MRI as a biomarker for mild neonatal encephalopathy

Ongoing loss of viable neurons for weeks after mild hypoxia-ischaemia

Mild hypoxic-ischaemic encephalopathy is common in neonates, and there are no evidence-based therapies. By school age, 30-40% of those patients experience adverse neurodevelopmental outcomes. The nature and progression of mild injury is poorly understood. We studied the evolution of mild perinatal brain injury using longitudinal two-photon imaging of transgenic fluorescent calcium-sensitive and insensitive proteins to provide a novel readout of neuronal viability and activity at cellular resolution in vitro and in vivo. In vitro, perinatal organotypic hippocampal cultures underwent 15-20 min of oxygen-glucose deprivation. In vivo, mild hypoxia-ischaemia was completed at post-natal day 10 with carotid ligation and 15 min of hypoxia (FiO2, 0.08). Consistent with a mild injury, minimal immediate neuronal death was seen in vitro or in vivo, and there was no volumetric evidence of injury by ex vivo MRI 2.5 weeks after injury (n = 3 pups/group). However, in both the hippocampus and neocortex, these mild injuries resulted in delayed and progressive neuronal loss by the second week after injury compared to controls; measured by fluorophore quenching (n = 6 slices/group in vitro, P < 0.001; n = 8 pups/group in vivo, P < 0.01). Mild hypoxia-ischaemia transiently suppressed cortical network calcium activity in vivo for over 2 h after injury (versus sham, n = 13 pups/group; P < 0.01). No post-injury seizures were seen. By 24 h, network activity fully recovered, and there was no disruption in the development of normal cortical activity for 11 days (n = 8 pups/group). The participation in network activity of individual neurons destined to die in vivo was indistinguishable from those that survived up to 4 days post-injury (n = 8 pups/group). Despite a lack of significant immediate neuronal death and only transient disruptions of network activity, mild perinatal brain injury resulted in a delayed and progressive increase of neuronal death in the hippocampus and neocortex. Neurons that died late were functioning normally for days after injury, suggesting a new pathophysiology of neuronal death after mild injury. Critically, the neurons destined to die late demonstrated multiple biomarkers of viability long after mild injury, suggesting their later death may be modified with neuroprotective interventions.

Ongoing loss of viable neurons for weeks after mild perinatal hypoxia-ischemia

Mild hypoxic-ischemic encephalopathy is common in neonates with no evidence-based therapies, and 30-40% of patients experience adverse outcomes. The nature and progression of mild injury is poorly understood. Thus, we studied the evolution of mild perinatal brain injury using longitudinal two-photon imaging of transgenic fluorescent proteins as a novel readout of neuronal viability and activity at cellular resolution. In vitro, perinatal murine organotypic hippocampal cultures underwent 15-20 minutes of oxygen-glucose deprivation. In vivo, mild hypoxia-ischemia was completed in post-natal day 10 mouse pups of both sexes with carotid ligation and 15 minutes of hypoxia. Consistent with a mild injury, minimal immediate neuronal death was seen and there was no volumetric evidence of injury by ex vivo MRI 2.5 weeks after injury. In both the hippocampus and neocortex, these mild injuries resulted in a significantly delayed and progressive neuronal loss in the second week after injury, measured by fluorophore quenching. Mild hypoxia-ischemia transiently suppressed cortical network activity followed by normal maturation. No post-injury seizures were seen. The participation in network activity of individual neurons destined to die was indistinguishable from those that survived for 4 days post-injury. In conclusion, our results showed that mild perinatal brain injury resulted in a prolonged increase of neuronal death. Neurons that died late were functioning normally for days after injury, suggesting a new pathophysiology of neuronal death. Critically, the neurons destined to die late demonstrated multiple biomarkers of viability long after mild injury, suggesting their later death may be modified with neuroprotective interventions.

SIGNIFICANCE STATEMENT

Neonatal encephalopathy due to peripartum hypoxia-ischemia (HI) is a major cause of neonatal mortality and morbidity worldwide. Of these infants, most are categorized as having mild HI. Infants with mild HI have significant long-term disabilities. There are currently no evidence-based therapies, largely because the progression and pathophysiology of mild injury is poorly understood. We have identified, for the first time, that mild perinatal HI results in a delayed and prolonged increase in neuronal death. The cortical and hippocampal neurons that die over a week after injury participate normally in neural network activity and exhibit robust viability for many days after injury, indicating a novel pathophysiology of neuronal death. Clinically, these data suggest an extended therapeutic window for mild perinatal HI.

