Cerebrovascular complications and parvovirus infection in homozygous sickle cell disease

Viral Infection and Ischemic Stroke: Emerging Trends and Mechanistic Insights

Population studies have suggested that viral infections may be contributing to risk of ischemic stroke, although the mechanisms for this are unclear. In this review, we examine the epidemiological evidence supporting the involvement of viral diseases, including influenza, COVID-19, chronic herpesvirus infections, and hepatitis C in current trends of stroke incidence. To support these associations, we highlight the virus-host interactions that are critical in the context of stroke, including direct effects of acute and persistent viral infections on vascular function, inflammation, and thrombosis. Additionally, we evaluate the systemic changes that occur during viral infection that can predispose individuals to ischemic stroke, including alterations in blood pressure regulation, coagulation, and lipid metabolism. Our review emphasizes the need to further elucidate precise mechanisms involved in viral infections and stroke risk. Future research will inform the development of targeted interventions for stroke prevention in the context of viral diseases.

The Role of Infection and Inflammation in the Pathogenesis of Pediatric Arterial Ischemic Stroke

Infections play an important role in the pathogenesis of acute ischemic stroke (AIS) in neonates and children. In neonates, chorioamnionitis or intrauterine inflammation has been implicated as a common risk factor for AIS. In infants and children, recent investigations demonstrated that even minor childhood infections are associated with subsequent increased risk for AIS. Post-infectious inflammatory mechanisms following infections with herpesviruses may lead to focal cerebral arteriopathy (FCA), one of the most common causes of AIS in a previously healthy child. Other agents such as parvovirus B19, dengue virus, and SARS-CoV-2 have recently been implicated as other potential triggers. Infections are compelling treatable stroke risk factors, with available therapies for both pathogens and downstream inflammatory effects. However, infections are common in childhood, while stroke is uncommon. The ongoing VIPS II (Vascular effects of Infection in Pediatric Stroke) study aims to identify the array of pathogens that may lead to childhood AIS and whether either unusual strains or unusual combinations of pathogens explain this paradox. Immune modulation with corticosteroids for FCA is another active area of research, with European and U.S. trials launching soon. The results of these new pediatric stroke studies combined with findings emerging from the larger field of immune-mediated post-infectious diseases will likely lead to new approaches to the prevention and treatment of pediatric stroke. This review highlights recent developments from both clinical and animal model research enhancing our understanding of this relationship between infection, inflammation, and stroke in neonates and children.

Neurological Manifestations Associated with Parvovirus B19 Infection in Immunocompetent Children: Case Series and Systematic Review

An increasing number of reports have described human parvovirus B19 infection in association with a variety of neurological manifestations, especially in children. This study assessed the clinical and laboratory outcomes found in a case series of immunocompetent children who tested positive for parvovirus B19 by qualitative polymerase chain reaction assays of cerebrospinal fluid, in a tertiary referral center in the western Brazilian Amazon. We screened 178 children with clinically diagnosed central nervous system infections (meningoencephalitis). Of these, five (2.8%) were positive for parvovirus B19. A literature review also presented herein identified a further 50 cases of parvovirus B19 with neurological manifestations. Thus, even if the classic signs of parvovirus B19 infection are absent, such as the well-known rash, children with signs of neurological infection should also be evaluated for parvovirus B19 infection.

Hydroxycarbamide treatment reduces transcranial Doppler velocity in the absence of transfusion support in children with sickle cell anaemia, elevated transcranial Doppler velocity, and cerebral vasculopathy: the EXTEND trial

EXpanding Treatment for Existing Neurological Disease (EXTEND) investigated whether hydroxycarbamide lowers transcranial Doppler (TCD) velocities in Jamaican children with sickle cell anaemia (SCA) and elevated TCD velocity with or without previous stroke. Forty-three children (age 2-17 years) with baseline maximum time-averaged mean velocity (TAMV) ≥ 170 cm/s were stratified into three risk categories based on treatment status and stroke history: Group 1 (no history of stroke, on hydroxycarbamide, n = 12); and Groups 2 (no stroke, no hydroxycarbamide, n = 21) and 3 (previous stroke, no hydroxycarbamide, n = 10). Open-label hydroxycarbamide at 20 mg/kg/day was commenced, with escalation to maximum tolerated dose (MTD) based on mild marrow suppression (average dose 25·4 ± 4·5 mg/kg/day). TCD was performed every six months with brain magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) at baseline and after 18-months of hydroxycarbamide. The maximum TAMV decreased significantly compared to baseline (24 ± 30 cm/s, P < 0·0001), with similar declines in all groups. Clinical stroke occurred in five children, one in Group 1, none in Group 2, and four in Group 3, P = 0·0032, comparing group incidence rates. Brain MRI/MRA was stable in children without clinical stroke. EXTEND documents the feasibility and benefits of hydroxycarbamide at MTD to lower TCD velocities and reduce stroke risk in children with SCA and no history of primary stroke in low-resource settings without transfusion management.

