Spectral electroencephalography profile of rapid eye movement sleep at sleep onset in narcolepsy type 1.

Abstract

The sleep-onset rapid eye movement (REM) period (SOREMP), the hallmark of narcolepsy, may be a specific state and not the simple anticipation of REM sleep. We analyzed the electroencephalographic spectral content in untreated patients with narcolepsy type 1 (NT1) during the sleep-onset period (SOP) and during nocturnal REM sleep in two consecutive nocturnal recordings from 31 patients with NT1 (mean age 34 ± 15 years, 18 males) and a single nocturnal recording from 36 controls (mean age 38 ± 13 years, 21 males). The SOP was defined as the first 10 min starting at the beginning of the first epoch of any sleep stage, and further divided into two consecutive 5-min periods (SOP-1 and SOP-2); 1 min of artifact-free quiet wakefulness after lights-off was identified as well as 5 min of REM sleep in the middle of the night and another 5 min during the last REM sleep period. Electroencephalographic spectral analysis was performed using the C3/A2 channel. The SOP-1 and, more strikingly, SOP-2 had significantly less delta and sigma activity in patients with NT1 in the SOREMP condition versus both controls and patients with NT1 without SOREMP. SOP-2 also showed less theta and alpha activity. Conversely, sigma and beta activity were more represented during SOREMP compared with the nocturnal REM period in patients with NT1. The analysis of the SOP supports the concept that SOREMP is a different state compared with both nocturnal REM sleep and non-REM sleep onset.