Brain development of the preterm neonate after neonatal hydrocortisone treatment for chronic lung disease

Early, low-dose hydrocortisone and near-term brain connectivity in extremely preterm infants

BACKGROUND

Postnatal steroids are used to prevent bronchopulmonary dysplasia in extremely preterm infants but may have adverse effects on brain development. We assessed connectivity metrics of major cerebral and cerebellar white matter pathways at near-term gestational age among infants who did or did not receive a standardized regimen of hydrocortisone during the first 10 days of life.

METHODS

Retrospective cohort study.

PARTICIPANTS

Infants born <28 weeks: Protocol group (n = 33) received at least 50% and not more than 150% of an intended standard dose of 0.5 mg/kg hydrocortisone twice daily for 7 days, then 0.5 mg/kg per day for 3 days; Non-Protocol group (n = 22), did not receive protocol hydrocortisone or completed <50% of the protocol dose. We assessed group differences in near-term diffusion MRI mean fractional anisotropy (FA) and mean diffusivity (MD) across the corticospinal tract, inferior longitudinal fasciculus, corpus callosum and superior cerebellar peduncle.

RESULTS

Groups were comparable in gestational age, post-menstrual age at scan, medical complications, bronchopulmonary dysplasia, and necrotizing enterocolitis. No significant large effect group differences were identified in mean FA or MD in any cerebral or cerebellar tract.

CONCLUSION(S)

Low dose, early, postnatal hydrocortisone was not associated with significant differences in white matter tract microstructure at near-term gestational age.

IMPACT

This study compared brain microstructural connectivity as a primary outcome among extremely preterm infants who did or did not receive early postnatal hydrocortisone. Low dose hydrocortisone in the first 10 days of life was not associated with significant differences in white matter microstructure in major cerebral and cerebellar pathways. Hydrocortisone did not have a significant effect on early brain white matter circuits.

Effect of Systemic Hydrocortisone on Brain Abnormalities and Regional Brain Volumes in Ventilator-dependent Infants Born Preterm: Substudy of the SToP-BPD Study

OBJECTIVE

To evaluate whether a high cumulative dose of systemic hydrocortisone affects brain development compared with placebo when initiated between 7 and 14 days after birth in ventilated infants born preterm.

STUDY DESIGN

A double-blind, placebo-controlled, randomized trial was conducted in 16 neonatal intensive care units among infants born at <30 weeks of gestation or with a birth weight of <1250 g who were ventilator-dependent in the second week after birth. Three centers performed MRI at term-equivalent age. Brain injury was assessed on MRI using the Kidokoro scoring system and compared between the 2 treatment groups. Both total and regional brain volumes were calculated using an automatic segmentation method and compared using multivariable regression analysis adjusted for baseline variables.

RESULTS

From the 3 centers, 78 infants participated in the study and 59 had acceptable MRI scans (hydrocortisone group, n = 31; placebo group, n = 28). Analyses of the median global brain abnormality score of the Kidokoro score showed no difference between the hydrocortisone and placebo groups (median, 7; IQR, 5-9 vs median, 8, IQR, 4-10, respectively; P = .92). In 39 infants, brain tissue volumes were measured, showing no differences in the adjusted mean total brain tissue volumes, at 352 ± 32 mL in the hydrocortisone group and 364 ± 51 mL in the placebo group (P = .80).

CONCLUSIONS

Systemic hydrocortisone started in the second week after birth in ventilator-dependent infants born very preterm was not found to be associated with significant differences in brain development compared with placebo treatment.

TRIAL REGISTRATION

The SToP-BPD study was registered with the Netherlands Trial Register (NTR2768; registered on 17 February 2011; https://www.trialregister.nl/trial/2640) and the European Union Clinical Trials Register (EudraCT, 2010-023777-19; registered on 2 November 2010; https://www.clinicaltrialsregister.eu/ctr-search/trial/2010-023777-19/NL).

The Association of Dexamethasone and Hydrocortisone with Cerebellar Growth in Premature Infants

OBJECTIVES

Corticosteroids are used to prevent or treat lung disease of prematurity. While neurological side effects have been reported, detailed effects on cerebellar growth are unknown. This study aimed to compare cerebellar growth in premature infants who received dexamethasone or hydrocortisone to premature infants who did not receive postnatal corticosteroids.

STUDY DESIGN

Retrospective case-control study in infants born at a gestational age of <29 weeks and admitted to two level 3 neonatal intensive care units. Exclusion criteria were severe congenital anomalies and cerebellar or severe supratentorial lesions. Infants were treated with dexamethasone (unit 1) or hydrocortisone (unit 2) for chronic lung disease. Controls (unit 1) did not receive postnatal corticosteroids. Sequential head circumference (HC) and ultrasound measurements of transcerebellar diameter (TCD), biparietal diameter (BPD), and corpus callosum-fastigium length (CCFL) were performed until 40 weeks' postmenstrual age (PMA). Growth was assessed using linear mixed models correcting for PMA at measurement, sex, HC z-score at birth, and a propensity score indicating illness severity. Group differences before treatment were assessed using linear regression.

RESULTS

346 infants were included (68 dexamethasone, 37 hydrocortisone, 241 controls). Before starting corticosteroids, TCD, BPD, and HC measurements did not differ between patients and controls at a comparable PMA. After starting treatment, both types of corticosteroid had a negative association with TCD growth. BPD, CCFL, and HC growth were not negatively affected.

CONCLUSION

Administration of dexamethasone and hydrocortisone are both associated with impaired cerebellar growth in premature infants without evident negative associations with cerebral growth.

Systemic postnatal corticosteroids and magnetic resonance imaging measurements of corpus callosum and cerebellum of extremely preterm infants

AIM

To compare the size of the corpus callosum (CC) and cerebellum on magnetic resonance imaging (MRI) brain scans conducted at term equivalent age (TEA) in extremely preterm infants who received systemic postnatal corticosteroids (PCS) to extremely preterm infants who did not receive systemic PCS and determine the dose-dependent effects on these outcomes.

METHODS

Single-centre retrospective cohort study including extremely preterm infants (born < 26 weeks' gestation) who had MRI brain scans at TEA. CC and cerebellar measurements were evaluated by two radiologists who were blinded to steroid use and their independent measurements were averaged. Comparative analyses were conducted between exposed (to systemic PCS) and non-exposed groups.

