Prognostic value of brain proton MR spectroscopy and diffusion tensor imaging in newborns with hypoxic-ischemic encephalopathy treated by brain cooling

MRI predictors of long-term outcomes of neonatal hypoxic ischaemic encephalopathy: a primer for radiologists

This review aims to serve as a foundational resource for general radiologists, enhancing their understanding of the role of Magnetic Resonance Imaging (MRI) in early prognostication for newborns diagnosed with hypoxic ischaemic encephalopathy (HIE). The article explores the application of MRI as a predictive instrument for determining long-term outcomes in newborns affected by HIE. With HIE constituting a leading cause of neonatal mortality and severe long-term neurodevelopmental impairments, early identification of prognostic indicators is crucial for timely intervention and optimal clinical management. We examine current literature and recent advancements to provide an in-depth overview of MRI predictors, encompassing brain injury patterns, injury scoring systems, spectroscopy, and diffusion imaging. The potential of these MRI biomarkers in predicting long-term neurodevelopmental outcomes and the probability of epilepsy is also discussed.

Prevalence of hearing impairment in neonatal encephalopathy due to hypoxia-ischemia: a systematic review and meta-analysis

BACKGROUND

This systematic review was undertaken to estimate the overall prevalence of hearing impairment in survivors of neonatal HIE.

METHODS

PubMed, EMBASE, CINAHL, EMCARE and Cochrane databases, mednar (gray literature) were searched till January 2023. Randomized controlled trials and observational studies were included. The main outcome was estimation of overall prevalence of hearing impairment in survivors of HIE.

RESULTS

A total of 71studies (5821 infants assessed for hearing impairment) were included of which 56 were from high income countries (HIC) and 15 from low- or middle-income countries (LMIC). Overall prevalence rate of hearing impairment in cooled infants was 5% (95% CI: 3-6%, n = 4868) and 3% (95% CI: 1-6%, n = 953) in non-cooled HIE infants. The prevalence rate in cooled HIE infants in LMICs was 7% (95% CI: 2-15%) and in HICs was 4% (95% CI: 3-5%). The prevalence rate in non-cooled HIE infants in LMICs was 8% (95% CI: 2-17%) and HICs was 2% (95% CI: 0-4%).

CONCLUSIONS

These results would be useful for counseling parents, and in acting as benchmark when comparing institutional data, and while monitoring future RCTs testing new interventions in HIE. There is a need for more data from LMICs and standardization of reporting hearing impairment.

IMPACT

The overall prevalence rate of hearing impairment in cooled infants with HIE was 5% (95% CI: 3-6%) and 3% (95% CI: 1-6%) in the non-cooled infants. The prevalence rate in cooled HIE infants in LMICs was 7% (95% CI: 2-15%) and in HICs was 4% (95% CI: 3-5%). The prevalence rate in non-cooled HIE infants in LMICs was 8% (95% CI: 2-17%) and HICs was 2% (95% CI: 0-4%). These results would be useful for counseling parents, and in acting as benchmark when comparing institutional data, and while monitoring future RCTs testing new interventions in HIE.

Quantification of Diffusion Magnetic Resonance Imaging for Prognostic Prediction of Neonatal Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is the leading cause of acquired neonatal brain injury with the risk of developing serious neurological sequelae and death. An accurate and robust prediction of short- and long-term outcomes may provide clinicians and families with fundamental evidence for their decision-making, the design of treatment strategies, and the discussion of developmental intervention plans after discharge. Diffusion tensor imaging (DTI) is one of the most powerful neuroimaging tools with which to predict the prognosis of neonatal HIE by providing microscopic features that cannot be assessed by conventional magnetic resonance imaging (MRI). DTI provides various scalar measures that represent the properties of the tissue, such as fractional anisotropy (FA) and mean diffusivity (MD). Since the characteristics of the diffusion of water molecules represented by these measures are affected by the microscopic cellular and extracellular environment, such as the orientation of structural components and cell density, they are often used to study the normal developmental trajectory of the brain and as indicators of various tissue damage, including HIE-related pathologies, such as cytotoxic edema, vascular edema, inflammation, cell death, and Wallerian degeneration. Previous studies have demonstrated widespread alteration in DTI measurements in severe cases of HIE and more localized changes in neonates with mild-to-moderate HIE. In an attempt to establish cutoff values to predict the occurrence of neurological sequelae, MD and FA measurements in the corpus callosum, thalamus, basal ganglia, corticospinal tract, and frontal white matter have proven to have an excellent ability to predict severe neurological outcomes. In addition, a recent study has suggested that a data-driven, unbiased approach using machine learning techniques on features obtained from whole-brain image quantification may accurately predict the prognosis of HIE, including for mild-to-moderate cases. Further efforts are needed to overcome current challenges, such as MRI infrastructure, diffusion modeling methods, and data harmonization for clinical application. In addition, external validation of predictive models is essential for clinical application of DTI to prognostication.

Imaging of Hypoxic-Ischemic Injury (in the Era of Cooling)

Hypoxic-ischemic injury (HII) is a major worldwide contributor of term neonatal mortality and long-term morbidity. At present, therapeutic hypothermia is the only therapy that has demonstrated efficacy in reducing severe disability or death in infants with moderate to severe encephalopathy. MRI and MRS performed during the first week of life are adequate to assess brain injury and offer prognosis. Patterns of injury will depend on the gestation age of the neonate, as well as the degree of hypotension.

Magnetic resonance imaging and spectroscopy in evaluation of hypoxic ischemic encephalopathy in pediatric age group

Background

Hypoxic ischemic encephalopathy is a major cause of pediatric mortality and morbidity, with possible long-term neurologic sequel, such as cerebral palsy. With improvements in care of at-risk neonates, more children survive. This makes it increasingly important to assess, soon after birth, the prognosis of children with hypoxic-ischemic encephalopathy. The aim of the study was to assess the additive role of magnetic resonance spectroscopy over conventional MRI in diagnosis and early prediction of pathological motor development in neonates with hypoxic ischemic encephalopathy.

Results

MRS ratios showed significant difference between unfavorable and normal outcome infants. MRS ratios as Lac/Cr, NAA/Cr and NAA/Cho within basal ganglia, thalamus and white matter can significantly differentiate between patients with normal and pathological outcome at 1 year.

Lac/Cr positively correlates with the severity of HIE. Both NAA/Cr and NAA/Cho negatively correlate with the severity of the disease. Ratios cutoff values as Lac/Cr above 0.38 and 0.42 in basal ganglia and white matter, respectively, NAA/Cr below 0.9 and 0.8 in basal ganglia and occipital white matter, respectively, and NAA/Cho below 0.29 and 0.31 in basal ganglia and frontal white matter, respectively, were significantly predictive of pathological outcome.

Conclusion

High Lac/Cr, low NAA/Cr and low NAA/Cho ratios within examined regions of the brain including deep grey matter nuclei as well as white matter are associated with an adverse outcome in infants with perinatal asphyxia. MRS is an accurate quantitative MR biomarker within the neonatal period for prediction of neurodevelopmental outcome after perinatal HIE. MRS may be useful in early clinical management decisions, and counseling parents thereby ensuring appropriate early intervention and rehabilitation.

Comparison of Predictive Values of Magnetic Resonance Biomarkers Based on Scan Timing in Neonatal Encephalopathy Following Therapeutic Hypothermia

OBJECTIVE

To determine the optimal quantitative magnetic resonance (MR) biomarker in neonatal encephalopathy following therapeutic hypothermia based on scan timing.

STUDY DESIGN

This retrospective study included 98 neonates (35-41 weeks of gestation) with neonatal encephalopathy, who underwent therapeutic hypothermia; diffusion-weighted imaging and proton MR spectroscopy were performed at 24-96 hours (n = 56) and 7-14 days (n = 92) after birth, respectively, to estimate apparent diffusion coefficient (ADC) values, N-acetylaspartate and N-acetylaspartylglutamate (tNAA), lactate, and choline concentrations, and lactate/tNAA, tNAA/choline ratios in the deep gray matter. Adverse outcomes included death or neurodevelopmental impairment at 18-22 months of age. We used receiver operating characteristic curves to examine the prognostic accuracy of each MR biomarker.

