Positive and negative stroke signs revisited: dissociations between synergies, weakness, and impaired reaching dexterity

Stroke affects more than ten million individuals in the world each year, with most victims experiencing motor deficits usually referred to collectively as hemiparesis. While hemiparesis is one of the most common and clinically recognizable abnormalities, it remains under-characterized in terms of its behavioral subcomponents and how they combine to produce the overall post-stroke motor deficit. Hemiparesis is comprised of both negative and positive motor signs. Negative signs consist of weakness and loss of motor control (dexterity), whereas positive signs consist of spasticity, abnormal resting posture, and intrusive movement synergies whereby multiple muscles or joints become co-activated during voluntary movement. How positive and negative signs interact, and whether a common mechanism generates them, remains poorly understood. Here we employed a planar reaching task to assess post-stroke arm dexterity loss, which we compared to the Fugl-Meyer stroke scale; a measure primarily reflecting abnormal synergies. We examined 53 patients with hemiparesis after a first-time ischemic stroke. Reaching kinematics were markedly more impaired in patients with subacute (<3 months) compared to chronic (>6 months) stroke even when matched for Fugl-Meyer score. While our reaching dexterity task mitigated the effect of weakness on synergies through the use of arm-weight support, we found that the Fugl-Meyer scale was a poor predictor of arm dexterity. This suggests a dissociation between abnormal synergies (reflected in the Fugl-Meyer scale) and loss of dexterity, which in turns suggests that different mechanisms may generate these particular positive and negative signs. At the same time, dynamometry suggested that Fugl-Meyer scores may capture weakness as well as abnormal synergies, in line with these two deficits sharing a neural substrate. These findings have two important implications: First, clinical studies that test for efficacy of rehabilitation interventions should specify which component of hemiparesis they are targeting and how they propose to measure it. Second, there may be an opportunity to design specific rehabilitation interventions to address specific subcomponents of the hemiparesis syndrome.

EFFECTIVENESS OF COMBINED USE OF ARM ABILITY TRAINING WITH ARM WEIGHT SUPPORT TO IMPROVE UPPER EXTREMITY FUNCTIONAL SKILLS AND ADL SKILLS IN PARKINSONISM PATIENTS

OBJECTIVE: This study is to determine the effectiveness of combined use of arm ability training with arm weight support to improve upper extremity functional skills and ADL skills in Parkinsonism patients. METHOD: Thirty subjects with parkinsonism ( 5 months to 10 years of Parkinson’s disease) were selected, who fulfilled the inclusion and exclusion criteria and according to the screening measures using UPDRS, Hoehn and Yahr scale and MMSE. Baseline assessment (Pre-test) was done using FMA, UEFI, and Katz index. After baseline assessment arm ability training (AAT) combined with arm weight support (45 minutes) was given to the patients for 12 weeks, 45 minutes in a day for 3 days in a week and post-intervention assessment (Post-test) was taken after 12 weeks by using the same outcome measures. RESULT: Post- training there was a significant improvement in all the outcome measures. The result of the study showed evidence of benefit of the practice of Arm ability training with Arm weight support in Parkinsonism; enhance improvement as a result of Arm ability training along with Arm weight support were found in FMA-UE is x= 97.00 (volitional movement), UEFI is x= 46.20 ( Hand functionality), Katz Index is x= 5.20 (Autonomy of ADL). The post-test has showed a greater improvement than from the pre-test in all the outcome measure (FMA-UE-P=0.001, UEFI-P=0.001 and Katz Index- P=0.001). The Pre and Post score comparison of outcome variables shown improvement in upper extremity functional skills and in Activities of Daily living skills following the intervention programme. CONCLUSION: The Arm ability training techniques with Arm weight support was found to be effective in improving upper extremity functional skills as well as ADL skills among the Parkinsonism patients. The Arm ability training combined with Arm weight support can be used with other occupational therapy intervention to provide additional benefits to the Parkinsonism patients. KEYWORDS: upper extremity functional skills, Activities of Daily Living, Arm ability training, Arm weight support, Parkinson’s disease.

Technology-aided assessment of functionally relevant sensorimotor impairments in arm and hand of post-stroke individuals

Background Assessing arm and hand sensorimotor impairments that are functionally relevant is essential to optimize the impact of neurorehabilitation interventions. Technology-aided assessments should provide a sensitive and objective characterization of upper limb impairments, but often provide arm weight support and neglect the importance of the hand, thereby questioning their functional relevance. The Virtual Peg Insertion Test (VPIT) addresses these limitations by quantifying arm and hand movements as well as grip forces during a goal-directed manipulation task requiring active lifting of the upper limb against gravity. The aim of this work was to evaluate the ability of the VPIT metrics to characterize arm and hand sensorimotor impairments that are relevant for performing functional tasks. Methods Arm and hand sensorimotor impairments were systematically characterized in 30 chronic stroke patients using conventional clinical scales and the VPIT. For the latter, ten previously established kinematic and kinetic core metrics were extracted. The validity and robustness of these metrics was investigated by analyzing their clinimetric properties (test-retest reliability, measurement error, learning effects, concurrent validity). Results Twenty-three of the participants, the ones with mild to moderate sensorimotor impairments and without strong cognitive deficits, were able to successfully complete the VPIT protocol (duration 16.6 min). The VPIT metrics detected impairments in arm and hand in 90.0% of the participants, and were sensitive to increased muscle tone and pathological joint coupling. Most importantly, significant moderate to high correlations between conventional scales of activity limitations and the VPIT metrics were found, thereby indicating their functional relevance when grasping and transporting objects, and when performing dexterous finger manipulations. Lastly, the robustness of three out of the ten VPIT core metrics in post-stroke individuals was confirmed. Conclusions This work provides evidence that technology-aided assessments requiring goal-directed manipulations without arm weight support can provide an objective, robust, and clinically feasible way to assess functionally relevant sensorimotor impairments in arm and hand in chronic post-stroke individuals with mild to moderate deficits. This allows for a better identification of impairments with high functional relevance and can contribute to optimizing the functional benefits of neurorehabilitation interventions.

