Selectively reduced posterior corpus callosum size in a population-based sample of young adults born with low birth weight

Brain MRI findings and their association with visual impairment in young adolescents born very preterm

PURPOSE

Very preterm birth increases risk for neonatal white matter injury, but there is limited data on to what extent this persists into adolescence and how this relates to ophthalmological outcomes. The aim of this study was to assess brain MRI findings in 12-year-old children born very preterm compared to controls and their association with concurrent ophthalmological outcomes.

METHODS

We included 47 children born very preterm and 22 full-term controls (gestational age <32 and >37 weeks, respectively). Brain MRI findings were studied in association with concurrent ophthalmological outcomes at 12-year follow-up.

RESULTS

Evans index (0.27 vs 0.25, p<0.001) and a proposed "posterior ventricle index" (0.47 vs 0.45, p=0.018) were increased in children born very preterm. Higher gestational age associated with larger corpus callosum area (β=10.7, 95%CI 0.59-20.8). Focal white matter lesions were observed in 15 (32%) of very preterm children and in 1 (5%) of full-term controls. Increased posterior ventricle index increased risk for visual acuity ≤1.0 (OR=1.07×1011, 95%CI=7.78-1.48×1021) and contrast sensitivity <0.5 (OR=2.6×1027, 95%CI=1.9×108-3.5×1046). Decreased peritrigonal white matter thickness associated with impaired visual acuity (β=0.04, 95%CI 0.002-0.07).

CONCLUSION

More white matter lesions and evidence of lower white matter volume were found in children born very preterm compared with full-term controls at 12-year follow-up. The association between larger posterior ventricle index and reduced visual acuity and contrast sensitivity suggests disturbances of the posterior visual pathway due to diffuse white matter lesions.

Effects of maternal stress and nutrient restriction during gestation on offspring neuroanatomy in humans

Cognitive and mental health are major determinants of quality of life, allowing integration into society at all ages. Human epidemiological and animal studies indicate that in addition to genetic factors and lifestyle, prenatal environmental influences may program neuropsychiatric disorders in later life. While several human studies have examined the effects of prenatal stress and nutrient restriction on brain function and mental health in later life, potentially mediating effects of prenatal stress and nutrient restriction on offspring neuroanatomy in humans have been studied only in recent years. Based on neuroimaging and anatomical data, we comprehensively review the studies in this emerging field. We relate prenatal environmental influences to neuroanatomical abnormalities in the offspring, measured in utero and throughout life. We also assess the relationship between neuroanatomical abnormalities and cognitive and mental disorders. Timing- and gender-specific effects are considered, if reported. Our review provides evidence for adverse effects of an unfavorable prenatal environment on structural brain development that may contribute to the risk for cognitive, behavioral and mental health problems throughout life.

Disentangling the relation between left temporoparietal white matter and reading: A spherical deconvolution tractography study

Diffusion tensor imaging (DTI) studies have shown that left temporoparietal white matter is related to phonological aspects of reading. However, DTI lacks the sensitivity to disentangle whether phonological processing is sustained by intrahemispheric connections, interhemispheric connections, or projection tracts. Spherical deconvolution (SD) is a nontensor model which enables a more accurate estimation of multiple fiber directions in crossing fiber regions. Hence, this study is the first to investigate whether the observed relation with reading aspects in left temporoparietal white matter is sustained by a particular pathway by applying a nontensor model. Second, measures of degree of diffusion anisotropy, which indirectly informs about white matter organization, were compared between DTI and SD tractography. In this study, 71 children (5-6 years old) participated. Intrahemispheric, interhemispheric, and projection pathways were delineated using DTI and SD tractography. Anisotropy indices were extracted, that is, fractional anisotropy (FA) in DTI and quantitative hindrance modulated orientational anisotropy (HMOA) in SD. DTI results show that diffusion anisotropy in both the intrahemispheric and projection tracts was positively correlated to phonological awareness; however, the effect was confounded by subjects' motion. In SD, the relation was restricted to the left intrahemispheric connections. A model comparison suggested that FA was, relatively to HMOA, more confounded by fiber crossings; however, anisotropy indices were highly related. In sum, this study shows the potential of SD to quantify white matter microstructure in regions containing crossing fibers. More specifically, SD analyses show that phonological awareness is sustained by left intrahemispheric connections and not interhemispheric or projection tracts.

Corpus callosum and motor development in healthy term infants

BACKGROUND

Corpus callosum atrophy has been associated with cognitive and motor deficits in elderly people. However, the role of the corpus callosum in infant development is unclear. The aim of this study was to assess the impact of corpus callosum size on motor development in infants.

METHODS

We investigated cerebral ultrasonograms performed on healthy infants aged 4 to 6 months. The correlation between the development of rolling over and corpus callosum size was calculated for determining odds ratios. Covariates, including gestational age, sex, age in months, and head circumference were tested using logistic regression.

RESULTS

We investigated 244 cerebral ultrasonograms performed on term infants from 2009 to 2011. The percentage of rolling over development in the examined infants increased with age (47.8%, 78.4%, and 97.5% at ages 4, 5, and 6 months, respectively). There was no significant difference in the development of rolling over between male (67.9%) and female (73.6%) children or among different gestational age groups. After the other covariates in the logistic model were adjusted, only age and corpus callosum size (length and thickness) were significantly associated with the development of rolling over: 3.86 times the odds (confidence interval, 2.1 to 7.0) for age in months, 1.14 times the odds (confidence interval, 1.0 to 1.3) for corpus callosum length, and 3.92 times the odds (confidence interval, 1.6 to 9.6) for corpus callosum thickness.

CONCLUSIONS

Corpus callosum size is positively associated with the development of rolling over in healthy term infants, independent of the gestational age, sex, age, and head circumference.

Ventricular dilatation in ex-prematures: only confined to the occipital region? MRI-based normative standards for 19-year-old ex-prematures without major handicaps

BACKGROUND

Premature birth may be associated with white matter injury later developing with widening of the ventricles. However, population-based data on normal ventricular size by age are sparse, making the evaluation of possible ventricular dilatation difficult.

PURPOSE

To present the linear measurements of the ventricular system, to compare these to subjectively assessed ventricular size, and to examine differences in ventricular size between ex-prematures and controls.

MATERIAL AND METHODS

Eligible survivors (n = 113) from the initial birth cohort (n = 217, born in 1986-1988, birth weight <2000 g) underwent MRI during 2006-2007. One hundred and three were ex-premature and included in the study. The ventricular size was subjectively judged by a pediatric neuroradiologist, and scored as normal, mildly, moderately, or severely dilated. Objective measurements, including width and depth of the frontal and occipital horns, were performed in a blinded fashion, by a pediatric radiologist.

RESULTS

The normative standards for different parts of the ventricular system in ex-premature young adults varied considerably. We found significant associations between the objective measurements and the subjectively classification of ventricular dilatation. Ex-prematures had smaller heads than those born term (control group). After adjustment for head circumference, there were no significant group differences regarding the frontal horns, but the occipital horns were proportionately wider among ex-prematures.

CONCLUSION

Young adults born prematurely, with a birth weight <2000 g, do not have larger lateral ventricles than healthy controls born term, even after correcting for a smaller head size. However, they do have larger occipital horns, confirming previous studies and strengthening our belief of a specific vulnerability of the occipital region.