RESULTS

Deep gray matter tNAA concentrations showed the best prognostic value, with an area under the curve (AUC) of 0.97 and 1.00 at 24-96 hours and 7-14 days after birth, respectively. At 24-96 hours of age, ADC values, lactate concentrations, and lactate/tNAA ratios showed prognostic value with AUCs of 0.90, 0.95, and 0.97, respectively. At 7-14 days of age, the AUCs of ADC values, lactate, and lactate/tNAA ratios were 0.61, 0.67, and 0.80, respectively; these were lower than those at 24-96 hours of age.

CONCLUSIONS

During the first 2 weeks of life, the deep gray matter tNAA concentration was the most accurate quantitative MR biomarker. Although ADC values, lactate levels, and lactate/tNAA ratios also showed high prognostic value during 24-96 hours of life, only tNAA retained high prognostic value in the second week of life.

Oleuropein Activates Neonatal Neocortical Proteasomes, but Proteasome Gene Targeting by AAV9 Is Variable in a Clinically Relevant Piglet Model of Brain Hypoxia-Ischemia and Hypothermia

Cerebral hypoxia-ischemia (HI) compromises the proteasome in a clinically relevant neonatal piglet model. Protecting and activating proteasomes could be an adjunct therapy to hypothermia. We investigated whether chymotrypsin-like proteasome activity differs regionally and developmentally in the neonatal brain. We also tested whether neonatal brain proteasomes can be modulated by oleuropein, an experimental pleiotropic neuroprotective drug, or by targeting a proteasome subunit gene using recombinant adeno-associated virus-9 (AAV). During post-HI hypothermia, we treated piglets with oleuropein, used AAV-short hairpin RNA (shRNA) to knock down proteasome activator 28γ (PA28γ), or enforced PA28γ using AAV-PA28γ with green fluorescent protein (GFP). Neonatal neocortex and subcortical white matter had greater proteasome activity than did liver and kidney. Neonatal white matter had higher proteasome activity than did juvenile white matter. Lower arterial pH 1 h after HI correlated with greater subsequent cortical proteasome activity. With increasing brain homogenate protein input into the assay, the initial proteasome activity increased only among shams, whereas HI increased total kinetic proteasome activity. OLE increased the initial neocortical proteasome activity after hypothermia. AAV drove GFP expression, and white matter PA28γ levels correlated with proteasome activity and subunit levels. However, AAV proteasome modulation varied. Thus, neonatal neocortical proteasomes can be pharmacologically activated. HI slows the initial proteasome performance, but then augments ongoing catalytic activity. AAV-mediated genetic manipulation in the piglet brain holds promise, though proteasome gene targeting requires further development.

Comparison of fractional anisotropy and apparent diffusion coefficient among hypoxic ischemic encephalopathy stages 1, 2, and 3 and with nonasphyxiated newborns in 18 areas of brain

Purpose

To determine the area and extent of injury in hypoxic encephalopathy stages by diffusion tensor imaging (DTI) using parameters apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values and their comparison with controls without any evidence of asphyxia. To correlate the outcome of hypoxia severity clinically and significant changes on DTI parameter.

Materials and Methods

DTI was done in 50 cases at median age of 12 and 20 controls at median age of 7 days. FA and apparent diffusion coefficient (ADC) were measured in several regions of interest (ROI). Continuous variables were analyzed using Student's t-test. Categorical variables were compared by Fisher's exact test. Comparison among multiple groups was done using analysis of variance (ANOVA) and post hoc Bonferroni test.

Results

Abnormalities were more easily and accurately determined in ROI with the help of FA and ADC values. When compared with controls FA values were significantly decreased and ADC values were significantly increased in cases, in ROI including both right and left side of thalamus, basal ganglia, posterior limb of internal capsule, cerebral peduncle, corticospinal tracts, frontal, parietal, temporal, occipital with P value < 0.05. The extent of injury was maximum in stage-III. There was no significant difference among males and females.

Conclusion

Compared to conventional magnetic resonance imaging (MRI), the evaluation of FA and ADC values using DTI can determine the extent and severity of injury in hypoxic encephalopathy. It can be used for early determination of brain injury in these patients.

Integrating neuroimaging biomarkers into the multicentre, high-dose erythropoietin for asphyxia and encephalopathy (HEAL) trial: rationale, protocol and harmonisation

INTRODUCTION

MRI and MR spectroscopy (MRS) provide early biomarkers of brain injury and treatment response in neonates with hypoxic-ischaemic encephalopathy). Still, there are challenges to incorporating neuroimaging biomarkers into multisite randomised controlled trials. In this paper, we provide the rationale for incorporating MRI and MRS biomarkers into the multisite, phase III high-dose erythropoietin for asphyxia and encephalopathy (HEAL) Trial, the MRI/S protocol and describe the strategies used for harmonisation across multiple MRI platforms.

METHODS AND ANALYSIS

Neonates with moderate or severe encephalopathy enrolled in the multisite HEAL trial undergo MRI and MRS between 96 and 144 hours of age using standardised neuroimaging protocols. MRI and MRS data are processed centrally and used to determine a brain injury score and quantitative measures of lactate and n-acetylaspartate. Harmonisation is achieved through standardisation-thereby reducing intrasite and intersite variance, real-time quality assurance monitoring and phantom scans.

ETHICS AND DISSEMINATION

IRB approval was obtained at each participating site and written consent obtained from parents prior to participation in HEAL. Additional oversight is provided by an National Institutes of Health-appointed data safety monitoring board and medical monitor.

TRIAL REGISTRATION NUMBER

NCT02811263; Pre-result.

Fractional anisotropy from diffusion tensor imaging correlates with acute astrocyte and myelin swelling in neonatal swine models of excitotoxic and hypoxic-ischemic brain injury

The specific cytopathology that causes abnormal fractional anisotropy (FA) and mean diffusivity (MD) from diffusion tensor imaging (DTI) after neonatal hypoxia-ischemia (HI) is not completely understood. The panoply of cell types in the brain might contribute differentially to changes in DTI metrics. Because glia are the predominant cell type in brain, we hypothesized that changes in FA and MD would signify perturbations in glial microstructure. Using a 3-Tesla clinical scanner, we conducted in vivo DTI MRI in nine neonatal piglets at 20-96 h after excitotoxic brain injury from striatal quinolinic acid injection or global HI. FA and MD from putamen, caudate, and internal capsule in toto were correlated with astrocyte swelling, neuronal excitotoxicity, and white matter injury. Low FA correlated with more swollen astrocytes immunophenotyped by aquaporin-4 (AQP4), glial fibrillary acidic protein (GFAP), and glutamate transporter-1 (GLT-1). Low FA was also related to the loss of neurons with perineuronal GLT-1+ astrocyte decorations, large myelin swellings, lower myelin density, and oligodendrocyte cell death identified by 2',3'-cyclic nucleotide 3'-phosphodiesterase, bridging integrator-1, and nuclear morphology. MD correlated with degenerating oligodendrocytes and depletion of normal GFAP+ astrocytes but not with astrocyte or myelin swelling. We conclude that FA is associated with cytotoxic edema in astrocytes and oligodendrocyte processes as well as myelin injury at the cellular level. MD can detect glial cell death and loss, but it may not discern subtle pathology in swollen astrocytes, oligodendrocytes, or myelin. This study provides a cytopathologic basis for interpreting DTI in the neonatal brain after HI.

