The correlation of CTG repeat length with material and social deprivation in myotonic dystrophy

Work participation in adults with rare genetic diseases - a scoping review

BACKGROUND

Work participation is a crucial aspect of health outcome and an important part of life for most people with rare genetic diseases. Despite that work participation is a social determinant of health and seems necessary for understanding health behaviours and quality of life, it is an under-researched and under-recognized aspect in many rare diseases. The objectives of this study was to map and describe existing research on work participation, identify research gaps, and point to research agendas in a selection of rare genetic diseases.

METHODS

A scoping review was performed by searching relevant literature in bibliographic databases and other sources. Studies addressing work participation in people with rare genetic diseases published in peer reviewed journals were assessed using EndNote and Rayyan. Data were mapped and extracted based on the research questions concerning the characteristics of the research.

RESULTS

Of 19,867 search results, 571 articles were read in full text, and 141 satisfied the eligibility criteria covering 33 different rare genetic diseases; 7 were reviews and 134 primary research articles. In 21% of the articles the primary aim was to investigate work participation. The extent of studies varied between the different diseases. Two diseases had more than 20 articles, but most had only one or two articles. Cross-sectional quantitative studies were predominant, with few utilizing prospective or qualitative design. Nearly all articles (96%) reported information about work participation rate, and 45% also included information about factors associated with work participation and work disability. Due to differences in methodologies, cultures and respondents, comparison between and within diseases are difficult. Nevertheless, studies indicated that many people with different rare genetic diseases experience challenges related to work, closely associated to the symptoms of the disease.

CONCLUSION

While studies indicate high prevalence of work disability in many patients with rare diseases, the research is scarce and fragmented. More research is warranted. Information about the unique challenges of living with different rare diseases is crucial for health and welfare systems to better facilitate work participation. In addition, the changing nature of work in the digital age, may also open up new possibilities for people with rare genetic diseases and should be explored.

Multiple Case Study of Changes in Participation of Adults with Myotonic Dystrophy Type 1: Importance of Redesigning Accomplishment and Resilience

Background: Myotonic dystrophy type 1 (DM1) is the most prevalent adult form of neuromuscular disorders, for which a decrease of participation with age is known. However, little is known about facilitators and barriers to participation, especially from the perspective of both patients and caregivers. Objective: This study explored and explained changes in participation post-diagnosis with myotonic dystrophy type 1 from the perspective of six adults, their relatives and nurse case managers. Methods: A multiple case study was carried out with these triads (n =  6) using semi-structured individual interviews, medical charts, and a participation patient-reported outcome measure. The six cases were built around three women and three men (age: 40–56 years; disease duration: 19–39 years). Their “relatives” were mainly family members. Nurse case managers had done annual follow-ups with all the adults for approximately ten years. Changes in participation were characterized generally by: 1) heterogeneity, 2) insidious increase in restrictions, and more specifically by: 3) redesigning accomplishment, 4) progressive social isolation, 5) restrictions in life-space mobility, and 6) increasingly sedentary activities. Results: Important facilitators of participation were the adult’s resilience, highly meaningful activities, social support, living arrangement, and willingness to use technical aids. Barriers were mostly related to symptoms and a precarious social network, and were affected by misfit and potential syndemic interactions between personal (e.g., comorbidities) and environmental (e.g., stigma) factors. Conclusion: This study identified key facilitators and barriers and their underlying processes, which should be integrated into the evaluation and intervention framework to optimize participation over time.

Responsiveness of Daytime Sleepiness and Fatigue Scales in Myotonic Dystrophy Type 1

Daytime sleepiness and fatigue are prominent symptoms of myotonic dystrophy type 1 (DM1) that can be amenable to treatment in the context of randomized controlled trials. No study has yet documented whether self-reported measures of daytime sleepiness and fatigue can detect change over time and the meaning of this change. The aim was to explore indicators of responsiveness to change and interpretability for the Daytime Sleepiness Scale and the Fatigue Severity Scale in 115 DM1 prospectively followed patients. Results suggest that these two self-reported questionnaires are sufficiently sensitive to detect changes beyond expected measurement error over time in this population.

Predictors of participation restriction over a 9-year period in adults with myotonic dystrophy type 1

PURPOSE

For slowly progressive neuromuscular disease, prognostic approach and long-term monitoring of participation is a crucial part of rehabilitation services. To improve the prognostic approach, professionals must identify individuals at risk of having higher participation restriction. This study aimed to identify personal and environmental predictors of participation restriction over nine years in adults with myotonic dystrophy type 1 (DM1).

METHODS

A secondary analysis of a longitudinal design comparing baseline with a follow-up nine years later was used with a multidimensional assessment of participation and personal and environmental factors. Based on theoretical models, multiple linear regressions were used.

RESULTS

One hundred and fourteen adults with DM1 were included in the study (63.2% women; 78.9% adult onset; mean (SD) age of 43.5 (10.4) years). When age, sex, phenotype, and education were controlled for, participation restriction was predicted by a longer time to stand and walk, lower grip strength, higher body mass index, absence of perceived impact of myotonia in daily living, use of adapted transportation from community services, and perception of obstacle in physical environment (p < 0.001, adjusted R² = 0.50).

