Pathophysiology of spastic paresis. II: Emergence of muscle overactivity

Spasticity in adults with cerebral palsy and multiple sclerosis measured by objective clinically applicable technique

OBJECTIVE

The present study evaluated ankle stiffness in adults with and without neurological disorders and investigated the accuracy and reproducibility of a clinically applicable method using a dynamometer.

METHODS

Measurements were obtained from 8 healthy subjects (age 39.3), 9 subjects with spastic cerebral palsy (CP) (age 39.8) and 8 subjects with multiple sclerosis (MS) (age 49.9). Slow and fast dorsiflexion stretches of the ankle joint were performed to evaluate passive muscle-tendon-joint stiffness, reflex mediated stiffness and range of movement (ROM), respectively. Intra/inter-rater reliability for passive and reflex mediated ankle muscle stiffness was assessed for all groups.

RESULTS

Subjects with CP and MS showed significantly larger values of passive stiffness in the triceps surae muscle tendon complex and smaller ROM compared to healthy individuals, while no significant difference in reflex mediated stiffness. Measurements of passive muscle-tendon-joint stiffness and reflex mediated stiffness showed good to excellent inter- and intra-rater reliability (ICC: 0.62-0.91) in all groups.

CONCLUSION

Increased stiffness was found in subjects with CP and MS with a clinically applicable method that provides valid and reproducible measurement of passive ankle muscle-tendon-joint stiffness and reflex mediated stiffness.

SIGNIFICANCE

The present technique may provide important supplementary information for the clinician.

Temporal Indices of Ankle Clonus and Relationship to Electrophysiologic and Clinical Measures in Persons With Spinal Cord Injury

BACKGROUND AND PURPOSE

Clonus arising from plantar flexor hyperreflexia is a phenomenon that is commonly observed in persons with spastic hypertonia. We assessed the temporal components of a biomechanical measure to quantify ankle clonus, and validated these in persons with spasticity due to spinal cord injury.

METHODS

In 40 individuals with chronic (>1 year) spinal cord injury, we elicited ankle clonus using a standardized mechanical perturbation (drop test). We examined reliability and construct validity of 2 components of the drop test: clonus duration (timed with a stopwatch) and number of oscillations in the first 10-second interval (measured via optical motion capture). We compared these measures to the Spinal Cord Assessment Tool for Spastic reflexes (SCATS) clonus score and H-reflex/M-wave (H/M) ratio, a clinical and electrophysiologic measure, respectively.

RESULTS

Intra- and interrater reliability of clonus duration measurement was good [intraclass correlation coefficient, ICC (2, 1) = 1.00]; test-retest reliability was good both at 1 hour [ICC (2, 2) = 0.99] and at 1 week [ICC (2, 2) = 0.99]. Clonus duration was moderately correlated with SCATS clonus score (r = 0.58). Number of oscillations had good within-session test-retest reliability [ICC (2, 1) > 0.90] and strong correlations with SCATS clonus score (r = 0.86) and soleus H/M ratio (r = 0.77).

DISCUSSION AND CONCLUSIONS

Clonus duration and number of oscillations as measured with a standardized test are reliable and valid measures of plantar flexor hyperreflexia that are accessible for clinical use. Tools for objective measurement of ankle clonus are valuable for assessing effectiveness of interventions directed at normalizing reflex activity associated with spasticity.Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A179).

Early Shortening of Wrist Flexor Muscles Coincides With Poor Recovery After Stroke

Background. The mechanism and time course of increased wrist joint stiffness poststroke and clinically observed wrist flexion deformity is still not well understood. The components contributing to increased joint stiffness are of neural reflexive and peripheral tissue origin and quantified by reflexive torque and muscle slack length and stiffness coefficient parameters. Objective. To investigate the time course of the components contributing to wrist joint stiffness during the first 26 weeks poststroke in a group of patients, stratified by prognosis and functional recovery of the upper extremity. Methods. A total of 36 stroke patients were measured on 8 occasions within the first 26 weeks poststroke using ramp-and-hold rotations applied to the wrist joint by a robot manipulator. Neural reflexive and peripheral tissue components were estimated using an electromyography-driven antagonistic wrist model. Outcome was compared between groups cross-sectionally at 26 weeks poststroke and development over time was analyzed longitudinally. Results. At 26 weeks poststroke, patients with poor recovery (Action Research Arm Test [ARAT] ≤9 points) showed a higher predicted reflexive torque of the flexors (P < .001) and reduced predicted slack length (P < .001) indicating shortened muscles contributing to higher peripheral tissue stiffness (P < .001), compared with patients with good recovery (ARAT ≥10 points). Significant differences in peripheral tissue stiffness between groups could be identified around weeks 4 and 5; for neural reflexive stiffness, this was the case around week 12. Conclusions. We found onset of peripheral tissue stiffness to precede neural reflexive stiffness. Temporal identification of components contributing to joint stiffness after stroke may prompt longitudinal interventional studies to further evaluate and eventually prevent these phenomena.

Electrodiagnostic and nerve ultrasonographic features in upper limb spasticity: an observational study

To better understand the effects of spasticity on peripheral nerves, we evaluated the electrodiagnostic and nerve ultrasonographic features of the median and ulnar nerves in adults with upper limb spasticity. Twenty chronic stroke patients with spastic hemiparesis underwent nerve conduction study and nerve ultrasonography of the median and ulnar nerves at both upper limbs. Affected versus unaffected upper limb comparisons showed significant differences in the median and ulnar nerve distal motor latencies, compound muscle action potentials and F-wave minimal latencies. Furthermore, we observed a significantly greater median nerve crosssectional area at the elbow of the affected upper limb compared with the unaffected one. Our findings confirmed electrodiagnostic asymmetries and nerve ultrasonographic abnormalities in the affected versus the unaffected upper limb after stroke. Slight changes in lower motor neuron activity and spasticity might contribute to these alterations.

Mild Intrauterine Hypoperfusion Leads to Lumbar and Cortical Hyperexcitability, Spasticity, and Muscle Dysfunctions in Rats: Implications for Prematurity

Intrauterine ischemia-hypoxia is detrimental to the developing brain and leads to white matter injury (WMI), encephalopathy of prematurity (EP), and often to cerebral palsy (CP), but the related pathophysiological mechanisms remain unclear. In prior studies, we used mild intrauterine hypoperfusion (MIUH) in rats to successfully reproduce the diversity of clinical signs of EP, and some CP symptoms. Briefly, MIUH led to inflammatory processes, diffuse gray and WMI, minor locomotor deficits, musculoskeletal pathologies, neuroanatomical and functional disorganization of the primary somatosensory and motor cortices, delayed sensorimotor reflexes, spontaneous hyperactivity, deficits in sensory information processing, memory and learning impairments. In the present study, we investigated the early and long-lasting mechanisms of pathophysiology that may be responsible for the various symptoms induced by MIUH. We found early hyperreflexia, spasticity and reduced expression of KCC2 (a chloride cotransporter that regulates chloride homeostasis and cell excitability). Adult MIUH rats exhibited changes in muscle contractile properties and phenotype, enduring hyperreflexia and spasticity, as well as hyperexcitability in the sensorimotor cortex. Taken together, these results show that reduced expression of KCC2, lumbar hyperreflexia, spasticity, altered properties of the soleus muscle, as well as cortical hyperexcitability may likely interplay into a self-perpetuating cycle, leading to the emergence, and persistence of neurodevelopmental disorders (NDD) in EP and CP, such as sensorimotor impairments, and probably hyperactivity, attention, and learning disorders.

