Etiology of intellectual impairment in Duchenne muscular dystrophy

Brain Alteration Patterns in Children with Duchenne Muscular Dystrophy: A Machine Learning Approach to Magnetic Resonance Imaging

Background

Duchenne Muscular Dystrophy (DMD) is a genetic disease in which lack of the dystrophin protein causes progressive muscular weakness, cardiomyopathy and respiratory insufficiency. DMD is often associated with other cognitive and behavioral impairments, however the correlation of abnormal dystrophin expression in the central nervous system with brain structure and functioning remains still unclear.

Objective

To investigate brain involvement in patients with DMD through a multimodal and multivariate approach accounting for potential comorbidities.

Methods

We acquired T1-weighted and Diffusion Tensor Imaging data from 18 patients with DMD and 18 age- and sex-matched controls with similar cognitive and behavioral profiles. Cortical thickness, structure volume, fractional anisotropy and mean diffusivity measures were used in a multivariate analysis performed using a Support Vector Machine classifier accounting for potential comorbidities in patients and controls.

Results

the classification experiment significantly discriminates between the two populations (97.2% accuracy) and the forward model weights showed that DMD mostly affects the microstructural integrity of long fiber bundles, in particular in the cerebellar peduncles (bilaterally), in the posterior thalamic radiation (bilaterally), in the fornix and in the medial lemniscus (bilaterally). We also reported a reduced cortical thickness, mainly in the motor cortex, cingulate cortex, hippocampal area and insula.

Conclusions

Our study identified a small pattern of alterations in the CNS likely associated with the DMD diagnosis.

Age-associated sleep spindle characteristics in Duchenne muscular dystrophy

Brain oscillations of non-rapid eye movement sleep, including slow oscillations (SO, 0.5-1.5 Hz) and spindles (10-16 Hz), mirror underlying brain maturation across development and are associated with cognition. Hence, age-associated emergence and changes in the electrophysiological properties of these rhythms can lend insight into cortical development, specifically in comparisons between pediatric populations and typically developing peers. We previously evaluated age-associated changes in SOs in male patients with Duchenne muscular dystrophy (DMD), finding a significant age-related decline between 4 and 18 years. While primarily a muscle disorder, male patients with DMD can also have sleep, cognitive, and cortical abnormalities, thought to be driven by altered dystrophin expression in the brain. In this follow-up study, we characterized the age-associated changes in sleep spindles. We found that age-dependent spindle characteristics in patients with DMD, including density, frequency, amplitude, and duration, were consistent with age-associated trends reported in the literature for typically developing controls. Combined with our prior finding of age-associated decline in SOs, our results suggest that SOs, but not spindles, are a candidate intervention target to enhance sleep in patients with DMD.

Combining chromosomal microarray and clinical exome sequencing for genetic diagnosis of intellectual disability

Despite the current widespread use of chromosomal microarray analysis (CMA) and exome/genome sequencing for the genetic diagnosis of unexplained intellectual disability (ID) in children, gaining improved diagnostic yields and defined guidelines remains a significant challenge. This is a cohort study of children with unexplained ID. We analyzed the diagnostic yield and its correlation to clinical phenotypes in children with ID who underwent concurrent CMA and clinical exome sequencing (CES). A total of 154 children were included (110 [71.4%] male; mean [SD] age, 51.9 [23.1] months). The overall diagnosis yield was 26.0-33.8%, with CMA contributing 12.3-14.3% and CES contributing 13.6-19.4%, showing no significant difference. The diagnostic rate was significantly higher when gross motor delay (odds ratio, 6.69; 95% CI, 3.20-14.00; P < 0.001), facial dysmorphism (odds ratio, 9.34; 95% CI 4.29-20.30; P < 0.001), congenital structural anomaly (odds ratio 3.62; 95% CI 1.63-8.04; P = 0.001), and microcephaly or macrocephaly (odds ratio 4.87; 95% CI 2.05-11.60; P < 0.001) were presented. Patients with only ID without any other concomitant phenotype (63/154, 40.9%) exhibited a 6.3-11.1% diagnostic rate.

