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

Gaps in the Assessment and Care of Neurodevelopmental and Psychiatric Conditions Associated With Dystrophinopathy

INTRODUCTION/AIMS

While dystrophinopathies are primarily characterized by progressive muscle weakness with onset during childhood, dystrophin also plays a role in brain development. This study aimed to characterize how neurodevelopmental and psychiatric disorders are currently identified and managed in clinical care of those with Becker and Duchenne muscular dystrophy (BDMD).

METHODS

Parent Project Muscular Dystrophy (PPMD) disseminated surveys to caregivers and health care providers (HCPs) in the United States to assess the frequency and management of neurodevelopmental and psychiatric disorders of those with dystrophinopathy.

RESULTS

320 caregivers (C) and 74 HCPs responded to surveys. Caregivers indicated higher rates of neurodevelopmental and psychiatric disorders than HCPs, including anxiety (50.5% C, n = 112; 17.8% HCP, n = 19), attention-deficit hyperactivity disorder (ADHD) (32.0% C, n = 73; 15.9% HCP, n = 17), obsessive-compulsive disorder (OCD) (25.9% C, n = 57; 11.2% HCP, n = 12), depression (21.6% C, n = 48; 18.7% HCP, n = 20), and autism spectrum disorder (ASD) (21.0% C, n = 47; 10.3% HCP, n = 11). Results also indicated gaps in the assessment and care of these conditions, including lack of routine screening, reduced access to psychologists and psychiatrists, and lack of clarity amongst HCPs about who should manage neurodevelopmental and psychiatric concerns in those with dystrophinopathy.

DISCUSSION

Closing the identified gaps in assessment, perception, and care will require increased awareness of neurodevelopmental and psychiatric conditions in dystrophinopathy and screening tools to facilitate early identification of these conditions during routine clinical care.

Cognitive changes and brain structural abnormalities in female carriers of DMD pathogenic variants

BACKGROUND

Skeletal and cardiac muscle damage have been increasingly recognized in female carriers of DMD pathogenic variants (DMDc). Little is known about cognitive impairment in these women or whether they have structural brain damage.

OBJECTIVE

To characterize the cognitive profile in a Brazilian cohort of DMDc and determine whether they have structural brain abnormalities using multimodal MRI.

METHODS

Thirty-three DMDc and 33 age-matched healthy women were recruited. The Addenbrooke cognitive examination revised (ACE-R) and the Beck depression inventory (BDI) were used to assess cognition and depressive symptoms. 3T Brain MRI was acquired for both groups. Using volumetric T1 sequence, we computed cerebral cortical thickness (FreeSurfer), basal ganglia (T1 Multi-atlas) and cerebellar (Cerebnet) volumetry. Diffusion tensor imaging (DTI) assessed white-matter integrity (DTI Multi-atlas). Groups were compared using a generalized linear model with Bonferroni-corrected p values < 0.05.

RESULTS

Mean age of DMDc was 38.2 ± 8.2 years, 48.5% of them had abnormal cognition, but only 15% showed meaningful depressive symptoms. Multiple cognitive domains were affected: Attention in 51.5%, Verbal Fluency in 36.4%, Visuospatial Ability in 36.4%, Language in 27.3%, and Memory in 21.2%. Multimodal MRI revealed bilateral, symmetric atrophy in parieto-occipital cortices in DMDc relative to controls, but no basal ganglia, white matter, or cerebellar changes. Parietal cortex thinning correlated with attention, memory, and verbal fluency scores.

INTERPRETATION

DMDc should no longer be seen as 'asymptomatic'. They have cognitive abnormalities and cerebral structural changes compared to healthy women. These manifestations should be actively identified and managed in clinical practice.

Early motor, cognitive, language, behavioural and social emotional development in infants and young boys with Duchenne Muscular Dystrophy- A systematic review

Duchenne Muscular Dystrophy (DMD) is an X-linked recessive disorder caused by mutations in the dystrophin gene. Deficiency of the dystrophin protein causes not only motor, but also cognitive, language, behavioural and social emotional problems. This is the first systematic review investigating five early developmental domains in boys with DMD between 0 and 6 years old. Interactions between different domains and links with mutation types and sites were explored. A systematic search was performed in PubMed, Web of Science and Scopus. An adapted version of the Scottish Intercollegiate Guidelines Network (SIGN) Checklists for case-control and cohort studies was used to evaluate quality. Fifty-five studies of high or acceptable quality were included. One was an RCT of level 1b; 50 were cohort studies of level 2b; and four were an aggregation of case-control and cohort studies receiving levels 2b and 3b. We found that young boys with DMD experienced problems in all five developmental domains, with significant interactions between these. Several studies also showed relationships between mutation sites and outcomes. We conclude that DMD is not only characterised by motor problems but by a more global developmental delay with a large variability between boys. Our results emphasise the need for harmonisation in evaluation and follow-up of young boys with DMD. More high-quality research is needed on the different early developmental domains in young DMD to facilitate early detection of difficulties and identification of associated early intervention strategies.

Pathogenic variants associated with speech/cognitive delay and seizures affect genes with expression biases in excitatory neurons and microglia in developing human cortex

Background & Objective

Congenital brain malformations and neurodevelopmental disorders (NDDs) are common pediatric neurological disorders and result in chronic disability. With the expansion of genetic testing, new etiologies for NDDs are continually uncovered, with as many as one third attributable to single-gene pathogenic variants. While our ability to identify pathogenic variants has continually improved, we have little understanding of the underlying cellular pathophysiology in the nervous system that results from these variants. We therefore integrated phenotypic information from subjects with monogenic diagnoses with two large, single-nucleus RNA-sequencing (snRNAseq) datasets from human cortex across developmental stages in order to investigate cell-specific biases in gene expression associated with distinct neurodevelopmental phenotypes.

Methods

Phenotypic data was gathered from 1) a single-institution cohort of 84 neonates with pathogenic single-gene variants referred to Duke Pediatric Genetics, and 2) a cohort of 4,238 patients with neurodevelopmental disorders and pathogenic single-gene variants enrolled in the Deciphering Developmental Disorders (DDD) study. Pathogenic variants were grouped into genesets by neurodevelopmental phenotype and geneset expression across cortical cell subtypes was compared within snRNAseq datasets from 86 human cortex samples spanning the 2nd trimester of gestation to adulthood.

Results

We find that pathogenic variants associated with speech/cognitive delay or seizures involve genes that are more highly expressed in cortical excitatory neurons than variants in genes not associated with these phenotypes (Speech/cognitive: p=2.25×10-7; Seizures: p=7.97×10-12). A separate set of primarily rare variants associated with speech/cognitive delay or seizures, distinct from those with excitatory neuron expression biases, demonstrated expression biases in microglia. We also found that variants associated with speech/cognitive delay and an excitatory neuron expression bias could be further parsed by the presence or absence of comorbid seizures. Variants associated with speech/cognitive delay without seizures tended to involve calcium regulatory pathways and showed greater expression in extratelencephalic neurons, while those associated with speech/cognitive delay with seizures tended to involve synaptic regulatory machinery and an intratelencephalic neuron expression bias (ANOVA by geneset p<2×10-16).

Conclusions

By combining extensive phenotype datasets from subjects with neurodevelopmental disorders with massive human cortical snRNAseq datasets across developmental stages, we identified cell-specific expression biases for genes in which pathogenic variants are associated with speech/cognitive delay and seizures. The involvement of genes with enriched expression in excitatory neurons or microglia highlights the unique role both cell types play in proper sculpting of the developing brain. Moreover, this information begins to shed light on distinct cortical cell types that are more likely to be impacted by pathogenic variants and that may mediate the symptomatology of resulting neurodevelopmental disorders.

