Multivariate analysis of risk of perinatal telencephalic leucoencephalopathy

Extreme prematurity: Risk and resiliency

Individuals born extremely preterm (before 28 weeks of gestation) comprise only about 0.7% of births in the United States and an even lower proportion in other high resource countries. However, these individuals account for a disproportionate number of children with cerebral palsy, intellectual deficit, autism spectrum disorder, attention deficit hyperactivity disorder, and epilepsy. This review describes two large multiple center cohorts comprised of individuals born extremely preterm: the EPICURE cohort, recruited 1995 in the United Kingdom and the Republic of Ireland, and the Extremely Low Gestational Age Newborn (ELGAN), recruited 2002-2004 in five states in the United States. The primary focus of these studies has been neurodevelopmental disorders, but also of interest are growth, respiratory illness, and parent- and self-reported global health and well-being. Both of these studies indicate that among individuals born extremely preterm the risks of most neurodevelopmental disorders are increased. Early life factors that contribute to this risk include perinatal brain damage, some of which can be identified using neonatal head ultrasound, bronchopulmonary dysplasia, and neonatal systemic inflammation. Prenatal factors, particularly the family's socioeconomic position, also appear to contribute to risk. For most adverse outcomes, the risk is higher in males. Young adults born extremely preterm who have neurodevelopmental impairment, as compared to those without such impairment, rate their quality of life lower. However, young adults born extremely preterm who do not have neurodevelopmental impairments rate their quality of life as being similar to that of young adults born at term. Finally, we summarize the current state of interventions designed to improve the life course of extremely premature infants, with particular focus on efforts to prevent premature birth and on postnatal efforts to prevent adverse neurodevelopmental outcomes.

Placental programming, perinatal inflammation, and neurodevelopment impairment among those born extremely preterm

Individuals born extremely preterm are at significant risk for impaired neurodevelopment. After discharge from the neonatal intensive care, associations between the child's well-being and factors in the home and social environment become increasingly apparent. Mothers' prenatal health and socioeconomic status are associated with neurodevelopmental outcomes, and emotional and behavioral problems. Research on early life risk factors and on mechanisms underlying inter-individual differences in neurodevelopment later in life can inform the design of personalized approaches to prevention. Here, we review early life predictors of inter-individual differences in later life neurodevelopment among those born extremely preterm. Among biological mechanisms that mediate relationships between early life predictors and later neurodevelopmental outcomes, we highlight evidence for disrupted placental processes and regulated at least in part via epigenetic mechanisms, as well as perinatal inflammation. In relation to these mechanisms, we focus on four prenatal antecedents of impaired neurodevelopment, namely, (1) fetal growth restriction, (2) maternal obesity, (3) placental microorganisms, and (4) socioeconomic adversity. In the future, this knowledge may inform efforts to detect and prevent adverse outcomes in infants born extremely preterm. IMPACT: This review highlights early life risk factors and mechanisms underlying inter-individual differences in neurodevelopment later in life. The review emphasizes research on early life risk factors (fetal growth restriction, maternal obesity, placental microorganisms, and socioeconomic adversity) and on mechanisms (disrupted placental processes and perinatal inflammation) underlying inter-individual differences in neurodevelopment later in life. The findings highlighted here may inform efforts to detect and prevent adverse outcomes in infants born extremely preterm.

Neonatal white matter damage and the fetal inflammatory response

In 1962 a long-recognized pathologic abnormality in neonatal brains characterized by multiple telencephalic focal white matter necroses was renamed periventricular leukomalacia (PVL) and the authors inappropriately asserted that their entity was caused by anoxia. They also failed to include three other white matter histologic abnormalities. In this essay, we identify the breadth of white matter pathology, especially in very preterm newborns, and show that none of the four histologic expressions of white matter damage, including focal necrosis, are associated with hypoxemia or correlates as hypotension, but are instead associated with markers of fetal or perinatal inflammation, particularly in preterm babies. We begin with the background needed to evaluate the evidence.

