[Respiratory failure: respiratory disorder during sleep in patients with myotonic dystrophy]

Myotonic dystrophy (MyD) patients have been reported to show severe nocturnal desaturation related to sleep respiratory disorders. However, the reason of respiratory failure in MyD has remained unclear. In this study, ten patients with MyD underwent overnight polysomnography to evaluate the mechanisms which would cause respiratory failure, compared with Duchenne muscular dystrophy (DMD) patients in these three views: 1) sleep-related nocturnal desaturation, 2) histopathological evaluation of respiratory muscles, and 3) abnormalities of respiratory center. Nocturnal desaturation was more prominent in MyD rather than DMD. Apnea-hypopnea index (AHI) was higher in MyD than DMD. Type of respiratory disorder during sleep was mainly central apnea-hypopnea pattern, including Cheyne-Stokes respiration. In histopathological findings, central core change in respiratory muscle related to respiratory muscle fatigue was found less frequently in MyD than DMD. In respiratory center function, MyD showed hyporesponse to both alveolar hypercapnic and hypoxic stimulation. However, DMD showed normal response to both stimulations. We concluded that respiratory failure in patients with MyD would be attributed to respiratory center disorder rather than respiratory muscle weakness, which is the main cause of respiratory failure in patients with DMD.