CONCLUSIONS

The majority of predictors of participation restriction can be advantageously modified by rehabilitation and environmental changes, such as politics targeting community services provision or physical environment and services accessibility.Implications for rehabilitationPredictors could better inform rehabilitation professional to recognize individuals at risk of higher participation restriction over time and to target specific interventions based on a prognostic approach.Rehabilitation professionals could inform the people living with myotonic dystrophy type 1 and their relatives of the multifactorial nature of occurrence of participation restriction to diminish the "fatality" associated with a genetic progressive disorder.Predictors allow professionals to assess and intervene in the management of specific factors depending on the rehabilitation goal.Identifying individual with myotonic dystrophy with higher risk of participation restriction could help implement a long-term community based rehabilitation intervention plan targeting both personal and environmental factors.

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.

Predicting daytime sleepiness and fatigue: a 9-year prospective study in myotonic dystrophy type 1

OBJECTIVE

Daytime sleepiness and fatigue are prominent symptoms of myotonic dystrophy type I (DM1) that exact a heavy toll on patients' quality of life, but information is scarce on their predictive factors. This study aimed to determine factors that may influence levels of daytime sleepiness and fatigue in a large cohort of DM1 patients followed for 9 years.

METHODS

This study included 115 patients with DM1 at baseline (Time 1, T1) and at Time 2 (T2) who were questioned for daytime sleepiness, fatigue, history of depression, psychological distress, pain, hypothyroidism, and sleep habits. Also, their muscular impairment and intellectual quotient were evaluated. Regression models were used to identify correlates of daytime sleepiness and fatigue while controlling for time effect.

RESULTS

Both daytime sleepiness and fatigue increased between T1 and T2, but their rate of change are higher when CTG repeat number is higher (p < 0.05). Also, higher psychological distress level is associated with higher daytime sleepiness and fatigue levels both at T1 and T2 (p < 0.01). Moreover, patients with a history of depression report higher daytime sleepiness levels both at T1 and T2 (p < 0.05). In addition, patients with higher fatigue levels both at T1 and T2 have more severe muscular impairment (p < 0.01) and report a longer habitual sleep duration (p < 0.05). Finally, a higher BMI and a history of hypothyroidism predict higher daytime sleepiness levels at T2 (p < 0.05).

CONCLUSION

This study identified potentially modifiable risk factors of future daytime sleepiness and fatigue in DM1 patients, including BMI, psychological distress, hypothyroidism, and sleep habits.

Patient-reported study of the impact of pediatric-onset myotonic dystrophy

INTRODUCTION

The prevalence and impact of symptoms affecting individuals with pediatric forms of myotonic dystrophy type-1 (DM1) are not well understood.

METHODS

Patients from the United States, Canada, and Sweden completed a survey that investigated 20 themes associated with pediatric-onset DM1. Participants reported the prevalence and importance of each theme affecting their lives. Surveys from participants were matched with surveys from their caregivers for additional analysis.

RESULTS

The most prevalent symptomatic themes included problems with hands or fingers (79%) and gastrointestinal issues (75%). Problems with urinary/bowel control and gastrointestinal issues were reported to have the greatest impact on patients' lives. Responses from participants and their caregivers had varying levels of agreement among symptomatic themes.

DISCUSSION

Many symptoms have meaningful impact on disease burden. The highest levels of agreement between caregivers and individuals with pediatric forms of myotonic dystrophy were found for physical activity themes.

Progressive Decline in Daily and Social Activities: A 9-year Longitudinal Study of Participation in Myotonic Dystrophy Type 1

OBJECTIVE

To describe and compare changes in participation over a 9-year period in women and men with myotonic dystrophy type 1 (DM1). To compare participation restrictions with available reference values from a typical aging population living in the community.

DESIGN

Descriptive longitudinal design comparing data from baseline (2002) with data from follow-up (2011).

SETTING

Neuromuscular clinic and participant's home.

PARTICIPANTS

Adults with DM1 participated in the follow-up study (N=115).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The Assessment of Life Habits measured participation in 10 domains of daily and social activities. The minimal clinically important difference is 0.5 on a 10-point scale for participation accomplishment level.

RESULTS

A total of 62% of participants were women, and the mean age was 52.3±10.3 years. A decline (P<.01) was observed with increasing difficulty and assistance required in global participation (mean ± SD, -0.5±0.9), social activities subscore (-0.6±1.2), nutrition (-0.7±1.4), fitness (-1.0±1.6), personal care (-0.7±1.2), mobility (-0.5±1.9), community life (-0.8±1.9), and recreation (-1.5±3.0). More life areas are disrupted over time: 8 domains were below reference values from a population aged 55-64 years at follow-up compared with 2 domains at baseline. Satisfaction with participation remains high and stable over time.

CONCLUSION

As disease duration increases, global participation and more daily and social domains were restricted with increasing difficulty and assistance required. Adults with DM1 showed not only age-associated but disease-specific changes in participation. Description over time of participation could improve clinical assessment and guide interdisciplinary management of DM1, leading to higher rehabilitation success. Further investigation of the factors influencing changes in participation is required to support disease management and services planning.

Relationships between Lower Limb Muscle Strength Impairments and Physical Limitations in DM1

BACKGROUND

Although adult and late-onset DM1 phenotypes DM1 present distinct lower limb weaknesses portraits, resulting physical limitations have never been described separately for each phenotype.

