Neonatal arterial ischaemic stroke: obstetric issues

Peripheral immune cells and perinatal brain injury: a double-edged sword?

Perinatal brain injury is the leading cause of neurological mortality and morbidity in childhood ranging from motor and cognitive impairment to behavioural and neuropsychiatric disorders. Various noxious stimuli, including perinatal inflammation, chronic and acute hypoxia, hyperoxia, stress and drug exposure contribute to the pathogenesis. Among a variety of pathological phenomena, the unique developing immune system plays an important role in the understanding of mechanisms of injury to the immature brain. Neuroinflammation following a perinatal insult largely contributes to evolution of damage to resident brain cells, but may also be beneficial for repair activities. The present review will focus on the role of peripheral immune cells and discuss processes involved in neuroinflammation under two frequent perinatal conditions, systemic infection/inflammation associated with encephalopathy of prematurity (EoP) and hypoxia/ischaemia in the context of neonatal encephalopathy (NE) and stroke at term. Different immune cell subsets in perinatal brain injury including their infiltration routes will be reviewed and critical aspects such as sex differences and maturational stage will be discussed. Interactions with existing regenerative therapies such as stem cells and also potentials to develop novel immunomodulatory targets are considered. IMPACT: Comprehensive summary of current knowledge on the role of different immune cell subsets in perinatal brain injury including discussion of critical aspects to be considered for development of immunomodulatory therapies.

What is known about neuroplacentology in fetal growth restriction and in preterm infants: A narrative review of literature

The placenta plays a fundamental role during pregnancy for fetal growth and development. A suboptimal placental function may result in severe consequences during the infant's first years of life. In recent years, a new field known as neuroplacentology has emerged and it focuses on the role of the placenta in fetal and neonatal brain development. Because of the limited data, our aim was to provide a narrative review of the most recent knowledge about the relation between placental lesions and fetal and newborn neurological development. Papers published online from 2000 until February 2022 were taken into consideration and particular attention was given to articles in which placental lesions were related to neonatal morbidity and short-term and long-term neurological outcome. Most research regarding the role of placental lesions in neurodevelopment has been conducted on fetal growth restriction and preterm infants. Principal neurological outcomes investigated were periventricular leukomalacia, intraventricular hemorrhages, neonatal encephalopathy and autism spectrum disorder. No consequences in motor development were found. All the considered studies agree about the crucial role played by placenta in fetal and neonatal neurological development and outcome. However, the causal mechanisms remain largely unknown. Knowledge on the pathophysiological mechanisms and on placenta-related risks for neurological problems may provide clues for early interventions aiming to improve neurological outcomes, especially among pediatricians and child psychiatrists.

Neonatal stroke: Clinical characteristics and neurodevelopmental outcomes

BACKGROUND

Neonatal stroke can potentially result in significant neurological sequelae in affected infants. Studies on neurodevelopmental outcomes and the need for rehabilitation therapies in the first two years are limited. We aimed to describe the clinical characteristics, diagnostic evaluation, and neurodevelopmental outcomes of a cohort of infants with neonatal stroke.

METHODS

A retrospective cohort study of infants with neonatal stroke, from 2011 to 2020. Maternal and infant characteristics were described. Placental pathology, echocardiogram results, and prothrombotic evaluations were reported. The neurodevelopmental outcomes using Bayley scale of infant development (BSID III), rates of epilepsy and cerebral palsy, and the need for rehabilitation therapies at two years were described.

RESULTS

During the study period, 55 infants had neonatal stroke. Majority (93%) were term or late preterm infants. Maternal chorioamnionitis and perinatal HIE were diagnosed in about a third of the infants. Most (66%) of the infants presented with seizures. On brain MRI, the lesions were unilateral in 76% and arterial in origin in 86% of the infants. Meconium exposure (42%), intrauterine inflammation/infection (37%) and fetal vascular malperfusion (16%) were seen on placental histopathology. At two-year BSID III assessment, median (min, max) composite cognitive, language, and motor scores were 100 (55-145), 97 (47-124), and 100 (46-141), respectively. Among this cohort, epilepsy (27%), cerebral palsy (16%) and the need for rehabilitation therapies (physical -24%, occupational -18%, speech -21%) were reported at two years.

