White matter damage in preterm newborns--an epidemiologic perspective

Topography of cerebral white-matter disease of prematurity studied prospectively in 1607 very-low-birthweight infants

The objective of this study was to evaluate to what extent (1) the characteristics of localization, distribution, and size of echodense and echolucent abnormalities enable individuals to be designated as having either periventricular hemorrhagic infarction or periventricular leukomalacia and (2) the characteristics of periventricular hemorrhagic infarction and periventricular leukomalacia are independent occurrences. The population for this study consisted of 1607 infants with birthweights of 500 to 1500 g, born between January 1991 and December 1993, who had at least one cranial ultrasound scan read independently by at least two ultrasonographers. The ultrasound data collection form diagrammed six standard coronal views. The cerebrum was divided into 17 zones in each hemisphere. All abnormalities were described as being echodense or echolucent and were classified on the basis of their size, laterality, location, and evolution. Eight percent (134/1607) of infants had at least one white-matter abnormality. The prevalence of white-matter disease decreased with increasing gestational age. Most abnormalities were small or medium sized and unilateral; only large echodensities tended to be bilateral and asymmetric. Large abnormalities, whether echodense or echolucent, were more likely than smaller abnormalities to be widespread, and the extent of cerebral involvement was independent of whether abnormalities were unilateral or bilateral. Large abnormalities were relatively more likely than small abnormalities to involve anterior planes. Small abnormalities, whether echodense or echolucent, or whether unilateral or bilateral, preferentially occurred near the trigone. Using the characteristics of location, size, and laterality/symmetry, we were able to allocate only 53% of infants with white-matter abnormalities to periventricular hemorrhagic infarction or periventricular leukomalacia. Assuming that periventricular leukomalacia and periventricular hemorrhagic infarction are independent and do not share risk factors, and that each occurs in approximately 5% of infants, we would have expected 0.25%, or about 4 individuals, to have abnormalities with characteristics of both periventricular leukomalacia and periventricular hemorrhagic infarction, whereas we found 63 such infants. Most infants with white-matter disease could not be clearly designated as having periventricular hemorrhagic infarction or periventricular leukomalacia only. Periventricular hemorrhagic infarction contributes to the risk of periventricular leukomalacia occurrence, or the two sorts of abnormalities share common risk antecedent factors. The descriptive term echodense or echolucent and the generic term white-matter disease of prematurity should be used instead of periventricular leukomalacia or periventricular hemorrhagic infarction when referring to sonographically defined white-matter abnormalities.

The fetal inflammatory response syndrome and cerebral palsy: yet another challenge and dilemma for the obstetrician

There is increasing evidence demonstrating a relationship between intrauterine infection and the development of neonatal intraventricular haemorrhage and periventricular leukomalacia with the subsequent occurrence of cerebral palsy, which is thought to be mediated through the generation of pro-inflammatory cytokines by the fetus. In the light of this relationship, a review of the current management of intrapartum infection and the associated complications of intrauterine infection such as preterm labour and preterm premature rupture of the membranes would seem timely along with the development of potential strategies which might prevent or ameliorate the effects of the fetal inflammatory response syndrome. The suggested changes in the understanding and management of the fetal inflammatory response syndrome provide a challenge and pose a dilemma for the practising obstetrician.

Placental lesion multiplicity: risk factor for IUGR and neonatal cranial ultrasound abnormalities

OBJECTIVE

To determine whether placental lesions are risk factors for neurologic morbidities in intrauterine growth restricted (IUGR) infants, we compared the incidence of cranial ultrasound (CUS) abnormalities and the number and type of placental lesions in IUGR cases and gestational age-matched appropriate for gestational age (AGA) controls.

STUDY DESIGN

Retrospective case-control study of 94 singleton IUGR and 145 AGA infants. Medical records, CUS reports, and placental histology were reviewed. Analyses included chi2, t-test, analysis of variance and logistic regressions to identify those variables significantly associated with IUGR and those associated with CUS abnormalities.

RESULTS

The incidence of CUS abnormalities was 1.7-fold higher in IUGR cases (50%) than controls (29.7%) (p<0.05). A total placental lesion score of > or =3 was associated with an increased risk for IUGR (OR 14.18, 3.41-58.99; p<0.001) and increased risk for CUS abnormality (OR 12.571, 3.33-47.416; p<0.05). In a logistic regression model only > or =2 placental lesions, IUGR and gestational age <30 weeks were significant independent predictors of CUS abnormalities.

CONCLUSIONS

The severity of placental abnormalities expressed as the cumulative number of placental lesions is a significant risk factor for IUGR and perinatal brain injury. These results suggest that abnormal uteroplacental or fetoplacental blood flow may adversely affect intrauterine growth and increase the risk for brain injury.

Cerebral white matter damage in the preterm infant: pathophysiology and risk factors

Based on clinical, epidemiologic, and experimental studies, the aetiology of white matter damage, specifically periventricular leukomalacia (PVL), is multifactorial and involves pre- and perinatal factors possibly including genetic factors, hypoxic-ischaemic insults, infection, excess cytokines, free radical production, increased excitatory amino acid release, and trophic factor deficiencies. The article summarizes research findings about the aetiology of white matter damage and cerebral palsy in preterm infants. The information is organized according to specific antecedents, for which we present epidemiological and neurobiological data. The most important prenatal factor appears to be intrauterine infection. We discuss the evidence supporting the hypothesis that the foetal inflammatory response contributes to neonatal brain injury and later developmental disability. We recently established an animal model of excitotoxic lesions in the developing mouse brain. Brain damage was induced by intra-cortical injections of ibotenate, a glutamatergic agonist. When administered on post-natal day 5 ibotenate induced the formation of white matter cysts. Our animal model could be used to further explore the mechanisms involved in the formation of PVL. Potentially preventive strategies will be discussed.

