The intrinsic connectivity distribution: a novel contrast measure reflecting voxel level functional connectivity

Resting-state fMRI (rs-fMRI) holds promise as a clinical tool to characterize and monitor the phenotype of different neurological and psychiatric disorders. The most common analysis approach requires the definition of one or more regions-of-interest (ROIs). However this need for a priori ROI information makes rs-fMRI inadequate to survey functional connectivity differences associated with a range of neurological disorders where the ROI information may not be available. A second problem encountered in fMRI measures of connectivity is the need for an arbitrary correlation threshold to determine whether or not two areas are connected. This is problematic because in many cases the differences in tissue connectivity between disease groups and/or control subjects are threshold dependent. In this work we propose a novel voxel-based contrast mechanism for rs-fMRI, the intrinsic connectivity distribution (ICD), that neither requires a priori information to define a ROI, nor an arbitrary threshold to define a connection. We show the sensitivity of previous methods to the choice of connection thresholds and evaluate ICD using a survey study comparing young adults born prematurely to healthy term control subjects. Functional connectivity differences were found in hypothesized language processing areas in the left temporal-parietal areas. In addition, significant clinically-relevant differences were found between preterm and term control subjects, highlighting the importance of whole brain surveys independent of a priori information.

Practice parameter: neuroimaging of the neonate: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society

OBJECTIVE

The authors reviewed available evidence on neonatal neuroimaging strategies for evaluating both very low birth weight preterm infants and encephalopathic term neonates.

IMAGING FOR THE PRETERM NEONATE

Routine screening cranial ultrasonography (US) should be performed on all infants of <30 weeks' gestation once between 7 and 14 days of age and should be optimally repeated between 36 and 40 weeks' postmenstrual age. This strategy detects lesions such as intraventricular hemorrhage, which influences clinical care, and those such as periventricular leukomalacia and low-pressure ventriculomegaly, which provide information about long-term neurodevelopmental outcome. There is insufficient evidence for routine MRI of all very low birth weight preterm infants with abnormal results of cranial US.

IMAGING FOR THE TERM INFANT

Noncontrast CT should be performed to detect hemorrhagic lesions in the encephalopathic term infant with a history of birth trauma, low hematocrit, or coagulopathy. If CT findings are inconclusive, MRI should be performed between days 2 and 8 to assess the location and extent of injury. The pattern of injury identified with conventional MRI may provide diagnostic and prognostic information for term infants with evidence of encephalopathy. In particular, basal ganglia and thalamic lesions detected by conventional MRI are associated with poor neurodevelopmental outcome. Diffusion-weighted imaging may allow earlier detection of these cerebral injuries.

RECOMMENDATIONS

US plays an established role in the management of preterm neonates of <30 weeks' gestation. US also provides valuable prognostic information when the infant reaches 40 weeks' postmenstrual age. For encephalopathic term infants, early CT should be used to exclude hemorrhage; MRI should be performed later in the first postnatal week to establish the pattern of injury and predict neurologic outcome.

Astrocyte-derived VEGF mediates survival and tube stabilization of hypoxic brain microvascular endothelial cells in vitro

Chronic sublethal hypoxia has been associated with changes in neurovascular behavior, mediated, in part, by induction of vascular endothelial growth factor-A (VEGF-A(165)). In this report we demonstrate that RBE4 cells (derived from rodent cerebral microvasculature), when cultured in three-dimensional collagen gels: (1) Are induced to undergo increased tube formation in response to VEGF-A(165) in a dose-dependent manner; (2) undergo apoptosis under mild hypoxic conditions; (3) are rescued from the effects of hypoxia by the addition of exogenous VEGF-A(165) in a dose-dependent and inhibitable manner or by co-culture with primary newborn rat astrocytes, which are induced to express increased amounts of VEGF-A in hypoxic conditions. Further, we demonstrate that: (4) The observed astrocyte-produced, VEGF-mediated protection from apoptosis (survival) is inhibitable with soluble recombinant VEGF receptor-1 (sFlt), and is associated with a robust induction of MAPK tyrosine phosphorylation. These findings illustrate the importance of VEGF in the process of neurovascular survival in response to injury in developing brain and provide insight into the signaling pathways involved.

Antenatal therapies and the developing brain

This chapter presents a review of basic science and human studies of two commonly used pharmacologic agents (antenatal steroids and magnesium sulfate), in pregnancies at risk of preterm delivery, and examines the effects of these therapies on the developing brain. Very low birthweight (VLBW) infants are known to be at risk of both short-term and long-term neurodevelopmental sequelae; therefore, an understanding of the mechanisms contributing to both neuroprotective and neurotoxic effects of antenatal therapies on the immature brain and potential effects on long-term outcome are critical. Although the short-term beneficial effects of a single course of antenatal steroids are well documented, the experimental animal literature suggests detrimental effects on neurodevelopment of multiple doses. In addition, clinical studies of repeat doses suggest a negative impact on head and brain growth. The animal and human data on the effects of MgSO(4)are also mixed with both beneficial effects or no effects on neurodevelopment. This review will discuss the potential impact of single versus multiple doses and timing of doses on the brain.

Neonatal auditory activation detected by functional magnetic resonance imaging

The objective of this study was to detect auditory cortical activation in non-sedated neonates employing functional magnetic resonance imaging (fMRI). Using echo-planar functional brain imaging, subjects were presented with a frequency-modulated pure tone; the BOLD signal response was mapped in 5 mm-thick slices running parallel to the superior temporal gyrus. Twenty healthy neonates (13 term, 7 preterm) at term and 4 adult control subjects. Blood oxygen level-dependent (BOLD) signal in response to auditory stimulus was detected in all 4 adults and in 14 of the 20 neonates. FMRI studies of adult subjects demonstrated increased signal in the superior temporal regions during auditory stimulation. In contrast, signal decreases were detected during auditory stimulation in 9 of 14 newborns with BOLD response. fMRI can be used to detect brain activation with auditory stimulation in human infants.

Regional brain volume abnormalities and long-term cognitive outcome in preterm infants

CONTEXT

Preterm infants have a high prevalence of long-term cognitive and behavioral disturbances. However, it is not known whether the stresses associated with premature birth disrupt regionally specific brain maturation or whether abnormalities in brain structure contribute to cognitive deficits.

OBJECTIVE

To determine whether regional brain volumes differ between term and preterm children and to examine the association of regional brain volumes in prematurely born children with long-term cognitive outcomes.

DESIGN AND SETTING

Case-control study conducted in 1998 and 1999 at 2 US university medical schools.

