A 9-year-old boy sits up in bed 2 hours after falling asleep, walks around the house with eyes open but unresponsive, and has no memory of the event next morning. Polysomnography during such an episode would most likely show:

• A Tonic EMG suppression with desynchronised EEG and rapid eye movements
• B Sleep spindles and K-complexes with normal muscle tone
• C High-voltage delta-wave EEG arising from deep non-REM sleep ✓
• D Theta-frequency EEG with marked phasic muscle twitches

Explanation

Somnambulism (sleepwalking) and night terrors are disorders of arousal that arise from stage N3 slow-wave sleep, typically in the first third of the night when N3 predominates, and are common in children because they have the greatest proportion of N3. Option A describes REM sleep, from which dream enactment behaviour rather than quiet wandering occurs, and option B describes stage N2.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.