CONCLUSION

Neonatal stroke presented commonly in term or late preterm infants with seizures. It was unilateral and arterial in origin in most infants. Maternal chorioamnionitis and perinatal HIE were the most commonly associated conditions at birth. About one-fifth of the infants had mild or severe developmental delays at two years. Epilepsy, cerebral palsy, and need for rehabilitation therapies were noted in a significant proportion of infants at two years.

Perinatal Arterial Ischemic Stroke in Fetal Vascular Malperfusion: A Case Series and Literature Review

Fetal vascular malperfusion includes a continuum of placental histologic abnormalities increasingly associated with perinatal brain injury, namely arterial ischemic stroke. Here, we describe the clinical-neuroimaging features of 5 neonates with arterial ischemic stroke and histologically proved fetal vascular malperfusion. All infarcts involved the anterior territories and were multiple in 2 patients. In 2 neonates, there were additional signs of marked dural sinus congestion, thrombosis, or both. A mixed pattern of chronic hypoxic-ischemic encephalopathy and acute infarcts was noted in 1 patient at birth. Systemic cardiac or thrombotic complications were present in 2 patients. These peculiar clinical-radiologic patterns may suggest fetal vascular malperfusion and should raise the suspicion of this rare, underdiagnosed condition carrying important implications in patient management, medicolegal actions, and future pregnancy counseling.

Perinatal stroke

Perinatal stroke is a heterogeneous syndrome resulting from brain injury of vascular origin that occurs between 20 weeks of gestation and 28 days of postnatal life. The incidence of perinatal stroke is estimated to be between 1:1600 and 1:3000 live births (approximately 2500 children per year in the United States), though its actual incidence is difficult to estimate because it is likely underdiagnosed. Perinatal arterial ischemic stroke (PAIS) accounts for approximately 70% of cases of perinatal stroke. Cerebral sinovenous thrombosis, while less common, also accounts for a large proportion of the morbidity and mortality seen with perinatal stroke. Hemorrhagic stroke leads to disruption of neurologic function due to intracerebral hemorrhage that is nontraumatic in origin. While most cases of PAIS fall into one of these three categories, other patterns of injury should also be considered perinatal stroke. In some cases, the etiology of PAIS is not known but is idiopathic. This chapter will review the classification, risk factors, pathogenesis, clinical presentation, management, and long-term sequelae of perinatal stroke.

Perinatal Stroke

Perinatal strokes are a diverse but specific group of focal cerebrovascular injuries that occur early in brain development and affect an estimated 5 million people worldwide. The objective of this review is to describe the epidemiology, clinical presentations, pathophysiology, outcomes, and management for the 6 subtypes of perinatal stroke. Some perinatal strokes are symptomatic in the first days of life, typically with seizures, including neonatal arterial ischemic stroke, neonatal hemorrhagic stroke, and cerebral sinovenous thrombosis. The remaining subtypes present in the first year of life or later, usually with motor asymmetry and include arterial presumed perinatal ischemic stroke, presumed perinatal hemorrhagic stroke, and in utero periventricular venous infarction. The consequences of these injuries include cerebral palsy, epilepsy, and cognitive and behavioral challenges, in addition to the psychosocial impact on families. While there have been significant advances in understanding mechanisms of both injury and recovery, there is still a great deal to learn regarding causation and the optimization of outcomes.

Perinatal stroke: mechanisms, management, and outcomes of early cerebrovascular brain injury

Perinatal stroke encompasses a heterogeneous group of focal neurological injuries early in brain development that probably affects more than 5 million people worldwide. Many such injuries are symptomatic in the first days of life, including neonatal arterial ischaemic stroke, cerebral sinovenous thrombosis, and neonatal haemorrhagic stroke. The remaining focal neurological injuries usually present later in the first year with motor asymmetry, such as arterial presumed perinatal ischaemic stroke, periventricular venous infarction, and presumed perinatal haemorrhagic stroke. The numerous sequelae of these injuries include hemiparesis (cerebral palsy), epilepsy, and cognitive, language, and behavioural challenges. In this Review we summarise each perinatal stroke disease, examining the epidemiology, pathophysiology, acute management, and outcomes, including the effect on parents and families, and emerging therapies to mitigate these lifelong morbidities.

Placental Pathology in Neonatal Stroke: A Retrospective Case-Control Study

OBJECTIVE

To assess the association of placental abnormalities with neonatal stroke.

