Brain Lesions and Sleep Onset REM Periods in Routine EEG

Rapid eye movement (REM) sleep usually occurs after 90 minutes of consolidated sleep. Sleep onset REM Period (SOREMP) occurs when REM sleep latency is less than 15 minutes. It is a rare phenomenon, mostly associated with sleep deprivation and narcolepsy. Patients undergoing routine Electroencephalogram (EEG) studies for other reasons than sleep disorders can occasionally have SOREMPs. The objective of this study was to determine the frequency of patients with SOREMPS in routine EEG and to evaluate its possible etiologies. This is a retrospective study of all EEGs performed in the EEG/sleep laboratory from Hospital de Santa Maria-Lisbon, during last 6 years. EEGs with REM sleep were selected. Both ambulatory and EEGs performed in the acute setting were included along with Data for cranial CT-scan or MRI. In 6 years, only 8 patients had SOREMPs, among them, it was possible to obtain cranial MRI or CT-scan in 7 patients (one died). One patient with a psychiatric disorder, showed no lesions on MRI. The other 6 had lesions involving brainstem (n=5) or diencephalon (n=1). The etiologies were inflammatory (2), vascular (3) and infectious (1). All lesions except one were acute. These results suggest that when SOREMPs are detected, lesions involving REM sleep structures should be searched for.