The clinical significance of seizures in critically ill young infants requiring intensive care.

The aetiology, severity of systemic and biochemical abnormalities, seizure duration, EEGs and CT scans have been reviewed in previously normal young infants with an acute critical illness occurring after the first week of life; none of whom had birth asphyxia. Findings were related to outcome in an attempt to evaluate the significance of seizures during the acute phase of severe illness. In three years seizures occurred in 54/251 (22%) young infants requiring ventilatory support. In these patients the acute illness was most commonly infection and encephalitis/encephalopathy. Twenty-one died, 24 had good or moderate outcome and 9 poor outcome (follow-up 6-27 months). The outcome was not directly related to diagnosis, but to systemic and biochemical changes, the most important being severe hypotension (40/54). After correction of these factors, in survivors, increasing number of days over which seizures occurred during the acute phase of illness was related to worsening outcome (tau(c) = 0.66, p less than 0.0001). In many of these patients one of three abnormal low density changes (generalized, boundary zone and focal) were seen on CT scan and were not uncommonly associated with focal/multifocal clonic seizures and characteristic type, distribution and evolution of EEG discharge. In the 45 patients with EEGs from presentation, severity of encephalopathy assessed by predominant background EEG activity was most closely related to outcome, irrespective of aetiology and seizures. There was a significant relationship between graded severity of background EEG activities and outcome both in the initial and serial recordings (tauB = 0.70, p less than 0.0001 and 0.75, p less than 0.0001 respectively). Seizures are a common occurrence in the previously well young infant with an acute critical illness necessitating intensive care. Prompt recognition and treatment may influence outcome in patients with a potentially reversible encephalopathy. However, in many patients seizures reflect severe, often multifactorial cerebral insult with variable morphological changes, EEG patterns and clinical outcome.