Stroke in children with sickle cell disease

Pathophysiology of Vascular Stenosis and Remodeling in Moyamoya Disease

Moyamoya disease (MMD) and moyamoya syndrome (MMS) are progressive vascular pathologies unique to the cerebrovasculature that are important causes of stroke in both children and adults. The natural history of MMD is characterized by primary progressive stenosis of the supraclinoid internal carotid artery, followed by the formation of fragile collateral vascular networks. In MMS, stenosis and collateralization occur in patients with an associated disease or condition. The pathological features of the stenosis associated with MMD include neointimal hyperplasia, disruption of the internal elastic lamina, and medial attenuation, which ultimately lead to progressive decreases in both luminal and external arterial diameter. Several molecular pathways have been implicated in the pathophysiology of stenosis in MMD with functions in cellular proliferation and migration, extracellular matrix remodeling, apoptosis, and vascular inflammation. Importantly, several of these molecular pathways overlap with those known to contribute to diseases of systemic arterial stenosis, such as atherosclerosis and fibromuscular dysplasia (FMD). Despite these possible shared mechanisms of stenosis, the contrast of MMD with other stenotic pathologies highlights the central questions underlying its pathogenesis. These questions include why the stenosis that is associated with MMD occurs in such a specific and limited anatomic location and what process initiates this stenosis. Further investigation of these questions is critical to developing an understanding of MMD that may lead to disease-modifying medical therapies. This review may be of interest to scientists, neurosurgeons, and neurologists involved in both moyamoya research and treatment and provides a review of pathophysiologic processes relevant to diseases of arterial stenosis on a broader scale.

Prevalence of Stroke in Asian Patients with Sickle Cell Anemia: A Systematic Review and Meta-Analysis

Sickle cell anemia (SCA) is an inherited autosomal recessive disease. It is caused due to point mutation that substitutes glutamate with valine at the sixth amino acid position of the beta chain of hemoglobin molecules leading to the sickling of the red blood cells and decreased structural deformability. Silent cerebral infarcts are the most common neurological complication of SCA, while overt stroke comprises substantial burden in patients with SCA. This meta-analysis aimed to find the pooled prevalence of overt stroke in SCA patients and discuss the importance of screening them. PubMed, Embase, and Google Scholar were the electronic databases used to search the studies. A total of 765 articles were retrieved upon detailed searching in the abovementioned databases. After a series of removing duplicate articles, title and abstract screening, and full-text review, 20 articles were found eligible and included in the study. The total number of participants from all the included studies was 3,956, and pooled prevalence of stroke in patients with sickle cell anemia in Asia was found to be 5% (95% CI: 4%, 6%) with a range from 1 to 41%. Stroke occurrence in sickle cell anemia patients is an emergency complication that needs immediate intervention and management. Because of the high prevalence of stroke in patients with sickle cell anemia, clinicians should focus on its prevention and treatment strategies.

Clinical Presentation and Stroke Incidence Differ by Moyamoya Etiology

INTRODUCTION

Moyamoya arteriopathy, which can be idiopathic or associated with sickle cell disease, neurofibromatosis, Down syndrome, or cranial radiation therapy, is a progressive cerebral arteriopathy associated with high rates of incident and recurrent stroke. Little is known about how these subgroups differ with respect to clinical presentation, radiographic findings, stroke risk, and functional outcomes.

METHODS

Using ICD codes, we identified children ages 28 days to 18 years treated for moyamoya arteriopathy at our tertiary care center between 2003 and 2019. Demographic, clinical, and radiographic data were extracted from the medical record. The Pediatric Stroke Recurrence and Recovery Questionnaire was administered to consenting participants.

RESULTS

Sixty-nine patients met inclusion criteria (33 idiopathic, 18 sickle cell disease, 11 neurofibromatosis, 6 Down syndrome, 1 cranial radiation therapy). Median follow-up time was 7.7 years; 24 patients had at least 5 years of follow-up data. Frequency of stroke at presentation differed by subgroup (P < .001). Of patients with at least 2 years of follow-up, 33 (55%) experienced stroke. The proportion of patients experiencing stroke differed by subgroup (50% of idiopathic cases, 72% of sickle cell disease, 11% of neurofibromatosis, and 100% of Down syndrome, P = .003). The frequency of bilateral versus unilateral disease (P = .001) and stroke-free survival following presentation (P = .01) also differed by subgroup.

CONCLUSIONS

In this single-center cohort, moyamoya subgroups differed with respect to clinical and radiographic characteristics, with neurofibromatosis-associated moyamoya syndrome having a milder phenotype and Down syndrome-associated moyamoya portending a more aggressive course. These findings need confirmation in a larger, multi-center cohort with longer duration of follow-up.

Prevalence of and Risk Factors for Cerebral Microbleeds in Moyamoya Disease and Syndrome in the American Population

BACKGROUND AND PURPOSE

Cerebral microbleeds (CMB) are reported to be frequent in moyamoya disease (MMD) and moyamoya syndrome (MMS) in the Asian population. It is associated with an increased risk of intracerebral hemorrhage. The significance of CMB in MMD/MMS in non-Asian populations has not been well established. Our study aimed to investigate the prevalence of CMB in MMD/MMS in a moymoya cohort with a majority of non-Asians and to identify risk factors for developing a CMB and its predictive value for subsequent vascular events.

