Analysis of MRI and neurological outcome in encephalopathic neonates treated with whole-body hypothermia

Neonatal encephalopathy remains an important cause of mortality and morbidity in the newborn period, associated with a 10 to 75% risk of death and a 30 to 100% risk of major neurological sequelae in survivors for moderate and severe encephalopathy, respectively. Hypothermia has been increasingly adopted as therapy for babies with this condition encephalopathy, since it reduces mortality and disability after asphyxia or depression at birth.
Of note, the early and accurate assessment of the severity of brain injury, which accounts for the risk for subsequent neurodevelopmental disability, is important for appropriate parental counseling and identification of patients who might benefit most from early intervention services. Previous data have shown qualitative and quantitative assessment of magnetic resonance imaging (MRI) to have prognostic significance for neurodevelopmental outcome. However, up to date, quantitative methods to assess MRI information have not been evaluated in the hypothermia-treated population.
On this basis, an American group has conducted a study to evaluate the quantitative assessment of brain MRIs performed in infants with moderate-to-severe encephalopathy treated with whole-body hypothermia. In particular, they performed a retrospective analysis of clinical data and MRI studies in 47 full-term infants. Apparent diffusion coefficients (ADCs) and T1 and T2 intensity ratios were measured in the basal ganglia and thalamus on MRI images taken within the second week of life. Unfavourable outcome was defined as (1) severe neurological deficits at discharge and (2) cerebral palsy/severe motor deficit at follow-up through age 9 months.
In total, severe encephalopathy was present in 38% of evaluated subjects. Unfavourable outcome was observed 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 similar between groups, while T2 ratios in both the basal ganglia and thalamus were significantly higher in patients with unfavourable outcome, both at discharge and in follow-up. Differences in T2 intensity ratio remained significant also after adjustment for covariates (gestational age, seizures, and Apgar score at 10 min). In conclusion, these findings suggest that MRI assessment of brain injuries can provide useful prognostic information in hypothermia-treated encephalopatic newborns. More precisely, basal ganglia and thalamic T2 signal intensity ratios are predictive of death or severe neurological deficit at discharge and cerebral palsy/severe motor impairment at 9-month follow-up. Although not a replacement for interpretation by an experienced neuroradiologist, MRI can be used as an objective adjunct to qualitative reading. Since no single variable will have 100% accuracy in predicting outcome, a combination of variables with additive prognostic information is needed to improve prediction. It is important to confirm these findings in prospectively evaluated cohorts that are followed long term and to determine whether injuries to other brain regions (for example, cortical and frontal white matter) are similarly predictive of long-term cognitive outcome.

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