Quantification and Rehabilitation of Unilateral Spatial Neglect in Immersive Virtual Reality: A Validation Study in Healthy Subjects.

Unilateral spatial neglect is a common sensorimotor disorder following the occurrence of a stroke, for which prismatic adaptation is a promising rehabilitation method. However, the use of prisms for rehabilitation often requires the use of specific equipment that may not be available in clinics. To address this limitation, we developed a new software package that allows for the quantification and rehabilitation of unilateral spatial neglect using immersive virtual reality. In this study, we compared the effects of virtual and real prisms in healthy subjects and evaluated the performance of our virtual reality tool (HTC Vive) against a validated motion capture tool. Ten healthy subjects were randomly exposed to virtual and real prisms, and measurements were taken before and after exposure. Our findings indicate that virtual prisms are at least as effective as real prisms in inducing aftereffects (4.39° ± 2.91° with the virtual prisms compared to 4.30° ± 3.49° with the real prisms), but that these effects were not sustained beyond 2 h regardless of exposure modality. The virtual measurements obtained with our software showed excellent metrological qualities (ICC = 0.95, error = 0.52° ± 1.18°), demonstrating its validity and reliability for quantifying deviation during pointing movements. Overall, our results suggest that our virtual reality software (Virtualis, Montpellier, France) could provide an easy and reliable means of quantifying and rehabilitating spatial neglect. Further validation of these results is required in individuals with unilateral spatial neglect.

Validity and Reliability of Kinect v2 for Quantifying Upper Body Kinematics during Seated Reaching.

Kinematic analysis of the upper limbs is a good way to assess and monitor recovery in individuals with stroke, but it remains little used in clinical routine due to its low feasibility. The aim of this study is to assess the validity and reliability of the Kinect v2 for the analysis of upper limb reaching kinematics. Twenty-six healthy participants performed seated hand-reaching tasks while holding a dumbbell to induce behaviour similar to that of stroke survivors. With the Kinect v2 and with the VICON, 3D upper limb and trunk motions were simultaneously recorded. The Kinect assesses trunk compensations, hand range of motion, movement time and mean velocity with a moderate to excellent reliability. In contrast, elbow and shoulder range of motion, time to peak velocity and path length ratio have a poor to moderate reliability. Finally, instantaneous hand and elbow tracking are not precise enough to reliably assess the number of velocity peaks and the peak hand velocity. Thanks to its ease of use and markerless properties, the Kinect can be used in clinical routine for semi-automated quantitative diagnostics guiding individualised rehabilitation of the upper limb. However, engineers and therapists must bear in mind the tracking limitations of the Kinect.

The reserve of joint torque determines movement coordination.

Humans coordinate biomechanical degrees of freedom to perform tasks at minimum cost. When reaching a target from a seated position, the trunk-arm-forearm coordination moves the hand to the well-defined spatial goal, while typically minimising hand jerk and trunk motion. However, due to fatigue or stroke, people visibly move the trunk more, and it is unclear what cost can account for this. Here we show that people recruit their trunk when the torque at the shoulder is too close to the maximum. We asked 26 healthy participants to reach a target while seated and we found that the trunk contribution to hand displacement increases from 11 to 27% when an additional load is handled. By flexing and rotating the trunk, participants spontaneously increase the reserve of anti-gravitational torque at the shoulder from 25 to 40% of maximal voluntary torque. Our findings provide hints on how to include the reserve of torque in the cost function of optimal control models of human coordination in healthy fatigued persons or in stroke victims.

Recovering arm function in chronic stroke patients using combined anodal HD-tDCS and virtual reality therapy (ReArm): a study protocol for a randomized controlled trial.