Technology-aided assessment of functionally relevant sensorimotor impairments in arm and hand of post-stroke individuals

BackgroundAssessing arm and hand sensorimotor impairments that are functionally relevant is essential to optimize the impact of neurorehabilitation interventions. Technology-aided assessments should provide a sensitive and objective characterization of upper limb impairments, but often provide arm weight support and neglect the importance of the hand, thereby questioning their functional relevance. The Virtual Peg Insertion Test (VPIT) addresses these limitations by quantifying arm movements and grip forces during a goal-directed manipulation task without arm weight support. The aim of this work was to evaluate the potential and robustness of the VPIT metrics to inform on sensorimotor impairments in arm and hand, and especially identify the functional relevance of the detected impairments.MethodsArm and hand sensorimotor impairments were systematically characterized in 30 chronic stroke patients using conventional clinical scales and the VPIT. For the latter, ten previously established kinematic and kinetic core metrics were extracted and compared to conventional clinical scales of impairment and activity limitations. Additionally, the robustness of the VPIT metrics was investigated by analyzing their clinimetric properties (test-retest reliability, measurement error, and learning effects).ResultsTwenty-three of the participants, the ones with mild to moderate sensorimotor impairments and without strong cognitive deficits, were able to successfully complete the VPIT protocol (duration 16.6 min). The VPIT metrics detected impairments in arm and hand in 90.0% of the participants, and were sensitive to increased muscle tone and pathological joint coupling. Most importantly, moderate to high significant correlations between conventional scales of activity limitations and the VPIT metrics were found, thereby indicating their functional relevance when grasping and transporting lightweight objects as well as dexterous finger manipulations. Lastly, the robustness of three out of the ten VPIT core metrics in post-stroke individuals was confirmed.ConclusionsThis work provides evidence that technology-aided assessments requiring goal-directed manipulations without arm weight support can provide an objective, robust, and clinically feasible way to assess functionally relevant sensorimotor impairments in arm and hand in chronic post-stroke individuals with mild to moderate deficits. This allows better identifying impairments with high functional relevance and can contribute to optimizing the functional benefits of neurorehabilitation interventions.Retrospectively registered: clinicaltrials.gov/ct2/show/NCT03135093

Effects of arm weight support on neuromuscular activation during reaching in chronic stroke patients

To better understand how arm weight support (WS) can be used to alleviate upper limb impairment after stroke, we investigated the effects of WS on muscle activity, muscle synergy expression, and corticomotor excitability (CME) in 13 chronic stroke patients and 6 age-similar healthy controls. For patients, lesion location and corticospinal tract integrity were assessed using magnetic resonance imaging. Upper limb impairment was assessed using the Fugl-Meyer upper extremity assessment with patients categorised as either mild or moderate-severe. Three levels of WS were examined: low=0, medium=50 and high=100 % of full support. Surface EMG was recorded from 8 upper limb muscles, and muscle synergies were decomposed using non-negative matrix factorisation from data obtained during reaching movements to an array of 14 targets using the paretic or dominant arm. Interactions between impairment level and WS were found for the number of targets hit, and EMG measures. Overall, greater WS resulted in lower EMG levels, although the degree of modulation between WS levels was less for patients with moderate-severe compared to mild impairment. Healthy controls expressed more synergies than patients with moderate-severe impairment. Healthy controls and patients with mild impairment showed more synergies with high compared to low weight support. Transcranial magnetic stimulation was used to elicit motor-evoked potentials (MEPs) to which stimulus-response curves were fitted as a measure of corticomotor excitability (CME). The effect of WS on CME varied between muscles and across impairment level. These preliminary findings demonstrate that WS has direct and indirect effects on muscle activity, synergies, and CME and warrants further study in order to reduce upper limb impairment after stroke.

Compensating the effects of FES-induced muscle fatigue by rehabilitation robotics during arm weight support

Motor functions can be hindered in consequence to a stroke or a spinal cord injury. This often results in partial paralyses of the upper limb. The effectiveness of rehabilitation therapy can be improved by the use of rehabilitation robotics and Functional Electrical Stimulation (FES). We consider a hybrid arm weight support combining both. In order to compensate the effect of FES-induced muscle fatigue, we introduce a method to substitute the decreasing level of FES support by cable-driven robotics. We evaluated the approach in a trial with one healthy subject performing repetitive arm lifting. The controller automatically adapted the support and thus no increase in user generated volitional effort was observed when FES induced muscle fatigue occured.