Antithrombotic therapy in neonates and children: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter about antithrombotic therapy in neonates and children is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs, and Grade 2 suggests that individual patient values may lead to different choices (for a full understanding of the grading, see Guyatt et al in this supplement, pages 123S-131S). In this chapter, many recommendations are based on extrapolation of adult data, and the reader is referred to the appropriate chapters relating to guidelines for adult populations. Within this chapter, the majority of recommendations are separate for neonates and children, reflecting the significant differences in epidemiology of thrombosis and safety and efficacy of therapy in these two populations. Among the key recommendations in this chapter are the following: In children with first episode of venous thromboembolism (VTE), we recommend anticoagulant therapy with either unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) [Grade 1B]. Dosing of IV UFH should prolong the activated partial thromboplastin time (aPTT) to a range that corresponds to an anti-factor Xa assay (anti-FXa) level of 0.35 to 0.7 U/mL, whereas LMWH should achieve an anti-FXa level of 0.5 to 1.0 U/mL 4 h after an injection for twice-daily dosing. In neonates with first VTE, we suggest either anticoagulation or supportive care with radiologic monitoring and subsequent anticoagulation if extension of the thrombosis occurs during supportive care (Grade 2C). We recommend against the use of routine systemic thromboprophylaxis for children with central venous lines (Grade 1B). For children with cerebral sinovenous thrombosis (CSVT) without significant intracranial hemorrhage (ICH), we recommend anticoagulation initially with UFH, or LMWH and subsequently with LMWH or vitamin K antagonists (VKAs) for a minimum of 3 months (Grade 1B). For children with non-sickle-cell disease-related acute arterial ischemic stroke (AIS), we recommend UFH or LMWH or aspirin (1 to 5 mg/kg/d) as initial therapy until dissection and embolic causes have been excluded (Grade 1B). For neonates with a first AIS, in the absence of a documented ongoing cardioembolic source, we recommend against anticoagulation or aspirin therapy (Grade 1B).

Association between iron-deficiency anemia and stroke in young children

OBJECTIVE

Iron-deficiency anemia occurs with a peak prevalence of 4% to 8% in children between 1 and 3 years of age. Case reports have suggested an association between iron-deficiency anemia in healthy children and ischemic stroke. Our objective was to investigate whether iron-deficiency anemia is associated with stroke in young children.

METHODS

A case-control study was conducted of case patients who were selected from the stroke registry at the Hospital for Sick Children (Toronto, Ontario, Canada) and control subjects selected from a database of healthy children who were prospectively enrolled in an outpatient setting. Children were aged 12 to 38 months and were previously healthy with no identifiable risk factors for stroke. Age, gender, mean corpuscular volume, platelet count, and hemoglobin and ferritin levels were collected. Iron-deficiency anemia was defined as a hemoglobin level of <110 g/L, mean corpuscular volume <73 fL, and serum ferritin level <12 microg/L. Stroke was defined according to clinical and radiologic criteria.

RESULTS

Case (n = 15) and control (n = 143) subjects were similar with respect to median age and percentage of boys. Case patients had a lower median hemoglobin level and mean corpuscular volume and a higher median platelet count. Iron-deficiency anemia was significantly more common among case patients (8 [53%] of 15) than control subjects (13 [9%] of 143).

CONCLUSIONS

Previously healthy children with stroke were 10 times more likely to have iron-deficiency anemia than healthy children without stroke. Furthermore, children with iron-deficiency anemia accounted for more than half of all stroke cases in children without an underlying medical illness, which suggests that iron-deficiency anemia is a significant risk factor for stroke in otherwise healthy young children. Primary prevention and early identification of iron-deficiency anemia must remain a priority.

Early cognitive outcome after neonatal stroke

The purpose of this study was to assess the cognitive development of 27 children with nonhemorrhagic neonatal stroke (occurring within the first 28 days of life). The cognitive evaluation consisted of the Bayley Scales of Infant Development, administered at 12 and/or 24 months poststroke. Compared with the normative sample, children with neonatal stroke obtained significantly lower scores on the Bayley Psychomotor Development Index at 12 months poststroke and on the Bayley Mental and Psychomotor Development Indices at 24 months poststroke. Outcome did not differ based on stroke type or laterality of infarct. However, there was a trend toward higher scores on the Bayley Psychomotor Development Index at 24 months in the left hemisphere group compared to the right hemisphere group. Overall, children with neonatal stroke evidenced significant impairment within the first 2 years poststroke. Further research is required to confirm whether cognitive impairments in these children resolve, remain in the low-average range, or increase with development as more complex skills are learned.

Quantified Corticospinal Tract Diffusion Restriction Predicts Neonatal Stroke Outcome

Background and Purpose— Neonatal arterial ischemic stroke occurs in ≥1:4000 births. Many children experience motor deficits but acute predictors of outcome are lacking. Diffusion-weighted MRI changes in descending corticospinal tracts remote from arterial ischemic stroke may represent pre-Wallerian degeneration. We verify and quantify this signal and correlate it with motor outcome.

Methods— Fourteen neonates with acute arterial ischemic stroke and ≥12 months follow-up with the Pediatric Stroke Outcome Measure were included. Quantitative measurements of descending corticospinal tracts diffusion-weighted MRI signal were developed using Image J software.

