White matter NAA/Cho and Cho/Cr ratios at MR spectroscopy are predictive of motor outcome in preterm infants

Improved Recovery of Complete Spinal Cord Transection by a Plasma-Modified Fibrillar Scaffold

Complete spinal cord injury causes an irreversible disruption in the central nervous system, leading to motor, sensory, and autonomic function loss, and a secondary injury that constitutes a physical barrier preventing tissue repair. Tissue engineering scaffolds are presented as a permissive platform for cell migration and the reconnection of spared tissue. Iodine-doped plasma pyrrole polymer (pPPy-I), a neuroprotective material, was applied to polylactic acid (PLA) fibers and implanted in a rat complete spinal cord transection injury model to evaluate whether the resulting composite implants provided structural and functional recovery, using magnetic resonance (MR) imaging, diffusion tensor imaging and tractography, magnetic resonance spectroscopy, locomotion analysis, histology, and immunofluorescence. In vivo, MR studies evidenced a tissue response to the implant, demonstrating that the fibrillar composite scaffold moderated the structural effects of secondary damage by providing mechanical stability to the lesion core, tissue reconstruction, and significant motor recovery. Histologic analyses demonstrated that the composite scaffold provided a permissive environment for cell attachment and neural tissue guidance over the fibers, reducing cyst formation. These results supply evidence that pPPy-I enhanced the properties of PLA fibrillar scaffolds as a promising treatment for spinal cord injury recovery.

1H-magnetic resonance spectroscopy and its role in predicting neurodevelopmental impairment in preterm neonates: A systematic review

To assess the diagnostic utility of proton (1H) magnetic resonance spectroscopy in early diagnosis of neurodevelopmental impairment in preterm newborns. Systematic review performed in compliance with the PRISMA statements. Eligible articles were searched in MEDLINE, Scopus, and ISI Web of Science databases using the following medical subject headings and terms: "magnetic resonance spectroscopy," "infant," and "newborn." Studies of any design published until 20 December 2021 and fulfilling the following criteria were selected: (1) studies including newborns with gestational age at birth <37 weeks which underwent at least one 1H-MRS scan within 52 weeks' postmenstrual age and neurodevelopmental assessment within 4 years of age; (2) studies in which preterm newborns with congenital infections, genetic disorders, and brain congenital anomalies were clearly excluded. Data regarding the relationship between metabolite ratios in basal ganglia, thalamus, and white matter, and neurodevelopment were analysed. The quality assessment of included studies was performed according to the criteria from the QUADAS-2. N-acetylaspartate (NAA)/choline (Cho) was the most studied metabolite ratio. Lower NAA/Cho ratio in basal ganglia and thalamus was associated with adverse motor, cognitive, and language outcomes, and worse global neurodevelopment. Lower NAA/Cho ratio in white matter was associated with cognitive impairment. However, some associations came from single studies or were discordant among studies. The quality of included studies was low. 1H-MRS could be a promising tool for early diagnosis of neurodevelopmental impairment. However, further studies of good quality are needed to define the relationship between metabolite ratios and neurodevelopment.

Neurometabolic changes in neonates with congenital heart defects and their relation to neurodevelopmental outcome

BACKGROUND

Altered neurometabolite ratios in neonates undergoing cardiac surgery for congenital heart defects (CHD) may serve as a biomarker for altered brain development and neurodevelopment (ND).

METHODS

We analyzed single voxel 3T PRESS H¹-MRS data, acquired unilaterally in the left basal ganglia and white matter of 88 CHD neonates before and/or after neonatal cardiac surgery and 30 healthy controls. Metabolite ratios to Creatine (Cr) included glutamate (Glu/Cr), myo-Inositol (mI/Cr), glutamate and glutamine (Glx/Cr), and lactate (Lac/Cr). In addition, the developmental marker N-acetylaspartate to choline (NAA/Cho) was evaluated. All children underwent ND outcome testing using the Bayley Scales of Infant and Toddler Development Third Edition (BSID-III) at 1 year of age.

RESULTS

White matter NAA/Cho ratios were lower in CHD neonates compared to healthy controls (group beta estimate: -0.26, std. error 0.07, 95% CI: -0.40 - 0.13, p value <0.001, FDR corrected p value = 0.010). We found no correlation between pre- or postoperative white matter NAA/Cho with ND outcome while controlling for socioeconomic status and CHD diagnosis.

CONCLUSION

Reduced white matter NAA/Cho in CHD neonates undergoing cardiac surgery may reflect a delay in brain maturation. Further long-term MRS studies are needed to improve our understanding of the clinical impact of altered metabolites on brain development and outcome.

IMPACT

NAA/Cho was reduced in the white matter, but not the gray matter of CHD neonates compared to healthy controls. No correlation to the 1-year neurodevelopmental outcome (Bayley-III) was found. While the rapid change of NAA/Cho with age might make it a sensitive marker for a delay in brain maturation, the relationship to neurodevelopmental outcome requires further investigation.

Magnetic resonance spectroscopy brain metabolites at term and 3-year neurodevelopmental outcomes in very preterm infants

BACKGROUND

Noninvasive advanced neuroimaging and neurochemical assessment can identify subtle abnormalities and predict neurodevelopmental impairments. Our objective was to quantify white matter metabolite levels and evaluate their relationship with neurodevelopmental outcomes at age 3 years.

METHODS

Our study evaluated a longitudinal prospective cohort of very premature infants (<32 weeks gestational age) with single-voxel proton magnetic resonance spectroscopy from the centrum semiovale performed at term-equivalent age and standardized cognitive, verbal, and motor assessments at 3 years corrected age. We separately examined metabolite ratios in the left and right centrum semiovale. We also conducted an exploratory interaction analysis for high/low socioeconomic status (SES) to evaluate the relationship between metabolites and neurodevelopmental outcomes, after adjusting for confounders.

RESULTS

We found significant relationships between choline/creatine levels in the left and right centrum semiovale and motor development scores. Exploratory interaction analyses revealed that, for infants with low SES, there was a negative association between choline/creatine in the left centrum semiovale and motor assessment scores at age 3 years.

CONCLUSIONS

Brain metabolites from the centrum semiovale at term-equivalent age were associated with motor outcomes for very preterm infants at 3 years corrected age. This effect may be most pronounced for infants with low SES.

IMPACT

Motor development at 3 years corrected age for very preterm infants is inversely associated with choline neurochemistry within the centrum semiovale on magnetic resonance spectroscopy at term-equivalent age, especially in infants with low socioeconomic status. No prior studies have studied metabolites in the centrum semiovale to predict neurodevelopmental outcomes at 3 years corrected age based on high/low socioeconomic status. For very preterm infants with lower socioeconomic status, higher choline-to-creatine ratio in central white matter is associated with worse neurodevelopmental outcomes.

