Nicotinamide Riboside Improves Ataxia Scores and Immunoglobulin Levels in Ataxia Telangiectasia.

BACKGROUND: Treatment of animal models with ataxia telangiectasia (A-T) with nicotinamide riboside (NR) improved their neurological outcome and survival. OBJECTIVE: The aim of this study is to investigate the effects of NR in patients with A-T. METHODS: In this open-label, proof-of-concept study, 24 patients with A-T were treated with NR during four consecutive months. The effects of NR on ataxia, dysarthria, quality of life, and laboratory parameters were analyzed. RESULTS: During treatment, ataxia scores improved; mean total Scale for the Assessment and Rating of Ataxia and International Cooperative Ataxia Rating Scale scores decreased to 2.4 and 10.1 points, respectively. After NR withdrawal, ataxia scores worsened. In immunodeficient patients, the mean serum IgG concentration increased substantially until the end of the study period with 0.52 g/L. Untargeted metabolomics analysis revealed increased plasma levels of NR metabolites and purine nucleosides during treatment. Adverse effects did not occur. CONCLUSIONS: Treatment with NR is tolerated well and associated with improvement in ataxia and serum immunoglobulin concentrations in patients with A-T. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Reliability and Responsiveness of the Observable Movement Quality Scale for Children with Mild to Moderate Motor Impairments.

AIM: The Observable Movement Quality (OMQ) scale measures generic movement quality and is used alongside standardized age-adequate motor performance tests. The scale consists of 15 items, each focusing on a different aspect; together, the entire construct of movement quality is assessed. This study aimed to determine interrater and intrarater reliability, and responsiveness of the OMQ scale. METHODS: A prospective intervention study with pre-post design in pediatric physical therapy practices. For interrater reliability, 3 physical therapists observed video-recorded motor assessments of 30 children with mild to moderate motor impairments -aged 4 to 12 years-using the OMQ scale. One therapist scored baseline assessment a second time for intrarater reliability, and to calculate smallest detectable change (SDC). Responsiveness (n = 28) was tested by comparing outcomes before and after intervention. RESULTS: Interrater reliability was moderate to good (ICC2,1: 0.79); intrarater reliability was high (ICC2,1: 0.97). Responsiveness results revealed an SDC of 2.4 and a minimal important change of 2.5; indicating sufficient validity in differentiating groups of children showing improved versus unchanged movement quality. CONCLUSION: The OMQ scale is reliable and responsive to change when used to assess movement quality in clinical practice for children with mild to moderate motor impairments, aged 4-12 year.

Outcome measures for children with mitochondrial disease: consensus recommendations for future studies from a Delphi-based international workshop.

Although there are no effective disease-modifying therapies for mitochondrial diseases, an increasing number of trials are being conducted in this rare disease group. The use of sensitive and valid endpoints is essential to test the effectiveness of potential treatments. There is no consensus on which outcome measures to use in children with mitochondrial disease. The aims of this two-day Delphi-based workshop were to (i) define the protocol for an international, multi-centre natural history study in children with mitochondrial myopathy and (ii) to select appropriate outcome measures for a validation study in children with mitochondrial encephalopathy. We suggest two sets of outcome measures for a natural history study in children with mitochondrial myopathy and for a proposed validation study in children with mitochondrial encephalopathy.

The early postnatal nutritional intake of preterm infants affected neurodevelopmental outcomes differently in boys and girls at 24 months.