STUDY DESIGN

This retrospective case-control study at 3 academic medical centers examined placental specimens for 46 children with neonatal arterial or venous ischemic stroke and 99 control children without stroke, using a standard protocol. Between-group comparisons used χ² and Fisher exact t test. Correlations used Spearman correlation coefficient.

RESULTS

Case placentas were more likely than controls to meet criteria for ≥1 of 5 major categories of pathologic abnormality (89% vs 62%; OR, 5.1; 95% CI, 1.9-14.0; P = .0007) and for ≥2 categories (38% vs 8%; OR, 7.3; 95% CI, 2.9-19.0; P < .0001). Fetal vascular malperfusion occurred in 50% of cases and 17% of controls (OR, 4.8; 95% CI, 2.2-10.5; P = .0001). Amniotic fluid inflammation occurred in 46% of cases with arterial ischemic stroke vs 25% of controls (OR, 2.6; 95% CI, 1.1-6.1; P = .037). There was evidence of a "stress response" (meconium plus elevated nucleated red blood cells) in 24% of cases compared with 1% of controls (OR, 31; 95% CI, 3.8-247.0; P < .0001).

CONCLUSIONS

Placental abnormality was more common in children with neonatal stroke compared with controls. All placental findings represent subacute-to-chronic intrauterine stressors. Placental thrombotic processes were associated with both arterial and venous stroke. Our findings provide evidence for specific mechanisms that may predispose to acute perinatal stroke. Amniotic fluid inflammation associated with neonatal arterial ischemic stroke deserves further investigation.

Sexually Dimorphic Outcomes after Neonatal Stroke and Hypoxia-Ischemia

Cohort studies have demonstrated a higher vulnerability in males towards ischemic and/or hypoxic-ischemic injury in infants born near- or full-term. Male sex was also associated with limited brain repair following neonatal stroke and hypoxia-ischemia, leading to increased incidence of long-term cognitive deficits compared to females with similar brain injury. As a result, the design of pre-clinical experiments considering sex as an important variable was supported and investigated because neuroprotective strategies to reduce brain injury demonstrated sexual dimorphism. While the mechanisms underlining these differences between boys and girls remain unclear, several biological processes are recognized to play a key role in long-term neurodevelopmental outcomes: gonadal hormones across developmental stages, vulnerability to oxidative stress, modulation of cell death, and regulation of microglial activation. This review summarizes the current evidence for sex differences in neonatal hypoxic-ischemic and/or ischemic brain injury, considering the major pathways known to be involved in cognitive and behavioral deficits associated with damages of the developing brain.

Distinguishing Arterial Ischemic Stroke From Hypoxic-Ischemic Encephalopathy in the Neonate at Birth

OBJECTIVE

To identify perinatal risk factors that can distinguish arterial ischemic stroke from hypoxic-ischemic encephalopathy at birth.

METHODS

This is a cohort study of all neonates born at 35 weeks of gestation or greater admitted to our neonatal intensive care unit from January 1, 2010, to December 31, 2015, that compares neonates with stroke with those with hypoxic-ischemic encephalopathy undergoing whole-body hypothermia with abnormal brain magnetic resonance imaging.

RESULTS

During this 6-year period, there were 22 neonates with stroke and 47 with hypoxic-ischemic encephalopathy undergoing whole-body hypothermia with abnormal magnetic resonance imaging. Three neonates triaged to hypothermia initially thought to have hypoxic-ischemic encephalopathy were later diagnosed with stroke. All neonates with stroke had a negative thrombophilia workup. Neonates with stroke had a significantly higher incidence of seizures and increased initial platelet counts on univariate analysis. A multivariable model of variables with P<.1 on univariate analysis present within 6 hours of birth found significant increases in nonreassuring fetal heart rate tracings, sentinel events, low Apgar score at 5 minutes, and metabolic acidosis at birth with hypoxic-ischemic encephalopathy. Stroke was associated with a significantly increased initial platelet count.

CONCLUSION

Stroke is associated with increased initial platelet counts and is not associated with cesarean delivery for nonreassuring fetal heart rate tracings, sentinel events, or perinatal metabolic acidosis. Stroke is a form of neonatal brain injury not associated with perinatal risk factors that allow early identification.

