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

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.

Apparent diffusion coefficient values can predict neuromotor outcome in term neonates with hypoxic-ischaemic encephalopathy

AIM

To determine the apparent diffusion coefficient (ADC) in brain structures during the first 2 weeks of life and its relation with neurological outcome for hypoxic-ischaemic encephalopathy (HIE) in term neonates.

METHODS

We retrospectively evaluated 56 term-born neonates. The ADC values were measured for 11 brain regions. The clinical outcomes at least 2 years of age were defined as normal outcome, mild disability and severe disability. The area under curves (AUCs) by ROC analysis were performed to predict the neurodevelopmental outcomes. The clinical outcomes were compared between favourable outcome and adverse outcome and also between normal outcome and unfavourable outcome.

RESULTS

Thirty-four patients were judged as normal outcome, 10 as mild disability and 12 as severe disability. When the clinical outcomes were compared between favourable outcome and adverse outcome, the AUC on the 1st week was highest value at the thalamus. When the clinical outcomes were compared between normal outcome and unfavourable outcome, the AUC on the 1st week was highest at the thalamus.

CONCLUSION

The ADC values in the thalamus in the 1st week can predict the neurological outcome. The ADC values in centrum semiovale on the 2nd week can be used to predict neurodevelopmental outcomes.

Development of the corpus callosum and cognition after neonatal encephalopathy

OBJECTIVE

Neonatal imaging studies report corpus callosum abnormalities after neonatal hypoxic-ischaemic encephalopathy (HIE), but corpus callosum development and relation to cognition in childhood are unknown. Using magnetic resonance imaging (MRI), we examined the relationship between corpus callosum size, microstructure and cognitive and motor outcomes at early school-age children cooled for HIE (cases) without cerebral palsy compared to healthy, matched controls. A secondary aim was to examine the impact of HIE-related neonatal brain injury on corpus callosum size, microstructure and growth.

METHODS

Participants aged 6-8 years underwent MRI, the Movement Assessment Battery for Children Second Edition and Wechsler Intelligence Scale for Children Fourth Edition. Cross-sectional area, volume, fractional anisotropy and radial diffusivity of the corpus callosum and five subdivisions were measured. Multivariable regression was used to assess associations between total motor score, full-scale IQ (FSIQ) and imaging metrics.

RESULTS

Adjusting for age, sex and intracranial volume, cases (N = 40) compared to controls (N = 39) demonstrated reduced whole corpus callosum area (β = -26.9, 95% confidence interval [CI] = -53.17, -0.58), volume (β = -138.5, 95% CI = -267.54, -9.56), fractional anisotropy and increased radial diffusivity (P < 0.05) within segments II-V. In cases, segment V area (β = 0.18, 95% CI = 0.004, 0.35), volume (β = 0.04, 95% CI = 0.001, 0.079), whole corpus callosum fractional anisotropy (β = 13.8 95% CI = 0.6, 27.1) and radial diffusivity (β = -11.3, 95% CI = -22.22, -0.42) were associated with FSIQ. Growth of the corpus callosum was restricted in cases with a FSIQ ≤85, and volume was reduced in cases with mild neonatal multifocal injury compared to white matter injury alone.

INTERPRETATION

Following neonatal HIE, morphological and microstructural changes in the corpus callosum are associated with reduced cognitive function at early school age.

Restricted diffusion of the callosal splenium is highly specific for seizures in neonates

BACKGROUND

To determine whether restricted diffusion of the callosal splenium is specific for seizure activity in neonates.

METHODS

We performed a retrospective chart review of 123 neonates who had a diagnosis of hypoxic ischemic encephalopathy (HIE) who underwent therapeutic cooling and had magnetic resonance imaging (MRI) within the first 10 days of life. The regions examined for injury include the callosal splenium, cortex, deep gray matter, and subcortical white matter. Neurodevelopmental outcomes were secondarily assessed using the Bayley Scales of Infant Development at 12 to 18 months of age and > 18 months of age. APGAR scores and pH, two important markers of hypoxia/ischemia and encephalopathy, were also analyzed in relation to these outcomes.

RESULTS

Approximately 41% of the neonates had at least one abnormal region on brain MRI, and 21% had abnormal signal in the splenium. Clinical and/or electrographic seizures were documented in 32%. Changes in the splenium had a sensitivity of 54%, specificity of 94%, and positive predictive value of 81% for seizure presence. The presence of seizures and splenium lesion was associated poor developmental outcomes at 12 to 18 months of age. APGAR scores at 10 minutes, but not lowest pH was associated with splenial changes.

