To evaluate whether features of the early electroencephalographic (EEG) background could guide the optimal duration of continuous video EEG monitoring for seizure detection in newborn infants treated with therapeutic hypothermia for hypoxic ischemic encephalopathy (HIE).

Retrospective cohort study of 114 consecutive infants treated with therapeutic hypothermia for moderate to severe HIE at a level IV neonatal intensive care unit (NICU) between 2012 and 2018. All infants were monitored with continuous video EEG through cooling and rewarming. Archived samples from the first 24 hours of these EEG traces were reviewed systematically and classified by background characteristics.

Electrographic seizures occurred in 56 of the 114 infants (49%). Seizure onset was within the first 24 hours after initiation of continuous video EEG in 49 if these 56 infants (88%), between 24 and 48 hours in 4 infants (7%), and >72 hours in 3 infants (5%). Infants with a normal or mildly abnormal EEG background either had seizure onset within the first 24 hours or never developed seizures. Four patients with seizure onset between 24 and 48 hours had markedly abnormal EEG backgrounds. The 3 patients with seizure onset beyond 72 hours had moderate or severely abnormal early continuous video EEG backgrounds.

The use of early continuous video EEG background categorization may be appropriate to guide the duration of continuous video EEG for infants with HIE treated with therapeutic hypothermia. Some infants may reasonably be monitored for 24 hours rather than throughout cooling and rewarming without a significant risk of missed seizures. This could have significant implications for continuous video EEG resource utilization.