Cortical Sensorimotor Integration as a Neural Origin of Impaired Grip Force Direction Control following Stroke.

BACKGROUND: Stroke is a major cause of disability worldwide. Upper limb impairment is prevalent after stroke. One of the post-stroke manifestations is impaired grip force directional control contributing to diminished abilities to grip and manipulate objects necessary for activities of daily living. The objective of this study was to investigate the neural origin of the impaired grip force direction control following stroke. Due to the importance of online adjustment of motor output based on sensory feedback, it was hypothesized that grip force direction control would be associated with cortical sensorimotor integration in stroke survivors. METHODS: Ten chronic stroke survivors participated in this study. Cortical sensorimotor integration was quantified by short latency afferent inhibition (SAI), which represents the responsiveness of the primary motor cortex to somatosensory input. Grip force direction control was assessed during paretic grip. RESULTS: Grip force direction control was significantly associated with SAI. This relationship was independent of sensory impairment level. CONCLUSIONS: Cortical sensorimotor integration may play a significant role in the grip force direction control important for gripping and manipulating objects with the affected hand following stroke. This knowledge may be used to inform personalized rehabilitation treatment. For example, for patients with impaired grip force direction control, behavioral therapy focusing on feedback motor control, augmented by use of brain stimulation to reinforce cortical sensorimotor integration such as paired associative stimulation, may be applied.

Different gait pattern in adolescence with patellofemoral instability.

BACKGROUND: Patellofemoral instability influences the gait pattern and activity level in adolescents. However, gait biomechanics to cope with recurrent patella instability and its relation to radiological findings has hardly been studied. METHODS: We retrospectively analyzed kinematic and kinetic gait analysis data, magnetic resonance images and X-ray of 32 adolescents with unilateral recurrent patellofemoral instability aged 12 to 18 years. Subjects were assigned to 3 groups based on their sagittal knee moment in the loading response and mid stance phase. Kinematic and kinetic differences among the groups were analyzed using a one-way ANOVA. A multinomial logistic regression model provided a further analysis of the relationship between gait biomechanics and MRI as well as X-ray parameters. FINDINGS: All three groups showed different characteristics of the knee kinematics during loading response and single stance: while the patella-norm-loading group showed a slightly reduced knee flexion (p ã€ˆ0,01), the patella-unloading group kept the knee nearly extended (p < 0,01) and patella-overloading group showed an increased knee flexion (p = 0,01) compared to the other groups. In single stance the patella-overloading group maintained increased knee flexion (p < 0,01) compared to patella-unloading group and patella-norm-loading group. None of the radiological parameters proved to be related to gait patterns. INTERPRETATION: The paper describes different gait coping strategies and their clinical relevance in subjects with patellofemoral instability. However, we did not find any relation of gait biomechanics to skeletal morphology.

White Matter Integrity and Chronic Poststroke Upper Limb Function: An ENIGMA Stroke Recovery Analysis.

BACKGROUND: Integrity of the corticospinal tract (CST) is an important biomarker for upper limb motor function following stroke. However, when structurally compromised, other tracts may become relevant for compensation or recovery of function. METHODS: We used the ENIGMA Stroke Recovery data set, a multicenter, retrospective, and cross-sectional collection of patients with upper limb impairment during the chronic phase of stroke to test the relevance of tracts in individuals with less and more severe (laterality index of CST fractional anisotropy ≥0.25) CST damage in an observational study design. White matter integrity was quantified using fractional anisotropy for the CST, the superior longitudinal fascicle, and the callosal fibers interconnecting the primary motor cortices between hemispheres. Optic radiations served as a control tract as they have no a priori relevance for the motor system. Pearson correlation was used for testing correlation with upper limb motor function (Fugl-Meyer upper extremity). RESULTS: From 1235 available data sets, 166 were selected (by imaging, Fugl-Meyer upper extremity, covariates, stroke location, and stage) for analyses. Only individuals with severe CST damage showed a positive association of fractional anisotropy in both callosal fibers interconnecting the primary motor cortices (r[21]=0.49; P=0.025) and superior longitudinal fascicle (r[21]=0.51; P=0.018) with Fugl-Meyer upper extremity. CONCLUSIONS: Our data support the notion that individuals with more severe damage of the CST depend on residual pathways for achieving better upper limb outcome than those with less affected CST.

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 ß 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.

