Brain White Matter Development Over the First 13 Years in Very Preterm and Typically Developing Children Based on the T 1-w/T 2-w Ratio

Brain volume and neurodevelopment at 13 years following sepsis in very preterm infants

BACKGROUND

Associations of neonatal infection with brain growth and later neurodevelopmental outcomes in very preterm (VP) infants are unclear. This study aimed to assess associations of neonatal sepsis in VP infants with (1) brain growth from term-equivalent age to 13 years; and (2) 13-year brain volume and neurodevelopmental outcomes.

METHODS

224 infants born VP ( < 30 weeks' gestation/<1250 g birthweight) were recruited. Longitudinal brain volumes for 68 cortical and 14 subcortical regions were derived from MRI at term-equivalent, 7 and/or 13 years of age for 216 children (79 with neonatal sepsis and 137 without). 177 children (79%) had neurodevelopmental assessments at age 13. Of these, 63 with neonatal sepsis were compared with 114 without. Brain volumetric growth trajectories across time points were compared between sepsis and no-sepsis groups using mixed effects models. Linear regressions compared brain volume and neurodevelopmental outcome measures at 13 years between sepsis and no sepsis groups.

RESULTS

Growth trajectories were similar and there was little evidence for differences in brain volumes or neurodevelopmental domains at age 13 years between those with or without sepsis.

CONCLUSIONS

Neonatal sepsis in children born VP does not appear to disrupt subsequent brain development, or to have functional consequences in early adolescence.

IMPACT STATEMENT

Neonatal sepsis has been associated with poorer short-term neurodevelopmental outcomes and reduced brain volumes in very preterm infants. This manuscript provides new insights into the long-term brain development and neurodevelopmental outcomes of very preterm-born children who did or did not have neonatal sepsis. We found that regional brain volumes up to 13 years, and neurodevelopmental outcomes at age 13, were similar between those with and without neonatal sepsis. The links between neonatal sepsis and long-term neurodevelopment remain unclear.

Executive functioning challenges of adolescents born extremely and very preterm

Background

Children born very preterm (VPT; <32 weeks) are at increased risk of executive functioning (EF) difficulties. But less is known about the nature and extent of these executive difficulties during late adolescence, particularly across multiple EF domains and in response to varying degrees of executive demand.

Methods

Using data from a prospective longitudinal study, this paper describes the EF profiles of 92 VPT and 68 full-term (FT) adolescents at age 17 years. Relations between gestational age (GA) and later EF performance, in addition to neonatal predictors, were examined.

Results

VPT-born adolescents performed less well than FT adolescents across the domains of working memory, planning, and cognitive flexibility, with the largest differences observed for those born <28 weeks GA (effect sizes -0.6 to -1.0 SD), and when task demands were high. The effects of GA on EF outcome were fully mediated by neonatal medical complexity (b = 0.169, t = -1.73) and term equivalent white matter abnormalities (b = 0.107, t = -3.33).

Conclusion

Findings support the need for long-term cognitive support for individuals born very preterm, particularly those exposed to high levels of medical and neurological risk, with these factors largely explaining associations between GA and EF outcome.

Microbiome depletion prior to repeat mild TBI differentially alters social deficits and prefrontal cortex plasticity in adolescent and adult rats

Although aging, repeat mild traumatic brain injury (RmTBI), and microbiome modifications independently change social behavior, there has been no investigation into their cumulative effects on social behavior and neuroplasticity within the prefrontal cortex. Therefore, we examined how microbiome depletion prior to RmTBI affected social behavior and neuroplasticity in adolescent and adult rats. Play, temperament analysis, elevated plus maze, and the hot/cold plate assessed socio-emotional function. Analyses of perineuronal nets (PNNs) and parvalbumin (PV) interneurons was completed. Social-emotional deficits were more pronounced in adults, with microbiome depletion attenuating social behavior deficits associated with RmTBI in both age groups. Microbiome depletion increased branch length and PNN arborization within the PFC but decreased the overall number of PNNs. Adults and males were more vulnerable to RmTBI. Interestingly, microbiome depletion may have attenuated the changes to neuroplasticity and subsequent social deficits, suggesting that the microbiome is a viable, but age-specific, target for RmTBI therapeutics.

Longitudinal assessment of brain lesions in children with cerebral palsy and association with motor functioning

BACKGROUND

The semi-quantitative scale of structural brain Magnetic Resonance Imaging (sqMRI) is a valid and reliable measure of brain lesion extent in children with cerebral palsy (CP) >3-years. This system scores lesion burden for each major brain region. The sum of the scores gives a global score ranging from 0 to 48.

PURPOSE

To investigate how sqMRI scores changed from infancy to school-age, and whether these were associated with lesion load, age at first assessment, and gross motor function and its changes.

