Biased postural vertical in humans with hemispheric cerebral lesions

Effects of galvanic vestibular stimulation on postural righting reactions in hemiplegia

Patients with post-stroke hemiplegia often exhibit reduced ability to maintain sitting balance, a crucial factor for predicting prognosis. Galvanic vestibular stimulation (GVS) influences postural control by stimulating vestibular organ. Although several studies have focused on GVS in static postures, no studies have demonstrated the influence of GVS on righting reactions. Therefore, we aimed to investigate the effects of GVS on postural righting reactions in seated patients with stroke-induced hemiplegia. Using a vertical board (VB), righting reactions were induced by tilting the VB at 10° after patients sat for 1 min. Patients adjusted their bodies until feeling vertical upon prompt. Twenty-two left hemiplegic patients with cerebrovascular disease participated, divided into two groups undergoing right cathode GVS (RC-GVS) followed by left cathode GVS or vice versa, preceded by sham stimulation. Centre of pressure and the joint angle were measured. During the postural righting reactions towards the paralysed side, RC-GVS enhanced the righting reactions and moved the mean position on the x-axis (COPx) to the right and the mean position on the y-axis (COPy) to the front. During the postural righting reaction towards the right side, RC-GVS induced resistance against the righting reaction, COPx was deflected to the right, COPy was deflected backward, and the angle of the neck tilt increased. The findings revealed that GVS with anodal stimulation on the paralysed side could promote righting reactions in patients with post-stroke hemiplegia. SIGNIFICANCE STATEMENT: The study findings suggest that using the contralesional placement of the anode promotes righting reactions, and galvanic vestibular stimulation can induce joint movements in the neck and trunk by polarising it to act as resistance against righting reactions.

Dynamic changes of the direction and angle of radiographic ocular lateral deviation in patients with lateropulsion after stroke onset

OBJECTIVE

To examine if radiographic ocular lateral deviation (rOLD) could be provoked in stroke patients with mild-to-moderate lateropulsion according to vertical perception.

METHODS

In this single-center, retrospective study, acute stroke patients with mild-to-moderate lateropulsion assessed by the Scale for Contraversive Pushing were enrolled. Computed tomography or magnetic resonance imaging was performed on all patients on admission and then according to their conditions. The direction and angle of rOLD were compared among three groups according to the responsible lesion: lateral medullary (LM), pontine (P), and hemispheric (H).

RESULTS

Sixty-six patients (male, 47; average age, 67 years) were enrolled and divided into the LM (n = 37), P (n = 8), and H (n = 21) groups. All patients had body tilt. Patients in the LM group showed body tilt to the ipsilesional side during hospitalization, while those in the P and H groups tilted to the contralesional side. All patients had rOLD at the final assessment at an average of 13 days after onset; patients in the P and H groups showed contralateral rOLD, while those in the LM group showed ipsilateral rOLD if they did not have cerebellar or pontine lesions. Significant decreases in the angle and changes in direction of rOLD according to lesion site were observed during hospitalization.

CONCLUSION

Serial changes in rOLD findings after stroke onset are different according to the responsible lesion. The direction of rOLD in most patients is in accordance with vertical perception after the acute stage of stroke.

Spatial neglect encompasses impaired verticality representation after right hemisphere stroke

Spatial neglect after right hemisphere stroke (RHS) was recently found to encompass lateropulsion, a deficit in body orientation with respect to gravity caused by altered brain processing of graviception. By analogy, we hypothesized that spatial neglect after RHS might encompass an altered representation of verticality. We also assumed a strong relation between body neglect and impaired postural vertical, both referring to the body. To tackle these issues, we performed contingency and correlation analyses between two domains of spatial neglect (body, extra-body) and two modalities of verticality perception (postural, visual) in 77 individuals (median age = 67) with a first-ever subacute RHS (1-3 months). All individuals with a transmodal (postural and visual) tilt in verticality perception (n = 26) had spatial neglect, but the reverse was not found. Correlation and multivariate analyses revealed that spatial neglect (and notably body neglect) was associated more with postural than visual vertical tilts. These findings indicate that after RHS, an impaired verticality representation results from a kind of graviceptive neglect, bearing first on somaesthetic graviception and second on vestibular graviception. They also suggest that the human brain uses not only a mosaic of 2D representations but also 3D maps involving a transmodal representation of verticality.

Association between spatial neglect and impaired verticality perception after stroke: A systematic review

BACKGROUND

Although most research on spatial neglect (SN) has focused on spatial perception deficits with regard to the lateral (left-right) axis, deficits of spatial perception with regard to the vertical (up-down) axis, such as disturbances in the perception of verticality (e.g., judgement of vertical orientations), have also been suggested.

OBJECTIVE

We aimed to systematically analyse reported associations between SN and characteristics of verticality perception while considering the time post-stroke.

METHODS

PubMed, Web of Science, Scopus, PubPsych and PsycArticles databases were searched on May 24, 2022 for articles written in English that evaluated the association between SN and verticality perception (i.e., the subjective visual vertical [SVV], subjective postural vertical [SPV] and subjective haptic vertical [SHV]) in adults after stroke. Left and right SN were considered and had to be assessed using standardized methods. Data were manually extracted, and risk of bias was assessed with the Newcastle-Ottawa Scale. The tilt of the line/chair relative to the gravitational vector and its direction, together with uncertainty (i.e., variability across measurements), were evaluated.