Considerations for the Optimization of Induced White Matter Injury Preclinical Models

White matter (WM) injury in relation to acute neurologic conditions, especially stroke, has remained obscure until recently. Current advances in imaging technologies in the field of stroke have confirmed that WM injury plays an important role in the prognosis of stroke and suggest that WM protection is essential for functional recovery and post-stroke rehabilitation. However, due to the lack of a reproducible animal model of WM injury, the pathophysiology and mechanisms of this injury are not well studied. Moreover, producing selective WM injury in animals, especially in rodents, has proven to be challenging. Problems associated with inducing selective WM ischemic injury in the rodent derive from differences in the architecture of the brain, most particularly, the ratio of WM to gray matter in rodents compared to humans, the agents used to induce the injury, and the location of the injury. Aging, gender differences, and comorbidities further add to this complexity. This review provides a brief account of the techniques commonly used to induce general WM injury in animal models (stroke and non-stroke related) and highlights relevance, optimization issues, and translational potentials associated with this particular form of injury.

Infection-induced inflammation and cerebral injury in preterm infants

Preterm birth and infectious diseases are the most common causes of neonatal and early childhood deaths worldwide. The rates of preterm birth have increased over recent decades and account for 11% of all births worldwide. Preterm infants are at significant risk of severe infection in early life and throughout childhood. Bacteraemia, inflammation, or both during the neonatal period in preterm infants is associated with adverse outcomes, including death, chronic lung disease, and neurodevelopmental impairment. Recent studies suggest that bacteraemia could trigger cerebral injury even without penetration of viable bacteria into the CNS. Here we review available evidence that supports the concept of a strong association between bacteraemia, inflammation, and cerebral injury in preterm infants, with an emphasis on the underlying biological mechanisms, clinical correlates, and translational opportunities.

Effects of interleukin-6 on the expression of tight junction proteins in isolated cerebral microvessels from yearling and adult sheep

OBJECTIVES

The blood-brain barrier is a selective diffusion barrier between brain parenchyma and the intravascular compartment. Tight junctions are integral components of the blood-brain barrier. Pro-inflammatory cytokines are important in the pathogenesis of brain injury and could modify the protein constituents of tight junctions. We hypothesized that interleukin-6 (IL-6) downregulates key protein constituents of endothelial tight junctions (e.g. occludin and claudin-5).

METHODS

We examined the effects of IL-6 on tight junction protein expression using an in vitro blood-brain barrier model. We isolated microvessels from yearling and adult ovine cerebral cortex and placed them into culture with IL-6 concentrations of 0 (control, phosphate-buffered saline), 1, 10, and 100 ng/ml for 24 h. Cerebral microvessels were harvested, Western immunoblot performed for occludin and claudin-5, densitometry performed, and results expressed as a ratio to control values.

RESULTS

Western immunoblot analysis showed that treatment with 100 ng/ml of IL-6, but not the lower concentrations, reduced (p < 0.05) occludin expression in microvessels from yearling and adult sheep and claudin-5 in microvessels from adult sheep. However, treatment with 10 ng/ml of IL-6 increased claudin-5 in microvessels from yearling sheep. The percent of lactate dehydrogenase released from the microvessels into the surrounding media was not increased by IL-6 treatment, suggesting that the reductions in tight junction proteins did not result from cell death. Treatment of adult cerebral cortical microvessels with IL-6 preincubated with anti-IL-6 monoclonal antibodies partially attenuated the reduction in claudin-5.

CONCLUSION

We conclude that IL-6 modulates tight junction protein expression in cerebral cortical microvessels from yearling and adult sheep.

Innate immune regulation by toll-like receptors in the brain

The innate immune system plays an important role in cerebral health and disease. In recent years the role of innate immune regulation by toll-like receptors in the brain has been highlighted. In this paper the expression of toll-like receptors and endogenous toll-like receptor ligands in the brain and their role in cerebral ischemia will be discussed. Further, the ability of systemic toll-like receptor ligands to induce cerebral inflammation will be reviewed. Finally, the capacity of toll-like receptors to both increase (sensitization) and decrease (preconditioning/tolerance) the vulnerability of the brain to damage will be disclosed. Studies investigating the role of toll-like receptors in the developing brain will be emphasized.

Systemic responses of preterm newborns with presumed or documented bacteraemia

AIM

To compare the frequency of elevated concentrations of inflammation-related proteins in the blood of infants born before the 28th week of gestation who had documented bacteraemia and those who had presumed (antibiotic-treated but culture-negative) bacteraemia to those who had neither.

