ICD-117A20	NARCOLEPSY Narcolepsy
ICD-10G47.4	Narcolepsy and cataplexy
DSM-5-TRG47.4xx	Narcolepsy

1. Definition and nosology

Narcolepsy (ICD-11: 7A20; DSM-5-TR: G47.4xx) — irresistible daytime sleep episodes; two types: Type 1 (with cataplexy, orexin-A/hypocretin deficiency) and Type 2 (without cataplexy).

2. History

• Gélineau J.B. (1880) — the term narcolepsy.
• Mignot E. et al. (2000) — discovery of the orexin/hypocretin system in narcolepsy etiology.

3. Epidemiology

• Prevalence: 25–50 per 100,000.
• Onset: 10–25 years (bimodal).
• Comorbidity: OSA, depressive symptoms, OCD.

4. Aetiology and pathogenesis

• Type 1 — autoimmune damage to orexin-A neurons (CSF orexin <110 pg/ml); HLA-DQB1*06:02 strong association.
• H1N1 vaccine (Pandemrix, 2009) — increased incidence of narcolepsy type 1 in Scandinavian countries (Miller E. BMJ 2013).
• Type 2 — etiology not fully clear.

5. Clinical features

Classic tetrad

• Excessive daytime sleepiness (EDS) — irresistible sleep attacks.
• Cataplexy (Type 1) — sudden partial or complete loss of muscle tone triggered by emotion (laughter, anger); consciousness preserved.
• Sleep paralysis — inability to move at sleep onset or upon awakening.
• Hypnagogic/hypnopompic hallucinations — visual/auditory hallucinations at sleep transition.

Complete tetrad rare; EDS main feature.

6. Diagnosis

6.1 Unified diagnostic criteria

A. EDS ≥ 3 months.

B. MSLT — mean sleep latency ≤8 min + ≥2 SOREMPs (Sleep Onset REM Period); or CSF orexin-A <110 pg/ml.

C. Type 1 — cataplexy + orexin deficiency; Type 2 — no cataplexy, normal orexin.

6.2 Source-specific clarifications

• ICSD-3 (International Classification of Sleep Disorders) — AASM.
• HLA typing and CSF orexin — in atypical cases.

6.3 Diagnostic algorithm

1. Clinical interview.
2. PSG (night) + MSLT (day) — gold standard.
3. CSF orexin — selective.
4. HLA-DQB1*06:02 — supportive.

6.4 Differential diagnosis

7. Examination and assessment

• Epworth.
• PSG + MSLT.
• CSF orexin, HLA-DQB1*06:02.

8. Treatment

1. EDS: modafinil, armodafinil, solriamfetol, pitolisant; stimulants (methylphenidate, amphetamine) in refractory cases.
2. Cataplexy: sodium oxybate (Xyrem) — gold standard; new — calcium/magnesium/potassium/sodium oxybate (Xywav, FDA 2020, low sodium); SSRI/SNRI (venlafaxine, fluoxetine); pitolisant.
3. Behavior — planned daytime naps (15–20 min)
4. Driving restriction if EDS present.

Source-specific specifications

• AASM Treatment Guidelines (Maski 2021).
• FDA approvals — pitolisant 2019, solriamfetol 2019, Xywav 2020.

Treatment methods

1. Sodium Oxybate (Xyrem/Xywav) — GHB; two doses at night; effect on cataplexy and EDS.
2. Modafinil/Armodafinil — First-line for EDS.
3. Pitolisant — H3 receptor antagonist; for EDS and cataplexy.
4. SSRI/SNRI for cataplexy — Venlafaxine, fluoxetine off-label.
5. MSLT — ≥2 SOREMP diagnostic.

9. Prognosis

• Chronic; functional improvement with pharmacotherapy.
• Comorbidity (MDD, OSA) intervention essential.

10. Myths and misconceptions

Myth 1: “Narcolepsy is just EDS alone”

Evidence: Tetrad (EDS + cataplexy + paralysis + hallucinations); SOREMPs differentiating in MSLT.

Myth 2: “Cataplexy is a seizure”

Evidence: consciousness preserved; EEG no epileptic activity; emotional trigger.

Myth 3: “H1N1 vaccine causes narcolepsy — vaccines should be avoided”

Evidence: Risk indicated specifically with Pandemrix (2009 Scandinavia); other vaccines are safe; avoiding vaccination overall is not recommended.

Myth 4: “The patient can drive”

Evidence: Driving must be restricted in a narcoleptic patient with EDS.

11. Sources

1. WHO. ICD-11. 7A20 Narcolepsy. 2024.
2. APA. DSM-5-TR. 2022.
3. Maski K. et al. AASM CPG. J Clin Sleep Med 2021;17(9):1881–1893.
4. Miller E. et al. Risk of narcolepsy in children and young people receiving AS03 adjuvanted pandemic A/H1N1 2009 influenza vaccine. BMJ 2013;346:f794.
5. Mignot E. et al. The role of cerebrospinal fluid hypocretin measurement in the diagnosis of narcolepsy. Arch Neurol 2002;59(10):1553–1562.