Phase advancement of slow-wave sleep in a patient with periodic hypersomnia.

Twenty-four-hour polysomnographic recordings were obtained during asymptomatic (ASP) and symptomatic (SP) periods in a patient with periodic hypersomnia. During both periods, an abnormal sleep architecture was detected, with a greater sleep fragmentation during the SP. An unexpected finding was a shortening of the latency of slow-wave sleep, with a difference of more than 5 hours between the ASP and the SP. The greater fragmentation of rapid eye movement sleep during the SP may suggest a disorganization of the ultradian rhythm of rapid eye movement sleep.