Regional variability in therapeutic hypothermia eligibility criteria for neonatal hypoxic-ischemic encephalopathy

Early induced therapeutic hypothermia represents the cornerstone treatment in neonates with probable hypoxic-ischemic encephalopathy. The selection of patients for treatment usually involves meeting criteria indicating evidence of perinatal hypoxia-ischemia and the presence of moderate or severe encephalopathy. In this review, we highlight the variability that exists between some of the different regional and national eligibility guidelines. Determining the potential presence of perinatal hypoxia-ischemia may require either one, two or three signs amongst history of acute perinatal event, prolonged resuscitation at delivery, abnormal blood gases and low Apgar score, with a range of cutoff values. Clinical neurological exams often define the severity of encephalopathy differently, with varying number of domains required for determining eligibility and blurred interpretation of findings assigned to different severity grades in different systems. The role of early electrophysiological assessment is weighted differently. A clinical implication is that infants may receive different care depending on the location in which they are born. This could also impact epidemiological data, as inference of rates of moderate-severe encephalopathy based on therapeutic hypothermia rates are misleading and influenced by different eligibility methods used. We would advocate that a universally endorsed single severity staging of encephalopathy is vital for standardizing management and neonatal outcome. IMPACT: Variability exists between regional and national therapeutic hypothermia eligibility guidelines for neonates with probable hypoxic-ischemic encephalopathy. Differences are common in both criteria indicating perinatal hypoxia-ischemia and criteria defining moderate or severe encephalopathy. The role of early electrophysiological assessment is also weighted unequally. This reflects in different individual care and impacts research data. A universally endorsed single severity staging of encephalopathy would be crucial for standardizing management.

Neonatal well-being and timing of brain injury in persons with cerebral palsy born at term or late preterm

AIM

To describe the distribution of neuroimaging patterns in a term/late preterm population-based cohort with cerebral palsy (CP), ascertain associations between neuroimaging patterns and neonatal well-being, estimate the proportion with antenatal or perinatal timing of neuropathology, and apply this information to the understanding of common mechanisms of brain injury and causal pathways.

METHOD

The cohort for this observational study comprised 1348 persons born between 1999 and 2017 in Victoria, Australia. Using algorithms designed for the study, neonatal well-being and timing of brain injury were tabulated for the whole cohort and across neuroimaging patterns and birth epochs.

RESULTS

Clinical and demographic profiles, neonatal well-being, and timing of brain injury differed across neuroimaging patterns. An estimated 57% of the cohort had a complicated neonatal period. Timing of brain injury was antenatal in 57% and perinatal in 41%. A decrease in the relative proportions of perinatal timing of brain injury was observed over a period when the rates of CP in live births at term decreased.

INTERPRETATION

This study begins to bridge the knowledge gap about causation in CP, moving towards better description of the main mechanisms of brain injury and their contribution within CP cohorts, and facilitating the ability to monitor changes over time and the success of preventive measures.

WHAT THIS PAPER ADDS

In a population-based, term/late preterm cohort with cerebral palsy, 57% had a complicated neonatal period. In the same cohort, 57% had presumed antenatal timing of brain injury. The relative proportion with perinatal injury decreased over time.

Microstructural Alterations in Projection and Association Fibers in Neonatal Hypoxia-Ischemia

BACKGROUND

Diffusion MRI (dMRI) is known to be sensitive to hypoxic-ischemic encephalopathy (HIE). However, existing dMRI studies used simple diffusion tensor metrics and focused only on a few selected cerebral regions, which cannot provide a comprehensive picture of microstructural injury.

PURPOSE

To systematically characterize the microstructural alterations in mild, moderate, and severe HIE neonates compared to healthy neonates with advanced dMRI using region of interest (ROI), tract, and fixel-based analyses.

STUDY TYPE

Prospective.

POPULATION

A total of 42 neonates (24 males and 18 females).

FIELD STRENGTH/SEQUENCE

3-T, diffusion-weighted echo-planar imaging.

