-2, and center of pressure values were worse in G1 than in CG. Center of pressure area in all conditions and velocity of oscillation in the following conditions: open/closed eyes, optokinetic stimulation, and visual–vestibular interaction showed worse values in G2 than in CG. Center of pressure area in the following conditions: open/closed eyes, saccadic and optokinetic stimuli, visual–vestibular interaction, and unstable surface with eyes closed showed worse values in G2 than in G1.

Conclusion

Older adults with vestibular disorder presented reduced limit of stability and increased postural sway in the following conditions: conflict between visual and somatosensory information and visual–vestibular interaction. Deterioration in postural control was significantly associated with history of falls.

Postural response characterization in elderly patients with bilateral vestibular hypofunction

CONCLUSIONS

The measurement of the energy consumption (EC) of the body's center of pressure (COP) to maintain the upright stance position was higher in elderly patients with bilateral vestibular hypofunction (BVH) compared with a control group and may be a valid parameter in the assessment of balance disorders.

OBJECTIVE

The aim of the study was to evaluate the energy consumption of the COP in elderly patients with BVH.

METHODS

The COP was recorded on a force platform (FP) for eight elderly patients with BVH related to aging and eight normal control group subjects. The EC of the COP was calculated using the discrete wavelet transform. The two groups were tested in standing position on the FP in three sensory conditions:1, eyes open; 2, eyes closed; and 3, standing on a foam pad placed on the force platform. Wilcoxon's rank test and multi-factor analysis of variance were used, with the level of significance set at 0.05.

RESULTS

BVH patients showed higher values of EC of the COP signal measured in arbitrary units compared with the control group (conditions 1 and 2). None of the BVH patients could perform the test in condition 3. BVH patients had increased EC in the frequency band between 0.1 and 0.78 Hz when the visual information was canceled (condition 2).

Vestibular rehabilitation strategies and factors that affect the outcome

Ever since the introduction of Cawthorne-Cooksey exercises, vestibular rehabilitation (VR) has been gaining popularity in the treatment of the dizzy patient. Numerous studies support the effectiveness of VR in improving balance/walking skills, eye-head coordination and the quality of life of the patient. Different rehabilitation protocols have been used to treat patients with peripheral and central vestibular disorders. Assessment of the patients' progress is based on the patients' selfperception of dizziness and their functional skills. Factors such as age, medication, time of onset of vertigo and home based VR have been evaluated on their effect on the rehabilitation's outcome. The aim of this review is to evaluate rehabilitation strategies and discuss the factors that affect the outcome.

Multiple timescales in postural dynamics associated with vision and a secondary task are revealed by wavelet analysis

Discrete wavelet analysis is used to resolve the center of pressure time series data into several timescale components, providing new insights into postural control. Healthy young and elderly participants stood quietly with their eyes open or closed and either performed a secondary task or stood quietly. Without vision, both younger and older participants had reduced energy in the long timescales, supporting the concept that vision is used to control low frequency postural sway. Furthermore, energy was increased at timescales corresponding to closed-loop (somatosensory and vestibular) and open-loop mechanisms, consistent with the idea of a shift from visual control to other control mechanisms. However, a relatively greater increase was observed for older adults. With a secondary task a similar pattern was observed-increased energy at the short and moderate timescales, decreased energy at long timescales. The possibility of a common strategy-at the timescale level-in response to postural perturbations is considered.

Rehabilitation of Balance After Stroke With Multisensorial Training: A Single-Blind Randomized Controlled Study

Objective. To compare 2 rehabilitation strategies to improve balance after stroke: (1) a multisensorial approach based on higher intensity of balance tasks and exercise during visual deprivation and (2) a conventional neurodevelopmentaltheory-based treatment (NDT) that used a general approach for sensorimotor rehabilitation. Methods . This prospective, multicenter, randomized, parallel-group study measured outcomes with blinded assessors. Sixty-eight patients able to walk without human assistance were entered from 3 to 15 months (mean, 7 months) after a first hemispheric stroke. They received 20 sessions in 4 weeks of NDT or multisensorial rehabilitation. On day 0, day 30, and day 90, assessment included the Berg Balance Scale (BBS), posturography, gait (velocity, double stance phase, climbing 10 steps, amount of walking per day), the Functional Independence Measure, and the Nottingham Health Profile. Results. All subjects improved significantly in balance and walking parameters. Regarding the main dependent variable (BBS on day 30), no difference between groups was found. Analysis of secondary outcomes suggested small differences in favor of the experimental group, but the differences are not likely to be clinically relevant. Conclusion. No evidence was found for the superiority of a multisensorial rehabilitation program in ambulatory patients with impairments beyond the time of inpatient therapy. Additional studies are recommended.

Postural visual dependence after recent stroke: assessment by optokinetic stimulation

INTRODUCTION

This study was conducted to assess visual dependence of postural control early after stroke.

DESIGN

Case control study.

SETTING

A Physical Medicine and Rehabilitation Department.

