REM sleep without muscle atonia (stage 1-REM) and its relation to delirious behavior during sleep in patients with degenerative diseases involving the brain stem.

Nocturnal sleep was examined in 12 patients with degenerative diseases involving the brain stem and in 2 patients with late cerebellar cortical atrophy (LCCA). A peculiar sleep state, characterized by the concomitant appearance of a low-voltage mixed frequency EEG, rapid eye movements (REMs) and tonic EMG in mental muscles, repeatedly appeared during nocturnal sleep in all of the 12 patients with degenerative diseases involving the brain stem and it was called stage 1-REM after Tachibana et al. In 8 of the 12 patients, delirious or oneiric behavior appeared during, or soon after, the episodes of stage 1-REM. Inner experiences reported by one of the subjects well corresponded to his behavior during the episode of stage 1-REM. Stage 1-REM was not observed during nocturnal sleep of the patients with LCCA. These results indicate that a degenerative lesion in the brain stem induced stage 1-REM and delirious behavior during nocturnal sleep through abolishing muscle atonia of REM sleep and causing dissociation of the functional components characterizing REM sleep.