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PubMed2005

[Evaluation of balance in neurologic and geriatric disorders].

OBJECTIVE: To analyse the clinical usefulness and metrological properties of the main techniques and indices used to assess balance disorders. METHODS: More than 4000 abstracts referenced in MEDLINE and dealing with postural control and postural disorders (wide screening) were reviewed to determine the main postural techniques and indices used in a clinical context. We retained abstracts with a high citation frequency and those with interesting findings. Corresponding key words were identified for a specific search of articles that we analysed. RESULTS: Postural assessment tools can be classified as scales of ordinal items, tests based on metric or chronometric measurement, posturography, and verticality perception. These techniques are complementary, and their association is recommended in a clinical context. Regarding generic tools, the Falls-related Efficacy Scale (FES) and the Activities-specific Balance Confidence scale (ABC scale) would be enhanced if comparatively analysed and reworked to allow for a feasible and reliable assessment of the fear of falling. Despite a wide diffusion in numerous postural fields worldwide, the Berg Balance Scale (BBS) and the Functional Reach Test (FRT) do not have the required criteria to remain the gold standards they were in the 1990s. Static posturography should be normalised and yield more reliable indices. The clinical relevance of the subjective assessment of visual, haptic, and postural verticals are questionable, especially to explain postural disability. Regarding specific tools, the Tinetti test (TT) and the Time Up and Go test (TUG) are the most suited to assess postural capacities in very elderly people, in whom the predictive validity of the postural assessment of falls is still modest. In stroke patients, the Postural Assessment Scale for Stroke (PASS), posturography, lateropulsion assessment, and vertically perception are interesting and complementary techniques. Postural assessment relies mainly upon the 5 postural items of the Unified Parkinson Disease Rating Scale (UPDRS) in people with Parkinson disease and upon the Romberg test and posturography in patients with cerebellar or proprioceptive ataxia. Some novel postural scales for patients with multiple sclerosis or spinal cord injury are also emerging. CONCLUSION: Among numerous tools that contribute to the assessment of postural disorders, only the most recent ones (developed in the last 10 years) have undergone complete validation. It is now crucial to compare these tools, not only in terms of reproducibility and internal consistency, but also overall, in terms of feasibility, responsiveness, and predictive validity for a given population.

Aged↗

PubMed2000

Vestibular and visual contribution to fish behavior under microgravity.

Vestibular and visual information are two major factors fish use for controlling their posture under 1 G conditions. Parabolic flight experiments were carried out to observe the fish behavior under microgravity for several different strains of Medaka fish (Oryzias latipes). There existed a clear strain-difference in the behavioral response of the fish under microgravity: Some strains looped, while other strains did not loop at all. However, even the latter strains looped under microgravity conditions when kept in complete darkness, suggesting the contribution of visual information to the posture control under microgravity. In the laboratory, eyesight (visual acuity) was checked for each strain, using a rotating striped-drum apparatus. The results also showed a strain-difference, which gave a clue to the different degree of adaptability to microgravity among different strains. Beside loopings, some fish exhibited rolling movement around their body axis. Tracing each fish during and between parabolas, it was shown that to which side each fish rolls was determined specifically to each individual fish, and not to each strain. Thus, rolling direction is not genetically determined. This may support the otolith asymmetry hypothesis. Fish of a mutant strain (ha strain, having homozygous recessive of one gene ha) have some malfunction in otolith-vestibular system, and their behavior showed they are not dependent on gravity. Morphological abnormalities of their ear vesicles during the embryonic and baby stages were noted. Their eyesight and dorsal light responses were also studied. Progress in the project of establishing a new strain which has good eyesight and, at the same time, being deficient in otolith-vestibular system was reported. Crosses between the strain of good eyesight and ha strain were made, and to some extent, F2 fish have already shown such characteristics suited for living under microgravity conditions.

Animals↗

PubMed1999

Gradual development of the ventral funiculus input to lumbar motoneurons in the neonatal rat.

