Impaired muscle growth precedes development of increased stiffness of the triceps surae musculotendinous unit in children with cerebral palsy

Supported Standing and Supported Stepping Devices for Children with Non-Ambulant Cerebral Palsy: An Interdependence and F-Words Focus

Children functioning at Gross Motor Function Classification System (GMFCS) levels IV-V cannot maintain an aligned standing position or take steps without support. Upright positioning and mobility devices have psycho-social significance for these children and their families, enhancing use of vision, communication, functioning and emotional well-being. Standers and supported stepping devices facilitate opportunities for biomechanical loading, potentially helping to build and maintain muscle and bone integrity, and they promote physical development. However, families are often required to choose between these two devices for their young child. This study aims to synthesize evidence for use and benefits of both supported standing and stepping devices through the lens of two contemporary theoretical frameworks to support clinical reasoning and implementation. The F-words for childhood development (functioning, family, fitness, fun, friends, future) and the interdependence-Human Activity Assistive Technology (iHAAT) models were combined to illustrate the complex interactions between the child, family, caregivers, peers and contextual factors when implementing standing and stepping devices with children at GMFCS levels IV and V. Supported standing and stepping devices provide complementary benefits, and both may be necessary starting at 9-15 months. We propose they both be included ON-Time, along with other age-appropriate positioning and mobility devices, to promote more equitable developmental opportunities for children with non-ambulant cerebral palsy.

Longitudinal trajectory of medial gastrocnemius muscle growth in the first years of life

AIM

To define the longitudinal trajectory of gastrocnemius muscle growth in 6- to 36-month-old children with and without spastic cerebral palsy (SCP) and to compare trajectories by levels of gross motor function (Gross Motor Function Classification System, GMFCS) and presumed brain-lesion timing.

METHOD

Twenty typically developing children and 24 children with SCP (GMFCS levels I-II/III-IV = 15/9), were included (28/16 females/males; mean age at first scan 15.4 months [standard deviation 4.93, range 6.24-23.8]). Three-dimensional freehand ultrasound was used to repeatedly assess muscle volume, length, and cross-sectional area (CSA), resulting in 138 assessments (mean interval 7.9 months). Brain lesion timing was evaluated with magnetic resonance imaging classification. Linear mixed-effects models defined growth rates, adjusted for GMFCS levels and presumed brain-lesion timing.

RESULTS

At age 12 months, children with SCP showed smaller morphological muscle size than typically developing children (5.8 mL vs 9.8 mL, p < 0.001), while subsequently no differences in muscle growth were found between children with and without SCP (muscle volume: 0.65 mL/month vs 0.74 mL/month). However, muscle volume and CSA growth rates were lower in children classified in GMFCS levels III and IV than typically developing children and those classified in GMFCS levels I and II, with differences ranging from -56% to -70% (p < 0.001).

INTERPRETATION

Muscle growth is already hampered during infancy in SCP. Muscle size growth further reduces with decreasing functional levels, independently from the brain lesion. Early monitoring of muscle growth combined with early intervention is needed.

Gastrocnemius medialis and Achilles tendon properties do not differ between children with unilateral or bilateral spastic cerebral palsy

Spastic cerebral palsy (SCP) is a common neurodevelopmental disorder in children, which can be categorized into unilateral and bilateral subtypes. Most studies examining the muscle-tendon properties of the lower extremities in individuals with SCP do not distinguish between subtypes. However, spastic muscle morphology is an important determinant for its function. Therefore, differences in muscle-tendon pathology might lead to different treatment strategies. The aim of this retrospective study was to investigate the muscle-tendon properties between children with unilateral SCP and those with bilateral SCP. Overall, 33 ambulatory children (15 with unilateral SCP and 18 with bilateral SCP, Gross Motor Function Classification System Level I-III) were included. Ankle joint range of motion, isometric muscle strength, and muscle-tendon properties of the gastrocnemius medialis (GM) muscle-tendon unit (MTU) (e.g., muscle volume, tissue lengthening behavior) were assessed with isokinetic dynamometry, 3D motion capture, and ultrasound, respectively. Independent t-tests or Mann-Whitney tests were used to test for group differences (α = 0.05). Effect sizes (Cohen's d) were also calculated. No significant differences in any assessed parameter were found between children with unilateral SCP and children with bilateral SCP (p > 0.05, d < 0.57). Our findings suggest that the functional and morphological properties of the GM MTU are similarly developed in children with unilateral SCP and children with bilateral SCP. We assume that activity levels might be the decisive factor. Nonetheless, our investigations need be extended by including gait parameters and associated tissue dynamics.

F-words e ingredientes das intervenções precoces para crianças com paralisia cerebral não deambuladoras: uma revisão de escopo

Cuidados centrados na família (incluindo coaching e intervenções fornecidas pelo cuidador) e treinamento parental formal são estratégias eficazes para crianças nos níveis IV e V do GMFCS. Os ingredientes de tecnologia assistiva podem promover várias F-words (funcionalidade, saúde, família, diversão, amigos e futuro). O menor nível de evidência foi encontrado para diversão, amigos e futuro. Outros fatores (prestação de serviços, treinamento profissional, dose de terapia, modificações ambientais) são relevantes para crianças pequenas nos níveis IV e V do GMFCS. Esta revisão de escopo identificou os ingredientes de intervenções precoces para crianças com paralisia cerebral em risco de não serem deambuladoras, e os mapeou-os de acordo com a estrutura das F-words. O treinamento formal dos pais e a tecnologia assistiva se destacaram como estratégias para abordar com várias F-words.

F-words and early intervention ingredients for non-ambulant children with cerebral palsy: A scoping review

AIM

To explore the ingredients of early interventions provided to young children with cerebral palsy (CP) who are classified in Gross Motor Function Classification System (GMFCS) levels IV and V, and to identify the 'F-words' addressed by the interventions.

METHOD

Searches were completed in four electronic databases. Inclusion criteria were the original experimental studies that fitted the following PCC components: population, young children (aged 0-5 years, at least 30% of the sample) with CP and significant motor impairment (GMFCS levels IV or V, at least 30% of the sample); concept, non-surgical and non-pharmacological early intervention services measuring outcomes from any of the International Classification of Functioning, Disability and Health domains; and context, studies published from 2001 to 2021, from all settings and not limited to any specific geographical location.

RESULTS

Eighty-seven papers were included for review, with qualitative (n = 3), mixed-methods (n = 4), quantitative descriptive (n = 22), quantitative non-randomized (n = 39), and quantitative randomized (n = 19) designs. Fitness (n = 59), family (n = 46), and functioning (n = 33) ingredients were addressed by most experimental studies, whereas studies on fun (n = 6), friends (n = 5), and future (n = 14) were scarce. Several other factors (n = 55) related to the environment, for example, service provision, professional training, therapy dose, and environmental modifications, were also relevant.

INTERPRETATION

Many studies positively supported formal parent training and use of assistive technology to promote several F-words. A menu of intervention ingredients was provided, with suggestions for future research, to incorporate them into a real context within the family and clinical practice.

WHAT THIS PAPER ADDS

Family-centred care (including coaching and caregiver-delivered interventions) and formal parental training are effective strategies for children in GMFCS levels IV and V. Assistive technology ingredients (power, mobility, supported, sitting, stepping, and standing) may promote several 'F-words' (functioning, fitness, family, fun, friends, and future). The lowest level of evidence was found for fun, friends, and future. Other factors (service provision, professional training, therapy dose, environmental modifications) are relevant for young children in GMFCS levels IV and V.

F-Wörter und Interventionsinhalte in der Frühförderung nicht gehfähiger Kinder mit Cerebralparese: eine umfangreiche Literaturübersicht

Ziel

Untersuchung der Inhalte von Frühfördermaßnahmen für Kleinkinder mit Cerebralparese (CP) mit Gross Motor Function Classification System (GMFCS) Level IV und V und die Identifikation von „F‐Wörtern“, die von den Maßnahmen adressiert werden.

Methode

Recherche in vier elektronischen Datenbanken. Einschlusskriterien: experimentelle Originalstudien, die die folgenden PCC‐Komponenten erfüllten: Population: Kleinkinder (im Alter von 0–5 Jahre, mindestens 30% der Stichprobe) mit CP und erheblicher motorischer Beeinträchtigung (GMFCS‐Levels IV oder V, mindestens 30% der Stichprobe); Konzept: nicht‐chirurgische und nicht‐pharmakologische Leistungen der Frühförderung, die Ergebnisse aus einem der Bereiche der Internationalen Klassifikation der Funktionsfähigkeit, Behinderung und Gesundheit (ICF) messen; und Kontext: Studien, die zwischen 2001 und 2021 veröffentlicht wurden, in allen Konstellationen und nicht auf einen bestimmten geografischen Ort beschränkt.

Ergebnisse

87 Studien wurden in dieser Literaturübersicht berücksichtigt, mit qualitativen (n = 3), Mixed Methods (n = 4), quantitativ deskriptiven (n = 22), quantitativ nicht‐randomisierten (n = 39) und quantitativ randomisierten (n = 19) Designs. Die meisten experimentellen Studien befassten sich mit Fitness (n = 59), Familie (n = 46) und Funktion (n = 33), während es nur wenige Studien zu den Bereichen Spaß (n = 6), Freunde (n = 5) und Zukunft (n = 14) gab. Verschiedene Umweltfaktoren (n = 55) waren ebenfalls bedeutsam, z. B. das Angebot an Dienstleistungen, Berufsausbildung, Therapiedosis und Umweltanpassungen.

