Contractile Properties of Hypertrofic Muscles in Patients With Non-Dystrophic Myotonia

Study Overview
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Brief Summary
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In myotonia congenita (MC), mutations in the CLCN1 gene coding a key chloride channel expressed in muscle cells cause myotonia. On examination, the myotonia can be demonstrated as delayed muscle relaxation of muscle contractions after mechanical stimulations. Existing literature describe no muscle weakness in MC patients, however a recent muscle MRI study in non-dystrophic myotonia patients found structural abnormalities in affected muscles when examined using T1 and STIR imaging. The question remains whether the signs of structural changes in the muscle are merely due to the myotonia, or long-term effects of elevated stress of the tissue, and if so, whether those changes lead to clinically significant loss of contractile properties of the muscle. This study examines if the contractile properties of myotonic muscles are impaired in MC patients. 40 patients with Thomsens disease (n=20) and Beckers disease (n=20), respectively, will be included along with 20 healthy controls. Peak muscle torque is measured in the hand by hand dynamometer and in the thigh and calf muscles with a Biodex System 4 Pro Dynamometer and the cross-sectional area of the muscles are examined on T1-weighed and Dixon-MRI-scan. With the obtained data peak torque in strength tests, muscle hypertrophy, fat fraction in muscle tissue and contractility of the muscles, compared with healthy controls, will be assessed.

Official Title
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Contractile Properties of Hypertrofic Muscles in Patients With Non-Dystrophic Myotonia

Conditions
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Non-Dystrophic Myotonia, Myotonia Congenita

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age <18 years Molecularly verified MC (Thomsens or Beckers disease) Exclusion Criteria: Conditions that may impair results of the study, evaluated by the investigator Clausphobia Pregnancy or breastfeeding Metallic objects in and around the body that are not MR-compatible

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| MC<br>MC patients with either dominant (Thomsens) or recessive (Becker) myotonia. | |
| Healthy Controls<br>Healthy controls age- and gender matched. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Contractile properties | To investigate if contractile properties of the muscles are impaired in MC patients compared with healthy controls. | 1 year | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Measuring muscle hypertrophy in upper and lower limbs | Visualizing and measuring hypertrophy on MRI of affected muscles in the forearm, thigh and calf of MC patients compared with muscles in healthy controls. | 1 year |