BACKGROUND: After a stroke, 80% of the chronic patients have difficulties to use their paretic upper limb (UL) in activities of daily life (ADL) even after rehabilitation. Virtual reality therapy (VRT) and anodal transcranial direct current stimulation (tDCS) are two innovative methods that have shown independently to positively impact functional recovery of the paretic UL when combined with conventional therapy. The objective of the project will be to evaluate the impact of adding anodal high-definition (HD)-tDCS during an intensive 3-week UL VRT and conventional therapy program on paretic UL function in chronic stroke. METHODS: The ReArm project is a quadruple-blinded, randomized, sham-controlled, bi-centre, two-arm parallel, and interventional study design. Fifty-eight chronic (> 3 months) stroke patients will be recruited from the Montpellier and Nimes University Hospitals. Patients will follow a standard 3-week in-patient rehabilitation program, which includes 13 days of VRT (Armeo Spring, 1 × 30 min session/day) and conventional therapy (3 × 30 min sessions/day). Twenty-nine patients will receive real stimulation (4x1 anodal HD-tDCS montage, 2 mA, 20 min) to the ipsilesional primary motor cortex during the VRT session and the other 29 patients will receive active sham stimulation (2 mA, 30 s). All outcome measures will be assessed at baseline, at the end of rehabilitation and again 3 months later. The primary outcome measure will be the wolf motor function test. Secondary outcomes will include measures of UL function (Box and Block Test), impairment (Fugl Meyer Upper Extremity), compensation (Proximal Arm Non-Use), ADL (Actimetry, Barthel Index). Other/exploratory outcomes will include pain, fatigue, effort and performance, kinematics, and motor cortical region activation during functional motor tasks. DISCUSSION: This will be the first trial to determine the impact of adding HD-tDCS during UL VRT and conventional therapy in chronic stroke patients. We hypothesize that improvements in UL function will be greater and longer-lasting with real stimulation than in those receiving sham. TRIAL REGISTRATION: The ReArm project was approved by The French Research Ethics Committee, (Comité de Protection des Personnes-CPP SUD-EST II, N°ID-RCB: 2019-A00506-51, http://www.cppsudest2.fr/ ). The ReArm project was registered on ClinicalTrials.gov ( NCT04291573 , 2nd March 2020.

Inertial measurement unit compared to an optical motion capturing system in post-stroke individuals with foot-drop syndrome.

BACKGROUND: Functional electrical stimulation (FES) can be used for compensation of foot-drop for post-stroke individuals by pre-programmed fixed stimulation; however, this stimulation seems no more effective than mechanical ankle foot orthoses. OBJECTIVE: We evaluated the metrological quality of inertial sensors for movement reconstruction as compared with the gold-standard motion capturing system, to couple FES with inertial sensors to improve dorsiflexion on the paretic side, by using an adaptive stimulation taking into account individuals' performance post-stroke. METHODS: Adults with ischemic or hemorrhagic stroke presenting foot-drop and able to walk 10m, were included from May 2016 to June 2017. Those with passive ankle dorsiflexion<0° with the knee stretched were excluded. Synchronous gait was analyzed with the VICON© system as the gold standard and inertial measurement units (IMUs) worn by participants. The main outcome was the dorsiflexion angle at the heel strike and mid-swing phase obtained from IMUs and the VICON system. Secondary outcomes were: stride length, walking speed, maximal ankle dorsiflexion velocity and fatigue detection. RESULTS: We included 26 participants [18 males; mean age 58 (range 45-84) years]. During heel strike, the dorsiflexion angle measurements demonstrated a root mean square error (RMSE) of 5.5°; a mean average error (MAE) of 3.9°; Bland-Altman bias of -0.1° with limits of agreement -10.9° to+10.7° and good intra-class correlation coefficient (ICC) at 0.87 between the 2 techniques. During the mid-swing phase, the RMSE was 5.6; MAE 3.7°; Bland-Altman bias -0.9° with limits of agreement -11.7° to+9.8° and ICC 0.88. Good agreement was demonstrated for secondary outcomes and fatigue detection. CONCLUSIONS: IMU-based reconstruction algorithms were effective in measuring ankle dorsiflexion with small biases and good ICCs in adults with ischemic or hemorrhagic stroke presenting foot-drop. The precision obtained is sufficient to observe the fatigue influence on the dorsiflexion and therefore to use IMUs to adapt FES.

