Periods of Activity and Quiescence in the Premature EEG

Abstract

Periods of inactivity or quiescence (Q) alternating with periods of activity (A) were measured in 184 prematures, compared to 277 full-term infants. Q periods appeared in all prematures up to 32 wks conceptional age (CA), and then the incidence curve linearly fell to near-zero (8 %) at term. The A periods increased from 2 % of the recording time at 24 wks to 80 % at 34 wks. Other measures of central tendency showed an increase in A or A+Q with age until 34 wks and a decrease in Q until 29 wks. Except when using percentile and mean values which show great variability, a pair of A and Q values are usually independent of each other. On the other hand, high A values often precede or follow the highest A's and high Q's similarly are often grouped together. Q and A periods were studied with regard to clinical outcome. Patients who later expired in the neonatal period showed no increase in A with age, in contrast to living patients showing a significant increase with age. The longest durations of Q (after A) and shortest durations of A (after Q) were seen in patients who later expired followed by living patients with major sequelae, and then by normals or those with only minor sequelae. The clinical categories of major vs. minor sequelae were also different with regard to the longest A period measured. For prognostic purposes, curves (based on % of recording time with A) are presented that allow a successful prediction of survival or death and also predict generally a good or poor prognosis. Neurophysiological, neuroanatomical and neuropathological implications are discussed.

Key words

EEG - EEG in prematures - EEG activity and quiescence