Brain metabolite concentrations are associated with illness severity scores and white matter abnormalities in very preterm infants

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.

Hypertensive disorders of pregnancy and alterations in brain metabolites in preterm infants: A multi-voxel proton MR spectroscopy study

BACKGROUND

Infants born to mothers with hypertensive disorders of pregnancy (HDP) have adverse neurodevelopmental consequences in later life. Magnetic resonance spectroscopy (MRS) is used to predict subsequent neurodevelopment in the field of perinatology.

AIM

We aimed to determine whether exposure to HDP in utero leads to alterations in brain metabolites in preterm infants using multi-voxel proton MRS at term-equivalent age.

STUDY DESIGN

Retrospective cohort study.

SUBJECTS

A total of 103 preterm infants born before 34 weeks of gestation at Nagoya University Hospital between 2010 and 2018 were eligible. Twenty-seven infants were born to mothers with HDP (HDP group), and 76 were born to mothers without HDP (non-HDP group).

OUTCOME MEASURES

The peak area ratios of N-acetylaspartate (NAA)/choline (Cho), NAA/creatine (Cr), and Cho/Cr were evaluated at 10 designated regions of interest (bilateral frontal lobes, basal ganglia, thalami, temporal lobes, and occipital lobes).

RESULTS

The peak area ratios of NAA/Cho and NAA/Cr in the bilateral thalami were significantly higher in the HDP group than in the non-HDP group after adjustment for covariates (postmenstrual age at MRS assessment and infant sex). No significant differences were observed in other regions. Preeclampsia, abnormal umbilical artery blood flow, and fetal growth restrictions were significantly associated with increased NAA/Cho and NAA/Cr ratios in the thalami.

CONCLUSIONS

Based on the evidence that NAA/Cho and NAA/Cr ratios constantly increase with postmenstrual age in normal brain development, exposure to maternal HDP in utero may accelerate brain maturation and increase neuronal activity in preterm infants.

GABA and glutamate in the preterm neonatal brain: In-vivo measurement by magnetic resonance spectroscopy

Cognitive and behavioral disabilities in preterm infants, even without obvious brain injury on conventional neuroimaging, underscores a critical need to identify the subtle underlying microstructural and biochemical derangements. The gamma-aminobutyric acid (GABA) and glutamatergic neurotransmitter systems undergo rapid maturation during the crucial late gestation and early postnatal life, and are at-risk of disruption after preterm birth. Animal and human autopsy studies provide the bulk of current understanding since non-invasive specialized proton magnetic resonance spectroscopy (¹H-MRS) to measure GABA and glutamate are not routinely available for this vulnerable population due to logistical and technical challenges. We review the specialized ¹H-MRS techniques including MEscher-GArwood Point Resolved Spectroscopy (MEGA-PRESS), special challenges and considerations needed for interpretation of acquired data from the developing brain of preterm infants. We summarize the limited in-vivo preterm data, highlight the gaps in knowledge, and discuss future directions for optimal integration of available in-vivo approaches to understand the influence of GABA and glutamate on neurodevelopmental outcomes after preterm birth.

Age and Sex Influences Gamma-aminobutyric Acid Concentrations in the Developing Brain of Very Premature Infants

Gamma-aminobutyric acid (GABA) and glutamate are principal neurotransmitters essential for late gestational brain development and may play an important role in prematurity-related brain injury. In vivo investigation of GABA in the preterm infant with standard proton magnetic resonance spectroscopy (1H-MRS) has been limited due to its low concentrations in the developing brain, and overlap in the spectrum by other dominant metabolites. We describe early postnatal profiles of in vivo GABA and glutamate concentrations in the developing preterm brain measured by using the J-difference editing technique, Mescher-Garwood point resolved spectroscopy. We prospectively enrolled very preterm infants born ≤32 weeks gestational age and non-sedated 1H-MRS (echo time 68 ms, relaxation time 2000 ms, 256 signal averages) was acquired on a 3 Tesla magnetic resonance imaging scanner from a right frontal lobe voxel. Concentrations of GABA + (with macromolecules) was measured from the J-difference spectra; whereas glutamate and composite glutamate + glutamine (Glx) were measured from the unedited (OFF) spectra and reported in institutional units. We acquired 42 reliable spectra from 38 preterm infants without structural brain injury [median gestational age at birth of 28.0 (IQR 26.0, 28.9) weeks; 19 males (50%)] at a median postmenstrual age of 38.4 (range 33.4 to 46.4) weeks. With advancing post-menstrual age, the concentrations of glutamate OFF increased significantly, adjusted for co-variates (generalized estimating equation β = 0.22, p = 0.02). Advancing postnatal weeks of life at the time of imaging positively correlated with GABA + (β = 0.06, p = 0.02), glutamate OFF (β = 0.11, p = 0.02) and Glx OFF (β = 0.12, p = 0.04). Male infants had higher GABA + (1.66 ± 0.07 vs. 1.33 ± 0.11, p = 0.01) concentrations compared with female infants. For the first time, we report the early ex-utero developmental profile of in vivo GABA and glutamate stratified by age and sex in the developing brain of very preterm infants. This data may provide novel insights into the pathophysiology of neurodevelopmental disabilities reported in preterm infants even in the absence of structural brain injury.

