Evolution of pattern of injury and quantitative MRI on days 1 and 3 in term newborns with hypoxic-ischemic encephalopathy

Advances in Neuroimaging Biomarkers and Scoring

MRI of the brain is a critical tool in the diagnosis, evaluation, and management of neonatal encephalopathy (NE). More than simply a diagnostic and prognostic tool, MRI informs the biology, nature, and timing of the disease process resulting in NE, of which the largest single etiology is hypoxic-ischemic encephalopathy (HIE). Historically, 2 major patterns of injury were seen in HIE: a basal ganglia/thalamus predominant pattern and a watershed pattern of injury. The advent of therapeutic hypothermia for NE/HIE, alongside improvements in the application of imaging technology in newborn infants, has resulted in progressively more advanced MRI scoring systems.

Point of care magnetic resonance neonatal neuroimaging applications and early imaging in infants under active therapeutic hypothermia: a perspective

As care of the most vulnerable infants in the neonatal intensive care unit (NICU) evolves, improved and real-time understanding of brain health becomes key. The availability of an in-NICU magnetic resonance imaging (MRI) scanner provides unique options to bedside care providers and researchers. We present our perspective on the 1-Tesla MRI unit in our NICU and its utilities and applications both in the clinical and research fields. We also discuss our experience with early and serial MRI in a cohort of infants with hypoxic-ischemic encephalopathy while undergoing therapeutic hypothermia, using a compatible cooling blanket and monitoring apparatus with special insight into the planning and organization between providers, and parental perspectives around early, detailed imaging.

Insights from serial magnetic resonance imaging in neonatal encephalopathy in term infants

BACKGROUND

Limited serial neuroimaging studies use magnetic resonance imaging (MRI) to define the evolution of hypoxic-ischemic insults to the brain of term infants and encompass both the primary injury and its secondary impact on cerebral development. The optimal timing of MRI to fully evaluate the impact of hypoxic-ischemic encephalopathy on brain development and associated neurodevelopmental sequelae remains unknown.

METHODS

Goals: (a) review literature related to serial neuroimaging in term infants with HIE; (b) describe pilot data in two infants with HIE treated with therapeutic hypothermia who had a brain injury at day 3-5 and underwent four additional MRIs over the next 12 weeks of life and developmental evaluation at 24 months of age.

RESULTS

Early MRI defines primary injury on diffusion-weighted imaging, yet the full impact may not be fully apparent until after 1 month of life.

CONCLUSION

The full impact of an ischemic injury on the neonatal brain may not be fully visible until several weeks after the initial insult. This suggests the benefit of obtaining later time points for MRI to fully define the extent of injury and its neurodevelopmental impact.

IMPACT

Few studies inform the nature of the evolution of brain injury with hypothermia in HIE, limiting understanding of potential neuroprotection. MRI is the standard of care for prognosis in infants with HIE, however timing for optimal prognostic prediction remains unclear. Insights from MRI after the first week of life may assist in defining the full extent of brain injury and prognostic significance. A pilot study using five MRI timepoints up to 3 months of age, is presented. More data is required with a systematic evaluation of the impact of early brain injury on brain development in term infants with HIE following TH.

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.

Temporal Evolution of Signal Alterations in the Deep Gray Nuclei in term Neonates With Hypoxic-Ischemic Brain Injury: A Comprehensive Review

The deep gray nuclei are paired interconnected gray nuclei comprising the basal ganglia and thalami. Injury to the deep gray nuclei secondary to hypoxic-ischemic injury is associated with poor short- and long-term clinical outcomes. The signal changes following hypoxic-ischemic injury are dynamic and evolve over a period of time from injury to resolution. Radiologically relevant events following hypoxic-ischemic injury include the onset of anaerobic metabolism immediately following hypoxic-ischemic injury, increase in cytotoxic edema followed by its resolution, and the onset and progression of neuronal necrosis and gliosis. Appearance of lactate peak on proton spectroscopy is the initial radiologic evidence of hypoxic-ischemic injury. Diffusion-weighted imaging has the highest prognostic value and pseudo-normalizes following 1 week of hypoxic-ischemic injury. Recommended timing for magnetic resonance imaging (MRI) is between 4 and 7 days. MR imaging performed between 1 and 6 months underestimates the extent of injury because radiologic changes are subtle. This review provides a detailed timeline of radiologic abnormalities in the deep gray nuclei following hypoxic-ischemic injury.