METHODS

The moyamoya database was compiled by screening for MMD/MMS among patients admitted to the Zale-Lipshy University Hospital at the University of Texas Southwestern Medical Center. We identified and analyzed data of 67 patients with MMD or MMS. Patients were characterized as CMB+ or CMB- based on MRI findings. In CMB+ patients, the total number and location of CMB were identified. Univariate and multivariate logistic regression were used to identify risk factors for developing CMB and whether CMB are associated with the development of subsequent vascular events.

RESULTS

Out of a total of 67 patients, 11 (16%) had CMB. Males had significantly higher odds of having CMB as compared to females (OR 1.76; 95% CI 1.40-24.3, p = 0.021). The incidence of CMB was also associated with age at diagnosis (mean age of CMB+ patients vs. CMB- patients: 44 vs. 34 years, respectively, p = 0.024), smoking (p = 0.006), and hemorrhagic stroke at presentation (p = 0.034). Logistic regression with multivariate analysis found that gender and age at diagnosis remained statistically significant. New ischemic events occurred in 2 (20%) out of 10 CMB+ patients and 13 (23%) out of 55 CMB- patients, respectively (p = 0.79). While 2 (3%) CMB- patients had a new cerebral hemorrhage during follow-up, none of the CMB+ patients did.

CONCLUSIONS

CMB are less prevalent in MMD/MMS in the USA than in Asia. An older age at diagnosis and male gender were associated with CMB. The presence of CMB was not associated with an increased risk of a subsequent ischemic or hemorrhagic stroke.

Moyamoya disease in a Moroccan baby: a case report

Background

A stroke in a baby is uncommon, recent studies suggested that their incidence is rising. Moyamoya disease is one of the leading causes of stroke in babies. This condition is mostly described in Japan. In Morocco, moyamoya disease has rarely been reported and a few cases were published. We report a rare Moroccan case of a 23-month-old baby boy who presented with left-sided hemiparesis and was diagnosed as having moyamoya disease.

Case presentation

A 23-month-old full-term Moroccan baby boy born to a non-consanguineous couple was referred to our hospital with the complaint of sudden onset left-sided hemiparesis. On neurological examination, there were no signs of meningeal irritation, his gait was hemiplegic, tone was decreased over left side, power was 2/5 over left upper and lower limb, and deep tendon reflexes were exaggerated. Preliminary neuroimaging suggested an arterial ischemic process. Clinical and laboratory evaluation excluded hematologic, metabolic, and vasculitic causes. Cerebral angiography confirmed the diagnosis of moyamoya disease. Our patient was treated with acetylsalicylic acid 5 mg/kg per day and referred to follow-up with pediatric neurosurgeon. Cerebral revascularization surgery using encephaloduroarteriosynangiosis was performed. At 8-month follow-up, his hemiparesis had improved and no further ischemic events had occurred.

Conclusion

This case highlights the importance of considering moyamoya disease to be one of the classic etiologies of acute ischemic strokes in children from North Africa. It also emphasizes the rare presentation among the African population and the use of neurovascular imaging techniques to facilitate diagnosis of moyamoya disease.

Pediatric Intracranial Aneurysms: Considerations and Recommendations for Follow-Up Imaging

BACKGROUND

Pediatric intracranial aneurysms (IAs) are rare. Compared with adult IAs, they are more commonly giant, fusiform, or dissecting. Treatment often proves more complex, and recurrence rate and de novo aneurysmogenesis incidence are higher. A consensus regarding the most appropriate algorithm for following pediatric IAs is lacking.

METHODS

We sought to generate recommendations based on the reported experience in the literature with pediatric IAs through a thorough review of the PubMed database, discussion with experienced neurointerventionalists, and our own experience.

RESULTS

Digital subtraction angiography (DSA) was utilized immediately post-operatively for microsurgically-clipped and endovascularly-treated IAs, at 6-12 months postoperatively for endovascularly-treated IAs, and in cases of aneurysmal recurrence or de novo aneurysmogenesis discovered by non-invasive imaging modalities. Computed tomographic angiography was the preferred imaging modality for long-term follow-up of microsurgically clipped IAs. Magnetic resonance angiography (MRA) was the preferred modality for following IAs that were untreated, endovascularly-treated, or microsurgically-treated in a manner other than clipping.

CONCLUSIONS

We propose incidental untreated IAs to be followed by magnetic resonance angiography without contrast enhancement. Follow-up modality and interval for treated pediatric IAs is determined by initial aneurysmal complexity, treatment modality, and degree of posttreatment obliteration. Recurrence or de novo aneurysmogenesis requiring treatment should be followed by digital subtraction angiography and appropriate retreatment. Computed tomography angiography is preferred for clipped IAs, whereas contrast-enhanced magnetic resonance angiography is preferred for lesions treated endovascularly with coil embolization and lesions treated microsurgically in a manner other than clipping.