Connectomic disturbances in Duchenne muscular dystrophy with mild cognitive impairment

Duchenne muscular dystrophy (DMD) is frequently associated with mild cognitive deficits. However, the underlying disrupted brain connectome and the neural basis remain unclear. In our current study, 38 first-episode, treatment-naive patients with DMD and 22 matched healthy controls (HC) were enrolled and received resting-sate functional magnetic resonance imaging scans. Voxel-based degree centrality (DC), seed-based functional connectivity (FC), and clinical correlation were performed. Relative to HC, DMD patients had lower height, full Intellectual Quotients (IQ), and IQ-verbal comprehension. Significant increment of DC of DMD patients were found in the left dorsolateral prefrontal cortex (DLPFC.L) and right dorsomedial prefrontal cortex (DMPFC.R), while decreased DC were found in right cerebellum posterior lobe (CPL.R), right precentral/postcentral gyrus (Pre/Postcentral G.R). DMD patients had stronger FC in CPL.R-bilateral lingual gyrus, Pre/Postcentral G.R-Insular, and DMPFC.R-Precuneus.R, had attenuated FC in DLPFC.L-Insular. These abnormally functional couplings were closely associated with the extent of cognitive impairment, suggested an over-activation of default mode network and executive control network, and a suppression of primary sensorimotor cortex and cerebellum-visual circuit. The findings collectively suggest the distributed brain connectome disturbances maybe a neuroimaging biomarker in DMD patients with mild cognitive impairment.

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.

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.

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.

Influence of full-length dystrophin on brain volumes in mouse models of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) affects besides muscle also the brain, resulting in memory and behavioral problems. The consequences of dystrophinopathy on gross macroscopic alterations are unclear. To elucidate the effect of full-length dystrophin expression on brain morphology, we used high-resolution post-mortem MRI in mouse models that either express 0% (mdx), 100% (BL10) or a low amount of full-length dystrophin (mdx-XistΔhs). While absence or low amounts of full-length dystrophin did not significantly affect whole brain volume and skull morphology, we found differences in volume of individual brain structures. The results are in line with observations in humans, where whole brain volume was found to be reduced only in patients lacking both full-length dystrophin and the shorter isoform Dp140.

Cognitive dysfunction in Duchenne muscular dystrophy: a possible role for neuromodulatory immune molecules

Duchenne muscular dystrophy (DMD) is an X chromosome-linked disease characterized by progressive physical disability, immobility, and premature death in affected boys. Underlying the devastating symptoms of DMD is the loss of dystrophin, a structural protein that connects the extracellular matrix to the cell cytoskeleton and provides protection against contraction-induced damage in muscle cells, leading to chronic peripheral inflammation. However, dystrophin is also expressed in neurons within specific brain regions, including the hippocampus, a structure associated with learning and memory formation. Linked to this, a subset of boys with DMD exhibit nonprogressing cognitive dysfunction, with deficits in verbal, short-term, and working memory. Furthermore, in the genetically comparable dystrophin-deficient mdx mouse model of DMD, some, but not all, types of learning and memory are deficient, and specific deficits in synaptogenesis and channel clustering at synapses has been noted. Little consideration has been devoted to the cognitive deficits associated with DMD compared with the research conducted into the peripheral effects of dystrophin deficiency. Therefore, this review focuses on what is known about the role of full-length dystrophin (Dp427) in hippocampal neurons. The importance of dystrophin in learning and memory is assessed, and the potential importance that inflammatory mediators, which are chronically elevated in dystrophinopathies, may have on hippocampal function is also evaluated.

Diffusion tensor imaging study in Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a progressive muscle disorder associated with an intellectual deficit which is non-progressive. The aim of this study was to investigate brain microstructural changes in DMD and to explore the relationship between such changes and cognitive impairment.

METHODS

All participants (12 DMD patients, 14 age-matched healthy boys), intelligence quotients (IQs) [both full (FIQ) and verbal (VIQ)] were evaluated using the Wechsler intelligence scale for children China revised (WISC-CR) edition, and brain gray matter (GM) and white matter (WM) changes were mapped using diffusion tensor imaging (DTI) with fractional anisotropy (FA). The differences between groups were analyzed using the t-test and the association of cognition with neuroimaging parameters was evaluated using Pearson's correlation coefficient.