PARTICIPANTS

A consecutive sample of 25 eight-year-old preterm children recruited from a longitudinal follow-up study of preterm infants and 39 term control children who were recruited from the community and who were comparable with the preterm children in age, sex, maternal education, and minority status.

MAIN OUTCOME MEASURES

Volumes of cortical subdivisions, ventricular system, cerebellum, basal ganglia, corpus callosum, amygdala, and hippocampus, derived from structural magnetic resonance imaging scans and compared between preterm and term children; correlations of regional brain volumes with cognitive measures (at age 8 years) and perinatal variables among preterm children.

RESULTS

Regional cortical volumes were significantly smaller in the preterm children, most prominently in sensorimotor regions (difference: left, 14.6%; right, 14.3% [P<.001 for both]) but also in premotor (left, 11.2%; right, 12.6% [P<.001 for both]), midtemporal (left, 7.4% [P =.01]; right, 10.2% [P<.001]), parieto-occipital (left, 7.9% [P =.01]; right, 7.4% [P =.005]), and subgenual (left, 8.9% [P =.03]; right, 11.7% [P =.01]) cortices. Preterm children's brain volumes were significantly larger (by 105. 7%-271.6%) in the occipital and temporal horns of the ventricles (P<. 001 for all) and smaller in the cerebellum (6.7%; P =.02), basal ganglia (11.4%-13.8%; P</=.005), amygdala (left, 20.2% [P =.001]; right, 30.0% [P<.001]), hippocampus (left, 16.0% [P =.001]; right, 12.0% [P =.007]), and corpus callosum (13.1%-35.2%; P</=.01 for all). Volumes of sensorimotor and midtemporal cortices were associated positively with full-scale, verbal, and performance IQ scores (P<.01 for all).

CONCLUSIONS

Our data indicate that preterm birth is associated with regionally specific, long-term reductions in brain volume and that morphological abnormalities are, in turn, associated with poorer cognitive outcome. JAMA. 2000;284:1939-1947.

Adaptive mechanisms of developing brain. The neuroradiologic assessment of the preterm infant

Since the 1980s, cranial sonography has been routinely performed in premature infants. This has produced a wealth of information about the more dramatic central nervous system lesions of IVH, PVL, and late VM. This information has included timing and evolution of these lesions and their eventual correlation with outcome. For two reasons the advent of MR imaging scanning has produced an interest in using this modality to evaluate these same infants. First, MR imaging gives an obviously superior image, and its ability to detect lesions is far superior to that of ultrasound. Second, the ability of cranial sonography to detect all of the children with CP or low IQ is limited. In our studies of outcome in very low-birth weight infants grade 3 to 4 IVH, PVL, or VM are able to detect only about 50% of the infants who developed CP by 3 years. This condition should be highly correlated with structural brain disease; an imaging modality that was more sensitive to central nervous system lesions should offer an advantage in predicting outcome. In the only prospective assessment of the ability of these two modalities to predict outcome at 3 years, van de Bor and colleagues found MR imaging did not do better than cranial sonography. This was largely because both modalities detected the most severe lesions, and most children with milder lesions on MR imaging had normal outcome. Studies of late (age 1 to teenage years) MR imaging scans in preterm infants show that a high percentage have white matter lesions but these lesions correlate poorly with outcome. If our concern when counseling parents is to alert them when a serious adverse outcome is likely in their child, then cranial sonography is to be favored precisely because it is less able to detect subtle lesions, which the developing brain has the capacity to overcome. On the other hand, if our aim is to detect all lesions, even though these lesions do not predict serious adverse outcomes, then MR imaging is to be favored. Research aimed at discovering etiologies and mechanisms of brain injury in these high-risk infants should use the more sensitive modality MR imaging. Finally, the interesting observation that preterm infants fare as well as they do despite MR imaging-identified lesions might stimulate research studying the adaptive mechanisms of developing brain.

Outcome of children in the indomethacin intraventricular hemorrhage prevention trial

BACKGROUND

For preterm infants, intraventricular hemorrhage (IVH) may be associated with adverse neurodevelopmental outcome. We have demonstrated that early low-dose indomethacin treatment is associated with a decrease in both the incidence and severity of IVH in very low birth weight preterm infants. In addition, we hypothesized that the early administration of low-dose indomethacin would not be associated with an increase in the incidence of neurodevelopmental handicap at 4.5 years of age in our study children.

METHODS

To test this hypothesis, we provided neurodevelopmental follow-up for the 384 very low birth weight survivors of the Multicenter Randomized Indomethacin IVH Prevention Trial. Three hundred thirty-seven children (88%) were evaluated at 54 months' corrected age, and underwent neurodevelopmental examinations, including the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R), the Peabody Picture Vocabulary Test-Revised (PPVT-R), and standard neurologic examinations.

RESULTS

Of the 337 study children, 170 had been randomized to early low-dose indomethacin therapy and 167 children had received placebo. Twelve (7%) of the 165 indomethacin children and 11 (7%) of the 158 placebo children who underwent neurologic examinations were found to have cerebral palsy. For the 233 English-monolingual children for whom cognitive outcome data follow, the mean gestational age was significantly younger for the children who received indomethacin than for those who received placebo. In addition, although there were no differences in the WPPSI-R or the PPVT-R scores between the 2 groups, analysis of the WPPSI-R full-scale IQ by function range demonstrated significantly less mental retardation among those children randomized to early low-dose indomethacin (for the indomethacin study children, 9% had an IQ <70, 12% had an IQ of 70-80, and 79% had an IQ >80, compared with the placebo group, for whom 17% had an IQ <70, 18% had an IQ of 70-80, and 65% had an IQ >80). Indomethacin children also experienced significantly less difficulty with vocabulary skills as assessed by the PPVT-R when compared with placebo children.

CONCLUSIONS

These data suggest that, for preterm neonates, the early administration of low-dose indomethacin therapy is not associated with adverse neurodevelopmental function at 54 months' corrected age.

Neuronal VEGF expression correlates with angiogenesis in postnatal developing rat brain

When exposed to chronic sublethal hypoxia the developing brain responds with increases in permeability and angiogenesis. Vascular endothelial growth factor (VEGF) may mediate this response. Here, we present data on the localization of VEGF in the rat brain cortex during postnatal development and its correlation to vascularization. We reared newborn rats under normoxic conditions and in hypoxic chambers (FiO(2) 9.5%), removed them at postnatal days (P) 3, 8, 13, 24, and 33 and prepared the cortical brain tissue for immunohistochemistry, in situ hybridization (ISH), Western blot analyses and vessel density counting. When compared to age-matched controls, hypoxic-reared animals displayed a significant increase in platelet endothelial cell adhesion molecule 1 (PECAM-1) protein levels, cerebral microvascular lumen diameter and number and density of vessels (number of capillaries per area). In control animals, ISH and immunohistochemistry revealed that localization of VEGF is restricted almost exclusively to cortical neurons at early stages of development. As the vascular bed begins to stabilize, predominant VEGF expression switches to maturing glial cells which invest vessels while neuronal expression is reduced to a basal level. In hypoxic animals, early localization of VEGF is also restricted to cortical neurons, however, during later developmental stages, glial cells express elevated levels of VEGF protein and high neuronal expression also persists. Thus chronic sublethal hypoxia disrupts the temporal-spatial expression of VEGF, which correlates with continuing hypoxia-driven angiogenesis.

