Heterogeneity of comprehensive clinical phenotype and longitudinal adaptive function and correlation with computational predictions of severity of missense genotypes in KIF1A-associated neurological disorder.

PURPOSE: Pathogenic variants in Kinesin Family Member 1A (KIF1A) are associated with KIF1A-associated neurological disorder (KAND). We report the clinical phenotypes and correlate genotypes of individuals with KAND. METHODS: Medical history and adaptive function were assessed longitudinally. In-person evaluations included neurological, motor, ophthalmologic and cognitive assessments. RESULTS: We collected online data on 177 individuals. Fifty-seven individuals were also assessed in-person. Most individuals had de novo heterozygous missense likely pathogenic/pathogenic KIF1A variants. The most common characteristics were hypotonia, spasticity, ataxia, seizures, optic nerve atrophy, cerebellar atrophy, and cognitive impairment. Mean Vineland Adaptive Behavior Composite score (VABS-ABC) was low (M=62.9, SD=19.1). The mean change in VABS-ABC over time was -3.1 (SD=7.3). The decline in VABS-ABC was associated with the age at first assessment and abnormal electroencephalogram/seizure. There was a positive correlation between Evolutionary Scale Model (ESM) score for the variants and final VABS-ABC (p=0.003). Abnormal electroencephalogram/seizure, neuroimaging result, and ESM explain 34% of the variance in final VABS-ABC (p<0.001). CONCLUSION: In-person assessment confirmed caregiver report and identified additional visual deficits. Adaptive function declined over time consistent with both the neurodevelopmental and neurodegenerative nature of the condition. Using ESM score assists in predicting phenotype across a wide range of unique variants.

Clinical phenotypic spectrum of CTNNB1 neurodevelopmental disorder.

Pathogenic heterozygous loss of function variants in CTNNB1 are associated with CTNNB1 neurodevelopmental disorder. We report the clinical phenotype of individuals with CTNNB1 neurodevelopmental disorder using both caregiver-reported data (medical history, adaptive function, quality of life, and behavior issues) and in-person clinical assessments (neurological, motor, and cognitive function) in 32 individuals with likely pathogenic or pathogenic CTNNB1 variants. Most individuals had truncal hypotonia, muscle weakness, hypertonia, dystonia, microcephaly, and many had a history of tethered cord. Visual problems included strabismus, hyperopia, and familial exudative vitreoretinopathy. Half of individuals walked without an assistive device. The mean Gross Motor Functional Measure-66 score was 56.6 (SD = 14.8). Average time to complete Nine-Hole Peg Test was slower than norms. Mean general conceptual ability composite scores from Differential Ability Scales Second Edition were very low (M = 58.3, SD = 11.3). Fifty-five percent of individuals had low adaptive functioning based on the Vineland Adaptive Behavioral Scales. Based upon the Child Behavior Checklist total problems score, the majority (65%) of individuals had behavioral challenges. The mean overall Quality of Life Inventory-Disability score was 81.7 (SD = 11.9). These data provide a detailed characterization of clinical features in individuals with CTNNB1 neurodevelopmental disorder.

Longitudinal changes in clinical outcome measures in COL6-related dystrophies and LAMA2-related dystrophies.