RESULTS

Thirteen studies were included (431 participants after stroke); at least 191 participants exhibited SN. Mainly the first 3 to 6 months post-stroke were evaluated. SN was associated with SVV misperception, which resulted in larger SVV tilts (mostly in the contralesional direction) and uncertainty in participants with than without SN. SVV tilt magnitudes ranged from a mean/median of -8.9° to -2.3° in SN participants and from -1.6° to 0.6° in non-SN participants, the latter falling within normative ranges. For SPV and SHV measurements, the magnitude of tilt and the uncertainty were insufficiently assessed or results were inconclusive.

CONCLUSIONS

SN was associated with larger SVV tilts and uncertainty, which suggests that SVV misperception is a key feature of SN. This observation highlights the importance of regular SVV assessment in people with SN in clinical practice.

PROSPERO

CRD42019127616.

Does Hippotherapy Improve the Functions in Children with Cerebral Palsy? Systematic Review Based on the International Classification of Functioning

Objective: To perform a systematic review of the literature regarding scientific reality of hippotherapy in children with cerebral palsy graded according to France HAS (Haute Autorité de Santé) recommendations and applied to the International Classification of Functioning. Methods: The research in MEDLINE and Cochrane Library databases was performed using the keywords: "Equestrian therapy," "Riding for the disabled," "Hippotherapy," "Equine-movement therapy," and "Therapeutic horse (back) riding." The methodological quality of the articles was assessed using four levels of proof and three guideline grades (A: strong; B: moderate; C: poor). Results: Seven prospective, randomized controlled studies and one systematic review confirm the level of proof of hippotherapy in children with cerebral palsy with grade B. Hippotherapy in children with cerebral palsy contributes to improve motor function, symmetry of muscle contraction, spasticity, posture, and walking. Fifty prospective no randomized studies confirm the level with grade C for balance, motor coordination, lumbopelvic mobility, walking speed, functional development, and social behavior. Conclusions: Hippotherapy in children with cerebral palsy can be recommended. Regarding the literature data, the level of proof of hippotherapy in children with cerebral palsy is moderate (grade B).

Multisensory Interactions in Head and Body Centered Perception of Verticality

Percepts of verticality are thought to be constructed as a weighted average of multisensory inputs, but the observed weights differ considerably between studies. In the present study, we evaluate whether this can be explained by differences in how visual, somatosensory and proprioceptive cues contribute to representations of the Head In Space (HIS) and Body In Space (BIS). Participants (10) were standing on a force plate on top of a motion platform while wearing a visualization device that allowed us to artificially tilt their visual surroundings. They were presented with (in)congruent combinations of visual, platform, and head tilt, and performed Rod & Frame Test (RFT) and Subjective Postural Vertical (SPV) tasks. We also recorded postural responses to evaluate the relation between perception and balance. The perception data shows that body tilt, head tilt, and visual tilt affect the HIS and BIS in both experimental tasks. For the RFT task, visual tilt induced considerable biases (≈ 10° for 36° visual tilt) in the direction of the vertical expressed in the visual scene; for the SPV task, participants also adjusted platform tilt to correct for illusory body tilt induced by the visual stimuli, but effects were much smaller (≈ 0.25°). Likewise, postural data from the SPV task indicate participants slightly shifted their weight to counteract visual tilt (0.3° for 36° visual tilt). The data reveal a striking dissociation of visual effects between the two tasks. We find that the data can be explained well using a model where percepts of the HIS and BIS are constructed from direct signals from head and body sensors, respectively, and indirect signals based on body and head signals but corrected for perceived neck tilt. These findings show that perception of the HIS and BIS derive from the same sensory signals, but see profoundly different weighting factors. We conclude that observations of different weightings between studies likely result from querying of distinct latent constructs referenced to the body or head in space.

Comparison of two methods based on one psychophysical paradigm to measure the subjective postural vertical in standing

The perception of verticality can be altered with age or due to neurological diseases. Different procedures have been described to measure the subjective postural vertical (SPV). A deviation from the earth vertical was either described as a single position or as a sector defined by two positions representing the edges of the perceived verticality. In this study, for the first time, we investigated if these two methods produce equal values, and consequently can be merged to set normative values. SPV in standing was tested in 24 healthy young adults (28.4 (5.2) years of age, 12 women). Each participant performed both methods in the sagittal and the frontal plane. Absolute and constant error values were found to be similar for both methods in both planes with a mean difference of less than 0.3° (p > 0.148). The mean width of the SPV sector was 3.9° (0.9°) in the sagittal and 3.7° (1.4°) in the frontal plane, ranging in the mean from -5.5° to 8.1° in the sagittal and -5.3° to 4.3° in the frontal plane. SPV values significantly differed in range between both methods in both planes with a mean difference of more than 3.1° (p<0.002). Results show that both methods, SPVposition and SPVsector, produce equal error values when applied with otherwise similar methodological settings and can therefore be used alternatively or within the same meta-analysis. The SPVsector, however, led to wider range values and was less frequently rated as the preferred method to represent the participants' subjective verticality.

Balance, Lateropulsion, and Gait Disorders in Subacute Stroke

OBJECTIVE

To test the hypothesis that impaired body orientation with respect to gravity (lateropulsion) would play a key role in poststroke balance and gait disorders.

METHODS

Cohort study of 220 individuals consecutively admitted to a neurorehabilitation ward after a first hemisphere stroke (DOBRAS cohort [Determinants of Balance Recovery After Stroke] 2012-2018, ClinicalTrials.gov: NCT03203109), with clinical data systematically collected at 1 month, then at discharge. Primary outcomes were balance and gait disorders, quantified by the Postural Assessment Scale for Stroke and the modified Fugl-Meyer Gait Assessment, to be explained by all deficits on day 30, including lateropulsion assessed with the Scale for Contraversive Pushing. Statistics comprised linear regression analysis, univariate and multivariate analyses, and receiver operating characteristic curves.