AIM: This study assessed whether increased amino acid and energy intake in preterm infants during the first week of life was associated with improved neurodevelopment at the corrected age (CA) of 24 months. METHODS: We evaluated preterm infants from two consecutive cohorts in 2004 (Cohort 1) and 2005 (Cohort 2) with different nutritional intakes in the Netherlands. Nutritional intake and growth were recorded until week 5 and after discharge. Neurodevelopment was determined using the Bayley Scales of Infant Development - Second Edition at a CA of 24 months. RESULTS: Compared to Cohort 1 (n = 56), Cohort 2 (n = 56) received higher nutritional intake during week 1 (p < 0.001). The weight gain in Cohort 2 was higher until week 5, especially among boys (p < 0.002). The mean Mental Developmental Index (MDI) scores did not differ, but Cohort 2 was associated with an increased chance of having an MDI ≥ 85, with an odds ratio of 6.4 and 95% confidence interval (CI) of 1.5-27.4, among all girls with a higher protein intake (5.3, 1.2-23.3). The Psychomotor Developmental Index increased with increasing nutritional intake, especially among boys (ß-coefficient 3.1, 95% CI 0.2-6.0). CONCLUSION: Higher nutritional intake was associated with different improvements in growth and neurodevelopment in boys and girls.

Quantitative muscle ultrasonography in the follow-up of juvenile dermatomyositis.

INTRODUCTION: We explored the use of quantitative muscle ultrasonography (QMUS) for follow-up of juvenile dermatomyositis (JDM). METHODS: Seven JDM patients were evaluated at diagnosis and 1, 3, 6, 12, and 24 months using the Childhood Myositis Assessment Scale (CMAS) and QMUS. Muscle thickness (MT) and quantitative muscle echo intensity (EI) were assessed with QMUS in 4 muscles. RESULTS: Six patients experienced a monocyclic course. At diagnosis EI was slightly increased, and MT was relatively normal. After start of treatment MT first decreased and EI increased, with normalization of EI within 6-12 months (n = 4). One patient had higher EIs at diagnosis and slower normalization, indicating fibrosis, despite early normalization of CMAS. One patient experienced a chronic course, with high EIs and atrophy during follow-up. CONCLUSIONS: QMUS can provide additional information for follow-up of JDM regarding disease severity and residual muscle damage, particularly after normalization of CMAS.

The United States reference values of the Bayley III motor scale are suitable in Suriname.

To determine if the United States reference values of the Bayley Scales of Infant and Toddler Development, version III motor scale are suitable for Surinamese infants, we assessed 151 healthy infants at 3, 12, 24 and 36 months of age. The mean fine motor, gross motor, and composite scores of the total group did not significantly differ from the US norms, although some significant but not clinically relevant differences were found (lower fine motor scores at 12 months, lower gross motor and total composite scores at 24 months, and higher scores for gross motor and composite scores at 3 months).

Educational programs for learning to observe movement quality in physical therapy: a design-based research approach.

Introduction: Movement observation is a core aspect in physical therapists' diagnosis to determine which interventions are adequate to improve functional abilities. The aim of this study was to derive design principles for an educational program for the development of observational skills.Methods: We used a qualitative approach within a design-based research methodology. In four rounds, 8 physical therapy students, 16 teachers, and 9 practitioners participated in five Nominal Group Technique meetings and six interviews. Meetings and interviews were transcribed verbatim and analyzed using thematic analysis.Results: We identified three themes, each with several design principles: (1) didactics; (2) professional content; and (3) conditions for optimal learning. We developed a proto-theory underpinned with underlying educational theories.Conclusions: To learn observational skills, students, facilitated by an experienced teacher, need to take the lead in their own learning process. This might imply a need for additional training for teachers. A realistic context is a precondition for learning; it might be necessary to increase possibilities for observations in clinical contexts or to invest in training for (simulated) patients as participants in education. Further research is needed to test the applicability of the design principles and a proto-theory for other professionals with a focus on observation and analysis of movements.

Individual longitudinal neurodevelopmental trajectories of children treated with hypothermia for perinatal asphyxia from 3 months to 5 years of age.