Fat Embolism Syndrome in Sickle Cell Disease

Fat embolism syndrome is a devastating complication of sickle cell disease resulting from extensive bone marrow necrosis and associated with high mortality rates, while survivors often suffer severe neurological sequelae. Despite that, the syndrome remains under-recognised and under-diagnosed. Paradoxically, it affects exclusively patients with mild forms of sickle cell disease, predominantly HbSC and HbSβ⁺. A significant number of cases occur in the context of human parvovirus B19 infection. We provide here a brief summary of the existing literature and describe our experience treating 8 patients in our institution. One patient had HbSS, 6 HbSC and 1 HbSβ⁺. All patients developed type I respiratory failure and neurological involvement either at presentation or within the first 72 h. The most striking laboratory abnormality was a 100-fold increase of the serum ferritin from baseline. Seven patients received emergency red cell exchange and 1 simple transfusion. Two patients (25%) died, 2 patients (25%) suffered severe neurological impairment and 1 (12%) mild neurological impairment on discharge, while 3 (38%) patients made a complete recovery. With long-term follow-up, 1 patient with severe neurological impairment and one patient with mild neurological impairment made dramatic improvements, making the long-term complete recovery or near complete recovery rate 63%. Immediate red cell exchange transfusion can be lifesaving and should be instituted as soon as the syndrome is suspected. However, as the outcomes remain unsatisfactory despite the increasing use of red cell exchange, we suggest additional therapeutic measures such as therapeutic plasma exchange and pre-emptive transfusion for high risk patients.

American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support

BACKGROUND

Red cell transfusions remain a mainstay of therapy for patients with sickle cell disease (SCD), but pose significant clinical challenges. Guidance for specific indications and administration of transfusion, as well as screening, prevention, and management of alloimmunization, delayed hemolytic transfusion reactions (DHTRs), and iron overload may improve outcomes.

OBJECTIVE

Our objective was to develop evidence-based guidelines to support patients, clinicians, and other healthcare professionals in their decisions about transfusion support for SCD and the management of transfusion-related complications.

METHODS

The American Society of Hematology formed a multidisciplinary panel that was balanced to minimize bias from conflicts of interest and that included a patient representative. The panel prioritized clinical questions and outcomes. The Mayo Clinic Evidence-Based Practice Research Program supported the guideline development process. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to form recommendations, which were subject to public comment.

RESULTS

The panel developed 10 recommendations focused on red cell antigen typing and matching, indications, and mode of administration (simple vs red cell exchange), as well as screening, prevention, and management of alloimmunization, DHTRs, and iron overload.

CONCLUSIONS

The majority of panel recommendations were conditional due to the paucity of direct, high-certainty evidence for outcomes of interest. Research priorities were identified, including prospective studies to understand the role of serologic vs genotypic red cell matching, the mechanism of HTRs resulting from specific alloantigens to inform therapy, the role and timing of regular transfusions during pregnancy for women, and the optimal treatment of transfusional iron overload in SCD.

Sickle Cell Disease and Stroke

Cerebral infarction is a common complication of sickle cell disease and may manifest as overt stroke or cognitive impairment associated with "silent" cerebral infarction on magnetic resonance imaging. Vasculopathy may be diagnosed on transcranial Doppler or magnetic resonance angiography. The risk factors in sickle cell disease for cognitive impairment, overt ischemic stroke, silent cerebral infarction, overt hemorrhagic stroke, and vasculopathy defined by transcranial Doppler or magnetic resonance angiography overlap, with severe acute and chronic anemia, acute chest crisis, reticulocytosis, and low oxygen saturation reported with the majority. However, there are differences reported in different cohorts, which may reflect age, geographic location, or neuroimaging techniques, for example, magnetic resonance imaging field strength. Regular blood transfusion reduces, but does not abolish, the risk of neurological complications in children with sickle cell disease and either previous overt stroke or silent cerebral infarction or abnormal transcranial Doppler. There are relatively few data on the use of hydroxyurea or other management strategies. Early assessment of the risk of neurocognitive complications is likely to become increasingly important in the management of sickle cell disease.

Stroke Prevalence in Children With Sickle Cell Disease in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

Objectives. The prevalence of stroke among children with sickle cell disease (SCD) in sub-Saharan Africa was systematically reviewed. Methods. Comprehensive searches of PubMed, Embase, and Web of Science were performed for articles published between 1980 and 2016 (English or French) reporting stroke prevalence. Using preselected inclusion criteria, titles and abstracts were screened and full-text articles were reviewed. Results. Ten full-text articles met selection criteria. Cross-sectional clinic-based data reported 2.9% to 16.9% stroke prevalence among children with SCD. Using available sickle gene frequencies by country, estimated pediatric mortality, and fixed- and random-effects model, the number of affected individuals is projected as 29 800 (95% confidence interval = 25 571-34 027) and 59 732 (37 004-82 460), respectively. Conclusion. Systematic review enabled the estimation of the number of children with SCD stroke in sub-Saharan Africa. High disease mortality, inaccurate diagnosis, and regional variability of risk hamper more precise estimates. Adopting standardized stroke assessments may provide more accurate determination of numbers affected to inform preventive interventions.