RESULTS

Eighty-three extremely preterm infants with mean (SD) 24.9 (0.91) weeks' gestational age, 721.8 (156) g birthweight were included; 38 with systemic PCS exposure and 45 without exposure. After adjustment for birthweight and other significant neonatal morbidities, there was no significant difference noted in corpus callosum length (CCL) between unexposed and exposed groups (adjusted mean (SE) 39.5 (0.57) mm vs. 38.5 (0.62) mm; P = 0.29). Similarly, the ratios of CCL/fronto-occipital diameter (FOD) and CCL/biparietal diameter (BPD) were not significantly different between the groups (CCL/FOD (0.40 (0.01) vs. 0.41 (0.01); P = 0.70) and CCL/BPD (0.51 (0.01) vs. 0.52 (0.01); P = 0.62)). Finally, no significant differences in cerebellar measurements, such as vermian height (adjusted mean (SE) 24.0 (0.46) mm vs. 23.5 (0.51 mm); P = 0.47) and transcerebellar diameter (adjusted mean (SE) 49.3 (0.74) mm vs. 4.78 (0.82) mm; P = 0.22) were found. No dose-dependent effects of systemic PCS on CC and cerebellar measurements were identified.

CONCLUSIONS

Systemic PCS use in extremely preterm infants was not associated with a change in the CC and cerebellar measurements on MRI brain scan at TEA.

Effects of postnatal glucocorticoids on brain structure in preterm infants, a scoping review

Glucocorticoids (GC) are used in neonatal intensive care units to prevent or reduce the severity of chronic lung disease in preterm infants and have been implicated in impaired neurodevelopment. Our objective was to identify what is known about the effects of postnatal GC treatment in human preterm infants on structural brain development and to identify gaps in the literature. Following Arksey and O'Malley's scoping review methodological framework, we searched scientific literature databases for original research on human preterm infants, postnatal GCs, and brain structure. 11 studies assessed the effects of GCs on structural brain outcomes. 56 studies reported brain injury, but not structure. Dexamethasone was consistently associated with decreased total and regional brain volumes, including cerebellar volumes. Hydrocortisone was often, but not always associated with absence of brain volume differences. No studies examined the impact of inhaled GC on brain structure. Additional research on the effects of neonatal GCs after preterm birth on a variety of structural brain measures is required for understanding contributions to neurodevelopment and informing practice guidelines.

Duration of mechanical ventilation is more critical for brain growth than postnatal hydrocortisone in extremely preterm infants

Hydrocortisone is used in preterm infants. However, early disruption of growth velocities was observed in infants exposed to hydrocortisone. This retrospective study aimed to explore the postnatal brain growth of extremely preterm infants requiring hydrocortisone treatment as well as its association with perinatal factors. Extremely preterm infants exposed to hydrocortisone from 2011 to 2016 who survived up to 12 months were included. Each of them was matched with two infants not treated with hydrocortisone exhibiting similar gestational ages and nearly similar birth head circumferences. The outcome variables were brain tissue areas on MRIs performed at term-equivalent age and postnatal head circumference growth up to a corrected age of 12 months. Univariate and multiple regression analyses were performed. Infants treated with hydrocortisone (n=20) were matched with 40 infants not exposed to hydrocortisone. The infants exposed to hydrocortisone exhibited a lower birth weight (p=0.04) and a longer duration of mechanical ventilation (p<0.0001). Infants treated with hydrocortisone exhibited a smaller basal ganglia/thalamus area (p=0.04) at term-equivalent age and a smaller head circumference at a corrected age of 12 months (p=0.003). However, the basal ganglia/thalamus area and the postnatal brain growth were independently associated with the duration of mechanical ventilation and not with hydrocortisone. Interestingly, a significant interaction between hydrocortisone and sex was observed (p=0.04).Conclusion: This study supports previous data that indicated no obvious impact of hydrocortisone on brain growth and highlights the relationship between the severity of the neonatal course and postnatal brain growth in extremely preterm infants. What is Known: • Postnatal hydrocortisone disrupts transiently growth velocities including the head circumference growth. • Postnatal hydrocortisone has less impact on neurodevelopment than dexamethasone. What is New: • Hydrocortisone prescribed for infants in the most severe conditions did not show independent effect on brain growth up to the corrected age of 12 months. However, a different effect of hydrocortisone according to sex can't be excluded and needs further explorations. • Perinatal factors as birth weight and duration of mechanical ventilation were determinant for the subsequent brain growth.

Corticosteroids for Neonatal Hypotension

Several limitations and controversies surround the definition of hypotension; however, it remains one of the most common problems faced by neonates. Approximately 15% to 30% of neonates with hypotension fail to respond to volume and/or vasopressor or inotropes. They are considered to have refractory hypotension. Although it is thought to have multiple causes, absolute and relative adrenal insufficiency is considered as the main reason for refractory hypotension. This article focuses on the role of adrenal insufficiency in causing refractory hypotension in preterm and term infants, the different options of corticosteroids available, and their risk/benefit profiles.

Prophylactic hydrocortisone in extremely preterm infants and brain MRI abnormality

OBJECTIVE

To determine whether early low-dose hydrocortisone treatment in extremely preterm infants is associated with brain damage assessed by MRI at term equivalent of age (TEA).

PATIENTS AND OUTCOMES

This is a predefined secondary analysis of brain abnormalities, observed by MRI at TEA, of patients randomly assigned to receive either placebo or hydrocortisone in the PREMILOC trial. Outcomes were based on brain abnormalities graded according to Kidokoro scores.

RESULTS

Among 412 survivors at TEA, 300 MRIs were performed and 295 were suitable for analysis. Kidokoro scoring was completed for 119/148 and 110/147 MRIs in the hydrocortisone and placebo groups, respectively. The distribution of the Kidokoro white matter (WM) subscore and other subscores was not significantly different between the two groups. There was, however, a significant association between a higher overall Kidokoro score and hydrocortisone treatment (5.84 (SD 3.51) for hydrocortisone and 4.98 (SD 2.52) for placebo; mean difference, 0.86; 95% CI 0.06 to 1.66; p=0.04). However, hydrocortisone was not statistically associated with moderate-to-severe brain lesions (Kidokoro overall score ≥6) in a multivariate logistic regression model accounting for potential confounding variables (adjusted OR (95% CI) 1.27 (0.75 to 2.14), p=0.38). Bronchopulmonary dysplasia at 36 weeks postmenstrual age significantly predicted both WM damage (adjusted OR (95% CI) 2.70 (1.03 to 7.14), p=0.04) and global brain damage (adjusted OR (95% CI) 2.18 (1.19 to 3.99), p=0.01).

CONCLUSIONS

Early hydrocortisone exposure in extremely preterm infants is not statistically associated with either WM brain damage or overall moderate-to-severe brain lesions when adjusted for other neonatal variables.

TRIAL REGISTRATION NUMBER

EudraCT number 2007-002041-20, NCT00623740.

Hydrocortisone and bronchopulmonary dysplasia: variables associated with response in premature infants

OBJECTIVE

The primary objective was to evaluate hydrocortisone's efficacy for decreasing respiratory support in premature infants with developing bronchopulmonary dysplasia (BPD). Secondary objectives included assessment of the impact of intrauterine growth restriction (IUGR), maternal history of chorioamnionitis, side effects and route of administration associated with hydrocortisone's efficacy. Dexamethasone as second-line treatment to decrease respiratory support was reviewed.

METHODS

Retrospective chart review of preterm infants requiring respiratory support receiving hydrocortisone.