Association of cerebral metabolic rate following therapeutic hypothermia with 18-month neurodevelopmental outcomes after neonatal hypoxic ischemic encephalopathy

BACKGROUND

Therapeutic hypothermia (TH) is standard of care for moderate to severe neonatal hypoxic ischemic encephalopathy (HIE) but many survivors still suffer lifelong disabilities and benefits of TH for mild HIE are under active debate. Development of objective diagnostics, with sensitivity to mild HIE, are needed to select, guide, and assess response to treatment. The objective of this study was to determine if cerebral oxygen metabolism (CMRO2) in the days after TH is associated with 18-month neurodevelopmental outcomes as the first step in evaluating CMRO2's potential as a diagnostic for HIE. Secondary objectives were to compare associations with clinical exams and characterise the relationship between CMRO2 and temperature during TH.

METHODS

This was a prospective, multicentre, observational, cohort study of neonates clinically diagnosed with HIE and treated with TH recruited from the tertiary neonatal intensive care units (NICUs) of Boston Children's Hospital, Brigham and Women's Hospital, and Beth Israel Deaconess Medical Center between December 2015 and October 2019 with follow-up to 18 months. In total, 329 neonates ≥34 weeks gestational age admitted with perinatal asphyxia and suspected HIE were identified. 179 were approached, 103 enrolled, 73 received TH, and 64 were included. CMRO2 was measured at the NICU bedside by frequency-domain near-infrared and diffuse correlation spectroscopies (FDNIRS-DCS) during the late phases of hypothermia (C), rewarming (RW) and after return to normothermia (NT). Additional variables were body temperature and clinical neonatal encephalopathy (NE) scores, as well as findings from magnetic resonance imaging (MRI) and spectroscopy (MRS). Primary outcome was the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) at 18 months, normed (SD) to 100 (15).

FINDINGS

Data quality for 58 neonates was sufficient for analysis. CMRO2 changed by 14.4% per °C (95% CI, 14.2-14.6) relative to its baseline at NT while cerebral tissue oxygen extraction fraction (cFTOE) changed by only 2.2% per °C (95% CI, 2.1-2.4) for net changes from C to NT of 91% and 8%, respectively. Follow-up data for 2 were incomplete, 33 declined and 1 died, leaving 22 participants (mean [SD] postnatal age, 19.1 [1.2] month; 11 female) with mild to moderate HIE (median [IQR] NE score, 4 [3-6]) and 21 (95%) with BSID-III scores >85 at 18 months. CMRO2 at NT was positively associated with cognitive and motor composite scores (β (SE) = 4.49 (1.55) and 2.77 (1.00) BSID-III points per 10-10 moL/dl × mm2/s, P = 0.009 and P = 0.01 respectively; linear regression); none of the other measures were associated with the neurodevelopmental outcomes.

INTERPRETATION

Point of care measures of CMRO2 in the NICU during C and RW showed dramatic changes and potential to assess individual response to TH. CMRO2 following TH outperformed conventional clinical evaluations (NE score, cFTOE, and MRI/MRS) at predicting cognitive and motor outcomes at 18 months for mild to moderate HIE, providing a promising objective, physiologically-based diagnostic for HIE.

FUNDING

This clinical study was funded by an NIH grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, United States (R01HD076258).

Comparative evaluation of approach to cardiovascular care in neonatal encephalopathy undergoing therapeutic hypothermia

OBJECTIVE

To analyze the association between cardiovascular care and adverse outcome in infants undergoing therapeutic hypothermia for neonatal encephalopathy (NE).

STUDY DESIGN

This was a retrospective cohort study of 176 infants with NE and hypotension, admitted to the SickKids Hospital (Center A, n = 86) or Semmelweis University (Center B, n = 90).

RESULT

The lowest systolic/diastolic blood pressures were comparable amongst centers; however, proportion of cardiovascular support was lower in Center A (51% vs 97% in Center B). Overall rate of death or abnormal MRI (adverse outcome) were comparable between centers, although pattern differed with more basal ganglia injury in Center B. A 24-hour longer duration of cardiovascular support increased the odds for adverse outcome by 14%.

CONCLUSION

We demonstrated that management of hemodynamic instability in infants with NE was markedly different in two high-volume NICUs and showed that longer duration of cardiovascular medication is an independent risk factor for adverse outcome.