Genetic, laboratory and clinical risk factors in the development of overt ischemic stroke in children with sickle cell disease

Cerebrovascular disease, particularly stroke, is one of the most severe clinical complications associated with sickle cell disease and is a significant cause of morbidity in both children and adults. Over the past two decades, considerable advances have been made in the understanding of its natural history and enabled early identification and treatment of children at the highest risk. Transcranial Doppler screening and regular blood transfusions have markedly reduced the risk of stroke in children. However, transcranial Doppler has a limited positive predictive value and the pathophysiology of cerebrovascular disease is not completely understood. In this review, we will focus on the current state of knowledge about risk factors associated with ischemic stroke in patients with sickle cell disease. A search of PubMed was performed to identify studies. Full texts of the included articles were reviewed and data were summarized in a table. The coinheritance of alpha-thalassemia plays a protective role against ischemic stroke. The influence of other genetic risk factors is controversial, still preliminary, and requires confirmatory studies. Recent advances have established the reticulocyte count as the most important laboratory risk factor. Clinical features associated with acute hypoxemia as well as silent infarcts seem to influence the development of strokes in children. However, transcranial Doppler remains the only available clinical prognostic tool to have been validated. If our understanding of the many risk factors associated with stroke advances further, it may be possible to develop useful tools to detect patients at the highest risk early, improving the selection of children requiring intensification therapy.

Parvovirus B19 Infection in Children With Arterial Ischemic Stroke

BACKGROUND AND PURPOSE

Case-control studies suggest that acute infection transiently increases the risk of childhood arterial ischemic stroke. We hypothesized that an unbiased pathogen discovery approach utilizing MassTag-polymerase chain reaction would identify pathogens in the blood of childhood arterial ischemic stroke cases.

METHODS

The multicenter international VIPS study (Vascular Effects of Infection in Pediatric Stroke) enrolled arterial ischemic stroke cases, and stroke-free controls, aged 29 days through 18 years. Parental interview included questions on recent infections. In this pilot study, we used MassTag-polymerase chain reaction to test the plasma of the first 161 cases and 34 controls enrolled for a panel of 28 common bacterial and viral pathogens.

RESULTS

Pathogen DNA was detected in no controls and 14 cases (8.7%): parvovirus B19 (n=10), herpesvirus 6 (n=2), adenovirus (n=1), and rhinovirus 6C (n=1). Parvovirus B19 infection was confirmed by serologies in all 10; infection was subclinical in 8. Four cases with parvovirus B19 had underlying congenital heart disease, whereas another 5 had a distinct arteriopathy involving a long-segment stenosis of the distal internal carotid and proximal middle cerebral arteries.

CONCLUSIONS

Using MassTag-polymerase chain reaction, we detected parvovirus B19-a virus known to infect erythrocytes and endothelial cells-in some cases of childhood arterial ischemic stroke. This approach can generate new, testable hypotheses about childhood stroke pathogenesis.

Reticulocyte count is the most important predictor of acute cerebral ischemia and high-risk transcranial Doppler in a newborn cohort of 395 children with sickle cell anemia

Stroke is a severe clinical manifestation of sickle cell anemia (SCA). Despite the prognostic relevance of transcranial Doppler (TCD), more accurate tools to assess stroke risk in children with SCA are required. Here, we describe the effect of clinical, laboratory, and molecular features on the risk of stroke and high-risk TCD in children from the newborn cohort of Minas Gerais, Brazil. Outcomes studied were acute cerebral ischemia and high-risk TCD. Clinical and hematological data were retrieved from children's records. Genetic markers, which were known for their association with stroke risk, were genotyped by polymerase chain reaction/restriction fragment length polymorphism and sequencing. The cumulative incidence of acute cerebral ischemia by the age of 8 years was 7.4 % and that of high-risk TCD by the age of 11.5 years was 14.2 %. The final multivariate model for acute cerebral ischemia risk included high white blood cell count and reticulocyte count, acute chest syndrome rate, and the single nucleotide polymorphisms (SNPs) TEK rs489347 and TNF-α rs1800629. The model for high-risk TCD included high reticulocyte count and the SNPs TEK rs489347 and TGFBR3 rs284875. Children with risk factors should be considered for intensive risk monitoring and for intervention therapy.

Prevalence of acute kidney injury during pediatric admissions for acute chest syndrome

BACKGROUND

Patients with sickle cell disease are at risk for developing chronic kidney disease (CKD). Acute kidney injury (AKI) has been linked to progression to CKD, but limited data exist to determine its role in acute complications of sickle cell disease. We hypothesized that AKI occurs in pediatric patients admitted for acute chest syndrome (ACS) and prolongs hospitalization.