BACKGROUND: Hypothermia for perinatal asphyxia is a common treatment to decrease morbidity. This study aims to describe a) individual longitudinal neurodevelopmental trajectories over 5 years in children with perinatal asphyxia treated with hypothermia and b) the correlation between movement quality at 3 months and motor developmental outcomes at 5 years of age. METHODS: In this longitudinal cohort study, 18 children (12 male) were assessed at 3 (t1), 6 (t2), 12 (t3), and 24 (t4) months, and at the age of 5 (t5) years, with standardized norm-referenced tests. RESULTS: Six children showed abnormal movement quality assessed with General Movements (t1) and all showed severe neurodevelopmental disabilities at t5. The 12 children without severe disabilities, showed a significant normalization of z-scores over the five assessment points (linear mixed model analysis). At t5, four of these children scored mildly delayed motor or cognitive development. CONCLUSION AND IMPLICATIONS: Children without anomalies on the MRI before hospital discharge and normal movement quality at 3 months of age showed normal neurodevelopment at the age of 5, however, individual motor trajectories showed variability over time. Presents of abnormal GMs tend to detect CP and developmental problems, advocating a developmental surveillance to determine need for early intervention.

Construct Validity of the Observable Movement Quality Scale in Pediatrics: Hypothesis Testing of a Formative Measurement Model.

BACKGROUND: The Observable Movement Quality (OMQ) Scale measures generic movement quality. Each item of the OMQ Scale focuses on a different element; together, the 15 items assess the whole construct of movement quality. OBJECTIVE: The aim of this study was to determine the construct validity of the OMQ Scale using 7 hypotheses defined to conform to the Consensus-Based Standards for the Selection of Health Measurement Instruments. DESIGN: This was an exploratory validation study. METHODS: A pediatric physical therapist assessed motor performance in 101 children using an age-specific motor test and the OMQ Scale. The direction, magnitude, and rationale for 7 hypotheses, which concerned relationships (n = 2), probability of low scores (n = 4), and difference between diagnosis subgroups (n = 1), were defined. RESULTS: The results confirmed 6 of the 7 hypotheses, indicating sufficient construct validity. Significant positive relationships were found between OMQ Scale total scores and the severity of motor disabilities (r = 0.72) and z scores on motor tests (r = 0.60). Probabilities for low scores on OMQ Scale items-exceeding the chi-square critical value-were confirmed for children diagnosed with spasticity, psychomotor retardation, mitochondrial diseases, and ataxia; however, probabilities for low OMQ Scale item scores on strength regulation in children with ataxia were not confirmed. OMQ Scale total scores for children who were not ambulatory because of neurological conditions were significantly different from those for children who were not ambulatory because of fatigue (r = 0.66). LIMITATIONS: The sample of children was based on theoretical assumptions about relevant variations in clinical representations; on the basis of the results, it appears that children with low strength regulation were underrepresented. CONCLUSION: The confirmation of nearly all hypotheses supported the validity of the OMQ Scale for measuring movement quality in clinical practice in addition to standardized age-adequate motor performance tests.

Motor performance in five-year-old extracorporeal membrane oxygenation survivors: a population-based study.