Interpretation

Viele Studien unterstützen Elternschulungen und den Einsatz assistiver Technologien zur Förderung verschiedener F‐Wörter. Ein „Menü“ von Inhalten der Frühförderung wurden ermittelt, mit Vorschlägen für weitere Forschung, um diese in der klinischen Praxis mit Familien umzusetzen.

Was dieser Artikel beiträgt

F-words e ingredientes de las intervenciones tempranas dirigidas a niños no ambulantes con parálisis cerebral: Una revisión exploratoria

La atención centrada en la familia (incluyendo coaching e intervenciones realizadas por los cuidadores) y el entrenamiento formal de los padres son estrategias efectivas para los niños con niveles IV y V de la GMFCS. Los ingredientes de la tecnología de apoyo pueden promover varias "F-words" (funcionamiento, estado físico, familia, diversión, amigos y futuro). Se encontró el nivel más bajo de evidencia para diversión, amigos y futuro. Otros factores (provisión de servicios, formación profesional, dosis de terapia, modificaciones del entorno) son relevantes para los niños pequeños con niveles IV y V de la GMFCS. Ingredientes de la intervención y F-words en intervenciones tempranas dirigidas a niños no ambulantes con parálisis cerebral.

Testing spasticity mechanisms in chronic stroke before and after intervention with contralesional motor cortex 1 Hz rTMS and physiotherapy

BACKGROUND

Previous studies showed that repetitive transcranial magnetic stimulation (rTMS) reduces spasticity after stroke. However, clinical assessments like the modified Ashworth scale, cannot discriminate stretch reflex-mediated stiffness (spasticity) from passive stiffness components of resistance to muscle stretch. The mechanisms through which rTMS might influence spasticity are also not understood.

METHODS

We measured the effects of contralesional motor cortex 1 Hz rTMS (1200 pulses + 50 min physiotherapy: 3×/week, for 4-6 weeks) on spasticity of the wrist flexor muscles in 54 chronic stroke patients using a hand-held dynamometer for objective quantification of the stretch reflex response. In addition, we measured the excitability of three spinal mechanisms thought to be related to post-stroke spasticity: post-activation depression, presynaptic inhibition and reciprocal inhibition before and after the intervention. Effects on motor impairment and function were also assessed using standardized stroke-specific clinical scales.

RESULTS

The stretch reflex-mediated torque in the wrist flexors was significantly reduced after the intervention, while no change was detected in the passive stiffness. Additionally, there was a significant improvement in the clinical tests of motor impairment and function. There were no significant changes in the excitability of any of the measured spinal mechanisms.

CONCLUSIONS

We demonstrated that contralesional motor cortex 1 Hz rTMS and physiotherapy can reduce the stretch reflex-mediated component of resistance to muscle stretch without affecting passive stiffness in chronic stroke. The specific physiological mechanisms driving this spasticity reduction remain unresolved, as no changes were observed in the excitability of the investigated spinal mechanisms.

Measuring resistance to externally induced movement of the wrist joint in chronic stroke patients using an objective hand-held dynamometer

Objective

We evaluated the resistance to externally induced wrist extension in chronic stroke patients. We aimed to objectively measure and distinguish passive (muscle and soft tissue stiffness) and active (spasticity and spastic dystonia) components of the resistance.

Methods

We used a hand-held dynamometer, which measures torque, joint movement and electromyography (EMG) simultaneously, to assess the resistance to externally induced wrist extension. Slow and fast stretches were applied to the affected and unaffected wrists in 57 chronic stroke patients (57 ± 11 years). We extracted from the data parameters that represent passive and muscle activity components and assessed the validity, test-retest reliability and the clinical utility of the measurement.

Results

The analysis showed (1) a significant difference in the passive and muscle activity components between the affected and unaffected sides; (2) a significant correlation between passive and muscle activity components and the modified Ashworth scale (MAS); (3) a significant difference between the subgroups of patients stratified by the MAS; (4) an excellent intra-rater reliability on each of the passive and muscle activity components with intra-class coefficients between 0.92 and 0.99; (5) and small measurement error.

Conclusions

Using a hand-held dynamometer, we were able to objectively measure the resistance to muscle stretch in the wrist joint in chronic stroke patients and discriminate muscle overactivity components from muscle and soft tissue stiffness. We demonstrated validity, test-retest reliability and the clinical utility of the measurement.

Significance

Quantification of the different components of resistance to externally induced movement enables the objective evaluation of neurorehabilitation effects in chronic stroke patients.

Resident muscle stem cell myogenic characteristics in postnatal muscle growth impairments in children with cerebral palsy

Children with cerebral palsy (CP), a perinatal brain alteration, have impaired postnatal muscle growth, with some muscles developing contractures. Functionally, children are either able to walk or primarily use wheelchairs. Satellite cells are muscle stem cells (MuSCs) required for postnatal development and source of myonuclei. Only MuSC abundance has been previously reported in contractured muscles, with myogenic characteristics assessed only in vitro. We investigated whether MuSC myogenic, myonuclear, and myofiber characteristics in situ differ between contractured and noncontractured muscles, across functional levels, and compared with typically developing (TD) children with musculoskeletal injury. Open muscle biopsies were obtained from 36 children (30 CP, 6 TD) during surgery; contracture correction for adductors or gastrocnemius, or from vastus lateralis [bony surgery in CP, anterior cruciate ligament (ACL) repair in TD]. Muscle cross sections were immunohistochemically labeled for MuSC abundance, activation, proliferation, nuclei, myofiber borders, type-1 fibers, and collagen content in serial sections. Although MuSC abundance was greater in contractured muscles, primarily in type-1 fibers, their myogenic characteristics (activation, proliferation) were lower compared with noncontractured muscles. Overall, MuSC abundance, activation, and proliferation appear to be associated with collagen content. Myonuclear number was similar between all muscles, but only in contractured muscles were there associations between myonuclear number, MuSC abundance, and fiber cross-sectional area. Puzzlingly, MuSC characteristics were similar between ambulatory and nonambulatory children. Noncontractured muscles in children with CP had a lower MuSC abundance compared with TD-ACL injured children, but similar myogenic characteristics. Contractured muscles may have an intrinsic deficiency in developmental progression for postnatal MuSC pool establishment, needed for lifelong efficient growth and repair.

A comprehensive normative reference database of muscle morphology in typically developing children aged 3-18 years-a cross-sectional ultrasound study

During childhood, muscle growth is stimulated by a gradual increase in bone length and body mass, as well as by other factors, such as physical activity, nutrition, metabolic, hormonal, and genetic factors. Muscle characteristics, such as muscle volume, anatomical cross-sectional area, and muscle belly length, need to continuously adapt to meet the daily functional demands. Pediatric neurological and neuromuscular disorders, like cerebral palsy and Duchenne muscular dystrophy, are characterized by impaired muscle growth, which requires treatment and close follow-up. Nowadays ultrasonography is a commonly used technique to evaluate muscle morphology in both pediatric pathologies and typically developing children, as it is a quick, easy applicable, and painless method. However, large normative datasets including different muscles and a large age range are lacking, making it challenging to monitor muscle over time and estimate the level of pathology. Moreover, in order to compare individuals with different body sizes as a result of age differences or pathology, muscle morphology is often normalized to body size. Yet, the usefulness and practicality of different normalization techniques are still unknown, and clear recommendations for normalization are lacking. In this cross-sectional cohort study, muscle morphology of four lower limb muscles (medial gastrocnemius, tibialis anterior, the distal compartment of the semitendinosus, rectus femoris) was assessed by 3D-freehand ultrasound in 118 typically developing children (mean age 10.35 ± 4.49 years) between 3 and 18 years of age. The development of muscle morphology was studied over the full age range, as well as separately for the pre-pubertal (3-10 years) and pubertal (11-18 years) cohorts. The assumptions of a simple linear regression were checked. If these assumptions were fulfilled, the cross-sectional growth curves were described by a simple linear regression equation. Additional ANCOVA analyses were performed to evaluate muscle- or gender-specific differences in muscle development. Furthermore, different scaling methods, to normalize muscle morphology parameters, were explored. The most appropriate scaling method was selected based on the smallest slope of the morphology parameter with respect to age, with a non-significant correlation coefficient. Additionally, correlation coefficients were compared by a Steiger's Z-test to identify the most efficient scaling technique. The current results revealed that it is valid to describe muscle volume (with exception of the rectus femoris muscle) and muscle belly length alterations over age by a simple linear regression equation till the age of 11 years. Normalizing muscle morphology data by allometric scaling was found to be most useful for comparing muscle volumes of different pediatric populations. For muscle lengths, normalization can be achieved by either allometric and ratio scaling. This study provides a unique normative database of four lower limb muscles in typically developing children between the age of 3 and 18 years. These data can be used as a reference database for pediatric populations and may also serve as a reference frame to better understand both physiological and pathological muscle development.

Associations between muscle morphology and spasticity in children with spastic cerebral palsy

INTRODUCTION

Due to the heterogeneous clinical presentation of spastic cerebral palsy (SCP), which makes spasticity treatment challenging, more insight into the complex interaction between spasticity and altered muscle morphology is warranted.

AIMS

We studied associations between spasticity and muscle morphology and compared muscle morphology between commonly observed spasticity patterns (i.e. different muscle activation patterns during passive stretches).