Proton Magnetic Resonance Spectroscopy Lactate/N-Acetylaspartate Within 48 h Predicts Cell Death Following Varied Neuroprotective Interventions in a Piglet Model of Hypoxia-Ischemia With and Without Inflammation-Sensitization

Despite therapeutic hypothermia, survivors of neonatal encephalopathy have high rates of adverse outcome. Early surrogate outcome measures are needed to speed up the translation of neuroprotection trials. Thalamic lactate (Lac)/N-acetylaspartate (NAA) peak area ratio acquired with proton (1H) magnetic resonance spectroscopy (MRS) accurately predicts 2-year neurodevelopmental outcome. We assessed the relationship between MR biomarkers acquired at 24-48 h following injury with cell death and neuroinflammation in a piglet model following various neuroprotective interventions. Sixty-seven piglets with hypoxia-ischemia, hypoxia alone, or lipopolysaccharide (LPS) sensitization were included, and neuroprotective interventions were therapeutic hypothermia, melatonin, and magnesium. MRS and diffusion-weighted imaging (DWI) were acquired at 24 and 48 h. At 48 h, experiments were terminated, and immunohistochemistry was assessed. There was a correlation between Lac/NAA and overall cell death [terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)] [mean Lac/NAA basal ganglia and thalamus (BGT) voxel r = 0.722, white matter (WM) voxel r = 0.784, p < 0.01] and microglial activation [ionized calcium-binding adapter molecule 1 (Iba1)] (BGT r = -0.786, WM r = -0.632, p < 0.01). Correlation with marker of caspase-dependent apoptosis [cleaved caspase 3 (CC3)] was lower (BGT r = -0.636, WM r = -0.495, p < 0.01). Relation between DWI and TUNEL was less robust (mean diffusivity BGT r = -0.615, fractional anisotropy BGT r = 0.523). Overall, Lac/NAA correlated best with cell death and microglial activation. These data align with clinical studies demonstrating Lac/NAA superiority as an outcome predictor in neonatal encephalopathy (NE) and support its use in preclinical and clinical neuroprotection studies.

Diffusion tensor imaging in neonatal encephalopathy: a systematic review

BACKGROUND AND OBJECTIVE

Diffusion tensor imaging (DTI) during the first few days of life can be used to assess brain injury in neonates with neonatal encephalopathy (NE) for outcome prediction. The goal of this review was to identify specific white matter tracts of interest that can be quantified by DTI as being altered in neonates with this condition, and to investigate its potential prognostic ability.

METHODS

Searches of Medline and the Cochrane Database of Systematic Reviews were conducted to identify studies with diffusion data collected in term-born neonates with NE.

RESULTS

19 studies were included which described restricted diffusion in encephalopathic neonates as compared with healthy controls, with the posterior limb of the internal capsule and the genu and splenium of the corpus callosum identified as particular regions of interest. Restricted diffusion was related to adverse outcomes in the studies that conducted a follow-up of these infants.

CONCLUSIONS

Obtaining diffusion measures in these key white matter tracts early in life before pseudonormalisation can occur can not only identify the extent of the damage but also can be used to examine the effectiveness of treatment and to predict neurodevelopmental outcome.

Predictors of Outcomes in Hypoxic-Ischemic Encephalopathy following Hypothermia: A Meta-Analysis

INTRODUCTION

Prediction of neurodevelopmental outcome in infants with hypoxic-ischemic encephalopathy remains an important challenge. Various studies have shown that the predictive ability of different modalities changed after the introduction of therapeutic hypothermia. This paper reviews the diagnostic test accuracy of the different modalities that are being used to predict neurodevelopmental outcomes following therapeutic hypothermia.

METHODS

A systematic literature search was performed using Embase and PubMed. Two reviewers independently included eligible studies and extracted data. The quality of the studies was assessed using the Quality in Prognosis Studies Tool. Meta-analyses were performed where possible.

RESULTS

Forty-seven articles and 3 conference abstracts were included, reporting on 3,072infants of whom 39% died or had an adverse neurodevelopmental outcome. A meta-analysis could be performed using 37 articles on (amplitude-integrated) electroencephalography (EEG), conventional magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI), and proton magnetic resonance spectroscopy (1H-MRS). Amplitude-integrated EEG (aEEG) at 24 and 72 h showed similar high diagnostic OR, while aEEG at 6 h and EEG performed less, both due to a low specificity. For MRI, most studies reported scoring systems in which early (<8 days) MRI performed better than late (≥8 days) MRI. Injury to the posterior limb of the internal capsule on MRI or to the thalami on DWI were strong individual predictors, as was an increased lactate/N-acetylaspartate peak on 1H-MRS.

CONCLUSIONS

In the era of therapeutic hypothermia, the different modalities remain good predictors of neurodevelopmental outcome. However, timing should be taken into account. aEEG may initially be false positive and gets more reliable after 24 h. In contrast, MRI should be used during the first week, as its predictive value decreases afterwards.

Neonatal Functional and Structural Connectivity Are Associated with Cerebral Palsy at Two Years of Age

OBJECTIVE

The accuracy of structural magnetic resonance imaging (MRI) to predict later cerebral palsy (CP) in newborns with perinatal brain injury is variable. Diffusion tensor imaging (DTI) and task-based functional MRI (fMRI) show promise as predictive tools. We hypothesized that infants who later developed CP would have reduced structural and functional connectivity as compared with those without CP.

STUDY DESIGN

We performed DTI and fMRI using a passive motor task at 40 to 48 weeks' postmenstrual age in 12 infants with perinatal brain injury. CP was diagnosed at age 2 using a standardized examination.

RESULTS

Five infants had CP at 2 years of age, and seven did not have CP. Tract-based spatial statistics showed a widespread reduction of fractional anisotropy (FA) in almost all white matter tracts in the CP group. Using the median FA value in the corticospinal tracts as a cutoff, FA was 100% sensitive and 86% specific to predict CP compared with a sensitivity of 60 to 80% and a specificity of 71% for structural MRI. During fMRI, the CP group had reduced functional connectivity from the right supplemental motor area as compared with the non-CP group.

CONCLUSION

DTI and fMRI obtained soon after birth are potential biomarkers to predict CP in newborns with perinatal brain injury.

Neurodevelopmental effect of intracranial hemorrhage observed in hypoxic ischemic brain injury in hypothermia-treated asphyxiated neonates - an MRI study

BACKGROUND

Identification of early signs of hypoxic ischemic encephalopathy (HIE) with magnetic resonance imaging (MRI) has proven of prognostic significance. Yet, the importance of intracranial hemorrhage (ICH), being present concomitantly had not been investigated yet, despite the known influence of hypothermia on hemostasis. We aimed to determine whether presence of ICH on MRI alongside the signs of HIE have an impact on prognosis in neonates with the clinical diagnosis of HIE.

METHODS

A retrospective study of consecutively sampled 108 asphyxiated term infants admitted to a tertiary neonatal intensive care unit (between 2007 and 2016), treated with whole body hypothermia and having brain MRI within 1 week of life was conducted. Presence or absence of HIE signs on MRI (basal ganglia-thalamus, watershed pattern and total brain injury) and on MR spectroscopy (lactate peak with decreased normal metabolites measured by Lac/NAA ratio) and/or of the five major types of ICH were recorded. Neurodevelopmental outcome was measured with Bayley Scales of Infant Development-II (BSID-II) test. Death or abnormal neurodevelopment (BSID-II score < 85) was defined as poor outcome in Chi-square test. Multivariate logistic regression analysis was performed on survivors.

RESULTS

MRI and MR-spectroscopy (MRS) signs of HIE were present in 72% (n = 78). 36% (n = 39) of neonates had ICH, being mainly small in size. Chi-square test showed a relationship between neurodevelopmental outcome and initial MRI. Unadjusted logistic regression showed that neonates presenting MRI and MRS signs of HIE have 6.23 times higher odds for delayed mental development (OR = 6.2292; CI95% = [1.2642; 30.6934], p = 0.0246), than infants without imaging alterations; with no ICH effect on outcome. Adjustment for clinical and imaging parameters did not change the pattern of results, i.e. HIE remained an independent risk factor for delayed neurodevelopment (OR = 6.2496; CI95% = [1.2018; 32.4983], p = 0.0294), while ICH remained to have no significant effect.

CONCLUSION

HIE related MRI abnormalities proved to be important prognostic factors of poor outcome in cooled asphyxiated infants when present, suggesting that early MRI with MRS is beneficial for prognostication. Interestingly, ICHs present in about one third of all cases had no significant effect on neurodevelopmental outcome, despite the known hemostasis altering effects of hypothermia.

Proteasome Biology Is Compromised in White Matter After Asphyxic Cardiac Arrest in Neonatal Piglets

Background

Neurological deficits in hypoxic‐ischemic encephalopathy, even with therapeutic hypothermia, are partially attributed to white matter injury. We theorized that proteasome insufficiency contributes to white matter injury.

