Etiology of impaired selective motor control: emerging evidence and its implications for research and treatment in cerebral palsy

Relative phase measures of intersegmental coordination describe motor control impairments in children with cerebral palsy who exhibit stiff-knee gait

BACKGROUND

The purpose of this retrospective study was to explore lower limb intersegmental coordination as a clinically important indicator of motor control mechanisms in individuals with cerebral palsy exhibiting stiff-knee gait. We used the relative phase of thigh and foot segments around foot-off to describe motor control, given the relevance of the pre-swing phase of gait to the existence of stiff-knee gait.

METHODS

Traditional gait parameters and thigh/foot intersegmental coordination were calculated using pre-and postoperative kinematic data from a cohort of 54 subjects (92 legs) with spastic cerebral palsy. All participants had stiff-knee gait, walked without assistive devices, and underwent rectus femoris transfer surgery to improve swing period knee flexion. Analyses included correlations between a) preoperative intersegmental coordination and gait variables (knee flexion range, rate and gait performance) and b) pre-to-postoperative intersegmental coordination change and change in gait variables.

FINDINGS

Thigh/foot intersegmental coordination significantly (P < 0.001) correlated with knee flexion range, rate and walking speed. Postoperative intersegmental coordination was significantly more uncoupled than preoperative. Pre-to-postoperative intersegmental coordination improvement also significantly correlated with improvements in knee flexion range, rate and walking speed. Pre-to-postoperative changes in intersegmental coordination accounted for 43% and 36% of variance in knee flexion range change and knee flexion rate change respectively.

INTERPRETATION

Intersegmental coordination is a clinically important factor in knee flexion limitations associated with stiff-knee gait for individuals with cerebral palsy. These findings are a foundation for further study of intersegmental coordination measures as complements to traditional instrumented gait analysis.

Relationship between sensorimotor cortical activation as assessed by functional near infrared spectroscopy and lower extremity motor coordination in bilateral cerebral palsy

Background

Evaluation of task-evoked cortical responses during movement has been limited in individuals with bilateral cerebral palsy (CP), despite documented alterations in brain structure/function and deficits in motor control.

Objective

To systematically evaluate cortical activity associated with lower extremity tasks, and relate activation parameters to clinical measures in CP.

Methods

28 ambulatory participants (14 with bilateral CP and 14 with typical development) completed five motor tasks (non-dominant ankle dorsiflexion, hip flexion and leg cycling as well as bilateral dorsiflexion and cycling) in a block design while their sensorimotor cortex was monitored using functional near infrared spectroscopy (fNIRS), in addition to laboratory and clinical measures of performance.

Results

Main effects for group and task were found for extent of fNIRS activation (number of active channels; p < 0.001 and p = 0.010, respectively), magnitude of activation (sum of beta values; p < 0.001 for both), and number of active muscles (p = 0.001 and p < 0.001, respectively), but no group by task interactions. Collectively, subgroups with CP and especially those with greater impairments, showed higher extent and magnitude of cortical sensorimotor activation as well as higher amounts of concurrent activity in muscles not required for task performance. Magnitude of fNIRS activation during non-dominant dorsiflexion correlated with validated measures of selective control (r = −0.60, p = 0.03), as well as mobility and daily activity (r = −0.55, p = 0.04 and r = −0.52, p = 0.05, respectively) and self-reported gait function (r = −0.68, p = 0.01) in those with CP.

Conclusions

The association between higher activity in the sensorimotor cortex and decreased selectivity in cortical organization suggests a potential neural mechanism of motor deficits and target for intervention.

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First fNIRS comparison of a range of lower extremity tasks in children with and without bilateral CP.

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FNIRS showed a greater amount and extent of activation of sensorimotor cortices in CP.

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Greater activation correlated with a greater number of muscles involved in the task.

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fNIRS results correlated to clinical measures of motor control and function.

The validity and reliability of the Test of Arm Selective Control for children with cerebral palsy: a prospective cross-sectional study

AIM

This study examined the reliability and validity of the Test of Arm Selective Control (TASC) to examine upper extremity selective voluntary motor control in children and adolescents with all types of spastic cerebral palsy (CP).

METHOD

Fifty-six participants with CP, ranging in age from 5 years 9 months to 18 years 11 months (average 11y 7mo, SD 3y 9mo; 25 males, 31 females), participated in this prospective cross-sectional study. They were evaluated using the TASC and several clinical measures.