Lactylation may be a Novel Posttranslational Modification in Inflammation in Neonatal Hypoxic-Ischemic Encephalopathy

Perinatal hypoxia-ischemia remains the most common cause of acute neonatal brain injury and is associated with a high death rate and long-term neurological abnormalities such as memory and cognitive deficits and dyskinesia. Hypoxia-ischemia triggers an inflammatory cascade in the brain that is amplified by the activation of immune cells and the influx of peripheral immune cells into the brain parenchyma in response to cellular injury. Thus, acute cerebral hypoxic-ischemic inflammation is a major contributor to the pathogenesis of newborn hypoxic-ischemic brain injury. Lactate is a glycolysis end product that can regulate inflammation through histone lactylation, a unique posttranslational modification that was identified in recent studies. The purpose of this review is to outline the recent improvements in our understanding of microglia-mediated hypoxic-ischemic inflammation and to further discuss how histone lactylation regulates inflammation by affecting macrophage activation. These findings may suggest that epigenetic reprogramming-associated lactate input is linked to disease outcomes such as acute neonatal brain injury pathogenesis and the therapeutic effects of drugs and other strategies in relieving neonatal hypoxic-ischemic brain injury. Therefore, improving our knowledge of the reciprocal relationships between histone lactylation and inflammation could lead to the development of new immunomodulatory therapies for brain damage in newborns.

Brain proton magnetic resonance spectroscopy and neurodevelopment after preterm birth: a systematic review

BACKGROUND

Preterm infants are at risk of neurodevelopmental impairments. At present, proton magnetic resonance spectroscopy (¹H-MRS) is used to evaluate brain metabolites in asphyxiated term infants. The aim of this review is to assess associations between cerebral ¹H-MRS and neurodevelopment after preterm birth.

METHODS

PubMed and Embase were searched to identify studies using ¹H-MRS and preterm birth. Eligible studies for this review included ¹H-MRS of the brain, gestational age ≤32 weeks, and neurodevelopment assessed at a corrected age (CA) of at least 12 months up to the age of 18 years.

RESULTS

Twenty papers evaluated ¹H-MRS in preterm infants at an age between near-term and 18 years and neurodevelopment. ¹H-MRS was performed in both white (WM) and gray matter (GM) in 12 of 20 studies. The main regions were frontal and parietal lobe for WM and basal ganglia for GM. N-acetylaspartate/choline (NAA/Cho) measured in WM and/or GM is the most common metabolite ratio associated with motor, language, and cognitive outcome at 18-24 months CA.

CONCLUSIONS

NAA/Cho in WM assessed at term-equivalent age was associated with motor, cognitive, and language outcome, and NAA/Cho in deep GM was associated with language outcome at 18-24 months CA.

IMPACT

In preterm born infants, brain metabolism assessed using ¹H-MRS at term-equivalent age is associated with motor, cognitive, and language outcomes at 18-24 months. ¹H-MRS at term-equivalent age in preterm born infants may be used as an early indication of brain development. Specific findings relating to NAA were most predictive of outcome.

Association of Cerebral Blood Flow and Brain Tissue Relaxation Time With Neurodevelopmental Outcomes of Preterm Neonates: Multidelay Arterial Spin Labeling and Synthetic MRI Study

OBJECTIVES

Both cerebral blood flow (CBF) and brain tissue relaxation times are known to reflect maturation in the neonatal brain. However, we do not yet know if these factors are associated with neurodevelopmental outcomes. The objective of this study was to acquire CBF and relaxation time in preterm neonates, using multidelay arterial spin labeling and synthetic magnetic resonance imaging (MRI), and show their association with later neurodevelopmental outcomes.

MATERIALS AND METHODS

In this prospective study, preterm neonates were recruited, and multidelay arterial spin labeling and synthetic MRI were performed between September 2017 and December 2018. These neonates underwent the Bayley Scales of Infant Development test at 18 months of age, and both cognitive and motor outcome scores were measured. Transit time-corrected CBF and T1 and T2 relaxation time values were measured for different brain regions. The measured values were correlated with gestational age (GA) at birth and corrected GA at the MRI scan. Simple and multiple linear regression analyses were performed for the measured values and neurodevelopmental outcome scores.

RESULTS

Forty-nine neonates (median [interquartile range] GA, 30 [2] weeks, 209 [17] days; 28 boys) underwent MRI scans at or near term-equivalent age (median [interquartile range] corrected GA, 37 [2] weeks, 258 [14] days). Transit time-corrected CBF (coefficient, 0.31-0.59) and relaxation time (coefficient, -0.39 to -0.86) values showed significant correlation with corrected GA but not with GA. After controlling for GA, the frontal white matter CBF in preterm neonates showed a negative relationship with cognitive outcome scores (β = -0.97; P = 0.029). Frontal white matter T1 relaxation times showed a positive relationship with cognitive outcome scores (β = 0.03; P = 0.025) after controlling for GA.

CONCLUSIONS

Higher CBF values and lower T1 relaxation times in frontal white matter were associated with poorer cognitive outcomes. As quantitative neuroimaging markers, CBF and relaxation times may help predict neurodevelopmental outcomes in preterm neonates.

In vivo Human MR Spectroscopy Using a Clinical Scanner: Development, Applications, and Future Prospects

MR spectroscopy (MRS) is a unique and useful method for noninvasively evaluating biochemical metabolism in human organs and tissues, but its clinical dissemination has been slow and often limited to specialized institutions or hospitals with experts in MRS technology. The number of 3-T clinical MR scanners is now increasing, representing a major opportunity to promote the use of clinical MRS. In this review, we summarize the theoretical background and basic knowledge required to understand the results obtained with MRS and introduce the general consensus on the clinical utility of proton MRS in routine clinical practice. In addition, we present updates to the consensus guidelines on proton MRS published by the members of a working committee of the Japan Society of Magnetic Resonance in Medicine in 2013. Recent research into multinuclear MRS equipped in clinical MR scanners is explained with an eye toward future development. This article seeks to provide an overview of the current status of clinical MRS and to promote the understanding of when it can be useful. In the coming years, MRS-mediated biochemical evaluation is expected to become available for even routine clinical practice.

Altered brain metabolite concentration and delayed neurodevelopment in preterm neonates

BACKGROUND

A very-low-birth-weight (VLBW) preterm infants is associated with an increased risk of impaired neurodevelopmental outcomes. In this study, we investigated how neonatal brain metabolite concentrations changed with postmenstrual age and examined the relationship between changes in concentration (slopes) and neurodevelopmental level at 3-4 years.

METHODS

We retrospectively examined 108 VLBW preterm infants who had brain single-voxel magnetic resonance spectroscopy at 34-42 weeks' postmenstrual age. Neurodevelopment was assessed using a developmental test, and subjects were classified into four groups: developmental quotient <70, 70-84, 85-100, and >100. One-way analyses of covariance and multiple-comparison post hoc tests were used to compare slopes.

RESULTS

We observed correlations between postmenstrual age and the concentrations of N-acetylaspartate and N-acetylaspartylglutamate (tNAA) (p < 0.001); creatine and phosphocreatine (p < 0.001); glutamate and glutamine (p < 0.001); and myo-inositol (p = 0.049) in the deep gray matter; and tNAA (p < 0.001) in the centrum semiovale. A significant interaction was noted among the tNAA slopes of the four groups in the deep gray matter (p = 0.022), and we found a significant difference between the <70 and 85-100 groups (post hoc, p = 0.024).

