Source:Nosarti C, Giouroukou E, Healy E, et al. Grey and white matter distribution in very preterm adolescents mediates neurodevelopmental outcome.
–217; doi:10.1093/brain/awm282

Because preterm infants often experience cognitive difficulties through adolescence,1 investigators from King’s College, London, sought to determine if adolescents who were born very preterm (VPT) would show diffuse white matter (WM) and grey matter (GM) abnormalities, especially in the prefrontal and temporal cortices. Such abnormalities could be a possible explanation for the cognitive deficits observed in VPT populations.

MRI data of brains of 218 adolescents (ages 14–15 years) who were born at <33 weeks gestation (VPT) and 128 controls born at term were compared using voxel-based morphometry, and the findings correlated with neurodevelopmental outcomes. Voxel-based morphometry is a neuroimaging analysis technique applied to structural MRI imaging that allows for calculation of focal brain volumes.

VPT study participants had been born at a mean gestational age of 29 weeks and had a mean birth weight of 1,276 grams; their mean age at the time of assessment was 15.2 years. VPT participants and controls were assessed with neurodevelopmental scales testing language, executive function, and in particular cognitive flexibility fluency, semantic fluency, conceptual tracking, verbal and non-verbal memory, and visual-motor integration.

Compared to control participants, VPT adolescents showed reduced GM in temporal and frontal lobes, occipital cortices, and cerebellum and increases in adjacent GM, predominantly in temporal and frontal lobes. WM was decreased in the brainstem, internal capsule, temporal and frontal regions, and showed excesses in temporal, parietal, and frontal regions. The greatest WM and GM alterations occurred in VPT individuals with evidence of periventricular hemorrhage and ventricular dilatation on neonatal ultrasound. VPT adolescents had lower scores than controls on measures of language and executive function and their cognitive function was more likely to be impaired (27% vs 14%, respectively; P=.013). Gestational age was positively associated with GM and WM volumes.

Specific cognitive deficits and neurodevelopmental delay associated with VPT birth may be related, at least in part, to altered grey and white matter volumes. The authors conclude that specific cognitive deficits associated with VPT birth could be used in the identification of those individuals who may be at increased risk for specific types of cognitive impairment as adolescents.

Dr. Millichap has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.

The strengths of this study include the large number of subjects and the quantitative method of MRI measurement of brain tissue volumes. Weaknesses are the heterogeneity of the study population and the inability to account for potential differences in test subjects and full-term birth controls. Standard of NICU care and environmental or other unknown factors may modify brain development and subsequent neuropsychological function.

Previous studies have shown that infants born VPT and of low birth weight (<2500g) are at risk of hemorrhage and hypoxicischemic damage that results in dilated ventricles, loss of white matter, and enlarged subarachnoid...

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