Mechanisms of injury to white matter adjacent to a large intraventricular hemorrhage in the preterm brain

Racial and geographic disparities in neonatal brain care

In this review, we explore race-based disparities in neonatology and their impact on brain injury and neurodevelopmental outcomes. We discuss the historical context of healthcare discrimination, focusing on the post-Civil War era and the segregation of healthcare facilities. We highlight the increasing disparity in infant mortality rates between Black and White infants, with premature birth being a major contributing factor, and emphasize the role of prenatal factors such as metabolic syndrome and toxic stress in affecting neonatal health. Furthermore, we examine the geographic and historical aspects of racial disparities, including the consequences of redlining and limited access to healthcare facilities or nutritious food options in Black communities. Finally, we delve into the higher incidence of brain injuries in Black neonates, as well as disparities in adverse neurodevelopmental outcome. This evidence underscores the need for comprehensive efforts to address systemic racism and provide equitable access to healthcare resources.

A Review of the Occurrence of Intraventricular Hemorrhage in Preterm Newborns and its Future Neurodevelopmental Consequences

Intraventricular hemorrhage (IVH) is a type of bleeding that occurs through the germinal matrix and comes through the ependymal cells into the ventricular cavity. It is mostly seen in preterm neonates but can also be seen sometimes in term neonates. Various factors predispose to preterm delivery; it can be spontaneous or medically induced. Spontaneous IVH occurs in cases of intrauterine infections in the mother, and it can be induced in cases of medical emergencies such as preeclampsia and eclampsia. The brain of a preterm newborn is not fully developed as it does not have pericytes and proteins, so it can bleed very quickly, which can cause IVH. Also, the vessels supplying the germinal matrix are immature and highly vascularized. IVH has four grades based on findings detected on cranial ultrasound and MRI. Management includes medical and surgical management; medical management includes phenobarbitone used for seizures and prophylaxis. Surgical management includes drainage, irrigation, and fibrinolytic therapy (DRIFT), and neuro-endoscopic lavage. IVH causes various short-term and long-term neurodevelopmental consequences. Long-term complications include cerebral palsy and intellectual disability, which hamper the life of the child. It mainly presents with seizures, flaccidity, decerebrate posture, etc. Various preventive measures can be taken to tackle IVH in newborns. First of all, preterm delivery should be avoided, and intrauterine infections in mothers should be treated. The administration of corticosteroids should be done for all preterm deliveries as it helps in the maturation of organs. The administration of magnesium sulfate should be done as it is neuroprotective and reduces cerebral palsy in the future. Delayed cord clamping is to be done to reduce recurrent blood transfusions and decrease the risk of IVH. This article explains the pathogenesis, management, prevention, and future outcomes of IVH.

Posthemorrhagic ventricular dilatation late intervention threshold and associated brain injury

OBJECTIVE

To systematically assess white matter injury (WMI) in preterm infants with posthemorrhagic ventricular dilatation (PHVD) using a high-threshold intervention strategy.

STUDY DESIGN

This retrospective analysis included 85 preterm infants (≤34 weeks of gestation) with grade 2-3 germinal matrix-intraventricular hemorrhage. Cranial ultrasound (cUS) scans were assessed for WMI and ventricular width and shape. Forty-eight infants developed PHVD, 21 of whom (intervention group) underwent cerebrospinal fluid drainage according to a predefined threshold (ventricular index ≥p97+4 mm or anterior horn width >10 mm, and the presence of frontal horn ballooning). The other 27 infants underwent a conservative approach (non-intervention group). The two PHVD groups were compared regarding ventricular width at two stages: the worst cUS for the non-intervention group (scans showing the largest ventricular measurements) versus pre-intervention cUS in the intervention group, and at term equivalent age. WMI was classified as normal/mild, moderate and severe.

RESULTS

The intervention group showed significantly larger ventricular index, anterior horn width and thalamo-occipital diameter than the non-intervention group at the two timepoints. Moderate and severe WMI were more frequent in the infants with PHVD (p<0.001), regardless of management (intervention or conservative management). There was a linear relationship between the severity of PHVD and WMI (p<0.001).