CONCLUSIONS

In VLBW preterm infants, the slopes of tNAA concentrations (adjusted for postmenstrual age) were associated with lower developmental quotients at 3-4 years.

IMPACT

In very-low-birth-weight preterm-born infants, a slower increase in tNAA brain concentration at term-equivalent age was associated with poorer developmental outcomes at 3-4 years. The increase in tNAA concentration in very-low-birth-weight infants was slower in poorer developmental outcomes, and changes in tNAA concentration appeared to be more critical than changes in tCho for predicting developmental delays. While tNAA/tCho ratios were previously used to examine the correlation with neurodevelopment at 1-2 years, we used brain metabolite concentrations.

Quantitative Diffusion and Spectroscopic Neuroimaging Combined with a Novel Early-Developmental Assessment Improves Models for 1-Year Developmental Outcomes

BACKGROUND AND PURPOSE

Preterm infants are at risk for overt and silent CNS injury, with developmental consequences that are difficult to predict. The novel Specific Test of Early Infant Motor Performance, administered in preterm infants at term age, is indicative of later developmental gross motor and cognitive scores at 12 months. Here, we assessed whether functional performance on this early assessment correlates with CNS integrity via MR spectroscopy or diffusional kurtosis imaging and whether these quantitative neuroimaging methods improve predictions for future 12-month developmental scores.

MATERIALS AND METHODS

MR spectroscopy and quantitative diffusion MR imaging data were acquired in preterm infants (n = 16) at term. Testing was performed at term and 3 months using the Specific Test of Early Infant Motor Performance and the Bayley Scales of Infant and Toddler Development, Third Edition, at 12 months. We modeled the relationship of MR spectroscopy and diffusion MR imaging data with both test scores via multiple linear regression.

RESULTS

MR spectroscopy NAA ratios at a TE of 270 ms in the frontal WM and basal ganglia and kurtosis metrics in major WM tracts correlated strongly with total Specific Test of Early Infant Motor Performance scores. The addition of MR spectroscopy and diffusion separately improved the functional predictions of 12-month outcomes.

CONCLUSIONS

Microstructural integrity of the major WM tracts and metabolism in the basal ganglia and frontal WM strongly correlate with early developmental performance, suggesting that the Specific Test of Early Infant Motor Performance reflects CNS integrity after preterm birth. This study demonstrates that combining quantitative neuroimaging and early functional movement improves the prediction of 12-month outcomes in premature infants.

Seeing the fetus from a DOHaD perspective: discussion paper from the advanced imaging techniques of DOHaD applications workshop held at the 2019 DOHaD World Congress

Advanced imaging techniques are enhancing research capacity focussed on the developmental origins of adult health and disease (DOHaD) hypothesis, and consequently increasing awareness of future health risks across various subareas of DOHaD research themes. Understanding how these advanced imaging techniques in animal models and human population studies can be both additively and synergistically used alongside traditional techniques in DOHaD-focussed laboratories is therefore of great interest. Global experts in advanced imaging techniques congregated at the advanced imaging workshop at the 2019 DOHaD World Congress in Melbourne, Australia. This review summarizes the presentations of new imaging modalities and novel applications to DOHaD research and discussions had by DOHaD researchers that are currently utilizing advanced imaging techniques including MRI, hyperpolarized MRI, ultrasound, and synchrotron-based techniques to aid their DOHaD research focus.

Functional thalamocortical connectivity at term equivalent age and outcome at 2 years in infants born preterm

Infants born preterm are at high risk of long-term motor and neurocognitive deficits. In the majority of these infants structural MRI at the time of normal birth does not predict motor or cognitive outcomes accurately, and many infants without apparent brain lesions later develop motor and cognitive deficits. Thalamocortical connections are known to be necessary for normal brain function; they develop during late fetal life and are vulnerable to perinatal adversity. This study addressed the hypothesis that abnormalities in the functional connectivity between cortex and thalamus underlie neurocognitive impairments seen after preterm birth. Using resting state functional connectivity magnetic resonance imaging (fMRI) in a group of 102 very preterm infants without major focal brain lesions, we used partial correlations between thalamus and functionally-derived cortical areas to determine significant connectivity between cortical areas and thalamus, and correlated the parameter estimates of these connections with standardised neurocognitive assessments in each infant at 20 months of age. Pre-motor association cortex connectivity to thalamus correlates with motor function, while connectivity between primary sensory-motor cortex and thalamus correlates with cognitive scores. These results demonstrate the importance and vulnerability of functional thalamocortical connectivity development in the perinatal period for later neurocognitive functioning.

Role of Magnetic Resonance Spectroscopy in Evaluation of Cerebral Metabolic Status Before and After Carotid Endarterectomy/Thromboendarterectomy and Carotid Artery Stenting in Patients with Asymptomatic Critical Internal Carotid Artery Stenosis

BACKGROUND The relative efficacy of carotid endarterectomy (CEA)/thromboendarterectomy (TEA) and carotid artery stenting (CAS) already has been compared in randomized controlled trials and a meta-analysis, but only limited data exist describing the status of cerebral metabolism before and after these interventions. The aim of the present study was to compare metabolic changes before and after treatment of carotid stenosis and assess their potential clinical implications.   MATERIAL AND METHODS Patients with asymptomatic unilateral critical internal CAS were imaged with proton 3T magnetic resonance spectroscopy (H-MRS) because the technique is more sensitive than regular magnetic resonance imaging for detection of the early signs of ischemic events. Abnormal metabolite ratios detected with H-MRS may precede actual morphological changes associated with hypoperfusion as well as reperfusion changes. Ipsilateral and contralateral middle cerebral artery vascular territories were both evaluated before and after vascular intervention. H-MRS was performed within 24 h before and after surgery. Correlations in the metabolic data from H-MRS for N-acetylaspartic acid (NAA)+N-acetylaspartylglutamate, creatinine (Cr)+phosphocreatinine, and phosphocholine+glycerophosphocholine (Cho) were sought. RESULTS H-MRS voxels from 11 subjects were analyzed. Values for dCho/CrI, dCho/CrC and Cho/Naal (P<0.001) were significantly higher ipsilaterally than contralaterally. Ratios for dNaa/ChoC and Cho/NaaC were significantly higher on the non-operated side (P<0.001). CONCLUSIONS H-MRS may be helpful for assessment of patients with CAS, particularly because unlike other modalities, it reveals postoperative changes in metabolic brain status. Initial results indicate the important role of perioperative neuroprotective treatment.