The etiology and outcome of cerebral ventriculomegaly at term in very low birth weight preterm infants

BACKGROUND

Despite improvements in survival data, the incidence of neurodevelopmental handicaps in preterm infants remains high. To prevent these handicaps, one must understand the pathophysiology behind them. For preterm infants, cerebral ventriculomegaly (VM) may be associated with adverse neurodevelopmental outcome. We hypothesized that although the causes of VM are multiple, the incidence of handicap at 4.5 years of age in preterm infants with this ultrasonographic finding at term would be high.

METHODS

To test this hypothesis, we provided neurodevelopmental follow-up for all 440 very low birth weight survivors of the Multicenter Randomized Indomethacin Intraventricular Hemorrhage (IVH) Prevention Trial. A total of 384 children (87%) were evaluated at 54 months' corrected age (CA), and 257 subjects were living in English-speaking, monolingual households and are included in the following data analysis.

RESULTS

Moderate to severe low pressure VM at term was documented in 11 (4%) of the English-speaking, monolingual survivors. High grade IVH and bronchopulmonary dysplasia (BPD) were both risk factors for the development of VM. Of 11 (45%) children with VM, 5 suffered grades 3 to 4 IVH, compared with 2/246 (1%) children without VM who experienced grades 3 to 4 IVH. Similarly, 9/11 (82%) children with VM had BPD, compared with 120/246 (49%) children without VM who had BPD. Logistic regression analysis was performed using birth weight, gestational age, gender, Apgar score at 5 minutes, BPD, sepsis, moderate to severe VM, periventricular leukomalacia, grade of IVH, and maternal education to predict IQ <70. Although maternal education was an important and independent predictor of adverse cognitive outcome, in this series of very low birth weight prematurely born children, VM was the most important predictor of IQ <70 (OR: 19.0; 95% CI: 4.5, 80.6). Of children with VM, 6/11 (55%) had an IQ <70, compared with 31/246 (13%) of children without VM. Children with VM had significantly lower verbal and performance scores compared with children without VM.

CONCLUSIONS

These data suggest that, for preterm neonates, VM at term is a consequence of the vulnerability of the developing brain. Furthermore, its presence is an important and independent predictor of adverse cognitive and motor development at 4.5 years' CA.

Early-onset intraventricular hemorrhage in preterm neonates: incidence of neurodevelopmental handicap

The neurodevelopmental outcome of very low birth weight infants experiencing early-onset intraventricular hemorrhage (IVH) occurring within the first 6 postnatal hours was compared with that of their peers without early-onset IVH at 3 years corrected age. The 440 surviving preterm infants (birth weight 600 to 1,250 g) who had been enrolled in a multicenter, prospectively randomized, controlled trial evaluating the efficacy of postnatal indomethacin to prevent IVH were evaluated with the Stanford-Binet Intelligence Scale and neurological examinations at 3 years corrected age. All study infants had echoencephalography between 5 and 11 hours of life, and testing is reported for all children residing in English monolingual households at 3 years corrected age (i.e., from the obstetric due date). Fifty five of the 73 (75%) infants with IVH within the first 5 to 11 hours survived to 3 years of age, compared with 385 of the 432 (89%) children without early-onset hemorrhage who were alive at 3 years corrected age (P<.001). Eleven of the 29 (38%) English monolingual children with early-onset IVH had Stanford-Binet intelligence quotient scores of less than 70, compared with 47 of the 249 (19%) children without early IVH (P = .03). Similarly, 7 of 28 (25%) early IVH children were found to have cerebral palsy, compared with 20 of 241 (8%) children without early IVH (P = .01). These data suggest that infants who experience the early onset of IVH are at high risk for both cognitive and motor handicaps at 3 years corrected age.

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.

Stroke in a neonate heterozygous for factor V Leiden

Activated protein C resistance is the most common hereditary coagulation abnormality and is caused by the factor V Leiden mutation. A newborn who developed seizures within hours after delivery and was found to have a bihemispheric stroke is described. This patient, determined to be heterozygous for factor V Leiden, is the first reported case of neonatal stroke associated with this common mutation.

An in vitro three-dimensional coculture model of cerebral microvascular angiogenesis and differentiation

The microvasculature of the developing brain is plastic and responds differently to the many insults associated with preterm birth. We developed three-dimensional in vitro culture models for the study of the responses of the developing cerebral microvasculature. Beagle brain microvascular endothelial cells (BBMEC) were isolated by differential centrifugation from newborn beagle pups on postnatal Day 1 and placed in three-dimensional culture dispersed in a collagen gel. Alternatively, BBMEC were placed in a three-dimensional coculture with neonatal rat forebrain astrocytes. Cultures were analyzed for extracellular matrix components at 1 and 6 d, and total RNA was extracted for Northern analyses. Urokinase plasminogen activator activity was assayed in both mono- and cocultures of the two cell types. Studies of three-dimensional BBMEC/astrocyte cocultures demonstrated progressive tube formation with only low levels of endothelial proliferation. By 6 d in three-dimensional coculture, the BBMEC formed capillarylike tubes with a wrapping of glial processes, and basement membrane protein synthesis was noted. Urokinase plasminogen zymography suggested intercellular signaling by the two cell types. These data suggest that the three-dimensional beagle brain germinal matrix microvascular endothelial cell/neonatal rat astrocyte coculture provides a good model for the investigation of microvascular responses in the developing brain.

Chronic postnatal hypoxia increases the numbers of cortical neurons

Premature infants have been shown to undergo prolonged periods of sublethal hypoxia. There is considerable evidence to link these hypoxic events with neurodevelopmental disorders. As an animal model for this clinical problem, rats were raised from the third day of life in a chamber where the O2 level was 9.5%. After 30 days of hypoxia the rats were sacrificed and their brains processed for determination of the number of cortical neurons. This work was performed to test the hypothesis that chronic hypoxia would result in increased cortical cell death. The hypoxic rats had lower body and brain weights as well as decreased cortical volumes. However, hypoxic rats had increased neuronal density and significantly more cortical neurons than controls (P < 0.05). The results of this study suggest that chronic sublethal hypoxia may lead to reduction in the amount of programmed cell death in the developing neocortex.

