[Excessive daytime sleepiness: etiology, differential diagnosis and diagnostic procedures]

This article gives an overview on frequent causes of excessive daytime sleepiness in clinical practice. Specifically, the insufficient sleep syndrome, sleep disordered breathing, narcolepsy, restless legs syndrome/periodic limb movements in sleep, and circadian disorders causing daytime sleepiness are discussed. Other possible causes including symptomatic daytime sleepiness associated with various medical conditions are mentioned. Different methods to determine daytime sleepiness are discussed in the final section.