Neonatal brain metabolite concentrations: Associations with age, sex, and developmental outcomes

Age and sex differences in brain metabolite concentrations in early life are not well understood. We examined the associations of age and sex with brain metabolite levels in healthy neonates, and investigated the associations between neonatal brain metabolite concentrations and developmental outcomes. Forty-one infants (36–42 gestational weeks at birth; 39% female) of predominantly Hispanic/Latina mothers (mean 18 years of age) underwent MRI scanning approximately two weeks after birth. Multiplanar chemical shift imaging was used to obtain voxel-wise maps of N-acetylaspartate (NAA), creatine, and choline concentrations across the brain. The Bayley Scales of Infant and Toddler Development, a measure of cognitive, language, and motor skills, and mobile conjugate reinforcement paradigm, a measure of learning and memory, were administered at 4 months of age. Findings indicated that postmenstrual age correlated positively with NAA concentrations in multiple subcortical and white matter regions. Creatine and choline concentrations showed similar but less pronounced age related increases. Females compared with males had higher metabolite levels in white matter and subcortical gray matter. Neonatal NAA concentrations were positively associated with learning and negatively associated with memory at 4 months. Age-related increases in NAA, creatine, and choline suggest rapid development of neuronal viability, cellular energy metabolism, and cell membrane turnover, respectively, during early life. Females may undergo earlier and more rapid regional developmental increases in the density of viable neurons compared to males.

Feed-forward neural networks using cerebral MR spectroscopy and DTI might predict neurodevelopmental outcome in preterm neonates

Objectives

We aimed to evaluate the ability of feed-forward neural networks (fNNs) to predict the neurodevelopmental outcome (NDO) of very preterm neonates (VPIs) at 12 months corrected age by using biomarkers of cerebral MR proton spectroscopy (¹H-MRS) and diffusion tensor imaging (DTI) at term-equivalent age (TEA).

Methods

In this prospective study, 300 VPIs born before 32 gestational weeks received an MRI scan at TEA between September 2013 and December 2017. Due to missing or poor-quality spectroscopy data and missing neurodevelopmental tests, 173 VPIs were excluded. Data sets consisting of 103 and 115 VPIs were considered for prediction of motor and cognitive developmental delay, respectively. Five metabolite ratios and two DTI characteristics in six different areas of the brain were evaluated. A feature selection algorithm was developed for receiving a subset of characteristics prevalent for the VPIs with a developmental delay. Finally, the predictors were constructed employing multiple fNNs and fourfold cross-validation.

Results

By employing the constructed fNN predictors, we were able to predict cognitive delays of VPIs with 85.7% sensitivity, 100% specificity, 100% positive predictive value (PPV) and 99.1% negative predictive value (NPV). For the prediction of motor delay, we achieved a sensitivity of 76.9%, a specificity of 98.9%, a PPV of 90.9% and an NPV of 96.7%.

Conclusion

FNNs might be able to predict motor and cognitive development of VPIs at 12 months corrected age when employing biomarkers of cerebral ¹H-MRS and DTI quantified at TEA.

Key Points

• A feed-forward neuronal network is a promising tool for outcome prediction in premature infants.

• Cerebral proton magnetic resonance spectroscopy and diffusion tensor imaging can be used for the construction of early prognostic biomarkers.

• Premature infants that would most benefit from early intervention services can be spotted at the time of optimal neuroplasticity.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-07053-8) contains supplementary material, which is available to authorized users.

Altered brain metabolism contributes to executive function deficits in school-aged children born very preterm

BACKGROUND

Executive function deficits in children born very preterm (VPT) have been linked to anatomical abnormalities in white matter and subcortical brain structures. This study aimed to investigate how altered brain metabolism contributes to these deficits in VPT children at school-age.

METHODS

Fifty-four VPT participants aged 8-13 years and 62 term-born peers were assessed with an executive function test battery. Brain metabolites were obtained in the frontal white matter and the basal ganglia/thalami, using proton magnetic resonance spectroscopy (MRS). N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr, glutamate + glutamine (Glx)/Cr, and myo-Inositol (mI)/Cr were compared between groups and associations with executive functions were explored using linear regression.

RESULTS

In the frontal white matter, VPT showed lower Glx/Cr (mean difference: -5.91%, 95% CI [-10.50, -1.32]), higher Cho/Cr (7.39%, 95%-CI [2.68, 12.10]), and higher mI/Cr (5.41%, 95%-CI [0.18, 10.64]) while there were no differences in the basal ganglia/thalami. Lower executive functions were associated with lower frontal Glx/Cr ratios in both groups (β = 0.16, p = 0.05) and higher mI/Cr ratios in the VPT group only (interaction: β = -0.17, p = 0.02).

CONCLUSION

Long-term brain metabolite alterations in the frontal white matter may be related to executive function deficits in VPT children at school-age.

IMPACT

Very preterm birth is associated with long-term brain metabolite alterations in the frontal white matter. Such alterations may contribute to deficits in executive function abilities. Injury processes in the brain can persist for years after the initial insult. Our findings provide new insights beyond structural and functional imaging, which help to elucidate the processes involved in abnormal brain development following preterm birth. Ultimately, this may lead to earlier identification of children at risk for developing deficits and more effective interventions.

Nutrition and the developing brain: the road to optimizing early neurodevelopment: a systematic review

BACKGROUND

Neonatal intensive care practices have resulted in marked improvements in the survival of premature infants; however, they remain at significant risk for adverse neurodevelopmental outcomes. The impact of current nutritional practices on brain development following early extra-uterine exposure in premature infants is not well known.

METHODS

We performed a systematic review to investigate nutritional effects on postnatal brain development in healthy term and prematurely born infants utilizing advanced magnetic resonance imaging tools.

RESULTS

Systematic screen yielded 595 studies for appraisal. Of these, 22 total studies were selected for inclusion in the review, with findings summarized in a qualitative, descriptive fashion.

CONCLUSION

Fat and energy intake are associated with improved brain volume and development in premature infants. While breast milk intake and long-chain polyunsaturated fatty acid supplementation has been proven beneficial in term infants, the impact in preterm infants is less well understood.

Identifying the translational complexity of magnetic resonance spectroscopy in neonates and infants

Little attention has been paid to relating MRS outputs of vendor-supplied platforms to those from research software. This comparison is crucial to advance MRS as a clinical prognostic tool for disease or injury, recovery, and outcome. The work presented here investigates the agreement between metabolic ratios reported from vendor-provided and LCModel fitting algorithms using MRS data obtained on Siemens 3 T TIM Trio and 3 T Skyra MRI scanners in a total of 55 premature infants and term neonates with hypoxic ischemic encephalopathy (HIE). We compared peak area ratios in single voxels placed in basal ganglia (BG) and frontal white matter (WM) using standard PRESS (TE = 30 ms and 270 ms) and STEAM (TE = 20 ms) MRS sequences at multiple times after birth from 5 to 60 days. A total of 74 scans met quality standards for inclusion, reflecting a spectrum of neonatal disease and several months of early infant development. For the long TE PRESS sequence, N-acetylaspartate (NAA) and Choline (Cho) ratios to Creatine (Cr) correlated strongly between LCModel and vendor-supplied software in the BG. For shorter TEs, the ratios of NAA/Cr and Cho/Cr were more closely related using STEAM at TE = 20 ms in BG and WM, which was significantly better than using PRESS at TE = 30 ms in the BG of HIE infants. At short TEs, however, it is still unclear which MRS sequence, STEAM or PRESS, is superior and thus more work is required in this regard for translating research-generated MRS ratios to clinical diagnosis and prognostication, and unlocking the potential of MRS for in vivo metabolomics. MRS at both long and short TEs is desirable for standard metabolites such as NAA, Cho and Cr, along with important lower concentration metabolites such as myo-inositol and glutathione.