Short developmental milestone risk assessment tool to identify Duchenne muscular dystrophy in primary care

BACKGROUND

In patients without a family history, Duchenne muscular dystrophy (DMD) is typically diagnosed at around 4-5 years of age. It is important to diagnose DMD during infancy or toddler stage in order to have timely access to treatment, opportunities for reproductive options, prevention of potential fatal reactions to inhaled anesthetics, awareness of a child's abilities needed for good parenting, and opportunities for enrolment in clinical trials.

METHOD

We aimed to develop a short risk assessment tool based on developmental milestones that may contribute to the early detection of boys with DMD in primary care. As part of the case-control 4D-DMD study (Detection by Developmental Delay in Dutch boys with DMD), data on developmental milestones, symptoms and therapies for 76 boys with DMD and 12,414 boys from a control group were extracted from the health records of youth health care services and questionnaires. Multiple imputation, diagnostic validity and pooled backward logistic regression analyses with DMD (yes/no) as the dependent variable and attainment of 26 milestones until 36 months of age (yes/no) as the independent variable were performed. Descriptive statistics on symptoms and therapies were provided.

RESULTS

A tool with seven milestones assessed at specific ages between 12 and 36 months resulted in a sensitivity of 79% (95CI:67-88%), a specificity of 95.8% (95%CI:95.3-96.2), and a positive predictive value of 1:268 boys. Boys with DMD often had symptoms (e.g. 43% had calf muscle pseudohypertrophy) and were referred to therapy (e.g. 59% for physical therapy) before diagnosis.

DISCUSSION

This tool followed by the examination of other DMD-related symptoms could be used by youth health care professionals during day-to-day health assessments in the general population to flag children who require further action.

CONCLUSIONS

The majority of boys (79%) with DMD can be identified between 12 and 36 months of age with this tool. It increases the initial a priori risk of DMD from 1 in 5,000 to approximately 1 in 268 boys. We expect that other neuromuscular disorders and disabilities can also be found with this tool.

Draft Guidance for Industry Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, and Related Dystrophinopathies - Developing Potential Treatments for the Entire Spectrum of Disease

Background

Duchenne muscular dystrophy (DMD) and related dystrophinopathies are neuromuscular conditions with great unmet medical needs that require the development of effective medical treatments.

Objective

To aid sponsors in clinical development of drugs and therapeutic biological products for treating DMD across the disease spectrum by integrating advancements, patient registries, natural history studies, and more into a comprehensive guidance.

Methods

This guidance emerged from collaboration between the FDA, the Duchenne community, and industry stakeholders. It entailed a structured approach, involving multiple committees and boards. From its inception in 2014, the guidance underwent revisions incorporating insights from gene therapy studies, cardiac function research, and innovative clinical trial designs.

Results

The guidance provides a deeper understanding of DMD and its variants, focusing on patient engagement, diagnostic criteria, natural history, biomarkers, and clinical trials. It underscores patient-focused drug development, the significance of dystrophin as a biomarker, and the pivotal role of magnetic resonance imaging in assessing disease progression. Additionally, the guidance addresses cardiomyopathy's prominence in DMD and the burgeoning field of gene therapy.

Conclusions

The updated guidance offers a comprehensive understanding of DMD, emphasizing patient-centric approaches, innovative trial designs, and the importance of biomarkers. The focus on cardiomyopathy and gene therapy signifies the evolving realm of DMD research. It acts as a crucial roadmap for sponsors, potentially leading to improved treatments for DMD.

Association between neurodevelopmental impairments and motor function in Duchenne muscular dystrophy

OBJECTIVE

We explored various prognostic factors of motor outcomes in corticosteroid-naive boys with Duchenne Muscular Dystrophy (DMD).

METHODS

The associations between parent-reported neurodevelopmental concerns (speech delay, speech and language difficulties (SLD), and learning difficulties), DMD mutation location, and motor outcomes (6-minute walk distance (6MWD), North Star Ambulatory Assessment (NSAA) total score, 10-meter walk/run velocity, and rise from floor velocity) were studied in 196 corticosteroid-naive boys from ages 4 to less than 8 years.

RESULTS

Participants with SLD walked 25.8 fewer meters in 6 minutes than those without SLD (p = 0.005) but did not demonstrate statistical differences in NSAA total score, 10-meter walk/run velocity, and rise from floor velocity. Participants with distal DMD mutations with learning difficulties walked 51.8 fewer meters in 6 minutes than those without learning difficulties (p = 0.0007). Participants with distal DMD mutations were slower on 10-meter walk/run velocity, and rise from floor velocity (p = 0.02) than those with proximal DMD mutations. Participants with distal DMD mutations, who reported speech delay or learning difficulties, were slower on rise from floor velocity (p = 0.04, p = 0.01) than those with proximal DMD mutations. The mean NSAA total score was lower in participants with learning difficulties than in those without (p = 0.004).

INTERPRETATION

Corticosteroid-naive boys with DMD with distal DMD mutations may perform worse on some timed function tests, and that those with learning difficulties may perform worse on the NSAA. Pending confirmatory studies, our data underscore the importance of considering co-existing neurodevelopmental symptoms on motor outcome measures.

Detecting early signs in Duchenne muscular dystrophy: comprehensive review and diagnostic implications

Despite the early onset of clinical signs suggestive of Duchenne muscular dystrophy (DMD), a diagnosis is often not made until four years of age or older, with a diagnostic delay of up to two years from the appearance of the first symptoms. As disease-modifying therapies for DMD become available that are ideally started early before irreversible muscle damage occurs, the importance of avoiding diagnostic delay increases. Shortening the time to a definite diagnosis in DMD allows timely genetic counseling and assessment of carrier status, initiation of multidisciplinary standard care, timely initiation of appropriate treatments, and precise genetic mutation characterization to assess suitability for access to drugs targeted at specific mutations while reducing the emotional and psychological family burden of the disease. This comprehensive literature review describes the early signs of impairment in DMD and highlights the bottlenecks related to the different diagnostic steps. In summary, the evidence suggests that the best mitigation strategy for improving the age at diagnosis is to increase awareness of the early symptoms of DMD and encourage early clinical screening with an inexpensive and sensitive serum creatine kinase test in all boys who present signs of developmental delay and specific motor test abnormality at routine pediatrician visits.

Duchenne Muscular Dystrophy from Brain to Muscle: The Role of Brain Dystrophin Isoforms in Motor Functions

Brain function and its effect on motor performance in Duchenne muscular dystrophy (DMD) is an emerging concept. The present study explored how cumulative dystrophin isoform loss, age, and a corticosteroid treatment affect DMD motor outcomes. A total of 133 genetically confirmed DMD patients from Sri Lanka were divided into two groups based on whether their shorter dystrophin isoforms (Dp140, Dp116, and Dp71) were affected: Group 1, containing patients with Dp140, Dp116, and Dp71 affected (n = 98), and Group 2, containing unaffected patients (n = 35). A subset of 52 patients (Group 1, n = 38; Group 2, n = 14) was followed for up to three follow-ups performed in an average of 28-month intervals. The effect of the cumulative loss of shorter dystrophin isoforms on the natural history of DMD was analyzed. A total of 74/133 (56%) patients encountered developmental delays, with 66/74 (89%) being in Group 1 and 8/74 (11%) being in Group 2 (p < 0.001). Motor developmental delays were predominant. The hip and knee muscular strength, according to the Medical Research Council (MRC) scale and the North Star Ambulatory Assessment (NSAA) activities, "standing on one leg R", "standing on one leg L", and "walk", declined rapidly in Group 1 (p < 0.001 In the follow-up analysis, Group 1 patients became wheelchair-bound at a younger age than those of Group 2 (p = 0.004). DMD motor dysfunction is linked to DMD mutations that affect shorter dystrophin isoforms. When stratifying individuals for clinical trials, considering the DMD mutation site and its impact on a shorter dystrophin isoform is crucial.

