Neonatal seizures: characteristics of EEG ictal activity in preterm and fullterm infants

The neonatal EEG remains one of oldest, yet most valuable, diagnostic and prognostic tests in neonates. The goals of this study were to determine the relationships between the morphology, frequency, and distribution of ictal discharges in the neonatal EEG with age, EEG background activity, and etiology. A total of 156 ictal events were evaluated in 11 preterm (PT) and 25 fullterm (FT) infants. Most of the infants had severe abnormalities of background activity although ictal discharges occurred on both normal and abnormal backgrounds. There was a trend for a closer relationship between behavioral changes during the electroencephalographic seizure when the background activity was normal or moderately abnormal than when background activity was severely abnormal. In both PT and FT infants, the most common site of seizure origin was the temporal lobe. FT infants commonly had sharp waves, spikes, sharp and slow waves, and spike and slow waves at the onset of the ictus while rhythmic delta activity was most common in the PT infants. PT infants typically had a regional onset to the ictus whereas FT infants most frequently had a focal onset. Duration of the ictal events was similar in PT and FT infants and a change in morphology or frequency of the discharges was common during propagation of the ictal discharges in both age groups. There was not a clear relationship between onset, morphology, frequency, or propagation patterns and etiology in either the PT or FT infants. Our results demonstrate that while the type of ictal discharge is related to gestational age, there is a rich variety in the onset, morphology, and frequency of the ictal discharges in both PT and FT infants and that neonatal ictal patterns lack a close correlation with underlying pathology.