The Impact of Early Neuroimaging and Developmental Assessment in a Preterm Infant Diagnosed with Cerebral Palsy

Premature infants are at risk for cerebral palsy (CP) that is typically diagnosed between 18-24 months. We present a case study of an infant who was discharged from the neonatal intensive care unit (NICU) without obvious neurological deficits but was later diagnosed with hemiplegic CP. The infant was enrolled in an infant motor study, which included neuroimaging and developmental motor assessments. At term, anatomical MRI showed bilateral periventricular leukomalacia, abnormal brain metabolites in frontal white matter via MR spectroscopy (MRS), and low fractional anisotropy (FA) values obtained from diffusional kurtosis imaging (DKI) in several cortical white matter tracts compared to a group of typically developing infants without neuroimaging abnormalities. In addition, the infant scored below average on a developmental assessment administered at term and three months as well as on the standard Bayley III assessment at 12 months. Abnormal neuroimaging and low scores on the early developmental assessment prompted referral for intervention services at two months. With intensive therapy, by 45 months, the infant was average in self-care, mobility, and communication skills, although below average in visual motor and gross motor coordination. This case highlights the clinical impact of early detection and referral using combined neuroimaging and developmental testing.

Neurocognitive Functions in Infants with Malnutrition; Relation with Long-chain Polyunsaturated Fatty Acids, Micronutrients Levels and Magnetic Resonance Spectroscopy

PURPOSE

Malnutrition may influence neurocognitive development in children by directly affecting the brain structural development, or indirectly by affecting the children's cognition experience. Malnutrition alters the cell numbers, cell migration, synaptogenesis, and neurotransmission due to inadequate availability of necessary micronutrients to support cell growth. We aimed to analyze neurocognitive development in infants with malnutrition and its association with long chain polyunsaturated fatty acids (LC-PUFA), micronutrients levels and magnetic resonance spectroscopy (MRS) findings.

METHODS

The study included two groups; group 1, infants with malnutrition (n=24), group 2; healthy infants (n=21). Peripheral blood was obtained from the participants for studying micronutrients and LC-PUFA levels. The neurocognitive development was analyzed by the use of an Ankara Developmental Screening Inventory test. MRS were performed on all infants.

RESULTS

All parameters of neurocognitive development and serum calcium (9.6±0.9 mg/dL vs. 10.4±0.3 mg/dL, p<0.05) and magnesium (2.02±0.27 mg/dL vs. 2.2±0.14 mg/dL, p<0.05) levels were noted as being low in infants with marked malnutrition. No difference was found in LC-PUFA levels between healthy and malnourished infants. Thalamic choline/creatine levels were significantly high in infants with malnutrition (1.33±0.22 vs. 1.18±0.22, p<0.05). Total neurocognitive development in infants was positively correlated with serum calcium levels (p<0.05, r=0.381).

CONCLUSION

Calcium supplementation may improve neurocognitive development in malnourished infants.

Fetal and neonatal neuroimaging

Magnetic resonance imaging (MRI) can provide detail of the soft tissues of the fetal and neonatal brain that cannot be obtained by any other imaging modality. Conventional T1 and T2 weighted sequences provide anatomic detail of the normally developing brain and can demonstrate lesions, including those associated with preterm birth, hypoxic ischemic encephalopathy, perinatal arterial stroke, infections, and congenital malformations. Specialized imaging techniques can be used to assess cerebral vasculature (magnetic resonance angiography and venography), cerebral metabolism (magnetic resonance spectroscopy), cerebral perfusion (arterial spin labeling), and function (functional MRI). A wealth of quantitative tools, most of which were originally developed for the adult brain, can be applied to study the developing brain in utero and postnatally including measures of tissue microstructure obtained from diffusion MRI, morphometric studies to measure whole brain and regional tissue volumes, and automated approaches to study cortical folding. In this chapter, we aim to describe different imaging approaches for the fetal and neonatal brain, and to discuss their use in a range of clinical applications.

Early Diagnosis of Spastic Cerebral Palsy in Infants with Periventricular White Matter Injury Using Diffusion Tensor Imaging

BACKGROUND AND PURPOSE

Periventricular white matter injury is the common cause of spastic cerebral palsy. However, the early diagnosis of spastic cerebral palsy still remains a challenge. Our aim was to investigate whether infants with periventricular white matter injury with bilateral spastic cerebral palsy have unique lesions different from those in infants without cerebral palsy and to evaluate the efficiency of DTI in the early diagnosis of spastic cerebral palsy.

MATERIALS AND METHODS

Infants with periventricular white matter injury and controls underwent MR imaging at 6-18 months of age. Fractional anisotropy was calculated from DTI. Cerebral palsy was diagnosed by 24-30 months of age. Subjects were divided into 3 groups: infants with periventricular white matter injury with bilateral spastic cerebral palsy, infants with periventricular white matter injury without cerebral palsy, and controls. Tract-Based Spatial Statistics and Automated Fiber Quantification were used to investigate intergroup differences. Receiver operating characteristic curves were used to assess the diagnostic accuracy of spastic cerebral palsy. Correlations between motor function scores and fractional anisotropy were evaluated along white matter tracts.

RESULTS

There were 20, 19, and 33 subjects in periventricular white matter injury with spastic cerebral palsy, periventricular white matter injury without cerebral palsy, and control groups, respectively. Decreased fractional anisotropy in the corticospinal tract was only observed in infants with periventricular white matter injury with spastic cerebral palsy, whereas decreased fractional anisotropy in the posterior thalamic radiation and genu and splenium of the corpus callosum was seen in both periventricular white matter injury subgroups. Fractional anisotropy in the corticospinal tract at the internal capsule level was effective in differentiating infants with periventricular white matter injury with spastic cerebral palsy from those without cerebral palsy by a threshold of 0.53, and it had strong correlations with motor function scores.

CONCLUSIONS

Corticospinal tract lesions play a crucial role in motor impairment related to spastic cerebral palsy in infants with periventricular white matter injury. Fractional anisotropy in the corticospinal tract at the internal capsule level could aid in the early diagnosis of spastic cerebral palsy with high diagnostic accuracy.

Prenatal neural origins of infant motor development: Associations between fetal brain and infant motor development

Functional circuits of the human brain emerge and change dramatically over the second half of gestation. It is possible that variation in neural functional system connectivity in utero predicts individual differences in infant behavioral development, but this possibility has yet to be examined. The current study examines the association between fetal sensorimotor brain system functional connectivity and infant postnatal motor ability. Resting-state functional connectivity data was obtained in 96 healthy human fetuses during the second and third trimesters of pregnancy. Infant motor ability was measured 7 months after birth using the Bayley Scales of Infant Development. Increased connectivity between the emerging motor network and regions of the prefrontal cortex, temporal lobes, posterior cingulate, and supplementary motor regions was observed in infants that showed more mature motor functions. In addition, females demonstrated stronger fetal-brain to infant-behavior associations. These observations extend prior longitudinal research back into prenatal brain development and raise exciting new ideas about the advent of risk and the ontogeny of early sex differences.

