Neonatal brain imaging and the identification of metabolic acidemia and hypoxic-ischemic encephalopathy.

OBJECTIVE: To determine the precision with which intrapartum metabolic acidemia and hypoxic-ischemic encephalopathy (HIE) in term and near-term infants can be identified by neonatal brain imaging.

STUDY DESIGN: This is a case-control study whose inclusion criteria were neonates born at > or =34 weeks gestation with a cord gas at delivery, suspected neurological abnormalities, and computed tomography (CT) or magnetic resonance (MR) imaging of the brain. Neonates with chromosomal and major congenital malformations were excluded. Brain imaging for neonates with and without metabolic acidemia (pH < 7.0 and base deficit > 12 mM) at birth and HIE were retrospectively reviewed by a neuroradiologist blinded to their clinical course and compared.

RESULTS: There were 54 neonates admitted to the NICU at a single university hospital between 1992 and 2006 that met these inclusion criteria of which 27 had metabolic acidemia at birth. There were 16 diagnosed clinically as having HIE at the time of neonatal discharge, 13 from the acidemic group and 3 from the nonacidemic group. Radiological signs of basal ganglia injury were significantly more common in neonates with metabolic acidemia (29.6%, 3.7%, p = 0.02) and HIE (37.5%, 7.9%, p = 0.01). Logistic regression corrected for gestational age showed that radiological signs of basal ganglia injury could identify the presence of HIE with area under the ROC curve of 0.71, sensitivity 37.5%, specificity 92.1%, positive predictive value 66.7%, and negative predictive value of 77.8%.

CONCLUSION: Radiological signs of basal ganglia injury on early neonatal imaging are associated with metabolic acidemia and HIE, but is not precise enough to serve as a gold standard in the identification of these conditions.