MR spectroscopy of normative premature newborns

Impact of bronchopulmonary dysplasia on brain GABA concentrations in preterm infants: Prospective cohort study

BACKGROUND

Bronchopulmonary dysplasia (BPD) is associated with cognitive-behavioral deficits in very preterm (VPT) infants, often in the absence of structural brain injury. Advanced GABA-editing techniques like Mescher-Garwood point resolved spectroscopy (MEGA-PRESS) can quantify in-vivo gamma-aminobutyric acid (GABA+, with macromolecules) and glutamate (Glx, with glutamine) concentrations to investigate for neurophysiologic perturbations in the developing brain of VPT infants.

OBJECTIVE

To investigate the relationship between the severity of BPD and basal-ganglia GABA+ and Glx concentrations in VPT infants.

METHODS

MRI studies were performed on a 3 T scanner in a cohort of VPT infants [born ≤32 weeks gestational age (GA)] without major structural brain injury and healthy-term infants (>37 weeks GA) at term-equivalent age. MEGA-PRESS (TE68ms, TR2000ms, 256averages) sequence was acquired from the right basal-ganglia voxel (∼3cm3) and metabolite concentrations were quantified in institutional units (i.u.). We stratified VPT infants into no/mild (grade 0/1) and moderate-severe (grade 2/3) BPD.

RESULTS

Reliable MEGA-PRESS data was available from 63 subjects: 29 healthy-term and 34 VPT infants without major structural brain injury. VPT infants with moderate-severe BPD (n = 20) had the lowest right basal-ganglia GABA+ (median 1.88 vs. 2.28 vs. 2.12 i.u., p = 0.025) and GABA+/choline (0.73 vs. 0.99 vs. 0.88, p = 0.004) in comparison to infants with no/mild BPD and healthy-term infants. The GABA+/Glx ratio was lower (0.34 vs. 0.44, p = 0.034) in VPT infants with moderate-severe BPD than in infants with no/mild BPD.

CONCLUSIONS

Reduced GABA+ and GABA+/Glx in VPT infants with moderate-severe BPD indicate neurophysiologic perturbations which could serve as early biomarkers of future cognitive deficits.

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.

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.

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.

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.

Edited magnetic resonance spectroscopy in the neonatal brain

J-difference-edited spectroscopy is a valuable approach for the detection of low-concentration metabolites with magnetic resonance spectroscopy (MRS). Currently, few edited MRS studies are performed in neonates due to suboptimal signal-to-noise ratio, relatively long acquisition times, and vulnerability to motion artifacts. Nonetheless, the technique presents an exciting opportunity in pediatric imaging research to study rapid maturational changes of neurotransmitter systems and other metabolic systems in early postnatal life. Studying these metabolic processes is vital to understanding the widespread and rapid structural and functional changes that occur in the first years of life. The overarching goal of this review is to provide an introduction to edited MRS for neonates, including the current state-of-the-art in editing methods and editable metabolites, as well as to review the current literature applying edited MRS to the neonatal brain. Existing challenges and future opportunities, including the lack of age-specific reference data, are also discussed.

A correlation between Magnetic Resonance Spectroscopy (1-H MRS) and the neurodevelopment of two-year-olds born preterm in an EPIRMEX cohort study

BACKGROUND

Preterm infants are at risk of neurodevelopmental impairments. At present, proton magnetic resonance spectroscopy (1H-MRS) is currently used to evaluate brain metabolites in asphyxiated term infants. The purpose of this study was to identify in the preterm EPIRMEX cohort any correlations between (1H-MRS) metabolites ratio at term equivalent age (TEA) and neurodevelopmental outcomes at 2 years.

METHODS

Our study included EPIRMEX eligible patients who were very preterm infants (gestational age at birth ≤32 weeks) and who underwent a brain MRI at TEA and ¹H-MRS using a monovoxel technique. The volumes of interest (VOI) were periventricular white matter posterior area and basal ganglia. The ratio of N Acetyl Aspartate (NAA) to Cho (Choline), NAA to Cr (creatine), Cho to Cr, and Lac (Lactate) to Cr were measured. Neurodevelopment was assessed at 24 months TEA with ASQ (Ages and Stages Questionnaire).