Abnormal neurodevelopmental outcomes are very likely in cases of bilateral neonatal arterial ischaemic stroke

AIM

Neonatal arterial ischaemic stroke (AIS) is an important cause of severe neurological disability. This study aimed to analyse the clinical manifestations and outcomes of AIS patients.

METHODS

We enrolled neonates with AIS admitted to Severance Children's Hospital and Gangnam Severance Hospital between 2008 and 2015. AIS was confirmed using magnetic resonance imaging (MRI). We retrospectively reviewed the clinical manifestations, MRI findings, electroencephalography (EEG) findings and neurodevelopmental outcomes.

RESULTS

The study comprised 29 neonates (18 boys). The mean follow-up period was 15.4 months (range 6-44 months), and the mean age at diagnosis was 8.1 days. Seizure was the most common symptom (66%). Bilateral involvement was more common than unilateral involvement (52%). The middle cerebral artery was the most commonly identified territory (79%). Abnormal EEG findings were noted in 93% of the cases. Neurodevelopment was normal in 11 (38%) patients, while cerebral palsy and delayed development were noted in eight (28%) and six (21%) patients, respectively. Patients with bilateral involvement were very likely to have abnormal neurodevelopmental outcomes.

CONCLUSION

Our study showed that abnormal neurodevelopmental outcomes were very likely after cases of neonatal AIS with bilateral involvement, and clinicians should consider early and more effective interventions in such cases.

Evaluation of hypercoagulability state in perinatal arterial ischemic stroke with rotation thromboelastometry

BACKGROUND

Perinatal arterial ischemic stroke (PAIS) is an important cause of pediatric morbidity and mortality. The etiology of PAIS remains unknown. Several maternal-neonatal disorders, and especially prothrombotic risk factors, have been reported in infants with perinatal stroke (PS). Rotation thromboelastometry (ROTEM) can analyze the coagulation system, from the beginning of coagulation, through clot formation, and ending with fibrinolysis. The aim of this study was to evaluate the hypercoagulability state in PAIS patients using ROTEM.

METHODS

Patients were obtained by evaluating hospital files retrospectively. Twenty patients with PAIS and 19 healthy controls were included in the study. Prothrombotic risk factors and standard coagulation parameters were collected for all patients. Thromboelastometry (TEM) analysis was performed with the ROTEM® Coagulation Analyzer model Gamma 2500 (Tem International, Munich, Germany). Patients were separated into two groups; Group 1 included PAIS patients with prothrombotic risk factors and Group 2 included patients with no prothrombotic risk factors.

RESULTS

Group 1 includes six patients and Group 2 includes fourteen. Maternal risk factors were reported in 55 % and prothrombotic risk factors were detected in 30 % of the patients. ROTEM analyses were done mean age of 11.2 ± 9.4 months. ROTEM analysis showed that maximum clot firmness (MCF) value on both groups was significantly higher than in the control group, which is consistent with a hypercoagulable state. There was no statistical difference between the MCF values of Group 1 and Group 2. No significant correlations were found between the ROTEM parameters and the hematological parameters.

CONCLUSION

The etiology of PAIS is still unclear. Prothrombotic risk factors may be an important etiology for PAIS. However, standard hematological tests for evaluating prothrombotic risk factors are limited. In our study, ROTEM analyses showed higher maximum clot firmness in PAIS patients compared to controls. ROTEM analyses may suggest a hypercoagulable state due to abnormal fibrinolysis in PAIS patients. Normative data and further research is needed to validate our findings.

Perinatal arterial ischemic stroke related to carotid artery occlusion

BACKGROUND

The aetiology of perinatal arterial ischemic stroke remains speculative. It is however widely accepted that the aetiology is multifactorial, involving various maternal, placental, foetal and neonatal risk factors. A resulting thromboembolic process is hypothesized and the placenta identified as the most plausible source. An arteriopathy, as observed in a significant proportion of childhood ischemic stroke, is thought to be rare.

METHODS

We report here five cases of perinatal stroke that differ from the vast majority by documented carotid occlusion, and add eleven other similar cases from the literature.

RESULTS

In the majority, an intraluminal thrombus of placental origin is the most probable hypothesis, while in the remaining ones, one can reasonably presume a direct vessel wall injury related to a traumatic delivery, yet generally unproven by imaging.