CONCLUSIONS

Preterm infants with PHVD who undergo a high-threshold intervention strategy associate an increased risk of WMI.

Free Radicals and Neonatal Brain Injury: From Underlying Pathophysiology to Antioxidant Treatment Perspectives

Free radicals play a role of paramount importance in the development of neonatal brain injury. Depending on the pathophysiological mechanisms underlying free radical overproduction and upon specific neonatal characteristics, such as the GA-dependent maturation of antioxidant defenses and of cerebrovascular autoregulation, different profiles of injury have been identified. The growing evidence on the detrimental effects of free radicals on the brain tissue has led to discover not only potential biomarkers for oxidative damage, but also possible neuroprotective therapeutic approaches targeting oxidative stress. While a more extensive validation of free radical biomarkers is required before considering their use in routine neonatal practice, two important treatments endowed with antioxidant properties, such as therapeutic hypothermia and magnesium sulfate, have become part of the standard of care to reduce the risk of neonatal brain injury, and other promising therapeutic strategies are being tested in clinical trials. The implementation of currently available evidence is crucial to optimize neonatal neuroprotection and to develop individualized diagnostic and therapeutic approaches addressing oxidative brain injury, with the final aim of improving the neurological outcome of this population.

Hemoglobin induces oxidative stress and mitochondrial dysfunction in oligodendrocyte progenitor cells

Oligodendrocyte progenitor cells (OPCs) in the infant brain give rise to mature oligodendrocytes that myelinate CNS axons. OPCs are particularly vulnerable to oxidative stress that occurs in many forms of brain injury. One common cause of infant brain injury is neonatal intraventricular hemorrhage (IVH), which releases blood into the CSF and brain parenchyma of preterm infants. Although blood contains the powerful oxidant hemoglobin, the direct effects of hemoglobin on OPCs have not been studied. We utilized a cell culture system to test if hemoglobin induced free radical production and mitochondrial dysfunction in OPCs. We also tested if phenelzine (PLZ), an FDA-approved antioxidant drug, could protect OPCs from hemoglobin-induced oxidative stress. OPCs were isolated from Sprague Dawley rat pups and exposed to hemoglobin with and without PLZ. Outcomes assessed included intracellular reactive oxygen species levels using 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA) fluorescent dye, oxygen consumption using the XFe96 Seahorse assay, and proliferation measured by BrdU incorporation assay. Hemoglobin induced oxidative stress and impaired mitochondrial function in OPCs. PLZ treatment reduced hemoglobin-induced oxidative stress and improved OPC mitochondrial bioenergetics. The effects of hemoglobin and PLZ on OPC proliferation were not statistically significant, but showed trends towards hemoglobin reducing OPC proliferation and PLZ increasing OPC proliferation (P=0.06 for both effects). Collectively, our results indicate that hemoglobin induces mitochondrial dysfunction in OPCs and that antioxidant therapy reduces these effects. Therefore, antioxidant therapy may hold promise for white matter diseases in which hemoglobin plays a role, such as neonatal IVH.

The hidden consequence of intraventricular hemorrhage: persistent cerebral desaturation after IVH in preterm infants

BACKGROUND

Previous studies describe a short-term decrease in cerebral oxygen saturation (StO2) after intraventricular hemorrhage (IVH) in premature infants; little is known about long-term implications.

METHODS

Infants born <30 weeks gestational age (GA) were included. Clinical characteristics, hemoglobin measurements, the highest grade of IVH, and white matter injury (WMI) were noted. NIRS monitoring occurred daily or every other day for 4 weeks; weekly through 36 weeks GA. Recordings were error-corrected before calculation of mean StO2 and fractional tissue oxygen extraction (FTOE). Mean StO2 and FTOE were plotted by postnatal age and injury group (IVH/no IVH; WMI/no WMI). Non-linear regression by locally estimated scatterplot smoothing was used to generate the best-fit line and CI.