Hemiparetic cerebral palsy: etiological risk factors and neuroimaging

The purpose of this paper, which was conducted on 175 children with hemiparetic cerebral palsy (H-CP), was to verify the etiological risk period for this disease. Etiological risk factors (ERF) were detected through anamnesis: 23% in the prenatal period, 18% in the perinatal period and 59% of the patients the period was undefined (ERF in the prenatal and perinatal period was 41% and no ERF was 18% of the cases. The computerized tomographic scan (CT) and MRI were performed on all the patients, who were then classified according to their etiopathogenic data: CT1= normal (18%); CT 2= unilateral ventricular enlargement (25%); CT 3= cortical/ subcortical cavities (28%); CT4= hemispheric atrophy and other findings (14%); CT 5= malformations (15%). CT 5 was associated with physical malformations beyond the central nervous system and with prenatal ERF's, while CT 2 was associated with the perinatal ERF's, mainly in premature births. Magnetic resonance imaging was performed on 57 patients and demonstrated a good degree of concordance with the CT. Etiology remained undefined in only 37% of the cases after neuroimaging was related to ERF. A high perinatal RF frequency (59%) was observed and emphasized the need for special care during this period.

Possible strategies to protect the preterm brain against the fetal inflammatory response

The accruing evidence that a fetal inflammatory response is the link between antenatal infection and white matter damage in the preterm newborn infant offers room for speculation how this harmful sequence could be interrupted. Enhancement of endogenous protection, response modification, and damage limitation downstream could be helpful strategies for intervention design. Appropriate observational and experimental studies are needed before clinical interventions can be initiated.

Perinatal risk factors for cranial ultrasound abnormalities in neonates born after spontaneous labour before 34 weeks

OBJECTIVE

The aim of this study was to identify risk factors for cranial ultrasound abnormalities in neonates born after spontaneous preterm labour with or without prolonged premature rupture of the membranes (PROM).

METHODS

The presence of intraventricular haemorrhage and cystic periventricular leucomalacia was investigated in a cohort of neonates born between 24 and 34 weeks using cranial ultrasound. A stepwise forward logistic regression was performed to analyse the influence of antenatal and postnatal variables on cranial ultrasound abnormalities.

RESULTS

The study group consisted of 205 neonates and cranial ultrasound abnormalities were identified in 27 infants. Early onset neonatal infectious disease (OR 3.09, 95% CI 1.24--7.70, P=0.01) increased the risk for cranial ultrasound abnormalities. Gestational age at birth (OR 0.96, 95% CI 0.93--0.99, P=0.03) and a full course of antenatal steroids (OR 0.33, 95% CI 0.13--0.85, P=0.02) reduced the risk for cranial ultrasound abnormalities.

CONCLUSION

Early onset neonatal infectious disease is an independent risk factor for cranial ultrasound abnormalities in the very preterm neonate born after spontaneous labour with or without PROM.

Early neonatal brain injury in histologic chorioamnionitis

The relation between clinical or histologic chorioamnionitis and early neonatal adverse neurologic outcome was investigated (n = 483). Histologic, but not clinical, evidence of chorioamnionitis was found to be a significant predictor of periventricular echodensity (odds ratio, 2.4; 95% CI, 1.8-3.2), echolucency (3.3; 1.9-5.6), ventriculomegaly (2.7; 1.8-4.2), intraventricular hemorrhage > or =3 (3.5; 2.4-5.2), and seizures (2.3; 1.4-3.7).

Infection and preterm birth: evidence of a common causal relationship with bronchopulmonary dysplasia and cerebral palsy

Subclinical genital tract infection has been clearly established as a significant cause of spontaneous preterm birth, particularly in early gestations. Bacterial vaginosis organisms rank highly among the pathogens involved in preterm labour and there is considerable beneficial evidence from the use of prophylactic antibiotics for women at high risk of preterm birth. The pathogenesis involves activation of macrophages and the generation of pro-inflammatory cytokines. Bronchopulmonary dysplasia is seen in the most immature of survivors and appears to be secondary to interruption of normal development and maturation of the lungs. The link between chorioamnionitis and lung injury in utero and subsequent development of bronchopulmonary dysplasia has now been substantiated. Exposure to pro-inflammatory cytokines is implicated in the impairment of the fetal lung. A significant body of evidence supports the association between chorioamnionitis, periventricular leukomalacia and cerebral palsy. Biological mechanisms that explain the association between chorioamnionitis and fetal brain injury involve pro-inflammatory cytokines. Similarity in the pattern of expression of cytokines suggests a common pathway for the initiation of preterm labour and also injury to the lung and the central nervous system of the fetus.

The relationship between placental and other perinatal risk factors for neurologic impairment in very low birth weight children

Placental abnormalities reflect antenatal disease processes that may interact with other perinatal risk factors to affect long-term outcome. We performed a nested case control analysis of placental and clinical risk factors associated with neurologic impairment (NI) at 20-mo corrected age (60 cases and 59 controls) using data collected in a prospective study of very low birth weight (less than 1500 g) infants born between 1983 and 1991. In a preliminary analysis we explored the relationship between clinical infection and histologic chorioamnionitis (CA). Only histologic CA with a fetal vascular response correlated with either clinical CA or early onset neonatal sepsis. We then assessed the relative contribution of the nine risk factors (four placental and five clinical) associated with NI at the univariate level by multiple logistic regression. Three risk factors were independent predictors of NI: severe cranial ultrasound abnormalities (odds ratio 13.6, 95% confidence intervals 4.5-66.7), multiple placental lesions (odds ratio 13.2, 95% confidence intervals 1.3-137.0), and oxygen dependence at 36 wk (odds ratio 4.2, 95% confidence intervals 1.2-14.6). Finally, a series of logistic regressions was conducted with the dependent variable changing as we moved back along the causal chain to explore the relationships between risk factors operating at different stages. This analysis suggested that antenatal variables that were not independent predictors of NI by multiple logistic regression exerted their effects through the following intermediate pathways: fetal grade 3 histologic CA via chorionic vessel thrombi, clinical CA via grade 3 villous edema, and grade 3 villous edema via severe cranial ultrasound abnormalities.

