Chloride channel dysfunction study in myotonic dystrophy type 1 using repeated short exercise tests

This exploratory study aimed to evaluate the electrophysiological profiles of patients with myotonic dystrophy type 1 (DM1) and to assess their correlations with genotype and phenotype.

Twenty-two patients with genetically confirmed DM1 were included. Global motor testing score, severity of myotonia, occurrence of cardiac disturbances, and CTG repeat number were recorded. All patients underwent repeated short exercise tests after 7 min of cooling.

Two trajectories could be distinguished following 3 periods of exercise, although most clearly following the third exercise period. Cardiac disturbances were more common among patients who had a B-type trajectory (larger decrement in compound muscle potential amplitude and slower recovery) following the third exercise period.

While the electrophysiological pattern in each profile appeared to confirm chloride muscle channel impairment, the B-type trajectory may suggest dysfunction of other muscle channels in DM1 and their link with cardiac disturbances. Muscle Nerve 54: 104-109, 2016.