METHOD

Twenty-five patients impaired by severe hemiplegia due to a recent first stroke, were examined. Fourteen had a right and 11 a left hemispheric lesion. There were aged 52+/-13 years, time since stroke was 30+/-12 days. Patients' data were compared to data for 25 healthy subjects. Sitting posture was assessed on a dynamic balance, using two parameters: frontal plane displacement of the centre of pressure under optokinetic stimulation (OKS), and the total length of centre of pressure displacement for the stability reaction. On the basis of 90th percentile control data, patients' behaviour was classified as totally visuo independent (VI), totally visuo dependent (VD) or mixed.

RESULTS

Body tilt under OKS was greater in patients than controls. No control subject was totally VD, 19 subjects were totally VI. Four patients were totally VD and only six were VI. The only clinical parameter linked to the effect of OKS was the sensitivity impairment. Overall patients with visuospatial neglect were the most perturbed, but two were totally visuo independent.

DISCUSSION AND CONCLUSION

Assessment of postural variations in sitting under OKS is proposed for estimating visual dependence early after stroke. Individual reactions are more important than mean group reactions. Visual dependence is not solely due to neurological impairment, implying that previous physiological behaviour may be involved. Knowledge of these characteristics may affect rehabilitation programmes.

Physical therapy for central vestibular dysfunction

OBJECTIVE

To determine if vestibular physical therapy (PT) leads to improved functional outcomes in people with central vestibular dysfunction.

DESIGN

Retrospective case series.

SETTING

Outpatient PT clinic.

PARTICIPANTS

Forty-eight patients with central vestibular dysfunction met the criteria for inclusion in this retrospective chart review. The 48 patients were divided into various subgroups including central vestibulopathy, cerebellar dysfunction, stroke, mixed central and peripheral vestibulopathy, and posttraumatic central disorders.

INTERVENTION

Patients were treated with a custom-designed PT program for a mean of 5 visits over an average of 5 months.

MAIN OUTCOME MEASURES

Patients completed the Activities-Specific Balance Confidence Scale, the Dizziness Handicap Inventory (DHI), the Dynamic Gait Index, the Timed Up & Go test, and the Five Times Sit-to-Stand (FTSTS) Test.

RESULTS

Significant differences were demonstrated between initial evaluation and discharge in each of the assessment measures for the entire group. Post hoc tests were performed to determine if there was a significant difference in any of the assessment measures by diagnosis. Central vestibular diagnostic subgroup was shown to affect pre- to postintervention differences in the functional and disability measures (P< or =.05). With the exception of the FTSTS, effect sizes of change due to PT intervention were greater in those persons with severe disability at baseline as determined by a DHI score of more than 60.

CONCLUSIONS

Patients with central vestibular dysfunctions improved in both subjective and objective measures of balance after PT intervention. Persons with cerebellar dysfunction improved the least.

Análisis de la interacción visuo-vestibular y la influencia visual en el control postural

INTRODUCTION

Postural control depends on a coordinate function of the visual, somatosensory and vestibular systems. A correct analysis of each of them is necessary, in order to obtain an adequate postural evaluation.

METHODS

A normal and a pathological vestibular group of subjects are study. A dynamometric platform studied was performed for every subject in both groups. A scalogram, the centre of pressure variation velocity, and the area, were the parameters analyzed.

RESULTS

In both groups, parameters showed higher values when propioceptive and visual system were altered. A pattern of visual dependence was identified in both groups. The scalogram in the normal group showed a minimal centre of pressure variation. In contrast, the pathological group showed a major variation, with differences depending on the compensation status.

CONCLUSIONS

Our study protocol with posturography is an adequate instrument of postural evaluation, which discriminates the visual dependence and aids to evaluate the compensation.

Changes in postural control parameters after vestibular rehabilitation in patients with central vestibular disorders

OBJECTIVE

The aim of this study was to determine postural responses before and after a vestibular rehabilitation program (VRP) in 14 patients with central vestibular disorders (CVD).

MATERIAL AND METHODS

The confidence ellipse (CE) of the center of pressure distribution area and the sway velocity (SV) were the parameters used for the quantitative assessment of postural control (PC). These two parameters were analyzed before and after a VRP for two visual conditions. Behavioral postural responses were studied by means of the time-frequency scalogram using wavelets and the sway frequency content was measured in arbitrary units of energy density.

RESULTS

Ten patients showed a significant decrease in the CE and SV after the rehabilitative treatment, thus improving their PC. Seven of these patients were assessed again after a period of 12 +/- 5 months, during which they had not received any physical training. All of them showed increases in the CE and SV, indicating an impairment of PC.

CONCLUSIONS

Many CVD patients damage the neural mechanisms involved in retaining the plastic changes in the PC parameters after rehabilitative treatment. Continuation of training may be necessary in order to maintain the improvement in PC obtained with a VRP.

Chronic Dizziness

The mainstay of treatment is a specialized form of physical therapy that intentionally induces symptoms of dizziness with head movements, moving visual targets, and changes in position. Patients must be motivated to experience discomfort during the early stages of rehabilitation, doing the types of activities that they likely have been avoiding. Time must be spent convincing the patient of the necessity to deliberately provoke dizziness in order for the exercises to work. It is important to not overmedicate with vestibular suppressants, and to treat any co-existing mood or anxiety disorder, as these interfere with the adaptive plasticity that is the basis of successful rehabilitation.