Methods and Results

Neonatal piglets received hypoxia‐ischemia (HI) or sham procedure with normothermia, hypothermia, or hypothermia+rewarming. Some received a proteasome activator drug (oleuropein) or white matter–targeted, virus‐mediated proteasome knockdown. We measured myelin oligodendrocyte glycoprotein, proteasome subunit 20S (P20S), proteasome activity, and carbonylated and ubiquitinated protein levels in white matter and cerebral cortex. HI reduced myelin oligodendrocyte glycoprotein levels regardless of temperature, and myelin oligodendrocyte glycoprotein loss was associated with increased ubiquitinated and carbonylated protein levels. Ubiquitinated and carbonyl‐damaged proteins increased in white matter 29 hours after HI during hypothermia to exceed levels at 6 to 20 hours. In cortex, ubiquitinated proteins decreased. Ubiquitinated and carbonylated protein accumulation coincided with lower P20S levels in white matter; P20S levels also decreased in cerebral cortex. However, proteasome activity in white matter lagged behind that in cortex 29 hours after HI during hypothermia. Systemic oleuropein enhanced white matter P20S and protected the myelin, whereas proteasome knockdown exacerbated myelin oligodendrocyte glycoprotein loss and ubiquitinated protein accumulation after HI. At the cellular level, temperature and HI interactively affected macroglial P20S enrichment in subcortical white matter. Rewarming alone increased macroglial P20S immunoreactivity, but this increase was blocked by HI.

Conclusions

Oxidized and ubiquitinated proteins accumulate with HI‐induced white matter injury. Proteasome insufficiency may drive this injury. Hypothermia did not prevent myelin damage, protect the proteasome, or preserve oxidized and ubiquitinated protein clearance after HI.

Ultrasound Predicts White Matter Integrity after Hypothermia Therapy in Neonatal Hypoxic-Ischemic Injury

BACKGROUND

Hypoxic-ischemic injury (HII) is a major cause of neonatal death and neurodevelopmental disability. Head ultrasounds (HUS) in neonates with HII often show enhanced gray/white matter differentiation. We assessed the significance of this finding in predicting white matter structural integrity measured by diffusion tensor imaging (DTI) in neonates with HII.

METHODS

We performed a quantitative region of interest-based analysis of white and gray matter echogenicity within the cingulate gyrus on pre- and posthypothermia HUS. We also completed a quantitative analysis of fractional anisotropy (FA) and mean (MD), axial (AD), and radial (RD) diffusivity within the bilateral anterior and posterior centrum semiovale (CSO) on posthypothermia brain magnetic resonance imaging. For HUS studies, we calculated a white-to-gray matter echogenicity ratio (WGR) and subsequently correlated it to DTI measurements.

RESULTS

Forty-two term neonates with HII who underwent hypothermia therapy were included. Significant correlation was found between prehypothermia WGR and MD, AD, and RD values in the left anterior CSO (r = .38-.40, P = .02). Prehypothermia WGR also correlated with the following: MD and RD in the right anterior CSO (r = .35-.36, P = .04), MD and AD in the right posterior CSO (r = .32-.45, P = .008-.03), and AD in the left posterior CSO (r = .47, P = .005). No significant correlation was found either between prehypothermia WGR and FA values in the bilateral anterior and posterior CSO or between posthypothermia WGR and all DTI scalars in the bilateral anterior and posterior CSO.

CONCLUSIONS

Prehypothermia HUS WGR may predict posthypothermia white matter structural integrity and is potentially an early and easily obtainable biomarker of severity in neonatal HII.

Altered plasma-type gelsolin and amyloid-β in neonates with hypoxic-ischaemic encephalopathy under therapeutic hypothermia

Hypoxic-ischemic encephalopathy (HIE) is a severe neonatal complication responsible for ∼23% of all neonatal deaths. Also, 30-70% of these patients will suffer lifetime disabilities, including learning impairment, epilepsy or cerebral palsy. However, biomarkers for HIE screening, or monitoring disease progression are limited. Herein, we sought to evaluate the clinical usefulness of plasma-type gelsolin (pGSN) and amyloid-beta (Aβ) 40 and 42 as prognostic biomarkers for HIE. pGSN has been previously suggested as a feasible marker in other brain injuries and amyloid-beta 40 and 42 are classically assessed in neurodegenerative diseases. However, to our knowledge, they have not been previously assessed in HIE patients. We have analyzed plasma pGSN and Aβ 40 and 42 levels in 55 newborns (16 controls, 16 mild and 23 moderate-severe HIE) at birth, during 72 h of therapeutic hypothermia, a gold-standard treatment for HIE, and 24 h after hypothermia. Aβ levels were lower in HIE patients, and pGSN levels were progressively reduced in mild and moderate-severe HIE patients. The fact that pGSN reductions could predict the severity of HIE and significantly correlated with the time to undergo hypothermia supports the prognostic value of plasmatic pGSN. Further studies are warranted to investigate the role of pGSN in neonatal HIE.

Circulating blood cellular glucose transporters - Surrogate biomarkers for neonatal hypoxic-ischemic encephalopathy assessed by novel scoring systems

OBJECTIVE

We examined Red Blood Cell (RBC) Glucose Transporter isoform 1 (GLUT1) and White Blood Cell (WBC) Glucose Transporter isoform 3 (GLUT3) protein concentrations to assess their potential as surrogate biomarkers for the presence of hypoxic-ischemic encephalopathy (HIE) and response to therapeutic hypothermia (TH), with respect to the neurodevelopmental prognosis.

STUDY DESIGN

A prospective feasibility study of 10 infants with HIE and 8 age-matched control subjects was undertaken. Following parental consent, blood samples were obtained at baseline before institution of TH (<6 h of life), during TH, at rewarming and post-TH in the HIE group with a baseline sample from the control group. GLUT1 and GLUT3 were measured by Enzyme-linked immunosorbent assay (ELISA) with brain biomarkers, Neuron-Specific Enolase (NSE) and Glial Fibrillary Acidic Protein (GFAP). Novel "HIE-high risk" and "Neurological" scores were developed to help identify HIE and to assess severity and prognosis, respectively.

RESULTS

RBC GLUT1 concentrations were increased at the baseline pre-TH time point in HIE versus control subjects (p = .006), normalizing after TH (p = .05). An association between GLUT1 and NSE concentrations (which was reflective of the HIE-high risk and the Neuro-scores) in controls and HIE pre-TH was seen (R² = 0.36, p = .008), with GLUT1 demonstrating 90% sensitivity and 88% specificity for presence of HIE identified by Sarnat Staging. WBC GLUT3 concentrations were low and no different in HIE versus control, and GFAP concentrations trended higher during re-warming (p = .11) and post-TH (p = .16). We demonstrated a significant difference between HIE and controls for both the "HIE-high risk" and the "Neurological" Scores. The latter score revealing the severity of clinical neurological illness correlated with the corresponding RBC GLUT1 (R² value = 0.39; p = .006).

CONCLUSION

Circulating RBC GLUT1 concentrations with NSE demonstrate a significant potential in reflecting the severity of HIE pre-TH and gauging effectiveness of TH. In contrast, the low neonatal WBC GLUT3 concentrations make discerning differences between degrees of HIE as well as assessing effectiveness of TH difficult. The HIE-high risk and Neurological scores may extend the "Sarnat staging" towards assessing severity and neuro-developmental prognosis of HIE.

Multimodal MRI Imaging of Apoptosis-Triggered Microstructural Alterations in the Postnatal Cerebral Cortex

Prematurely born children often develop neurodevelopmental delay that has been correlated with reduced growth and microstructural alterations in the cerebral cortex. Much research has focused on apoptotic neuronal cell death as a key neuropathological features following preterm brain injuries. How scattered apoptotic death of neurons may contribute to microstructural alterations remains unknown. The present study investigated in a rat model the effects of targeted neuronal apoptosis on cortical microstructure using in vivo MRI imaging combined with neuronal reconstruction and histological analysis. We describe that mild, targeted death of layer IV neurons in the developing rat cortex induces MRI-defined metabolic and microstructural alterations including increased cortical fractional anisotropy. Delayed architectural modifications in cortical gray matter and myelin abnormalities in the subcortical white matter such as hypomyelination and microglia activation follow the acute phase of neuronal death and axonal degeneration. These results establish the link between mild cortical apoptosis and MRI-defined microstructure changes that are reminiscent to those previously observed in preterm babies.