RESULTS

Lateropulsion was frequent, especially after right hemisphere stroke (RHS, D30, 48%; discharge 24%), almost always in right-handers. Among all deficits, impaired body orientation (lateropulsion) had the most detrimental effect on balance and gait. After RHS, balance disorders were proportional to lateropulsion severity, which alone explained almost all balance disorders at initial assessment (90%; 95% confidence interval [CI] [86-94], p < 0.001) and at discharge (92%; 95% CI 89-95, p < 0.001) and also the greatest part of gait disorders at initial assessment (66%; 95% CI 56-77, p < 0.001) and at discharge (68%; 95% CI 57-78, p < 0.001).

CONCLUSION

Lateropulsion is the primary factor altering poststroke balance and gait at the subacute stage and therefore should be systematically assessed. Poststroke balance and gait rehabilitation should incorporate techniques devoted to misorientation with respect to gravity.

Spatial orientation: Model-based approach to multi-sensory mechanisms

Perception of spatial orientation is generated through multimodal sensory integration. In this process, there are systematic errors with changes in the head or body position, which reflect challenges for the brain in maintaining a common sensory reference frame for spatial orientation. Here, we focus on this multisensory aspect of spatial orientation. We review a Bayesian spatial perception model that can be used as a framework to study sensory contributions to spatial orientation during lateral head tilts and probe neural networks involved in this process.

Centre of pressure displacements produced in sitting during virtual reality training in younger and older adults and patients who have had a stroke

Purpose: Poor sitting balance is common after stroke and makes leaning and reaching while sitting difficult and dangerous. Virtual reality training (VRT) uses computer hardware and software to track a person's movements and allow him or her to interact with a virtual environment. VRT games are available to train sitting balance after stroke; however, it is unknown how challenging they are. The objectives of this study were to characterize the centre of pressure displacements generated during the performance of VRT in stroke patients (ST) and compare their performance to that of young (YA) and older adults (OA).Materials and Methods: Eight ST participants who could stand for at least four minutes were recruited from an inpatient stroke rehabilitation unit for this cross-sectional, observational pilot study. Eight YA and eight OA were recruited from the community. Participants sat on a pressure mat and played 17 VRT game/difficulty combinations. The area, range and average velocity of centre of pressure displacement were determined for each game/difficulty.Results: Virtually manoeuvring a motorcycle around barriers and leaning to move a ball down a maze produced the greatest displacement of the centre of pressure, particularly in the mediolateral direction. OA moved further and faster in the mediolateral direction than YA. ST's performance was more variable.Conclusions: Some VRT games were more likely to push participants to challenge their limits of stability. Others required less displacement but more trunk stability. These results can guide which VRT games are used for the rehabilitation of sitting balance after stroke.Implications for rehabilitationSome virtual reality training games produce greater displacements of the centre of pressure in sitting than others, suggesting that careful matching between game challenge and desired therapeutic outcome is necessary when selecting games.Virtual reality training performed in sitting with feet on the floor challenges sitting balance in the frontal plane more so than in the sagittal plane.Older adults tend to lean more than younger adults while individuals with stroke move more or less than others, depending on the game.

Decreased Respiratory Muscle Function Is Associated with Impaired Trunk Balance among Chronic Stroke Patients: A Cross-sectional Study

The abdominal muscles play a role in trunk balance. Abdominal muscle thickness is asymmetrical in stroke survivors, who also have decreased respiratory muscle function. We compared the thickness of the abdominal muscles between the affected and less affected sides in stroke survivors. In addition, the relationship between respiratory muscle function and trunk balance was evaluated. Chronic stroke patients (18 men, 15 women; mean age, 58.94 ± 12.30 years; Mini-Mental Status Examination score ≥ 24) who could sit without assist were enrolled. Abdominal muscle thickness during rest and contraction was measured with ultrasonography, and the thickening ratio was calculated. Respiratory muscle function assessment included maximum respiratory pressure, peak flow, and air volume. Trunk function was evaluated using the Trunk Impairment Scale, and trunk balance was estimated based on the center of pressure velocity and path length within the limit of stability in sitting posture. Abdominal muscles were significantly thinner on the affected side, and the thickening ratio was lower in the affected side (P < 0.05). In addition, the higher thickening ratio of the affected side showed significant relationship with higher trunk function. Moreover, higher respiratory muscle function was significantly correlated with higher level of trunk function and balance in stroke patients (P < 0.05). Thus, chronic stroke survivors have decreased abdominal muscle thickness on the affected side, and respiratory muscle function has positive correlation with trunk function and balance. We propose that respiratory muscle training should be included as part of trunk balance training in chronic stroke patients.