CONCLUSIONS

Restricted diffusion of the callosal splenium is specific for recent seizures in neonates with HIE. Seizures and splenial lesion represent risk factors for poor neurodevelopmental outcomes. Child neurologists and neonatologists should consider splenial signal abnormality in their assessment of neonates at risk for seizures and counsel families about likely outcomes accordingly.

Diffusion restriction in the corticospinal tract and the corpus callosum of term neonates with hypoxic-ischemic encephalopathy

BACKGROUND

Diffusion-weighted imaging performed shortly after brain injury has been shown to facilitate visualization of acute corticospinal tract injury known as "pre-Wallerian degeneration."

OBJECTIVE

The aim of this study was to determine whether diffusion restriction in the corticospinal tract and corpus callosum occurs within the first 2 weeks after birth in neonates with neonatal hypoxic-ischemic encephalopathy.

MATERIALS AND METHODS

We enrolled a consecutive series of 66 infants diagnosed with hypoxic-ischemic encephalopathy who underwent MRI. We evaluated diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values to assess the presence of restricted diffusion in the corticospinal tract and corpus callosum. Next, we compared ADC values in the corticospinal tract and in the splenium and genu of the corpus callosum of infants with abnormal pattern on MRI with those of control infants, who showed a normal pattern on MRI. We attempted to follow all infants with hypoxic-ischemic encephalopathy until 18 months of age and assess them using a standardized neurologic examination.

RESULTS

After exclusions, we recruited 25 infants with abnormal MRI and 20 with normal MRI (controls). Among these 45 neonates, pre-Wallerian degeneration was visualized in the corticospinal tract in 10 neonates and in the corpus callosum in 12. The ADC values in the corticospinal tract in the first week were significantly lower than they were in the second week. Infants with pre-Wallerian degeneration in the corticospinal tract showed an unfavorable outcome.

CONCLUSION

Pre-Wallerian degeneration was visualized in the corticospinal tract and corpus callosum and was associated with extensive brain injury caused by hypoxic-ischemic encephalopathy. The changes in signal were observed to evolve over time within the first 2 weeks. The clinical outcome of infants having pre-Wallerian degeneration in the corticospinal tract was unfavorable.

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.

Therapeutic hypothermia for neonatal hypoxic-ischaemic encephalopathy in India (THIN study): a randomised controlled trial

OBJECTIVE

To evaluate the neuroprotective effect of therapeutic hypothermia (TH) induced by phase changing material (PCM) on MRI biomarkers in infants with hypoxic-ischaemic encephalopathy (HIE) in a low-resource setting.

DESIGN

Open-label randomised controlled trial.

SETTING

One neonatal intensive care unit in a tertiary care centre in India.

PATIENTS

50 term/near-term infants admitted within 5 hours after birth with predefined physiological criteria and signs of moderate/severe HIE.

INTERVENTIONS

Standard care (n=25) or standard care plus 72 hours of hypothermia (33.5°C±0.5°C, n=25) induced by PCM.

MAIN OUTCOME MEASURES

Primary outcome was fractional anisotropy (FA) in the posterior limb of the internal capsule (PLIC) on neonatal diffusion tensor imaging analysed according to intention to treat.

RESULTS

Primary outcome was available for 22 infants (44%, 11 in each group). Diffusion tensor imaging showed significantly higher FA in the cooled than the non-cooled infants in left PLIC and several white matter tracts. After adjusting for sex, birth weight and gestational age, the mean difference in PLIC FA between groups was 0.026 (95% CI 0.004 to 0.048, p=0.023). Conventional MRI was available for 46 infants and demonstrated significantly less moderate/severe abnormalities in the cooled (n=2, 9%) than in the non-cooled (n=10, 43%) infants. There was no difference in adverse events between groups.

CONCLUSIONS

This study confirmed that TH induced by PCM reduced brain injury detected on MRI in infants with moderate HIE in a neonatal intensive care unit in India. Future research should focus on optimal supportive treatment during hypothermia rather than looking at efficacy of TH in low-resource settings.

TRIAL REGISTRATION NUMBER

CTRI/2013/05/003693.

Prognostic Value of Clinical Tests in Neonates With Hypoxic-Ischemic Encephalopathy Treated With Therapeutic Hypothermia: A Systematic Review and Meta-Analysis

Background and Objective: There remains an unmet clinical need for markers that predict outcomes in the hypothermia-treated (HT) infants with HIE. The aim of this meta-analysis was to investigate the prognostic accuracy of currently available clinical tests performed in the immediate post-natal period for predicting neurological outcomes between 18 months and 3 years of age in HT near-term and term infants with perinatal asphyxia and HIE.