Muscle Shortening and Spastic Cocontraction in Gastrocnemius Medialis and Peroneus Longus in Very Young Hemiparetic Children

Objectives

Muscle shortening and spastic cocontraction in ankle plantar flexors may alter gait since early childhood in cerebral palsy (CP). We evaluated gastrosoleus complex (GSC) length, and gastrocnemius medialis (GM) and peroneus longus (PL) activity during swing phase, in very young hemiparetic children with equinovalgus.

Methods

This was an observational, retrospective, and monocentric outpatient study in a pediatric hospital. Ten very young hemiparetic children (age 3 ± 1 yrs) were enrolled. These CP children were assessed for muscle extensibility (Tardieu scale X_V1) in GSC (angle of arrest during slow-speed passive ankle dorsiflexion with the knee extended) and monitored for GM and PL electromyography (EMG) during the swing phase of gait. The swing phase was divided into three periods (T1, T2, and T3), in which we measured a cocontraction index (CCI), ratio of the Root Mean Square EMG (RMS-EMG) from each muscle during that period to the peak 500 ms RMS-EMG obtained from voluntary plantar flexion during standing on tiptoes (from several 5-second series, the highest RMS value was computed over 500 ms around the peak).

Results

On the paretic side: (i) the mean X_V1-GSC was 100° (8°) (median (SD)) versus 106° (3°) on the nonparetic side (p = 0.032, Mann-Whitney); (ii) X_V1-GSC diminished with age between ages of 2 and 5 (Spearman, ρ = 0.019); (iii) CCI_GM and CCI_PL during swing phase were higher than on the nonparetic side (CCI_GM, 0.32 (0.20) versus 0.15 (0.09), p < 0.01; CCI_PL, 0.52 (0.30) versus 0.24 (0.17), p < 0.01), with an early difference significant for PL from T1 (p = 0.03).

Conclusions

In very young hemiparetic children, the paretic GSC may rapidly shorten in the first years of life. GM and PL cocontraction during swing phase are excessive, which contributes to dynamic equinovalgus. Muscle extensibility (X_V1) may have to be monitored and preserved in the first years of life in children with CP. Additional measurements of cocontraction may further help target treatments with botulinum toxin, especially in peroneus longus.

Evolution of upper limb kinematics four years after subacute robot-assisted rehabilitation in stroke patients

Purpose: To assess functional status and robot-based kinematic measures four years after subacute robot-assisted rehabilitation in hemiparesis. Materials and methods: Twenty-two patients with stroke-induced hemiparesis underwent a ≥3-month upper limb combined program of robot-assisted and occupational therapy from two months post-stroke, and received community-based therapy after discharge. Four years later, 19 (86%) participated in this follow-up study. Assessments 2, 5 and 54 months post-stroke included Fugl-Meyer (FM), Modified Frenchay Scale (MFS, at Month 54) and robot-based kinematic measures of targeting tasks in three directions, north, paretic and non-paretic: distance covered, velocity, accuracy (root mean square (RMS) error from straight line) and smoothness (number of velocity peaks; upward changes in accuracy and smoothness represent worsening). Analysis was stratified by FM score at two months: ≥17 (Group 1) or <17 (Group 2). Correlation between impairment (FM) and function (MFS) was explored at 54 months. Results: FM scores were stable from 5 to 54 months (+1[-2;4], median [1st; 3rd quartiles], ns). Kinematic changes (three directions pooled) were: distance -1[-17;2]% (ns); velocity, -8[-32;28]% (ns); accuracy, +6[-13;98]% (ns); smoothness, +44[-6;126]% (p < 0.05). Group 2 showed decline vs. Group 1 (p < 0.001) in FM (Group 1, +3[1;5], p < 0.01; Group 2, -7[-11;-1], ns) and accuracy (Group 1, -3[-27;38]%, ns; Group 2, +29[17;140]%, p < 0.001). At 54 months, FM and MFS were highly correlated (Pearson's rho = 0.89; p < 0.001). Conclusions: While impairment appeared stable four years after robot-assisted upper limb training during subacute post-stroke phase, movement kinematics deteriorated despite community-based therapy, especially in more severely impaired patients. Trial registration: EudraCT 2016-005121-36. Registration: 2016-12-20. Date of enrolment of the first participant to the trial: 2009-11-24.

Early movement restriction leads to enduring disorders in muscle and locomotion

Motor control and body representation in the central nervous system (CNS) as well as musculoskeletal architecture and physiology are shaped during development by sensorimotor experience and feedback, but the emergence of locomotor disorders during maturation and their persistence over time remain a matter of debate in the absence of brain damage. By using transient immobilization of the hind limbs, we investigated the enduring impact of postnatal sensorimotor restriction (SMR) on gait and posture on treadmill, age-related changes in locomotion, musculoskeletal histopathology and Hoffmann reflex in adult rats without brain damage. SMR degrades most gait parameters and induces overextended knees and ankles, leading to digitigrade locomotion that resembles equinus. Based on variations in gait parameters, SMR appears to alter age-dependent plasticity of treadmill locomotion. SMR also leads to small but significantly decreased tibial bone length, chondromalacia, degenerative changes in the knee joint, gastrocnemius myofiber atrophy and muscle hyperreflexia, suggestive of spasticity. We showed that reduced and atypical patterns of motor outputs, and somatosensory inputs and feedback to the immature CNS, even in the absence of perinatal brain damage, play a pivotal role in the emergence of movement disorders and musculoskeletal pathologies, and in their persistence over time. Understanding how atypical sensorimotor development likely contributes to these degradations may guide effective rehabilitation treatments in children with either acquired (ie, with brain damage) or developmental (ie, without brain injury) motor disabilities.

Mirror therapy and treadmill training for a patient with chronic stroke: A case report

INTRODUCTION

A large proportion of patients with chronic stroke have permanent lower limb functional disability leading to reduced levels of independent mobility. Individually, both mirror therapy and treadmill training have been shown to improve aspects of lower limb functioning in patients with stroke. This case report examined whether a new combination of both interventions would lead to improvements in lower limb functional disability for a patient with chronic stroke.

CASE DESCRIPTION

The participant was a 50-year-old female who had a left middle cerebral artery infarction (47 months' post stroke). Due to hemiparesis, she had lower limb motor impairment and gait deficits.

INTERVENTION

The participant engaged in a combination of mirror therapy and treadmill training for 30 minutes per day, 3 days per week, for 4 weeks.

OUTCOMES

Modified Ashworth Scale, Fugl-Meyer Assessment-Lower Extremity and the 10 m Walk Test demonstrated clinically meaningful change. The 6 Minute Walk Test did not demonstrate meaningful change.

DISCUSSION

The positive outcomes from this new combination therapy for this participant are encouraging given the relatively small dose of training and indicate the potential benefit of mirror therapy as an adjunct to treadmill training for enhancing lower limb muscle tone, motor function and walking velocity in patients with chronic stroke.

Physical therapy in patients with disorders of consciousness: Impact on spasticity and muscle contracture

BACKGROUND

Spasticity is a frequent complication after severe brain injury, which may prevent the rehabilitation process and worsen the patients' quality of life.

OBJECTIVES

In this study, we investigated the correlation between spasticity, muscle contracture, and the frequency of physical therapy (PT) in subacute and chronic patients with disorders of consciousness (DOC).

