ICD-117A21–7A26	HYPERSOMNIA Hypersomnolence disorders
ICD-10F51.1	Nonorganic hypersomnia
DSM-5-TRF51.11	Hypersomnolence Disorder

1. Definition and nosology

Hypersomnia (ICD-11: 7A21–7A26; DSM-5-TR: F51.11 Hypersomnolence Disorder) — excessive daytime sleepiness or sleep episodes (after ≥ 7 hours of nighttime sleep); functional impairment. In the context of idiopathic hypersomnia, narcolepsy, or other sleep disorders.

2. History

In the 1970s–1980s, differentiation from narcolepsy developed; AASM clinical guidelines.

3. Epidemiology

• Idiopathic hypersomnia: ~50/100,000.
• Kleine-Levin syndrome — rare (~1/1 million); recurrent episodes of hypersomnia + appetite/sexual disturbance.
• Comorbidity: depressive symptoms, OSA, narcolepsy.

4. Aetiology and pathogenesis

• Unknown (idiopathic) — neurobiological dysregulation hypothesis.
• Dysregulation of the GABA-ergic system (idiopathic).
• Secondary — Kleine-Levin (autoimmune suspicion), post-TBI, MS, depressive disorder.

5. Clinical features

• Excessive Daytime Sleepiness (EDS).
• Long night sleep (≥ 9 hours) is insufficient.
• “Sleep drunkenness” — confusion, disorientation upon awakening.
• Daytime sleep episodes are prolonged and non-restorative (in contrast to narcolepsy, where they are brief and restorative).
• Kleine-Levin — 1–2 week episodes of hypersomnia + hyperphagia + disinhibited behavior.

6. Diagnosis

6.1 Unified diagnostic criteria

A. Even after sufficient sleep (≥7 hours), excessive sleepiness or prolonged sleep.

B. Frequency and duration — ≥3 times per week, ≥3 months.

C. Significant distress or functional impairment.

D. Not fully explained by another sleep disorder, substance, or medical condition.

6.2 Source-specific clarifications

• AASM Practice Parameters — diagnostic PSG and MSLT (Multiple Sleep Latency Test).
• Idiopathic hypersomnia — mean sleep latency on MSLT ≤ 8 min; SOREMP ≤ 1 (different from narcolepsy).

6.3 Diagnostic algorithm

1. Clinical interview and sleep diary.
2. Epworth Sleepiness Scale.
3. PSG + MSLT (excluding narcolepsy).
4. Medical assessment — thyroid, anemia, depressive, OSA.

6.4 Differential diagnosis

7. Examination and assessment

• Epworth, PSG + MSLT.
• Medical laboratory tests.

8. Treatment

1. Modafinil, armodafinil — first-line.
2. Stimulants (methylphenidate, amphetamine) - refractory.
3. Low-sodium oxybate (Xywav, FDA 2021) — the only agent approved for idiopathic hypersomnia.
4. Pitolisant (FDA 2019) — approved for narcolepsy; solriamfetol (FDA 2019) — approved for narcolepsy and obstructive sleep apnoea; both off-label in idiopathic hypersomnia.
5. Sleep hygiene and behavioral intervention (planned daytime naps).
6. Kleine-Levin — supportive; asymptomatic between episodes.

Source-specific specifications

• AASM Treatment Guidelines (Maski K. et al. 2021).

Treatment methods

1. Modafinil/Armodafinil — Wakefulness-promoting; first-line; headache, anxiety side effects.
2. Multiple Sleep Latency Test (MSLT) — 5 sleep attempts with 2-hour intervals; sleep latency measurement.
3. Pitolisant and Solriamfetol — New medications; in refractory cases.

9. Prognosis

Chronic; functional improvement with pharmacotherapy.

10. Myths and misconceptions

Myth 1: “Daytime sleepiness is ‘laziness’”

Evidence: Clinical condition; increased risk of mortality and accidents.

Myth 2: “Caffeine is sufficient for hypersomnia”

Evidence: Caffeine adjunct; modafinil or stimulant required.

Myth 3: “Hypersomnia is only a symptom of depression”

Evidence: idiopathic hypersomnia is a distinct disorder; MSLT differentiates.

11. Sources

1. WHO. ICD-11. 7A21–7A26 Hypersomnolence disorders. 2024.
2. APA. DSM-5-TR. 2022.
3. Maski K. et al. Treatment of central disorders of hypersomnolence: AASM Clinical Practice Guideline. J Clin Sleep Med 2021;17(9):1881–1893.