Results— Ipsilesional descending corticospinal tract diffusion-weighted MRI signal was abnormal in 10 neonates with decreased apparent diffusion coefficients ( P <0.001). Poor outcome correlated with: (1) percentage of peduncle ( P =0.002); (2) length of descending corticospinal tracts P <0.001); and (3) volume of descending corticospinal tracts ( P =0.002). None of: (1) any peduncle; (2) any posterior limb of the internal capsule; or (3) infarct volume correlated with outcome. All children without descending corticospinal tracts signal had normal outcome. Chronic Wallerian degeneration was seen in all children with hemiparesis. Software-assisted analysis was superior to visual inspection with excellent reliability (intra-class correlation coefficient ≥0.9).

Conclusion— Descending corticospinal tracts diffusion-weighted MRI signal is predictive of motor outcome from neonatal arterial ischemic stroke. This accurate, reliable, and simple tool will impact decision making in acute neonatal stroke.

Pediatric stroke: rehabilitation of focal injury in the developing brain

This review provides an overview of pediatric ischemic stroke to serve as a foundation for the discussion of rehabilitation strategies following focal injury in the developing brain. Cerebrovascular disease is an important cause of acquired brain injury in neonates and children. Ischemic strokes are caused by a multitude of risk factors and advances in neuroimaging have improved diagnosis and understanding of pathophysiology. Pediatric stroke provides the ideal model for the study of injury and recovery in a plastic nervous system. Though their brains likely posses greater potential and unique reorganizational skills, most children suffer neurological morbidity after stroke. An improved understanding of these systems is helping us understand, validate, and improve traditional approaches to rehabilitation while opening the door to new opportunities to improve outcome. All aspects of a patient's function, from the physical to psychological, including issues unique to children and their families, must be addressed and are reviewed. New advances and future directions for research are highlighted.

Cerebral sinovenous thrombosis and idiopathic nephrotic syndrome in childhood: report of four new cases and review of the literature

INTRODUCTION

Nephrotic children are prone to develop thromboembolic complications secondary to an acquired hypercoagulable state. Cerebral sinovenous thrombosis (CSVT) is increasingly recognised in this population, but clinical characteristics and outcome are not well documented.

PATIENTS AND METHODS

The database of the Canadian Pediatric Ischemic Stroke Registry (Toronto Site) containing prospectively enrolled children from 1992-2004 with CSVT identified four children with NS. A pooled literature analysis retrieved 17 additional cases reports.

RESULTS

CSVT presented in the majority of cases during the first flare or within 6 months after the onset of NS and was found to occur more often in SSNS/SDNS (n=13) than in SRNS (n=4). Clinical manifestations were non-specific and consisted primarily of seizures (n=8) and signs of raised intracranial pressure (n=16). Imaging studies revealed a predilection for superior sagittal sinus involvement (n=21) and rare parenchymal lesions (n=4). The most consistent biological risk factors were a severe hypoalbuminaemia (n=14) and, to a lesser extent, decreased antithrombin (AT) levels (n=9/16). Deficiency of other coagulation inhibitors (protein S, protein C) was not identified. Inherited thrombophilia was documented in a single case, suggesting that acquired, more than genetic, coagulation factors are involved. Anticoagulation was safe, and the outcome was good in most patients, and no recurrence of thrombotic event was reported.

DISCUSSION

In conclusion, CSVT is now a well-described complication of NS with potential morbidity. A high index of suspicion is required, especially in young children with NS presenting neurological symptoms. Reliable biological predictors of CSVT are lacking.

Stroke in the fetus and neonate

Multiple patterns of focal ischemic injury in the fetal and perinatal brain are now recognized as important causes of neurological disability in children. Strokes may be arterial or venous, symptomatic or subclinical, and can occur across multiple timeframes. Establishing the importance of an increasing number of potential risk factors and translating that knowledge into an improved understanding of pathophysiology are major challenges. Advanced neuroimaging has facilitated increased recognition of perinatal stroke and an improved understanding of plasticity mechanisms in the developing brain. Better outcome prediction will assist in patient selection for advancing neuroprotective strategies to reduce cerebral palsy and other adverse outcomes suffered by most children.

Pediatric stroke initiatives and preliminary studies: What is known and what is needed?

Cerebrovascular disorders are increasingly recognized as important causes of mortality and morbidity in the pediatric population. However, there have been no clinical trials performed to assess the safety and tolerability of acute interventions or secondary preventative treatments. In 2002, the International Pediatric Stroke Study was launched to create a network of investigators, with an interest in developing standards of practice, as well as design and implement the first-ever clinical trials in pediatric stroke. This article reviews existing studies in pediatric stroke epidemiology, risk factors, outcomes, as well as experience with antithrombotic trials in children. From there, current and future initiatives in the development of clinical trials in pediatric stroke are evaluated.

