Movement-related cortical potentials in myotonic dystrophy

Objective: To investigate a possible deficit of the voluntary movement mechanism within the central nervous system (CNS) in patients with myotonic dystrophy (MyD). Methods: Movement-related cortical potentials preceding voluntary extension of the right middle and index fingers were studied in 9 patients with MyD and compared with those in 11 age-matched healthy subjects and 9 age-matched patients with other neuromuscular disorders (NMDs). Results: The amplitudes of Bereitschaftspotential was smaller in MyD patients than in age-matched controls and age-matched patients with other NMDs although there was no statistically significant difference. The amplitude of negative slope was significantly smaller in MyD patients than in age-matched controls and age-matched patients with other NMDs. Clinical findings such as age, disease duration, degree of motor impairment and cognitive function had no effect on the individual electrophysiological parameters. Conclusions: The present results suggest that subclinical abnormalities exist in CNS function associated with motor preparation and execution, which is independent of muscle weakness.