Cognitive profile in Duchenne muscular dystrophy boys without intellectual disability: The role of executive functions

Motor imagery ability of children with duchenne muscular dystrophy: Reliability and validity of kinesthetic and Visual Imagery Questionnaire-10, and its association with cognitive status

PURPOSE

To investigate validity and reliability of the Kinesthetic and Visual Imagery Questionnaire-10 (KVIQ-10) in children with Duchenne Muscular Dystrophy (DMD), to compare the motor imagery (MI) ability with age-matched controls, and to examine the relationship between MI ability and cognitive status.

METHODS

The research involved 38 children who were diagnosed with DMD, as well as 20 healthy controls aged between 7 and 18 years. The KVIQ-10 was assessed for its test-retest reliability, internal consistency, construct and concurrent validity. The Motor Imagery Questionnaire for Children (MIQ-C) was selected as the gold standard test for concurrent validity. Cognitive function was assessed using the Modified Mini Mental Test (MMMT) and Montreal Cognitive Assessment (MoCA).

RESULTS

KVIQ-10 showed excellent test-retest reliability (ICC>0.90) and high internal consistency (Cronbach's alpha>0.70). A moderate-to-strong association was found between KVIQ-10 and MIQ-C subscales (p < 0.001). KVIQ-10 and MIQ-C subscores were statistically lower in the DMD group (p ≤ 0.05). A correlation was found between MoCA and KVIQ-10 in children with DMD (p ≤ 0.05).

CONCLUSIONS

The KVIQ-10 is a reliable and valid measure to assess the MI ability of children with DMD whose imagery ability was determined to be impaired.

CLINICAL TRIAL REGISTRATION NUMBER AND URL

NCT05559710 (https://classic.

CLINICALTRIALS

gov/ct2/show/NCT05559710?term=NCT05559710&draw=2&rank=1).

Duchenne Muscular Dystrophy-Associated Neurobehavioral Difficulties: Insights from Clinical Practice

Background

Emerging evidence underscores the high prevalence of neurobehavioral difficulties like ADHD, ASD and OCD, in patients with Duchenne muscular dystrophy (DMD). The substantial impact of these complex behavioral challenges in addition to motor function decline on the well-being of affected individuals and their families is increasingly evident. However, a uniform approach for effective screening, assessment and management of the neurobehavioral symptoms remains elusive.

Objective

We explored strategies used by healthcare professionals with clinical expertise in DMD to address neurobehavioral symptoms, in order to uncover diverse practices and to identify potential directions for clinical approaches in managing DMD neurobehavioral symptoms.

Methods and results

Twenty-eight respondents from 16 different countries completed an online survey. Only 35% of the centers systematically screened for neurobehavioral difficulties in their DMD population. Predominant screening methods included history taking and clinical observation. Common neurobehavioral difficulties encompassed learning challenges, dependency from adults, anxiety, concentration difficulties, and social deficits. The participating centers frequently employed parental counseling and liaison with psychosocial healthcare professionals for psychosocial intervention.

Conclusion

This study underscores the complex behavioral landscape in DMD, highlighting the need for validated screening, assessment and management strategies and collaborative efforts in implementing these. We advocate for international consensus recommendations for screening, assessment and management of neurobehavioral difficulties in DMD to enhance patient care and communication across healthcare settings.

Neurocognitive functioning among children and young people with Duchenne Muscular Dystrophy: A systematic review and meta-analysis

Objective: The neurocognitive aspects of DMD have received less attention than the physiological sequalae. This study conducted a systematic review and meta-analysis of available literature on the neurocognitive profile of children and young people with DMD. Method: Five databases (EMBASE, Medline, PsycInfo, Scopus and Web of Science) and the grey literature was searched on 27th January 2023. Eligible articles were available in English and reported neurocognitive outcomes. Neurocognitive domains reported in a comparable way across a minimum of three studies were included. The neurocognitive domains of Full-Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ) and Working memory (WMI) derived from Wechsler scales and receptive vocabulary ability derived from the Peabody Picture Verbal Test (PPVT) were included. A single mean meta-analysis was completed. Results: Relevant data was extracted and presented for 38 eligible studies; 2 of which are from grey literature. Results suggest children with DMD perform around 1SD below non-clinical norms for FSIQ, PIQ, VIQ and WMI. Unlike VIQ, scores derived from the PPVT were within the non-clinical norms. Studies were of moderate - high quality, there was significant heterogeneity and no publication bias. Conclusion: A systematic review of working memory has not previously been completed, it appears that children with DMD perform around 1SD below the mean, like FSIQ, PIQVIQ and WMI. The PPVT is a measure of receptive verbal ability and caution is recommended around the interchangeability of PPVT scores and the wider construct of verbal intelligence.