RESULTS

A total of 48 patients were included. Successful extubation was achieved in 50% of intubated patients after hydrocortisone treatment with no major complications. In our small study, history of maternal chorioamnionitis, IUGR or route of administration did not affect the response. Rescue dexamethasone after hydrocortisone therapy was ineffective in the ten patients who failed extubation following hydrocortisone.

CONCLUSION

Hydrocortisone is effective in decreasing respiratory support in patients with developing BPD without major complications. Randomized studies are warranted to confirm our findings.

Recent advances in preclinical and clinical multimodal MR in the newborn brain

Aside from injury identification, MRI of the newborn brain has given us insight into cortical and white matter development, identified windows of vulnerabilities, enabled the introduction of therapeutic hypothermia which has become the standard of care in neonatal asphyxia, and is fostering leapfrogging discoveries in the field of neuro-genetics. This article reviews the main advances in recent years in newborn brain imaging both in preclinical and clinical research.

Cerebellar injury in preterm infants

Although preterm birth is best known to result in adverse neurodevelopmental outcomes through injury of the supratentorial structures, including intraventricular hemorrhage and periventricular leukomalacia, the cerebellum has become increasingly recognized as an important target for injury and adverse motor and cognitive outcomes. Undergoing the most dramatic growth during the preterm period, the cerebellum is vulnerable to large and small hemorrhages, as well as hypoplasia resulting from a number of potentially modifiable risk factors. These factors include contact with intraventricular blood, crossed cerebrocerebellar diaschisis, postnatal glucocorticoid exposure, pain and opioid exposure, nutrition and somatic growth, cardiorespiratory factors, and socioeconomic status. Strategies targeting these factors may result in prevention of the motor and cognitive deficits seen after cerebellar hemorrhage or hypoplasia.

An evaluation of hydrocortisone dosing for neonatal refractory hypotension

OBJECTIVE

The objective of the study was to compare blood pressure, vasoactive medication requirements and adverse outcomes after administration of high- versus low-dose hydrocortisone (HC) in preterm infants.

STUDY DESIGN

This is a retrospective analysis of 106 infants ⩽28 weeks gestational age with hypotension requiring vasoactive infusions and high-dose (4 mg kg^-1 per day, n=50), low-dose (1 to 3 mg kg^-1 per day, n=20) or no HC (n=36) from 2011 to 2015. Groups were compared by two-tailed t-test or χ², and correlation estimated by multivariable logistic regression.

RESULTS

There were no differences in measured efficacy between the low- and high-dose groups. Infants with pre-treatment cortisol >15 mcg dl^-1 who received HC therapy showed less improvement in vasoactive burden, increased hyperglycemia (P=0.015) and increased death independent of HC dose (odds ratio 26.3, 3.5 to 198.3, P=0.002).

CONCLUSION

These results support using the lowest effective HC dose in preterm infants. In addition, HC therapy should likely be avoided in infants who are not cortisol deficient.

Brain Lesions among Orally Fed and Gastrostomy-Fed Dysphagic Preterm Infants: Can Routine Qualitative or Volumetric Quantitative Magnetic Resonance Imaging Predict Feeding Outcomes?

INTRODUCTION

The usefulness of qualitative or quantitative volumetric magnetic resonance imaging (MRI) in early detection of brain structural changes and prediction of adverse outcomes in neonatal illnesses warrants further investigation. Our aim was to correlate certain brain injuries and the brain volume of feeding-related cortical and subcortical regions with feeding method at discharge among preterm dysphagic infants.

MATERIALS AND METHODS

Using a retrospective observational study design, we examined MRI data among 43 (22 male; born at 31.5 ± 0.8 week gestation) infants who went home on oral feeding or gastrostomy feeding (G-tube). MRI scans were segmented, and volumes of brainstem, cerebellum, cerebrum, basal ganglia, thalamus, and vermis were quantified, and correlations were made with discharge feeding outcomes. Chi-squared tests were used to evaluate MRI findings vs. feeding outcomes. ANCOVA was performed on the regression model to measure the association of maturity and brain volume between groups.

RESULTS

Out of 43 infants, 44% were oral-fed and 56% were G-tube fed at hospital discharge (but not at time of the study). There was no relationship between qualitative brain lesions and feeding outcomes. Volumetric analysis revealed that cerebellum was greater (p < 0.05) in G-tube fed infants, whereas cerebrum volume was greater (p < 0.05) in oral-fed infants. Other brain regions did not show volumetric differences between groups.

CONCLUSION

This study concludes that neither qualitative nor quantitative volumetric MRI findings correlate with feeding outcomes. Understanding the complexity of swallowing and feeding difficulties in infants warrants a comprehensive and in-depth functional neurological assessment.

Hydrocortisone use in ventilated extremely preterm infants decreased bronchopulmonary dysplasia with no effects on neurodevelopment after two years

AIM

We assessed the outcomes of ventilated extremely premature infants treated with late postnatal corticosteroids from 2005-2008, according to permissive or restrictive policies in two centres.

METHODS

This retrospective study included inborn infants below 27 weeks of gestational age who were ventilator dependent after 14 days. Centre P permitted postnatal corticosteroids but centre R restricted their use. The effects on infants were assessed in hospital and after two years using multivariable analysis.

RESULTS

We compared 62 infants from centre P, including 92% who received hydrocortisone, and 48 infants from centre R, including 13% who received betamethasone. Infants from both centres had comparable baseline characteristics and perinatal management, but bronchopulmonary dysplasia (BPD) rates were significantly lower in centre P (30% versus 71%, p < 0.001) and this centre was significantly associated with a younger post-conceptional age at oxygen weaning, with an adjusted hazard ratio (aHR) of 0.45 and an aHR of 0.51at discharge. At two years of corrected age, 18% of centre P infants and 30% of centre R infants showed poor neurodevelopmental outcome (p = 0.18).

CONCLUSION

Using hydrocortisone after 14 days on ventilated extremely preterm infants was associated with decreased BPD, with no apparent effects on neurodevelopment at two years of corrected age.

New means to assess neonatal inflammatory brain injury

Preterm infants are especially vulnerable to infection-induced white matter injury, associated with cerebral palsy, cognitive and psychomotor impairment, and other adverse neurological outcomes. The etiology of such lesions is complex and multifactorial. Furthermore, timing and length of exposure to infection also influence neurodevelopmental outcomes. Different mechanisms have been posited to mediate the observed brain injury including microglial activation followed by subsequent release of pro-inflammatory species, glutamate-induced excitotoxicity, and vulnerability of developing oligodendrocytes to cerebral insults. The prevalence of such neurological impairments requires an urgent need for early detection and effective neuroprotective strategies. Accordingly, noninvasive methods of monitoring disease progression and therapy effectiveness are essential. While diagnostic tools using biomarkers from bodily fluids may provide useful information regarding potential risks of developing neurological diseases, the use of magnetic resonance imaging/spectroscopy has emerged as a promising candidate for such purpose. Various pharmacological agents have demonstrated protective effects in the immature brain in animal models; however, few studies have progressed to clinical trials with promising results.