Normative data for human postural vertical: A systematic review and meta-analysis

Perception of verticality is required for normal daily function, yet the typical human detection error range has not been well characterized. Vertical misperception has been correlated with poor postural control and functionality in patients after stroke and after vestibular disorders. Until now, all the published studies that assessed Subjective Postural Vertical (SPV) in the seated position used small groups to establish a reference value. However, this sample size does not represent the healthy population for comparison with conditions resulting in pathological vertical. Therefore, the primary objective was to conduct a systematic review with meta-analyses of Subjective Postural Vertical (SPV) data in seated position in healthy adults to establish the reference value with a representative sample. The secondary objective was to investigate the methodological characteristics of different assessment protocols of SPV described in the literature. A systematic literature search was conducted using Medline, EMBASE, and Cochrane libraries. Mean and standard deviation of SPV in frontal and sagittal planes were considered as effect size measures. Sixteen of 129 identified studies met eligibility criteria for our systematic review (n = 337 subjects in the frontal plane; n = 187 subjects in sagittal plane). The meta-analyses measure was estimated using the pooled mean as the estimator and its respective error. Mean reference values were 0.12°±1.49° for the frontal plane and 0.02°±1.82° for the sagittal plane. There was a small variability of the results and this systematic review resulted in representative values for SPV. The critical analysis of the studies and observed homogeneity in the sample suggests that the methodological differences used in the studies did not influence SPV assessment of directional bias in healthy subjects. These data can serve as a reference for clinical studies in disorders of verticality.

Disturbance of verticality perception and postural dysfunction in Parkinson's disease

OBJECTIVES

Verticality perception is known to be abnormal in Parkinson's disease (PD), but in which stage respective dysfunctions arise and how they relate to postural disorders remains to be settled. These issues were studied with respect to different dimensions of the subjective visual vertical (SVV) in relation to clinical parameters of postural control.

MATERIALS & METHODS

All participants had to orientate a luminous line at random planar orientations to a strictly vertical position using an automated operator system. The SVV was analyzed in 58 PD patients and 28 control subjects with respect to (i) the angle between true and subjective vertical (deviation) and (ii) the variability of this across five measurements (variability). Results were referred to the subjective upright head position (SUH), the disease stage, and clinical gait/balance features assessed by the MDS-UPDRS and the Tinetti test.

RESULTS

Parkinson's disease patients had significantly higher SVV deviation and variability than controls. With respect to disease stage, deviation developed before abnormal variability. SVV variability was associated with poor balance and gait performance, as well as postural instability. Deficits in SUH and SVV deviation were correlated and mostly unidirectional, but did not correspond to the side of motor symptom dominance.

CONCLUSIONS

Visual verticality perception in PD is deviated already in early stages, conceivably as a relatively static internal misrepresentation of object orientation. Variability about verticality perception emerges in more advanced stages and is associated with postural and balance abnormalities.

The effects of exercise on perception of verticality in adolescent idiopathic scoliosis

PURPOSE

Visual and proprioceptive cues are important for body orientation to maintain correct posture. This study investigated the effects of exercise training on subjective visual, postural, and haptic perception of verticality in patients with scoliosis.

SUBJECTS AND METHODS

Thirty-two female adolescents with moderate idiopathic scoliosis were randomly allocated to "Core Stabilization Exercise (CSE)," "Body Awareness," or "Traditional Exercise (TE)" groups. Each group completed a 1-hour supervised program, two days per week for 10 weeks while continuing to wear spinal braces. Perceptual visual, postural, and haptic estimates were assessed before and after treatment.

RESULTS

Subjective visual vertical perception only improved in the awareness group. Subjective visual horizontal perception, postural vertical perception, total postural perception scores, total haptic perception scores, and haptic perception 45° to the right were significantly improved in the stabilization and awareness groups. For the 60° right and 60° left postural perception parameters, as well as the 45° left haptic perception parameters, perception improved only in the stabilization group. No improvement was observed in the traditional group.

CONCLUSION

Improvements in visual, postural, and haptic verticality perception within the stabilization exercise training and Basic Body Awareness group treatment suggest the addition of these exercise methods for the treatment of idiopathic scoliosis to improve internal body orientation.

Perception of Upright: Multisensory Convergence and the Role of Temporo-Parietal Cortex

We inherently maintain a stable perception of the world despite frequent changes in the head, eye, and body positions. Such "orientation constancy" is a prerequisite for coherent spatial perception and sensorimotor planning. As a multimodal sensory reference, perception of upright represents neural processes that subserve orientation constancy through integration of sensory information encoding the eye, head, and body positions. Although perception of upright is distinct from perception of body orientation, they share similar neural substrates within the cerebral cortical networks involved in perception of spatial orientation. These cortical networks, mainly within the temporo-parietal junction, are crucial for multisensory processing and integration that generate sensory reference frames for coherent perception of self-position and extrapersonal space transformations. In this review, we focus on these neural mechanisms and discuss (i) neurobehavioral aspects of orientation constancy, (ii) sensory models that address the neurophysiology underlying perception of upright, and (iii) the current evidence for the role of cerebral cortex in perception of upright and orientation constancy, including findings from the neurological disorders that affect cortical function.

Rod and frame test and posture under optokinetic stimulation used to explore two complementary aspects of the visual influence in postural control after stroke

BACKGROUND

Balance rehabilitation should consider individual comportments according to visual input (VI). Indeed, visual dependence (VD), defined as the predominance given to the VI whatever the circumstances, frequent after stroke it could disturb balance. Because the term VD is a bit restrictive and cannot be deduced from clinical tests, the term visual sensitivity (VS) is preferred here.

HYPOTHESIS

VI could have different influence depending on the task for a given individual.

METHODS

We retrospectively compared 2 VS tests routinely used: the rod and frame test (RFT) and optokinetic stimulation (OKS). In RFT, VS was defined by a misperception of the visual verticality induced by a tilted frame (VS RFT) and in OKS by tilted sitting posture induced by rotational OKS (VS OKS). We studied the relations between VS RFT and VS OKS.