RESULTS

A total of 69 very preterm infants had a 1H-MRS at TEA. In white matter there was a significant correlation between a reduction in the NAA/Cho ratio and a total ASQ and/or abnormal communication score, and an increase in the Lac/Cr ratio and an abnormality of fine motor skills. In the gray nuclei there was a trend correlation between the reduction in the NAA/Cho ratio and sociability disorders; and the increase in the Lac/Cr ratio and an anomaly in problem-solving.

CONCLUSIONS

Using NAA as a biomarker, the vulnerability of immature oligodendrocytes in preterm children at TEA was correlated to neurodevelopment at 2 years. Similarly, the presence of lactate at TEA was associated with abnormal neurodevelopment at 2 years in the preterm brain.

How does the convergence of prematurity and congenital heart disease impact the developing brain?

Prematurity and congenital heart disease (CHD) are individually associated with increased risk of brain injury and adverse neurodevelopmental outcomes. Delayed brain development in newborns with CHD has been documented to begin in utero and predisposes newborns with CHD to brain injury. Little is known about the combined risks when prematurity and CHD co-occur. The purpose of this review is to highlight the unique vulnerability of preterm newborns with CHD to brain dysmaturation and brain injury, and the urgent need for prospective research.

Current human brain applications and challenges of dynamic hyperpolarized carbon-13 labeled pyruvate MR metabolic imaging

The ability of hyperpolarized carbon-13 MR metabolic imaging to acquire dynamic metabolic information in real time is crucial to gain mechanistic insights into metabolic pathways, which are complementary to anatomic and other functional imaging methods. This review presents the advantages of this emerging functional imaging technology, describes considerations in clinical translations, and summarizes current human brain applications. Despite rapid development in methodologies, significant technological and physiological related challenges continue to impede broader clinical translation.

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.

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.

Neuroimaging Findings of Organic Acidemias and Aminoacidopathies

Although individual cases of inherited metabolic disorders are rare, overall they account for a substantial number of disorders affecting the central nervous system. Organic acidemias and aminoacidopathies include a variety of inborn errors of metabolism that are caused by defects in the intermediary metabolic pathways of carbohydrates, amino acids, and fatty acid oxidation. These defects can lead to the abnormal accumulation of organic acids and amino acids in multiple organs, including the brain. Early diagnosis is mandatory to initiate therapy and prevent permanent long-term neurologic impairments or death. Neuroimaging findings can be nonspecific, and metabolism- and genetics-based laboratory investigations are needed to confirm the diagnosis. However, neuroimaging has a key role in guiding the diagnostic workup. The findings at conventional and advanced magnetic resonance imaging may suggest the correct diagnosis, help narrow the differential diagnosis, and consequently facilitate early initiation of targeted metabolism- and genetics-based laboratory investigations and treatment. Neuroimaging may be especially helpful for distinguishing organic acidemias and aminoacidopathies from other more common diseases with similar manifestations, such as hypoxic-ischemic injury and neonatal sepsis. Therefore, it is important that radiologists, neuroradiologists, pediatric neuroradiologists, and clinicians are familiar with the neuroimaging findings of organic acidemias and aminoacidopathies. ^©RSNA, 2018.

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.

Predicting motor outcomes with 3 month prone hip angles in premature infants

PURPOSE

This study used kinematic analysis to identify a reliable and rapid assessment method for abnormal patterns of motor development in preterm infants.

METHODS

In a retrospective analysis, we examined video of n= 35 preterm infants at 3mo corrected age (CA) who had concurrent Test of Infant Motor Performance (TIMP) scores. Hyperflexion at the hip produces common gait anomalies seen in children with CP, therefore we analyzed hip angle in the prone head lift position at 3 months CA. Magnetic Resonance Spectroscopy (MRS) was performed at term equivalent (n= 23) and Bayley-III neurodevelopmental tests were performed at 1 year (n= 28). We correlated hip angles with TIMP and Bayley-III scores, and MRS neuronal metabolites.