Evolution of neuropsychological and behavioral profile in a cohort of pediatric patients with Becker muscular dystrophy in a longitudinal study

It has long been reported that neuropsychological deficits may be present in dystrophinopathies, specifically non-progressive cognitive impairment and a global deficit in executive functions; this neurocognitive profile has been less explored in patients with Becker than Duchenne muscular dystrophy (BMD/DMD). We conducted a longitudinal study to explore the evolution of neuropsychological and behavioural profile in a cohort of paediatric BMD. Seventeen patients with BMD without intellectual disability were assessed using a full battery of tests, including intellectual, adaptive and executive functioning, language and behavioral features. Tests were performed at baseline and after 12 months. The results showed adequate cognitive and adaptive profile with falls in Working Memory, as well as lower scores in executive functions. An improvement was observed in Processing Speed. Behavioral questionnaires confirmed a negative trend, while in normal ranges. We found a statistically significant difference between T0 and T1 in some items exploring executive functions. No statistically significant difference was observed stratifying patients by mutation site or IQ level. In conclusion, our study suggests that BMD patients have a stable neurocognitive profile, while a deflection in the executive functions may be observed. We recommend a careful monitoring to intercept learning disabilities and promptly start a multimodal rehabilitation.

Difficulties in social cognitive functioning among pediatric patients with muscular dystrophies

Introduction

Pediatric muscular dystrophies (MDs) are a heterogeneous group of rare neuromuscular diseases characterized by progressive muscle degeneration. A neuropsychosocial approach is crucial for these patients due to associated cognitive, behavioral, and psychiatric comorbidities; however, the social cognitive domain has not been adequately addressed.

Methods

This study aimed to analyze on social cognition performance in a pediatric MD patient cohort. This cross-sectional study included 32 pediatric patients with MD and 32 matched-healthy controls. The Social Perception Domain of the NEPSY-II, the Reading the Mind in the Eyes Test-Child and Happé's Strange Stories Test were administered. General intelligence and behavioral and emotional symptoms were controlled for to eliminate covariables' possible influence. The assessments were performed remotely.

Results

Children with MDs performed significantly worse on most of the social cognition tasks. The differences found between the groups could be explained by the level of general intelligence for some aspects more related to theory of mind (ToM) (TM NEPSY-II: F = 1.703, p = .197; Verbal task: F = 2.411, p = .125; RMET-C: F = 2.899, p = .094), but not for emotion recognition. Furthermore, these differences were also independent of behavioral and emotional symptoms.

Discussion

In conclusion, social cognition is apparently impaired in pediatric patients with MD, both for emotion recognition and ToM. Screening assessment in social cognition should be considered to promote early interventions aimed at improving these patient's quality of life.

Adults living with Duchenne muscular dystrophy: old and new challenges in a cohort of 19 patients in their third to fifth decade

BACKGROUND AND PURPOSE

Advances in multidisciplinary care are extending overall survival in Duchenne muscular dystrophy (DMD) patients. Our research objective was to delineate the clinical characteristics of this particular cohort and identify novel challenges associated with the disease.

METHODS

Nineteen individuals aged 25-48 years (median 34 years) with a confirmed diagnosis of out-of-frame DMD gene mutation were selected.

RESULTS

All patients were mechanically ventilated (5/19 via tracheostomy), with different patterns of cardiomyopathy. Swallowing and nutritional issues were frequent (median body mass index 18.95), with six cases requiring artificial enteral feeding (median age at start 29 years), as well as bone density alterations (11/19, 58%). Only 2/19 had been on long-term prednisone therapy. Issues requiring at-home/hospital assistance were respiratory infections (15/19, 79%), gastroenterological symptoms (9/19, 47%, including toxic megacolon and rectal perforation after repeated enemas), metabolic acidosis (2/19, 11%) and recurrent ischaemic strokes (1/19, 5%). From a social perspective, augmented-alternative communication devices were necessary for 7/19 (37%), with most of the patients being assisted at home and 2/19 institutionalized. Eight/19 (42%) patients experienced psychiatric symptoms (median age at presentation 16 years) and 9/19 (47%) chronic pain (median age at onset 23 years), in both cases treated with psychoactive/analgesic drugs without major adverse events. The patients' subjective perception of physical health resulted in unfavourable scores, whilst the subjective assessment of mental health unexpectedly showed more positive values compared to other chronic neurological conditions.