Does Early Cerebral Near-Infrared Spectroscopy Monitoring Predict Outcome in Neonates with Hypoxic Ischaemic Encephalopathy? A Systematic Review of Diagnostic Test Accuracy

INTRODUCTION

Hypoxic ischaemic encephalopathy (HIE) remains one of the top 10 contributors to the global burden of disease. Early objective biomarkers are required. Near-infrared spectroscopy (NIRS) may provide a valuable insight into cerebral perfusion and metabolism. We aimed to determine whether early NIRS monitoring (<6 h of age) can predict outcome as defined by grade of encephalopathy, brain MRI findings, and/or neurodevelopmental outcome at 1-2 years in infants with HIE.

METHODS

We searched PubMed, Scopus, Web of Science, Embase, and The Cochrane Library databases (July 2019). Studies of infants born ≥36+0 weeks gestation with HIE who had NIRS recording commenced before 6 h of life were included. We planned to provide a narrative of all the studies included, and if similar clinically and methodologically, the results would be pooled in a meta-analysis to determine test accuracy.

RESULTS

Seven studies were included with a combined total of 161 infants. Only 1 study included infants with mild HIE. A range of different oximeters and probes were utilized with varying outcome measures making comparison difficult. Although some studies showed a trend towards higher cSO2 values before 6 h in infants with adverse neurodevelopmental outcomes, in the majority, this was not significant until beyond 24 h of life.

CONCLUSION

Very little data currently exists to assess the use of early NIRS to predict outcome in infants with HIE. Further studies using a standardized approach are required before NIRS can be evaluated as a potential objective assessment tool for early identification of at-risk infants.

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.

Neuroimaging in the term newborn with neonatal encephalopathy

Neuroimaging is widely used to aid in the diagnosis and clinical management of neonates with neonatal encephalopathy (NE). Yet, despite widespread use clinically, there are few published guidelines on neuroimaging for neonates with NE. This review outlines the primary patterns of brain injury associated with hypoxic-ischemic injury in neonates with NE and their frequency, associated neuropathological features, and risk factors. In addition, it provides an overview of neuroimaging methods, including the most widely used scoring systems used to characterize brain injury in these neonates and their utility as predictive biomarkers. Last, recommendations for neuroimaging in neonates with NE are presented.

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.

Evaluation of Altered Glutamatergic Activity in a Piglet Model of Hypoxic-Ischemic Brain Damage Using 1H-MRS

Methods

Twenty-five newborn piglets were selected and then randomly assigned to the control group (n = 5) and the model group (n = 20) subjected to HI. HI was induced by blocking bilateral carotid blood flow under simultaneous inhalation of a 6% oxygen mixture. ¹H-MRS data were acquired from the basal ganglia at the following time points after HI: 6, 12, 24, and 72 h. Changes in protein levels of EAAT2 and GluR2 were determined by immunohistochemical analysis. Correlations among metabolite concentrations, metabolite ratios, and the protein levels of EAAT2 and GluR2 were investigated.

Results

The Glu level sharply increased after HI, reached a transient low level of depletion that approached the normal level in the control group, and subsequently increased again. Negative correlations were found between concentrations of Glu and EAAT2 protein levels (R _s = -0.662, P < 0.001) and between the Glu/creatine (Cr) ratio and EAAT2 protein level (R _s = -0.664, P < 0.001). Moreover, changes in GluR2 protein level were significantly and negatively correlated with those in Glu level (the absolute Glu concentration, R _s = -0.797, P < 0.001; Glu/Cr, R _s = -0.567, P = 0.003).

Conclusions

Changes in Glu level measured by ¹H-MRS were inversely correlated with those in EAAT2 and GluR2 protein levels following HI, and the results demonstrated that ¹H-MRS can reflect the early changes of glutamatergic activity in vivo.

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.

Neuron-Specific Enolase in Cerebrospinal Fluid Predicts Brain Injury After Sudden Unexpected Postnatal Collapse

BACKGROUND

Biomarkers of brain injury with high predictive value in newborns in critical neurological status are increasingly required. Neuron-specific enolase in cerebrospinal fluid has been shown to be highly predictive in newborns with perinatal hypoxic-ischemic encephalopathy, but its utility has not been examined in sudden unexpected postnatal collapse.

PURPOSE

We analyzed whether the levels of neuron-specific enolase in cerebrospinal fluid can be a useful biomarker to estimate the severity of brain injury in neonates after a sudden unexpected postnatal collapse.