The in vitro brainstem-spinal cord preparation of newborn rats (0 to six-days-old) was used to investigate the development of pathways descending ventrally from the brainstem, which are important for the control of posture and locomotion. The ventral funiculus of the spinal cord was stimulated at the cervical (C1) level. Responses were recorded at the lumbar level from either motoneurons or ventral roots using intracellular microelectrodes or suction electrodes, respectively. Responses consisted of a pure excitation lasting 15 ms, followed by mixed excitatory/inhibitory responses. The inhibition was, at least partly, mediated by glycine. Excitatory amino acid transmission appears to be responsible for the excitation. The characteristics of the ventral funiculus-evoked postsynaptic potentials and ventral root potentials changed significantly with age. Their latency decreased whereas the slope and the area, measured over the first 15 ms, increased. The increase of the ventral funiculus input to motoneurons was slightly more pronounced than that of the monosynaptic dorsal root-evoked potentials from day 0 to day 4. These data suggest a gradual arrival of ventral descending axons in the lumbar enlargement which may be responsible for the gradual acquisition of postural control that takes place during the first days after birth. This is a prerequisite for the development of the adult pattern of quadrupedal locomotion, with elevated trunk.

Aging↗

PubMed1991

Postural sway characteristics of the elderly under normal and altered visual and support surface conditions.

One of the most pervasive findings in the literature on the aged is the general slowing of cognitive-motor responses with advancing age. Hence, an increased slowness in the processing of information from vestibular, visual, and somatosensory systems could contribute greatly to a decline in postural stability. To examine this question, in a cross-sectional investigation, postural sway behavior of elderly (n = 18) and young (n = 10) adults was examined under conditions that stressed the slower integrative mechanisms rather than the reflexive mechanisms of postural control. The postural sway behavior of young and elderly subjects was examined for a prolonged duration (80 s), under altered visual and/or support surface (5 cm thick foam surface) conditions, and contrasted with normal stance. Results showed that the exclusion or disruption of one of the sensory inputs, alone, was not consistently sufficient to differentiate between elderly and young adults, because of compensation by the remaining sensory sources. Both alterations together (i.e., visual and surface), however, had a substantially greater effect upon the elderly than the young.

Adult↗

PubMedDate not supplied

Can short-latency vestibulospinal reflexes in lower leg muscles be elicited by tapping the head?

A gentle tap on the forehead evoked short-latency motor responses in the sternocleidomastoid muscle, which may be vestibulocollic reflexes with characteristics similar to those elicited by clicks. We tested this paradigm in subjects standing upright, in order to determine the differential effects of taps on the forehead on the patterns and latencies of spinal stretch and vestibulospinal reflexes, which are important for postural control. Taps on the forehead elicited short-latency inhibitory electromyographic responses in both gastrocnemius muscles with a mean latency of 48.3 +/- 3.1 ms (onset) to 98.3 +/- 6.3 ms (end). Taps on the sternum elicited similar responses from the gastrocnemius muscles, indicating that vestibular stimulation is not essential for eliciting these responses. Both responses may play a role in predetermining the strategy for correcting body perturbations. The actual reflex is probably elicited by somatosensory input from the neck, which converges with vestibular input for the multisensory control of posture.

Acceleration↗

PubMed2000

Mutant Medaka fish having a deficiency in otolith-vestibular system and their behavior in microgravity.

Vestibular and visual senses are two major factors fish use for controlling their posture under 1 G conditions. From various studies in the past (parabolic flights and some ground-laboratory experiments), I came to have a hypothesis that "heavily eye-dependent" fish are tolerant to microgravity (micro-G). Theoretically, for "heavily eye-dependent" fish, the following three types may exist. (a) Fish having good eyesight, and having an ordinary sensitivity to gravity, (b) Fish having an ordinary eyesight, and having less sensitivity to gravity, (c) Fish having good eyesight, and having less sensitivity to gravity. In Medaka fish (Oryzias latipes), these three types have successfully been obtained. In this paper, the behavior of such different types of Medaka fish under micro-G will be studied by use of parabolic flights of an airplane. The ground-laboratory experiments are also reported, which focus on the contribution of both vestibular and visual senses to the posture control for each of three types of Medaka fish.

Animals↗

PubMed1982

Vestibular function assessment in patients with Meniere's disease: the vestibulospinal system.