Magnetic resonance spectroscopy assessment of brain injury after moderate hypothermia in neonatal encephalopathy: a prospective multicentre cohort study

Background

In neonatal encephalopathy, the clinical manifestations of injury can only be reliably assessed several years after an intervention, complicating early prognostication and rendering trials of promising neuroprotectants slow and expensive. We aimed to determine the accuracy of thalamic proton magnetic resonance (MR) spectroscopy (MRS) biomarkers as early predictors of the neurodevelopmental abnormalities observed years after neonatal encephalopathy.

Methods

We did a prospective multicentre cohort study across eight neonatal intensive care units in the UK and USA, recruiting term and near-term neonates who received therapeutic hypothermia for neonatal encephalopathy. We excluded infants with life-threatening congenital malformations, syndromic disorders, neurometabolic diseases, or any alternative diagnoses for encephalopathy that were apparent within 6 h of birth. We obtained T₁-weighted, T₂-weighted, and diffusion-weighted MRI and thalamic proton MRS 4–14 days after birth. Clinical neurodevelopmental tests were done 18–24 months later. The primary outcome was the association between MR biomarkers and an adverse neurodevelopmental outcome, defined as death or moderate or severe disability, measured using a multivariable prognostic model. We used receiver operating characteristic (ROC) curves to examine the prognostic accuracy of the individual biomarkers. This trial is registered with ClinicalTrials.gov, number NCT01309711.

Findings

Between Jan 29, 2013, and June 25, 2016, we recruited 223 infants who all underwent MRI and MRS at a median age of 7 days (IQR 5–10), with 190 (85%) followed up for neurological examination at a median age of 23 months (20–25). Of those followed up, 31 (16%) had moderate or severe disability, including one death. Multiple logistic regression analysis could not be done because thalamic N-acetylaspartate (NAA) concentration alone accurately predicted an adverse neurodevelopmental outcome (area under the curve [AUC] of 0·99 [95% CI 0·94–1·00]; sensitivity 100% [74–100]; specificity 97% [90–100]; n=82); the models would not converge when any additional variable was examined. The AUC (95% CI) of clinical examination at 6 h (n=190) and at discharge (n=167) were 0·72 (0·65–0·78) and 0·60 (0·53–0·68), respectively, and the AUC of abnormal amplitude integrated EEG at 6 h (n=169) was 0·73 (0·65–0·79). On conventional MRI (n=190), cortical injury had an AUC of 0·67 (0·60–0·73), basal ganglia or thalamic injury had an AUC of 0·81 (0·75–0·87), and abnormal signal in the posterior limb of internal capsule (PLIC) had an AUC of 0·82 (0·76–0·87). Fractional anisotropy of PLIC (n=65) had an AUC of 0·82 (0·76–0·87). MRS metabolite peak-area ratios (n=160) of NAA–creatine (<1·29) had an AUC of 0·79 (0·72–0·85), of NAA–choline had an AUC of 0·74 (0·66–0·80), and of lactate–NAA (>0·22) had an AUC of 0·94 (0·89–0·97).

Interpretation

Thalamic proton MRS measures acquired soon after birth in neonatal encephalopathy had the highest accuracy to predict neurdevelopment 2 years later. These methods could be applied to increase the power of neuroprotection trials while reducing their duration.

Funding

National Institute for Health Research UK.

Value of assessment of multivoxel proton chemical shift imaging to predict long term outcome in patients after out-of-hospital cardiac arrest: A preliminary prospective observational study

BACKGROUND

Existing methods to predict recovery after out-of-hospital cardiac arrest (OHCA) lack of accuracy. The aim of this study was to determine whether quantitative proton chemical shift imaging (¹H-CSI) during the subacute stage of OHCA can predict neurological outcome of such patients.

METHODS

This monocentric prospective observational study was conducted in a Intensive Care Unit of a teaching hospital. Forty consecutive patients with OHCA were enrolled between January 1st 2011-December 31st 2013. Multivoxel ¹H-CSI values were compared to structural magnetic resonance imaging (MRI) sequences (fluid-attenuated inversion recovery and diffusion-weighted imaging). Ratios of N-acetyl-aspartate (NAA) to creatine (Cr) and choline compounds were analyzed using region of interest in bilateral lenticular cores and thalami. The outcome evaluated was the Cerebral Performance Category (CPC) at 6 months, dichotomized as favorable (CPC 1-2) and unfavorable outcome (CPC 3-5). The performance was compared by area under the receiver operating characteristic (ROC_AUC) curves analysis.

RESULTS

Twenty nine OHCA had an interpretable MRI. Eight patients (28%) had favorable outcome at 6 months. The worst NAA/Cr in lenticular cores was the best ¹H-CSI marker, with 80% sensitivity (95% confidence interval (CI), 57-94) and a 100% specificity (95% CI, 63-100) with a positive predictive value of 100%. Prognostic accuracy, as quantified by the ROC_AUC, was higher with the worst NAA/Cr in lenticular cores (ROC_AUC 0.88; 95% CI, 0.70-0.97) than with the structural MRI sequences.

CONCLUSION

In this preliminary study we found that multivoxel ¹H-CSI in lenticular cores was highly predictive of unfavorable outcome at 6 months.

Proton Magnetic Resonance Spectroscopy Biomarkers in Neonates With Hypoxic-Ischemic Encephalopathy: A Systematic Review and Meta-Analysis

Background: Hypoxic-ischemic encephalopathy (HIE) is a major contributor to child mortality and morbidity. Reliable prognostication for HIE is of key importance. Proton magnetic resonance spectroscopy (¹H-MRS) is a quantitative, non-invasive method that has been demonstrated to be a suitable complementary tool for prediction. The aim of this study was to investigate the prognostic capability of ¹H-MRS in the era of therapeutic hypothermia (TH).

Methods: Databases, namely MEDLINE, Embase, Web of Science, and the Cochrane library (Cochrane Center Register of Controlled Trials), were searched for studies published before July 17, 2017. Study selection and data extraction were performed by two independent reviewers. The mean difference (MD) or standardized MD (SMD) and 95% confidence interval (CI) were calculated using random-effects models. Subgroup analyses were conducted based on the use of TH.

Results: Among the 1,150 relevant studies, seven were included for meta-analysis, but only two small studies were conducted under TH. For ¹H-MRS measurement, three peak area ratios revealed predictive values for adverse outcomes in TH subgroup and the combined results (with and without TH): N-acetylaspartate (NAA)/creatine in basal ganglia/thalamus (BG/T) in TH (MD −0.31, 95%CI −0.55 to −0.07) and combined results (MD −0.37, 95% CI −0.49 to −0.25); NAA/choline in BG/T in TH (MD −0.89, 95%CI −1.43 to −0.35) and combined results (MD −0.25, 95%CI −0.42 to −0.07); and myo-inositol/choline in cerebral cortex in TH (MD −1.94, 95%CI −3.69 to −0.19) and combined results (MD −1.64, 95%CI −2.64 to −0.64). Moreover, NAA relative concentration is associated with adverse outcomes: in TH (MD −0.04, 95%CI −0.06 to −0.02) and combined results (MD −0.06, 95%CI −0.11 to −0.01) in white matter; in TH (MD −0.04, 95%CI −0.07 to −0.01) and combined results (MD −0.05, 95%CI −0.07 to −0.02) in gray matter.

Conclusions: NAA may be a potential marker in outcome prediction for all HIE subjects. It seems that MDs for the ratios including NAA are larger than for its relative concentration, and therefore are more likely to be measurable in a clinical context. Larger prospective multicenter studies with a standardized protocol for both measurement protocols and analysis methods are required in future studies.

Conventional MRI scan and DTI imaging show more severe brain injury in neonates with hypoxic-ischemic encephalopathy and seizures

BACKGROUND

Neonates with hypoxic-ischemic encephalopathy (HIE) and seizures have poorer outcome for undetermined reasons.

AIMS

Our aim was to determine if brain imaging was more abnormal in neonates with HIE and electrographically confirmed seizures and whether this was impacted by seizure burden.