ASSESSMENT

Fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), fiber density (FD), fiber cross-section (FC), and fiber density and cross-section (FDC) were calculated in 40 ROIs and 6 tracts. Fixel-based analysis was performed to assess group differences in individual fiber components within a voxel (fixel).

STATISTICAL TESTS

One-way analysis of covariance (ANCOVA) to compare dMRI metrics among severe/moderate/mild HIE and control groups and general linear model for fixel-wise group differences (age, sex, and body weight as covariates). Adjusted P value < 0.05 was considered statistically significant.

RESULTS

For severe HIE, ROI-based analysis revealed widespread regions, including the deep nuclei and white matter with reduced FA, while in moderate injury, only FC was decreased around the posterior watershed zones. Tract-based analysis demonstrated significantly reduced FA, FD, and FC in the right inferior fronto-occipital fasciculus (IFOF), right inferior longitudinal fasciculus (ILF), and splenium of corpus callosum (SCC) in moderate HIE, and in right IFOF and left anterior thalamic radiation (ATR) in mild HIE. Correspondingly, we found altered fixels in the right middle-posterior IFOF and ILF, and in the central-to-right part of SCC in moderate HIE.

DATA CONCLUSION

For severe HIE, extensive microstructural injury was identified. For moderate-mild HIE, association fiber injury in posterior watershed area with a rightward lateralization was found.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 3.

The role of early functional neuroimaging in predicting neurodevelopmental outcomes in neonatal encephalopathy

Reliably assessing the early neurodevelopmental outcomes in infants with neonatal encephalopathy (NE) is of utmost importance to advise parents and implement early and personalized interventions. We aimed to evaluate the accuracy of neuroimaging modalities, including functional magnetic resonance imaging (fMRI) in predicting neurodevelopmental outcomes in NE. Eighteen newborns with NE due to presumed perinatal asphyxia (PA) were included in the study, 16 of whom underwent therapeutic hypothermia. Structural magnetic resonance imaging (MRI), and fMRI during passive visual, auditory, and sensorimotor stimulation were acquired between the 10th and 14th day of age. Clinical follow-up protocol included visual and auditory evoked potentials and a detailed neurodevelopmental evaluation at 12 and 18 months of age. Infants were divided according to sensory and neurodevelopmental outcome: severe, moderate disability, or normal. Structural MRI findings were the best predictor of severe disability with an AUC close to 1.0. There were no good predictors to discriminate between moderate disability versus normal outcome. Nevertheless, structural MRI measures showed a significant correlation with the scores of neurodevelopmental assessments. During sensorimotor stimulation, the fMRI signal in the right hemisphere had an AUC of 0.9 to predict absence of cerebral palsy (CP). fMRI measures during auditory and visual stimulation did not predict sensorineural hearing loss or cerebral visual impairment.

CONCLUSION

In addition to structural MRI, fMRI with sensorimotor stimulation may open the gate to improve the knowledge of neurodevelopmental/motor prognosis if proven in a larger cohort of newborns with NE.

WHAT IS KNOWN

• Establishing an early, accurate neurodevelopmental prognosis in neonatal encephalopathy remains challenging. • Although structural MRI has a central role in neonatal encephalopathy, advanced MRI modalities are gradually being explored to optimize neurodevelopmental outcome knowledge.

WHAT IS NEW

• Newborns who later developed cerebral palsy had a trend towards lower fMRI measures in the right sensorimotor area during sensorimotor stimulation. • These preliminary fMRI results may improve future early delineation of motor prognosis in neonatal encephalopathy.

Brain Injury in Infants Evaluated for, But Not Treated with, Therapeutic Hypothermia

Defining neonatal encephalopathy clinically to qualify for therapeutic hypothermia is challenging. This study examines magnetic resonance imaging outcomes of 39 infants who were evaluated and not cooled using criteria inclusive of mild encephalopathy. Infants evaluated for therapeutic hypothermia are at risk for brain injury and may benefit from neuroimaging and follow-up.