METHODS

This is a prospective observational study of near-term infants who were consecutively admitted with sudden unexpected postnatal collapse in two neonatal intensive care units during a nine-year period. Variables were collected and analyzed regarding the perinatal period, clinical course, severity of encephalopathy, amplitude-integrated encephalography, magnetic resonance imaging findings, and outcome. Neuron-specific enolase in cerebrospinal fluid samples were obtained in 18 infants with sudden unexpected postnatal collapse between 12 and 72 hours after the collapse and compared with those of 29 controls.

RESULTS

The levels of neuron-specific enolase in cerebrospinal fluid were higher in patients than in controls (P < 0.001). Levels of neuron-specific enolase in cerebrospinal fluid in infants with sudden unexpected postnatal collapse were significantly higher in patients who presented severe encephalopathy, seizures, abnormal amplitude-integrated encephalography background, or brain injury on magnetic resonance imaging. Receiver operator characteristic curve analysis revealed a neuron-specific enolase in cerebrospinal fluid cutoff value of maximum predictive accuracy of 61 ng/mL (area under the curve, 1.0; sensitivity, specificity, positive predictive value, and negative predictive value, 100%) for identifying infants who died or had adverse outcomes.

CONCLUSIONS

Levels of neuron-specific enolase in cerebrospinal fluid obtained between 12 and 72 hours after a sudden unexpected postnatal collapse event seem to be a useful biomarker for identifying newborns with severe brain injury and for predicting outcome.

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.

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

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

Pattern of Brain Injury Predicts Long-Term Epilepsy Following Neonatal Encephalopathy

OBJECTIVE

To determine if patterns of hypoxic-ischemic brain injury on magnetic resonance imaging (MRI) in term newborns predict subsequent childhood epilepsy.

METHODS

This retrospective cohort study includes term newborns with encephalopathy (n = 181) born between 2004-2012 and admitted to British Columbia Children's Hospital. MRI was performed between 3 and 5 days of age. The predominant patterns of hypoxic-ischemic injury were classified as Normal, Watershed, Basal Nuclei, Total, and Focal-Multifocal. Lesions in hippocampus, motor and occipital cortex were noted.

RESULTS

Of 181 newborns, 166 (92%) survived the neonatal period, and 132 (80%) had follow-up with a median duration of 61 months (IQR: 28-95). Twenty-three children (17%) developed epilepsy. A higher proportion with Watershed, Basal Nuclei, or Total patterns developed epilepsy (P < .001). Injury to motor cortex, hippocampus, and occipital lobe (P < .01) were independent risk factors for epilepsy. In the adjusting logistic model, Watershed (odds ratio = 16.0, 95% CI [1.3, 197.2], P = .03) and Basal Nuclei injury (odds ratio = 19.4, 95% CI [1.9, 196.3], P = .01) remained independent risk factors. Therapeutic hypothermia did not alter these associations. Severity of brain injury and recurrent neonatal seizures are other clinical risk factors.

SIGNIFICANCE

In term newborns with hypoxic-ischemic encephalopathy, the predominant pattern of Watershed and Basal Nuclei injury are valuable predictors for development of epilepsy in later childhood.

Cerebral oxygen metabolism during and after therapeutic hypothermia in neonatal hypoxic-ischemic encephalopathy: a feasibility study using magnetic resonance imaging

BACKGROUND

Therapeutic hypothermia is the standard-of-care treatment for infants diagnosed with moderate-to-severe hypoxic-ischemic encephalopathy (HIE). MRI for assessing brain injury is usually performed after hypothermia because of logistical challenges in bringing acutely sick infants receiving hypothermia from the neonatal intensive care unit (NICU) to the MRI suite. Perhaps examining and comparing early cerebral oxygen metabolism disturbances to those after rewarming will lead to a better understanding of the mechanisms of brain injury in HIE and the effects of therapeutic hypothermia.

OBJECTIVE

The objectives were to assess the feasibility of performing a novel T2-relaxation under spin tagging (TRUST) MRI technique to measure venous oxygen saturation very early in the time course of treatment, 18-24 h after the initiation of therapeutic hypothermia, to provide a framework to measure neonatal cerebral oxygen metabolism noninvasively, and to compare parameters between early and post-hypothermia MRIs.

MATERIALS AND METHODS

Early (18-24 h after initiating hypothermia) MRIs were performed during hypothermia treatment in nine infants with HIE (six with moderate and three with severe HIE). Six infants subsequently had an MRI after hypothermia. Mean values of cerebral blood flow, oxygen extraction fraction, and cerebral metabolic rate of oxygen from MRIs during hypothermia were compared between infants with moderate and severe HIE; and in those with moderate HIE, we compared cerebral oxygen metabolism parameters between MRIs performed during and after hypothermia.