OBJECTIVE

To characterize the lower limb weaknesses and physical limitations among the DM1 adult and late-onset phenotypes separately and to document the contribution of weaknesses on mobility to optimize the management of this population.

METHODS

The strength of four muscle groups among 198 participants was quantified. Participants were categorized according to the severity of their muscular involvement using the Muscular Impairment Rating Scale (MIRS). Physical limitations were assessed using the Timed up-and-go (TUG), Berg Balance Scale (BBS) and 10 meters comfortable walking speed (10MWT). Multiple linear regressions were performed to identify the contribution of each muscle group to the mobility tests scores.

RESULTS

Late-onset demonstrated less weakness and physical limitations (p < 0.001 - 0.002) than the adult phenotype, but 21.9-47.5% of participants with this phenotype showed mobility scores below reference values. Physical limitations were observed in the first two MIRS grades (37.5-42.1% of the participants) for the TUG and 10MWT. Ankle dorsiflexors and knee extensors were the two muscle groups that showed the strongest relationships with mobility scores.

CONCLUSION

Although less impaired, the late-onset phenotype shows significant lower limb muscle weakness associated with physical limitations. The surprising presence of quantitative lower limb muscle weakness in the first two MIRS grades needs to be considered when using this scale. Both ankle dorsiflexors and knee extensors appear to be good indicators of physical limitations in DM1.

A. Social cognition in myotonic dystrophy type 1: Specific or secondary impairment?

AIMS

The cognitive profile of Myotonic Dystrophy type 1 (DM1) has been described in recent decades. Moreover, DM1 patients show lowered social engagement and difficulties in social-cognitive functions. The aim of the present study is to explore whether social cognition impairment is present in DM1 taking into account the overall cognitive condition.

METHOD

38 patients and a control group paired in age and gender participated in the study. All the participants had an IQ within the normal range. Subjects were administered an abbreviated neuropsychological battery which comprised a facial emotion recognition test (POFA) and Faux Pas Test, as well as a self-report questionnaire on cognitive and affective empathy (TECA).

RESULTS

Statistically significant differences were found only for facial emotion recognition (U = 464.0, p = .006) with a moderate effect size (.31), with the controls obtaining a higher score than the patients. Analyzing each emotion separately, DM1 patients scored significantly lower than controls on the recognition of anger and disgust items. Emotion recognition did not correlate with genetic load, but did correlate negatively with age. No differences were found between patients and controls in any of the other variables related to Theory of Mind (ToM) and empathy.

CONCLUSION

DM1 does not manifest specific impairments in ToM since difficulties in this area predominantly rely on the cognitive demand of the tasks employed. However, a more basic process such as emotion recognition appears as a core deficit. The role of this deficit as a marker of aging related decline is discussed.

A 9-year follow-up study of quantitative muscle strength changes in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder presenting with major muscle impairments. However, few studies have addressed muscle strength progression using quantitative methods. The aims of this study were to document muscle strength changes in eight muscle groups among adults with DM1 over a 9-year period, and to compare this progression between phenotypes (adult and late-onset) and sex. Patients with a genetic diagnosis of DM1 with the late-onset or the adult phenotype were recruited at baseline through the clinical registry of the Saguenay Neuromuscular Clinic. The maximum isometric muscle strength was measured at baseline and 9 years later using a standardized protocol of quantitative muscle testing. Muscle groups included were shoulder abductors, elbow flexors/extensors, wrist extensors, hip flexors, knee flexors/extensors, and ankle dorsiflexors. For the whole group, a mean loss of 24.5-52.8% was observed over the 9-year period for all muscle groups, except for hip flexors which remained stable. Generally, men were stronger and showed a significant greater rate of decline of muscle strength than women. The adult and late-onset phenotypes taken separately also showed a significant and similar decline over the 9-year period, except for the wrist and knee extensors where muscle strength of participants with the adult phenotype decreased faster than in the late-onset phenotype. The similar rate of decline of muscle strength loss observed between phenotypes highlights the need to develop interventions to prevent this decline, even for patients with the late-onset phenotype who are often considered as mildly impaired, and therefore neglected by the rehabilitation services.

Effect and impact of mechanical ventilation in myotonic dystrophy type 1: a prospective cohort study

Few studies have assessed the impact of home ventilation in patients with myotonic dystrophy type 1 (DM1) and no specific recommendations are available. We assessed the survival associated with category of home ventilation adherence of patients with DM1 followed up at a home ventilation unit using a Cox proportional hazards model. 218 patients were included; those who refused or delayed their acceptance of non-invasive ventilation were at higher risk for severe events (invasive ventilation or death) (P=0.03). Risk of death was associated with orthopnoea (HR 2.37; 95% CI 1.17 to 4.80; P<0.02) and adherence category (100 to 90% vs >75%: HR 3.26; 95% CI 1.32 to 8.04; P<0.03). Failure to use home ventilation as prescribed may be associated with increased mortality in patients with DM1.

Survey of Canadian Myotonic Dystrophy Patients' Access to Computer Technology

BACKGROUND

Myotonic dystrophy type 1 is an autosomal dominant condition affecting distal hand strength, energy, and cognition. Increasingly, patients and families are seeking information online. An online neuromuscular patient portal under development can help patients access resources and interact with each other regardless of location. It is unknown how individuals living with myotonic dystrophy interact with technology and whether barriers to access exist. We aimed to characterize technology use among participants with myotonic dystrophy and to determine whether there is interest in a patient portal.