METHODS

The subjects of this study are the 868 infants born at 14 institutions for whom information about protein measurements on at least two of the three protocol days (days 1, 7, and 14) was available and who did not have Bell stage 3 necrotizing enterocolitis or isolated bowel perforation, which were strongly associated with bacteraemia in this sample.

RESULTS

Newborns with presumed early (week 1) bacteraemia had elevated concentrations of only a few inflammation-related proteins, while those who had presumed late (weeks 2-4) bacteraemia did not have any elevations. In contrast, newborns who had documented early bacteraemia had a moderately strong signal, while those who had documented late bacteraemia had a stronger signal with more protein concentrations elevated on two separate occasions a week apart.

CONCLUSIONS

Culture-confirmed early and late bacteraemia are accompanied/followed by systemic inflammatory responses not seen with presumed early and late bacteraemia.

Infection and white matter injury in infants with congenital cardiac disease

More than 60% of newborns with severe congenital cardiac disease develop perioperative brain injuries. Known risk factors include: pre-operative hypoxemia, cardiopulmonary bypass characteristics, and post-operative hypotension. Infection is an established risk factor for white matter injury in premature newborns. In this study, we examined term infants with congenital cardiac disease requiring surgical repair to determine whether infection is associated with white matter injury. Acquired infection was specified by site - bloodstream, pneumonia, or surgical site infection - according to strict definitions. Infection was present in 23 of 127 infants. Pre- and post-operative imaging was evaluated for acquired injury by a paediatric neuroradiologist. Overall, there was no difference in newly acquired post-operative white matter injury in infants with infection (30%), compared to those without (31%). When stratified by anatomy, infants with transposition of the great arteries, and bloodstream infection had an estimated doubling of risk of white matter injury that was not significant, whereas those with single ventricle anatomy had no apparent added risk. When considering only infants without stroke, the estimated association was higher, and became significant after adjusting for duration of inotrope therapy. In this study, nosocomial infection was not associated with white matter injury. Nonetheless, when controlling for risk factors, there was an association between bloodstream infection and white matter injury in selected sub-populations. Infection prevention may have the potential to mitigate long-term neurologic impairment as a consequence of white matter injury, which underscores the importance of attention to infection control for these patients.

The relationship between early concentrations of 25 blood proteins and cerebral white matter injury in preterm newborns: the ELGAN study

OBJECTIVE

To evaluate whether concentrations of inflammation-related proteins are elevated in the blood of preterm newborns who develop cerebral white matter damage.

STUDY DESIGN

We measured 25 proteins in blood collected on days 1, 7, and 14 from 939 infants born before the 28th week of gestation. Brain ultrasound scans were read by at least two sonologists, who agreed on the presence or absence of lesions. A protein concentration was considered elevated if it was in the highest quartile for gestational age and the day on which the specimen was collected.

RESULTS

In time-oriented models, elevated concentrations of vascular endothelial growth factor receptor 1, serum amyloid A, and macrophage inflammatory protein 1β on day 1 and interleukin-8 on day 7 were associated with increased risk of ventriculomegaly. Elevated concentrations of macrophage inflammatory protein 1β on day 1 and intercellular adhesion molecule 1 on day 7 were associated with increased risk of an echolucent lesion. Infants with elevated concentrations of inflammation-related proteins on two separate days were at significantly increased risk for ventriculomegaly, but at only modestly increased risk for an echolucent lesion.

CONCLUSIONS

Concentrations of inflammation-related proteins in the circulation in the first days after preterm birth provide information about the risk of sonographic white matter damage. The inflammatory process might begin in utero.

Lame from birth: early concepts of cerebral palsy

Deformations have been attributed to supernatural causes since antiquity. Cerebral palsy was associated with God's wrath, witchcraft, the evil eye, or maternal imagination. Greek scholars recommended prevention by tight swaddling, a custom that persisted into modern times. In the Middle Ages, the midwife's negligence was held responsible as was difficult teething. Morgagni described in 1769 that the neonatal brain can liquefy, and Bednar described leukomalacia in 1850 as a distinct disorder of the newborn. In 1861, Little associated cerebral palsies with difficult or protracted labor and neonatal asphyxia, but he was challenged by Freud, who in 1897 declared that most cases are prenatal in origin. In 1868, Virchow demonstrated inflammatory changes, a view recently confirmed by Leviton and Nelson. Although a causal relationship of cerebral palsy to the birth never has been established, the habit to put the blame for cerebral palsy on someone remained a frequent attitude.

