Primary Hypersomnia Differential Diagnoses

Updated: Sep 04, 2018
  • Author: Adrian Preda, MD, DFAPA; Chief Editor: Ana Hategan, MD, FRCPC  more...
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Diagnostic Considerations

Before making a diagnosis of hypersomnolence, consider the following:

  • Is there a temporal relationship between the onset, exacerbation, and remission of the hypersomnia and its associated features/conditions?

  • Is there a family history of hypersomnia versus associated features (a general medical condition, depression, etc.)?

In addition, carefully consider factors such as age of onset, typical versus atypical features, and course. Such determinations should help in differentiating among the following entities. [66, 74, 75]

Behaviorally induced insufficient sleep syndrome

Behaviorally induced insufficient sleep syndrome (BIISS) is characterized by chronic insufficient nocturnal sleep, typically sleeping 2–3 more hours on weekend days than weekdays. Actigraphy is helpful to rule out IBISS as many patients' subjective view of their sleep time is not accurate. BIISS must be ruled out as it can present with similar PSG/MSLT findings as IH. [76, 71, 13]  

Normal sleep variation

"Long sleepers" (ie, individuals with a greater than average sleep duration) do not present with excessive daytime sleepiness, sleep drunkenness, or automatic behaviors as long as they obtain their regular amount of sleep. [66] An understanding of the individual’s sleep baseline is required before making a diagnosis.

Chronic insufficient sleep

The nocturnal sleep duration should be qualified as adequate before a diagnosis of idiopathic hypersomnia is made. An average sleep duration of less than 7 hours can result in excessive daytime sleepiness similar in presentation to hypersomnolence. If this is suspected, patients should be instructed to document their sleep duration in sleep diaries. Often, an improvement in daytime symptoms is noted following an increase in sleep duration, contrasted with idiopathic hypersomnia where there is no change to excessive daytime sleepiness with increased sleep duration. When in doubt, a sleep extension trial can be prescribed for 10–14 days to clarify the diagnosis. [66]

Substance-induced sleep disorder, hypersomnia type

This should be diagnosed if hypersomnia is secondary to the use or abuse of prescription medications, over-the-counter drugs, or illicit drugs. Of note, hypersomnia can be a direct result of using a specific drug (eg, benzodiazepines, antihistamines) or can occur as a result of stopping a previously used/abused drug (eg, stimulants, cocaine). When in doubt, a drug screen can help to clarify the diagnosis.

Upper airway resistance syndrome (breathing-related sleep disorder)

This syndrome is associated with excessive daytime sleepiness and heavy snoring causing frequent arousals during nocturnal sleep. Obesity is common; patients may have anatomic abnormalities of the upper airway, such as a high, narrow, arched palate; malocclusion of the mouth; or retrognathia.

Polysomnographic recording shows short alpha-electroencephalogram arousals lasting 3–14 seconds. [77] Monitoring esophageal pressure or quantifying airflow using a pneumotachometer is required to confirm the presence of this syndrome. The use of nasal continuous positive airway pressure as a therapeutic test can help to confirm the diagnosis.

Posttraumatic hypersomnia

Posttraumatic hypersomnia may mimic hypersomnolence. Symptoms usually develop 6–18 months after head trauma.

Other neurologic disorders

Imaging studies of the brain may identify a communicating hydrocephalus or brain tumor with daytime hypersomnolence as the presenting symptom/chief complaint, in the absence of any other neurologic signs or symptoms.

Hypersomnia secondary to other general medical conditions

Excessive daytime hypersomnia also may occur from frequent chronic pain or from repeated awakenings because of an underlying medical disorder.

As the use of medications can result in hypersomnia, a careful history and chronology of the symptoms are necessary to clarify the underlying cause. In the hospital, especially in intensive care units, hypersomnia may also be secondary to a disruption of the sleep-wake cycle or, in severe cases, may reflect an underlying delirium due to a general medical condition.

Major depressive disorder

Hypersomnia may be the presenting feature of primary depression, which should be excluded by performing a careful psychiatric evaluation. To complicate matters further, patients with primary hypersomnia are at increased risk of developing a major depressive disorder. Therefore, all patients with hypersomnia should receive a careful mental status and psychiatric evaluation for depression. The purpose of the psychiatric evaluation is to determine if there are dynamic family, work, or interpersonal issues that may cause or contribute to the depression.

Characteristic symptoms include depressed mood, anhedonia (a loss of interest and pleasure), decreased energy, psychomotor agitation or retardation, decreased or increased appetite (which may result in weight loss or gain), decreased attention and concentration, decreased libido, feelings of guilt or worthlessness, and, in severe cases, suicidal ideation, delusional thought processes, or auditory hallucinations.

The most common sleep disturbance reported in melancholic depression is poor sleep. Sleep disturbances such as difficulty in sleep initiation and sleep maintenance and/or early awakening are common. Subsequent daytime tiredness resulting in frequent or prolonged naps may be mistaken for excessive daytime sleepiness.

Hypersomnia associated with increased appetite, weight gain, mood reactivity (meaning the mood brightens in response to positive events), leaden paralysis (ie, a leaden feeling in the arms or legs), and rejection sensitivity is characteristic of atypical depression.

If depression is present, a careful history clarifying the chronology of symptoms (did hypersomnia precede or follow the associated depressive symptoms) is required to clarify the primary diagnosis.


Excessive daytime sleepiness, a history of cataplexy, and the presence of sleep-onset REM periods should allow the differentiation of narcolepsy from idiopathic hypersomnia. In the absence of cataplexy, the disorder may be difficult to differentiate. especially given that CSF hypocretin-1 levels are found to be normal in 80% of patients with narcolepsy without cataplexy and 100% of patients with IH. [58, 78, 79] A diagnosis of narcolepsy requires the presence of 2 or more sleep-onset REM periods on the Multiple Sleep Latency Test. Association with the human leukocyte antigen HLA-DR15 and HLA-DQ6 haplotype is common. [10, 62, 63, 64]  

By contrast, patients with primary hypersomnia usually present with longer and less interrupted nocturnal sleep, have more difficulties waking up, and have more sleepiness during the daytime (rather than the more discrete "sleep attacks" in narcolepsy).

Primary hypersomnia patients also have longer and less refreshing daytime sleep episodes, with little or no dreaming during daytime naps (as opposed to the sleep-onset REM periods seen in narcolepsy). [66]

Circadian rhythm sleep disorders

Delayed sleep phase syndrome is a diagnostic consideration in some patients whose main complaints are extreme difficulty awakening at a desired time and excessive morning sleepiness. An abnormal sleep-wake schedule (with shifted or irregular hours) is often present in individuals with circadian rhythm sleep disorder. [66] These patients do not have excessive daytime sleepiness in the latter half of the day and are not able to fall asleep until late at night.

Other psychiatric disorders

Hypersomnia associated with dysthymia and related mood disorders is observed frequently. The presentation is usually later in life. A low-grade chronic depression and an inability to cope with stressful situations are observed. The sleep disturbance in psychiatric patients with the chief complaint of hypersomnia appears to be associated with a centrally driven hyperarousal, whereas primary hypersomnia is associated with a centrally driven hypoarousal. Multiple Sleep Latency Test findings do not demonstrate short sleep latency.

Persistent or relapsing fatigue that does not resolve with bedrest characterizes chronic fatigue syndrome. Polysomnographic recording shows reduced sleep efficiency and alpha intrusion into sleep on electroencephalogram (EEG).

Differential Diagnoses