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Waveform Window #38: EEG Stages of Neonatal Hypoxic Ischemic Encephalopathy: From Background Suppression to Resolution of Neonatal Seizures

EEG testing is frequently ordered when there is a clinical suspicion of seizures or when a patient is placed on a hypothermia protocol following anoxic brain injury. Hypoxic ischemic encephalopathy (HIE) is a common indication for neonatal EEG recording in the neonatal intensive care unit, as seizures have been reported in as many as 26% of neonates with HIE (Shellhaas et al. 2011; Tsuchida et al. 2013; Massaro et al. 2015). Overall seizure burden has been shown to be significantly reduced in neonates receiving therapeutic hypothermia for HIE (Boylan et al. 2015); therefore, EEG is very important during the cooling protocol and is more critical in neonates as they are often sedated or on paralytic medication, which may increase the risk for undetected subclinical seizure activity. At the same time, there is a particularly high risk of overdiagnosis in critically ill neonates, with some benign movements mislabeled as seizures (Orivoli et al. 2015). For these reasons, accurate diagnosis generally requires the use of continuous EEG monitoring (Boylan et al. 2015). Neonatal seizures related to HIE have a mean onset around 13–24 hours postpartum, with a maximum seizure burden at around 19 hours postpartum (Lynch et al. 2015). Therefore, it is of utmost importance that continuous EEG monitoring be started as soon as possible. However, in the very early stages of HIE, neonatal seizures are often missed for various reasons, including the lack of uniform availability of EEG technologists to perform the recording. This report describes a neonate with HIE in which we recorded all of the stages of seizure development during the initial week of neonatal HIE.