Cerebral palsy secondary to perinatal ischemic stroke

Congenital hemiplegia is the most common form of cerebral palsy in children born at term, and stroke is the number one cause. Neonatal ischemic stroke includes perinatal arterial ischemic stroke, presumed pre- or perinatal stroke, and cerebral sinovenous thrombosis, all of which have emerged as important contributors to cerebral palsy. Of increasing interest is how the overlapping list of associations and risks for stroke and cerebral palsy relate to each other. Stroke-induced injury is focal, and the preservation of normal areas of brain may afford unique opportunities for plastic adaptation. The implications of this essential difference are stressed in a discussion of how the epidemiology, pathophysiology, diagnosis, and therapeutic advancements in perinatal stroke relate to the outcome of cerebral palsy.

Therapeutic approaches and advances in pediatric stroke

Evidence-based therapeutic interventions for pediatric ischemic cerebrovascular disease are beginning to emerge. The primary therapeutic target is usually the pathological prothrombotic disturbance that underlies the majority of pediatric stroke. A battle between anticoagulation and anti-platelet therapies continues to provide controversy and is the inspiration for upcoming randomized trials. Supportive care and neuroprotective strategies are an important consideration in children with stroke. Attempts to determine the safety of acute thrombolytic interventions are also underway. Finally, unique medical and surgical treatments for specific diseases leading to stroke in children continue to evolve. After briefly summarizing the epidemiology, pathophysiology, diagnosis, and outcomes of ischemic strokes in children, treatment approaches and alternatives will be reviewed in detail with emphasis placed on current areas of controversy and future directions for clinical research.

The Risks and Safety of Clopidogrel in Pediatric Arterial Ischemic Stroke

Background and Purpose— The purpose of this study was to determine safety and tolerability of clopidogrel in children with arterial ischemic stroke (AIS). Clopidogrel is the alternative antiplatelet medication when aspirin is not tolerated or fails. The possible risks and safety of clopidogrel in children with AIS have not been assessed.

Methods— This is a prospective consecutive cohort study of children with AIS who were started on clopidogrel. Seventeen children were included.

Results— Two children developed subdural hematomas while on clopidogrel in conjunction with aspirin. Two others had headache or hand numbness. No other side effects like rash or gastrointestinal upsets were reported.

Conclusions— We found clopidogrel to be relatively well tolerated in the pediatric population. In combination with aspirin and in the presence of other risk factors, intracranial bleeding may be seen.

Urgent Clinical Challenges in Children With Ischemic Stroke

Background and Purpose— Clinical trials are lacking in pediatric stroke. As a result, physicians caring for children with stroke face significant challenges. The patient characteristics and specific nature of clinical challenges facing practicing clinicians can inform the design of and priorities for developing relevant clinical trials.

Methods— Physicians consulted the 1-800-NOCLOTS toll-free pediatric stroke telephone consultation service on children (birth to 18 years) with ischemic stroke. Pediatric neurologist or hematologists provided telephone consultation and documented caller and patient characteristics, antithrombotic treatments and callers’ questions for entry into a computerized database. Children referred from January 1, 1995 to January 1, 2004, comprised the study cohort.

Results— Stroke consults were completed on 1065 children located predominantly in the United States (76%). Children had arterial ischemic stroke (AIS; 679; 64%) or cerebral sinovenous thrombosis (CSVT; 386; 36%) and were 54% male and 16% neonates. Risk factors and antithrombotic agents (none, aspirin, warfarin, and heparins) differed by stroke type. In 60% of patients, callers had not initiated antithrombotic therapy. Callers’ questions for both stroke types usually concerned treatment selection (83%), but for AIS, questions more frequently ( P <0.0001) concerned the selection and interpretation of etiological investigations.

Conclusions— Research is urgently needed in pediatric stroke to provide direction for management in “real-life” settings. Research efforts should address the unique challenges within different stroke types and include observational studies addressing investigation of the child with AIS. For AIS and CSVT, randomized controlled trials investigating the efficacy of antithrombotic treatment are urgently needed.

Primary central nervous system vasculitis in children

OBJECTIVE

Primary angiitis of the central nervous system (PACNS) is a severe and ill-defined neurologic disease. The goal of this study was to characterize the presenting features, treatment, and neurologic outcome of PACNS in children (cPACNS) and to define the predictors of disease progression in order to identify high-risk patients with cPACNS.

METHODS

The cohort comprised consecutive patients diagnosed as having cPACNS based on clinical and vascular imaging findings, including identification of arterial stenosis on conventional angiography or magnetic resonance (MR) angiography. Disease progression was defined angiographically at >3 months after initial angiography. Clinical data obtained in prospectively collected standardized assessments and results of laboratory tests, including detection of cerebrospinal fluid abnormalities, were noted, and neuroimaging studies were reanalyzed. Predictors of progression were identified and tested in multivariate regression models.

RESULTS

Sixty-two consecutive patients with cPACNS (38 male, 24 female, median age 7.2 years) were included. Two distinct subgroups were identified, those with progressive disease and those with nonprogressive disease. Progressive cPACNS was found in 20 of 62 children and was predicted by a clinical presentation of neurocognitive dysfunction, multifocal parenchymal lesions on MR imaging, and evidence of distal stenoses on angiography.

CONCLUSION

The spectrum of PACNS in children includes both progressive and nonprogressive forms. Characteristic features at diagnosis can be used to predict later progression, to identify a distinct high-risk cPACNS cohort, and to help guide selection of patients for immunosuppressive therapy.

