The origin of excessive daytime sleepiness in the Prader-Willi syndrome.

The polygraphically recorded sleep-wake continuum of 21 Prader-Willi syndrome (PWS) patients was compared with that of 19 normal people. In the Prader-Willi group, excessive daytime sleepiness (EDS) is found in 95% of subjects, and rapid eye movement (REM) sleep disorders occur in 52%. These two features were significantly different from the normal group of subjects. No indications were found for the presence of the apnoea syndrome. The REM sleep disorders are: sleep onset rapid eye movements (SOREM), REM sleep in naps, many arousals during REM sleep, and a significant decrease in total REM sleep. These disturbances in the Prader-Willi group, combined with the presence of EDS and sometimes of cataplexy, are likely to be expressions of a narcoleptic syndrome although this was not sustained by the HLA-DR2 expression above normal. The quality of life of PWS subjects can be improved in some cases by treating them as narcoleptic patients.