A 19-year-old man presents with sudden bilateral loss of muscle tone triggered by laughter, excessive daytime sleepiness, and sleep paralysis. Hypocretin-1 (orexin-A) in his CSF is undetectable. Which EEG finding during sleep-onset is characteristic of his condition?

• A Sleep spindles appearing within 2 minutes of sleep onset
• B Prolonged slow-wave sleep (N3) at sleep onset
• C Vertex sharp waves persisting beyond 10 minutes
• D Sleep-onset REM periods (SOREMPs) within 15 minutes of sleep onset ✓

Explanation

The clinical triad of excessive daytime sleepiness, cataplexy, and sleep paralysis combined with absent CSF hypocretin-1 is diagnostic of narcolepsy type 1. The pathognomonic polysomnographic finding is sleep-onset REM periods (SOREMPs) — entry into REM sleep within 15 minutes of sleep onset — occurring in ≥2 naps on the Multiple Sleep Latency Test (MSLT). Normal individuals do not enter REM until approximately 90 minutes after sleep onset. Loss of hypocretin neurons in the lateral hypothalamus underlies the disorder.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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