RESULTS

Compared to the normal controls, the DMD group had lower FIQ (82.0±15.39 vs. 120.21±16.06) and significantly lower splenium of corpus callosum (CC) FA values (P<0.05). Splenium of CC FA was positively correlated with VIQ (r=0.588, P=0.044).

CONCLUSIONS

There were microstructural changes of splenium of CC in DMD patients, which was associated with cognitive impairment.

Abnormalities in brain structure and biochemistry associated with mdx mice measured by in vivo MRI and high resolution localized (1)H MRS

Duchenne muscular dystrophy (DMD), an X-linked disorder caused by the lack of dystrophin, is characterized by the progressive wasting of skeletal muscles. To date, what is known about dystrophin function is derived from studies of dystrophin-deficient animals, with the most common model being the mdx mouse. Most studies on patients with DMD and in mdx mice have focused on skeletal muscle and the development of therapies to reverse, or at least slow, the severe muscle wasting and progressive degeneration. However, dystrophin is also expressed in the CNS. Both mdx mice and patients with DMD can have cognitive and behavioral changes, but studies in the dystrophic brain are limited. We examined the brain structure and metabolites of mature wild type (WT) and mdx mice using magnetic resonance imaging and spectroscopy (MRI/MRS). Both structural and metabolic alterations were observed in the mdx brain. Enlarged lateral ventricles were detected in mdx mice when compared to WT. Diffusion tensor imaging (DTI) revealed elevations in diffusion diffusivities in the prefrontal cortex and a reduction of fractional anisotropy in the hippocampus. Metabolic changes included elevations in phosphocholine and glutathione, and a reduction in γ-aminobutyric acid in the hippocampus. In addition, an elevation in taurine was observed in the prefrontal cortex. Such findings indicate a regional structural change, altered cellular antioxidant defenses, a dysfunction of GABAergic neurotransmission, and a perturbed osmoregulation in the brain lacking dystrophin.

Psychological aspects in children affected by duchenne de boulogne muscular dystrophy

Impairment of intelligence in Duchenne muscular dystrophy (DMD) patients was described by Duchenne de Boulogne himself in 1868. Further studies report intelligence disorders with mayor impairment of memory. The aim of the present study was to assess the presence of affective and personality disorders in a group of children affected by DMD. Twenty six male DMD patients, mean age eleven and four months years old, were assessed for their affective and personality disorder. Only eight subjects had a total IQ below average with major difficulties in verbal and visual-spatial memory, comprehension, arithmetic and vocabulary. All the subjects presented some disorders: tendency to marginalization and isolation, self-depreciation, sense of insecurity, hypochondriac thoughts and marked state of anxiety. These disorders are often a dynamic prolongation of a psychological process which starts when the diagnosis is made and continues, in a slow and latent fashion, throughout the evolution of the disease.

The roles of the dystrophin-associated glycoprotein complex at the synapse

Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and is characterized by progressive muscle wasting. A number of Duchenne patients also present with mental retardation. The dystrophin protein is part of the highly conserved dystrophin-associated glycoprotein complex (DGC) which accumulates at the neuromuscular junction (NMJ) and at a variety of synapses in the peripheral and central nervous systems. Many years of research into the roles of the DGC in muscle have revealed its structural function in stabilizing the sarcolemma. In addition, the DGC also acts as a scaffold for various signaling pathways. Here, we discuss recent advances in understanding DGC roles in the nervous system, gained from studies in both vertebrate and invertebrate model systems. From these studies, it has become clear that the DGC is important for the maturation of neurotransmitter receptor complexes and for the regulation of neurotransmitter release at the NMJ and central synapses. Furthermore, roles for the DGC have been established in consolidation of long-term spatial and recognition memory. The challenges ahead include the integration of the behavioral and mechanistic studies and the use of this information to identify therapeutic targets.

Duchenne muscular dystrophy: a cerebellar disorder?