Crises in Sickle Cell Disease

In spite of significant strides in the treatment of sickle cell disease (SCD), SCD crises are still responsible for high morbidity and early mortality. While most patients initially seek care in the acute setting for a seemingly uncomplicated pain episode (pain crisis or vaso-occlusive crisis), this initial event is the primary risk factor for potentially life-threatening complications. The pathophysiological basis of these illnesses is end-organ ischemia and infarction combined with the downstream effects of hemolysis that results from red blood cell sickling. These pathological changes can occur acutely and lead to a dramatic clinical presentation, but are frequently superimposed over a milieu of chronic vasculopathy, immune dysregulation, and decreased functional reserve. In the lungs, acute chest syndrome is a particularly ominous lung injury syndrome with a complex pathogenesis and potentially devastating sequelae, but all organ systems can be affected. It is, therefore, critical to understand the SCD patients' susceptibility to acute complications and their risk factors so that they can be recognized promptly and managed effectively. Blood transfusions remain the mainstay of therapy for all severe acute crises. Recommendations and indications for the safest and most efficient implementation of transfusion strategies in the critical care setting are therefore presented and discussed, together with their pitfalls and potential future therapeutic alternatives. In particular, the importance of extended phenotypic red blood cell matching cannot be overemphasized, due to the high prevalence of severe complications from red cell alloimmunization in SCD.

Moyamoya Biomarkers

Moyamoya disease (MMD) is an arteriopathy of the intracranial circulation predominantly affecting the branches of the internal carotid arteries. Heterogeneity in presentation, progression and response to therapy has prompted intense study to improve the diagnosis and prognosis of this disease. Recent progress in the development of moyamoya-related biomarkers has stimulated marked interest in this field. Biomarkers can be defined as biologically derived agents-such as specific molecules or unique patterns on imaging-that can identify the presence of disease or help to predict its course. This article reviews the current categories of biomarkers relevant to MMD-including proteins, cells and genes-along with potential limitations and applications for their use.

The current state of imaging pediatric hemoglobinopathies

The hemoglobinopathies are a group of genetic disorders with a broad spectrum of clinical manifestations and radiologic findings. The imaging of pediatric hemoglobinopathies, which is influenced by concomitant hemosiderosis and the sequela of chelation therapy, has evolved over the years along with ever-improving technology. This article reviews and illustrates the most common radiographic and cross-sectional imaging findings of the 2 best known and clinically relevant hemoglobinopathies in pediatric patients, sickle cell disease and β-thalassemia.

A safe therapeutic apheresis protocol in paediatric patients weighing 11 to 25 kg

BACKGROUND AND OBJECTIVES

Erythrocytapheresis and leukapheresis (LPE) of small children are logistically complex and many centres are reluctant to perform these procedures. In children, both sickle cell and leukaemic emergencies demand prompt action to prevent additional morbidity but detailed protocols for small children are lacking, and often are performed using guidelines shown to work in larger patients. We report a 3-year experience with children weighing 11-25 kg at a large academic medical centre.

MATERIALS AND METHODS

All patients were treated with the COBE® Spectra apheresis system; circuit was primed with blood not adjusted for haematocrit and anticoagulant citrate dextrose A was used as anticoagulation. Procedures were performed in the paediatric intensive care unit by apheresis nursing staff.

RESULTS

Twenty-five apheresis procedures in 19 patients were performed; 17 of 19 patients presented with sickle cell-related acute complications and two (2/19) with newly diagnosed acute leukaemia and hyperleucocytosis. None of the patients required medications during the procedures. Vital signs and clinical condition remained stable and did not worsen during or postapheresis. One patient had a delayed haemolytic transfusion reaction 1 week posterythrocytapheresis as he developed alloantibodies as a result of the procedure. All sickle cell patients achieved a target haematocrit of 21-30% and Haemoglobin A of ≥68%. Both leukaemia patients who underwent LPE had no further signs of leukostasis and achieved marked reductions in leucocyte counts.

CONCLUSIONS

Apheresis of children weighing 11-25 kg can be safely performed without increased morbidity. We outline a protocol that can be used to perform apheresis with minimal complications.

Childhood arterial ischemic stroke: a review of etiologies, antithrombotic treatments, prognostic factors, and priorities for future research

Childhood arterial ischemic stroke (AIS) is a rare, but serious, medical condition, which is fatal in approximately 3% and associated with both acute and long-term neurologic impairment in over 70% of cases. Common etiologies include sickle cell disease, congenital heart disease, arterial dissection, prothrombotic conditions, and preceding viral infections; however, one in four cases is considered idiopathic. To date, no randomized controlled clinical trials (RCTs) have been conducted to establish evidence for current therapeutic strategies outside of sickle cell disease, thus, treatment strategies are largely shaped by consensus-based guidelines, in which, beyond the acute period, aspirin is the mainstay of therapy and anticoagulation is reserved for select circumstances. In recent years, evidence on prognostic factors has accumulated, helping to inform the future design of prognostically stratified RCTs. In this narrative review, we discuss the current understanding of etiologies, consensus-based treatment recommendations, contemporary treatment data, and prognostic factors in childhood AIS. We also identify priorities for future research.