METHODS

Spasticity and muscle morphology of the medial gastrocnemius (MG) and semitendinosus (ST) were defined in 74 children with SCP (median age 8 years 2 months, GMFCS I/II/III: 31/25/18, bilateral/unilateral: 46/27). Using an instrumented assessment, spasticity was quantified as the difference in muscle activation recorded during passive stretches at low and high velocities and was classified in mixed length-/velocity-dependent or pure velocity-dependent activation patterns. Three-dimensional freehand ultrasound was used to assess muscle morphology (volume and length) and echogenicity intensity (as a proxy for muscle quality). Spearman correlations and Mann-Whitney-U tests defined associations and group differences, respectively.

RESULTS

A moderate negative association (r = -0.624, p < 0.001) was found between spasticity and MG muscle volume, while other significant associations between spasticity and muscle morphology parameters were weak. Smaller normalized muscle volume (MG p = 0.004, ST p=<0.001) and reduced muscle belly length (ST p = 0.015) were found in muscles with mixed length-/velocity-dependent patterns compared to muscles with pure velocity-dependent patterns.

DISCUSSION

Higher spasticity levels were associated with smaller MG and ST volumes and shorter MG muscles. These muscle morphology alterations were more pronounced in muscles that activated during low-velocity stretches compared to muscles that only activated during high-velocity stretches.

Supported-standing interventions for children and young adults with non-ambulant cerebral palsy: A scoping review

AIM

To describe the evidence, outcomes, and lived experience of supported standing for children and young adults with cerebral palsy aged 25 years or younger, classified in Gross Motor Function Classification System levels IV and V.

METHOD

This scoping review included searches in eight electronic databases and manual searching from database inception to May 2020 and updated on 21st February 2022. Two of three reviewers independently screened titles and abstracts and extracted and appraised data. Methodological quality and risk of bias were appraised using tools appropriate to study type. Content analysis and frequency effect sizes were calculated for qualitative and descriptive evidence.

RESULTS

From 126 full-text references, 59 citations (one study was reported over two citations) were included: 16 systematic reviews, 17 intervention studies reporting over 18 citations, eight analytical cross-sectional studies, five descriptive cross-sectional/survey studies, five qualitative studies, and one mixed-methods study were identified, along with six clinical guidelines. Maintenance of bone mineral density and contracture prevention outcomes were supported by the most experimental studies and evidence syntheses, while evidence supporting other outcomes was primarily quasi-experimental or descriptive. Qualitative evidence suggests that programmes are influenced by attitudes, device, child, and environmental factors.

INTERPRETATION

Individualized assessment and prescription are essential to match personal and environmental needs. Although experimental evidence is limited due to many factors, lived-experience and cohort data suggest that successful integration of standing programmes into age-appropriate and meaningful activities may enhance function, participation, and overall health.

The reliability of the measurement of muscle volume using magnetic resonance imaging in typically developing infants by two raters

To assess intra-rater and inter-rater reliability of the manual segmentation of Magnetic Resonance Imaging (MRI) for the in vivo measurement of infant muscle volume of the knee extensor and flexor muscles by two raters. Muscles of the knee extensor and flexor muscle of ten typically developing infants (86 days ± 7 days) were scanned with MRI (Proton density sequence). Scans were then segmented using Slicer software, and volumes rendered by two raters. Intra-rater and inter-rater reliability were assessed using intra-class correlation (ICC), with mean difference (MD), standard error of the mean (SEM), and minimal detectable change (MDC) for each muscle calculated. ICCs for Intra-rater reliability of the segmentation process for the muscle volume of the muscles of the knee extensors and flexor muscles were 0.901-0.972, and 0.776-0.945 respectively, with inter-rater reliabilities between 0.914-0.954 and 0.848-0.978, for the knee extensor and flexors muscles respectively. For intra-rater reliability, MD ≤ - 0.47 cm³, MDCs for were < 1.09 cm³ and for inter-rater MD ≤ - 1.40 cm³, MDCs for were < 1.63 cm³ for all muscles. MRI segmentation for muscle volumes showed good to excellent reliability, though given the small volumes of the muscles themselves, variations between raters are amplified. Care should be taken in the reporting and interpretation of infant muscle volume.

Progressive resistance training for children with cerebral palsy: A randomized controlled trial evaluating the effects on muscle strength and morphology

Children with spastic cerebral palsy often present with muscle weakness, resulting from neural impairments and muscular alterations. While progressive resistance training (PRT) improves muscle weakness, the effects on muscle morphology remain inconclusive. This investigation evaluated the effects of a PRT program on lower limb muscle strength, morphology and gross motor function. Forty-nine children with spastic cerebral palsy were randomized by minimization. The intervention group (nparticipants = 26, age: 8.3 ± 2.0 years, Gross Motor Function Classification System [GMFCS] level I/II/III: 17/5/4, nlegs = 41) received a 12-week PRT program, consisting of 3-4 sessions per week, with exercises performed in 3 sets of 10 repetitions, aiming at 60%-80% of the 1-repetition maximum. Training sessions were performed under supervision with the physiotherapist and at home. The control group (nparticipants = 22, age: 8.5 ± 2.1 year, GMFCS level I/II/III: 14/5/3, nlegs = 36) continued usual care including regular physiotherapy and use of orthotics. We assessed pre- and post-training knee extension, knee flexion and plantar flexion isometric strength, rectus femoris, semitendinosus and medial gastrocnemius muscle morphology, as well as functional strength, gross motor function and walking capacity. Data processing was performed blinded. Linear mixed models were applied to evaluate the difference in evolution over time between the control and intervention group (interaction-effect) and within each group (time-effect). The α-level was set at p = 0.01. Knee flexion strength and unilateral heel raises showed a significant interaction-effect (p ≤ 0.008), with improvements in the intervention group (p ≤ 0.001). Moreover, significant time-effects were seen for knee extension and plantar flexion isometric strength, rectus femoris and medial gastrocnemius MV, sit-to-stand and lateral step-up in the intervention group (p ≤ 0.004). Echo-intensity, muscle lengths and gross motor function showed limited to no changes. PRT improved strength and MV in the intervention group, whereby strength parameters significantly or close to significantly differed from the control group. Although, relative improvements in strength were larger than improvements in MV, important effects were seen on the maintenance of muscle size relative to skeletal growth. In conclusion, this study proved the effectiveness of a home-based, physiotherapy supervised, PRT program to improve isometric and functional muscle strength in children with SCP without negative effects on muscle properties or any serious adverse events. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT03863197.

Medial gastrocnemius growth in children who are typically developing: Can changes in muscle volume and length be accurately predicted from age?

Muscle size is an important determinant of muscular fitness and health, and so it is important to have accurate estimates of actual muscle growth in children. This study compared actual versus age-predicted growth rates of the medial gastrocnemius (MG) muscle in young children over a 12-month period. Three-dimensional ultrasound was used to measure MG length and volume in 50 children (mean ± standard deviation [SD] age = 70.3 ± 29.9 months) to establish age-predicted muscle growth rates using a least-squares linear regression. Twenty children (mean ± SD age = 78.5 ± 27.2 months) were followed up at 6 and 12 months to establish actual muscle growth of MG volume and length. These data were then compared to their age-predicted muscle growth from the linear regression equation using paired t-tests and Bland-Altman limits of agreement method. Age-predicted MG growth significantly underestimated actual muscle growth for both volume and length at each timepoint. On average, actual muscle volume and length were 11.5% and 21.5% greater than the age-predicted volume and length respectively. Caution is warranted when predicting future muscle size in young children based solely on age.

Rehabilitation After Single-Event Multilevel Surgery for Children and Young Adults With Cerebral Palsy: A Systematic Review

ABSTRACT

This review sought to describe and analyze published protocols for rehabilitation after single-event multilevel surgery for people with cerebral palsy, to identify their differences and limits, and to introduce a common step-by-step framework for future descriptions and assessments of postoperative rehabilitation protocols.The MEDLINE, Embase, CINAHL, and the Cochrane Library databases were searched. Inclusion criteria were as follows: (1) single-event multilevel surgery, (2) full-text reports published after 1985, and (3) articles with a method section describing the rehabilitation protocol. Interventions were coded using the Oxford Levels of Evidence and the Methodological Index for Non-Randomized Studies Index.Twenty-four articles were included in the review. Studies included patients aged 4-30 yrs with spastic cerebral palsy (hemiplegia, diplegia, and quadriplegia). The mean postoperative rehabilitation duration was 4.5 mos, with 4 sessions per week, and rehabilitation took place in a rehabilitation center. This review provides relevant information about the modalities, contents, limits, and difficulties associated with the post-SEMS rehabilitation protocol reported in the literature. Pain was identified as a major problem.A more precise and comprehensive description of post-SEMS rehabilitation protocols would be useful. The proposed five-step framework could be used by future studies to standardize their protocol description in terms of objective, content, and intensity.

Do Muscle Changes Contribute to the Neurological Disorder in Spastic Paresis?

Background

At the onset of stroke-induced hemiparesis, muscle tissue is normal and motoneurones are not overactive. Muscle contracture and motoneuronal overactivity then develop. Motor command impairments are classically attributed to the neurological lesion, but the role played by muscle changes has not been investigated.

Methods

Interaction between muscle and command disorders was explored using quantified clinical methodology-the Five Step Assessment. Six key muscles of each of the lower and upper limbs in adults with chronic poststroke hemiparesis were examined by a single investigator, measuring the angle of arrest with slow muscle stretch (XV1) and the maximal active range of motion against the resistance of the tested muscle (XA). The coefficient of shortening CSH = (XN-XV1)/XN (XN, normally expected amplitude) and of weakness CW = (XV1-XA)/XV1) were calculated to estimate the muscle and command disorders, respectively. Composite CSH (CCSH) and CW (CCW) were then derived for each limb by averaging the six corresponding coefficients. For the shortened muscles of each limb (mean CSH > 0.10), linear regressions explored the relationships between coefficients of shortening and weakness below and above their median coefficient of shortening.