Microbiologic and histologic characteristics of the extremely preterm infant's placenta predict white matter damage and later cerebral palsy. the ELGAN study

Inflammatory phenomena seem to contribute to the occurrence of perinatal cerebral white matter damage and CP. The stimulus that initiates the inflammation remains obscure. One thousand two hundred forty-six infants born before the 28th postmenstrual week had a protocol ultrasound scan of the brain read concordantly by two independent sonologists. Eight hundred ninety-nine of the children had a neurologic examination at approximately 24-mo postterm equivalent. The placenta of each child had been biopsied under sterile conditions and later cultured. Histologic slides of the placenta were examined specifically for this study. Recovery of a single microorganism predicted an echolucent lesion, whereas polymicrobial cultures and recovery of skin flora predicted both ventriculomegaly and an echolucent lesion. Diparetic CP was predicted by recovery of a single microorganism, multiple organisms, and skin flora. Histologic inflammation predicted ventriculomegaly and diparetic CP. The risk of ventriculomegaly associated with organism recovery was heightened when accompanied by histologic inflammation, but the risk of diparetic CP was not. Low-virulence microorganisms isolated from the placenta, including common skin microflora, predict ultrasound lesions of the brain and diparetic CP in the very preterm infant. Organism recovery does not seem to be needed for placenta inflammation to predict diparetic CP.

Fetal inflammatory response and brain injury in the preterm newborn

Preterm birth can be caused by intrauterine infection and maternal/fetal inflammatory responses. Maternal inflammation (chorioamnionitis) is often followed by a systemic fetal inflammatory response characterized by elevated levels of proinflammatory cytokines in the fetal circulation. The inflammation signal is likely transmitted across the blood-brain barrier and initiates a neuroinflammatory response. Microglial activation has a central role in this process and triggers excitotoxic, inflammatory, and oxidative damage in the developing brain. Neuroinflammation can persist over a period of time and sensitize the brain to subinjurious insults in early and chronic phases but may offer relative tolerance in the intermediate period through activation of endogenous anti-inflammatory, protective, and repair mechanisms. Neuroinflammatory injury not only destroys what exists but also changes what develops.

Cytokines and perinatal brain damage

Perinatal brain damage has been implicated in the pathogenesis of neurodevelopmental impairments and psychiatric illnesses. This article reviews evidence that infection outside of the brain can damage the brain, and discusses specific cytokines and pathomechanisms that probably mediate the putative effect of remote infection on the developing brain. Events associated with increased circulating inflammatory cytokines, chemokines, and immune cells are described. Finally, studies of genetic variation in susceptibility to cytokine-related brain damage are reviewed.

Preterm histologic chorioamnionitis: impact on cord gas and pH values and neonatal outcome

OBJECTIVE

The purpose of this study was to further delineate the impact of preterm chorioamnionitis on a spectrum of neonatal outcomes using a large tertiary hospital population.

STUDY DESIGN

The perinatal/neonatal and placental pathology databases of St. Joseph's Health Care, London, Ontario, Canada, were used to obtain the umbilical cord gas and pH values, incidence of adverse neonatal outcomes, patient demographics, and placental pathology reports for all preterm (25 to 34 weeks of gestation), singleton, liveborn infants with no major anomalies who were delivered with spontaneous onset of labor or for suspected chorioamnionitis between November 1, 1995, and October 31, 2003. Patient groupings on the basis of placental inflammation and clinical chorioamnionitis were studied by a comparison of mean values and incidences for those neonatal outcomes that were available from the database with the use of linear and logistic regression analysis and controlling for potentially confounding variables.