Central nervous system events in children with sickle cell disease presenting acutely with headache

OBJECTIVE

To determine the frequency of acute care visits and risk factors for central nervous system (CNS) events in children with homozygous sickle cell disease (SCD-SS) with an acute headache.

STUDY DESIGN

This is a retrospective cohort study of acute care visits for headache in children with SCD-SS. The prevalence of headache visits, neuroimaging evaluation, and acute CNS events were calculated and clinical and laboratory variables assessed.

RESULTS

Headache was the chief complaint in 102 of 2685 acute care visits (3.8%) by children with SCD-SS. Acute CNS events were detected in 6.9% of these visits. Neuroimaging was performed in 42.2% of visits, and acute CNS events were identified in 16.3% of studies. Factors associated with acute CNS events included older age, history of stroke, transient ischemic attack, or seizure, neurologic symptoms, focal neurologic exam findings, and elevated platelets.

CONCLUSIONS

Acute headache is common in pediatric SCD-SS and more frequently associated with acute CNS events than in the general pediatric population. A history of stroke, transient ischemic attack, seizures, neurologic symptoms, focal neurologic exam, or elevated platelet counts at presentation warrant confirmatory imaging studies. Whether a more limited workup is adequate for other children should be confirmed in a larger, prospective study.

Childhood moyamoya disease and moyamoya syndrome: a pictorial review

Moyamoya disease is an uncommon chronic cerebrovasculopathy, characterized by progressive stenosis of the terminal portion of the internal carotid artery and its main branches, in association with the development of compensatory collateral vessels at the base of the brain. The etiology is unknown, and was originally considered exclusive to East Asia, with particular prevalence in Japan. Moyamoya disease is increasingly diagnosed throughout the world, and represents an important cause of childhood stroke in Western countries. In some cases, similar angiographic features are evident in children with other medical conditions, such as sickle cell disease and Down syndrome. In these instances, the term "moyamoya syndrome" is used. Diagnosing the vasculopathy, excluding possible associated conditions, and planning treatment and follow-up imaging comprise important aspects of clinical management. We review the key imaging features of childhood moyamoya disease and syndrome, present examples of its associations, and discuss new neuroradiologic methods that may be useful in management.

Neuroimaging in assessment of risk of stroke in children with sickle cell disease

PURPOSE

Stroke and subclinical "silent infarcts" are major causes of morbidity in children with Sickle Cell Disease (SCD). Ischemic strokes are more common in younger children while hemorrhagic strokes are more frequent in adults. The goal of neuroimaging in acute stroke is to document whether the stroke is ischemic or hemorrhagic, to assess the extent of parenchymal abnormalities and to determine the presence of other cerebrovascular lesions. Computed Tomography (CT) is the primary modality for the assessment of acute stroke patients because of its 24/7 availability and ability to exclude hemorrhagic causes. Magnetic resonance imaging (MRI) and MR angiography (MRA) are recommended to determine precisely extent of infarction and detect cerebrovascular abnormalities. The goal of neuroimaging in patients with hemorrhagic stroke is to identify an arteriovenous malformation or aneurysm(s) amenable to surgery or catheter intervention.The risk of first stroke is very high in asymptomatic children with intracranial arterial mean velocities over 200 cm/s on transcranial Doppler (TCD) examination. The risk can be substantially reduced if chronic blood transfusions are timely implemented. Large cerebral vessel disease detected by TCD can be confirmed or excluded by MRI/MRA. Those with evidence of parenchymal and/or cerebrovascular lesions should be followed by preventive therapy. In patients with neurologic symptoms and negative MRI/MRA findings Positron Emission Tomography or single photon emission CT is recommended. There are no specific neuroimaging findings that suggest that blood transfusions can be safely halted in children with SCD.

Childhood and teenage stroke

OBJECTIVE

The purpose of this manuscript is to review the various etiologies and to discuss the therapeutic issues in childhood stroke.

METHODS

A PubMed search of literature pertaining to childhood stroke was conducted from 1983 to 2008 using specific key search words pertinent to cerebrovascular disorders in childhood.

RESULTS

The analysis of the multiple causes of childhood stroke including arterial ischemic strokes and cerebral venous thrombosis was presented. Current therapy and outcome data in childhood stroke are also discussed throughout the length of the article.

CONCLUSIONS

With increasing vigilance among physicians and improved neuroimaging modalities, the diagnosis of childhood stroke is now made earlier, with increasing frequency and greater accuracy. However, larger and well-controlled studies regarding the optimal management of childhood stroke in terms of the use of both antithrombotic drugs and anticoagulation are still needed in addition to longitudinal follow-up studies of children with stroke.

Association of the Methylenetetrahydrofolate Reductase A1298C but not the C677T Single Nucleotide Polymorphism with Sickle Cell Disease in Bahrain

The association of methylenetetrahydrofolate reductase (MTHFR) gene mutations, C677T and A1298C, together with changes in homocysteine (Hcy) levels was investigated in 106 sickle cell disease patients and 156 healthy controls from Bahrain. The mutation analysis was done by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). While the frequencies of the mutant alleles C677T and A1298C were comparable between patients and controls, the frequency of the A1298C (C/C) (p = 0.03) but not C677T (T/T) (p = 0.67) genotype, and of the 677T/1298C haplotype were significantly higher in the patients (p = 0.05). Homocysteine levels were normal in all subjects. This suggests that the A1298C, but not C677T, mutation is associated with the genotype of sickle cell disease.