Cyrulnik, S.C., and V.J. Hinton. Duchenne muscular dystrophy: A cerebellar disorder? NEUROSCI. BIOBEHAV. REV. Duchenne muscular dystrophy (DMD) is a genetic disorder that is often associated with cognitive deficits. These cognitive deficits have been linked to the absence of dystrophin, a protein product which is normally found in multiple tissues throughout the body. In the current paper, we argue that it is the absence of dystrophin in the cerebellum that is responsible for the cognitive deficits observed. We begin by reviewing data that document structural and functional abnormalities in the brains of individuals with DMD and mdx mice. We briefly review the cognitive deficits associated with DMD, and then present neuroimaging and neuropsychological evidence to indicate that the cerebellum is involved in the same aspects of cognition that are impaired in children with DMD. It is our contention that the development of brain pathways in the cerebellum (e.g., cerebro-cerebellar loops) without dystrophin may result in altered brain function presenting as cognitive deficits in DMD.

Cognitive impairment in neuromuscular disorders

Several studies have suggested the presence of central nervous system involvement manifesting as cognitive impairment in diseases traditionally confined to the peripheral nervous system. The aim of this review is to highlight the character of clinical, genetic, neurofunctional, cognitive, and psychiatric deficits in neuromuscular disorders. A high correlation between cognitive features and cerebral protein expression or function is evident in Duchenne muscular dystrophy, myotonic dystrophy (Steinert disease), and mitochondrial encephalomyopathies; direct correlation between tissue-specific protein expression and cognitive deficits is still elusive in certain neuromuscular disorders presenting with or without a cerebral abnormality, such as congenital muscular dystrophies, congenital myopathies, amyotrophic lateral sclerosis, adult polyglucosan body disease, and limb-girdle muscular dystrophies. No clear cognitive deficits have been found in spinal muscular atrophy and facioscapulohumeral dystrophy.

Altered regional brain glucose metabolism in Duchenne muscular dystrophy: a pet study

The basis for cognitive impairment in Duchenne muscular dystrophy (DMD) is not well understood but may be related to abnormal expression of dystrophin in brain. The aim of this study was to determine whether regional brain glucose metabolism is altered in children with DMD and whether such metabolic disturbances are localized to regions shown to be normally rich in dystrophin expression. Ten boys (mean age, 11.8 years) with DMD and 17 normal adults as a control group (mean age, 27.6 years) underwent 2-deoxy-2[(18)F]fluoro-D-glucose positron emission tomography (PET) and neuropsychological evaluation. The PET data were analyzed by statistical parametric mapping (SPM). The SPM analysis showed five clusters of decreased glucose metabolism in children with DMD, including the medial temporal structures and cerebellum bilaterally and the sensorimotor and lateral temporal cortex on the right side. At the voxel level, significant glucose hypometabolism was found in the right postcentral and middle temporal gyri, uncus, and VIIIB cerebellar lobule, as well as in the left hippocampal gyrus and cerebellar lobule. The neuropsychological profile of the DMD group revealed borderline nonverbal intellectual functioning, impaired manual dexterity bilaterally, borderline cognitive functioning, and internalizing behavioral difficulties. Our findings demonstrate region-specific hypometabolism, as well as cognitive and behavioral deficits in DMD children. As the regions showing hypometabolism on PET include those normally rich in dystrophin expression, it will be important to determine whether the hypometabolic regions also show cytoarchitectural abnormalities related to the lack of dystrophin.

Abnormalities in brain biochemistry associated with lack of dystrophin: studies of the mdx mouse

Biochemical abnormalities have been reported in dystrophin-deficient muscle of boys with Duchenne (severe Xp21) muscular dystrophy or in the murine (mdx) model of the disease. These abnormalities include altered energy metabolism and responses to osmotic shock. In contrast, the situation in brain is less well understood and it is probable that dystrophin is playing a different role (or roles) in this organ. In this study we conclude that the elevation in choline-containing compounds reported in mdx brain is confined to cerebellum and hippocampus in older (> 6 months) mice. We report alterations in glucose metabolism in mdx brain under normal, awake conditions, and a reduced response of brain metabolism to the gamma-aminobutyric acid(A) receptor agonist muscimol. Using brain cortical slices we found no difference in the response of dystrophic tissue to hypoosmotic shock, but increased, substrate-dependent oxygen consumption rates at low oxygen partial pressures.