RESULTS

We analysed data for 84 patients, mean age 55±10years, 45±30days after stroke. Scores for both tests were correlated with autonomy measured by the functional independence measure (r=-0.3, p=0.01 and r=-0.2, p=0.02). VS OKS score was also correlated with balance measured by the postural assessment scale for stroke (r=-0.3, p=0.03). VS RFT score was not correlated with VS OKS score (p=0.4, r=0.04).

DISCUSSION - CONCLUSION

A patient may display VS for one test without sensitivity for the other because these tests investigate different neural organisation - perception for RFT or action for OKS. Their relation to balance disorders should be further investigated to build individualized rehabilitation programs.

Effects of sit-to-stand training combined with transcutaneous electrical stimulation on spasticity, muscle strength and balance ability in patients with stroke: A randomized controlled study

Sit-to-stand is a fundamental movement of human being for performing mobility and independent activity. However, Stroke people symptoms experience difficulty in conducting the sit-to-stand due to paralysis and especially ankle spasticity. Recently, transcutaneouselectrical- stimulation (TENS) is used to reduce pain but also to manage spasticity. The purpose of this study was to determine (1) whether TENS would lead to ankle spasticity reduction and (2) whether sit-to-stand training combined with TENS would improve spasticity, muscle strength and balance ability in stroke patients. Forty-stroke patients were recruited and were randomly divided into two groups: TENS group (n=20) and sham group (n=20). All participants underwent 30-sessions of sit-to-stand training (for 15-min, five-times per week for 6-weeks). Prior to each training session, 30-min of TENS over the peroneal nerve was given in TENS group, whereas sham group received non-electrically stimulated TENS for the same amount of time. Composite-Spasticity-Score was used to assess spasticity level of ankle plantar-flexors. Isometric strength in the extensor of hip, knee and ankle were measured by handheld dynamometer. Postural-sway distance was measured using a force platform. The spasticity score in the TENS group (2.6±0.8) improved significantly greater than the sham group (0.7±0.8, p<0.05). The muscle strength of hip extensor in the TENS group (2.7±1.1kg) was significantly higher than the sham group (1.0±0.8kg, p<0.05). Significant improvement in postural-sway was observed in the TENS group compared to the sham group (p<0.05). Thus, sit-to-stand training combined with TENS may be used to improve the spasticity, balance function and muscle strength in stroke patients.

Surface Electromyography of Lumbar Paraspinal Muscles During Seated Passive Tilting of Patients With Lateropulsion Following Stroke

Background. Patients with lateropulsion (pushing) following stroke push toward the contralesional side. Their response to a passive tilt while seated has not been studied with surface electromyography (sEMG) of lumbar paraspinal muscles.

Objective. To compare onset, response duration, and trends in lumbar paraspinal muscle activity among patients with stroke, patients with stroke and lateropulsion, and healthy controls during seated passive tilting.

Method. Seated subjects were passively tilted in the frontal plane at slow and fast speeds. Bilateral sEMG electrodes at the level of lumbar vertebrae 3 recorded paraspinal muscle activity. Surface EMG onset, response duration, and type of muscle activity were compared for 15 patients with stroke and lateropulsion, 12 patients with uncomplicated stroke, and 16 healthy, aged controls. Correlations were assessed between the Burke Lateropulsion Scale (BLS) and both sEMG onset and sEMG response duration.

Results. Onset of muscle activity was similar in all groups. Patients with lateropulsion showed decreased sEMG response duration in weak-sided paraspinal muscle activity during slow, passive tilting to the strong side. They had more variable muscle activity during fast, passive tilting to the weak side than controls. BLS scores did not correlate with dependent variables.

Conclusions. Patients with lateropulsion activated paraspinal muscles with similar onset time as controls during seated passive tilting. Lateropulsion influences weak-sided paraspinal response duration during passive tilting. Graviceptive neglect may explain some of this difficulty with sustaining contractions, but weakness may also be a contributing factor.

Evolution of Subjective Visual Vertical Perturbation After Stroke

Objective. The perception of visual verticality is often perturbed after stroke and might be an underlying component of imbalance. The aim of this study was to describe the evolution of visual vertical (VV) perturbation and to investigate the factors affecting it.

Methods. Thirty patients with hemiplegia after a single hemispheric stroke (17 left lesioned [LL] and 13 right lesioned [RL]) were studied. Visual verticality was tested within 45 days of stroke, and then at 3 and 6 months. Subjects sat in a dark room and adjusted a luminous rod to the vertical position. The differences between patients’ adjustments and vertical were calculated. The effects on VV evolution of the side, size, type, and location of the lesion were tested.

Results. Sixty percent of the recent stroke patients had an initial inaccurate perception of verticality, and 39% of these patients recovered during the 1st 3 months after stroke. The evolution of VV tilt depended on the side of the lesion ( P = 0.01), with better recovery in LL patients. None of the other factors studied affected VV normalization.

Conclusions. The poorer recovery of vertical perception after right-side stroke might be due to the predominant role of the right hemisphere in spatial cognition, and might be involved in the poorer recovery of balance after stroke in RL patients.

What is backward disequilibrium and how do i treat it? A complex patient case study

BACKGROUND AND PURPOSE

Postural vertical refers to a component of an individual's perception of verticality that is derived from information about the direction of gravitational forces. Backward disequilibrium (BD) is a postural disorder observed in some older adults who have a distortion in their perception of postural vertical. Individuals with BD sustain their center of mass (COM) posterior to their base of support and resist correction of COM alignment. The purposes of this case study are to describe a patient with BD and propose a physical therapy management program for this condition.

