Delays in Grip Initiation and Termination in Persons With Stroke: Effects of Arm Support and Active Muscle Stretch Exercise

Decoding hand and wrist movement intention from chronic stroke survivors with hemiparesis using a user-friendly, wearable EMG-based neural interface

OBJECTIVE

Seventy-five percent of stroke survivors, caregivers, and health care professionals (HCP) believe current therapy practices are insufficient, specifically calling out the upper extremity as an area where innovation is needed to develop highly usable prosthetics/orthotics for the stroke population. A promising method for controlling upper extremity technologies is to infer movement intention non-invasively from surface electromyography (EMG). However, existing technologies are often limited to research settings and struggle to meet user needs.

APPROACH

To address these limitations, we have developed the NeuroLife® EMG System, an investigational device which consists of a wearable forearm sleeve with 150 embedded electrodes and associated hardware and software to record and decode surface EMG. Here, we demonstrate accurate decoding of 12 functional hand, wrist, and forearm movements in chronic stroke survivors, including multiple types of grasps from participants with varying levels of impairment. We also collected usability data to assess how the system meets user needs to inform future design considerations.

MAIN RESULTS

Our decoding algorithm trained on historical- and within-session data produced an overall accuracy of 77.1 ± 5.6% across 12 movements and rest in stroke participants. For individuals with severe hand impairment, we demonstrate the ability to decode a subset of two fundamental movements and rest at 85.4 ± 6.4% accuracy. In online scenarios, two stroke survivors achieved 91.34 ± 1.53% across three movements and rest, highlighting the potential as a control mechanism for assistive technologies. Feedback from stroke survivors who tested the system indicates that the sleeve's design meets various user needs, including being comfortable, portable, and lightweight. The sleeve is in a form factor such that it can be used at home without an expert technician and can be worn for multiple hours without discomfort.

SIGNIFICANCE

The NeuroLife EMG System represents a platform technology to record and decode high-resolution EMG for the real-time control of assistive devices in a form factor designed to meet user needs. The NeuroLife EMG System is currently limited by U.S. federal law to investigational use.

Deficits in neuromuscular control of increasing force in patients with chronic lateral epicondylitis

Objective: This study investigated the neuromuscular control of increasing and releasing force in patients with chronic lateral epicondylitis (CLE). Methods: Fifteen patients with CLE (10 males, 5 females, 46.5 ± 6.3 years) and fifteen healthy participants (9 males, 6 females, 45.3 ± 2.5 years) participated in this study. In addition to power grip and maximal voluntary contraction (MVC) of wrist extension, force fluctuation dynamics and characteristics of inter-spike intervals (ISI) of motor units (MUs) with various recruitment thresholds in the extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) during a designated force-tracking task with a trapezoidal target (0%-75%-0% MVC) were assessed. Results: Besides a smaller MVC of wrist extension, the patients exhibited significantly greater task errors (p = 0.007) and force fluctuations (p = 0.001) during force increment than the healthy counterparts. Nevertheless, no force variables significantly differed between groups during force release (p > 0.05). During force increment, the amplitudes of the motor unit action potential of the ECRB and ECRL muscles of the patients were smaller than those of the heathy counterparts (p < 0.001). The patient group also exhibited a higher percentage of motor units (MU) with lower recruitment threshold (<5% MVC) in the ECRL/ECRB muscles and a lower percentage of MU with higher recruitment threshold (>40% MVC) in the ECRB muscle, compared to the healthy group. During force increment, the patient group exhibited a higher rate of decrease in inter-spike intervals (ISIs) of motor units with lower recruitment thresholds (<10% MVC) in the ECRB and ECRL muscles, compared to the control group (p < 0.005). Conclusion: The patients with CLE exhibited more pronounced impairment in increasing force than in releasing force. This impairment in increasing force is attributed to deficits in tendon structure and degenerative changes in the larger motor units of the wrist extensors. To compensate for the neuromuscular deficits, the rate of progressive increase in discharge rate of the remaining smaller motor units (MUs) is enhanced to generate force. Significance: The deficits in neuromuscular control observed in CLE with degenerative changes cannot be fully explained by the experimental pain model, which predicts pain-related inhibition on low-threshold motor units.

Delayed Muscle Activity in Stroke Survivors with Upper-Limb Hemiparesis

Stroke is the leading cause of disability worldwide, and nearly 80% of stroke survivors suffer from upper-limb hemiparesis. Myoelectric exoskeletons can restore dexterity and independence to stroke survivors with upper-limb hemiparesis. However, the ability of patients to dexterously control myoelectric exoskeletons is limited by an incomplete understanding of the electromyographic (EMG) hallmarks of hemiparesis, such as muscle weakness and spasticity. Here we show that stroke survivors with upper-limb hemiparesis suffer from delayed voluntary muscle contraction and delayed muscle relaxation. We quantified the time constants of EMG activity associated with initiating and terminating voluntary hand grasps and extensions for both the paretic and non-paretic hands of stroke survivors. We found that the initiation and termination time constants were greater on the paretic side for both hand grasps and hand extensions. Notably, the initiation time constant during hand extension was approximately three times longer for the paretic hand than for the contralateral non-paretic hand (0.618 vs 0.189 s). We also show a positive correlation between the initiation and termination time constants and clinical scores on the Modified Ashworth Scale. The difficulty stroke survivors have in efficiently modulating their EMG presents a challenge for appropriate control of assistive myoelectric devices, such as exoskeletons. This work constitutes an important step towards understanding EMG differences after stroke and how to accommodate these EMG differences in assistive myoelectric devices. Real-time quantitative biofeedback of EMG time constants may also have broad implications for guiding rehabilitation and monitoring patient recovery.Clinical Relevance- After a stroke, muscle activity changes, and these changes make it difficult to use muscle activity to drive assistive and rehabilitative technologies. We identified slower muscle contraction and muscle relaxation as a key difference in muscle activity after a stroke. This quantifiable difference in muscle activity can be used to develop better assistive technologies, guide rehabilitation, and monitor patient recovery.

Associating Functional Neural Connectivity and Specific Aspects of Sensorimotor Control in Chronic Stroke

Hand sensorimotor deficits often result from stroke, limiting the ability to perform daily living activities. Sensorimotor deficits are heterogeneous among stroke survivors. Previous work suggests a cause of hand deficits is altered neural connectivity. However, the relationships between neural connectivity and specific aspects of sensorimotor control have seldom been explored. Understanding these relationships is important for developing personalized rehabilitation strategies to improve individual patients' specific sensorimotor deficits and, thus, rehabilitation outcomes. Here, we investigated the hypothesis that specific aspects of sensorimotor control will be associated with distinct neural connectivity in chronic stroke survivors. Twelve chronic stroke survivors performed a paretic hand grip-and-relax task while EEG was collected. Four aspects of hand sensorimotor grip control were extracted, including reaction time, relaxation time, force magnitude control, and force direction control. EEG source connectivity in the bilateral sensorimotor regions was calculated in α and β frequency bands during grip preparation and execution. Each of the four hand grip measures was significantly associated with a distinct connectivity measure. These results support further investigations into functional neural connectivity signatures that explain various aspects of sensorimotor control, to assist the development of personalized rehabilitation that targets the specific brain networks responsible for the individuals' distinct sensorimotor deficits.

Altered flexor carpi radialis motor axon excitability properties after cerebrovascular stroke

Background

Spinal motoneurons may become hyperexcitable after a stroke. Knowledge about motoneuron hyperexcitability remains clinically important as it may contribute to a number of phenomena including spasticity, flexion synergies, and abnormal limb postures. Hyperexcitability seems to occur more often in muscles that flex the wrist and fingers (forearm flexors) compared to other upper limb muscles. The cause of hyperexcitability remains uncertain but may involve plastic changes in motoneurons and their axons.

Aim

To characterize intrinsic membrane properties of flexor carpi radialis (FCR) motor axons after stroke using nerve excitability testing.

Methods

Nerve excitability testing using threshold tracking techniques was applied to characterize FCR motor axon properties in persons who suffered a first-time unilateral cortical/subcortical stroke 23 to 308  days earlier. The median nerve was stimulated at the elbow bilaterally in 16 male stroke subjects (51.4 ± 2.9 y) with compound muscle action potentials recorded from the FCR. Nineteen age-matched males (52.7 ± 2.4 y) were also tested to serve as controls.