Integrated genomic, proteomic and cognitive assessment in Duchenne Muscular Dystrophy suggest astrocyte centric pathology

Introduction

Documented Duchenne Muscular Dystrophy (DMD) biomarkers are confined to Caucasians and are poor indicators of cognitive difficulties and neuropsychological alterations.

Materials and methods

This study correlates serum protein signatures with cognitive performance in DMD patients of South Asian origin. Study included 25 DMD patients aged 6-16 years. Cognitive profiles were assessed by Wechsler Intelligence Scale for Children. Serum proteome profiling of 1317 proteins was performed in eight DMD patients and eight age-matched healthy volunteers.

Results

Among the several novel observations we report, better cognitive performance in DMD was associated with increased serum levels of MMP9 and FN1 but decreased Siglec-3, C4b, and C3b. Worse cognitive performance was associated with increased serum levels of LDH-H1 and PDGF-BB but reduced GDF-11, MMP12, TPSB2, and G1B. Secondly, better cognitive performance in Processing Speed (PSI) and Perceptual Reasoning (PRI) domains was associated with intact Dp116, Dp140, and Dp71 dystrophin isoforms while better performance in Verbal Comprehension (VCI) and Working Memory (WMI) domains was associated with intact Dp116 and Dp140 isoforms. Finally, functional pathways shared with Alzheimer's Disease (AD) point towards an astrocyte-centric model for DMD.

Conclusion

Astrocytic dysfunction leading to synaptic dysfunction reported previously in AD may be a common pathogenic mechanism underlying both AD and DMD, linking protein alterations to cognitive impairment. This new insight may pave the path towards novel therapeutic approaches targeting reactive astrocytes.

Health-related quality of life in children and adolescents with Duchenne muscular dystrophy and comorbid attention-deficit hyperactivity disorder using propensity-score matching

OBJECTIVE

This study aimed to assess and compare the health-related quality of life (HRQoL) in a group of paediatric patients with Duchenne muscular dystrophy (DMD) with and without comorbid attention-deficit hyperactivity disorder (ADHD) diagnosis using a propensity-scoring method (PSM).

METHOD

Data used in this study obtained from a cross-sectional and web-based survey to investigate the HRQoL for paediatric DMD patients. Data about those who diagnosed with ADHD was elicited for analysis. PSM was used to ensure generation of 1:5 matched pairs with no differences in several background characteristics between DMD patients with and without ADHD. Wilcoxon rank sum test and Multiple logistic regression models were used to measure the differences in HRQoL between matched DMD patients with and without ADHD.

RESULTS

After PSM, 630 DMD patients were assigned to the 'No ADHD' group, and successfully matched with another 126 DMD patients in the ADHD comparison group. Compared to DMD patients without ADHD, those with ADHD were more likely to report having symptoms and side-effects. Additionally, paediatric DMD patients with ADHD reported a significantly lower HRQoL on the subscales of emotional, social, and school functioning as compared to those without ADHD.

CONCLUSION

This study demonstrated a higher burden of clinical symptoms, health service utilization, and psychosocial factors on HRQoL in DMD patients with ADHD compared to those without ADHD. Future studies using global data may provide meaningful comparisons with our results, and the efficacy of ADHD programs in DMD patients can be compared based on their HRQoL.

Neuro-Cardio-Autonomic Modulations in Children with Duchenne Muscular Dystrophy

BACKGROUND AND OBJECTIVE

Duchenne muscular dystrophy (DMD) is a degenerative X-linked muscle disease. Death frequently results from complications in cardiopulmonary systems. Preclinical/early diagnosis of cardiac autonomic abnormalities may aid initiate cardioprotective therapy and enhance prognosis.

METHODS

A cross sectional, prospective study of 38 DMD boys compared with 37 age-matched healthy controls was conducted. Lead II electrocardiography and beat-to-beat blood pressure were recorded to assess heart rate variability (HRV), blood pressure variability (BPV), and baroreceptor sensitivity (BRS) in a standardized environment. Data were analysed and correlated with disease severity and genotype.

RESULTS

In the DMD group, the median age at assessment was 8 years [IQR 7-9 years], the median age at disease onset was 3 years [IQR, 2-6 years], and the mean duration of illness was 4 years [IQR, 2.5-5]. DNA sequencing showed deletions in 34/38 (89.5 %) and duplications in 4/38 (10.5%) patients. The median heart rate in DMD children was significantly higher [101.19 (Range, 94.71-108.49)] /min compared to controls [81 (Range, 76.2-92.76)] /min (p < 0.05). All the assessed HRV and BPV parameters were significantly impaired in DMD cases except for the coefficient of variance of systolic blood pressure. Further, BRS parameters were also significantly reduced in DMD, excluding alpha-LF. A positive correlation was found between alpha HF with age at onset and duration of illness.

CONCLUSION

This study demonstrates a distinct early impairment of neuro-cardio-autonomic regulation in DMD. Simple yet effective non-invasive techniques such as HRV, BPV, and BRS may help identify cardiac dysfunction in a pre-clinical state, paving the way for early cardio-protective therapies and limiting disease progression in DMD patients.

Associations Between Self-Reported Behavioral and Learning Concerns and DMD Isoforms in Duchenne Muscular Dystrophy

Background: Duchenne muscular dystrophy (DMD) is an X-linked recessive neuromuscular disorder resulting from loss of dystrophin. In addition to its role in muscle, isoforms of dystrophin are expressed in different cell types of the brain, and DMD has been linked to language delays, behavioral abnormalities and learning disabilities. Objective: To determine whether disruption of specific DMD isoforms, age, corticosteroid use, ambulation status, or country are associated with behavioral and/or learning concerns in DMD. Methods: De-identified data were collected from the Duchenne Registry from 2007– 2019. Females, patients with BMD, and those without genetic testing reports were excluded from the cohort. For the genetic analysis, patients were divided into four subgroups based on the location of their mutation and the predicted isoforms affected. Bivariate analysis was conducted using chi-square for categorical variables. Two multivariate logistic regressions were used to assess independent associations with behavioral and learning concerns, respectively, and to estimate the effect size of each variable. Results: DMD mutations disrupting expression of Dp140 and Dp71 were associated with a higher likelihood of reported behavioral and learning concerns. Corticosteroid use, categorical age, and country were other factors associated with behavior and learning concerns. Conclusion: This data adds to our current understanding of DMD isoforms, their mutational consequence and impact on behavior and learning.