OBJECTIVE: To identify the rate of change of clinical outcome measures in children with 2 types of congenital muscular dystrophy (CMD), COL6-related dystrophies (COL6-RDs) and LAMA2-related dystrophies (LAMA2-RDs). METHODS: Over the course of 4 years, 47 individuals (23 with COL6-RD and 24 with LAMA2-RD) 4 to 22 years of age were evaluated. Assessments included the Motor Function Measure 32 (MFM32), myometry (knee flexors and extensors, elbow flexors and extensors), goniometry (knee and elbow extension), pulmonary function tests, and quality-of-life measures. Separate linear mixed-effects models were fitted for each outcome measurement, with subject-specific random intercepts. RESULTS: Total MFM32 scores for COL6-RDs and LAMA2-RDs decreased at a rate of 4.01 and 2.60 points, respectively, each year (p < 0.01). All muscle groups except elbow flexors for individuals with COL6-RDs decreased in strength between 1.70% (p < 0.05) and 2.55% (p < 0.01). Range-of-motion measurements decreased by 3.21° (p < 0.05) at the left elbow each year in individuals with LAMA2-RDs and 2.35° (p < 0.01) in right knee extension each year in individuals with COL6-RDs. Pulmonary function demonstrated a yearly decline in sitting forced vital capacity percent predicted of 3.03% (p < 0.01) in individuals with COL6-RDs. There was no significant change in quality-of-life measures analyzed. CONCLUSION: Results of this study describe the rate of change of motor function as measured by the MFM32, muscle strength, range of motion, and pulmonary function in individuals with COL6-RDs and LAMA2-RDs.

Executive Functioning in the Dystrophinopathies and the Relation to Underlying Mutation Position.

OBJECTIVES: The aim of this study was to investigate executive skills in children with dystrophinopathy and to examine the association between executive functions and dystrophin gene mutation position. METHODS: Fifty boys with dystrophinopathy (mean age, 11 years 0 months; ages range, 5 to 17 years) completed measures of intellectual functioning (IF), working memory and executive functioning [including Digit Span (working memory) and measures from the NIH Toolbox (selective attention/inhibitory control, set shifting, working memory, and processing speed)]. Parents completed the Behavior Rating Inventory of Executive Function (BRIEF). Mutation positions were categorized into three groups (upstream exon 30, 31-62, and downstream exon 63). Paired-samples t tests compared performance on executive measures to IF, and a one-way (three-group) multivariate analysis of covariance compared cognitive performance with mutation location controlling for motor functioning. RESULTS: Mean performance on all executive measures was significantly lower than IF. Parents were also more likely to rate their child with dystrophinopathy as having clinically significant executive difficulties on the Shift, Emotional Control, and Behavior Regulation indices of the BRIEF. Mutation analyses resulted in small groups limiting power to detect subtle differences. Those with a downstream mutation position had significantly poorer performance on IF and Total Digit Span, but not on other measures of executive function including behavior. CONCLUSIONS: Individuals with dystrophinopathy have executive skill deficits, but they are not generally associated with more distal mutations. (JINS, 2019, 25, 146-155).

Executive Skills and Academic Achievement in the Dystrophinopathies.

OBJECTIVES: To examine academic performance in dystrophinopathy as a function of dystrophin gene mutation position as well as intellectual function, executive skills, socioeconomic status (SES), behavior, and physical ability. METHODS: In a cross-sectional study, boys with dystrophinopathy (ages 5-17; n=50) completed tests of academics (Woodcock-Johnson-III: spelling, reading, calculation and total scores), executive functioning (selective attention/inhibitory control, set shifting, working memory, and processing speed), single word comprehension and nonverbal reasoning. Motor skills were assessed and parents provided demographic information and child behavioral assessments. Dystrophin gene mutation positions were dichotomized into groups (upstream versus downstream of exon 43, location of isoforms previously linked to intellectual impairment). Genetic mutation groups were compared on measures of academic achievement, and multiple regression analyses examined unique and joint contributions of executive skills, intelligence quotient (IQ), SES, motor abilities, behavior, and mutation positions to academic outcomes. RESULTS: Academic performance was slightly, yet significantly, lower than IQ and varied as a function of dystrophin gene position, wherein boys possessing the downstream mutation exhibited greater impairment than boys with the upstream mutation. Digit span forward (indexing verbal span), but no other measure of executive function, contributed significant variance to total academic achievement, spelling and calculation. CONCLUSIONS: Weak academic performance is associated with dystrophinopathy and is more common in downstream mutations. A specific deficit in verbal span may underlie inefficiencies observed in children with dystrophinopathy and may drive deficits impacting academic abilities. (JINS, 2018, 24, 928-938).