Magnetic resonance spectroscopy in preterm infants: association with neurodevelopmental outcomes

OBJECTIVE

To compare magnetic resonance spectroscopy (MRS) metabolite ratios in preterm infants at term-equivalent age with those in term infants and to evaluate the association between MRS metabolites and neurodevelopmental outcomes at 18 months corrected age in preterm infants.

DESIGN

We studied infants born at a gestational age <37 weeks and weighing <1500 g during 2009-2013 using MRS at term-equivalent age. Infants with major brain abnormalities were excluded. The ratios of N-acetylaspartate (NAA) to creatine (Cre), NAA to choline-containing compounds (Cho) and Cho to Cre in the frontal white matter and thalamus were measured using multivoxel point-resolved proton spectroscopy sequence. Neurodevelopmental outcomes were assessed at 18 months corrected age.

RESULTS

Thirty-three preterm infants and 16 term infants were enrolled in this study. Preterm infants with normal development at 18 months showed significantly lower NAA/Cho ratios in the frontal white matter than term infants. There were no differences in the Cre/Cho ratios between preterm and term infants. At 18 months corrected age, 9 preterm infants with a mild developmental delay showed significantly lower NAA/Cho ratios in the thalamus than 24 preterm infants with normal development.

CONCLUSIONS

Preterm infants at term-equivalent age showed reduced MRS metabolites (NAA/Cho) compared with term infants. Decreased NAA/Cho ratios in the thalamus were associated with neurodevelopmental delay at 18 months corrected age in preterm infants.

The long-term effect of erythropoiesis stimulating agents given to preterm infants: a proton magnetic resonance spectroscopy study on neurometabolites in early childhood

BACKGROUND

Erythropoiesis stimulating agents (ESAs) are neuroprotective in cell and animal models of preterm birth. Prematurity has been shown to alter neurometabolite levels in children in studies using proton magnetic resonance spectroscopy (1H-MRS).

OBJECTIVE

We hypothesized that ESA treatment in premature infants would tend to normalize neurometabolites by 4-6 years of age.

MATERIALS AND METHODS

Children in a longitudinal study of neurodevelopment underwent MRI and 1H-MRS at approximately 4 years and 6 years of age. Prematurely born children (500-1,250 g birth weight) received ESAs (erythropoietin or darbepoetin) or placebo during their neonatal hospitalization, and these groups were compared to healthy term controls. 1H-MRS spectra were obtained from the anterior cingulate (gray matter) and frontal lobe white matter, assessing combined N-acetylaspartate and N-acetylaspartylglutamate (tNAA), myo-inositol, choline compounds (Cho), combined creatine and phosphocreatine, and combined glutamate and glutamine.

RESULTS

No significant (P≤0.5) group differences were observed for any metabolite level. Significant age-related increases in white-matter tNAA and Cho were observed, as well as a trend for increased gray-matter tNAA.

CONCLUSION

Neither prematurity nor neonatal ESA treatment was associated with differences in brain metabolite levels in the children of this study at a significance level of 0.05. These findings suggest that earlier differences that might have existed had normalized by 4-6 years of age or were too small to be statistically significant in the current sample.

When are metabolic ratios superior to absolute quantification? A statistical analysis

Metabolite levels measured using magnetic resonance spectroscopy (MRS) are often expressed as ratios rather than absolute concentrations. However, the inter-subject variability of the denominator metabolite can introduce uncertainty into a metabolite ratio. In a clinical setting, there are no guidelines on whether ratios or absolute quantification should be used for a more accurate classification of normal versus abnormal results based on their statistical properties. In a research setting, the choice of one over the other can have significant implications on sample size, which must be factored in at the study design stage. Herein, we derive the probability distribution function for the ratio of two normally distributed random variables, and present analytical expressions for the comparison of ratios with absolute quantification in terms of both sample size and area under the receiver operator characteristic curve. The two approaches are compared for typical metabolite values found in the literature, and their respective merits are illustrated using previously acquired clinical MRS data in two pathologies: mild traumatic brain injury and multiple sclerosis. Our analysis shows that the decision between ratios and absolute quantification is non-trivial: in some cases, ratios might offer a reduction in sample size, whereas, in others, absolute quantification might prove more desirable for individual (i.e. clinical) use. The decision is straightforward and exact guidelines are provided in the text, given that population means and standard deviations of numerator and denominator can be reliably estimated.

Neurodevelopmental Abnormalities and Congenital Heart Disease: Insights Into Altered Brain Maturation

In the past 2 decades, it has become evident that individuals born with congenital heart disease (CHD) are at risk of developing life-long neurological deficits. Multifactorial risk factors contributing to neurodevelopmental abnormalities associated with CHD have been identified; however, the underlying causes remain largely unknown, and efforts to address this issue have only recently begun. There has been a dramatic shift in focus from newly acquired brain injuries associated with corrective and palliative heart surgery to antenatal and preoperative factors governing altered brain maturation in CHD. In this review, we describe key time windows of development during which the immature brain is vulnerable to injury. Special emphasis is placed on the dynamic nature of cellular events and how CHD may adversely impact the cellular units and networks necessary for proper cognitive and motor function. In addition, we describe current gaps in knowledge and offer perspectives about what can be done to improve our understanding of neurological deficits in CHD. Ultimately, a multidisciplinary approach will be essential to prevent or improve adverse neurodevelopmental outcomes in individuals surviving CHD.

Brain metabolite alterations in infants born preterm with intrauterine growth restriction: association with structural changes and neurodevelopmental outcome

BACKGROUND

Intrauterine growth restriction and premature birth represent 2 independent problems that may occur simultaneously and contribute to impaired neurodevelopment.

OBJECTIVE

The objective of the study was to assess changes in the frontal lobe metabolic profiles of 1 year old intrauterine growth restriction infants born prematurely and adequate-for-gestational-age controls, both premature and term adequate for gestational age and their association with brain structural and biophysical parameters and neurodevelopmental outcome at 2 years.

STUDY DESIGN

A total of 26 prematurely born intrauterine growth restriction infants (birthweight <10th centile for gestational age), 22 prematurely born but adequate for gestational age controls, and 26 term adequate-for-gestational-age infants underwent brain magnetic resonance imaging and magnetic resonance spectroscopy at 1 year of age during natural sleep, on a 3 Tesla scanner. All brain T1-weighted and diffusion-weighted images were acquired along with short echo time single-voxel proton spectra from the frontal lobe. Magnetic resonance imaging/magnetic resonance spectroscopy data were processed to derive structural, biophysical, and metabolic information, respectively. Neurodevelopment was evaluated at 2 years of age using the Bayley Scales 3rd edition, assessing cognitive, language, motor, socioemotional, and adaptive behavior.