INTRODUCTION: Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a cardio-pulmonary bypass technique to provide life support in acute reversible cardio-respiratory failure when conventional management is not successful. Most neonates receiving ECMO suffer from meconium aspiration syndrome (MAS), congenital diaphragmatic hernia (CDH), sepsis or persistent pulmonary hypertension (PPH). In five-year-old children who underwent VA-ECMO therapy as neonates, we assessed motor performance related to growth, intelligence and behaviour, and the association with the primary diagnosis. METHODS: In a prospective population-based study (n = 224) 174 five-year-old survivors born between 1993 and 2000 and treated in the two designated ECMO centres in the Netherlands (Radboud University Medical Centre Nijmegen and Sophia Children's Hospital, Erasmus MC - University Medical Center Rotterdam) were invited to undergo follow-up assessment including a paediatric assessment, the movement assessment battery for children (MABC), the revised Amsterdam intelligence test (RAKIT) and the child behaviour checklist (CBCL). RESULTS: Twenty-two percent of the children died before the age of five, 86% (n = 149) of the survivors were assessed. Normal development in all domains was found in 49% of children. Severe disabilities were present in 13%, and another 9% had impaired motor development combined with cognitive and/or behavioural problems. Chi-squared tests showed adverse outcome in MABC scores (P < 0.001) compared with the reference population in children with CDH, sepsis and PPH, but not in children with MAS. Compared with the Dutch population height, body mass index (BMI) and weight for height were lower in the CDH group (P < 0.001). RAKIT and CBCL scores did not differ from the reference population. Total MABC scores, socio-economic status, growth and CBCL scores were not related to each other, but negative motor outcome was related to lower intelligence quotient (IQ) scores (r = 0.48, P < 0.001). CONCLUSIONS: The ECMO population is highly at risk for developmental problems, most prominently in the motor domain. Adverse outcome differs between the primary diagnosis groups. Objective evaluation of long-term developmental problems associated with this highly invasive technology is necessary to determine best evidence-based practice. The ideal follow-up programme requires an interdisciplinary team, the use of normal-referenced tests and an international consensus on timing and actual outcome measurements.

Natural variability of daily physical activity measured by accelerometry in children with a mitochondrial disease.

In this exploratory study we aimed to select the most valid and feasible accelerometer to measure daily physical activity at home in 10 children with mitochondrial disease. Using the experimentally-selected GENEActiv, good to excellent short- and long-term test-retest reliability of daily physical activity was found. Especially in children with more severe limitations daily physical activity seemed more stable and less susceptible to weather conditions. Moreover, small standard errors of measurement were found, indicating high precision of this measuring method. We conclude that measuring daily physical activity using accelerometry is a promising outcome measure for future studies in this unique population.

Interrater Reliability of the Observable Movement Quality Scale for Children.

Purpose: The authors investigated the interrater reliability, the standard deviation of the random measurement error, and the limits of agreement (LoA) of the Observable Movement Quality (OMQ) scale in children. Movement quality is important in the recognition of motor problems, and the OMQ scale, a questionnaire used by paediatric physical therapists, has been developed for use with an age-specific motor test to observe movement quality and score relative to what is expected for a child's age. Method: Paediatric physical therapists (n=28; 2 men, 26 women) observed video-recorded assessments of age-related motor tests in children (n=9) aged 6 months to 6 years and filled in the OMQ scale (possible score range 15-75 points). For our analyses, we used linear mixed models without fixed effects. Results: The interrater reliability was moderate (intra-class correlation coefficient [ICC2,1]: 0.67, 95% CI: 0.47, 0.88); neither work setting nor work experience exerted any influence on it. The standard deviation of the random measurement error was 5.7, and the LoA was 31.5. Item agreement was good (proportion of observed agreement [Po] total 0.82-0.99). Conclusion: The OMQ scale showed moderate interrater reliability when being used by therapists who were unfamiliar with the questionnaire and who had received only 2 hours of training. Feedback from the participants suggested a need for more comprehensive training in using the OMQ scale in clinical practice.

