Relationship between hypersomnia and respiratory disorder during sleep in Prader-Willi syndrome

To assess whether hypersomnia in Prader-Willi syndrome (PWS) patients is re lated to the respiratory disorder during sleep (RDDS), we made a systematic evaluation regarding the relationship between the two disorders in three p atients. All patients showed hypersomnia manifested as the long duration of night sleep and shortened sleep latencies of multiple sleep latency test. Although magnetic resonance imaging and laboratory studies revealed obstruc tion of the upper airway and mild increase of esophageal pressure during sl eep, the number of other apneic episodes or awakenings was not as frequent. From the above results, we speculate that the mechanism of excessive dayti me sleepiness in PWS is not caused by RDDS and quite resembles that of esse ntial hypersomnia.