Pial synangiosis in patients with moyamoya syndrome and sickle cell anemia: perioperative management and surgical outcome

Object

Many children with sickle cell anemia (SCA) also have clinical and radiographic findings of an arteriopathy suggestive of moyamoya syndrome. These patients may continue to experience strokes despite optimal medical management. The authors wished to define features of moyamoya syndrome associated with SCA and determine the results of surgical revascularization in these patients at early and late follow-up.

Methods

The authors reviewed the clinical and radiographic records of all patients with moyamoya syndrome and SCA who underwent cerebral revascularization surgery using a standardized surgical procedure—pial synangiosis—from 1985 to 2008.

Results

Twelve patients had SCA and moyamoya syndrome. Six patients were female and 6 were male. The average patient age at surgery was 11.3 years (range 3–22 years). All patients presented with ischemic symptoms, 11 (92%) with previous transient ischemic attacks, and 10 (83%) with completed strokes. Eleven patients (92%) had radiographic evidence of previous stroke at presentation. None presented with hemorrhage. Surgical treatment included pial synangiosis in all patients. Complications included 1 perioperative stroke, 1 wound infection, and 1 perioperative pneumonia. The average length of hospital stay was 5.7 days (including a 24-hour preoperative admission for hydration) and average blood loss was 92.5 ml/hemisphere (in a total of 19 hemispheres). Clinical and radiographic follow-up with an average of 49 months (range 9–144 months) demonstrated no worsening in neurological status in any patient. No clinical or radiographic evidence of new infarcts was observed in any patient at late follow-up, despite disease progression in 13 (68%) of 19 hemispheres.

Conclusions

The clinical and radiographic features of moyamoya syndrome associated with SCA appear comparable to primary moyamoya disease. Successful treatment of these patients requires multidisciplinary care involving hematologists, anesthesiologists, and neurosurgeons. Operative treatment of moyamoya syndrome using pial synangiosis appears to be safe and confers long-lasting protection against further stroke in this population, and provides an alternative for failure of optimal medical therapy in patients. This study underscores the potential merit of screening patients with SCA for moyamoya syndrome.

MRI abnormalities of the brain in one-year-old children with sickle cell anemia

BACKGROUND

Sickle cell anemia (SCA) frequently results in damage to the central nervous system (CNS), but the age of onset of these effects is uncertain. We performed MRI examinations of the brain in infants with SCA, who were evaluated as part of the multicenter randomized double-blinded Pediatric Hydroxyurea Phase III Clinical Trial (BABY HUG).

METHODS

Determination of eligibility for enrollment in the trial originally required baseline MRI and magnetic resonance angiography (MRA) of the brain. A standardized imaging protocol was utilized across eight clinical centers. MRI/MRA exams were reviewed by a panel of three neurology/neuroradiology readers and interpretations reported to the coordinating center. Results were correlated with patient age, gender, history, WBC count, platelet count, hemoglobin (Hb), HbF level, score on the Bayley Scales of Infant Development, and velocity on transcranial Doppler ultrasonography (TCD).

RESULTS

Twenty-three subjects with HbSS were examined at average age 13.7 months (range 10-18 months); 13 were male. Three (13%, CI: 3-34%) had silent infarcts on MRI, two in the right frontal area and one bilaterally. None had MRA abnormalities. The lesions were correlated with increased right-sided TCD velocity and low HbF level, but not with age, history, Hb level, developmental score, or left-sided velocity.

CONCLUSIONS

Silent brain infarcts occur in a small but significant number of infants with SCA as early as a year of age. This finding indicates a need for thorough evaluation of the CNS very early in life in children with SCA in order to develop timely intervention strategies.

Management of stroke in infants and children: a scientific statement from a Special Writing Group of the American Heart Association Stroke Council and the Council on Cardiovascular Disease in the Young

PURPOSE

The purpose of this statement is to review the literature on childhood stroke and to provide recommendations for optimal diagnosis and treatment. This statement is intended for physicians who are responsible for diagnosing and treating infants, children, and adolescents with cerebrovascular disease.

METHODS

The Writing Group members were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee. The panel included members with several different areas of expertise. Each of the panel's recommendations was weighted by applying the American Heart Association Stroke Council's Levels of Evidence grading algorithm. After being reviewed by panel members, the manuscript was reviewed by 4 expert peer reviewers and by members of the Stroke Council Leadership Committee and was approved by the American Heart Association Science Advisory and Coordinating Committee. We anticipate that this statement will need to be updated in 4 years.

RESULTS

Evidence-based recommendations are provided for the prevention of ischemic stroke caused by sickle cell disease, moyamoya disease, cervicocephalic arterial dissection, and cardiogenic embolism. Recommendations on the evaluation and management of hemorrhagic stroke also are provided. Protocols for dosing of heparin and warfarin in children are suggested. Also included are recommendations on the evaluation and management of perinatal stroke and cerebral sinovenous thrombosis in children.