Brain injury following mild hypoxic-ischemic encephalopathy in neonates-Ten-year experience in a tertiary perinatal center

OBJECTIVE

We aimed to evaluate abnormal magnetic resonance imaging (MRI) findings in neonates with mild hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

This was a single-center, retrospective study of mild HIE conducted from 2011 to 2020. Almost all neonates with mild HIE received management targeted to a temperature of 36 ± 0.5°C for 72 h and underwent MRI (135 of 145). We evaluated medical records and assessed amplitude-integrated electroencephalography (aEEG).

RESULT

All participants survived until discharge. Abnormal MRI findings were present in 23/135 (17%) neonates. The normal versus abnormal MRI-finding groups had similar characteristics, except discontinuous aEEG patterns (p = 0.002) and inotropic drugs (p = 0.035). Regression analyses showed discontinuous aEEG patterns (odds ratio = 19.3, 95% confidence interval=1.88-197, p = 0.013) being associated with higher odds of abnormal MRI findings.

CONCLUSION

Our study suggests that a discontinuous aEEG pattern is associated with abnormal MRI findings and can be used to discuss the definition of mild HIE.

Differences in standardized neonatal encephalopathy exam criteria may impact therapeutic hypothermia eligibility

BACKGROUND

Therapeutic hypothermia (TH) is routinely provided to those with moderate or severe neonatal encephalopathy (NE). Subtle differences exist in the standardized exams used to define NE severity. We aimed to assess if an infant's TH eligibility status differed if they were evaluated using either the NICHD/Neonatal Research Network's (NICHD-NRN) or TOBY/British Association of Perinatal Medicine's (TOBY-BAPM) neurological exam.

METHODS

Encephalopathic infants ≥36 weeks with evidence of perinatal asphyxia and complete documentation of the neurological exam &lt;6 h of age were included. TH eligibility using the NICHD-NRN and TOBY-BAPM criteria was determined based upon the documented exams.

RESULTS

Ninety-one encephalopathic infants were included. Despite good agreement between the two exams (κ = 0.715, p &lt; 0.001), TH eligibility differed between them (p &lt; 0.001). A total of 47 infants were deemed eligible by at least one method-46 using NICHD-NRN and 35 using TOBY-BAPM. Of the 12 infants eligible per NICHD-NRN, but ineligible per TOBY-BAPM, two developed electrographic seizures and seven demonstrated hypoxic-ischemic cerebral injury.

CONCLUSIONS

Both the NICHD-NRN and TOBY-BAPM exams are evidence-based. Despite this, there is a significant difference in the number of infants eligible for TH depending on which exam is used. The NICHD-NRN exam identifies a greater proportion as eligible.

IMPACT

There are subtle differences in the NICHD-NRN and TOBY-BAPM's encephalopathy exams used to determine eligibility for TH. This results in a significant difference in the proportion of infants determined to be eligible for TH depending on which encephalopathy exam is used. The NICHD-NRN encephalopathy exam identifies more infants as being eligible for TH than the TOBY-BAPM encephalopathy exam. This may result in different rates of cooling depending on which evidence-based neurological exam for evaluation of encephalopathy a center uses.

Concentration of Serum Biomarkers of Brain Injury in Neonates With a Low Cord pH With or Without Mild Hypoxic-Ischemic Encephalopathy

Objective

To determine the concentrations of four neuroprotein biomarkers and 68 miRNAs in neonates with low cord pH and/or mild hypoxic-ischemic encephalopathy (HIE).

Study Design

A prospective cohort study enrolled neonates with low cord pH (n = 18), moderate-severe HIE (n = 40), and healthy controls (n = 38). Groups provided serum samples at 0–6 h of life. The concentrations of biomarkers and miRNAs were compared between cohorts.

Result

The low cord pH and moderate-severe HIE groups had increased concentrations of GFAP, NFL and Tau compared to controls (P < 0.05, P < 0.001, respectively). NFL concentrations in mild HIE was higher than controls (P < 0.05) but less than moderate-severe HIE (P < 0.001). Of 68 miRNAs, 36 in low cord pH group and 40 in moderate-severe HIE were upregulated compared to controls (P < 0.05). Five miRNAs in low cord pH group (P < 0.05) and 3 in moderate-severe HIE were downregulated compared to controls (P < 0.05).

Conclusion

A biomarker panel in neonates with low cord pH may help clinicians make real-time decisions.