CONCLUSION

We hypothesize that most of these cases share similar pathophysiology with the more common perinatal arterial ischemic stroke but differ by a persistent identified thrombus in the carotid artery at the time of first imaging, leading to a more severe and extended ischemic damage responsible for an adverse neurological outcome.

A Primer for Nurses on Perinatal/Neonatal Stroke

Perinatal or neonatal stroke is not uncommon, but diagnosis is often missed. Perinatal nurses are often the first health professionals in the position to observe the most typical symptom of stroke in a newborn, which is focal seizure. Etiology, symptoms and outcomes are reviewed and discussed through the context of the author's personal story.

Sexually dimorphic outcomes and inflammatory responses in hypoxic-ischemic encephalopathy

Background

Neonatal hypoxic-ischemic encephalopathy (HIE) is an important cause of motor and cognitive impairment in children. Clinically, male infants are more vulnerable to ischemic insults and suffer more long-term deficits than females; however, the mechanisms underlying this sex difference remain elusive. Inflammatory processes initiated by microglial activation are fundamental in the pathophysiology of ischemia. Recent studies report a sexual dimorphism in microglia numbers and expression of activation markers in the neonatal brain under normal conditions. How these basal sex differences in microglia affect HIE remains largely unexplored. This study investigated sex differences in ischemic outcomes and inflammation triggered by HIE. We hypothesize that ischemia induces sex-specific brain injury in male and female neonates and that microglial activation and inflammatory responses play an important role in this sexual dimorphism.

Methods

Male and female C57BL6 mice were subjected to 60-min Rice-Vanucci modeling (RVM) at post-natal day 10 (P10) to induce HIE. Stroke outcomes were measured 1, 3, 7, and 30 days after stroke. Microglial activation and inflammatory responses were evaluated by flow cytometry and cytokine analysis.

Results

On day 1 of HIE, no difference in infarct volumes or seizure scores was seen between male and female neonates. However, female neonates exhibited significantly smaller infarct size and fewer seizures compared to males 3 days after HIE. Females also had less brain tissue loss and behavioral deficits compared to males at the chronic stage of HIE. Male animals demonstrated increased microglial activation and up-regulated inflammatory response compared to females at day 3.

Conclusions

HIE leads to an equivalent primary brain injury in male and female neonates at the acute stage that develops into sexually dimorphic outcomes at later time points. An innate immune response secondary to the primary injury may contribute to sexual dimorphism in HIE.

Circulating miRNA profiles provide a biomarker for severity of stroke outcomes associated with age and sex in a rat model

Small non-coding RNA [miRNA (microRNA)] found in the circulation have been used successfully as biomarkers and mechanistic targets for chronic and acute disease. The present study investigated the impact of age and sex on miRNA expression following ischaemic stroke in an animal model. Adult (6 month) and middle-aged (11-12 months) female and male rats were subject to MCAo (middle cerebral artery occlusion) using ET-1 (endothelin-1). Circulating miRNAs were analysed in blood samples at 2 and 5 days post-stroke, and brain miRNAs were analysed at 5 days post-stroke. Although stroke-associated infarction was observed in all groups, infarct volume and sensory-motor deficits were significantly reduced in adult females compared with middle-aged females, adult males or middle-aged males. At 2 days post-stroke, 21 circulating miRNAs were differentially regulated and PCA (principal component analysis) confirmed that most of the variance was due to age. At 5 days post-stroke, 78 circulating miRNAs exhibited significantly different regulation, and most of the variance was associated with sex. A small cohort (five) of miRNAs, miR-15a, miR-19b, miR-32 miR-136 and miR-199a-3p, were found to be highly expressed exclusively in adult females compared with middle-aged females, adult males and middle-aged males. Predicted gene targets for these five miRNAs analysed for KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways revealed that the top ten KEGG pathways were related to growth factor signalling, cell structure and PI3K (phosphoinositide 3-kinase)/Akt and mTOR (mammalian target of rapamycin) signalling. Overall, the pattern of circulating miRNA expression suggests an early influence of age in stroke pathology, with a later emergence of sex as a factor for stroke severity.