RESULTS

Hip angle positively correlated with TIMP at 3 months (r= 0.642, p≤ 0.001), but not with Bayley-III at 1 year (r= 0.122, p= 0.529). Hip angle correlated negatively with myo-inositol (mI) ratios in frontal white matter tracts (mI/Cr r= -0.520, p= 0.011).

CONCLUSIONS

These results suggest prone hip angle may be a quantitative proxy for the 42-item TIMP at 3 months, and that hypertonicity in the hip flexor musculature is a manifestation of white matter metabolic abnormalities (elevated mI ratios) that may indicate occult white matter injury.

Normal lactate concentration range in the neonatal brain

OBJECTIVE

Lactate peaks are occasionally observed during in vivo magnetic resonance spectroscopy (MRS) scans of the neonatal brain, even in healthy patients. The purpose of this study was to investigate the normal range of neonatal brain lactate concentration, as a definitive normal range would be clinically valuable.

METHODS

Using a clinical 3T scanner (echo/repetition times, 30/5000ms), single-voxel MRS data were obtained from the basal ganglia (BG) and centrum semiovale (CS) in 48 healthy neonates (postconceptional age (PCA), 30-43weeks), nine infants (age, 1-12months old), and 20 children (age, 4-15years). Lactate concentrations were calculated using an MRS signal quantification program, LCModel. Correlations between regional lactate concentration and PCA (neonates), or age (all subjects) were investigated.

RESULTS

Absolute lactate concentrations of the BG and CS were as follows: neonates, 0.77mM (0-2.02) [median (range)] and 0.77 (0-1.42), respectively; infants, 0.38 (0-0.79) and 0.49 (0.17-1.17); and children, 0.17 (0-0.76) and 0.22 (0-0.80). Overall, subjects' lactate concentrations decreased significantly with age (Spearman: BG, n=61, ρ=-0.38, p=0.003; CS, n=68, ρ=-0.57, p<0.001). However, during the neonatal period no correlations were detected between lactate concentration in either region and PCA.

CONCLUSION

We determined normal ranges of neonatal lactate concentration, which may prove useful for diagnostic purposes. Further studies regarding changes in brain lactate concentration during development would help clarify the reasons for higher concentrations observed during the neonatal period, and contribute to improvements in diagnoses.

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.

Proton magnetic resonance spectroscopy and outcome in term neonates with chorioamnionitis

OBJECTIVE

Evaluate brain metabolites, which reflect neuroinflammation, and relate to neurodevelopmental outcomes in healthy term neonates exposed to chorioamnionitis.

STUDY DESIGN

Thirty-one healthy term neonates with documented fetal inflammatory response after maternal chorioamnionitis underwent magnetic resonance spectroscopy (MRS), with voxels placed in basal ganglia (BG) and frontal white matter. Bayley III examinations were performed at 12 months of age.

RESULT

Infants with below average outcomes did not show the same increase in NAA/Cho ratios postnatally as the group with normal outcomes. Decreased NAA/Cho and increased Lac/Cr in BG correlated with lower motor and cognitive composite scores, respectively, controlling for postnatal age. In males, increased lactate/NAA in BG were associated with lower motor scores. Funisitis severity was associated with decreased NAA/Cho and increased mI/NAA in males.

CONCLUSION

In healthy term newborns with chorioamnionitis, MRS ratios shortly after birth may provide evidence of occult neuroinflammation, which may be associated with worse performance on 1-year neurodevelopmental tests.

Brain maturation in neonatal rodents is impeded by sevoflurane anesthesia

BACKGROUND

A wealth of data shows neuronal demise after general anesthesia in the very young rodent brain. Herein, the authors apply proton magnetic resonance spectroscopy (1HMRS), testing the hypothesis that neurotoxic exposure during peak synaptogenesis can be tracked via changes in neuronal metabolites.

