Affective symptoms and apathy in myotonic dystrophy type 1 a systematic review and meta-analysis

Common Characteristics Between Frailty and Myotonic Dystrophy Type 1: A Narrative Review

Myotonic dystrophy type 1 (DM1) is an inherited neuromuscular disorder often considered a model of accelerated aging due to the early appearance of certain age-related clinical manifestations and cellular and molecular aging markers. Frailty, a state of vulnerability related to aging, has been recently studied in neurological conditions but has received considerably less attention in neuromuscular disorders. This narrative review aims to describe 1) the common characteristics between Fried's frailty phenotype criteria (muscular weakness, slow gait speed, weight loss, exhaustion/fatigue, and low physical activity) and DM1, and 2) the psychological and social factors potentially contributing to frailty in DM1. This review gathered evidence suggesting that DM1 patients meet four of the five frailty phenotype criteria. Additionally, longitudinal studies report the deterioration of these criteria over time in DM1. Patients also exhibit psychological/cognitive and social factors that might contribute to frailty. Monitoring frailty criteria in the DM1 population could help to implement timely preventions and interventions to reduce the disease burden and severity of frailty symptoms.

Resistance training in women with myotonic dystrophy type 1: a multisystemic therapeutic avenue

Myotonic dystrophy type 1 (DM1) is a hereditary disease characterized by muscular impairments. Fundamental and clinical positive effects of strength training have been reported in men with DM1, but its impact on women remains unknown. We evaluated the effects of a 12-week supervised strength training on physical and neuropsychiatric health. Women with DM1 performed a twice-weekly supervised resistance training program (3 series of 6-8 repetitions of squat, leg press, plantar flexion, knee extension, and hip abduction). Lower limb muscle strength, physical function, apathy, anxiety and depression, fatigue and excessive somnolence, pain, and patient-reported outcomes were assessed before and after the intervention, as well as three and six months after completion of the training program. Muscle biopsies of the vastus lateralis were also taken before and after the training program to assess muscle fiber growth. Eleven participants completed the program (attendance: 98.5 %). Maximal hip and knee extension strength (p < 0.006), all One-Repetition Maximum strength measures (p < 0.001), apathy (p = 0.0005), depression (p = 0.02), pain interference (p = 0.01) and perception of the lower limb function (p = 0.003) were significantly improved by training. Some of these gains were maintained up to six months after the training program. Strength training is a good therapeutic strategy for women with DM1.

Differences in respiratory function, depressive symptoms and quality of life between patients with hereditary motor and sensory neuropathy and myotonic dystrophy undergoing maintenance rehabilitation

Hereditary motor and sensory neuropathy (HMSN) and myotonic dystrophy (MD) are chronic neuromuscular diseases that cause progressive muscular impairment and impact patient's quality of life. Conflicting findings in existing literature underscore the need for focussed research on specific health aspects in these patients. The aim of the study was to explore the differences in respiratory function, depressive symptoms and quality of life between patients with HMSN and MD undergoing maintenance rehabilitation. Our prospective observational study included 62 HMSN patients (median age 53.5, range 19-79 years; 38 women) and 50 MD patients (median age 54.0, range 18-77 years; 34 women) undergoing maintenance rehabilitation. They performed respiratory function tests (vital capacity, forced vital capacity, forced expiratory volume and peak expiratory flow) and respiratory muscle strength tests (maximum inspiratory pressure, maximum expiratory pressure and sniff nasal inspiratory force). The Center for Epidemiological Studies-Depression Scale was used to evaluate depression, and their health-related quality of life was assessed using the Quality of Life in Genetic Neuromuscular Disease Questionnaire. Using logistic regression, we examined group-difference in presence of depressive symptoms while accounting for age, symptoms duration, and marital status. Multiple linear regression was used to assess the difference in quality-of-life scores, adjusting for age, gender, and symptoms' duration. The HMSN group achieved statistically significantly better results than the MD group on all respiratory measures (about 17% absolute difference in the respiratory function measures and 30% relative difference in the respiratory muscle strength measures on average). Both groups exhibited a high level of depression symptoms (HMSN 24%, MD 44%; estimated adjusted odds-ratio MD vs. HMSN 1.9, 95% CI 0.8-4.5, P  = 0.127). We did not find a statistically significant difference between the groups regarding quality-of-life domains, though a trend towards better quality-of-life among the HMSN patients could be observed. The implication for future practice is that the MD patients would potentially benefit the most from targeted respiratory-rehabilitation interventions, and both groups could benefit from focussed mental-health interventions.

