Electrographic Seizures in Preterm and Full-Term Neonates: Clinical Correlates, Associated Brain Lesions, and Risk for Neurologic Sequelae

Abstract

Electrographically confirmed seizures in preterm and term neonates were compared with respect to clinical correlates, incidence, associated brain lesions, and risk for neurologic sequelae. Over a 4-year period, 92 neonates from a neonatal intensive care unit population of 4020 admissions at a large obstetric hospital with 40845 livebirths had electrographically confirmed seizures. Sixty-two neonates were preterm and 30 were full-term for gestational age. Chi-square calculations were used to compare the two groups. While the incidence of seizures for all neonates admitted to a neonatal intensive care unit was 2.3%, outborn neonates were more likely to have seizures than inborn neonates. Preterm neonates of ≤30 weeks gestational age had a seizure frequency of 3.9%, which was significantly higher than that of older preterm neonates and full-term neonates. Clinical criteria contemporaneous with electrographic seizures were noted in only 28 (45%) of 62 preterm, and 16 (53%) of 30 full-term neonates. Subtle seizures coincident with electrographically confirmed seizures were the most predominant clinical type for both term and preterm neonates (71% and 68%, respectively). The distribution of clonic, myoclonic, and tonic seizures was also similar for both groups. Autonomic signs coincident with electrographically confirmed seizures (ie, blood pressure, heart rate, oxygenation, respiration changes) were more frequently observed in preterm than full-term neonates with subtle seizures; 7 (37%) of 19 compared with 1 (6%) of 16. Electrical seizures without clinical correlates were noted more frequently than electroclinical seizures for both populations. Fifteen (54%) of 28 of the preterm coincident group and 10 (63%) of 16 of the full-term group had isolated electrographic seizures without clinical seizures on the same or other records, in addition to exhibiting electroclinical seizures. More preterm neonates had a later onset of seizures (>48 hours of life) than term neonates (53% vs 13%, respectively). Ischemic brain lesions were noted in 23 (77%) of 30 of full-term compared with 24 (39%) of 62 preterm neonates. Intraventricular hemorrhange with ventriculomegaly or intraparenchymal involvement was seen in 26 (45%) of 72 preterm neonates compared with 1 (3%) of 30 full-term neonates. Mortality was greater in the preterm than in the term populations, 36 (58%) of 52, compared with 10 (30%) of 30, and a normal outcome was documented in 9 (25%) of 36 preterm neonates compared with 12 (60%) of 30 full-term survivors. However, the incidence of surviving preterm neonates epilepsy developed was the same as the fullterm survivor group at a mean age of 6 ½ years. While the electroclinical expression of neonatal seizures occurs in both preterm and full-term populations, clinical correlates, incidence, etiologic factors, and outcome factors differ between the two populations.