METHODS

Surveys were mailed to 156 participants with myotonic dystrophy type 1 registered with the Canadian Neuromuscular Disease Registry.

RESULTS

Seventy-five participants (60% female) responded; almost half were younger than 46 years. Most (84%) used the internet; almost half of the responders (47%) used social media. The complexity and cost of technology were commonly cited reasons not to use technology. The majority of responders (76%) were interested in a myotonic dystrophy patient portal.

CONCLUSIONS

Patients in a Canada-wide registry of myotonic dystrophy have access to and use technology such as computers and mobile phones. These patients expressed interest in a portal that would provide them with an opportunity to network with others with myotonic dystrophy and to access information about the disease.

A 9-year follow-up study of the natural progression of upper limb performance in myotonic dystrophy type 1: A similar decline for phenotypes but not for gender

This study aimed to document and compare the decline of upper limb performance among adults with myotonic dystrophy type 1 according to phenotype and gender. A longitudinal descriptive design compared upper limb performance at baseline and follow-up of 70 women and 38 men with the late-onset or adult phenotypes. Grip strength and pinch strength as well as gross dexterity and fine dexterity were assessed. All four performance measures decreased significantly (p <0.001). The decline over time was similar for individuals with the late-onset and adult-onset phenotypes, but differed according to gender. For late-onset and adult-onset phenotypes respectively, women lost less grip strength than men: 0.4 and minus 0.8 kg (2.0% and -9.4%) in women vs. minus 7.4 and minus 3.1 kg (-19.2% and -30.7%) in men. A similar situation was found for gross dexterity: minus 3.0 and minus 3.2 blocks (-4.6% and -5.9%) in women vs. minus 12.4 and minus 8.7 blocks (-19.4% and -16.6%) in men. Pinch gauge had the smallest standard deviations and was one of the only measurement tools with significant detectable changes in relation to the standard error of measurement. Given these results, health professionals and researchers should consider phenotype and gender differently when planning health services or future studies. Indeed, as their upper limb strength and dexterity differed, even if their decline was similar, the phenotypes should not be pooled. Finally, the use of the pinch gauge to assess long-term change in upper limb ability seems preferable to the three other measurements.

Cognitive decline over time in adults with myotonic dystrophy type 1: A 9-year longitudinal study

Myotonic dystrophy type 1 (DM1) is an inherited neuromuscular disease with multisystemic involvement including the central nervous system. The evolution of the cognitive profile is a matter of debate, whether an eventual decline could be global or process-specific. Study aims are to describe, compare and document the clinical relevance of the progression of cognitive abilities in DM1 patients with adult and late-onset phenotypes. A total of 115 DM1 patients (90 adult; 25 late-onset) were assessed twice within a 9-year period on cognitive abilities (language, memory, visual attention, processing speed, visuoconstructive abilities and executive functions) and intellectual functioning (WAIS-R 7). A significant worsening over time was observed for verbal memory, visual attention, and processing speed. The progression in cognitive scores correlated with age and disease duration, but not with nCTG, muscular impairment nor education at baseline. Intellectual functioning remained stable. The rate of decline was higher among the late-onset phenotype than in the adult phenotype. Results showed that executive functions, language, and visual memory are impaired earlier in adult life, while verbal memory, visual attention, and processing speed decline later. Globally, results suggest an early and accelerated normal ageing process. This longitudinal study was based on the largest sample and the longest time period studied to date. These findings are highly relevant for clinical practice and genetic counselling.

The prevalence of neuromuscular disease in the paediatric population in Yorkshire, UK; variation by ethnicity and deprivation status

AIM

Previous studies suggest a higher prevalence of neurological disease within certain ethnic communities, but have not specifically considered neuromuscular diseases (NMDs). The aim of this study was to calculate the prevalence and relationship of NMDs to ethnicity and deprivation status.

METHOD

We undertook a retrospective case-note review of those younger than 16 years with a confirmed diagnosis of NMD in a single centre in Yorkshire in 2010.

RESULTS

Two-hundred and sixty-one cases were included. The population (0-16y) in Yorkshire was 707 961. The overall prevalence was 36.9 per 100 000 (95% confidence interval [CI] 34.6-39.1). Dystrophin-related muscle disease was the most common condition, with a prevalence of 16.9 per 100 000 males (95% CI 14.7-19.1). There was a significant difference between ethnic groups, with a total NMD prevalence of 91.2 per 100 000 (95% CI 81.6-100.7) in the South Asian ethnic group compared with 28.7 per 100 000 (95% CI 26.4-30.9) in the White group. Prevalence of non-dystrophin-related NMDs was four times higher in South Asian than in White children. There was a linear relation between increased prevalence and increased deprivation.

INTERPRETATION

This study confirms higher levels of NMD, particularly recessively inherited NMDs within the South Asian population, as well as a link with higher deprivation. This has implications for service provision and resource allocation.

Stanford Chronic Disease Self-Management Program in myotonic dystrophy: New opportunities for occupational therapists

Background.

Chronic disease self-management is a priority in health care. Personal and environmental barriers for populations with neuromuscular disorders might diminish the efficacy of self-management programs, although they have been shown to be an effective intervention in many populations. Owing to their occupational expertise, occupational therapists might optimize self-management program interventions.