The Role of Cognition, Affective Symptoms, and Apathy in Treatment Adherence with Noninvasive Home Mechanical Ventilation in Myotonic Dystrophy

Background

Chronic respiratory failure often occurs in myotonic dystrophy type 1 (DM1) and can be treated with noninvasive home mechanical ventilation (HMV). Treatment adherence with HMV is often suboptimal in patients with DM1, but the reasons for that are not well understood.

Objective

The aim of this exploratory study was to gain insight in the prevalence of mild cognitive impairment, affective symptoms, and apathy and to investigate their role in HMV treatment adherence in DM1.

Methods

The Montreal Cognitive Assessment (MoCA), the Hospital Anxiety and Depression Scale (HADS), and the Apathy Evaluation Scale (AES) were used to assess cognition, affective symptoms, and apathy in DM1 patients that use HMV. Patients with low treatment adherence (average daily use HMV <5 h or <80% of the days) were compared with patients with high treatment adherence (average daily use of HMV≥5 h and ≥80% of the days).

Results

Sixty patients were included. Abnormal scores were found in 40% of the total group for the MoCA, in 72-77% for the AES, and in 18% for HADS depression. There was no difference between the high treatment adherence group (n = 39) and the low treatment adherence group (n = 21) for the MoCA, AES, and HADS depression. The HADS anxiety was abnormal in 30% of the total group, and was significantly higher in the low treatment adherence group (p = 0.012). Logistic regression analysis revealed that a higher age and a higher BMI were associated with a greater chance of high treatment adherence.

Conclusions

This exploratory study showed that cognitive impairment and apathy are frequently present in DM1 patients that use HMV, but they are not associated with treatment adherence. Feelings of anxiety were associated with low treatment adherence. Higher age and higher BMI were associated with high treatment adherence with HMV.

Executive functions and daily functioning in myotonic dystrophy type 1 ecological assessment with virtual reality

Central nervous system dysfunction is characteristic of patients with myotonic dystrophy type 1 (DM1). Although no consensus exists regarding the exact cognitive profile of these patients, executive dysfunction has been suggested to play a role. Due to the impact of executive functions on daily performance, this study aimed to describe executive functioning in an ecological manner and to analyze its impact - and that of other clinical variables - on the functional performance of DM1 patients. A Virtual Reality executive functioning test (Nesplora Ice Cream), the Wechsler Adult Intelligence Scale-Fourth Edition, and self-report questionnaires (AES, FSS, ESS and LIFE-H) were administered to 20 patients. Statistical analyses included correlation and multiple regression analyses to analyze the best predictors of daily performance. DM1 patients did not show major difficulties in the executive functioning tasks or in their overall performance on daily habits. However, both cold and hot executive functions still seem necessary for the correct accomplishment of life habits, since planning and level of apathy explained 47.6% of the total variance of daily functioning. This was the first study to assess executive functions in DM1 using Virtual Reality, and our findings open a debate about their actual impairment in this population.

Characterization of theory of mind performance in patients with myotonic dystrophy type 1

INTRODUCTION

Myotonic dystrophy type 1 (DM1) is associated with motor dysfunction as well as psychological and cognitive impairments, including altered social cognition. Theory of mind (ToM) impairments have been reported in this disease but their nature and their cognitive/cerebral correlates have yet to be determined.

METHODS

Fifty DM1 patients and 50 healthy controls were assessed using the Movie for the Assessment of Social Cognition, which quantifies impairments in affective and cognitive components of ToM through the depiction of everyday situations. We also measured the study participants' cognitive, behavioral and social abilities, quality of life, and brain MRI characteristics.

RESULTS

DM1 patients presented a significant impairment in ToM performance compared to controls (p < .001). The patients' errors were related to hypomentalizations (p < .001 vs controls) but not to hypermentalizations (p = .95). The affective component was affected (p < .001 vs controls) but not the cognitive component (p = .09). The ToM impairment was associated with demographic variables (older age and a lower educational level), genetic findings (a larger CTG triplets repeat expansion) and cognitive scores (slower information processing speed). Associations were also found with brain MRI variables (lower white matter and supratentorial volumes) but not with behavioral or social variables.