Results

Axon parameters after stroke were consistent with bilateral hyperpolarization of the resting potential. Nonparetic and paretic side axons were modeled by a 2.6-fold increase in pump currents (IPumpNI) together with an increase (38%-33%) in internodal leak conductance (GLkI) and a decrease (23%-29%) in internodal H conductance (Ih) relative to control axons. A decrease (14%) in Na⁺ channel inactivation rate (Aah) was also needed to fit the paretic axon recovery cycle. "Fanning out" of threshold electrotonus and the resting I/V slope (stroke limbs combined) correlated with blood potassium [K⁺] (R = -0.61 to 0.62, p< 0.01) and disability (R = -0.58 to 0.55, p < 0.05), but not with spasticity, grip strength, or maximal FCR activity.

Conclusion

In contrast to our expectations, FCR axons were not hyperexcitable after stroke. Rather, FCR axons were found to be hyperpolarized bilaterally post stroke, and this was associated with disability and [K⁺]. Reduced FCR axon excitability may represent a kind of bilateral trans-synaptic homeostatic mechanism that acts to minimize motoneuron hyperexcitability.

Early microglial response, myelin deterioration and lethality in mice deficient for very long chain ceramide synthesis in oligodendrocytes

The sphingolipids galactosylceramide (GalCer), sulfatide (ST) and sphingomyelin (SM) are essential for myelin stability and function. GalCer and ST are synthesized mostly from C22-C24 ceramides, generated by Ceramide Synthase 2 (CerS2). To clarify the requirement for C22-C24 sphingolipid synthesis in myelin biosynthesis and stability, we generated mice lacking CerS2 specifically in myelinating cells (CerS2ΔO/ΔO ). At 6 weeks of age, normal-appearing myelin had formed in CerS2ΔO/ΔO mice, however there was a reduction in myelin thickness and the percentage of myelinated axons. Pronounced loss of C22-C24 sphingolipids in myelin of CerS2ΔO/ΔO mice was compensated by greatly increased levels of C18 sphingolipids. A distinct microglial population expressing high levels of activation and phagocytic markers such as CD64, CD11c, MHC class II, and CD68 was apparent at 6 weeks of age in CerS2ΔO/ΔO mice, and had increased by 10 weeks. Increased staining for denatured myelin basic protein was also apparent in 6-week-old CerS2ΔO/ΔO mice. By 16 weeks, CerS2ΔO/ΔO mice showed pronounced myelin atrophy, motor deficits, and axon beading, a hallmark of axon stress. 90% of CerS2ΔO/ΔO mice died between 16 and 26 weeks of age. This study highlights the importance of sphingolipid acyl chain length for the structural integrity of myelin, demonstrating how a modest reduction in lipid chain length causes exposure of a denatured myelin protein epitope and expansion of phagocytic microglia, followed by axon pathology, myelin degeneration, and motor deficits. Understanding the molecular trigger for microglial activation should aid the development of therapeutics for demyelinating and neurodegenerative diseases.

MCP extensors respond faster than flexors in individuals with severe-to-moderate stroke-caused impairment: Evidence of uncoupled neural pathways

Damage in the corticospinal system following stroke produces imbalance between flexors and extensors in the upper extremity, eventually leading to flexion-favored postures. The substitution of alternative tracts for the damaged corticospinal tract is known to excessively activate flexors of the fingers while the fingers are voluntarily being extended. Here, we questioned whether the cortical source or/and neural pathways of the flexors and extensors of the fingers are coupled and what factor of impairment influences finger movement. In this study, a total of seven male participants with severe-to-moderate impairment by a hemiplegic stroke conducted flexion and extension at the metacarpophalangeal (MCP) joints in response to auditory tones. We measured activation and de-activation delays of the flexor and extensor of the MCP joints on the paretic side, and force generation. All participants generated greater torque in the direction of flexion (p = 0.017). Regarding co-contraction, coupled activation of the extensor is also made during flexion in the similar way to coupled activation of the flexor made during extension. As opposite to our expectation, we observed that during extension, the extensor showed marginally significantly faster activation (p = 0.66) while it showed faster de-activation (p = 0.038), in comparison to activation and de-activation of the flexor during flexion. But movement smoothness was not affected by those factors. Our results imply that the cortical source and neural pathway for the extensors of the MCP joints are not coupled with those for the flexors of the MCP joints.

Characterization of the influence of the dominant tract on hand closing post stroke based on the Fugl-Meyer score

While stroke survivors with moderate or mild impairment are typically able to open their hand at will, those with severe impairment cannot. Abnormal synergies govern the arm and hand in stoke survivors with severe impairment, so hand opening, which is required to overcome the working synergy, is an extremely difficult task for them to achieve. It is universally accepted that alternative tracts including the cortico-reticulospinal tract (CRST), employed in the case that the corticospinal tract (CST) is damaged by stroke, brings about such abnormal synergies. Here we note that hand closing is enabled by alternative tracts as well as the CST, and a research question arises: Does motor characteristics while closing the hand depend on the integrity of the CST? In this study, we evaluate the abilities of 17 stroke survivors to flex and relax the metacarpophalangeal (MCP) joints and investigate whether motor characteristics can be distinguished based on CST integrity which is estimated using upper-extremity Fugl-Meyer (UEFM) scores. UEFM scores have been perceived as an indirect indicator of CST integrity. We found that participants with the UEFM score above a certain value, who are assumed to use the CST, moves the MCP joints more smoothly (P < 0.05) and activates the flexors to flex the joints faster (P < 0.05), in comparison to participants with low UEFM scores, who are assumed to preferentially use alternative tracts. The results imply that use of alternative tracts (i.e. the CRST) results in a degradation in movement smoothness and slow activation of MCP flexors. We present evidence that responses of flexors of the MCP joints following stroke depend on the degree of impairment which is hypothesized to originate from preferentially use of different neural motor pathways.

Use of cyproheptadine hydrochloride (HCl) to reduce neuromuscular hypertonicity in stroke survivors: A Randomized Trial: Reducing Hypertonicity in Stroke

OBJECTIVES

The goal of this study was to examine how the administration and dosing of the anti-serotonergic medication cyproheptadine hydrochloride (HCl) affects involuntary muscle hypertonicity of the spastic and paretic hands of stroke survivors.

MATERIALS AND METHODS

A randomized, double-blinded, placebo-controlled longitudinal intervention study was performed as a component of a larger clinical trial. 94 stroke survivors with chronic, severe hand impairment, rated as levels 2 or 3 on the Chedoke-McMaster Stroke Assessment Stage of Hand (CMSA-H), were block randomized to groups receiving doses of cyproheptadine HCl or matched doses of placebo. Doses were increased from 4 mg BID to 8 mg TID over 3 weeks. Outcomes were assessed at baseline and after each of the three weeks of intervention. Primary outcome measure was grip termination time; other measures included muscle strength, spasticity, coactivation of the long finger flexors, and recording of potential adverse effects such as sleepiness and depression.

RESULTS

89 participants (receiving cyproheptadine HCl: 44, receiving placebo: 45) completed the study. The Cyproheptadine group displayed significant reduction in grip termination time, in comparison with the Placebo group (p<0.05). Significant change in the Cyproheptadine group (45% time reduction) was observed after only one week at the 4mg BID dosage. The effect was pronounced for those participants in the Cyproheptadine group with more severe hand impairment (CMSA-H level 2) at baseline. Conversely, no significant effect of Group * Session interaction was observed for spasticity (p=0.6) or coactivation (p=0.53). There were no significant changes in strength (p=0.234) or depression (p=0.441) during the trial.

CONCLUSIONS

Use of cyproheptadine HCl was associated with a significant reduction in relaxation time of finger flexor muscles, without adversely affecting voluntary strength, although spasticity and coactivation were unchanged. Decreasing the duration of involuntary flexor activity can facilitate object release and repeated prehensile task performance.

REGISTRATION

Clinical Trial number: NCT02418949.

Use of an EMG-Controlled Game as a Therapeutic Tool to Retrain Hand Muscle Activation Patterns Following Stroke: A Pilot Study

BACKGROUND/PURPOSE

To determine the feasibility of training with electromyographically (EMG) controlled games to improve control of muscle activation patterns in stroke survivors.

METHODS

Twenty chronic stroke survivors (>6 months) with moderate hand impairment were randomized to train either unilaterally (paretic only) or bilaterally over 9 one-hour training sessions. EMG signals from the unilateral or bilateral limbs controlled a cursor location on a computer screen for gameplay. The EMG muscle activation vector was projected onto the plane defined by the first 2 principal components of the activation workspace for the nonparetic hand. These principal components formed the x- and y-axes of the computer screen.