METHODS

109 patients with subacute and chronic disorders of consciousness (Vegetative state/Unresponsive wakefulness syndrome - VS/UWS; minimally conscious state - MCS and patients who emerged from MCS - EMCS) were included in the study (39 female; mean age: 40±13.5y; 60 with traumatic etiology; 35 VS/UWS, 68 MCS, 6 EMCS; time since insult: 38±42months). The number of PT sessions (i.e., 20 to 30 minutes of conventional stretching of the four limbs) was collected based on patients' medical record and varied between 0 to 6 times per week (low PT = 0-3 and high PT = 4-6 sessions per week). Spasticity was measured with the Modified Ashworth Scale (MAS) on every segment for both upper (UL) and lower limbs (LL). The presence of muscle contracture was assessed in every joint. We tested the relationship between spasticity and muscle contracture with the frequency of PT as well as other potential confounders such as time since injury or anti-spastic medication intake.

RESULTS

We identified a negative correlation between the frequency of PT and MAS scores as well as the presence of muscle contracture. We also identified that patients who received less than four sessions per week were more likely to be spastic and suffer from muscle contracture than patients receiving 4 sessions or more. When separating subacute (3 to 12 months post-insult) and chronic (>12months post-insult) patients, these negative correlations were only observed in chronic patients. A logit regression model showed that frequency of PT influenced spasticity, whereas neither time since insult nor medication had a significant impact on the presence of spasticity. On the other hand, PT, time since injury and medication seemed to be associated with the presence of muscle contracture.

CONCLUSION

Our results suggest that, in subacute and chronic patients with DOC, PT could have an impact on patients' spasticity and muscles contractures. Beside PT, other factors such as time since onset and medication seem to influence the development of muscle contractures. These findings support the need for frequent PT sessions and regular re-evaluation of the overall spastic treatment for patients with DOC.

Gait phenotypes in paediatric hereditary spastic paraplegia revealed by dynamic time warping analysis and random forests

The Hereditary Spastic Paraplegias (HSP) are a group of heterogeneous disorders with a wide spectrum of underlying neural pathology, and hence HSP patients express a variety of gait abnormalities. Classification of these phenotypes may help in monitoring disease progression and personalizing therapies. This is currently managed by measuring values of some kinematic and spatio-temporal parameters at certain moments during the gait cycle, either in the doctor´s surgery room or after very precise measurements produced by instrumental gait analysis (IGA). These methods, however, do not provide information about the whole structure of the gait cycle. Classification of the similarities among time series of IGA measured values of sagittal joint positions throughout the whole gait cycle can be achieved by hierarchical clustering analysis based on multivariate dynamic time warping (DTW). Random forests can estimate which are the most important isolated parameters to predict the classification revealed by DTW, since clinicians need to refer to them in their daily practice. We acquired time series of pelvic, hip, knee, ankle and forefoot sagittal angular positions from 26 HSP and 33 healthy children with an optokinetic IGA system. DTW revealed six gait patterns with different degrees of impairment of walking speed, cadence and gait cycle distribution and related with patient's age, sex, GMFCS stage, concurrence of polyneuropathy and abnormal visual evoked potentials or corpus callosum. The most important parameters to differentiate patterns were mean pelvic tilt and hip flexion at initial contact. Longer time of support, decreased values of hip extension and increased knee flexion at initial contact can differentiate the mildest, near to normal HSP gait phenotype and the normal healthy one. Increased values of knee flexion at initial contact and delayed peak of knee flexion are important factors to distinguish GMFCS stages I from II-III and concurrence of polyneuropathy.

Effect on Passive Range of Motion and Functional Correlates After a Long-Term Lower Limb Self-Stretch Program in Patients With Chronic Spastic Paresis

BACKGROUND

In current health care systems, long-duration stretching, performed daily, cannot be obtained through prescriptions of physical therapy. In addition, the short-term efficacy of the various stretching techniques is disputed, and their long-term effects remain undocumented.

OBJECTIVE

To evaluate changes in extensibility in 6 lower limb muscles and in ambulation speed after a ≥1-year self-stretch program, the Guided Self-rehabilitation Contract (GSC), in individuals with chronic spastic paresis.

DESIGN

Retrospective study.

SETTING

Neurorehabilitation clinic.

PARTICIPANTS

Patients diagnosed with hemiparesis or paraparesis at least 1 year before the initiation of a GSC and who were then involved in the GSC program for at least 1 year.

INTERVENTIONS

For each patient, specific muscles were identified for intervention among the following: gluteus maximus, hamstrings, vastus, rectus femoris, soleus, and gastrocnemius. Prescriptions and training for a daily, high-load, prolonged, home self-stretching program were primarily based on the baseline coefficient of shortening, defined as C_SH = [(X_N -X_V1)/X_N] (X_V1 = PROM, passive range of motion; X_N = normally expected amplitude).

MAIN OUTCOME MEASUREMENTS

Six assessments were performed per year, measuring the Tardieu X_V1 or maximal slow stretch range of motion angle (PROM), C_SH, 10-m ambulation speed, and its functional ambulation category (Perry's classification: household, limited, or full). Changes from baseline in self-stretched and nonself-stretched muscles were compared, with meaningful X_V1 change defined as ΔX_V1 >5° for plantar flexors and >10° for proximal muscles. Correlation between the composite X_V1 (mean PROM for the 6 muscles) and ambulation speed also was evaluated.

RESULTS

Twenty-seven GSC participants were identified (14 women, mean age 44 years, range 29-59): 18 with hemiparesis and 9 with paraparesis. After 1 year, 47% of self-stretched muscles showed meaningful change in PROM (ΔX_V1) versus 14% in nonself-stretched muscles (P < .0001, χ²). ΔC_SH was -31% (95% confidence interval [95% CI] -41.5 to -15.2) in self-stretched versus -7% (95% CI -11.9 to -2.1) in nonself-stretched muscles (P < .0001, t-test). Ambulation speed increased by 41% (P < .0001) from 0.81 m/s (95% CI 0.67-0.95) to 1.15 m/s (95% CI 1.01-1.29). Eight of the 12 patients (67%) who were in limited or household categories at baseline moved to a higher functional ambulation category. There was a trend for a correlation between composite X_V1 and ambulation speed (r = 0.44, P = .09) in hemiparetic patients.

CONCLUSION

Therapists should consider prescribing and monitoring a long-term lower limb self-stretch program using GSC, as this may increase muscle extensibility in adult-onset chronic paresis.

LEVEL OF EVIDENCE

III.

Characterizing Normal and Pathological Gait through Permutation Entropy

Cerebral palsy is a physical impairment stemming from a brain lesion at perinatal time, most of the time resulting in gait abnormalities: the first cause of severe disability in childhood. Gait study, and instrumental gait analysis in particular, has been receiving increasing attention in the last few years, for being the complex result of the interactions between different brain motor areas and thus a proxy in the understanding of the underlying neural dynamics. Yet, and in spite of its importance, little is still known about how the brain adapts to cerebral palsy and to its impaired gait and, consequently, about the best strategies for mitigating the disability. In this contribution, we present the hitherto first analysis of joint kinematics data using permutation entropy, comparing cerebral palsy children with a set of matched control subjects. We find a significant increase in the permutation entropy for the former group, thus indicating a more complex and erratic neural control of joints and a non-trivial relationship between the permutation entropy and the gait speed. We further show how this information theory measure can be used to train a data mining model able to forecast the child’s condition. We finally discuss the relevance of these results in clinical applications and specifically in the design of personalized medicine interventions.