CASE DESCRIPTION AND INTERVENTION

The patient was an 83-year-old woman admitted for home care services 4 months after falling and sustaining a displaced right femoral neck fracture and subsequent hemiarthroplasty. Details of the clinical examination, diagnosis, and intervention are provided and a treatment protocol for physical therapy management is suggested.

OUTCOMES

During the episode of care, the patient (1) decreased her dependence on caregivers, (2) surpassed minimal detectable change or minimal clinically important improvements in gait speed and on the Short Physical Performance Battery and Performance-Oriented Mobility Assessment, and (3) achieved her primary goal of staying in her own apartment at an assisted living facility.

DISCUSSION

Knowledge of BD coupled with a thorough clinical examination may assist physical therapists in identifying this condition and employing the specific intervention we have proposed. We believe that failure to recognize and manage our patient's condition appropriately would have led to nursing home placement.Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A94).

Maintaining Trunk and Head Upright Optimizes Visual Vertical Measurement After Stroke

Background. Visual vertical (VV) measurement provides information about spatial cognition and is now part of postural disorders assessment. Guidelines for clinical VV measurement after stroke remain to be established, especially regarding the orientation settings for patients who do not sit upright. Objectives. We analyzed the need to control body orientation while patients estimate the VV. Methods. VV orientation and variability were assessed in 20 controls and 36 subacute patients undergoing rehabilitation after a first hemisphere stroke, in 3 settings: body not maintained (trunk and head free), partially maintained (trunk maintained, head free), or maintained (trunk and head). VV was analyzed as a function of trunk and head tilt, also quantified. Results. Trunk and head orientations were independent. The ability to sit independently was affected by a tilted trunk. The setting had a strong effect on VV orientation and variability in patients with contralesional trunk tilt (n = 11; trunk orientation −18.4 ± 11.7°). The contralesional VV bias was severe and consistent under partially maintained (−8.4 ± 5.2°) and maintained (−7.8 ± 3.5°) settings, whereas various individual behaviors reduced the mean bias under the nonmaintained setting (−3.6 ± 9.3°, P < .05). VV variability was lower under the maintained (1.5 ± 0.2°) than nonmaintained (3.7 ± 0.4°, P < .001) and partially maintained (3.6 ± 0.2°, P < .001) settings. In contrast, setting had no effect in patients with satisfactory postural control in sitting. Conclusion. Subject setting improves VV measurement in stroke patients with postural disorders. Maintaining the trunk upright enhances the validity of VV orientation, and maintaining the head upright enhances the validity of within-subject variability. Measuring VV without any body maintaining is valid in patients with satisfactory balance abilities.

Time to Recovery From Lateropulsion Dependent on Key Stroke Deficits

Background. Lateropulsion, a postural control disorder, delays recovery following hemispheric stroke. The number of stroke impairments may lead to differential recovery rates, depending on the intact systems available for recovery from lateropulsion. Objective. To study the impact of key postural control deficits on lateropulsion rate of recovery following stroke. Methods. Through retrospective analysis: 169 patients with hemispheric stroke in an in-patient rehabilitation facility were divided into 3 groups: (1) motor deficits only; (2) motor and hemianopic or visual–spatial deficits or motor and proprioceptive deficits; and (3) motor, proprioceptive, and hemianopic or visual–spatial deficits. Kaplan–Meier survival analysis determined if time to recovery from lateropulsion (achieving a score of 0 or 1 on the Burke Lateropulsion Scale) differed by group. Results. Log rank tests showed that time to recovery from lateropulsion differed based on the number of deficits (group, P = .012). Post hoc analyses by lesion side showed that group differences only occurred in right brain lesion ( P < .05) as compared with left brain lesions ( P = .34). Patients recovered from lateropulsion during in-patient rehabilitation if they had only motor deficits; those with all 3 postural control deficits showed the most protracted recovery. Conclusions. Rate of recovery from lateropulsion after stroke is dependent on the side of lesion, and number of key motor, proprioceptive, and/or hemianopic or visual–spatial deficits. The more postural control systems affected, the slower the recovery. Our data identify patients likely to need protracted rehabilitation targeting key postural control deficits.

[Is the sense of verticality vestibular?]

The vestibular system constitutes an inertial sensor, which detects linear (otoliths) and angular (semicircular canals) accelerations of the head in the three dimensions. The otoliths are specialized in the detection of linear accelerations and can be used by the brain as a "plumb line" coding earth gravity acceleration (direction). This property of otolithic system suggested that the sense of verticality is supported by the vestibular system. The preeminence of vestibular involvement in the sense of verticality stated in the 1900s was progressively supplanted by the notion of internal models of verticality. The internal models of verticality involve rules and properties of integration of vestibular graviception, somaesthesic graviception, and vision. The construction of a mental representation of verticality was mainly modeled as a bottom-up organization integrating visual, somatosensory and vestibular information without any cognitive modulations. Recent studies reported that the construction of internal models of verticality is not an automatic multi-sensory integration process but corresponds to more complex mechanisms including top-down influences such as awareness of body orientation or spatial representations.

Sensory reweighting in controls and stroke patients

OBJECTIVE

To test sensitivity to proprioceptive, vestibular and visual stimulations of stroke patients with regard to balance.