RESULTS

During the initial hypothermia MRI at 23.5±5.2 h after birth, infants with severe HIE had lower oxygen extraction fraction (P=0.04) and cerebral metabolic rate of oxygen (P=0.03) and a trend toward lower cerebral blood flow (P=0.33) compared to infants with moderate HIE. In infants with moderate HIE, cerebral blood flow decreased and oxygen extraction fraction increased between MRIs during and after hypothermia (although not significantly); cerebral metabolic rate of oxygen (P=0.93) was not different.

CONCLUSION

Early MRIs were technically feasible while maintaining hypothermic goal temperatures in infants with HIE. Cerebral oxygen metabolism early during hypothermia is more disturbed in severe HIE. In infants with moderate HIE, cerebral blood flow decreased and oxygen extraction fraction increased between early and post-hypothermia scans. A comparison of cerebral oxygen metabolism parameters between early and post-hypothermia MRIs might improve our understanding of the evolution of HIE and the benefits of hypothermia. This approach could guide the use of adjunctive neuroprotective strategies in affected infants.

Fetal and neonatal neuroimaging

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

Early Glycemic Profile Is Associated with Brain Injury Patterns on Magnetic Resonance Imaging in Hypoxic Ischemic Encephalopathy

OBJECTIVE

To investigate whether the early glycemic profile in infants with hypoxic ischemic encephalopathy is associated with distinct patterns of brain injury on magnetic resonance imaging (MRI).

STUDY DESIGN

We performed a secondary analysis of 178 prospectively enrolled infants who received therapeutic hypothermia for hypoxic ischemic encephalopathy. Glycemic profiles were identified by glucose concentrations within 24 hours after birth: normoglycemia (all glucose concentrations of >47 to ≤150 mg/dL; n = 62); hypoglycemia (≥1 concentration ≤47 mg/dL; n = 17); hyperglycemia (≥1 concentration >150 mg/dL; n = 76); and labile glucose (both hypoglycemia and hyperglycemia; n = 23). Patterns of brain injury were identified for 151 infants based on Barkovich scores from the postrewarming brain MRIs at a median age of 9 days.

RESULTS

A normal brain MRI was reported in 37 of 62 infants (60%) with normal blood glucose values compared with 37 of 116 infants (32%) with an abnormal glucose profile (adjusted for Sarnat stage of encephalopathy and Apgar score at 5 minutes; P = .02). The distribution of MRI patterns of brain injury differed among the glycemic groups (P = .03). The odds of predominant watershed or focal-multifocal injury was higher in infants with hypoglycemia (aOR, 6; 95% CI, 1.5-24.2) and labile glucose (6.6; 95% CI, 1.6-27) compared with infants with normoglycemia. Infants with labile glucose had higher odds (5.6; 95% CI, 1.1-29.3) of predominant basal ganglia or global injury compared with infants with normal blood glucose values.

CONCLUSIONS

The early glycemic profile in infants with hypoxic ischemic encephalopathy is associated with specific patterns of brain injury on MRI. Further investigation is needed to explore its prognostic significance and role as a phenotype biomarker.

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.

Imaging the term neonatal brain

Brain imaging is important for the diagnosis and management of sick term neonates. Although ultrasound and computed tomography may provide some information, magnetic resonance imaging is now the brain imaging modality of choice because it is the most sensitive technique for detecting and quantifying brain abnormalities and does not expose infants to radiation. This statement describes the principles, roles and limitations of these three imaging modalities and makes recommendations for appropriate use in term neonates. The primary focus is the brain of term infants with neonatal encephalopathy, many of whom are diagnosed with hypoxic-ischemic encephalopathy.

A validated clinical MRI injury scoring system in neonatal hypoxic-ischemic encephalopathy

BACKGROUND

Deep nuclear gray matter injury in neonatal hypoxic-ischemic encephalopathy (HIE) is associated with worse neurodevelopmental outcomes. We previously published a qualitative MRI injury scoring system utilizing serial T1-weighted, T2-weighted and diffusion-weighted imaging (DWI), weighted for deep nuclear gray matter injury.

OBJECTIVES

To establish the validity of the MRI scoring system with neurodevelopmental outcome at 18-24 months.

