Seizures in Pre-term Infants Less than 29 Weeks: Incidence, Etiology, and Response to Treatment

Abstract

Introduction. Seizures are neurological emergencies with short- and long-term adverse effects in pre-term infants. They may present with or without abnormal movements (clinical versus subclinical). Thus, the true incidence of seizures may be under-reported. Current research indicates that most seizures occur in the first few days of life, are associated with intraventricular hemorrhage (IVH), and show low response to anticonvulsant drugs. The purpose of this study was to evaluate incidence, etiology, clinical antecedents, mortality, and response to treatment of seizures in extremely pre-term infants.

Methods. This is a retrospective cohort study of pre-term infants < 29 weeks gestation from January 2011 to December 2013. Presence or absence of seizure was the outcome. Data extraction included demographics, medications, co-morbidities, mortality, and details of seizures. A multivariable prediction model was developed to evaluate risk for seizures.

Results. Analysis included 269 pre-term infants. Incidence of EEG-confirmed seizures was 40% (108/269); 49% were clinical and 51% were subclinical. Seizures occurred in 72% of infants ≤ 24 weeks, 57% of those 25-26 weeks, and 23% of those 27-28 weeks. Most seizures (85%) occurred after day eight of life. Mortality was 14% in those with seizures versus 5% in those without (p = 0.019). The model showed seizures were associated significantly with gestational age and medications, while controlling for sex, APGAR score, and co-morbidities, including IVH. At discharge, anticonvulsants were continued in 66% (72/108) of infants with seizures.

Conclusion. The incidence of seizures was highest in infants born most premature. Contrary to previous research, nearly two-thirds of pre-term infants with seizures did not have IVH or cystic periventricular leukomalacia; apnea of prematurity was a common presentation of subclinical seizures; and the majority of treated infants responded to Phenobarbital. These findings need be explored in future research.