PURPOSE: Studies conducted on both animal and adult human subjects have demonstrated that a decrease in cerebral blood flow (CBF) causes cerebrocortical dysfunction resulting in an abnormal electroencephalogram (EEG). Although it is assumed that in premature infants with patent ductus arteriosus (PDA), the shunt will decrease CBF and alter the cerebrocortical function thus resulting in an abnormal EEG, this has yet to be firmly established. This comparative study, therefore, measures EEG as effected by CBF before and after PDA closures. Furthermore, in order to observe the effect of PDA on CBF and EEGs, the results were compared against a control group made up of premature infants without PDA. METHOD: All subjects were premature infants admitted to the neonatal intensive care unit of Chungbuk National University Hospital between February and August of 1997, were under gestational age (GA) 36 weeks, and weighed less than 2 kilograms: PDA group (group I consisted of 8 with PDA and respiratory distress syndrom (RDS); group II of 5 with PDA but without RDS) and Control group (group III of 6 without PDA but with RDS; group IV of 12 with neither PDA nor RDS). Studies were performed on the third and seventh day after birth and continued weekly throughout the period of study. Using Acuson 128XP/10c Doppler Echo cardiography, we measured the peak systolic velocity (PVS), the end-diastolic velocity (EDV) and the area under the velocity curve (AUVC) of the anterior cerebral artery (ACA), the blood flow of the left carotid artery and the descending aorta, calculated the LA/Ao ratio and conducted EEG's. RESULTS: 1) Birth weight and gestational age There was a significant difference between group I and group IV. However, when contrasting the two control groups overall, we found no significant variation. 2) In the PDA group, the infants were treated as follows: four infants were performed PDA ligations and seven were administrated indomethacine, resulting in 5 successful closures. Two infants had PDA which closed naturally without any treatment.3) PSV, DV, AUVC in the PDA group before and after closureThe incidence of decreased cerebral blood flow tended to increase after the PDA closure; however, the variation was not significant. In the groupes with RDS, on the other hand, the increase of CBF was significant after treatment, especially in group III.4) Incidence of abnormal EEGsThe preliminary EEG was abnormal for the above infants, with the background EEG appearing as suppressed or sharp and spike wave discharges. There was no significant difference in the results of the two groups and all EEG's were normalized in subsequent examinations. CONCLUSION: The decreased cerebral blood flow in premature infants with PDA increased following closure of the shunt; however, this increase was not significant. In groupes with RDS, the decreased cerebral blood flow significantly increased as the RDS improved, especially in group III. Nonetheless, despite the observed changes in CBF, we were unable to detect a corresponding change in the EEGs of the newborns in this study.