DISCUSSION

DM1 patients display a ToM impairment, characterized by predominant hypomentalizations concerning the affective component. This impairment might result from structural brain abnormalities observed in DM1.

Role of respiratory characteristics in treatment adherence with noninvasive home mechanical ventilation in myotonic dystrophy type 1, a retrospective study

Chronic respiratory insufficiency is common in patients with myotonic dystrophy type 1 (DM1) and can be treated with noninvasive home mechanical ventilation (HMV). HMV is not always tolerated well resulting in low treatment adherence. We aimed to analyze if baseline respiratory characteristics such as pulmonary function, level of pCO2 and presence of sleep apnea are associated with HMV treatment adherence in DM1 patients. Pulmonary function testing, polysomnography and blood gas measurement data of DM1 patients were retrospectively collected. Initiation of HMV and treatment adherence after one year was documented. Patients with low treatment adherence (average daily use of HMV <5 h) were grouped with patients that discontinued HMV and compared with patients with high treatment adherence (average daily use of HMV >5 h). HMV was initiated in 101 patients. After one year, 58 patients had low treatment adherence. There were no differences between the low and high treatment adherence group regarding the respiratory characteristics. None of the included predictors (gender, age, body mass index, cytosine-thymine-guanine repeat length, FVC, daytime pCO2, bicarbonate, nighttime pCO2, nighttime base excess, apnea-hypopnea index and mean saturation during sleep) was able to significantly predict high treatment adherence. In conclusion, the respiratory characteristics are not associated with treatment adherence with HMV in DM1 patients and cannot be used to identify patients at risk for low HMV treatment adherence.

Longitudinal changes in white matter as measured with diffusion tensor imaging in adult-onset myotonic dystrophy type 1

Myotonic dystrophy type 1 is characterized by neuromuscular degeneration. Our objective was to compare change in white matter microstructure (fractional anisotropy, radial and axial diffusivity), and functional/clinical measures. Participants underwent yearly neuroimaging and neurocognitive assessments over three-years. Assessments encompassed full-scale intelligence, memory, language, visuospatial skills, attention, processing speed, and executive function, as well as clinical symptoms of muscle/motor function, apathy, and hypersomnolence. Mixed effects models were used to examine differences. 69 healthy adults (66.2% women) and 41 DM1 patients (70.7% women) provided 156 and 90 observations, respectively. There was a group by elapsed time interaction for cerebral white matter, where DM1 patients exhibited declines in white matter (all p<0.05). Likewise, DM1 patients either declined (motor), improved more slowly (intelligence), or remained stable (executive function) for functional outcomes. White matter was associated with functional performance; intelligence was predicted by axial (r = 0.832; p<0.01) and radial diffusivity (r = 0.291, p<0.05), and executive function was associated with anisotropy (r = 0.416, p<0.001), and diffusivity (axial: r = 0.237, p = 0.05 and radial: r = 0.300, p<0.05). Indices of white matter health are sensitive to progression in DM1. These results are important for clinical trial design, which utilize short intervals to establish treatment efficacy.

267th ENMC International workshop: psychological interventions for improving quality of life in slowly progressive neuromuscular disorders

This workshop aimed to develop recommendations for psychological interventions to support people living with slowly progressive neuromuscular disorders (NMD). The workshop comprised clinicians, researchers, people living with NMD and their relatives. First, participants considered the key psychological challenges presented by NMD and the impact of NMD on relationships and mental health. Later, several psychological approaches for enhancing well-being in NMD were described. The results of randomised controlled trials of Cognitive Behaviour Therapy and Acceptance and Commitment Therapy for improving fatigue, quality of life, and mood in adults with NMD were examined. Then the group considered ways to adapt therapies for cognitive impairments or neurodevelopmental differences that occur in some NMD, alongside ways to support children and adolescents with NMD and their family members. Based on the evidence from randomised controlled trials, carefully conducted observational studies, and the coherence of these data with the experience of those living with NMD, the group recommends that psychological interventions should be embedded in the routine clinical care offered to people living with NMD.

