Dysmature EEG pattern in EEGs of preterm infants with cognitive impairment: maturation arrest caused by prolonged mild CNS depression.

The significance of mild sustained brain injury in the pathogenesis of perinatal brain damage was investigated using serial EEG recordings performed on 102 early preterm infants surviving beyond 2 years of age. Sixteen infants (16%) elicited mild depression of background EEG activities in the neonatal period. Of nine infants with mild depression of prolonged duration (more than 3 weeks), five (56%) were diagnosed as having cognitive impairment in the follow up study. Four showed no signs of cerebral palsy, while one had cerebral palsy. The infants with cognitive impairment showed mild prolonged depressions in background EEG activities in the early neonatal period and dysmature EEG patterns in the late neonatal period. They also showed maturation arrest in EEG patterns during prolonged mild depression of background EEG activities. In addition to strong sudden depression of CNS causing deep white matter injury and motor impairment, prolonged mild depression is another mode of brain injury in early preterm infants which can induce future cognitive impairment.