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.

Dietary essential fatty acids, long-chain polyunsaturated fatty acids, and visual resolution acuity in healthy fullterm infants: a systematic review

BACKGROUND

Biologically active neural tissue is rich in docosahexaenoic acid (DHA), an omega-3 long-chain polyunsaturated fatty acid (LCPUFA). We conducted a systematic review to examine the nature of discordant results from studies designed to test the hypothesis that dietary DHA leads to better performance on visually-based tasks in healthy, fullterm infants. We also conducted a meta-analysis to derive combined estimates of behavioral- and electrophysiologic-based visual resolution acuity differences and sample sizes that would be useful in planning future research.

STUDY DESIGN AND METHODS

Twelve empirical studies on LCPUFA intake during infancy and visual resolution acuity were identified through bibliographic searches, examination of monograph and review article reference lists, and written requests to researchers in the field. Works were reviewed for quality and completeness of information. Study design and conduct information was extracted with a standardized protocol. Acuity differences between groups consuming a source of DHA and groups consuming DHA-free diets were calculated as a common outcome from individual studies; this difference score was evaluated against a null value of zero and then used, with the method of DerSimonian and Laird (Meta-analysis in clinical trials. Control Clin Trials 1986;7:177-188), to derive combined estimates of visual resolution acuity differences within seven age categories. RESULTS OF RANDOMIZED COMPARISONS: The combined visual resolution acuity difference measured with behaviorally based methods between DHA-supplemented formula fed groups and DHA-free formula fed groups is 0.32+/-0.09 octaves (combined difference+/-S.E.M., P=0.0003) at 2 months of age. The direction of this value indicates higher acuity in DHA-fed groups. RESULTS OF NON-RANDOMIZED STUDY DESIGNS: The combined visual resolution acuity difference measured with behaviorally based methods between human milk fed groups and DHA-free formula fed groups is 0.49+/-0.09 octaves (P< or =0.000001) at 2 months of age and 0.18+/-0.08 octaves (P=0.04) at 4 months of age. Acuity differences for electrophysiologic-based measures are also greater than zero at 4 months (0.37+/-0.16 octaves, P=0.02).

CONCLUSION

Some aspect of dietary n-3 intake is associated with performance on visual resolution acuity tasks at 2, and possibly, 4 months of age in healthy fullterm infants. Whether n-3 intake confers lasting advantage in the development of visually based processes is still in question.

Rapid ischemic cell death in immature oligodendrocytes: a fatal glutamate release feedback loop

Ischemic injury of immature oligodendrocytes is a major component of the brain injury associated with cerebral palsy, the most common human birth disorder. We now report that cultured immature oligodendrocytes [O4(+)/galactoceramide (GC)(-)] are exquisitely sensitive to ischemic injury (80% of cells were dead after 25.5 min of oxygen and glucose withdrawal). This rapid ischemic cell death was mediated by Ca(2+) influx via non-NMDA glutamate receptors. The receptors were gated by the release of glutamate from the immature oligodendrocytes themselves via reverse glutamate transport and included a significant element of autologous feedback of glutamate from cells onto their own receptors. High (> or = 100 microM) extracellular glutamate was protective against ischemic injury as a result of non-NMDA glutamate receptor desensitization. Other potential pathways of Ca(2+) influx, such as voltage-gated Ca(2+) channels, NMDA receptors, or the Na(+)-Ca(2+) exchanger, did not significantly contribute to ischemic Ca(2+) influx or cell injury. Release of Ca(2+) from intracellular stores was also not an important factor. In agreement with previous studies, more mature oligodendrocytes (O4(-)/GC(+)) were found to be less sensitive to ischemic injury than were the immature cells studied here.

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.

Randomized placebo-controlled trial of a 42-day tapering course of dexamethasone to reduce the duration of ventilator dependency in very low birth weight infants: outcome of study participants at 1-year adjusted age

OBJECTIVE

Ventilator-dependent preterm infants are often treated with a prolonged tapering course of dexamethasone to decrease the risk and severity of chronic lung disease. The objective of this study was to assess the effect of this therapy on developmental outcome at 1 year of age.

METHODS

Study participants were 118 very low birth weight infants who, at 15 to 25 days of life, were not weaning from assisted ventilation and were then enrolled in a randomized, placebo-controlled, double-blind trial of a 42-day tapering course of dexamethasone. Infants were examined at 1 year of age, adjusted for prematurity, by a pediatrician and a child psychologist. A physical and neurologic examination was performed, and the Bayley Scales of Infant Development were administered. All examiners were blind to treatment group.

RESULTS

Groups were similar in terms of birth weight, gestational age, gender, and race. A higher percentage of dexamethasone recipients had major intracranial abnormalities diagnosed by ultrasonography (21% vs 11%). Group differences were not found for Bayley Mental Development Index (median [range] for dexamethasone-treated group, 94 [50-123]; for placebo group, 90 [28-117]) or Psychomotor Development Index Index (median [range]) for dexamethasone-treated group, 78 (50-109); for placebo-treated group, 81 [28-117]). More dexamethasone-treated infants had cerebral palsy (25% vs 7%) and abnormal neurologic examination findings (45% vs 16%). In stratified analyses, adjusted for major cranial ultrasound abnormalities, these associations persisted (OR values for cerebral palsy, 5.3; 95% CI: 1.3-21.4; OR values for neurologic abnormality 3.6; 95% CI: 1.2-11.0).

CONCLUSIONS

A 42-day tapering course of dexamethasone was associated with an increased risk of cerebral palsy. Possible explanations include an adverse effect of this therapy on brain development and/or improved survival of infants who either already have neurologic injury or who are at increased risk for such injury.

