Manually controlled instrumented spasticity assessments: a systematic review of psychometric properties

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Treatment response to botulinum neurotoxin-A in children with cerebral palsy categorized by the type of stretch reflex muscle activation

While Botulinum NeuroToxin-A (BoNT-A) injections are frequently used to reduce the effects of hyperactive stretch reflexes in children with cerebral palsy (CP), the effects of this treatment vary strongly. Previous research, combining electromyography (EMG) with motion analysis, defined different patterns of stretch reflex muscle activation in muscles, those that reacted more to a change in velocity (velocity dependent -VD), and those that reacted more to a change in length (length dependent -LD). The aim of this study was to investigate the relation between the types of stretch reflex muscle activation in the semitendinosus with post-BoNT-A outcome as assessed passively and with 3D gait analysis in children with spastic CP. Eighteen children with spastic CP (10 bilaterally involved) between the ages of 12 and 18 years were assessed before and on average, 8 weeks post-treatment. EMG and motion analysis were used to assess the degree and type of muscle activation dependency in the semitendinosus during passive knee extensions performed at different joint angular velocities. Three-dimensional gait analysis was used to assess knee gait kinematics as a measure of functional outcome. Pre-treatment, 9 muscles were classified as VD and 9 as LD, but no differences between the groups were evident in the baseline knee gait kinematics. Post-treatment, stretch reflex muscle activation decreased significantly in both groups but the reduction was more pronounced in those muscles classified pre-treatment as VD (-72% vs. -50%,p= 0.005). In the VD group, these changes were accompanied by greater knee extension at initial contact and during the swing phase of gait. In the LD group, there was significantly increased post-treatment knee hyperextension in late stance. Although results vary between patients, the reduction of stretch reflex muscle activation in the semitendinosus generally translated to an improved functional outcome, as assessed with 3D gait analysis. However, results were less positive for those muscles with pre-treatment length-dependent type of stretch reflex muscle activation. The study demonstrates the relevance of categorizing the type of stretch reflex muscle activation as a possible predictor of treatment response

Revising the stretch reflex threshold method to measure stretch hyperreflexia in cerebral palsy

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Joint and muscle assessments of the separate effects of Botulinum NeuroToxin-A and lower-leg casting in children with cerebral palsy

Botulinum NeuroToxin-A (BoNT-A) injections to the medial gastrocnemius (MG) and lower-leg casts are commonly combined to treat ankle equinus in children with spastic cerebral palsy (CP). However, the decomposed treatment effects on muscle or tendon structure, stretch reflexes, and joint are unknown. In this study, BoNT-A injections to the MG and casting of the lower legs were applied separately to gain insight into the working mechanisms of the isolated treatments on joint, muscle, and tendon levels. Thirty-one children with spastic CP (GMFCS I-III, age 7.4 +/- 2.6 years) received either two weeks of lower-leg casts or MG BoNT-A injections. During full range of motion slow and fast passive ankle rotations, joint resistance and MG stretch reflexes were measured. MG muscle and tendon lengths were assessed at resting and at maximum dorsiflexion ankle angles using 3D-freehand ultrasound. Treatment effects were compared using non-parametric statistics. Associations between the effects on joint and muscle or tendon levels were performed using Spearman correlation coefficients (p < 0.05). Increased joint resistance, measured during slow ankle rotations, was not significantly reduced after either treatment. Additional joint resistance assessed during fast rotations only reduced in the BoNT-A group (-37.6%, p = 0.013, effect size = 0.47), accompanied by a reduction in MG stretch reflexes (-70.7%, p = 0.003, effect size = 0.56). BoNT-A increased the muscle length measured at the resting ankle angle (6.9%, p = 0.013, effect size = 0.53). Joint angles shifted toward greater dorsiflexion after casting (32.4%, p = 0.004, effect size = 0.56), accompanied by increases in tendon length (5.7%, p = 0.039, effect size = 0.57; r = 0.40). No associations between the changes in muscle or tendon lengths and the changes in the stretch reflexes were found. We conclude that intramuscular BoNT-A injections reduced stretch reflexes in the MG accompanied by an increase in resting muscle belly length, whereas casting resulted in increased dorsiflexion without any changes to the muscle length. This supports the need for further investigation on the effect of the combined treatments and the development of treatments that more effectively lengthen the muscle

Reliability of Processing 3-D Freehand Ultrasound Data to Define Muscle Volume and Echo-intensity in Pediatric Lower Limb Muscles with Typical Development or with Spasticity

This investigation assessed the processer reliability of estimating muscle volume and echo-intensity of the rectus femoris, tibialis anterior and semitendinosus. The muscles of 10 typically developing children (8.15 [1.40] y) and 15 children with spastic cerebral palsy (7.67 [3.80] y; Gross Motor Function Classification System I = 5, II = 5, III = 5) were scanned with 3-D freehand ultrasonography. For the intra-processer analysis, the intra-class correlations coefficients (ICCs) for muscle volume ranged from 0.943–0.997, with relative standard errors of measurement (SEM%) ranging from 1.24%–8.97%. For the inter-processer analysis, these values were 0.853 to 0.988 and 3.47% to 14.02%, respectively. Echo-intensity had ICCs >0.947 and relative SEMs <4% for both analyses. Muscle volume and echo-intensity can be reliably extracted for the rectus femoris, semitendinosus and tibialis anterior in typically developing children and children with cerebral palsy. The need for a single processer to analyze all data is dependent on the size of the expected changes or differences