METHODS

1HMRS spectra were acquired in the brain (thalamus) of neonatal rat pups 24 and 48 h after sevoflurane exposure on postnatal day (PND) 7 and 15 and in unexposed, sham controls. A repeated measure ANOVA was performed to examine whether changes in metabolites were different between exposed and unexposed groups. Sevoflurane-induced neurotoxicity on PND7 was confirmed by immunohistochemistry.

RESULTS

In unexposed PND7 pups (N = 21), concentration of N-acetylaspartate (NAA; [NAA]) increased by 16% from PND8 to PND9, whereas in exposed PND7 pups (N = 19), [NAA] did not change and concentration of glycerophosphorylcholine and phosphorylcholine ([GPC + PCh]) decreased by 25%. In PND15 rats, [NAA] increased from PND16 to PND17 for both the exposed (N = 14) and the unexposed (N = 16) groups. Two-way ANOVA for PND7 pups demonstrated that changes over time observed in [NAA] (P = 0.031) and [GPC + PCh] (P = 0.024) were different between those two groups.

CONCLUSIONS

The authors demonstrated that normal [NAA] increase from PND8 to PND9 was impeded in sevoflurane-exposed rats when exposed at PND7; however, not impeded when exposed on PND15. Furthermore, the authors showed that noninvasive 1HMRS is sufficiently sensitive to detect subtle differences in developmental time trajectory of [NAA]. This is potentially clinically relevant because 1HMRS can be applied across species and may be useful in providing evidence of neurotoxicity in the human neonatal brain.

Assessing Temporal Brain Metabolite Changes in Preterm Infants Using Multivoxel Magnetic Resonance Spectroscopy

PURPOSE

To investigate temporal changes in brain metabolites during the first year of life in preterm infants using multivoxel proton magnetic resonance spectroscopy ((1)H-MRS).

METHODS

Seventeen infants born at 29 (25-33) gestational week (median, range) weighing 1104 (628-1836) g underwent 1.5-T multivoxel (1)H-MRS at 42 postconceptional week (PCW) and at 3, 6, 9, and 12 months after. We measured N-acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, myo-inositol (Ins)/Cr, NAA/Cho, and Ins/Cho ratios in the frontal lobe (FL) and basal ganglia and thalamus (BG + Th). Linear regression analyses were performed to identify longitudinal changes in infants showing normal imaging findings and normal development. We also evaluated ratios of subjects with abnormal imaging findings and/or development using the 95% confidence intervals (CIs) of regression equations in normal subjects.

RESULTS

In the 13 infants with normal development, NAA/Cr and NAA/Cho ratios showed significant positive correlations with PCWs in the FL (r = 0.64 and 0.83, respectively, both P < 0.01) and BG + Th (r = 0.79 and 0.87, respectively, both P < 0.01), while Cho/Cr and Ins/Cr ratios revealed significant negative correlations with PCWs in the FL (r =-0.69 and -0.58, respectively, both P < 0.01) and BG + Th (r =-0.74 and -0.72, respectively, both P < 0.01). Ins/Cho ratios in the FL did not significantly correlate with PCWs (r =-0.19, P = 0.18), while those in the BG + Th showed significant negative correlation with PCWs (r =-0.44, P < 0.01). The metrics in the abnormal group were within the normal group 95% CIs in all periods except a few exceptions.

CONCLUSIONS

Longitudinal multivoxel MRS is able to detect temporal changes in major brain metabolites during the first year of life in preterm infants.

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.

Early metabolic development of posteromedial cortex and thalamus in humans analyzed via in vivo quantitative magnetic resonance spectroscopy