Synaptic alterations as a neurodevelopmental trait of Duchenne muscular dystrophy

Dystrophinopaties, e.g., Duchenne muscular dystrophy (DMD), Becker muscular dystrophy and X-linked dilated cardiomyopathy are inherited neuromuscular diseases, characterized by progressive muscular degeneration, which however associate with a significant impact on general system physiology. The more severe is the pathology and its diversified manifestations, the heavier are its effects on organs, systems, and tissues other than muscles (skeletal, cardiac and smooth muscles). All dystrophinopaties are characterized by mutations in a single gene located on the X chromosome encoding dystrophin (Dp427) and its shorter isoforms, but DMD is the most devasting: muscular degenerations manifests within the first 4 years of life, progressively affecting motility and other muscular functions, and leads to a fatal outcome between the 20s and 40s. To date, after years of studies on both DMD patients and animal models of the disease, it has been clearly demonstrated that a significant percentage of DMD patients are also afflicted by cognitive, neurological, and autonomic disorders, of varying degree of severity. The anatomical correlates underlying neural functional damages are established during embryonic development and the early stages of postnatal life, when brain circuits, sensory and motor connections are still maturing. The impact of the absence of Dp427 on the development, differentiation, and consolidation of specific cerebral circuits (hippocampus, cerebellum, prefrontal cortex, amygdala) is significant, and amplified by the frequent lack of one or more of its lower molecular mass isoforms. The most relevant aspect, which characterizes DMD-associated neurological disorders, is based on morpho-functional alterations of selective synaptic connections within the affected brain areas. This pathological feature correlates neurological conditions of DMD to other severe neurological disorders, such as schizophrenia, epilepsy and autistic spectrum disorders, among others. This review discusses the organization and the role of the dystrophin-dystroglycan complex in muscles and neurons, focusing on the neurological aspect of DMD and on the most relevant morphological and functional synaptic alterations, in both central and autonomic nervous systems, described in the pathology and its animal models.

Walking alone milestone combined reading-frame rule improves early prediction of Duchenne muscular dystrophy

OBJECTIVE

To explore the potential of walking alone milestone combined reading-frame rule to improve the early diagnosis of Duchenne muscular dystrophy (DMD).

METHOD

To retrospectively describe the genotype and phenotype of Duchenne and Becker muscular dystrophies (BMD) patients with deletions and duplicates in the dystrophin gene. The sensitivity and specificity of the reading frame rule were calculated and compared to that of the combined reading frame rule and walking alone milestone. The diagnostic coincidence rate of two different methods was analyzed.

RESULT

One hundred sixty-nine male DMD/BMD patients were enrolled, including 17 cases of BMD and 152 cases of DMD. The diagnostic coincidence rate, diagnostic sensitivity, and specificity of the reading-frame rule for DMD/BMD were 85.2, 86.8, and 70.59%, respectively. The sensitivity and specificity of the reading frame principle combined with the walking alone milestone for DMD/BMD were 96.05 and 70.59%, respectively. The diagnostic coincidence rate increased to 93.49%, significantly different from that predicted by reading- frame rule (P < 0.05).

CONCLUSION

The reading-frame rule combined with the walking alone milestone significantly improved the early diagnosis rate of DMD.

Health Profile of Preterm Males With Duchenne Muscular Dystrophy

In this retrospective cohort study, we characterize the health profile of preterm males with Duchenne muscular dystrophy. Major clinical milestones (ambulation cessation, assisted ventilation use, and onset of left ventricular dysfunction) and corticosteroids use in males with Duchenne muscular dystrophy identified through a population-based surveillance system were analyzed using Kaplan-Meier survival curves and Cox proportional hazards modeling. The adjusted risk of receiving any respiratory intervention among preterm males with Duchenne muscular dystrophy was 87% higher than among the corresponding full-term males with Duchenne muscular dystrophy. The adjusted risks for ambulation cessation and left ventricular dysfunction were modestly elevated among preterm compared to full-term males, but the 95% confidence intervals contained the null. No difference in the start of corticosteroid use between preterm and full-term Duchenne muscular dystrophy males was observed. Overall, the disease course seems to be similar between preterm and full-term males with Duchenne muscular dystrophy; however, pulmonary function seems to be affected earlier among preterm males with Duchenne muscular dystrophy.

Complexity of skeletal muscle degeneration: multi-systems pathophysiology and organ crosstalk in dystrophinopathy

Duchenne muscular dystrophy is a highly progressive muscle wasting disorder due to primary abnormalities in one of the largest genes in the human genome, the DMD gene, which encodes various tissue-specific isoforms of the protein dystrophin. Although dystrophinopathies are classified as primary neuromuscular disorders, the body-wide abnormalities that are associated with this disorder and the occurrence of organ crosstalk suggest that a multi-systems pathophysiological view should be taken for a better overall understanding of the complex aetiology of X-linked muscular dystrophy. This article reviews the molecular and cellular effects of deficiency in dystrophin isoforms in relation to voluntary striated muscles, the cardio-respiratory system, the kidney, the liver, the gastrointestinal tract, the nervous system and the immune system. Based on the establishment of comprehensive biomarker signatures of X-linked muscular dystrophy using large-scale screening of both patient specimens and genetic animal models, this article also discusses the potential usefulness of novel disease markers for more inclusive approaches to differential diagnosis, prognosis and therapy monitoring that also take into account multi-systems aspects of dystrophinopathy. Current therapeutic approaches to combat muscular dystrophy are summarised.

Resting-state functional MRI shows altered default-mode network functional connectivity in Duchenne muscular dystrophy patients

Duchenne muscular dystrophy (DMD) is an X-linked recessive neuromuscular disorder caused by absence of dystrophin protein. Dystrophin is expressed in muscle, but also in the brain. Difficulties with attention/inhibition, working memory and information processing are well described in DMD patients but their origin is poorly understood. The default mode network (DMN) is one of the networks involved in these processes. Therefore we aimed to assess DMN connectivity in DMD patients compared to matched controls, to better understand the cognitive profile in DMD. T1-weighted and resting state functional MRI scans were acquired from 33 DMD and 24 male age-matched controls at two clinical sites. Scans were analysed using FMRIB Software Library (FSL). Differences in the DMN were assessed using FSL RANDOMISE, with age as covariate and threshold-free cluster enhancement including multiple comparison correction. Post-hoc analyses were performed on the visual network, executive control network and fronto-parietal network with the same methods. In DMD patients, the level of connectivity was higher in areas within the control DMN (hyperconnectivity) and significant connectivity was found in areas outside the control DMN. No hypoconnectivity was found and no differences in the visual network, executive control network and fronto-parietal network. We showed differences both within and in areas outside the DMN in DMD. The specificity of our findings to the DMN can help provide a better understanding of the attention/inhibition, working memory and information processing difficulties in DMD.

Combined Cell Therapy in the Treatment of Neurological Disorders

Cell therapy of neurological diseases is gaining momentum. Various types of stem/progenitor cells and their derivatives have shown positive therapeutic results in animal models of neurological disorders and in clinical trials. Each tested cell type proved to have its advantages and flaws and unique cellular and molecular mechanism of action, prompting the idea to test combined transplantation of two or more types of cells (combined cell therapy). This review summarizes the results of combined cell therapy of neurological pathologies reported up to this point. The number of papers describing experimental studies or clinical trials addressing this subject is still limited. However, its successful application to the treatment of neurological pathologies including stroke, spinal cord injury, neurodegenerative diseases, Duchenne muscular dystrophy, and retinal degeneration has been reported in both experimental and clinical studies. The advantages of combined cell therapy can be realized by simple summation of beneficial effects of different cells. Alternatively, one kind of cells can support the survival and functioning of the other by enhancing the formation of optimum environment or immunomodulation. No significant adverse events were reported. Combined cell therapy is a promising approach for the treatment of neurological disorders, but further research needs to be conducted.