RESULTS

The recruitment goal (n = 20) was met over 9 months, with no screen failure, no attrition, and 97.8% adherence rate. After training, both groups significantly decreased the time to move the cursor to a novel sequence of targets (P = 0.006) by reducing normalized path length of the cursor movement (P = 0.005), and improved the Wolf Motor Function Test (WMFT) quality score (P = 0.01). No significant group difference was observed. No significant change was seen in the WMFT time or Box and Block Test.

DISCUSSION/CONCLUSIONS

Stroke survivors could successfully use the EMG-controlled games to train control of muscle activation patterns. While the nonparetic limb EMG was used in this study to create target EMG patterns, the system supports various means for creating target patterns per user desires. Future studies will employ training with the EMG-controlled games in conjunction with functional task practice for a longer intervention duration to improve overall hand function.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A379).

Bilateral upper extremity motor priming (BUMP) plus task-specific training for severe, chronic upper limb hemiparesis: study protocol for a randomized clinical trial

BACKGROUND

Various priming techniques to enhance neuroplasticity have been examined in stroke rehabilitation research. Most priming techniques are costly and approved only for research. Here, we describe a priming technique that is cost-effective and has potential to significantly change clinical practice. Bilateral motor priming uses the Exsurgo priming device (Exsurgo Rehabilitation, Auckland, NZ) so that the less affected limb drives the more affected limb in bilateral symmetrical wrist flexion and extension. The aim of this study is to determine the effects of a 5-week protocol of bilateral motor priming in combination with task-specific training on motor impairment of the affected limb, bimanual motor function, and interhemispheric inhibition in moderate to severely impaired people with stroke.

METHODS

Seventy-six participants will be randomized to receive either 15, 2-h sessions, 3 times per week for 5 weeks (30 h of intervention) of bilateral motor priming and task-specific training (experimental group) or the same dose of control priming plus the task-specific training protocol. The experimental group performs bilateral symmetrical arm movements via the Exsurgo priming device which allows both wrists to move in rhythmic, symmetrical wrist flexion and extension for 15 min. The goal is one cycle (wrist flexion and wrist extension) per second. The control priming group receives transcutaneous electrical stimulation below sensory threshold for 15 min prior to the same 45 min of task-specific training. Outcome measures are collected at pre-intervention, post-intervention, and follow-up (8 weeks post-intervention). The primary outcome measure is the Fugl-Meyer Test of Upper Extremity Function. The secondary outcome is the Chedoke Arm and Hand Activity Index-Nine, an assessment of bimanual functional tasks.

DISCUSSION

To date, there are only 6 studies documenting the efficacy of priming using bilateral movements, 4 of which are pilot or feasibility studies. This is the first large-scale clinical trial of bilateral priming plus task-specific training. We have previously completed a feasibility intervention study of bilateral motor priming plus task-specific training and have considerable experience using this protocol.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03517657 . Retrospectively registered on May 7, 2018.

A low-dimensional representation of arm movements and hand grip forces in post-stroke individuals

Characterizing post-stroke impairments in the sensorimotor control of arm and hand is essential to better understand altered mechanisms of movement generation. Herein, we used a decomposition algorithm to characterize impairments in end-effector velocity and hand grip force data collected from an instrumented functional task in 83 healthy control and 27 chronic post-stroke individuals with mild-to-moderate impairments. According to kinematic and kinetic raw data, post-stroke individuals showed reduced functional performance during all task phases. After applying the decomposition algorithm, we observed that the behavioural data from healthy controls relies on a low-dimensional representation and demonstrated that this representation is mostly preserved post-stroke. Further, it emerged that reduced functional performance post-stroke correlates to an abnormal variance distribution of the behavioural representation, except when reducing hand grip forces. This suggests that the behavioural repertoire in these post-stroke individuals is mostly preserved, thereby pointing towards therapeutic strategies that optimize movement quality and the reduction of grip forces to improve performance of daily life activities post-stroke.

Effect of novel training to normalize altered finger force direction post-stroke: study protocol for a double-blind randomized controlled trial

BACKGROUND

Functional task performance requires proper control of both movement and force generation in three-dimensional space, especially for the hand. Control of force in three dimensions, however, is not explicitly treated in current physical rehabilitation. To address this gap in treatment, we have developed a tool to provide visual feedback on three-dimensional finger force. Our objective is to examine the effectiveness of training with this tool to restore hand function in stroke survivors.

METHODS

Double-blind randomized controlled trial. All participants undergo 18 1-h training sessions to practice generating volitional finger force of various target directions and magnitudes. The experimental group receives feedback on both force direction and magnitude, while the control group receives feedback on force magnitude only. The primary outcome is hand function as measured by the Action Research Arm Test. Other outcomes include the Box and Block Test, Stroke Impact Scale, ability to direct finger force, muscle activation pattern, and qualitative interviews.

DISCUSSION

The protocol for this clinical trial is described in detail. The results of this study will reveal whether explicit training of finger force direction in stroke survivors leads to improved motor control of the hand. This study will also improve the understanding of neuromuscular mechanisms underlying the recovery of hand function.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03995069 . Registered on June 21, 2019.

Comprehensive Assessment of the Time Course of Biomechanical, Electrophysiological and Neuro-Motor Effects after Botulinum Toxin Injections in Elbow Flexors of Chronic Stroke Survivors with Spastic Hemiplegia: A Cross Sectional Observation Study

Botulinum neurotoxin (BoNT) is commonly used to manage focal spasticity in stroke survivors. This study aimed to a perform comprehensive assessment of the effects of BoNT injection. Twelve stroke subjects with spastic hemiplegia (age: 52.0 ± 10.1 year; 5 females) received 100 units of BoNT to the spastic biceps brachii muscles. Clinical, biomechanical, electrophysiological, and neuro-motor assessments were performed one week (wk) before (pre-injection), 3 weeks (wks) after, and 3 months (mons) after BoNT injection. BoNT injection significantly reduced spasticity, muscle strength, reflex torque, and compound muscle action potential (CMAP) amplitude of spastic elbow flexors (all p < 0.05) during the 3-wks visit, and these values return to the pre-injection level during the 3-mons visit. Furthermore, the degree of reflex torque change was negatively correlated to the amount of non-reflex component of elbow flexor resistance torque. However, voluntary force control and non-reflex resistance torque remained unchanged throughout. Our results revealed parallel changes in clinical, neurophysiological and biomechanical assessment after BoNT injection; BoNT injection would be more effective if hypertonia was mainly mediated by underlying neural mechanisms. BoNT did not affect voluntary force control of spastic muscles.

Limited Add-On Effects of Unilateral and Bilateral Transcranial Direct Current Stimulation on Visuo-Motor Grip Force Tracking Task Training Outcome in Chronic Stroke. A Randomized Controlled Trial

Background: This randomized controlled trial investigated if uni- and bihemispheric transcranial direct current stimulation (tDCS) of the motor cortex can enhance the effects of visuo-motor grip force tracking task training and transfer to clinical assessments of upper extremity motor function.

Methods: In a randomized, double-blind, sham-controlled trial, 40 chronic stroke patients underwent 5 days of visuo-motor grip force tracking task training of the paretic hand with either unilateral or bilateral (N = 15/group) or placebo tDCS (N = 10). Immediate and long-term (3 months) effects on training outcome and motor recovery (Upper Extremity Fugl-Meyer, UE-FM, Wolf Motor Function Test, and WMFT) were investigated.

Results: Trained task performance significantly improved independently of tDCS in a curvilinear fashion. In the anodal stimulation group UE-FM scores were higher than in the sham group at day 5 (adjusted mean difference: 2.6, 95%CI: 0.6–4.5, p = 0.010) and at 3 months follow up (adjusted mean difference: 2.8, 95%CI: 0.8–4.7, p = 0.006). Neither training alone, nor the combination of training and tDCS improved WMFT performance.

Conclusions: Visuo-motor grip force tracking task training can facilitate recovery of upper extremity function. Only minimal add-on effects of anodal but not dual tDCS were observed.

Clinical Trial Registration:https://clinicaltrials.gov/ct2/results?recrs=&cond=&term=NCT01969097&cntry=&state=&city=&dist=, identifier: NCT01969097, retrospectively registered on 25/10/2013.