Impact of a 12-week strength training program on fatigue, daytime sleepiness, and apathy in men with myotonic dystrophy type 1

Background: Myotonic dystrophy type 1 (DM1) is a multisystemic neuromuscular disorder causing a plea of impairments, of which fatigue and apathy are some of the most frequent non-muscular symptoms. No curative treatment exists to date, and patients only have access to limited effective care, which are intended to decrease the burden of specific symptoms in daily life. Objective: This study aimed to assess whether a 12-week strength-training program has an impact on fatigue/daytime sleepiness, apathy, and patient-reported health in men with DM1. Methods: Eleven participants completed the Fatigue and Daytime Sleepiness Scale (FDSS) and the Myotonic Dystrophy Health Index (MDHI) at baseline, at 6 and 12 weeks, and 6 and 9 months. Also, the Apathy Evaluation Scale (AES) was filled out at baseline, at 12 weeks, and 6 and 9 months. Results: Results show significant effects of the training program both on apathy and fatigue/daytime sleepiness, effects that are respectively greater at three and six months after the end of the program than at its very end. However, no difference was observed regarding the overall disease burden. Conclusion: These findings are promising for patients with DM1 considering that few non-pharmacological treatments are available.

Unravelling the impact of frontal lobe impairment for social dysfunction in myotonic dystrophy type 1

Myotonic dystrophy type 1 is an autosomal dominant multisystemic disorder affecting muscular and extra muscular systems, including the central nervous system. Cerebral involvement in myotonic dystrophy type 1 is associated with subtle cognitive and behavioural disorders, of major impact on socio-professional adaptation. The social dysfunction and its potential relation to frontal lobe neuropsychology remain under-evaluated in this pathology. The neuroanatomical network underpinning that disorder is yet to disentangle. Twenty-eight myotonic dystrophy type 1 adult patients (mean age: 46 years old) and 18 age and sex-matched healthy controls were included in the study. All patients performed an exhaustive neuropsychological assessment with a specific focus on frontal lobe neuropsychology (motivation, social cognition and executive functions). Among them, 18 myotonic dystrophy type 1 patients and 18 healthy controls had a brain MRI with T1 and T2 Flair sequences. Grey matter segmentation, Voxel-based morphometry and cortical thickness estimation were performed with Statistical Parametric Mapping Software SPM12 and Freesurfer software. Furthermore, T2 white matter lesions and subcortical structures were segmented with Automated Volumetry Software. Most patients showed significant impairment in executive frontal functions (auditory working memory, inhibition, contextualization and mental flexibility). Patients showed only minor difficulties in social cognition tests mostly in cognitive Theory of Mind, but with relative sparing of affective Theory of Mind and emotion recognition. Neuroimaging analysis revealed atrophy mostly in the parahippocampal and hippocampal regions and to a lesser extent in basal ganglia, regions involved in social navigation and mental flexibility, respectively. Social cognition scores were correlated with right parahippocampal gyrus atrophy. Social dysfunction in myotonic dystrophy type 1 might be a consequence of cognitive impairment regarding mental flexibility and social contextualization rather than a specific social cognition deficit such as emotion recognition. We suggest that both white matter lesions and grey matter disease could account for this social dysfunction, involving, in particular, the frontal-subcortical network and the hippocampal/arahippocampal regions, brain regions known, respectively, to integrate contextualization and social navigation.

Psychopharmacological Treatments for Mental Disorders in Patients with Neuromuscular Diseases: A Scoping Review

Mental disorders are observed in neuromuscular diseases, especially now that patients are living longer. Psychiatric symptoms may be severe and psychopharmacological treatments may be required. However, very little is known about pharmacotherapy in these conditions. We aimed to summarize the current knowledge on the use of psychopharmacological treatments for mental disorders in patients living with a neuromuscular disease. A scoping review was performed using the methodology of the Joanna Briggs Institute. Four databases were searched from January 2000 to July 2021. Articles were screened based on titles and abstracts. Full-text papers published in peer-reviewed journals in English were selected. Twenty-six articles met eligibility criteria, all being case reports/series focusing on the psychopharmacological control of psychiatric symptoms for the following conditions: myasthenia gravis (n = 11), Duchenne (n = 5) and Becker (n = 3) muscular dystrophy, mitochondrial disorders (n = 3), glycogen storage disease (n = 1), myotonic dystrophy (n = 1), hyperkalemic periodic paralysis (n = 1), and congenital myasthenic syndrome (n = 1). None of the articles provided details on the decision-making process to choose a specific drug/regimen or on follow-up strategies to monitor safety and efficacy. Larger studies showing real-world data would be required to guide consensus-based recommendations, thus improving current standards of care and, ultimately, the quality of life of patients and their families.