Different aspects of hand grip performance associated with structural connectivity of distinct sensorimotor networks in chronic stroke.

Knowledge regarding the neural origins of distinct upper extremity impairments may guide the choice of interventions to target neural structures responsible for specific impairments. This cross-sectional pilot study investigated whether different brain networks explain distinct aspects of hand grip performance in stroke survivors. In 22 chronic stroke survivors, hand grip performance was characterized as grip strength, reaction, relaxation times, and control of grip force magnitude and direction. In addition, their brain structural connectomes were constructed from diffusion tensor MRI. Prominent networks were identified based on a two-step factor analysis using the number of streamlines among brain regions relevant to sensorimotor function. We used regression models to estimate the predictive value of sensorimotor network connectivity for hand grip performance measures while controlling for stroke lesion volumes. Each hand grip performance measure correlated with the connectivity of distinct brain sensorimotor networks. These results suggest that different brain networks may be responsible for different aspects of hand grip performance, which leads to varying clinical presentations of upper extremity impairment following stroke. Understanding the brain network correlates for different hand grip performances may facilitate the development of personalized rehabilitation interventions to directly target the responsible brain network for specific impairments in individual patients, thus improving outcomes.

Neuroplasticity after upper-extremity rehabilitation therapy with sensory stimulation in chronic stroke survivors.

This study investigated the effect of using subthreshold vibration as a peripheral sensory stimulation during therapy on cortical activity. Secondary analysis of a pilot triple-blinded randomized controlled trial. Twelve chronic stroke survivors underwent 2-week upper-extremity task-practice therapy. Half received subthreshold vibratory stimulation on their paretic wrist (treatment group) and the other half did not (control). EEG connectivity and event-related de-/resynchronization for the sensorimotor network during hand grip were examined at pre-intervention, post-intervention and follow-up. Statistically significant group by time interactions were observed for both connectivity and event-related spectral perturbation. For the treatment group, connectivity increased at post-intervention and decreased at follow-up. Event-related desynchronization decreased and event-related resynchronization increased at post-intervention, which was maintained at follow-up. The control group had the opposite trend for connectivity and no change in event-related spectral perturbation. The stimulation altered cortical sensorimotor activity. The findings complement the clinical results of the trial in which the treatment group significantly improved gross manual dexterity while the control group did not. Increased connectivity in the treatment group may indicate neuroplasticity for motor learning, while reduced event-related desynchronization and increased event-related resynchronization may indicate lessened effort for grip and improved inhibitory control. EEG may improve understanding of neural processes underlying motor recovery.

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.

Concomitant sensory stimulation during therapy to enhance hand functional recovery post stroke.

BACKGROUND: Post-stroke hand impairment is prevalent and persistent even after a full course of rehabilitation. Hand diminishes stroke survivors' abilities for activities of daily living and independence. One way to improve treatment efficacy is to augment therapy with peripheral sensory stimulation. Recently, a novel sensory stimulation, TheraBracelet, has been developed in which imperceptible vibration is applied during task practice through a wrist-worn device. The objective of this trial is to determine if combining TheraBracelet with hand task practice is superior to hand task practice alone. METHODS: A double-blind randomized controlled trial will be used. Chronic stroke survivors will undergo a standardized hand task practice therapy program (3 days/week for 6 weeks) while wearing a device on the paretic wrist. The device will deliver TheraBracelet vibration for the treatment group and no vibration for the control group. The primary outcome is hand function measured by the Wolf Motor Function Test. Other outcomes include the Box and Block Test, Action Research Arm Test, upper extremity use in daily living, biomechanical measure of the sensorimotor grip control, and EEG-based neural communication. DISCUSSION: This research will determine clinical utility of TheraBracelet to guide future translation. The TheraBracelet stimulation is delivered via a wrist-worn device, does not interfere with hand motion, and can be easily integrated into clinical practice. Enhancing hand function should substantially increase stroke survivors' independence and quality of life and reduce caregiver burden. TRIAL REGISTRATION: NCT04569123 . Registered on September 29, 2020.

Predicting upper extremity motor improvement following therapy using EEG-based connectivity in chronic stroke.