The posteromedial cortex (PMC) including the posterior cingulate, retrosplenial cortex, and medial parietal cortex/precuneus is an epicenter of cortical interactions in a wide spectrum of neural activity. Anatomic connections between PMC and thalamic components have been established in animal studies, but similar studies do not exist for the fetal and neonatal period. Magnetic resonance spectroscopy (MRS) allows for noninvasive measurement of metabolites in early development. Using single-voxel 3-T MRS, healthy term neonates (n = 31, mean postconception age 41.5 weeks ± 3.8 weeks) were compared with control children (n = 23, mean age 9.4 years ± 5.1 years) and young adults (n = 10, mean age 24.1 years ± 2.6 years). LCModel-based calculations compared metabolites within medial parietal gray matter (colocalizing to the PMC), posterior thalamus, and parietal white matter voxels. Common metabolic changes existed for neuronal-axonal maturation and structural markers in the PMC, thalamus, and parietal white matter with increasing NAA and glutamate and decreasing myoinositol and choline with age. Key differences in creatine and glucose metabolism were noted in the PMC, in contrast to the thalamic and parietal white matter locations, suggesting a unique role of energy metabolism. Significant parallel metabolite developmental changes of multiple other metabolites including aspartate, glutamine, and glutathione with age were present between PMC and parietal white matter but not between PMC and thalamus. These findings offer insight into the metabolic architecture of the interface between structural and functional topology of brain networks. Further investigation unifying metabolic changes with functional and anatomic pathways may further enhance the understanding of the PMC in posterior default mode network development.

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.

Neonatal brain metabolite concentrations: an in vivo magnetic resonance spectroscopy study with a clinical MR system at 3 Tesla

Brain metabolite concentrations change dynamically throughout development, especially during early childhood. The purpose of this study was to investigate the brain metabolite concentrations of neonates (postconceptional age (PCA): 30 to 43 weeks) using single-voxel magnetic resonance spectroscopy (MRS) and to discuss the relationships between the changes in the concentrations of such metabolites and brain development during the neonatal period. A total of 83 neonatal subjects were included using the following criteria: the neonates had to be free of radiological abnormalities, organic illness, and neurological symptoms; the MR spectra had to have signal-to-noise ratios ≥ 4; and the estimated metabolite concentrations had to display Cramér-Rao lower bounds of ≤ 30%. MRS data (echo time/repetition time, 30/5000 ms; 3T) were acquired from the basal ganglia (BG), centrum semiovale (CS), and the cerebellum. The concentrations of five metabolites were measured: creatine, choline, N-acetylaspartate, myo-inositol, and glutamate/glutamine complex (Glx). One hundred and eighty-four MR spectra were obtained (83 BG, 77 CS, and 24 cerebellum spectra). Creatine, N-acetylaspartate, and Glx displayed increases in their concentrations with PCA. Choline was not correlated with PCA in any region. As for myo-inositol, its concentration decreased with PCA in the BG, whereas it increased with PCA in the cerebellum. Quantitative brain metabolite concentrations and their changes during the neonatal period were assessed. Although the observed changes were partly similar to those detected in previous reports, our results are with more subjects (n = 83), and higher magnetic field (3T). The metabolite concentrations examined in this study and their changes are clinically useful indices of neonatal brain development.

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

PURPOSE

To determine (a) whether diffuse white matter injury of prematurity is associated with an increased choline (Cho)-to-creatine (Cr) ratio and a reduced N-acetylaspartate (NAA)-to-Cho ratio and whether these measures can be used as biomarkers of outcome and (b) if changes in peak area metabolite ratios at magnetic resonance (MR) spectroscopy are associated with changes in T2 and fractional anisotropy (FA) at MR imaging.

MATERIALS AND METHODS

The local ethics committee approved this study, and informed parental consent was obtained for each infant. At term-equivalent age, 43 infants born at less than 32 weeks gestation underwent conventional and quantitative diffusion-tensor and T2-weighted MR imaging. Single-voxel point-resolved proton (hydrogen 1) MR spectroscopy was performed from a 2-cm(3) voxel centered in the posterior periventricular white matter. Outcome was evaluated by using Bayley scales at a corrected age of 1 year. Associations were investigated with Pearson product moment or Spearman rank order correlation. Differences in ratios in infants with and infants without impairment were tested by using t tests.