The Relationship Between Medial Gastrocnemius Lengthening Properties and Stretch Reflexes in Cerebral Palsy

Stretch reflex hyperactivity in the gastrocnemius of children with spastic cerebral palsy (CP) is commonly evaluated by passively rotating the ankle joint into dorsiflexion at different velocities, such as applied in conventional clinical spasticity assessments. However, surface electromyography (sEMG) collected from the medial gastrocnemius (MG) during such examination reveals unexplained heterogeneity in muscle activation between patients. Recent literature also highlights altered muscle tensile behavior in children with spastic CP. We aimed to document MG muscle and tendon lengthening during passive ankle motion at slow and fast velocity and explore its interdependence with the elicited hyperactive stretch reflex. The ankle of 15 children with CP (11 ± 3 years, GMFCS 9I 6II, 8 bilateral, 7 unilateral) and 16 typically developing children (TDC) was passively rotated over its full range of motion at slow and fast velocity. Ultrasound, synchronized with motion-analysis, was used to track the movement of the MG muscle-tendon junction and extract the relative lengthening of muscle and tendon during joint rotation. Simultaneously, MG sEMG was measured. Outcome parameters included the angular and muscle lengthening velocities 30 ms before EMG onset and the gain in root mean square EMG during stretch, as a measure of stretch reflex activity. Compared to slow rotation, the muscle lengthened less and stretch reflex activity was higher during fast rotation. These velocity-induced changes were more marked in CP compared to TDC. In the CP group, muscle-lengthening velocity had higher correlation coefficients with stretch reflex hyperactivity than joint angular velocity. Muscles with greater relative muscle lengthening during slow rotation had earlier and stronger stretch reflexes during fast rotation. These initial results suggest that ankle angular velocity is not representative of MG muscle lengthening velocity and is less related to stretch reflex hyperactivity than MG muscle lengthening. In addition, muscles that lengthened more during slow joint rotation were more likely to show a velocity-dependent stretch reflex. This interdependence of muscle lengthening and stretch reflexes may be important to consider when administering treatment. However, muscle and tendon lengthening properties alone could not fully explain the variability in stretch reflexes, indicating that other factors should also be investigated.

Ultrasonographic Evaluation of Botulinum Toxin Injection Site for the Medial Approach to Tibialis Posterior Muscle in Chronic Stroke Patients with Spastic Equinovarus Foot: An Observational Study

The tibialis posterior muscle is a frequent target for injection of botulinum toxin during the management of spastic equinovarus foot in adults with post-stroke spasticity. Although it is deep-seated, the needle insertion into the tibialis posterior muscle is usually performed using anatomical landmarks and safety information obtained from healthy subjects and cadavers. Our aim was to evaluate the botulinum toxin injection site for the medial approach to the tibialis posterior muscle in chronic stroke patients with spastic equinovarus foot. Forty-six patients were evaluated at the affected middle lower leg medial surface with ultrasonography according to the following parameters: tibialis posterior muscle depth, thickness, and echo intensity. As to the spastic tibialis posterior, we found a mean muscle depth of 26.5 mm and a mean muscle thickness of 10.1 mm. Furthermore we observed a median tibialis posterior muscle echo intensity of 3.00 on the Heckmatt scale. The tibialis posterior muscle thickness was found to be inversely associated with its depth (p < 0.001) and echo intensity (p = 0.006). Furthermore, tibialis posterior muscle depth was found to be directly associated with its echo intensity (p = 0.004). Our findings may usefully inform manual needle placement into the tibialis posterior for the botulinum toxin treatment of spastic equinovarus foot in chronic stroke patients.

On Denny-Brown's 'spastic dystonia' - What is it and what causes it?

In this review, we will work around two simple definitions of two different entities, which most often co-exist in patients with lesions to central motor pathways: Spasticity is "Enhanced excitability of velocity-dependent responses to phasic stretch at rest", which will not be the subject of this review, while Spastic dystonia is tonic, chronic, involuntary muscle contraction in the absence of any stretch or any voluntary command (Gracies, 2005). Spastic dystonia is a much less well understood entity that will be the subject this review. Denny-Brown (1966) observed involuntary sustained muscle activity in monkeys with lesions restricted to the motor cortices . He further observed that such involuntary muscle activity persisted following abolition of sensory input to the spinal cord and concluded that a central mechanism rather than exaggerated stretch reflex activity had to be involved. He coined the term spastic dystonia to describe this involuntary tonic activity in the context of otherwise exaggerated stretch reflexes. Sustained involuntary muscle activity in the absence of any stretch or any voluntary command contributes to burdensome and disabling body deformities in patients with spastic paresis. Yet, little has been done since Denny-Brown's studies to determine the pathophysiology of this non- stretch or effort related sustained involuntary muscle activity following motor lesions and there is a clear need for research studies in order to improve current therapy. The purpose of the present review is to discuss some of the possible mechanisms that may be involved in the hope that this may guide future research. We discuss the existence of persistent inward currents in spinal motoneurones and present the evidence that the channels involved may be upregulated following central motor lesions. We also discuss a possible contribution from alterations in synaptic inputs from surviving or abnormally branched sensory and descending fibres leading to over-activity and lack of motor coordination. We finally discuss evidence of alterations in motor cortical representational maps and basal ganglia lesions.

Break-out session highlights

A popular feature of the Multiple Sclerosis Experts Summit is interactive break-out sessions to discuss various aspects of multiple sclerosis (MS), including MS spasticity and general management of MS patients. The format encourages participation and active discussion, thus providing attendees with the opportunity to exchange their experiences of the day-to-day management of MS in clinical practice. Following feedback provided by each session leader, key messages are summarized and presented in a plenary session by the Summit chair. Topics covered in this year's country break-out sessions included: triggering factors for MS; decision-making in MS and the importance of patients’ risk perception; assessment and management of MS spasticity.

Botulinum Toxin Treatment in Multiple Sclerosis-a Review

Purpose of review The purpose of this review is to provide updated information on the role of botulinum neurotoxin (BoNT) therapy in multiple sclerosis (MS). This review aims to answer which symptoms of multiple sclerosis may be amenable to BoNT therapy. Recent findings We searched the literature on the efficacy of BoNTs for treatment of MS symptoms up to April 1st 2017 via the Yale University Library's search engine including but not limited to Pub Med and Ovis SP. The level of efficacy was defined according to the assessment's criteria set forth by the Subcommittee on Guideline Development of the American Academy of Neurology. Significant efficacy was found for two indications based on the available blinded studies (class I and II) and has been suggested for several others through open-label clinical trials. Summary There is level A evidence (effective- two or more class I) that injection of BoNT-A into the bladder's detrusor muscle improves MS-related neurogenic detrusor overactivity (NDO) and MS-related overactive (OA) bladder. There is level B evidence (probably effective- two class II studies) for utility of intramuscular BoNT-A injections for spasticity of multiple sclerosis. Emerging data based on retrospective class IV studies demonstrates that intramuscular injection of BoNTs may help other symptoms of MS such as focal tonic spasms, focal myokymia, spastic dysphagia, and double vision in internuclear ophthalmoplegia. There is no data on MS-related trigeminal neuralgia and sialorrhea, two conditions which have been shown to respond to BoNT therapy in non-MS population.