White matter disorders of prematurity: association with intraventricular hemorrhage and ventriculomegaly. The Developmental Epidemiology Network

OBJECTIVES

Because intraventricular hemorrhage (IVH) often precedes the development of sonographically defined white matter damage (WMD) in very preterm infants, we sought to identify the IVH characteristics that predict WMD.

HYPOTHESES

We evaluated variations on the null hypothesis that infants with IVH are no more likely than infants without IVH to have WMD. These variations dealt with characteristics of the IVH (presence or absence of ventriculomegaly) or characteristics of the WMD (size, localization, and laterality).

METHODS

A total of 1605 infants weighing 500 to 1500 g at birth between January 1991 and December 1993 underwent standardized cranial ultrasound studies with 6 standard coronal and 5 sagittal views at postnatal days 1 to 3, 7 to 10, and at 3 to 8 weeks.

RESULTS

A total of 129 (8%) infants had WMD, either an echodensity alone (n = 59), an echolucency alone (n = 18), or both (n = 52). In analyses that controlled for gestational age, IVH was associated with a fivefold to ninefold increased risk of WMD regardless of size, laterality, or extent of lesions (P </=.0005). Compared with infants with neither IVH nor ventriculomegaly, infants with both were at 18- to 29-fold greater risk of WMD (P </=.0005).

CONCLUSIONS

In this study IVH and ventriculomegaly were powerful predictors of WMD occurrence, whether small or large, unilateral or bilateral, localized or diffuse.

Prenatal factors and adult mental and physical health

OBJECTIVE

To review research on prenatal influences on adult mental and physical health and draw implications for future directions in psychiatric research.

METHOD

Schizophrenia is selected as an example from mental health and cardiovascular disease as an example from physical health. For each of these disorders, empirical findings on prenatal influences are reviewed, and the methods used to demonstrate them are critiqued.

RESULTS

Research on prenatal antecedents of these conditions has proceeded in parallel: intriguing findings have related fetal growth restriction or fetal insult to adult health; similar types of causal pathways have been proposed to explain the relationships; and research has been plagued by similar limitations, including lack of precise prenatal exposure data and difficulty of controlling confounding. The prevailing view of disease causation, which is not well-suited to investigation of prenatal antecedents, impedes research in both fields. Yet, there has been little interchange between researchers in the 2 fields.

CONCLUSIONS

We propose a causal paradigm that could serve as a guide for future investigations on the prenatal antecedents of adult health and promote interchange between research on mental and physical health. The paradigm reflects current thinking in epidemiology by encompassing not only risk factors as traditionally conceived but also causal chains over time and causal influences at multiple levels of organization. Implications for the design of new research are illustrated with reference to an ongoing study.

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.

White matter injury in the preterm infant: an important determination of abnormal neurodevelopment outcome

Periventricular white matter injury, specifically cystic periventricular leukomalacia (PVL) and ipsilateral hemorrhage into white matter associated with periventricular-intraventricular hemorrhage (PV-IVH), contribute significantly to neonatal mortality and long-term neurodevelopmental deficits in the premature infant. The first lesion PVL occurs in approximately 3-4% of infants of birth weight (BW) < 1500 grams. It manifests either as a focal or diffuse lesion within white matter. Although the pathogenesis of PVL is complex and likely multifactorial, principle contributors include vascular factors which markedly increase the risk for ischemia during periods of systemic hypotension and the intrinsic vulnerability of the oligodendrocyte to neurotoxic factors such as free radicals or cytokines. Clinical associations with PVL include a history of chorioamnionitis, prolonged rupture of membranes, asphyxia, sepsis, hypocarbia, etc. The vast majority of infants exhibit long-term neurodevelopmental deficits that affect motor, cognitive and visual function. The second lesion, the ipsilateral hemorrhage into white matter lesion associated with PV-IVH, occurs in approximately 10-15% of infants of BW < 1000 grams. The white matter injury appears to be a venous infarction with hemorrhage occurring as a secondary phenomenon. Prevention of this lesion has to include prevention of the associated PV-IVH. In this regard, the antenatal administration of glucocorticoids has been associated with a significant reduction in the sonographic incidence of severe IVH and the associated white matter involvement. The postnatal administration of indomethacin to high risk infants appears to hold the most promise at the current time in preventing this lesion. The neurodevelopmental outcome with extensive white matter injury is universally poor, affecting long-term motor and cognitive deficits; the long-term outcome is more favorable with lesser involvement. A clearer understanding of pathogenesis of both conditions is essential so as to provide targeted preventative strategies.

Brain injury in the premature infant: overview of clinical aspects, neuropathology, and pathogenesis

Brain injury in the premature infant is an extremely important problem, in part because of the large absolute number of infants affected yearly. The two principal brain lesions that underlie the neurological manifestations subsequently observed in premature infants are periventricular hemorrhagic infarction and periventricular leukomalacia. The emphases of this article are the neurology, neuropathology, and pathogenesis of these two lesions. Recent work suggests that the ultimate goal, prevention of the lesions, is potentially achievable. Periventricular hemorrhagic infarction may be preventable by prevention of germinal matrix/intraventricular hemorrhage, and periventricular leukomalacia, by detection of impaired cerebrovascular autoregulation, prevention of impaired cerebral blood flow, and interruption of the cascade to oligodendroglial cell death by such agents as free-radical scavengers.

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.

Antenatal glucocorticoid, magnesium exposure, and the prevention of brain injury of prematurity

Prevention of perinatal white matter injury with or without severe intraventricular hemorrhage (IVH) is critical to reduce cerebral palsy (CP) in premature infants. Antenatal therapies that may afford neuroprotection include glucocorticoids, which are associated with a significant reduction in severe IVH, and magnesium, which is associated with reduced CP. Potential protective mechanisms of glucocorticoids include a direct effect on brain, improved respiratory function, and more stable blood pressure hemodynamics. Because magnesium is often administered to mothers with pregnancy-induced hypertension, a condition associated with reduction in severe IVH, the independent neuroprotective role of magnesium remains unclear and warrants additional studies.