BACKGROUND: Uncertain prognosis presents a challenge for therapists in determining the most efficient course of rehabilitation treatment for individual patients. Cortical Sensorimotor network connectivity may have prognostic utility for upper extremity motor improvement because the integrity of the communication within the sensorimotor network forms the basis for neuroplasticity and recovery. OBJECTIVE: To investigate if pre-intervention sensorimotor connectivity predicts post-stroke upper extremity motor improvement following therapy. METHODS: Secondary analysis of a pilot triple-blind randomized controlled trial. Twelve chronic stroke survivors underwent 2-week task-practice therapy, while receiving vibratory stimulation for the treatment group and no stimulation for the control group. EEG connectivity was obtained pre-intervention. Motor improvement was quantified as change in the Box and Block Test from pre to post-therapy. The association between ipsilesional sensorimotor connectivity and motor improvement was examined using regression, controlling for group. For negative control, contralesional/interhemispheric connectivity and conventional predictors (initial clinical motor score, age, time post-stroke, lesion volume) were examined. RESULTS: Greater ipsilesional sensorimotor alpha connectivity was associated with greater upper extremity motor improvement following therapy for both groups (p < 0.05). Other factors were not significant. CONCLUSION: EEG connectivity may have a prognostic utility for individual patients' upper extremity motor improvement following therapy in chronic stroke.

Does femoral anteversion and internally rotated gait correlate in subjects with patellofemoral instability?

BACKGROUND: Patellar instability is a considerable problem that leads to pain and anxiety during simple functional tasks. Femoral derotational osteotomy has become a common surgical procedure to improve patella mechanics, stability and loading. However, it remains unclear if static (MRI measured) femoral anteversion is sufficient to capture the dynamic femoral rotation during walking and represents a good indication for the surgical procedure. This research investigates the relationship between static femoral anteversion and internally rotated gait in adolescents with patellofemoral instability. METHODS: This retrospective study included 30 adolescents with recurrent patella instability (minimum three patella dislocations) aged 12 to 18 years (28 female/2 male; 22 unilateral/8 bilateral). All participants were assessed with 3D gait analysis and the femoral anteversion was examined using a rotational MRI. Multiple kinematic parameter were correlated with the ipsilateral femoral anteversion and tibia torsion using the Pearson coefficient. FINDINGS: The correlation between parameters of dynamic hip rotation (e.g. maximum and mean internal hip rotation in stance and swing) and MRI measured femoral anteversion (mean 26.5° ± 9°) was weak and did not reach statistical significance. We found 47% (14 out of 30) subjects with increased femoral anteversion but normal hip rotation in stance. INTERPRETATION: There was no relationship between increased femoral anteversion and dynamic hip rotation. Consequently, femoral anteversion should not be used as the only indication for femoral derotational osteotomy. Three-dimensional gait analysis might be necessary to assess the appropriate surgical intervention in adolescents with patello femoral instability.

Is there a relationship between muscle-tendon properties and a variety of functional tasks in children with spastic cerebral palsy?

BACKGROUND: Cerebral palsy (CP) is the most common motor and movement disability in childhood. The mechano-morphological alterations of the spastic muscle itself as well as the functional limitations in CP are well documented. However, the relationship between muscle tendon properties and functional tests in CP remains unknown. RESEARCH QUESTION: The aim of this study was to explore the relationship between spastic muscle mechano-morphological properties and functional performance in children with CP. METHODS: This study included retrospective data from 22 children with spastic cerebral palsy with a mean age of 12.8 years (19 GMFCS I/3 GMFC II, 15 male/7 female, 8 unilateral involved/14 bilateral). Mechano-morphological properties of gastrocnemius (GM) and Achilles tendon (AT) were correlated with a variety of functional measures, maximal isometric strength, the Muscle Power Sprint test (MPST), 6-minute walk test (6MWT) and 3D-gait analysis using the Pearson Coefficient. RESULTS: Muscle-tendon properties were normalized to remove anthropometric dimensions because of strong associations with anthropometric data. Higher isometric muscle strength was related to longer normalized GM fascicle lengths (r = 0.67, p < 0.01). The distance reached in the 6MWT positively correlated with normalized GM fascicle lengths (r = 0.61, p < 0.01). Higher AT stiffness was associated with faster performance in the MPST (r = 0.77, p < 0.01). Finally, there was an association between ankle power and both longer normalized AT length and shorter muscle belly (r = 0.60 and r = 0.54, p < 0.01). SIGNIFICANCE: The findings of this study give more insight into the function specific adaptations of a spastic muscle-tendon unit. While walking, assessed through the 6MWT, was related to normalized gastrocnemius fascicle length, sprint performance was associated with an increased AT stiffness. These results provide a better understanding of the relationship between functional tasks and spastic muscle-tendon properties, which offers potential for improved and targeted interventions in CP.