The state-of-the-art approach to clinical assessment of vestibular disturbances includes a number of procedures in which it is assumed that the status of major vestibular pathways is quantified independently from converging somatosensory and visual influences. Although it has been known for some time that this approach has limitations in a highly integrative system in which inputs from a number of sensory modalities interact, a practical remedy has been only recently forthcoming. Using an approach to assessment of the vestibulospinal system developed by Nashner, the application of moving platform techniques has been the first to systematically identify the interactions among vestibular, visual, and proprioceptive senses and determine the role of vestibular losses in the process of postural control. A group of Meniere's disease patients were studied in order to determine whether or not such tests could be used as an effective vestibular screening method for Meniere's disease patients in remission, and whether the ability of Meniere's disease patients to use vision and proprioception to compensate for their vestibular disorders, could be assessed. Results indicated that quantitative evaluation of the vestibulospinal system was a very effective vestibular screening test. Furthermore, the adaptive ability of the subject can be estimated by varying the amounts of visual and proprioceptive vestibular information available to the patient for the control of postural sway. Preliminary results indicate that such a technique would be of great value clinically for the initial and on-going evaluation of patients with Meniere's disease and for pre and post-therapeutic evaluation of the Meniere's disease patient.

Adult↗

PubMed2001

Transitions in a postural task: do the recruitment and suppression of degrees of freedom stabilize posture?

In this study, we examined flexibility in postural coordination by inducing transitions between postural patterns. Previous work demonstrated that the postural control system produces two task-specific postural patterns as a function of the frequency of support surface translation. For slow translation frequencies (<0.5 Hz), subjects ride on the platform reminiscent of upright stance (ride pattern), and for fast frequencies (> or =0.75 Hz) subjects actively fixed the head and trunk in space (head fixed pattern) during anterior-posterior platform motion. To study the adaptation of the postural control system, we had subjects stand on a support surface undergoing increases (from 0.2 to 1.0 Hz in 0.1-Hz steps) and decreases (from 1.0 to 0.2 Hz in 0.1-Hz steps) in translation frequency with the eyes open and closed. Kinematic measures of sagittal plane body motion revealed a gradual transition between these two postural patterns as a function of frequency scaling. In both the increasing and decreasing frequency conditions with visual input, center of mass displacements gradually decreased and increased, respectively, whereas upper-trunk (and head) displacement decreased gradually within the ride pattern until a head fixed pattern was observed without any significant changes in displacement for translation frequencies at and above 0.6 Hz. Without visual input, the scaling of the ride pattern was similar except the transition to the head fixed pattern never emerged with increasing frequency; instead, a less stable pattern exhibiting slow drift in head-trunk anterior-posterior motion (drift pattern) was observed at and above 0.5 Hz oscillations. The stability of the head fixed pattern at fast frequencies was clearly dependent on visual input suggesting that vision was more critical for trunk and head control in space at high than low translation frequencies. Head velocity was kept constant, and lower with vision, as translation frequency (and velocity) changed suggesting a head velocity threshold constraint across postural patterns. The gradual transition from the ride to the head fixed pattern was made possible by the recruitment of available degrees of freedom in the form of ankle, then knee, and then hip joint motion. In turn, the transition from the head fixed or drift pattern was made possible by the gradual suppression of available degrees of freedom in the form of reducing hip, then knee, and then ankle motion. The gradual change in postural kinematics without instabilities and hysteresis suggests that the ability to recruit and suppress biomechanical degrees of freedom allows the postural control system to gradually change postural strategies without suffering a loss of stability. The results are discussed in light of possible self-organizing mechanisms in the multisensory control of posture.

Adult↗

PubMed2002

Postural instability in idiopathic Parkinson's disease: the role of medication and unilateral pallidotomy.

