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

Effect of voxelotor on cerebral perfusion and cerebral oxygen metabolism and cardiac stress in adult patients with sickle cell disease

Sickle cell disease (SCD) is complicated by silent cerebral infarcts (SCIs), for which anemia is an important risk factor. Despite normal oxygen delivery (OD), cerebral vascular reserve (CVR), and cerebral metabolic rate of oxygen (CMRO2) are diminished in SCD, possibly causing the formation of SCIs. Voxelotor inhibits polymerization by increasing the hemoglobin oxygen binding, ameliorating hemolytic anemia. Furthermore, anemia is related to cardiac complications. Our aims were to assess the effect of voxelotor on markers of cerebral perfusion, cerebral oxygen metabolism, and markers of cardiac stress in SCD patients. Cerebral hemodynamics and oxygen metabolism were measured with MRI before and after 3 months of voxelotor treatment (1500 mg/day) in 18 adults with SCD (HbSS/HbSβ0-thalassemia). Hemoglobin levels significantly increased (p = .001) and markers of hemolysis decreased (p < .05). OD increased from 6.5 (IQR, 6.0-7.1) mL O2/100 g/min to 8.1 (IQR, 7.2-8.7) mL O2/100 g/min (p = .001). CBF and CVR did not change. CMRO2 decreased from 2.0 (IQR, 1.9-2.1) mL O2/100 g/min to 1.9 (IQR, 1.6-2.1) mL O2/100 g/min (p = .03). N-terminal pro-B type natriuretic peptide (NT-proBNP) levels decreased (p = .048) and maximum tricuspid regurgitation flow velocity (TRVmax) normalized in all but one patient with increased TRVmax. Voxelotor treatment in patients with severe SCD did not decrease CBF despite increased Hb levels. Cerebral oxygen metabolism slightly decreased, despite raised OD, most likely due to drug-induced increase in oxygen binding. Nonetheless, voxelotor improved clinically validated markers of cardiac stress.

Cerebral Oxygen Metabolic Stress in Children and Adults With Large Vessel Vasculopathy Due to Sickle Cell Disease

BACKGROUND AND OBJECTIVES

Large vessel vasculopathy (LVV), or moyamoya syndrome, increases the risk of stroke in patients with sickle cell disease (SCD), yet effective treatments are lacking. In atherosclerotic carotid disease, previous studies demonstrated elevated oxygen extraction fraction (OEF) as a predictor of ipsilateral stroke. In a SCD cohort, we examined hemispheric hemodynamic and oxygen metabolic dysfunction as tissue-based biomarkers of cerebral ischemic risk in patients with LVV.

METHODS

Children and adults with SCD were recruited from a SCD clinic associated with a tertiary medical center and underwent prospective brain MRI and MR angiography. LVV was defined as ≥75% stenosis in a major anterior circulation artery, excluding occlusion or previous revascularization surgery. Baseline characteristics, cerebral blood flow (CBF), normalized OEF (nOEF), infarct volume, white matter microstructure, and brain volume were compared in hemispheres with vs without LVV. In a cross-sectional analysis, mixed-effects linear multivariable models examined the effect of LVV on: (1) CBF and nOEF, as tissue markers of hemodynamic and oxygen metabolic stress, respectively, and (2) endpoints of cerebral ischemic injury including infarct volume, white matter microstructure, and brain volume.

RESULTS

Of 155 patients (22 [12-31] years, 57% female), 33 (21%) had ≥25% stenosis, 22 (14%) had ≥50% stenosis, 14 (9%) had 75%-99% stenosis, and 5 (3%) had 100% occlusion. After excluding hemispheres with previous revascularization surgery, LVV was present in 16 hemispheres from 11 patients. Hemispheres with (N = 16) vs without (N = 283) LVV had lower CBF (25.2 vs 32.1 mL/100 g/min, p = 0.01) and higher nOEF (0.99 vs 0.95, p = 0.02). On multivariable analysis, CBF was nonsignificantly lower (β = -0.16, p = 0.07) while nOEF remained higher in hemispheres with LVV (β = 0.04, p = 0.03). Moreover, LVV was associated with greater hemispheric infarct volume, microstructural disruption, and atrophy.

DISCUSSION

Beyond greater infarct burden, LVV was associated with hemispheric atrophy and white matter microstructural injury. As an indicator of active hypoxia, elevated nOEF likely represents a compensatory response to flow-limiting stenosis in hemispheres with LVV. The study is limited by a small number of patients with severe stenosis. Future studies are needed to evaluate the potential of tissue-based CBF and nOEF in assessing stroke risk and guide timely treatment of vasculopathy in SCD.

2024 Guideline for the Primary Prevention of Stroke: A Guideline From the American Heart Association/American Stroke Association

AIM

The "2024 Guideline for the Primary Prevention of Stroke" replaces the 2014 "Guidelines for the Primary Prevention of Stroke." This updated guideline is intended to be a resource for clinicians to use to guide various prevention strategies for individuals with no history of stroke.

METHODS

A comprehensive search for literature published since the 2014 guideline; derived from research involving human participants published in English; and indexed in MEDLINE, PubMed, Cochrane Library, and other selected and relevant databases was conducted between May and November 2023. Other documents on related subject matter previously published by the American Heart Association were also reviewed.

STRUCTURE

Ischemic and hemorrhagic strokes lead to significant disability but, most important, are preventable. The 2024 primary prevention of stroke guideline provides recommendations based on current evidence for strategies to prevent stroke throughout the life span. These recommendations align with the American Heart Association's Life's Essential 8 for optimizing cardiovascular and brain health, in addition to preventing incident stroke. We also have added sex-specific recommendations for screening and prevention of stroke, which are new compared with the 2014 guideline. Many recommendations for similar risk factor prevention were updated, new topics were reviewed, and recommendations were created when supported by sufficient-quality published data.

The Association Between Sickle Cell Anemia and Cognitive Dysfunction: A Systematic Review

A kind of hemoglobinopathy known as sickle cell anemia (SCA) is characterized by aberrant hemoglobin molecules. The most frequent neurological side effects linked to SCA include neurocognitive dysfunction, asymptomatic cerebral infarction, and ischemic stroke. This study aims to investigate the relationship between SCA and cognitive dysfunction. We systematically searched electronic databases like PubMed, MEDLINE, Science Direct, and Scopus. Two independent reviewers screened and extracted data from eligible studies. Eighteen studies, including 2,457 participants in total and nearly half of them 1,151 (46.8%) were males, were included in our data. The prevalence of cognitive dysfunction in the adult population ranged from 11.5% to 70%. Cognitive dysfunction among adults was significantly associated with poorer educational status, reduced family income, decreased kidney function, older age, stroke history, and vasculopathy. The prevalence of cognitive dysfunction in children ranged from 10.2% to 68.2%. The decline in cognitive function among adults was significantly associated with children over the age of four, abnormal transcranial Doppler and previous stroke, school absence, age beyond 13, and increased BMI. Cognitive function deficiencies are a defining feature of SCA that affects people of all ages. These findings suggest that if cognitive decline is not slowed down, or better still, stopped, medical interventions targeting a variety of sequelae in this population will be ineffective. Future analyses of this population's cognition should evaluate the environmental and other biological variables.