Antecedents of cerebral palsy in a multicenter trial of indomethacin for intraventricular hemorrhage

OBJECTIVES

To determine if cerebral palsy (CP) rates were lower in the active treatment group compared with the control group, as improved survival rates of very low-birth-weight infants are postulated to be the cause of the increased incidence of CP in preterm infants, to evaluate relationships between multiple prenatal, perinatal, and postnatal variables and CP to understand better its antecedents in very low-birth-weight infants in the era of surfactant replacement therapy, and to determine the usefulness of a cranial ultrasonographic (US) scan in predicting CP.

DESIGN

Inception cohort follow-up study as part of a randomized controlled trial of low-dose indomethacin sodium for the prevention of intraventricular hemorrhage.

SETTING

Neonatal intensive care units at 3 medical centers.

PATIENTS

Infants with birth weights between 600 and 1250 g were eligible, and 505 infants were enrolled in the original study. Of these infants, 440 (87%) survived; neurologic examinations were completed on 381 infants (86%) at 36 months corrected age.

MAIN OUTCOME MEASURES

Statistical analyses were performed to identify the antecedents of CP, including the results of frequent cranial US scans obtained throughout the newborn period.

RESULTS

Cerebral palsy was found in 36 (9.5%) of 381 infants at 36 months corrected age (range, 33-39 months corrected age). Univariate analysis identified chorioamnionitis, treatment with surfactant, bronchopulmonary dysplasia, and abnormal cranial US findings as antecedents of CP. Periventricular leukomalacia and ventriculomegaly were associated with the highest detection rates for CP (37% and 30%, respectively) with acceptable false-positive rates. Multivariate analysis identified bronchopulmonary dysplasia and an abnormal cranial US scan showing grade 3 to 4 intraventricular hemorrhage, periventricular leukomalacia, or ventriculomegaly as independent predictors of CP. Odds ratios for the detection of CP using cranial US findings tabulated by hospital day were in the range of 7 to 26 beginning on day 2.

CONCLUSION

The results suggest that cranial US findings are useful predictors of CP during a patient's stay in the hospital.

Vascular endothelial growth factor mediates reactive angiogenesis in the postnatal developing brain

Although chronic sublethal hypoxia has been shown to promote angiogenesis in the developing brain, the pathogenesis of this response is unknown. We hypothesized that this response may be mediated in part by vascular endothelial growth factor (VEGF). We reared newborn rats (P3) in a chamber with FIO2 of 9.5 +/- 1% (exposed, E). At P33, the animals were removed from the chamber and the brains prepared for immunohistochemistry, mRNA extraction, or horseradish peroxidase (HRP) permeability studies. We also isolated beagle brain germinal matrix endothelial cells from PND 1 beagle pups and placed them in three-dimensional (3-D) coculture with PND 1 rat forebrain astrocytes. Cultures were grown for 6 days in 11% O2 and compared to control 3-D cocultures. When compared to age-matched controls, the experimental rats had significantly increased cortical vascular density (vessels/mm2: 518 +/- 18 vs. 400 +/- 15, P = 0.025). HRP studies demonstrated significantly increased permeability in all cortical vessels examined in experimental rats compared to controls. Compared to controls, VEGF mRNA from hypoxic pups was increased 2.4 times, and immunohistochemical studies of VEGF protein confirmed this finding. Similarly, when compared to controls, hypoxic cocultures of brain microvascular endothelial cells and astrocytes demonstrated significant increase in tubelike structures representing in vitro angiogenesis. Additionally, astrocyte VEGF protein levels increased 4.4-fold in hypoxic compared to control astrocyte cultures and VEGF protein levels increased 1.7-fold in hypoxic compared to control cocultures. Finally, addition of VEGF (10 ng/ml culture medium) to BBMEC alone in 3-D culture elicited not only significant proliferation (P = 0.001) but also increased tube formation. These data demonstrate that the developing brain responds to chronic sublethal hypoxia with increases in permeability and angiogenesis and suggest that VEGF mediates this response.

Neurodevelopmental outcome at 36 months' corrected age of preterm infants in the Multicenter Indomethacin Intraventricular Hemorrhage Prevention Trial

OBJECTIVES

Low-dose indomethacin has been shown to prevent intraventricular hemorrhage (IVH) in very low birth weight neonates, and long-term neurodevelopmental follow-up data are needed to validate this intervention. We hypothesized that the early administration of low-dose indomethacin would not be associated with adverse cognitive outcome at 36 months' corrected age (CA).

METHODS

We enrolled 431 neonates of 600 to 1250 g birth weight with no IVH at 6 to 12 hours in a randomized, prospective trial to determine whether low-dose indomethacin would prevent IVH. A priori, neurodevelopmental follow-up examinations, including the Stanford-Binet Intelligence Scale and Peabody Picture Vocabulary Test-Revised, and standard neurologic examinations were planned at 36 months' CA.

RESULTS

Three hundred eighty-four of the 431 infants survived (192 [92%] of 209 infants receiving indomethacin versus 192 [86%] of 222 infants receiving saline), and 343 (89%) children were examined at 36 months' CA. Thirteen (8%) of the 166 infants who received indomethacin and 14 (8%) of 167 infants receiving the placebo were found to have cerebral palsy. There were no differences in the incidence of deafness or blindness between the two groups. For the 248 English-monolingual children for whom IQ data follow, the mean gestational age was significantly younger for the infants who received indomethacin than for those who received the placebo. None of the 115 infants who received indomethacin was found to have ventriculomegaly on cranial ultrasound at term, compared with 5 of 110 infants who received the placebo. The mean +/- SD Stanford-Binet IQ score for the 126 English-monolingual children who had received indomethacin was 89.6 +/- 18.92, compared with 85.0 +/- 20.79 for the 122 English-monolingual children who had received the placebo. Although maternal education was strongly correlated with Stanford-Binet IQ at 36 months' CA, there was no difference in educational levels between mothers of the infants receiving indomethacin and the placebo.

CONCLUSIONS

Indomethacin administered at 6 to 12 hours as prophylaxis against IVH in very low birth weight infants does not result in adverse cognitive or motor outcomes at 36 months' CA.