Obstetric risk factors for periventricular leukomalacia among preterm infants

OBJECTIVE

To evaluate the obstetric antecedents of cystic periventricular leukomalacia and transient echodense periventricular lesions among preterm infants.

DESIGN

A cohort study of preterm singleton infants born between 25 and 33 weeks gestation.

SETTING

Pavia, Italy.

POPULATION

Three hundred and forty-nine infants admitted to a Division of Neonatal Intensive Care who were screened for periventricular leukomalacia.

METHOD

The obstetric factors in infants with either cystic periventricular leukomalacia or transient echodense periventricular lesions were compared to those in infants with negative cranial ultrasonographic findings. Stepwise multiple logistic regression analysis was used to evaluate the association between risk factors and outcomes adjusting for confounders.

RESULTS

The prevalence of cystic periventricular leukomalacia and transient echodense lesions was 5.7% (20/349) and 14% (49/349), respectively. The main risk factors for cystic leukomalacia were first trimester haemorrhage (OR 4.49; 95% CI 1.63-12.39), maternal urinary tract infection on admission (OR 5.71; 95% CI 1.91-17.07), and neonatal acidosis (pH < 7.2) at birth (OR 5.97; 95% CI 1.93-18.52). Meconium-stained amniotic fluid (OR 3.95; 95% CI 1.42-10.98) and long term (> 72 hours) ritodrine tocolysis (OR 2.54; 95% CI 1.28-5.05) were associated with an increased risk of echodense lesions. The likelihood of overall leukomalacia (cystic plus echodense periventricular lesions) was increased among cases with meconium-stained amniotic fluid (OR 4.06; 95% CI 1.65-10.0), long-term ritodrine tocolysis (OR 2.56; 95% CI 1.38-4.72), maternal infection (OR 1.73; 95% CI 1.0-3.0), and acidosis at birth (OR 1.98; 95% CI 1.0-3.98).

CONCLUSIONS

This study confirms that maternal infection, acidosis at birth, and meconium-stained amniotic fluid increase the risk of periventricular leukomalacia in preterm infants. Long-term ritodrine use seems to increase the risk for transient echodense lesions.

[Periventricular leukomalacia. I. Histological and pathophysiological aspects]

The term 'periventricular leukomalacia' (PVL) usually covers necrotic and/or gliotic lesions from perinatal origin occurring in the periventricular ring of telencephalic white matter. PVLs are found post-mortem in one third of brains from autopsies of premature infants; PVLs are diagnosed in 4 to 10% of infants born before 33 weeks of gestation and remaining alive more than 3 days after birth. PVL is very rare in at term infants. The proportion of PVLs from prenatal origin is estimated between one third and one half of cases. Recent progresses in neuroepidemiology, developmental neurobiology and imaging methods permit to revisit the pathophysiology of PVLs on a multifactorial basis. The final result of these multiple factors seem to be calcium influx due to glutamatergic overactivation triggered by cytokines, infection and inflammation, and deficit in neurotrophic factors. Periventricular topography can be explained by properties of intracerebral vascular wall at this stage of angiogenesis and by perfusion failure/hypoxia.

Trends in mortality and cerebral palsy in a geographically based cohort of very low birth weight neonates born between 1982 to 1994

OBJECTIVE

To analyze whether the increasing survival of very low birth weight infants during the 1980s and 1990s has increased the risk of cerebral palsy among survivors.

METHODS

The study cohort consisted of 2076 consecutively born infants, with birth weights of 500 to 1500 g and no major anomaly, born July 1, 1982, through June 30, 1994, to residents of a 17-county region in North Carolina. These infants had a mean birth weight of 1096 g (standard deviation, 251 g) and a mean gestational age of 29 weeks (standard deviation, 3 weeks). One thousand five hundred sixty-eight infants (76%) survived to 1 year adjusted age, at which point 1282 infants (82%) were examined at our medical center. The diagnosis of cerebral palsy was made only if the examining pediatrician and a pediatric physical therapist agreed on the diagnosis. To analyze trends across time, the Cochran-Armitage chi2 test and logistic regression were applied to data for infants categorized into six 2-year epochs according to year of birth.

RESULTS

Mortality did not change significantly through 1990, and then began to decrease in 1990 to 1994. During the study period, mortality decreased from 36.8% between 1982 and 1984, to 13.8% between 1992 and 1994. The prevalence of cerebral palsy among survivors was constant from 1982 to 1988 (11.3%), decreased slightly from 1988 to 1990 (9.2%), and was lowest in 1990 to 1994 (5.2%). These secular trends in mortality and cerebral palsy risk remained significant when adjusted for gestational age, gender, and race. When adjusted for surfactant use, the trend in mortality was no longer significant, whereas the trend in cerebral palsy risk persisted.

CONCLUSIONS

The increasing survival of very low birth weight infants in the 1980s and 1990s has not resulted in an increased prevalence of cerebral palsy among survivors.

Increased risk of spastic diplegia among very low birth weight children after preterm labor or prelabor rupture of membranes

Our objective was to study the association of spastic diplegia (SDP; N = 29) with the initiator of preterm birth in a regional cohort of 312 6-year-old very low birth weight children (< or =1500 gm). We determined the prevalence of SDP among those children born after idiopathic preterm onset of labor (POOL) or prelabor rupture of membranes (PROM) (12% SDP), and among those born after pregnancy-induced hypertension or other medical indications for preterm delivery (4% SDP). Stratification showed that 83% of the children with diplegia were born after POOL or PROM. The threefold increased risk of SDP among those children born after POOL or PROM compared with the remainder of the cohort (crude odds ratio 3.2, 95% confidence interval 1.2 to 8.5) remained elevated after controlling for perinatal and neonatal variables (odds ratio 2.4 to 2.7) in logistic regression models. We conclude that birth after POOL or PROM increases the risk of SDP among very low birth weight children and speculate that this might be related to infectious processes leading to both POOL or PROM and SDP.

