Neuropathologic studies of the encephalopathy of prematurity in the late preterm infant

Grade 7 school performance of children born preterm: a retrospective Canadian Cohort study

IMPORTANCE

Data on the middle school outcomes of preterm children are limited and have methodologic issues.

OBJECTIVE

To study the association between preterm birth and grade 7 school performance.

METHODS

A retrospective population-based cohort study of children born in Manitoba, Canada between 1994 and 2006 using their grade 7 school performance data. A secondary sibling cohort was created comprising children born preterm and their full-term siblings. Primary exposure was preterm birth categorized as <28, 28-33 and 34-36 weeks gestation. The two co-primary grade 7 outcome measures were: not meeting the mathematics competencies, and not meeting the student engagement competencies. Multivariable logistic regression models tested the association between preterm birth and both co-primary outcomes; adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

7653 preterm (gestational age median [IQR]: 35 weeks [34,36]) and 110,313 term (40 [39,40]) were included. 43% of < 28 weeks, 18% of 28-33 weeks and 17% of 34-36 weeks had the mathematics co-primary outcome compared to 13% of term children. The corresponding % for the student engagement outcome were 42%, 24%, 24% and 24% respectively. Preterm birth was associated with the mathematics (<28 weeks: 5.48, 3.89-7.70; 28-33 weeks: 1.47, 1.27-1.70; 34-36 weeks: 1.26, 1.16-1.35) and student engagement outcomes (<28 weeks: 2.49, 1.76-3.51; 28-33 weeks: 1.21, 1.06-1.39; 34-36 weeks: 1.09, 1.01-1.16). However, there was no difference in outcomes among the sibling cohort.

CONCLUSIONS AND RELEVANCE

Children born preterm had lower grade 7 performance compared to children born term in this population-based cohort. Screening and supports for them in their middle school years are warranted.

A role for immunohistochemical stains in perinatal brain autopsies

Identification of central nervous system injury is a critical part of perinatal autopsies; however, injury is not always easily identifiable due to autolysis and immaturity of the developing brain. Here, the role of immunohistochemical stains in the identification of perinatal brain injury was investigated. Blinded semiquantitative scoring of injury was performed on sections of frontal lobe from 76 cases (51 liveborn and 25 stillborn) using H&E, GFAP, Iba-1, and β-APP stains. Digital image analysis was used to quantify GFAP and Iba-1 staining. Commonly observed pathologies included diffuse white matter gliosis (DWMG) and white matter necrosis (WMN). DWMG scores were very similar on H&E and GFAP stains for liveborn subjects. For stillborn subjects, DWMG scores were significantly higher on GFAP stain than H&E. β-APP was needed for identification of WMN in 71.4% of stillborn subjects compared to 15.4% of liveborn subjects. Diffuse staining for Iba-1 within cortex and white matter was positively correlated with subject age. Staining quantification on digital image analysis was highly correlated to semiquantitative scoring. Overall, GFAP and β-APP stains were most helpful in identifying white matter injury not seen on H&E in stillborn subjects. Immunostains may therefore be warranted as an integral part of stillborn brain autopsies.

Single-center Experience with Therapeutic Hypothermia for Hypoxic-Ischemic Encephalopathy in Infants with <36 Weeks' Gestation

OBJECTIVE

 Hypoxic-ischemic encephalopathy (HIE) is a leading cause of morbidity and mortality in neonates. Therapeutic hypothermia (TH) has improved outcomes and mortality in infants with >36 weeks' gestational age (GA) with moderate-to-severe HIE. There are limited data on the safety and efficacy of TH in preterm infants with HIE. This study describes our experience and examines the safety of TH in neonates with <36 weeks' GA.

STUDY DESIGN

A single-center, retrospective study of preterm neonates born at <36 weeks' GA with moderate-to-severe HIE and treated with TH, compared to a cohort of term neonates with HIE (≥37 weeks' GA), was conducted. The term cohort was matched for degree of background abnormality on electroencephalogram, sex, inborn versus outborn status, and birth year. Medical records were reviewed for pregnancy and delivery complications, need for transfusion, sedation and antiseizure medications, electroencephalography and imaging findings, and in-hospital mortality.