Sickle cell disease vasculopathy: a state of nitric oxide resistance

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by microvascular vaso-occlusion with erythrocytes containing polymerized sickle (S) hemoglobin, erythrocyte hemolysis, vasculopathy, and both acute and chronic multiorgan injury. It is associated with steady state increases in plasma cell-free hemoglobin and overproduction of reactive oxygen species (ROS). Hereditary and acquired hemolytic conditions release into plasma hemoglobin and other erythrocyte components that scavenge endothelium-derived NO and metabolize its precursor arginine, impairing NO homeostasis. Overproduction of ROS, such as superoxide, by enzymatic (xanthine oxidase, NADPH oxidase, uncoupled eNOS) and nonenzymatic pathways (Fenton chemistry), promotes intravascular oxidant stress that can likewise disrupt NO homeostasis. The synergistic bioinactivation of NO by dioxygenation and oxidation reactions with cell-free plasma hemoglobin and ROS, respectively, is discussed as a mechanism for NO resistance in SCD vasculopathy. Human physiological and transgenic animal studies provide experimental evidence of cardiovascular and pulmonary resistance to NO donors and reduced NO bioavailability that is associated with vasoconstriction, decreased blood flow, platelet activation, increased endothelin-1 expression, and end-organ injury. Emerging epidemiological data now suggest that chronic intravascular hemolysis is associated with certain clinical complications: pulmonary hypertension, cutaneous leg ulcerations, priapism, and possibly stroke. New therapeutic strategies to limit intravascular hemolysis and ROS generation and increase NO bioavailability are discussed.

Sickle cell disease complicated by post-streptococcal glomerulonephritis, cerebral hemorrhage and reversible posterior leucoencephalopathy syndrome

A patient with homozygous hemoglobin SS disease presented with an intracerebral hemorrhage complicating reversible posterior leucoencephalopathy syndrome (RPLS), secondary to hypertension associated with acute post-streptococcal glomerulonephritis (APSGN). Distinguishing potentially reversible causes of central nervous system events from primary cerebral infarction or hemorrhage in patients with sickle cell disease is important because the management and prognosis of these complications is very different. Similarly, because of the difference in prognosis between APSGN and other forms of sickle cell nephropathy, it is also important to differentiate these conditions.

Role of brain inflammation in epileptogenesis

Inflammation is known to participate in the mediation of a growing number of acute and chronic neurological disorders. Even so, the involvement of inflammation in the pathogenesis of epilepsy and seizure-induced brain damage has only recently been appreciated. Inflammatory processes, including activation of microglia and astrocytes and production of proinflammatory cytokines and related molecules, have been described in human epilepsy patients as well as in experimental models of epilepsy. For many decades, a functional role for brain inflammation has been implied by the effective use of anti-inflammatory treatments, such as steroids, in treating intractable pediatric epilepsy of diverse causes. Conversely, common pediatric infectious or autoimmune diseases are often accompanied by seizures during the course of illness. In addition, genetic susceptibility to inflammation correlated with an increased risk of epilepsy. Mounting evidence thus supports the hypothesis that inflammation may contribute to epileptogenesis and cause neuronal injury in epilepsy. We provide an overview of the current knowledge that implicates brain inflammation as a common predisposing factor in epilepsy, particularly childhood epilepsy.

Pinch-off syndrome in patients with sickle cell disease receiving erythrocytapheresis

A 6-year-old female with homozygous sickle cell disease had a central venous access device (CVAD) placed to facilitate chronic erythrocytapheresis. Erythrocytapheresis was ineffective due to the rare pinch-off syndrome causing communication between the dual lumen tubing. Awareness of and monitoring for the pinch-off syndrome is indicated in people with sickle cell disease and a CVAD for chronic erythrocytapheresis.

Pediatric stroke: current developments

PURPOSE OF REVIEW

Pediatric arterial ischemic stroke is relatively rare but carries a considerable impact and high risk of recurrence--especially in patients with sickle cell disease and various forms of vasculopathy. We will discuss risk factors, vascular physiology, and primary/secondary/rehabilitative therapies. Goals for future investigation and treatment are suggested.

RECENT FINDINGS

Risk factors include chronic disease, vasculopathy, acute illness, cardiac disease, head and neck trauma, infection, and prothrombic disorders. Research has begun to implicate genetic risk factors--initially in sickle cell disease and more recently in prothrombotic disorders, moyamoya, and nitric oxide regulation. The vascular physiology of pediatric arterial ischemic stroke, especially sickle cell disease stroke, is currently undergoing study in animal models and in humans. No primary prevention therapy for pediatric arterial ischemic stroke is known. Various primary and secondary prevention therapies are used, however, in at-risk sickle cell disease patients. Aspirin, coumadin, and heparin are often initiated as secondary prevention therapies for non-sickle cell disease-associated arterial ischemic stroke, but no studies have assessed efficacy.

SUMMARY

Pediatric arterial ischemic stroke is under-recognized and under-studied. Investigation into the hemodynamic aspects of arterial ischemic stroke, although best studied thus far in sickle cell disease, has been neglected. It is likely that enhanced study of hemodynamics and autoregulation will elucidate both new prevention opportunities and novel treatments.