Results

A total of 80 persons with chronic hemiparesis with complete lower limb assessments [27 women, mean age 47 (SD 17), time since lesion 8.8 (7.2) years], and 32 with upper limb assessments [18 women, age 32 (15), time since lesion 6.4 (9.3) years] were identified. The composite coefficient of shortening was greater in the lower than in the upper limb (0.12 ± 0.04 vs. 0.08 ± 0.04; p = 0.0002, while the composite coefficient of weakness was greater in the upper limb (0.28 ± 0.12 vs. 0.15 ± 0.06, lower limb; p < 0.0001). In the lower limb shortened muscles, the coefficient of weakness correlated with the composite coefficient of shortening above the 0.15 median CSH (R = 0.43, p = 0.004) but not below (R = 0.14, p = 0.40).

Conclusion

In chronic hemiparesis, muscle shortening affects the lower limb particularly, and, beyond a threshold of severity, may alter descending commands. The latter might occur through chronically increased intramuscular tension, and thereby increased muscle afferent firing and activity-dependent synaptic sensitization at the spinal level.

Muscle architecture, growth, and biological Remodelling in cerebral palsy: a narrative review

Cerebral palsy (CP) is caused by a static lesion to the brain occurring in utero or up to the first 2 years of life; it often manifests as musculoskeletal impairments and movement disorders including spasticity and contractures. Variable manifestation of the pathology across individuals, coupled with differing mechanics and treatments, leads to a heterogeneous collection of clinical phenotypes that affect muscles and individuals differently. Growth of muscles in CP deviates from typical development, evident as early as 15 months of age. Muscles in CP may be reduced in volume by as much as 40%, may be shorter in length, present longer tendons, and may have fewer sarcomeres in series that are overstretched compared to typical. Macroscale and functional deficits are likely mediated by dysfunction at the cellular level, which manifests as impaired growth. Within muscle fibres, satellite cells are decreased by as much as 40-70% and the regenerative capacity of remaining satellite cells appears compromised. Impaired muscle regeneration in CP is coupled with extracellular matrix expansion and increased pro-inflammatory gene expression; resultant muscles are smaller, stiffer, and weaker than typical muscle. These differences may contribute to individuals with CP participating in less physical activity, thus decreasing opportunities for mechanical loading, commencing a vicious cycle of muscle disuse and secondary sarcopenia. This narrative review describes the effects of CP on skeletal muscles encompassing substantive changes from whole muscle function to cell-level effects and the effects of common treatments. We discuss growth and mechanics of skeletal muscles in CP and propose areas where future work is needed to understand these interactions, particularly the link between neural insult and cell-level manifestation of CP.

Reduced Cross-Sectional Muscle Growth Six Months after Botulinum Toxin Type-A Injection in Children with Spastic Cerebral Palsy

Botulinum Neurotoxin type-A (BoNT-A) injections are widely used as first-line spasticity treatment in spastic cerebral palsy (SCP). Despite improved clinical outcomes, concerns regarding harmful effects on muscle morphology have been raised. Yet, the risk of initiating BoNT-A to reduce muscle growth remains unclear. This study investigated medial gastrocnemius (MG) morphological muscle growth in children with SCP (n = 26, median age of 5.2 years (3.5)), assessed by 3D-freehand ultrasound prior to and six months post-BoNT-A injections. Post-BoNT-A MG muscle growth of BoNT-A naive children (n = 11) was compared to (a) muscle growth of children who remained BoNT-A naive after six months (n = 11) and (b) post-BoNT-A follow-up data of children with a history of BoNT-A treatment (n = 15). Six months after initiating BoNT-A injection, 17% decrease in mid-belly cross-sectional area normalized to skeletal growth and 5% increase in echo-intensity were illustrated. These muscle outcomes were only significantly altered when compared with children who remained BoNT-A naive (+4% and -3%, respectively, p < 0.01). Muscle length growth persevered over time. This study showed reduced cross-sectional growth post-BoNT-A treatment suggesting that re-injections should be postponed at least beyond six months. Future research should extend follow-up periods investigating muscle recovery in the long-term and should include microscopic analysis.

Using both electromyography and movement disorder assessment improved the classification of children with dyskinetic cerebral palsy

AIM

Children with dyskinetic cerebral palsy (CP) are often severely affected and effective treatment is difficult, due to different underlying disease mechanisms. Comprehensive systematic movement disorder evaluations were carried out on patients with this disorder.

METHODS

Patients born from 1995 to 2007 were identified from the Danish Cerebral Palsy Register and referrals to the neuropaediatric centre, Rigshospitalet, Copenhagen. They were classified by gross motor function, manual functional ability, communication ability, dystonia and spasticity. Electromyography was carried out on the upper and lower limbs. Magnetic resonance imaging scans were revised, and aetiological searches for underlying genetic disorders were performed.

RESULTS

We investigated 25 patients with dyskinetic CP at a mean age of 11.7 years. Dystonia, spasticity and rigidity were found in the upper limbs of 21, four and six children, respectively, and in the lower limbs of 18, 18 and three children. The mean total Burke-Fahn-Marsden score for dystonia was 45.02, and the mean Disability Impairment Scale level was 38% for dystonia and 13% for choreoathetosis. Sustained electromyography activity was observed in 20/25 children. Stretching increased electromyography activity more in children with spasticity. There were 10 re-classifications.

CONCLUSION

The children had heterogenic characteristics, and 40% were reclassified after systematic movement disorder evaluation.

Typical m. triceps surae morphology and architecture measurement from 0 to 18 years: A narrative review

The aim of this review was to report on the imaging modalities used to assess morphological and architectural properties of the m. triceps surae muscle in typically developing children, and the available reliability analyses. Scopus and MEDLINE (Pubmed) were searched systematically for all original articles published up to September 2020 measuring morphological and architectural properties of the m. triceps surae in typically developing children (18 years or under). Thirty eligible studies were included in this analysis, measuring fibre bundle length (FBL) (n = 11), pennation angle (PA) (n = 10), muscle volume (MV) (n = 16) and physiological cross‐sectional area (PCSA) (n = 4). Three primary imaging modalities were utilised to assess these architectural parameters in vivo: two‐dimensional ultrasound (2DUS; n = 12), three‐dimensional ultrasound (3DUS; n = 9) and magnetic resonance imaging (MRI; n = 6). The mean age of participants ranged from 1.4 years to 18 years old. There was an apparent increase in m. gastrocnemius medialis MV and pCSA with age; however, no trend was evident with FBL or PA. Analysis of correlations of muscle variables with age was limited by a lack of longitudinal data and methodological variations between studies affecting outcomes. Only five studies evaluated the reliability of the methods. Imaging methodologies such as MRI and US may provide valuable insight into the development of skeletal muscle from childhood to adulthood; however, variations in methodological approaches can significantly influence outcomes. Researchers wishing to develop a model of typical muscle development should carry out longitudinal architectural assessment of all muscles comprising the m. triceps surae utilising a consistent approach that minimises confounding errors.

Stimuli for Adaptations in Muscle Length and the Length Range of Active Force Exertion-A Narrative Review

Treatment strategies and training regimens, which induce longitudinal muscle growth and increase the muscles’ length range of active force exertion, are important to improve muscle function and to reduce muscle strain injuries in clinical populations and in athletes with limited muscle extensibility. Animal studies have shown several specific loading strategies resulting in longitudinal muscle fiber growth by addition of sarcomeres in series. Currently, such strategies are also applied to humans in order to induce similar adaptations. However, there is no clear scientific evidence that specific strategies result in longitudinal growth of human muscles. Therefore, the question remains what triggers longitudinal muscle growth in humans. The aim of this review was to identify strategies that induce longitudinal human muscle growth. For this purpose, literature was reviewed and summarized with regard to the following topics: (1) Key determinants of typical muscle length and the length range of active force exertion; (2) Information on typical muscle growth and the effects of mechanical loading on growth and adaptation of muscle and tendinous tissues in healthy animals and humans; (3) The current knowledge and research gaps on the regulation of longitudinal muscle growth; and (4) Potential strategies to induce longitudinal muscle growth. The following potential strategies and important aspects that may positively affect longitudinal muscle growth were deduced: (1) Muscle length at which the loading is performed seems to be decisive, i.e., greater elongations after active or passive mechanical loading at long muscle length are expected; (2) Concentric, isometric and eccentric exercises may induce longitudinal muscle growth by stimulating different muscular adaptations (i.e., increases in fiber cross-sectional area and/or fiber length). Mechanical loading intensity also plays an important role. All three training strategies may increase tendon stiffness, but whether and how these changes may influence muscle growth remains to be elucidated. (3) The approach to combine stretching with activation seems promising (e.g., static stretching and electrical stimulation, loaded inter-set stretching) and warrants further research. Finally, our work shows the need for detailed investigation of the mechanisms of growth of pennate muscles, as those may longitudinally grow by both trophy and addition of sarcomeres in series.