METHOD

The postural control of 20 hemiparetic patients after a single hemispheric stroke that had occurred at least 6 months before the study along with 20 controls was probed with vibration, optokinetic, and vestibular galvanic stimulations. Balance was assessed using a force platform (PF) with two miniature inertial sensors placed on the head (C1) and the trunk (C2) under each sensory condition and measured by three composite scores as the mean displacement of the body (PF, C1, C2) during the stimulation. A subject with a composite score greater than the 75th percentile of the composite scores found in the control subjects was arbitrarily considered to be sensitive to that stimulation.

RESULTS

Both control and stroke patients showed large inter-individual variations in response to the three types of sensory stimulation. Among the hemiparetic patients, nearly 65% were sensitive to the optokinetic stimulation, 60% to the galvanic stimulation and 65% to the vibration stimulation. In contrast to the control group, all the hemiparetic subjects were sensitive to at least one type of stimulation.

CONCLUSION

Stroke patients are highly dependent on visual, proprioceptive and vestibular information in order to control their standing posture and individually differ in their relative sensitivity to each type of sensory stimulation.

SIGNIFICANCE

Contrarily to what one might suppose, the increased visual dependence manifested by stroke patients does not necessarily entail any neglect of proprioceptive and vestibular information.

[Early rehabilitation for neurologic patients]

Rehabilitation improves the functional prognosis of patients after a neurologic lesion, and tendency is to begin rehabilitation as soon as possible. This review focuses on the interest and the feasibility of very early rehabilitation, initiated from critical care units. It is necessary to precisely assess patients' impairments and disabilities in order to define rehabilitation objectives. Valid and simple tools must support this evaluation. Rehabilitation will be directed to preventing decubitus complications and active rehabilitation. The sooner rehabilitation is started; the better functional prognosis seems to be.

Reorientation to vertical modulated by combined support surface tilt and virtual visual flow in healthy elders and adults with stroke

We explored how changes in visual attention impacted postural motor performance in healthy elders and adults post-stroke within a virtual reality environment, including when vestibular information was not perceptible. Visual dependence in 13 healthy (50-80 years) and 13 adults post-stroke (49-70 years) was assessed with a rod-and-frame task. Three degree support surface dorsiflexion tilts at 30°/s were combined with 30° and 45°/s continuous pitch rotations of the visual environment. The support surface remained tilted for 30 s followed by a 0.1°/s return to neutral during continued visual field rotation. Body displacement and ankle muscle responses were recorded, and wavelet transforms calculated. Muscle frequencies and kinematic measures were examined with functional principal component analysis, and weights compared through mixed model repeated measures ANOVA. Both populations exhibited increased backward sway with pitch upward visual field motion; adults post-stroke produced significantly larger muscle responses. Lateral sway was most regulated when visual flow velocity matched platform velocity. Visual flow summed with direction of support surface instability and visually dependent individuals produced more controlled lateral sway when viewing a dynamic visual field. Provoking postural instability within a dynamic visual flow field could serve as a training tool for postural stabilizing actions, particularly when visual dependence is exhibited.

Influence of sensory loss on the perception of verticality in stroke patients

PURPOSE

The aim of this study was to investigate the relationship between somatosensory loss and perception of verticality in stroke patients suffering single-hemisphere lesions.

METHOD

Somatosensory loss was measured using the Rivermead Assessment for Somatosensory Performance (RASP). Perception of verticality was assessed with the Subjective Visual Vertical (SVV) and the Subjective Postural Vertical (SPV) tests. Absolute Values of SVV and SPV were used to analyze the amount of deviation in relation to somatosensory loss.

RESULTS

Thirty-two patients were included in the study (mean age = 45.91 SD = 31.88 years). Analysis showed that somatosensory loss was related to results of the SVV (r = -0.552, p = 0.001, Pearson Rank) and the SPV (r = -0.661, p < 0.001, Spearman Ï). Furthermore, results showed that both joint-related (SVV: r = -0.411, p = 0.019, Pearson Rank; SPV: r = -0.597, p = 0.001, Spearman Ï) and skin-related (SVV: r = -0.595, p < 0.001, Pearson Rank; SPV: r = -0.663, p < 0.001, Spearman Ï) somatosensory information is related to verticality perception.

CONCLUSIONS

This study provides evidence that perception of verticality is related to somatosensory loss, which means that somatosensory loss will lead to a larger amount of deviation of SVV and SPV in relation to the gravitational vector. Furthermore, it is interesting to note that both SVV and SPV are influenced by somatosensory loss.

IMPLICATIONS FOR REHABILITATION

• Somatosensory information is related to both visual and postural aspects of verticality perception. • Both joint- and cutaneous-related modalities of sensory information are related to perception of verticality. • Sensory training could be important in the recovery of verticality perception.

Neuroimaging in stroke and non-stroke pusher patients

Pusher behavior (PB) is a disorder of postural control affecting patients with encephalic lesions. This study has aimed to identify the brain substrates that are critical for the occurrence of PB, to analyze the influence of the midline shift (MS) and hemorrhagic stroke volume (HSV) on the severity and prognosis of the PB. We identified 31 pusher patients of a neurological unit, mean age 67.4±11.89, 61.3% male. Additional neurological and functional examinations were assessed. Neuroimaging workup included measurement of the MS, the HSV in patients with hemorrhagic stroke, the analysis of the vascular territory, etiology and side of the lesion. Lesions in the parietal region (p=0.041) and thalamus (p=0.001) were significantly more frequent in PB patients. Neither the MS nor the HSV were correlated with the PB severity or recovery time.