New Horizons in Mild Hypoxic-ischemic Encephalopathy: A Standardized Algorithm to Move past Conundrum of Care

Hypoxic-ischemic encephalopathy (HIE) presents clinically with a neonatal encephalopathy (NE) whereby the mild spectrum is difficult to classify immediately after birth. For decades trials have focused exclusively on infants with moderate-severe HIE s, as these infants were easier to identify after birth and had the highest risk of adverse outcomes. Twenty years after those trials, the PRIME study finally solved the first part of the conundrum by providing a definition of mild HIE in the first 6 hours. There is strong biological plausibility and preclinical evidence supporting the efficacy of therapeutic hypothermia (TH) but there is a lack of comparative clinical data to establish the risk-benefit in mild HIE. The fundamental question of how best to manage mild HIE remains unanswered. This review will summarize (1) the evidence that neonates with mild HIE are at significant risk for adverse outcomes, (2) the gaps/controversies in management, and (3) an algorithm of care is proposed to ensure standardized management of mild HIE and the direction of future trials.

Challenges in developing therapeutic strategies for mild neonatal encephalopathy

There is increasing evidence that infants with mild neonatal encephalopathy (NE) have significant risks of mortality, brain injury and adverse neurodevelopmental outcomes. In the era of therapeutic hypothermia, infants need to be diagnosed within 6 hours of birth, corresponding with the window of opportunity for treatment of moderate to severe NE, compared to the retrospective grading over 2 to 3 days, typically with imaging and formal electroencephalographic assessment in the pre-hypothermia era. This shift in diagnosis may have increased the apparent prevalence of brain damage and poor neurological outcomes seen in infants with mild NE in the era of hypothermia. Abnormal short term outcomes observed in infants with mild NE include seizures, abnormal neurologic examination at discharge, abnormal brain magnetic resonance imaging and difficulty feeding. At 2 to 3 years of age, mild NE has been associated with an increased risk of autism, language and cognitive deficits. There are no approved treatment strategies for these infants as they were not included in the initial randomized controlled trials for therapeutic hypothermia. However, there is already therapeutic creep, with many centers treating infants with mild NE despite the limited evidence for its safety and efficacy. The optimal duration of treatment and therapeutic window of opportunity for effective treatment need to be specifically established for mild NE as the evolution of injury is likely to be slower, based on preclinical data. Randomized controlled trials of therapeutic hypothermia for infants with mild NE are urgently required to establish the safety and efficacy of treatment. This review will examine the evidence for adverse outcomes after mild NE and dissect some of the challenges in developing therapeutic strategies for mild NE, before analyzing the evidence for therapeutic hypothermia and other strategies for treatment of these infants.

Process variations between Swiss units treating neonates with hypoxic-ischemic encephalopathy and their effect on short-term outcome

OBJECTIVE

To compare therapeutic hypothermia (TH) treatment of term and near-term neonates with hypoxic-ischemic encephalopathy (HIE) between neonatal units.

STUDY DESIGN

Population-based, retrospective analysis of TH initiation and maintenance, and of diagnostic imaging. The comparison between units was based on crude data analysis, indirect standardization, and adjusted logistic regression.

RESULTS

TH was provided to 570 neonates with HIE between 2011 and 2018 in 10 Swiss units. We excluded 121 off-protocol cooled neonates to avoid selection bias. Of the remaining 449 neonates, the outcome was favorable to international benchmarks, but there were large unit-to-unit variations in baseline perinatal data and TH management. A total of 5% neonates did not reach target temperature within 7 h (3-10% between units), and 29% experienced over- or undercooling (0-38%).

CONCLUSION

Although the neonates had favorable short-term outcomes, areas for improvement remain for Swiss units in both process and outcome measures.

MRI Score Ability to Detect Abnormalities in Mild Hypoxic-Ischemic Encephalopathy

BACKGROUND

Magnetic resonance imaging (MRI) scores have been well validated in moderate/severe hypoxic-ischemic encephalopathy (HIE). Infants with mild HIE can have different patterns of injury, yet different scores have not been compared in this group of infants. Our objective was to compare the ability of three = MRI scores to detect abnormalities in infants with mild HIE, and infants with moderate/severe HIE were included for comparison.