CONCLUSIONS

The analysis of adults living with DMD reveals several new health-related issues, such as the management of emergencies and safety of pharmacological treatments for psychiatric symptoms, chronic pain management, as well as an increasing caregivers burden.

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.

Gene therapy for Duchenne muscular dystrophy: an update on the latest clinical developments

INTRODUCTION

Duchenne muscular dystrophy (DMD) is one of the most severe and devastating neuromuscular hereditary diseases with a male newborn incidence of 20 000 cases each year. The disease caused by mutations (exon deletions, nonsense mutations, intra-exonic insertions or deletions, exon duplications, splice site defects, and deep intronic mutations) in the DMD gene, progressively leads to muscle wasting and loss of ambulation. This situation is painful for both patients and their families, calling for an emergent need for effective treatments.

AREAS COVERED

In this review, the authors describe the state of the gene therapy approach in clinical trials for DMD. This therapeutics included gene replacement, gene substitution, RNA-based therapeutics, readthrough mutation, and the CRISPR approach.

EXPERT OPINION

Only a few drug candidates have yet been granted conditional approval for the treatment of DMD. Most of these therapies have only a modest capability to restore the dystrophin or improve muscle function, suggesting an important unmet need in the development of DMD therapeutics. Complementary genes and cellular therapeutics need to be explored to both restore dystrophin, improve muscle function, and efficiently reconstitute the muscle fibers in the advanced stage of the disease.

Startle responses in Duchenne muscular dystrophy: a novel biomarker of brain dystrophin deficiency

Duchenne muscular dystrophy (DMD) is characterized by loss of dystrophin in muscle, however patients also have variable degree of intellectual disability and neurobehavioural co-morbidities. In contrast to muscle, in which a single full-length dystrophin isoform (Dp427) is produced, multiple isoforms are produced in the brain, and their deficiency accounts for the variability of CNS manifestations, with increased risk of comorbidities in patients carrying mutations affecting the 3' end of the gene, which disrupt expression of shorter Dp140 and Dp71 isoforms. A mouse model (mdx mouse) lacks Dp427 in muscle and CNS and exhibits exaggerated startle responses to threat, linked to the deficiency of dystrophin in limbic structures such as the amygdala, which normalize with postnatal brain dystrophin-restoration therapies. A pathological startle response is not a recognized feature of DMD, and its characterization has implications for improved clinical management and translational research. To investigate startle responses in DMD, we used a novel fear-conditioning task in an observational study of 56 males aged 7-12 years (31 affected boys, mean age 9.7 ± 1.8 years; 25 controls, mean age 9.6 ± 1.4 years). Trials of two neutral visual stimuli were presented to participants: one 'safe' cue presented alone; one 'threat' cue paired with an aversive noise to enable conditioning of physiological startle responses (skin conductance response and heart rate). Retention of conditioned physiological responses was subsequently tested by presenting both cues without the aversive noise in an 'Extinction' phase. Primary outcomes were the initial unconditioned skin conductance and change in heart rate responses to the aversive 'threat' and acquisition and retention of conditioned responses after conditioning. Secondary and exploratory outcomes were neuropsychological measures and genotype associations. The mean unconditioned skin conductance response was greater in the DMD group than controls [mean difference 3.0 µS (1.0, 5.1); P = 0.004], associated with a significant threat-induced bradycardia only in the patient group [mean difference -8.7 bpm (-16.9, -0.51); P = 0.04]. Participants with DMD found the task more aversive than controls, with increased early termination rates during the Extinction phase (26% of DMD group versus 0% of controls; P = 0.007). This study provides the first evidence that boys with DMD show similar increased unconditioned startle responses to threat to the mdx mouse, which in the mouse respond to brain dystrophin restoration. Our study provides new insights into the neurobiology underlying the complex neuropsychiatric co-morbidities in DMD and defines an objective measure of this CNS phenotype, which will be valuable for future CNS-targeted dystrophin-restoration studies.

Wechsler Scale Intelligence Testing in Males with Dystrophinopathies: A Review and Meta-Analysis

BACKGROUND

Intelligence scores in males with Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD) remain a major issue in clinical practice. We performed a literature review and meta-analysis to further delineate the intellectual functioning of dystrophinopathies.