METHODS

We conducted a 6-year retrospective review of pediatric patients with ACS admitted to a single medical institution.

RESULTS

Of the 149 pediatric patients admitted for ACS during the 6-year study period, 12 (8 %) developed AKI. Comparison of patients with and without AKI revealed a significant association between AKI and a larger drop in hemoglobin value from baseline (2.7 vs. 1.4 g/dL; p = 0.003), a lower hemoglobin value at admission (6.4 vs. 7.5 g/dL; p = 0.03), and an increased white blood cell count at admission (33.1 vs. 19.8 × 10(9)/L; p < 0.0001), respectively. AKI (p < 0.0001) together with need for advanced respiratory support (biphasic positive airway pressure or mechanical ventilation) (p < 0.0001) and need for exchange transfusion (p < 0.0001) were associated with prolonged hospitalization.

CONCLUSIONS

Clinicians should monitor pediatric patients hospitalized for ACS for the development of AKI as a potentially modifiable risk factor for prolonged hospitalization.

Acute encephalitis and encephalopathy associated with human parvovirus B19 infection in children

Reports of neurologic manifestations of human parvovirus B19 (B19) infection have been on the rise. Acute encephalitis and encephalopathy is the most common, accounting for 38.8% of total B19-associated neurological manifestations. To date, 34 children with B19 encephalitis and encephalopathy have been reported, which includes 21 encephalitis and 13 encephalopathy cases. Ten (29%) were immunocompromised and 17 (39%) had underlying diseases. Fever at the onset of disease and rash presented in 44.1% and 20.6% of patients, respectively. Neurological manifestations include alteration of consciousness occurred in all patients, seizures in 15 (44.1%) patients, and focal neurologic signs in 12 (35.3%) patients. Anemia and pleocytosis in cerebrospinal fluid (CSF) occurred in 56.3% and 48.1% of patients, respectively. Serum Anti-B19 IgM (82.6%) and CSF B19 DNA (90%) were positive in the majority of cases. Some patients were treated with intravenous immunoglobulins and/or steroids, although an accurate evaluation of the efficacy of these treatment modalities cannot be determined. Nineteen (57.6%) patients recovered completely, 11 (33.3%) patients had some neurological sequelae and 3 (8.8%) patients died. Although the precise pathogenesis underlying the development of B19 encephalitis and encephalopathy is unclear, direct B19 infection or NS1protein of B19 toxicity in the brain, and immune-mediated brain injuries have been proposed.

Unexpected Anemia and Reticulocytopenia in an Adolescent With Sickle Cell Anemia Receiving Chronic Transfusion Therapy

In a patient with sickle cell disease receiving chronic transfusion, exacerbation of anemia with reticulocytopenia must prompt consideration of a delayed hemolytic transfusion reaction with hyperhemolysis, as further transfusion may worsen this condition; definitive diagnosis is sometimes difficult. Anemia evolving during parvovirus B19-induced erythroid hypoplasia (transient aplastic crisis) should be attenuated in chronic transfusion patients due to superior survival of transfused over endogenous red blood cells. A 16-year-old with sickle cell disease receiving chronic transfusion of modified intensity (goal to maintain hemoglobin S<50%) who developed symptomatic anemia with reticulocytopenia was later shown to have had transient aplastic crisis.

How we prevent and manage infection in sickle cell disease

Sickle cell disease (SCD) affects approximately 100,000 people in the US, 12,500 in the UK, and millions worldwide. SCD is typified by painful vaso-occlusive episodes, haemolytic anaemia and organ damage. A secondary complication is infection, which can be bacterial, fungal or viral. Universal newborn screening, routine use of penicillin prophylaxis, availability of conjugated vaccines against S. pneumoniae and comprehensive care programmes instituted during the past few decades in industrialized countries have dramatically reduced childhood mortality and improved life expectancy. Yet patients with SCD remain at increased risk of infection. Unfortunately, the treatment of most bacterial infections that are common in SCD is not based on the results of randomized controlled clinical trials. In their absence, treatment decisions are based on consensus guidelines, clinical experience or adapting treatment applied in other diseases. This leads to wide variation in treatment among institutions and even between treating physicians in a single institution. Prevention of infection, when possible, is most important and we focus on prevention through targeted prophylaxis and vaccination. We will share our management strategies for managing the more common infections in SCD and provide the rationale for our recommendations.

Chronic and acute anemia and extracranial internal carotid stenosis are risk factors for silent cerebral infarcts in sickle cell anemia

Baseline hemoglobin levels lower than 7 g/dL, acute anemia, and extracranial internal carotid stenosis are significant and independent risk factors for SCI in SCA.