Purpose.

This study aimed to adapt the Stanford Chronic Disease Self-Management Program (CDSMP) for people with myotonic dystrophy type 1 (DM1) and assess its acceptability and feasibility in this population.

Method.

Using an adapted version of the Stanford CDSMP, a descriptive pilot study was conducted with 10 participants (five adults with DM1 and their caregivers). A semi-structured interview and questionnaires were used.

Findings.

The Stanford CDSMP is acceptable and feasible for individuals with DM1. However, improvements are required, such as the involvement of occupational therapists to help foster concrete utilization of self-management strategies into day-to-day tasks using their expertise in enabling occupation.

Implications.

Although adaptations are needed, the Stanford CDSMP remains a relevant intervention with populations requiring the application of self-management strategies.

Truths and misinformation: a qualitative exploration of myotonic dystrophy

BACKGROUND

Myotonic dystrophy (DM1) is an autosomal dominant, progressive, and multisystem condition that impacts affected individuals physically, socially, and emotionally. Understanding individuals' perceptions of their disease is critical to ensuring appropriate information, education, and counseling.

METHODS

We conducted a content analysis of findings from a larger study that used a novel, qualitative research approach called photovoice to explore nine patients' experiences of living with DM1. Participants took pictures that illustrated barriers or facilitators to living with DM1; their photographs then formed the basis of semistructured interviews. Transcripts were analyzed and, among themes, we identified one titled "DM1 truths and misinformation" that described participants' disease knowledge. Analysis revealed four categories within this broader theme: "the physical and emotional cost of DM1," "managing my DM1," "genetics and me" and "patients as advocates and educators."

RESULTS

Findings showed that DM1 participants had good core knowledge with respect to their disease and its implications. However, each participant held as fact fragments of misinformation that shaped decision-making and pointed to a clear need for strategies to mitigate variable interpretation of health information.

CONCLUSIONS

We conclude that there is a need for increased education and awareness about symptoms, genetic information and treatment strategies for patients, their family members, and health care providers.

Comparisons of intellectual capacities between mild and classic adult-onset phenotypes of myotonic dystrophy type 1 (DM1)

Background

Myotonic dystrophy type 1 (DM1) is an autosomal dominant genetic multisystem disorder and the commonest adult-onset form of muscular dystrophy. DM1 results from the expansion of an unstable trinucleotide cytosine-thymine-guanine (CTG) repeat mutation. CTG repeats in DM1 patients can range from 50 to several thousands, with a tendency toward increased repeats with successive generations (anticipation). Associated findings can include involvements in almost every systems, including the brain, and cognitive abnormalities occur in the large majority of patients. The objectives are to describe and compare the intellectual abilities of a large sample of DM1 patients with mild and classic adult-onset phenotypes, to estimate the validity of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) in DM1 patients with muscular weakness, and to appraise the relationship of intelligence quotient (IQ) to CTG repeat length, age at onset of symptoms, and disease duration.

Methods

A seven-subtest WAIS-R was administered to 37 mild and 151 classic adult-onset DM1 patients to measure their Full-Scale (FSIQ), Verbal (VIQ) and Performance IQ (PIQ). To control for potential bias due to muscular weakness, Standard Progressive Matrices (SPM), a motor-independent test of intelligence, were also completed.

Results

Total mean FSIQ was 82.6 corresponding to low average IQ, and 82% were below an average intelligence. Mild DM1 patients had a higher mean FSIQ (U=88.7 vs 81.1, p<0.001), VIQ (U=87.8 vs 82.3, p=0.001), and PIQ (U=94.8 vs 83.6, p<0.001) than classic adult-onset DM1 patients. In both mild and classic adult-onset patients, all subtests mean scaled scores were below the normative sample mean. FSIQ also strongly correlate with SPM (r_s=0.67, p<0.001), indicating that low intelligence scores are not a consequence of motor impairment. FSIQ scores decreased with both the increase of (CTG)n (r_s=−0.41, p<0.001) and disease duration (r_s=−0.26, p=0.003).

Conclusions

Results show that intellectual impairment is an extremely common and important feature in DM1, not only among the classic adult-onset patients but also among the least severe forms of DM1, with low IQ scores compared to general reference population. Health care providers involved in the follow-up of these patients should be aware of their intellectual capacities and should adapt their interventions accordingly.

Natural history of skeletal muscle involvement in myotonic dystrophy type 1: a retrospective study in 204 cases

Myotonic dystrophy type 1 (DM1) is the most frequent muscular dystrophy in adult. The aim of this study was to investigate the natural history of skeletal muscle weakness in adults, in a cross-sectional, retrospective study. In a cohort of 204 adult DM1 patients, we quantified muscle impairment, handgrip force and physical disability. Muscle strength was similarly affected in the legs and in the arms, the right and left side, and distally more than proximally in patients. The earliest and the most affected skeletal muscles were the digit flexors, foot dorsiflexors and neck flexors; whereas the elbow and knee extensors and flexors were the least affected muscle groups. The rate of decline of the muscle strength was -0.111 units/year. The handgrip values were lower in DM1 patients than the normative values and the rate of decline in handgrip force per year was -0.24 kg. Limitation in mobility or walking is observed in 84 % of DM1 patients but requirement of wheelchair is infrequent (3 %). The decrease in muscle strength, handgrip force and the increase in physical disability were highly correlated with duration of the disease and the number of CTG repeats in the blood. Significant association was found between decline in muscle strength and the age at onset, physical disability and the age of patients at evaluation, handgrip force and gender. Decline in muscle weakness is very slow and although limitation when walking is a common manifestation of DM1 in patients, the requirement of wheelchair is infrequent.