Assessment of dental caries in children with organic lesions of the nervous system using ICDAS II criteria

Studies of the dental status of children with cerebral palsy (CP) indicate a high prevalence and intensity of damage to the hard tissues of the teeth. The risk of developing dental diseases is known to increase significantly as the severity of neurological symptoms increase. The purpose of the study was to assess the incidence of dental caries using the International Caries Detection and Assessment System (ICDAS II) criteria in children with organic diseases of the nervous system depending on the severity of motor impairment. A number of 122 children (mean age 8.8±3.7 years) with spastic forms of cerebral palsy were examined. They were divided into groups according to the Gross Motor Function Classification System – Expanded & Revised (GMFCS-ER). All patients underwent a neurological examination, and the state of dental caries was determined using the ICDAS II criteria. In children with cerebral palsy, lesions of the occlusal surfaces of the teeth predominate, lesions of the proximal surfaces appeared to be three times less, but more than three times higher than in healthy children. Higher intensity of the carious process and the frequency of deep cavities are observed in children with cerebral palsy with severe motor impairment, according to GMFCS-ER. Establishing the features of caries development in children with cerebral palsy depending on the severity of neurological symptoms according to the ICDAS II system is an essential factor in determining the direction of preventive measures that should be taken for this group of children.

Muscle architecture and passive lengthening properties of the gastrocnemius medialis and Achilles tendon in children who idiopathically toe-walk

Children who idiopathically toe-walk (ITW) habitually operate at greater plantarflexion angles and thus, at shorter muscle-tendon unit (MTU) lengths than typically developing (TD) children. Therefore, it is often assumed that habitual use of the gastrocnemius muscle in this way will cause remodelling of the muscle-tendon architecture compared to TD children. However, the gastrocnemius muscle architecture of children who ITW has never been measured. It is essential that we gain a better understanding of these muscle-tendon properties, to ensure that appropriate clinical interventions can be provided for these children. Five children who ITW (age 8 ± 2 years) and 14 TD children (age 10 ± 2 years) participated in this study. Ultrasound was combined with isokinetic dynamometry and surface electromyography, to measure muscle architecture at common positions and passive lengthening properties of the gastrocnemius muscle and tendon across full range of motion. Regardless of which common condition groups were compared under, both the absolute and normalised to MTU muscle belly and fascicle lengths were always longer, and the Achilles tendon length was always shorter in children who ITW than TD children (p < 0.05; large effect sizes). The passive lengthening properties of the muscle and tendon were not different between groups (p > 0.05); however, passive joint stiffness was greater in children who ITW at maximum dorsiflexion (p = 0.001) and at a joint moment common to all participants (p = 0.029). Consequently, the findings of this pilot study indicate a remodelling of the relative MTU that does not support the concept that children who ITW commonly experience muscle shortening. Therefore, greater consideration of the muscle and tendon properties are required when prescribing clinical interventions that aim to lengthen the MTU, and treatments may be better targeted at the Achilles tendon in children who ITW.

Skeletal muscle maximal mitochondrial activity in ambulatory children with cerebral palsy

AIM

To compare skeletal muscle mitochondrial enzyme activity and mitochondrial content between independently ambulatory children with cerebral palsy (CP) and typically developing children.

METHOD

Gracilis biopsies were obtained from 12 children during surgery (n=6/group, children with CP: one female, five males, mean age 13y 4mo, SD 5y 1mo, 4y 1mo-17y 10mo; typically developing children: three females, three males, mean age 16y 5mo, SD 1y 4mo, 14y 6mo-18y 2mo). Spectrophotometric enzymatic assays were used to evaluate the activity of mitochondrial electron transport chain complexes. Mitochondrial content was evaluated using citrate synthase assay, mitochondrial DNA copy number, and immunoblots for specific respiratory chain proteins.

RESULTS

Maximal enzyme activity was significantly (50-80%) lower in children with CP versus typically developing children, for complex I (11nmol/min/mg protein, standard error of the mean [SEM] 1.7 vs 20.7nmol/min/mg protein, SEM 4), complex II (6.9nmol/min/mg protein, SEM 1.2 vs 21nmol/min/mg protein, SEM 2.7), complex III (31.9nmol/min/mg protein, SEM 7.4 vs 72.7nmol/min/mg protein, SEM 7.2), and complex I+III (7.4nmol/min/mg protein, SEM 2.5 vs 31.8nmol/min/mg protein, SEM 9.3). Decreased electron transport chain activity was not the result of lower mitochondrial content.

INTERPRETATION

Skeletal muscle mitochondrial electron transport chain enzymatic activity but not mitochondrial content is reduced in independently ambulatory children with CP. Decreased mitochondrial oxidative capacity might explain reported increased energetics of movement and fatigue in ambulatory children with CP. What this paper adds Skeletal muscle mitochondrial electron transport chain enzymatic activity is reduced in independently ambulatory children with cerebral palsy (CP). Mitochondrial content appears to be similar between children with CP and typically developing children.

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.

The Contribution of Decreased Muscle Size to Muscle Weakness in Children With Spastic Cerebral Palsy

Muscle weakness is a common clinical symptom in children with spastic cerebral palsy (SCP). It is caused by impaired neural ability and altered intrinsic capacity of the muscles. To define the contribution of decreased muscle size to muscle weakness, two cohorts were recruited in this cross-sectional investigation: 53 children with SCP [median age, 8.2 (IQR, 4.1) years, 19/34 uni/bilateral] and 31 children with a typical development (TD) [median age, 9.7 (IQR, 2.9) years]. Muscle volume (MV) and muscle belly length for m. rectus femoris, semitendinosus, gastrocnemius medialis, and tibialis anterior were defined from three-dimensional freehand ultrasound acquisitions. A fixed dynamometer was used to assess maximal voluntary isometric contractions for knee extension, knee flexion, plantar flexion, and dorsiflexion from which maximal joint torque (MJT) was calculated. Selective motor control (SMC) was assessed on a 5-point scale for the children with SCP. First, the anthropometrics, strength, and muscle size parameters were compared between the cohorts. Significant differences for all muscle size and strength parameters were found (p ≤ 0.003), except for joint torque per MV for the plantar flexors. Secondly, the associations of anthropometrics, muscle size, gross motor function classification system (GMFCS) level, and SMC with MJT were investigated using univariate and stepwise multiple linear regressions. The associations of MJT with growth-related parameters like age, weight, and height appeared strongest in the TD cohort, whereas for the SCP cohort, these associations were accompanied by associations with SMC and GMFCS. The stepwise regression models resulted in ranges of explained variance in MJT from 29.3 to 66.3% in the TD cohort and from 16.8 to 60.1% in the SCP cohort. Finally, the MJT deficit observed in the SCP cohort was further investigated using the TD regression equations to estimate norm MJT based on height and potential MJT based on MV. From the total MJT deficit, 22.6–57.3% could be explained by deficits in MV. This investigation confirmed the disproportional decrease in muscle size and muscle strength around the knee and ankle joint in children with SCP, but also highlighted the large variability in the contribution of muscle size to muscle weakness.

Stretch-induced satellite cell deformation incontracturedmuscles in children with cerebral palsy

Satellite cells (SCs) are quiescent, adult skeletal muscle stem cells responsible for postnatal muscle growth and repair. Children with cerebral palsy (CP) have muscle contractures with reduced SC abundance, extracellular matrix abnormalities and reduced serial sarcomere number resulting in greatly increased in vivo sarcomere length, perhaps due to impaired sarcomere addition, compared to children with typical development (TD). Stretch is a strong activator of SCs that leads to addition of sarcomeres during bone-muscle growth. Mechanical loading and subsequent deformation of intracellular structures can lead to activation and proliferation, perhaps by cytoskeletal transmissions of extracellular mechanical signals to the nuclei. The primary aim of this study was to determine the effect of ex vivo stretch-induced sarcomere length change on SC deformation in children with CP and TD. Muscle biopsies were obtained from twelve children (7 CP, 5 TD) during surgery. Fiber bundles were labeled with fluorescent antibodies for Pax7 (SC), DRAQ5 (nuclei), and alpha-actinin (sarcomere protein). Fibers were stretched using a custom jig and imaged using confocal microscopy. SC nuclear length, height and aspect ratio underwent increased deformation with increasing sarcomere length (p < 0.05) in both groups. Slopes of association for SC nuclear length, aspect ratio and sarcomere lengths were similar between CP and TD. Our results indicate that SC in children with CP undergo similar deformation as TD across sarcomere lengths.

Long-term BTX-A effects on bi-articular muscle: Higher passive force, limited length range of active force production and unchanged intermuscular interactions

Botulinum toxin type-A (BTX-A) is commonly used for spasticity management aiming at reducing joint stiffness and increasing joint range of motion in CP patients. However, previous animal studies showed acutely increased passive forces and a narrowerlength range of active force exertion (l_range) for muscles exposed. BTX-A can spread affecting mechanics of several muscles in a compartment, but it was shown acutely to diminishepimuscular myofascial force transmission (EMFT). Yet, our understanding of these effects in the long-term is limited and they need to be tested in a bi-articular muscle. The goal was to test the following hypotheses in a long-term rat model: exposure to BTX-A (i) has no effects onl_rangeand passive forces of bi-articular extensor digitorum longus (EDL) muscle and (ii) diminishes EMFT. Male Wistar rats were divided into two groups: BTX-A and control (0.1 units of BTX-A or only saline was injected into the tibialis anterior). Isometric proximal and distal EDL forces were measured simultaneously, one-month post-injection. Proximally and distally lengthening the muscle showed that BTX-A causes a significantly narrowerl_range(by 14.7% distally and 32.2% proximally) and significantly increased passive muscle forces (over 2-fold both distally and proximally). Altering muscle position at constant length showed that BTX-A does not change EMFT. The findings reject both hypotheses showing that long-term exposure to BTX-A compromises bi-articular muscle's contribution to motion for both joints and the muscle's mechanical interaction with the surroundings remains unaffected. These effects which may compromise long-term spasticity management should be studied in CP patients.