A Hand Exoskeleton for Stroke Survivors' Activities of Daily Life. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:6734-6737. [PMID: 34892653 DOI: 10.1109/embc46164.2021.9629805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Stroke is a leading cause of disability in the U.S. Hand impairment is a common consequence of stroke, potentially impacting all facets of life as the hands are the primary means of interacting with the world. Typically, therapy is the prescribed treatment after stroke. However, a majority of stroke survivors have limited recovery and thus chronic impairment. Assistive, rather than therapeutic, devices may help these individuals restore lost function and improve independence and engagement in society. Current assistive devices, however, typically fail to address the greatest barriers to successful use with stroke survivors. In the hand, weakness and incoordination arise from a seemingly paradoxical combination of limited voluntary activation of muscles and involuntary neuromuscular hyperexcitability. Thus, profound strength deficits can be accompanied by substantial forces opposing the intended movement. The assistive device presented in this paper can provide both sufficient flexion and extension assistance to overcome these barriers. A single actuator for each digit provides flexion or extension assistance through push-pull cables guided along the dorsal side of the hand. User intent can be decoded from Electromyographic (EMG) signals to drive the device throughout the movement. EMG control is customized to the capabilities of each user by examining the voluntary EMG workspace.

Pilot Test of Dosage Effects in HEXORR II for Robotic Hand Movement Therapy in Individuals With Chronic Stroke

Impaired use of the hand in functional tasks remains difficult to overcome in many individuals after a stroke. This often leads to compensation strategies using the less-affected limb, which allows for independence in some aspects of daily activities. However, recovery of hand function remains an important therapeutic goal of many individuals, and is often resistant to conventional therapies. In prior work, we developed HEXORR I, a robotic device that allows practice of finger and thumb movements with robotic assistance. In this study, we describe modifications to the device, now called HEXORR II, and a clinical trial in individuals with chronic stroke. Fifteen individuals with a diagnosis of chronic stroke were randomized to 12 or 24 sessions of robotic therapy. The sessions involved playing several video games using thumb and finger movement. The robot applied assistance to extension movement that was adapted based on task performance. Clinical and motion capture evaluations were performed before and after training and again at a 6-month followup. Fourteen individuals completed the protocol. Fugl-Meyer scores improved significantly at the 6 month time point compared to baseline, indicating reductions in upper extremity impairment. Flexor hypertonia (Modified Ashworth Scale) also decreased significantly due to the intervention. Motion capture found increased finger range of motion and extension ability after the intervention that continued to improve during the followup period. However, there was no change in a functional measure (Action Research Arm Test). At the followup, the high dose group had significant gains in hand displacement during a forward reach task. There were no other significant differences between groups. Future work with HEXORR II should focus on integrating it with functional task practice and incorporating grip and squeezing tasks.

Trial Registration:ClinicalTrials.gov, NCT04536987. Registered 3 September 2020 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT04536987.

Investigating Inducible Muscle Overactivity in Acquired Brain Injury and the Impact of Botulinum Toxin A

OBJECTIVE

To investigate the pattern of change in muscle overactivity during repetitive grasp/release using dynamic computerized dynamometry (DCD; objective 1) and the effect of botulinum toxin A (BTX-A; objective 2).

DESIGN

Secondary analysis of an observational cohort study.

SETTING

Hospital outpatient spasticity management service.

PARTICIPANTS

A convenience sample (N=65), comprising adults with upper motor neuron syndrome affecting the arm after acquired brain injury (ABI; n=38) and participants without ABI (n=27).

INTERVENTIONS

After clinical assessment, a subgroup of participants with ABI (n=28) underwent BTX-A injections as part of their spasticity management.

MAIN OUTCOME MEASURES

Post hoc DCD data processing extracted the values of minimum force generation between 10 sequential contractions. The pattern of change was analyzed.

RESULTS

The ABI injected group exerted greater force at baseline than both other groups (ABI injected=1.04 kg, ABI noninjected=0.74 kg, participants without ABI=0.53 kg; P=.011). After the first contraction, minimum force values increased for all groups and were greatest in the ABI injected group. With subsequent cycles, the group without ABI showed a linear pattern of decreasing force generation, whereas both ABI groups showed a quadratic increasing pattern, which was of greater magnitude in the ABI injected group. After injection, values for the ABI injected group showed a 51% reduction in inducible muscle overactivity (P=.003) to magnitudes similar to those of the ABI noninjected group.

CONCLUSIONS

This study showed that hand relaxation deteriorated during repetitive movements in people with spasticity, a feature hypothesized to adversely influence everyday hand function. After BTX-A injection, the magnitude but not the pattern of this inducible muscle overactivity improved.

A New Definition of Poststroke Spasticity and the Interference of Spasticity With Motor Recovery From Acute to Chronic Stages

The relationship of poststroke spasticity and motor recovery can be confusing. "True" motor recovery refers to return of motor behaviors to prestroke state with the same end-effectors and temporo-spatial pattern. This requires neural recovery and repair, and presumably occurs mainly in the acute and subacute stages. However, according to the International Classification of Functioning, Disability and Health, motor recovery after stroke is also defined as "improvement in performance of functional tasks," i.e., functional recovery, which is mainly mediated by compensatory mechanisms. Therefore, stroke survivors can execute motor tasks in spite of disordered motor control and the presence of spasticity. Spasticity interferes with execution of normal motor behaviors ("true" motor recovery), throughout the evolution of stroke from acute to chronic stages. Spasticity reduction does not affect functional recovery in the acute and subacute stages; however, appropriate management of spasticity could lead to improvement of motor function, that is, functional recovery, during the chronic stage of stroke. We assert that spasticity results from upregulation of medial cortico-reticulo-spinal pathways that are disinhibited due to damage of the motor cortex or corticobulbar pathways. Spasticity emerges as a manifestation of maladaptive plasticity in the early stages of recovery and can persist into the chronic stage. It coexists and shares similar pathophysiological processes with related motor impairments, such as abnormal force control, muscle coactivation and motor synergies, and diffuse interlimb muscle activation. Accordingly, we propose a new definition of spasticity to better account for its pathophysiology and the complex nuances of different definitions of motor recovery.

Effects of a Soft Robotic Hand for Hand Rehabilitation in Chronic Stroke Survivors

OBJECTIVES

Soft robotic hands are proposed for stroke rehabilitation in terms of their high compliance and low inherent stiffness. We investigated the clinical efficacy of a soft robotic hand that could actively flex and extend the fingers in chronic stroke subjects with different levels of spasticity.

METHODS

Sixteen chronic stroke subjects were recruited into this single-group study. Subjects underwent 20 sessions of 1-hour EMG-driven soft robotic hand training. Training effect was evaluated by the pre-training and post-training assessments with the clinical scores: Action Research Arm Test(ARAT), Fugl-Meyer Assessment for Upper Extremity(FMA-UE), Box-and-Block test(BBT), Modified Ashworth Scale(MAS), and maximum voluntary grip strength.

RESULTS

For all the recruited subjects (n = 16), significant improvement of upper limb function was generally observed in ARAT (increased mean=2.44, P = 0.032), FMA-UE (increased mean=3.31, P = 0.003), BBT (increased mean=1.81, P = 0.024), and maximum voluntary grip strength (increased mean=2.14 kg, P < 0.001). No significant change was observed in terms of spasticity with the MAS (decreased mean=0.11, P = 0.423). Further analysis showed subjects with mild or no finger flexor spasticity (MAS<2, n = 9) at pre-training had significant improvement of upper limb function after 20 sessions of training. However, for subjects with moderate and severe finger flexor spasticity (MAS=2,3, n = 7) at pre-training, no significant change in clinical scores was shown and only maximum voluntary grip strength had significant increase.

CONCLUSION

EMG-driven rehabilitation training using the soft robotic hand with flexion and extension could be effective for the functional recovery of upper limb in chronic stroke subjects with mild or no spasticity.