Early developmental milestones in Duchenne muscular dystrophy

AIM

To investigate the differences in attainment of developmental milestones between young males with Duchenne muscular dystrophy (DMD) and young males from the general population.

METHOD

As part of the case-control 4D-DMD study (Detection by Developmental Delay in Dutch boys with Duchenne Muscular Dystrophy), data on developmental milestones for 76 young males with DMD and 12 414 young males from a control group were extracted from the health care records of youth health care services. The characteristics of DMD were acquired from questionnaires completed by parents. Logistic regression analyses were performed with milestone attainment (yes/no) as the dependent variable and DMD (yes/no) as the independent variable, with and without adjustment for age at visit.

RESULTS

The mean number of available milestones was 43 (standard deviation [SD]=13, range: 1-59) in the DMD group and 40 (SD=15, range: 1-60) in the control group. The presence of developmental delay was evident at 2 to 3 months of age, with a higher proportion of young males with DMD failing to attain milestones of gross/fine motor activity, adaptive behaviour, personal/social behaviour, and communication (range age-adjusted odds ratios [ORs]=2.3-4.0, p<0.01). Between 12 and 36 months of age, differences in the attainment of developmental milestones concerning gross motor activity increased with age (range age-adjusted ORs=10.3-532, p<0.001). We also found differences in developmental milestones concerning fine motor activity, adaptive behaviour, personal/social behaviour, and communication between 12 and 48 months of age (range age-adjusted ORs=2.5-9.7, p<0.01).

INTERPRETATION

We found delays in the attainment of motor and non-motor milestones in young males with DMD compared to the control group. Such delays were already evident a few months after birth. Developmental milestones that show a delay in attainment have the potential to aid the earlier diagnosis of DMD.

Longitudinal Evaluation of Working Memory in Duchenne Muscular Dystrophy

Objective: The developmental maturation of forward and backward digit spans—indices of working memory—in boys with nonsense (nm) Duchenne muscular dystrophy (DMD) (nmDMD) was assessed using prospective, longitudinal data. Methods: Fifty-five boys of the 57 subjects with genetically confirmed nmDMD—who were from the placebo arm of a 48-week-long phase 2b clinical trial—were evaluated. Forward and backward digit spans were obtained every 12 weeks for a total of five assessments in all study subjects. Changes in forward and backward digit spans were evaluated based on age, corticosteroid treatment, and DMD mutation location. Results: Boys with nmDMD had lower mean scores on normalized forward digit span. Normalized forward digit spans were comparable between subjects stratified by age and between corticosteroid-naïve and corticosteroid-treated subjects. When stratified by DMD mutation location, normalized forward digit spans were lower in nmDMD subjects with mutations downstream of DMD exon 30, exon 45, and exon 63, both at baseline evaluation and at follow-up evaluation at 48 weeks. On average, normalized backward digit span scores were stable over 48 weeks in these subjects. Developmental growth modeling showed that subjects with nmDMD mutations upstream of DMD exon 30, upstream of DMD exon 45, and upstream of DMD exon 63 appeared to make better gains in working memory than subjects with mutations downstream of DMD exon 30, downstream of DMD exon 45, and downstream of DMD exon 63. Conclusion: Performance in working memory shows deficits in nmDMD and differed based on nmDMD location. Maturation in cognition was seen over a 48-week period. The developmental trajectory of working memory in this cohort was influenced by DMD mutation location.

Cognition of the mothers of patients with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) has been found to be associated with cognitive impairment. However, few studies have addressed cognitive impairment among mothers of children with DMD. In the present study, the neuropsychological profiles of both carrier mothers (C-Ms) and noncarrier mothers (NC-Ms) were examined, and the findings were compared with healthy control mothers (HC-Ms). There were 90 participants, consisting of 31 C-Ms, 24 NC-Ms, and 35 HC-Ms, each of whom completed a neuropsychological test battery. C-Ms had poorer cognition performance in attention, working memory, immediate verbal memory, visuospatial skills, and executive functions than NC-Ms, and HC-Ms. This study provides evidence that there may be cognitive impairment in mothers of patients with DMD. The cognitive impairment of C-Ms has similarities to that seen in children with DMD.

Cognitive Deficits in Myopathies

Myopathies represent a wide spectrum of heterogeneous diseases mainly characterized by the abnormal structure or functioning of skeletal muscle. The current paper provides a comprehensive overview of cognitive deficits observed in various myopathies by consulting the main libraries (Pubmed, Scopus and Google Scholar). This review focuses on the causal classification of myopathies and concomitant cognitive deficits. In most studies, cognitive deficits have been found after clinical observations while lesions were also present in brain imaging. Most studies refer to hereditary myopathies, mainly Duchenne muscular dystrophy (DMD), and myotonic dystrophies (MDs); therefore, most of the overview will focus on these subtypes of myopathies. Most recent bibliographical sources have been preferred.

Point, walk, talk: Links between three early milestones, from observation and parental report

Around their first birthdays, infants begin to point, walk, and talk. These abilities are appreciable both by researchers with strictly standardized criteria and caregivers with more relaxed notions of what each of these skills entails. Here, we compare the onsets of these skills and links among them across two data collection methods: observation and parental report. We examine pointing, walking, and talking in a sample of 44 infants studied longitudinally from 6 to 18 months. In this sample, links between pointing and vocabulary were tighter than those between walking and vocabulary, supporting a unified sociocommunicative growth account. Indeed, across several cross-sectional and longitudinal analyses, pointers had larger vocabularies than their nonpointing peers. In contrast to previous work, this did not hold for walkers' versus crawlers' vocabularies in our sample. Comparing across data sources, we find that reported and observed estimates of the growing vocabulary and of age of walk onset were closely correlated, while agreement between parents and researchers on pointing onset and talking onset was weaker. Taken together, these results support a developmental account in which gesture and language are intertwined aspects of early communication and symbolic thinking, whereas the shift from crawling to walking appears indistinct from age in its relation with language. We conclude that pointing, walking, and talking are on similar timelines yet distinct from one another, and discuss methodological and theoretical implications in the context of early development. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Physical exertion exacerbates decline in the musculature of an animal model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a genetic disorder caused by loss of the protein dystrophin. In humans, DMD has early onset, causes developmental delays, muscle necrosis, loss of ambulation, and death. Current animal models have been challenged by their inability to model the early onset and severity of the disease. It remains unresolved whether increased sarcoplasmic calcium observed in dystrophic muscles follows or leads the mechanical insults caused by the muscle's disrupted contractile machinery. This knowledge has important implications for patients, as potential physiotherapeutic treatments may either help or exacerbate symptoms, depending on how dystrophic muscles differ from healthy ones. Recently we showed how burrowing dystrophic (dys-1) C. elegans recapitulate many salient phenotypes of DMD, including loss of mobility and muscle necrosis. Here, we report that dys-1 worms display early pathogenesis, including dysregulated sarcoplasmic calcium and increased lethality. Sarcoplasmic calcium dysregulation in dys-1 worms precedes overt structural phenotypes (e.g., mitochondrial, and contractile machinery damage) and can be mitigated by reducing calmodulin expression. To learn how dystrophic musculature responds to altered physical activity, we cultivated dys-1 animals in environments requiring high intensity or high frequency of muscle exertion during locomotion. We find that several muscular parameters (e.g., size) improve with increased activity. However, longevity in dystrophic animals was negatively associated with muscular exertion, regardless of effort duration. The high degree of phenotypic conservation between dystrophic worms and humans provides a unique opportunity to gain insight into the pathology of the disease as well as the initial assessment of potential treatment strategies.