Neurodevelopmental Outcomes of Extremely Preterm Infants Randomized to Stress Dose Hydrocortisone

Objective

To compare the effects of stress dose hydrocortisone therapy with placebo on survival without neurodevelopmental impairments in high-risk preterm infants.

Study Design

We recruited 64 extremely low birth weight (birth weight ≤1000g) infants between the ages of 10 and 21 postnatal days who were ventilator-dependent and at high-risk for bronchopulmonary dysplasia. Infants were randomized to a tapering 7-day course of stress dose hydrocortisone or saline placebo. The primary outcome at follow-up was a composite of death, cognitive or language delay, cerebral palsy, severe hearing loss, or bilateral blindness at a corrected age of 18–22 months. Secondary outcomes included continued use of respiratory therapies and somatic growth.

Results

Fifty-seven infants had adequate data for the primary outcome. Of the 28 infants randomized to hydrocortisone, 19 (68%) died or survived with impairment compared with 22 of the 29 infants (76%) assigned to placebo (relative risk: 0.83; 95% CI, 0.61 to 1.14). The rates of death for those in the hydrocortisone and placebo groups were 31% and 41%, respectively (P = 0.42). Randomization to hydrocortisone also did not significantly affect the frequency of supplemental oxygen use, positive airway pressure support, or need for respiratory medications.

Conclusions

In high-risk extremely low birth weight infants, stress dose hydrocortisone therapy after 10 days of age had no statistically significant effect on the incidence of death or neurodevelopmental impairment at 18–22 months. These results may inform the design and conduct of future clinical trials.

Trial Registration

ClinicalTrials.gov NCT00167544

Dexamethasone but not the equivalent doses of hydrocortisone induces neurotoxicity in neonatal rat brain

BACKGROUND

The use of dexamethasone (Dex) in premature infants to treat or prevent chronic lung disease adversely affects neurodevelopment. Recent clinical studies suggest that hydrocortisone (HC) is a safer alternative to Dex. We compared the effects of Dex and HC on neurotoxicity in newborn rats.

METHODS

Rat pups of a neurodevelopmental stage equivalent to premature human neonates were administered Dex or HC either as a single dose on postnatal day (PD) 6, repeated doses on PD 4 to 6 or tapering doses at PD 3 to 6 by i.p. injection. Brain weight, caspase-3 activity, and apoptotic cells were measured at PD 7; learning capability, memory, and motor function were measured at juvenile age.

RESULTS

Dex decreased both body and brain weight gain, while HC did not. Tapering and repeated doses of Dex increased caspase-3 activity, cleaved caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells but HC, except at high doses, did not. Dex impaired learning and memory capability at juvenile age, while the rats exposed to HC showed normal cognitive behavior.

CONCLUSION

HC is probably safer to use than Dex in the immediate postnatal period in neonatal rats. Cautious extrapolation of these findings to human premature infants is required.

Bronchopulmonary dysplasia is associated with delayed structural brain maturation in preterm infants

BACKGROUND

In recent years, cerebral magnetic resonance imaging (MRI) has been increasingly used to depict the wide spectrum of preterm brain injury. Furthermore, it has already been demonstrated by MRI at term-equivalent age (TEA) that preterm infants show delayed brain maturation as compared to term infants, and this delay has been related to neurobehavioral outcome.

OBJECTIVES

The aim of the current study was to investigate the influence of prevalent neonatal risk factors for adverse outcome on structural brain maturation in very preterm infants at TEA.

METHODS

One hundred and thirty very preterm infants born at a mean gestational age of 29.7 weeks were included. MRI was performed at TEA and given a validated 'total maturation score'. Brain maturation scores were compared with neonatal data.

RESULTS

In univariate analysis, bronchopulmonary dysplasia (BPD), late-onset sepsis and retinopathy of prematurity were significantly associated with delayed brain maturation. Furthermore, infants with delayed maturation had been ventilated significantly longer and more often suffered from severe arterial hypotension. In multivariate analysis, BPD remained significant as predictor of delayed brain maturation.

CONCLUSIONS

This study is the first to show that delayed structural brain maturation as evaluated by MRI at TEA is preceded by BPD, which is known to be a predictor of adverse outcome in preterm infants. This finding adds further evidence to show that adverse outcome in preterm infants may have additional neural correlates that exceed common brain injury.

Glucocorticoids promote neural progenitor cell proliferation derived from human induced pluripotent stem cells

Glucocorticoids (GCs) are frequently used for treating and preventing chronic lung disease and circulatory dysfunction in premature infants. However, there is growing concern about the detrimental effects of systemic GC administration on neurodevelopment. The first choice of GCs to minimize the adverse effects on the developing brain is still under debate. We investigated the effect of commonly used GCs such as dexamethasone (DEX), betamethasone (BET) and hydrocortisone (HDC) on the proliferation of human-induced pluripotent stem cell (iPSC)-derived neuronal progenitor cells (NPCs). In this study, NPCs were treated with various concentrations of GCs and subjected to cell proliferation assays. Furthermore, we quantified the number of microtubule-associated protein 2 (MAP2) positive neurons in NPCs by immunostaining. All GCs promoted NPC proliferation in a dose-dependent manner. We also confirmed that MAP2-positive neurons in NPCs increased upon GC treatment. However, differential effects of GCs on MAP2 positive neurons were observed when we treated NPCs with H₂O₂. The total numbers of NPCs increased upon any GC treatment even under oxidative conditions but the numbers of MAP2 positive neurons increased only by HDC treatment. GCs promoted human iPSCs–derived NPC proliferation and the differential effects of GCs became apparent under oxidative stress. Our results may support HDC as the preferred choice over DEX and BET to prevent adverse effects on the developing human brain.

Glucocorticoid Induced Cerebellar Toxicity in the Developing Neonate: Implications for Glucocorticoid Therapy during Bronchopulmonary Dysplasia

Prematurely born infants commonly suffer respiratory dysfunction due to the immature state of their lungs. As a result, clinicians often administer glucocorticoid (GC) therapy to accelerate lung maturation and reduce inflammation. Unfortunately, several studies have found GC therapy can also produce neuromotor/cognitive deficits and selectively stunt the cerebellum. However, despite its continued use, relatively little is known about how exposure to this hormone might produce neurodevelopmental deficits. In this review, we use rodent and human research to provide evidence that GC therapy may disrupt cerebellar development through the rapid induction of apoptosis in the cerebellar external granule layer (EGL). The EGL is a transient proliferative region responsible for the production of over 90% of the neurons in the cerebellum. During normal development, endogenous GC stimulation is thought to selectively signal the elimination of the EGL once production of new neurons is complete. As a result, GC therapy may precociously eliminate the EGL before it can produce enough neurons for normal cerebellar function. It is hoped that this review may provide information for future clinical research in addition to translational guidance for the safer use of GC therapy.