Physics-based simulations to predict the differential effects of motor control and musculoskeletal deficits on gait dysfunction in cerebral palsy : a retrospective case study

Physics-based simulations of walking have the theoretical potential to support clinical decision-making by predicting the functional outcome of treatments in terms of walking performance. Yet before using such simulations in clinical practice, their ability to identify the main treatment targets in specific patients needs to be demonstrated. In this study, we generated predictive simulations of walking with a medical imaging based neuro-musculoskeletal model of a child with cerebral palsy presenting crouch gait. We explored the influence of altered muscle-tendon properties, reduced neuromuscular control complexity, and spasticity on gait dysfunction in terms of joint kinematics, kinetics, muscle activity, and metabolic cost of transport. We modeled altered muscle-tendon properties by personalizing Hill-type muscle-tendon parameters based on data collected during functional movements, simpler neuromuscular control by reducing the number of independent muscle synergies, and spasticity through delayed muscle activity feedback from muscle force and force rate. Our simulations revealed that, in the presence of aberrant musculoskeletal geometries, altered muscle-tendon properties rather than reduced neuromuscular control complexity and spasticity were the primary cause of the crouch gait pattern observed for this child, which is in agreement with the clinical examination. These results suggest that muscle-tendon properties should be the primary target of interventions aiming to restore an upright gait pattern for this child. This suggestion is in line with the gait analysis following muscle-tendon property and bone deformity corrections. Future work should extend this single case analysis to more patients in order to validate the ability of our physics-based simulations to capture the gait patterns of individual patients pre- and post-treatment. Such validation would open the door for identifying targeted treatment strategies with the aim of designing optimized interventions for neuro-musculoskeletal disorders

Medial gastrocnemius muscle stiffness cannot explain the increased ankle joint range of motion following passive stretching in children with cerebral palsy.

Stretching is often used to increase/maintain joint range of motion (ROM) in children with cerebral palsy (CP) but the effectiveness of these interventions is limited. Therefore, this study aimed to determine the acute changes in muscle-tendon lengthening properties that contribute to increased ROM after a bout of stretching in children with CP. Eleven children with spastic CP (age:12.1(3)y, 5/6 hemiplegia/diplegia, 7/4 GMFCS level I/II) participated in this study. Each child received 3 sets of 5 × 20 s passive, manual static dorsiflexion stretches separated by 30 s rest, and 60 s rest between sets. Pre- and immediately post-stretching, ultrasound was used to measure medial gastrocnemius fascicle lengthening continuously over the full ROM and an individual common ROM pre- to post-stretching. Simultaneously, 3D motion of two marker clusters on the shank and the foot was captured to calculate ankle angle, and ankle joint torque was calculated from manually applied torques and forces on a 6DoF load cell. After stretching, ROM was increased (9.9° (12.0), P = 0.005). Over a ROM common to both pre and post measurements, there were no changes in fascicle lengthening or torque. The maximal ankle joint torque tolerated by the participants increased (2.9(2.4) Nm, P = 0.003) and at this highest passive torque maximal fascicle length was 2.8(2.4) mm greater (P = 0.009) when compared to before stretching. These results indicate that the stiffness of the muscle fascicles in children with CP remain unaltered by an acute bout of stretching. This article is protected by copyright. All rights reserved

Muscle and tendon lengthening behaviour of the medial gastrocnemius during ankle joint rotation in children with cerebral palsy.

NEW FINDINGS: What is the central question of this study? Which structures of the medial gastrocnemius muscle-tendon unit contribute to its lengthening during joint rotation and thus receive the stretching stimulus? What is the main finding and its importance? We show, for the first time, that muscle and tendon lengthen in a different manner in children with cerebral palsy compared with typically developing children during a similar amount of muscle-tendon unit lengthening or joint rotation. This indicates possible differences in mechanical muscle and tendon properties attributable to cerebral palsy, which are not evident by assessment of muscle function at the level of a joint. ABSTRACT: Children with cerebral palsy (CP) commonly present with reduced ankle range of motion (ROM) attributable, in part, to changes in mechanical properties of the muscle-tendon unit (MTU). Detailed information about how muscle and tendon interact to contribute to joint rotation is currently lacking but might provide essential information to explain the limited effectiveness of stretching interventions in children with CP. The purpose of this study was to quantify which structures contribute to MTU lengthening and thus receive the stretch during passive ankle joint rotation. Fifteen children with CP (age, in mean ± SD, 11.4 ± 3 years) and 16 typically developing (TD) children (age, in mean ± SD, 10.2 ± 3 years) participated. Ultrasound was combined with motion tracking, joint torque and EMG to record fascicle, muscle and tendon lengthening of the medial gastrocnemius during passive ankle joint rotations over the full ROM and a common ROM. In children with CP, relative to MTU lengthening, muscle and fascicles lengthened less (CP, 50.4% of MTU lengthening; TD, 63% of MTU lengthening; P < 0.04) and tendon lengthened more (CP, 49.6% of MTU lengthening; TD, 37% of MTU lengthening; P < 0.01) regardless of the ROM studied. Differences between groups in the amount of lengthening of the underlying structures during a similar amount of joint rotation and MTU displacement indicate possible differences in tissue mechanical properties attributable to CP, which are not evident by assessment at the level of a joint. These factors should be considered when assessing and treating muscle function in children with CP, for example during stretching exercises, because the muscle might not receive much of the applied lengthening stimulus

