Abstracts

Rationale: Rationale: Therapeutic hypothermia (TH) is standard of care for newborns with hypoxic-ischemic encephalopathy (HIE). While seizures during TH are considered an important risk factor for brain injury, little is known about the prognostic value of EEG background and evoked potentials in this critical population. Aim: To describe the association of EEG background and evoked potentials with radiological and neurodevelopmental outcome in newborns with HIE treated with TH. Methods: Methods: From March 2009 to December 2013, we prospectively studied 40 consecutive newborns treated with TH for HIE who were monitored with EEG during hypothermia and rewarming and seen in our follow-up program. Background EEG pattern in the first 24 hours of recording was analyzed and classified into 5 patterns according to criteria published by Nash et al., Neurology 2011 (normal, excessively discontinuous, depressed and undifferentiated, burst-suppression, and extremely low-voltage and unreactive pattern). MRI was performed shortly after rewarming and repeated after 6 months. Brain injury was scored as "none/mild" or "moderate/severe" (Barkovich et al., AJNR, 1998). Neurodevelopmental outcome was assessed at 6 months of age using neurological evaluation and Griffiths Mental Development Scale (GMDS). Results: Results: 37 newborns (19 males) completed a full 72 hours TH with continuous video-EEG monitoring. Early EEG was normal in 28 (70%), excessively discontinuous in 6 (15%), low voltage and undifferentiated in 4 (10%), and extremely low voltage and unreactive in 2 (5%). In the 4 patients with an initially depressed and undifferentiated pattern, EEG turned into a burst-suppression pattern within the first 24 hours of recording. EEG seizures were present in 19/40 newborns (47%). Five patients died. Three of them died during TH or immediately before MRI, including both newborns with extremely low voltage and unreactive early EEG pattern, and the one with initially a low voltage/undifferentiated pattern that evolved into burst suppression and status epilepticus. One patient died after the neonatal period. Four patients were lost to follow up. The early MRI and neurodevelopmental outcome of the remaining 31 patients in correlation with early EEG is presented in the table. Conclusions: Conclusions: Severely abnormal EEG patterns, including burst-suppression and extremely low-voltage and unreactive, correlate with severe pattern on MRI and poor outcome (death or severe neurocognitive impairment). A normal EEG pattern in the first 24 hours of recording was associated in most patients with normal MRI and normal neurolodevelopmental outcome. Only one patient presenting with initially normal EEG showed severe brain MRI injury. Status epilepticus but not isolated seizures were associated with severe MRI injury and death or severe neurodevelopmental impairment.