METHOD

Published, peer-reviewed articles assessing intelligence, using Wechsler Scales, of males with DMD or BMD were searched from 1960 to 2022. Meta-analysis with random-effects models was conducted, assessing weighted, mean effect sizes of full-scale IQ (FSIQ) scores relative to normative data (Mean = 100, Standard Deviation = 15). Post hoc we analysed differences between performance and verbal intelligence scores.

RESULTS

43 studies were included, reporting data on 1472 males with dystrophinopathies; with FSIQ scores available for 1234 DMD (k = 32) and 101 BMD (k = 7). DMD males score, on average, one standard deviation below average (FSIQ = 84.76) and significantly lower than BMD (FSIQ = 92.11). Compared to a previous meta-analysis published in 2001, we find, on average, significantly higher FSIQ scores in DMD.

CONCLUSION

Males with Duchenne have, on average, significantly lower FSIQ scores than BMD males and the general population. Clinicians must consider lower intelligence in dystrophinopathies to ensure good clinical practice.

Language Development in Preschool Duchenne Muscular Dystrophy Boys

BACKGROUND

the present study aims to assess language in preschool-aged Duchenne muscular dystrophy (DMD) boys with normal cognitive quotients, and to establish whether language difficulties are related to attentional aspects or to the involvement of brain dystrophin isoforms.

METHODS

20 children aged between 48 and 72 months were assessed with language and attention assessments for preschool children. Nine had a mutation upstream of exon 44, five between 44 and 51, four between 51 and 63, and two after exon 63. A control group comprising 20 age-matched boys with a speech language disorder and normal IQ were also used.

RESULTS

lexical and syntactic comprehension and denomination were normal in 90% of the boys with Duchenne, while the articulation and repetition of long words, and sentence repetition frequently showed abnormal results (80%). Abnormal results were also found in tests assessing selective and sustained auditory attention. Language difficulties were less frequent in patients with mutations not involving isoforms Dp140 and Dp71. The profile in Duchenne boys was different form the one observed in SLI with no cognitive impairment.

CONCLUSION

The results of our observational cross-sectional study suggest that early language abilities are frequently abnormal in preschool Duchenne boys and should be assessed regardless of their global neurodevelopmental quotient.

The neurocognitive profile of adults with Becker muscular dystrophy in the Netherlands

Background:

In Becker muscular dystrophy evidence for neurocognitive and behavioral comorbidity is evolving. More insight into the extend of these problems is of great importance for early detection and remediation in clinical practice.

Objective:

In this study we aimed to describe the neurocognitive and behavioral features of a Dutch adult cohort of BMD patients, and to evaluate correlations to motor function outcomes.

Methods:

28 adult BMD patients were included. Intelligence, executive functioning, verbal memory and reaction times were assessed cross-sectionally. Additionally, patients completed questionnaires on behavioral and emotional symptoms, psychosocial and executive functions. Results were compared to normative data and correlated with disease severity as measured by the 10-meter run/walk test and Performance of the Upper Limb version 1.2.

Results:

15 patients (53.6%) had a high educational level despite frequent grade repeating (48.3%) during primary or secondary school. Neuropsychological testing revealed that intellectual abilities, verbal memory, processing speed and executive functioning were statistically significant below average, but still within normal range. Regarding outcomes of the behavioral questionnaires, no significant differences were reported compared to the norm population. No relevant correlations with disease severity were found.

Conclusions:

This cohort of adult BMD patients exhibits minor cognitive impairments and no significant behavioral problems. The lower outcomes on processing speed and verbal memory, combined with the relatively high prevalence of grade repeating during primary and secondary school, implies that these minor impairments played a role in childhood. However, the on average high educational levels suggests that they grow out of their cognitive impairments with ageing.