Association between postnatal dexamethasone for treatment of bronchopulmonary dysplasia and brain volumes at adolescence in infants born very preterm

OBJECTIVES

To compare brain volumes in adolescents who were born extremely preterm (<28 weeks gestation) who had received postnatal dexamethasone, and to determine if there was a postnatal dexamethasone dose-response effect on brain volumes.

STUDY DESIGN

Geographical cohort study of extremely preterm adolescents born in 1991-1992 in Victoria, Australia. T1-weighted magnetic resonance imaging was performed at 18 years of age. Segmented and parcellated brain volumes were calculated using an automated segmentation method (FreeSurfer) and compared between groups, with and without adjustment for potential confounders. The relationships between total postnatal dexamethasone dose and brain volumes were explored using linear regression.

RESULTS

Of the 148 extremely preterm participants, 55 (37%) had received postnatal dexamethasone, with a cumulative mean dose of 7.7 mg/kg. Compared with participants who did not receive postnatal dexamethasone, those who did had smaller total brain tissue volumes (mean difference -3.6%, 95% CI [-7.0%, -0.3%], P value = .04) and smaller white matter, thalami, and basal ganglia volumes (all P < .05). There was a trend of smaller total brain and white matter volumes with increasing dose of postnatal dexamethasone (regression coefficient -7.7 [95% CI -16.2, 0.8] and -3.2 [-6.6, 0.2], respectively).

CONCLUSIONS

Extremely preterm adolescents who received postnatal dexamethasone in the newborn period had smaller total brain tissue volumes than those who did not receive postnatal dexamethasone, particularly white matter, thalami, and basal ganglia. Vulnerability of brain tissues or structures associated with postnatal dexamethasone varies by structure and persists into adolescence.

Evidence for adverse effect of perinatal glucocorticoid use on the developing brain

The use of glucocorticoids (GCs) in the perinatal period is suspected of being associated with adverse effects on long-term neurodevelopmental outcomes for preterm infants. Repeated administration of antenatal GCs to mothers at risk of preterm birth may adversely affect fetal growth and head circumference. Fetal exposure to excess GCs during critical periods of brain development may profoundly modify the limbic system (primarily the hippocampus), resulting in long-term effects on cognition, behavior, memory, co-ordination of the autonomic nervous system, and regulation of the endocrine system later in adult life. Postnatal GC treatment for chronic lung disease in premature infants, particularly involving the use of dexamethasone, has been shown to induce neurodevelopmental impairment and increases the risk of cerebral palsy. In contrast to studies involving postnatal dexamethasone, long-term follow-up studies for hydrocortisone therapy have not revealed adverse effects on neurodevelopmental outcomes. In experimental studies on animals, GCs has been shown to impair neurogenesis, and induce neuronal apoptosis in the immature brains of newborn animals. A recent study has demonstrated that dexamethasone-induced hypomyelination may result from the apoptotic degeneration of oligodendrocyte progenitors in the immature brain. Thus, based on clinical and experimental studies, there is enough evidence to advice caution regarding the use of GCs in the perinatal period; and moreover, the potential long-term effects of GCs on brain development need to be determined.

Steroids and injury to the developing brain: net harm or net benefit?

Deleterious effects result from both glucocorticoid insufficiency and excess glucocorticoid tissue exposure in the developing brain. Accumulating evidence suggests a net benefit of postnatal glucocorticoid therapy when administered shortly after the first week of life to premature infants with early and persistent pulmonary dysfunction, particularly in those with evidence of relative adrenal insufficiency. The decision to treat with steroids should ensure maximum respiratory benefit at the lowest possible neurologic risk, while avoiding serious systemic complications. Ongoing clinical trials must validate this approach.

Inflammatory injury to the neonatal brain - what can we do?

Perinatal brain damage is one of the leading causes of life long disability. This damage could be hypoxic-ischemic, inflammatory, or both. This mini-review discusses different interventions aiming at minimizing inflammatory processes in the neonatal brain, both before and after insult. Current options of anti-inflammatory measures for neonates remain quite limited. We describe current anti-inflammatory intervention strategies such as avoiding perinatal infection and inflammation, and reducing exposure to inflammatory processes. We describe the known effects of anti-inflammatory drugs such as steroids, antibiotics, and indomethacin, and the possible anti-inflammatory role of other substances such as IL-1 receptor antagonists, erythropoietin, caffeine, estradiol, insulin-like growth factor, and melatonin as well as endogenous protectors, and genetic regulation of inflammation. If successful, these may decrease mortality and long-term morbidity among term and pre-term infants.

Hydrocortisone treatment for bronchopulmonary dysplasia and brain volumes in preterm infants

OBJECTIVE

To assess whether there was an adverse effect on brain growth after hydrocortisone (HC) treatment for bronchopulmonary dysplasia (BPD) in a large cohort of infants without dexamethasone exposure.

STUDY DESIGN

Infants who received HC for BPD between 2005 and 2011 and underwent magnetic resonance imaging at term-equivalent age were included. Control infants born in Geneva (2005-2006) and Utrecht (2007-2011) were matched to the infants treated with HC according to segmentation method, sex, and gestational age. Infants with overt parenchymal pathology were excluded. Multivariable analysis was used to determine if there was a difference in brain volumes between the 2 groups.

RESULTS

Seventy-three infants treated with HC and 73 matched controls were included. Mean gestational age was 26.7 weeks, and mean birth weight was 906 g. After correction for gestational age, postmenstrual age at time of scanning, the presence of intraventricular hemorrhage, and birth weight z-score, no differences were found between infants treated with HC and controls in total brain tissue or cerebellar volumes.

CONCLUSIONS

In the absence of associated parenchymal brain injury, no reduction in brain tissue or cerebellar volumes could be found at term-equivalent age between infants with or without treatment with HC for BPD.

Potential mechanisms of cerebellar hypoplasia in prematurity

INTRODUCTION

The cerebellum undergoes dramatic growth and maturation over the neonatal period after preterm birth and is thus particularly sensitive to impaired development due to various clinical factors.

METHODS

Impairments in growth can occur independent of cerebellar parenchymal damage, such as from local hemorrhage, resulting from reduced expression of sonic hedgehog signaling to trigger the appropriate expansion of the granule precursor cells.

RESULTS

The primary risk factors for impaired cerebellar development include postnatal glucocorticoid exposure, which has direct effects on the sonic hedgehog pathway, and supratentorial brain injury, including intraventricular hemorrhage and white matter injury, which may result in crossed cerebellar diaschisis and local toxic effects of blood products on the external granular layer. Other cardiorespiratory and nutritional factors may also exist. Impaired cerebellar development is associated with adverse outcomes in motor and cognitive development.

CONCLUSION

New approaches to care to counteract these risk factors may help improve long-term outcome after preterm birth.