Neurological aspects of human parvovirus B19 infection: a systematic review

Parvovirus B19 has been linked with various clinical syndromes including neurological manifestations. However, its role in the latter remains not completely understood. Although the last 10 years witnessed a surge of case reports on B19-associated neurological aspects, the literature data remains scattered and heterogeneous, and epidemiological information on the incidence of B19-associated neurological aspects cannot be accurately extrapolated. The aim of this review is to identify the characteristics of cases of B19-associated neurological manifestations. A computerized systematic review of existing literature concerning cases of B19-related neurological aspects revealed 89 articles describing 129 patients; 79 (61.2%) were associated with CNS manifestations, 41 (31.8%) were associated with peripheral nervous system manifestations, and 9 (7.0%) were linked with myalgic encephalomyelitis. The majority of the cases (50/129) had encephalitis. Clinical characteristic features of these cases were analyzed, and possible pathological mechanisms were also described. In conclusion, B19 should be included in differential diagnosis of encephalitic syndromes of unknown etiology in all age groups. Diagnosis should rely on investigation of anti-B19 IgM antibodies and detection of B19 DNA in serum or CSF. Treatment of severe cases might benefit from a combined regime of intravenous immunoglobulins and steroids. To confirm these outcomes, goal-targeted studies are recommended to exactly identify epidemiological scenarios and explore potential pathogenic mechanisms of these complications. Performing retrospective and prospective and multicenter studies concerning B19 and neurological aspects in general, and B19 and encephalitic syndromes in particular, are required. © 2014 The Authors. Reviews in Medical Virology published by John Wiley & Sons, Ltd.

Measles, mumps, rubella, and human parvovirus B19 infections and neurologic disease

While the systemic disorders associated with measles, mumps, and rubella viruses and human parvovirus B19 tend to be mild, each virus can produce potentially life-threatening neurologic disease in human hosts, especially when these viruses infect young children. Two of the viruses, rubella and parvovirus B19, can be vertically transmitted to fetuses during maternal infection and cause congenital infection. Neurologic complications are common after intrauterine infection with the rubella virus, a condition known as the congenital rubella syndrome. Two, measles and rubella viruses, can induce "slow viral" infections, serious, disorders that can occur several years after the initial exposure to the virus and typically have fatal outcomes.

Stroke in sickle cell anemia patients: a need for multidisciplinary approaches

Sickle cell anemia (SCA) is an autosomal recessive disorder, with Mendelian inheritance pattern, caused by a missense mutation in the β-polypeptide chain of the hemoglobin B. SCA preferentially affects populations in countries where malaria was/is present (e.g. Africa, USA, Brazil). Thereby, in USA, the incidence of SCA is relatively high, around 1/500, and the prevalence is about 1/1000. In Brazil, SCA represents a major public health problem with an incidence ranging from 1/2000 to 1/600 depending on the regions. Homozygotic patients present more severe medical conditions and reduced life expectancy than heterozygous individuals who generally are asymptomatic. Eventually, this life-threatening disease displays a complex etiology owing to heterogeneous phenotypes and clinical outcomes, subsequently affecting the management of the patients. One of the most critical complications associated with SCA is stroke, a leading neurologic cause of death and disability. About 24% of SCA patients have a stroke by the age of 45 and 11% by the age of 20. From the general population, twin and familial aggregation studies as well as genome-wide association studies (GWAS), mostly in pediatric populations with ischemic stroke, showed that the risk of stroke has a substantial genetic component. Nevertheless, to fully characterize genomic contributors of stroke and permit reliable personalized medicine, multidisciplinary studies incorporating knowledge from clinical medicine, epidemiology, genetics, and molecular biology, are required. In this manuscript, stroke in SCA patients is extensively reviewed with emphasis to the US and Brazilian populations. Recent advances in genomics analysis of stroke in SCA patients are highlighted.

Molecular and phylogenetic analyses of human Parvovirus B19 isolated from Brazilian patients with sickle cell disease and β-thalassemia major and healthy blood donors

Human Parvovirus B19 (B19V) is a recognized cause of life-threatening conditions among patients with hemoglobinopathies. This study investigates B19V infection in patients with sickle cell disease and β-thalassemia using different experimental approaches. A total of 183 individuals (144 with sickle cell disease and 39 with β-thalassemia major) and 100 healthy blood donors were examined for B19V using anti-B19V IgG enzyme immunoassay, quantitative PCR, DNA sequencing, and phylogenetic analysis. Viremia was documented in 18.6% of patients and 1% of donors, and was generally characterized by low viral load (VL); however, acute infections were also observed. Anti-B19V IgG was detected in 65.9% of patients with sickle cell disease and in 60% of donors, whereas the patients with thalassemia exhibited relatively low seroreactivity. The seroprevalence varied among the different age groups. In patients, it progressively increased with age, whereas in donors it reached a plateau. Based on partial NS1 fragments, all isolates detected were classified as subgenotype 1A with a tendency to elicit genetically complex infections. Interestingly, quasispecies occurred in the plasma of not only patients but also donors with even higher heterogeneity. The partial NS1 sequence examined did not exhibit positive selection. Quantitation of B19V with a conservative probe is a technically and practically useful approach. The extensive spread of B19V subgenotype 1A in patients and donors and its recent introduction into the countryside of the São Paulo State, Brazil were demonstrated; however, it is difficult to establish a relationship between viral sequences and the clinical outcomes of the infection.