Effects of repeated abobotulinumtoxinA injections in upper limb spasticity

Introduction: The efficacy of single injections of abobotulinumtoxinA (Dysport) is established in adults with upper limb spasticity. In this study we assessed the effects of repeated injections of abobotulinumtoxinA over 1 year. Methods: Patients (n = 258, safety population) received 500 U, 1,000 U, or 1,500 U (1,500‐U dose included 500‐U shoulder injections) for up to 4 or 5 treatment cycles. Assessments included treatment‐emergent adverse events (TEAEs), muscle tone, passive and active range of motion (X_V1, X_A), angle of catch (X_V3), Disability Assessment Scale (DAS) score, Modified Frenchay Scale (MFS) score, and Physician Global Assessment (PGA) score. Results: The incidence of TEAEs decreased across cycles. Muscle tone reduction and X_V1 remained stable across cycles, whereas X_V3 and X_A continued to improve at the finger, wrist, and elbow flexors. DAS and PGA improved across cycles. MFS improved best with 1,500 U. Discussion: A favorable safety profile and continuous improvements in active movements and perceived and active function were associated with repeated abobotulinumtoxinA injections in upper limb muscles. Muscle Nerve57: 245–254, 2018

How plastic are human spinal cord motor circuitries?

Human and animal studies have documented that neural circuitries in the spinal cord show adaptive changes caused by altered supraspinal and/or afferent input to the spinal circuitry in relation to learning, immobilization, injury and neurorehabilitation. Reversible adaptations following, e.g. the acquisition or refinement of a motor skill rely heavily on the functional integration between supraspinal and sensory inputs to the spinal cord networks. Accordingly, what is frequently conceived as a change in the spinal circuitry may be a change in either descending or afferent input or in the relative integration of these, i.e. a change in the neuronal weighting. This is evident from findings documenting only task-specific functional changes after periods of altered inputs whereas resting responses remain unaffected. In fact, the proximity of the spinal circuitry to the outer world may demand a more rigid organization compared to the highly flexible cortical circuits. The understanding of all of this is important for the planning and execution of neurorehabilitation.

Is spasticity always the same? An observational study comparing the features of spastic equinus foot in patients with chronic stroke and multiple sclerosis

Spasticity is common in stroke and multiple sclerosis. To treat spasticity we have a wide range of interventions, whose application may depend not only on the severity of spasticity but also on its etiology. Consequently, a better understanding of muscle spasticity in different neurological diseases may inform clinicians as to the more appropriate therapeutic approach. Our aim was to compare the clinical and ultrasonographic features of spastic equinus in patients with chronic stroke and multiple sclerosis. Thirty-eight patients with secondary progressive multiple sclerosis and 38 chronic stroke patients with spastic equinus were evaluated at the affected ankle according to the following outcomes: modified Ashworth scale, Tardieu scale, passive range of motion, spastic gastrocnemius muscle echo intensity and thickness. Affected calf muscles tone was significantly greater in patients with chronic stroke (modified Ashworth scale P=0.008; Tardieu scale angle P=0.004) as well as spastic gastrocnemius muscle echo intensity (P<0.001). Affected ankle range of motion was significantly greater in patients with multiple sclerosis (P<0.001) as well as spastic gastrocnemius muscle thickness (medialis: P=0.003; lateralis: P=0.004). Our findings evidenced that the same pattern of spasticity (equinus foot) has some different features according to its etiology. This may help the management of spasticity.

Altered viscoelastic properties of stroke-affected muscles estimated using ultrasound shear waves - Preliminary data

As a result of a brain injury such as stroke, the skeletal muscles may undergo numerous structural and functional alterations. These abnormal changes are linked to muscle weakness, joint contracture, and abnormal muscle tone and eventually, result in motor impairment. A subset of these alterations affects passive muscle stiffness, i.e., viscoelastic properties. However, in vivo estimation of changes in viscoelastic properties is a challenging task. Here, we used the shear wave velocity, estimated through ultrasound SuperSonic imaging (SSI), as a surrogate for viscoelastic properties. We estimated shear wave group and phase velocities (dispersion), and thus, quantified both elasticity and viscosity of the muscle tissue, respectively in muscles of hemiplegic stroke survivors. In these individuals, we found significantly higher group and phase velocities in the stroke-affected muscles (p<; 05) compared to those of the contralateral non-affected side. We hypothesize that in addition to changes in neural and contractile properties, there are also, changes in elastic and tissue dispersive properties through local mechanisms. An enhanced understanding of post-stroke changes in skeletal muscles will lead to better and targeted interventions for rehabilitation.

Change in Coefficient of Fatigability Following Rapid, Repetitive Movement Training in Post-Stroke Spastic Paresis: A Prospective Open-Label Observational Study

BACKGROUND

In post-stroke patients, the possibility of performing an active ankle dorsiflexion movement is favorable for the recovery of gait. Moreover, the fatigue due to repetitive active ankle dorsiflexion could reduce the speed gait. We assessed the change in coefficient of fatigability of active ankle dorsiflexion after a home-based self-rehabilitative procedure in post-stroke patients.

METHODS

In a prospective open-label observational study conducted in 2 university hospitals, a home-based self-rehabilitation treatment comprising two 12-minute sessions per day (3 times per week for 3 months) was performed by 10 outpatients with post-stroke lower limb impairment. Each session consisted of three 1-minute series of repeated active ankle dorsiflexion efforts at maximal speed on the paretic side, each one followed by 3-minute bouts of triceps surae stretch. Coefficients of fatigability of dorsiflexion and 10-meter barefoot ambulation speed were evaluated at baseline and at the end of the program.

RESULTS

At 3 months of follow-up, there was a decrease in the coefficients of fatigability of ankle dorsiflexion, both with knee flexed and extended (respectively from 8% to 2% and from 6% to 2%; P < .01), associated with an increase in comfortable ambulation speed (from .24 to .26 m/s; P < .05).

CONCLUSIONS

The reduction of coefficient of fatigability of ankle dorsiflexion, together with walking speed improvement, suggested the effectiveness of self-rehabilitation using alternated periods of self-stretch and rapid alternating efforts in the paretic lower limb after stroke.

Dose-Dependent Effects of AbobotulinumtoxinA (Dysport) on Spasticity and Active Movements in Adults With Upper Limb Spasticity: Secondary Analysis of a Phase 3 Study

BACKGROUND

AbobotulinumtoxinA has beneficial effects on spasticity and active movements in hemiparetic adults with upper limb spasticity (ULS). However, evidence-based information on optimal dosing for clinical use is limited.

OBJECTIVE

To describe joint-specific dose effects of abobotulinumtoxinA in adults with ULS.

DESIGN

Secondary analysis of a phase 3 study (NCT01313299).

SETTING

Multicenter, international, double-blind, placebo-controlled clinical trial.

PARTICIPANTS

A total of 243 adults with ULS >6 months after stroke or traumatic brain injury, aged 52.8 (13.5) years and 64.3% male, randomized 1:1:1 to receive a single-injection cycle of placebo or abobotulinumtoxinA 500 U or 1000 U (total dose).

METHODS

The overall effects of injected doses were assessed in the primary analysis, which showed improvement of angles of catch in finger, wrist, and elbow flexors and of active range of motion against these muscle groups. This secondary analysis was performed at each of the possible doses received by finger, wrist, and elbow flexors to establish possible dose effects.

MAIN OUTCOME MEASURES

Angle of arrest (X_V1) and angle of catch (X_V3) were assessed with the Tardieu Scale, and active range of motion (X_A).

RESULTS

At each muscle group level (finger, wrist, and elbow flexors) improvements in all outcome measures assessed (X_V1, X_V3, X_A) were observed. In each muscle group, increases in abobotulinumtoxinA dose were associated with greater improvements in X_V3 and X_A, suggesting a dose-dependent effect.

CONCLUSIONS

Previous clinical trials have established the clinical efficacy of abobotulinumtoxinA by total dose only. The wide range of abobotulinumtoxinA doses per muscle groups used in this study allowed observation of dose-dependent improvements in spasticity and active movement. This information provides a basis for future abobotulinumtoxinA dosing recommendations for health care professionals based on treatment objectives and quantitative assessment of spasticity and active range of motion at individual joints.

