Neonatal seizures: background EEG activity and the electroclinical correlation in full-term neonates with hypoxic-ischemic encephalopathy. Analysis by computer-synchronized long-term polygraphic video-EEG monitoring.
Between 1994 and 2000, 30 full-term newborns affected by seizures secondary to hypoxic-ischemic encephalopathy, underwent computerised, polygraphic, video-EEG recordings during the first 48 hours of life, in our neonatal intensive care unit. In this longitudinal study, recordings lasted an average of 10.5 hours. We studied EEG ictal discharges that lacked a clinical correlate, the semeiotics, and the electroclinical correlation during seizures, by reviewing the time-synchronised, video-EEG recordings obtained during these six years. The aim of this investigation was to evaluate the relationship between background EEG activity and the electroclinical correlation or dissociation of the seizures. When background activity was depressed and undifferentiated, the seizures were characterised by the electroclinical dissociation except in instances of focal tonic seizures. With all other background patterns, seizures were invariably accompanied by the electrical correlate, the only exception being ocular signs and oral-buccal-lingual movements, which occurred both with and without paroxysmal discharges. Ocular signs and oral-buccal-lingual movements were very frequent and were observed with all patterns of background activity. Only on one occasion were they the sole clinical expression of seizures. In our patients, the electroclinical dissociation was constant only if background EEG activity was depressed and undifferentiated. The constant electroclinical dissociation of seizures was closely correlated with the type of background activity, which, in turn, is indicative of severe cerebral damage. (Published with videosequences.)