Early life intervention with glucocorticoids has negative effects on motor development and neuropsychological function in 14-17 year-old adolescents

OBJECTIVE

To reduce the risk of bronchopulmonary dysplasia, preterm infants receive neonatal treatment with glucocorticoids, mostly dexamethasone (DEX). Compared to current protocols, treatment regimens of the late 1980s - early 1990s prescribed high doses of DEX for an extensive period up to 6 weeks. Worldwide at least one million children have been treated with this dose regimen. Previous studies have shown adverse effects of neonatal treatment with the glucocorticoid dexamethasone (DEX) on outcome in children aged 7-10 years. On the other hand, treatment with another glucocorticoid, hydrocortisone (HC), was not related to adverse effects in childhood. In the current study we determined the consequences of early life intervention with DEX or HC in adolescents (age 14-17 years). Besides motor function and intellectual capacities, we also examined fundamental neuropsychological functions which have so far received little attention.

METHODS

In an observational cohort study we compared 14-17 year-old adolescents who received DEX (.5 mg/kg/day tapering off to .1 mg/kg/day over 21 days, n=63), or HC (5 mg/kg/day tapering off to 1 mg/kg/day over 22 days, n=67), or did not receive neonatal glucocorticoids (untreated, n=71) after premature birth (gestational age<32 weeks). Because gestational age was shorter and duration of ventilation was longer in the DEX-treated group, all analyses were corrected for these potential confounders. Motor function, IQ, and neuropsychological functions were assessed.

RESULTS

DEX-treated group participants scored lower on gross motor skill tasks than their HC-treated and untreated counterparts. A higher proportion of DEX-treated girls needed special education compared to the other groups. DEX-treated adolescents performed poorer on neuropsychological tasks measuring alertness, visuomotor coordination, and emotion recognition. The HC-treated group did not differ from the untreated group.

CONCLUSIONS

Even after 14-17 years, neonatal treatment with .5 mg/kg/day DEX was associated with adverse effects on motor function, school level, and neuropsychological functions, whereas treatment with the clinically equally effective dose of 5 mg/kg/day HC was not. Potential physiological mechanisms underlying the differences in dexamethasone and hydrocortisone effects are discussed. Based on the current findings, we recommend early identification of neuropsychological deficits after DEX treatment in order to specify extra educational needs.

Pilot randomized trial of hydrocortisone in ventilator-dependent extremely preterm infants: effects on regional brain volumes

OBJECTIVE

To test the hypothesis that high-risk ventilator-dependent extremely low birth weight (birth weight ≤1000 g) infants treated with 7 days of hydrocortisone will have larger total brain tissue volumes than placebo treated infants.

STUDY DESIGN

A predetermined sample size of 64 extremely low birth weight infants, between 10-21 days old and ventilator-dependent with a respiratory index score ≥2, were randomized to systemic hydrocortisone (17 mg/kg cumulative dose) or saline placebo. Primary outcome was total brain tissue volume. Volumetric magnetic resonance imaging was performed at 38 weeks postmenstrual age; brain tissue regions were segmented and quantified automatically with a high degree of accuracy and 9 structures were segmented manually. All analyses of regional brain volumes were adjusted by postmenstrual age at magnetic resonance imaging scan.

RESULTS

The study groups were similar at baseline and 8 infants died in each arm. Unadjusted total brain tissue volume (mean ± SD) in the hydrocortisone (N = 23) and placebo treated infants (N = 21) was 272 ± 40.3 cm(3) and 277.8 ± 59.1 cm(3), respectively (adjusted mean difference: 6.35 cm(3) (95% CI: (-20.8, 32.5); P = .64). Three of the 31 hydrocortisone treated infants and 5 of the 33 placebo treated infants survived without severe bronchopulmonary dysplasia (relative risk 0.62, 95% CI: 0.13, 2.66; P = .49). No significant differences were noted in prespecified secondary outcomes of regional structural volumes or days on respiratory support. No adverse effects of hydrocortisone were observed.

CONCLUSIONS

Low dose hydrocortisone in high-risk ventilator-dependent infants after a week of age had no discernible effect on regional brain volumes or pulmonary outcomes prior to neonatal intensive care unit discharge.

Hydrocortisone and long-term outcomes in very-low-birthweight infants

BACKGROUND

The long-term effects of hydrocortisone (HDC) used for very-low-birthweight (VLBW) infants with chronic lung disease (CLD) are not fully understood. The aim of this study was to examine the short-term clinical effects and long-term impact of a physiological replacement dose of HDC on acute deterioration of CLD in VLBW infants.

METHODS

This prospective case-control study included 110 of the 174 VLBW infants admitted to our facility between 2003 and 2006 who were followed up to a corrected age of 18 months. Infant deaths and infants with congenital deformities were excluded from the study. The infants were classified into the following three groups: infants with CLD and treated with HDC (1-2 mg/kg/dose) due to progressive deterioration in oxygenation (CLD treatment group; n = 24); infants with CLD but not treated with HDC (CLD untreated group; n = 40); and infants without CLD (non-CLD group; n = 46).

RESULTS

The fraction of inspired oxygen (F(I) O(2) ) in the CLD treatment group improved significantly after treatment (P < 0.01). There were no significant differences among the three groups in terms of growth and neurodevelopmental quotient at the corrected age of 18 months following adjustment for birthweight, sex, and presence of light-for-date infants. There were also no significant intergroup differences in all three areas of developmental quotient.

CONCLUSIONS

Physiological doses of HDC replacement are effective in treating acute deterioration in oxygenation in VLBW infants with CLD. Furthermore, this treatment modality did not adversely affect the growth and development of infants at the corrected age of 18 months.

Cooperativity and complementarity: synergies in non-classical and classical glucocorticoid signaling

Glucocorticoids (GCs) are an ubiquitous class of steroid hormones that exert a wide array of physiological effects. Traditionally, GC action has been considered to primarily involve transcriptional effects following the binding of hormone to the glucocorticoid receptor (GR) and subsequent activation or repression of target genes. However, a number of findings suggest that cellular responses following GC exposure may be mediated by transcription-independent, or "non-classical," mechanisms. We have added to this growing body of work by recently uncovering a novel GC signaling pathway that operates through plasma membrane GRs to limit gap junction intercellular signaling and limit the proliferation of neural progenitor cells (NPCs). In this review, we highlight our current state of knowledge of non-classical GR signaling, in particular as it applies to neuronal function. Using NPCs as a cellular model, we speculate on the components of this non-classical pathway and the mechanisms whereby a number of cytoplasmic and nuclear signaling events may be integrated.

Brain tissue volumes in preterm infants: prematurity, perinatal risk factors and neurodevelopmental outcome: a systematic review

OBJECTIVE

To evaluate the clinical value of neonatal brain tissue segmentation in preterm infants according to the literature.

METHODS

A structured literature search was undertaken in MEDLINE/Pubmed. This included all publications on volumetric brain tissue assessment in preterm infants at term-equivalent age (TEA) compared to brain tissue volumes of term-born infants, related to perinatal risk factors or related to neurodevelopmental outcome.