DISPLACE study shows poor quality of transcranial doppler ultrasound for stroke risk screening in sickle cell anemia

ABSTRACT

Children with sickle cell anemia (SCA) are at increased risk of stroke when compared with their age-based counterparts. The Stroke Prevention Trial in Sickle Cell Anemia (STOP) previously demonstrated that with the use of transcranial Doppler ultrasound (TCD; Sickle Stroke Screen) and chronic red cell transfusion, the risk of stroke is reduced by over 90%. The STOP criteria detailed the type and method of measurement required; the time-averaged mean maximum velocity (TAMMV). Unfortunately, it has been difficult to adhere to the appropriate TAMMV measurements. The objectives of this study were to assess the quality of TCD and transcranial Doppler imaging (TCDi) reports to determine the report quality and accuracy. This is a subanalysis of the DISPLACE (Dissemination and Implementation of Stroke Prevention Looking at the Care Environment) study. Over 12 000 TCD/TCDi reports were collected during this study from 28 institutions; 391 TCDs were reviewed for this subanalysis. There were significant variations in the vessels being assessed, the velocities used to define abnormal results, and who was interpreting the scans. In 52% of reports, it was impossible to identify whether the TAMMV was what was measured. Similarly, it was only clear in 42% of reports that the TAMMV was used to interpret the examination as normal/abnormal. Given this inconsistency, we strongly recommend standardization of TCD/TCDi reporting, specialized training for those performing and interpreting the scans in the use of TCD/TCDi in patients with SCA, internal quality assurance, and institutional quality improvement work to ensure appropriate use of this potentially lifesaving technology.

Genetic Variants Associated with the Risk of Stroke in Sickle Cell Anemia: Systematic Review and Meta-Analysis

Sickle cell anemia (SCA) is the most common cause of stroke in children. As it is a rare disease, studies investigating the association with complications like stroke in SCD have small sample sizes. Here, we performed a systematic review and meta-analysis of the studies exploring an association of genetic variants with stroke to get a better indication of their association with stroke. PubMed and Google Scholar were searched to identify studies that had performed an association analysis of genetic variants for the risk of stroke in SCA patients. After screening of eligible studies, summary statistics of association analysis with stroke and other general information were extracted. Meta-analysis was performed using the fixed effect method on the tool METAL and forest plots were plotted using the R program. The random effect model was performed as a sensitivity analysis for loci where significant heterogeneity was observed. 407 studies were identified using the search term and after screening 37 studies that cumulatively analyzed 11,373 SCA patients were included. These 37 studies included a total of 2,222 SCA patients with stroke, predominantly included individuals of African ancestry (N = 16). Three of these studies performed whole exome sequencing while 35 performed single nucleotide-based genotyping. Though the studies reported association with 132 loci, meta-analyses could be performed only for 12 loci that had data from two or more studies. After meta-analysis we observed that four loci were significantly associated with risk for stroke: -α3.7 kb Alpha-thalassemia deletion (P = 0.00000027), rs489347-TEK (P = 0.00081), rs2238432-ADCY9 (P = 0.00085), rs11853426-ANXA2 (P = 0.0034), and rs1800629-TNF (P = 0.0003396). Ethnic representation of regions with a high prevalence of SCD like the Mediterranean basin and India needs to be improved for genetic studies on associated complications like stroke. Larger genome-wide collaborative studies on SCD and associated complications including stroke need to be performed.

Neurological abnormalities among pediatric patients with sickle cell disease in Saudi Arabia: a single-center retrospective study

Introduction

Sickle cell disease (SCD) is a common inherited blood disorder characterized by the production of abnormal sickle-shaped red blood cells. SCD can lead to various complications including neurological issues. Early detection and treatment are crucial for preventing these complications. This study aimed to describe the neurological manifestations, radiological findings, and neurological diagnosis related to SCD in Saudi children with the aim of contributing to the formulation of population-based guidelines for screening and treating SCD-related neurological complications.

Methods

This descriptive retrospective study included pediatric patients aged < 14 years diagnosed with SCD who were regularly followed up at the hematology clinic in KAMC, Jeddah, Saudi Arabia, from January 2008 to January 2022. Demographic and clinical data were collected from the clinical charts of 101 participants.

Results

This study included 101 patients with SCD with a mean age of 23 months at diagnosis. Among these, 59% had SCD and high fetal hemoglobin (HbF) levels. Neurological sequelae, including seizures, stroke, and other abnormalities, were observed in 26.7% of patients. There were no significant differences in the onset of neurological issues between the patients with SCD-high HbF and those with other SCD phenotypes.

Discussion

This study highlights the increased risk of brain injury and neurocognitive deficits in children with SCD. The occurrence of neurological sequelae in many patients emphasizes the need for early detection and intervention. Some patients experience neurological complications despite having high HbF levels, suggesting that further interventions are needed. This study has some limitations, including its small sample size and retrospective nature.

Conclusion

Early detection and intervention are crucial for neurological complications in patients with SCD. This study emphasizes the need for further research and effective treatment strategies considering the presence of neurological complications despite the presence of high HbF levels. Large-scale studies and population-specific guidelines are warranted for better understanding and management of SCD-related neurological complications in the Saudi population.

Screening for cognitive impairment in adults with sickle cell disease: A systematic review and meta-analysis

Neurovascular disease such as symptomatic stroke, silent brain infarcts and vascular cognitive impairment are common complications of sickle cell disease (SCD) that can have devastating consequences on quality of life, employment, and social functioning.  Early recognition of neurovascular disease is a prerequisite for the timely optimization of medical care and to connect patients to adaptive resources. While cognitive impairment has been well described in children, currently available data are limited in adults. As a result, guidance on the optimal cognitive screening strategies in adults is scarce. We conducted a systematic review to identify the different screening tools that have been evaluated in SCD. A meta-analysis was performed to estimate the prevalence of suspected cognitive impairment in this population. In this qualitative synthesis, we present 8 studies that evaluated 6 different screening tools. Patient characteristics that impacted on cognitive screening performance included age, education level, and a prior history of stroke. We report a pooled prevalence of 38% [14-62%] of suspected cognitive impairment. We discuss the relative benefits and limitations of the different screening tools to help clinicians select an adapted approach tailored to their specific patients' needs. Further studies are needed to establish and validate cognitive screening strategies in patients with diverse cultural and educational backgrounds.

