All-night spectral and microstate EEG analysis in patients with recurrent isolated sleep paralysis

Sleep in people with recurrent isolated sleep paralysis (RISP) is disturbed even outside episodes and beyond REM sleep. Spectral analysis of full-night polysomnography recordings from 17 RISP patients and 17 controls revealed significantly higher theta power in REM and NREM 2 stages in RISP patients, with a similar trend in other stages. Alpha power showed a downward trend in deep sleep. EEG microstate analysis during NREM 3 found preserved prototypical generators but abnormal temporal dynamics, including altered transitions between microstates C and D and between A and B. The findings suggest that understanding RISP requires examining processes beyond REM, and microstate dynamics may serve as functional biomarkers.

Study at a glance

Abstract

The pathophysiology of recurrent isolated sleep paralysis (RISP) has yet to be fully clarified. Very little research has been performed on electroencephalographic (EEG) signatures outside RISP episodes. This study aimed to investigate whether sleep is disturbed even without the occurrence of a RISP episode and in a stage different than conventional REM sleep. 17 RISP patients and 17 control subjects underwent two consecutive full-night video-polysomnography recordings. Spectral analysis was performed on all sleep stages in the delta, theta, and alpha band. EEG microstate (MS) analysis was performed on the NREM 3 phase due to the overall high correlation of subject template maps with canonical templates. Spectral analysis showed a significantly higher power of theta band activity in REM and NREM 2 sleep stages in RISP patients. The observed rise was also apparent in other sleep stages. Conversely, alpha power showed a downward trend in RISP patients' deep sleep. MS maps similar to canonical topographies were obtained indicating the preservation of prototypical EEG generators in RISP patients. RISP patients showed significant differences in the temporal dynamics of MS, expressed by different transitions between MS C and D and between MS A and B. Both spectral analysis and MS characteristics showed abnormalities in the sleep of non-episodic RISP subjects. Our findings suggest that in order to understand the neurobiological background of RISP, there is a need to extend the analyzes beyond REM-related processes and highlight the value of EEG microstate dynamics as promising functional biomarkers of RISP.