Rehabilitation of the upper arm early after stroke: Video games versus conventional rehabilitation. A randomized controlled trial.

BACKGROUND: Few rehabilitation methods have proven their efficacy in increasing sensori-motor recovery and/or function of the upper limb (UL) after stroke. Video games (VGs) are promising tools in this indication. OBJECTIVE: To compare UL rehabilitation by using VGs and conventional rehabilitation (CR) in patients with sub-acute stroke. DESIGN: Single-blind, multicentric trial, with central randomization and stratification by center. SETTING: Physical and rehabilitation medicine departments of 2 university hospitals. PARTICIPANTS: Adults within 3 months after a first vascular cerebral accident, with UL Fugl Meyer Score (UL-FMS)<30/66 and without major cognitive impairment. INTERVENTION: A 45-min additional session of conventional occupational therapy (OT) or a VG-based OT session as add-on therapy to usual rehabilitation programs, 5 days/week for 6 weeks. MAIN OUTCOME MEASURES: Primary outcome: UL-FMS. Secondary outcome: Box and Block Test (BBT), Wolf Motor Function test (WMFT), Motor Activity Log (MAL), Barthel Index and quality of life (SF-36). RESULTS: We included 51 patients (20 women) at a mean (SD) of 27.2 (19.4) days post-stroke (mean age 58 years [range 24-83]), 26 in the CR group and 25 in the VG group (23 in each group at 6-month follow-up). The mean duration of the additional rehabilitation session was similar in both groups: 29.3 (4.3) vs 28.0 (4.4) min in CR and VG groups. Shoulder pain occurred in 4 patients in the VG group versus 7 in the CR group. At day 45, gain in UL-FMS did not significantly differ between the groups (CR mean 17.8 [14.6] vs VG 24.1 [14.8]; P=0.10), whereas gain in BBT was doubled in the VG group (CR 7.4 [12.2] vs VG 15.7 [16.3]; P=0.02). At 6-month follow-up, the study was inconclusive about between-group differences in UL-FMS, BBT and other criteria. Post-hoc analysis showed that gains in UL-FMS or BBT were significantly higher in the VG than CR group for patients included within 30 days post-stroke. CONCLUSION: In general, we cannot conclude that video gaming and conventional OT led to different long-term sensorimotor recovery of the UL after sub-acute stroke. However, when applied within the first month after stroke, video gaming was more efficient than conventional rehabilitation on both sensorimotor recovery and gross grasping function. TRIAL REGISTRATION: ClinicalTrials.gov (NCT01554449).

Time course of sensorimotor cortex reorganization during upper extremity task accompanying motor recovery early after stroke: An fNIRS study.

BACKGROUND: The acute phase of stroke is accompanied by functional changes and interplay of both hemispheres. However, our understanding of how the time course of upper limb functional motor recovery is related to the progression of brain reorganization in the sensorimotor areas remains limited. This study aimed to assess the time course of hemodynamic patterns of cortical sensorimotor areas using functional near infrared spectroscopy (fNIRS) and motor recovery within three months after a stroke. METHOD: Eight right-handed first ischemic/hemorrhagic stroke patients (60±8 years, 3 women) with mild to severe hemiparesis were examined with repetitive fNIRS measurements and motor recovery tests (Fugl-Meyer score) during two months. Hemodynamic changes over the ipsilesional and contralesional sensorimotor areas were collected from a multi-channel fNIRS system during intermittent isometric muscle contractions at self-selected submaximal force levels for each arm. Lateralization index was computed to evaluate the changes in the interhemispheric balance between the cortical sensorimotor areas. RESULTS: Lateralization index values during non-paretic arm movements showed no significant changes over time in patients and were comparable to those observed in eight healthy controls. Paretic-arm movements were associated early with a bilateral cortical activity before shifting to ipsilesional patterns (p < 0.01). Progressive lateralization observed over the two months (p < 0.05) evolved concomitantly with an increase in the Fugl-Meyer score (p < 0.001). CONCLUSIONS: Cortical reorganization monitoring using fNIRS during the first weeks after stroke may be applied for assessing progressive brain plasticity in addition to clinical measures of performance.