Intraventricular hemorrhage in the preterm infant

Intraventricular hemorrhage (IVH) is a common neonatal morbidity among premature infants which is diagnosed by cranial ultrasound in the newborn special care unit. Although very premature infants are more likely to experience the highest grades of hemorrhage, a number of perinatal and postnatal events have been shown to be associated with its occurrence. Factors such as vaginal delivery, labor, and intrapartum asphyxia have been associated with early onset of hemorrhage, whereas antenatal exposure to steroids may be protective. Respiratory Distress Syndrome has also been associated with hemorrhage. Since infants with a history of IVH have increased mortality rates and are at increased risk of seizures, periventricular leukomalacia, hydrocephalus, and neurodevelopmental handicap, many investigators have studied management techniques and pharmacologic interventions to decrease the incidence of IVH, including muscle paralysis, phenobarbital, Vitamin E, indomethacin, ethamsylate and surfactant. Our investigations have shown that low dose indomethacin (0.1 mg/kg i.v.) at 6-12 postnatal hours and every 24 h for two more doses decreases the incidence of all grades of IVH within the first 5 days of life. Although tremendous progress has been made in the understanding of the pathogenesis and prevention of IVH, innovative animal and human studies are needed to further reduce the incidence of this important neonatal morbidity.

Prevention of intraventricular hemorrhage in preterm infants

Prematurely born infants with intraventricular hemorrhage (IVH) suffer significant morbidity and mortality, particularly those infants with high grade hemorrhage. The more premature infants have a higher incidence, experiencing more severe IVH. Early onset IVH is also likely to be severe and to progress to a higher grade. The etiology of intraventricular hemorrhages is clearly multifactorial, with differing sets of risk factors for early onset and later occurring hemorrhage. Prevention requires multilayered strategies, both prenatal and postnatal. These strategies are discussed in detail, highlighting unresolved controversies. Certain recommendations for prevention can be made. These include efforts to prevent preterm delivery, transfer of high risk mothers to tertiary care centers and antenatal maternal steroid use. Postnatally, the importance of optimal resuscitation and neonatal care practices is stressed, particularly those which minimize cerebral blood flow fluctuation. Postnatal indomethacin use should be considered in most infants. Further investigation of other strategies is necessary, including multicenter randomized trials to further evaluate antenatal pharmacologic agents, as well as the relative efficacy of different modes of delivery. The different risk factors for early onset versus later onset IVH must be more clearly delineated. Most importantly, any strategy must include sustained neurodevelopmental followup.

Antenatal steroids, delivery mode, and intraventricular hemorrhage in preterm infants

OBJECTIVE

The relationship between antenatal steroids, delivery mode, and early-onset intraventricular hemorrhage was examined in very-low-birth-weight infants.

STUDY DESIGN

A total of 505 preterm infants (birth weight 600 to 1250 gm) were enrolled in a multicenter, prospectively randomized, controlled trial evaluating the efficacy of postnatal indomethacin to prevent intraventricular hemorrhage. All infants had echoencephalography between 5 and 11 hours of life.

RESULTS

Seventy-three infants had intraventricular hemorrhage within the first 5 to 11 hours (mean age at echoencephalography 7.5 hours). Four hundred thirty-two infants did not have early intraventricular hemorrhage. There was less antenatal steroid treatment (19% vs 32%, p = 0.03) and more vaginal deliveries (71% vs 45%, p < 0.0001) in the group with early intraventricular hemorrhage. Of 152 infants who received antenatal steroids, those delivered by cesarean section had significantly less early-onset intraventricular hemorrhage than did those delivered vaginally (4% vs 17%, p = 0.02). Of the 353 not exposed to antenatal steroids, 10% of infants delivered by cesarean section and 22% delivered vaginally had early intraventricular hemorrhage (p = 0.003).

CONCLUSION

These data are the first to suggest that both antenatal steroids and cesarean section delivery have an important and independent role in lowering the risk of early-onset intraventricular hemorrhage.

Germinal matrix microvascular maturation correlates inversely with the risk period for neonatal intraventricular hemorrhage

The risk period for intraventricular hemorrhage (IVH) of the preterm neonate is the first 3-4 postnatal days. For infants of < 34 weeks' gestation, this risk period is independent of gestational age. We hypothesized that this risk period is attributable to the perinatal induction of maturation of the germinal matrix microvasculature and tested this hypothesis by examining changes in the classical ultrastructural features of the blood-brain barrier over the first ten postnatal days in the newborn beagle model for neonatal IVH. Newborn beagle pups (n = 6) were anesthetized and systemically perfused and the brains were removed and prepared for electron microscopic examination. Examination of electron micrographs from the germinal matrix of animals on the first, fourth and tenth postnatal days demonstrated no difference in perimeter lengths and capillary and endothelial cell areas; in contrast, luminal areas significantly decreased across postnatal age (P = 0.04). Significant increases were found in basement membrane area between days 1 and 4 (P = 0.01) and tight junction length (day 1 vs. day 10, P = 0.02). In addition, on day 1, 19% of germinal matrix capillary perimeter was determined not to be covered by supporting cell processes, while by day 10, only 5% was bare. In contrast, the microvessels of the white matter exhibited no changes in these parameters during these three time points. These studies are consistent with the concept that basal lamina deposition and organization precede increases in endothelial cell tight junction formation and coverage by supporting cells.

Low-dose indomethacin therapy and extension of intraventricular hemorrhage: a multicenter randomized trial

We enrolled 61 neonates of 600 to 1250 gm birth weight with evidence of low-grade intraventricular hemorrhage at 6 to 11 hours of age in a prospective, randomized, placebo-controlled trial to test the hypothesis that indomethacin (0.1 mg/kg given intravenously at 6 to 12 postnatal hours and every 24 hours for two more doses) would prevent extension of intraventricular hemorrhage. Twenty-seven infants were assigned to receive indomethacin; 34 infants received saline placebo. There were no significant differences between the two groups in birth weight, gestational age, sex, Apgar scores, percentage of infants treated with surfactant, or distribution of hemorrhages at the time of the first cranial sonogram (echo-encephalogram). Within the first 5 days, 9 of 27 indomethacin-treated and 12 of 34 saline solution-treated infants had extension of their initial intraventricular hemorrhage (p = 1.00). Four indomethacin-treated and three saline solution-treated infants had parenchymal extension of the hemorrhage. Indomethacin was associated with closure of a patent ductus arteriosus by the fifth day of life (p = 0.003). There were no differences in adverse events attributed to indomethacin. We conclude that in very low birth weight infants with low grade intraventricular hemorrhage within the first 6 postnatal hours, prophylactic indomethacin therapy promotes closure of the patent ductus arteriosus and is not associated with adverse events, but does not affect the cascade of events leading to parenchymal involvement of intracranial hemorrhage.