Ageing of the postural vertical

A postural vertical (PV) tilted backward has been put forward as a reason explaining the backward disequilibrium often observed in elderly fallers. This raises the question of a possible ageing process of the PV involving a backward tilt of verticality perception increasing with age. We have explored this hypothesis by measuring PV in pitch using the wheel paradigm in 87 healthy subjects aged from 20 to 97 years. The possibility that this physiological ageing accelerated in the second part of life was also analysed. Two indices were calculated: the mean orientation (PV-orient) and the dispersion (PV-uncert). The correlation between age and PV-orient was r = -0.2 (p < 0.05). Added to the fact that PV was twice as shifted backward in the 38 seniors over 50 years (-1.15 degrees +/- 1.40 degrees ) as in the 49 young adults under 50 years (-0.45 degrees +/- 0.97 degrees ; t = 2.75, p < 0.01), this indicates the existence of a physiological ageing process on the direction perceived as vertical by the whole body, with a slight backward shift of PV throughout the life span. The correlation between age and PV-uncert was r = 0.35 (p < 0.001) in all subjects and r = 0.59 (p < 0.001) in seniors. This indicates that subjects get less and less accurate in their perception of the postural vertical with age, especially very old subjects who show great uncertainty in determining with their body the direction of the vertical. Taken together, these findings indicate that the internal model of verticality is less robust in elderly people. This may play a part in their postural decline.

How vestibular stimulation interacts with illusory hand ownership

Artificial stimulation of the peripheral vestibular system has been shown to improve ownership of body parts in neurological patients, suggesting vestibular contributions to bodily self-consciousness. Here, we investigated whether galvanic vestibular stimulation (GVS) interferes with the mechanisms underlying ownership, touch, and the localization of one's own hand in healthy participants by using the "rubber hand illusion" paradigm. Our results show that left anodal GVS increases illusory ownership of the fake hand and illusory location of touch. We propose that these changes are due to vestibular interference with spatial and/or temporal mechanisms of visual-tactile integration leading to an enhancement of visual capture. As only left anodal GVS lead to such changes, and based on neurological data on body part ownership, we suggest that this vestibular interference is mediated by the right temporo-parietal junction and the posterior insula.

Analysis of dynamic sitting balance on the independence of gait in hemiparetic patients

The purpose of this study was to investigate the relationship between dynamic sitting balance and walking ability in stroke patients. Patients were evaluated using functional independence measure (FIM), and those with a locomotion score of 5 or below were categorized into the dependent walking and below group (dependent group) and those with a score of 6 or above were categorized into the independent walking group (independent group). They were asked to take a sitting position at the center of an unstable platform (seesaw). The experimenter passively tilted the unstable platform to the paretic side or non-paretic side by 10 degrees in the frontal plane. The unstable platform was released suddenly, with the experimenter supporting the platform with both hands, and the subjects were asked to control their posture so that their body axis came to the vertical position and the platform came to the horizontal position in the frontal plane. As a result, the body axis of left hemiplegic patients significantly tilted to the non-paretic side. On the other hand, in the dependent group in the right as well as left hemiplegic patients, the patients heads were tilted to the side from which tilting was started, though not significantly in both conditions. This study demonstrated that patients with poor walking function have a deviated verticality of the head and the body axis. We surmise that patients whose body axis tilts towards the non-paretic side during a dynamic balance maintenance task like this test would have lower walking independence.

Backward disequilibrium in elderly subjects

Backward disequilibrium is observed frequently in daily clinical practice. However, there are no epidemiological data concerning this postural disorder. Defined by a posterior position of the centre of mass with respect to the base of support, backward disequilibrium is abnormal postural behavior, usually characterized by a posterior trunk tilt in standing and sitting positions, which predisposes subjects to backward falls. Many afflictions whether they are somatic (degenerative, ischemic and traumatic brain lesions), psychosomatic (psychomotor disadaptation syndrome, confinement to bed, nonuse situations) or psychological (depression) can cause backward disequilibrium. A vicious circle of falls, and loss of autonomy can arise and this is the main consequence of backward disequilibrium. Thus, in this paper, we review backward disequilibrium in elderly subjects with regard to the causes, consequences, assessment, and management.

Is Visuospatial Hemineglect Really a Determinant of Postural Control Following Stroke? An Acute-Phase Study

Objective. The purpose of this study was to determine the independent contribution of visuospatial hemineglect to impaired postural control in the acute phase (<2 weeks) of stroke compared with other possible clinical and biological determinants. Methods. This study was conducted in 4 hospitals in the mid-east region of the Netherlands. A total of 78 consecutive patients with a first-ever acute supratentorial stroke was included. Functional balance was measured with the Trunk Impairment Scale, the Trunk Control Test, the Berg Balance Scale, and the Functional Ambulation Categories. Visuospatial hemineglect was assessed by means of an asymmetry index obtained from the Behavioral Inattention Test. The Motricity Index, vibration threshold, sustained attention, and the presence of hemianopia were registered as other possible clinical determinants. Stepwise backward multiple linear regression analysis was performed introducing all selected clinical determinants as well as age and poststroke time as possible biological determinants. Results. Hemineglect was present in 17 patients (21.8%). The groups with and without hemineglect were different for gender and the proportion of right hemisphere strokes, but not for age, type of stroke, or poststroke time. Neglect patients had on average lower scores on all functional balance tests as well as on the clinical assessments. Multivariate linear regression showed that, besides hemineglect, only muscle strength and age independently contributed to impaired balance explaining 65% to 72% of variance of the selected outcomes. Conclusion. This study showed that hemineglect independently contributes to impaired postural control in the acute phase of stroke.