RESULTS

 Forty-two neonates born at <36 weeks' GA with HIE received TH between 2005 and 2022. Data from 42 term neonates were analyzed for comparison. The average GA of the preterm cohort was 34.6 weeks and 39.3 weeks for the term cohort. Apgar scores, degree of acidosis, and need for blood product transfusions were similar between groups. Preterm infants were more likely to require inotropic support (55 vs. 29%, p = 0.026) and hydrocortisone (36 vs. 12%, p = 0.019) for hypotension. The proportion of infants without evidence of injury on magnetic resonance imaging was similar in both groups: 43 versus 50% in preterm and term infants, respectively. No significant difference was found in mortality between groups.

CONCLUSION

 In this single-center cohort, TH in preterm infants appears to be as safe as in term infants, with no significant increase in intracranial bleeds or mortality. Preterm infants more frequently required inotropes and steroids for hypotension. Further research is needed to determine efficacy of TH in preterm infants.

KEY POINTS

· TH is used off-protocol in preterm infants.. · Preterm and term infants have similar mortality.. · Preterm cohort required more inotropic support..

Evaluation of cerebral autoregulation of oxygen by NIRS method during postnatal transition period in term and late preterm newborns without resuscitation requirement

BACKGROUND

Pulse oximetry is commonly used to monitor arterial oxygen saturation and heart rate during the transition period and reference intervals have been determined. However, the effect of the change in arterial oxygen saturation on tissue oxygenation does not seem to be the same. So, a non-invasive method for monitoring cerebral or regional tissue oxygenation will be potentially useful for vulnerable infants. This study aims to evaluate the effectiveness of cerebral autoregulation in the first 10 min after delivery in term and late preterm newborns without resuscitation requirement.

METHODS

Cerebral tissue oxygen saturation was measured in the first 10 min after birth with near-infrared spectroscopy (NIRS) from the left forehead. Peripheral oxygen saturation was measured with pulse oximetry from the right hand and cerebral fractional tissue oxygen extraction was calculated.

RESULTS

Nineteen late preterms and 20 term infants were included in the study. There was no statistically significant difference between median cerebral tissue oxygen saturation and cerebral fractional tissue oxygen extraction values of late preterm and term infants (p < 0.001). There was a strong inverse relationship between cerebral tissue oxygen saturation and cerebral fractional tissue oxygen extraction (p < 0.001).

CONCLUSIONS

In late preterm infants similar to term infants, arterial oxygen saturation and cerebral tissue oxygen saturation increased with time, but inverse reduction of cerebral fractional tissue oxygen extraction showed the presence of an active autoregulation in the brain. This can be interpreted as the ability of the brain to protect itself from hypoxia by regulating oxygen uptake during normal fetal-neonatal transition process. A larger scale multi-center randomized control trial is now needed to further inform practice.

Perinatal hypoxic-ischemic brain injury: What's behind the "ribbon effect"?

Ribbon effect describes a perceived macroscopic color reversal of the gray and white matter, characterized by a pale cortex and diffusely dusky underlying white matter. This finding is thought to be unique to the perinatal period and indicative of hypoxic-ischemic injury. However, the clinical and microscopic correlates of this macroscopic finding have not been clearly defined. A 21-year retrospective study of autopsies was performed. Ribbon effect was seen in 190 subjects, ages 20 weeks gestation to 9.5 months adjusted age. Clinical associations and radiographic findings were similar in ribbon effect cases and controls. A variety of histologic findings were observed including acute neuronal injury, diffuse white matter gliosis, and white matter necrosis. Only white matter vascular congestion was significantly correlated to the macroscopic severity of ribbon effect; the severity of white matter injury and acute neuronal injury were not significantly correlated to ribbon effect. While hypoxic-ischemic changes were present in nearly all cases of ribbon effect, the location, severity, and chronicity of these changes varied considerably, and similar findings were observed in controls. The presence of ribbon effect therefore does not predict microscopic findings apart from vascular congestion, highlighting the importance of microscopic examination in perinatal brain autopsies.

Grade 3 school performance among children born preterm: a population-based cohort study

OBJECTIVE

To study the association between prematurity and grade 3 school performance in a contemporary cohort of children.

METHODS

Population-based retrospective cohort study in Manitoba, Canada. Children born between 1999 and 2011 who had their grade 3 school performance data available were eligible. Preterm birth (<37 weeks) was the exposure of interest assessed using multivariable logistic regression models. Our primary outcomes were 'needs ongoing help' or 'outside the range' in at least two of each of the (1) four numeracy and (2) three reading competencies.