Prevention of neurovascular complications in children with Sickle Cell Disease in the real-world setting: What adult medicine physicians should know

Neurovascular complications represent one of the most detrimental manifestations of Sickle Cell Disease (SCD), affecting many patients since infancy. They include overt stroke, silent cerebral infarcts and neurocognitive disorders. In fact, neurodevelopment can be impaired in children resulting in cognitive dysfunction in adults with SCD. This review is meant to resume the most recent guidelines about the prevention of SCD neurovascular complications and to highlight the open challenges in their implementation. Transcranial Doppler, Magnetic Resonance Imaging/Angiography and neurocognitive test are useful screening tools. Chronic transfusion regimen, hematopoietic stem cell transplantation and neurocognitive rehabilitation find indications in the context of primary and secondary prevention of neurovascular complications of SCD. However, international guidelines are often difficult to bring into the real world due to the lack of appropriate instruments and trained personnel. Many challenges have still to be faced to guarantee the best possible neurocognitive function to each child affected by SCD.

Molecular and environmental contributors to neurological complications in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobinopathy in which affected hemoglobin polymerizes under hypoxic conditions resulting in red cell distortion and chronic hemolytic anemia. SCD affects millions of people worldwide, primarily in Sub-Saharan Africa and the Indian subcontinent. Due to vaso-occlusion of sickled red cells within the microvasculature, SCD affects virtually every organ system and causes significant morbidity and early mortality. The neurological complications of SCD are particularly devastating and diverse, ranging from overt stroke to covert cerebral injury, including silent cerebral infarctions and blood vessel tortuosity. However, even individuals without evidence of neuroanatomical changes in brain imaging have evidence of cognitive deficits compared to matched healthy controls likely due to chronic cerebral hypoxemia and neuroinflammation. In this review, we first examined the biological contributors to SCD-related neurological complications and then discussed the equally important socioenvironmental contributors. We then discuss the evidence for neuroprotection from the two primary disease-modifying therapies, chronic monthly blood transfusions and hydroxyurea, and end with several experimental therapies designed to specifically target these complications.

White-matter abnormalities and cognitive dysfunction are linked to astrocyte activation in sickle mice

White-matter injury in sickle-cell disease (SCD) includes silent cerebral infarction diagnosed by diffusion tensor imaging (DTI), a complication associated with cognitive dysfunction in children with SCD. The link between white-matter injury and cognitive dysfunction has not been fully elucidated. The goal of this study was to define whether cerebrovascular lesions and cognitive function in SCD are linked to neuroaxonal damage and astrocyte activation in humanized Townes' SCD mice homozygous for human sickle hemoglobin S (SS) and control mice homozygous for human normal hemoglobin A (AA). Mice underwent MRI with DTI and cognitive testing, and histology sections from their brains were stained to assess microstructural tissue damage, neuroaxonal damage, and astrocyte activation. Fractional anisotropy, showing microstructural cerebrovascular abnormalities identified by DTI in the white matter, was significantly associated with neuronal demyelination in the SS mouse brain. SS mice had reduced learning and memory function with a significantly lower discrimination index compared with AA control mice in the novel object recognition tests. Neuroaxonal damage in the SS mice was synchronously correlated with impaired neurocognitive function and activation of astrocytes. The interplay between astrocyte function and neurons may modulate cognitive performance in SCD.

Cerebrovascular disease in sickle cell disease

Sickle cell disease (SCD) is the most common type of hereditary anaemia and genetic disorder worldwide. Cerebrovascular disease is one of its most devastating complications, with consequent increased morbidity and mortality. Current guidelines suggest that children and adults with SCD who develop acute ischaemic stroke should be transfused without delay. Those with acute ischaemic stroke aged over 18 years who present within 4.5 hours of symptom onset should be considered for intravenous thrombolysis; older patients with conventional vascular risk factors are the most likely to benefit. Endovascular thrombectomy should be considered carefully in adults with SCD as there are few data to guide how the prevalence of cerebral vasculopathy may confound the expected benefits or risks of intervention. We present a practical approach to cerebrovascular disease in sickle cell patients based on the available evidence and our experience.

Efficacy and safety of pharmacological interventions for managing sickle cell disease complications in children and adolescents: Systematic review with network meta-analysis

This study aimed to synthesize the evidence on the effects of disease-modifying agents for managing sickle cell disease (SCD) in children and adolescents by means of a systematic review with network meta-analyses, surface under the cumulative ranking curve (SUCRA) and stochastic multicriteria acceptability analyses (SMAA) (CRD42022328471). Eightteen randomized controlled trials (hydroxyurea [n = 7], l-arginine [n = 3], antiplatelets [n = 2], immunotherapy/monoclonal antibodies [n = 2], sulfates [n = 2], docosahexaenoic acid [n = 1], niprisan [n = 1]) were analyzed. SUCRA and SMAA demonstrated that hydroxyurea at higher doses (30 mg/kg/day) or at fixed doses (20 mg/kg/day) and immunotherapy/monoclonal antibodies are more effective for preventing vaso-occlusive crisis (i.e., lower probabilities of incidence of this event; 14, 25, and 30%, respectively), acute chest syndrome (probabilities ranging from 8 to 30%), and needing of transfusions (11-31%), while l-arginine (100-200 mg/kg) and placebo were more prone to these events. Therapies were overall considered safe; however, antiplatelets and sulfates may lead to more severe adverse events. Although the evidence was graded as insufficient and weak, hydroxyurea remains the standard of care for this population, especially if a maximum tolerated dose schedule is considered.

Importance of assessing biomarkers and physiological parameters of anemia-induced tissue hypoxia in the perioperative period

Anemia is associated with increased risk of Acute Kidney Injury (AKI), stroke and mortality in perioperative patients. We sought to understand the mechanism(s) by assessing the integrative physiological responses to anemia (kidney, brain), the degrees of anemia-induced tissue hypoxia, and associated biomarkers and physiological parameters. Experimental measurements demonstrate a linear relationship between blood Oxygen Content (C_aO₂) and renal microvascular PO₂ (y = 0.30x + 6.9, r² = 0.75), demonstrating that renal hypoxia is proportional to the degree of anemia. This defines the kidney as a potential oxygen sensor during anemia. Further evidence of renal oxygen sensing is demonstrated by proportional increase in serum Erythropoietin (EPO) during anemia (y = 93.806*10^-0.02, r² = 0.82). This data implicates systemic EPO levels as a biomarker of anemia-induced renal tissue hypoxia. By contrast, cerebral Oxygen Delivery (DO₂) is defended by a profound proportional increase in Cerebral Blood Flow (CBF), minimizing tissue hypoxia in the brain, until more severe levels of anemia occur. We hypothesize that the kidney experiences profound early anemia-induced tissue hypoxia which contributes to adaptive mechanisms to preserve cerebral perfusion. At severe levels of anemia, renal hypoxia intensifies, and cerebral hypoxia occurs, possibly contributing to the mechanism(s) of AKI and stroke when adaptive mechanisms to preserve organ perfusion are overwhelmed. Clinical methods to detect renal tissue hypoxia (an early warning signal) and cerebral hypoxia (a later consequence of severe anemia) may inform clinical practice and support the assessment of clinical biomarkers (i.e., EPO) and physiological parameters (i.e., urinary PO₂) of anemia-induced tissue hypoxia. This information may direct targeted treatment strategies to prevent adverse outcomes associated with anemia.

