Idiopathic hypersomnia is not well-characterized. Cause is presumed to be dysfunction of the central nervous system.
Excessive daytime sleepiness is the main symptom; sleep time may or may not be prolonged.
In idiopathic hypersomnia with a long sleep time, the history or sleep logs indicate > 10 hours of nocturnal sleep; in idiopathic hypersomnia without a long sleep time, it is > 6 hours but< 10 hours. In both cases, polysomnography shows no evidence of other sleep abnormalities. Multiple sleep latency testing shows short sleep latencies (< 8 minutes) with fewer than 2 REM periods.
Treatment of idiopathic hyperinsomnia is similar to that of narcolepsy (eg, modafinil), except that anticataplectic drugs are unnecessary.