MATERIALS AND METHODS

Twenty-eight children with CP underwent MRI and motor (Gross Motor Function Measure-66; GMFM-66) assessments when <40-months and again when 8-12-years. We investigated whether (i) toddler/preschool-age sqMRI scores (Time 1) reflected school-age sqMRI scores (Time 2); (ii) temporal changes in sqMRI scores (Time 1-Time 2 difference) were related to the child's age at Time 1 and lesion extent; (iii) early or later sqMRI scores were associated with motor functioning; (iv) sqMRI scores' longitudinal changes were associated with motor changes.

RESULTS

Except for the corticosubcortical (grey-matter only) layers, sqMRI scores were significantly higher ('higher lesion load') at Time 1 than at Time 2. Age at Time 1 was not associated with temporal changes in global sqMRI scores. Higher lesion load at Time 2, but not at Time 1, was associated with smaller temporal changes in the global sqMRI score. The sqMRI scores were associated with concurrent, but not future or past motor GMFM-66 scores. Longitudinal changes in sqMRI scores were not associated with longitudinal changes in motor GMFM-66 scores.

CONCLUSION

sqMRI scores of brain lesion extent at school-age are lower and a better indication of later-life motor functioning than very early life sqMRI scores. It may be best to interpret MRI white matter lesions with caution in very early life due to possible changes in lesion appearance and the unpredictable role of functional plasticity.

Childhood development of brain white matter myelin: a longitudinal T1w/T2w-ratio study

Myelination of human brain white matter (WM) continues into adulthood following birth, facilitating connection within and between brain networks. In vivo MRI studies using diffusion weighted imaging (DWI) suggest microstructural properties of brain WM increase over childhood and adolescence. Although DWI metrics, such as fractional anisotropy (FA), could reflect axonal myelination, they are not specific to myelin and could also represent other elements of WM microstructure, for example, fibre architecture, axon diameter and cell swelling. Little work exists specifically examining myelin development. The T1w/T2w ratio approach offers an alternative non-invasive method of estimating brain myelin. The approach uses MRI scans that are routinely part of clinical imaging and only require short acquisition times. Using T1w/T2w ratio maps from three waves of the Neuroimaging of the Children's Attention Project (NICAP) [N = 95 (208 scans); 44% female; ages 9.5-14.20 years] we aimed to investigate the developmental trajectories of brain white matter myelin in children as they enter adolescence. We also aimed to investigate whether longitudinal changes in myelination of brain WM differs between biological sex. Longitudinal regression modelling suggested non-linear increases in WM myelin brain wide. A positive parabolic, or U-shaped developmental trajectory was seen across 69 of 71 WM tracts modelled. At a corrected level, no significant effect for sex was found. These findings build on previous brain development research by suggesting that increases in brain WM microstructure from childhood to adolescence could be attributed to increases in myelin.

Repetitive mild traumatic brain injury alters central and peripheral clock gene expression in the adolescent rat

Mild traumatic brain injury (mTBI) or concussion is a common injury worldwide leading to substantial medical costs and a high burden on society. In adolescents, falls and sports related trauma are often the causes of mTBI. Importantly, critical brain growth and development occurs during this sensitive period making the prospect of a brain injury a worrying phenomenon. Upwards of 70% of patients report circadian disruption following these injuries and this has been shown to impede recovery. Therefore, we sought to determine if core circadian clock gene expression was disrupted in rat model of repetitive mTBI (RmTBI). Male and female adolescent rats (n = 129) received sham or RmTBI. The animals were then euthanized at different times throughout the day and night. Tissue from the hypothalamus, cerebellum, hippocampus, liver, and small intestine were evaluated for the expression of per1, per2, cry1, clock, bmal1 and rev-erb-α. We found most clock genes varied across the day/night indicating circadian expression patterns. In the hypothalamus we found RmTBI altered the expression of cry1 and bmal1 in addition to sex differences in per2, cry1, clock, bmal1 and rev-erb- α. In the cerebellum, per1, per2, cry1, clock, bmal1 and rev-erb-α rhythms were all knocked out by RmTBI in addition to sex differences in cry1, clock and bmal1 expression. We also detected a significant decrease in overall expression of all clock genes in males in the middle of the night. In the hippocampus we found that RmTBI changed the rhythm of rev-erb-α expression in addition to sex differences in bmal1 expression. In the liver we detected strong rhythms in all genes examined, however only per2 expression was knocked out by RmTBI, in addition we also detected sex differences in per2 and cry1. We also detected an overall decrease in female clock gene expression in the early night. In the small intestine, RmTBI altered cry1 expression and there were sex differences in rev-erb-α. These results indicate that RmTBI alters core circadian clock gene expression in the central and peripheral nervous system in a time, tissue and sex dependent manner. This may be disrupting important phase relationships between the brain and peripheral nervous system and contributing to post-injury symptomology and also highlights the importance for time and sex dependent assessment of injury outcomes.