Trajectory formation principles are the same after mild or moderate stroke.

When we make rapid reaching movements, we have to trade speed for accuracy. To do so, the trajectory of our hand is the result of an optimal balance between feed-forward and feed-back control in the face of signal-dependant noise in the sensorimotor system. How far do these principles of trajectory formation still apply after a stroke, for persons with mild to moderate sensorimotor deficits who recovered some reaching ability? Here, we examine the accuracy of fast hand reaching movements with a focus on the information capacity of the sensorimotor system and its relation to trajectory formation in young adults, in persons who had a stroke and in age-matched control participants. We find that persons with stroke follow the same trajectory formation principles, albeit parameterized differently in the face of higher sensorimotor uncertainty. Higher directional errors after a stroke result in less feed-forward control, hence more feed-back loops responsible for segmented movements. As a consequence, movements are globally slower to reach the imposed accuracy, and the information throughput of the sensorimotor system is lower after a stroke. The fact that the most abstract principles of motor control remain after a stroke suggests that clinicians can capitalize on existing theories of motor control and learning to derive principled rehabilitation strategies.

[From rehabilitation to re-adaptation, preparing the return home]. / De la rééducation à la réadaptation, préparer le retour à domicile.

After a serious head trauma, the return home constitutes a key moment in the patient's reintegration. It is prepared by a multi-disciplinary team throughout the rehabilitation and re-adaptation process, taking into account the patient's prognosis for recovery.

Percutaneous Needle Tenotomy for the Treatment of Muscle and Tendon Contractures in Adults With Brain Damage: Results and Complications.

OBJECTIVE: To study the results and complications of percutaneous needle tenotomy for superficial retracted tendons in patients with brain damage. DESIGN: Prospective observational study. SETTING: University hospital. PARTICIPANTS: Patients with severe brain damage (N=38; mean age, 60.7y; age range, 24-93y; 21 women) requiring surgical management of contractures and eligible for percutaneous needle tenotomy were enrolled between February 2015 and February 2016. INTERVENTIONS: The percutaneous needle tenotomy gesture was performed by a physical medicine and rehabilitation physician trained by an orthopedic surgeon, under local or locoregional anesthesia. Treated tendons varied among patients. MAIN OUTCOME MEASURES: All patients were evaluated at 1, 3, and 6 months to assess surgical outcomes (joint range of motion [ROM], pain, and functional improvement) while screening for complications. RESULTS: Improvements in ROM (37/38) and contractures-related pain (12/12) were satisfactory. Functional results were satisfactory (Goal Attainment Scale score ≥0) for most patients (37/38): nursing (n=12), putting shoes on (n=8), getting in bed or sitting on a chair (n=6), verticalization (n=7), transfers and gait (n=8), and grip (n=2). Five patients had complications related to the surgical gesture: cast-related complications (n=2), hand hematoma (n=2), and cutaneous necrosis of the Achilles tendon in a patient with previous obliterative arteriopathy of the lower limbs (n=1). CONCLUSIONS: Percutaneous needle tenotomy yields good results in the management of selected superficial muscle and tendon contractures. The complications rate is very low, and this treatment can be an alternative to conventional surgery in frail patients with neurologic diseases.

[Living after a stroke]. / La vie après un accident vasculaire cérébral. Un processus lent et complexe qui doit être coordonné.

After a stroke, patients and their proxies require help in coping with various changes. The transition from hospital to home needs to be organized with the necessary adaptations and material or human aids. Ambulatory rehabilitation such as physiotherapy or speech therapy is frequently provided for several months, but is generally not required on the long term. Self-management programs, adapted sport and leisure activities are valuable. Patients' proxies and families need to be supported, and marital and sexual issues need to be addressed. Support programs exist to enhance leisure and social participation, and to facilitate outdoor mobility. When return to work is possible, patients need be counseled according to their wishes and capacities, and to be addressed to appropriate organizations.