RESULTS

Sixteen prospective cohort studies, described in 30 articles, fulfilled the criteria. Preterm infants displayed total and regional brain tissue alterations compared to healthy, term-born controls. These alterations seemed more prominent with decreasing gestational age. White matter injury, intraventricular haemorrhage, postnatal corticosteroid therapy, intra-uterine growth retardation and chronic lung disease were frequently associated with volume changes. Associations between volume alterations at TEA and neurodevelopmental outcome in early childhood were shown in a few studies.

CONCLUSIONS

Preterm birth is associated with brain tissue volume alterations that become more pronounced in the presence of perinatal risk factors and white matter injury. Moreover, associations between volumetric alterations as early as TEA and long-term neurodevelopmental impairments are scarce.

Preterm cerebellar growth impairment after postnatal exposure to glucocorticoids

As survival rates of preterm newborns improve as a result of better medical management, these children increasingly show impaired cognition. These adverse cognitive outcomes are associated with decreases in the volume of the cerebellum. Because animals exhibit reduced preterm cerebellar growth after perinatal exposure to glucocorticoids, we sought to determine whether glucocorticoid exposure and other modifiable factors increased the risk for these adverse outcomes in human neonates. We studied 172 preterm neonatal infants from two medical centers, the University of British Columbia and the University of California, San Francisco, by performing serial magnetic resonance imaging examinations near birth and again near term-equivalent age. After we adjusted for associated clinical factors, antenatal betamethasone was not associated with changes in cerebellar volume. Postnatal exposure to clinically routine doses of hydrocortisone or dexamethasone was associated with impaired cerebellar, but not cerebral, growth. Alterations in treatment after preterm birth, particularly glucocorticoid exposure, may help to decrease risk for adverse neurological outcome after preterm birth.

Common lesions in the newborn brain

With the wider use of magnetic resonance imaging, the recognition of different patterns of injury has become established. These patterns vary in relation to the level of immaturity of the infant. This review will outline the major patterns of abnormality that are found in the term born and preterm infant.

Inotropes in preterm infants--evidence for and against

There is significant uncertainty regarding the optimal circulatory management of preterm infants, with research in the field limited by the paucity of safe, reproducible biomarkers of circulatory function. This review discusses the physiology and pathophysiology of circulatory function in preterm infants, describes the mode of action and evidence for and against commonly used and recently trialled inotropic therapies and provides recommendations for managing circulatory dysfunction in the transitional period and in the context of sepsis/necrotizing enterocolitis. We recommend a pragmatic approach of assessing multiple aspects of circulatory function (blood pressure alone correlates weakly with volume of flow) in each infant, tailoring therapy on the basis of the change in function desired and frequently reassessing response to intervention.

Cerebellar volume and proton magnetic resonance spectroscopy at term, and neurodevelopment at 2 years of age in preterm infants

AIM

To assess the relation between cerebellar volume and spectroscopy at term equivalent age, and neurodevelopment at 24 months corrected age in preterm infants.

METHODS

Magnetic resonance imaging of the brain was performed around term equivalent age in 112 preterm infants (mean gestational age 28wks 3d [SD 1wk 5d]; birthweight 1129g [SD 324g]). Cerebellar volume (60 males, 52 females), and proton magnetic resonance spectroscopy ((1) H-MRS) of the cerebellum in a subgroup of 58 infants were assessed in relation to cognitive, fine motor, and gross motor scores on the Bayley Scales of Infant and Toddler Development-III. Different neonatal variables and maternal education were regarded possible confounders.

RESULTS

Cerebellar volume was significantly associated with postmenstrual age at time of magnetic resonance imaging. Cerebellar volume corrected for postmenstrual age was significantly and positively associated with cognition. Cognitive scores related significantly with N-acetylaspartate/choline (NAA/Cho) ratio obtained from cerebellar (1) H-MRS in 53 infants. Correction for neonatal and maternal variables did not change these results. Cerebellar variables were not related to motor performance.

INTERPRETATION

In preterm infants, both cerebellar volume and cerebellar NAA/Cho ratio at term equivalent age were positively associated with cognition; however, no relation was found with motor outcome at 2 years of age. These findings support the importance of the cerebellum in cognitive development in preterm infants.

Regulation of corticoid and serotonin receptor brain system following early life exposure of glucocorticoids: long term implications for the neurobiology of mood

Potent glucocorticoids (GC) administered early in life have improved premature infant survival dramatically. However, these agents may increase the risk for physical, neurological and behavior alterations. Anxiety, depression and attention difficulties are commonly described in adolescent and young adult survivors of prematurity. In the present study we administered vehicle, dexamethasone, or hydrocortisone to Sprague-Dawley rat pups on postnatal days 5 and 6, mimicking a short term clinical protocol commonly used in human infants. Two systems that are implicated in the regulation of stress and behavior were assessed: the limbic-hypothalamic-pituitary-adrenal axis [LHPA; glucocorticoid and mineralocorticoid receptors within] and the Serotonin (5-HT) system. We found that as adults, male Sprague-Dawley pups treated with GC showed agent specific altered growth, anxiety-related behavior, changes in corticoid response to novelty and gene expression changes within LHPA and 5-HT-related circuitry. The data suggest that prolonged GC-receptor stimulation during the early neonatal period can contribute to the development of individual differences in stress response and anxiety-related behavior later in life.

Perinatal cerebellar injury in human and animal models

Cerebellar injury is increasingly recognized through advanced neonatal brain imaging as a complication of premature birth. Survivors of preterm birth demonstrate a constellation of long-term neurodevelopmental deficits, many of which are potentially referable to cerebellar injury, including impaired motor functions such as fine motor incoordination, impaired motor sequencing and also cognitive, behavioral dysfunction among older patients. This paper reviews the morphogenesis and histogenesis of the human and rodent developing cerebellum, and its more frequent injuries in preterm. Most cerebellar lesions are cerebellar hemorrhage and infarction usually leading to cerebellar abnormalities and/or atrophy, but the exact pathogenesis of lesions of the cerebellum is unknown. The different mechanisms involved have been investigated with animal models and are primarily hypoxia, ischemia, infection, and inflammation Exposure to drugs and undernutrition can also induce cerebellar abnormalities. Different models are detailed to analyze these various disturbances of cerebellar development around birth.

Hydrocortisone vs. dexamethasone treatment for bronchopulmonary dysplasia and their effects on general movements in preterm infants

INTRODUCTION

Hydrocortisone (HC) and dexamethasone (DXM) are used to treat preterm infants at risk for bronchopulmonary dysplasia (BPD). This may, however, affect their long-term neurological development. We aimed to determine the effect of HC and DXM therapy in preterm infants on neurological functioning as assessed by the quality of general movements (GMs) until 3 months after term.