Neurodevelopmental Needs in Young Boys with Duchenne Muscular Dystrophy (DMD): Observations from the Cooperative International Neuromuscular Research Group (CINRG) DMD Natural History Study (DNHS)

INTRODUCTION

Duchenne muscular dystrophy (DMD) is the most common X-linked neuromuscular condition manifested by progressive skeletal muscle weakness, cardiopulmonary involvement and cognitive deficits. Neurodevelopmental symptoms and signs are under-appreciated in this population despite the recognition that cognition has a major impact on quality-of-life. We describe the neurodevelopmental needs in a large cohort of young boys with DMD from the DMD Natural History Study (DNHS). We explore the association between neurodevelopmental needs and DMD mutation location, and with glucocorticoid use.   Methods: We prospectively evaluated 204 participants between ages 4 to less than 9 years of age with DMD as part of a large, longitudinal, international DNHS. We obtained parent- or primary care-giver report of neurodevelopmental needs as part of their study visit. We assessed the relationship between parent/care-giver neurodevelopmental needs and DMD mutation location, and glucocorticoid use.

RESULTS

The neurodevelopmental needs that were most commonly reported included speech delay (33%), mild developmental delay (24%), significant behavioral problems (16.5%), language impairment (14.5%), learning disability (14.5%), attention-deficit hyperactivity disorder (5%) and autism spectrum disorder (3%). Neurodevelopmental needs were more commonly reported by care-givers in those with DMD mutations downstream of exon 51. There was no relationship between care-giver reported neurodevelopmental needs and glucocorticoid use.

CONCLUSION

Neurodevelopmental needs are highly prevalent in young boys with DMD. Care-givers report higher neurodevelopmental needs when subjects have DMD mutations downstream of exon 51. Early interventions aimed at cognitive health are critical to improve the quality-of-life of individuals with DMD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00468832.

The clinical spectrum and genetic variability of limb-girdle muscular dystrophy in a cohort of Chinese patients

Background

Limb-girdle muscular dystrophy (LGMD) is a commonly diagnosed hereditary muscular disorder, characterized by the progressive weakness of the limb-girdle muscles. Although the condition has been well-characterized, clinical and genetic heterogeneity can be observed in patients with LGMD. Here, we aimed to describe the clinical manifestations and genetic variability among a cohort of patients with LGMD in South China.

Results

We analyzed the clinical information, muscle magnetic resonance imaging (MRI) findings, and genetic results obtained from 30 patients (24 families) with clinically suspected LGMD. In 24 probands, 38 variants were found in total, of which 18 were shown to be novel. Among the 30 patients, the most common subtypes were dysferlinopathy in eight (26.67%), sarcoglycanopathies in eight [26.67%; LGMD 2C in three (10.00%), LGMD 2D in three (10.00%), and LGMD 2F in two (6.67%)], LGMD 2A in seven (23.33%), followed by LGMD 1B in three (10.00%), LGMD 2I in three (10.00%), and early onset recessive Emery-Dreifuss-like phenotype without cardiomyopathy in one (3.33%). Furthermore, we also observed novel clinical presentations for LGMD 1B, 2F, and 2I patients with hypermobility of the joints in the upper limbs, a LGMD 2F patient with delayed language development, and other manifestations. Moreover, distinct distributions of fatty infiltration in patients with LGMD 2A, dysferlinopathy, and the early onset recessive Emery-Dreifuss-like phenotype without cardiomyopathy were also observed based on muscle MRI results.

Conclusions

In this study, we expanded the clinical spectrum and genetic variability found in patients with LGMD, which provided additional insights into genotype and phenotype correlations in this disease.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0859-6) contains supplementary material, which is available to authorized users.

Descriptive Phenotype of Obsessive Compulsive Symptoms in Males With Duchenne Muscular Dystrophy

Increased rates of clinically significant internalizing disorders (obsessive compulsive disorder, anxiety, and depression) have been demonstrated in males with Duchenne muscular dystrophy, and a Duchenne muscular dystrophy neuropsychiatric syndrome has been suggested. Although symptoms of depression are widely recognized, some of the other internalizing symptoms are less frequently identified. Through a retrospective chart review of 107 males with Duchenne muscular dystrophy, we identified 15 patients with obsessive compulsive disorder spectrum symptoms; 11 of those also had anxiety symptoms. Many of these patients received selective serotonin reuptake inhibitor treatment, commonly noting improvement in symptoms. Here we describe the clinical features of several patients in detail to facilitate early recognition and consideration for treatment for patients with Duchenne muscular dystrophy and internalizing psychiatric symptoms. The results of this cohort showed a significantly increased rate of obsessive compulsive disorder spectrum symptoms (14%) compared to the general population.

Is There a Delay in Diagnosis of Duchenne Muscular Dystrophy Among Preterm-Born Males?

The objective of this study was to investigate whether males who were born preterm took longer to receive a Duchenne muscular dystrophy diagnosis than term males. Data for males with Duchenne muscular dystrophy identified through a population-based surveillance system were analyzed using a Kaplan-Meier estimator. The first signs and symptoms were noted at a median age of 2 years in both groups. Median age when first signs and symptoms prompted medical evaluation was 2.59 years among preterm and 4.01 years among term males. Median age at definitive diagnosis was 4.25 years and 4.92 years for preterm and term males, respectively. Neither difference was statistically significant. Preterm males tended to be seen for their initial medical evaluation earlier than term males, though they were not diagnosed significantly earlier. It may take clinicians longer after the initial evaluation of preterm males to arrive at a Duchenne muscular dystrophy diagnosis.

Delayed onset of ambulation in boys with Duchenne muscular dystrophy: Potential use as an endpoint in clinical trials

Individuals with Duchenne muscular dystrophy (DMD) often exhibit delayed motor and cognitive development, including delayed onset of ambulation. Data on age when loss of independent ambulation occurs are well established for DMD; however, age at onset of walking has not been well described. We hypothesize that an effective medication given in early infancy would advance the age when walking is achieved so that it is closer to age-matched norms, and that this discrete event could serve as the primary outcome measure in a clinical trial. This study examined three data sets, Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet); Dutch Natural History Survey (DNHS); and Parent Project Muscular Dystrophy (PPMD). The distribution of onset of ambulation in DMD (mean ± SD) and median age, in months, at the onset of ambulation was 17.3 (±5.5) and 16.0 in MD STARnet, 21.8 (±7.1) and 20.0 in DNHS, and 16.1 (±4.4) and 15 in PPMD. Age of ambulation in these data sets were all significantly later (P <0.001) than the corresponding age for typically developing boys, 12.1 (±1.8). A hypothetical clinical trial study design and power analyses are presented based on these data.

Reversal of neurobehavioral social deficits in dystrophic mice using inhibitors of phosphodiesterases PDE5A and PDE9A

Duchenne muscular dystrophy is caused by mutations in the DYSTROPHIN gene. Although primarily associated with muscle wasting, a significant portion of patients (approximately 25%) are also diagnosed with autism spectrum disorder. We describe social behavioral deficits in dystrophin-deficient mice and present evidence of cerebellar deficits in cGMP production. We demonstrate therapeutic potential for selective inhibitors of the cGMP-specific PDE5A and PDE9A enzymes to restore social behaviors in dystrophin-deficient mice.

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).