RESULTS

NAA/Cho and Cho/Cr ratios correlated with the scaled gross motor score and the composite motor score, independent of gestational age (P < .05). FA at diffusion-tensor MR imaging and T2 at MR imaging correlated with the NAA/Cho ratio (P < .05 for both) but not with the Cho/Cr ratio. Infants with motor scores of less than 85 (impaired) had an increased Cho/Cr ratio (P < .03) and a reduced NAA/Cho ratio (P < .01) compared to those without impairment. A combination of increased Cho/Cr ratio and decreased NAA/Cho ratio predicted impaired motor outcome at a corrected age of 1 year with a sensitivity of 0.80 (95% confidence interval [CI]: 0.57, 0.94) and a specificity of 0.80 (95% CI: 0.66, 0.88).

CONCLUSION

The combination of Cho/Cr and NAA/Cho ratios measured in the posterior periventricular white matter at term-equivalent age is predictive of motor outcome at 1 year in infants born at less than 32 weeks gestation.

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

BACKGROUND

Magnetic resonance spectroscopy allows for the noninvasive study of brain metabolism and therefore may provide useful information about brain injuries. We examined the associations of brain metabolite ratios in very preterm infants with white matter lesions and overall health status at birth.

METHODS

Spectroscopy data were obtained from 99 very preterm infants (born ≤32 wk gestation) imaged shortly after birth and from 67 of these infants at term-equivalent age. These data were processed using LCModel. Multiple regression was used to examine the association of metabolite ratios with focal noncystic white matter lesions visible on conventional magnetic resonance imaging (MRI) and with at-birth illness severity scores.

RESULTS

Within 2 wk of birth, the ratio of N-acetylaspartate + N-acetylaspartylglutamate to creatine + phosphocreatine was significantly lower in those infants showing white matter abnormalities on conventional MRI. Increased lactate to creatine + phosphocreatine and lactate to glycerophosphocholine + phosphocholine ratios were significantly associated with increasing severity of Clinical Risk Index for Babies II and Apgar scores taken at 1 and 5 min after birth.

CONCLUSION

Both overall health status at birth and white matter injury in preterm neonates are reflected in metabolite ratios measured shortly after birth. Long-term follow-up will provide additional insight into the prognostic value of these measures.

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.

Regional neonatal brain absolute thermometry by 1H MRS

Therapeutic hypothermia is standard care for infants with moderate to severe encephalopathy. (1) H MRS thermometry (MRSt) measures regional brain absolute temperature using the temperature-dependent water chemical shift. This study evaluates the clinical feasibility of MRSt in human neonates, and correlates white matter (WM) and thalamus (Thal) MRSt with conventional rectal temperature (Trectal ) measurement. Fifty-six infants born at term underwent perinatal MRSt for suspected hypoxic-ischaemic brain injury and 33 infants born preterm had MRSt at a term-equivalent age; 56 of the 89 had Trectal measured after MRSt of either a Thal or posterior WM voxel, or both. MRSt used point-resolved spectroscopy (no water suppression; TR = 1370 ms; TE = 288 ms; 1.5 × 1.5 × 1.5 cm(3) Thal and 1.1 × 1.3 × 1.4 cm(3) WM voxels). Time domain data were phase and frequency corrected before summation and motion-corrupted data were excluded from further analysis using simple criteria [preprocessing + quality assurance (QA)]. Two published water temperature-dependence calibrations [both using cerebral creatine (Cr), choline (Cho) and N-acetylaspartate (Naa) as independent reference peaks] were compared. The temperature measurements derived from Cr, Cho and Naa were combined to give a single amplitude-weighted combination temperature (TAWC ). WM and Thal TAWC correlated linearly with Trectal (Thal slope, 0.82 ± 0.04, R(2) = 0.85, p < 0.05; WM slope, 0.95 ± 0.04, R(2) = 0.78, p < 0.05). Preprocessing + QA improved the correlation between WM TAWC and Trectal (R(2) increased from 0.27 to 0.78, p < 0.001). Both calibration datasets showed specific inconsistencies between the temperatures calculated using Cr, Cho and Naa reference peaks when applied to this neonatal dataset. Neonatal MRSt is clinically feasible. Preprocessing + QA improved MRSt reliability in WM. The consideration of MRSt calibration internal biases is necessary before combining MRSt temperatures from multiple reference peaks to obtain TAWC.