COpenhagen Neuroplastic TRaining Against Contractures in Toddlers (CONTRACT): protocol of an open-label randomised clinical trial with blinded assessment for prevention of contractures in infants with high risk of cerebral palsy

INTRODUCTION

Contractures are frequent causes of reduced mobility in children with cerebral palsy (CP) already at the age of 2-3 years. Reduced muscle use and muscle growth have been suggested as key factors in the development of contractures, suggesting that effective early prevention may have to involve stimuli that can facilitate muscle growth before the age of 1 year. The present study protocol was developed to assess the effectiveness of an early multicomponent intervention, CONTRACT, involving family-oriented and supervised home-based training, diet and electrical muscle stimulation directed at facilitating muscle growth and thus reduce the risk of contractures in children at high risk of CP compared with standard care.

METHODS AND ANALYSIS

A two-group, parallel, open-label randomised clinical trial with blinded assessment (n=50) will be conducted. Infants diagnosed with CP or designated at high risk of CP based on abnormal neuroimaging or absent fidgety movement determined as part of General Movement Assessment, age 9-17 weeks corrected age (CA) will be recruited. A balanced 1:1 randomisation will be made by a computer. The intervention will last for 6 months aiming to support parents in providing daily individualised, goal-directed activities and primarily in lower legs that may stimulate their child to move more and increase muscle growth. Guidance and education of the parents regarding the nutritional benefits of docosahexaenic acid (DHA) and vitamin D for the developing brain and muscle growth will be provided. Infants will receive DHA drops as nutritional supplements and neuromuscular stimulation to facilitate muscle growth. The control group will receive standard care as offered by their local hospital or community. Outcome measures will be taken at 9, 12, 18, 24, 36 and 48 months CA. Primary and secondary outcome measure will be lower leg muscle volume and stiffness of the triceps surae musculotendinous unit together with infant motor profile, respectively.

ETHICS AND DISSEMINATION

Full approval from the local ethics committee, Danish Committee System on Health Research Ethics, Region H (H-19041562). Experimental procedures conform with the Declaration of Helsinki.

TRIAL REGISTRATION NUMBER

NCT04250454.

EXPECTED RECRUITMENT PERIOD

1 January 2021-1 January 2025.

Mechanical properties of ankle joint and gastrocnemius muscle in spastic children with unilateral cerebral palsy measured with shear wave elastography

The aim of this study was to describe passive mechanical and morphological properties of the ankle joint and gastrocnemius medialis (GM) muscle in paretic and contralateral legs in highly functional children with unilateral cerebral palsy (UCP) using shear wave elastography (SWE). SWE measurements on the GM muscle were performed in both paretic and contralateral legs during passive ankle dorsiflexion using a dynamometer in 11 children (mean age: 10 years 6 months) with UCP. Torque-angle and shear modulus-angle relationships were fitted using an exponential model to determine passive ankle joint and GM muscle stiffness respectively. Based on shear-modulus-angle relationship, slack angle and shear modulus of GM muscle were compared between legs. GM and Achilles tendon length were determined at rest using ultrasonography. No significant difference was found between legs for passive ankle joint (p = 0.26; 11.2%; 95 %CI: 31.9, -9.4) and GM muscle passive stiffness (p = 0.62; -4.4%; 95 %CI: 14.7, -23.4). GM shear modulus at a common angle was significantly higher on the paretic leg (p = 0.02; +56.5%; 95 %CI: 100.5, 12.6). GM slack angle on the paretic leg was significantly shifted to a more plantarflexed position (p = 0.04; +25.5%; 95 %CI: 49.7, 1.3) and this was associated with a non-significant lower muscle length compared to the contralateral leg (p = 0.05; -4.5%; 95 %CI: -0.4, -8.7). Increased passive tension on the paretic leg when compared to the contralateral one may be explained in large part by muscle shortening. The role of altered mechanical properties remains unknown.

Reliability of Shear Wave Elastography and Ultrasound Measurement in Children with Unilateral Spastic Cerebral Palsy

In clinical practice, few data exist on the feasibility of performing reliable shear wave elastography (SWE) and ultrasonography (US) measurements in spastic muscles of children with cerebral palsy (CP). Ten children with unilateral CP took part in SWE and US assessment of the tibialis anterior and medialis gastrocnemius muscles during two sessions separated by a 1-wk interval. Intra- and inter-investigator reliability of shear modulus (µ) and muscle thickness (MT) measurements, at neutral and maximal dorsiflexion angles on both legs, was assessed by two investigators with different levels of experience. Reliability was assessed with the coefficient of variation (CV), standard error of measurement and intra-class correlation coefficient (ICC). Reliability of the µ measurement was insufficient, regardless of angle position (CV >10% and >20% for neutral and maximal dorsiflexion angles, respectively). The intra- and inter-investigator reliability of MT measurements was good (CV >10%, ICC >0.74) for both muscles in both legs. SWE measurements must be performed using a rigorous standardized protocol while MT should be considered an important parameter to monitor change in muscle morphology.

Musculoskeletal Pathology in Cerebral Palsy: A Classification System and Reliability Study

This article presents a classification of lower limb musculoskeletal pathology (MSP) for ambulant children with cerebral palsy (CP) to identify key features from infancy to adulthood. The classification aims to improve communication, and to guide referral for interventions, which if timed appropriately, may optimise long-term musculoskeletal health and function. Consensus was achieved by discussion between staff in a Motion Analysis Laboratory (MAL). A four-stage classification system was developed: Stage 1: Hypertonia: Abnormal postures are dynamic. Stage 2: Contracture: Fixed shortening of one or more muscle-tendon units. Stage 3: Bone and joint deformity: Torsional deformities and/or joint instability (e.g., hip displacement or pes valgus), usually accompanied by contractures. Stage 4: Decompensation: Severe pathology where restoration of optimal joint and muscle-tendon function is not possible. Reliability of the classification was tested using the presentation of 16 clinical cases to a group of experienced observers, on two occasions, two weeks apart. Reliability was found to be very good to excellent, with mean Fleiss' kappa ranging from 0.72 to 0.84. Four-stages are proposed to classify lower limb MSP in children with CP. The classification was reliable in a group of clinicians who work together. We emphasise the features of decompensated MSP in the lower limb, which may not always benefit from reconstructive surgery and which can be avoided by timely intervention.

Measuring skeletal muscle morphology and architecture with imaging modalities in children with cerebral palsy: a scoping review

AIM

To investigate the use of ultrasound and magnetic resonance imaging (MRI) methodologies to assess muscle morphology and architecture in children with cerebral palsy (CP).

METHOD

A scoping review was conducted with systematic searches of Medline, Embase, Scopus, Web of Science, PubMed, and PsycInfo for all original articles published up to January 2019 utilizing ultrasound and/or MRI to determine morphological and architectural properties of lower limb skeletal muscle in children with CP.

RESULTS

Eighty papers used ultrasound (n=44), three-dimensional ultrasound (n=16), or MRI (n=20) to measure at least one muscle parameter in children and adolescents with CP. Most research investigated single muscles, predominantly the medial gastrocnemius muscle, included children classified in Gross Motor Function Classification System levels I (n=62) and II (n=65), and assessed fascicle length (n=35) and/or muscle volume (n=35). Only 21 papers reported reliability of imaging techniques. Forty-six papers assessed measures of Impairment (n=39), Activity (n=24), and Participation (n=3).

INTERPRETATION

Current research study design, variation in methodology, and preferences towards investigation of isolated muscles may oversimplify the complexities of CP muscle but provide a foundation for the understanding of the changes in muscle parameters in children with CP.

WHAT THIS PAPER ADDS

Current evidence is biased towards the medial gastrocnemius muscle and more functionally able children with cerebral palsy (CP). Variations in imaging techniques and joint positioning limit comparisons between studies. Clinimetric testing of parameters of CP muscle is not always considered. Assessment of parameter(s) of muscle with measures of participation is sparse.

Muscle Characteristics in Pediatric Hereditary Spastic Paraplegia vs. Bilateral Spastic Cerebral Palsy: An Exploratory Study

Hereditary spastic paraplegia (HSP) is a neurological, genetic disorder that predominantly presents with lower limb spasticity and muscle weakness. Pediatric pure HSP types with infancy or childhood symptom onset resemble in clinical presentation to children with bilateral spastic cerebral palsy (SCP). Hence, treatment approaches in these patient groups are analogous. Altered muscle characteristics, including reduced medial gastrocnemius (MG) muscle growth and hyperreflexia have been quantified in children with SCP, using 3D-freehand ultrasound (3DfUS) and instrumented assessments of hyperreflexia, respectively. However, these muscle data have not yet been studied in children with HSP. Therefore, we aimed to explore these MG muscle characteristics in HSP and to test the hypothesis that these data differ from those of children with SCP and typically developing (TD) children. A total of 41 children were retrospectively enrolled including (1) nine children with HSP (ages of 9–17 years with gross motor function levels I and II), (2) 17 age-and severity-matched SCP children, and (3) 15 age-matched typically developing children (TD). Clinically, children with HSP showed significantly increased presence and severity of ankle clonus compared with SCP (p = 0.009). Compared with TD, both HSP and SCP had significantly smaller MG muscle volume normalized to body mass (p ≤ 0.001). Hyperreflexia did not significantly differ between the HSP and SCP group. In addition to the observed pathological muscle activity for both the low-velocity and the change in high-velocity and low-velocity stretches in the two groups, children with HSP tended to present higher muscle activity in response to increased stretch velocity compared with those with SCP. This exploratory study is the first to reveal MG muscle volume deficits in children with HSP. Moreover, high-velocity-dependent hyperreflexia and ankle clonus is observed in children with HSP. Instrumented impairment assessments suggested similar altered MG muscle characteristics in pure HSP type with pediatric onset compared to bilateral SCP. This finding needs to be confirmed in larger sample sizes. Hence, the study results might indicate analogous treatment approaches in these two patient groups.