Dystrophin genetic variants and autism

Loss-of-function variants in the dystrophin gene, a well-known cause of muscular dystrophies, have emerged as a mutational risk mechanism for autism spectrum disorder (ASD), which in turn is a highly prevalent (~ 1%) genetically heterogeneous neurodevelopmental disorder. Although the association of intellectual disability with the dystrophinopathies Duchenne (DMD) and Becker muscular dystrophy (BMD) has been long established, their association with ASD is more recent, and the dystrophin genotype-ASD phenotype correlation is unclear. We therefore present a review of the literature focused on the ASD prevalence among dystrophinopathies, the relevance of the dystrophin isoforms, and most particularly the relevance of the genetic background to the etiology of ASD in these patients. Four families with ASD-DMD/BMD patients are also reported here for the first time. These include a single ASD individual, ASD-discordant and ASD-concordant monozygotic twins, and non-identical ASD triplets. Notably, two unrelated individuals, which were first ascertained because of the ASD phenotype at ages 15 and 5 years respectively, present rare dystrophin variants still poorly characterized, suggesting that some dystrophin variants may compromise the brain more prominently. Whole exome sequencing in these ASD-DMD/BMD individuals together with the literature suggest, although based on preliminary data, a complex and heterogeneous genetic architecture underlying ASD in dystrophinopathies, that include rare variants of large and medium effect. The need for the establishment of a consortia for genomic investigation of ASD-DMD/BMD patients, which may shed light on the genetic architecture of ASD, is discussed.

Intellectual disability in paediatric patients with genetic muscle diseases

The differential diagnosis of genetic muscle disease has become increasingly difficult due to the rapid progress in genetic medicine in recent years. Where classifications based on the clinical picture were attributed to one gene only a few years ago, today we know that a variety of clinical presentations can result from the same mutation and, conversely, various genes are associated with a similar phenotype. A significant consideration in assessing a patient with muscle weakness is the presence or absence of intellectual disability, thus narrowing the differential diagnostic approach in any child with an as yet undiagnosed muscle disease. Intellectual disability in neuromuscular diseases is often associated with behavioural disorders and may be correlated with abnormal brain imaging. Conversely, brain involvement can sometimes be seen without intellectual disability, but may be associated with an epilepsy risk and is helpful for the differential diagnosis. This review focuses on the three most common causes of paediatric muscle diseases with intellectual disability, dystrophinopathies, myotonic dystrophy type 1 and dystroglycanopathies. It also summarises differential diagnostic considerations when assessing a child with a genetic muscle disease and intellectual disability. The recent scientific literature on this topic is reviewed, the frequency of intellectual disability assessed, and specific clinical features are described. Where available, data on disease onset, progression and serum creatine kinase levels are presented and the pattern of muscle involvement described in an algorithm. Central nervous involvement and brain imaging analysis was reviewed and included.

Neural substrates of neuropsychological profiles in dystrophynopathies: A pilot study of diffusion tractography imaging

Introduction

Cognitive difficulties and neuropsychological alterations in Duchenne and Becker muscular dystrophy (DMD, BMD) boys are not yet sufficiently explored, although this topic could have a relevant impact, finding novel biomarkers of disease both at genetics and neuroimaging point of view. The current study aims to: 1) analyze the neuropsychological profile of a group of DMD and BMD boys without cognitive impairment with an assessment of their executive functions; 2) explore the structural connectivity in DMD, BMD, and age-matched controls focusing on cortico-subcortical tracts that connect frontal cortex, basal ganglia, and cerebellum via the thalamus; 3) explore possible correlations between altered structural connectivity and clinical neuropsychological measures.

Materials and methods

This pilot study included 15 boys (5 DMD subjects, 5 BMD subjects, and 5 age-matched typically developing, TD). They were assessed using a neuropsychological assessment protocol including cognitive and executive functioning assessment and performed a 1.5T MRI brain exam including advance Diffusion Weighted Imaging (DWI) method for tractography. Structural connectivity measurements were extracted along three specific tracts: Cortico-Ponto-Cerebellar Tract (CPCT), Cerebellar-Thalamic Tract (CTT), and Superior Longitudinal Fasciculus (SLF). Cortical-Spinal Tract (CST) was selected for reference, as control tract.

Results

Regarding intellectual functioning, a major impairment in executive functions compared to the general intellectual functioning was observed both for DMD (mean score = 86.20; SD = 11.54) and for BMD children (mean score = 88; SD = 3.67). Mean FA resulted tendentially always lower in DMD compared to both BMD and TD groups for all the examined tracts. The differences in FA were statistically significant for the right CTT (DMD vs BMD, p = 0.002, and DMD vs TD, p = 0.0015) and the right CPCT (DMD vs TD, p = 0.008). Concerning DMD, significant correlations emerged between FA-R-CTT and intellectual quotients (FIQ, p = 0.044; ρs = 0.821), and executive functions (Denomination Total, p = 0.044, ρs = 0.821; Inhibition Total, p = 0.019, ρs = 0.900). BMD showed a significant correlation between FA-R-CPCT and working memory index (p = 0.007; ρs = 0.949).