Objectif : étudier la fiabilité interévaluateur, l'écart-type (ÉT) de l'erreur de mesure aléatoire et les limites de concordance (LdC) de l'échelle de qualité de mouvements observables (QMO) chez les enfants. La qualité des mouvements est importante pour déceler les problèmes moteurs, et l'échelle de QMO, un questionnaire auquel recourent les physiothérapeutes pédiatriques, a été mise au point pour être utilisée conjointement avec un test de motricité adapté à l'âge afin d'observer la qualité des mouvements et un score relatif aux attentes en fonction de l'âge de l'enfant. Méthodologie : les physiothérapeutes pédiatriques (n=28; deux hommes, 26 femmes) ont observé des évaluations enregistrées sur vidéo des tests de motricité adaptés à l'âge chez des enfants (n=9) de six mois à six ans et ont rempli l'échelle de QMO (éventail possible des résultats de 15 à 75 points). Dans les analyses, les chercheurs ont utilisé les modèles linéaires mixtes sans effet fixe. Résultats : la fiabilité interévaluateur était modérée (coefficient de corrélation intraclasse [CCI2,1] : 0,67, IC à 95 % : 0,47, 0,88); ni le lieu de travail ni l'expérience de travail n'y exerçait d'influence. L'ÉT de l'erreur de mesure aléatoire était de 5,7, et la LdC, de 31,5. La concordance des points était bonne (proportion du total de concordance observée [Po] : 0,82 à 0,99). Conclusion : l'échelle de QMO a révélé une fiabilité interévaluateur modérée lorsqu'elle était utilisée par des physiothérapeutes qui ne connaissaient pas le questionnaire et dont la formation s'était limitée à seulement deux heures. Selon les commentaires de participants, il faudrait une formation plus approfondie pour utiliser l'échelle de QMO en pratique clinique.

Implicit and explicit motor sequence learning in children born very preterm.

BACKGROUND: Motor skills can be learned explicitly (dependent on working memory (WM)) or implicitly (relatively independent of WM). Children born very preterm (VPT) often have working memory deficits. Explicit learning may be compromised in these children. AIMS: This study investigated implicit and explicit motor learning and the role of working memory in VPT children and controls. METHODS: Three groups (6-9 years) participated: 20 VPT children with motor problems, 20 VPT children without motor problems, and 20 controls. A nine button sequence was learned implicitly (pressing the lighted button as quickly as possible) and explicitly (discovering the sequence via trial-and-error). RESULTS: Children learned implicitly and explicitly, evidenced by decreased movement duration of the sequence over time. In the explicit condition, children also reduced the number of errors over time. Controls made more errors than VPT children without motor problems. Visual WM had positive effects on both explicit and implicit performance. CONCLUSION: VPT birth and low motor proficiency did not negatively affect implicit or explicit learning. Visual WM was positively related to both implicit and explicit performance, but did not influence learning curves. These findings question the theoretical difference between implicit and explicit learning and the proposed role of visual WM therein.

Domains of Daily Physical Activity in Children with Mitochondrial Disease: A 3D Accelerometry Approach.

Feasible, sensitive and clinically relevant outcome measures are of extreme importance when designing clinical trials. For paediatric mitochondrial disease, no robust end point has been described to date. The aim of this study was to select the domains of daily physical activity, which can be measured by 3D accelerometry, that could serve as sensitive end points in future clinical trials in children with mitochondrial disorders.In this exploratory observational study, 17 patients with mitochondrial disease and 16 age- and sex-matched controls wore 3D accelerometers at the upper leg, upper arm, lower arm and chest during one weekend. Using the raw data obtained by the accelerometers, we calculated the following outcome measures: (1) average amount of counts per hour the sensors were worn; (2) the maximal intensity; (3) the largest area under the curve during 30 min and (4) categorized activities lying, standing or being dynamically active. Measuring physical activity during the whole weekend was practically feasible in all participants. We found good face validity by visually correlating the validation videos and activity diaries to the accelerometer data-graphs. Patients with mitochondrial disorders had significantly lower peak intensity and were resting more, compared to their age- and sex-matched peers.Finally, we suggest domains of physical activity that could be included when measuring daily physical activity in children with mitochondrial disorders, preferably using more user-friendly devices. These include peak activity parameters for the arms (all patients) and legs (ambulatory patients). We recommend using or developing devices that measure these domains of physical activity in future clinical studies.

Perceived Motor Competence Differs From Actual Performance in 8-Year-Old Neonatal ECMO Survivors.

