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.
(See also Approach to the Patient With a Sleep or Wakefulness Disorder.)
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.
Diagnosis of Idiopathic Hypersomnia
History or sleep logs
Sleep tests
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. Typically, patients with idiopathic hypersomnia have difficulty waking up, and when they awaken, they experience a period of sleep inertia characterized by drowsiness, decreased cognition, and motor impairment.
Treatment of Idiopathic Hypersomnia
Similar to that of narcolepsy
Treatment of idiopathic hypersomnia is similar to that of narcolepsy; ie, it is treated with wake-promoting drugs (eg, modafinil; sodium oxybate; a combination drug that contains calcium, magnesium, potassium, and sodium oxybates).