Brain function in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the second most commonly occurring genetically inherited disease in humans. It is an X-linked condition that affects approximately one in 3300 live male births. It is caused by the absence or disruption of the protein dystrophin, which is found in a variety of tissues, most notably skeletal muscle and neurones in particular regions of the CNS. Clinically DMD is characterized by a severe pathology of the skeletal musculature that results in the premature death of the individual. An important aspect of DMD that has received less attention is the role played by the absence or disruption of dystrophin on CNS function. In this review we concentrate on insights into this role gained from investigation of boys with DMD and the genetically most relevant animal model of DMD, the dystrophin-deficient mdx mouse. Behavioural studies have shown that DMD boys have a cognitive impairment and a lower IQ (average 85), whilst the mdx mice display an impairment in passive avoidance reflex and in short-term memory. In DMD boys, there is evidence of disordered CNS architecture, abnormalities in dendrites and loss of neurones, all associated with neurones that normally express dystrophin. In the mdx mouse, there have been reports of a 50% decrease in neurone number and neural shrinkage in regions of the cerebral cortex and brainstem. Histological evidence shows that the density of GABA(A) channel clusters is reduced in mdx Purkinje cells and hippocampal CA1 neurones. At the biochemical level, in DMD boys the bioenergetics of the CNS is abnormal and there is an increase in the levels of choline-containing compounds, indicative of CNS pathology. The mdx mice also display abnormal bioenergetics, with an increased level of inorganic phosphate and increased levels of choline-containing compounds. Functionally, DMD boys have EEG abnormalities and there is some preliminary evidence that synaptic function is affected adversely by the absence of dystrophin. Electrophysiological studies of mdx mice have shown that hippocampal neurones have an increased susceptibility to hypoxia. These recent findings on the role of dystrophin in the CNS have implications for the clinical management of boys with DMD.

Brain biochemistry in Duchenne muscular dystrophy: a 1H magnetic resonance and neuropsychological study

Duchenne muscular dystrophy (DMD) is a progressive muscle disorder associated with an intellectual deficit which is non-progressive. We obtained localised 1H magnetic resonance spectra from the left frontal lobe and left cerebellum of 15 boys with DMD (mean age 106 months+/-32) and 15 similarly aged control boys (mean age 115 months+/-31); all boys underwent a battery of neuropsychological tests. We found a significant (P<0.01) increase in the ratio of choline-containing compounds to N-acetylaspartate (Cho/NA) in the left cerebellum in boys with DMD compared with control boys. There was no change in the creatine/NA ratio and a significant increase (P=0.03) in the Cho/creatine ratio, suggesting that the change in Cho/NA ratio was due to an increase in choline-containing compounds; this increase has been previously observed in the brain of the murine model of DMD, the mdx mouse. No significant changes were observed in spectra obtained from left frontal lobe in DMD compared to controls. We also observed a significant association between Cho/NA in the left cerebellum, and the performance of DMD boys on the Matrix Analogies Test (MAT). The MAT is a test of visuo-spatial ability and non-verbal reasoning which requires neither manual dexterity nor a verbal response for an adequate performance. A comparison of DMD boys whose cerebellar Cho/NA fell within 2 standard deviations of the control norm (0.56+/-0.24) with DMD boys whose cerebellar Cho/NA was outside this range (i.e. >0.80) revealed a significant difference in ability on the MAT (P<0.05). DMD boys whose Cho/NA ratio is more than two standard deviations higher than controls perform significantly better on the MAT than DMD boys whose Cho/NA ratio is within the normal range. This finding suggests that the observed elevation in Cho/NA and Cho/creatine is not associated with intellectual deficit (as sampled by the MAT), and may represent a compensatory mechanism. The possible interpretations of these metabolic changes are discussed.

