ABSTRACT
<p><b>BACKGROUND</b>Kleine-Levin syndrome (KLS) is a rare sleep disorder characterized by recurrent episodes of hypersomnia. Polysomnographic (PSG) researches of KLS have been reported only in few publications in the past decades. This study aimed to investigate the characteristics of PSG of KLS.</p><p><b>METHODS</b>This study, which was conducted from March 2010 to July 2014, included seven patients diagnosed with KLS in the Sleep and Wake Disorder Center of Huashan Hospital, Fudan University (Shanghai, China). PSG and multiple sleep latency tests (MSLT) were performed during their episodes and the results were evaluated.</p><p><b>RESULTS</b>Five of the seven patients were males. The mean age at KLS onset was 15.6 ± 3.6 years. The number of episodes ranged from 2 to 7. The duration of episodes lasted from 4 to 11 days. The sleep architecture and proportion were normal in most of the patients. The average value of mean sleep latency was 6.9 ± 4.1 min. No sleep-onset rapid eye movement (SOREM) was detected in three of the patients, whereas one patient experienced one period of SOREM, and such episodes occurred twice in other two patients.</p><p><b>CONCLUSIONS</b>We found that sleep architecture and proportion were normal in most KLS patients. However, the results of PSG and MSLT had no specificity for KLS patients.</p>