Non-dystrophic myotonias (MND) are rare neuromuscular diseases caused by mutations in the voltage-dependent channels of skeletal muscles, resulting in delayed muscle relaxation after voluntary contraction. They include various conditions such as congenital myotonia, congenital paramyotonia and sodium channel myotonia. The main characteristic is myotonia, muscle stiffness accompanied by pain, fatigue and weakness. Symptoms vary in intensity, and fluctuation complicates clinical assessment.

Until now, no validated scale to assess the severity of myotonia is the subject of a consensus among neurologists. It therefore seems necessary to establish a scale to simply and quickly assess the severity of myotonia to fill this need.

The areas of this future scale were identified by the study coordinator based on existing questionnaires and scales. These areas have been validated by a scientific committee composed of expert neurologists.

The main objective of the study is to validate the adequacy and formulation of the scale questions by involving 10 patients who will complete the questionnaire twice to assess its fidelity. At the end of the study, the committee will exclude inappropriate questions. The goal is to create a reliable scale to assess the severity of myotonia.

Inclusion criteria:

• Male or female, over 18 years of age;
• With genetically diagnosed non-dystrophic myotonia;
• Affiliated with a Social Security system;
• Able to read, understand and speak French
• Having expressed his non-opposition

Exclusion criteria:

• Subject participating in an interventional study with experimental drug or in the exclusion period of an interventional study;
• Pregnant or lactating women for women of childbearing age;
• Patient protected by law under guardianship or curators, or who cannot participate in a clinical study under Article L. 1121-16 of the French Public Health Code