Prolonged polysomnography in a case with recurrent hypersomnia.

An 18-year-old male patient with recurrent hypersomnia (RH) was evaluated using prolonged polysomnography (PSG). During symptomatic period (SMP), the patient showed both 'dissociated stage REM' (DREM), REM sleep without muscle atonia and 'dissociated stage 1' (DSt-1), and stage 1 sleep with rapid eye movement. These stages were observed in the morning or following daytime record. They decreased during asymptomatic period (ASMP). It has been said that RH is caused by dysfunction of the hypothalamus and midbrain limbic system. The present result suggests also that RH involves dysfunction of the brain stem.