RESULTS

Of the 186 956 eligible children, 101 436 children (7187 preterm (gestational age, median (IQR) 35 weeks (34, 36)) and 94 249 term (40 weeks (39,40)) were included. Overall, 19% of preterm and 14% of term children had the numeracy outcome (adjusted OR (aOR) 1.38; 95% CI 1.29 to 1.47, p<0.001), while 19% and 13% had the reading outcome (aOR 1.38; 1.29 to 1.48, p<0.001). These differences showed a gestational age gradient. Gestational age (for numeracy, <28 weeks aOR 4.93 (3.45 to 7.03), 28-33 weeks 1.72 (1.50 to 1.98), 34-36 weeks 1.24 (1.15 to 1.34); for reading, <28 weeks 3.51 (2.40 to 5.14), 28-33 weeks 1.72 (1.49 to 1.98), 34-36 weeks 1.24 (1.17-1.37)), male sex, small for gestational age and maternal medical and sociodemographic factors were associated with the numeracy and reading outcomes in this cohort.

CONCLUSIONS AND RELEVANCE

Children born preterm had poorer performance in grade 3 numeracy and reading proficiencies than children born full term. All children born preterm, not just those born extremely preterm, should be screened for reading and numeracy performance in school and strategies implemented to address any deficits.

Therapeutic Interventions in Rat Models of Preterm Hypoxic Ischemic Injury: Effects of Hypothermia, Caffeine, and the Influence of Sex

Infants born prematurely have an increased risk of experiencing brain injury, specifically injury caused by Hypoxia Ischemia (HI). There is no approved treatment for preterm infants, in contrast to term infants that experience Hypoxic Ischemic Encephalopathy (HIE) and can be treated with hypothermia. Given this increased risk and lack of approved treatment, it is imperative to explore and model potential treatments in animal models of preterm injury. Hypothermia is one potential treatment, though cooling to current clinical standards has been found to be detrimental for preterm infants. However, mild hypothermia may prove useful. Caffeine is another treatment that is already used in preterm infants to treat apnea of prematurity, and has shown neuroprotective effects. Both of these treatments show sex differences in behavioral outcomes and neuroprotective effects, which are critical to explore when working to translate from animal to human. The effects and research history of hypothermia, caffeine and how sex affects these treatment outcomes will be explored further in this review article.

Ultrasound measurements of brain structures differ between moderate-late preterm and full-term infants at term equivalent age

BACKGROUND

Brain growth in moderate preterm (MP; gestational age (GA) 32⁺⁰-33⁺⁶ weeks) and late preterm infants (LP; GA 34⁺⁰-36⁺⁶ weeks) may be impaired, even in the absence of brain injury.

AIMS

The aims of this study were to assess brain measurements of MP and LP infants, and to compare these with full-term infants (GA > 37 weeks) using linear cranial ultrasound (cUS) at term equivalent age (TEA).

STUDY DESIGN

cUS data from two prospective cohorts were combined. Two investigators performed offline measurements on standard cUS planes. Eleven brain structures were compared between MP, LP and full-term infants using uni- and multivariable linear regression. Results were adjusted for postmenstrual age at cUS and corrected for multiple testing.

RESULTS

Brain measurements of 44 MP, 54 LP and 52 full-term infants were determined on cUS scans at TEA. Biparietal diameter and basal ganglia-insula width were smaller in MP (-9.1 mm and - 1.7 mm, p < 0.001) and LP infants (-7.0 mm and - 1.7 mm, p < 0.001) compared to full-term infants. Corpus callosum - fastigium length was larger in MP (+2.2 mm, p < 0.001) than in full-term infants. No significant differences were found between MP and LP infants.

CONCLUSIONS

These findings suggest that brain growth in MP and LP infants differs from full-term infants. Whether these differences have clinical implications remains to be investigated.