Characteristics of the severely impaired hand in survivors of stroke with chronic impairments

Background: Diminished sensorimotor control of the hand is one of the most common outcomes following stroke. This hand impairment substantially impacts overall function and quality of life; standard therapy often results in limited improvement. Mechanisms of dysfunction of the severely impaired post-stroke hand are still incompletely understood, thereby impeding the development of new targeted treatments.Objective: To identify and determine potential relationships among the mechanisms responsible for hand impairment following strokeMethods: This cohort study observed stroke survivors (n = 95) with severe, chronic hand impairment (Chedoke-McMaster Hand score = 2-3). Custom instrumentation created precise perturbations and measured kinematic responses. Muscle activation was recorded through electromyography. Strength, spasticity, muscle relaxation time, and muscle coactivation were quantified.Results: Maximum grip strength in the paretic hand was only 12% of that achieved by the nonparetic hand, and only 6 of 95 participants were able to produce any net extension force. Despite force deficits, spastic reflex response of the finger flexor evoked by imposed stretch averaged 90.1 ± 26.8% of maximum voluntary activation, relaxation time averaged 3.8 ± 0.8 seconds, and coactivation during voluntary extension exceeded 30% of maximum contraction, thereby resulting in substantial net flexion. Surprisingly, these hypertonicity measures were not significantly correlated with each other.Conclusions: Survivors of severe, chronic hemiparetic stroke experience profound weakness of both flexion and extension that arises from increased involuntary antagonist activation and decreased voluntary activation. The lack of correlation amongst hypertonicity measures suggests that these phenomena may arise from multiple, potentially independent mechanisms that could require different treatments.

Change in motor cortex activation for muscle release by motor learning

For central nervous system disorders' rehabilitation, it is important to accurately understand motor control and implement an appropriate motor learning process to induce neuroplastic changes. The neurophysiological studies have revealed that neural control mechanisms are crucial during both the onset of muscular activities and muscle release after contraction. When performing various movements during daily activities, muscle relaxation control enables precise force output and timing control. Moreover, surround inhibition is a functional mechanism in the motor system. Surround inhibition of the motor system may be involved in the selective execution of desired movements. This review demonstrates cortical excitability resulting from motor learning, movement control mechanisms including muscle relaxation and the suppression of nontarget muscle groups, and the voluntary drive's importance that is required for movement.

The Effects of Botulinum Toxin Injections on Spasticity and Motor Performance in Chronic Stroke with Spastic Hemiplegia

Spastic muscles are weak muscles. It is known that muscle weakness is linked to poor motor performance. Botulinum neurotoxin (BoNT) injections are considered as the first-line treatment for focal spasticity. The purpose of this study was to quantitatively investigate the effects of BoNT injections on force control of spastic biceps brachii muscles in stroke survivors. Ten stroke survivors with spastic hemiplegia (51.7 ± 11.5 yrs; 5 men) who received 100 units of incobotulinumtoxinA or onabotulinumtoxinA to the biceps brachii muscles participated in this study. Spasticity assessment (Modified Ashworth Scale (MAS) and reflex torque) and muscle strength of elbow flexors, as well as motor performance assessment (force variability of submaximal elbow flexion) were performed within one week before (pre-injection) and 3~4 weeks (3-wk) after BoNT injections. As expected, BoNT injections reduced the MAS score and reflex torque, and elbow flexor strength on the spastic paretic side. However, motor performance remained within similar level before and after injections. There was no change in muscle strength or motor performance on the contralateral arm after BoNT injections. The results of this study provide evidence that BoNT injections can reduce spasticity and muscle strength, while motor performance of the weakened spastic muscle remains unchanged.

On Stopping Voluntary Muscle Relaxations and Contractions: Evidence for Shared Control Mechanisms and Muscle State-Specific Active Breaking

Control of the body requires inhibiting complex actions, involving contracting and relaxing muscles. However, little is known of how voluntary commands to relax a muscle are cancelled. Action inhibition causes both suppression of muscle activity and the transient excitation of antagonist muscles, the latter being termed active breaking. We hypothesized that active breaking is present when stopping muscle relaxations. Stop signal experiments were used to compare the mechanisms of active breaking for muscle relaxations and contractions in male and female human participants. In experiments 1 and 2, go signals were presented that required participants to contract or relax their biceps or triceps muscle. Infrequent Stop signals occurred after fixed delays (0-500 ms), requiring that participants cancelled go commands. In experiment 3, participants increased (contract) or decreased (relax) an existing isometric finger abduction depending on the go signal, and cancelled these force changes whenever Stop signals occurred (dynamically adjusted delay). We found that muscle relaxations were stopped rapidly, met predictions of existing race models, and had Stop signal reaction times that correlated with those observed during the stopping of muscle contractions, suggesting shared control mechanisms. However, stopped relaxations were preceded by transient increases in electromyography (EMG), while stopped contractions were preceded by decreases in EMG, suggesting a later divergence of control. Muscle state-specific active breaking occurred simultaneously across muscles, consistent with a central origin. Our results indicate that the later stages of action inhibition involve separate excitatory and inhibitory pathways, which act automatically to cancel complex body movements.SIGNIFICANCE STATEMENT The mechanisms of how muscle relaxations are cancelled are poorly understood. We showed in three experiments involving multiple effectors that stopping muscle relaxations involves transient bursts of EMG activity, which resemble cocontraction and have onsets that correlate with Stop signal reaction time. Comparison with the stopping of matched muscle contractions showed that active breaking was muscle state specific, being positive for relaxations and negative for contractions. The two processes were also observed to co-occur in agonist-antagonist pairs, suggesting separate pathways. The rapid, automatic activation of both pathways may explain how complex actions can be stopped at any stage of their execution.

Changes in ipsilesional hand motor function differ after unilateral injury to frontal versus frontoparietal cortices in Macaca mulatta

We tested the hypothesis that injury to frontoparietal sensorimotor areas causes greater initial impairments in performance and poorer recovery of ipsilesional dexterous hand/finger movements than lesions limited to frontal motor areas in rhesus monkeys. Reaching and grasping/manipulation of small targets with the ipsilesional hand were assessed for 6-12 months post-injury using two motor tests. Initial post-lesion motor skill and long-term recovery of motor skill were compared in two groups of monkeys: (1) F2 group-five cases with lesions of arm areas of primary motor cortex (M1) and lateral premotor cortex (LPMC) and (2) F2P2 group-five cases with F2 lesions + lesions of arm areas of primary somatosensory cortex and the anterior portion of area 5. Initial post-lesion reach and manipulation skills were similar to or better than pre-lesion skills in most F2 lesion cases in a difficult fine motor task but worse than pre-lesion skill in most F2P2 lesion cases in all tasks. Subsequently, reaching and manipulation skills improved over the post-lesion period to higher than pre-lesion skills in both groups, but improvements were greater in the F2 lesion group, perhaps due to additional task practice and greater ipsilesional limb use for daily activities. Poorer and slower post-lesion improvement of ipsilesional upper limb motor skill in the F2P2 cases may be due to impaired somatosensory processing. The persistent ipsilesional upper limb motor deficits frequently observed in humans after stroke are probably caused by greater subcortical white and gray matter damage than in the localized surgical injuries studied here.

Brain Activity Underlying Muscle Relaxation

Fine motor control of not only muscle contraction but also muscle relaxation is required for appropriate movements in both daily life and sports. Movement disorders such as Parkinson’s disease and dystonia are often characterized by deficits of muscle relaxation. Neuroimaging and neurophysiological studies suggest that muscle relaxation is an active process requiring cortical activation, and not just the cessation of contraction. In this article, we review the neural mechanisms of muscle relaxation, primarily utilizing research involving transcranial magnetic stimulation (TMS). Several studies utilizing single-pulse TMS have demonstrated that, during the relaxation phase of a muscle, the excitability of the corticospinal tract controlling that particular muscle is more suppressed than in the resting condition. Other studies, utilizing paired-pulse TMS, have shown that the intracortical inhibition is activated just before muscle relaxation. Moreover, muscle relaxation of one body part suppresses cortical activities controlling other body parts in different limbs. Therefore, the cortical activity might not only be a trigger for muscle relaxation of the target muscles but could also bring about an inhibitory effect on other muscles. This spread of inhibition can hinder the appropriate contraction of muscles involved in multi-limb movements such as those used in sports and the play of musical instruments. This may also be the reason why muscle relaxation is so difficult for beginners, infants, elderly, and the cognitively impaired.

