Which feature is characteristic of narcolepsy and helps distinguish it from other sleep disorders?

• A. Insomnia with difficulty staying asleep.
• B. Sleepwalking only at night.
• C. Sleep apnea with snoring.
• D. Daytime sleep attacks with features such as cataplexy, sleep paralysis, hypnagogic hallucinations.

Answer: (D)

Narcolepsy is defined by sudden, irresistible daytime sleep attacks that intrude into wakefulness, paired with REM-related phenomena such as cataplexy, sleep paralysis, and hypnagogic hallucinations. This combination is unique to narcolepsy and distinguishes it from other sleep disorders. Insomnia centers on trouble staying asleep, not daytime sleepiness with REM intrusion. Sleepwalking occurs during non-REM sleep at night, not as daytime attacks with REM symptoms. Sleep apnea involves breathing interruptions during sleep and often snoring, without the hallmark REM-phenomena cluster.