RESULTS

A total of 1237 recordings from 185 infants were included; mean length = 6.5 h; mean GA = 26.3 w; mean BW = 951 g; overall/severe IVH incidence was 29/8%, WMI incidence was 16%. IVH was independently associated with an acute drop in StO2, which remained lower for 68 d. Severe IVH was associated with lower StO2 values than mild IVH. WMI was associated with early and persistent elevation of FTOE.

CONCLUSION

IVH of any grade is associated with a prolonged cerebral desaturation and WMI is associated with prolonged elevation of FTOE. This finding is exacerbated for infants with severe IVH.

IMPACT

The longitudinal impact of IVH on cerebral oxygenation has not been previously studied. IVH is associated with persistent cerebral desaturation, months in length, and is independent of anemia. More severe IVH is associated with worsened cerebral hypoxia. Infants later diagnosed with white matter injury have an early and persistent elevation of cerebral oxygen extraction (cFTOE). This cerebral desaturation, below previously identified normative ranges, may provide insight into the mechanistic link between IVH and white matter injury.

Pattern of intracranial findings detected on magnetic resonance imaging in surviving infants born before 29 weeks of gestation

Despite the positive survival trend in infants born prematurely, the risk for development of intracranial lesions has remained unchanged. However, there are limitations to our understanding of the pattern of the magnetic resonance imaging (MRI) -detected brain pathology in the preterm infants surviving to discharge. The present study outlines the type of intracranial lesions and factors allied with the neonatal brain hemorrhage (NBH) and white matter injury (WMI) seen on MRI at term-equivalent age or close to discharge in infants born before 29 weeks of gestation. We obtained demographic and clinical data, and reports of serial cranial ultrasound (CUS) performed during first month of life and qualitative MRI at term-equivalent age or close to discharge. Statistical comparison was conducted with respect to the MRI results that were classified as normal, WMI, and NBH using univariate and logistic regression analysis. One hundred and ninety three infants with MRI at term-equivalent age or close to discharge were included in final analysis. They were less mature and had a higher prevalence of pathological findings on CUS as compared with 249 other survivors born with gestational ages less than 29 weeks during the assigned study period. MRI was normal in 72.5% [95% Confidence Interval (95% CI 65.9%-78.4%)], showed WMI in 9.8% (95%CI 6.4%-14.9%) and NBH in 17.6% (95%CI 12.9–23.6) of the studied infants. Intracranial hemorrhages had also been reported in 42.2% of the infants with WMI. Except for moderate agreement with prior CUS results, no other factors were associated with the MRI detected pathological findings. In general, the likelihood for detection of WMI and NBH on MRI at term-equivalent age or close to discharge was reduced by approximately 80% and 70%, respectively if the serial CUS had not shown any abnormalities during the first month of life.

In Premature Newborns Intraventricular Hemorrhage Causes Cerebral Vasospasm and Associated Neurodisability via Heme-Induced Inflammasome-Mediated Interleukin-1 Production and Nitric Oxide Depletion

BACKGROUND

Intraventricular hemorrhage (IVH) occurs in 60-70% of neonates weighing 500-750 g and 10-20% of those weighing 1,000-1,500 g. All forms of IVH have been associated with neurocognitive deficits. Both subarachnoid and IVHs have been associated with delayed vasospasm leading to neurological deficits. Pathways linking hemoglobin release from blood clots to vasospasm include heme-induced activation of inflammasomes releasing interleukin-1 (IL-1) that can cause calcium dependent and independent vasospasm. Free hemoglobin is a potent scavenger of nitric oxide (NO). Depletion of NO, a potent endogenous vasodilator, has been associated with features of vasospasm.

HYPOTHESIS

In premature newborns, IVH causes cerebral vasospasm and associated neurodisability via heme-induced increased inflammasome-mediated IL-1 production and NO depletion.