Facial memory deficits in myotonic dystrophy type 1

OBJECTIVES

To evaluate facial memory ability (FMA) in patients with myotonic dystrophy type 1 (DM1). We also explored the relationship between FMA and neuropsychological data, disease-related factors, and CTG repeat expansion size.

MATERIALS AND METHODS

Patients with DM1 (n = 33) and healthy subjects (n = 30) were tested with the faces task of the Rivermead Behavioural Memory Test - Extended version (RBMT-E) and an additional set of neuropsychological tests. Clinical data were collected, and CTG repeat size was quantified in blood lymphocytes.

RESULTS

Low results on the faces task were more common in patients with DM1 compared with healthy subjects (P < 0.05), with 36% of the patients showing a poor/impaired performance. DM1 patients with deficits in FMA performed significantly worse on tests measuring visual-construction ability and memory. Furthermore, these patients more often falsely recognised unknown faces as known. Deficits in FMA were not associated with any disease-related factor, including CTG repeat expansion size.

CONCLUSIONS

These findings revealed deficits in FMA in the DM1 group, which was associated with reduced construction- and visual memory ability.

Prevalence of Lifestyle Risk Factors in Myotonic Dystrophy Type 1

Background:

The prevalence of unhealthy lifestyle habits such as smoking has seldom been described in neuromuscular disorders, including myotonic dystrophy type 1 (DM1). However, it is essential to document the unhealthy lifestyle habits as they can exacerbate existing impairments and disabilities. The objectives are: 1) To determine the prevalence of risk factors among individuals with DM1; 2) To compare the prevalence among classic and mild phenotypes.

Method:

A survey was done on a sample of two-hundred (200) patients with DM1 as part of a larger study. Lifestyle risk factors included being overweight or obese, tobacco smoking, illicit drug use, excessive alcohol consumption and physical inactivity. A registered nurse administered the validated public health survey. Categorization of risk factors were based on national standards and compared with provincial and regional prevalences.

Results:

50% of DM1 patients were overweight or obese, 23.6% were regular smokers, and 76% were physically inactive. Except for overweight and obesity, significant differences were observed between patients with classic and mild phenotypes for all the other lifestyle risk factors: those with the classic phenotype being more often regular smokers, consuming more often illicit drugs and being less physically active.

Conclusions:

The results of this study will provide guidance for the development of better adapted and focussed health promotion interventions in the future.

Clinical, psychosocial, and central correlates of quality of life in myotonic dystrophy type 1 patients

AIMS

To identify sociodemographic, clinical, and central correlates of health-related quality of life (HRQoL) in DM1 patients.

METHODS

200 DM1 patients had assessments of muscular impairment, CTG repeats, and intelligence. Validated instruments were used to assess sociodemographic and clinical factors as well as social support, social participation, daytime sleepiness, fatigue, personality, mood, and quality of life. Regression analysis was used to identify correlates of SF-36 physical and mental component summary scores.

RESULTS

Patients scored lower on all SF-36 physical health subscales compared with normative data but did not differ with respect to mental health function. Regression analysis revealed that psychological distress, fatigue, severe muscular impairment, emotional stability, not having worked within the last 12 months, and lower intellectual quotient were associated with lower scores in physical health function. Moreover, neuroticism, daytime sleepiness, dissatisfaction with social participation, and lower conscientiousness were associated with lower scores in mental health function.

CONCLUSION

DM1 has an impact on SF-36 physical summary scores but not on mental summary scores. Factors such as fatigue, daytime sleepiness, psychological distress, unemployment, and social participation dissatisfaction that significantly affect HRQoL in DM1 are amenable to treatment and psychosocial interventions, namely by providing care that integrate health, social, and community services.

Synaptic protein dysregulation in myotonic dystrophy type 1: Disease neuropathogenesis beyond missplicing

The toxicity of expanded transcripts in myotonic dystrophy type 1 (DM1) is mainly mediated by the disruption of alternative splicing. However, the detailed disease mechanisms in the central nervous system (CNS) have not been fully elucidated. In our recent study, we demonstrated that the accumulation of mutant transcripts in the CNS of a mouse model of DM1 disturbs splicing in a region-specific manner. We now discuss that the spatial- and temporal-regulated expression of splicing factors may contribute to the region-specific spliceopathy in DM1 brains. In the search for disease mechanisms operating in the CNS, we found that the expression of expanded CUG-containing RNA affects the expression and phosphorylation of synaptic vesicle proteins, possibly contributing to DM1 neurological phenotypes. Although mediated by splicing regulators with a described role in DM1, the misregulation of synaptic proteins was not associated with missplicing of their coding transcripts, supporting the view that DM1 mechanisms in the CNS have also far-reaching implications beyond the disruption of a splicing program.

Patient-reported impact of symptoms in myotonic dystrophy type 1 (PRISM-1)

OBJECTIVE

To determine the most critical symptoms in a national myotonic dystrophy type 1 (DM1) population and to identify the modifying factors that have the greatest effect on the severity of these symptoms.

