Neurodevelopmental outcome following hypoxic ischaemic encephalopathy and therapeutic hypothermia is related to right ventricular performance at 24-hour postnatal age

OBJECTIVE

Our aim was to determine whether right ventricular (RV) dysfunction at 24-hour postnatal age predicts adverse developmental outcome among patients with hypoxic ischaemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH).

DESIGN

Neonates≥35 weeks with HIE/TH were enrolled in a physiological study in the neonatal period (n=46) and either died or underwent neurodevelopmental follow-up at 18 months (n=43). The primary outcome was a composite of death, diagnosis of cerebral palsy or any component of the Bayley Scores of Infant Development III<70. We hypothesised that tricuspid annulus plane systolic excursion (TAPSE) <6 mm and/or RV fractional area change (RV-FAC) <0.29 would predict adverse outcome.

RESULTS

Nine patients died and 34 patients were followed up at a mean age of 18.9±1.4 months. Both indices of RV systolic performance were abnormal in 15 (35%) patients, TAPSE <6 mm only was abnormal in 4 (9%) patients and RV-FAC <0.29 only was abnormal in 5 (12%) patients (19 had with normal RV function). Although similar at admission, neonates with RV dysfunction had higher cardiovascular and neurological illness severity by 24 hours than those without and severe MRI abnormalities (70% vs 53%, p=0.01) were more common. On logistic regression, TAPSE <6 mm (OR 3.6, 95% CI 1.2 to 10.1; p=0.017) and abnormal brain MRI [OR 21.7, 95% CI 1.4 to 336; p=0.028) were independently associated with adverse outcome. TAPSE <6 mm predicted outcome with a 91% sensitivity and 81% specificity.

CONCLUSIONS

The role of postnatal cardiovascular function on neurological outcomes among patients with HIE who receive TH merits further study. Quantitative measurement of RV function at 24 hours may provide an additional neurological prognostic tool.

Resilience and Vulnerability: Neurodevelopment of Very Preterm Children at Four Years of Age

Children born very preterm (VPT) are at high-risk for altered brain development and impaired neurodevelopmental outcomes but are not well-studied before school-age. We investigated 64 four-year-olds: 37 VPT children [<32 weeks gestational age [GA]; 22 males; mean GA: 28.8 weeks ± 1.6], 25 full-term (FT) children (12 males), plus two VPT cases with ventriculomegaly and exceptionally resilient outcomes. All children underwent high-resolution structural magnetic resonance imaging and developmental assessments. Measures of brain volume, cortical thickness, and surface area were obtained. Children born VPT demonstrated reduced cerebral and cerebellar white matter volumes yet increased cerebral gray matter, temporal lobe, occipital lobe and ventricle volumes after adjusting for total brain volume. Cortical thickness was greater in the VPT children compared to FT children across all lobes. On developmental assessments, the VPT children scored lower on average than FT children while the two cases had intact cognitive abilities. In addition to larger ventricle volumes, the two cases had white matter and gray matter volumes within the ranges of the FT children. The VPT children displayed distinct differences in structural brain volumes at 4 years of age, consistent with delayed maturation. The cases with persistent ventriculomegaly and good cognitive outcomes displayed typical gray matter and increased white matter volumes, indicating a potential protective developmental phenomenon contributing to their intact cognitive abilities.

Resilience and Vulnerability: Neurodevelopment of Very Preterm Children at Four Years of Age

Children born very preterm (VPT) are at high-risk for altered brain development and impaired neurodevelopmental outcomes but are not well-studied before school-age. We investigated 64 four-year-olds: 37 VPT children [<32 weeks gestational age [GA]; 22 males; mean GA: 28.8 weeks ± 1.6], 25 full-term (FT) children (12 males), plus two VPT cases with ventriculomegaly and exceptionally resilient outcomes. All children underwent high-resolution structural magnetic resonance imaging and developmental assessments. Measures of brain volume, cortical thickness, and surface area were obtained. Children born VPT demonstrated reduced cerebral and cerebellar white matter volumes yet increased cerebral gray matter, temporal lobe, occipital lobe and ventricle volumes after adjusting for total brain volume. Cortical thickness was greater in the VPT children compared to FT children across all lobes. On developmental assessments, the VPT children scored lower on average than FT children while the two cases had intact cognitive abilities. In addition to larger ventricle volumes, the two cases had white matter and gray matter volumes within the ranges of the FT children. The VPT children displayed distinct differences in structural brain volumes at 4 years of age, consistent with delayed maturation. The cases with persistent ventriculomegaly and good cognitive outcomes displayed typical gray matter and increased white matter volumes, indicating a potential protective developmental phenomenon contributing to their intact cognitive abilities.

