Does abnormal neuronal excitability exist in myotonic dystrophy? II. Effects of the antiarrhythmic drug hydroquinidine on apathy and hypersomnia

An abnormal neuronal excitability in myotonic dystrophy (MD) might contribu te to psychomotor and behavioral disturbances of MD patients. To gain new i nsights into the pathophysiology of MD, we determined whether the antiarrhy thmic drug hydroquinidine could ameliorate apathy and hypersomnia besides s low saccadic eye movements in these patients. The study was conducted in a randomized, placebo-controlled, double-blind, crossover manner. Ten ambulat ory patients without contraindications to hydroquinidine administration wer e enrolled. Hydroquinidine (450 mg/day) or placebo was given orally for 6 w eeks with a washout period of 6 weeks between treatments. Apathy was evalua ted by means of the apathy evaluation scale (AES) and hypersomnia by a slee p diary. Two patients withdrew in the first week of active treatment becaus e of nausea and epigastralgia. The drug significantly reduced AES scores an d daily sleep time compared to placebo. Thus, hydroquinidine can ameliorate apathy and hypersomnia in MD. However, the possibility of proarrhythmia an d the high frequency of cardiac disturbances in MD seriously limit the ther apeutic perspective. The effects on eye movements are presented in a compan ion paper.