Dynamic bimanual force control in chronic stroke: contribution of non-paretic and paretic hands

Dynamic force modulation is critical for performing skilled bimanual tasks. Unilateral motor impairments after stroke contribute to asymmetric hand function. Here, we investigate the impact of stroke on dynamic bimanual force control and compare the contribution of each hand to a bimanual task. Thirteen chronic stroke and thirteen healthy control participants performed bimanual, isometric finger flexion during visually guided, force tracking of a trapezoidal trajectory with force increment and decrement phases. We quantified the accuracy and variability of total force from both hands. Individual hand contribution was quantified with the proportion of force contributed to total force and force variability of each hand. The total force output was 53.10% less accurate and 56% more variable in the stroke compared with the control group. The variability of total force was 91.10% greater in force decrement than increment phase. In stroke group, the proportion of force and force variability contributed by each hand differed across the two phases. During force decrement, the proportion of force contributed by the non-paretic hand reduced and force variability of the non-paretic hand increased, compared with the increment phase. The control group showed no differences in each hand's contribution across the two force phases. In conclusion, dynamic bimanual force modulation is impaired after stroke, with greater deficits in force decrement than force increment. The non-paretic and paretic hands adapt differentially to dynamic bimanual task constraints. During force decrement, the non-paretic hand preferentially assumes force modulation, while the paretic hand produces steady force to meet the force requirements.

Differences between flexion and extension synergy-driven coupling at the elbow, wrist, and fingers of individuals with chronic hemiparetic stroke

OBJECTIVE

The flexion and extension synergies were quantified at the paretic elbow, forearm, wrist, and finger joints within the same group of participants for the first time. Differences in synergy expression at each of the four joints were examined, as were the ways these differences varied across the joints.

METHODS

Twelve post-stroke individuals with chronic moderate-to-severe hemiparesis and six age-matched controls participated. Participants generated isometric shoulder abduction (SABD) and shoulder adduction (SADD) at four submaximal levels to progressively elicit the flexion and extension synergies, respectively. Isometric joint torques and EMG were recorded from shoulder, elbow, forearm (radio-ulnar), wrist, and finger joints and muscles.

RESULTS

SABD elicited strong wrist and finger flexion torque that increased with shoulder torque level. SADD produced primarily wrist and finger flexion torque, but magnitudes at the wrist were less than during SABD. Findings contrasted with those at the elbow and forearm, where torques and EMG generated due to SABD and SADD were opposite in direction.

CONCLUSIONS

Flexion and extension synergy expression are more similar at the hand than at the shoulder and elbow. Specific bulbospinal pathways that may underlie flexion and extension synergy expression are discussed.

SIGNIFICANCE

Whole-limb behavior must be considered when examining paretic hand function in moderately-to-severely impaired individuals.

Development of an EMG-Controlled Serious Game for Rehabilitation

A majority of the seven million stroke survivors in the U.S. have hand impairments, adversely affecting performance of a variety of activities of daily living, because of the fundamental role of the hand in performing functional tasks. Disability in stroke survivors is largely attributable to damaged neuronal pathways, which result in inappropriate activation of muscles, a condition prevalent in distal upper extremity muscles following stroke. While conventional rehabilitation methods focus on the amplification of existing muscle activation, the effectiveness of therapy targeting the reorganization of pathological activation patterns is often unexplored. To encourage modulation of activation level and exploration of the activation workspace, we developed a novel platform for playing a serious game through electromyographic control. This system was evaluated by a group of neurologically intact subjects over multiple sessions held on different days. Subjects were assigned to one of two groups, training either with their non-dominant hand only (unilateral) or with both hands (bilateral). Both groups of subjects displayed improved performance in controlling the cursor with their non-dominant hand, with retention from one session to the next. The system holds promise for rehabilitation of control of muscle activation patterns.

Controlling pre-movement sensorimotor rhythm can improve finger extension after stroke

OBJECTIVE

Brain-computer interface (BCI) technology is attracting increasing interest as a tool for enhancing recovery of motor function after stroke, yet the optimal way to apply this technology is unknown. Here, we studied the immediate and therapeutic effects of BCI-based training to control pre-movement sensorimotor rhythm (SMR) amplitude on robot-assisted finger extension in people with stroke.

APPROACH

Eight people with moderate to severe hand impairment due to chronic stroke completed a four-week three-phase protocol during which they practiced finger extension with assistance from the FINGER robotic exoskeleton. In Phase 1, we identified spatiospectral SMR features for each person that correlated with the intent to extend the index and/or middle finger(s). In Phase 2, the participants learned to increase or decrease SMR features given visual feedback, without movement. In Phase 3, the participants were cued to increase or decrease their SMR features, and when successful, were then cued to immediately attempt to extend the finger(s) with robot assistance.

MAIN RESULTS

Of the four participants that achieved SMR control in Phase 2, three initiated finger extensions with a reduced reaction time after decreasing (versus increasing) pre-movement SMR amplitude during Phase 3. Two also extended at least one of their fingers more forcefully after decreasing pre-movement SMR amplitude. Hand function, measured by the box and block test (BBT), improved by 7.3  ±  7.5 blocks versus 3.5  ±  3.1 blocks in those with and without SMR control, respectively. Higher BBT scores at baseline correlated with a larger change in BBT score.

SIGNIFICANCE

These results suggest that learning to control person-specific pre-movement SMR features associated with finger extension can improve finger extension ability after stroke for some individuals. These results merit further investigation in a rehabilitation context.

A pilot study into reaching performance after severe to moderate stroke using upper arm support

Stroke effects millions of people each year and can have a significant impact on the ability to use the impaired arm and hand. One of the results of stroke is the development of an abnormal shoulder-elbow flexion synergy, where lifting the arm can cause the elbow, wrist, and finger flexors to involuntarily contract, reducing the ability to reach with the arm and hand opening. This study explored the effect of using support at the upper arm to improve hand and arm reaching performance. Nine participants were studied while performing a virtual reaching task under three conditions: while the weight of their impaired arm was supported by a robot arm, while unsupported, and while using their non-impaired arm. Most subjects exhibited faster and more accurate reaching while supported compared to unsupported. For the subjects who could voluntarily open their hand, most were able to more swiftly open their hand when using upper arm support. In many cases, performance with support was not statistically different than the unaffected arm and hand. Muscle activity of the impaired limb with upper arm support showed decreased effort to lift the arm and reduced biceps activity in most subjects, pointing to a reduction in the abnormal flexion synergy while using upper arm support. While arm support can help to reduce the activation of abnormal synergies, weakness resulting from hemiparesis remains an issue impacting performance. Future systems will need to address both of these causes of disability to more fully restore function after stroke.

[The restoration of the shoulder joint function in the patients presenting with hemiparesis during the acute phase of hemispheric stroke]

The impaired function of the shoulder joint resulting from cerebral stroke is a common disorder involving permanent total disability as well as impaired capability of self-care. The functional pathological changes in the shoulder joint and the dynamics of the patients' health status during the acute period of cerebral stroke remain virtually unexplored.

AIM

The objective of the present study was to obtain a deeper insight into the process of recovery of the movements in the shoulder joint of the patients presenting with hemiparesis during the acute period of hemispheric stroke based on the results of the analysis of the biomechanical data and the targeted training with biofeedback (BFB).

MATERIAL AND METHODS

The study included three groups comprised of 25 subjects each. One (control) group included the subjects having neither neurological nor orthopedic pathology. The second group consisted of the patients receiving the conventional treatment in the combination with therapeutic physical exercises (TPE). Group 3 was composed of the patients given the standard course of conventional and physical (TPE) therapy complemented by biofeedback training (the TPE/BFB group). The study included clinical investigations and biomechanical registration of the movements of the shoulder joints and trunk.

RESULTS

The results of the study gave evidence that the patients presenting with hemiparesis during the acute period of hemispheric ischemic stroke including those treated with the application of the active means and methods of rehabilitation, such as BFB training, showed no appreciable dynamics of the parameters being evaluated with the use of the relevant clinical scales. The biomechanical study has demonstrated that the movements in the shoulder joints (in a single plain) of the patients comprising the control group are characterized by the presence of the main component with a maximum amplitude in the plane of this movement and additional components (in other planes with a significantly lower amplitude); they are accompanied by the ancillary movements of the trunk. Functionally, the condition of paresis at the level of the shoulder joint is characterized by a decrease in the amplitude of the primary movement and the increase of one of the additional amplitudes, with the growing amplitude of the auxiliary movements of the trunk. The biomechanical methods for the objective assessment have revealed the following functional changes in the shoulder joints: the 6% improvement of flexion in the group of the patients treated with the use of therapeutic physical exercises and the 10% improvement in those treated with the combination of TPE and BFB. Moreover, abduction in the patients of these two groups improved by 4% and 9% respectively.