Whole-body vibration in neonatal transport: a review of current knowledge and future research challenges

Interfacility transport to tertiary care for high-risk neonates has become an integral part of equitable access to optimal perinatal healthcare. Excellence in clinical care requires expertise in transport medicine and the coordination of safe transport processes. However, concerns remain regarding environmental stressors involved in the transportation of sick high-risk neonates, including noise and vibration. In order to mitigate the potential deleterious effects of these physical stressors during transport, further knowledge of the burden of exposure, injury mechanisms and engineering interventions/modifications as adjuncts during transport would be beneficial. We reviewed the current literature with a focus on the contribution of new and emerging technologies in the transport environment with particular reference to whole-body vibration. This review intends to highlight what is known about vibration as a physical stressor in neonates and areas for further research; with the goal to making recommendations for minimizing these stressors during transport.

Longitudinal Study of White Matter Development and Outcomes in Children Born Very Preterm

Identifying trajectories of early white matter development is important for understanding atypical brain development and impaired functional outcomes in children born very preterm (<32 weeks gestational age [GA]). In this study, 161 diffusion images were acquired in children born very preterm (median GA: 29 weeks) shortly following birth (75), term-equivalent (39), 2 years (18), and 4 years of age (29). Diffusion tensors were computed to obtain measures of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), which were aligned and averaged. A paediatric atlas was applied to obtain diffusion metrics within 12 white matter tracts. Developmental trajectories across time points demonstrated age-related changes which plateaued between term-equivalent and 2 years of age in the majority of posterior tracts and between 2 and 4 years of age in anterior tracts. Between preterm and term-equivalent scans, FA rates of change were slower in anterior than posterior tracts. Partial least squares analyses revealed associations between slower MD and RD rates of change within the external and internal capsule with lower intelligence quotients and language scores at 4 years of age. These results uniquely demonstrate early white matter development and its linkage to cognitive functions.

Associations of Perinatal Clinical and Magnetic Resonance Imaging Measures with Developmental Outcomes in Children Born Very Preterm

OBJECTIVE

To identify perinatal risk factors associated with long-term neurocognitive and behavioral impairments in children born very preterm using a multivariate, partial least squares approach.

STUDY DESIGN

Twenty-seven perinatal clinical and magnetic resonance imaging measures were collected at birth and during the neonatal intensive care stay for 105 neonates born very preterm (≤ 32 weeks gestational age). One-half of the children returned for neuropsychological assessments at 2 and 4 years of age. Parent-reported behavioral measures were also obtained at 4 years of age. Three partial least squares analyses were performed to determine associations between clinical and radiologic measures with cognitive outcomes at 2 and 4 years of age, as well as with behavioral measures at 4 years of age.

RESULTS

Within the first components of each analysis, only intrauterine growth restriction, male sex, and absence of antenatal corticosteroid use were associated with poorer cognitive and language ability at 2 and 4 years of age, accounting for 79.6% and 71.4% of the total variance, respectively. In addition, white matter injury at term-equivalent age contributed to more problematic internalizing behaviors, behavioral symptoms, and impaired executive function at 4 years of age, accounting for 67.9% of the total variance.

CONCLUSIONS

Using this data-driven multivariate approach, specific measures in prenatal and early postnatal life are shown to be selectively and significantly associated with cognitive and behavioral outcomes in children born very preterm. Early detection of risk factors can help inform prognoses of children at greatest risk of long-term impairments.

Visual functional magnetic resonance imaging of preterm infants

AIM

The aim of this study was to determine the feasibility of undertaking visual functional magnetic resonance imaging (fMRI) in very preterm children.