Brain Pathogenesis and Potential Therapeutic Strategies in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy that affects multiple systems including the muscle and heart. The mutant CTG expansion at the 3'-UTR of the DMPK gene causes the expression of toxic RNA that aggregate as nuclear foci. The foci then interfere with RNA-binding proteins, affecting hundreds of mis-spliced effector genes, leading to aberrant alternative splicing and loss of effector gene product functions, ultimately resulting in systemic disorders. In recent years, increasing clinical, imaging, and pathological evidence have indicated that DM1, though to a lesser extent, could also be recognized as true brain diseases, with more and more researchers dedicating to develop novel therapeutic tools dealing with it. In this review, we summarize the current advances in the pathogenesis and pathology of central nervous system (CNS) deficits in DM1, intervention measures currently being investigated are also highlighted, aiming to promote novel and cutting-edge therapeutic investigations.

Cognitive Deficits, Apathy, and Hypersomnolence Represent the Core Brain Symptoms of Adult-Onset Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 is the most common form of muscular dystrophy in adults, and is primarily characterized by muscle weakness and myotonia, yet some of the most disabling symptoms of the disease are cognitive and behavioral. Here we evaluated several of these non-motor symptoms from a cross-sectional time-point in one of the largest longitudinal studies to date, including full-scale intelligence quotient, depression, anxiety, apathy, sleep, and cerebral white matter fractional anisotropy in a group of 39 adult-onset myotonic dystrophy type 1 participants (27 female) compared to 79 unaffected control participants (46 female). We show that intelligence quotient was significantly associated with depression (P < 0.0001) and anxiety (P = 0.018), but not apathy (P < 0.058) or hypersomnolence (P = 0.266) in the DM1 group. When controlling for intelligence quotient, cerebral white matter fractional anisotropy was significantly associated with apathy (P = 0.042) and hypersomnolence (P = 0.034), but not depression (P = 0.679) or anxiety (P = 0.731) in the myotonic dystrophy type 1 group. Finally, we found that disease duration was significantly associated with apathy (P < 0.0001), hypersomnolence (P < 0.001), IQ (P = 0.038), and cerebral white matter fractional anisotropy (P < 0.001), but not depression (P = 0.271) or anxiety (P = 0.508). Our results support the hypothesis that cognitive deficits, hypersomnolence, and apathy, are due to the underlying neuropathology of myotonic dystrophy type 1, as measured by cerebral white matter fractional anisotropy and disease duration. Whereas elevated symptoms of depression and anxiety in myotonic dystrophy type 1 are secondary to the physical symptoms and the emotional stress of coping with a chronic and debilitating disease. Results from this work contribute to a better understanding of disease neuropathology and represent important therapeutic targets for clinical trials.

Noninvasive Home Mechanical Ventilation in Adult Myotonic Dystrophy Type 1: A Systematic Review

INTRODUCTION

Chronic hypercapnic respiratory failure induces considerable morbidity and mortality in patients with myotonic dystrophy type 1 (DM1). This study systematically reviews the effects of noninvasive home mechanical ventilation (HMV) on gas exchange, quality of life, survival, and compliance in DM1 patients.

METHODS

A systematic Medline and Embase search was performed (January 1995 to January 2020). Records were screened for eligibility criteria, data were extracted from included studies, and risk of bias was assessed. We present findings mainly using a narrative synthesis.

RESULTS

Twenty-eight relevant full-text articles were screened for eligibility criteria. Nine studies were included. Randomized controlled trials were not found. Studies had either an observational (n = 8) or interventional (n = 1) design. In the pooled data analysis, HMV showed to improve mean oxygen saturation with 4.8% and decreased mean carbon dioxide values with 3 mm Hg. Compliance varied widely between studies, from no use to more than 12 h per day. Quality of life was not studied extensively, but some studies reported positive effects of HMV on symptoms of chronic respiratory failure. HMV may improve survival in DM1 patients with chronic hypercapnic respiratory failure.

