Hypersynchronous delta waves and somnambulism: brain topography and effect of sleep deprivation

STUDY OBJECTIVES: Hypersynchronous delta activity (HSD) is usually described as several continuous high-voltage delta waves (> or = 150 microV) in the sleep electroencephalogram of somnambulistic patients. However, studies have yielded varied and contradictory results. The goal of the present study was to evaluate HSD over different electroencephalographic derivations during the non-rapid eye movement (NREM) sleep of somnambulistic patients and controls during normal sleep and following 38 hours of sleep deprivation, as well as prior to sleepwalking episodes. DESIGN: N/A. SETTING: Sleep disorders clinic. PATIENTS: Ten adult sleepwalkers and 10 sex- and age-matched control subjects were investigated polysomnographically during a baseline night and following 38 hours of sleep deprivation. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: During normal sleep, sleepwalkers had a significantly higher ratio of HSD over the time spent in stage 2, 3 and 4 on frontal and central derivations when compared with controls. Sleep deprivation resulted in a significant increase in the ratio of the time in HSD over the time in stage 4 on the frontal lead in both groups and on the central lead in controls. There was no evidence for a temporal accumulation of HSD prior to the episodes. CONCLUSIONS: HSD shows a clear frontocentral gradient across all subjects during both baseline and recovery sleep and has relatively low specificity for the diagnosis of NREM parasomnias. Increases in HSD after sleep deprivation may reflect an enhancement of the homeostatic process underlying sleep regulation.