METHODS

We performed a cross-sectional study of 278 adult patients with DM1 from the national registry of patients with DM1 between April and August 2010. We assessed the prevalence and relative significance of 221 critical DM1 symptoms and 14 disease themes. These symptoms and themes were chosen for evaluation based on prior interviews with patients with DM1. Responses were categorized by age, CTG repeat length, gender, and duration of symptoms.

RESULTS

Participants with DM1 provided symptom rating survey responses to address the relative frequency and importance of each DM1 symptom. The symptomatic themes with the highest prevalence in DM1 were problems with hands or arms (93.5%), fatigue (90.8%), myotonia (90.3%), and impaired sleep or daytime sleepiness (87.9%). Participants identified fatigue and limitations in mobility as the symptomatic themes that have the greatest effect on their lives. We found an association between age and the average prevalence of all themes (p < 0.01) and between CTG repeat length and the average effect of all symptomatic themes on participant lives (p < 0.01).

CONCLUSIONS

There are a wide range of symptoms that significantly affect the lives of patients with DM1. These symptoms, some previously underrecognized, have varying levels of importance in the DM1 population and are nonlinearly dependent on patient age and CTG repeat length.

Myotonic dystrophy type 1, daytime sleepiness and REM sleep dysregulation

Myotonic dystrophy type 1 (DM1), or Steinert's disease, is the most common adult-onset form of muscular dystrophy. DM1 also constitutes the neuromuscular condition with the most significant sleep disorders including excessive daytime sleepiness (EDS), central and obstructive sleep apneas, restless legs syndrome (RLS), periodic leg movements in wake (PLMW) and periodic leg movements in sleep (PLMS) as well as nocturnal and diurnal rapid eye movement (REM) sleep dysregulation. EDS is the most frequent non-muscular complaint in DM1, being present in about 70-80% of patients. Different phenotypes of sleep-related problems may mimic several sleep disorders, including idiopathic hypersomnia, narcolepsy without cataplexy, sleep apnea syndrome, and periodic leg movement disorder. Subjective and objective daytime sleepiness may be associated with the degree of muscular impairment. However, available evidence suggests that DM1-related EDS is primarily caused by a central dysfunction of sleep regulation rather than by sleep fragmentation, sleep-related respiratory events or periodic leg movements. EDS also tends to persist despite successful treatment of sleep-disordered breathing in DM1 patients. As EDS clearly impacts on physical and social functioning of DM1 patients, studies are needed to identify the best appropriate tools to identify hypersomnia, and clarify the indications for polysomnography (PSG) and multiple sleep latency test (MSLT) in DM1. In addition, further structured trials of assisted nocturnal ventilation and randomized trials of central nervous system (CNS) stimulant drugs in large samples of DM1 patients are required to optimally treat patients affected by this progressive, incurable condition.

Myotonic dystrophy types 1 and 2

Myotonic dystrophies (dystrophia myotonica, or DM) are inherited disorders characterized by myotonia and progressive muscle degeneration, which are variably associated with a multisystemic phenotype. To date, two types of myotonic dystrophy, type 1 (DM1) and type 2 (DM2), are known to exist; both are autosomal dominant disorders caused by expansion of an untranslated short tandem repeat DNA sequence (CTG)(n) and (CCTG)(n), respectively. These expanded repeats in DM1 and DM2 show different patterns of repeat-size instability. Phenotypes of DM1 and DM2 are similar but there are some important differences, most conspicuously in the severity of the disease (including the presence or absence of the congenital form), muscles primarily affected (distal versus proximal), involved muscle fiber types (type 1 versus type 2 fibers), and some associated multisystemic phenotypes. The pathogenic mechanism of DM1 and DM2 is thought to be mediated by the mutant RNA transcripts containing expanded CUG and CCUG repeats. Strong evidence supports the hypothesis that sequestration of muscle-blind like (MBNL) proteins by these expanded repeats leads to misregulated splicing of many gene transcripts in corroboration with the raised level of CUG-binding protein 1. However, additional mechanisms, such as changes in the chromatin structure involving CTCN-binding site and gene expression dysregulations, are emerging. Although treatment of DM1 and DM2 is currently limited to supportive therapies, new therapeutic approaches based on pathogenic mechanisms may become feasible in the near future.

Cognitive/personality pattern and triplet expansion size in adult myotonic dystrophy type 1 (DM1): CTG repeats, cognition and personality in DM1

BACKGROUND

Although central nervous system (CNS) involvement in adult myotonic dystrophy type 1 (DM1) was described long ago, the large number of variables affecting the cognitive and personality profile have made it difficult to determine the effect of DM1 on the brain. The aim of this study was to define the cognitive and personality patterns in adult DM1 patients, and to analyse the relationship between these clinical patterns and their association with the underlying molecular defect.

METHOD

We examined 121 adult DM1 patients with confirmed molecular CTG repeat expansion and 54 control subjects using comprehensive neuropsychological tests and personality assessments with the Millon Clinical Multiaxial Inventory (MCMI)-II. We used a multiple linear regression model to assess the effect of each variable on cognition and personality adjusted to the remainders.