RESULTS

There were 660 infants who met the inclusion criteria and had placental pathology available of whom 368 (56%) had no placental inflammation, 114 (17%) had placental chorioamnionitis, and 178 (27%) had placental funisitis. Umbilical cord partial pressure oxygen and base excess values were generally higher in the placental inflammation/clinical chorioamnionitis groups, in keeping with enhanced oxygen delivery and an overall decrease in the metabolic contribution to acidosis attributed to altered lactate metabolism in these infants. After adjusting for confounders (primarily differences in gestational age), the incidence of respiratory distress syndrome was significantly decreased in the placental inflammation/clinical chorioamnionitis groups, in keeping with cytokine-induced synthesis of surfactant proteins in these infants. Although the incidence of bronchopulmonary dysplasia, intraventricular hemorrhage, and periventricular leukomalacia was generally unchanged among the groups studied, that for intraventricular hemorrhage and periventricular leukomalacia was lowest in the placental inflammation/no clinical chorioamnionitis patients and highest in the placental inflammation/clinical chorioamnionitis patients, suggesting a differential effect of clinical chorioamnionitis for these outcomes.

CONCLUSION

Overall, infants born preterm with intrauterine infection were better oxygenated and showed less metabolic acidosis at birth and had incidences of respiratory distress syndrome and intraventricular hemorrhage, which were variably lower. Although there are likely threshold levels of inflammatory cytokines that do give rise to adverse outcome, a minimal level of cytokines may also be beneficial for the transition at birth from intrauterine to extrauterine existence when preterm pending the circumstances (ie, exposure to antenatal steroids) and emphasizing the complex relationship among preterm birth, infection, and adverse neonatal outcome.

Perinatal infections, prematurity and brain injury

PURPOSE OF REVIEW

The association between perinatal infection and brain injury is widely accepted but a cause-and-effect relationship has not yet been proven. This article summarizes available evidence and current primary publications for debate.

RECENT FINDINGS

Work completed during the review period has reinforced current understanding of perinatal infection, prematurity and brain injury. In animal experiments: lipopolysaccharides have been further implicated in brain injury, not only as a cause of brain injury but also as mediators of preconditioning and protection. Recent studies suggest that cerebral injury following low-dose lipopolysaccharide administration may become compensated in adulthood. Other studies have emphasized the complexity of the response by showing that plasma cytokine levels may not reflect those in the central nervous system or inflammatory events in the brain.

SUMMARY

Perinatal infection and maternofetal inflammation is strongly associated with preterm birth. Inflammation probably represents an important mechanism for cerebral damage, and both overt lesions and maldevelopment can result. Epidemiological data and multiple animal models to link infection, inflammation and brain damage exist, but proof of causation is elusive.

Cerebral palsy in very preterm infants: new epidemiological insights

The focus of this review is on new insights from recent epidemiological research on cerebral palsy in preterm infants. These include: 1) a better understanding of issues related to diagnosis and classification; 2) new information about the brain abnormalities underlying cerebral palsy in preterm infants; and 3) a better understanding of biological mechanisms that may underlie previously described epidemiological associations. Ongoing efforts to improve the diagnosis and classification of cerebral palsy have been enhanced by findings from serial examinations of cohorts of very preterm infants. Cranial ultrasonography through the anterior fontanelle of very preterm infants has provided information about grossly evident brain damage, found in about one-half of preterm infants who develop cerebral palsy. Insights into the pathophysiologic basis for certain epidemiologic associations have come from studies of experimental brain damage in animals and clinical studies of neurologic disorders in adults. Much of the current epidemiological research into the causes of cerebral palsy in preterm infants has focused on two potential mechanisms of brain damage. One mechanism involves insufficient cerebral perfusion; the other, cytokine-mediated damage, potentially triggered by events such as maternal infection (e.g., intrauterine or periodontal infection), neonatal infection (e.g., sepsis and necrotizing enterocolitis), and neonatal oxygen- or ventilator-induced lung injury. In addition to the preterm infant's increased exposure to such damaging factors, the high frequency of cerebral palsy in these infants might be due, in part, to insufficient levels of developmentally regulated protective substances, such as thyroid hormone and glucocorticoids. Models of causation currently are being investigated using recently developed methods for quantifying, with small quantities of blood, biomolecules that are suspected to either promote or protect against brain damage in the neonate. Clinical investigations now under way can be expected to identify strategies to be tested in clinical trials that could lower the risk of cerebral palsy in very preterm infants.