RESULTS

TASC and Manual Ability Classification System (r=-0.529, p<0.001), TASC and ABILHAND-Kids (r=0.596, p<0.001), and TASC and affected extremities (r=-0.486, p=0.001) were moderately correlated. There was a weak correlation between the TASC and Gross Motor Function Classification System (r=-0.363, p=0.006) and no correlation between the TASC and age (p=0.366) or rater (p=0.713). Interrater reliability for upper extremity total score (intraclass correlation coefficient [ICC]=0.92-0.94) and upper extremity limb scores (ICC=0.92-0.96) was high for two independent rater groups (p≤0.001). Average time to administer was 16 minutes, 18 seconds.

INTERPRETATION

The TASC is a reliable and valid tool for objective assessment of selective voluntary motor control. Clinically this measure may guide the selection of medical, surgical, or therapy interventions and may improve outcome prognosis.

WHAT THIS PAPER ADDS

The Test of Arm Selective Control (TASC) demonstrates a high degree of reliability and multiple aspects of validity when assessing upper extremity selective control in those with cerebral palsy. The TASC is an upper limb companion to the Selective Control Assessment of the Lower Extremity.

Are mechanically sensitive regulators involved in the function and (patho)physiology of cerebral palsy-related contractures?

Skeletal muscle tissue is mechanosensitive, as it is able to sense mechanical impacts and to translate these into biochemical signals making the tissue adapt. Among its mechanosensitive nature, skeletal muscle tissue is the largest metabolic organ of the human body. Disturbances in skeletal muscle mechanosensing and metabolism cause and contribute to many diseases, i.e. muscular dystrophies/myopathies, cardiovascular diseases, COPD or diabetes mellitus type 2. A less commonly focused muscle-related disorder is clinically known as muscle contractures that derive from cerebral palsy (CP) conditions in young and adults. Muscle contractures are characterized by gradually increasing passive muscle stiffness resulting in complete fixation of joints. Different mechanisms have been identified in CP-related contractures, i.e. altered calcium handling, altered metabolism or altered titin regulation. The muscle-related extracellular matrix (ECM), specifically collagens, plays a role in CP-related contractures. Herein, we focus on mechanically sensitive complexes, known as costameres (Cstms), and discuss their potential role in CP-related contractures. We extend our discussion to the ECM due to the limited knowledge of its role in CP-related contractures. The aims of this review are (1) to summarize CP-related contracture mechanisms, (2) to raise novel hypotheses on the genesis of contractures with a focus on Cstms, and (3) to stimulate novel approaches to study CP-related contractures.

Effects of Botulinum Toxin-A and Goal-Directed Physiotherapy in Children with Cerebral Palsy GMFCS Levels I & II

AIMS

To evaluate short and long-term effects of botulinum toxin-A combined with goal-directed physiotherapy in children with cerebral palsy (CP).

METHOD

A consecutive selection of 40 children, ages 4-12 years, diagnosed with unilateral or bilateral CP, and classified in GMFCS levels I-II. During the 24 months, 9 children received one BoNT-A injection, 10 children two injections, 11 children three injections, and 10 children received four injections. 3D gait analysis, goal-attainment scaling, and body function assessments were performed before and at 3, 12, and 24 months after initial injections.

RESULTS

A significant but clinically small long-term improvement in gait was observed. Plantarflexor spasticity was reduced after three months and remained stable, while passive ankle dorsiflexion increased after 3 months but decreased slightly after 12 months. Goal-attainment gradually increased, reached the highest levels at 12 months, and levels were maintained at 24 months.

CONCLUSION

The treatments' positive effect on spasticity reduction was identified, but did not relate to improvement in gait or goal-attainment. No long-term positive change in passive ankle dorsiflexion was observed. Goal attainment was achieved in all except four children. The clinical significance of the improved gait is unclear. Further studies are recommended to identify predictors for positive treatment outcome.

Selective voluntary motor control measures of the lower extremity in children with upper motor neuron lesions: a systematic review

AIM

Recovery and trainability of impaired selective voluntary motor control (SVMC) of the lower extremity in children with upper motor neuron lesions has received little attention. To facilitate an evidence-based debate about this topic, this review evaluates the evidence level of the psychometric properties of SVMC measures.

METHOD

MEDLINE, Embase, CINAHL, PsycINFO, Scopus, Cochrane and PEDro databases were systematically searched up to July 2016. Two independent raters scored the methodological quality in accordance to the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist. The overall level of evidence was scored according to Cochrane criteria.