Acute silent cerebral ischemia and infarction during acute anemia in children with and without sickle cell disease

We hypothesized that the silent cerebral infarcts (SCI), which affect up to 40% of children with sickle cell disease (SCD), could occur in the setting of acute anemic events. In a prospective observational study of children with and without SCD hospitalized for an illness associated with acute anemia, we identified acute silent cerebral ischemic events (ASCIE) in 4 (18.2%) of 22 with SCD and in 2 (6.7%) of 30 without SCD, using diffusion-weighted magnetic resonance imaging. Children with ASCIE had lower hemoglobin concentration than those without (median 3.1 vs 4.4 g/dL, P = .003). The unique temporal features of stroke on diffusion-weighted magnetic resonance imaging permit estimation of incidence rates for ASCIE of 421 (95% confidence interval, 155-920) per 100 patient-years during acute anemic events for all patients. For children with SCD, the estimated incidence was 663 (95% confidence interval, 182-1707) which is much higher than previously reported. Acute anemic events are common in children with SCD and prevalence could partially account for the high SCI. Some ASCIE (1 of 4 in our study) may be reversible. Alterations in management may be warranted for children with severe anemia to identify unrecognized ischemic brain injury that may have permanent neurocognitive sequelae.

Prospects for primary stroke prevention in children with sickle cell anaemia

This review will focus on the strengths and limitations associated with the current standard of care for primary prevention of ischaemic strokes in children with sickle cell anaemia (SCA) - transcranial Doppler ultrasound (TCD) screening followed by regular blood transfusion therapy when TCD measurement is above a threshold defined by a randomized clinical trial (RCT). The theoretical basis for potential alternative strategies for primary prevention of neurological injury in SCA is also discussed. These strategies will include, but will not be limited to: immunizations to prevent bacterial infections, particularly in low income countries; management of elevated blood pressure; and targeted strategies to increase baseline haemoglobin levels with therapies such as hyroxycarbamide or potentially definitive haematopoietic stem cell transplant.

The epidemiology, evaluation and treatment of stroke in adults with sickle cell disease

Stroke is a frequent and severe complication in adults with sickle cell disease. Ischemic stroke often causes physical and cognitive disability, while hemorrhagic stroke has a high mortality rate. As more children survive, the number of strokes in adults is increasing, yet stroke remains poorly understood. We review the epidemiology of ischemic and hemorrhagic stroke in adults with sickle cell disease and outline a practical approach to the evaluation of stroke including both sickle cell disease specific and general risk factors. We discuss the acute treatment and secondary prevention of stroke in this population based on the evidence in children with sickle cell disease and the general population, in addition to the limited studies in adults with sickle cell disease.

Associated risk factors for silent cerebral infarcts in sickle cell anemia: low baseline hemoglobin, sex, and relative high systolic blood pressure

The most common form of neurologic injury in sickle cell anemia (SCA) is silent cerebral infarction (SCI). In the Silent Cerebral Infarct Multi-Center Clinical Trial, we sought to identify risk factors associated with SCI. In this cross-sectional study, we evaluated the clinical history and baseline laboratory values and performed magnetic resonance imaging of the brain in participants with SCA (HbSS or HbSβ° thalassemia) between the ages of 5 and 15 years with no history of overt stroke or seizures. Neuroradiology and neurology committees adjudicated the presence of SCI. SCIs were diagnosed in 30.8% (251 of 814) participants who completed all evaluations and had valid data on all prespecified demographic and clinical covariates. The mean age of the participants was 9.1 years, with 413 males (50.7%). In a multivariable logistic regression analysis, lower baseline hemoglobin concentration (P < .001), higher baseline systolic blood pressure (P = .018), and male sex (P = .030) were statistically significantly associated with an increased risk of an SCI. Hemoglobin concentration and systolic blood pressure are risk factors for SCI in children with SCA and may be therapeutic targets for decreasing the risk of SCI. This study is registered at www.clinicaltrials.gov as #NCT00072761.

Childhood chorea-encephalopathy associated with recent parvovirus B19 infection in two Jamaican children

This case report highlights the course of two healthy unrelated children with an encephalopathy characterised by dyskinesia, seizures, hemiparesis and behavioural change associated with recent human parvovirus B19 infection. The cases are compared with a previously described case of childhood chorea encephalopathy associated with human parvovirus B19 infection.

