Quantitative analysis of magnetic resonance images and neurological outcome in encephalopathic neonates treated with whole-body hypothermia

Abstract

To evaluate whether quantitative measures from magnetic resonance imaging (MRI) performed in hypothermia-treated encephalopathic newborns can differentiate patients with unfavorable neurological outcome. Retrospective analysis of clinical data and MRI studies was performed in 47 full-term infants treated with whole-body hypothermia for neonatal encephalopathy. Apparent diffusion coefficients (ADCs) and T1 and T2 intensity ratios were measured in the basal ganglia and thalamus on axial MRI images. Unfavorable outcome was defined as (1) death or severe neurological deficits at discharge and (2) death or cerebral palsy/severe motor deficit at follow-up through age 9 months. Differences between groups with favorable versus unfavorable neurological outcome at each time point were compared. Optimal cutoff values for significant MR variables were determined with receiver operating curve analyses. Sensitivity and specificity of these cutoff values for predicting unfavorable outcome were calculated and results were compared with qualitative MRI interpretation. Infants presented with a median pH of 6.86, base deficit of 20 and Apgar scores of 1, 3 and 4 at 1, 5 and 10 min, respectively. Severe encephalopathy was present in 38%. Unfavorable outcome was present in 9 patients at discharge and in 13 of 26 patients with available follow-up data through 9 months. ADC values and T1 ratios were not significantly different between groups at either time point. T2 ratios in both the basal ganglia and thalamus were significantly higher in patients with unfavorable outcome, both at discharge and in follow-up. T2 intensity ratio in the basal ganglia and thalamus remained significantly associated with death or severe neurological deficit at discharge, after controlling for covariates in logistic regression analysis. Sensitivity and specificity of T2 intensity ratio for predicting unfavorable outcome at discharge were comparable to qualitative grading of injury in the basal ganglia and thalamus by a neuroradiologist. Increased T2 signal intensity in the basal ganglia or thalamus in patients with hypothermia-treated neonatal encephalopathy is associated with unfavorable neurological outcome at discharge and later with motor deficit/cerebral palsy. Quantitative methods to assess MRI evidence of brain injury are important for providing objective measures to predict outcome in this high-risk population.