LEVEL OF EVIDENCE

I.

Real-Time Control of an Exoskeleton Hand Robot with Myoelectric Pattern Recognition

Robot-assisted training provides an effective approach to neurological injury rehabilitation. To meet the challenge of hand rehabilitation after neurological injuries, this study presents an advanced myoelectric pattern recognition scheme for real-time intention-driven control of a hand exoskeleton. The developed scheme detects and recognizes user’s intention of six different hand motions using four channels of surface electromyography (EMG) signals acquired from the forearm and hand muscles, and then drives the exoskeleton to assist the user accomplish the intended motion. The system was tested with eight neurologically intact subjects and two individuals with spinal cord injury (SCI). The overall control accuracy was [Formula: see text] for the neurologically intact subjects and [Formula: see text] for the SCI subjects. The total lag of the system was approximately 250[Formula: see text]ms including data acquisition, transmission and processing. One SCI subject also participated in training sessions in his second and third visits. Both the control accuracy and efficiency tended to improve. These results show great potential for applying the advanced myoelectric pattern recognition control of the wearable robotic hand system toward improving hand function after neurological injuries.

Different Effects of Cold Stimulation on Reflex and Non-Reflex Components of Poststroke Spastic Hypertonia

OBJECTIVE

To use an established biomechanical approach to quantify reflex and non-reflex responses from spastic-paretic elbow flexors in response to controlled cold and heat stimulation.

METHODS

Thirteen spastic-hemiplegic stroke subjects were tested in the experiment. The spastic elbow joint was stretched into extension for 50° at two speeds (5°/s and 100°/s) in a customized apparatus. Thermal stimulation (HEAT at heat pain threshold, COLD at 0°C, or BASELINE at room temperature) was applied to the thenar eminence of the contralateral hand immediately prior to stretching for at least 30 s.

RESULTS

Total torque was greater at 100°/s than at 5°/s. Total torque was significantly increased after COLD, but not HEAT as compared to BASELINE. When normalized to total torque at baseline, HEAT decreased total torque by 6.3%, while COLD increased total torque by 11.0%. There was no significant difference in the reflex torque among three thermal conditions.

CONCLUSION

The findings demonstrate differentiated effects of cold stimulation on the total resistance from spastic muscles. They provide objective evidence for anecdotal clinical observations of increased muscle spasticity by cold exposure.

Spasticity, Motor Recovery, and Neural Plasticity after Stroke

Spasticity and weakness (spastic paresis) are the primary motor impairments after stroke and impose significant challenges for treatment and patient care. Spasticity emerges and disappears in the course of complete motor recovery. Spasticity and motor recovery are both related to neural plasticity after stroke. However, the relation between the two remains poorly understood among clinicians and researchers. Recovery of strength and motor function is mainly attributed to cortical plastic reorganization in the early recovery phase, while reticulospinal (RS) hyperexcitability as a result of maladaptive plasticity, is the most plausible mechanism for poststroke spasticity. It is important to differentiate and understand that motor recovery and spasticity have different underlying mechanisms. Facilitation and modulation of neural plasticity through rehabilitative strategies, such as early interventions with repetitive goal-oriented intensive therapy, appropriate non-invasive brain stimulation, and pharmacological agents, are the keys to promote motor recovery. Individualized rehabilitation protocols could be developed to utilize or avoid the maladaptive plasticity, such as RS hyperexcitability, in the course of motor recovery. Aggressive and appropriate spasticity management with botulinum toxin therapy is an example of how to create a transient plastic state of the neuromotor system that allows motor re-learning and recovery in chronic stages.

Spinal Cord Stimulation for Spasticity: Historical Approaches, Current Status, and Future Directions

INTRODUCTION

Millions of people worldwide suffer with spasticity related to irreversible damage to the brain or spinal cord. Typical antecedent events include stroke, traumatic brain injury, and spinal cord injury, although insidious onset is also common. Regardless of the cause, the resulting spasticity leads to years of disability and reduced quality of life. Many treatments are available to manage spasticity; yet each is fraught with drawbacks including incomplete response, high cost, limited duration, dose-limiting side effects, and periodic maintenance. Spinal cord stimulation (SCS), a once promising therapy for spasticity, has largely been relegated to permanent experimental status.

METHODS

In this review, our goal is to document and critique the history and assess the development of SCS as a treatment of lower limb spasticity. By incorporating recent discoveries with the insights gained from the early pioneers in this field, we intend to lay the groundwork needed to propose testable hypotheses for future studies.

RESULTS

SCS has been tested in over 25 different conditions since a potentially beneficial effect was first reported in 1973. However, the lack of a fully formed understanding of the pathophysiology of spasticity, archaic study methodology, and the early technological limitations of implantable hardware limit the validity of many studies. SCS offers a measure of control for spasticity that cannot be duplicated with other interventions.

CONCLUSIONS

With improved energy-source miniaturization, tailored control algorithms, novel implant design, and a clearer picture of the pathophysiology of spasticity, we are poised to reintroduce and test SCS in this population.

Spatial Analysis of Multichannel Surface EMG in Hemiplegic Stroke

We investigated spatial activation patterns of upper extremity muscles during isometric force generation in both intact persons and in hemispheric stroke survivors. We used a 128-channel surface electromyogram (EMG) grid to record the electrical activity of biceps brachii muscles during these contractions. EMG data were processed to develop 2-D root mean square (RMS) maps of muscle activity. Our objective was to determine whether motor impairments following stroke were associated with changes in the muscle activity maps and in the spatial distribution of muscular activation. We found that, for a given subject, spatial patterns in muscle activity maps were consistent across all measured contraction levels differing only the RMS EMG. However, the maps from opposite arms (stroke-affected versus non-affected) of stroke survivors were significantly different from each other, especially when compared with the differences observed intact participants. Our analyses revealed that chronic stroke altered the size and location of the active region in these maps. The former is potentially related to disruption of fiber and tissue structure, possibly linked to factors such as extracellular fat accumulation, connective tissue infiltration, muscle fiber atrophy, fiber shortening, and fiber loss. Changes in spatial patterns in muscle activity maps may also be linked to a shift in the location of the innervation zone or the endplate region of muscles. Furthermore, the textural analysis of EMG activity maps showed a larger pixel-to-pixel variability in stroke-affected muscles. Alterations in the muscle activity maps were also related to functional impairment (estimated using Fugl-Meyer score) and to the degree of spasticity (estimated using the modified Ashworth scale). Overall, our investigation revealed that the muscle architecture and morphology were significantly altered in the chronic stroke.

New perspectives on the development of muscle contractures following central motor lesions

Muscle contractures are common in patients with central motor lesions, but the mechanisms responsible for the development of contractures are still unclear. Increased or decreased neural activation, protracted placement of a joint with the muscle in a short position and muscle atrophy have been suggested to be involved, but none of these mechanisms are sufficient to explain the development of muscle contractures alone. Here we propose that changes in tissue homeostasis in the neuromuscular-tendon-connective tissue complex is at the heart of the development of contractures, and that an integrated physiological understanding of the interaction between neural, mechanical and metabolic factors, as well as genetic and epigenetic factors, is necessary in order to unravel the mechanisms that result in muscle contractures. We hope thereby to contribute to a reconsideration of how and why muscle contractures develop in a way which will open a window towards new insight in this area in the future.