The vascular endothelial cell-expressed prion protein doppel promotes angiogenesis and blood-brain barrier development

The central nervous system (CNS) contains a complex network of blood vessels that promote normal tissue development and physiology. Abnormal control of blood vessel morphogenesis and maturation is linked to the pathogenesis of various neurodevelopmental diseases. The CNS-specific genes that regulate blood vessel morphogenesis in development and disease remain largely unknown. Here, we have characterized functions for the gene encoding prion protein 2 (Prnd) in CNS blood vessel development and physiology. Prnd encodes the glycosylphosphatidylinositol (GPI)-linked protein doppel, which is expressed on the surface of angiogenic vascular endothelial cells, but is absent in quiescent endothelial cells of the adult CNS. During CNS vascular development, doppel interacts with receptor tyrosine kinases and activates cytoplasmic signaling pathways involved in endothelial cell survival, metabolism and migration. Analysis of mice genetically null for Prnd revealed impaired CNS blood vessel morphogenesis and associated endothelial cell sprouting defects. Prnd^-/- mice also displayed defects in endothelial barrier integrity. Collectively, these data reveal novel mechanisms underlying doppel control of angiogenesis in the developing CNS, and may provide new insights about dysfunctional pathways that cause vascular-related CNS disorders.

[Psychomotor development in late premature newborns at five years. Comparison with term newborns using the ASQ3®]

INTRODUCTION

Late prematures (LP) belong to a subgroup of many premature babies with a risk of delayed psychomotor development (PMD). Many subtle changes pass unnoticed if adequate assessment tools are not used. The Ages & Stages Questionnaires 3® (ASQ3®) for parents appears simple and useful for the detection of risk of impairment of PMD, and is recommended by scientific societies that study LP.

OBJECTIVES

To evaluate the risk of impaired PMD in LP at 5years-old, and compare them with term newborns (TNB) using the ASQ3.

PATIENTS AND METHODS

Data were collected on the LP born in a third level hospital in 2010, as well as 2TNB of the same gender for each LP. The prenatal and postnatal morbidity variables were compared. At 5years, their families (excluding those with other neurological risks) were asked to complete the ASQ3. The cut-off point was determined for the total score of the ASQ3 that would discriminate the risk of PMD impairment using ROC analysis. The cut-off point to determine a change in each domain was obtained according to the ASQ3 manual.

RESULTS

The ASQ3 was completed for 88 (47%) and 131 (35%) TNB. All the overall mean scores and those for domains were lower in LP, with no significant differences found between the two groups. A risk of PMD impairment (≤253 points) was observed in 7LP compared to 4TNB, with no significant difference. More maternal, foetal, and neonatal illnesses were observed in 195LP than in the 390TNB. In the univariate analysis, male gender and restricted uterine growth (RUG) were factors associated with a risk of PMD impairment and only RUG in the multivariate analysis.

CONCLUSION

The risk of PMD impairment between LP and TNB at 5years appears not to be shown, with no significant differences between both, and with the values obtained in the ASQ3 being slightly lower in the LP. Male gender and RUG negatively influence this risk.

Neurologic Injury and Brain Growth in the Setting of Long-Gap Esophageal Atresia Perioperative Critical Care: A Pilot Study

We previously showed that infants born with long-gap esophageal atresia (LGEA) demonstrate clinically significant brain MRI findings following repair with the Foker process. The current pilot study sought to identify any pre-existing (PRE-Foker process) signs of brain injury and to characterize brain and corpus callosum (CC) growth. Preterm and full-term infants (n = 3/group) underwent non-sedated brain MRI twice: before (PRE-Foker scan) and after (POST-Foker scan) completion of perioperative care. A neuroradiologist reported on qualitative brain findings. The research team quantified intracranial space, brain, cerebrospinal fluid (CSF), and CC volumes. We report novel qualitative brain findings in preterm and full-term infants born with LGEA before undergoing Foker process. Patients had a unique hospital course, as assessed by secondary clinical end-point measures. Despite increased total body weight and absolute intracranial and brain volumes (cm3) between scans, normalized brain volume was decreased in 5/6 patients, implying delayed brain growth. This was accompanied by both an absolute and relative CSF volume increase. In addition to qualitative findings of CC abnormalities in 3/6 infants, normative CC size (% brain volume) was consistently smaller in all infants, suggesting delayed or abnormal CC maturation. A future larger study group is warranted to determine the impact on the neurodevelopmental outcomes of infants born with LGEA.