CONFIRMATION OF HYPOTHESIS AND IMPLICATIONS

This hypothesis could be confirmed in the IVH animal model with visualization of any associated vasospasm by angiography and in newborns with IVH by transcranial Doppler ultrasonography and correlation with cerebrospinal fluid IL-1 and NO metabolite levels. Confirmation of the role of heme in activation of inflammasomes causing IL-1 production and NO binding could be achieved by measuring the effect of heme scavenging interventions on IL-1 levels and levels of NO metabolites. In addition to removal of the accumulated blood of an IVH by drainage, irrigation, and fibrinolytic therapy intrathecal application of vasodilators and heme scavenging agents like haptoglobin and haemopexin and systemic treatment with inhibitors of inflammasomes like telmisartan could be used to prevent and treat cerebral vasospasm, and thus reduce the risk of associated brain injury in premature neonates.

Isolated Cystic Periventricular Leukomalacia Differs from Cystic Periventricular Leukomalacia with Intraventricular Hemorrhage in Prevalence, Risk Factors and Outcomes in Preterm Infants

BACKGROUND

Cystic periventricular leukomalacia (cPVL) is the most severe white matter injury and is often associated with intraventricular hemorrhage (IVH) in preterm infants.

OBJECTIVE

The aim of this study was to investigate the prevalence, risk factors and neurodevelopmental outcomes of isolated cPVL and cPVL with low-grade and high-grade IVH in premature infants.

METHODS

From 2001 to 2012, 9,964 infants with <31 weeks' gestational age (GA) admitted to Taiwan hospitals were enrolled. cPVL was classified into three groups: isolated cPVL, cPVL with low-grade (I/II) IVH, and cPVL with high-grade (III) IVH.

RESULTS

Of 7,805 infants with complete ultrasound data, 286 (3.7%) had cPVL. Among the cPVL infants, 93 (32.5%) were isolated, 118 (41.3%) had low-grade IVH and 75 (26.2%) had high-grade IVH. The risk of cPVL with IVH was significantly higher among infants with <27 weeks' GA than those with ≥27 weeks' GA, in contrast to that of isolated cPVL. Using infants without cPVL and IVH as the reference group, the most significant predictor of isolated cPVL was neonatal sepsis (odds ratio 2.39; 95% confidence interval 1.52-3.77), while 5-min Apgar score <5 (2.50; 1.48-4.21) and prolonged mechanical ventilation (2.19; 1.42-3.42) were associated with cPVL with low-grade IVH, and GA <27 weeks (2.63; 1.56-4.42), pneumothorax (3.04; 1.40-6.65) and prolonged mechanical ventilation (3.36; 1.88-6.01) contributed to cPVL with high-grade IVH. cPVL infants with low-grade and high-grade IVH had a higher risk of abnormal neurodevelopmental outcomes than infants with isolated cPVL at the age of 24 months.

CONCLUSIONS

Isolated cPVL, cPVL with low-grade IVH and cPVL with high-grade IVH had different risk factors and neurodevelopmental outcomes, suggestive of different causal pathways.

Systems approach to the study of brain damage in the very preterm newborn

Background: A systems approach to the study of brain damage in very preterm newborns has been lacking.

Methods: In this perspective piece, we offer encephalopathy of prematurity as an example of the complexity and interrelatedness of brain-damaging molecular processes that can be initiated inflammatory phenomena.

Results: Using three transcription factors, nuclear factor-kappa B (NF-κB), Notch-1, and nuclear factor erythroid 2 related factor 2 (NRF2), we show the inter-connectedness of signaling pathways activated by some antecedents of encephalopathy of prematurity.

Conclusions: We hope that as biomarkers of exposures and processes leading to brain damage in the most immature newborns become more readily available, those who apply a systems approach to the study of neuroscience can be persuaded to study the pathogenesis of brain disorders in the very preterm newborn.