Survival and developmental disability in infants with birth weights of 501 to 800 grams, born between 1979 and 1994

OBJECTIVE

Because the survival rate has increased for extremely low birth weight neonates, many have raised the concern that the rate of developmental disability among survivors will also increase. To address this concern, we analyzed changes over time in survival and major neurosensory impairment in a sample of extremely low birth weight infants born between July 1, 1979, and June 30, 1994.

METHODS

The study sample included 513 infants with birth weights of 501 to 800 g who were cared for in either of the two neonatal intensive care units that serve a 17-county region in northwest North Carolina and who were born to mothers residing in that region. At 1 year of age (corrected for gestation), survivors were examined by a pediatrician and were tested using the Bayley Scales of Infant Development. Major neurosensory impairment was defined as cerebral palsy, a Bayley Mental Developmental Index <68, or blindness. A total of 209/216 (97%) of survivors were examined at 1 year of age. Epoch of birth was defined as follows: epoch 1, July 1, 1979 to June 30, 1984; epoch 2, July 1, 1984 to June 30, 1989; and epoch 3, July 1, 1989 to June 30, 1994.

RESULTS

Survival rates for epochs 1, 2, and 3 were, respectively, 24/120 (20%), 63/175 (36%), and 129/218 (59%). In contrast, the proportions with a major neurosensory impairment did not increase over time; rates for successive epochs were 6/24 (25%), 17/61 (28%), and 26/124 (21%). Rates of cerebral palsy were 3/24 (13%), 12/61 (20%), and 9/124 (7%); rates of delayed mental development were 4/24 (17%), 12/61 (20%), and 17/124 (14%); and rates of blindness were 2/24 (8%), 0/62, and 5/124 (4%), respectively.

CONCLUSIONS

This analysis suggests that the increasing survival of extremely low birth weight neonates since the late 1970s has not resulted in an increased rate of major developmental problems identifiable at 1 year of age.

Brain injury in the premature infant--from pathogenesis to prevention

Brain injury in the premature infant is an extremely important problem, in part because of the large absolute number of infants affected yearly. The two principal brain lesions that underlie the neurological manifestations subsequently observed in premature infants are periventricular hemorrhagic infarction and periventricular leukomalacia. The emphases of this article are the neurology, neuropathology and pathogenesis of these two lesions. Recent work suggests that the ultimate goal, prevention of the lesions, is potentially achievable. Periventricular hemorrhagic infarction may be preventable by prevention of germinal matrix-intraventricular hemorrhage, and periventricular leukomalacia, by detection of impaired cerebrovascular autoregulation, prevention of impaired cerebral blood flow and interruption of the cascade to oligodendroglial cell death by such agents as free radical scavengers.

The vulnerability of the fetal sheep brain to hypoxemia at mid-gestation

Our aim was to test the hypothesis that a brief episode of hypoxemia near mid-gestation in fetal sheep will result in damage to the fetal brain with the extent and type of damage in any particular region being related to the developmental processes occurring at the time of the insult. Hypoxemia was induced, sufficient to reduce arterial O2 content by approximately 50%, by restricting utero-placental blood flow in 14 chronically catheterised fetuses for 6 h or 12 h at 84 days of gestation (term 145-8 days). Age-matched fetuses (n = 14; 4 operated and 10 unoperated) were used as controls. Fetuses were killed 7 days after being exposed to hypoxemia, and brains removed for histological analysis at the light and ultrastructural levels. Body weights of hypoxemic fetuses did not differ significantly from controls but brain weights were significantly reduced both in absolute terms and when expressed in relation to body weight (P < 0.05). Most fetuses exposed to hypoxemia sustained no gross brain damage. However, in one hypoxemic fetus from a multiple pregnancy there was extensive leucomalacia in the cortical white matter; mild focal damage was seen in another 8 hypoxemic fetuses. In the cerebral cortex (frontal lobe) the surface folding index was significantly reduced (P < 0.05) in hypoxemic fetuses compared to controls suggesting that gyral formation had been delayed. In these fetuses there were also degenerating neurons in the deeper cortical layers. In the hippocampus of hypoxemic fetuses there was a delay (P < 0.05), compared to controls, in the migration of cells from the germinal layer to the pyramidal layer in the CA1 region, and decreases (P < 0.05) in the density (area1) of neurons in the pyramidal layer and in the width of stratum oriens. In the cerebellum of hypoxemic fetuses there was a decrease (P < 0.05), compared to controls, in the density (area1) of mitotic bodies in the external granule cell layer. However, there were no significant differences in the number of pyknotic cells in this layer, in the density of Purkinje cells, in their somal area, or in the width of the external granule cell or molecular layers. There was an increase (P < 0.05) in the proportion of the brain parenchyma occupied by blood vessels in both the hippocampus and cortex of hypoxemic fetuses compared to controls. This study has shown that an hypoxemic insult near mid-gestation can result, one week later, in white matter damage and in neuronal death in the hippocampus and to a lesser extent in the cerebral cortex and cerebellum. It can also retard neuronal migration and the growth of neural processes in the hippocampus where development is well established at this age. Such brain damage could result in less than optimal neuronal connectivity and could affect function postnatally.

Ischaemic cerebral injury, intrauterine growth retardation, and placental infarction

Two hundred and twenty-five consecutive autopsies performed on fetuses >20 weeks' gestation were reviewed, and 37 growth-retarded stillborn fetuses without multiple congenital abnormalities or evidence of intrauterine infection were identified. Histological evidence of ischaemic cerebral injury was found in 31 of the 37 cases and placental infarction was seen in 26 of 36 placentas. Of the 31 cases with cerebral ischaemia, 24 had placental infarcts. Twenty-six of 27 stillborn fetuses >26 weeks' gestation showed histological evidence of cerebral ischaemia. It was concluded that in the group of growth-retarded fetuses studied, there was a high incidence of both cerebral and placental ischaemic abnormality.

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.