Newborns and preterm infants at term equivalent age: A semi-quantitative assessment of cerebral maturity

BACKGROUND AND PURPOSE

Currently available MRI scoring systems of cerebral maturation in term and preterm infant at term equivalent age do not include the changes of transient fetal compartments that persist to term age. We studied the visibility and the pattern of these structures in healthy term newborns compared to preterm infants at term equivalent age in order to investigate if they can be included in a new MRI score system. We hypothesized that transient fetal compartments are different in both groups, and that these differences can be characterized using the clinical T2-weighted MRIs.

MATERIALS AND METHODS

Using 3T MRI T2-weighted brain sequences of 21 full-term and 41 preterm infants (< 32 weeks), scanned at term equivalent age, 3 raters independently scored the maturation level of 3 transient fetal compartments: the periventricular crossroads, von Monakow segments of the white matter, and the subplate compartment. These 3 new items were included in a scoring system along with validated parameters of brain maturation (germinal matrix, bands of migration, subarachnoid space and quality of gyrification). A cumulative maturity score was calculated separately for both groups of newborns by adding together each item. More mature were the brain structures, higher was the cumulative maturity score.

RESULTS

Cumulative maturity score distinguished full-term from preterm infants (mean score 41/60 ± 1.4 versus 37/60 ± 2.5 points, p < 0.001), with an increase of 0.5 points for each supplemental gestational week at birth (r = 0.5, 95% CI 0.5 - 0.85). While a majority of transient fetal compartments were less mature in preterm group at term equivalent age, von Monakow segments of the white matter and subplate compartment presented a more advanced maturational stage in the preterm group compared to the term group. No subject had all scored items in the most mature state. Except a slight intra-rater agreement for von Monakow segment II, inter- and intra-rater agreements were moderate to excellent indicating the potential of the developed scoring system in routine clinical practice.

CONCLUSION

Brain transient fetal structures can be assessed on regular T2-weighted MRI in newborns. Their appearance differs between term and preterm babies. However our results suggest a more complex situation, with both delayed and accelerated maturation pattern in preterm infants. It remains to be determined if these differences could be biomarkers of the future neurodevelopment of preterm infants.

A machine learning investigation of volumetric and functional MRI abnormalities in adults born preterm

Imaging studies have characterized functional and structural brain abnormalities in adults after premature birth, but these investigations have mostly used univariate methods that do not account for hypothesized interdependencies between brain regions or quantify accuracy in identifying individuals. To overcome these limitations, we used multivariate machine learning to identify gray matter volume (GMV) and amplitude of low frequency fluctuations (ALFF) brain patterns that best classify young adults born very preterm/very low birth weight (VP/VLBW; n = 94) from those born full-term (FT; n = 92). We then compared the spatial maps of the structural and functional brain signatures and validated them by assessing associations with clinical birth history and basic cognitive variables. Premature birth could be predicted with a balanced accuracy of 80.7% using GMV and 77.4% using ALFF. GMV predictions were mediated by a pattern of subcortical and middle temporal reductions and volumetric increases of the lateral prefrontal, medial prefrontal, and superior temporal gyrus regions. ALFF predictions were characterized by a pattern including increases in the thalamus, pre- and post-central gyri, and parietal lobes, in addition to decreases in the superior temporal gyri bilaterally. Decision scores from each classification, assessing the degree to which an individual was classified as a VP/VLBW case, were predicted by the number of days in neonatal hospitalization and birth weight. ALFF decision scores also contributed to the prediction of general IQ, which highlighted their potential clinical significance. Combined, the results clarified previous research and suggested that primary subcortical and temporal damage may be accompanied by disrupted neurodevelopment of the cortex.

Late preterm births: New insights from neonatal neuroimaging and neurobehaviour

With increasing evidence of neurodevelopmental problems faced by late preterm children, there is a need to explore possible underlying brain structural changes. The use of brain magnetic resonance imaging has provided insights of smaller and less mature brains in infants born late preterm, associated with developmental delay at 2 years. Another useful tool in the newborn period is neurobehavioural assessment, which has also been shown to be suboptimal in late preterm infants compared with tern infants. Suboptimal neurobehaviour is also associated with poorer 2-year neurodevelopment in late preterm infants. More research into these tools will provide a better understanding of the underlying processes of developmental deficits of late preterm children. The value of their role in clinical care remains to be determined.

