MRI to predict neurodevelopmental outcomes in preterm infants

Very preterm infants are at high risk for adverse neurodevelopmental outcomes, with 5% to 15% having cerebral palsy, severe neurosensory impairment, or both, and 25% to 50% having cognitive, behavioral, and social difficulties. Therefore, a major issue is the identification of infants who are most likely to develop these disabilities and could benefit from early intervention. The use of risk indexes based on several risk factors (such as bronchopulmonary dysplasia, sepsis, surgery, postnatal use of corticosteroids, intraventricular hemorrhage and periventricular leukomalacia) showed limited effectiveness in identifying infants who are at high risk. One useful prognostic tool may be magnetic resonance imaging (MRI) during the neonatal period. This method presents several advantages with respect to cranial ultrasonography, such as high sensitivity for white-matter and gray-matter abnormalities, which are very frequent in preterm infants and are associated with impaired working memory and early neurodevelopmental delay.

A recent study, published on the New England Journal of Medicine, evaluated 167 very preterm infants (gestational age (GA) at birth, 30 weeks or less) in order to assess the associations between qualitatively defined white-matter and gray-matter abnormalities on MRI at term equivalent (GA of 40 weeks) and the risks of severe cognitive or psychomotor delay, cerebral palsy, and neurosensory impairment at 2 years of age, corrected for prematurity.

The results showed that, at two years of age, 17% of infants presented severe cognitive delay, 10% severe psychomotor delay, 10% cerebral palsy, and 11% neurosensory impairment. Moderate-to-severe cerebral white-matter abnormalities were found in 21% of infants and were predictive of the following adverse outcomes at two years of age: cognitive delay (odds ratio (OR)=3.6), motor delay (OR=10.3), cerebral palsy (OR=9.6), and neurosensory impairment (OR=4.2). Moderate-to-severe white-matter abnormalities on MRI were significant predictors of severe motor delay and cerebral palsy also after adjustment for other measures during the neonatal period, including findings on cranial ultrasonography. Gray-matter abnormalities were identified in 49% of infants and were also associated with the same adverse outcomes, even if the correlations were weaker. Taken together, these results suggest that white-matter abnormalities and, to a lesser extent, gray-matter ones, are associated with an elevated risk of severe cognitive delay, severe psychomotor delay, cerebral palsy, and neurosensory impairment. The association is stronger when abnormalities are moderate or severe. This can confirm the relevance of early structural neurologic abnormalities for the development of neurodevelopmental risk. In conclusion, abnormal findings on MRI at term equivalent in very preterm infants are strongly associated with adverse neurodevelopmental outcomes at two years of age. Moreover, these results suggest a role for MRI at term equivalent in risk stratification for these infants.

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