Purpose of review 

Nonrapid eye movement (NREM) parasomnias are common sleep disorders that potentially have significant personal, social and forensic implications. They represent a unique opportunity in nature to explore the coexistence of sleep and wake-state in the human brain.

Recent findings 

Neuroimaging and electroencephalography have advanced our understanding of NREM-parasomnia pathophysiology, and the interplay between wakefulness and sleep. These disorders are increasingly viewed as resulting from an evolutionary process with a basis in uni-hemispheric brain activity in sleep seen in some animals, maintaining consciousness and ability to act against life-threatening situations. Although current classification of NREM parasomnia phenotypes distinguishes between disorders of arousal and other types of behaviours, evidence increasingly points to there being a significant overlap between the various phenotypes. Treatment practice appears more standardized nowadays based on larger case series, but randomized control trials are still needed.

Summary 

NREM-parasomnia is a very common disorder of uncertain pathogenesis but of known pathophysiology, the diagnosis of which remains primarily clinical.