Postural instability (PI) is common in idiopathic Parkinson's disease (IPD). We measured sensory and motor contributions to PI in 50 patients with advanced IPD, off and on medication and in a subset pre- and 3, 6 and 12 months post-unilateral pallidotomy, using computerized dynamic posturography [specifically, the Sensory Organization Test (SOT) and the Unified Parkinson's Disease Rating Scale (UPDRS) subscale PIGD (Postural Instability and Gait Disorder)]. Off medication, all patients had abnormal PIGD scores. The group could be separated into those with normal SOT equilibrium scores (SOTN) and those, the majority, with abnormal postural control when sensory feedback was limited (SOTABN). Medication improved the PIGD scores but worsened the SOT scores in the majority of patients. Increases in spontaneous sway in some patients contributed to the negative effect of medication on SOT scores. However, this could not explain the detrimental effect of medication on SOT scores in at least 40% of patients. On the other hand, pallidotomy improved both PIGD and SOT scores in both groups. A predictor of good outcome from pallidotomy concerning PI was the degree of worsening of the effect that medication had on SOT5 scores. PI in IPD appears to be multifactorial. We propose that the PIGD score reflects sensory and motor aspects of postural control, with normal sensory feedback, while the SOT equilibrium scores measure the sensory organizational process of postural control in the presence of altered sensory inputs. There is a dissociation between the effects of medication and pallidotomy on motor and sensory components of postural control, which may reflect the underlying pathophysiological mechanism responsible for these different components of PI. We suggest that patients with advanced IPD and PI on medication should consider adjuvant surgical treatment for better postural control.

Adult↗

PubMed2003

Influence of regular proprioceptive and bioenergetic physical activities on balance control in elderly women.

BACKGROUND: Balance disorders increase considerably with age due to a decrease in posture regulation quality, and are accompanied by a higher risk of falling. Conversely, physical activities have been shown to improve the quality of postural control in elderly individuals and decrease the number of falls. The aim of this study was to evaluate the impact of two types of exercise on the visual afferent and on the different parameters of static balance regulation. METHODS: Static postural control was evaluated in 44 healthy women aged over 60 years. Among them, 15 regularly practiced proprioceptive physical activities (Group I), 12 regularly practiced bioenergetic physical activities (Group II), and 18 controls walked on a regular basis (Group III). RESULTS: Group I participants displayed lower sway path and area values, whereas Group III participants displayed the highest, both in eyes-open and eyes-closed conditions. Group II participants displayed intermediate values, close to those of Group I in the eyes-open condition and those of Group III in the eyes-closed condition. Visual afferent contribution was more pronounced for Group II and III participants than for Group I participants. CONCLUSIONS: Proprioceptive exercise appears to have the best impact on balance regulation and precision. Besides, even if bioenergetic activity improves postural control in simple postural tasks, more difficult postural tasks show that this type of activity does not develop a neurosensorial proprioceptive input threshold as well, probably on account of the higher contribution of visual afferent.

Aged↗

PubMed2000

Visual control of postural orientation and equilibrium in congenital nystagmus.

PURPOSE: To investigate how humans with congenital nystagmus (CN) use visual information to stabilize and orient their bodies in space. METHODS: Center of foot pressure (COP) and head displacements in the lateral plane were recorded using a sway platform and Schottky barrier photodetector, respectively. In experiment 1, a comparison was made of the oscillatory characteristics of body sway with eyes open compared with eyes closed. Experiment 2 studied the postural readjustments made in response to absolute or relative motion (motion parallax) of objects in the visual scene, generated by lateral displacement of background scenery. RESULTS: Experiment 1 revealed that subjects with CN were not able to use visual information to stabilize COP but were able to stabilize the head at frequencies lower than 1 Hz. Experiment 2 showed that in response to the displacement of a visual display, for both absolute motion and motion parallax, subjects with CN reoriented their body in space in a manner similar to control subjects. CONCLUSIONS: The results suggest that despite involuntary eye movements, subjects with CN use orientation cues to control their posture, but not dynamic cues useful to control the rapid oscillations that are particularly important at the level of COP. These findings suggest that in CN, visual control of posture is restricted by low-frequency sampling of the visual scene.

Adult↗

PubMed2000

Nonlinear measures of heart rate time series: influence of posture and controlled breathing.

In this study, we investigated measures of nonlinear dynamics and chaos theory in regards to heart rate variability in 27 normal control subjects in supine and standing postures, and 14 subjects in spontaneous and controlled breathing conditions. We examined minimum embedding dimension (MED), largest Lyapunov exponent (LLE) and measures of nonlinearity (NL) of heart rate time series. MED quantifies the system's complexity, LLE predictability and NL, a measure of deviation from linear processes. There was a significant decrease in complexity (P < 0.00001), a decrease in predictability (P < 0.00001) and an increase in nonlinearity (P = 0.00001) during the change from supine to standing posture. Decrease in MED, and increases in NL score and LLE in standing posture appear to be partly due to an increase in sympathetic activity of the autonomous nervous system in standing posture. An improvement in predictability during controlled breathing appears to be due to the introduction of a periodic component.

