Disorganized patterns: chronic-stage EEG abnormality of the late neonatal period following severely depressed EEG activities in early preterm infants.

EEG recordings were performed within 72 hours following the birth of 55 preterm infants with a gestational age of less than 29 weeks. Seventeen infants (31%) manifested moderately to severely depressed EEG activities during this period. Eight of the infants died within a few days after birth, and 9 survived. We recorded EEGs from the surviving infants serially throughout the neonatal period, and evaluated EEG findings in the recovery phase following depressed EEG activities. At 1 to 3 weeks after birth, EEGs revealed an abnormal morphology of background activities in 8 of 9 cases; this was also true of the EEGs of 6 cases at 4 weeks or more of postnatal age. The latter 6 cases demonstrated deep white matter injury on cranial ultrasonography, and all of them later developed cerebral palsy. Based on the foregoing, EEG findings of early preterm infants in the late neonatal period are considered a useful means to detect deep white-matter injury and to allow neurological prognosis.