Exercise intervention protocol in children and young adults with cerebral palsy: the effects of strength, flexibility and gait training on physical performance, neuromuscular mechanisms and cardiometabolic risk factors (EXECP)

Background

Individuals with cerebral palsy (CP) have problems in everyday tasks such as walking and climbing stairs due to a combination of neuromuscular impairments such as spasticity, muscle weakness, reduced joint flexibility and poor coordination. Development of evidence-based interventions are in pivotal role in the development of better targeted rehabilitation of CP, and thus in maintaining their motor function and wellbeing. Our aim is to investigate the efficacy of an individually tailored, multifaceted exercise intervention (EXECP) in children and young adults with CP. EXECP is composed of strength, flexibility and gait training. Furthermore, this study aims to verify the short-term retention of the adaptations three months after the end of the EXECP intervention.

Methods

Twenty-four children and young adults with spastic CP will be recruited to participate in a 9-month research project with a 3-month training intervention, consisting of two to three 90-min sessions per week. In each session, strength training for the lower limbs and trunk muscles, flexibility training for the lower limbs and inclined treadmill gait training will be performed. We will evaluate muscle strength, joint flexibility, neuromuscular and cardiometabolic parameters. A nonconcurrent multiple baseline design with two pre-tests and two post-tests all interspaced by three months is used. In addition to the CP participants, 24 typically developing age and sex-matched participants will perform the two pre-tests (i.e. no intervention) to provide normative data.

Discussion

This study has a comprehensive approach examining longitudinal effects of wide variety of variables ranging from physical activity and gross motor function to sensorimotor functions of the brain and neuromuscular and cardiometabolic parameters, providing novel information about the adaptation mechanisms in cerebral palsy. To the best of our knowledge, this is the first intervention study providing supervised combined strength, flexibility and gait training for young individuals with CP.

Trial registration number

ISRCTN69044459, prospectively registered (21/04/2017).

The size and echogenicity of the tibialis anterior muscle is preserved in both limbs in young children with unilateral spastic cerebral palsy

PURPOSE

The primary of this study was to compare the volume, length, echo intensity, and growth rate of the medial gastrocnemius (MG) and tibialis anterior (TA) muscle of both limbs (more-involved and less-involved) in children with unilateral spastic cerebral palsy (USCP), with those of an age-matched typically developing (TD) group. A secondary aim in the USCP group was to explore the associations between these muscle parameters and discrete ankle positions during phase of gait.

METHODS

Muscle parameters were assessed using 3D ultrasound. Maximal ankle dorsiflexion in stance and swing during walking were determined from 2D video analysis. Group differences in muscle size and echo intensity were assessed using a two-way analysis of covariance (age-by-group), with the interaction term used to compare muscle growth rates. Associations between muscle parameters and maximal ankle dorsiflexion in stance and swing were assessed using backwards multiple linear regression analyses.

RESULTS

The MG of both limbs in children with USCP had signs of impaired muscle development (smaller volume and length, higher echo intensity and lower growth rate). There was no evidence of impaired muscle development of TA between limbs or compared the TD children. Tibialis anterior volume, length, echo intensity and MG volume explained 66% and 83% of the variance in maximal ankle dorsiflexion position in the stance and swing phases of walking, respectively.

CONCLUSIONS

Unlike the MG, the TA volume and growth rate in children with USCP are equivalent between limbs and compared to TD children. For the more-involved limb only, TA volume, length, and echo intensity appear associated with maximal ankle dorsiflexion during walking and represent important muscle parameters that could be targeted in with early exercise therapy.Implications for rehabilitationTibialis anterior (TA) size and echogenicity appear normal in both limbs in young children with unilateral spastic cerebral palsy (USCP); findings that could indicate sufficient mechanical stimulus and muscle anabolism to maintain normal muscle growth.Tibialis anterior size and echogenicity are associated with maximal ankle dorsiflexion in both stance and swing phase of walking in young children with USCP; though such relations appear isolated to the more-involved limb.Early therapeutic interventions that target TA are likely to be successful in maintaining muscle size and may offset the negative effects of medial gastrocnemius atrophy in the development of fixed ankle equinus of the more-involved limb and improve ankle positioning during gait.

Clinical Relevance of State-of-the-Art Analysis of Surface Electromyography in Cerebral Palsy

Surface electromyography (sEMG) can be used to assess the integrity of the neuromuscular system and its impairment in neurological disorders. Here we will consider several issues related to the current clinical applications, difficulties and limited usage of sEMG for the assessment and rehabilitation of children with cerebral palsy. The uniqueness of this methodology is that it can determine hyperactivity or inactivity of selected muscles, which cannot be assessed by other methods. In addition, it can assist for intervention or muscle/tendon surgery acts, and it can evaluate integrated functioning of the nervous system based on multi-muscle sEMG recordings and assess motor pool activation. The latter aspect is especially important for understanding impairments of the mechanisms of neural controllers rather than malfunction of individual muscles. Although sEMG study is an important tool in both clinical research and neurorehabilitation, the results of a survey on the clinical relevance of sEMG in a typical department of pediatric rehabilitation highlighted its limited clinical usage. We believe that this is due to limited knowledge of the sEMG and its neuromuscular underpinnings by many physiotherapists, as a result of lack of emphasis on this important methodology in the courses taught in physical therapy schools. The lack of reference databases or benchmarking software for sEMG analysis may also contribute to the limited clinical usage. Despite the existence of educational and technical barriers to a widespread use of, sEMG does provide important tools for planning and assessment of rehabilitation treatments for children with cerebral palsy.

Gastrocnemius Medialis Muscle Geometry and Extensibility in Typically Developing Children and Children With Spastic Paresis Aged 6-13 Years

Gait of children with spastic paresis (SP) is frequently characterized by a reduced ankle range of motion, presumably due to reduced extensibility of the triceps surae (TS) muscle. Little is known about how morphological muscle characteristics in SP children are affected. The aim of this study was to compare gastrocnemius medialis (GM) muscle geometry and extensibility in children with SP with those of typically developing (TD) children and assess how GM morphology is related to its extensibility. Thirteen children with SP, of which 10 with a diagnosis of spastic cerebral palsy and three with SP of unknown etiology (mean age 9.7 ± 2.1 years; GMFCS: I-III), and 14 TD children (mean age 9.3 ± 1.7 years) took part in this study. GM geometry was assessed using 3D ultrasound imaging at 0 and 4 Nm externally imposed dorsal flexion ankle moments. GM extensibility was defined as its absolute length change between the externally applied 0 and 4 Nm moments. Anthropometric variables and GM extensibility did not differ between the SP and TD groups. While in both groups, GM muscle volume correlated with body mass, the slope of the regression line in TD was substantially higher than that in SP (TD = 3.3 ml/kg; SP = 1.3 ml/kg, p < 0.01). In TD, GM fascicle length increased with age, lower leg length and body mass, whereas in SP children, fascicle length did not correlate with any of these variables. However, the increase in GM physiological cross-sectional area as a function of body mass did not differ between SP and TD children. Increases in lengths of tendinous structures in children with SP exceeded those observed in TD children (TD = 0.85 cm/cm; SP = 1.16 cm/cm, p < 0.01) and even exceeded lower-leg length increases. In addition, only for children with SP, body mass (r = -0.61), height (r = -0.66), muscle volume (r = - 0.66), physiological cross-sectional area (r = - 0.59), and tendon length (r = -0.68) showed a negative association with GM extensibility. Such negative associations were not found for TD children. In conclusion, physiological cross-sectional area and length of the tendinous structures are positively associated with age and negatively associated with extensibility in children with SP.

Mechanisms of reduced plantarflexor function in Cerebral palsy: smaller triceps surae moment arm and reduced muscle force

Both muscle forces, and moment arm (MA) could contribute to reduced muscle moment in people with Cerebral Palsy (CP). Current reports in CP are conflicting. The tendon travel method of estimating MA requires constant force, but passive force is high and variable in CP, and range of motion is limited. Therefore, the purpose of this study was to examine triceps surae muscle MA in 12 subjects with mild to moderate CP (15-32 years) and 10 typically developing peers (TD, 17-26 years) by tendon travel and by visually measuring the apparent MA. MA was calculated at 90° and at a reference angle (∼106°) with zero net passive moment. The tendon travel (28.8 ± 5.6 mm) and visual methods (29.1 ± 5.5 mm) yielded similar MA in CP (p = 0.94) at the reference angle. TD had significantly larger triceps surae muscle MA than CP subjects (p = 0.002), 35.4 ± 4.1 mm at the reference angle for tendon travel and 35.4 ± 3.6 mm by the visual method. Test/retest revealed less bias (0.8 mm) using the visual method. Calculated active peak isometric force was significantly less in CP (1983.8 ± 887.0 N) than TD (4104.9 ± 1154.9 N, p < 0.001). There are challenges in estimating MA in CP, but the visual method is more reliable. Although a shorter moment arm would reduce the joint moment, joint angular velocity for a given velocity of muscle shortening would be enhanced. Strength training may mitigate the effects of the smaller moment arm and reduced joint moment generated in those with CP.

