Differential diagnosis of hypersomnias

The term hypersomnia is used to identify disorders that are associated with excessive sleepiness, such as idiopathic hypersomnia or narcolepsy. Sleepiness is considered excessive when there is an increased amount of sleep or an increased drive toward sleep during the wake period, making a person unable to sustain wakefulness or alertness. Patients who have excessive sleepiness tend to have involuntary sleep episodes during activities. The hypersomnias either shorten or fragment the major sleep period or are a manifestation of central nervous system dysfunction. This article discusses disorders, including the hypersomnias, that should be considered when evaluating individuals with excessive sleepiness.