Dynamical structure of center-of-pressure trajectories in patients recovering from stroke

Contains fulltext : 50308.pdf (publisher's version ) (Closed access)In a recent study, De Haart et al. (Arch Phys Med Rehabil 85:886-895, 2004) investigated the recovery of balance in stroke patients using traditional analyses of center-of-pressure (COP) trajectories to assess the effects of health status, rehabilitation, and task conditions like standing with eyes open or closed and standing while performing a cognitive dual task. To unravel the underlying control processes, we reanalyzed these data in terms of stochastic dynamics using more advanced analyses. Dimensionality, local stability, regularity, and scaling behavior of COP trajectories were determined and compared with shuffled and phase-randomized surrogate data. The presence of long-range correlations discarded the possibility that the COP trajectories were purely random. Compared to the healthy controls, the COP trajectories of the stroke patients were characterized by increased dimensionality and instability, but greater regularity in the frontal plane. These findings were taken to imply that the stroke patients actively (i.e., cognitively) coped with the stroke-induced impairment of posture, as reflected in the increased regularity and decreased local stability, by recruiting additional control processes (i.e., more degrees of freedom) and/or by tightening the present control structure while releasing non-essential degrees of freedom from postural control. In the course of rehabilitation, dimensionality stayed fairly constant, whereas local stability increased and regularity decreased. The progressively less regular COP trajectories were interpreted to indicate a reduction of cognitive involvement in postural control as recovery from stroke progressed. Consistent with this interpretation, the dual task condition resulted in less regular COP trajectories of greater dimensionality, reflecting a task-related decrease of active, cognitive contributions to postural control. In comparison with conventional posturography, our results show a clear surplus value of dynamical measures in studying postural control

Changing patterns of cognitive-motor interference (CMI) over time during recovery from stroke

Objective: To explore the extent and nature of change in cognitive-motor interference (CMI) among rehabilitating stroke patients who showed dual-task gait decrement at initial assessment. Design: Experimental, with in-subjects, repeated measures design. Setting: Rehabilitation centre for adults with acquired, nonprogressive brain injury. Subjects: Ten patients with unilateral stroke, available for reassessment 1-9 months following their participation in a study of CMI after brain injury. Measures: Median stride duration; mean word generation. Methods: Two x one-minute walking trials, two x one-minute word generation trials, two x one-minute trials of simultaneous walking and word generation; 10-metre walking time; Barthel ADL Scale score. Results: Seven out of ten patients showed reduction over time in dual-task gait decrement. Three out of ten showed reduction in cognitive decrement. Only one showed concomitant reduction in gait and word generation decrement. Conclusion: Extent of CMI during relearning to walk after a stroke reduced over time in the majority of patients. Effects were more evident in improved stride duration than improved cognitive performance. Measures of multiple task performance should be included in assessment for functional recovery

A pilot study comparing the cognitive demand of walking for transfemoral amputees using the intelligent prosthesis with that using conventionally damped knees

OBJECTIVE: To compare the cognitive demand of walking when using a conventional prosthesis with that using a microprocessor-controlled prosthesis. DESIGN: Ten unilateral transfemoral amputees wearing conventional pneumatic swing phase control (conventional prosthesis) prostheses walked on a treadmill which enforced a pattern of constantly varying speeds. The subjects simultaneously performed a simple or a complex distracting task. Following a period of accustomization, the subjects performed the same test wearing a prosthesis with microprocessor control of swing phase damping (the Intelligent Prosthesis). OUTCOME MEASURES: The three-dimensional trajectory (sway) of a retroreflective marker attached to the forehead was measured by a video-based motion analysis system, and used as a measure of gait quality. The ratio of the sway for the complex task over the simple task (the 'automation index') was used as a measure of the degree of automation of gait. RESULTS: No significant differences were found in the automation index between the two devices. However, the total sway for the conventional prosthesis was significantly higher. Sway during the complex distracting task was significantly higher than during the simple task. CONCLUSIONS: The microprocessor-controlled prosthesis was not found to be less cognitively demanding than a conventional prosthesis

Instruments for assessment of impairments and activity limitations in patients with hand conditions: an European delphi study

Objective: To reach multidisciplinary European consensus on the assessment tools for impairments and activity limitations in patients with hand conditions. Design: Electronic Delphi method. Subjects: Thirty experts from European societies for hand therapy, hand surgery, and physical and rehabilitation medicine. Methods: In 3 rounds, participants were asked which of 13 preselected categories of the Brief International Classification of Functioning, Disability and Health (ICF) Core Set for Hand Conditions should be assessed. In addition, they were asked to choose which of 55 preselected instruments they preferred for each category by confirming or rejecting instrument-specific statements. Results: All 13 preselected ICF categories were considered relevant. Consensus was based on >= 75% agreement. After 3 rounds, 9 instruments were selected: Shape Texture Identification Test, Semmes Weinstein Monofilament Test, Visual Analogue Scale for pain, goniometer, Jamar Dynamometer, Pinch Gauge Device, Cold Intolerance Symptom Severity questionnaire, Canadian Occupational Performance Measure, and Disabilities of the Arm, Shoulder and Hand Questionnaire. It remained undecided whether to use the Nine-Hole Pegboard Test or the Purdue Pegboard Test. Conclusion: In this European Delphi study, multidisciplinary consensus was reached on 9 assessment tools for impairments and activity limitations in patients with hand conditions addressing 13 categories of the Brief ICF Core Set for Hand Conditions

Somatosensation, circulation and stance balance in elderly dysvascular transtibial amputees

Objective: To establish the relationship between poor lower limb somatosensory and circulatory status with standing balance, falls history, age and mobility level in dysvascular transtibial amputees (TTAs). Design: Within-subjects evaluation of somatosensation, circulation and stance balance measures in dysvascular transtibial amputees. Setting: Physiotherapy department of a tertiary metropolitan hospital in Australia. Participants: Twenty-two community-dwelling unilateral dysvascular transtibial amputee volunteers, aged between 54 and 86 recruited from a metropolitan hospital outpatient amputee clinic. Main outcome measures: Lower limb vibration sense, light touch sensation and circulatory status were related to centre of pressure excursion during quiet stance, dynamic balance measures of forward and lateral reach distance, and demographic information such as falls history and mobility level. Results: Overall, poor somatosensory status was associated with poor stance balance. There was an association between poor vibration and circulation and increased centre of pressure excursion in quiet stance and reduced reach distance, whereas poor light touch was linked with even weight-bearing in quiet stance. Poor vibration sense was associated with a history of frequent falls. Conclusions: Compromised lower limb somatosensation and circulation was linked with poor balance and a history of frequent falls in the elderly dysvascular amputee population