MATERIALS AND METHODS

MRI scans from neonates with moderate to severe HIE treated with therapeutic hypothermia were evaluated. Signal abnormality was scored on T1-weighted, T2-weighted and DWI sequences and assessed using an established system in five regions: (a) subcortical: caudate nucleus, globus pallidus and putamen, thalamus and the posterior limb of the internal capsule; (b) white matter; (c) cortex, (d) cerebellum and (e) brainstem. MRI injury was graded as none, mild, moderate or severe. Inter-rater reliability was tested on a subset of scans by two independent and blinded neuroradiologists. Surviving infants underwent the Bayley Scales of Infant and Toddler Development-III (Bayley-III) at 18-24 months. Data were analyzed using univariate and multivariate linear and logistic regression.

RESULTS

Fifty-seven eligible neonates underwent at least one MRI scan in the first 2 weeks of life. Mean postnatal age at scan 1 was 4±2 days in 50/57 (88%) neonates and 48/54 (89%) surviving infants underwent scan 2 at 10±2 days. In 54/57 (95%) survivors, higher MRI injury grades were significantly associated with worse outcomes in the cognitive, motor and language domains of the Bayley-III.

CONCLUSION

A qualitative MRI injury scoring system weighted for deep nuclear gray matter injury is a significant predictor of neurodevelopmental outcome at 18-24 months in neonates with HIE.

Early Imaging and Adverse Neurodevelopmental Outcome in Asphyxiated Newborns Treated With Hypothermia

BACKGROUND

Brain injury can be identified as early as day two of life in asphyxiated newborns treated with hypothermia, when using diffusion magnetic resonance imaging (MRI). However, it remains unclear whether these diffusion changes can predict future neurodevelopment. This study aimed to determine whether abnormal early diffusion changes in newborns treated with hypothermia are associated with adverse neurodevelopmental outcome at age two years.

METHODS

Asphyxiated newborns treated with hypothermia were enrolled prospectively. They underwent magnetic resonance imaging (MRI) at specific time points over the first month of life, including diffusion-weighted imaging and diffusion-tensor imaging. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured in different regions of interest. Adverse neurodevelopmental outcome was defined as cerebral palsy, global developmental delay, and/or seizure disorder around age two years. ADC and FA values were compared between the newborns developing or not developing adverse outcome.

RESULTS

Twenty-nine asphyxiated newborns treated with hypothermia were included. Among the newborns developing adverse outcome, ADC values were significantly decreased on days two to three of life and increased around day ten of life in the thalamus, posterior limb of the internal capsule, and the lentiform nucleus. FA values decreased in the same regions around day 30 of life. These newborns also had increased ADC around day ten of life and around day 30 of life, and decreased FA around day 30 of life in the anterior and posterior white matter.

CONCLUSIONS

Diffusion changes that were evident as early as day two of life, when the asphyxiated newborns were still treated with hypothermia, were associated with later abnormal neurodevelopmental outcome.

Using clinically acquired MRI to construct age-specific ADC atlases: Quantifying spatiotemporal ADC changes from birth to 6-year old

Diffusion imaging is critical for detecting acute brain injury. However, normal apparent diffusion coefficient (ADC) maps change rapidly in early childhood, making abnormality detection difficult. In this article, we explored clinical PACS and electronic healthcare records (EHR) to create age-specific ADC atlases for clinical radiology reference. Using the EHR and three rounds of multiexpert reviews, we found ADC maps from 201 children 0-6 years of age scanned between 2006 and 2013 who had brain MRIs with no reported abnormalities and normal clinical evaluations 2+ years later. These images were grouped in 10 age bins, densely sampling the first 1 year of life (5 bins, including neonates and 4 quarters) and representing the 1-6 year age range (an age bin per year). Unbiased group-wise registration was used to construct ADC atlases for 10 age bins. We used the atlases to quantify (a) cross-sectional normative ADC variations; (b) spatiotemporal heterogeneous ADC changes; and (c) spatiotemporal heterogeneous volumetric changes. The quantified age-specific whole-brain and region-wise ADC values were compared to those from age-matched individual subjects in our study and in multiple existing independent studies. The significance of this study is that we have shown that clinically acquired images can be used to construct normative age-specific atlases. These first of their kind age-specific normative ADC atlases quantitatively characterize changes of myelination-related water diffusion in the first 6 years of life. The quantified voxel-wise spatiotemporal ADC variations provide standard references to assist radiologists toward more objective interpretation of abnormalities in clinical images. Our atlases are available at https://www.nitrc.org/projects/mgh_adcatlases. Hum Brain Mapp 38:3052-3068, 2017. © 2017 Wiley Periodicals, Inc.