RESULTS

We identified 3590 studies, of which 17 were included. COSMIN scores ranged from 'poor' to 'excellent' for studies investigating measurement properties of the Selective Motor Control test, modified Trost test, Gillette's Selective Motor Control test, Selective Control Assessment of the Lower Extremity (SCALE), kinematic measures, electromyography, and torque steadiness. Studies assessing the SCALE scored highest on COSMIN items. Evidence levels for SCALE's validity and reliability properties were moderate, while for the other SVMC measures these ranged from unknown to moderate. Responsiveness was not assessed.

INTERPRETATION

Further psychometric studies of SVMC measures are needed to provide a scientific contribution to the ongoing debate of SVMC trainability.

Spinal cord injury in hypertonic newborns after antenatal hypoxia-ischemia in a rabbit model of cerebral palsy

While antenatal hypoxia-ischemia (H-I) is a well-established cause of brain injury, the effects of H-I on the spinal cord remain undefined. This study examined whether hypertonia in rabbits was accompanied by changes in spinal architecture. Rabbit dams underwent global fetal H-I at embryonic day 25 for 40min. High resolution diffusion tensor imaging was performed on fixed neonatal CNS. Fractional anisotropy (FA) and regional volumetric measurements were compared between kits with and without hypertonia after H-I and sham controls using Tract Based Spatial Statistics. Hypertonic kits showed evidence of damage from hypoxia not only in the brain, but in spinal cord as well. Hypertonic kits showed reduced FA and thickness in corticospinal tracts, external capsule, fimbria, and in white and gray matter of both cervical and lumbar spinal cord. Dorsal white matter of the spinal cord was the exception, where there was thickening and increased FA in hypertonic kits. Direct damage to the spinal cord was demonstrated in a subset of dams imaged during H-I with a 3T magnetic resonance scanner, where apparent diffusion coefficient in fetal spinal cords acutely decreased during hypoxia. Hypertonic kits showed subsequent decreases in lumbar motoneuron counts and extensive TUNEL- and Fluoro-Jade C-positive labeling was present in the spinal cord 48h after H-I, demonstrating spinal neurodegeneration. We speculate that global H-I causes significant loss of both spinal white and gray matter in hypertonic newborns due to direct H-I injury to the spinal cord as well as due to upstream brain injury and consequent loss of descending projections.

Neurologic Correlates of Gait Abnormalities in Cerebral Palsy: Implications for Treatment

Cerebral palsy (CP) is the most common movement disorder in children. A diagnosis of CP is often made based on abnormal muscle tone or posture, a delay in reaching motor milestones, or the presence of gait abnormalities in young children. Neuroimaging of high-risk neonates and of children diagnosed with CP have identified patterns of neurologic injury associated with CP, however, the neural underpinnings of common gait abnormalities remain largely uncharacterized. Here, we review the nature of the brain injury in CP, as well as the neuromuscular deficits and subsequent gait abnormalities common among children with CP. We first discuss brain injury in terms of mechanism, pattern, and time of injury during the prenatal, perinatal, or postnatal period in preterm and term-born children. Second, we outline neuromuscular deficits of CP with a focus on spastic CP, characterized by muscle weakness, shortened muscle-tendon unit, spasticity, and impaired selective motor control, on both a microscopic and functional level. Third, we examine the influence of neuromuscular deficits on gait abnormalities in CP, while considering emerging information on neural correlates of gait abnormalities and the implications for strategic treatment. This review of the neural basis of gait abnormalities in CP discusses what is known about links between the location and extent of brain injury and the type and severity of CP, in relation to the associated neuromuscular deficits, and subsequent gait abnormalities. Targeted treatment opportunities are identified that may improve functional outcomes for children with CP. By providing this context on the neural basis of gait abnormalities in CP, we hope to highlight areas of further research that can reduce the long-term, debilitating effects of CP.

Selective motor control correlates with gait abnormality in children with cerebral palsy

Children with bilateral cerebral palsy (CP) commonly have limited selective motor control (SMC). This affects their ability to complete functional tasks. The impact of impaired SMC on walking has yet to be fully understood. Measures of SMC have been shown to correlate with specific characteristics of gait, however the impact of SMC on overall gait pattern has not been reported. This study explored SMC data collected as part of routine gait analysis in children with bilateral CP. As part of their clinical assessment, SMC was measured with the Selective Control Assessment of the Lower Extremities (SCALE) in 194 patients with bilateral cerebral palsy attending for clinical gait analysis at a single centre. Their summed SCALE score was compared with overall gait impairment, as measured by Gait Profile Score (GPS). Score on SCALE showed a significant negative correlation with GPS (r_s=-0.603, p<0.001). Cerebral injuries in CP result in damage to the motor tracts responsible for SMC. Our results indicate that this damage is also associated with changes in the development of walking pattern in children with CP.