Exploration of the nature of spasticity in children with cerebral palsy based on biomechanical and electrophysiological measurements

Spasticity occurs in 85% of children diagnosed with cerebral palsy (CP). It is defined as a motor disorder that is characterized by velocity-dependent hyper-sensitivity of stretch reflexes. When a muscle with spasticity is stretched, this hypersensitivity causes a pathological increase in muscle activity and a subsequent disruption of fluent motion. Spasticity can cause pain, lead to secondary muscle and bone deformities and limits normal mobility and everyday functionality. To effectively treat spasticity, it is of utmost importance that its assessment is carried out accurately and provides quantitative data.In standard clinical practice, the severity of the patient s spasticity is assessed by grading thelevel of resistance felt when stretching a passive muscle. An alternative approach involves the measurement of the joint angle at which the movement is disrupted during a quick passive stretch. Both assessments relyon the subjective interpretation of the clinician who performs the tests. Furthermore, the reliability of these methods is compromised, since the velocity at which the muscle is being stretched is uncontrolled. Also, it is always possible that an increase in resistance during a passive stretch is not caused by spasticity, but by non-neural mechanical muscle properties, such as stiffness. As such, these clinical scales and approaches have been deemed invalid and unreliable for the assessment of spasticity.Many attempts have been made to find an alternative, more objective form of spasticity assessment. However, due to its complex pathophysiology, spasticity has proved to be difficult to isolate. Thus far, its assessment is only feasible in research settings with methods that are difficult to apply in clinical environments, and this difficultyespecially applies to pediatric populations. Consequently, the scope ofthis PhD was to create a reliable, valid and clinically applicable method for spasticity assessment in children with CP, which could also be used to explore the nature of spasticity in these children.The first part of the PhD project reviewed the existing literature on spasticity assessment (Chapter 1). The results of this review showed that, despite the abundance of research carried out on the topic, not one method was proven to be sufficiently sound for the assessment of multiple muscles in children with CP. Additionally, there is no consensus regarding theassessment protocol or the types of parameters that can quantify spasticity. Nevertheless, the identified literature created a framework upon which to construct a new method.The second part of the PhD project focused on the development of the instrumented spasticity assessment(ISA) (Chapter 2, 3). ISA simultaneously collects electrophysiological and biomechanical signals during passive muscle stretches at different velocities. It has been designed to assess spasticity in four lower limb muscles, but the method can easily be extended to other muscles. The parameters obtained from integrated signal processing provide an objective,quantitative measure of spasticity. The studies outlined in Chapters 2 and 3 of this PhD set out to test the applicability of these parameters for spasticity assessment in children with CP. The study results showed that the developed parameters were: (A) reliable; (B) able to distinguish between non-involved muscles and muscles with spasticity; (C) sensitive to treatment with Botulinum Toxin A (BTX); (D) usable to predict the effect of treatment with BTX; and (E) sensitive enough to differentiate between different BTX injection techniques.These findings went far beyond the initial expectations of the research. They not only confirmed ISA s suitability for the assessment of spasticity in clinical environments, but also established ISA as a method to fine-tune existing forms of treatment and to improve management protocols. The findings from this part of the research are far-reaching, since they create a firm platform from which to explore many other possible avenues that can benefit clinical practice.In the third part of the PhD project, we used ISA to unveil the heterogeneity of spasticity in children with CP (Chapter 4). In order to do so, the results we obtained by testing ISA on a large number of children were used to classify muscles into sub-groups according to their activation pattern and stretch-reflex thresholds. Preliminary results show that different muscles tend to cluster into one or the othersub-group. Nevertheless, the actual etiology that underlies this classification remains unexplored. In a next step, the research focused on analyzing the influence of spasticity versus the influence of non-neural mechanical muscle properties on the resistance that occurs during passive muscle stretch. In a final part, the relation between ISA parameters andmarkers of spasticity during gait was explored. Even though this research uncovered several interesting moderate to good relations between ISA and gait, the results confirmed that other influences besides spasticitymight also be important in defining how children with CP walk.Inconclusion, this doctoral thesis has made a fundamental contribution tothe everyday clinical management of spasticity by providing a means to quantitatively describe this complex phenomenon. This step is central tofurther improving the way spasticity is treated and lays the groundworkfor many future investigations that will undoubtedly contribute to the better care of children with CP.status: publishe