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.

Perinatal neuroprotection update

Antepartum, intrapartum, and neonatal events can result in a spectrum of long-term neurological sequelae, including cerebral palsy, cognitive delay, schizophrenia, and autism spectrum disorders [1]. Advances in obstetrical and neonatal care have led to survival at earlier gestational ages and consequently increasing numbers of periviable infants who are at significant risk for long-term neurological deficits. Therefore, efforts to decrease and prevent cerebral insults attempt not only to decrease preterm delivery but also to improve neurological outcomes in infants delivered preterm. We recently published a comprehensive review addressing the impacts of magnesium sulfate, therapeutic hypothermia, delayed cord clamping, infections, and prevention of preterm delivery on the modification of neurological risk [2]. In this review, we will briefly provide updates to the aforementioned topics as well as an expansion on avoidance of toxin and infections, specifically the Zika virus.

Brain imaging in cooled encephalopathic neonates does not differ between four and 11 days after birth

AIM

The optimal timing of magnetic resonance imaging (MRI) in encephalopathic infants treated with hypothermia is unknown, and this study examined whether early scans differed from later scans.

METHODS

We assessed paired MRI scans carried out on 41 cooled encephalopathic infants at a median of four and 11 days using two scoring systems: the Rutherford injury scores for the basal ganglia and thalami (BGT), white matter and the posterior limb of the internal capsule, and the Bonifacio injury scores for the BGT and watershed area.

RESULTS

Both systems produced consistent injury severity scores in 37 of 41 infants on both days, with Rutherford scores predicting poor outcome in six early scans and seven later scans (K = 0.91) and Bonifacio doing the same in seven and nine scans (K = 0.85). A white matter/watershed score of two or a BGT score of one indicated severe changes by day 11 in three infants, but lower scores did not.

CONCLUSION

Magnetic resonance imaging scans indicated that the Rutherford and Bonifacio systems produced similar scores in 37 of 41 cooled encephalopathic infants at a median of four and 11 days. Infants with an early white matter/watershed scores of two or a BGT score of one may worsen and should be rescanned.

Injury to the Cerebellum in Term Asphyxiated Newborns Treated with Hypothermia

BACKGROUND AND PURPOSE

Until now, most studies of brain injury related to term neonatal encephalopathy have focused on the cerebrum and ignored the cerebellum. We sought to evaluate whether cerebellar injury occurs in term asphyxiated neonates.

MATERIALS AND METHODS

Asphyxiated neonates treated with hypothermia were enrolled prospectively. Severity of brain injury in the cerebrum was scored on each MR imaging obtained during the first month of life; cerebellar injury was recorded when mentioned in the imaging or autopsy report. In addition, for some of the neonates, the ADC and fractional anisotropy were measured in 4 regions of interest in the cerebellum.

RESULTS

One hundred seventy-two asphyxiated neonates met the criteria for hypothermia. Cerebellar injury was visible only on conventional imaging of 4% of the neonates for whom brain imaging was available, but it was reported in the autopsy report of 72% of the neonates who died. In addition, 41 of the asphyxiated neonates had a total of 84 ADC and fractional anisotropy maps. Neonates with brain injury described only in the cerebrum demonstrated ADC and fractional anisotropy changes similar to those of the neonates with brain injury in the cerebrum and cerebellum--increased ADC around day 10 of life and decreased fractional anisotropy on day 2-3 of life, around day 10 of life, and around 1 month of age.

CONCLUSIONS

The cerebellum may be injured in term neonates after birth asphyxia. These cerebellar injuries are only rarely visible on conventional imaging, but advanced neuroimaging techniques may help to identify them.

Evolution of Apparent Diffusion Coefficient and Fractional Anisotropy in the Cerebrum of Asphyxiated Newborns Treated with Hypothermia over the First Month of Life

The objective of this study was to assess the evolution of diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) over the first month of life in asphyxiated newborns treated with hypothermia and to compare it with that of healthy newborns. Asphyxiated newborns treated with hypothermia were enrolled prospectively; and the presence and extent of brain injury were scored on each MRI. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured in the basal ganglia, in the white matter and in the cortical grey matter. Sixty-one asphyxiated newborns treated with hypothermia had a total of 126 ADC and FA maps. Asphyxiated newborns developing brain injury eventually had significantly decreased ADC values on days 2-3 of life and decreased FA values around day 10 and 1 month of life compared with those not developing brain injury. Despite hypothermia treatment, asphyxiated newborns may develop brain injury that still can be detected with advanced neuroimaging techniques such as DWI and DTI as early as days 2-3 of life. A study of ADC and FA values over time may aid in the understanding of how brain injury develops in these newborns despite hypothermia treatment.