Preventing stroke among children with sickle cell anemia: an analysis of strategies that involve transcranial Doppler testing and chronic transfusion

BACKGROUND

Transcranial Doppler ultrasonography can identify children with sickle cell anemia who are at elevated risk of stroke and may benefit from chronic transfusions. Uncertainty about the risk/benefit trade-offs of chronic transfusion has led some clinicians to decide not to offer transcranial Doppler ultrasonography screening.

OBJECTIVES

Our goals were to (1) compare the projected benefits and risks of 6 primary stroke-prevention strategies, (2) estimate the optimal frequency of screening, and (3) identify key assumptions that influence the risk/benefit relationship.

METHODS

We designed a decision model to compare 6 primary stroke-prevention strategies: (1) annual transcranial Doppler ultrasonography screening until age 16 with children at high risk of stroke receiving monthly transfusion for life; (2) annual transcranial Doppler ultrasonography until age 16 with transfusions until age 18; (3) biannual transcranial Doppler ultrasonography until age 16 with transfusions until age 18; (4) annual transcranial Doppler ultrasonography until age 10 with transfusion until age 18; (5) 1-time screening at age 2 with transfusion until age 18; and (6) no intervention. Assumptions were derived from the published literature.

RESULTS

For a hypothetical cohort of 2-year-old children, the optimal strategy was transcranial Doppler ultrasonography screening annually until age 10 with children at high risk receiving monthly transfusions until age 18. The optimal strategy would prevent 32% of strokes predicted to occur without intervention. The optimal strategy led to benefits similar to more intensive screening and transfusion strategies but resulted in fewer adverse events. All the intervention strategies resulted in net losses in life expectancy, because the projected mortality averted by stroke prevention was outweighed by the projected increase in mortality from transfusion. Results were sensitive to adherence rates to iron-chelation therapy.

CONCLUSIONS

The optimal stroke-prevention strategy was projected to be annual transcranial Doppler ultrasonography screening until age 10 with transfusion for children at high risk until age 18. Better adherence to chelation therapy would improve life expectancy in all intervention strategies.

Therapy Insight: stroke risk and its management in patients with sickle cell disease

Children with sickle cell disease, a chronic hemolytic anemia, present with a wide variety of neurological syndromes, including ischemic and hemorrhagic stroke, transient ischemic attacks, 'soft neurological signs', seizures, headache, coma, visual loss, altered mental status, cognitive difficulties, and covert or 'silent' infarction. Those with ischemic stroke usually have stenosis or occlusion of the distal internal carotid and proximal middle cerebral arteries. Indefinite transfusion prevents recurrence in most patients who have had a stroke, and can prevent first stroke in those with high transcranial Doppler velocities. High white cell count, low hemoglobin and oxyhemoglobin desaturation predict neurological complications. Other risk factors for overt ischemic stroke include hypertension, previous transient ischemic attack, covert infarction and chest crisis. For hemorrhagic stroke, aneurysms are common in adults but not children, who often present with hypertension after transfusion or corticosteroids. Seizures are particularly common in patients with cerebrovascular disease and covert infarction; the latter is also associated with hyposplenism and infrequent pain. Factors associated with cognitive difficulties include thrombocytosis, infarction, large-vessel disease, and perfusion abnormality on neuroimaging. As well as investigating the role of genes and the possibility that hydroxyurea or blood pressure control reduce neurological complications, we should explore the modifiable effects of poor nutrition, chronic infection, hemolysis and oxyhemoglobin desaturation on stroke risk.

Treatment and prevention of stroke in children with sickle cell disease

Stroke is one of the major complications in children with sickle cell disease (SCD). Ischemic stroke is associated with small asymptomatic subcortical infarcts to large territorial lesions causing major disability. Intracranial hemorrhages may be caused by aneurysm rupture or by leakage from moyamoya vessels or venous sources. There have been no acute stroke treatment studies in SCD, but hydration and exchange transfusion are often recommended. However, there is an evidence base for primary and to some extent secondary stroke prevention. Primary prevention of stroke was demonstrated in the Stroke Prevention Trial in Sickle Cell Anemia (STOP), in which children with transcranial Doppler (TCD) mean blood flow velocities of 200 cm/second (previously shown to indicate high stroke risk) or higher were randomized to either regular blood transfusions or no transfusion. The study showed a very significant 90% reduction in first stroke with transfusion. In STOP2, discontinuing transfusions after 30 months or more (even with normal TCD) resulted in a high rate of reversion to abnormal TCD values and stroke. TCD screening of all children with SCD, and initiation and maintenance of chronic transfusion to maintain hemoglobin S below 30% in the high-risk group, is the only proven prevention strategy for stroke in SCD. Hydroxyurea is being studied as secondary stroke prevention at this time. No recommendation specific to SCD regarding the use of antiplatelet agents or anticoagulants in ischemic stroke can be made. Bone marrow transplantation can be curative for SCD, and limited data support its use to prevent stroke in SCD.

