NEUROPHYSIOLOGICAL ASSESSMENT OF BRAIN-FUNCTION AND MATURATION .2. A MEASURE OF BRAIN DYSMATURITY IN HEALTHY PRETERM NEONATES

Severe brain disorders can be expressed as markedly abnormal encephalo pathic EEG patterns in neonates who are usually neurologically depress ed, with abnormal levels of reactivity and tone, This symptomatic grou p is now a minority of medically ill neonates as a result of more vigo rous fetal and neonatal resuscitative efforts, Most neonates alternati vely express brain dysfunction as more pervasive alterations in EEG-sl eep organization or maturation, usually in the absence or after resolu tion of abnormal clinical signs, One form of dysfunction is expressed as neurophysiologic dysmaturity, Brain dysmaturity may reflect altered rates of development in infants who sustained prenatal or postnatal s tresses, as discussed in the first part of this review, We now summari ze our findings of dysmature EEG-sleep development at conceptional ter m ages in an asymptomatic preterm cohort during a prolonged extrauteri ne period before discharge from the nursery, Dysmaturity of EEG-sleep function was expressed as delayed and/or accelerated physiologic behav iors, as compared with behaviors expected for the conceptional age, Dy smature brain function at conceptional term ages was also associated w ith poorer neurodevelopmental performances at 12 and 24 months of age, Neuronal pathways which subserve state-specific neurophysiologic beha viors will functionally adapt to stress by either slowing or accelerat ing neurological maturation, Through ontogenetic brain adaptation, whi ch continues during postnatal development, a balance is maintained bet ween the needs of the present developmental stage and anticipated need s during subsequent stages of maturation, How medical complications an d environmental influences interact to promote greater brain dysmaturi ty in the neonate is still unknown, EEG sleep study can serve as a use ful neurophysiologic screening procedure for the child suspected of ha ving a subclinical presentation of an emerging static encephalopathy; longitudinal studies will then document deviations from expected ontog eny in the vulnerable child who is later stressed by environmental and socioeconomic factors. (C) 1997 by Elsevier Science Inc. All rights r eserved.