CONCLUSION

This review shows that HMV can improve gas exchange and relieve symptoms with a possible survival benefit in DM1 patients with chronic hypercapnic respiratory failure. Future studies should focus on developing strategies to optimize the timing of HMV initiation and to promote compliance.

Neurocognitive Features of Motor Premanifest Individuals With Myotonic Dystrophy Type 1

Objective

The goal of the study was to identify brain and functional features associated with premanifest phases of adult-onset myotonic dystrophy type 1 (i.e., PreDM1).

Methods

This cross-sectional study included 68 healthy adults (mean age = 43.4 years, SD = 12.9), 13 individuals with PreDM1 (mean age: 47.4 years, SD = 16.3), and 37 individuals with manifest DM1 (mean age = 45.2 years, SD = 9.3). The primary outcome measures included fractional anisotropy (FA), motor measures (Muscle Impairment Rating Scale, Grooved Pegboard, Finger-Tapping Test, and grip force), general cognitive abilities (Wechsler Adult Intelligence Scales), sleep quality (Scales for Outcomes in Parkinson's Disease–Sleep), and apathy (Apathy Evaluation Scale).

Results

Individuals with PreDM1 exhibited an intermediate level of white matter FA abnormality, where whole-brain FA was lower relative to healthy controls (difference of the estimated marginal mean [EMM_difference] = 0.02, 95% confidence interval (CI) 0.01–0.03, p < 0.001), but the PreDM1 group had significantly higher FA than did individuals with manifest DM1 (EMM_difference = 0.02, 95% CI 0.009–0.03, p < 0.001). Individuals with PreDM1 exhibited reduced performance on the finger-tapping task relative to control peers (EMM_difference = 5.70, 95% CI 0.51–11.00, p = 0.03), but performance of the PreDM1 group was better than that of the manifest DM1 group (EMM_difference = 5.60, 95% CI 0.11–11.00, p = 0.05). Hypersomnolence in PreDM1 was intermediate between controls (EMM_difference = −1.70, 95% CI −3.10–0.35, p = 0.01) and manifest DM1 (EMM_difference = −2.10, 95% CI −3.50–0.60, p = 0.006).

Conclusions

Our findings highlight key CNS and functional deficits associated with PreDM1, offering insight in early disease course.

Human brain pathology in myotonic dystrophy type 1: A systematic review

Brain involvement in myotonic dystrophy type 1 (DM1) is characterized by heterogeneous cognitive, behavioral, and affective symptoms and imaging alterations indicative of widespread grey and white matter involvement. The aim of the present study was to systematically review the literature on brain pathology in DM1. We conducted a structured search in EMBASE (index period 1974–2017) and MEDLINE (index period 1887–2017) on December 11, 2017, using free text and index search terms related to myotonic dystrophy type 1 and brain structures or regions. Eligible studies were full‐text studies reporting on microscopic brain pathology of DM1 patients without potentially interfering comorbidity. We discussed the findings based on the anatomical region and the nature of the anomaly. Neuropathological findings in DM1 can be classified as follows: (1) protein and nucleotide deposits; (2) changes in neurons and glial cells; and (3) white matter alterations. Most findings are unspecific to DM1 and may occur with physiological aging, albeit to a lesser degree. There are similarities and contrasts with Alzheimer's disease; both show the appearance of neurofibrillary tangles in the limbic system without plaque occurrence. Likewise, there is myelin loss and gliosis, and there are dilated perivascular spaces in the white matter resemblant of cerebral small vessel disease. However, we did not find evidence of lacunar infarction or microbleeding. The various neuropathological findings in DM1 are reflective of the heterogeneous clinical and neuroimaging features of the disease. The strength of conclusions from this study's findings is bounded by limited numbers of participants in studies, methodological constraints, and lack of assessed associations between histopathology and clinical or neuroimaging findings.