The expanding range of parvoviruses which infect humans

The first human parvoviruses to be described (1960s) were the adeno-associated viruses (AAVs, now classed as dependoviruses), originally identified as contaminants of cell cultures, followed by parvovirus B19 (B19V) in 1974, the first parvovirus to be definitively shown to be pathogenic. More recently two new groups of parvoviruses, the human bocaviruses (HuBoV) and the Parv4 viruses have been identified. These four groups of human viruses are all members of different genera within the Parvovirus family, and have very different biology, epidemiology and disease associations from each other. This review will provide an overview of the virological, pathogenic and clinical features of the different human paroviruses, and how these new viruses and their variants fit into the current understanding of parvovirus infection.

Acute silent cerebral infarction in children with sickle cell anemia

Silent cerebral infarctions (SCI) occur in up to 35% of children with sickle cell anemia (HbSS) but are rarely recognized during the initial 10-14 days when diffusion weighted magnetic resonance imaging (MRI) can differentiate acute infarctions from remote events. We report acute SCI in seven children with HbSS who had areas of restricted diffusion on MRI without persistent focal neurologic deficits. Four had acute SCI identified following acute anemic events. Our observations suggest that SCI are detectible in the acute phase, present with subtle neurologic symptoms, result in permanent neurologic injury, and may be caused by acute anemic events.

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.

The excess burden of stroke in hospitalized adults with sickle cell disease

This report compares the relative rates and risk factors associated with stroke in adults versus children with sickle cell disease (SCD) in the United States over the last decade. We identified incident strokes in patients with SCD using ICD-9 codes for acute stroke and SCD and the California Patient Discharge Databases. We estimated SCD prevalence by using the incidence of SCD at birth with adjustment for early mortality from SCD. We identified 255 acute strokes (70 primary hemorrhagic and 185 ischemic) among 69,586 hospitalizations for SCD-related complications from 1998 to 2007. The rate of stroke in children [<18 years old (310/100,000 person-years)] was similar to young adults [18-34 years old (360/100,000 person-years)], but much higher in middle-aged [35-64 years old (1,160/100,000 person-years)] and elderly adults [> or =65 years old (4,700/100,000 person-years)]. Stroke was associated with hypertension in children and hypertension, diabetes mellitus, hyperlipidemia, atrial fibrillation, and renal disease in adults. Most acute strokes (75%) and in-hospital deaths from stroke (91%) occurred in adults. Our results suggest that the rate of stroke in SCD peaks in older adults and is three-fold higher than rates previously reported in African-Americans of similar age (35-64 years) without SCD. Stroke in SCD is associated with several known adult risk factors for ischemic and hemorrhagic stroke. Studies for the primary and secondary prevention of stroke in adults with SCD are urgently needed.

Simultaneous acute splenic sequestration and transient aplastic crisis in children with sickle cell disease

Acute splenic sequestration crisis (ASSC) is a hematological emergency in young children with sickle cell disease (SCD), characterized by worsening anemia and splenomegaly, usually with reticulocytosis and thrombocytopenia. Transient aplastic crisis (TAC) due to parvovirus B19 infection occurs in older children with SCD, and typically manifests as worsening anemia with reticulocytopenia and no splenomegaly. Five older children with SCD (4 HbSC, 1 HbSS on hydroxyurea) developed ASSC concurrent with TAC and had a severe clinical course. Our cases suggest that older children with SCD and acute parvovirus infection should be monitored closely for splenomegaly and multi-system dysfunction.

Persistent adeno-associated virus 2 and parvovirus B19 sequences in post-mortem human cerebellum

We previously reported in a large cohort (N = 104) of post-mortem tissues the detection of both the non-pathogenic adeno-associated virus (AAV2) in approximately 13% and the pathogenic human parvovirus B19 (B19) in approximately 42% of human brains, particularly the dorsolateral prefrontal cortex. Multiple animal parvoviruses target the developing cerebellum (CBLM) resulting in hypoplasia and ataxia, but very little is known about the human parvoviruses and their ability to infect or cause disease in the CBLM. We have now confirmed in the above cohort the presence of AAV2 and B19 sequences in the CBLM. Our results show that approximately 27% and approximately 70% of human CBLM are positive by nested polymerase chain reaction for AAV2 and B19 sequences, respectively. We also document in a second cohort (N = 10) the presence of AAV2 (50%) and B19 (100%) sequences in the CBLM and correlate our results for B19 with studies from matched sera. Eighty percent (80%) of this cohort was positive for anti-B19 IgG, while none were IgM+, suggesting that most individuals had been previously infected with B19 but none acutely. To our knowledge, this study is the first to demonstrate that both AAV2 and B19 sequences are present at relatively high frequencies in the CBLM and are likely due to persistent rather than acute infection. Further studies will lead to insights into AAV2- and/or B19-CBLM interactions including mechanisms of infection, persistence, and possibly neuropathology, including cerebellar hypoplasia and ataxia.

Acute encephalopathy with human parvovirus B19 infection in hereditary spherocytosis

A 9-year-old girl with hereditary spherocytosis developed aplastic crisis and encephalopathy associated with human parvovirus B19 (PVB19) infection. During the clinical course, we followed PVB19 DNA in her plasma and cerebrospinal fluid by real-time polymerase chain reaction and found that her symptoms of encephalopathy had occurred at the peak viral load. PVB19-associated encephalopathy might occur as a result of direct invasion by PVB19.