Difficulties in performing clinical trials of antithrombotic therapy in neonates and children

The practice of evidence-based medicine is based on the results of properly designed, conducted and analyzed studies. Evidence for the safety and efficacy of therapies is established through clinical trials. However, there are a number of difficulties in the design and management of clinical trials in children. We explore the theoretical and ethical issues and difficulties of designing and conducting clinical trials in children, and illustrate the ways in which these challenges were encountered in two clinical trials assessing anticoagulant therapy in children with thrombophilia (PROTEKT (PROphylaxis of ThromboEmbolism in Kids Trial) and REVIVE (REVIparin in Venous ThromboEmbolism)). Means for overcoming these challenges are also addressed.

Short-term intellectual outcome after arterial ischemic stroke and sinovenous thrombosis in childhood and infancy

Arterial ischemic stroke is approximately four times more prevalent than sinovenous thrombosis and has been associated with a worse neurologic outcome than sinovenous thrombosis; however, no data are available comparing intellectual outcome after pediatric arterial ischemic stroke and sinovenous thrombosis. We report the short-term intellectual outcome (mean 5.8 months since stroke) in a sample of 72 children, 47 with arterial ischemic stroke, and 25 with sinovenous thrombosis. Intellectual outcome measures were the Full-Scale IQ of the age-appropriate Wechsler intelligence test for older children and the Mental Developmental Index of the Bayley Scales of Infant Development for younger children. Stroke type did not directly influence intellectual outcome. Intellectual outcome was in the normal range whether the children had suffered an arterial ischemic stroke or a sinovenous thrombosis.

Post-varicella arteriopathy of childhood: Natural history of vascular stenosis

OBJECTIVE

To determine the course of vascular changes in childhood post-varicella arteriopathy (PVA) and its relationship to recurrent arterial ischemic stroke or TIA (AIS/TIA).

METHODS

Subjects were children with AIS/TIA occurring <1 year after varicella, ischemic localization consistent with unilateral disease affecting the supraclinoid internal carotid artery or proximal anterior or middle cerebral arteries, and no identified AIS/TIA etiology other than PVA. Charts, brain MRI, and sequential cerebral vessel imaging (selective cerebral angiography or MR angiography [SCA/MRA]) were retrospectively reviewed.

RESULTS

Twenty-three children had varicella at age 1.0 to 10.4 years and had single or multiple AIS/TIAs 4 to 47 weeks later. Initial SCA/MRA was performed within 1 month of presentation, and each child had one to five repeat SCA/MRAs during a 4- to 87-month period. There was vascular stenosis in 19 children, maximal on initial studies in 15 of these. Subsequent stenosis regression occurred in 17 children. In 11 of these, one or two additional SCA/MRAs showed further regression as long as 48 months after presentation; there was no restenosis. Eight of 23 children had recurrent AIS/TIA with antithrombotic therapy within 33 weeks of presentation, including 1 of 17 children with documented stenosis regression.

CONCLUSION

Vascular stenosis of childhood post-varicella arteriopathy takes a monophasic course, generally with subsequent stenosis regression and only occasional stenosis progression after arterial ischemic stroke/TIA. Arterial ischemic stroke/TIA rarely recurs with antithrombotic prophylaxis after stenosis regression occurs.

Angiography-negative primary central nervous system vasculitis in children: A newly recognized inflammatory central nervous system disease

Inflammatory central nervous system (CNS) diseases in childhood comprise a wide spectrum of heterogeneous conditions. We studied 4 children with primary CNS vasculitis in whom results of magnetic resonance imaging studies were abnormal but results of conventional angiography were normal. We determined that angiography-negative, biopsy-confirmed primary small-vessel CNS vasculitis is a previously unrecognized distinct disease entity in children. The diagnosis must be considered in a child with a progressive, acquired diffuse or focal neurologic deficit, even if the results of conventional angiography are normal. A lesional brain biopsy is required to confirm the diagnosis. Use of immunosuppressive therapy plus aspirin leads to an excellent neurologic outcome.

Toward the definition of cerebral arteriopathies of childhood

PURPOSE OF REVIEW

To facilitate and standardize the diagnosis of cerebrovascular conditions in childhood, particularly in the field of arterial ischemic diseases.

RECENT FINDINGS

Progress in diagnostic techniques in the past decade have led to newly established etiologies for childhood stroke, most of which represent some form of vascular pathology. These advances must be integrated into a modern nomenclature system with revised definitions of stroke and arterial wall diseases-arteriopathies-in childhood.

SUMMARY

This nomenclature system is intended to facilitate and enhance clinical research in childhood stroke, particularly multicenter collaborative studies.