Systemic inflammation and cerebral palsy risk in extremely preterm infants

The authors hypothesized that among extremely preterm infants, elevated concentrations of inflammation-related proteins in neonatal blood are associated with cerebral palsy at 24 months. In 939 infants born before 28 weeks gestation, the authors measured blood concentrations of 25 proteins on postnatal days 1, 7, and 14 and evaluated associations between elevated protein concentrations and cerebral palsy diagnosis. Protein elevations within 3 days of birth were not associated with cerebral palsy. Elevations of tumor necrosis factor-α, tumor necrosis factor-α-receptor-1, interleukin-8, and intercellular adhesion molecule-1 on at least 2 days were associated with diparesis. Recurrent-persistent elevations of interleukin-6, E-selectin, or insulin-like growth factor binding protein-1 were associated with hemiparesis. Diparesis and hemiparesis were more likely among infants who had at least 4 of 9 protein elevations that previously have been associated with cognitive impairment and microcephaly. Repeated elevations of inflammation-related proteins during the first 2 postnatal weeks are associated with increased risk of cerebral palsy.

Risk factors of germinal matrix intraventricular hemorrhage in premature infants

OBJECTIVE

To determine whether some clinical parameters can be used to predict the hemorrhage and whether the relationship between these clinical variables and the grades of hemorrhage is linear.

METHODS

A total of 230 premature infants, born at a gestational age less than 34 weeks were retrospectively reviewed. Germinal matrix-intraventricular hemorrhage (GM-IVH), the grade of the hemorrhage, and clinical data were assessed with a checklist. Variables were analyzed by using Mann Whitney U and Fisher's exact tests and then multiple logistic regression analysis was used to evaluate the independent risk factors.

FINDINGS

Resuscitation, gestational age, hypotension, multiple birth, and birth weight were found to be independent risk factors. We determined non-linear relationship between the grades of hemorrhage and the clinical parameters. But when we classified hemorrhages as grade 1, grade 2-3 and grade 4, the relationships were found linear.

CONCLUSION

Premature infants who had resuscitation, low gestational age, hypotension, multiple birth, and low birth weight are more likely to have GM-IVH. The relationship between the clinical variables and the grades of GM-IVH does not seem to be linear.

Systemic inflammation, intraventricular hemorrhage, and white matter injury

To see if the systemic inflammation profile of 123 infants born before the 28th week of gestation who had intraventricular hemorrhage without white matter injury differed from that of 68 peers who had both lesions, we compared both groups to 677 peers who had neither. Cranial ultrasound scans were read independently by multiple readers until concordance. The concentrations of 25 proteins were measured with multiplex arrays using an electrochemiluminescence system. Infants who had both hemorrhage and white matter injury were more likely than others to have elevated concentrations of C-reactive protein and interleukin 8 on days 1, 7, and 14, and elevated concentrations of serum amyloid A and tumor necrosis factor-α on 2 of these days. Intraventricular hemorrhage should probably be viewed as 2 entities: hemorrhage alone and hemorrhage with white matter injury. Each entity is associated with inflammation, but the combination has a stronger inflammatory signal than hemorrhage alone.

Early cranial ultrasound lesions predict microcephaly at age 2 years in preterm infants

To assess how well early ultrasound lesions in preterm newborns predict reduced head circumference at 2 years, the investigators followed 923 children born before the 28th week of gestation who were not microcephalic at birth. Six percent of children who had a normal ultrasound scan were microcephalic compared with 15% to 20% who had intraventricular hemorrhage, an echolucent lesion, or ventriculomegaly. The odds ratios (95% confidence intervals) for microcephaly associated with different ultrasound images were intraventricular hemorrhage, 1.5 (0.8-3.0); ventriculomegaly, 3.3 (1.8-6.0); an echodense lesion, 1.6 (0.7-3.5); and an echolucent lesion, 3.1 (1.5-6.2). Ventriculomegaly and an echolucent lesion had very similar low positive predictive values (24% and 27%, respectively) and high negative predictive values (91% and 90%, respectively) for microcephaly. Ventriculomegaly had a higher sensitivity for microcephaly than did an echolucent lesion (24% vs 16%, respectively). Focal white-matter lesion (echolucent lesion) and diffuse white-matter damage (ventriculomegaly) predict an increased risk of microcephaly.