La vie après un accident vasculaire cérébral. De nombreux changements surviennent après un accident vasculaire cérébral, qui nécessitent un accompagnement du patient et de ses proches. Le retour à domicile doit être organisé, en adaptant le domicile, et en prévoyant les aides humaines et matérielles nécessaires. Après la sortie, la kinésithérapie voire l'orthophonie sont souvent prescrites pendant plusieurs mois, mais ne doivent généralement pas être maintenues au long cours. Ce sont les auto-exercices, les activités physiques adaptées et la reprise d'activités de loisir qui sont ensuite nécessaires. L'accompagnement doit soutenir les aidants familiaux et aborder les questions de couple et de sexualité. Les activités de loisir et sociales ainsi que les déplacements extérieurs peuvent être facilités par différentes structures. Quand cela est possible les patients doivent être conseillés dans leur projet professionnel et adressés si besoin aux organismes adéquats.

Continuous gait cycle index estimation for electrical stimulation assisted foot drop correction.

BACKGROUND: Walking impairment after stroke can be addressed with the use of drop foot stimulators (DFS). Many studies have demonstrated that DFS improves walking speed, reduces spasticity and reduces the physiologic effort of walking. Current DFS, through activation of the common peroneal nerve, elicit ankle dorsiflexion during swing phase of gait. DFS are generally piloted by force sensing resistor placed in the shoe of the affected side with stimulation triggered ON by heel rise and triggered OFF by heel strike. A tilt sensor can also be used with stimulation triggered by the tilt of the shank of the affected leg. These triggering approaches are the standard for initiating stimulation. However, the real-time modulation of FES intensity to provide more optimized delivery of stimulation and also to regulate dorsiflexion in the presence of disturbances, such as fatigue and spasticity may increase the number of potential users of DFS. Concerning research domain, stimulators that would allow modulating the stimulation pattern in between heel rise and strike events would allow exploring new stimulation strategies. We propose to extract continuous information: the gait cycle index (GCI), from one inertial measurement unit (IMU) measuring shank tilt angle. In order to illustrate the use of this real-time information, we show the feasibility of piloting an electrical stimulator. METHODS: 12 subjects with post-stroke hemiplegia participated. A wireless IMU was placed on the unaffected shank and was used to estimate GCI. Subjects performed 3 trials in each of the 3 conditions: C1 no stimulation aid, C2 electrical stimulation assistance triggered by heel switch, C3 electrical stimulation assistance triggered from GCI. RESULTS: 1) the proposed algorithm was able to real-time estimate GCI, 2) events could be extracted from GCI information in order to trig a DFS. CONCLUSION: The estimation of the continuous GCI in individuals with stroke is possible. Events can be extracted from this information in order to trig a stimulator. These results are a first step towards the possibility to investigate new DFS paradigms based on real-time modulation of stimulation parameters.

The contribution of kinematics in the assessment of upper limb motor recovery early after stroke.

BACKGROUND: Kinematic assessment of upper limb motor recovery after stroke may be related to clinical scores while being more sensitive and reliable than clinical evaluation alone. OBJECTIVE: To identify the potential of kinematics in assessing upper limb recovery early poststroke. METHODS: Thirteen patients were included within 1 month poststroke and evaluated once a week for 6 weeks and at 3 months with (a) the Fugl-Meyer Assessment (FMA) and (b) kinematic analysis of reach-to-grasp movements. The link between clinical and kinematic data was identified using mixed model with random coefficient analysis. RESULTS: Movement time, trajectory length, directness, smoothness, mean and maximum velocity of the hand were sensitive to change over time and distinguished between movements of paretic, nonparetic, and healthy control limbs. The FMA score increased with movement smoothness over time, explaining 62.5% of FMA variability. CONCLUSION: Kinematic analysis of reach-to-grasp movements is relevant to assess upper limb recovery early poststroke, and is linked to the FMA. Kinematics could provide more accurate real-time indicators of patients' recovery as compared with the sole use of clinical scores, although it remains challenging to establish the universality of the reaching model in relation to motor recovery after stroke.