Arterial ischemic strokes in infants and children: an overview of current approaches

Stroke in children is increasingly recognized. The incidence exceeds 8 per 100,000 per year. Important differences in stroke in newborns and children compared with adults, as well as a paucity of clinical trials, create challenges in the diagnosis and management of pediatric arterial ischemic stroke (AIS). The neurological presentation of AIS can be subtle. Radiographic diagnosis of acute AIS is also challenging because CT scan may be normal early on. Risk factors include vascular, intravascular, and embolic disorders; frequently, there are multiple risk factors in a given child, necessitating thorough investigations. More than 50% have a vasculopathy including postvaricella angiopathy, dissection, moyamoya, or vasculitis. Intravascular mechanisms are frequently present, including dehydration. Hematological or prothrombotic conditions are also associated with AIS in children, and include sickle cell disease and prothrombotic disorders. The latter have been identified in from one third to one half of children with AIS, are usually acquired, and frequently act in concert with other risk factors for stroke. The most common embolic source is congenital heart disease, which is present in 25% of children with AIS. Outcomes include death in 6% and neurological deficits in two thirds of children. Given that no clinical trials have been completed in pediatric stroke to date, treatment is empiric. Initial neuroprotective strategies aim to reduce the size of the infarct. For older children antithrombotic agents (antiplatelet drugs and anticoagulants) are given to reduce the 20 to 30% risk of recurrence. There are coordinated research efforts currently being initiated, which over the next decade will result in clinical trials in this understudied condition.

Health-related quality of life and its relationship to neurological outcome in child survivors of stroke

BACKGROUND

Ischemic stroke during infancy and childhood has the potential to result in neurological impairments and affect a child's ability to function at home, school, and play. There are limited data on the effect of ischemic stroke on quality of life (QOL) of child survivors of ischemic stroke.

OBJECTIVE

To examine parent and child perspectives on QOL and examine factors that correlate with reduced QOL for child survivors of stroke.

METHODS

A prospective single-center cohort design was used. Participants included children 2-18 years of age surviving ischemic stroke. The Pediatric Quality of Life 4.0 Generic Inventory Scale (PedsQL) parent proxy-report (2-18 years of age) and child self-report (5-18 years of age) were completed by participants. Scores were compared with standardized normative data of healthy children and those with chronic medical conditions. Neurological deficits were measured with the Pediatric Stroke Outcome Measure, a standardized evaluation for children. The relationships between stroke type, neurological deficit, and health-related quality of life (HRQOL) were examined.

RESULTS

We assessed the QOL in 84 children with arterial ischemic stroke and 16 with cerebral sinovenous thrombosis at a mean age of 8.4 (4.12) years; 4.4 (2.93) years after their stroke. Results showed that both the parent-proxy and child self-report HRQOL scores were significantly reduced (P>.01) compared with normative data of healthy children. Of greatest concern for both parents and children was the effect of stroke on school, followed by its impact on emotional and social functions. In contrast to other studies, scores in physical domain were better than those in the psychosocial domain. Multivariate analysis showed that of neurological deficits after stroke was a significant predictor of poor HRQOL (P>.05). The children with poor neurological recovery had the lowest mean PedsQL scores and their QOL was significantly poorer compared with normative data of children with chronic health conditions (ie, diabetes, cancer).

CONCLUSION

The PedsQL appears to be a promising assessment tool of HRQOL for children following stroke. Both parent and child perspectives should be included because of the potential for there to be significant differences in perspectives. Although severity of neurological outcome is a significant predictor of reduced HRQOL, it accounted for a small proportion of variance in QOL scores. Further research is required to delineate other factors that are significant predictors of outcome.

Increased anticardiolipin antibody IgG titers do not predict recurrent stroke or TIA in children

BACKGROUND

Increased anticardiolipin antibody (ACLA) immunoglobulin (Ig) G titers are commonly found in children with arterial ischemic stroke (AIS) or TIA (AIS/TIA). The associated risk of recurrent thromboembolism is unknown.

OBJECTIVE

To determine the risk of recurrent thromboembolism associated with persistently increased ACLA titers of the IgG isotype in children with AIS/TIA.

METHODS

The authors studied a cohort of children surviving first AIS/TIA tested by standardized ELISA for beta2-glycoprotein I-dependent ACLA of the IgG isotype. Children with ACLA titers >15 IgG phospholipid (GPL) units (per manufacturer's cutoff point) on more than two occasions > or =6 weeks apart were classified as ACLA-positive (ACLA+) and compared with ACLA-negative (ACLA-) children with respect to recurrent thromboembolic events (AIS/TIA, sinovenous thrombosis, and extracerebral thromboembolism).

RESULTS

The authors recruited 34 ACLA+ children and 151 ACLA- children. Most ACLA+ children (30/34; 88%) had ACLA titers < or =40 GPL units. During the follow-up period (median duration, 2.8 years for ACLA+ children and 3.0 years for ACLA- children), AIS/TIA recurred in 26% of ACLA+ children and in 38% of ACLA- children; none developed sinovenous thrombosis or extracerebral thromboembolism. Based on survival analysis, this difference was nonsignificant (p = 0.54). Using binary partition evaluation, no titer criteria for ACLA positivity (range, 0 to 60 GPL units) predicted recurrent AIS/TIA.

CONCLUSION

In children surviving arterial ischemic stroke/TIA, increased anticardiolipin antibody immunoglobulin G titers do not predict recurrent thromboembolism.

