What is central hypersomnia?

What is Central Hypersomnia?

Central hypersomnia (also called central disorders of hypersomnolence) is a group of neurological disorders characterized by excessive daytime sleepiness that is not caused by disturbed nocturnal sleep, sleep deprivation, circadian rhythm misalignment, or other sleep disorders like obstructive sleep apnea. 1, 2

Core Definition and Distinguishing Features

The defining feature is an inability to maintain wakefulness and alertness during the major waking episode of the day, resulting in unintentional sleep episodes at inappropriate times or irresistible sleepiness. 1 This is fundamentally different from fatigue or tiredness—patients have an increased sleep propensity and actually fall asleep, not just feel tired. 1

Critical Diagnostic Requirement

Any other sleep disorder that disrupts nocturnal sleep (such as obstructive sleep apnea or restless legs syndrome) must be adequately treated before diagnosing a central hypersomnia. 1, 2 For example, if a patient has both sleep apnea and persistent sleepiness, the sleep apnea must be controlled first before considering an independent diagnosis of central hypersomnia. 1

Primary Types of Central Hypersomnia

The major categories include:

Narcolepsy Type 1 (with cataplexy)

• Excessive daytime sleepiness plus definite cataplexy (sudden muscle weakness triggered by emotions) 2
• Often accompanied by hypnagogic hallucinations (vivid dreams while falling asleep), sleep paralysis, and disturbed nocturnal sleep 1, 2
• Caused by loss of hypocretin-producing neurons in the hypothalamus 3
• Prevalence approximately 0.05% with slight male predominance 1

Narcolepsy Type 2 (without cataplexy)

• Excessive daytime sleepiness without cataplexy 2
• May include automatic behaviors, hypnagogic hallucinations, and sleep paralysis 2
• Pathophysiology not fully understood 3

Idiopathic Hypersomnia

• Two subtypes based on total sleep time: 1, 2
  • With long sleep time: Total sleep exceeding 10 hours, present for at least 3 months, often with unrefreshing sleep and significant sleep inertia (difficulty waking) 2
  • Without long sleep time: Total sleep 6-10 hours, present for at least 3 months 2
• Daily, chronic excessive sleepiness persisting for years without episodic pattern 4

Kleine-Levin Syndrome

• Rare disorder with relapsing-remitting episodes of severe hypersomnia lasting days to weeks, with complete return to baseline between episodes 4
• Accompanied by cognitive and behavioral disturbances during episodes 4
• Mean onset at age 15 years, predominantly affects adolescent males (68-78%) 4

Secondary Causes of Central Hypersomnia

Medical Conditions

Neurological disorders are the most common medical causes: 2

• Parkinson's disease 1, 2
• Dementia with Lewy bodies 1
• Post-traumatic brain injury, stroke, multiple sclerosis 2
• Myotonic dystrophy, Niemann-Pick disease type C 2

Metabolic/endocrine disorders: 2

• Hypothyroidism
• Hepatic encephalopathy

Genetic syndromes: 2

• Prader-Willi syndrome
• Down syndrome (often due to obstructive sleep apnea) 5

Medication and Substance-Related

This is a common and often overlooked cause, especially in older adults taking multiple medications: 2

• Current use of sedating medications: benzodiazepines, opioids, antihistamines, certain antidepressants 2
• Recent discontinuation of stimulant medications 2
• Recreational drug use or withdrawal 2

Psychiatric Disorders

• Depression can present with hypersomnia and mimic primary hypersomnia 2

Diagnostic Approach

Clinical History

Obtain history from both patient and bed partner when possible: 1

• Characterize the sleepiness: onset, frequency, duration, any remissions 1
• Ask specifically about cataplexy, response to napping, dreaming during naps, hypnagogic hallucinations, sleep paralysis, automatic behaviors 1
• Document all medical, neurologic, psychiatric conditions 1
• Complete medication history including recreational drugs and alcohol 1
• Screen for other sleep disorders (sleep apnea, restless legs syndrome) 1
• Assess nighttime sleep duration 1

Use validated questionnaires: 1

• Epworth Sleepiness Scale (ESS) is the most commonly used 1, 6
• Sleep diaries are valuable assessment tools 1

Physical Examination

Perform thorough physical and neurologic examination: 1

• Cognitive assessment is valuable for diagnosis and monitoring treatment response 1

Diagnostic Testing

Multiple Sleep Latency Test (MSLT) is essential for diagnosis: 1, 2

• Involves 4-5 daytime naps at 2-hour intervals 1
• Measures latency to sleep onset and type of sleep 1
• Mean sleep latency ≤8 minutes indicates objective excessive sleepiness 2
• Presence of REM sleep on ≥2 naps is indicative of narcolepsy 1

Overnight polysomnography (PSG) must be performed before MSLT: 1, 2

• Rules out other sleep disorders 2
• Ensures adequate sleep the night before MSLT 2

Brain MRI is recommended: 1, 2

• Identifies structural causes: tumors, multiple sclerosis, intracranial bleeds, strokes 1
• Particularly important given increased risk of neurodegenerative disease in older adults 2

Laboratory testing: 1, 2

• Thyroid stimulating hormone
• Liver function tests
• Complete blood count
• Serum chemistry

Cerebrospinal fluid hypocretin levels: 1, 2

• Can confirm narcolepsy type 1 in the absence of MSLT 1, 2

Clinical Impact and Importance

Central disorders of hypersomnolence significantly impact quality of life through: 2

• Cognitive impairment
• Increased risk of accidents
• Social withdrawal (especially with cataplexy) 1
• Occupational difficulties

In older adults, hypersomnia may represent an early sign of neurodegenerative disease and requires thorough evaluation. 2

Common Pitfalls

Medications are a common and frequently overlooked cause of hypersomnia, particularly in older adults on multiple medications. 2 Always review and consider withdrawing sedating medications before pursuing extensive workup. 1

Do not diagnose central hypersomnia until other sleep disorders are adequately treated. 1 This is a critical diagnostic requirement that prevents misdiagnosis.

Common medications can complicate interpretation of MSLT studies in older adults. 1 Consider timing of testing relative to medication use.