Non-invasive measurement of biochemical profiles in the healthy fetal brain

Proton magnetic resonance spectroscopy (¹H-MRS) of the fetal brain can be used to study emerging metabolite profiles in the developing brain. Identifying early deviations in brain metabolic profiles in high-risk fetuses may offer important adjunct clinical information to improve surveillance and management during pregnancy.

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.

Socioeconomic status and brain injury in children born preterm: modifying neurodevelopmental outcome

Improved intensive care therapies have increased the survival of children born preterm. Yet, many preterm children experience long-term neurodevelopmental sequelae. Indeed, preterm birth remains a leading cause of lifelong neurodevelopmental disability globally, posing significant challenges to the child, family, and society. Neurodevelopmental disability in children born preterm is traditionally linked to acquired brain injuries such as white matter injury and to impaired brain maturation resulting from neonatal illness such as chronic lung disease. Socioeconomic status (SES) has long been recognized to contribute to variation in outcome in children born preterm. Recent brain imaging data in normative term-born cohorts suggest that lower SES itself predicts alterations in brain development, including the growth of the cerebral cortex and subcortical structures. Recent evidence in children born preterm suggests that the response to early-life brain injuries is modified by the socioeconomic circumstances of children and families. Exciting new data points to the potential of more favorable SES circumstances to mitigate the impact of neonatal brain injury. This review addresses emerging evidence suggesting that SES modifies the relationship between early-life exposures, brain injury, and neurodevelopmental outcomes in children born preterm. Better understanding these relationships opens new avenues for research with the ultimate goal of promoting optimal outcomes for those children born preterm at highest risk of neurodevelopmental consequence.

Detection of occult abnormalities in the deep gray matter nuclei of neonates with punctate white matter lesions by magnetic resonance spectroscopy

PURPOSE

Punctate white matter lesions (PWML) are common in preterm neonates and have also been reported in the full term. While most studies focus on white matter abnormalities, gray matter (GM) alterations are generally ignored due to the lack of abnormalities on conventional MRI. This study aims to investigate whether magnetic resonance spectroscopy is a sensitive and practical method to detect occult alterations of deep GM nuclei in these neonates.

METHODS

Neonates with PWML and controls with no MRI abnormalities were retrospectively studied. Apparent diffusion coefficient values and metabolic ratios (Cho/Cr, NAA/Cho, and NAA/Cr) in the lenticular nucleus and the thalamus were compared between the PWML and control groups.

RESULTS

Forty-two neonates with PWML (grades I, II, and III contained 14, 21, and 7 subjects, respectively) and 50 controls were enrolled. Apparent diffusion coefficient values in the lenticular nucleus and the thalamus were not significantly different between the PWML and the control groups. The NAA/Cho ratio was significantly lower in the PWML group than in the control group in both regions, whereas a lower NAA/Cr ratio was only observed in the thalamus. Significantly lower ratios of NAA/Cho in both regions and NAA/Cr in the thalamus were detected in the grade II and III subgroup, whereas the thalamic NAA/Cho ratio was decreased in the grade I group compared with controls.

CONCLUSIONS

Magnetic resonance spectroscopy is a sensitive method for detecting the occult deep GM abnormalities for the study cohort of neonates with PWML when compared with subjects without PWML.