STUDY DESIGN

Single center retrospective review.

SUBJECTS

Forty-eight term neonates with HIE (with and without seizures) underwent MRI brain scans before age 14 days between the years 2008 and 2013.

OUTCOME MEASURES

Images were rated using a MRI injury score and fractional anisotropy (FA) values were extracted from diffusion tensor imaging (DTI).

RESULTS

The seizure group (n = 25) had significantly more injury within white matter, basal ganglia, posterior limb of internal capsule, and watershed areas compared to the group without seizures (n = 23). The severity of injury in all measured areas increased with increasing seizure severity. The seizure group also had lower FA values in posterior limb of the internal capsule and the splenium of corpus callosum.

CONCLUSIONS

Neonates with HIE and seizures had more brain injury that occurred in areas typically affected by HIE and was greater with higher seizure burden. Seizures may be a marker of more severe brain injury or seizures themselves may amplify brain damage from HIE.

[Current status of the application of 1H-magnetic resonance spectroscopy in neonates with hypoxic-ischemic encephalopathy]

OBJECTIVE

To investigate the current status of the application of ¹H-magnetic resonance spectroscopy (¹H-MRS) in neonates with hypoxic-ischemic encephalopathy (HIE), and to describe the trend of research in the field.

METHODS

PubMed, EMBASE, and Web of Science were searched for English articles published up to January 10, 2018, with the combination of key words and MeSH terms. The articles were screened according to inclusion and exclusion criteria. Excel 2016, Bicomb 2.0, and VOSviewer1.6.6 were used to analyze the key words, to perform a cluster analysis of hot words, and to plot the knowledge map.

RESULTS

A total of 66 articles were included, and 27 high-frequency key words were extracted. The results showed that ¹H-MRS was mainly used in four directions of the clinical practice and scientific research on HIE. In clinical practice, ¹H-MRS attracted wide attention as a clinical examination for HIE and a tool for prognostic evaluation; in scientific research, ¹H-MRS was used in animal experiments and studies associated with mild hypothermia therapy.

CONCLUSIONS

As an auxiliary means of magnetic resonance imaging, ¹H-MRS plays an important role in investigating the pathogenesis of neonatal HIE, improving existing therapies, and evaluating the prognosis of neonates with HIE.

Early detection of neonatal hypoxic-ischemic white matter injury: an MR diffusion tensor imaging study

The purpose of this study was to compare diffusion tensor metrics in normal age-matched neonates with survivors of hypoxic–ischemic encephalopathy (HIE) and extracorporeal membrane oxygenation (ECMO). Thirty-five normal, 27 HIE, and 13 ECMO infants underwent MRI at 3 T. Neurodevelopmental assessments were performed. Fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) of the inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, anterior commissure, genu corpus callosum and splenium of the corpus callosum, anterior and posterior limb of the internal capsule, superior longitudinal fasciculus, and the centrum semiovale were analyzed with tract-based spatial statistics modified for use in neonates. Linear regression analysis was performed, and 95% confidence intervals were created for age effects on the tensor metrics with the control patients. Two-sample t-test was done to determine whether there was a difference in the tensor metrics between the normal and patient cohort. There was a statistically significant age effect on the FA and RD in the selected regions of the brain (F<0.05) and a group difference in the FA and RD between the normal and the HIE group (P<0.05). The group difference in the FA and RD between the normal and ECMO groups was seen in the anterior commissure, genu corpus callosum, right inferior longitudinal fasciculus, fronto-occipital fasciculus, centrum semiovale, and superior longitudinal fasciculus (P<0.05). Patients who were outside the 95% confidence intervals of the FA, AD, and RD overlapped with those with abnormalities clinically and on the conventional MRI. In conclusion, diffusion tensor imaging can play a significant role in detecting infants with early indications of hypoxic–ischemic brain injury.

Therapeutic hypothermia for neonates with hypoxic ischemic encephalopathy

Therapeutic hypothermia (TH) is a recommended regimen for newborn infants who are at or near term with evolving moderate-to-severe hypoxic ischemic encephalopathy (HIE). The Task Force of the Taiwan Child Neurology Society and the Taiwan Society of Neonatology held a joint meeting in 2015 to establish recommendations for using TH on newborn patients with HIE. Based on current evidence and experts' experiences, this review article summarizes the key points and recommendations regarding TH for newborns with HIE, including: (1) selection criteria for TH; (2) choices of method and equipment for TH; (3) TH prior to and during transport; (4) methods for temperature maintenance, monitoring, and rewarming; (5) systemic care of patients during TH, including the care of respiratory and cardiovascular systems, management of fluids, electrolytes, and nutrition, as well as sedation and drug metabolism; (6) monitoring and management of seizures; (7) neuroimaging, prognostic factors, and outcomes; and (8) adjuvant therapy for TH.

[Quantitative evaluation of white matter development in fetus with growth restriction by diffusion tensor imaging]

OBJECTIVE

To investigate whether fetal growth restriction (FGR) has an adverse effect on white matter development.

METHODS

A total of 28 full-term small for gestational age (SGA) infants were enrolled as study subjects and 15 full-term appropriate for gestational age infants were enrolled as control group. Conventional head magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were performed for all infants. The white matter was divided into 122 regions. The two groups were compared in terms of fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity of different brain regions.

RESULTS

Compared with the control group, the SGA group had a significantly lower fractional anisotropy in 16 brain regions (P<0.01), a significantly higher mean diffusivity in 7 brain regions (P<0.05), a significantly higher axial diffusivity in 8 brain regions (P<0.05), and a significantly higher radial diffusivity in 16 brain regions (P<0.05).

CONCLUSIONS

FGR may cause abnormalities in the maturity and integrity of white matter fiber tracts.

Prognostic Value of the Apparent Diffusion Coefficient in Newborns with Hypoxic-Ischaemic Encephalopathy Treated with Therapeutic Hypothermia

BACKGROUND

Apparent diffusion coefficient (ADC) quantification has been proven to be of prognostic value in term newborns with hypoxic-ischaemic encephalopathy (HIE) who were treated under normothermia.

OBJECTIVES

To evaluate the prognostic value of ADC in standardized brain regions in neonates with HIE who were treated with therapeutic hypothermia (TH).

METHODS

This prospective cohort study included 54 term newborns who were admitted with HIE and treated with TH. All magnetic resonance imaging examinations were performed between days 4 and 6 of life, and ADC values were measured in 13 standardized regions of the brain. At 2 years of age we explored whether ADC values were related to composite outcomes (death or survival with abnormal neurodevelopment).

RESULTS

The severity of HIE is inversely related to ADC values in different brain regions. We found that lower ADC values in the posterior limb of the internal capsule (PLIC), the thalami, the semioval centre, and frontal and parietal white matter were related to adverse outcomes. ADC values in the PLIC and thalami are good predictors of adverse outcomes (AUC 0.86 and 0.76).

CONCLUSIONS

Low ADC values in the PLIC, thalamus, semioval centre, and frontal and parietal white matter in full-term infants with HIE treated with TH were associated with a poor outcome.

Diffusion Tensor Imaging Colour Mapping Threshold for Identification of Ventilation-Induced Brain Injury after Intrauterine Inflammation in Preterm Lambs

PURPOSE

The aim of this study is to examine whether advanced magnetic resonance imaging (MRI) techniques can detect early brain injury caused by intrauterine inflammation and inappropriate initial respiratory support in preterm lambs.

HYPOTHESIS

Neuropathology caused by intrauterine inflammation is exacerbated by mechanical ventilation at birth and is detectable with advanced MRI techniques.

METHODS

Pregnant ewes received intra-amniotic lipopolysaccharide (LPS) 7 days prior to delivery at ~125 days of gestation (85% of gestation), whereupon lambs were delivered and randomised to receive an injurious (LPS + INJ, n = 6) or protective (LPS + PROT, n = 6) ventilation strategy. MRI of the brain was conducted 90 min after preterm delivery, using structural, diffusion tensor imaging (DTI), and magnetic resonance spectroscopy (MRS) techniques. A colour map threshold technique was utilised to compare distributions of low diffusivity voxels in the brains of LPS-exposed lambs with those not exposed to LPS (PROT, n = 7 PROT and INJ, n = 10).