Low-Dose Indomethacin and Prevention of Intraventricular Hemorrhage: A Multicenter Randomized Trial

Objectives. Parenchymal involvement of intraventricular hemorrhage (IVH) is a major risk factor for neurodevelopmental handicap in very low birth weight neonates. Previous trials have suggested that indomethacin would lower the incidence and severity of IVH in very low birth weight neonates.

Methods. We enrolled 431 neonates of 600- to 1250-g birth weight with no evidence for IVH at 6 to 11 hours of age in a prospective, randomized, placebo-controlled trial to test the hypothesis that low-dose indomethacin (0.1 mg/kg intravenously at 6 to 12 postnatal hours and every 24 hours for two more doses) would lower the incidence and severity of IVH. Serial cranial ultrasound examinations and echocardiographs were performed.

Results. There were no differences in the birth weight, gestational age, sex, Apgar scores, and percent of neonates treated with surfactant between the indomethacin and placebo groups. Within the first 5 days, 25 (12%) indomethacin-treated and 40 (18%) placebo-treated neonates developed IVH (P = .03, trend test). Only one indomethacin-treated patient experienced grade 4 IVH compared with 10 placebo-treated neonates (P = .01). Sixteen indomethacin-treated neonates and 29 control neonates died (P = .08); there was a difference favoring indomethacin with respect to survival time (P = .06).

Eighty-six percent of all neonates had a patent ductus arteriosus on the first postnatal day; indomethacin was associated with significant ductal closure by the fifth day of life (P &lt; .001). There were no differences in adverse events attributed to indomethacin between the two treatment groups.

Conclusions. Low-dose prophylactic indomethacin significantly lowers the incidence and severity of IVH, particularly the severe form (grade 4 IVH). In addition,indomethacin closes the patent ductus arteriosus and is not associated with significant adverse drug events in very low birth weight neonates.

Short-term response to dietary therapy in molybdenum cofactor deficiency

Molybdenum cofactor deficiency was diagnosed in a 3-month-old girl who presented with microcephaly, developmental delay, severe irritability, and lactic acidosis. Dietary methionine restriction, with cysteine supplementation, was associated with moderate short-term clinical improvement, including a resumption in predicted head growth, modest developmental progress, and a reduction in irritability. Clinical relapse was associated with noncompliance of dietary therapy 2 months later. Urinary sulfite levels measured by commercial dipsticks were useful in following therapy. Molybdenum cofactor deficiency is probably frequently underdiagnosed due to the lack of specific clinical or laboratory features. Screening of infants at risk for the presence of urinary sulfites or serum hypouricemia, or both, is both rapid and inexpensive.

Intraventricular hemorrhage and prematurity

Intraventricular hemorrhage or hemorrhage into the germinal matrix tissues of the developing brain with possible rupture into the ventricular system and parenchyma remains a major problem of preterm neonates and is believed to be attributed to alterations in cerebral blood flow to a damaged germinal matrix capillary bed. Topics discussed in this article include germinal matrix anatomy and physiology, neuropathology, risk of hemorrhage, diagnostic imaging techniques, clinical manifestations, posthemorrhagic hydrocephalus, treatment, and outcomes.

Infantile chorea following abrupt withdrawal of diazepam and pentobarbital therapy

The acute onset of chorea was seen in a ten week-old male following abrupt cessation of a seven-day course of sedation with diazepam and pentobarbital. These movements slowly resolved over a six-day period and the infant was without neurologic sequelae one week after his chorea resolved. A cerebral MRI was normal. We speculate that the mechanism by which chorea may occur as a withdrawal phenomenon to benzodiazepine/barbiturate treatment is by a functional overactivity of the dopaminergic system in the basal ganglia.

Risk factors for early intraventricular hemorrhage in low birth weight infants

Because earlier studies suggested that preterm infants with germinal matrix hemorrhage or intraventricular hemorrhage or both (GMH/IVH) present within the first 12 postnatal hours are at greatest risk for the development of high-grade hemorrhage and neurodevelopmental disability, we examined the risk factors for this insult among 229 neonates of 600 to 1250 gm birth weight in a multicenter study. All had echoencephalography (ECHO) within the first 11 hours and serially for the next 20 days; risk factor data were collected prospectively. Forty-three infants had GMH/IVH within the first 5 to 11 hours (mean age at ECHO 7.7 hours): 18 GMH and 21 grade II, 1 grade III, and 3 grade IV IVH. One hundred eighty-six infants did not have GMH/IVH at a mean age of 7.9 hours. Both groups of infants were similar in birth weight, gestational age, maternal risk factors, cord pH values, and surfactant therapy before ECHO. The group with early IVH had more vertex presentations than the group without early IVH (79% vs 55%, p = 0.043), less maternal tocolytic use (42% vs 60%, p = 0.029), and more vaginal deliveries (67% vs 44%, p = 0.005). In the first 21 days, severe IVH developed in 12 infants with early IVH and in 6 infants without early IVH (p < 0.001). There were more neonatal deaths (16% vs 6%, p = 0.035) and more deaths at any time during the primary hospitalization (23% vs 9%, p = 0.010) among the early IVH group than among the group without early IVH. Multivariate analysis indicated that the mode of delivery, fetal presentation, and birth weight were important and independent prognostic indicators of IVH.

Indomethacin promotes germinal matrix microvessel maturation in the newborn beagle pup

BACKGROUND AND PURPOSE

Although indomethacin has been demonstrated to prevent germinal matrix and intraventricular hemorrhage in clinical and animal studies, the mechanism of action of this agent to prevent hemorrhage remains unclear. Previous studies have demonstrated both that the microvessels in the germinal matrix of newborn beagle pups undergo basement membrane maturation during the first 4 postnatal days and that indomethacin may promote laminin deposition in tumor cell culture systems.

METHODS

We employed the newborn beagle pup model to test the hypothesis that indomethacin may stimulate laminin deposition in germinal matrix microvessels. Newborn pups were randomized to receive either 0.1 mg/kg/dose i.p. indomethacin or an equal volume of saline diluent. Pups received doses of study medication once a day for 1, 2, or 3 days and were studied on postnatal days 1, 2, 3, or 4. Pups were anesthetized and systemically perfused with buffered formalin; the brains were removed and prepared for immunohistochemical study.

RESULTS

Sections stained with Bandeiraea lectin demonstrated that there was no difference in germinal matrix vessel density among the postnatal ages studied; similarly, there were no differences in vessel density between saline- and indomethacin-treated animals at any postnatal age. Quantification of germinal matrix stained intensity by confocal microscopy demonstrated significant increases in indomethacin-treated pups for both laminin staining at postnatal days 2 (p = 0.05) and 3 (p = 0.0009) and type V collagen staining at postnatal day 2 (p = 0.011). Although staining for beta 1 integrins increased across postnatal ages, there were no differences between saline- and indomethacin-treated animals.