Knockout of vascular early response gene worsens chronic stroke outcomes in neonatal mice

Vascular early response gene (Verge) is a novel immediate early gene that is highly expressed during developmental angiogenesis and after ischemic insults in adult brain. However, the role of Verge after neonatal injury is not known. In the present study, we investigated the hypothesis that Verge contributes to vascular remodeling and tissue repair after neonatal ischemic injury. The Rice-Vanucci model (RVM) was employed to induce neonatal stroke in both Verge knockout (KO) and wild-type (WT) postnatal day 10 (P10) mice. Histological and behavioral outcomes at acute (24h), subacute (7 days) and chronic (30 days) phases were evaluated. Angiogenesis, neurogenesis, and glial scar formation were also examined in the ischemic brain. No significant differences in outcomes were found between WT and Verge mice at 24h or 7 days after stroke. However genetic deletion of Verge led to pronounced cystic cavitation, decreased angiogenensis and glial scar formation in the ischemic hemisphere compared to WT mice at 30 days. Verge KO mice also had significantly worse functional outcomes at 30 days which was accompanied by decreased neurogenesis and angiogenesis in the ischemic hemisphere. Our study suggests that Verge plays an important role in the induction of neurogenesis and angiogenesis after ischemia, contributes to improved tissue repair, and enhances chronic functional recovery.

Epidemiology and aetiology of neonatal seizures

Neonatal seizures constitute the most frequent and distinctive neurological symptom in the neonatal period. Seizures in the neonatal period differ considerably from those observed later in life with respect to their aetiological profile and clinical presentation. In addition, the aetiological profile in preterm infants is different from that seen in term infants. Hypoxic-ischaemic encephalopathy is the most frequent cause of neonatal seizures in term babies followed by focal ischaemia (stroke), cerebral malformations and metabolic disturbances. In preterm neonates, intraventricular haemorrhage and infections cause most of the seizures reported in this group. Better neuroimaging techniques have reduced the number of undiagnosed cases, and the institution of newer neuroprotective strategies has influenced the outcome.

Maternal hypertension and intrapartum fever are associated with increased risk of ischemic stroke during infancy

AIM

To examine maternal hypertension, diabetes, and intrapartum fever as potential risk factors for ischemic stroke in infants.

METHOD

We conducted a retrospective cohort study of 226,117 children born from January 2000 to December 2007 who were enrolled in the South Carolina Medicaid program. We linked maternal and child Medicaid billing records and birth certificate data. Children with ischemic stroke were identified based on the International Classification of Diseases, Ninth Revision (ICD-9), code 434 in the child's billing data. Independent variables and covariates were identified using ICD-9 codes and birth certificate data. We modeled the odds of ischemic stroke diagnosis in infants, either before 30 days of life or before 365 days.

RESULTS

Forty-three children were diagnosed with ischemic stroke before 30 days and 161 before 365 days. Maternal hypertension (odds ratio 2.31 before 30 d) and intrapartum fever (odds ratio 3.36 <30 d) were significantly associated with odds of ischemic stroke before 30 days and before 365 days; maternal diabetes was not.

INTERPRETATION

Maternal hypertension and intrapartum fever appear to be risk factors for ischemic stroke in infants. Additional research is needed to determine the mechanism(s) underlying these associations and to develop effective preventive methods for high-risk infants.

Interactions between age, sex, and hormones in experimental ischemic stroke

Age, sex, and gonadal hormones have profound effects on ischemic stroke outcomes, although how these factors impact basic stroke pathophysiology remains unclear. There is a plethora of inconsistent data reported throughout the literature, primarily due to differences in the species examined, the timing and methods used to evaluate injury, the models used, and confusion regarding differences in stroke incidence as seen in clinical populations vs. effects on acute neuroprotection or neurorepair in experimental stroke models. Sex and gonadal hormone exposure have considerable independent impact on stroke outcome, but these factors also interact with each other, and the contribution of each differs throughout the lifespan. The contribution of sex and hormones to experimental stroke will be the focus of this review. Recent advances and our current understanding of age, sex, and hormone interactions in ischemic stroke with a focus on inflammation will be discussed.

Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Neonates and children differ from adults in physiology, pharmacologic responses to drugs, epidemiology, and long-term consequences of thrombosis. This guideline addresses optimal strategies for the management of thrombosis in neonates and children.

