Cognitive profile and neuropsychiatric disorders in Becker muscular dystrophy: A systematic review of literature

Characterisation of a large, single-centre cohort of patients with Becker muscular dystrophy to inform standardised care guidelines

AIMS

This retrospective, cross-sectional study aimed to characterise a large cohort of paediatric and adult patients with Becker muscular dystrophy (BMD) to inform clinical care.

RESULTS

The analysis included data from 163 male patients with genetically confirmed BMD followed up at a highly specialised neuromuscular centre between 1982 and 2023. The mean age at last neuromuscular assessment was 33.2 years (range 1.4-86.3). Large deletions in the DMD gene were the most common variants (78% of cases), followed by large duplications and small variants, each accounting for 11% of cases. BMD diagnosis was prompted by skeletal muscle symptoms in 52.2% of cases, a positive family history in 27.6%, neuropsychiatric issues or diagnoses in 9.7%, incidental findings in 6.7%, and cardiomyopathy in 3.8%. Twenty-three percent of patients were non-ambulant at last evaluation, with a mean age at loss of ambulation (LoA) of 42.2 years (range 11.2-77.6 years). Disease duration correlated with the severity of motor impairment (expressed as fully ambulant, ambulant with limitation, ambulant with aids, non-ambulant) at last assessment. Cardiac involvement was observed in 52.3% of patients. Severe respiratory impairment was rare and more prevalent in non-ambulant patients. Neuropsychiatric issues were common (44.2%), but only 18.4% of patients had a formal diagnosis.

CONCLUSIONS

Retrospective analyses of clinical case records contribute to improved understanding of the variability of phenotypes of BMD. Combined with data from other large cohorts, these findings can contribute to the development of standard of care guidelines for BMD and inform the design of clinical trials of novel therapies.

The role of dystrophin isoforms and interactors in the brain

Dystrophin is a protein crucial for maintaining the structural integrity of skeletal muscle. So far, attention has been focused on the role of dystrophin in muscle, in view of the devastating progression of weakness and early death that characterizes Duchenne muscular dystrophy. However, in the last few years, the role of shorter dystrophin isoforms, including development and adult expression-specific mechanisms, has been a greater focus. Within the cerebral landscape, various cell types, such as glia, oligodendrocytes and Purkinje, cerebellar granule and vascular-associated cells express a spectrum of dystrophin isoforms, including Dp427, Dp140, Dp71 and Dp40. The interaction of these isoforms with a multitude of proteins suggests their involvement in neurotransmission, influencing several circuit functions. This review presents the intricate interactions among dystrophin isoforms and diverse protein complexes across different cell types and brain regions, as well as the associated clinical complications. We focus on studies investigating protein interactions with dystrophin in the past 30 years at a biochemical level. In essence, the brain's dystrophin landscape is a thrilling exploration of diversity, challenging preconceptions and opening new avenues for understanding CNS physiology. It also holds potential therapeutic implications for neurological complications involving brain dystrophin deficiency. By revealing the molecular complexities related to dystrophin, this review paves the way for future investigations and therapeutic interventions for this CNS aspect of Duchenne 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.

Navigating adulthood: Exploring the transition needs of adolescents and young adults affected by Duchenne or Becker muscular dystrophy

For individuals with Duchenne or Becker muscular dystrophy (DMD and BMD, respectively), transitioning to adulthood presents significant challenges. Although considerable attention has been given to facilitating medical transitions due to the complexity of these conditions, less focus has been placed on other aspects of the transition, such as achieving independence. This study assessed the transition needs of people with DMD or BMD, exploring various domains including health, education, employment, living arrangements, transportation, daily activities, and independent personal life. Men with DMD or BMD participated in this cross-sectional study. Transition to adulthood was assessed using Transition Readiness Assessment for Young Adults with DMD. The questionnaire evaluates transitions in health care, education and employment, housing and transportation, activities of daily living, and independent life and autonomy. Factors associated with and predicting transition to adulthood were evaluated using Spearman's correlations and multiple regression analysis. Forty-two people with DMD or BMD (mean age: 24.3±5.3) participated in this study. The transition domains in which most participants needed help were education and employment (52.5%) and activities of daily living (57.0%). Transition needs that stood out included palliative care (66.6%), employment and education support (76.1%), social worker consultation for housing assistance (76.1%), and assistive device consultation (64.2%). Mobility and breathing function did not correlate with transition level. Number of siblings positively correlated with and predicted most transition domains. Older age predicted only education and employment status. In conclusion, the analysis showed that the most problematic transition domains among people with DMD or BMD were activities of daily living and education and employment. In most transition domains, help needed did not decrease with age and was not affected by function. However, adolescents and adults with more siblings typically reported being more ready to transit to adult life.