The prevention and management of stroke in sickle cell anaemia

Perhaps the most important clinical complication of sickle cell anaemia is stroke, an event that occurs in approximately 5-10% of children who inherit this disorder. To prevent recurrent or progressive CNS damage, the institution of regular red blood cell (RBC) transfusions is the standard of care. In addition, children at high risk of developing stroke, as screened by transcranial Doppler, also benefit from regular RBC transfusions for stroke prevention. In this review, standard and novel techniques of RBC transfusion, and also alternative therapies to treat children with or at risk for stroke are considered. In addition, haematopoietic cell transplantation, the only curative option for sickle cell anaemia, is considered, and speculation about its present and future application in this clinical setting is discussed.

Hypoxic adaptation during development: relation to pattern of neurological presentation and cognitive disability

Children with acute hypoxic-ischaemic events (e.g. stroke) and chronic neurological conditions associated with hypoxia frequently present to paediatric neurologists. Failure to adapt to hypoxia may be a common pathophysiological pathway linking a number of other conditions of childhood with cognitive deficit. There is evidence that congenital cardiac disease, asthma and sleep disordered breathing, for example, are associated with cognitive deficit, but little is known about the mechanism and whether there is any structural change. This review describes what is known about how the brain reacts and adapts to hypoxia, focusing on epilepsy and sickle cell disease (SCD). We prospectively recorded overnight oxyhaemoglobin saturation (SpO2) in 18 children with intractable epilepsy, six of whom were currently or recently in minor status (MS). Children with MS were more likely to have an abnormal sleep study defined as either mean baseline SpO2 <94% or >4 dips of >4% in SpO2/hour (p = .04). In our series of prospectively followed patients with SCD who subsequently developed acute neurological symptoms and signs, mean overnight SpO2 was lower in those with cerebrovascular disease on magnetic resonance angiography (Mann-Whitney, p = .01). Acute, intermittent and chronic hypoxia may have detrimental effects on the brain, the clinical manifestations perhaps depending on rapidity of presentation and prior exposure.

Electroencephalography hyperventilation and stroke in children with sickle cell disease

A recent study and report in which hyperventilation was used during electroencephalography (EEG) in 6 children with sickle cell disease (SCD) and seizures, without serious complication, prompted a cautionary response regarding the potential risks attending the practice of EEG hyperventilation in SCD patients. Earlier reports of neurological impairment and stroke precipitated by the routine use of hyperventilation in children with SCD are reviewed, the mechanism and management of vascular infarction following hyperventilation are discussed, and readers are reminded of the AEEGS guidelines and contraindications to routine hyperventilation, which include SCD and trait and cerebrovascular disorders. The frequent nonobservance of these guideline recommendations among neurologists, and the need to more widely inform practitioners of the risks of hyperventilation in SCD are discussed.

Transfusion Management in Sickle Cell Disease

Sickle cell disease (SCD) is the most commonly inherited hemoglobinopathy in the United States. Blood transfusion is a critical part of the multidisciplinary approach necessary in the management of SCD; however, blood transfusions are not without complications. The successful use of transfusion as a treatment strategy in SCD requires the critical review and knowledge of transfusion methods, generally accepted indications, clinical situations in which transfusion generally is not considered, the selection of blood products, and strategies to prevent transfusion-related complications.

Moyamoya syndrome associated with hemolytic anemia due to Hb Alesha

Moyamoya angiopathy is a well-known complication of sickle cell disease but has rarely been observed in other hemoglobinopathies. The authors describe a previously unreported association of hemolytic anemia due to a rare unstable hemoglobinopathy with abnormal oxygen affinity (Hb Alesha) and moyamoya syndrome in a 10-year-old girl. At age 4 she had recurrent migraine-with-aura-like symptoms. Cranial MRI, Doppler, and EEG examinations were not conclusive. Deterioration of her neurologic symptoms prompted a renewed EEG examination at 10 years of age, which revealed a re-buildup phenomenon. MRI and MR angiography now showed moyamoya angiopathy with stenotic and occlusive lesions of both internal carotid and middle cerebral arteries. Conventional angiography confirmed these findings. Reperfusion with three extra-intracranial bypasses terminated the transient ischemic attacks. The authors suggest that chronic hypoxemia may be the cause of occlusive moyamoya angiopathy in Hb Alesha and possibly other unstable hemoglobinopathies with altered oxygen affinity.

Defining stroke risk in children with sickle cell anaemia

Sickle cell anaemia (SCA) is the most common cause of childhood stroke, occurring with the highest frequency before the age of 6 years. Despite the relative frequency of stroke in SCA, few predictors of risk exist. Anaemia, leucocytosis, hypertension, silent infarction, and history of acute chest syndrome are well-documented risk factors for ischaemic stroke in SCA. Recent data suggest that other environmental and genetic factors, many unrelated to SCA, influence the development of cerebrovascular disease. Non-invasive assessment of individual stroke risk using transcranial Doppler ultrasonography has provided a means of selecting and prophylactically treating SCA children at highest risk. With the ultimate goal of preventing stroke, the information gained from the studies reviewed here may lead to improved prediction of stroke so that clinical trials to assess risk-based therapy may be carried out on selected children with SCA.