Altered glutamatergic metabolism associated with punctate white matter lesions in preterm infants

Preterm infants (∼10% of all births) are at high-risk for long-term neurodevelopmental disabilities, most often resulting from white matter injury sustained during the neonatal period. Glutamate excitotoxicity is hypothesized to be a key mechanism in the pathogenesis of white matter injury; however, there has been no in vivo demonstration of glutamate excitotoxicity in preterm infants. Using magnetic resonance spectroscopy (MRS), we tested the hypothesis that glutamate and glutamine, i.e., markers of glutamatergic metabolism, are altered in association with punctate white matter lesions and "diffuse excessive high signal intensity" (DEHSI), the predominant patterns of preterm white matter injury. We reviewed all clinically-indicated MRS studies conducted on preterm infants at a single institution during a six-year period and determined the absolute concentration of glutamate, glutamine, and four other key metabolites in the parietal white matter in 108 of those infants after two investigators independently evaluated the studies for punctate white matter lesions and DEHSI. Punctate white matter lesions were associated with a 29% increase in glutamine concentration (p = 0.002). In contrast, there were no differences in glutamatergic metabolism in association with DEHSI. Severe DEHSI, however, was associated with increased lactate concentration (p = 0.001), a marker of tissue acidosis. Findings from this study support glutamate excitotoxicity in the pathogenesis of punctate white matter lesions, but not necessarily in DEHSI, and suggest that MRS provides a useful biomarker for determining the pathogenesis of white matter injury in preterm infants during a period when neuroprotective agents may be especially effective.

Pediatric brain injury: can DTI scalars predict functional outcome?

Diffusion imaging has made significant inroads into the clinical diagnosis of a variety of diseases by inferring changes in microstructure, namely cell membranes, myelin sheath and other structures that inhibit water diffusion. This review discusses recent progress in the use of diffusion parameters in predicting functional outcome. Studies in the literature using only scalar parameters from diffusion measurements, such as apparent diffusion coefficient (ADC) and fractional anisotropy (FA), are summarized. Other more complex mathematical models and post-processing uses are also discussed briefly.

Therapeutic hypothermia for neonatal encephalopathy results in improved microstructure and metabolism in the deep gray nuclei

BACKGROUND AND PURPOSE

Therapeutic hypothermia has reduced morbidity and mortality and is associated with a lower burden of lesions on conventional imaging in NE. However, its effects on brain microstructure and metabolism have not been fully characterized. We hypothesized that therapeutic hypothermia improves measures of brain microstructure and metabolism.

MATERIALS AND METHODS

Forty-one neonates with moderate/severe NE (29 treated with hypothermia, 12 nontreated) and 12 healthy neonates underwent MR imaging, DTI, and (1)H-MR spectroscopy. MR imaging scans were scored by the predominant pattern of brain injury: normal, watershed, and BG/thalamus. ADC, FA, Lac:NAA, and NAA:Cho values from bilateral BG and thalamus ROIs were averaged. T test and linear regression analysis were used to determine the association between hypothermia and MR imaging quantitative measures.

RESULTS

Conventional MR imaging findings were normal in 41% of treated neonates; all nontreated neonates had brain injury. Values of MR imaging metrics were closer to normal in treated neonates compared with nontreated neonates: ADC was 63% higher in the BG and 116% higher in the thalamus (both P < .05), and Lac:NAA was 76% lower (P = .04) in the BG. Treated neonates with normal MR imaging findings had normal (1)H-MR spectroscopy metabolites, and ADC was higher by 35% in the thalamus (P = .03) compared with healthy neonates.

CONCLUSIONS

Therapeutic hypothermia may reduce disturbances of brain metabolism and preserve its microstructure in the setting of NE, possibly by minimizing cytotoxic edema and cell death. Long-term follow-up studies are required to determine whether early post-treatment DTI and (1)H-MR spectroscopy will be useful biomarkers of treatment response.