Third Trimester Cerebellar Metabolite Concentrations are Decreased in Very Premature Infants with Structural Brain Injury

Advanced neuroimaging techniques have improved our understanding of microstructural changes in the preterm supratentorial brain as well as the cerebellum and its association with impaired neurodevelopmental outcomes. However, the metabolic interrogation of the developing cerebellum during the early postnatal period after preterm birth remains largely unknown. Our study investigates the relationship between cerebellar neurometabolites measured by proton magnetic spectroscopy (¹H-MRS) in preterm infants with advancing post-menstrual age (PMA) and brain injury during ex-utero third trimester prior to term equivalent age (TEA). We prospectively enrolled and acquired high quality ¹H-MRS at median 33.0 (IQR 31.6-35.2) weeks PMA from a voxel placed in the cerebellum of 53 premature infants born at a median gestational age of 27.0 (IQR 25.0-29.0) weeks. ¹H-MRS data were processed using LCModel software to calculate absolute metabolite concentrations of N-acetylaspartate (NAA), choline (Cho) and creatine (Cr). We noted positive correlations of cerebellar concentrations of NAA, Cho and Cr (Spearman correlations of 0.59, 0.64 and 0.52, respectively, p value < 0.0001) and negative correlation of Cho/Cr ratio (R -0.5, p value 0.0002) with advancing PMA. Moderate-to-severe cerebellar injury was noted on conventional magnetic resonance imaging (MRI) in 14 (26.4%) of the infants and were noted to have lower cerebellar NAA, Cho and Cr concentrations compared with those without injury (p value < 0.001). Several clinical complications of prematurity including necrotizing enterocolitis, systemic infections and bronchopulmonary dysplasia were associated with altered metabolite concentrations in the developing cerebellum. We report for the first time that ex-utero third trimester cerebellar metabolite concentrations are decreased in very preterm infants with moderate-to-severe structural cerebellar injury. We report increasing temporal trends of metabolite concentrations in the cerebellum with advancing PMA, which was impaired in infants with brain injury on MRI and may have early diagnostic and prognostic value in predicting neurodevelopmental outcomes in very preterm infants.

Longitudinal investigation of the metabolome of 3D aggregating brain cell cultures at different maturation stages by 1H HR-MAS NMR

The aim of the present study was to establish the developmental profile of metabolic changes of 3D aggregating brain cell cultures by ¹H high-resolution magic angle spinning (HR-MAS) NMR spectroscopy. The histotypic 3D brain aggregate, containing all brain cell types, is an excellent model for mechanistic studies including OMICS analysis; however, their metabolic profile has not been yet fully investigated. Chemometric analysis revealed a clear separation of samples from the different maturation time points. Metabolite concentration evolutions could be followed and revealed strong and various metabolic alterations. The strong metabolite evolution emphasizes the brain modeling complexity during maturation, possibly reflecting physiological processes of brain tissue development. The small observed intra- and inter-experimental variabilities show the robustness of the combination of ¹H-HR-MAS NMR and 3D brain aggregates, making it useful to investigate mechanisms of toxicity that will ultimately contribute to improve predictive neurotoxicology. Graphical Abstract ᅟ.

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.

Basic Principles and Clinical Applications of Magnetic Resonance Spectroscopy in Neuroradiology

Magnetic resonance spectroscopy is a powerful tool to assist daily clinical diagnostics. This review is intended to give an overview on basic principles of the technology, discuss some of its technical aspects, and present typical applications in daily clinical routine in neuroradiology.

Pregnancy outcomes in two growth restricted fetuses with in utero cerebral lactate

Elevated cerebral lactate is increasingly detected by magnetic resonance spectroscopy in the human fetus diagnosed with various pathologic conditions. However, the significance of detectable cerebral lactate remains uncertain. We present two cases of fetal cerebral lactate with adverse pregnancy outcomes.

Serial cranial ultrasonography or early MRI for detecting preterm brain injury?

OBJECTIVE

To investigate detection ability and feasibility of serial cranial ultrasonography (CUS) and early MRI in preterm brain injury.

DESIGN

Prospective cohort study.

SETTING

Level III neonatal intensive care unit.

PATIENTS

307 infants, born below 29 weeks of gestation.

METHODS

Serial CUS and MRI were performed according to standard clinical protocol. In case of instability, MRI was postponed or cancelled. Brain images were assessed by independent experts and compared between modalities.

MAIN OUTCOME MEASURES

Presence of preterm brain injury on either CUS or MRI and discrepant imaging findings on CUS and MRI.

RESULTS

Serial CUS was performed in all infants; early MRI was often postponed (n=59) or cancelled (n=126). Injury was found in 146 infants (47.6%). Clinical characteristics differed significantly between groups that were subdivided according to timing of MRI. 61 discrepant imaging findings were found. MRI was superior in identifying cerebellar haemorrhage; CUS in detection of acute intraventricular haemorrhage, perforator stroke and cerebral sinovenous thrombosis.