RESULTS

Prematurely born intrauterine growth restriction infants had slightly smaller brain volumes and increased frontal lobe white matter mean diffusivity compared with both prematurely born but adequate for gestational age and term adequate for gestational age controls. Frontal lobe N-acetylaspartate levels were significantly lower in prematurely born intrauterine growth restriction than in prematurely born but adequate for gestational age infants but increased in prematurely born but adequate for gestational age compared with term adequate-for-gestational-age infants. The prematurely born intrauterine growth restriction group also showed slightly lower choline compounds, borderline decrements of estimated glutathione levels, and increased myoinositol to choline ratios, compared with prematurely born but adequate for gestational age controls. These specific metabolite changes were locally correlated to lower gray matter content and increased mean diffusivity and reduced white matter fraction and fractional anisotropy. Prematurely born intrauterine growth restriction infants also showed a tendency for poorer neurodevelopmental outcome at 2 years, associated with lower levels of frontal lobe N-acetylaspartate at 1 year within the preterm subset.

CONCLUSIONS

Preterm intrauterine growth restriction infants showed altered brain metabolite profiles during a critical stage of brain maturation, which correlate with brain structural and biophysical parameters and neurodevelopmental outcome. Our results suggest altered neurodevelopmental trajectories in preterm intrauterine growth restriction and adequate-for-gestational-age infants, compared with term adequate-for-gestational-age infants, which require further characterization.

Correlating early motor skills to white matter abnormalities in preterm infants using diffusion tensor imaging

PURPOSE

Diffusion tensor imaging (DTI) can detect injury to specific white matter (WM) tracts involved with sensorimotor processing and may provide sensitive measures for latent or nascent motor skills. We hypothesized that DTI measures of WM fractional anisotropy (FA) could predict early motor scores on a standardized assessment in a cohort of preterm infants at risk for WM injury.

METHODS

In this prospective study, preterm infants (n= 26, 11 female, 15 male, mean gestational age 29.1 ± 2.5) underwent the Test of Infant Motor Performance (TIMP) at term and at 12 weeks corrected age (CA) and underwent an non-sedated magnetic resonance imaging (MRI) with DTI at a mean of 42 ± 1.5 weeks CA. Fractional anisotropy (FA) was measured by Voxelwise statistical analysis using Tract-Based Spatial Statistics (TBSS) in the specific regions of interest.

RESULTS

Significant differences were found between infants with poor versus average performance on motor assessments at 12-weeks and FA values in several left hemispheric WM tracts (p< 0.05). High FA of the left anterior limb of the internal capsule (ALIC) predicted mean increase in TIMP scores on specific items for head lift in prone and head lift turn to sound (p= 0.045 and p= 0.002).

CONCLUSION

Subtle WM injury, as indicated by low FA in left WM tracts, can predict outcomes of early motor skills performance testing at 3 months. Early DTI may identify infants with silent WM injury who need early intervention. Further studies may establish if individual tract FA improve after targeted treatment.

Altered posterior cingulate brain metabolites and cognitive dysfunction in preterm adolescents

BACKGROUND

Extremely preterm (EP, <28 wk gestation) individuals have increased the risk of cognitive deficits compared with controls. The posterior cingulate region has an important role in cognitive function, but how this is affected by preterm birth is unknown. We aimed to compare brain metabolite ratios of neurons and cell membranes between EP 18-y olds and controls, and explore the association between metabolite ratios and cognitive outcomes.

METHOD

A regional cohort of 150 EP and 134 controls were recruited for the study. Cerebral metabolites were measured using proton magnetic resonance spectroscopy (MRS) obtained from a left posterior cingulate voxel. Total N-acetylaspartate (tNAA, neuronal marker)/total creatine (tCr), and total choline (tCho, cell membrane marker)/tCr ratios were compared between groups using linear regression. Metabolite ratios were correlated with tests of general intelligence (IQ), memory, and attention using linear or logistic regression.

RESULTS

Compared with controls, EP had lower tNAA/tCr (mean difference (95% CI) of -2.27% (-4.09, -0.45)) and tCho/tCr (mean difference (95% CI) of -11.11% (-20.37, -1.85)), all P = 0.02. Higher tCho/tCr correlated with better IQ in the EP group only; whereas higher tNAA/tCr ratios correlated with better scores in working memory and attention in both groups.

CONCLUSION

EP birth is associated with long-term brain metabolite ratio alterations. This may underlie poorer cognitive performance in EP survivors.

Longitudinal development in the preterm thalamus and posterior white matter: MRI correlations between diffusion weighted imaging and T2 relaxometry

Infants born prematurely are at increased risk of adverse neurodevelopmental outcome. The measurement of white matter tissue composition and structure can help predict functional performance. Specifically, measurements of myelination and indicators of myelination status in the preterm brain could be predictive of later neurological outcome. Quantitative imaging of myelin could thus serve to develop biomarkers for prognosis or therapeutic intervention; however, accurate estimation of myelin content is difficult. This work combines diffusion MRI and multi-component T2 relaxation measurements in a group of 37 infants born very preterm and scanned between 27 and 58 weeks equivalent gestational age. Seven infants have longitudinal data at two time points that we analyze in detail. Our aim is to show that measurement of the myelin water fraction is achievable using widely available pulse sequences and state-of-the-art algorithmic modeling of the MR imaging procedure and that a multi-component fitting routine to multi-shell diffusion weighted data can show differences in neurite density and local spatial arrangement in grey and white matter. Inference on the myelin water fraction allows us to demonstrate that the change in diffusion properties of the preterm thalamus is not solely due to myelination (that increase in myelin content accounts for about a third of the observed changes) whilst the decrease in the posterior white matter T2 has no significant component that is due to myelin water content. This work applies multi-modal advanced quantitative neuroimaging to investigate changing tissue properties in the longitudinal setting. Hum Brain Mapp 37:2479-2492, 2016. © 2016 Wiley Periodicals, Inc.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

Transdifferentiation-Induced Neural Stem Cells Promote Recovery of Middle Cerebral Artery Stroke Rats

Induced neural stem cells (iNSCs) can be directly transdifferentiated from somatic cells. One potential clinical application of the iNSCs is for nerve regeneration. However, it is unknown whether iNSCs function in disease models. We produced transdifferentiated iNSCs by conditional overexpressing Oct4, Sox2, Klf4, c-Mycin mouse embryonic fibroblasts. They expanded readily in vitro and expressed NSC mRNA profile and protein markers. These iNSCs differentiated into mature astrocytes, neurons and oligodendrocytes in vitro. Importantly, they reduced lesion size, promoted the recovery of motor and sensory function as well as metabolism status in middle cerebral artery stroke rats. These iNSCs secreted nerve growth factors, which was associated with observed protection of neurons from apoptosis. Furthermore, iNSCs migrated to and passed through the lesion in the cerebral cortex, where Tuj1+ neurons were detected. These findings have revealed the function of transdifferentiated iNSCs in vivo, and thus provide experimental evidence to support the development of personalized regenerative therapy for CNS diseases by using genetically engineered autologous somatic cells.

