Positive slow waves in the EEG of premature infants between 24 and 36 weeks of conceptional age

Objective The aim of this prospective and longitudinal study was to characterize EEG patterns during the first weeks of life in extremely premature infants. Methods Twenty-five extremely premature infants were included and weekly EEG recordings were obtained between 24 and 36 weeks of conceptional age (CA). Results Central (rolandic) positive slow waves (CPSW) were found to be the most reliable and characteristic pattern. CPSWs were frequent at 24 weeks CA and progressively diminished and disappeared around 34 weeks CA. CPSWs appeared isolated or in sequences, they occurred during periods of continuous or discontinuous EEG activity, during bursts or during intervals of discontinuous activity, and unilaterally or bilaterally. Temporal positive slow waves and theta rhythms occurred less often and did not decrease as a function of CA. In addition, the amount of discontinuity progressively decreased until 36 weeks CA. The duration of bursts stayed constant, while inter-burst intervals decreased as a function of CA. Conclusions Central positive slow waves are characteristic features of the EEG in the extremely premature infant. Significance The presence of CPSWs and their progressive disappearance until 34 weeks CA may represent a maturational marker in the EEG.