Cognitive and Neurobehavioral Profile in Boys With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy is a progressive neuromuscular condition that has a high rate of cognitive and learning disabilities as well as neurobehavioral disorders, some of which have been associated with disruption of dystrophin isoforms. Retrospective cohort of 59 boys investigated the cognitive and neurobehavioral profile of boys with Duchenne muscular dystrophy. Full-scale IQ of < 70 was seen in 27%; learning disability in 44%, intellectual disability in 19%; attention-deficit/hyperactivity disorder in 32%; autism spectrum disorders in 15%; and anxiety in 27%. Mutations affecting Dp260 isoform and 5'untranslated region of Dp140 were observed in 60% with learning disability, 50% intellectual disability, 77% with autism spectrum disorders, and 94% with anxiety. No statistically significant correlation was noted between comorbidities and dystrophin isoforms; however, there is a trend of cumulative loss of dystrophin isoforms with declining full-scale IQ. Enhanced psychology testing to include both cognitive and neurobehavioral disorders is recommended for all individuals with Duchenne muscular dystrophy.

Early Neurodevelopmental Findings Predict School Age Cognitive Abilities in Duchenne Muscular Dystrophy: A Longitudinal Study

Objective

Neurodevelopmental and cognitive difficulties are known to occur frequently in boys with Duchenne muscular dystrophy but so far none of the published studies have reported both early neurodevelopmental assessments and cognitive tests in the same cohort. The aim of the present longitudinal study was to establish the correlation between early neurodevelopmental assessments performed in preschool boys and the cognitive scales performed at school age or later.

Methods

We performed cognitive tests at school age (mean age 5.7 year ±1.7 SD) (69 months+19 SD) in a cohort of Duchenne boys, previously assessed using the Griffiths scales before the age of 4 years (mean age when the Griffiths scales were performed 30 months ±8.9 SD).

Results

The range of total Developmental quotients on the Griffiths ranged between 56 and 116 (mean 89 ± 15.6 SD). The total Intelligence Quotients on the Wechsler scales ranged between 35 and 119 (mean 87 ± 17.2 SD). There was a significant correlation between the findings on the two scales. P = <0.0001. When we subdivided the cohort according to site of mutations, there was a difference between boys with mutations upstream exon 44 and those with mutations in exon 44–45 affecting Dp140 on both Developmental and Intelligence Quotient (p 0.01 and p 0,003 respectively).

Conclusions

Our results confirm that Duchenne boys tend to slightly underperform on both neurodevelopmental and cognitive assessments. Early neurodevelopmental findings correlated with the cognitive results obtained at school age with a clear concordance between subscales exploring similar domains on the two scales.

Neuronal SH-SY5Y cells use the C-dystrophin promoter coupled with exon 78 skipping and display multiple patterns of alternative splicing including two intronic insertion events

Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disease caused by mutations in the dystrophin gene. One-third of DMD cases are complicated by mental retardation. Here, we used reverse transcription PCR to analyze the pattern of dystrophin transcripts in neuronal SH-SY5Y cells. Among the three alternative promoters/first exons at the 5'-end, only transcripts containing the brain cortex-specific C1 exon could be amplified. The C-transcript appeared as two products: a major product of the expected size and a minor larger product that contained the cryptic exon 1a between exons C1 and 2. At the 3'-end there was complete exon 78 skipping. Together, these findings indicate that SH-SY5Y cells have neuron-specific characteristics with regard to both promoter activation and alternative splicing. We also revealed partial skipping of exons 9 and 71. Four amplified products were obtained from a fragment covering exons 36-41: a strong expected product, two weak products lacking either exon 37 or exon 38, and a second strong larger product with a 568-bp insertion between exons 40 and 41. The inserted sequence matched the 3'-end of intron 40 perfectly. We concluded that a cryptic splice site was activated in SH-SY5Y cells to create the novel, unusually large, exon 41e (751 bp). In total, we identified seven alternative splicing events in neuronal SH-SY5Y cells, and calculated that 32 dystrophin transcripts could be produced. Our results may provide clues in the analysis of transcriptype-phenotype correlations as regards mental retardation in DMD.

Genetics and emerging treatments for Duchenne and Becker muscular dystrophy

Mutations in the DMD gene result in Duchenne or Becker muscular dystrophy due to absent or altered expression of the dystrophin protein. The more severe Duchenne muscular dystrophy typically presents around ages 2 to 5 with gait disturbance, and historically has led to the loss of ambulation by age 12. It is important for the practicing pediatrician, however, to be aware of other presenting signs, such as delayed motor or cognitive milestones, or elevated serum transaminases. Becker muscular dystrophy is milder, often presenting after age 5, with ambulation frequently preserved past 20 years and sometimes into late decades.

A mixed methods study of age at diagnosis and diagnostic odyssey for Duchenne muscular dystrophy

The delayed diagnosis of Duchenne muscular dystrophy (DMD) may be an ongoing problem internationally. We aimed to ascertain age at diagnosis and explore parents' experiences of the diagnosis of DMD in Australia. Using mixed methods, data were collected from laboratory and clinical record audits of testing for DMD in Victoria and Tasmania, interviews and a national survey of parents regarding their experiences from first noticing symptoms to receiving a diagnosis. The audits revealed that the median age at diagnosis for DMD was 5 years (n=49 during 2005-2010); this age had not changed substantially over this period. Fourteen parents interviewed reported age at diagnosis ranging from 2 to 8 years with a 6 month to 4 year delay between initial concerns about their child's development and receiving the DMD diagnosis. Sixty-two survey respondents reported the median age at diagnosis was 3 years and 9 months, while the median age when symptoms were noticed was 2 years and 9 months. Parents experienced many emotions in their search for a diagnosis and consulted with a wide range of health professionals. Half the survey respondents felt that their child could have been diagnosed earlier. Despite advances in testing technologies and increasing awareness of DMD, the age at diagnosis has remained constant in Australia. This mixed methods study shows that this diagnostic delay continues to have a negative impact on parents' experiences, places families at risk of having a second affected child and may have a deleterious effect on affected children's treatment.

Acetylcholine, GABA and neuronal networks: a working hypothesis for compensations in the dystrophic brain

Duchenne muscular dystrophy (DMD), a genetic disease arising from a mutation in the dystrophin gene, is characterized by muscle failure and is often associated with cognitive deficits. Studies of the dystrophic brain on the murine mdx model of DMD provide evidence of morphological and functional alterations in the central nervous system (CNS) possibly compatible with the cognitive impairment seen in DMD. However, while some of the alterations reported are a direct consequence of the absence of dystrophin, others seem to be associated only indirectly. In this review we reevaluate the literature in order to formulate a possible explanation for the cognitive impairments associated with DMD. We present a working hypothesis, demonstrated as an integrated neuronal network model, according to which within the cascade of events leading to cognitive impairments there are compensatory mechanisms aimed to maintain functional stability via perpetual adjustments of excitatory and inhibitory components. Such ongoing compensatory response creates continuous perturbations that disrupt neuronal functionality in terms of network efficiency. We have theorized that in this process acetylcholine and network oscillations play a central role. A better understating of these mechanisms could provide a useful diagnostic index of the disease's progression and, perhaps, the correct counterbalance of this process might help to prevent deterioration of the CNS in DMD. Furthermore, the involvement of compensatory mechanisms in the CNS could be extended beyond DMD and possibly help to clarify other physio-pathological processes of the CNS.

