Abstracts

Rationale: Hypoglycemia is commonly seen in term infants with neonatal encephalopathy (NE), especially of hypoxic-ischemic (HI) origin. The objective of this study was to determine if any radiologic features of hypoglycemia are associated with seizures in the neonatal period or development of epilepsy in later childhood.Methods: All term newborns (>36 weeks gestation) with encephalopathy seen at BC Children s and Women s Hospital between 2004 and 2012 were included in this retrospective study. Standardized MR imaging was performed on day 3 of life ( 12 hours) or as soon as infants were re-warmed after systemic hypothermia. MR studies were classified by the predominant pattern of injury. Radiologic evidence of hypoglycemic damage was diagnosed based on selective edema and/or restricted diffusion in the posterior white matter, pulvinar, anterior medial thalamic nuclei and optic radiations with or without occipital cortical involvement. An occipital score (0 to 3) was used to grade the extent of cortical changes in the occipital lobes. Chart reviews collected clinical information including demographics, severity of encephalopathy, neonatal seizures, clinical hypoglycemia and hypothermia therapy. Hypoglycemia was defined as blood glucose <46 mg/dL. 132/197 infants had long term clinical follow up and charts were used to record outcome data. Epilepsy was diagnosed clinically and confirmed with EEG. Results: The cohort consisted of 197 newborns (120 males [61%]) delivered at a median gestational age of 39.6 weeks (interquartile range (IQR): 38.4 40.6) with a median birth weight of 3314 grams (IQR: 2948 3700). The clinical features did not differ between newborns with or without radiologic findings of hypoglycemia. Neonatal seizures were significantly associated with pattern of injury (P<0.001), radiographic hypoglycemia (P=0.006), and occipital lobe score (P<0.001). Neonatal seizures were strongly associated with cerebral palsy (P<0.001), and subsequent development of epilepsy (P=0.024). Using a logistic regression to adjust for pattern of injury and systemic hypothermia, the radiologic evidence of hypoglycemic injury remained an independent risk factor for neonatal seizures (OR 4.4; P=0.015) but the occipital cortical injury score did not (P=0.35). The analysis for subsequent epilepsy revealed the opposite relationship. Radiologic hypoglycemic injury was not associated with epilepsy (P=0.48) but cortical injury in the occipital lobe was (OR 2.5; P=0.04). Systemic hypothermia (administered to 34% of the newborns) did not alter these associations.Conclusions: This is the first evidence showing that in term infants with suspected HIE, MR features of hypoglycemia are risk factors for neonatal seizures. However the only MR feature associated with subsequent development of epilepsy was the degree of occipital cortical injury. Systemic hypothermia did not appear to protect the patient from developing neonatal seizures or long term epilepsy if MR imaging features were present.