[The efficacy of botulinum toxin therapy in patients with upper limb spasticity due to traumatic brain injury]

Spasticity is a type of muscle hyperactivity that occurs in patients after focal lesions of the Central nervous system due to various diseases: stroke, traumatic brain injury or spinal cord injury, neurosurgical intervention, as well as multiple sclerosis and other diseases of the Central nervous system and is the most disability manifestation of the syndrome of upper motor neuron (UMNS). Focal spasticity of the upper limb requires a complex treatment. Botulinum toxin therapy is an effective treatment for focal/multifocal spasticity in reducing muscle tone and improving function with the highest level of evidence according to the latest American and European guidelines for treatment of spasticity. There are many publications devoted to BTA use in post-stroke patients. This article provides a review of the BTA use in patients with the upper limb spasticity due to severe traumatic brain injury. Some local data on the BTA efficacy in the cohort of patients with traumatic brain injury are also presented.

Botulinum toxin injection causes hyper-reflexia and increased muscle stiffness of the triceps surae muscle in the rat

Botulinum toxin is used with the intention of diminishing spasticity and reducing the risk of development of contractures. Here, we investigated changes in muscle stiffness caused by reflex activity or elastic muscle properties following botulinum toxin injection in the triceps surae muscle in rats. Forty-four rats received injection of botulinum toxin in the left triceps surae muscle. Control measurements were performed on the noninjected contralateral side in all rats. Acute experiments were performed, 1, 2, 4, and 8 wk following injection. The triceps surae muscle was dissected free, and the Achilles tendon was cut and attached to a muscle puller. The resistance of the muscle to stretches of different amplitudes and velocities was systematically investigated. Reflex-mediated torque was normalized to the maximal muscle force evoked by supramaximal stimulation of the tibial nerve. Botulinum toxin injection caused severe atrophy of the triceps surae muscle at all time points. The force generated by stretch reflex activity was also strongly diminished but not to the same extent as the maximal muscle force at 2 and 4 wk, signifying a relative reflex hyperexcitability. Passive muscle stiffness was unaltered at 1 wk but increased at 2, 4, and 8 wk (P < 0.01). These data demonstrate that botulinum toxin causes a relative increase in reflex stiffness, which is likely caused by compensatory neuroplastic changes. The stiffness of elastic elements in the muscles also increased. The data are not consistent with the ideas that botulinum toxin is an efficient antispastic medication or that it may prevent development of contractures.

Wireless, accelerometry-triggered functional electrical stimulation of the peroneal nerve in spastic paresis: A randomized, controlled pilot study

In hemiparesis, Wireless, Accelerometry-Triggered Functional Electrical Stimulation (WAFES) of the common peroneal nerve may hold intrinsic rehabilitative properties. The present pilot study analyzes WAFES against conventional therapy. Twenty adults with chronic hemiparesis (time since lesion 7(6) years; median (interquartile range)) were randomized into 2 10-week rehabilitation programs: a 45-minute (min) daily walk using WAFES (n = 10) and conventional physical therapy (CPT), 3 × 45 min per week (n = 10). The outcomes were 3D sagittal speed measurements, step length, cadence, maximal amplitude and velocity of hip, knee, and ankle during gait at free and fast speed without WAFES and clinical assessments of plantar flexor angles of shortening, spasticity, and weakness, before (D1) and after the program (W10). Kinematic and spasticity improvements occurred in the WAFES group only: (i) ankle dorsiflexion velocity (D1 versus W10, free speed, WAFES, +4(5)°/sec, p = 0.002; CPT, -3(8)°/sec, p = 0.007; fast, WAFES, +8(6)°/sec, p = 0.03; CPT, -1(4)°/sec, NS); (ii) maximal passive ankle dorsiflexion (WAFES,+26(85)%; CPT,+0(27)%; group-visit, p = 0.007) and knee flexion (WAFES, +13(17)%; CPT, -1(11)%; group-visit, p = 0.006) at fast speed only; (iii) 15% plantar flexor spasticity grade reduction with WAFES. Over 10 weeks, gait training using WAFES improved ankle and knee kinematics and reduced plantar flexor spasticity compared with CPT. Studies with longer WAFES use should explore functional effects.

Neuro-musculoskeletal simulation of instrumented contracture and spasticity assessment in children with cerebral palsy

Background

Increased resistance in muscles and joints is an important phenomenon in patients with cerebral palsy (CP), and is caused by a combination of neural (e.g. spasticity) and non-neural (e.g. contracture) components. The aim of this study was to simulate instrumented, clinical assessment of the hamstring muscles in CP using a conceptual model of contracture and spasticity, and to determine to what extent contracture can be explained by altered passive muscle stiffness, and spasticity by (purely) velocity-dependent stretch reflex.

Methods

Instrumented hamstrings spasticity assessment was performed on 11 children with CP and 9 typically developing children. In this test, the knee was passively stretched at slow and fast speed, and knee angle, applied forces and EMG were measured. A dedicated OpenSim model was created with motion and muscles around the knee only. Contracture was modeled by optimizing the passive muscle stiffness parameters of vasti and hamstrings, based on slow stretch data. Spasticity was modeled using a velocity-dependent feedback controller, with threshold values derived from experimental data and gain values optimized for individual subjects. Forward dynamic simulations were performed to predict muscle behavior during slow and fast passive stretches.

Results

Both slow and fast stretch data could be successfully simulated by including subject-specific levels of contracture and, for CP fast stretches, spasticity. The RMS errors of predicted knee motion in CP were 1.1 ± 0.9° for slow and 5.9 ± 2.1° for fast stretches. CP hamstrings were found to be stiffer compared with TD, and both hamstrings and vasti were more compliant than the original generic model, except for the CP hamstrings. The purely velocity-dependent spasticity model could predict response during fast passive stretch in terms of predicted knee angle, muscle activity, and fiber length and velocity. Only sustained muscle activity, independent of velocity, was not predicted by our model.

Conclusion

The presented individually tunable, conceptual model for contracture and spasticity could explain most of the hamstring muscle behavior during slow and fast passive stretch. Future research should attempt to apply the model to study the effects of spasticity and contracture during dynamic tasks such as gait.

Electronic supplementary material

The online version of this article (doi:10.1186/s12984-016-0170-5) contains supplementary material, which is available to authorized users.

Identifying the brain regions associated with acute spasticity in patients diagnosed with an ischemic stroke

Spasticity is a common impairment found in patients that have been diagnosed with a stroke. Little is known about the pathophysiology of spasticity at the level of the brain. This retrospective study was performed to identify an association between the area of the brain affected by an ischemic stroke and the presence of acute spasticity. Physical and occupational therapy assessments from all patients (n = 441) that had suffered a stroke and were admitted into a local hospital over a 4-year period were screened for inclusion in this study. Subjects that fit the inclusion criteria were grouped according to the presence (n = 42) or absence (n = 129) of acute spasticity by the Modified Ashworth Scale score given during the hospital admission assessment. Magnetic resonance images from 20 subjects in the spasticity group and 52 from the control group were then compared using lesion density plots and voxel-based lesion-symptom mapping. An association of acute spasticity with the gray matter regions of the insula, basal ganglia, and thalamus was found in this study. White matter tracts including the pontine crossing tract, corticospinal tract, internal capsule, corona radiata, external capsule, and the superior fronto-occipital fasciculus were also found to be significantly associated with acute spasticity. This is the first study to describe an association between a region of the brain affected by an infarct and the presence of acute spasticity. Understanding the regions associated with acute spasticity will aid in understanding the pathophysiology of this musculoskeletal impairment at the level of the brain.

