Idiopathic hypersomnia

Saba Ahmad MD (Dr. Ahmad of the University of Illinois in Chicago has no relevant financial relationships to disclose.)
Pallavi P Patwari MD (Dr. Patwari of Northwestern University has no relevant financial relationships to disclose.)
Antonio Culebras MD, editor. (Dr. Culebras of SUNY Upstate Medical University has no relevant financial relationships to disclose.)
Originally released October 11, 1993; last updated March 23, 2015; expires March 23, 2018

This article includes discussion of idiopathic hypersomnia (IH), which is characterized by excessive daytime sleepiness, difficulty awakening (sleep drunkenness), and undisturbed overnight sleep without cataplexy or known cause of excessive sleepiness.


Excessive sleepiness (hypersomnolence) of unknown etiology, which cannot be explained by another disorder, would be considered idiopathic hypersomnia. This should be clearly distinguished from other disorders that could present with complaints of excessive daytime sleepiness, such as narcolepsy, inadequate total sleep time, circadian rhythm disturbance, obstructive sleep apnea, or from hypersomnolence secondary to medical condition or medication. These patients frequently present in adolescence and may have symptoms of autonomic nervous system dysregulation but are most often affected because of inability to attend to daytime obligations such as school or work. Because the pathophysiology is unknown, management is limited to symptomatic treatment and education.

Key points


• The main symptom of idiopathic hypersomnia is an irresistible urge to sleep with periods of sleep during the daytime for at least 3 months.


• For idiopathic hypersomnia duration of sleep (with and without long sleep time) is no longer criteria for subtype distinction.


• Idiopathic hypersomnia can be associated with symptoms of autonomic nervous system dysregulation (orthostatic hypotension, syncope, headache, and Raynaud-type phenomena) and with significant sleep inertia (aka sleep drunkenness).


• The diagnosis of idiopathic hypersomnia is based on clinical features along with testing to rule out other causes of excessive daytime sleepiness (Multiple Sleep Latency Test, polysomography, and sometimes actigraphy).


• The differential diagnosis includes other conditions of excessive daytime sleepiness such as narcolepsy, obstructive sleep apnea, inadequate total sleep time, circadian rhythm disturbance, or hypersomnolence secondary to medical condition or medication.


• Treatment of idiopathic hypersomnia is primarily symptomatic involving education (sleep hygiene and lifestyle modifications) and wake-promoting agents such as stimulants.

Historical note and terminology

Prior to the use of polysomnographic studies, idiopathic hypersomnia was usually misdiagnosed as narcolepsy. Dement and colleagues first proposed that a diagnostic category other than narcolepsy should be used for patients who have excessive daytime sleepiness but do not have cataplexy, sleep paralysis, or sleep onset rapid eye movement episodes (Dement et al 1966). Subsequently, various labels were proposed to designate this entity: essential narcolepsy (Berti-Ceroni et al 1967), non-REM sleep narcolepsy (Passouant et al 1968), hypersomnia (Rechtschaffen and Roth 1969), hypersomnia with sleep drunkenness (Roth et al 1972), idiopathic hypersomnia (Roth 1976), idiopathic central nervous system hypersomnia (Anonymous 1979), and again idiopathic hypersomnia (American Sleep Disorders Association 1990). The previous sleep disorders classification parsed idiopathic hypersomnia into 2 categories based on sleep duration. Idiopathic hypersomnia with long sleep time (> 10 hours) entails excessive sleepiness with prolonged, unrefreshing naps up to 3 or 4 hours, major sleep episodes of at least 10 to 14 hours in duration with difficulty waking up or sleep drunkenness, and no cataplexy. Idiopathic hypersomnia without long sleep time (< 10 hours) reflects excessive sleepiness and unintended, unrefreshing naps, with the major sleep episode less than 10 hours, with difficulty waking up or sleep drunkenness, and no cataplexy (American Academy of Sleep Medicine 2005). The 3rd edition of the International Classification of Sleep Disorders (ICSD-3) no longer characterizes idiopathic hypersomnia based on sleep duration (suggesting a single, heterogenous condition) and falls within the larger category of central disorders hypersomnolence (American Academy of Sleep Medicine 2014).

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