Adult↗

PubMed1993

Balance improvements in older women: effects of exercise training.

BACKGROUND AND PURPOSE: Loss of lower-extremity strength increases the risk of falls in older persons. The purpose of this study was to test the hypothesis that a vigorous program of lower-extremity strengthening, walking, and postural control exercises would improve the single-stance balance of healthy older women and lower their risk of falls and fall-associated injuries. SUBJECTS: From a total of 38 respondents, 21 women were randomly assigned to either a treatment group (combined training, n = 12) or a control group (flexibility training, n = 9). The subjects ranged in age from 62 to 75 years (mean = 68, SD = 3.5). METHODS: A randomized control trial compared the effects of two exercise programs on static balance. The combined training group exercised three times per week on knee extension and sitting leg press machines, walked briskly for 20 minutes, and performed postural control exercises, which included simple tai chi movements. The flexibility training group performed postural control exercises weekly. Measurements of balance were obtained on a force platform in double and single stance, at baseline and following 6 months of exercise training. RESULTS: Double-stance measurements were unchanged after training. The mean displacement of the center of pressure in single stance improved 17% in the combined training group and did not change in the flexibility training group. A repeated-measures analysis of variance revealed that the difference in improvement between the combined training and flexibility training groups was not significant. DISCUSSION AND CONCLUSION: This is the first intervention trial to demonstrate improvements in single-stance postural sway in older women with exercise training. Additional studies with more subjects will be needed to determine whether a combined training program of resistance training, walking, and postural exercises can improve balance more than a program of postural control exercises alone.

Accidental Falls↗

PubMed2004

Balance control and adaptation during vibratory perturbations in middle-aged and elderly humans.

The objective was to investigate if healthy elderly people respond and adapt differently to postural disturbances compared to middle-aged people. Thirty middle-aged (mean age 37.8 years, range 24-56 years) and forty healthy elderly subjects (mean age 74.6 years, range 66-88 years) were tested with posturography. Body sway was evoked by applying pseudorandom vibratory stimulation to the belly of the gastrocnemius muscles of both legs simultaneously. The tests were performed both with eyes open and eyes closed. The anteroposterior body sway was measured with a force platform and analyzed with a method that considers the adaptive changes of posture and stimulation responses. The results showed that middle-aged people generally used a different postural control strategy as compared to the elderly. The elderly responded more rapidly to vibratory perturbation, used more high-frequency (>0.1 Hz) motions and the motion dynamics had a higher degree of complexity. Moreover, the elderly had diminished ability to use visual information to improve balance control. Altogether, despite having an effective postural control adaptation similar to that of middle-aged people, the elderly had more difficulty in withstanding balance perturbations. These findings suggest that the balance control deterioration associated with aging cannot be fully compensated for by postural control adaptation.

Adaptation, Physiological↗

PubMedDate not supplied

[Deficit of learning of posture voluntary control in patients with cortical lesions of various locations: cortical mechanisms of posture regulation].

Forty two hemiparetic patients after cerebrovascular accidents were trained to change the position of the center of pressure according to a target on the screen with the visual feedback control. The learning was substantially impaired in comparison with the group of healthy subjects. Patients with the right-hemispheric lesions showed somewhat greater learning deficit than patients with lesions in the left hemisphere. Lesion localization also affected the process of learning. The learning was disturbed to a greater extent in patients with lesions involving not only motor but also premotor and parietal cortical areas. In patients with parieto-temporal lesions the learning reached a very low level after three initial days of training, possibly, because of the deficit of sensory integration and of body scheme in the extra-personal space. Patients with combined lesions of the motor, premotor, and parietal areas showed the lowest results. The learning was shown to depend on the deficit of proprioception and extent of postural disturbances (asymmetry of body weight distribution and amplitude of the center of pressure oscillations) rather than on the extent of motor deficit (paresis and spasticity). However, the learning itself improved some motor disturbances.

