Background and Aims Arousal from sleep is an important survival mechanism. During sleep-EEG monitoring in healthy term infants we observed that the majority had frequent spontaneous jerky movements (SJM), resembling a Moro reflex, during quiet sleep (QS) followed by periods of marked EEG attenuation. This phenomenon was considered a spontaneous cortical arousal (SpCA). In this study we describe and quantify the observed phenomenon, and investigate factors that influence it.
Methods Video-EEG recordings of healthy term infants, aged 1 to 36 hrs, were examined for the presence of SpCAs associated with SJMs. Bursts of EEG activity associated with a SJM (BSJM) and subsequent lower voltage periods (LVSJM) of EEG attenuation were identified and labelled on each recording. These were compared to a similar pattern of bursts (B) and lower voltage (LV) periods of “normal” Tracé Alternant (TA) with no SJMs. An arousal index (AIQS) was calculated as the number of SpCAs per hour of QS. Factors that influenced the AIQS were investigated.
Results Eighty-seven video-EEGs were analysed. SJMs occurred during bursts of TA and were followed by significant EEG amplitude attenuation (median amplitude of LVSJM = 7.8 µV versus LV=12.8 µV, p<0.001).
The median AIQS was 23.9. A significant negative correlation was observed between the AIQS and infant’s birth weight (p=0.015). A trend towards a lower AIQS was observed with increasing gestational age (p=0.06).
Conclusion SJMs followed by periods of EEG attenuation signify SpCAs in healthy term newborn infants and may represent a normal developmental phenomenon.