Insulin-like Growth Factor-1 Prevents Hypoxia/Reoxygenation-Induced White Matter Injury in Sickle Cell Mice

Occlusion of cerebral blood vessels causes acute cerebral hypoxia-an important trigger of ischemic white matter injury and stroke in sickle cell disease (SCD). While chronic hypoxia triggers compensatory neuroprotection via insulin-like growth factor-1 (IGF-1) and hypoxia inducible factor-1α (HIF-1α), severe bouts of acute hypoxia and subsequent restoration of blood flow (hypoxia/reoxygenation, H/R) overwhelm compensatory mechanisms and cause neuroaxonal damage-identified as white matter lesions-in the brain. The neuroprotective role of IGF-1 in the pathogenesis of white matter injury in SCD has not been investigated; however, it is known that systemic IGF-1 is reduced in individuals with SCD. We hypothesized that IGF-1 supplementation may prevent H/R-induced white matter injury in SCD. Transgenic sickle mice homozygous for human hemoglobin S and exposed to H/R developed white matter injury identified by elevated expression of non-phosphorylated neurofilament H (SMI32) with a concomitant decrease in myelin basic protein (MBP) resulting in an increased SMI32/MBP ratio. H/R-challenge also lowered plasma and brain IGF-1 expression. Human recombinant IGF-1 prophylaxis significantly induced HIF-1α and averted H/R-induced white matter injury in the sickle mice compared to vehicle-treated mice. The expression of the IGF-1 binding proteins IGFBP-1 and IGFBP-3 was elevated in the IGF-1-treated brain tissue indicating their potential role in mediating neuroprotective HIF-1α signaling. This study provides proof-of-concept for IGF-1-mediated neuroprotection in SCD.

Early Strokes Are Associated with More Global Cognitive Deficits in Adults with Sickle Cell Disease

This study sought to link neurocognitive profiles in sickle cell disease (SCD) patients with clinical characteristics. We conducted a prospective cohort study of adults with SCD who underwent comprehensive neuropsychological assessment at the UMGGR clinic at Henri Mondor Hospital, Créteil (France). A cluster analysis was performed based on neuropsychological testing scores. The association between clusters and clinical profiles was assessed. Between 2017 and 2021, 79 patients with a mean age of 36 [range 19-65] years were included. On principal component analysis, a 5-factor model presented the best fit (Bartlett's sphericity test [χ2 (171) = 1345; p < 0.001]), explaining 72% of the variance. The factors represent distinct cognitive domains and anatomical regions. On hierarchical classification, three clusters emerged. Cluster 1 (n = 24) presented deficits in all five factors compared to Cluster 3 (n = 33). Cluster 2 (n = 22) had deficits in all factors, but to a lesser extent than Cluster 1. MoCA scores mirrored the severity of these cognitive deficits. Age, genotype and stroke prevalence did not differ significantly between clusters. However, the time of first stroke occurrence differed significantly between Cluster 1 and 2-3: 78% of strokes occurred during childhood, whereas 80% and 83% occurred during adulthood in Clusters 2 and 3, respectively. Educational attainment was also reduced in Cluster 1. SCD patients with childhood stroke seem to be at increased risk of a global cognitive deficit profile. In addition to existing methods of primary and secondary stroke prevention, early neurorehabilitation should be prioritized in order to reduce the long-term cognitive morbidity of SCD.

Efficacy and safety of pharmacological interventions for managing sickle cell disease in children and adolescents: protocol for a systematic review with network meta-analysis

INTRODUCTION

Sickle cell disease (SCD), an inherited haemoglobinopathy, has important impact on morbidity and mortality, especially in paediatrics. Previous systematic reviews are limited to adult patients or focused only on few therapies. We aim to synthesise the evidence on efficacy and safety of pharmacological interventions for managing SCD in children and adolescents.

METHODS AND ANALYSIS

This systematic review protocol is available at Open Science Framework (doi:10.17605/OSF.IO/CWAE9). We will follow international recommendations on conduction and report of systematic reviews and meta-analyses. Searches will be conducted in PubMed, Scopus and Web of Science (no language nor time restrictions) (first pilot searches performed in May 2022). We will include randomised controlled trials comparing the effects of disease-modifying agents in patients with SCD under 18 years old. Outcomes of interest will include: vaso-occlusive crisis, haemoglobin levels, chest syndrome, stroke, overall survival and adverse events. We will provide a narrative synthesis of the findings, and whenever possible, results will be pooled by means of pairwise or Bayesian network meta-analyses with surface under the cumulative ranking curve analyses. Different statistical methods and models will be tested. Dichotomous outcomes will be reported as OR, risk ratio or HR, while continuous data will be reported as standard mean differences, both with 95% CI/credibility interval. The methodological quality of the trials will be evaluated using the Risk of Bias 2.0 tool, and the certainty of the evidence will be assessed with the Grading of Recommendations Assessment, Development and Evaluation approach.

ETHICS AND DISSEMINATION

This study refers to a systematic review, so no ethics approval is necessary. We intent to publish our findings in international, peer-reviewed journal. Data will also be presented to peers in scientific events. Additionally, the results obtained in this study may contribute towards the update of therapeutic guidelines and for the development of health policies for SCD.

PROSPERO REGISTRATION NUMBER

CRD42022328471.

Normalization of cerebral hemodynamics after hematopoietic stem cell transplant in children with sickle cell disease

Children with sickle cell disease (SCD) demonstrate cerebral hemodynamic stress and are at high risk of strokes. We hypothesized that curative hematopoietic stem cell transplant (HSCT) normalizes cerebral hemodynamics in children with SCD compared with pre-transplant baseline. Whole-brain cerebral blood flow (CBF) and oxygen extraction fraction (OEF) were measured by magnetic resonance imaging 1 to 3 months before and 12 to 24 months after HSCT in 10 children with SCD. Three children had prior overt strokes, 5 children had prior silent strokes, and 1 child had abnormal transcranial Doppler ultrasound velocities. CBF and OEF of HSCT recipients were compared with non-SCD control participants and with SCD participants receiving chronic red blood cell transfusion therapy (CRTT) before and after a scheduled transfusion. Seven participants received matched sibling donor HSCT, and 3 participants received 8 out of 8 matched unrelated donor HSCT. All received reduced-intensity preparation and maintained engraftment, free of hemolytic anemia and SCD symptoms. Pre-transplant, CBF (93.5 mL/100 g/min) and OEF (36.8%) were elevated compared with non-SCD control participants, declining significantly 1 to 2 years after HSCT (CBF, 72.7 mL/100 g per minute; P = .004; OEF, 27.0%; P = .002), with post-HSCT CBF and OEF similar to non-SCD control participants. Furthermore, HSCT recipients demonstrated greater reduction in CBF (-19.4 mL/100 g/min) and OEF (-8.1%) after HSCT than children with SCD receiving CRTT after a scheduled transfusion (CBF, -0.9 mL/100 g/min; P = .024; OEF, -3.3%; P = .001). Curative HSCT normalizes whole-brain hemodynamics in children with SCD. This restoration of cerebral oxygen reserve may explain stroke protection after HSCT in this high-risk patient population.