Neurodevelopmental outcomes of the late preterm infant

Late preterm infants (born at 34^0/7-36^6/7 weeks gestation) have been found to have increased morbidity and mortality compared to full term infants. Research has also been done to explore longer-term neurodevelopmental outcomes. This review details neurodevelopmental outcomes from birth to adulthood for late preterm infants. Outcome studies indicate that they are at increased risk of developmental disability, school failure, behavior problems, social and medical disabilities, and death. Many questions still remain regarding late preterm infant neurodevelopmental outcomes and future research should be done into this topic. Given the high prevalence of late preterm births, even small differences in abilities, special education, and length of education may have broader consequences.

Clinical neuroimaging in the preterm infant: Diagnosis and prognosis

Perinatal care advances emerging over the past twenty years have helped to diminish the mortality and severe neurological morbidity of extremely and very preterm neonates (e.g., cystic Periventricular Leukomalacia [c-PVL] and Germinal Matrix Hemorrhage - Intraventricular Hemorrhage [GMH-IVH grade 3-4/4]; 22 to < 32 weeks of gestational age, GA). However, motor and/or cognitive disabilities associated with mild-to-moderate white and gray matter injury are frequently present in this population (e.g., non-cystic Periventricular Leukomalacia [non-cystic PVL], neuronal-axonal injury and GMH-IVH grade 1-2/4). Brain research studies using magnetic resonance imaging (MRI) report that 50% to 80% of extremely and very preterm neonates have diffuse white matter abnormalities (WMA) which correspond to only the minimum grade of severity. Nevertheless, mild-to-moderate diffuse WMA has also been associated with significant affectations of motor and cognitive activities. Due to increased neonatal survival and the intrinsic characteristics of diffuse WMA, there is a growing need to study the brain of the premature infant using non-invasive neuroimaging techniques sensitive to microscopic and/or diffuse lesions. This emerging need has led the scientific community to try to bridge the gap between concepts or ideas from different methodologies and approaches; for instance, neuropathology, neuroimaging and clinical findings. This is evident from the combination of intense pre-clinical and clinicopathologic research along with neonatal neurology and quantitative neuroimaging research. In the following review, we explore literature relating the most frequently observed neuropathological patterns with the recent neuroimaging findings in preterm newborns and infants with perinatal brain injury. Specifically, we focus our discussions on the use of neuroimaging to aid diagnosis, measure morphometric brain damage, and track long-term neurodevelopmental outcomes.

Children born at 32 to 35 weeks with birth asphyxia and later cerebral palsy are different from those born after 35 weeks

OBJECTIVE

The objectives of this study were to (1) establish the proportion of cerebral palsy (CP) that occurs with a history suggestive of birth asphyxia in children born at 32 to 35 weeks and (2) evaluate their characteristics in comparison with children with CP born at ⩾36 weeks with such a history.

STUDY DESIGN

Using the Canadian CP Registry, children born at 32 to 35 weeks of gestation with CP with a history suggestive of birth asphyxia were compared with corresponding ⩾36 weeks of gestation children.

RESULTS

Of the 163 children with CP born at 32 to 35 weeks and 738 born at ⩾36 weeks, 26 (16%) and 105 (14%) had a history suggestive of birth asphyxia, respectively. The children born at 32 to 35 weeks had more frequent abruptio placenta (35% vs 12%; odds ratio (OR) 4.1, 95% confidence interval (CI) 1.5 to 11.2), less frequent neonatal seizures (35% vs 72%; OR 0.20, 95% CI 0.08 to 0.52), more frequent white matter injury (47% vs 17%; OR 4.3, 95% CI 1.3 to 14.0), more frequent intraventricular hemorrhage (IVH) (40% vs 6%; OR 11.2, 95% CI 3.4 to 37.4) and more frequent spastic diplegia (24% vs 8%; OR 1.8, 95% CI 1.2 to 12.2) than the corresponding ⩾36 weeks of gestation children.

CONCLUSIONS

Approximately 1 in 7 children with CP born at 32 to 35 weeks had a history suggestive of birth asphyxia. They had different magnetic resonance imaging patterns of injury from those born at ⩾36 weeks and a higher frequency of IVH. Importantly, when considering hypothermia in preterm neonates with suspected birth asphyxia, prospective surveillance for IVH will be essential.