Methylphenidate treatment of a Chinese boy with Becker muscular dystrophy combined with attention deficit hyperactivity disorder: a case report

Background

Becker muscular dystrophy (BMD) is an X-linked recessive inherited disorder characterized by slowly progressing muscle weakness of the legs and pelvis, caused by mutations in the DMD gene, which encodes dystrophin protein. Different from Duchenne Muscular Dystrophy (DMD), in which dystrophin is completely absent in muscle tissue, while in BMD, the dystrophin gene can express some protein, but not enough. It has also been shown that a proportion of patients with DMD suffer from attention deficit hyperactivity disorder (ADHD), and the use of the stimulant methylphenidate has been suggested for the treatment of patients with DMD in combination with ADHD. However, there are no case reports on the treatment of co-occurring ADHD in BMD.

Case presentation

The patient was a 9-year-old boy who presented with elevated serum creatine kinase levels and inattention. The magnetic resonance imaging of the thigh muscles of both lower limbs suggested partial fatty infiltration of the gluteus maximus muscle bilaterally, and a novel heterozygous mutation (c.31 + 6 T > C) was identified in the DMD gene by Next Generation Sequencing (NGS) and the sequencing results were verified by using the Sanger method. The child was also diagnosed with co-morbid ADHD after a thorough evaluation and considering this new diagnosis, we started treatment with methylphenidate at a dose of 18 mg/day, and after 6 months of treatment, he showed a significant improvement in his attention span.

Conclusion

We identified a novel heterozygous mutation in the DMD gene, which will expand the spectrum of pathogenic variants in BMD. Simultaneously, methylphenidate treatment significantly improved attention in children with BMD co-morbid with ADHD, and this study provides value for future therapeutic protocols for BMD combined with ADHD. However, to the best of our knowledge, this is the only reported case report on the treatment of BMD co-morbid ADHD. So further studies are needed to determine the interrelationship between these disorders and their treatment.

Social cognition in two brothers with Becker muscular dystrophy: an exploratory study revealing divergent behavioral phenotypes

BACKGROUND AND OBJECTIVE

Only few studies investigated social cognition in Becker muscular dystrophy (BMD). However, brain dystrophin deficiency could be a neural substrate for cognitive, emotional, and neuropsychological features in BMD.

METHODS

We compared interoceptive accuracy and interpersonal comfort distance in two brothers with BMD presenting with the same genetic deletion and a healthy control. When possible, we collected neuropsychological and psychopathological assessments.

RESULTS

Our BMD patients were significantly different in interoceptive accuracy, with patient 1 being extremely accurate and patient 2 being significantly less accurate than his brother but more accurate than the control. Interestingly, they presented opposite patterns of interpersonal distance. Patient 1 was comfortable with very short interpersonal distance (≤50 cm from the confederate/object) vs the control and patient 2. By contrast, patient 2 preferred larger distance vs the control and patient 1. Patient 1 also presented difficulties in social and emotional skills on the psychopathological assessment.

CONCLUSIONS

We are aware this is a small sample; nonetheless, this is also the first description of such aspects in BMD and the first report ever of such divergent behavioral pattern. As impaired social cognition affects the quality of life and social relationship, further studies are needed for a closer understanding of involved mechanisms.

Epilepsy in Duchenne and Becker muscular dystrophies

OBJECTIVE

Duchenne and Becker muscular dystrophies (DMD and BMD) are dystrophinopathies caused by variants in DMD gene, resulting in reduced or absent dystrophin. These conditions, characterized by muscle weakness, also manifest central nervous system (CNS) comorbidities due to dystrophin expression in the CNS. Prior studies have indicated a higher prevalence of epilepsy in individuals with dystrophinopathy compared to the general population. Our research aimed to investigate epilepsy prevalence in dystrophinopathies and characterize associated electroencephalograms (EEGs) and seizures.

METHODS

We reviewed 416 individuals with dystrophinopathy, followed up at three centers between 2010 and 2023, to investigate the lifetime epilepsy prevalence and characterize EEGs and seizures in those individuals diagnosed with epilepsy. Associations between epilepsy and type of dystrophinopathy, genotype, and cognitive involvement were studied.

RESULTS

Our study revealed a higher epilepsy prevalence than the general population (1.4%; 95% confidence interval: 0.7-3.2%), but notably lower than previously reported in smaller dystrophinopathy cohorts. No significant differences were found in epilepsy prevalence between DMD and BMD or based on underlying genotypes. Cognitive impairment was not found to be linked to higher epilepsy rates. The most prevalent epilepsy types in dystrophinopathies resembled those observed in the broader pediatric population, with most individuals effectively controlled through monotherapy.

INTERPRETATION

The actual epilepsy prevalence in dystrophinopathies may be markedly lower than previously estimated, possibly half or even less. Our study provides valuable insights into the epilepsy landscape in individuals with dystrophinopathy, impacting medical care, especially for those with concurrent epilepsy.

Cognitive abnormalities in Becker muscular dystrophy: a mysterious link between dystrophin deficiency and executive functions

BACKGROUND

Distrophinopathies are a heterogeneous group of neuromuscular disorders due to mutations in the DMD gene. Different isoforms of dystrophin are also expressed in the cerebral cortex and Purkinje cells. Despite cognitive abnormalities in Duchenne muscular dystrophy subjects that have been described in the literature, little is known about a comprehensive cognitive profile in Becker muscular dystrophy patients.