Perinatal infection, fetal inflammatory response, white matter damage, and cognitive limitations in children born preterm

Only sparse information is available about a possible association between antenatal infection outside the brain and subsequent cognitive limitations among preterm infants. Based on published studies, we provide a theoretical schema that links them via the fetal inflammatory response and neonatal white matter damage. We conclude that the relationship between antenatal infection and cognitive limitations deserves much further attention by researchers interested in the prevention of this undesirable outcome of prematurity.

Antecedents of cerebral palsy in very low-birth weight infants

Research from the last two decades provides directions for efforts to prevent CP in VLBW infants. The pathogenesis of CP seems to involve factors operating both during pregnancy and in the neonatal period. The most important prenatal factor appears to be intrauterine infection. Perinatal infection and other risk factors, such as the death of a co-twin, placental abruption, and cerebral ischemia, could trigger a cytokine cascade resulting in damage to the developing brain. The low frequency of intrauterine infection in mothers with preeclampsia might explain the apparent protective effect of this disorder. If the brain damage attributed to intrauterine infection and other risk factors involves cytokines as intermediates, then blockade of the proinflammatory cascade or promotion of endogenous inhibitors might prevent CP. Other potentially preventive strategies include corticosteroids given to mothers (but not those given to neonates) and thyroid hormone.

Brain damage in preterm newborns: might enhancement of developmentally regulated endogenous protection open a door for prevention?

We present a two-component model of brain white matter damage in preterm neonates. The insult component comprises infection and hypoxia-ischemia, which are both associated with inflammation-related abnormalities in the white matter. The developmental component comprises at least three factors, ie, immaturity of the ependymal/endothelial, oligodendroglial, and endogenous protection systems. All three factors are likely contributors to an increased vulnerability of the preterm newborn's white matter. In this article, we focus on recent developments in oligodendrocyte biology that support the view of certain cytokines and growth factors as oligotrophins based on their capability to enhance oligodendrocyte development or survival. We suggest that research into networks of developmentally regulated endogenous protectors (such as oligotrophins) is necessary to broaden our perspectives in brain injury prevention in preterm newborns.

Association of chronic sublethal hypoxia with ventriculomegaly in the developing rat brain

Bronchopulmonary dysplasia remains a major cause of neurodevelopmental handicap in preterm infants. Because bronchopulmonary dysplasia may be associated with prolonged hypoxemia without obvious changes in systemic blood pressure, we developed an animal model of chronic sublethal hypoxia to test the hypothesis that this insult results in significant alterations in corticogenesis in the developing brain. Three groups of newborn rats were placed in a chamber with FIO2 9.5% on postnatal day 3 (P3). One group was sacrificed at P13; a second group was sacrificed at P33, and the third group was removed at P33 and reared in normoxia until sacrifice at P63. Control rats were those raised in room air for the corresponding periods of time. Rats were transcardially perfused and the brains were embedded in celloidin and prepared for morphometric analysis using standard stereology methods. Although experimental rat pups in the third group demonstrated 'catch-up' of body weight following return to normoxia, these studies demonstrated both failure of brain growth (p<0.01) and progressive cerebral ventriculomegaly (p<0.01). Decreased subcortical white matter (p<0. 05) and corpus callosum size (p<0.01) were noted at P63 in pups reared under conditions of chronic hypoxia. Decreases in cortical volume (p<0.05) were noted at all three experimental time points for hypoxic-reared pups when compared to control animals. These data suggest that chronic sublethal hypoxia may lead to severe impairments in corticogenesis in an animal model of developing brain.

Infection remote from the brain, neonatal white matter damage, and cerebral palsy in the preterm infant

This review synthesizes the literature supporting the hypothesis that infection during or even before pregnancy remote from the fetal brain leads to neonatal white matter damage (NWMD) and its long-term sequelae, including cerebral palsy. First, a framework of five dimensions is presented, including the spectrum of NWMD, its relationship with gestational age, its clinical spectrum, the expressions and correlates of infection, and the mother/child dyad. Second, a summary of the plethora of support for the remote infection/NWMD-hypothesis is presented by drawing on studies published over the past three decades. Although an epidemiological perspective is prominent, we invoke molecular explanations (especially the cytokine hypothesis) for observed associations. Third, the article concludes with a section on future studies needed to characterize and eliminate (pre-) pregnancy infections in the mother and to identify and evaluate potentially neuroprotective strategies in the fetus.