RESULTS

Patients performed significantly worse than controls in tests measuring executive function (principally cognitive inflexibility) and visuoconstructive ability. In the personality profile, some paranoid and aggressive traits were predominant. Furthermore, there was a significant negative correlation between the CTG expansion size and many of the neuropsychological and personality measures. The molecular defect also correlated with patients' daytime somnolence.

CONCLUSIONS

Besides muscular symptomatology, there is significant CTG-dependent involvement of the CNS in adult DM1 patients. Our data indicate that the cognitive impairment predominantly affects the fronto-parietal lobe.

Fatigue and daytime sleepiness in patients with myotonic dystrophy type 1: to lump or split?

We assessed the relationship and clinical correlates of fatigue and Excessive Daytime Sleepiness (EDS) in 200 myotonic dystrophy type 1 (DM1) patients by means of questionnaire and neuropsychological evaluation. Fatigue levels were higher in patients with EDS and daytime sleepiness levels higher in patients with excessive fatigue. However, EDS without fatigue was rarely observed. Also, DM1 patients with fatigue (with or without EDS) showed greater muscular impairment, CTG repeats, abnormalities regarding personality, depressive symptoms and lower health-related quality of life (HRQoL) than patients without these symptoms. These findings do not readily support the contention that fatigue and EDS constitute distinct clinical manifestations in DM1. Clinicians should systematically evaluate both symptoms since fatigue and EDS have a greater impact on HRQoL than fatigue alone. However, specific rating scales for fatigue in DM1 have yet to be devised.

Usefulness of clinical and electrocardiographic data for predicting adverse cardiac events in patients with myotonic dystrophy

BACKGROUND

Myotonic dystrophy type 1 (DM1) has been associated with an increased risk of sudden death, either by heart block or malignant ventricular arrhythmias. Identifying patients at risk remains difficult and no consensus has been reached regarding the best approach for follow-up and prevention of sudden death.

OBJECTIVES

To identify noninvasive clinical and electrocardiographic predictors of adverse cardiac events in patients with DM1.

METHODS

Clinical and serial electrocardiographic data on 428 patients with a DNA-proven diagnosis of DM1, followed during a mean period of 11.7 years, were reviewed. Variables associated with adverse cardiac events were identified.

RESULTS

Eleven patients (2.6%) experienced sudden death and 13 (3.0%) required implantation of a pacemaker. On univariate analysis, adverse events were associated with advancing age, prolongation of the PR, QRS and corrected QT (QTc) intervals, as well as the degree of neuromuscular impairment. No such relationship was found with the extent of genetic anomaly (number of cytosine-thymine-guanine repeats). However, multivariate analysis using Cox proportional hazards models showed that only baseline PR and QTc intervals were significantly linked to the end points of sudden death or pacemaker implantation; the age-adjusted RR was 3.7 (95% CI 1.5 to 8.6) if baseline PR was 200 ms or longer (P=0.003), and 3.0 (95% CI 1.0 to 8.8) if the baseline QTc was 450 ms or longer (P=0.047).

CONCLUSIONS

In a large unselected cohort of 428 patients with DM1, the cumulative incidence of sudden death was relatively low, and the delayed conduction on surface electrocardiogram was found to be potentially helpful for identifying patients at risk for sudden death or pacemaker implantation.

Predictors of disrupted social participation in myotonic dystrophy type 1

OBJECTIVE

To identify personal and environmental predictors of the most disrupted participation domains in people with myotonic dystrophy type 1 (DM1).

DESIGN

Cross-sectional study.

SETTING

Outpatient neuromuscular clinic.

PARTICIPANTS

Adults (n=200; 121 women), age 18 years or older (mean age, 47 y), with a confirmed diagnosis of DM1 were selected from the registry of a neuromuscular clinic (N=416). Fifty-two participants had the mild phenotype and 148 the adult phenotype.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Social participation in mobility, housing, employment, and recreation was assessed with the Life Habits Measure. Disrupted participation was based on whether help was needed in performing most life habits because of incapacities or environmental barriers. Environmental factors were assessed by using the Measure of the Quality of the Environment. Personal factors were assessed with standardized instruments including the Berg Balance Scale, the Krupp Fatigue Severity Scale, and manual muscle testing.

RESULTS

A large proportion of participants (45%-61%) reported disrupted participation in all 4 domains. Lower-extremity strength (odd ratios [OR], 15.0-5.5; P<.050) and higher fatigue (OR, 6.0-2.6; P<.05) were present in participants with disrupted participation. With regard to environmental factors, family support (OR, 3.6-2.5; P<.05) and public services (OR, 2.8-2.2; P<.05) were perceived as barriers for participants with disrupted participation in most domains.

CONCLUSIONS

This study identified personal and environmental factors that may influence the trajectory toward disrupted participation in individuals with DM1. Fatigue, strength, family support, and public services were found to be independent predictors of disrupted participation.

Preimplantation genetic diagnosis for myotonic dystrophy type 1 in the UK

Myotonic dystrophy type 1 (DM1) is a dominant multisystemic disorder caused by expansion of a trinucleotide repeat in a non-coding region of DMPK. Prenatal diagnosis (PND) is available; however, the decision to terminate affected pregnancies is difficult as the extent of disability is hard to predict from the size of the expansion. In preimplantation genetic diagnosis (PGD) genetic analysis is carried out before the establishment of pregnancy. This paper reviews the largest number of cycles of PGD for DM1 in the UK indicating that PGD is a practical option for affected couples.