Discussion and conclusion

In this pilot study, despite the limitation of sample size, the findings support the hypothesis of the involvement of a cerebellar-thalamo-cortical loop for the neuropsychological profile of DMD, as the CTT and the CPCT are involved in the network and the related brain structures are known to be implied in executive functions. Our results suggest that altered WM connectivity and reduced fibre organization in cerebellar tracts, probably due to the lack of dystrophin in the brain, may render less efficient some neuropsychological functions in children affected by dystrophinopathies. The wider multicentric study could help to better establish the role of cerebellar connectivity in neuropsychological profile for dystrophinopathies, identifying possible novel diagnostic and prognostic biomarkers.

Slow oscillation density and amplitude decrease across development in pediatric Duchenne and Becker muscular dystrophy

STUDY OBJECTIVES

From childhood through adolescence, brain rhythms during non-rapid eye movement (NREM) sleep show dramatic development that mirror underlying brain maturation. For example, the function and characteristics of slow oscillations (SOs, <1 Hz) in healthy children are linked to brain development, motor skill, and cognition. However, little is known of possible changes in pediatric populations with neurologic abnormalities.

METHODS

We measured slow oscillations in 28 Duchenne and Becker muscular dystrophy male patients from age 4 to 20 years old during overnight in-lab clinical sleep studies. We compared our pediatric patients by age to evaluate the developmental changes of SOs from childhood to early and late adolescence.

RESULTS

Consistent with the current neuro- and physically typical literature, we found greater slow oscillation density (count of SOs per minute of each sleep stage) in NREM N3 than N2, and significantly greater slow oscillation density in frontal compared to central and occipital regions. However, separating patients into age-defined groups (child, early adolescent, and late adolescent) revealed a significant age effect, with a specific decline in the rate and amplitude of SOs.

CONCLUSIONS

We found that with age, pediatric patients with Duchenne muscular dystrophy show a significant decline in slow oscillation density. Given the role that slow oscillations play in memory formation and retention, it is critical to developmentally characterize these brain rhythms in medically complex populations. Our work converges with previous pediatric sleep literature that promotes the use of sleep electroencephalographic markers as prognostic tools and identifies potential targets to promote our patients' quality of life.

Therapeutic Approaches for Duchenne Muscular Dystrophy: Old and New

Duchenne muscular dystrophy (DMD) is marked by pathogenic variants in the DMD gene, leading to reduced or absent dystrophin translation, muscle fiber destruction, loss of ambulation, cardiomyopathy, respiratory failure, and eventually death. Disease progression is slowed with use of prednisone or other corticosteroid agents. Gene replacement therapy, which is one of the focus points of this review, has emerged as the most promising potential treatment for DMD, though alternative RNA-based strategies have been employed for patients with specific pathogenic variants. While challenges remain, many of these novel therapeutic approaches hold promise for treating this devastating disease.

Longitudinal data of neuropsychological profile in a cohort of Duchenne muscular dystrophy boys without cognitive impairment

The aim of the study was to re-assess neuropsychological profile in a group of boys with Duchenne muscular dystrophy without intellectual disability and neuropsychiatric disorder three years apart from a previous evaluation, to establish possible changes over time. We were also interested in defining more in detail correlation between genotype and neuropsychological phenotype. Thirty-three of the previous 40 subjects (mean age at follow up: 10 years and 7 months) agreed to participate in the follow up study and to perform the new assessment. The results confirm a typical neuropsychological profile, with difficulty in the manipulation of stored information, poor abstract reasoning and planning capacity and impulsiveness, supporting the involvement of a cerebellar striatal cortical network for these children. The more detailed description of subgroups of subjects, according to the real expression of Dp140, let to reveal possible genotype-neuropsychological phenotype correlations, and a more general neuropsychological impairment emerged in boys without Dp140 expression.

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.