METHOD

Forty-seven infants born at less than 32 weeks gestational age (25 males, 22 females; mean (SD) age at birth 28.8 wks [1.9]) were scanned using 1.5 T MRI as part of a longitudinal neuroimaging study. These infants were scanned at preterm age (within 2 wks of birth) and at term-equivalent age. Quantitative T2* data and fMRI in response to visual stimuli (flashing strobe) were acquired in this population. T2* values were compared at preterm age and at term-equivalent age using a two-tailed t-test. A general linear model was used to evaluate occipital lobe response to visual stimuli.

RESULTS

T2* values were significantly higher at preterm age than at term-equivalent age in both the medial and lateral occipital lobes (preterm infants: 187.2 ms and 198.4 ms respectively; term infants: 110.9 ms and 133.2 ms respectively; p<0.002). Significant positive occipital lobe activation (q<0.01) was found in 3 out of 65 (5%) fMRIs carried out at preterm age and in 19 out of 26 (73%) scans carried out at term-equivalent age.

INTERPRETATION

Visual stimuli do not elicit a reliable blood oxygen level-dependent (BOLD) response in very preterm infants during the preterm period. This suggests that BOLD fMRI may not be the appropriate modality for investigating occipital lobe function in very preterm infants.

Optimized T1- and T2-weighted volumetric brain imaging as a diagnostic tool in very preterm neonates

BACKGROUND

T1- and T2-W MR sequences used for obtaining diagnostic information and morphometric measurements in the neonatal brain are frequently acquired using different imaging protocols. Optimizing one protocol for obtaining both kinds of information is valuable.

OBJECTIVE

To determine whether high-resolution T1- and T2-W volumetric sequences optimized for preterm brain imaging could provide both diagnostic and morphometric value.

MATERIALS AND METHODS

Thirty preterm neonates born between 24 and 32 weeks' gestational age were scanned during the first 2 weeks after birth. T1- and T2-W high-resolution sequences were optimized in terms of signal-to-noise ratio, contrast-to-noise ratio and scan time and compared to conventional spin-echo-based sequences.

RESULTS

No differences were found between conventional and high-resolution T1-W sequences for diagnostic confidence, image quality and motion artifacts. A preference for conventional over high-resolution T2-W sequences for image quality was observed. High-resolution T1 images provided better delineation of thalamic myelination and the superior temporal sulcus. No differences were found for detection of myelination and sulcation using conventional and high-resolution T2-W images.

CONCLUSION

High-resolution T1- and T2-W volumetric sequences can be used in clinical MRI in the very preterm brain to provide both diagnostic and morphometric information.

The importance of head growth patterns in predicting the cognitive abilities and literacy skills of small-for-gestational-age children

This study evaluated the effects of head growth compromise beginning in utero and continuing, in some cases, through the first 9 months of life on the cognitive and literacy skills of school-age small-for-gestational-age (SGA) children. Seventy-one SGA children, aged 7 to 9 years (gestational ages, 24-41 weeks) and 16 full-term appropriate-for-gestational-age control children of comparable socioeconomic backgrounds and age at testing completed tests assessing intelligence, receptive language, working memory, problem solving, visual-motor integration, phonological awareness, reading, and spelling. SGA children were subdivided into head-growth pattern groups based on their head circumference at birth and at 9 months postterm. Analyses showed that SGA children with poor prenatal and postnatal head growth had the worst outcomes, followed by those with prenatal brain compromise, but good postnatal head growth. SGA children with preserved head growth in utero as well as good head growth after birth demonstrated the best outcomes, although spelling skills were deficient relative to full-term peers. The Verbal and Full Scale IQ ratings of the SGA children who had experienced brain compromise in utero declined significantly from 5 to 8 years of age. We conclude that mild intrauterine growth retardation (IUGR) has a minimal effect on the development of cognitive or academic abilities, providing that brain growth in utero is not affected. IUGR that slows brain growth in utero impairs the acquisition of some cognitive and academic abilities, even when followed by good catch-up head growth after birth, whereas poor brain growth in utero followed by little or no catch-up head growth results in widespread impairments. Findings highlight the limits to brain plasticity and emphasize the importance of optimal prenatal and postnatal brain growth.