METHODS

This is a single-center prospective cohort study of infants ≥36 weeks' gestation with HIE born at a level III neonatal intensive care unit from 2017 to 2019. All infants with HIE underwent an MRI, but only infants with moderate/severe HIE underwent therapeutic hypothermia. At least two experienced MRI readers who were unaware of all clinical variables independently assigned three scores (Barkovich, NICHD NRN, and Weeke).

RESULTS

A total of 42 newborns with varying HIE severity underwent MRI on day five of life. In the overall cohort, abnormalities were reported in three (7%) infants using the Barkovich, in 10 (24%) using the NICHD NRN, and in 24 (57%) using the Weeke score. Agreement was excellent for each score: Barkovich score (k = 1.0), NICHD NRN (k = 0.92), and Weeke score (k = 0.9).

CONCLUSIONS

Subtle injury due to mild HIE was detected with the highest frequency using the Weeke score, while inter-rater reliability was excellent for all three scores. These findings suggest that infants with mild HIE and subtle MRI abnormalities may benefit from detailed scoring systems, which is important for studies investigating the benefit of hypothermia in mild HIE.

Significance of the ability to differentiate emotional prosodies for the early diagnosis and prognostic prediction of mild hypoxic-ischemic encephalopathy in neonates

BACKGROUND

Perinatal brain injury affects around 300,000 neonates in China each year, early diagnosis and active intervention are also crucial for timely treatment and better prognoses. As hearing is the earliest as well as the most sensitive sense to develop in neonates, we propose that the ability to differentiate among different emotional prosodies may differ between neonates with and without brain injuries.

METHODS

We enrolled full-term neonates admitted to the neonatology department of Peking University First Hospital from January 2016 to December 2016, conducted functional near-infrared spectroscopy (fNIRS) monitoring within 24 hr of admission, and analyzed changes in oxyhemoglobin (ΔHbO₂ ) and deoxyhemoglobin (ΔHb) to study the ability of neonates to differentiate among emotional prosodies. The neonates were followed up to 36 months for neurological outcome evaluation.

RESULTS AND CONCLUSIONS

We found that neonates showed the early ability to differentiate among emotional prosodies, responding most sensitively to positive emotions, and this ability may have been impaired following brain injury.

Reduced white-matter integrity and lower speed of information processing in adolescents with mild and moderate neonatal hypoxic-ischaemic encephalopathy

INTRODUCTION

Studies have shown that adolescents with moderate hypoxic-ischaemic encephalopathy (HIE) may have specific cognitive deficits, especially reduced speed of information processing. The aim of our study was to confirm these earlier findings find out whether the degree of impairment in speed of information processing correlates with the degree of white-matter impairment as measured by diffusion tensor imaging (DTI).

METHODS

Thirty-three participants (mean age 18y 5mo, SD 12mo; 19 male) with mild or moderate HIE and 32 neurotypical adolescents (mean age 17y 10mo, SD 12mo, 18 male) completed a comprehensive neuropsychological battery measuring short-term memory, inhibition, speed of information processing, long-term visual and verbal memory. Fourteen participants also underwent structural MRI and DTI scans.

RESULTS

After controlling for age, gender and maternal education we found a significant effect of HIE on speed of information processing (F_{(2, 64)} = 3.51, p < .037, η² = 0.115), but not on other neuropsychological domains. Using tract-based spatial statistics we were also able to confirm a correlation between the degree of impairment in this cognitive domain and fractional anisotropy in several white-matter tracts.

CONCLUSIONS

The long-term cognitive outcome of moderate HIE includes reduced speed of information processing and is in part mediated by reduced integrity of major white-matter tracts.

Therapeutic hypothermia for mild neonatal encephalopathy: a systematic review and meta-analysis

OBJECTIVES

To examine if therapeutic hypothermia reduces the composite outcome of death, moderate or severe disability at 18 months or more after mild neonatal encephalopathy (NE).

DATA SOURCE

MEDLINE, Cochrane database, Scopus and ISI Web of Knowledge databases, using 'hypoxic ischaemic encephalopathy', 'newborn' and 'hypothermia', and 'clinical trials' as medical subject headings and terms. Manual search of the reference lists of all eligible articles and major review articles and additional data from the corresponding authors of selected articles.

