Early EEG findings in hypoxic-ischemic encephalopathy predict outcomes at 2 years

We examined the evolution of electroencephalographic (EEG) changes after hypoxic injury.

Continuous, multichannel, video-EEG was recorded for term infants with hypoxic-ischemic encephalopathy, from <6 hours to 72 hours after delivery. One-hour segments at 6, 12, 24, and 48 hours of age of the EEG were analyzed visually, and neurologic outcome was assessed at 24 months.

Forty-four infants completed neurodevelopmental follow-up. Of those, 20 (45%) had abnormal outcomes. The EEG grade assigned correlated significantly with outcome. EEG abnormalities improved with time, with the worst EEG grade seen on the earliest recording in all cases. The best predictive ability was seen at 6 hours of age (area under the receiver operator characteristic curve: 0.958 [95% confidence interval: 0.88-1.04]; P = .000). Normal/mildly abnormal EEG results at 6, 12, or 24 hours had 100% positive predictive values for normal outcomes and negative predictive values of 67% to 76%. By 48 hours, many of the EEG findings had improved significantly. This led to the positive predictive value of abnormal EEG results being greater at 48 hours (93%), with a concurrent negative predictive value of 71%. EEG features that were associated with abnormal outcomes were background amplitude of <30 microV, interburst interval of >30 seconds, electrographic seizures, and absence of sleep-wake cycling at 48 hours.

Early EEG is a reliable predictor of outcome in HIE. A normal or mildly abnormal EEG results within 6 hours after birth were associated with normal neurodevelopmental outcomes at 24 months.