564 A Comparison of Electrographic Seizure Characteristics in Term Neonates with Hypoxic-Ischaemic Encephalopathy and Focal Cerebral Lesions

Background and aims: In term neonates with seizures, it is important to distinguish between hypoxic-ischaemic encephalopathy (HIE) and focal cerebral lesions as soon as possible to aid clinical intervention. We compared seizure onset, duration and morphology in term neonates with HIE and focal cerebral lesions. Methods: Term neonates with perinatal distress or abnormal neurology were recruited. Continuous multichannel video-EEG recording within 72 hours of birth was performed. Results: In 26 term neonates recruited, 13 had EEG seizures [HIE(n=5); focal arterial infarction(n=3); focal intraparenchymal haemorrhage(n=2); unknown pathology(n=3)]. EEG recordings commenced at a median age(range) of 6.0(1.8-59.2) hours. The median recording duration was 61.4(24.0-122.1) hours. The median seizure onset occurred earlier in HIE than in focal cerebral lesions [13.4(8.3-42.2) hours vs 38.6(18.0-59.7) hours]. The median total seizure burden per neonate with HIE was higher than in focal cerebral lesions [212.4(55.2-640.2) minutes vs 112.9(12.9-189.1) minutes]. Seizures were more frequent in HIE than in focal cerebral lesions (577 vs 113 events). Two neonates with severe HIE also had status epilepticus. Electrographic seizures in neonates with focal cerebral lesions originated from the site of injury displayed a characteristic spike wave focal morphology with minimal frequency change. Variable seizure morphologies and frequencies were seen in HIE. The background EEG activity in focal cerebral lesions was well preserved, though asymmetries were evident. The background EEG activity in HIE showed global abnormalities. Conclusions: The contrasting seizure characteristics in neonates with HIE and focal cerebral lesions may prove useful for automated seizure detection systems and guide appropriate management strategies.