Methods: A comprehensive review of the Embase, Cochrane library, and PubMed databases was performed to identify studies that evaluated the prognostic value of clinical tests for neurological outcomes in HT near-term and term infants with perinatal asphyxia and hypoxic-ischemic encephalopathy. Pooled sensitivity and specificity with corresponding 95% confidence intervals and area under the receiver operating characteristic (ROC) curve (AUC) were calculated.

Results: Of the 1,144 relevant studies, 26 studies describing four clinical tests conducted in 1458 HT near-term or term infants were included. For predicting an unfavorable neurological outcome, of the imaging techniques, MRI within 2 weeks of birth performed best on sensitivity 0.85 (95% CI 0.79–0.89), specificity 0.72 (95% CI 0.66–0.77), and AUC 0.88; among the neurophysiological tests, multichannel EEG (Electroencephalogram) demonstrated the sensitivity 0.63 (95% CI 0.49–0.76), specificity 0.82 (95% CI 0.70–0.91), and AUC 0.88, and for aEEG (amplitude-integrated electroencephalography) background pattern pooled sensitivity, specificity and AUC were 0.90 (95% CI 0.86–0.94), 0.46 (95% CI 0.42–0.51), and 0.78 whereas for SEPs (Somatosensory evoked potentials), pooled sensitivity and specificity were 0.52 (95% CI 0.34–0.69), 0.76 (95% CI 0.63–0.87), and AUC 0.84, respectively.

Conclusions: In the wake of the era of TH, MRI and neurophysiological tests (aEEG or EEG) were promising predictors of adverse outcomes, while SEPs need high-quality studies to confirm the findings. Continued follow-up of the children and well-designed large prospective studies are essential to determine whether these benefits are maintained in later childhood.

The splenium of the corpus callosum: embryology, anatomy, function and imaging with pathophysiological hypothesis

BACKGROUND AND PURPOSE

The splenium of the corpus callosum is the most posterior part of the corpus callosum. Its embryological development, anatomy, vascularization, function, imaging of pathology, possible pathophysiological mechanisms by which pathology may develop and the clinical consequences are discussed.

METHODS

A literature-based description is provided on development, anatomy and function. MR and CT images are used to demonstrate pathology. The majority of pathology, known to affect the splenium, and the clinical effects are described in three subsections: (A) limited to the splenium, with elaboration on pathophysiology of reversible splenial lesions, (B) pathology in the cerebral white matter extending into or deriving from the splenium, with special emphasis on tumors, and (C) splenial involvement in generalized conditions affecting the entire brain, with a hypothesis for pathophysiological mechanisms for the different diseases.

RESULTS

The development of the splenium is preceded by the formation of the hippocampal commissure. It is bordered by the falx and the tentorium and is perfused by the anterior and posterior circulation. It contains different caliber axonal fibers and the most compact area of callosal glial cells. These findings may explain the affinity of specific forms of pathology for this region. The fibers interconnect the temporal and occipital regions of both hemispheres reciprocally and are important in language, visuospatial information transfer and behavior. Acquired pathology may lead to changes in consciousness.

CONCLUSION

The development, location, fiber composition and vascularization of the splenium make it vulnerable to specific pathological processes. It appears to play an important role in consciousness.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Signal Change in the Mammillary Bodies after Perinatal Asphyxia

BACKGROUND AND PURPOSE

Research into memory deficits associated with hypoxic-ischemic encephalopathy has typically focused on the hippocampus, but there is emerging evidence that the medial diencephalon may also be compromised. We hypothesized that mammillary body damage occurs in perinatal asphyxia, potentially resulting in mammillary body atrophy and subsequent memory impairment.

MATERIALS AND METHODS

We retrospectively reviewed brain MRIs of 235 clinically confirmed full-term patients with hypoxic-ischemic encephalopathy acquired at a single center during 2004-2017. MRIs were performed within 10 days of birth (median, 6; interquartile range, 2). Two radiologists independently assessed the mammillary bodies for abnormal signal on T2-weighted and DWI sequences. Follow-up MRIs were available for 9 patients; these were examined for evidence of mammillary body and hippocampal atrophy.