OBJECTIVE: To assess perceived motor competence, social competence, self-worth, health-related quality of life, and actual motor performancein 8-year-old survivors of neonatal extracorporeal membrane oxygenation (ECMO). METHODS: In a prospective nationwide study, 135 children completed the extended version of the "athletic competence" domain of the Self Perception Profile for Children (SPPC) called the m-CBSK (Motor supplement of the Competentie BelevingsSchaal voor Kinderen) to assess perceived motor competence, the SPPC, and the Pediatric Quality of Life Inventory (PedsQL), andwere tested with the Movement Assessment Battery for Children. SD scores (SDS) were used to compare with the norm. RESULTS: The mean (SD) SDS for perceived motor competence, social competence, and self-worth were all significantly higher than the norm: 0.18 (0.94), P = .03; 0.35 (1.03), P < .001; and 0.32 (1.08), P < .001, respectively. The total PedsQL score was significantly below the norm: mean (SD) SDS: -1.26 (1.53), P < .001. Twenty-two percent of children had actual motor problems. The SDS m-CBSK and actual motor performance did not correlate (r = 0.12; P = .17). The SDS m-CBSK significantly correlated with the athletic competence domain of the SPPC (r = 0.63; P < .001). CONCLUSIONS: Eight-year-old ECMO survivors feel satisfied with their motor- and social competence, despite impaired PedsQL scores and motor problems. Because motor problems in ECMO survivorsdeteriorate throughout childhood, clinicians should be aware that these patients may tend to "overrate" their actual motor performance. Education andstrict monitoring of actual motor performanceare important to enable timelyintervention.

High variability of individual longitudinal motor performance over five years in very preterm infants.

AIM: To determine longitudinal motor performance in very preterm (VPT) infants from 6 months to 5 years of age for the entire cohort of infants, according to gender and gestational age and at the individual level. METHOD: Single-center, prospective longitudinal study of 201 VPT infants (106 boys) without severe impairments. OUTCOMES: Motor performance was assessed with the Bayley Scales of Infant Development (BSID-II-MS: 6, 12, 24 months) and the Movement Assessment Battery for Children (MABC-2-NL: 5 years). RESULTS: At 6, 12, and 24 months and then at 5 years, 77%, 80%, 48%, and 22% of the infants, respectively, showed delayed motor performance (<-1SD). At 5 years, girls performed significantly better than boys in manual dexterity and balance. MIXED MODEL ANALYSES: that examined interactions between time and gender and time and gestational age, revealed no significant interactions. The variance at child level was 29%. Linear mixed model analysis revealed that mean z-scores of -1.46 at 6 months of age declined significantly to -0.52 at 5 years. Individual longitudinal motor performance showed high variability. IMPLICATIONS: Longitudinal motor performance improved almost 1 SD over five years. However, the variability of individual longitudinal motor performance hampers evaluation in clinical care and research.

Behavioral, cognitive, and motor performance and physical development of five-year-old children who were born after intracytoplasmic sperm injection with the use of testicular sperm.

OBJECTIVE: To evaluate at the age of 5 years the behavioral, cognitive, and motor performance and physical development of children born after testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI). DESIGN: A prospective longitudinal cohort study. SETTING: Two university medical centers. PATIENT(S): A total of 103 5-year-olds who were born after TESE-ICSI. INTERVENTION(S): The follow-up of the children was performed by questionnaires at birth and again at 1 year and at 4 years of age. Five-year-old children were invited for individual assessment. Behavioral performance was assessed with the use of the Child Behavior Checklist for parents and teachers. Cognitive performance was assessed with the use of the Dutch Wechsler Preschool and Primary Scale of Intelligence test, 3rd version. Motor performance was assessed with the use of the Dutch Movement Assessment Battery for Children, 2nd version. Physical development was assessed by means of physical examination and medical history. MAIN OUTCOME MEASURE(S): Behavioral, cognitive, and motor performance and physical development. RESULT(S): Eighty-nine children were completely assessed, and 14 were partially assessed at the age of 5 years. The 5-year-old cohort assessed significantly better on behavioral and cognitive performance and significantly worse on motor performance-but still in the normal range-compared with the theoretic distribution in the general population. Four children (3.8%) of the 5-year-old cohort had developmental problems/delays. Two of them were previously diagnosed with a form of autism (pervasive developmental disorder-not otherwise specified). Two children had developmental problems based on our behavioral, cognitive, and/or motor assessments. CONCLUSION(S): The long-term effects on development and health in children born after TESE-ICSI procedures seem to be reassuring.