RESULTS

We found no difference in the quality of GMs between HC and DXM infants until term age. At 3 months, HC infants had a higher median motor optimality score (MOS) than DXM infants (25 vs. 21, P = 0.015). In the DXM group, MOS on the first day of treatment was lower than before treatment (10 vs. 11, P = 0.030).

DISCUSSION

MOS decreased in DXM infants on the first day following treatment and at 3 months after term. This was not the case in HC infants. Our study suggests that neurological functioning at 3 months after term is better in infants treated with HC than in infants treated with DXM.

METHODS

We performed a longitudinal, observational study including 56 preterm infants (n = 17 HC, n = 17 DXM, n = 22 controls). GM quality, videoed before and after treatment, was assessed. In addition, a MOS was assigned to details of the GMs.

Pulmonary effects of neonatal hydrocortisone treatment in ventilator-dependent preterm infants

Background/Objective. Hydrocortisone, administered to ventilated preterm neonates to facilitate extubation, has no adverse long-term effects, but short-term pulmonary effects have not been described previously. In the present study, we analyzed effects of hydrocortisone on ventilator settings and FiO₂ in ventilator-dependent preterm infants. Patients and Methods. Fifty-five preterm children were included in this retrospective cohort study. Hydrocortisone was administered at a postnatal age of > 7 days to treat chronic lung disease (CLD). Ventilator settings before and after hydrocortisone administration were recorded as well as FiO₂ at 36 weeks' gestational age. Presence of cerebral palsy was assessed at a mean corrected age of 24.1 months. Results. Hydrocortisone administered at a median postnatal age of 14 days significantly reduced FiO₂ from a median of 0.39 to 0.30, mean airway pressure (MAP) from a median of 10.0 cm H₂O to 7.6 cm H₂O, and PaCO₂ from a median of 53.5 mmHg to 47 mmHg. Extubation was achieved in all patients. CLD at 36 weeks was present in 11 of the 52 patients (21.1%). None developed cerebral palsy. Conclusions. Hydrocortisone was effective in reducing the FiO₂, MAP, and PaCO₂ and facilitated extubation. Hydrocortisone was not associated with cerebral palsy.

[Brain development of infant and MRI by diffusion tensor imaging]

Studying how the brain develops and becomes functional is important to understand how the man has been able to develop specific cognitive abilities, and to comprehend the complexity of some developmental pathologies. Thanks to magnetic resonance imaging (MRI), it is now possible to image the baby's immature brain and to consider subtle correlations between the brain anatomical development and the early acquisition of cognitive functions. Dedicated methodologies for image acquisition and post-treatment must then be used because the size of cerebral structures and the image contrast are very different in comparison with the adult brain, and because the examination length is a major constraint. Two recent studies have evaluated the developing brain under an original perspective. The first one has focused on cortical folding in preterm newborns, from 6 to 8 months of gestational age, assessed with T2-weighted conventional MRI. The second study has mapped the organization and maturation of white matter fiber bundles in 1- to 4-month-old healthy infants with diffusion tensor imaging (DTI). Both studies have enabled to highlight spatio-temporal differences in the brain regions' maturation, as well as early anatomical asymmetries between cerebral hemispheres. These studies emphasize the potential of MRI to evaluate brain development compared with the infant's psychomotor acquisitions after birth.

Glucocorticoid receptor stimulation and the regulation of neonatal cerebellar neural progenitor cell apoptosis

Glucocorticoids are used to treat respiratory dysfunction associated with premature birth but have been shown to cause neurodevelopmental deficits when used therapeutically. Recently, we established that acute glucocorticoid exposure at clinically relevant doses produces neural progenitor cell apoptosis in the external granule layer of the developing mouse cerebellum and permanent decreases in the number of cerebellar neurons. As the cerebellum naturally matures and neurogenesis is no longer needed, the external granule layer decreases proliferation and permanently disappears during the second week of life. At this same time, corticosterone (the endogenous rodent glucocorticoid) release increases and a glucocorticoid-metabolizing enzyme that protects the external granule layer against glucocorticoid receptor stimulation (11β-Hydroxysteroid-Dehydrogenase-Type 2; HSD2) naturally disappears. Here we show that HSD2 inhibition and raising corticosterone to adult physiological levels both can independently increase neural progenitor cell apoptosis in the neonatal mouse. Conversely, glucocorticoid receptor antagonism decreases natural physiological apoptosis in this same progenitor cell population suggesting that endogenous glucocorticoid stimulation may regulate apoptosis in the external granule layer. We also found that glucocorticoids which HSD2 can effectively metabolize generate less external granule layer apoptosis than glucocorticoids this enzyme is ineffective at breaking down. This finding may explain why glucocorticoids that this enzyme can metabolize are clinically effective at treating respiratory dysfunction yet seem to produce no neurodevelopmental deficits. Finally, we demonstrate that both acute and chronic glucocorticoid exposures produce external granule layer apoptosis but without appropriate control groups this effect becomes masked. These results are discussed in terms of their implications for glucocorticoid therapy and neurodevelopment during the perinatal period.

Comprehensive brain MRI segmentation in high risk preterm newborns

Most extremely preterm newborns exhibit cerebral atrophy/growth disturbances and white matter signal abnormalities on MRI at term-equivalent age. MRI brain volumes could serve as biomarkers for evaluating the effects of neonatal intensive care and predicting neurodevelopmental outcomes. This requires detailed, accurate, and reliable brain MRI segmentation methods. We describe our efforts to develop such methods in high risk newborns using a combination of manual and automated segmentation tools. After intensive efforts to accurately define structural boundaries, two trained raters independently performed manual segmentation of nine subcortical structures using axial T2-weighted MRI scans from 20 randomly selected extremely preterm infants. All scans were re-segmented by both raters to assess reliability. High intra-rater reliability was achieved, as assessed by repeatability and intra-class correlation coefficients (ICC range: 0.97 to 0.99) for all manually segmented regions. Inter-rater reliability was slightly lower (ICC range: 0.93 to 0.99). A semi-automated segmentation approach was developed that combined the parametric strengths of the Hidden Markov Random Field Expectation Maximization algorithm with non-parametric Parzen window classifier resulting in accurate white matter, gray matter, and CSF segmentation. Final manual correction of misclassification errors improved accuracy (similarity index range: 0.87 to 0.89) and facilitated objective quantification of white matter signal abnormalities. The semi-automated and manual methods were seamlessly integrated to generate full brain segmentation within two hours. This comprehensive approach can facilitate the evaluation of large cohorts to rigorously evaluate the utility of regional brain volumes as biomarkers of neonatal care and surrogate endpoints for neurodevelopmental outcomes.

Insights into early brain development from modern brain imaging and outcome studies

Recent brain imaging and outcome studies of infants born at very early gestation have cast new light on brain development at a vulnerable stage. Some of these new developments are reviewed in this editorial.

CONCLUSION

The anatomical differences between the brains of babies born extremely prematurely and those born at term appear to translate into disturbances of function. The challenge for paediatricians is to discover the causes, with the aim of promoting normal brain development.