RESULTS

No overt cerebral injury was identified on structural MRI images of any lamb. However, on DTI, axial diffusivity, radial diffusivity, and mean diffusivity values were lower and significantly more heterogeneous in specific brain regions of lambs in the LPS + INJ group compared to the LPS + PROT group. Colour mapping revealed lower diffusivity in the thalamus, periventricular white matter, internal capsule, and frontal white matter in the LPS + INJ group compared to LPS + PROT group. The MRS peak area ratios of lactate, relative to those for the metabolites creatine, choline, and N-acetylaspartate, were not different between LPS-exposed groups. Lambs exposed to LPS had lower diffusivity within the white matter regions assessed than non-LPS-treated control lambs.

CONCLUSION

DTI colour map threshold techniques detected early brain injury in preterm lambs exposed to intrauterine inflammation and detected differences between injurious and protective ventilation strategies. DTI mapping approaches are potentially useful for early detection of subtle brain injury in premature infants.

Early identification of hypoxic-ischemic encephalopathy by combination of magnetic resonance (MR) imaging and proton MR spectroscopy

Brain damage following a perinatal hypoxic-ischemic encephalopathy (HIE) can be diagnosed by different techniques. The aim of the present study was to combine magnetic resonance (MR) imaging with proton MR spectroscopy in HIE diagnosis and to evaluate their correlation with outcome. A prospective observational cohort study was performed between February 2012 and February 2013. Consecutive newborns, 24 full-term neonates with HIE (mild to moderate and severe group) and 5 normal neonates, were included. Two sequential MR studies were performed; a conventional MR imaging for observation in T1 weighted image (WI) and T2WI, and proton MR spectroscopy for observation in the left or right basal ganglia and thalamus. MR images were assessed and scored by two neuroradiologists who were blinded to the clinical condition of the infants. The mild to moderate group (n=13) and severe group (n=11) were similar in the visualization of punctate hyperintensity lesions on T1WI and brain edema on T2WI. The differences of N-acetylaspartate/creatine (Cr), choline/Cr and lactate/Cr in the basal ganglia and thalamus in the HIE group were significantly different (P<0.05) compared with the control group, while no significant difference was identified between the mild to moderate and severe group (P>0.05). In conclusion, MR spectroscopy is a complementary tool for the diagnosis of HIE.

Neuroimaging and Other Neurodiagnostic Tests in Neonatal Encephalopathy

Hypoxic-ischemic encephalopathy is associated with a high risk of morbidity and mortality in the neonatal period. Long-term neurodevelopmental disability is also frequent in survivors. Conventional MRI defines typical patterns of injury that reflect specific pathophysiologic mechanisms. Advanced magnetic resonance techniques now provide unique perspectives on neonatal brain metabolism, microstructure, and connectivity. The application of these imaging techniques has revealed that brain injury commonly occurs at or near the time of birth and evolves over the first weeks of life. Amplitude-integrated electroencephalogram and near-infrared spectroscopy are increasingly used as bedside tools in neonatal intensive care units to monitor brain function.

Diffusion tensor imaging study of pediatric patients with congenital hydrocephalus: 1-year postsurgical outcomes

OBJECTIVE The purpose of this study was to investigate white matter (WM) structural abnormalities using diffusion tensor imaging (DTI) in children with hydrocephalus before CSF diversionary surgery (including ventriculoperitoneal shunt insertion and endoscopic third ventriculostomy) and during the course of recovery after surgery in association with neuropsychological and behavioral outcome. METHODS This prospective study included 54 pediatric patients with congenital hydrocephalus (21 female, 33 male; age range 0.03-194.5 months) who underwent surgery and 64 normal controls (30 female, 34 male; age range 0.30-197.75 months). DTI and neurodevelopmental outcome data were collected once in the control group and 3 times (preoperatively and at 3 and 12 months postoperatively) in the patients with hydrocephalus. DTI measures, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) values were extracted from the genu of the corpus callosum (gCC) and the posterior limb of internal capsule (PLIC). Group analysis was performed first cross-sectionally to quantify DTI abnormalities at 3 time points by comparing the data obtained in the hydrocephalus group for each of the 3 time points to data obtained in the controls. Longitudinal comparisons were conducted pairwise between different time points in patients whose data were acquired at multiple time points. Neurodevelopmental data were collected and analyzed using the Adaptive Behavior Assessment System, Second Edition, and the Bayley Scales of Infant Development, Third Edition. Correlation analyses were performed between DTI and behavioral measures. RESULTS Significant DTI abnormalities were found in the hydrocephalus patients in both the gCC (lower FA and higher MD, AD, and RD) and the PLIC (higher FA, lower AD and RD) before surgery. The DTI measures in the gCC remained mostly abnormal at 3 and 12 months after surgery. The DTI abnormalities in the PLIC were significant in FA and AD at 3 months after surgery but did not persist when tested at 12 months after surgery. Significant longitudinal DTI changes in the patients with hydrocephalus were found in the gCC when findings at 3 and 12 months after surgery were compared. In the PLIC, trend-level longitudinal changes were observed between preoperative findings and 3-month postoperative findings, as well as between 3- and 12-month postoperative findings. Significant correlation between DTI and developmental outcome was found at all 3 time points. Notably, a significant correlation was found between DTI in the PLIC at 3 months after surgery and developmental outcome at 12 months after surgery. CONCLUSIONS The data showed significant WM abnormality based on DTI in both the gCC and the PLIC in patients with congenital hydrocephalus before surgery, and the abnormalities persisted in both the gCC and the PLIC at 3 months after surgery. The DTI values remained significantly abnormal in the gCC at 12 months after surgery. Longitudinal analysis showed signs of recovery in both WM structures between different time points. Combined with the significant correlation found between DTI and neuropsychological measures, the findings of this study suggest that DTI can serve as a sensitive imaging biomarker for underlying neuroanatomical changes and postsurgical developmental outcome and even as a predictor for future outcomes.

Interplay of brain structure and function in neonatal congenital heart disease

Objective

To evaluate whether structural and microstructural brain abnormalities in neonates with congenital heart disease (CHD) correlate with neuronal network dysfunction measured by analysis of EEG connectivity.

Methods

We studied a prospective cohort of 20 neonates with CHD who underwent continuous EEG monitoring before surgery to assess functional brain maturation and network connectivity, structural magnetic resonance imaging (MRI) to determine the presence of brain injury and structural brain development, and diffusion tensor MRI to assess brain microstructural development.

Results

Neonates with MRI brain injury and delayed structural and microstructural brain development demonstrated significantly stronger high‐frequency (beta and gamma frequency band) connectivity. Furthermore, neonates with delayed microstructural brain development demonstrated significantly weaker low‐frequency (delta, theta, alpha frequency band) connectivity. Neonates with brain injury also displayed delayed functional maturation of EEG background activity, characterized by greater background discontinuity.

Interpretation

These data provide new evidence that early structural and microstructural developmental brain abnormalities can have immediate functional consequences that manifest as characteristic alterations of neuronal network connectivity. Such early perturbations of developing neuronal networks, if sustained, may be responsible for the persistent neurocognitive impairment prevalent in adolescent survivors of CHD. These foundational insights into the complex interplay between evolving brain structure and function may have relevance for a wide spectrum of neurological disorders manifesting early developmental brain injury.

MR spectroscopy in children: protocols and pitfalls in non-tumorous brain pathology

Proton nuclear magnetic resonance spectroscopy (MRS) delivers information about cell content and metabolism in a noninvasive manner. The diagnostic strength of MRS lies in its evaluation of pathologies in combination with conventional magnetic resonance imaging (MRI). MRS in children has been most widely used to evaluate brain conditions like tumors, infections, metabolic diseases or learning disabilities and especially in neonates with hypoxic-ischemic encephalopathy. This article reviews some basic theoretical considerations, routine procedures, protocols and pitfalls and will illustrate the range of spectrum alterations occurring in some non-tumorous pediatric brain pathologies.