Motor performance after neonatal extracorporeal membrane oxygenation: a longitudinal evaluation.

OBJECTIVE: To assess longitudinally children's motor performance 5 to 12 years after neonatal extracorporeal membrane oxygenation (ECMO) and to evaluate associations between clinical characteristics and motor performance. METHODS: Two hundred fifty-four neonatal ECMO survivors in the Netherlands were tested with the Movement Assessment Battery for Children at 5, 8, and/or 12 years. Percentile scores were transformed to z scores for longitudinal evaluation (norm population mean = 0 and SD = 1). Primary diagnoses: meconium aspiration syndrome (n = 137), congenital diaphragmatic hernia (n = 49), persistent pulmonary hypertension of the newborn (n = 36), other diagnoses (n = 32). RESULTS: Four hundred fifty-six tests were analyzed. At 5, 8, and 12 years motor performance was normal in 73.7, 74.8, and 40.5%, respectively (vs 85% expected based on reference values; P < .001 at all ages). In longitudinal analyses mean (95% confidence interval [CI]) z scores were -0.42 (-0.55 to -0.28), -0.25 (-0.40 to -0.10) and -1.00 (-1.26 to -0.75) at 5, 8, and 12 years, respectively. Mean score at 8 years was significantly higher than at 5 years (difference 0.16, 95% CI 0.02 to 0.30), and mean score at 12 years was significantly lower than at both other ages (differences -0.59 and -0.75; 95% CI -0.33 to -0.84 and -0.49 to -1.00, respectively). Children with congenital diaphragmatic hernia encountered problems at all ages. The presence of chronic lung disease was negatively related with outcome. CONCLUSIONS: Motor problems in neonatal ECMO survivors persist throughout childhood and become more obvious with time.

Objective evaluation of muscle strength in infants with hypotonia and muscle weakness.

The clinical evaluation of an infant with motor delay, muscle weakness, and/or hypotonia would improve considerably if muscle strength could be measured objectively and normal reference values were available. The authors developed a method to measure muscle strength in infants and tested 81 typically developing infants, 6-36 months of age, and 17 infants with Prader-Willi Syndrome (PWS) aged 24 months. The inter-rater reliability of the measurement method was good (ICC=.84) and the convergent validity was confirmed by high Pearson's correlations between muscle strength, age, height, and weight (r=.79-.85). A multiple linear regression model was developed to predict muscle strength based on age, height, and weight, explaining 73% of the variance in muscle strength. In infants with PWS, muscle strength was significantly decreased. Pearson's correlations showed that infants with PWS in which muscle strength was more severely affected also had a larger motor developmental delay (r=.75).

Motor learning and working memory in children born preterm: a systematic review.

Children born preterm have a higher risk for developing motor, cognitive, and behavioral problems. Motor problems can occur in combination with working memory problems, and working memory is important for explicit learning of motor skills. The relation between motor learning and working memory has never been reviewed. The goal of this review was to provide an overview of motor learning, visual working memory and the role of working memory on motor learning in preterm children. A systematic review conducted in four databases identified 38 relevant articles, which were evaluated for methodological quality. Only 4 of 38 articles discussed motor learning in preterm children. Thirty-four studies reported on visual working memory; preterm birth affected performance on visual working memory tests. Information regarding motor learning and the role of working memory on the different components of motor learning was not available. Future research should address this issue. Insight in the relation between motor learning and visual working memory may contribute to the development of evidence based intervention programs for children born preterm.