CONCLUSIONS

These data suggest that indomethacin may stimulate basement membrane deposition in the germinal matrix microvessels of newborn beagle pups to prevent germinal matrix and/or intraventricular hemorrhage.

Beagle pup germinal matrix maturation studies

Intraventricular hemorrhage, or hemorrhage into the germinal matrix tissues of the developing brain, remains a common problem of preterm infants. The "risk period" for this insult is the first 3-4 postnatal days. We hypothesized that this risk period for hemorrhage is related to rapid perinatal maturation of the germinal matrix vasculature and employed the newborn beagle pup model for the study of this maturation. Newborn beagle pups (n = 30) were anesthetized and systemically perfused with buffered formalin; the brains were removed and prepared for immunohistochemical study. Sections stained with Bandeiraea lectin demonstrated that there was no difference in germinal matrix vessel density between postnatal days 1 and 4. Germinal matrix sections were also stained for antibodies to alpha-smooth muscle actin, collagen IV, collagen V, desmin, factor VIII-related antigen, fibronectin, glial fibrillary acidic protein, laminin, transferrin, and vimentin. Vasculature staining by alpha-smooth muscle actin was not noted until postnatal day 10, and differential staining was detected for antibodies to laminin and collagen V. Quantification of staining intensity by confocal microscopy demonstrated a significant increase in both extracellular matrix components at postnatal day 4 compared with day 1 (p less than 0.05 for both). These basement membrane proteins may add sufficient structural integrity to germinal matrix vessels to prevent capillary rupture and thus intraventricular hemorrhage.

Beagle puppy model of perinatal asphyxia: blockade of excitatory neurotransmitters

The N-methyl-D-aspartate receptor antagonist MK801 has been reported to prevent neuronal change in models of ischemia in adult animal systems. We studied the hypothesis that blockade of the N-methyl-D-aspartate receptor would prevent the depression of cerebral high-energy phosphates found in perinatal asphyxia without producing alterations in cerebral blood flow, and thus prevent neuropathologic damage. Newborn beagle puppies were anesthetized, tracheotomized, ventilated, and randomized to asphyxial insult (I = discontinuation of ventilatory support for 5 min) or no insult (NI) and drug treatment with MK801 (10 mg/kg intravenously) or an equal volume of saline (S). Puppies received MK801 or saline 15 min prior to I/NI. In S/I pups during insult, blood flow increased to brainstem structures but decreased elsewhere. MK801 had no effect on cerebral blood flow in either control or insulted puppies. 1H NMR studies demonstrated no effect of the MK801 on NI brains. Phosphocreatine levels were 1.7 +/- 0.1, 0.6 +/- 0.1, and 0.9 +/- 0.1 mmole/kg (mean: +/- S.D.) for the S/NI, S/I, and MK801/I pups, respectively. Cerebral lactate was 1.3 +/- 0.2, 3.0 +/- 0.7, and 2.0 +/- 0.4, respectively. The pH fell 0.8 units in the S/I puppies, compared to 0.4 units in the MK801/I puppies. We conclude that pretreatment with the N-methyl-D-aspartate receptor antagonist MK801 in part protects the developing brain against severe metabolic insult.

Thromboxane synthesis inhibitor in a beagle pup model of perinatal asphyxia

During perinatal asphyxia, cerebral blood flow is markedly reduced in the gray and white matter of the telencephalon. Since previous work has implicated prostaglandins in the control of blood flow, we tested the hypothesis that a thromboxane synthesis inhibitor would improve cerebral blood flow and blunt the metabolic alterations that accompany asphyxia. Forty-three newborn beagles 2-7 days old were anesthetized, ventilated, and randomized to insult (5 minutes of asphyxia) or no insult and received treatment with either the thromboxane synthesis inhibitor CGS 13080 (CIBA-GEIGY Corp.) (0.06 mg/kg/hr i.v. infusion) or saline. Cerebral blood flow was measured in 25 pups. Pups received treatment 30 minutes before insult or no insult. In pups randomized to insult and receiving saline, cerebral blood flow increased during insult in the medulla but decreased elsewhere. Pups randomized to insult and treated with thromboxane synthesis inhibitor had increased cerebral blood flow during insult in all cerebral regions studied. In addition, these pups experienced a significantly higher incidence of intraventricular hemorrhage than did pups randomized to insult and receiving saline. In other experiments with 18 pups, brain extracts were prepared for proton nuclear magnetic resonance spectral analysis of high-energy phosphorylated compounds and lactate levels. In pups exposed to insult and receiving saline, mean +/- SD phosphocreatine concentration fell from 1.9 +/- 0.1 to 0.4 +/- 0.1 mmol/kg, lactate concentration increased from 2.0 +/- 0.5 to 3.3 +/- 0.4 mmol/kg, and the calculated pH fell 0.8 units. There were no differences between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral thromboembolic disease in pediatric and adult inflammatory bowel disease: case report and review of the literature

Cerebral and retinal vascular disease are rare complications of inflammatory bowel disease. Most reports are of adult patients, with only seven instances described in children. The eighth case, a 14-year-old boy with ulcerative colitis and cerebral venous thrombosis is reported in whom the diagnosis was confirmed by magnetic resonance imaging. The adult and pediatric literature is also reviewed.

Randomized low-dose indomethacin trial for prevention of intraventricular hemorrhage in very low birth weight neonates

We admitted 36 preterm neonates (600 to 1250 gm birth weight) with normal 6-hour echoencephalograms to a randomized, placebo-controlled prospective trial to determine whether a low dose of indomethacin would prevent germinal matrix or intraventricular hemorrhage and permit adequate urinary output. Between the sixth and tenth postnatal hours, indomethacin (0.1 mg/kg) or placebo was administered intravenously every 24 hours for a total of three doses. Cardiac ultrasound studies to assess the status of the ductus arteriosus were performed at 6 postnatal hours and on day 5. Urinary output, serum electrolytes, serum indomethacin levels, and renal and clotting functions were monitored. No differences in birth weight, gestational age, or Apgar scores were noted between the two groups of infants. Two indomethacin-treated infants and three infants given placebo had significant urinary output difficulties, requiring that the study medication be withheld. Of 19 infants given indomethacin, two had germinal matrix or intraventricular hemorrhage, in comparison with 8 of 17 infants given saline solution (p = 0.02). Of the infants who had a left-to-right patent ductus arteriosus shunt before treatment, 64% of the indomethacin-treated and 33% of the saline solution-treated infants no longer had a patent ductus arteriosus on day 5. Ductal status appeared unrelated to the development of germinal matrix or intraventricular hemorrhage.

