Association Between Early EEG Background and Outcomes in Infants With Mild HIE Undergoing Therapeutic Hypothermia

Hypoxic-ischemic encephalopathy (HIE) occurs in 1-4:1000 live births. Although neonates with moderate-severe HIE have been studied over several decades, newborns with mild HIE remain understudied, including seizure occurrence, electroencephalography (EEG) characteristics, and outcome. We conducted a retrospective cohort study of neonates ≥35 weeks of gestation with mild HIE who underwent therapeutic hypothermia to correlate the early EEG background pattern with clinical course and outcomes. Of the included 29 neonates, 10 infants had a moderately to severely abnormal EEG background and 19 had either a normal or a mildly abnormal background. Those with moderately to severely abnormal background also had more multiorgan dysfunction (90% vs 42%, P = 0.02) and a higher incidence of subdural and intraventricular hemorrhages (80% vs 26%, P = 0.02). The overall seizure incidence was 20.7% and was significantly higher in newborns with more severely abnormal background compared to neonates with less abnormal background (50% vs 5%; P = 0.01; relative risk, 9.5; 95% confidence interval, 1.28-70.6). Seizure onset was between 11 and 63 hours of life. Regardless of the EEG background pattern, seizures were brief with an overall low seizure burden. None of the newborns with normal or mildly abnormal background had a new onset of seizures after 24 hours of recording or developed epilepsy during infancy. In neonates with mild HIE, early moderately to severely abnormal EEG background is common and strongly associated with an increased risk for seizures.