Immobilization leads to reduced stretch reflexes but increased central reflex gain in the rat

Plastic adaptations are known to take place in muscles, tendons, joints, and the nervous system in response to changes in muscle activity. However, few studies have addressed how these plastic adaptations are related. Thus this study focuses on changes in the mechanical properties of the ankle plantarflexor muscle-tendon unit, stretch reflex activity, and spinal neuronal pathways in relation to cast immobilization. The left rat hindlimb from toes to hip was immobilized with a plaster cast for 1, 2, 4, or 8 wk followed by acute electrophysiological recordings to investigate muscle stiffness and stretch reflex torque. Moreover, additional acute experiments were performed after 4 wk of immobilization to investigate changes in the central gain of the stretch reflex. Monosynaptic reflexes (MSR) were recorded from the L4 and L5 ventral roots following stimulation of the corresponding dorsal roots. Rats developed reduced range of movement in the ankle joint 2 wk after immobilization. This was accompanied by significant increases in the stiffness of the muscle-tendon complex as well as an arthrosis at the ankle joint at 4 and 8 wk following immobilization. Stretch reflexes were significantly reduced at 4-8 wk following immobilization. This was associated with increased central gain of the stretch reflex. These data show that numerous interrelated plastic changes occur in muscles, connective tissue, and the central nervous system in response to changes in muscle use. The findings provide an understanding of coordinated adaptations in multiple tissues and have important implications for prevention and treatment of the negative consequences of immobilization following injuries of the nervous and musculoskeletal systems.NEW & NOTEWORTHY Immobilization leads to multiple simultaneous adaptive changes in muscle, connective tissue, and central nervous system.

Systematic Review of Instrumented Measures of Skeletal Muscle Mechanical Properties: Evidence for the Application of Shear Wave Elastography with Children

The aim of this review was to identify instrumented devices that quantify skeletal muscle mechanical properties and to evaluate their potential clinical utility and clinimetric evidence with respect to children. Four databases were searched to identify articles reporting original clinimetric data for devices measuring muscle stiffness or elastic modulus, along a muscle's main fibre direction. Clinimetric evidence was rated using the Consensus-Based Standard for the Selection of Measurement Instruments (COSMIN) checklist. Sixty-five articles provided clinimetric data for two devices meeting our criteria: the Aixplorer and the Acuson. Both are shear wave elastography devices that determine the shear modulus of muscle tissue. The Aixplorer had strong construct validity and reliability, and the Acuson, moderate construct validity and reliability. Both devices have sound clinical utility with non-invasive application at various joint positions and data acquisition in real time, minimizing fatigue. Further research is warranted to evaluate utility for children with specific disorders of abnormal muscle structure or function.

Effect of an interval rehabilitation program with home-based, vibration-assisted training on the development of muscle and bone in children with cerebral palsy - an observational study

Objectives In children with cerebral palsy (CP), the most common cause of physical impairment in childhood, less muscle and bone growth has been reported, when compared with typically developing children. The aim of this study was to evaluate the effect of an intensive rehabilitation program including physiotherapy in combination with 6 months of home-based, vibration-assisted training on muscle and bone growth in children with CP. Methods We included children with CP, who participated in a rehabilitation program utilizing whole-body vibration (WBV). Muscle mass was quantified by appendicular lean mass index (App-LMI) and bone mass by total-body-less-head bone mineral content (TBLH-BMC) assessed by Dual-energy X-ray absorptiometry (DXA) at the beginning of rehabilitation and one year later. To assess the functional muscle-bone unit, the relation of TBLH-BMC to TBLH lean body mass (TBLH-LBM) was used. Results The study population included 128 children (52 females, mean age 11.9 ± 2.7). App-LMI assessed in kg/m2 increased significantly after rehabilitation. The age-adjusted Z-score for App-LMI showed no significant change. TBLH-BMC assessed in gram increased significantly. The Z-scores for TBLH-BMC decreased lesser than expected by the evaluation of the cross-sectional data at the beginning of rehabilitation. The parameter T B L H - B M C T B L H - L B M $\frac{TBLH-BMC}{TBLH-LBM}$ did not change relevantly after 12 months. Conclusions Muscle growth and to a lesser extent bone growth could be increased in children with CP. The intensive rehabilitation program including WBV seemed to have no direct effect on the bone, but the observed anabolic effect on the bone, may only been mediated through the muscle.

Over 25 Years of Pediatric Botulinum Toxin Treatments: What Have We Learned from Injection Techniques, Doses, Dilutions, and Recovery of Repeated Injections?

Botulinum toxin type A (BTXA) has been used for over 25 years in the management of pediatric lower and upper limb hypertonia, with the first reports in 1993. The most common indication is the injection of the triceps surae muscle for the correction of spastic equinus gait in children with cerebral palsy. The upper limb injection goals include improvements in function, better positioning of the arm, and facilitating the ease of care. Neurotoxin type A is the most widely used serotype in the pediatric population. After being injected into muscle, the release of acetylcholine at cholinergic nerve endings is blocked, and a temporary denervation and atrophy ensues. Targeting the correct muscle close to the neuromuscular junctions is considered essential and localization techniques have developed over time. However, each technique has its own limitations. The role of BTXA is flexible, but limited by the temporary mode of action as a focal spasticity treatment and the restrictions on the total dose deliverable per visit. As a mode of treatment, repeated BTXA injections are needed. This literature reviewed BTXA injection techniques, doses and dilutions, the recovery of muscles and the impact of repeated injections, with a focus on the pediatric population. Suggestions for future studies are also discussed.

A synthesis and appraisal of clinical practice guidelines, consensus statements and Cochrane systematic reviews for the management of focal spasticity in adults and children

Objective: To identify and appraise the existing clinical practice guidelines, consensus statements and Cochrane systematic reviews for the management of adult and paediatric focal spasticity to generate a single synthesized guideline.Methods: Systematic review of 12 electronic databases. Clinical practice guidelines, consensus statements and Cochrane systematic reviews for focal spasticity in adults and children. Included studies were appraised according to the AGREE II criteria.Results: A total of 25 papers were included in this review, comprising 12 clinical practice guidelines, nine consensus statements and four Cochrane systematic reviews. The areas most strongly endorsed were: (1) management to be provided by a multi-disciplinary team, (2) therapy should be goal-directed, (3) goals to be developed in conjunction with the patient and family, and (4) importance of follow-up evaluations. There was a greater focus on activity outcomes and classification in the paediatric papers. The guidelines varied considerably in their quality, with AGREE II scores ranging from 52.8 to 97.1%.Conclusions: This systematic review has synthesized the key elements regarding principles of focal spasticity management, outcome measures, physical interventions and educational recommendations into a single, readily applied guideline available for clinical use. Despite considerable variability in the quality of the guidelines, several strong themes emerged.Implications for rehabilitationFocal spasticity management should be multi-disciplinary, patient-centred and goal-directed.Routine measurement of impairment and activity are strongly endorsed.Botulinum toxin A injection should only be provided as part of an integrated approach to focal spasticity management.

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.

Multi-frequency bioimpedance: a non-invasive tool for muscle-health assessment of adults with cerebral palsy

Muscle contracture development is a major complication for individuals with cerebral palsy (CP) and has lifelong implications. In order to recognize contracture development early and to follow up on preventive interventions aimed at muscle health development, non-invasive, and easy to use methods are needed. The aim of the present study was to assess whether multi-frequency Bioimpedance (mfBIA) can be used to detect differences between skeletal muscle of individuals with CP and healthy controls. The mfBIA technique was applied to the medial gastrocnemius muscle of n = 24 adults with CP and n = 20 healthy controls of both genders. The phase angle (PA) and the centre frequency (fc) were significantly lower in individuals with CP when compared to controls; PA: - 25% for women and - 31.8% for men (P < 0.0001); fc: - 5.6% for women and - 5.2% for men (P < 0.009). The reactance (Xc) and the extracellular resistance (Re) of skeletal muscle from individuals with CP were significantly higher when compared to controls; Xc: + 9.9% for women and + 28.9% for men (P < 0.0001); Re: + 39.7% for women and + 91.2% for men (P < 0.0001). The present study shows that several mfBIA parameters differ significantly between individuals with CP and healthy controls. Furthermore, these changes correlated significantly with the severity of CP, as assessed using the GMFCS scale. The present data indicate that mfBIA shows promise in terms of being a useful diagnostic tool, capable of characterizing muscle health and its development in individuals with cerebral palsy.

Stretching Interventions in Children With Cerebral Palsy: Why Are They Ineffective in Improving Muscle Function and How Can We Better Their Outcome?

Hyper-resistance at the joint is one of the most common symptoms in children with cerebral palsy (CP). Alterations to the structure and mechanical properties of the musculoskeletal system, such as a decreased muscle length and an increased joint stiffness are typically managed conservatively, by means of physiotherapy involving stretching exercises. However, the effectiveness of stretching-based interventions for improving function is poor. This may be due to the behavior of a spastic muscle during stretch, which is poorly understood. The main aim of this paper is to provide a mechanistic explanation as to why the effectiveness of stretching is limited in children with CP and consider clinically relevant means by which this shortcoming can be tackled. To do this, we review the current literature regarding muscle and tendon plasticity in response to stretching in children with CP. First, we discuss how muscle and tendon interact based on their morphology and mechanical properties to provide a certain range of motion at the joint. We then consider the effect of traditional stretching exercises on these muscle and tendon properties. Finally, we examine possible strategies to increase the effectiveness of stretching therapies and we highlight areas of further research that have the potential to improve the outcome of non-invasive interventions in children with cerebral palsy.