Digit Span Performance in Children with Dystrophinopathy: A Verbal Span or Working Memory Contribution?

OBJECTIVES: In a large cohort of boys with dystrophinopathies and their unaffected siblings, we examined whether consistently observed performance on digit span is due primarily to a verbal span or executive deficit. We additionally assessed whether digit span performance contributed to the observed variability in reading performance noted in this population. METHODS: Performance of 170 boys with dystrophinopathy was compared to 95 unaffected sibling controls on measures of verbal function, reading, and digit span. Maximum digit span forward (DSF) and backward (DSB) lengths were converted to Z-scores using normative data. Independent sample t tests, analysis of variance, and hierarchical multiple regression were run (α=0.05). RESULTS: Probands performed worse than controls on digit span, even after accounting for differences in general verbal function (p<.0001). Differences were significant for both DSF (p<.005) and DSB (p<.0001) span length, and an interaction effect yielded significantly worse DSB compared with DSF (p=.01). Reading performance was also lower in probands (p<.0001). The contribution of general level of verbal function, and forward and backward span lengths, did not vary between groups. CONCLUSIONS: In boys with dystrophinopathy, decreased performance on digit span appears to be due to both decreased span forward (measuring verbal span only) and backward (measuring verbal span and working memory). The extent to which sibling controls exhibited better performance compared to the probands was significantly greater for backward span when compared with forward span. Thus, immediate verbal memory and executive control are differentially compromised among boys with dystrophinopathy, and both of these abilities independently contribute to reading performance. (JINS, 2016, 22, 777-784).

Resilience in children diagnosed with a chronic neuromuscular disorder.

OBJECTIVE: : To examine what contributes to resiliency in children living with Duchenne muscular dystrophy (DMD), a chronic, progressive neuromuscular disorder that also influences cognitive ability. The authors hypothesized that family and social support will moderate the effects of individual symptoms of illness severity and influence positive adjustment in boys with DMD. METHOD: : One hundred forty-six boys with DMD were included. Child adjustment, as determined by parent ratings of their son's behavior using the Total Behavior score from the Child Behavior Checklist (CBCL), was examined as an outcome measure. The contributions of individual variables (including age [which serves also as a proxy for degree of physical disability], wheelchair use, and estimated verbal IQ), family variables (the Parental Distress score from the Parent Stress Index), and social environment variables (the Social Competence score from the CBCL) on child adjustment were examined in a linear regression analysis. RESULTS: : Both family and social environment variables significantly contributed to the variance in the CBCL Total Behavior score. In contrast, individual factors that are related to illness severity (age, degree of physical involvement, and estimated verbal IQ) were not associated with child adjustment. CONCLUSION: : Increased children's social networks and decreased parents' stress levels positively contributed to good child adjustment, whereas degree of individual clinical severity did not. Thus, emphasis on providing opportunities for friendships and social support and on parents' adjustment will aid in children's resilience, ensuring they can live well, even while living with the significant burdens associated with DMD.

Association of autistic spectrum disorders with dystrophinopathies.

Parents of 85 boys with dystrophinopathies and 51 sibling controls completed the Social Communication Questionnaire, describing child behaviors associated with autism spectrum disorders and a rating of parental stress. Twenty-one boys with dystrophinopathies and no siblings received scores above the cut-point for possible autistic spectrum disorders. Mothers of identified children were given detailed interviews using the Autism Diagnostic Interview-Revised, and 16 boys (about 19% of the sample) met the criteria for autism spectrum disorders. Significant qualitative abnormalities in reciprocal social interactions and communication were evident in all, whereas restricted and repetitive behaviors were generally less pronounced in the group. Moreover, parents of boys with dystrophinopathy and autism spectrum disorders demonstrated significantly higher ratings of stress than parents of boys with dystrophinopathy alone. Increased attention to behavioral concerns associated with dystrophinopathies is necessary to ensure the well-being of the whole family.

Cognitive and adaptive deficits in young children with Duchenne muscular dystrophy (DMD).