The Effect of Functional Home-Based Strength Training Programs on the Mechano-Morphological Properties of the Plantar Flexor Muscle-Tendon Unit in Children With Spastic Cerebral Palsy.

PURPOSE: The purpose of this study was to investigate the effects of functional progressive resistance training (PRT) and high-intensity circuit training (HICT) on the mechano-morphological properties of the plantar flexor muscle-tendon unit in children with spastic cerebral palsy. METHODS: Twenty-two children (12.8 [2.6] y old, Gross Motor Function Classification System levels I/II = 19/3) were randomly assigned to either a PRT group or an HICT group. The interventions consisted of functional lower limb exercises, which were performed at home 3 times per week for 8 weeks. Measurements at baseline, preintervention, postintervention, and follow-up were taken to assess ankle joint range of motion and the properties of the gastrocnemius medialis, vastus lateralis, rectus femoris, and Achilles tendon (eg, thickness, strength, stiffness). RESULTS: Despite a nonsignificant increase in active torque in the HICT group, neither gastrocnemius medialis morphology nor Achilles tendon properties were significantly altered after the interventions. Vastus lateralis thickness increased following PRT only. CONCLUSIONS: Functional home-based strength training did not lead to significant changes at the muscular level in children with cerebral palsy. We therefore assume that a more specific stimulus of higher intensity combined with a longer training duration might be necessary to evoke changes in muscles and tendons in individuals with cerebral palsy.

Does Home-Based Progressive Resistance or High-Intensity Circuit Training Improve Strength, Function, Activity or Participation in Children With Cerebral Palsy?

OBJECTIVE: Does home-based progressive resistance or high-intensity circuit training improve strength, function, activity, or participation in children with cerebral palsy (CP)? DESIGN: This was the first study on high-intensity circuit training for children with CP. This study was conducted as a randomized prospective controlled pilot study. SETTING: Evaluation took place at the gait laboratory of the university hospital, training sessions were performed at home. PARTICIPANTS: Children (N=22) with CP (average age: 12y, 10mo, 19 Gross Motor Function Classification System level I, 3 level II) were randomly assigned either to progressive resistance training (PRT) or high-intensity circuit training (HICT). INTERVENTIONS: The PRT group trained with progressive overload, while the HICT group performed as many repetitions as possible within 30-second intervals (8wk, 3 times weekly in both groups). MAIN OUTCOME MEASURES: Outcome measures stretched over all domains of the International Classification of Functioning, Disability and Health and included muscle strength, muscle power sprint test (MPST), timed stairs test (TST), 6-minute walking test, Gait Profile Score (GPS), timed Up and Go test (TUGT) and participation questionnaires. RESULTS: Only the HICT group was able to improve strength. Furthermore, the HICT group scored better in the MPST, while PRT participants improved in the TST and TUGT. The HICT-group was able to show improvement in the subscores of the parent-reported participation questionnaire. Other measures of mobility or participation did not change. CONCLUSIONS: Both programs improved function specific to intervention. However, only the HICT group showed significant strength and participation improvements. Compliance was decent in both groups, but the average training unit was shorter in the HICT group. Both exercise programs showed functional benefits, but HICT might be the preferable option for strengthening in highly functional children with CP.

Correction to: Muscle and tendon morphology alterations in children and adolescents with mild forms of spastic cerebral palsy.

Following publication of the original article [1], the author requested for an acknowledgement to retrospectively be added to the 'Acknowledgements' section of the article [1].

Muscle and tendon morphology alterations in children and adolescents with mild forms of spastic cerebral palsy.