Sonographic diagnosis of intracranial hemorrhage and periventricular leukomalacia in premature African neonates

Transfontanelle ultrasound (US) was done prospectively and analyzed for intra-cranial hemorrhage (ICH) and periventricular leukomalacia (PVL) in 110 premature infants. The babies were divided into two subgroups according to their birth weights (BW): those with BW of 1500 g or less (n = 93) belonged to subgroup A while babies of BW between 1500 and 2500 g (n = 17) were placed in subgroup B. Overall incidence of ICH and PVL was 24.5 and 26.4%, respectively in the 110 cases studied. Under subgroup A, 26/93 (28.0%) cases had ICH while 22/93 (23.7%) cases had PVL. In subgroup B, 2/17 (11.8%) cases had ICH while PVL was noted in 7/17 (41.2%) cases. These results show that premature African children have a lower incidence of ICH but a higher incidence of PVL compared to babies from temperate regions. Genetic and environmental factors are probably responsible for these variations in the occurrence of both diseases in population groups from different geographical locations.

Experimentally induced intrauterine infection causes fetal brain white matter lesions in rabbits

OBJECTIVE

Periventricular leukomalacia, a common brain white matter lesion in preterm neonates, is a major risk factor for cerebral palsy. Epidemiologic studies have demonstrated an association between infection and periventricular leukomalacia. The purpose of this study was to determine whether ascending intrauterine infection could cause brain white matter lesions in the fetal rabbit.

STUDY DESIGN

Rabbits with timed pregnancies underwent hysteroscopy at 20 to 21 days of gestation (70%). Animals were allocated in a ratio of 2:1 for inoculation with either Escherichia coli (0.2 ml containing 10(3) to 10(4) colony-forming units) or sterile saline solution. Both groups were treated with ampicillin-sulbactam (Unasyn, 100 mg/kg per day; Pfizer, Seoul) every 8 hours until they were killed 5 to 6 days after hysteroscopy. Histologic examination of the placentas and fetal brains was conducted.

RESULTS

Forty-five animals underwent hysteroscopy; 31 were inoculated with E. coli and 14 with sterile saline solution. At the time the animals were killed, the rate of intrauterine infection was higher and there were fewer live fetuses in the E. coli-inoculated animals than in the saline solution group. Histologic evidence of brain white matter damage was identified in 12 fetuses born to 10 E. coli-inoculated rabbits but none in the saline solution group (p < 0.05). All rabbits with brain white matter lesions had evidence of intrauterine infection. Evidence of white matter damage included increased karyorrhexis, rarefaction, and disorganization of white matter. Apoptosis was demonstrated in areas of white matter damage by immunohistochemical studies.

CONCLUSION

Experimental ascending intrauterine infection can cause fetal brain white matter lesions.

Amniotic fluid inflammatory cytokines (interleukin-6, interleukin-1beta, and tumor necrosis factor-alpha), neonatal brain white matter lesions, and cerebral palsy

OBJECTIVE

Ultrasonographically detectable neonatal brain white matter lesions are the most important identifiable risk factor for cerebral palsy. Inflammatory cytokines released during the course of intrauterine infections have been implicated in the genesis of brain white matter lesions and subsequent cerebral palsy. This study was undertaken to determine whether fetuses who subsequently were diagnosed to have periventricular brain white matter lesions could be identified by determining the concentrations of inflammatory cytokines in the amniotic fluid.

STUDY DESIGN

Women with complicated preterm gestations underwent amniocentesis for clinical indications. Amniotic fluid concentrations of tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, and the natural interleukin-1 receptor antagonist were determined by immunoassay. Periventricular white matter lesions of the neonate were diagnosed by neurosonography. Univariate and multivariate analyses were conducted.

