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Narcolepsy type 1 — RACP Paediatrics MCQ

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HardNeurologyNarcolepsy type 1RACP Paediatrics

A 13-year-old presents with excessive daytime sleepiness and sudden episodes of bilateral muscle weakness triggered by laughter or strong emotions (cataplexy). Sleep onset REM periods are present on MSLT. CSF hypocretin (orexin) is undetectable. What is the most likely diagnosis?

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Correct answer: B — Narcolepsy type 1

Excessive daytime sleepiness with cataplexy (sudden loss of muscle tone triggered by emotions) in a child is narcolepsy type 1. The diagnosis is confirmed by MSLT showing sleep-onset REM periods (≥2 SOREMPs, mean sleep latency <8 min) and undetectable CSF hypocretin/orexin. It is caused by autoimmune destruction of hypothalamic hypocretin neurons. Treatment includes scheduled naps, stimulants (modafinil/methylphenidate), and sodium oxybate for cataplexy.

Reference: RCH Melbourne – 2023 – Sleep CPG; RACP Paediatric Curriculum – Neurology