Motor recovery of the ipsilesional upper limb in subacute stroke.

OBJECTIVE: To investigate the time-related changes in motor performance of the ipsilesional upper limb in subacute poststroke patients by using clinical and kinematic assessments. DESIGN: Observational, longitudinal, prospective, monocentric study. SETTING: Physical medicine and rehabilitation department. PARTICIPANTS: Stroke patients (n=19; mean age, 62.9y) were included less than 30 days after a first unilateral ischemic/hemorrhagic stroke. The control group was composed of age-matched, healthy volunteers (n=9; mean age, 63.1y). INTERVENTIONS: Clinical and kinematic assessments were conducted once a week during 6 weeks and 3 months after inclusion. Clinical measures consisted of Fugl-Meyer Assessment, Box and Block Test (BBT), Nine-Hole Peg Test (9HPT), and Barthel Index. We used a 3-dimensional motion recording system during a reach-to-grasp task to analyze movement smoothness, movement time, and peak velocity of the hand. Healthy controls performed both clinical (BBT and 9HPT) and kinematic evaluation within a single session. MAIN OUTCOME MEASURES: BBT and 9HPT. RESULTS: Recovery of ipsilesional upper arm capacities increased over time and leveled off after a 6-week period of rehabilitation, corresponding to 9 weeks poststroke. At study discharge, patients demonstrated similar ipsilesional clinical scores to controls but exhibited less smooth reaching movements. We found no effect of the hemispheric side of the lesion on ipsilesional motor deficits. CONCLUSIONS: Our findings provide evidence that ipsilesional motor capacities remain impaired at least 3 months after stroke, even if clinical tests fail to detect the impairment. Focusing on this lasting ipsilesional impairment through a more detailed kinematic analysis could be of interest to understand the specific neural network underlying ipsilesional upper-limb impairment.

Effect of coordination biofeedback on (re)learning preferred postural patterns in post-stroke patients.

After stroke, ankle-hip coordination during stance is characterized by changes in the postural system dynamics, specifically the disappearance of the in-phase pattern and the reduced stability of the anti-phase pattern. This study was conducted to assess the success of a coordination visual biofeedback for the (re)learning of the two preferred patterns, and to explore the effect of this treatment on postural and functional abilities. Twenty four patients were randomly assigned to one of two experimental groups or to a control group. During one month, patients from experimental groups followed a training protocol on the two preferred postural patterns using the biofeedback device. These two groups improved their in-phase coordination after the (re)learning compared with control group, and showed a related improvement of the functional independence measure. Results suggest that (re)learning the in-phase pattern is possible and seems to improve independence in poststroke patients.

Changes in preferred postural patterns following stroke during intentional ankle/hip coordination.

We compared the spatio-temporal postural organization between stroke patients and healthy controls in a bipedal standing task where participants had to intentionally produce two specific ankle/hip coordination patterns: in-phase and anti-phase. The pattern to reproduce was visually represented by a ankle-hip Lissajous figure, and a real-time biofeedback displayed the current coordination sur-imposed to the expected coordination. Contrary to the healthy participants who were successful at reproducing the two patterns, stroke patients were unable to produce the in-phase pattern. In addition, when the anti-phase pattern was required, a reduction of stability was observed for the stroke group. The impairment of postural capacities following stroke was thus accompanied by a disappearance of one of the two preferred patterns found in healthy participants, a result that have consequences for understanding the etiology of postural pattern formation and the elaboration of rehabilitation programs.

Sensitivity to change of two depression rating scales for stroke patients.

