Parasomnias and Sleep-Related Movement Disorders
NREM parasomnias
Disorders of arousal (confusional arousals, sleepwalking, sleep terrors) arise from N3, often in the first third of the night, with amnesia for the event and incomplete awakening. They are more common in children and may be triggered by sleep deprivation, fever, stress, or other sleep disorders (apnea, restless legs). Management emphasizes safety, trigger avoidance, and treatment of comorbid sleep disorders; scheduled awakenings or low-dose benzodiazepines are considered in refractory cases.
REM parasomnias
REM sleep behavior disorder (RBD) involves dream enactment with loss of normal REM atonia; polysomnography shows REM without atonia. It is associated with neurodegenerative synucleinopathies (Parkinson disease, Lewy body dementia, multiple system atrophy) and often precedes them by years. Treat with melatonin or clonazepam and ensure bedroom safety. Distinguish from sleep terrors (NREM) and from nightmares (no motor activity).
Other parasomnias and movements
Nightmare disorder occurs in REM with full recall and autonomic arousal. Sleep-related eating disorder and sexsomnia are complex behaviors. Restless legs syndrome (RLS) is a clinical diagnosis (urge to move, worse at rest, relieved by movement, worse in evening/night) and is associated with iron deficiency; check ferritin and treat deficiency. Periodic limb movements during sleep (PLMS) are repetitive limb movements on PSG; PLMS alone without symptoms does not require treatment.
Traps
Timing and stage of origin separate NREM from REM events. Do not diagnose RBD without PSG confirmation when the history is uncertain, and do not miss iron deficiency in RLS.
Worked example
An older man with violent dream enactment in the second half of the night: think RBD, obtain PSG, counsel on neuro risk and bedroom safety.