Neonatal epilepsy and underlying aetiology: to what extent do seizures and EEG abnormalities influence outcome?

Neonatal seizures constitute the most common and distinctive sign of neurological dysfunction in the first weeks of life and reflect a wide variety of underlying central nervous system disorders. Acute symptomatic seizures occur more often during the neonatal period than at any period of life and are associated with adverse long-term neurodevelopmental sequelae and an increased risk of post-neonatal epilepsy. The improvements of neonatal care in the last decades have changed the spectrum of insults to which the immature brain is exposed and facilitated a decrease in mortality of newborns with seizures. However, the prevalence of long-term morbidity in survivors remains unchanged. Whereas aetiology is presumed to be the main predictor of long-term outcome in neonates with seizures, there is converging evidence that specific electroencephalographic (EEG) abnormalities are related to unfavourable outcomes. Interictal EEG abnormalities, especially concerning background activity patterns, thus constitute a major indicator of disease severity and predictor of outcome, while the added value of sequential EEG assessments is so far controversial. Moreover, experimental as well as clinical studies of hypoxic-ischaemic encephalopathy support the notion that recurrent seizures may amplify injury to the developing brain beyond that associated with the underlying aetiology, thus justifying antiepileptic drug treatment. To date, unresolved issues in seizure detection and classification, in addition to the significant variation in gestational ages and brain insults of neonates, still impede clinical research of neonatal seizures. The wider use of long-term EEG or amplitude integrated EEG monitoring may prove crucial for timely neonatal seizure identification and treatment initiation, and thus ultimately improve outcome.