OBJECTIVE: To assess the sensitivity to change of two depression scales for stroke patients: the Aphasic Depression Rating Scale (ADRS), which is a 9-item external assessment, and the Visual Analog Mood Scale (VAMS), which is a visual self-assessment scale. PATIENTS: Forty-nine stroke patients admitted to two rehabilitation units. METHODS: Symptoms of depression were assessed twice at a one-month interval (D0-D30) using the ADRS, the VAMS, and by a trained psychologist (PSY). Sensitivity to change was assessed by effect size and standardized response mean. A one-way ANOVA on ranks was performed to determine if the scales distinguished between deteriorated, stable and improved patient status. Spearman's correlation coefficient (r) was used to assess the relationship between changes in PSY and changes in the ADRS and the VAMS between D0 and D30. RESULTS: Mean depression scores at D0 and D30 were 2.6 +/- 1.8 and 2.4 +/- 1.7 (ADRS/10), 3.1 +/- 2.9 and 3.0 +/- 3.2 (VAMS/10), 2.9 +/- 2.3 and 2.4 +/- 2.4 (PSY/10). Percentages of deteriorated, stable and improved patient status were 22%, 45% and 33% (ADRS); 41%, 22% and 37% (VAMS); and 20%, 41% and 39% (PSY). Changes in PSY correlated with the ADRS (r = 0.72, P<10( -6)) and the VAMS (r = 0.41, P<10(- 2)). The ADRS was better than the VAMS in terms of effect size, standardized response mean and ability to discriminate between deteriorated, stable and improved patient status. This result was partly due to the difficulty encountered by nine (19%) patients in understanding directions to complete the VAMS. CONCLUSIONS: The ADRS is more sensitive than the VAMS for detecting changes in post-stroke depression. The VAMS is less appropriate in very cognitively impaired stroke patients.

Contribution of each lower limb to upright standing in stroke patients.

BACKGROUND AND PURPOSE: To analyze the postural behavior of standing stroke patients: (1) To differentiate between postural impairment attributable to the neurological condition (deficits attributable to the cerebral lesion) and postural impairment attributable to new mechanical constraints caused by body weight asymmetry; (2) To assess the involvement of each limb in the postural impairment; (3) To better understand which clinical deficits underlie the postural impairment. METHODS: The posturographic characteristics of each limb in 41 stroke patients (first hemispheric stroke: 16 left, 25 right cerebral lesions) required to stand in their preferred posture were compared to those in 40 matched healthy individuals required to stand asymmetrically. RESULTS: Compared to normal individuals in a similar asymmetrical posture, stroke patients were more unstable. The weight bearing asymmetry and the lateral postural instability were mainly related to spatial neglect. The paretic limb was unable to bring into play a normal longitudinal pattern of the center of pressure, which reflects an impaired stabilization control. Overall postural instability occurred when the strong limb was unable to compensate for the postural impairment of the paretic limb. CONCLUSIONS: The weight bearing asymmetry of standing stroke patients is not the primary cause of their postural imbalance, which is rather the consequence of impaired control of postural stabilization involving both limbs. Weight bearing asymmetry may not be the principle target of rehabilitation programs aiming at restoring standing balance after stroke. Instead it is suggested that more account should be taken of the compensatory role of the strong limb.

Posturography in patients with stroke: estimating the percentage of body weight on each foot from a single force platform.

BACKGROUND AND PURPOSE: Posturography in patients with stroke is widely based on the use of a single force platform and the weightbearing asymmetry quantified from the lateral shift of the center of pressure toward the sound leg. Because the percentage of body weight on each side is a more concrete variable, the present study analyzed the possibility of inferring percentage of body weight from center of pressure. METHODS: Forty-five hemiparetic subjects were asked to stand on a dual platform in a standardized position 3 months after a hemispheric stroke. First, the relationship between the %BW on each foot and the lateral shift of center of pressure was established. Second, the model was tested with a healthy subject standing on a single force platform. RESULTS: The percentage of body weight may be simply modeled from the center of pressure shift, a center of pressure displacement of 10 mm corresponding to a 5% increase in body weight on this side (r=0.97, P<0.001). This linear model is reliable, accurate, and may be generalized to other stand widths. CONCLUSIONS: This finding should be useful for constructors and users of single force platforms, especially those involved in posturographic assessments of asymmetric conditions such as hemiparesis.