The goal of the current investigation was to examine adaptive behavior and cognitive skills in young children with Duchenne muscular dystrophy (DMD), a genetic disorder that causes progressive muscular weakness and concomitant cognitive deficits. Previous studies have documented specific language deficits in older children with DMD, but there are limited data on younger children. Twenty children with DMD who were between 3 and 6 years old and 20 unaffected family control children were recruited. Parents completed questionnaires relating to development and adaptive functioning, while children completed neuropsychological testing. Results of paired t tests indicate that children with DMD are rated as delayed relative to familial controls on measures of adaptive functioning, as assessed by the Vineland Adaptive Behavior Scales. Furthermore, children with DMD exhibit impairments on multiple measures of cognition, including measures of receptive language, expressive language, visuo-spatial skills, fine-motor skills, attention, and memory skills. Across all domains examined, the young children with DMD performed more poorly than their familial controls. These deficits appear to be more generalized than those reported in older children with this disorder. Dystrophin, a missing protein product, is hypothesized to be responsible for these cognitive and behavioral impairments.

Delayed developmental language milestones in children with Duchenne's muscular dystrophy.

OBJECTIVES: To document the attainment of developmental milestones in children with Duchenne's muscular dystrophy (DMD) and to determine whether early delays are associated with later performance on measures of cognition. STUDY DESIGN: Retrospective parental report was utilized to document the acquisition of 10 common developmental milestones in children with DMD (n = 130) and their unaffected siblings (n = 59). Children completed tests of cognitive functioning. RESULTS: Parents rated children with DMD as delayed on achieving both language and motor milestones more frequently than their unaffected siblings. Furthermore, those children with DMD who were rated as late talkers or late walkers performed more poorly on tests of cognitive function than their on-time peers. CONCLUSIONS: In addition to the commonly reported delays in motor milestones, the current study documents delays in the acquisition of language milestones as well. These early delays are associated with significant impairments in later cognitive functioning.

Social behavior problems in boys with Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a chronic, progressive pediatric disease that affects both muscle and brain. The objectives of the study were to examine parent reported behavior in children with DMD, investigate the influence of chronic illness, intellectual ability and etiology on behavior, and determine whether a specific behavioral profile is associated with DMD. Parental ratings of boys with DMD (n = 181) on the Child Behavior Checklist behavior scales were examined and compared to reported findings of children with other chronic illnesses, unaffected siblings of boys with DMD (n = 86), and children with cerebral palsy (CP) (n = 42). Increased ratings of general behavior problems were reported, and neither physical progression nor intellectual level contributed to behavioral ratings. Among the children with DMD, the Social Problem behavior scale had the greatest number of "clinically significant" ratings (34%). Between-group comparisons showed significantly more boys with DMD were rated as having social behavior problems than either the sibling or CP comparison groups. In addition to the increase in reported behavioral problems likely related to the effects of chronic illness, boys with DMD may be at heightened risk for specific social behavior problems. The specificity of the findings of the behavior profile in DMD may be partially due to the lack of dystrophin isoforms in the central nervous system, and not solely a reactive response to the illness.

Parental stress in mothers of boys with duchenne muscular dystrophy.

OBJECTIVE: To examine parental stress in mothers of boys with Duchenne muscular dystrophy (DMD). METHOD: Stress and its predictors were examined in mothers of boys with DMD (n = 112). Comparisons were made with mothers of healthy children (n = 800), children with cerebral palsy (CP; n = 28), siblings of boys with DMD (n = 46), and longitudinally (n = 16). RESULTS: The presence of problem child behaviors consistently predicted maternal stress. Stress related to child behavior was higher in the DMD versus the normative group. No differences in stress were found in the DMD versus CP groups. Stress related to boys with DMD versus siblings was not significantly different. Over time, maternal stress related to child variables diminished. CONCLUSION: Stress in mothers of boys with DMD is elevated, possibly due to increased problem behaviors, particularly in social interactions, rather than due to the physical demands of the disease alone.