RESULTS

In 31 neonates (13.2%), abnormal high mammillary body signal was seen on T2-weighted sequences, 4 with mild, 25 with moderate, and 2 with severe hypoxic-ischemic encephalopathy. In addition, restricted diffusion was seen in 6 neonates who had MR imaging between days 5 and 7. For these 31 neonates, the most common MR imaging pattern (41.9%) was abnormal signal restricted to the mammillary bodies with the rest of the brain appearing normal. Follow-up MRIs were available for 9 patients: 8 acquired between 3 and 19 months and 1 acquired at 7.5 years. There was mammillary body atrophy in 8 of the 9 follow-up MRIs.

CONCLUSIONS

Approximately 13% of full-term infants with hypoxic-ischemic encephalopathy showed abnormal high mammillary body signal on T2-weighted images during the acute phase, which progressed to mammillary body atrophy in all but 1 of the infants who had follow-up MR imaging. This mammillary body involvement does not appear to be related to the severity of encephalopathy, MR imaging patterns of hypoxic-ischemic encephalopathy, or pathology elsewhere in the brain.

Correlation Between White Matter Injury Identified by Neonatal Diffusion Tensor Imaging and Neurodevelopmental Outcomes Following Term Neonatal Asphyxia and Therapeutic Hypothermia: An Exploratory Pilot Study

AIM

Hypoxic-ischemic encephalopathy is associated with damage to deep gray matter; however, white matter involvement has become recognized. This study explored differences between patients and clinical controls on diffusion tensor imaging, and relationships between diffusion tensor imaging and neurodevelopmental outcomes.

METHOD

Diffusion tensor imaging was obtained for 31 neonates after hypoxic-ischemic encephalopathy treated with therapeutic hypothermia and 10 clinical controls. A subgroup of patients with hypoxic-ischemic encephalopathy (n = 14) had neurodevelopmental outcomes correlated with diffusion tensor imaging scalars.

RESULTS

Group differences in diffusion tensor imaging scalars were observed in the putamen, anterior and posterior centrum semiovale, and the splenium of the corpus callosum. Differences in these regions of interest were correlated with neurodevelopmental outcomes between ages 20 and 32 months.

CONCLUSION

Therapeutic hypothermia may not be a complete intervention for hypoxic-ischemic encephalopathy, as neonatal white matter changes may continue to be evident, but further research is warranted. Patterns of white matter change on neonatal diffusion tensor imaging correlated with neurodevelopmental outcomes in this exploratory pilot study.

Challenges in neurologic prognostication after neonatal brain injury

Parents often ask neonatologists and neurologists to determine neurologic prognosis in the preterm and term infant after neonatal brain injury. Prognostication in these populations remains rather full of uncertainties. Knowledge of available diagnostic tests and their limitations allows the clinician to synthesize the most likely outcomes after neurologic injury. In this review, we describe the diagnostic tools available to the clinician, active areas of research, and challenges in neurologic prognostication of the neonate.

MRI and spectroscopy in (near) term neonates with perinatal asphyxia and therapeutic hypothermia

BACKGROUND

Previous studies have demonstrated the association of abnormalities on diffusion-weighted MRI (DW-MRI) and proton magnetic resonance spectroscopy (¹H-MRS) in infants with perinatal asphyxia. The use of therapeutic hypothermia might change this association.

AIM

To study the association between DW-MRI and ¹H-MRS and outcome after perinatal asphyxia and therapeutic hypothermia in infants with a gestational age of ≥36 weeks.

PATIENTS AND METHODS

Infants with perinatal asphyxia and therapeutic hypothermia (n=88) were included when an MR examination was performed within 7 days after birth. Apparent diffusion coefficient (ADC) values of the basal ganglia and thalamus were calculated, as were lactate/N-acetylaspartate (LAC/NAA) and N-acetylaspartate/choline (NAA/Cho) ratios. Death or an abnormal neurodevelopment at ≥24 months was considered an adverse outcome. Receiver operating characteristic analysis was performed to determine cut-off levels.

RESULTS

Of the 88 infants, 22 died and 7 had an adverse neurodevelopmental outcome. In infants with an adverse outcome, ADC values of the basal ganglia and thalamus were significantly lower, and Lac/NAA ratios were significantly higher than in infants with a normal outcome. Areas under the curve of ADC of the basal ganglia, thalami and Lac/NAA ratio were 0.89, 0.88 and 0.87, respectively. NAA/Cho ratios were in this cohort not associated with outcome.

CONCLUSIONS

During and after therapeutic hypothermia, low ADC values and high Lac/NAA ratios of the basal ganglia and thalamus are associated with an adverse outcome in infants with perinatal asphyxia.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.