Central Nervous System Involvement as Outcome Measure for Clinical Trials Efficacy in Myotonic Dystrophy Type 1

Increasing evidences indicate that in Myotonic Dystrophy type 1 (DM1 or Steinert disease), an autosomal dominant multisystem disorder caused by a (CTG)n expansion in DMPK gene on chromosome 19q13. 3, is the most common form of inherited muscular dystrophy in adult patients with a global prevalence of 1/8000, and involvement of the central nervous system can be included within the core clinical manifestations of the disease. Variable in its severity and progression rate over time, likely due to the underlying causative molecular mechanisms; this component of the clinical picture presents with high heterogeneity involving cognitive and behavioral alterations, but also sensory-motor neural integration, and in any case, significantly contributing to the disease burden projected to either specific functional neuropsychological domains or quality of life as a whole. Principle manifestations include alterations of the frontal lobe function, which is more prominent in patients with an early onset, such as in congenital and childhood onset forms, here associated with severe intellectual disabilities, speech and language delay and reduced IQ-values, while in adult onset DM1 cognitive and neuropsychological findings are usually not so severe. Different methods to assess central nervous system involvement in DM1 have then recently been developed, these ranging from more classical psychometric and cognitive functional instruments to sophisticated psycophysic, neurophysiologic and especially computerized neuroimaging techniques, in order to better characterize this disease component, at the same time underlining the opportunity to consider it a suitable marker on which measuring putative effectiveness of therapeutic interventions. This is the reason why, as outlined in the conclusive section of this review, the Authors are lead to wonder, perhaps in a provocative and even paradoxical way to arise the question, whether or not the myologist, by now the popular figure in charge to care of a patient with the DM1, needs to remain himself a neurologist to better appreciate, evaluate and speculate on this important aspect of Steinert disease.

Brain Structural Features of Myotonic Dystrophy Type 1 and their Relationship with CTG Repeats

Background

Few adequately-powered studies have systematically evaluated brain morphology in adult-onset myotonic dystrophy type 1 (DM1).

Objective

The goal of the present study was to determine structural brain differences between individuals with and without adult-onset DM1 in a multi-site, case-controlled cohort. We also explored correlations between brain structure and CTG repeat length.

Methods

Neuroimaging data was acquired in 58 unaffected individuals (29 women) and 79 individuals with DM1 (50 women). CTG repeat length, expressed as estimated progenitor allele length (ePAL), was determined by small pool PCR. Statistical models were adjusted for age, sex, site, and intracranial volume (ICV).

Results

ICV was reduced in DM1 subjects compared with controls. Accounting for the difference in ICV, the DM1 group exhibited smaller volume in frontal grey and white matter, parietal grey matter as well as smaller volume of the corpus callosum, thalamus, putamen, and accumbens. In contrast, volumes of the hippocampus and amygdala were significantly larger in DM1. Greater ePAL was associated with lower volumes of the putamen, occipital grey matter, and thalamus. A positive ePAL association was observed for amygdala volume and cerebellar white matter.

Conclusions

Smaller ICV may be a marker of aberrant neurodevelopment in adult-onset DM1. Volumetric analysis revealed morphological differences, some associated with CTG repeat length, in structures with plausible links to key DM1 symptoms including cognitive deficits and excessive daytime somnolence. These data offer further insights into the basis of CNS disease in DM1, and highlight avenues for further work to identify therapeutic targets and imaging biomarkers.

Insulin Signaling as a Key Moderator in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant genetic disease characterized by multi-system involvement. Affected organ system includes skeletal muscle, heart, gastro-intestinal system and the brain. In this review, we evaluate the evidence for alterations in insulin signaling and their relation to clinical DM1 features. We start by summarizing the molecular pathophysiology of DM1. Next, an overview of normal insulin signaling physiology is given, and evidence for alterations herein in DM1 is presented. Clinically, evidence for involvement of insulin signaling pathways in DM1 is based on the increased incidence of insulin resistance seen in clinical practice and recent trial evidence of beneficial effects of metformin on muscle function. Indirectly, further support may be derived from certain CNS derived symptoms characteristic of DM1, such as obsessive-compulsive behavior features, for which links with altered insulin signaling has been demonstrated in other diseases. At the basic scientific level, several pathophysiological mechanisms that operate in DM1 may compromise normal insulin signaling physiology. The evidence presented here reflects the importance of insulin signaling in relation to clinical features of DM1 and justifies further basic scientific and clinical, therapeutically oriented research.