CONCLUSIONS

The method for the study of kinematics of the movements in the shoulder joints appears to be most sensitive and informative for the purpose of diagnostics of disorders of the motor function and assessment of the process of its restoration in the patients presenting with hemiparesis during the acute period of hemispheric stroke.

Pilot testing of the spring operated wearable enhancer for arm rehabilitation (SpringWear)

Background

Robotic devices for neurorehabilitation of movement impairments in persons with stroke have been studied extensively. However, the vast majority of these devices only allow practice of stereotyped components of simulated functional tasks in the clinic. Previously we developed SpringWear, a wearable, spring operated, upper extremity exoskeleton capable of assisting movements during real-life functional activities, potentially in the home. SpringWear assists shoulder flexion, elbow extension and forearm supination/pronation. The assistance profiles were designed to approximate the torque required to move the joint passively through its range. These three assisted DOF are combined with two passive shoulder DOF, allowing complex multi-joint movement patterns.

Methods

We performed a cross-sectional study to assess changes in movement patterns when assisted by SpringWear. Thirteen persons with chronic stroke performed range of motion (ROM) and functional tasks, including pick and place tasks with various objects. Sensors on the device measured rotation at all 5 DOF and a kinematic model calculated position of the wrist relative to the shoulder. Within subject t-tests were used to determine changes with assistance from SpringWear.

Results

Maximum shoulder flexion, elbow extension and forearm pronation/supination angles increased significantly during both ROM and functional tasks (p < 0.002). Elbow flexion/extension ROM also increased significantly (p < 0.001). When the subjects volitionally held up the arm against gravity, extension at the index finger proximal interphalangeal joint increased significantly (p = 0.033) when assisted by SpringWear. The forward reach workspace increased 19% (p = 0.002). Nine subjects could not complete the functional tasks unassisted and only one showed improvement on task completion with SpringWear.

Conclusions

SpringWear increased the usable workspace during reaching movements, but there was no consistent improvement in the ability to complete functional tasks. Assistance levels at the shoulder were increased only until the shoulder could be voluntarily held at 90 degrees of flexion. A higher level of assistance may have yielded better results. Also combining SpringWear with HandSOME, an exoskeleton for assisting hand opening, may yield the most dramatic improvements in functional task performance. These low-cost devices can potentially reduce effort and improve performance during task practice, increasing adherence to home training programs for rehabilitation.

Impact of Targeted Assistance of Multiarticular Finger Musculotendons on the Coordination of Finger Muscles During Isometric Force Production

Neurological injuries often cause degraded motor control. While rehabilitation efforts typically focus on movement kinematics, abnormal muscle activation patterns are often the primary source of impairment. Muscle-based therapies are likely more effective than joint-based therapy. In this paper, we examined the feasibility of biomimetic input mimicking the action of human musculotendons in altering hand muscle coordination. Twelve healthy subjects produced a submaximal isometric dorsal fingertip force, while a custom actuator provided assistance mirroring the actions of either the extrinsic extensor or the intrinsic muscles of the index finger. The biomimetic inputs reduced the activation level of all task-related muscles, but the degree of change was different across the muscles, resulting in significant changes in their coordination (co-contraction ratios) and force-electromyography correlations. Each biomimetic assistance particularly increased the neural coupling between its targeted muscle and the antagonist muscle. Subjects appeared to fully take advantage of the assistance, as they provided minimal level of effort to achieve the task goal. The targeted biomimetic assistance may be used to retrain activation patterns post-stroke by effectively modulating connectivity between the muscles in the functional context and could be beneficial to restore hand function and reduce disability.

An overview of robotic/mechanical devices for post-stroke thumb rehabilitation

PURPOSE

This article aims to clarify the current state-of-the-art of robotic/mechanical devices for post-stroke thumb rehabilitation as well as the anatomical characteristics and motions of the thumb that are crucial for the development of any device that aims to support its motion.

METHODS

A systematic literature search was conducted to identify robotic/mechanical devices for post-stroke thumb rehabilitation. Specific electronic databases and well-defined search terms and inclusion/exclusion criteria were used for such purpose. A reasoning model was devised to support the structured abstraction of relevant data from the literature of interest.

RESULTS

Following the main search and after removing duplicated and other non-relevant studies, 68 articles (corresponding to 32 devices) were left for further examination. These articles were analyzed to extract data relative to (i) the motions assisted/permitted - either actively or passively - by the device per anatomical joint of the thumb and (ii) mechanical-related aspects (i.e., architecture, connections to thumb, other fingers supported, adjustability to different hand sizes, actuators - type, quantity, location, power transmission and motion trajectory).

CONCLUSIONS

Most articles describe preliminary design and testing of prototypes, rather than the thorough evaluation of commercially ready devices. Defining appropriate kinematic models of the thumb upon which to design such devices still remains a challenging and unresolved task. Further research is needed before these devices can actually be implemented in clinical environments to serve their intended purpose of complementing the labour of therapists by facilitating intensive treatment with precise and repeatable exercises. Implications for Rehabilitation Post-stroke functional disability of the hand, and particularly of the thumb, significantly affects the capability to perform activities of daily living, threatening the independence and quality of life of the stroke survivors. The latest studies show that a high-dose intensive therapy (in terms of frequency, duration and intensity/effort) is the key to effectively modify neural organization and recover the motor skills that were lost after a stroke. Conventional therapy based on manual interaction with physical therapists makes the procedure labour intensive and increases the costs. Robotic/mechanical devices hold promise for complementing conventional post-stroke therapy. Specifically, these devices can provide reliable and accurate therapy for long periods of time without the associated fatigue. Also, they can be used as a means to assess patients? performance and progress in an objective and consistent manner. The full potential of robot-assisted therapy is still to be unveiled. Further exploration will surely lead to devices that can be well accepted equally by therapists and patients and that can be useful both in clinical and home-based rehabilitation practice such that motor recovery of the hand becomes a common outcome in stroke survivors. This overview provides the reader, possibly a designer of such a device, with a complete overview of the state-of-the-art of robotic/mechanical devices consisting of or including features for the rehabilitation of the thumb. Also, we clarify the anatomical characteristics and motions of the thumb that are crucial for the development of any device that aims to support its motion. Hopefully, this?combined with the outlined opportunities for further research?leads to the improvement of current devices and the development of new technology and knowledge in the field.

Spring operated wearable enhancer for arm rehabilitation (SpringWear) after stroke

A 5-DOF spring actuated exoskeleton, called SpringWear, was developed to increase range of motion in the affected arms of stroke patients. Theoretically perfect gravity compensation is provided at the shoulder elevation DOF. Additional torque is provided to assist weakness in forearm supination and elbow extension. Three stroke patients were tested. All of the assisted joints increased in range of motion, and larger gains should be possible with refinements in the available torque profiles. Additionally, finger range of motion was increased in one subject when asked to open the hand while holding the shoulder at 90 degrees of elevation.

Home-Based Therapy After Stroke Using the Hand Spring Operated Movement Enhancer (HandSOME)

In previous work, we developed a lightweight wearable hand exoskeleton (Hand Spring Operated Movement Enhancer) that improves range of motion and function in laboratory testing. In this pilot study, we added the ability to log movement data for extended periods and recruited ten chronic stroke subjects to use the device during reach and grasp task practice at home for 1.5 h/day, five days per week, and for four weeks. Seven subjects completed the study, performing 448 ± 651 hand movements per training day. After training, impairment was reduced (Fugl-Meyer test; gain = 4.9 ± 4.1; p = .039) and function was improved (Action Research Arm Test; gain = 3.3 ± 2.6; p = .032). There was a significant correlation between gains in the Action Research Arm Test and the number of movements during training (r = 0.90; p = .005). Proximal arm control also improved, as evidenced by a significant reduction in the reach path ratio (p = 0.038). Five subjects responded well to the treatment, having gains of six points or more on the Fugl-Meyer or action research arm test, and achieving significant gains in digit extension (gain = 19.8 ± 10.2°; p = 0.024). However, all of the gains that were significant immediately after training were no longer significant at the three month follow-up. This treatment approach appears promising, but longer periods of home training may be needed to achieve sustainable gains.

The Effect of Peripheral Nerve Stimulation on Shoulder Biomechanics: A Randomized Controlled Trial in Comparison to Physical Therapy

OBJECTIVE

To establish the effects on shoulder biomechanics from a peripheral nerve stimulation (PNS) treatment compared to physical therapy (PT) in stroke survivors with chronic hemiplegic shoulder pain.