CONCLUSIONS

Advanced serial CUS seems highly effective in diagnosing preterm brain injury, but may miss cerebellar abnormalities. Although MRI does identify these lesions, feasibility is limited. Improved safety, better availability and tailored procedures are essential for MRI to increase its value in clinical care.

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.

Magnetic resonance spectroscopy at term-equivalent age in extremely preterm infants: association with cognitive and language development

BACKGROUND

Proton magnetic resonance spectroscopy can be used to assess brain integrity and maturation with age.

OBJECTIVE

To compare regional cerebral magnetic resonance spectroscopy metabolite ratios in extremely low birth weight and healthy term control infants measured at term-equivalent age and to evaluate association between magnetic resonance spectroscopy metabolites and cognitive and language development at 18-22 months' corrected age.

METHODS

Single-voxel point-resolved spectroscopy sequence was performed in a prospective cohort of 43 infants. Magnetic resonance spectroscopy metabolite ratios of N-acetylaspartate to choline-containing compounds and N-acetylaspartate to myo-inositiol in the hippocampus, cortex, and subventricular zone were associated with Bayley mental, cognitive, and language scores at 18-22 months' corrected age.

RESULTS

The mean (±S.D.) gestation of the 31 extremely low birth weight population was 25 (±1.1) weeks and mean (±S.D.) birth weight was 749 (±133.9) g. Compared with healthy term control infants, extremely low birth weight infants exhibited consistently lower N-acetylaspartate-to-choline-containing compounds ratios in our three regions of interest, with differences reaching statistical significance for the subventricular zone and cortex regions. In multiple linear regression analyses, N-acetylaspartate-to-choline-containing compounds ratio in the subventricular zone, N-acetylaspartate-to-choline-containing compounds ratio in the cortex, and N-acetylaspartate-to-myo-inositiol ratio in the subventricular zone were significantly associated with Bayley mental scores at 18-22 months' corrected age.

CONCLUSIONS

Magnetic resonance spectroscopy metabolite abnormalities at term-equivalent age appear to be significantly associated with cognitive and language development in extremely low birth weight infants.

Early detection of ventilation-induced brain injury using magnetic resonance spectroscopy and diffusion tensor imaging: an in vivo study in preterm lambs

Background and Aim

High tidal volume (V_T) ventilation during resuscitation of preterm lambs results in brain injury evident histologically within hours after birth. We aimed to investigate whether magnetic resonance spectroscopy (MRS) and/or diffusion tensor imaging (DTI) can be used for early in vivo detection of ventilation-induced brain injury in preterm lambs.

Methods

Newborn lambs (0.85 gestation) were stabilized with a “protective ventilation” strategy (PROT, n = 7: prophylactic Curosurf, sustained inflation, V_T 7 mL/kg, positive end expiratory pressure (PEEP) 5 cmH₂O) or an initial 15 minutes of “injurious ventilation” (INJ, n = 10: V_T 12 mL/kg, no PEEP, late Curosurf) followed by PROT ventilation for the remainder of the experiment. At 1 hour, lambs underwent structural magnetic resonance imaging (Siemens, 3 Tesla). For measures of mean/axial/radial diffusivity (MD, AD, RD) and fractional anisotropy (FA), 30 direction DTI was performed. Regions of interests encompassed the thalamus, internal capsule, periventricular white matter and the cerebellar vermis. MRS was performed using a localized single-voxel (15×15×20 mm³, echo time 270 ms) encompassing suptratentorial deep nuclear grey matter and central white matter. Peak-area ratios for lactate (Lac) relative to N-acetylaspartate (NAA), choline (Cho) and creatine (Cr) were calculated. Groups were compared using 2-way RM-ANOVA, Mann-Whitney U-test and Spearman's correlations.

Results

No cerebral injury was seen on structural MR images. Lambs in the INJ group had higher mean FA and lower mean RD in the thalamus compared to PROT lambs, but not in the other regions of interest. Peak-area lactate ratios >1.0 was only seen in INJ lambs. A trend of higher mean peak-area ratios for Lac/Cr and Lac/Cho was seen, which correlated with lower pH in both groups.

Conclusion

Acute changes in brain diffusion measures and metabolite peak-area ratios were observed after injurious ventilation. Early MRS/DTI is able to detect the initiation of ventilation-induced brain injury.

