Sleep apnoea of central origin in a case of myotonic dystrophy.

We report the case of a 46-year-old male with myotonic dystrophy who developed daytime hypersomnia and dyspnoea. After a therapeutic tracheostomy, overnight polysomnographic studies were performed under three different ventilatory conditions. When the patient breathed spontaneously through a tracheal cannula, abnormal cyclical sleep increased and rapid eye movement (REM) sleep decreased markedly. The apnoea and hypopnoea index (AH index) was 35.1. When breathing spontaneously through his normal airway, there were many instances of cyclical sleep, but few instances of deep sleep and no episodes of REM sleep. The AH index was 58. Under assisted ventilation the patient's sleep pattern was normal. Our conclusion, therefore, is that these studies demonstrate the patient had sleep apnoea of central origin.