Computational cognitive modeling and validation of Dp140 induced alteration of working memory in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy has emerged as a model to assess cognitive domains. The DMD gene variant location and its association with variable degrees of cognitive impairment necessitate identification of a common denominator. Computer architectures provide a framework to delineate the mechanisms involved in the cognitive functioning of the human brain. Copy number variations in the 79 exons of DMD gene were screened in 84 DMD subjects by Multiplex Ligation-dependent Probe Amplification (MLPA). DMD subjects were categorized based on the presence or absence of DP140 isoform. The cognitive and neuropsychological assessments were carried out as per inclusion criteria using standard scales. Instance-based learning theory (IBLT) based on the partial matching process was developed to mimic Stroop Color and Word Task (SCWT) performance on Adaptive Control of Thought-Rational (ACT-R) cognitive architecture based on IBLT. Genotype-phenotype correlation was conducted based on the mutation location in DMD gene. Assessment of specific cognitive domains in DP140 - ve group corresponded to the involvement of multiple brain lobes including temporal (verbal and visual learning and memory), parietal (visuo-conceptual and visuo-constructive abilities) and frontal (sustained and focused attention, verbal fluency, cognitive control). Working memory axis was found to be the central domain through tasks including RAVLT trial 1, recency effect, digit span backward, working memory index, arithmetic subtests in the Dp140 - ve group. IBLT validated the non-reliance of DMD subjects on recency indicating affected working memory domain. Modeling strategy revealed altered working memory processes in DMD cases with affected Dp140 isoform. DMD brain was observed to rely on primacy than the recency suggesting alterations in working memory capacity. Modeling revealed lowered activation of DMD brain with Dp140 - ve in order to retrieve the instances.

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.

Combining genetics, neuropsychology and neuroimaging to improve understanding of brain involvement in Duchenne muscular dystrophy - a narrative review

Duchenne muscular dystrophy is a multifactorial disease including a cognitive phenotype. It is caused by mutations in the X-chromosomal DMD gene from which dystrophin is synthesized. Multiple isoforms of dystrophin have been identified. The full length dystrophin isoform Dp427_m is expressed predominantly in muscle. Other isoforms include: Dp427_c, Dp427_p, Dp260, Dp140, Dp116, Dp71 and Dp40. The majority of these isoforms are expressed in brain and several hypotheses exist on their role in subtypes of neurons and astrocytes. However, their function in relation to cognition remains unclear. Unlike progressive muscle wasting, cognitive involvement is not seen in all DMD patients and the severity varies greatly. To achieve a better understanding of brain involvement in DMD, a multidisciplinary approach is required. Here, we review the latest findings on dystrophin isoform expression in the brain; specific DMD-associated learning and behavioural difficulties; and imaging and spectroscopy findings relating to brain structure, networks, perfusion and metabolism. The main challenge lies in determining links between these different findings. If we can determine which factors play a role in the differentiation between severe and minor cognitive problems in DMD in the near future, we can both provide better advise for the patients and also develop targeted therapeutic interventions.

Longitudinal follow-up of verbal span and processing speed in Duchenne muscular dystrophy

Neurocognitive deficits are frequently described in Duchenne muscular dystrophy (DMD), but it is unknown how these progress over time. Our aim was to longitudinally assess verbal span capacity and information processing speed in DMD and to explore a genotype-phenotype relation. Verbal span and processing speed scores were available of 28 males with DMD on two time-points, with a mean time interval of 28.34 months (SD = 16.09). The cohort contained of six patients missing only dystrophin isoform Dp427, sixteen missing Dp427 and Dp140, and six were undeterminable. A lower verbal span capacity was found at the first and second assessment, whereas processing speed was normal at both time-points. Post-hoc analyses suggested lower scores on verbal span and processing speed for patients missing Dp427 and Dp140. In DMD, a developmental stagnation in verbal span capacity, irrespective of normal processing speed, is detected through longitudinal follow-up. This appears more pronounced in patients missing Dp427 and Dp140.

Dystrophin Dp71 and the Neuropathophysiology of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is caused by frameshift mutations in the DMD gene that prevent the body-wide translation of its protein product, dystrophin. Besides a severe muscle phenotype, cognitive impairment and neuropsychiatric symptoms are prevalent. Dystrophin protein 71 (Dp71) is the major DMD gene product expressed in the brain and mutations affecting its expression are associated with the DMD neuropsychiatric syndrome. As with dystrophin in muscle, Dp71 localises to dystrophin-associated protein complexes in the brain. However, unlike in skeletal muscle; in the brain, Dp71 is alternatively spliced to produce many isoforms with differential subcellular localisations and diverse cellular functions. These include neuronal differentiation, adhesion, cell division and excitatory synapse organisation as well as nuclear functions such as nuclear scaffolding and DNA repair. In this review, we first describe brain involvement in DMD and the abnormalities observed in the DMD brain. We then review the gene expression, RNA processing and functions of Dp71. We review genotype-phenotype correlations and discuss emerging cellular/tissue evidence for the involvement of Dp71 in the neuropathophysiology of DMD. The literature suggests changes observed in the DMD brain are neurodevelopmental in origin and that their risk and severity is associated with a cumulative loss of distal DMD gene products such as Dp71. The high risk of neuropsychiatric syndromes in Duchenne patients warrants early intervention to achieve the best possible quality of life. Unravelling the function and pathophysiological significance of dystrophin in the brain has become a high research priority to inform the development of brain-targeting treatments for Duchenne.