Structure and function: how to connect?

INTRODUCTION

The majority, but not all, of very preterm-born infants have difficulties with a variety of cognitive functions as children. It is critical to be able to predict as early as possible those who will have difficulties, to be able to direct appropriate interventions.

METHODS

We are conducting multimodal structural and functional MRI studies in very preterm-born infants and following them with behavioural and neuroimaging assessments until 4 years of age. We are also completing structural and more complex functional imaging in school-aged very preterm-born children.

RESULTS

A number of MRI measures between preterm and term age correlate with outcome at 2 years of age. Functional and structural differences are also seen at school age; examples from these various studies are presented.

CONCLUSION

Structural and functional studies in preterm-born versus term-born infants and children, particularly if completed longitudinally, provide important information on the evolution of brain-behaviour correlates and can help predict outcome in this high-risk population.

Resuscitation intensity at birth is associated with changes in brain metabolic development in preterm neonates

INTRODUCTION

Intensive resuscitation at birth has been linked to intraventricular haemorrhage (IVH) in the preterm neonate. However, the impact of less intensive resuscitation on more subtle alterations in brain metabolic development is largely unknown. Our objective was to determine the relationship between the intensity of neonatal resuscitation following preterm birth on brain metabolic development.

METHODS

One hundred thirty-three very preterm-born neonates (median gestational age [GA] 27 ± 2 weeks) underwent MR spectroscopic imaging early in life (median postmenstrual age 32 weeks) and again at term-equivalent age (median 40 weeks). Severity of white matter injury, IVH and cerebellar haemorrhage on magnetic resonance imaging were scored. Ratios of N-acetylaspartate (NAA) and lactate to choline (Cho) were calculated in eight regions of interest and were assessed in relation to intensiveness of resuscitation strategy (bag and mask, continuous positive airway pressure [CPAP], intubation, cardiopulmonary resuscitation [CPR]).

RESULTS

Within the first hour of life, 14 newborns had no intervention, 3 received bag and mask, 30 had CPAP, 79 were intubated and 7 had CPR. Resuscitated infants were more likely to have IVH (p = 0.02). More intensive resuscitation was associated with decreased NAA/Cho maturation (p < 0.001, adjusting for birth GA). Metabolic development was similar in neonates requiring CPAP in comparison to those receiving no intervention. The change in lactate/Cho did not differ across resuscitation categories (p = 0.8).

CONCLUSIONS

Intensity of resuscitation at birth is related to changes in metabolic brain development from early in life to term-equivalent age. Results suggest that preventing the need for intensive neonatal resuscitation may provide an opportunity to improve brain development in preterm neonates.

Quantitative MRI for studying neonatal brain development

Quantitative MRI techniques based on morphology and tissue microstructure dependent contrast provide a unique window on brain development in the neonatal period. The dramatic changes in morphology and MRI contrast that occur during this period have the potential to be used to identify normal and abnormal developmental trajectories that predict neurodevelopmental outcome in at risk populations. Here, we review these technologies focussing on two broad categories: gross morphological analysis and tissue microstructure assessment. With respect to morphology, we examine the role of image registration and atlas-based techniques, highlighting the challenges posed by the scale of the anatomical changes and the high incidence of radiologically abnormal scans in the premature infant population. With respect to microstructure, we examine the potential and remaining challenges for using quantitative MRI to dissociate processes of cell proliferation, neuronal maturation, and myelination by combining different signal contrasts. Recent progress from our group in this area is highlighted.

Brain development in infants born preterm: looking beyond injury

Infants born very preterm are high risk for acquired brain injury and disturbances in brain maturation. Although survival rates for preterm infants have increased in the last decades owing to improved neonatal intensive care, motor disabilities including cerebral palsy persist, and impairments in cognitive, language, social, and executive functions have not decreased. Evidence from neuroimaging studies exploring brain structure, function, and metabolism has indicated abnormalities in the brain development trajectory of very preterm-born infants that persist through to adulthood. In this chapter, we review neuroimaging approaches for the identification of brain injury in the preterm neonate. Advances in medical imaging and availability of specialized equipment necessary to scan infants have facilitated the feasibility of conducting longitudinal studies to provide greater understanding of early brain injury and atypical brain development and their effects on neurodevelopmental outcome. Improved understanding of the risk factors for acquired brain injury and associated factors that affect brain development in this population is setting the stage for improving the brain health of children born preterm.