AIM

The aim of this study was to assess cognitive functioning in Becker muscular dystrophy patients by using an extensive neuropsychological battery. Our hypothesis is that the most impaired functions are the highly intentional and conscious ones, such as working memory functions, which require a prolonged state of cellular activation.

METHODS

We performed an extensive neuropsychological assessment on 28 Becker muscular dystrophy patients from 18 to 65 years old. As control subjects, we selected 20 patients with limb-girdle muscular dystrophy, whose clinical picture was similar except for cognitive integrity. The evaluation, although extended to all areas, was focused on prefrontal control skills, with a distinction between inhibitory processes of selective attention and activating processes of working memory.

RESULTS AND CONCLUSIONS

Significant underperformances were found exclusively in the Dual Task and PASAT tests, to demonstrate a selective impairment of working memory that, while not causing intellectual disability, reduces the intellectual potential of patients with Becker muscular dystrophy.

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.

Two years of newborn screening for Duchenne muscular dystrophy as a part of the statewide Early Check research program in North Carolina

PURPOSE

Current and emerging treatments for Duchenne muscular dystrophy (DMD) position DMD as a candidate condition for newborn screening (NBS). In anticipation of the nomination of DMD for universal NBS, we conducted a prospective study under the Early Check voluntary NBS research program in North Carolina, United States.

METHODS

We performed screening for creatine kinase-MM (CK-MM), a biomarker of muscle damage, on residual routine newborn dried blood spots (DBS) from participating newborns. Total creatine kinase testing and next generation sequencing of an 86-neuromuscular gene panel that included DMD were offered to parents of newborns who screened positive. Bivariate and multivariable analyses were performed to assess effects of biological and demographic predictors on CK-MM levels in DBS.

RESULTS

We screened 13,354 newborns and identified 2 males with DMD. The provisional 1626 ng/mL cutoff was raised to 2032 ng/mL to improve specificity, and additional cutoffs (900 and 360 ng/mL) were implemented to improve sensitivity for older and low-birthweight newborns.

CONCLUSION

Population-scale screening for elevated CK-MM in DBS is a feasible approach to identify newborns with DMD. Inclusion of birthweight- and age-specific cutoffs, repeat creatine kinase testing after 72 hours of age, and DMD sequencing improve sensitivity and specificity of screening.

Social cognition in DMD and BMD dystrophinopathies: A cross-sectional preliminary study

Objective: The dystrophinopathies called Duchenne and Becker muscular dystrophies (DMD/BMD) are rare, progressive, incurable, and life-limiting paediatric-onset neuromuscular diseases. These diseases have long been associated with specific neuropsychological deficits. However, the performance of these patients in the social cognition domain has not been properly investigated. Thus, the main objective of this study was to compare the performance on social cognition between DMD/BMD patients and healthy age-matched boys. Method: This cross-sectional study included 20 DMD/BMD children and adolescents and 20 healthy controls. The protocol included the Social Perception Domain of the NEPSY-II, the Reading the Mind in the Eyes Test - Child and Happé's Strange Stories test. General intelligence was controlled to eliminate the possible influence of covariables. All the assessments were performed remotely. Results: Most social cognition tasks were worse in patients with DMD/BMD than in matched healthy controls. These differences remained even after controlling for the general intelligence variable, with the exception of Total Disgust Errors (F = 1.462, p = .234, η2p= .038) and Verbal task (F = 1.820, p = .185, η2p= .047) scores from the NEPSY-II. Conclusions: This is the first study to demonstrate that the neuropsychological domain of social cognition is impaired in DMD/BMD patients, independent of the level of general intelligence. Screening assessments in DMD/BMD patients should be promoted to allow social cognition difficulties to be detected at an early stage to enhance patients' quality of life and social development.

Brain Abnormalities in Becker Muscular Dystrophy: Evaluation by Voxel-Based DTI and Morphometric Analysis

BACKGROUND AND PURPOSE

Although various neuropsychological problems in Becker muscular dystrophy have attracted attention, there have been few related neuroimaging studies. We investigated brain abnormalities in patients with Becker muscular dystrophy using 3D T1WI and DTI.

MATERIALS AND METHODS

MR images were obtained for 30 male patients and 30 age-matched healthy male controls. We classified patients into Dp140+ and Dp140- subgroups based on their predicted dystrophin Dp140 isoform expression and performed voxel-based comparisons of gray and white matter volumes and DTI metrics among the patients, patient subgroups, and controls. ROI-based DTI analyses were also performed.

RESULTS

Significantly decreased fractional anisotropy was observed in the left planum temporale and right superior parietal lobule compared between the Becker muscular dystrophy and control groups. In the Dp140- subgroup, decreased fractional anisotropy was observed in the left planum temporale, but no significant changes were seen in the Dp140+ subgroup. The ROI-based analysis obtained the same results. No significant differences were evident in the gray or white matter volumes or the DTI metrics other than fractional anisotropy between the groups.

CONCLUSIONS

A DTI metric analysis is useful to detect white-matter microstructural abnormalities in Becker muscular dystrophy that may be affected by the Dp140 isoform expression.

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.