Sleep-wake cycles in preterm infants below 30 weeks of gestational age. Preliminary results of a prospective amplitude-integrated EEG study.

In the newborn, presence of sleep-wake cycles indicates integrity and maturity of the central nervous system. By spectral EEG analysis and polygraphic recordings subtle variations of EEG background activity and behavioural patterns corresponding to early sleep-wake cycles have been found in preterm infants as young as 27 weeks of gestation. The emergence of sleep-wake cycles at early gestational ages may have a positive predictive value for long-term neurological outcome. Sleep-wake cycles and their significance for later outcome have not been studied in very preterm infants so far. Accordingly, we prospectively investigated maturational changes of EEG activity and sleep-wake cycles in preterm infants below 30 weeks of gestational age using the Cerebral Function Monitor, an amplitude-integrated EEG. We present preliminary data on the emergence of sleep-wake cycles in preterm infants from this ongoing study. Of 100 infants enrolled during a 1-year period, 38 infants without neurological complications were included in the reference group. In this group (mean gestational age 27 weeks), we observed cyclical variations of EEG background activity resembling early sleep-wake cycles at a mean gestational age of 28 weeks and a median postnatal age of 6 days. It is hypothesised that these cyclical variations of EEG background activity may represent switches between thalamo-cortical and neo-cortical pattern generators and indicate integrity of central nervous system function. Amplitude-integrated EEG may thus serve as a useful noninvasive test for brain function in preterm infants.