RESULTS

Ninety-four women and their neonates were included in the study; white matter lesions were diagnosed in 24% (23/94) of the newborns. The mothers of newborns with brain white matter lesions had higher median concentrations of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 (but not interleukin-1 receptor antagonist) in amniotic fluid than did those who were delivered of newborns without white matter lesions (p < 0.01 for each). Acute histologic chorioaminionitis was more common in the placentas of neonate with white matter lesions than in those without these lesions (82% [18/22] vs 42% [30/71], p < 0.005). Neonates with white matter lesions were delivered at a lower mean gestational age and birth weight and had a higher rate of significant complications (including respiratory distress syndrome, intraventricular hemorrhage, and infection-related complications) than did those without white matter lesions. The differences in median interleukin-1beta and interleukin-6 levels between these two groups remained significant after adjustment for gestational age and birth weight (interleukin-6: odds ratio 5.7, 95% confidence interval 1.3 to 24.4; interleukin-1beta: odds ratio 4.4, 95% confidence interval 1.1 to 17.0). Of the 94 newborns included in this study, 11 died before age 6 months and eight had cerebral palsy; all eight had white matter lesions and elevated cytokine levels in amniotic fluid. Histologic chorioamnionitis was more common in the placentas of neonates with cerebral palsy than in those without cerebral palsy (86% [6/7] vs 44% [33/75], p < 0.05).

CONCLUSIONS

Infants at risk for development of brain white matter lesions can be identified by the concentrations of interleukin-6 and interleukin-1beta in amniotic fluid. Our findings support the hypothesis that inflammatory cytokines released during the course of intrauterine infection play a role in the genesis of brain white matter lesions.

Clinical aspects of perinatal hypoxic-ischemic brain injury

Perinatal hypoxic-ischemic cerebral injury is a significant cause of neurological morbidity and mortality in childhood. It is often difficult to determine the precise timing of such injury. Data from epidemiological and neuropathological studies have identified several maternal and fetal risk factors that seem to be associated with suspected prenatal brain injury. Hypoxic-ischemic cerebral injury that originates earlier in gestation may result in few, if any, clinical abnormalities during the newborn period. Clinical abnormalities may also be difficult to recognize in the premature newborn, and greater reliance must be placed on other adjunctive investigations, eg, neuroimaging. In contrast, term infants who sustain acute, intrapartum hypoxic-ischemic insult of sufficient magnitude to result in long-term sequelae invariably show recognizable encephalopathy during the newborn period. A combination of clinical data and adjunctive investigations during the neonatal period is a powerful predictive tool for long-term outcome.

White matter damage in preterm newborns--an epidemiologic perspective

Prior to 1980, white matter abnormalities of the preterm newborn were known exclusively as pathological entities, but now cranial ultrasonography can image white matter abnormalities in life. Ultrasonographic white matter echodensities and echolucencies in low birthweight babies predict later handicap (especially cerebral palsy) more accurately than any other antecedent. With the increased availability of high resolution cranial ultrasonography and the improved skill in obtaining and reading cranial ultrasonograms, rapid gains can be expected in our understanding of white matter disorders. These advances are likely to be made in the diagnosis and classification of white matter disorders and in their epidemiologic and prognostic features, topics explored in this review.

Neonatal Citrobacter meningitis: pathogenesis of cerebral abscess formation

In 2 premature infants with brief survival, the major pathological feature of Citrobacter meningitis consisted of vasculitis and infarction with necrosis and liquefaction of large portions of the white matter of the hemispheres. Areas of decreased density demonstrated on computed tomographic head scan represented infarction with necrosis, liquefaction, and cavitation and not a classic abscess. This finding has clinical significance, because surgical drainage of liquefied infarcts is rarely indicated and could further damage the relatively preserved cortex.

Acquired perinatal leukoencephalopathy

Between 36 and 44 weeks after conception, telencephalic white matter in the newborn appears to be particularly vulnerable to insults that result in morphological disturbances. Available evidence indicates that this disorder (or group of disorders), named acquired perinatal leukoencephalopathy, reflects a decrease in blood flow through the distal vessels supplying paraventricular white matter and/or a metabolic disturbance produced by, or in response to, an infectious agent. Major advances in our understanding of the causes, mechanisms, and sequelae of acquired perinatal leukoencephalopathy may be made in the next decade because of improvement in brain imaging techniques, improved survival of high-risk babies, and relatively routine follow-up of these high-risk babies.