Localise by state
- NREM disorders of arousal (sleepwalking, sleep terrors, confusional arousals): first third of night, incomplete awakening, autonomic surge, amnesia for the event, difficult to console; common in children, often benign.
- REM parasomnias: nightmares (recalled dysphoric dreams, later night) and REM sleep behaviour disorder (dream enactment from lost atonia — older adults, strong link to Parkinson's/dementia with Lewy bodies; warrants referral).
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Sleep terror vs nightmare (exam‑critical)
| Feature | Sleep terror | Nightmare |
|---|---|---|
| Stage | NREM (early) | REM (late) |
| Autonomic arousal | Marked | Variable |
| Recall | Poor/absent | Usually vivid |
| Consolable during event | No | (Awakens, then consolable) |
Red flags that change the workup 🚩
Stereotyped, brief, repetitive nocturnal events → consider nocturnal frontal‑lobe epilepsy (video‑EEG). New‑onset RBD in an older adult → neurology referral (synucleinopathy risk). Injurious behaviour, or first onset in adulthood, merits polysomnography.
Pitfalls
- Reassuring an adult with dream‑enactment behaviour instead of referring (missed RBD/neurodegeneration prodrome).
- Missing nocturnal epilepsy masquerading as parasomnia.
Pearls
- 🎯 Sleep terror = NREM, amnesic; nightmare = REM, recalled.
- 🩺 RBD in an older adult is a neurodegenerative red flag — don't just reassure.
Next → REM dysregulation as disease — narcolepsy (Concept 38).