The Development of Neuroimaging Biomarkers for Cognitive Decline in Sickle Cell Disease

Sickle cell disease (SCD) is complicated by neurologic complications including vasculopathy, hemorrhagic or ischemic overt stroke, silent cerebral infarcts and cognitive dysfunction. Patients with SCD, even in the absence of vasculopathy or stroke, have experience cognitive dysfunction that progresses with age. Transcranial Doppler ultrasound and structural brain MRI are currently used for primary and secondary stroke prevention, but laboratory or imaging biomarkers do not currently exist that are specific to the risk of cognitive dysfunction in patients with SCD. Recent investigations have used advanced MR sequences assessing cerebral hemodynamics, white matter microstructure and functional connectivity to better understand the pathophysiology of cognitive decline in SCD, with the long-term goal of developing neuroimaging biomarkers to be used in risk prediction algorithms and to assess the efficacy of treatment options for patients with SCD.

Stroke in sickle cell disease and the promise of recent disease modifying agents

Sickle cell disease (SCD) is an inherited hemoglobinopathy affecting approximately 100,000 individuals in the United States. Cerebrovascular disease is among the most common and debilitating complications of SCA, with 53% experiencing silent cerebral infarct by age 30 and 3.8% experiencing overt stroke by age 40 years. This review highlights the burden of cerebrovascular disease in SCD, including both stroke and silent cerebral infarct (SCI). We then discuss the pathophysiology of stroke and cerebral fat embolism in the absence of a patent foramen ovale. This review also reveals that options for primary and secondary stroke prevention in SCD are still limited to hydroxyurea and blood transfusion, and that the role of aspirin and anticoagulation in SCD stroke has not been adequately studied. Limited data suggest that the novel disease-modifying agents for SCD management may improve renal dysfunction, leg ulcers, and lower the abnormally high TCD flow velocity. Further research is urgently needed to investigate their role in stroke prevention in SCD, as these novel agents target the main stroke contributors in SCD - hemolysis and vaso-occlusion. This literature review also explores the role of healthcare disparities in slowing progress in SCD management and research in the United States, highlighting the need for more investment in patient and clinician education, SCD management, and research.

Neurodevelopmental Outcomes in Preterm Children with Sickle Cell Disease

OBJECTIVES

To explore the combined effect of pediatric sickle cell disease (SCD) and preterm birth on cognitive functioning.

METHODS

Cognitive functioning was examined in children ages 6-8 with high risk SCD genotypes born preterm (n = 20) and full-term (n = 59) and lower risk SCD genotypes/no SCD born preterm (n = 11) and full-term (n = 99) using tests previously shown to be sensitive to SCD-related neurocognitive deficits. Factorial ANOVAs and log linear analyses were conducted to examine the relationship between SCD risk, preterm birth status, and cognitive outcomes. Continuous scores were examined for specific tests. Children were categorized as having an abnormal screening outcome if at least one cognitive score was ≥1.5 standard deviations below the population mean.

RESULTS

Children with elevated risk due to high risk SCD and preterm birth performed worse than other groups on a test of expressive language but not on tests that emphasize processing speed and working memory. There was a three-way interaction between preterm status, SCD risk, and abnormal screening outcome, which was largely driven by the increased likelihood of abnormal cognitive scores for children with high risk SCD born preterm.

CONCLUSIONS

The combination of SCD and preterm birth may confer increased risk for language deficits and elevated rates of abnormal cognitive screenings. This suggests that neurodevelopmental risk imparted by comorbid SCD and preterm birth may manifest as heterogenous, rather than specific, patterns of cognitive deficits. Future studies are needed to clarify the domains of cognitive functioning most susceptible to disease-related effects of comorbid SCD and preterm birth.

Effect of Blood Transfusion on Cerebral Hemodynamics and Vascular Topology Described by Computational Fluid Dynamics in Sickle Cell Disease Patients

The main objective of this study was to demonstrate that computational fluid dynamics (CFD) modeling can be used to study the contribution of covert and overt vascular architecture to the risk for cerebrovascular disease in sickle cell disease (SCD) and to determine the mechanisms of response to therapy such as chronic red blood cell (cRBC) transfusions. We analyzed baseline (screening), pre-randomization and study exit magnetic resonance angiogram (MRA) images from 10 (5 each from the transfusion and observation arms) pediatric sickle SCD participants in the silent cerebral infarct transfusion (SIT) trial using CFD modeling. We reconstructed the intracranial portion of the internal carotid artery and branches and extracted the geometry using 3D Slicer. We cut specific portions of the large intracranial artery to include segments of the internal carotid, middle, anterior, and posterior cerebral arteries such that the vessel segment analyzed extended from the intracranial beginning of the internal carotid artery up to immediately after (~0.25 inches) the middle cerebral artery branching point. Cut models were imported into Ansys 2021R2/2022R1 and laminar and time-dependent flow simulation was performed. Change in time averaged mean velocity, wall shear stress, and vessel tortuosity were compared between the observation and cRBC arms. We did not observe a correlation between time averaged mean velocity (TAMV) and mean transcranial Doppler (TCD) velocity at study entry. There was also no difference in change in time average mean velocity, wall shear stress (WSS), and vessel tortuosity between the observation and cRBC transfusion arms. WSS and TAMV were abnormal for 2 (developed TIA) out of the 3 participants (one participant had silent cerebral infarctions) that developed neurovascular outcomes. CFD approaches allow for the evaluation of vascular topology and hemodynamics in SCD using MRA images. In this proof of principle study, we show that CFD could be a useful tool and we intend to carry out future studies with a larger sample to enable more robust conclusions.