DESIGN

Single-site, pilot, randomized controlled trial for adults with chronic shoulder pain after stroke. Participants were randomized to receive a 3-week treatment of single-lead PNS or physical therapy (PT). The outcomes included isometric shoulder abduction strength, pain-free shoulder external rotation range of motion (ROM), delay in initiation and termination of shoulder abduction electromyogram (EMG) activity, and the Fugl-Meyer Motor Assessment (upper extremity section). Outcomes were measured at baseline, and at weeks 1, 4, 12, and 16.

RESULTS

Twenty-five participants were recruited, 13 to PNS and 12 to PT. There were significant improvements for both PNS and PT in maximum isometric shoulder abduction strength, pain-free external rotation ROM, and Fugl-Meyer Motor Assessment. There were no significant changes in delay of initiation or termination of deltoid EMG with either treatment.

CONCLUSIONS

Both PNS and PT are capable of improving shoulder biomechanics in those with HSP, though changes in biomechanics alone do not account for the greater pain relief associated with PNS than PT.

Delayed grip relaxation and altered modulation of intracortical inhibition with aging

Grip relaxation is a voluntary action that requires an increase in short-interval intracortical inhibition (SICI) in healthy young adults, rather than a simple termination of excitatory drive. The way aging affects this voluntary inhibitory action and timing of grip relaxation is currently unknown. The objective of this study was to examine aging-related delays in grip relaxation and SICI modulation for the flexor digitorum superficialis muscle during grip relaxation. The main finding was that young adults increased SICI to relax their grips, whereas older adults did not increase SICI with a prolonged grip relaxation time (p < 0.05 for both SICI modulation and grip relaxation time). A secondary experiment showed that both young and older adults did not change H reflex excitability during grip relaxation. Our data suggest that grip relaxation is mediated by increased cortical inhibitory output in young adults, and aging-related impairment in increasing cortical inhibitory output may hamper timely cessation of muscle activity. Our data also suggest a lesser role of the spinal circuits in grip muscle relaxation. This knowledge may contribute to understanding of aging-related movement deterioration and development of interventions for improving modulation of SICI to improve muscle relaxation and movement coordination.

Motor planning poststroke: impairment in vector-coded reach plans

Healthy individuals appear to use both vector‐coded reach plans that encode movements in terms of their desired direction and extent, and target‐coded reach plans that encode the desired endpoint position of the effector. We examined whether these vector and target reach‐planning codes are differentially affected after stroke. Participants with stroke and healthy controls made blocks of reaches that were grouped by target location (providing target‐specific practice) and by movement vector (providing vector‐specific practice). Reach accuracy was impaired in the more affected arm after stroke, but not distinguishable for target‐ versus vector‐grouped reaches. Reach velocity and acceleration were not only impaired in both the less and more affected arms poststroke, but also not distinguishable for target‐ versus vector‐grouped reaches. As previously reported in controls, target‐grouped reaches yielded isotropic (circular) error distributions and vector‐grouped reaches yielded error distributions elongated in the direction of the reach. In stroke, the pattern of variability was similar. However, the more affected arm showed less elongated error ellipses for vector‐grouped reaches compared to the less affected arm, particularly in individuals with right‐hemispheric stroke. The results suggest greater impairment to the vector‐coded movement‐planning system after stroke, and have implications for the development of personalized approaches to poststroke rehabilitation: Motor learning may be enhanced by practice that uses the preserved code or, conversely, by retraining the more impaired code to restore function.

Improvement of hand function using different surfaces and identification of difficult movement post stroke in the Box and Block Test

This study determined the impact of changing block surfaces on hand function, as well as identified particularly time-consuming movement components post stroke, measured by the Box and Block Test (BBT). Eight chronic stroke survivors and eight age- and gender-matched control subjects participated in this study. The BBT score (number of blocks moved) and time for seven movement components were compared for three different block surfaces (wood, paper, and rubber). The rubber blocks improved BBT scores 8% (compared to all other conditions) not only for control subjects but also for the paretic and non-paretic hands of stroke survivors, by reducing movement time for finger closing and contact-to-lift. Modifying daily objects' surfaces with rubber could help stroke survivors' hand function. The paretic hand displayed notably slower movement for contact-to-lift, transport-release, reach before barrier, and reach after barrier suggesting that therapies may focus on goal directed reaching and object grasping/releasing.

Carryover effects of cyclical stretching of the digits on hand function in stroke survivors

OBJECTIVE

To investigate the longevity and cumulative impact of multiple sessions of passive, cyclical stretching of the digits on hand function in subacute stroke survivors.

DESIGN

Before-after trial with intervention repeated on 3 consecutive days.

SETTING

Research laboratory.

PARTICIPANTS

Individuals (N=27) with moderate to severe hand impairment, 2 to 6 months (subacute, n=12) and >7 months (chronic, n=15) poststroke.

INTERVENTIONS

Subjects wore an actuated glove orthosis that cyclically moved their fingers and thumb from a relaxed/flexed posture into neutral extension for 30 minutes on 3 consecutive days.

MAIN OUTCOME MEASURES

Three hand-specific tasks from the Graded Wolf Motor Function Test, Box and Block Test (BBT), grip strength, and lateral pinch strength. Recordings were taken before stretching and at 3 time points, each separated by 30 minutes after completion of stretching on each day.

RESULTS

Significant improvement was observed immediately after the stretching for both groups. Improvements in the subacute group were largely maintained up to 1 hour poststretching, with significant carryover from day to day for some outcomes measures such as the BBT (P=.006) and grip strength (P=.012). In contrast, improvements after stretching for the chronic group were transient, with the changes largely dissipating over time and no significant cumulative effect across days.

CONCLUSIONS

Cyclical stretching of the digits had a lasting and reinforcing effect on improving hand motor control for subacute stroke survivors. Incorporation of cyclical stretching before active hand therapy may prove to be a beneficial treatment for stroke survivors, especially during the subacute phase of recovery.

Involuntary contralateral upper extremity muscle activation pattern during unilateral pinch grip following stroke

STUDY DESIGN

Repeated measures design.

INTRODUCTION

Mirror activity refers to emergence of motion not only in the intended, but also in the contralateral limb.

PURPOSE

To characterize post-stroke mirror activities across multiple muscles during unilateral pinch.

METHODS

Chronic stroke survivors performed unilateral pinch grip using the paretic and nonparetic hand, while four muscles' EMGs were recorded for both hands.

RESULTS

During the paretic hand grip, the relaxed nonparetic hand showed mirror activity that was more pronounced for the intrinsic (FDI and thenar eminence) than extrinsic muscles (FDS and EDC). During the nonparetic hand grip, mirror activity in the paretic hand was suppressed for the intrinsic than extrinsic muscles.

CONCLUSION

Chronic stroke survivors' relaxed hand did not mirror the task hand's muscle activation pattern, but displayed altered muscle activation patterns depending on muscles and sides, possibly mediated by disturbed interhemispheric inhibition and relative reliance on corticospinal tracts among muscles.

LEVEL OF EVIDENCE

N/A.

Finger-thumb coupling contributes to exaggerated thumb flexion in stroke survivors

The purpose of this study was to investigate altered finger-thumb coupling in individuals with chronic hemiparesis poststroke. First, an external device stretched finger flexor muscles by passively rotating the metacarpophalangeal (MCP) joints. Subjects then performed isometric finger or thumb force generation. Forces/torques and electromyographic signals were recorded for both the thumb and finger muscles. Stroke survivors with moderate (n = 9) and severe (n = 9) chronic hand impairment participated, along with neurologically intact individuals (n = 9). Stroke survivors exhibited strong interactions between finger and thumb flexors. The stretch reflex evoked by stretch of the finger flexors of stroke survivors led to heteronymous reflex activity in the thumb, while attempts to produce isolated voluntary finger MCP flexion torque/thumb flexion force led to increased and undesired thumb force/finger MCP torque production poststroke with a striking asymmetry between voluntary flexion and extension. Coherence between the long finger and thumb flexors estimated using intermuscular electromyographic correlations, however, was small. Coactivation of thumb and finger flexor muscles was common in stroke survivors, whether activation was evoked by passive stretch or voluntary activation. The coupling appears to arise from subcortical or spinal sources. Flexor coupling between the thumb and fingers seems to contribute to undesired thumb flexor activity after stroke and may impact rehabilitation outcomes.