Selective dorsal rhizotomy: A multidisciplinary approach to treating spastic diplegia

Background:

Spasticity is a motor disorder that interferes with mobility and affects the quality of life. Different approaches have been utilized to address patients with spastic diplegia, among which is selective dorsal rhizotomy (SDR). Although SDR has been shown to be efficacious in treating spastic patients, many neurologists and neurosurgeons are not well aware of the procedure, its indications, and expected outcomes due to the limited number of centers performing this procedure.

Objectives:

The aim of this study is to describe the collaborative multidisciplinary approach between neurosurgeons, neurophysiologists, and physiotherapists in performing SDR. In addition, we delineate three illustrative cases in which SDR was performed in our patients.

Materials and Methods:

A retrospective review and analysis of the clinical records of our three patients who underwent SDR was conducted and reported. Patients’ outcomes were evaluated and compared to preoperative measurements based on clinical examination of power, tone (Ashworth scale), gait, and range of motion, as well as subjective functional assessment, gross motor function classification system, and gross motor function measure with follow-up at 6, 12, and 24 months postoperatively. A detailed description of our neurosurgical technique in performing SDR in collaboration with neurophysiology and physiotherapy monitoring is provided.

Results:

The three patients who underwent SDR using our multidisciplinary approach improved both functionally and objectively after the procedure. No intraoperative or postoperative complications were encountered. All patients were doing well over a long postoperative follow-up period.

Conclusion:

A multidisciplinary approach to treating spastic diplegia with SDR can provide good short-term and long-term outcomes in select patients suffering from spastic diplegia.

Longitudinal Association Between Gross Motor Capacity and Neuromusculoskeletal Function in Children and Youth With Cerebral Palsy

OBJECTIVE

To examine associations over longitudinal measurements between neuromusculoskeletal function and gross motor capacity in children and youth with cerebral palsy (CP).

DESIGN

A prospective cohort study.

SETTING

Rehabilitation departments of university medical centers and rehabilitations centers.

PARTICIPANTS

A sample (N=327) consisting of 148 children (aged 5-9y) and 179 youth (aged 11-20y) with CP, Gross Motor Function Classification System level I (n=180), level II (n=44), level III (n=36), level IV (n=34), and level V (n=33).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Gross motor capacity was assessed with the Gross Motor Function Measure-66 over a period of 2 to 4 years in different age cohorts. Neuromusculoskeletal function included selective motor control (SMC), muscle strength, spasticity, and range of motion (ROM) of the lower extremities.

RESULTS

Multilevel analyses showed that SMC was significantly associated with gross motor capacity in children and youth with CP, showing higher values and a more favorable course of gross motor capacity in those with better SMC. Strength was only associated with gross motor capacity in youth. Reduced ROM of hip (children) and knee extension (youth) and spasticity of the hip adductors (youth) were additionally-but more weakly-associated with lower values and a less favorable course of gross motor capacity.

CONCLUSIONS

Results indicate that children and youth with more severely impaired SMC and youth with reduced muscle strength have a less favorable course of gross motor capacity, while spasticity and reduced ROM are less determinative.

Motor Cortex Activity Organizes the Developing Rubrospinal System

The corticospinal and rubrospinal systems function in skilled movement control. A key question is how do these systems develop the capacity to coordinate their motor functions and, in turn, if the red nucleus/rubrospinal tract (RN/RST) compensates for developmental corticospinal injury? We used the cat to investigate whether the developing rubrospinal system is shaped by activity-dependent interactions with the developing corticospinal system. We unilaterally inactivated M1 by muscimol microinfusion between postnatal weeks 5 and 7 to examine activity-dependent interactions and whether the RN/RST compensates for corticospinal tract (CST) developmental motor impairments and CST misprojections after M1 inactivation. We examined the RN motor map and RST cervical projections at 7 weeks of age, while the corticospinal system was inactivated, and at 14 weeks, after activity returned. During M1 inactivation, the RN on the same side showed normal RST projections and reduced motor thresholds, suggestive of precocious development. By contrast, the RN on the untreated/active M1 side showed sparse RST projections and an immature motor map. After M1 activity returned later in adolescent cat development, RN on the active M1/CST side continued to show a substantial loss of spinal terminations and an impaired motor map. RN/RST on the inactivated side regressed to a smaller map and fewer axons. Our findings suggest that the developing rubrospinal system is under activity-dependent regulation by the corticospinal system for establishing mature RST connections and RN motor map. The lack of RS compensation on the non-inactivated side can be explained by development of ipsilateral misprojections from the active M1 that outcompete the RST. Significance statement: Skilled movements reflect the activity of multiple descending motor systems and their interactions with spinal motor circuits. Currently, there is little insight into whether motor systems interact during development to coordinate their emerging functions and, if so, the mechanisms underlying this process. This study examined activity-dependent interactions between the developing corticospinal and rubrospinal systems, two key systems for skilled limb movements. We show that the developing rubrospinal system competes with the corticospinal system in establishing the red nucleus motor map and rubrospinal tract connections. This is the first demonstration of one motor system steering development, and ultimately function, of another. Knowledge of activity-dependent competition between these two systems helps predict the response of the rubrospinal system following corticospinal system developmental injury.