STUDY SELECTION

Randomised and quasirandomised controlled trials comparing therapeutic hypothermia with usual care.

DATA EXTRACTION

Safety and efficacy data extracted independently by two reviewers and analysed.

RESULTS

We included the data on 117 babies with mild NE inadvertently recruited to five cooling trials (two whole-body cooling and three selective head cooling) of moderate and severe NE, in the meta-analysis. Adverse outcomes occurred in 11/56 (19.6%) of the cooled babies and 12/61 (19.7%) of the usual care babies (risk ratio 1.11 (95% CIs 0.55 to 2.25)).

CONCLUSIONS

Current evidence is insufficient to recommend routine therapeutic hypothermia for babies with mild encephalopathy and significant benefits or harm cannot be excluded.

A Total Sarnat Score in Mild Hypoxic-ischemic Encephalopathy Can Detect Infants at Higher Risk of Disability

To define mild hypoxic-ischemic encephalopathy and distinguish infants at risk of disability in the first 6 hours, this study stratified risk of disability by using early neurologic examination findings of infants enrolled in the Prospective Research for Infants with Mild Encephalopathy cohort. A total Sarnat score of ≥5 when performed at <6 hours of age detected future disability. TRIAL REGISTRATION: Clinicaltrials.gov: NCT01747863.

Caveats of Cooling: Available Evidence and Ongoing Investigations of Therapeutic Hypothermia

Therapeutic hypothermia (TH) mitigates the long-term effects of neuronal excitotoxicity and cell death seen in hypoxic-ischemic encephalopathy (HIE). It remains the most evidence-based therapy for HIE, but it is not without clinical controversy. The literature abounds with questions, such as "When should we start cooling-as early as the delivery room?" "Given the efficacy of TH for moderate to severe HIE when started within 6 hours of birth, can we expand the therapy to infants with mild HIE?" "What should the target temperature be?" "What is the optimal duration of treatment?" "Is early discontinuation acceptable if the examination findings normalize?" These questions about TH, its incomplete neurologic rescue, and variations in the delivery of this therapy have prompted this review. This article summarizes changing procedural considerations for TH, the level of neuromonitoring available, the use of sedation, and considerations for neuroimaging during and after TH.

Therapeutic hypothermia initiated within 6 hours of birth is associated with reduced brain injury on MR biomarkers in mild hypoxic-ischaemic encephalopathy: a non-randomised cohort study

OBJECTIVE

To examine the effect of therapeutic hypothermia on MR biomarkers and neurodevelopmental outcomes in babies with mild hypoxic-ischaemic encephalopathy (HIE).

DESIGN

Non-randomised cohort study.

SETTING

Eight tertiary neonatal units in the UK and the USA.

PATIENTS

47 babies with mild HIE on NICHD neurological examination performed within 6 hours after birth.

INTERVENTIONS

Whole-body cooling for 72 hours (n=32) or usual care (n=15; of these 5 were cooled for <12 hours).

MAIN OUTCOME MEASURES

MRI and MR spectroscopy (MRS) within 2 weeks after birth, and a neurodevelopmental outcome assessment at 2 years.

RESULTS

The baseline characteristics in both groups were similar except for lower 10 min Apgar scores (p=0.02) in the cooled babies. Despite this, the mean (SD) thalamic NAA/Cr (1.4 (0.1) vs 1.6 (0.2); p<0.001) and NAA/Cho (0.67 (0.08) vs 0.89 (0.11); p<0.001) ratios from MRS were significantly higher in the cooled group. Cooled babies had lower white matter injury scores than non-cooled babies (p=0.02). Four (27%) non-cooled babies with mild HIE developed seizures after 6 hours of age, while none of the cooled babies developed seizures (p=0.008). Neurodevelopmental outcomes at 2 years were available in 40 (85%) of the babies. Adverse outcomes were seen in 2 (14.3%) non-cooled babies, and none of the cooled babies (p=0.09).

CONCLUSIONS

Therapeutic hypothermia may have a neuroprotective effect in babies with mild HIE, as demonstrated by improved MRS biomarkers and reduced white matter injury on MRI. This may warrant further evaluation in adequately powered randomised controlled trials.

