Polysomnography in Kleine-Levin syndrome.

Cause and pathogenesis of the Kleine-Levin syndrome (KLS), a recurrent hypersomnia affecting mainly male adolescents, remain unknown, with only scant information on the sleep characteristics during episodes. We describe findings obtained with polysomnography (PSG) and Multiple Sleep Latency Test (MSLT) and correlation obtained between clinical and PSG findings from different episodes. Nineteen patients (17 male) were investigated with PSG and MSLT. Ten patients had data during both symptomatic episode and asymptomatic interval. The analyses considered day of onset of symptoms and relationship between this time of onset and day of recording during the symptomatic period. When PSG was performed early (before the end of the first half of the symptomatic period), an important reduction in slow wave sleep (SWS) was always present with progressive return to normal during the second half (with percentages very similar to those monitored during the asymptomatic period) despite persistence of clinical symptoms. REM sleep remained normal in the first half of the episode but decreased in the second half: the differences between first and second half of episodes were significant for SWS (p = 0.014) and REM sleep (p = 0.027). The overall mean sleep latency at MSLT was 9.51 +/- 4.82 minutes and 7 of 17 patients had two or more sleep onset REM periods during the symptomatic period. Important changes in sleep occur over time during the symptomatic period, with clear impairment of slow wave sleep at symptom onset. But Multiple Sleep Latency Test (MSLT) is of little help in defining sleep problems and findings from the MSLT do not correlate with symptom onset.