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Primary objective: To determine the sensitivity to change of neuromuscular functional outcomes during the natural (non-interventional) progression of myotonic dystrophy type 1 (DM1), in order to identify the most relevant and robust outcome measures for use in therapeutic trials.
Secondary objective: To compare patients with DM1 to healthy control subjects to assess the discriminative power of biomechanical and electrophysiological parameters.
Study design: This is an open-label, single-center observational study with no direct individual benefit.
Participants: Thirty patients with DM1 will be evaluated three times over a three-year period, while thirty control subjects will be assessed once.
Timeline: The planned inclusion period is 12 months, with a follow-up duration of 36 months, resulting in a total study duration of 48 months.
Functional assessment-particularly muscle strength-is essential for both diagnosis and longitudinal monitoring of neuromuscular diseases. In therapeutic trials, outcome measures must meet strict scientific requirements, including precision, sensitivity, and reliability. Muscle strength is frequently used as a primary or secondary endpoint in trials targeting neuromuscular disorders. Even modest functional improvements resulting from therapy must be detectable with sensitive measurement tools.
Myotonic dystrophy is the most common muscular dystrophy in adults, with an estimated prevalence of 1 in 8,000. It is a genetic disorder inherited in an autosomal dominant manner. Two genetically distinct forms are recognized: myotonic dystrophy type 1 (DM1, or Steinert disease) and the rarer, more recently identified type 2 (DM2). This study focuses on DM1 due to its higher prevalence and greater clinical severity.
The study will assess parameters related to myotonia, muscle strength, motor function, and neuromuscular excitability. Patients will be evaluated every 18 months over a three-year period. Control subjects will undergo a single assessment. The expected outcome is the identification of the most robust and sensitive parameters for longitudinal monitoring of DM1 patients, particularly in the context of future therapeutic trials.
A similar study will be conducted in parallel in Quebec (Principal Investigator: Prof. Jack Pumirat, CHU de Québec). Data common to both centers will be analyzed jointly.
Full description
Background and Rationale Assessment of functional capacities-particularly muscle strength-is essential for both diagnosis and follow-up of patients with neuromuscular diseases. In therapeutic trials, measurement tools must meet strict scientific requirements: accuracy, sensitivity, and reliability. Muscle strength is frequently used as a primary or secondary outcome in clinical trials. Even small functional improvements must be detectable to demonstrate therapeutic benefit.
Myotonic dystrophy is the most common adult muscular dystrophy (prevalence ~1/8,000). It is an autosomal dominant genetic disorder with two distinct forms: type 1 (DM1, Steinert disease) and type 2 (DM2), the latter being rarer. This study focuses on DM1 because of its higher prevalence and more severe clinical manifestations.
More than a century after its first description, DM1 remains highly complex. It shows extreme clinical variability in:
Marked intrafamilial variability is also observed.
Muscular manifestations include:
Despite advances in molecular understanding and preclinical therapies, validated, sensitive, and reproducible tools for longitudinal clinical assessment-especially muscle function-remain limited. Knowledge of the natural history of DM1 is incomplete, and few studies have used highly sensitive functional outcome measures.
Current Assessment Methods and Limitations
Muscle function is commonly evaluated using:
New Measurement Devices and Study Purpose Highly sensitive ergometers (e.g., MyoGrip, Myo-Ankle) have been developed to assess very weak patients. These devices have been technically validated, with established normative data and standardized procedures.
This study aims to validate these tools in adult DM1 patients and to improve understanding of disease progression. It is part of an international research program supporting gene therapy development and validation of reliable, non-invasive clinical outcome measures.
Study Design
Type: Monocentric, open-label, non-interventional study
Duration: 3 years of follow-up (total study duration: 48 months)
Participants:
Assessment points:
A parallel protocol is conducted in Québec (Canada). Study Objectives Primary Objective To determine the sensitivity to change of neuromuscular functional outcomes during the natural progression of DM1, in order to select the most relevant endpoints for therapeutic trials.
Secondary Objective To compare DM1 patients with healthy controls to assess the discriminative power of biomechanical and electrophysiological measures.
Outcome Measures
The study includes a comprehensive battery of assessments:
Myotonia Quantification
Ankle Strength Measurement
Strength of Selected Muscle Groups
o Eight representative muscle groups measured with a handheld dynamometer (IMADA).
Exercise-Induced Fatigability
Moviplate Test
o Measures rapid alternating wrist and finger movements over 30 seconds.
6-Minute Walk Test
Upper Limb Functional Tests
Balance Assessment
o Postural control measured on a force platform under four sensory conditions.
Additional Data Collected
Data will be anonymized and analyzed using SPSS and Statview. Analyses include:
Although no direct benefit is expected for participants, this study aims to:
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For patients:
For healthy subjects:
Exclusion criteria
50 participants in 2 patient groups
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Data sourced from clinicaltrials.gov
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