Brain localization and morphological changes in NREM parasomnias. A systematic review study.

Abstract

<h4>Background</h4>Individuals with NREM parasomnias exhibit abnormal slow-wave activity and fragmented sleep. Sleep-state dissociation is the prevailing concept of NREM parasomnia-episodes; typically emerging from N3/N2 stages of NREM sleep's first cycle at the turning-point of deep sleep and arousal. While these relations provide a frame to understand these conditions, their mechanism and brain-topography remain unclear.<h4>Methods</h4>We performed a systematic search of the literature (1/01/2015-20/06/2024) on brain-topographies and morphological changes based on neurophysiological and imaging studies in patients with NREM parasomnias.<h4>Results</h4>It was shown that immediately preceding clinical episodes, the EEG spectral power of delta and theta frequency-bands increased in parallel with its reduction in the cingulate, motor, and premotor/supplementary motor cortices. Far from clinical episodes, in NREM and REM sleep as well as in wakefulness, a cortico-cortical sleep-state dissociation occurred, too. In addition, the partial arousals of episodes evolved from 'deeper' sleep with lower-amplitude slow waves, compared to episode-free arousals of the same people with NREM parasomnias. A single MR-morphology study revealed decreased grey-matter volume in the left dorsal posterior cingulate and mid-cingulate cortices in patients with mixed NREM parasomnias.<h4>Conclusion</h4>Based on recent research, the state-dissociation evidenced in clinical episodes might characterize each vigilance state of people with NREM parasomnias, even outside the episodes, making sleep-wake dissociation a trait-like core feature of NREM parasomnias. The anterior cingulo-frontal regions seem to have central roles. PROSPERO registration ID: CRD42024552562.