Incidence, kinetics, and risk factors for intra- and extracranial cerebral arteriopathies in a newborn sickle cell disease cohort early assessed by transcranial and cervical color Doppler ultrasound

The risk of stroke in children with sickle cell disease (SCD) is detected by abnormal intracranial arterial time-averaged mean of maximum velocities (TAMVs ≥200 cm/s). Recently, extracranial internal carotid artery (eICA) arteriopathy has been reported, and a cross-sectional study showed that eICA-TAMVs ≥160 cm/s are significantly associated with eICA kinkings and stenosis. The cumulative incidence of and predictive risk factors for intracranial arteriopathy are well described in sickle cell anemia (SCA=SS/Sβ0) but are lacking for SC/Sβ+ children, as is the cumulative incidence of eICA arteriopathy. We report a prospective longitudinal cohort study including 493 children with SCD (398 SCA, 95 SC/Sβ+), all assessed by transcranial and cervical color Doppler ultrasound. Cerebral MRI/MRA data were available in 375 children with SCD and neck MRA in 365 children. eICA kinkings were defined as eICA tortuosities on neck MRA, with an internal acute angle between the two adjacent segments <90°. The median follow-up was 10.6 years. The cumulative incidence of kinkings was significantly lower in SC/Sβ+ children than in children with SCA, and no SC/Sβ+ child developed intra- or extracranial stenotic arteriopathy. The 10-year KM estimate of cumulative incidence (95% CI) for eICA-TAMVs ≥160 cm/s revealed its development in the 2nd year of life in children with SCA, reaching a plateau of 17.4% (13.2–21.6%) by about 10 years of age, while the plateau for eICA stenosis was 12.3% (8.3–16.3%). eICA assessment identified 13.5% (9.3–17.7%) patients at risk of stroke who were not detected by transcranial color Doppler ultrasound. We also show, for the first time, that in addition to a congenital origin, eICA kinkings sin patients with SCD can develop progressively with aging as a function of eICA-TAMVs, themselves related to anemia severity. Ongoing hydroxyurea treatment was significantly associated with a lower risk of abnormal intracranial arteriopathy and eICA kinkings. After adjustment with hydroxyurea, baseline low hemoglobin, high reticulocyte, and WBC counts remained independent risk factors for intracranial arteriopathy, while low hemoglobin and SEN β-haplotype number were independent risk factors for extracranial arteriopathy. The association between extracranial arteriopathy and SEN β-haplotype number suggested a genetic link between the ethnic origin and incidence of eICA kinkings. This prospective cohort study shows the importance of systematically assessing the eICA and of recording biological parameters during the 2nd year of life before any intensive therapy to predict the risk of cerebral arteriopathy and treat patients with severe baseline anemia.

A case-control and seven-year longitudinal neurocognitive study of adults with sickle cell disease in Ghana

Ageing in sickle cell disease (SCD) is associated with a myriad of end-organ complications, including cerebrovascular damage and cognitive impairment (CI). Although CI is very common in SCD, little is known about cognitive functioning and how it changes with age. This study examines cognitive patterns of 63 adults with SCD and 60 non-SCD, age- and education-matched controls in Ghana. Of those adults with SCD, 34 completed the neuropsychological battery at baseline and again seven years later. In cross-sectional data, adults with SCD performed worse than controls in all cognitive test domains (p < 0.01 for all). The seven-year follow-up data showed that the group exhibited a significant decline in visuospatial abilities (ranging from Cohen's d = 1.40 to 2.38), and to a lesser extent, in processing speed and executive functioning. Exploratory analyses showed a significant time-by-education interaction, indicating that education may be protective from decline in cognitive performance. These findings have implications for clinical practice. Early neuropsychological surveillance coupled with early assessment and remedial programmes will provide avenues for enhancing the quality of life of adults living with SCD in Ghana.

Quantification of Silent Cerebral Infarction on High-Resolution FLAIR and Cognition in Sickle Cell Anemia

Research in sickle cell anemia (SCA) has used, with limited race-matched control data, binary categorization of patients according to the presence or absence of silent cerebral infarction (SCI). SCI have primarily been identified using low-resolution MRI, with radiological definitions varying in lesion length and the requirement for abnormality on both fluid attenuated inversion recovery (FLAIR) and T1-weighted images. We aimed to assess the effect of published SCI definitions on global, regional, and lobar lesion metrics and their value in predicting cognition. One hundred and six patients with SCA and 48 controls aged 8-30 years underwent 3T MRI with a high-resolution FLAIR sequence and Wechsler cognitive assessment. Prevalence, number, and volume of lesions were calculated using a semi-automated pipeline for SCI defined as: (1) Liberal: any length (L-SCI); (2) Traditional: >3 mm in greatest dimension (T-SCI); (3) Restrictive; >3 mm in greatest dimension with a corresponding T1-weighted hypo-intensity (R-SCI). Globally, as hypothesized, there were large effects of SCI definition on lesion metrics in patients and controls, with prevalence varying from 24-42% in patients, and 4-23% in controls. However, contrary to hypotheses, there was no effect of any global metric on cognition. Regionally, there was a consistent distribution of SCI in frontal and parietal deep and juxta-cortical regions across definitions and metrics in patients, but no consistent distribution in controls. Effects of regional SCI metrics on cognitive performance were of small magnitude; some were paradoxical. These findings expose the challenges associated with the widespread use of SCI presence as a biomarker of white-matter injury and cognitive dysfunction in cross-sectional high-resolution MRI studies in patients with SCA. The findings indicate that with high-resolution MRI: (1) radiological definitions have a large effect on resulting lesion groups, numbers, and volumes; (2) there is a non-negligible prevalence of lesions in young healthy controls; and (3) at the group-level, there is no cross-sectional association between global lesion metrics and general cognitive impairment irrespective of lesion definition and metric. With high-resolution multi-modal MRI, the dichotomy of presence or absence of SCI does not appear to be a sensitive biomarker for the detection of functionally significant pathology; the search for appropriate endpoints for clinical treatment trials should continue.

Determinants of severity in sickle cell disease

Sickle cell disease is a very variable condition, with outcomes ranging from death in childhood to living relatively symptom free into the 8^th decade. Much of this variability is unexplained. The co-inheritance of α thalassaemia and factors determining HbF levels significantly modify the phenotype, but few other significant genetic variants have been identified, despite extensive studies. Environmental factors are undoubtedly important, with socio-economics and access to basic medical care explaining the huge differences in outcomes between many low- and high-income countries. Exposure to cold and windy weather seems to precipitate acute complications in many people, although these effects are unpredictable and vary with geography. Many studies have tried to identify prognostic factors which can be used to predict outcomes, particularly when applied in infancy. Overall, low haemoglobin, low haemoglobin F percentage and high reticulocytes in childhood are associated with worse outcomes, although again these effects are fairly weak and inconsistent.