MRI obtained during versus after hypothermia in asphyxiated newborns

OBJECTIVE

To assess whether the brain MRI results obtained during hypothermia identify the later brain injury observed in asphyxiated newborns after therapy is completed.

PATIENTS AND METHODS

Asphyxiated newborns treated with hypothermia were prospectively enrolled in this study if they had at least one MRI performed during hypothermia treatment and then another MRI performed around day 10 of life.

RESULTS

A total of 129 MRI scans were obtained from 43 asphyxiated newborns treated with hypothermia. Sixty per cent developed brain injury; all the brain injuries observed on the late scans were already present on day 2-3 of life during hypothermia, and the extent of injury was similar between the early and late scans. The brain MRI on day 2-3 of life had a sensitivity of 100% (95% CI 84% to 100%) and a specificity of 100% (95% CI 77% to 100%) to identify the presence and extent of later brain injury.

CONCLUSIONS

The brain MRIs performed during hypothermia already permit an accurate definition of the presence and extent of brain injury that later develop in asphyxiated newborns despite treatment. These results may have research and clinical implications for the care of these newborns.

Magnetic resonance imaging (MRI) and prognostication in neonatal hypoxic-ischemic injury: a vignette-based study of Canadian specialty physicians

Magnetic resonance imaging (MRI) could improve prognostication in neonatal brain injury; however, factors beyond technical or scientific refinement may impact its use and interpretation. We surveyed Canadian neonatologists and pediatric neurologists using general and vignette-based questions about the use of MRI for prognostication in neonates with hypoxic-ischemic injury. There was inter- and intra-vignette variability in prognosis and in ratings about the usefulness of MRI. Severity of predicted outcome correlated with certainty about the outcome. A majority of physicians endorsed using MRI results in discussing prognosis with families, and most suggested that MRI results contribute to end-of-life decisions. Participating neonatologists, when compared to participating pediatric neurologists, had significantly less confidence in the interpretation of MRI by colleagues in neurology and radiology. Further investigation is needed to understand the complexity of MRI and of its application. Potential gaps relative to our understanding of the ethical importance of these findings should be addressed.

Perinatal risk factors for severe injury in neonates treated with whole-body hypothermia for encephalopathy

OBJECTIVE

Our objective was to identify perinatal risk factors that are available within 1 hour of birth that are associated with severe brain injury after hypothermia treatment for suspected hypoxic-ischemic encephalopathy.

STUDY DESIGN

One hundred nine neonates at ≥35 weeks' gestation who were admitted from January 2007 to September 2012 with suspected hypoxic-ischemic encephalopathy were treated with whole-body hypothermia; 98 of them (90%) underwent brain magnetic resonance imaging (MRI) at 7-10 days of life. Eight neonates died before brain imaging. Neonates who had severe brain injury, which was defined as death or abnormal MRI results (cases), were compared with surviving neonates with normal MRI (control subjects). Logistic regression models were used to identify risk factors that were predictive of severe injury.

RESULTS

Cases and control subjects did not differ with regard to gestational age, birthweight, mode of delivery, or diagnosis of nonreassuring fetal heart rate before delivery. Cases were significantly (P < .05) more likely to have had an abruption, a cord and neonatal arterial gas level that showed metabolic acidosis, lower platelet counts, lower glucose level, longer time to spontaneous respirations, intubation, chest compressions in the delivery room, and seizures. In multivariable logistic regression, lower initial neonatal arterial pH (P = .004), spontaneous respiration at >30 minutes of life (P = .002), and absence of exposure to oxytocin (P = .033) were associated independently with severe injury with 74.3% sensitivity and 74.4% specificity.

CONCLUSION

Worsening metabolic acidosis at birth, longer time to spontaneous respirations, and lack of exposure to oxytocin correlated with severe brain injury in neonates who were treated with whole-body hypothermia. These risk factors may help quickly identify neonatal candidates for time-sensitive investigational therapies for brain neuroprotection.

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.