Correlation between the selective control assessment of lower extremity and pediatric balance scale scores in children with spastic cerebral palsy

[Purpose] The purpose of this study was to investigate the correlation between the Selective Control Assessment of Lower Extremity (SCALE) and Pediatric Balance Scales (PBS) in children with spastic cerebral palsy and further to test whether the SCALE is a valid tool to predict the PBS. [Subjects and Methods] A cross-sectional study was conducted to evaluate the SCALE and PBS in 23 children (9 females, 14 males, GMFCS level I–III) with spastic cerebral palsy. [Results] Both the SCALE and PBS scores for children with spastic hemiplegia were significantly higher than those for children with spastic diplegia. The scores for SCALE items were low for distal parts. The PBS items that were difficult for the participants to perform were items 8, 9, 10, and 14 with the highest difficulty experienced for item 8 followed by items 9, 10, and 14. The correlation coefficient (0.797) between the SCALE and PBS scores was statistically significant. The correlations between each SCALE item and the PBS scores were also statistically significant. SCALE items were significantly correlated with two PBS dimensions (standing and postural change). [Conclusion] In SCALE assessment, more severe deficits were observed in the distal parts. Standing and postural changes in the PBS method were difficult for the participants to perform. The two tests, that is, the SCALE and PBS, were highly correlated. Therefore, the SCALE is useful to prediction of PBS outcomes and is also applicable as a prognostic indicator for treatment planning.

[Course and neurological/behavioral development of preterm children]

Preterm birth remains a public health priority given that one child out of ten is born before 37 weeks of gestation. Survival without major neonatal morbidity has increased in high-income countries, in particular in France and in cases of extreme preterm birth before 27 weeks of gestation. Rate of severe handicaps, such as cerebral palsy, is probably decreasing, but specific cognitive disabilities in a variety of domains remain frequent, interfering with normal learning abilities at school and explaining the high rate of special education needs. Prevalence of sequelae increases when gestational age at birth decreases. However, because there are more moderate to late preterm children compared to very preterm children, the absolute number of children with specific cognitive or neurological disabilities is equivalent in these two groups. Better characterization of the development in a recent cohort of very preterm children is necessary to improve the early detection of variations in normal neurodevelopment and to propose trials with remediation actions targeting working memory and language for example. These protocols could decrease the rates of learning disabilities at school.

Activity-Based Therapies for Repair of the Corticospinal System Injured during Development

This review presents the mechanistic underpinnings of corticospinal tract (CST) development, derived from animal models, and applies what has been learned to inform neural activity-based strategies for CST repair. We first discuss that, in normal development, early bilateral CST projections are later refined into a dense crossed CST projection, with maintenance of sparse ipsilateral projections. Using a novel mouse genetic model, we show that promoting the ipsilateral CST projection produces mirror movements, common in hemiplegic cerebral palsy (CP), suggesting that ipsilateral CST projections become maladaptive when they become abnormally dense and strong. We next discuss how animal studies support a developmental “competition rule” whereby more active/used connections are more competitive and overtake less active/used connections. Based on this rule, after unilateral injury the damaged CST is less able to compete for spinal synaptic connections than the uninjured CST. This can lead to a progressive loss of the injured hemisphere’s contralateral projection and a reactive gain of the undamaged hemisphere’s ipsilateral CST. Knowledge of the pathophysiology of the developing CST after injury informs interventional strategies. In an animal model of hemiplegic CP, promoting injured system activity or decreasing the uninjured system’s activity immediately after the period of a developmental injury both increase the synaptic competitiveness of the damaged system, contributing to significant CST repair and motor recovery. However, delayed intervention, despite significant CST repair, fails to restore skilled movements, stressing the need to consider repair strategies for other neural systems, including the rubrospinal and spinal interneuronal systems. Our interventional approaches harness neural activity-dependent processes and are highly effective in restoring function. These approaches are minimally invasive and are poised for translation to the human.