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.

Severe parvovirus B19 encephalitis after renal transplantation

Human parvovirus B19 is a common cause of benign erythema infectiosum (fifth disease) in otherwise healthy children. Immunocompromized patients are at risk of developing chronic infections leading to chronic hyporegenerative anemia. We report the case of a nine-year-old boy who presented five days after renal transplantation with seizures and signs of encephalitis on MRI. The clinical course was characterized by anemia and seroconversion for parvovirus B19 accompanied by a high viral load (>10(9) copies per milliliter). A transfusion of red blood cells that the patient required after transplantation was found to be negative for parvovirus B19, leaving the donated organ as the most likely source of infection. Reduction of the immunosuppressive regimen led to complete recovery of the patient with a stable RBC count upon discharge. Parvovirus B19 infections should be considered in the differential diagnosis of seizures after solid organ transplantation.

Detection of adeno-associated virus 2 and parvovirus B19 in the human dorsolateral prefrontal cortex

Although animal parvoviruses have long been recognized as causes of brain pathology in multiple animal models, especially during early development, human parvoviruses are rarely thought of as neurotropic or causes of neuropathology in humans. However, several recent case reports have suggested possible associations of parvovirus B19 (B19) infection with various neurological and neuropsychiatric symptoms. Adeno-associated virus 2 (AAV2) is related to B19 but has thus far not been shown to be associated with any human disease but is of clinical interest because of the recent use of recombinant AAV vectors in human gene therapy, including gene delivery to the brain. To date, there have been no large-scale studies of the propensity of wild-type human parvoviruses to infect the brain. The Stanley Medical Research Institute Brain Collection offered a unique opportunity to study a large sample (n = 104) of dorsolateral prefrontal cortex (DLPC) DNAs isolated from unaffected control, schizophrenic, and bipolar disorder brains for the presence of parvoviral sequences. This is the first investigator-blinded study to document the presence of parvoviral sequences in the DLPC by utilizing highly sensitive nested polymerase chain reaction (nPCR) and DNA sequencing. Of the overall sample, 6.7% to 12.5% were positive for AAV2, and 14.4% to 42.3% were positive for B19 sequences, with no statistical differences among subgroups. This is the first report to demonstrate the presence of human parvoviruses in a large cohort of adult DLPC, which underscores the need to gain a better insight into the basic biology of parvovirus-brain interactions, including mechanisms of infection and persistence.

Sickle cell disease: ischemia and seizures

Although the prevalence of seizures in children with sickle cell disease (SCD) is 10 times that of the general population, there are few prospectively collected data on mechanism. With transcranial Doppler and magnetic resonance imaging (MRI) and angiography, we evaluated 76 patients with sickle cell disease, 29 asymptomatic and 47 with neurological complications (seizures, stroke, transient ischemic attack, learning difficulty, headaches, or abnormal transcranial Doppler), who also underwent bolus-tracking perfusion MRI. The six patients with recent seizures also had electroencephalography. Group comparisons (seizure, nonseizure, and asymptomatic) indicated that abnormal transcranial Doppler was more common in the seizure (4/6; 67%) and nonseizure (26/41; 63%) groups than in the asymptomatic (10/29; 34%) group (chi2; p = 0.045), but abnormal structural MRI (chi2; p = 0.7) or magnetic resonance angiography (chi2; p = 0.2) were not. Relative decreased cerebral perfusion was found in all seizure patients and in 16 of 32 of the remaining patients with successful perfusion MRI (p = 0.03). In the seizure patients, the perfusion abnormalities in five were ipsilateral to electroencephalographic abnormalities; one had normal electroencephalogram results. These findings suggest that vasculopathy and focal hypoperfusion may be factors in the development of sickle cell disease-associated seizures.

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.

Stroke in sickle cell disease in Africa: case report

Stroke, including asymptomatic cerebrovascular events, is a significant cause of morbidity and mortality in sickle cell disease, occurring with an incidence of 10 to 25%. Extensive research has established that cerebral stenosis, involving the circle of Willis, is the most common mechanism in children. We report a child with sickle cell disease who presented with cortical blindness and right-sided hemiplegia. Computerised tomography of the brain revealed an infarct involving the left parietal region and extending to the occipital region. Stroke in SCD is multifactorial, but high-risk individuals can be identified by simple well-established strategies such as transcranial doppler ultrasonography. There are approaches for both primary and secondary interventions, which have been shown to be effective and need to be incorporated into management guidelines for SCD patients. Before schemes are recommended into health care policies, research in the appropriate setting is required.

Risk factors and prediction of outcomes in children and adolescents who have sickle cell anemia

This article discusses risk factors and prediction in children and adolescents who have sickle cell anemia.