METHODS

The methods of this guideline follow those described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that where possible, pediatric hematologists with experience in thromboembolism manage pediatric patients with thromboembolism (Grade 2C). When this is not possible, we suggest a combination of a neonatologist/pediatrician and adult hematologist supported by consultation with an experienced pediatric hematologist (Grade 2C). We suggest that therapeutic unfractionated heparin in children is titrated to achieve a target anti-Xa range of 0.35 to 0.7 units/mL or an activated partial thromboplastin time range that correlates to this anti-Xa range or to a protamine titration range of 0.2 to 0.4 units/mL (Grade 2C). For neonates and children receiving either daily or bid therapeutic low-molecular-weight heparin, we suggest that the drug be monitored to a target range of 0.5 to 1.0 units/mL in a sample taken 4 to 6 h after subcutaneous injection or, alternatively, 0.5 to 0.8 units/mL in a sample taken 2 to 6 h after subcutaneous injection (Grade 2C).

CONCLUSIONS

The evidence supporting most recommendations for antithrombotic therapy in neonates and children remains weak. Studies addressing appropriate drug target ranges and monitoring requirements are urgently required in addition to site- and clinical situation-specific thrombosis management strategies.

Pediatric stroke

INTRODUCTION

Pediatric stroke, while increasingly recognized among practitioners as a clinically significant, albeit infrequent entity, remains challenging from the viewpoint of clinicians and researchers.

DISCUSSION

Advances in neuroimaging have revealed a higher prevalence of pediatric stroke while also provided a safer method for evaluating the child's nervous system and vasculature. An understanding of pathogenic mechanisms for pediatric stroke requires a division of ages (perinatal and childhood) and a separation of mechanism (ischemic and hemorrhagic). This article presents a review of the current literature with the recommended divisions of age and mechanism.

CONCLUSION

Guidelines for treatment, though limited, are also discussed.

The role of hypoxia-ischemia in term newborns with arterial stroke

The role of generalized hypoxia-ischemia in the genesis of perinatal focal arterial stroke remains puzzling. Animal studies have demonstrated that hypoxia-ischemia may alter blood flow through the ductus venosus, thereby increasing the risk for placental emboli entering the cerebral circulation. A retrospective review was performed of clinical records of all term newborns admitted to a tertiary perinatal center between January 1995 and May 2007 with acute arterial stroke on neuroimaging during the first week of life. Newborns were classified into 2 groups on the basis of neuroimaging abnormalities: stroke alone, or stroke and nonfocal hypoxic-ischemic brain injury. A total of 62 newborns had focal or multifocal stroke, 36 with stroke alone and 26 with stroke with nonfocal hypoxia-ischemia. Multiple risk factors for hypoxia-ischemia occurred in most newborns in both groups. These data indicate that hypoxia-ischemia may play a role in the genesis of stroke in the term newborn with or without evidence of nonfocal hypoxic-ischemic brain injury on neuroimaging.

Patterns of neonatal hypoxic-ischaemic brain injury

Enormous progress has been made in assessing the neonatal brain, using magnetic resonance imaging (MRI). In this review, we will describe the use of MRI and proton magnetic resonance spectroscopy in detecting different patterns of brain injury in (full-term) human neonates following hypoxic–ischaemic brain injury and indicate the relevance of these findings in predicting neurodevelopmental outcome.

MRI of perinatal brain injury

MRI is invaluable in assessing the neonatal brain following suspected perinatal injury. Good quality imaging requires adaptations to both the hardware and the sequences used for adults or older children. The perinatal and postnatal details often predict the pattern of lesions sustained and should be available to aid interpretation of the imaging findings. Perinatal lesions, the pattern of which can predict neurodevelopmental outcome, are at their most obvious on conventional imaging between 1 and 2 weeks from birth. Very early imaging during the first week may be useful to make management decisions in ventilated neonates but brain abnormalities may still be subtle using conventional sequences. Diffusion-weighted imaging (DWI) is very useful for the early identification of ischaemic tissue in the neonatal brain but may underestimate the final extent of injury, particularly basal ganglia and thalamic lesions. MR imaging is an excellent predictor of outcome following perinatal brain injury and can therefore be used as a biomarker in interventional trials designed to reduce injury and improve neurodevelopmental outcome.

Patterns of neonatal hypoxic-ischaemic brain injury

Enormous progress has been made in assessing the neonatal brain, using magnetic resonance imaging (MRI). In this review, we will describe the use of MRI and proton magnetic resonance spectroscopy in detecting different patterns of brain injury in (full-term) human neonates following hypoxic-ischaemic brain injury and indicate the relevance of these findings in predicting neurodevelopmental outcome.