High expression of tumor necrosis factor-alpha and interleukin-6 in periventricular leukomalacia

OBJECTIVE

Periventricular leukomalacia, a common neonatal brain white matter lesion, is a major risk factor for cerebral palsy. Subclinical chorioamnionitis is a risk factor for the development of periventricular leukomalacia, and inflammatory cytokines have been implicated as central mediators of brain injury in this disorder. To elucidate the relationship between the local expression of cytokines and periventricular leukomalacia, we studied neonatal brains to determine whether high expression of tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 was observed in these lesions.

STUDY DESIGN

Immunohistochemical staining for cytokines (tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6) was performed in 10% formalin-fixed, paraffin-embedded brain sections of 17 cases with periventricular leukomalacia. Specimens were obtained from autopsies performed between 1987 and 1994. Brain sections from 17 cases of neonatal deaths without periventricular leukomalacia lesions matched for gestational age at birth, duration of postnatal survival, and presence or absence of infection-related morbidity were used as controls.

RESULTS

The expression of tumor necrosis factor-alpha, interleukin-1 beta, or interleukin-6 was demonstrated in 88% (15/17) of cases with and in 18% (3/17) of cases without periventricular leukomalacia (p < 0.001). Cytokines were expressed mainly in hypertrophic astrocytes and microglial cells. The expression of tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 was identified in 82% (14/17), 29% (5/17), and 71% (12/17) of cases of periventricular leukomalacia, respectively. However, a significantly lower proportion of cases without periventricular leukomalacia expressed tumor necrosis factor-alpha (18%, 3/17) and interleukin-6 (6%, 1/17) than those with the disorder (p < 0.005 for each).

CONCLUSIONS

Expression of tumor necrosis factor-alpha and interleukin-6 was observed more frequently in brain lesions with periventricular leukomalacia than in those without periventricular leukomalacia. These findings provide strong support for the hypothesis that proinflammatory cytokines play a role in the genesis of periventricular leukomalacia.

Urinary tract infection during pregnancy: a risk factor for cerebral palsy?

OBJECTIVE

To assess a possible association of urinary tract infection (UTI) during pregnancy and cerebral palsy in offspring.

DESIGN

Secondary analysis of a case-control study using structured telephone interviews and birth certificate reviews.

SETTING

Cases from community-based agencies providing services to preschool children who were developmentally delayed.

PARTICIPANTS

One hundred twelve preschool children with cerebral palsy and 153 children without cerebral palsy.

MAIN OUTCOME MEASURES

Risk for cerebral palsy.

RESULTS

The prevalence of UTI among case mothers was 17.9% compared with 5.2% among control mothers. The crude odds ratio for risk of cerebral palsy for a mother with a UTI was 3.9, whereas the adjusted odds ratio was approximately 5, indicating that the risk of having a child with cerebral palsy was 4 to 5 times greater for mothers who had a UTI during pregnancy.

CONCLUSIONS

Urinary tract infection during pregnancy was found to be a risk factor for development of cerebral palsy in offspring. Assessment for UTI should occur at the initial prenatal visit and more frequently for women with symptoms or who are at risk. Pregnant women should be educated about preventive measures for UTI. Future research is needed to assess more directly the relationship between UTI during pregnancy and cerebral palsy in offspring.

Maternal intrauterine infection, cytokines, and brain damage in the preterm newborn

To evaluate the hypothesis that the proinflammatory cytokines IL-1, IL-6, and tumor necrosis factor-alpha might be the link between prenatal intrauterine infection (IUI) and neonatal brain damage, the authors review the relevant epidemiologic and cytokine literature. Maternal IUI appears to increase the risk of preterm delivery, which in turn is associated with an increased risk of intraventricular hemorrhage, neonatal white matter damage, and subsequent cerebral palsy. IL-1, IL-6, and TNF-alpha have been found associated with IUI, preterm birth, neonatal infections. and neonatal brain damage. Unifying models not only postulate the presence of cytokines in the three relevant maternal/fetal compartments (uterus, fetal circulation, and fetal brain) and the ability of the cytokines to cross boundaries (placenta and blood-brain barrier) between these compartments, but also postulate how proinflammatory cytokines might lead to IVH and neonatal white matter damage during prenatal maternal infection. Interrupting the proinflammatory cytokine cascade might prevent later disability in those born near the end of the second trimester.

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.

Significance of low birthweight for gestational age among very preterm infants

OBJECTIVE

To estimate the risk of specific adverse neonatal events resulting from the combined effects of prematurity and low birthweight in very preterm infants (delivered at 24-31 weeks of gestation).

DESIGN

A cohort study of specific adverse neonatal events in preterm infants born at between 24 and 31 weeks of gestation.

SETTING

Pavia, Italy.

POPULATION

Two hundred and thirty singleton infants with sonographically confirmed gestational age, delivered at 24 to 31 weeks of gestation.

METHODS

To evaluate the impact of a lower than expected birthweight on selected neonatal events independently of gestational age, we calculated birthweight standard deviation scores (differences between actual birthweight and fitted birthweight divided by fitted standard deviation) for each week of gestation.

RESULTS

After adjustment for gestational age and other confounders, there was a significant linear trend relating a decreasing birthweight SDS to an increased likelihood of neonatal death, intraventricular haemorrhage, severe respiratory distress syndrome, and acidosis. Compared with infants with SDS > or = 0 (> or = 50th centile of birthweight), infants with birthweight SDS < -1 (< 16th centile) had increased odds for neonatal death [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.42-9.6], grade III-IV intraventricular haemorrhage (OR 17.5, 95% CI 4.04-75.9), and neonatal acidosis (OR 3.22, 95% CI 1.41-7.4). The significance of birthweight SDS as a predictor of neonatal outcome, however, was lower than that of gestational age.

CONCLUSIONS

A lower than expected birthweight affects the likelihood of several adverse neonatal events in very preterm infants. However, a decreasing birthweight SDS affects neonatal outcome less than decreasing gestation does.