Improving Executive Functions at School in Children With Special Needs by Educational Robotics

Children with Special Needs represent a highly heterogeneous group in terms of neurofunctional, behavioral, and socio-cognitive characteristics, but they have in common a frequent impairment of Executive Functions. Educational Robotics is generally dedicated to study the effects of constructing and programming robots based on children's learning and academic achievement. Recently, we found that being engaged in progressively more challenging robot planning and monitoring (ER-Lab) promotes visual-spatial working memory and response inhibition in early childhood during typical development, and that an ER-Lab can be a feasible rehabilitative tool for children with Special Needs. The present study aimed to verify the efficacy of the ER-Lab on Executive Functions in children with Special Needs for the first time by using an RCT within their school environment. To pursue these aims, this study reports the results obtained in 42 first-grade children with Special Needs engaged in school Educational Robotics Laboratories (ER-Lab) to promote Executive Functions by means of enjoyable, intensive, and incrementally more challenging activities requiring them to program a bee-shaped robot called Bee-bot® (Campus Store). Several adaptations were done to meet different motor, cognitive, and social needs. All children were evaluated by means of standardized tests performed by each child before and at the end of the ER-Lab activities. Children with Special Needs had significantly improved inhibition skills, and children with attentional impairment had more benefits in their inhibition of motor responses tasks with respect to children with a language deficit. Results of the study and future perspectives on how ER-Lab programs could become a powerful tool in classrooms with children with special needs are discussed.

Muscular dystrophies

Muscular dystrophies are primary diseases of muscle due to mutations in more than 40 genes, which result in dystrophic changes on muscle biopsy. Now that most of the genes responsible for these conditions have been identified, it is possible to accurately diagnose them and implement subtype-specific anticipatory care, as complications such as cardiac and respiratory muscle involvement vary greatly. This development and advances in the field of supportive medicine have changed the standard of care, with an overall improvement in the clinical course, survival, and quality of life of affected individuals. The improved understanding of the pathogenesis of these diseases is being used for the development of novel therapies. In the most common form, Duchenne muscular dystrophy, a few personalised therapies have recently achieved conditional approval and many more are at advanced stages of clinical development. In this Seminar, we concentrate on clinical manifestations, molecular pathogenesis, diagnostic strategy, and therapeutic developments for this group of conditions.

Peptide-conjugate antisense based splice-correction for Duchenne muscular dystrophy and other neuromuscular diseases

Duchenne muscular dystrophy (DMD) is an X-linked disorder characterized by progressive muscle degeneration, caused by the absence of dystrophin. Exon skipping by antisense oligonucleotides (ASOs) has recently gained recognition as therapeutic approach in DMD. Conjugation of a peptide to the phosphorodiamidate morpholino backbone (PMO) of ASOs generated the peptide-conjugated PMOs (PPMOs) that exhibit a dramatically improved pharmacokinetic profile. When tested in animal models, PPMOs demonstrate effective exon skipping in target muscles and prolonged duration of dystrophin restoration after a treatment regime. Herein we summarize the main pathophysiological features of DMD and the emergence of PPMOs as promising exon skipping agents aiming to rescue defective gene expression in DMD and other neuromuscular diseases. The listed PPMO laboratory findings correspond to latest trends in the field and highlight the obstacles that must be overcome prior to translating the animal-based research into clinical trials tailored to the needs of patients suffering from neuromuscular diseases.

Implicit learning deficit in children with Duchenne muscular dystrophy: Evidence for a cerebellar cognitive impairment?

This study aimed at comparing implicit sequence learning in individuals affected by Duchenne Muscular Dystrophy without intellectual disability and age-matched typically developing children. A modified version of the Serial Reaction Time task was administered to 32 Duchenne children and 37 controls of comparable chronological age. The Duchenne group showed a reduced rate of implicit learning even if in the absence of global intellectual disability. This finding provides further evidence of the involvement of specific aspects of cognitive function in Duchenne muscular dystrophy and on its possible neurobiological substrate.