Moderate and late preterm infants exhibit widespread brain white matter microstructure alterations at term-equivalent age relative to term-born controls

Despite the many studies documenting cerebral white matter microstructural alterations associated with very preterm birth (<32 weeks' gestation), there is a dearth of similar research in moderate and late preterm infants (born 32-36 weeks' gestation), who experience higher rates of neurodevelopmental delays than infants born at term (≥ 37 weeks' gestation). We therefore aimed to determine whether whole brain white matter microstructure differs between moderate and late preterm infants and term-born controls at term-equivalent age, as well as to identify potential perinatal risk factors for white matter microstructural alterations in moderate and late preterm infants. Whole brain white matter microstructure was studied in 193 moderate and late preterm infants and 83 controls at term-equivalent age by performing Tract-Based Spatial Statistics analysis of diffusion tensor imaging data. Moderate and late preterm infants had lower fractional anisotropy and higher mean, axial and radial diffusivities compared with controls in nearly 70% of the brain's major white matter fiber tracts. In the moderate and late preterm group, being born small for gestational age and male sex were associated with lower fractional anisotropy, largely within the optic radiation, corpus callosum and corona radiata. In conclusion, moderate and late preterm infants exhibit widespread brain white matter microstructural alterations compared with controls at term-equivalent age, in patterns consistent with delayed or disrupted white matter microstructural development. These findings may underpin some of the neurodevelopmental delays observed in moderate and late preterm children.

Auditory brainstem maturation in normal-hearing infants born preterm: a meta-analysis

AIM

Children born preterm often have neurodevelopmental problems later in life. Abnormal maturation of the auditory brainstem in the presence of normal hearing might be a marker for these problems. We conducted a meta-analysis of auditory brainstem response (ABR) latencies at term age to describe differences in auditory brainstem maturation between normal-hearing preterm and term-born infants.

METHOD

Computerized databases were searched for studies published between 1995 and 2014 that reported ABR measurements at term age in infants born preterm in a case-control design. Five peaks reflect the conduction of a neural signal along the brainstem auditory pathway. We collected I to V interpeak latency data, and III to V interpeak latency data, which refers to the more central part of the pathway.

RESULTS

Preterm-born infants' III to V interval is significantly longer compared to infants born at term (0.081ms, effect-size=0.974), which also reflects on the I to V interval. Moreover, significantly increased ABR interpeak latencies of infants born preterm are related to lower gestational age and the need for neonatal intensive care treatment.

INTERPRETATION

The delayed conduction time towards and into the auditory brainstem at term age suggests atypical maturation of the brainstem in normal-hearing infants born preterm. Both the duration of gestation and the consequences of the preterm birth (intensive care needed) negatively affect maturation of the auditory brainstem, which may influence later development.

Birth Asphyxia and Hypoxic-Ischemic Brain Injury in the Preterm Infant

Birth asphyxia, also termed perinatal hypoxia-ischemia, is a modifiable condition as evidenced by improved outcomes of infants ≥36 weeks' gestation provided hypothermia treatment in randomized trials. Preterm animal models of asphyxia in utero demonstrate that hypothermia can provide short-term neuroprotection for the developing brain, supporting the interest in extending therapeutic hypothermia to preterm infants. This review focuses on the challenge of identifying preterm infants with perinatal asphyxia; the neuropathology of hypoxic-ischemic brain injury across extreme, moderate, and late preterm infants; and patterns of brain injury, use of therapeutic hypothermia, and approach to patient selection for neuroprotective treatments among preterm infants.

Dysregulation of FMRP/mTOR Signaling Cascade in Hypoxic-Ischemic Injury of Premature Human Brain

In this study the authors investigated whether dysregulation of the fragile X mental retardation protein and mammalian target of rapamycin signaling cascade can have a role in the pathogenesis of encephalopathy of prematurity following perinatal hypoxia-ischemia. The authors examined the brain tissue of newborns with encephalopathy and compared it to age-matched controls with normal brain development and adults. In normal controls, the fragile X mental retardation protein expression in cortical gray matter spiked 4-fold during 36-39 gestational weeks compared to the adult, with a concomitant suppression of p70S6K and S6. In encephalopathy cases, the developmental spike of fragile X mental retardation protein was not observed, and fragile X mental retardation protein levels remained significantly lower than in normal controls. Importantly, this fragile X mental retardation protein downregulation was followed by a significant overexpression of p70S6K and S6. These novel findings thus suggest that premature hypoxic-ischemic brain injury can affect the fragile X mental retardation protein/mammalian target of rapamycin pathway, as otherwise observed in inherited syndromes of cognitive disability and autism spectrum disorders.