Sinovenous thrombosis in children

Sinus thrombosis in children is increasingly recognized; however, the diagnosis is still frequently missed. Children may have an increased incidence of this disorder compared with adults, and neonates are at greatly increased risk compared with older children. Childhood CSVT carries significant long-term sequelae that include death or neurologic deficits in nearly 50% of cases. Neonates are not spared from these sequelae. At present, the approach to treatment is empiric but in the past decade treatment with anti-coagulants is supported by the unacceptable rates of adverse outcomes, the pathophysiology of CSVT, and the data supporting the efficacy and safety of anti-coagulation for adult CSVT. Among the most significant current and future developments in childhood CSVT is the evolution of accurate, noninvasive and economical neuroimaging techniques. The latter techniques have the potential to increase the detection rate of childhood CSVT, improve our understanding of the pathophysiology and define important subgroups of patients who best respond to treatment. An international interest in childhood CSVT is developing and, in the next decade, will enable the necessary multi-national clinical trials to provide evidence-based treatments and decrease the adverse outcomes.

Thromboembolic disease and antithrombotic therapy in newborns

This update uses an evidence based approach to analyze and present the epidemiology of neonatal thrombosis, etiologies, currently used techniques for diagnosis with their limitations, and current therapeutic approaches. In addition, the approaches to both prevention and optimal therapies are discussed. In Section I Dr. Paul Monagle addresses the epidemiology of neonatal thrombosis outside of the central nervous system in both arterial and venous locations, and those that occur in utero. The specific contributions of catheters and congenital prothrombotic disorders are delineated. Dr. Monagle also describes currently used techniques for the diagnosis of thrombotic events as well as their limitations and the current therapeutic approaches. In Section II, Dr. Gabrielle deVeber reviews the epidemiology of neonatal thrombosis within the central nervous system, in both arterial and venous locations and those that occur in utero. The neurological presentation, risk factors including congenital prothrombotic disorders, anatomical distribution, diagnostic tests, use of antithrombotic therapy and neurologic outcome of neonates with either sinovenous thrombosis or arterial ischemic stroke are discussed. In Section III, Dr. Anthony Chan reviews the current approaches to the prevention and treatment of neonatal thrombosis. Information on the differences in the response of neonates compared to adults to antithrombotic therapy and new approaches to the prevention and treatment of thrombosis in neonates are emphasized.

Stroke and the child's brain: an overview of epidemiology, syndromes and risk factors

Childhood stroke is emerging as a serious and frequent disorder. In contrast to adult stroke, the study of childhood stroke is in a very early stage of research development with no randomized controlled trials conducted to date outside of sickle cell stroke. The results of research in adults have limited applicability to children with stroke due to fundamental age-related differences in the neurological, cerebrovascular and coagulation systems. In recent years clinical and basic research studies have improved our understanding of childhood stroke. Population-based studies have resulted in an increased awareness of the frequencies and features of stroke syndromes in children. Cohort and case-control studies have led to an enhanced understanding of the multiple risk factors underlying childhood stroke. Advances in neuroimaging and in genetic and other laboratory testing approaches have resulted in an increased definition of stroke subtypes and risk factors.

Cerebral sinovenous thrombosis in children

BACKGROUND

Cerebral sinovenous thrombosis in children is a serious disorder, and information is needed about its prevention and treatment.

METHODS

The Canadian Pediatric Ischemic Stroke Registry was initiated in 1992 at the 16 pediatric tertiary care centers in Canada. Children (newborn to 18 years of age) with symptoms and radiographic confirmation of sinovenous thrombosis were included.

RESULTS

During the first six years of the registry, 160 consecutive children with sinovenous thrombosis were enrolled, and the incidence of the disorder was 0.67 cases per 100,000 children per year. Neonates were most commonly affected. Fifty-eight percent of the children had seizures, 76 percent had diffuse neurologic signs, and 42 percent had focal neurologic signs. Risk factors included head and neck disorders (in 29 percent), acute systemic illnesses (in 54 percent), chronic systemic diseases (in 36 percent), and prothrombotic states (in 41 percent). Venous infarcts occurred in 41 percent of the children. Fifty-three percent of the children received antithrombotic agents. Neurologic deficits were present in 38 percent of the children, and 8 percent died; half the deaths were due to sinovenous thrombosis. Predictors of adverse neurologic outcomes were seizures at presentation and venous infarcts.

CONCLUSIONS

Sinovenous thrombosis in children affects primarily neonates and results in neurologic impairment or death in approximately half the cases. The occurrence of venous infarcts or seizures portends a poor outcome.

Chickenpox and stroke in childhood: a study of frequency and causation

BACKGROUND AND PURPOSE

The purpose of this study was to determine whether infection with varicella is causal for arterial ischemic stroke (AIS) in children.

METHODS

First, a prospective cohort study was conducted in young children (aged 6 months to 10 years) with AIS at 2 institutions (cohort study). The presence of varicella infection <12 months before AIS was determined and compared with the published frequency of varicella infection in the healthy pediatric population. The clinical and radiographic features of AIS were compared between the varicella and nonvaricella study cohorts. Second, a literature search of varicella-associated AIS was conducted, and the clinical and radiographic features were compared with the study nonvaricella cohort.

RESULTS

In the cohort study, 22 (31%) of 70 consecutive children with AIS had a varicella infection in the preceding year compared with 9% in the healthy population. Children in the varicella cohort were more likely to have basal ganglia infarcts (P<0.001), abnormal cerebral vascular imaging (P<0.05), and recurrent AIS or transient ischemic attacks (P<0.05) than those in the nonvaricella cohort. The pooled literature analysis of 51 cases of varicella-associated AIS showed similar findings to the varicella cohort.

