Idiopathic Hypersomnia By Richard J Schwab, MD, University of Pennsylvania, Division of Sleep Medicine Reviewed / Revised May 2022 | Modified Sep 2022 View Patient Education Diagnosis Treatment Idiopathic hypersomnia is excessive daytime sleepiness with or without a long sleep time; it is differentiated from narcolepsy by lack of cataplexy, hypnagogic hallucinations, and sleep paralysis.