Protective effects of activated protein C on neurovascular unit in a rat model of intrauterine infection-induced neonatal white matter injury

Activated protein C (APC), a natural anticoagulant, has been reported to exert direct vasculoprotective, neural protective, anti-inflammatory, and proneurogenic activities in the central nervous system. This study was aimed to explore the neuroprotective effects and potential mechanisms of APC on the neurovascular unit of neonatal rats with intrauterine infection-induced white matter injury. Intraperitoneal injection of 300 μg/kg lipopolysaccharide (LPS) was administered consecutively to pregnant Sprague-Dawley rats at embryonic days 19 and 20 to establish the rat model of intrauterine infection- induced white matter injury. Control rats were injected with an equivalent amount of sterile saline on the same time. APC at the dosage of 0.2 mg/kg was intraperitoneally injected to neonatal rats immediately after birth. Brain tissues were collected at postnatal day 7 and stained with hematoxylin and eosin (H&E). Immunohistochemistry was used to evaluate myelin basic protein (MBP) expression in the periventricular white matter region. Blood-brain barrier (BBB) permeability and brain water content were measured using Evens Blue dye and wet/dry weight method. Double immunofluorescence staining and real-time quantitative PCR were performed to detect microglial activation and the expression of protease activated receptor 1 (PAR1). Typical pathological changes of white matter injury were observed in rat brains exposed to LPS, and MBP expression in the periventricular region was significantly decreased. BBB was disrupted and the brain water content was increased. Microglia were largely activated and the mRNA and protein levels of PAR1 were elevated. APC administration ameliorated the pathological lesions of the white matter and increased MBP expression. BBB permeability and brain water content were reduced. Microglia activation was inhibited and the PAR1 mRNA and protein expression levels were both down-regulated. Our results suggested that APC exerted neuroprotective effects on multiple components of the neurovascular unit in neonatal rats with intrauterine infection- induced white matter injury, and the underlying mechanisms might involve decreased expression of PAR1.

Brain morphometry and cognition in young adults born small for gestational age at term

OBJECTIVES

To examine brain volumes and cortical surface area and thickness and to relate these brain measures to cognitive function in young adults born small for gestational age (SGA) at term compared with non-SGA control patients.

STUDY DESIGN

This population-based follow-up study at age 20 years included 58 term-born SGA (birth weight <10th percentile, mean: 2915 g) and 81 non-SGA controls (birth weight ≥ 10th percentile, mean: 3707 g). Brain volumes and cortical surface area and thickness were investigated with magnetic resonance imaging, which was successfully obtained in 47 SGA patients and 61 control patients. Cognitive function was assessed using the Wechsler Adult Intelligence Scale, 3rd edition. A subgroup analysis was performed in the SGA group among subjects diagnosed with fetal growth restriction (FGR) based on repeated fetal ultrasound measurements.

RESULTS

The SGA group showed regional reductions in cortical surface area, particularly in the frontal, parietal, and temporal lobes. Total brain volume, cortical gray matter, cerebral white matter, and putamen volumes were reduced in the SGA group compared with control patients, but there were no differences in specific subcortical brain structure volumes when correcting for intracranial volume. Reductions were most pronounced among SGA subjects with FGR. No associations were found between brain measures and IQ measures in either group.

CONCLUSION

Young adults born SGA at term show a global reduction in brain volume as well as regional reductions in cortical surface area. We speculate whether these reductions may be confined to those exposed to FGR. None of the brain measures correlated with cognition.

[Recommendations for the perinatal management and follow up of late preterm newborns]

Prematurity is the main reason for neonatal morbidity and mortality, and has become one of the greatest problems in public health, especially in developed countries. Prematurity rate has increased during the last 2 decades. This increase may be attributed to late preterm babies, that is, those with a gestational age between 34(+0) and 36(+6) weeks. Perinatal morbidities, as well as long term complications, are more frequent in this population than in term babies. The incidence is more similar to the one observed in earlier premature babies. The SEN34-36 group of the Spanish Society of Neonatology suggests these recommendations for the management of late preterm babies. Strategies are offered not only for the early detection of possible complications, but also for the correction of these morbidities, and from the point of view of a family and development centered care. Follow up is strongly recommended due to the high rate of late morbidities.