CONCLUSION

In young children with AIS, there is a 3-fold increase in preceding varicella infection compared with published population rates, and varicella-associated AIS accounts for nearly one third of childhood AIS. Varicella-associated AIS has characteristic features, including a 2-fold increase in recurrent AIS and transient ischemic attacks. Varicella is an important risk factor for childhood AIS.

Isolated angiitis of the CNS in children

OBJECTIVE

To clarify the clinical features and pathologic manifestations of isolated angiitis of the CNS (IACNS) in children.

METHODS

The authors report two new cases and summarize the literature of childhood IACNS confirmed by pathology.

RESULTS

IACNS affecting small vessels (n = 5). Neurologic manifestations included headaches, focal seizures, and progressive, behavioral, or multifocal neurologic impairment. MRI showed multifocal, T2-hyperintense, cerebral lesions without mass effect or tumor-like lesions. CSF, erythrocyte sedimentation rate, and cerebral angiograms were often normal.CNS biopsy disclosed a nongranulomatous vasculitis. Children were treated with prednisone alone or combined with cyclophosphamide. One child died. Four children had a favorable outcome. IACNS affecting large and medium arteries (n =5). Three children presented with acute ischemic stroke or TIA. Brain CT showed ischemic infarcts. Two children presented with subarachnoid hemorrhage. In this group, CSF, erythrocyte sedimentation rate, and angiograms were often abnormal. No patient received immunosuppressive therapy. Five children died. Autopsy showed granulomatous IACNS (n =5).

CONCLUSIONS

Clinical and radiologic features correlate with the size of affected vessels. Prognosis differs between groups. Potential markers of poor outcome are acute stroke presentation secondary to large and medium-sized artery involvement, granulomatous angiitis, and delayed institution of immunosuppressive therapy.

Prothrombotic disorders and ischemic stroke in children

Childhood ischemic stroke, including arterial ischemic stroke (AIS) and sinovenous thrombosis (SVT), is relatively rare in children but can result in devastating morbidity and mortality. An understanding of the etiology of childhood stroke is important because strategies for primary and secondary prevention can be devised. Prothrombotic disorders may contribute to the etiology of childhood stroke, and include deficiencies of antithrombin, protein C, protein S, plasminogen, and presence of Factor V Leiden, Prothrombin gene G20210A, dysfibrinogenemia, antiphospholipid antibodies, hyperhomocysteinemia, and elevated lipoprotein (a). The overall incidence of prothrombotic disorders in childhood AIS is estimated to be 20% to 50% in most studies and, in childhood SVT, to be 33% to 99%. In addition, hyperlipidemia, polycythemia, iron deficiency anemia, and platelet disorders may result in a prothrombotic state associated with ischemic stroke. The etiologic contribution of these prothrombotic disorders to initial and recurrent stroke has not been clearly defined; however, additional risk factors are usually present in affected children. Given the prevalence of prothrombotic disorders in childhood stroke, and their likely causative role, children with stroke should be screened for prothrombotic disorders. Future prospective and multicenter studies will elucidate the contribution of specific prothrombotic disorders to initial and recurrent stroke, and optimal therapy.

Stroke in children: recognition, treatment, and future directions

Childhood stoke is increasingly recognized, but studies remain largely descriptive. Important differences from adult stroke include the following: (1) frequently delayed or missed diagnosis, (2) heterogenous and overlapping risk factors, and (3) developmental differences in the cerebrovascular, neurologic, and coagulation systems. These aspects limit the extrapolation of the results of adult stroke research and present challenges in caring for children with stroke. The incidence of childhood ischemic stroke exceeds 3.3 in 100,000 children per year, more than double the estimates from past decades. The increased incidence reflects, in part, increased survival in previously fatal conditions predisposing to stroke, including congenital heart disease, sickle cell anemia, and leukemia. Risk factors for stroke are recognized in more than 75% of children. Common risk factors include congenital heart disease and sickle cell disease. Progressive arteriopathies, including vasculitis and moyamoya syndrome, are rare in children with stroke; however, transient arteriopathies including post-varicella angiopathy are increasingly recognized. Prothrombotic abnormalities are frequently present but of unclear significance. Adverse outcomes after childhood stroke, including death in 10%, recurrence in 20%, and neurologic deficits in two thirds of survivors could be reduced with available stroke treatments. Aggressive prehospital emergency care and transfer could improve access to hyperacute stroke therapies including tPA. Currently, the diagnosis is delayed by more than 24 hours from onset in most children. As in adults, tPA will likely produce unacceptable rates of intracerebral hemmorrhage unless given within 3 hours of stroke symptom onset. The appropriate choices for in hospital treatment and secondary preventative strategies, including aspirin and anticoagulants, are controversial. Empiric recommendations are published; however, age-appropriate clinical trials are urgently needed. The large multinational networks of investigators necessary for designing and conducting these future trials are now being formed.

The use of low molecular weight heparin in pediatric patients: a prospective cohort study

OBJECTIVE

Low molecular weight heparins (LMWHs) offer several advantages over standard anticoagulant therapy (unfractionated heparin/warfarin) including predictable pharmacokinetics, minimal monitoring, and subcutaneous administration. Our objective was to determine the safety and efficacy of LMWHs in children.

