Parasomnias
NREM versus REM parasomnias
NREM parasomnias (confusional arousals, sleepwalking, sleep terrors) arise from slow-wave sleep, often in the first third of the night. They feature incomplete awakening, amnesia for the event, and variable autonomic activation. They are more common in children, can be triggered by sleep deprivation, fever, alcohol, and sedatives, and are often familial. Safety counseling and trigger avoidance are central.
REM parasomnias include REM sleep behavior disorder (RBD) and nightmares. RBD involves loss of REM atonia with dream enactment-often violent-typically in older adults, and is strongly associated with synucleinopathies (Parkinson disease, Lewy body dementia, multiple system atrophy). Diagnosis requires polysomnographic demonstration of REM without atonia (RSWA).
Other entities: sleep-related eating disorder, sleep paralysis, exploding head syndrome, and sleep enuresis. Disorders of arousal are not epilepsy, though frontal-lobe seizures can mimic them.
Traps: assuming sleepwalking indicates psychopathology; missing that RBD can precede neurodegenerative disease by years; and confusing night terrors (NREM, amnesia, first third of night) with nightmares (REM, recall, later in night). Also remember that dream enactment with injury warrants evaluation for RBD, and that antidepressants can precipitate RBD-like behavior.
Rule of thumb: Timing plus recall distinguishes them-NREM events early, amnestic; REM events later, with dream recall.
Worked example: An older man with violent dream enactment and PSG showing REM without atonia has RBD; counseling on bedroom safety and neurologically oriented follow-up are indicated.