Cerebral oxygen metabolic stress is increased in children with sickle cell anemia compared to anemic controls

Patients with sickle cell anemia (SCA) experience cerebral metabolic stress with an increase in oxygen extraction fraction (OEF) to compensate for reduced oxygen carrying capacity due to anemia. It remains unclear if anemia alone drives this metabolic stress. Using MRI, we collected voxel-wise OEF measurements to test our hypothesis that OEF would be elevated in anemic controls without SCA (AC) compared to healthy controls (HC), but OEF would be even higher in SCA compared to AC. Brain MRIs (N = 159) were obtained in 120 participants (34 HC, 27 AC, 59 SCA). While hemoglobin was lower in AC versus HC (p < 0.001), hemoglobin was not different between AC and SCA cohorts (p = 0.459). Whole brain OEF was higher in AC compared to HC (p < 0.001), but lower compared to SCA (p = 0.001). Whole brain OEF remained significantly higher in SCA compared to HC (p = 0.001) while there was no longer a difference between AC versus HC (p = 0.935) in a multivariate model controlling for age and hemoglobin. OEF peaked within the border zone regions of the brain in both SCA and AC cohorts, but the volume of white matter with regionally elevated OEF in AC was smaller (1.8%) than SCA (58.0%). While infarcts colocalized within regions of elevated OEF, more SCA participants had infarcts than AC (p < 0.001). We conclude that children with SCA experience elevated OEF compared to AC and HC after controlling for the impact of anemia, suggesting that there are other pathophysiologic factors besides anemia contributing to cerebral metabolic stress in children with SCA.

Assessment of functional shunting in patients with sickle cell disease

Silent cerebral infarcts (SCI) are common in patients with sickle cell disease (SCD) and are thought to be caused by a mismatch between oxygen delivery and consumption. Functional cerebrovascular shunting is defined as reduced oxygen offloading due to the rapid transit of blood through the capillaries caused by increased flow and has been suggested as a potential mechanism underlying reduced oxygenation and SCI. We investigated the venous arterial spin labeling signal (VS) in the sagittal sinus as a proxy biomarker of cerebral functional shunting, and its association with hemodynamic imaging and hematological laboratory parameters. We included 28 children and 38 adults with SCD, and ten healthy racematched adult controls. VS, cerebral blood flow (CBF), velocity in the brain feeding arteries, oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2) were measured before and after acetazolamide administration. VS was higher in patients with SCD compared to controls (P<0.01) and was increased after acetazolamide administration in all groups (P<0.01). VS was primarily predicted by CBF (P<0.01), but CBF-corrected VS was also associated with decreased CMRO2 (P<0.01). Additionally, higher disease severity defined by low hemoglobin and increased hemolysis was associated with higher CBF-corrected VS. Finally, CMRO2 was negatively correlated with fetal hemoglobin, and positively correlated with lactate dehydrogenase, which could be explained by changes in oxygen affinity. These findings provide evidence for cerebral functional shunting and encourage future studies investigating the potential link to aberrant capillary exchange in SCD.

Evolution of Extracranial Internal Carotid Artery Disease in Children With Sickle Cell Anemia

BACKGROUND

Cerebral arteriopathy in patients with sickle cell anemia mainly affects the intracranial anterior circulation. However, the extracranial internal carotid artery (eICA) can also be stenosed and responsible for ischemic lesions. In children with sickle cell anemia, we perform routine annual Doppler ultrasound assessment of the eICA and magnetic resonance imaging with 3-dimensional time-of-flight magnetic resonance angiography of the Willis circle and neck arteries in those with abnormal velocity. Our aim was to report the evolution of eICA stenoses from 2011 to the present as a function of therapy in a retrospective case-series study. We hypothesized that chronic transfusion (CTT) would be more effective than hydroxyurea and simple observation on the evolution of eICA stenosis.

METHODS

Eligibility criteria were a history of eICA velocity ≥160 cm/s with a minimum Doppler and magnetic resonance imaging follow-up of 1 year. eICAs were graded for stenosis according to NASCET (The North American Symptomatic Carotid Endarterectomy Trial). Magnetic resonance imaging was investigated for ischemic lesions. Treatment with hydroxyurea and CTT were obtained from the chart review.

RESULTS

Fifty-four patients were included. Eight patients had a stroke history. The median (range) follow-up was 4.7 years (1.1-9.2 years). On the first neck magnetic resonance angiography, stenosis was present in 48/54 (89%) patients. Kinking was found in 39/54 (72%) patients. On the last neck magnetic resonance angiography, the proportion of patients with eICA stenosis decreased to 39/54 (72%). ICA occlusion occurred in 5 patients despite CTT. Three patients had carotid webs without intracranial stenosis. The proportion of patients with improvement in stenosis score was 8% with no treatment intensification, 20% with hydroxyurea, and 48% with CTT (P=0.016). The mean (SD) change per year in stenosis score was 0.40 (0.60) without intensification, 0.20 (0.53) with hydroxyurea, and -0.18 (0.55) with CTT (P=0.006). Ischemic lesions were present initially in 46% of patients, and the incidence of progressive ischemic lesions was 2.5 events/100 patient-years. Cox regression analysis showed that the initial score for eICA stenosis was a significant predictive factor for the risk of new silent cerebral infarct events.

CONCLUSIONS

Our study reinforces the need to assess cervical arteries for better prevention of cerebral ischemia and encourage initiation of CTT in sickle cell anemia children with eICA stenosis.

Adaptive Functioning in Children and Adolescents With Sickle Cell Disease

OBJECTIVE

Risk for neurocognitive deficits in sickle cell disease (SCD) is well established, yet minimal research has evaluated the risk for deficits in adaptive functioning. We assessed adaptive functioning in pediatric patients with SCD to test the hypothesis that disease, treatment, and demographic factors were associated with adaptive outcomes.

METHODS

Two hundred fifty-six patients (57% HbSS/HbSß0-thalassemia and 43% HbSC/HbSß+-thalassemia), ages 8-18, received routine neuropsychological assessments as part of a larger prospective lifetime cohort study. Adaptive functioning was measured using the Behavior Assessment System for Children, Second or Third Edition. Adaptive scores were compared with normative values using t-test or Wilcoxon signed rank test and linear regression models were used to measure associations between adaptive functioning and age, hydroxyurea (HU) use, sickle genotype, and socioeconomic status. Furthermore, we examined the influence of intellectual and executive functioning on adaptive behavior using hierarchical linear regression analyses.

RESULTS

Parent ratings of adaptive functioning skills did not differ from normative expectations (all false discovery rate [FDR] adjusted p-value [pFDR] > 0.05). Social vulnerability was negatively associated with adaptive scores on most adaptive scales in both genotypes (pFDR < 0.05). HU treatment was not significantly associated with any adaptive scale. Overall IQ was positively associated with Functional Communication and Leadership only for those with HbSS/HbSß0-thalassemia. Higher parent ratings of executive difficulties were correlated with lower adaptive scores (estimate = -0.64, standard error = 0.051, p < .001).

CONCLUSIONS

Poorer parent-rated adaptive skills were associated with increased social vulnerability, lower Full-Scale IQ, and parent-rated executive difficulties. Most adaptive scores were in the normal range; however, parent ratings may not fully capture the impact of disease complications and neurocognitive deficits on daily functioning.