Beagle puppy model of perinatal asphyxia: alterations in cerebral blood flow and metabolism

Perinatal asphyxia remains a major cause of neurodevelopmental handicap. The neuropathologic and clinical sequelae of perinatal asphyxia are likely attributable to alterations in cerebral blood flow (CBF) to the developing brain with uncoupling of CBF and metabolism. The newborn beagle puppy model was used to study the control of CBF in physiologic and pathologic conditions in the developing brain. Pups, 2-10 days of age, were randomized to asphyxial insult (i.e., ventilator lines clamped for 5 min) or no insult. In the first series, pups underwent radioactive microsphere determinations of CBF immediately prior to insult (t = 0), at the end of insult (t = 5), and after 60 min of observation (t = 65). In the second series, utilizing a 2.0 tesla superconducting magnet, pups underwent continuous serial in vivo 31P nuclear magnetic resonance spectral analysis of cerebral hemispheric metabolic state. Animals exposed to insult had significant alterations in PO2, PCO2, pH, and mean arterial pressure at the end of insult compared to control pups (all pups: p less than 0.001). Serial CBF data demonstrated decreases in flow in cortical gray and white matter regions during insult and return to baseline 1 hour later; brainstem structures were hyperemic during insult. Analysis of phosphorylated metabolites inorganic phosphorus (Pi), phosphocreatine (PCr), and ATP demonstrated that during insult both the PCr/Pi and ATP/Pi ratios were depressed but by 20-30 min following insult, these ratios of cerebral phosphorylated metabolites had almost returned to baseline values. These data demonstrate that even after a severe asphyxial episode which results in electrocerebral silence, CBF and metabolism may return to normal.

Predictors of success for drug discontinuation following neonatal seizures

Guidelines for the discontinuation of antiepileptic drugs in neonatal seizures are not well defined. Some studies suggested possible criteria for antiepileptic drug discontinuation but no precise criteria have emerged. We performed a retrospective analysis of 58 infants with neonatal seizures during a 3 year period. Antiepileptic drugs were discontinued when patients were seizure-free for 3 months, had normal electroencephalography initially or at subsequent examination, and had a nonfocal examination. Normal initial electroencephalography was demonstrated to be a reliable predictor for discontinuing antiepileptic drugs successfully in 18 of 22 term infants; normal subsequent electroencephalography was a reliable predictor of successful discontinuation of antiepileptic drugs in 9 of 10 premature infants.

Beagle pup model of brain injury: regional cerebral blood flow and cerebral prostaglandins

Asphyxia is the most common cause of severe brain injury in very young children, and frequently results in lesions of the periventricular white matter in addition to other neuropathological changes. This study examines the effects of asphyxia on regional cerebral blood flow (rCBF) and the role of prostaglandins (PG's) in its control in the newborn beagle pup. Pups were anesthetized, tracheotomized, paralyzed, artificially ventilated, and randomly assigned to two groups: asphyxial insult produced by discontinuing ventilatory support, and no insult. Experiments for carbon-14-iodoantipyrine autoradiographic determination of rCBF and regional cerebral PG determination were performed on separate groups of pups. These studies demonstrated a significant increase in cortical gray PGE2 levels at a time when rCBF was significantly impaired in response to severe asphyxial insult. No such increase was noted in the periventricular white matter zones.

Beagle pup model of perinatal asphyxia: nimodipine studies

Calcium antagonists may be of significant benefit in the pharmacotherapy of cerebral ischemia, possibly by improving postischemic cerebral blood flow (CBF). This study evaluated the effects of the calcium antagonist nimodipine on CBF in a newborn beagle pup model of perinatal asphyxia lasting 5 minutes. Immediately after the asphyxial episode, nimodipine (2 micrograms/kg/min) or saline was infused for 10 minutes, following which [14C]iodoantipyrine determinations of CBF were performed. In noninsulted pups, nimodipine caused both significant decreases in CBF to cortical and deep gray structures as well as a decrease in mean arterial blood pressure (MABP) (p less than 0.05). In insulted pups, nimodipine similarly decreased MABP (p less than 0.001) and CBF to cortical and deep gray matter regions. Nimodipine appeared to have no effect on arterial blood gases and EEG tracings in either insulted or noninsulted pups. Although nimodipine may be shown to improve neurologic outcome in asphyxiated newborn infants, the limits of this study do not show the mechanism to be that of improving CBF.

Beagle puppy model of perinatal cerebral infarction. Regional cerebral prostaglandin changes during acute hypoxemia

Perinatal cerebral infarction, or stroke, is a not uncommon finding in newborns who survive after intensive care. Asphyxia, with its component parts hypoxemia and hypotension, represents the most common cause of perinatal cerebral infarction and may result in neuropathological changes in the periventricular white matter. Previous studies have demonstrated regional alterations in cerebral blood flow (CBF) in response to hypoxemic insult. This work examines the effects of hypoxemia on regional cerebral prostaglandin levels in the developing brain, since some observers believe that local CBF is controlled in part by prostaglandins. In this study, newborn beagle pups were anesthetized, subjected to tracheotomy and artificially ventilated to maintain normoxemia and normocarbia. Mean arterial blood pressure (MABP) was continuously monitored by means of an indwelling catheter and transducer, and craniectomies were performed. When the pups were physiologically stabilized, they were randomly assigned to receive acute hypoxemic insult (pO2 14.0 +/- 1.55 mm Hg, mean +/- standard deviation) accomplished by altering the oxygen concentration in the inspired air) or to receive no insult (mean pO2 84.3 +/- 13.0 mm Hg). Fifteen minutes following stable hypoxemic or normoxic conditions, all pups underwent in vivo freezing of the intracranial contents under anesthesia followed by rapid sacrifice. No significant differences were noted between the MABP, pH, or pCO2 values for the control and hypoxemic pups during the experimental period. Regional cerebral prostaglandin data demonstrated a significant increase in prostaglandin (PG)E2 in the gray matter of hypoxemic pups when compared to the normoxic controls (p less than 0.02). No significant differences were noted for 6-keto-PGE1 alpha, the stable metabolite of prostacyclin, or thromboxane (TX)B2, the stable metabolite of TXA2, in the gray matter. In addition, although 6-keto-PGE1 alpha was significantly lower in the periventricular white matter of the hypoxemic pups (p less than 0.05), there were no changes in the white matter in either PGE2 or TXA2. This regional differential synthesis of PGE2 in response to hypoxemic insult may explain the relative failure of CBF to the periventricular white matter and thus the neuropathological alterations attributed to it.