The dystrophin gene and cognitive function in the general population

The aim of our study is to investigate whether single-nucleotide dystrophin gene (DMD) variants associate with variability in cognitive functions in healthy populations. The study included 1240 participants from the Erasmus Rucphen family (ERF) study and 1464 individuals from the Rotterdam Study (RS). The participants whose exomes were sequenced and who were assessed for various cognitive traits were included in the analysis. To determine the association between DMD variants and cognitive ability, linear (mixed) modeling with adjustment for age, sex and education was used. Moreover, Sequence Kernel Association Test (SKAT) was used to test the overall association of the rare genetic variants present in the DMD with cognitive traits. Although no DMD variant surpassed the prespecified significance threshold (P<1 × 10(-4)), rs147546024:A>G showed strong association (β = 1.786, P-value = 2.56 × 10(-4)) with block-design test in the ERF study, while another variant rs1800273:G>A showed suggestive association (β = -0.465, P-value = 0.002) with Mini-Mental State Examination test in the RS. Both variants are highly conserved, although rs147546024:A>G is an intronic variant, whereas rs1800273:G>A is a missense variant in the DMD which has a predicted damaging effect on the protein. Further gene-based analysis of DMD revealed suggestive association (P-values = 0.087 and 0.074) with general cognitive ability in both cohorts. In conclusion, both single variant and gene-based analyses suggest the existence of variants in the DMD which may affect cognitive functioning in the general populations.

The influence of visual and tactile perception on hand control in children with Duchenne muscular dystrophy

AIM

To investigate tactile perception and manual dexterity, with or without visual feedback, in males with Duchenne muscular dystrophy (DMD).

METHOD

Forty males with DMD (mean age 9 y 8 mo, SD 2 y 3 mo; range 5-14 y), recruited from the teaching hospital of the School of Medicine of the University of São Paulo, with disease severity graded as '1' to '6' on the Vignos Scale and '1' on Brooke's Scale, and 49 healthy males (mean age 8 y 2 mo; range 5-11 y; SD 1 y 11 mo), recruited from a local education center, participated in the study. We assessed tactile perception using two-point discrimination and stereognosis tests, and manual dexterity using the Pick-Up test with the eyes either open or closed. Analysis of variance was used to compare groups; a p value of less than 0.05 was considered statistically significant.

RESULTS

Males with DMD exhibited no impairment in tactile perception, as measured by the two-point discrimination test and the number of objects correctly named in the stereognosis test. Manipulation during stereognosis was statistically slower with both hands (p<0.001), and manual dexterity was much worse in males with DMD when there was no visual feedback (p<0.001).

INTERPRETATION

Males with DMD exhibited disturbances in manipulation during stereognosis and dexterity tests. Hand control was highly dependent on visual information rather than on tactile perception. Motor dysfunction in males with DMD, therefore, might be related to altered neural control.

A new look at cytoskeletal NOS-1 and β-dystroglycan changes in developing muscle and brain in control and mdx dystrophic mice

BACKGROUND

Loss of dystrophin profoundly affects muscle function and cognition. Changes in the dystrophin-glycoprotein complex (DGC) including disruption of nitric oxide synthase (NOS-1) may result from loss of dystrophin or secondarily after muscle damage. Disruptions in NOS-1 and beta-dystroglycan (bDG) were examined in developing diaphragm, quadriceps, and two brain regions between control and mdx mice at embryonic day E18 and postnatal days P1, P10, and P28. Age-dependent differential muscle loading allowed us to test the hypothesis that DGC changes are dependent on muscle use.

RESULTS

Muscle development, including loss of central nucleation and the localization of NOS-1 and bDG, was earlier in diaphragm than quadriceps; these features were differentially disrupted in dystrophic muscles. The NOS-1/bDG ratio, an index of DGC stability, was higher in dystrophic diaphragm (P10-P28) and quadriceps (P28) than controls. There were also distinct regional differences in NOS-1 and bDG in brain tissues with age and strain. NOS-1 increased with age in control forebrain and cerebellum, and in mdx cerebellum; NOS-1 and bDG were higher in control than mdx mouse forebrain.

CONCLUSIONS

Important developmental changes in structure and muscle DGC preceded the hallmarks of dystrophy, and are consistent with the impact of muscle-specific differential loading during maturation.

Motor and cognitive assessment of infants and young boys with Duchenne Muscular Dystrophy: results from the Muscular Dystrophy Association DMD Clinical Research Network

Therapeutic trials in Duchenne Muscular Dystrophy (DMD) exclude young boys because traditional outcome measures rely on cooperation. The Bayley III Scales of Infant and Toddler Development (Bayley III) have been validated in developing children and those with developmental disorders but have not been studied in DMD. Expanded Hammersmith Functional Motor Scale (HFMSE) and North Star Ambulatory Assessment (NSAA) may also be useful in this young DMD population. Clinical evaluators from the MDA-DMD Clinical Research Network were trained in these assessment tools. Infants and boys with DMD (n = 24; 1.9 ± 0.7 years) were assessed. The mean Bayley III motor composite score was low (82.8 ± 8; p ≤ .0001) (normal = 100 ± 15). Mean gross motor and fine motor function scaled scores were low (both p ≤ .0001). The mean cognitive comprehensive (p=.0002), receptive language (p ≤ .0001), and expressive language (p = .0001) were also low compared to normal children. Age was negatively associated with Bayley III gross motor (r = -0.44; p = .02) but not with fine motor, cognitive, or language scores. HFMSE (n=23) showed a mean score of 31 ± 13. NSAA (n = 18 boys; 2.2 ± 0.4 years) showed a mean score of 12 ± 5. Outcome assessments of young boys with DMD are feasible and in this multicenter study were best demonstrated using the Bayley III.

Neuropsychological and neurobehavioral functioning in Duchenne muscular dystrophy: a review

Duchenne muscular dystrophy (DMD) is a genetic condition affecting predominantly boys that is characterized by fatal muscle weakness. While there is no cure, recent therapeutic advances have extended the lifespan of those with DMD considerably. Although the physiological basis of muscle pathology is well-documented, less is known regarding the cognitive, behavioral, and psychosocial functioning of those afflicted. Several lines of evidence point to central nervous system involvement as an organic feature of DMD, challenging our view of the disorder as strictly neuromuscular. This report provides a review of the literature on neuropsychological and neurobehavioral functioning in DMD. Recent research identifying associations with DMD and neuropsychiatric disorders is also discussed. Lastly, the review presents implications of findings related to nonmotor aspects of DMD for improving the quality of life in those affected. While the literature is often contradictory in nature, this review highlights some key findings for consideration by clinicians, educators and parents when developing therapeutic interventions for this population.

Early neurodevelopmental assessment in Duchenne muscular dystrophy

The aim of this study was to assess neurodevelopmental profile in young boys affected by Duchenne muscular dystrophy and to establish the correlation between neurodevelopmental findings, and the type and site of mutations. A structured neurodevelopmental assessment (Griffiths Scale of Mental Development) was performed in 81 DMD boys before the age of four years (range: 7-47 months). The mean total DQ was 87 (SD 15.3). Borderline DQ (between 70 and 84) was found in 32% and DQ below 70 in 12.3% of the patients. Children with mutations upstream or in exon 44 had higher DQ than those with mutations downstream exon 44 which are associated with involvement of dystrophin isoforms expressed at high levels in brain. The difference was significant for total and individual subscale DQ with the exception of the locomotor subscale. Items, such as ability to run fast, or getting up from the floor consistently failed in all children, irrespective of the age or of the site of mutation. Our results help to understand the possible different mechanisms underlying the various aspects of neurodevelopmental delay, suggesting that the involvement of brain dystrophin isoforms may cause a delay in the maturation of coordination and dexterity.