Neonatal neuroimaging findings in inborn errors of metabolism

Individually, metabolic disorders are rare, but overall they account for a significant number of neonatal disorders affecting the central nervous system. The neonatal clinical manifestations of inborn errors of metabolism (IEMs) are characterized by nonspecific systemic symptoms that may mimic more common acute neonatal disorders like sepsis, severe heart insufficiency, or neonatal hypoxic-ischemic encephalopathy. Certain IEMs presenting in the neonatal period may also be complicated by sepsis and cardiomyopathy. Early diagnosis is mandatory to prevent death and permanent long-term neurological impairments. Although neuroimaging findings are rarely specific, they play a key role in suggesting the correct diagnosis, limiting the differential diagnosis, and may consequently allow early initiation of targeted metabolic and genetic laboratory investigations and treatment. Neuroimaging may be especially helpful to distinguish metabolic disorders from other more common causes of neonatal encephalopathy, as a newborn may present with an IEM prior to the availability of the newborn screening results. It is therefore important that neonatologists, pediatric neurologists, and pediatric neuroradiologists are familiar with the neuroimaging findings of metabolic disorders presenting in the neonatal time period.

Microglial reaction in axonal crossroads is a hallmark of noncystic periventricular white matter injury in very preterm infants

Disabilities after brain injury in very preterm infants have mainly been attributed to noncystic periventricular white matter injury (PWMI). We analyzed spatiotemporal patterns of PWMI in the brains of 18 very preterm infants (25-29 postconceptional weeks [pcw]), 7 preterm infants (30-34 pcw), and 10 preterm controls without PWMI. In very preterm infants, we examined PWMI in detail in 2 axonal crossroad areas in the frontal lobe: C1 (lateral to the lateral angle of the anterior horn of the lateral ventricle, at the exit of the internal capsule radiations) and C2 (above the corpus callosum and dorsal angle of the anterior horn). These brains had greater microglia-macrophage densities and activation but lesser astroglial reaction (glial fibrillary acidic protein and monocarboxylate transporter 1 expression) than in preterm cases with PWMI. In preterm infants, scattered necrotic foci were rimmed by axonal spheroids and ionized calcium binding adaptor molecule 1-positive macrophages. Diffuse lesions near these foci consisted primarily of hypertrophic and reactive astrocytes associated with fewer microglia. No differences in Olig2-positive preoligodendrocytes between noncystic PWMI and control cases were found. These data show that the growing axonal crossroad areas are highly vulnerable to PWMI in very preterm infants and highlight differences in glial activation patterns between very preterm and preterm infants.

Procedural pain and brain development in premature newborns

OBJECTIVE

Preterm infants are exposed to multiple painful procedures in the neonatal intensive care unit (NICU) during a period of rapid brain development. Our aim was to examine relationships between procedural pain in the NICU and early brain development in very preterm infants.

METHODS

Infants born very preterm (N=86; 24-32 weeks gestational age) were followed prospectively from birth, and studied with magnetic resonance imaging, 3-dimensional magnetic resonance spectroscopic imaging, and diffusion tensor imaging: scan 1 early in life (median, 32.1 weeks) and scan 2 at term-equivalent age (median, 40 weeks). We calculated N-acetylaspartate to choline ratios (NAA/choline), lactate to choline ratios, average diffusivity, and white matter fractional anisotropy (FA) from up to 7 white and 4 subcortical gray matter regions of interest. Procedural pain was quantified as the number of skin-breaking events from birth to term or scan 2. Data were analyzed using generalized estimating equation modeling adjusting for clinical confounders such as illness severity, morphine exposure, brain injury, and surgery.

RESULTS

After comprehensively adjusting for multiple clinical factors, greater neonatal procedural pain was associated with reduced white matter FA (β=-0.0002, p=0.028) and reduced subcortical gray matter NAA/choline (β=-0.0006, p=0.004). Reduced FA was predicted by early pain (before scan 1), whereas lower NAA/choline was predicted by pain exposure throughout the neonatal course, suggesting a primary and early effect on subcortical structures with secondary white matter changes.

INTERPRETATION

Early procedural pain in very preterm infants may contribute to impaired brain development.