Biofeedback, Psychology↗

PubMed2003

Acceleration threshold detection during short anterior and posterior perturbations on a translating platform.

Balance control systems have usually been studied under two conditions, during quiet standing or under large postural perturbations of a magnitude that requires a postural adjustment to prevent falling. Between these two extremes lie perturbations that can be repeated and measured while not forcing adaptive strategies from the postural control system. Unlike other studies of postural control, we employed very short translations with varying accelerations at the edge of psychophysical detectability. These perturbations were vibration-free anterior or posterior translations of the platform on which a subject stood. Using a full Latin-square design set of perturbations in the forward or backward direction, with a smooth or jerk acceleration profile, and of length 4 or 20 mm, were presented to five subjects. Perceptual peak acceleration thresholds were determined by an iterative psychophysical method that forced the subjects to choose in which of two sequential intervals that they perceived a stimulus to have been presented. The only factor found that significantly correlated with detection was perturbation length. The 4 mm peak thresholds averaged 14.51 mm/s2 while 20 mm thresholds averaged 8.55 mm/s2. For the short perturbations employed in this study, detection of motion thus was dependent upon the magnitude of the acceleration, but it was independent of the acceleration profile (jerk versus smooth) or movement direction. By understanding the influences on the ability to perceptually detect motion underfoot, we can begin to understand what elements of the postural control system might be involved in the second-to-second control of balance.

Acceleration↗

PubMedDate not supplied

Nursing, maternal postures, and fetal position.

The objectives of this study were to (a) determine if a safe, simple, and economic nursing procedure--maternal posturing--would result in the rotation of a fetus in the posterior or transverse position to the optimal anterior position and (b) evaluate the relative effectiveness of a series of maternal postures for facilitating anterior fetal rotation. One hundred healthy women at term pregnancy were randomly assigned to four treatment and one control posture for a 10-minute period. At two nurse-midwifery clinics, one certified nurse-midwife postured the subjects and one midwife measured the dependent variable (fetal position) with Leopold's maneuvers. Hypotheses I-IV, which predicted that the four rotation postures would have a greater proportion of anterior fetal rotations than the control posture, were supported (p less than .000). Essentially all four postures were effective and there was little difference between the treatment postures. A second posturing was performed to determine if an additional 10 minutes in a treatment posture would result in an anterior fetal position. There was a greater proportion of anterior fetal rotations with the four rotation postures than the control posture. The Sims posture was used as a maintenance posture for anterior positions, and was successful when done on the opposite side of the fetal back. The theoretical explication of how maternal postures effect fetal rotation remains sound.

Adult↗

PubMed1998

Effect of altered sensory conditions on multivariate descriptors of human postural sway.

Multivariate descriptors of sway were used to test whether altered sensory conditions result not only in changes in amount of sway but also in postural coordination. Eigenvalues and directions of eigenvectors of the covariance of shnk and hip angles were used as a set of multivariate descriptors. These quantities were measured in 14 healthy adult subjects performing the Sensory Organization test, which disrupts visual and somatosensory information used for spatial orientation. Multivariate analysis of variance and discriminant analysis showed that resulting sway changes were at least bivariate in character, with visual and somatosensory conditions producing distinct changes in postural coordination. The most significant changes were found when somatosensory information was disrupted by sway-referencing of the support surface (P = 3.2 x 10(-10)). The resulting covariance measurements showed that subjects not only swayed more but also used increased hip motion analogous to the hip strategy. Disruption of vision, by either closing the eyes or sway-referencing the visual surround, also resulted in altered sway (P = 1.7 x 10(-10)), with proportionately more motion of the center of mass than with platform sway-referencing. As shown by discriminant analysis, an optimal univariate measure could explain at most 90% of the behavior due to altered sensory conditions. The remaining 10%, while smaller, are highly significant changes in posture control that depend on sensory conditions. The results imply that normal postural coordination of the trunk and legs requires both somatosensory and visual information and that each sensory modality makes a unique contribution to posture control. Descending postural commands are multivariate in nature, and the motion at each joint is affected uniquely by input from multiple sensors.

Adult↗