Is excessive daytime sleepiness with periodic leg movements during sleep a specific diagnostic category?

Thirty-four patients who presented with excessive daytime sleepiness (EDS) and who showed an elevated number of periodic leg movements during sleep (PLMS) were studied. None of these patients reported other symptoms or presented sleep laboratory manifestations of narcolepsy or of breathing disorders during sleep. A diagnosis of restless leg syndrome, head trauma or a past history of psychopathology or infectious diseases known to cause EDS were also ruled out. In addition, none of the patients reported a history of drug or alcohol abuse, chronic sleep deprivation or irregular sleep-wake schedule and none were taking medications known to influence sleep at the time of the study. Results of the present study showed no correlation between PLMS index and poor sleep efficiency or daytime sleepiness as measured by the multiple sleep latency test (MSLT). However, a significant negative correlation was found between sleep efficiency at night and the mean sleep latency on the MSLT. These results suggest not only that PLMS and nocturnal sleep disruption are not the primary cause of EDS, but that these sleepy patients have a high propensity to sleep both at night and during the daytime. Therefore, the presence of PLMS during nocturnal sleep recording should not preclude the diagnosis of idiopathic hypersomnia.