Antenatal and delivery risk factors simultaneously associated with neonatal death and cerebral palsy in preterm infants

To evaluate the simultaneous effects of antenatal and delivery risk factors on neonatal death and cerebral palsy in preterm infants, we conducted a cohort study of 363 singleton pregnancies delivered between 24 and 33 weeks gestation. Neurodevelopmental outcome of the infants was evaluated at 2 years of corrected age. Risk factors associated with death or cerebral palsy were analysed by politomous logistic regression. Overall, the mortality rate was 14.6% (53/363) and the prevalence of cerebral palsy among surviving infants was 12.3% (38/310). Decreasing gestation and meconium-stained amniotic fluid were the only antenatal factors associated with increased odds for both death and cerebral palsy. The effect magnitude and the predictive value of gestational age were greater for death than for cerebral palsy. After adjustment for confounders, prolonged (> or = 48 h) rupture of membranes (odds ratio 2.98, 95% confidence interval 1.12-7.96) and male sex of the infant (odds ratio 3.01, 95% confidence interval 1.32-6.71) were significantly associated only with cerebral palsy. We conclude that neonatal death and cerebral palsy share few common antenatal risk factors. The characteristics of antenatal risk factors for cerebral palsy suggest that bacterial infestation of the amniotic cavity may be implicated in the etiology of the cerebral impairment.

Maternal receipt of magnesium sulfate does not seem to reduce the risk of neonatal white matter damage

OBJECTIVE

To investigate whether in utero exposure to magnesium sulfate is associated with a lower incidence of cranial ultrasonographic abnormalities that predict cerebral palsy in infants who weigh less than 1501 g at birth.

DESIGN

For a prospective study of the antecedents of cranial ultrasonographic abnormalities, we enrolled infants who weighed 500 to 1500 g when born at five institutions. Data were collected by interview of the mothers and review of medical records. Protocol cranial ultrasonograms were obtained as close as possible to postnatal days 1, 7, and 21. Abnormality on cranial ultrasound scans was determined by a consensus committee of three sonologists.

RESULTS

Of the 1518 infants for whom we knew whether the mothers received magnesium sulfate, the first protocol cranial ultrasound scan was available for 1409 infants, the second for 1274 infants, and the third for 1050 infants. Forty-five percent of infants were exposed to magnesium sulfate before delivery. The major correlates of magnesium sulfate exposure were receipt of antenatal corticosteroids and a diagnosis of preeclampsia and/or pregnancy-induced hypertension. Maternal magnesium receipt was not associated with a reduced incidence of hypoechoic or hyperechoic images of white matter parenchyma, intraventricular hemorrhage, or ventriculomegaly, even when the sample was stratified by each of six potential confounders. When adjustment was made for gestational age, a measure of birth weight for gestational age, antenatal corticosteroid exposure, preeclampsia and pregnancy-induced hypertension, route of delivery, and the occurrence of any labor, the risk ratios for each cranial ultrasonographic abnormality associated with magnesium sulfate exposure hovered close to 1.

CONCLUSION

Maternal receipt of magnesium sulfate does not seem to be associated with an appreciably reduced risk of cranial ultrasonographically defined neonatal white matter damage, intraventricular hemorrhage, or ventriculomegaly.

Diagnosis of intracranial lesions in very-low-birthweight infants by ultrasound: incidence and association with potential risk factors

This study was designed to determine the frequencies of germinal matrix and ventricular haemorrhages as well as lesions in the white matter diagnosed by ultrasonography. In subsequent studies the effects of perinatal brain lesions on the cognitive and motor development of preterm children will be presented. Lesions of the white matter are probably more damaging than intraventricular and subependymal bleeds. Therefore, a modified classification of the lesions was used, clearly separating bleeds from white matter pathology. The study includes 291 infants with a body weight of < or = 1500 g consecutively admitted to the neonatal intensive-case unit at Karolinska Hospital from 1988 to 1993. Fifty-four (18.9%) died before 6 months. Two hundred and sixty-three infants were examined using ultrasound. Pathology due to bleeding was classified into three grades (B1-3) similar to Papile's first three grades. Pathology in periventricular white matter was classified into four groups (W1-4): W1 = subtle and We = distinctive white matter echodensities; W3 = cyst formation; W4 = large, intense echodensity. Forty-nine patients had abnormalities in the periventricular white matter (15 W1, 12 W2, 11 W3 and 11 W4) and 58 had subependymal (B1 = 29) or ventricular bleeding without (B2 = 13) or with dilatation (B3 = 16). Ventilator treatment was significantly associated with both B and W lesions. Low gestational age, low birthweight, small for gestational age, pre-eclampsia and caesarean section were significantly associated with B lesions whereas asphyxia, surfactant treatment, male patient sex and outborn were associate with W lesions; b 1-3 and W 1-4 lesions were thus partly associated with different potential risk factors. The pre- and perinatal potential risk factors could only partly explain the variance in the frequency of B and W lesions, indicating that there are yet unidentified risk factors for intracranial ultrasonographic pathology.

Transient dystonia in non-handicapped low-birthweight infants and later neurodevelopment

The aim of the present study was to evaluate the long-term prognostic significance of transient increase in muscle tone during infancy (dystonia) in very low-birthweight (VLBW) infants without cerebral palsy. Motor (Peabody Developmental Motor Scales), cognitive (Wechsler Preschool and Primary scale of Intelligence) and behavioural (Personality Inventory for Children, Yale Children's Inventory) development was assessed at 5 years of age. In a population-based sample of 50 VLBW children, transient dystonia was present in 14. In explorative analyses, transient dystonia was associated with low 1 min Apgar scores, neonatal bacterial infection, and lack of breast-milk in the neonatal period. Cognitive, neuromotor and behavioural development at 5 years of age was comparable in those with and without transient dystonia, although there was a statistically non-significant tendency towards more neuromotor problems in the dystonic children.