Non dystrophic myotonia

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.

In this clinical study, the aim is to investigate whether there is a difference in treatment of myotonia using two drugs. A difference there can justify the significantly higher cost when treated by Namuscla versus Lamotrigine.
According to the current corona pandemic, the investigators designed an app to use for data collection in the study. The app also ensures that patients who live far from the clinic more easily can participate.

This is a clinical trial to determine if Lamotrigine is non-inferior to Mexiletine for the treatment of myotonia in patients with Non-Dystrophic Myotonia.
Non-dystrophic Myotonia is a genetic condition for which there is no cure. It affects patients for the duration of their life and impacts work, leisure and can lead to significant morbidity.
The study is a cross-over design - participants will be randomized to either lamotrigine or mexiletine first for 8 weeks and then swap over after a week wash-out to the other medication for a further 8 weeks. Participants and investigators will be blinded to the treatment schedule. 60 participants will recruited through the clinical service, national registry and national liaison.