White matter tract integrity and developmental outcome in newborn infants with hypoxic-ischemic encephalopathy treated with hypothermia

AIM

To determine whether corpus callosum (CC) and corticospinal tract (CST) diffusion tensor imaging (DTI) measures relate to developmental outcome in encephalopathic newborn infants after therapeutic hypothermia.

METHOD

Encephalopathic newborn infants enrolled in a longitudinal study underwent DTI after hypothermia. Parametric maps were generated for fractional anisotropy, mean, radial, and axial diffusivity. CC and CST were segmented by DTI-based tractography. Multiple regression models were used to examine the association of DTI measures with Bayley-II Mental (MDI) and Psychomotor Developmental Index (PDI) at 15 months and 21 months of age.

RESULTS

Fifty-two infants (males n=32, females n=20) underwent DTI at median age of 8 days. Two were excluded because of poor magnetic resonance imaging quality. Outcomes were assessed in 42/50 (84%) children at 15 months and 35/50 (70%) at 21 months. Lower CC and CST fractional anisotropy were associated with lower MDI and PDI respectively, even after controlling for gestational age, birth weight, sex, and socio-economic status. There was also a direct relationship between CC axial diffusivity and MDI, while CST radial diffusivity was inversely related to PDI.

INTERPRETATION

In encephalopathic newborn infants, impaired microstructural organization of the CC and CST predicts poorer cognitive and motor performance respectively. Tractography provides a reliable method for early assessment of perinatal brain injury.

Therapeutic hypothermia modifies perinatal asphyxia-induced changes of the corpus callosum and outcome in neonates

What Is Known about this Subject?

Diffusion-weighted MRI has demonstrated changes in the corpus callosum of term neonates with perinatal asphyxia. The severity of cerebral changes demonstrated using diffusion-weighted MRI is difficult to assess without measuring values of the Apparent Diffusion Coefficient (ADC).

What Is New?

ADC values of the anterior part of the corpus callosum are slightly higher than of the posterior part in full term infants with perinatal asphyxia. Low ADC values of the corpus callosum were associated with an adverse outcome in infants with perinatal asphyxia. In infants treated with hypothermia lower ADC values than with normothermia were associated with a poor outcome, supporting neuroprotective effects of hypothermia

Background

Using MRI, changes can be detected in the corpus callosum (CC) following perinatal asphyxia which are associated with later neurodevelopmental outcome.

Aim

To study the association between the apparent diffusion coefficient of water (ADC) in the CC on MRI in neonates with perinatal asphyxia and neurodevelopmental outcome at 18 months of age.

Subjects, Methods

Of 121 infants 32 (26%) died and 13 (11%) survived with an adverse neurological outcome. Sixty-five (54%) received therapeutic hypothermia. MRI was performed within 7 days after birth using a 1.5 T or 3.0 T system, and ADC values were measured in the anterior and posterior CC. The association between ADC and composite outcome (death or abnormal neurodevelopment) was analyzed for both normothermia and hypothermia cases using receiver operating characteristics.

Results

ADC values of the posterior CC were lower than of the anterior part (mean difference 0.050 x 10^-3 mm²/s, p<0.001). Field strength did not affect ADC values. ADC values of the posterior part of the CC were significantly lower in infants with basal ganglia/thalamus or near total brain injury (p<0.001). Lower ADC values were associated with an adverse outcome, but cut-off levels were lower after hypothermia (1.024 x 10^-3 mm²/s vs 0.969 x 10^-3 mm²/s)

Conclusion

Low ADC values of the posterior part of the corpus callosum are associated with an adverse outcome in term or near term neonates with perinatal asphyxia. Therapeutic hypothermia slightly modifies this association, showing that lower values were needed for an adverse outcome.

Comparing tract-based spatial statistics and manual region-of-Interest labeling as diffusion analysis methods to detect white matter abnormalities in infants with hypoxic-Ischemic encephalopathy

PURPOSE

To compare manual region of interest (ROI) labeling and tract-based spatial statistics (TBSS) by their ability to detect group-wise differences in fractional anisotropy (FA) in the neonatal brain.

MATERIALS AND METHODS

Diffusion-weighted data were obtained for nine infants with hypoxic-ischemic encephalopathy (HIE) (six males, three females; gestational age [GA] range, 36-40 weeks; mean GA, 37.8 weeks) and 11 healthy-control infants (10 males, 1 female; GA range, 36-40 weeks; mean GA, 38.4 weeks) at 3T. For manual ROI labeling, ROIs were drawn freehand for each subject in eight, clinically relevant brain regions. For TBSS, all FA data underwent an optimized, automated protocol for neonates. Each method was evaluated for detection of decreased FA in HIE infants, sensitivity, specificity, and variability.

RESULTS

FA values from manual ROI and TBSS were strongly correlated (r = 0.94, P < 0.0001). Both methods found decreased FA in most ROIs for HIE infants. There was no significant interaction between method and group, indicating a similar ability to detect FA differences (F(1,19) = 0.599, P = 0.449). Sensitivity (manual: 0.709, TBSS: 0.694, 95% CI [-0.136, 0.163], P = 0.856), specificity (manual and TBSS: 0.716, 95% CI [-0.133, 0.133], P = 1), and standard error (manual: 0.009, TBSS: 0.007) were comparable.

CONCLUSION

Manual ROI labeling and TBSS are comparable methods of diffusion analysis to detect group differences in FA in the neonatal brain.

Early identification of brain injury in infants with hypoxic ischemic encephalopathy at high risk for severe impairments: accuracy of MRI performed in the first days of life

Background

Despite therapeutic hypothermia 30-70% of newborns with moderate or severe hypoxic ischemic encephalopathy will die or survive with significant long-term impairments. Magnetic resonance imaging (MRI) in the first days of life is being used for early identification of these infants and end of life decisions are relying more and more on it. The purpose of this study was to evaluate how MRI performed around day 4 of life correlates with the ones obtained in the second week of life in infants with hypoxic-ischemic encephalopathy (HIE) treated with hypothermia.

Methods

Prospective observational cohort study between April 2009 and July 2011. Consecutive newborns with HIE evaluated for therapeutic hypothermia were included. Two sequential MR studies were performed: an •early’ study around the 4th day of life and a •late’ study during the second week of life. MRI were assessed and scored by two neuroradiologists who were blinded to the clinical condition of the infants.

Results

Forty-eight MRI scans were obtained in the 40 newborns. Fifteen infants underwent two sequential MR scans. The localization, extension and severity of hypoxic-ischemic injury in early and late scans were highly correlated. Hypoxic-ischemic injury scores from conventional sequences (T1/T2) in the early MRI correlated with the scores of the late MRI (Spearman ρ = 0.940; p < .001) as did the scores between diffusion-weighted images in early scans and conventional images in late MR studies (Spearman ρ = 0.866; p < .001). There were no significant differences in MR images between the two sequential scans.

Conclusions

MRI in the first days of life may be a useful prognostic tool for clinicians and can help parents and neonatologist in medical decisions, as it highly depicts hypoxic-ischemic brain injury seen in scans performed around the second week of life.

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.

New imaging approaches to evaluate newborn brain injury and their role in predicting developmental disorders

PURPOSE OF REVIEW

This review highlights recent work using advanced imaging approaches that have improved our understanding of the underlying neural mechanisms associated with disrupted brain development or demonstrated the potential of MRI to provide objective biomarkers of cerebral injury that relate to subsequent neurodevelopmental performance.

RECENT FINDINGS

Preterm birth impacts on the development of thalamocortical connections to inferior frontal and medial temporal cortex, and cingulate gyri. Impairments to cortical development in these regions are evident in early adulthood and associated with lower intelligence quotient scores. Disruptions to microstructural development of cortical gray matter are prevalent in survivors of preterm birth and related to immaturity at birth, postnatal growth and neurodevelopmental performance. Brain dysmaturation is also evident in infants with congenital heart disease and is detectable prior to surgery, highlighting the influence of adverse conditions on in-utero brain development. In infants with hypoxic-ischemic encephalopathy who have undergone therapeutic hypothermia, quantitative magnetic resonance measures in the neonatal period are related to performance at 2 years.

SUMMARY

Advanced MRI approaches offer the opportunity to assess objectively brain structure and function, and a number of studies, spanning different patient groups, demonstrate their utility as early biomarkers of altered neurological outcome.