Brain abnormalities in Duchenne muscular dystrophy: phosphorus-31 magnetic resonance spectroscopy and neuropsychological study

Duchenne muscular dystrophy (DMD) is one of a range of muscular dystrophies caused by abnormalities of the short arm of the X chromosome (Xp21), which often cause mental retardation in addition to progressive muscular weakness. Normal dystrophin expression is lacking in both skeletal muscle and brain of affected subjects. Phosphorus-31 magnetic resonance spectroscopy has shown several abnormalities in skeletal muscle in DMD. We looked for similar abnormalities in brain in patients with DMD and related the findings to neuropsychological test results. We studied by magnetic resonance spectroscopy 19 boys (aged 76-167 months) diagnosed as having DMD and 19 control boys of similar age (87-135 months). Intelligence quotient (IQ) was assessed with the Wechsler Intelligence Scale for children. The DMD patients had significantly higher values than the controls in the brain ratios of inorganic phosphate to adenosine triphosphate (mean 0.53 [SD 0.21] vs 0.36 [0.09], p = 0.003), to phosphomonoesters (0.40 [0.07] vs 0.29 [0.07], p = 0.0001), and to phosphocreatine (0.44 [0.10] vs 0.37 [0.08], p = 0.02). There were significant differences between the DMD patients and the controls in full-scale IQ (76 [16] vs 101 [16], p = 0.0001), performance IQ (78 [17] vs 94 [14], p = 0.003), and verbal IQ (78 [17] vs 106 [17], p = 0.0001). These altered metabolite ratios parallel the findings in dystrophic muscle and suggest bioenergetic similarities in tissues that lack dystrophin.

Deletion status and intellectual impairment in Duchenne muscular dystrophy

The authors collected Verbal, Performance and Full-scale IQs for 74 patients in whom complete analysis of the dystrophin gene for deletions and duplications had been performed. There was a significant difference in the mean Full-scale IQ between patients with deletions at the 5' and 3' ends of the gene, with no patients with 5' deletions having mental retardation. No relationship was established between mental retardation and the presence or absence of deletions or length of deletions, and similar deletions were observed in the presence and absence of mental retardation. Although distal deletions were more commonly associated with mental retardation, there was no clear evidence for a particular region of the dystrophin gene being specifically responsible for IQ. The intellectual deficit seen in DMD may be a consequence of cerebral hypoxia, ue to malfunction of smooth muscle dystrophin.

End of life care in Duchenne muscular dystrophy

End of life care for patients with Duchenne muscular dystrophy (DMD) has become increasingly complex because of new technologies, changes in medical personnel over periods of time, emergence of home health care systems, and increasing patient and family autonomy in decision-making. In this review, we discuss the medical problems, particularly respiratory and cardiac failure, faced by DMD patients. Current concepts concerning the evaluation and options for treatment of these problems are presented as well as the ethical issues involved in the care of the DMD patient. These issues include the medical indications for treatment, patient preferences, quality-of-life issues, and contextual features related to legal, institutional, religious, geographic, cultural, social, and financial factors. We also present our experience at Loma Linda University Medical Center over the past 10 years in the development of a home mechanical ventilation program for DMD patients and an algorithm for the evaluation of these patients. Many patients with DMD do well on long-term ventilation, but some find that their quality of life is less than desirable and choose to discontinue this method of life-prolongation. Many of these new options are very expensive, making the decision to use them a difficult one. Ultimately, these are societal issues that require clear reflection on matters of resource allocation that should be performed by health care professionals, citizens, and health planners.

Head circumference and intellectual performance of patients with Duchenne muscular dystrophy

The head circumferences of 64 patients with Duchenne muscular dystrophy were measured and found to be greater than those of a normal population. The patients had relative, and in 12 cases, absolute macrocephaly. 47 of the 64 patients underwent intelligence testing and were found to be significantly intellectually impaired, particularly in verbal and language skills. There was no correlation between head circumference or absolute macrocephaly and intellectual performance. The cause of macrocephaly in these patients is unknown and its relevance to the aetiology of intellectual impairment in Duchenne muscular dystrophy is not yet clear.