Brain metabolite differences in one-year-old infants born small at term and association with neurodevelopmental outcome

OBJECTIVE

We assessed brain metabolite levels by magnetic resonance spectroscopy (MRS) in 1-year-old infants born small at term, as compared with infants born appropriate for gestational age (AGA), and their association with neurodevelopment at 2 years of age.

STUDY DESIGN

A total of 40 infants born small (birthweight <10th centile for gestational age) and 30 AGA infants underwent brain MRS at age 1 year on a 3-T scanner. Small-born infants were subclassified as late intrauterine growth restriction or as small for gestational age, based on the presence or absence of prenatal Doppler and birthweight predictors of an adverse perinatal outcome, respectively. Single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) data were acquired from the frontal lobe at short echo time. Neurodevelopment was evaluated at 2 years of age using the Bayley Scales of Infant and Toddler Development, Third Edition, assessing cognitive, language, motor, social-emotional, and adaptive behavior scales.

RESULTS

As compared with AGA controls, infants born small showed significantly higher levels of glutamate and total N-acetylaspartate (NAAt) to creatine (Cr) ratio at age 1 year, and lower Bayley Scales of Infant and Toddler Development, Third Edition scores at 2 years. The subgroup with late intrauterine growth restriction further showed lower estimated glutathione levels at age 1 year. Significant correlations were observed for estimated glutathione levels with adaptive scores, and for myo-inositol with language scores. Significant associations were also noticed for NAA/Cr with cognitive scores, and for glutamate/Cr with motor scores.

CONCLUSION

Infants born small show brain metabolite differences at 1 year of age, which are correlated with later neurodevelopment. These results support further research on MRS to develop imaging biomarkers of abnormal neurodevelopment.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

The predictive validity of neonatal MRI for neurodevelopmental outcome in very preterm children

Very preterm children are at a high risk for neurodevelopmental impairments, but there is variability in the pattern and severity of outcome. Neonatal magnetic resonance imaging (MRI) enhances the capacity to detect brain injury and altered brain development and assists in the prediction of high-risk children who warrant surveillance and early intervention. This review describes the application of conventional and advanced MRI with very preterm neonates, specifically focusing on the relationship between neonatal MRI findings and later neurodevelopmental outcome. Research demonstrates that conventional MRI is strongly associated with neurodevelopmental outcome in childhood. Further studies are needed to examine the role of advanced MRI techniques in predicting outcome in very preterm children, but early research findings are promising. In conclusion, neonatal MRI is predictive of later neurodevelopment but is dependent on appropriately trained specialists and should be interpreted in conjunction with other clinical and social information.

Reduced thalamic volume in preterm infants is associated with abnormal white matter metabolism independent of injury

INTRODUCTION

Altered thalamocortical development is hypothesized to be a key substrate underlying neurodevelopmental disabilities in preterm infants. However, the pathogenesis of this abnormality is not well-understood. We combined magnetic resonance spectroscopy of the parietal white matter and morphometric analyses of the thalamus to investigate the association between white matter metabolism and thalamic volume and tested the hypothesis that thalamic volume would be associated with diminished N-acetyl-aspartate (NAA), a measure of neuronal/axonal maturation, independent of white matter injury.

METHODS

Data from 106 preterm infants (mean gestational age at birth: 31.0 weeks ± 4.3; range 23-36 weeks) who underwent MR examinations under clinical indications were included in this study.

RESULTS

Linear regression analyses demonstrated a significant association between parietal white matter NAA concentration and thalamic volume. This effect was above and beyond the effect of white matter injury and age at MRI and remained significant even when preterm infants with punctate white matter lesions (pWMLs) were excluded from the analysis. Furthermore, choline, and among the preterm infants without pWMLs, lactate concentrations were also associated with thalamic volume. Of note, the associations between NAA and choline concentration and thalamic volume remained significant even when the sample was restricted to neonates who were term-equivalent age or older.

CONCLUSION

These observations provide convergent evidence of a neuroimaging phenotype characterized by widespread abnormal thalamocortical development and suggest that the pathogenesis may involve impaired axonal maturation.

Parenteral nutrition compromises neurodevelopment of preterm pigs

BACKGROUND

Despite advances in nutritional support and intensive care, preterm infants are at higher risk of compromised neurodevelopment.

OBJECTIVE

This study evaluated the contribution of total parenteral nutrition (PN) to compromised neurodevelopment after preterm birth.

METHODS

Preterm pigs were provided PN or enteral nutrition (EN) for 10 d. Neurodevelopment was assessed by observations of motor activity and evaluation of sensory/motor reflexes, brain weight, MRI, and cerebellar histology.

RESULTS

Despite similar gains in body weight, PN pigs had smaller brains (32 ± 0.4 vs. 35 ± 0.6 g; P = 0.0002) including the cerebellum, as well as reduced motor activity (P = 0.005), which corresponded to underdeveloped myelination (P = 0.004) measured by diffusion tensor imaging. PN resulted in lower serum triglycerides (17 ± 5.9 vs. 27 ± 3.1 mg/dL; P = 0.05), total cholesterol (31 ± 9.6 vs. 85 ± 8.1 mg/dL; P = 0.04), VLDL cholesterol (3.7 ± 1.2 vs. 5.7 ± 0.7 mg/dL; P = 0.04), and HDL cholesterol (16 ± 4.6 vs. 57 ± 7.3 mg/dL; P = 0.03) and nonsignificantly lower LDL cholesterol (10.7 ± 4.4 vs. 22.7 ± 2.9 mg/dL; P = 0.09).

CONCLUSIONS

The compromised neurodevelopment caused by total PN is a novel finding, was independent of confounding variables (disease, inconsistent gestational ages, diverse genetics, extrauterine growth retardation, and inconsistent neonatal intensive care unit protocols), and highlights a need to improve current PN solutions. The preterm pig is a translational animal model for improving nutrition support to enhance neurodevelopment of preterm infants requiring PN.

Focal necrosis and disturbed myelination in the white matter of newborn infants: a tale of too much or too little oxygen

White matter disease in preterm infants comes along with focal destructions or with diffuse myelination disturbance. Recent experimental work with transgenic mice paves the way for a unifying molecular model for both types of brain injury, placing oxygen sensing by oligodendrocyte precursor cells (OPCs) at the center stage. Mice genetically altered to mimic high local oxygen tension in oligodendroglia lineage cells (via deletion of hypoxia-inducible factor, HIF) develop white matter disease resembling cystic periventricular leukomalacia within the first 7 days of life. Mice in which local hypoxia is mimicked in oligodendroglial cells (via genetic inhibition of HIF decay) display arrested OPC maturation and subsequent hypomyelination, reminiscent of the diffuse white matter disease observed in preterm infants and infants with congenital heart disease. These recent experimental findings on oxygen sensing and myelination are awaiting integration into a clinical framework. Gene regulation in response to hyperoxia or hypoxia, rather than oxidative stress, may be an important mechanism underlying neonatal white matter disease.