METHODS

A prospective cohort of children treated with the LMWH enoxaparin (Rhone Poulenc Rorer) was monitored at the Hospital for Sick Children, Toronto, Canada, from March 1994 until July 1997.

RESULTS

There were 146 courses of LMWH administered for treatment and 31 courses for prophylaxis of thromboembolic events (TEs). Clinical resolution of TEs occurred in 94% of children receiving therapeutic doses of LMWH, and 96% of children receiving prophylactic doses of LMWH had no symptoms of recurrent or new TEs. Major bleeding occurred in 5% of children receiving therapeutic doses. Recurrent or new TEs occurred in 1% and 3% of children receiving therapeutic and prophylactic doses of LMWH, respectively.

CONCLUSION

LMWH appears to be efficacious and safe for both management and prophylaxis of TEs. The results of this cohort study justify a randomized controlled trial comparing LMWH with standard therapy for the management of TEs in children.

Prothrombotic disorders in infants and children with cerebral thromboembolism

BACKGROUND

To our knowledge, the contribution of prothrombotic conditions to cerebral thromboembolism has never been prospectively studied in a large series of pediatric patients.

METHODS

The Hospital for Sick Children, Toronto, Ontario, established a program in January 1992 to diagnose and treat children (term newborn to 18 years old) with arterial ischemic stroke or sinovenous thrombosis. The routine evaluation for prothrombotic conditions included plasminogen, antithrombin, protein C, free protein S, activated protein C resistance, IgG and IgM anticardiolipin antibody, and lupus anticoagulant. We analyzed samples taken within 2 years of the event. We report results on patients seen from January 1, 1992, to January 1, 1997.

RESULTS

Ninety-two patients (47 males and 45 females) entered the program during the study interval. Patients ranged from newborn to 18 years in age. Arterial ischemic stroke occurred in 78% of patients while sinovenous thrombosis occurred in 22%. All were tested for prothrombotic disorders. One or more abnormal results were present in 35 (38%) of the 92 patients. The majority (21/35) had multiple abnormal test results. The abnormal test results were anticardiolipin antibody (33%), plasminogen (9.5%), activated protein C resistance (9%), protein C (7%), antithrombin (12.5%), lupus anticoagulant (8%), and free protein S (11.5%). Male sex predicted the presence of prothrombotic abnormalities (relative risk, 1.7; 95% confidence interval, 1.2-2.5), but stroke type (relative risk, 0.8; 95% confidence interval, 0.7-1.1), age group, and presence of other risk factors did not predict abnormal testing.

CONCLUSIONS

A significant proportion (38%) of children with cerebral thromboembolism had evidence of prothrombotic conditions. In particular, there was a predominance of children with anticardiolipin antibody (33%). These data support a recommendation that children with cerebral thromboembolism be evaluated for prothrombotic disorders.

Anticoagulation therapy in pediatric patients with sinovenous thrombosis: a cohort study

OBJECTIVE

To assess the use of anticoagulant therapy in a consecutive cohort study of children with sinovenous thrombosis (SVT).

METHODS

A single institutional pilot study of anticoagulant therapy was conducted from January 1992 to December 1996 at the Hospital for Sick Children, Toronto, Ontario. Consecutive children with the diagnosis of SVT, made by computed tomography, magnetic resonance imaging (MRI), MRI with venography, ultrasonography, nuclear brain scanning, or conventional angiography were eligible for anticoagulant therapy. RADIOGRAPHIC EVALUATION: Most children underwent multiple radiographic tests for evaluation of the central nervous system. Of the 32 episodes of SVT, CT was performed in 30, MRI with or without venography in 26, ultrasonography in 11, and nuclear brain scanning in 5. The majority of the SVTs were located at the superior sagittal sinus (50%) and right lateral sinus complex (44%).

RESULTS

There were 30 consecutive children with 32 episodes of SVT during the 5-year study (2 girls had recurrent SVT). The median age was 6.2 years (age range, 3 days to 18 years), and the sex of the patients was evenly distributed (15 girls and 15 boys). The primary associated clinical conditions consisted of systemic lupus erythematosus (n = 5), renal disease (n = 3), perinatal distress (n = 2), congenital heart disease (n = 1), cerebral arteriovenous malformation (n = 1), and neurosurgery for refractory seizures (n= 1). The remainder were previously healthy children older than 1 month (n = 10) and newborns (n = 7). Eight children were ineligible for anticoagulant therapy because of an associated intracranial hemorrhage (n = 6), a postoperative bleeding risk after neurosurgery (n = 1), or a prolonged delay from the diagnosis to the time of referral (n = 1). Ten children received standard heparin, and 12 children received low-molecular-weight heparin (LMWH) (enoxaparin sodium). Eighteen children were treated with oral anticoagulants for 3 months after initial heparin therapy, and 4 patients received LMWH for the entire course of treatment. There was no intracranial hemorrhage in the 12 patients treated with LMWH, but there was 1 case of clinically silent bleeding in the standard heparin group.

CONCLUSIONS

The results of this pilot study suggest that anticoagulant therapy, in particular LMWH, is safe and may have a role in the treatment of children with SVT. A randomized controlled trial is warranted.