BACKGROUND: Early detection of changes at the muscular level before a contracture develops is important to gain knowledge about the development of deformities in individuals with spasticity. However, little information is available about muscle morphology in children with spastic diplegic cerebral palsy (CP) without contracture or equinus gait. Therefore, the aim of this study was to compare the gastrocnemius medialis (GM) and Achilles tendon architecture of children and adolescents with spastic CP without contracture or equinus gait to that of typically developing (TD) children. METHODS: Two-dimensional ultrasonography was used to assess the morphological properties of the GM muscle and Achilles tendon in 10 children with spastic diplegic CP (Gross Motor Function Classification System level I-II) and 12 TD children (mean age 12.0 (2.8) and 11.3 (2.5) years, respectively). The children with CP were not restricted in the performance of daily tasks, and therefore had a high functional capacity. Mean muscle and tendon parameters were statistically compared (independent t-tests or Mann-Whitney U-tests). RESULTS: When normalized to lower leg length, muscle-tendon unit length and GM muscle belly length were found to be significantly shorter (p < 0.05, effect size (ES) = 1.00 and 0.98, respectively) in the children with spastic CP. Furthermore, there was a tendency for increased Achilles tendon length when expressed as a percentage of muscle-tendon unit length (p = 0.08, ES = - 0.80) in the individuals with CP. This group also showed shorter muscle fascicles (3.4 cm vs. 4.4 cm, p < 0.01, ES = 1.12) and increased fascicle pennation angle (21.9° vs. 18.1°, p < 0.01, ES = - 1.36, respectively). However, muscle thickness and Achilles tendon cross-sectional area did not differ between groups. Resting ankle joint angle was significantly more plantar flexed (- 26.2° vs. - 20.8°, p < 0.05, ES = 1.06) in the children with CP. CONCLUSIONS: Morphological alterations of the plantar flexor muscle-tendon unit are also present in children and adolescents with mild forms of spastic CP. These alterations may contribute to functional deficits such as muscle weakness, and therefore have to be considered in the clinical decision-making process, as well as in the selection of therapeutic interventions.

Mechanical muscle and tendon properties of the plantar flexors are altered even in highly functional children with spastic cerebral palsy.

BACKGROUND: Recent ultrasound studies found increased passive muscle stiffness and no difference in tendon stiffness in highly impaired children and young adults with cerebral palsy. However, it is not known if muscle and tendon mechanical properties are already altered in highly functional children with cerebral palsy. Therefore, the purpose of this study was to compare the mechanical and material properties of the plantar flexors in highly functional children with cerebral palsy and typically developing children. METHODS: Besides strength measurements, ultrasonography was used to assess gastrocnemius medialis and Achilles tendon elongation and stiffness, Achilles tendon stress, strain, and Young's modulus in twelve children with cerebral palsy (GMFCS levels I and II) and twelve typically developing peers during passive dorsiflexion rotations as well as maximum voluntary contractions. FINDINGS: Despite no difference in ankle joint stiffness (P>0.05) between groups, passive but not active Achilles tendon stiffness was significantly decreased (-39%) and a tendency of increased passive muscle stiffness was observed even in highly functional children with cerebral palsy. However, material properties of the tendon were not altered. Maximum voluntary contraction showed reduced plantar flexor strength (-48%) in the cerebral palsy group. INTERPRETATION: Even in children with mild spastic cerebral palsy, muscle and tendon mechanical properties are altered. However, it appears that the Achilles tendon stiffness is different only when low forces act on the tendon during passive movements. Although maximum voluntary force is already decreased, forces acting on the Achilles tendon during activity appear to be sufficient to maintain typical material properties.

Does unilateral single-event multilevel surgery improve gait in children with spastic hemiplegia? A retrospective analysis of a long-term follow-up.

Single event multilevel surgery (SEMLS) has become a standard intervention for children with cerebral palsy (CP). SEMLS proved to improve the gait in bilateral spastic cerebral palsy and those improvements can be maintained in the long term. However there is no evidence on the long-term outcome of unilateral SEMLS in children with unilateral spastic cerebral palsy. The gait analyses and clinical data of 14 children (9 male/5 female, mean age 12.1) with unilateral CP (6 children Gross Motor Function Classification System Scale level I and 8 children level II) were retrospectively reviewed at four time-points: preoperatively, 1year, 3-5 years and approximately 10 years after unilateral SEMLS. The Gait Profile Score (GPS) of the affected leg was used as a main and the number of fine tuning procedures as well as complications rate (Clavien-Dindo classification) as secondary outcome measures. The gait improved postoperatively and the GPS of the affected leg significantly declined by 3.73° which is well above the minimal clinical important difference of 1.6°. No deterioration of GPS occurred throughout the follow-up period. Therefore the postoperative improvement was maintained long-term. However, additional fine-tuning procedures had to be performed during the follow-up in 5 children and three complications occurred (one level II and two level III). The results indicate that children with unilateral cerebral palsy benefit from unilateral SEMLS and maintain gait improvements long-term.