Early identification of neonatal mild hypoxic-ischemic encephalopathy by amide proton transfer magnetic resonance imaging: A pilot study

PURPOSE

This study aimed to evaluate the amide proton transfer (APT) values in neonates with mild hypoxic-ischemic encephalopathy (HIE) using APT imaging.

METHOD

A total of 30 full-term neonates with mild HIE (16 males and 14 females; mean postnatal age 4.2 days, age range 2-7 days) and 12 normal neonates (six males and six females; mean postnatal age 3.3 days, age range 2-5 days) underwent conventional magnetic resonance imaging and APT imaging. APT measurements were performed in multiple regions of interest (ROIs) in the brain. APT values were statistically analyzed to assess for significant differences between the mild HIE and normal neonates in different regions of the brain, and correlation with neonatal gestational age.

RESULTS

In 30 neonates with mild HIE, 10% (3/30) of the HIE patients had normal conventional MRI. There were significant differences in APT values of the HIE group in bilateral caudate, bilateral thalamus, bilateral centrum semiovale and left globus pallidus/putamen (p < 0.05), and no statistical difference was observed in right globus pallidus/putamen (p = 0.051) and brainstem (p = 0.073) between the two groups. Furthermore, APT values in bilateral caudate, bilateral globus pallidus/putamen, bilateral thalamus, and brainstem regions (p < 0.05) exhibited positive linear correlations with gestational age in the control group, except for bilateral centrum semiovale (right: Pearson's r = 0.554, p = 0.062; left: Pearson's r = 0.561, p = 0.058). In the mild HIE groups, no significant correlation with gestational age was found in all regions.

CONCLUSIONS

APT imaging is a feasible and useful technique with diagnostic capability for neonatal HIE.

Update on the current management of newborns with neonatal encephalopathy

Hypoxic-ischemic encephalopathy is a subtype of neonatal encephalopathy and a major contributor to global neonatal morbidity and mortality. Despite advances in obstetric and neonatal care there are still challenges in accurate determination of etiology of neonatal encephalopathy. Thus, identification of intrapartum risk factors and comprehensive evaluation of the neonate is important to determine the etiology and severity of neonatal encephalopathy. In developed countries, therapeutic hypothermia as a standard of care therapy for neonates with hypoxic-ischemic encephalopathy has proven to decrease incidence of death and neurodevelopmental disabilities, including cerebral palsy in surviving children. Advances in neuroimaging, brain monitoring modalities, and biomarkers of brain injury have improved the ability to diagnose, monitor, and treat newborns with encephalopathy. However, challenges remain in early identification of neonates at risk for hypoxic-ischemic brain injury, and determination of the timing and extent of brain injury. Using imaging studies such as Neonatal MRI and MR spectroscopy have proven to be most useful in predicting outcomes in infants with encephalopathy within the first week of life, although comprehensive neurodevelopmental assessments still remains the gold standard for determining long term outcomes. Future studies are needed to identify other newborns with encephalopathy that might benefit from therapeutic hypothermia and to determine the efficacy of other adjunctive neuroprotective strategies. This review focuses on newer evidence and advances in diagnoses and management of infants with neonatal encephalopathy, including novel therapies, as well as prognostication of outcomes to childhood.

Should therapeutic hypothermia be offered to babies with mild neonatal encephalopathy in the first 6 h after birth?

Infants with moderate to severe neonatal encephalopathy (NE) benefit significantly from therapeutic hypothermia, with reduced risk of death or disability. However, the need for therapeutic hypothermia for infants with milder NE remains unclear. It has been suggested that these infants should not be offered therapeutic hypothermia as they may not be at risk for adverse neurodevelopmental outcome and that the balance of risk against potential benefit is unknown. Several key questions need to be answered including first, whether one can define NE in the first 6 h after birth so as to accurately distinguish infants with brain injury who may be at risk for adverse neurodevelopmental consequences. Second, will treatment of infants with mild NE with therapeutic hypothermia improve or even worsen neurological outcomes? Although alternate treatment protocols for mild NE may be feasible, the use of the current approach combined with rigorous avoidance of hyperthermia and initiation of hypothermia as early as possible after birth may promote optimal outcomes. Animal experimental data support the potential for greater benefit for mild HIE compared with moderate to severe HIE. This review will summarize current knowledge of mild NE and the challenges to a trial in this population.