Instrumental indices for upper limb function assessment in stroke patients: a validation study

Background

Robotic exoskeletons are increasingly being used in objective and quantitative assessment of upper limb (UL) movements. A set of instrumental indices computed during robot-assisted reaching tasks with the Armeo®Spring has been proven to assess UL functionality. The aim of this study was to test the construct validity of this indices-based UL assessment when used with patients who have had a stroke.

Methods

Forty-four 45- to 79-year-old stroke patients with a Wolf Motor Function Test ability score (WMFT-FAS) ranging from 10 to 75 and a Motricity Index (MI) ranging from 14 to 33 at shoulder and elbow were enrolled, thus covering a wide range of impairments. Residual UL function was assessed by both the WMFT-FAS and the WMFT-TIME, as well as by a set of 9 numerical indices assessing movement accuracy, velocity and smoothness computed from a 3D endpoint trajectory obtained during the “Vertical Capture” task of the Armeo®Spring device. To explore which variables better represented motor control deficits, the Mann-Whitney U Test was used to compare patients’ indices to those obtained from 25 healthy individuals. To explore the inner relationships between indices and construct validity in assessing accuracy, velocity and smoothness, a factor analysis was carried out. To verify the indices concurrent validity, they were compared to both WMFT-FAS and WMFT-TIME by the Spearman’s correlation coefficient.

Results

Seven indices of stroke subjects were significantly different from those of healthy controls, with effect sizes in the range 0.35–0.74. Factor analysis confirmed that specific subsets of indices belonged to the domains of accuracy, velocity and smoothness (discriminant validity). One accuracy index, both velocity indices and two smoothness indices were significantly correlated with WMFT-FAS and WMFT-TIME (|rho| = 0.31–0.50) (concurrent validity). One index for each of the assessed movement domains was proven to have construct validity (discriminant and concurrent) and was selected. Moreover, the indices were able to detect differences in accuracy, velocity and/or smoothness in patients with the same WMFT level.

Conclusions

The proposed index-based UL assessment can be used to integrate and support clinical evaluation of UL function in stroke patients.

Awake behaving electrophysiological correlates of forelimb hyperreflexia, weakness and disrupted muscular synchronization following cervical spinal cord injury in the rat

Spinal cord injury usually occurs at the level of the cervical spine and results in profound impairment of forelimb function. In this study, we recorded awake behaving intramuscular electromyography (EMG) from the biceps and triceps muscles of the impaired forelimb during volitional and reflexive forelimb movements before and after unilateral cervical spinal cord injury (cSCI) in rats. C5/C6 hemicontusion reduced volitional forelimb strength by more than 50% despite weekly rehabilitation for one month post-injury. Triceps EMG during volitional strength assessment was reduced by more than 60% following injury, indicating reduced descending drive. Biceps EMG during reflexive withdrawal from a thermal stimulus was increased by 500% following injury, indicating flexor withdrawal hyperreflexia. The reduction in volitional forelimb strength was significantly correlated with volitional and reflexive biceps EMG activity. Our results support the hypothesis that biceps hyperreflexia and descending volitional drive both significantly contribute to forelimb strength deficits after cSCI and provide new insight into dynamic muscular dysfunction after cSCI. The use of multiple automated quantitative measures of forelimb dysfunction in the rodent cSCI model will likely aid the search for effective regenerative, pharmacological, and neuroprosthetic treatments for spinal cord injury.

Simulation of effects of botulinum toxin on muscular mechanics in time course of treatment based on adverse extracellular matrix adaptations

BTX effects on muscular mechanics are highly important, but their mechanism and variability in due treatment course is not well understood. Recent modeling shows that partial muscle paralysis per se causes restricted sarcomere shortening due to muscle fiber-extracellular matrix (ECM) mechanical interactions. This leads to two notable acute-BTX effects compared to pre-BTX treatment condition: (1) enhanced potential of active force production of the non-paralyzed muscle parts, and (2) decreased muscle length range of force exertion (ℓrange). Recent experiments also indicate increased ECM stiffness of BTX treated muscle. Hence, altered muscle fiber-ECM interactions and BTX effects are plausible in due treatment course. Using finite element modeling, the aim was to test the following hypotheses: acute-BTX treatment effects elevate with increased ECM stiffness in the long-term, and are also persistent post-BTX treatment. Model results confirm these hypotheses and show that restricted sarcomere shortening effect becomes more pronounced in the long-term and is persistent or reversed (for longer muscle lengths) post-BTX treatment. Consequently, force production capacity of activated sarcomeres gets further enhanced in the long-term. Remarkably, such enhanced capacity becomes permanent for the entire muscle post-treatment. Shift of muscle optimum length to a shorter length is more pronounced in the long-term, some of which remains permanent post-treatment. Compared to Pre-BTX treatment, a narrower ℓrange (20.3%, 27.1% and 3.4%, acute, long-term and post-BTX treatment, respectively) is a consistent finding. We conclude that ECM adaptations can affect muscular mechanics adversely both during spasticity management and post-BTX treatment. Therefore, this issue deserves major future attention.

Effects of a Resting Foot Splint in Early Brain Injury Patients

Objective

To assess the effectiveness of the resting foot splint to prevent ankle contracture.

Methods

We performed a randomized controlled trial in 33 patients with brain injury with ankle dorsiflexor weakness (muscle power ≤grade 2). Both groups continued conventional customized physical therapy, but the patients in the foot splint group were advised to wear a resting foot splint for more than 12 hours per day for 3 weeks. The data were assessed before and 3 weeks after the study. The primary outcome was the change in ankle dorsiflexion angle after 3 weeks.

Results

Before the study, there were no differences between groups in gender, age, time post-injury, brain injury type, initial edema, spasticity, passive range of ankle dorsiflexion, Fugl-Meyer score (FMS), or Functional Ambulation Classification. A significant improvement in ankle dorsiflexion angle, and FMS was found after 3 weeks in both groups. The splint group showed more spasticity than the control group after 3 weeks (p=0.04). The change of ankle dorsiflexion angle, foot circumference, spasticity, and FMS after adjusting initial value and spasticity were not significantly different between the 2 groups.

Conclusion

Wearing a resting foot splint for 3 weeks did not affect joint mobility in patients with subacute brain injury regularly attending personalized rehabilitation programs. Further studies of larger sample sizes with well controlled in spasticity are required to evaluate the effects of the resting foot splint.

Evaluation of low-level laser therapy in the treatment of masticatory muscles spasticity in children with cerebral palsy

Spasticity is a motor disorder frequently present in individuals with cerebral palsy (CP). This study aimed to evaluate the effect of low-level laser therapy (LLLT) on the spasticity of the masseter and anterior temporal muscle fibers in children with CP over three weeks of intermittent laser exposures. The bite force (BF) of the masticatory muscles and the amplitude of mouth opening were evaluated before and after laser irradiation in 30 children with CP. Both sides of the masseter and temporalis muscles were irradiated with low-intensity diode laser pulses of 808-nm wavelength six times over three consecutive weeks. During the subsequent three weeks of postlaser exposures, although no laser treatment was applied, the evaluation parameters were measured and recorded. A significant improvement in the amplitude of mouth opening and a decrease in the BF were observed in the weeks following LLLT (P<0.05 ). However, by the sixth week post-LLLT, the BF and the amplitude of mouth opening reverted to values equivalent to those obtained before the first application of LLLT. Our investigation revealed low-level energy exposures from a 808-nm diode laser to be an effective short-term therapeutic tool. This method increased the amplitude of mouth opening and decreased the muscle tonus of children with spastic CP over a time course of three weeks of intermittent laser applications.