Retinal atrophy and markers of systemic and cerebrovascular severity in homozygous sickle cell disease

Introduction

While paramacular retinal atrophy (PRA) is known to be found in 48% of eyes of adults and 42% of eyes of children with homozygous SCD (SS-SCD), the aim of this study is to assess the association between PRA and red blood cell (RBC) deformability, hematological markers and brain imaging abnormalities in SS-SCD.

Methods

This study is a subset of DREAM2, a prospective observational study performed between August 2015 and August 2016. Children (5–17 years) with SS-SCD and no history of large vessel vasculopathy, were included. Ophthalmological characteristics including visual acuity, fundus examination, OCT of central and temporal retina (with several retinal thickness measurements) were explored in relation with RBC deformability (ektacytometry), hematological and biochemical (hemolysis parameters), and neurological (cerebral oxygenation estimated by Near Infrared Spectroscopy, brain magnetic resonance imaging) investigations.

Results

17 children (5 boys; mean age: 13 years) with complete ophthalmological investigations were included in the analysis; 8 exhibited PRA. RBC deformability was found to be significantly lower in children with PRA for measurements made at 1.69 Pa (0.16 a.u ± 0.02 vs 0.21 a.u ± 0.03, p = 0.02) and above, as well as cerebral oxygenation (59.25% ± 9.9 vs 71.53% ± 4.9, p = 0.02). A significant positive correlation was found between temporal retinal thickness and hemoglobin level (ρ = 0.65, p = 0.007), hematocrit (ρ = 0.53, p = 0.04) and RBC deformability at 3 Pa (ρ = 0.75, p = 0.005) and above.

Conclusions

These results suggest that PRA could be an early marker of systemic severity and cerebral oxygenation in SCD. Whether it could help predicting cerebral vasculopathy requires further investigations.

Advances in the diagnosis and treatment of sickle cell disease

Sickle cell disease (SCD), which affects approximately 100,000 individuals in the USA and more than 3 million worldwide, is caused by mutations in the βb globin gene that result in sickle hemoglobin production. Sickle hemoglobin polymerization leads to red blood cell sickling, chronic hemolysis and vaso-occlusion. Acute and chronic pain as well as end-organ damage occur throughout the lifespan of individuals living with SCD resulting in significant disease morbidity and a median life expectancy of 43 years in the USA. In this review, we discuss advances in the diagnosis and management of four major complications: acute and chronic pain, cardiopulmonary disease, central nervous system disease and kidney disease. We also discuss advances in disease-modifying and curative therapeutic options for SCD. The recent availability of L-glutamine, crizanlizumab and voxelotor provides an alternative or supplement to hydroxyurea, which remains the mainstay for disease-modifying therapy. Five-year event-free and overall survival rates remain high for individuals with SCD undergoing allogeneic hematopoietic stem cell transplant using matched sibling donors. However, newer approaches to graft-versus-host (GVHD) prophylaxis and the incorporation of post-transplant cyclophosphamide have improved engraftment rates, reduced GVHD and have allowed for alternative donors for individuals without an HLA-matched sibling. Despite progress in the field, additional longitudinal studies, clinical trials as well as dissemination and implementation studies are needed to optimize outcomes in SCD.

Economic evaluation of regular transfusions for cerebral infarct recurrence in the Silent Cerebral Infarct Transfusion Trial

Children with preexisting silent cerebral infarcts on regular transfusion therapy had 50% lower hospitalization costs than standard care.

The incremental cost-effectiveness ratio for transfusion therapy to prevent infarct recurrence was $22 025 for every infarct prevented.

In 2020, the American Society of Hematology published evidence-based guidelines for cerebrovascular disease in individuals with sickle cell anemia (SCA). Although the guidelines were based on National Institutes of Health–sponsored randomized controlled trials, no cost-effectiveness analysis was completed for children with SCA and silent cerebral infarcts. We conducted a cost-effectiveness analysis comparing regular blood transfusion vs standard care using SIT (Silent Cerebral Infarct Transfusion) Trial participants. This analysis included a modified societal perspective with direct costs (hospitalization, emergency department visit, transfusion, outpatient care, and iron chelation) and indirect costs (special education). Direct medical costs were estimated from hospitalizations from SIT hospitals and unlinked aggregated hospital and outpatient costs from SIT sites by using the Pediatric Health Information System. Indirect costs were estimated from published literature. Effectiveness was prevention of infarct recurrence. An incremental cost-effectiveness ratio using a 3-year time horizon (mean SIT Trial participant follow-up) compared transfusion vs standard care. A total of 196 participants received transfusions (n = 90) or standard care (n = 106), with a mean age of 10.0 years. Annual hospitalization costs were reduced by 54% for transfusions vs standard care ($4929 vs $10 802), but transfusion group outpatient costs added $22 454 to $137 022 per year. Special education cost savings were $2634 over 3 years for every infarct prevented. Transfusion therapy had an incremental cost-effectiveness ratio of $22 025 per infarct prevented. Children with preexisting silent cerebral infarcts receiving blood transfusions had lower hospitalization costs but higher outpatient costs, primarily associated with the oral iron chelator deferasirox. Regular blood transfusion therapy is cost-effective for infarct recurrence in children with SCA. This trial is registered at www.clinicaltrials.gov as #NCT00072761.

Indications for transfusion in the management of sickle cell disease

The transfusion of red blood cells (RBCs) is a crucial treatment for sickle cell disease (SCD). While often beneficial, the frequent use of transfusions is associated with numerous complications. Transfusions should be offered with specific guidelines in mind. Here we present updates to the indications for transfusion of RBCs in SCD. We review recent publications and include expert perspectives from hematology and transfusion medicine. For some clinical indications, such as ischemic stroke, the role of transfusion has been well studied and can be applied almost universally. For many other clinical scenarios, the use of transfusion therapy has less conclusive data and therefore must be tailored to individual needs. We highlight the roles of RBC transfusions in preventing or mitigating neurological disease, in reducing perioperative complications, in managing acute chest syndrome, and in optimizing pregnancy outcomes in SCD. We further highlight various transfusion techniques and when each might be considered. Potential complications of transfusion are also briefly discussed.

Hematopoietic stem cell transplantation reverses white matter injury measured by diffusion-tensor imaging (DTI) in sickle cell disease patients

Brain injury in sickle cell disease (SCD) comprises a wide spectrum of neurological damage. Neurocognitive deficits have been described even without established neurological lesions. DTI is a rapid, noninvasive, and non-contrast method that enables detection of normal-appearing white matter lesions not detected by conventional magnetic resonance imaging (MRI). The aim of the study was to evaluate if stem cell transplantation can revert white matter lesions in patients with SCD. Twenty-eight SCD patients were evaluated with MRI and DTI before and after allogeneic hematopoietic stem cell transplantation (HSCT), compared with 26 healthy controls (HC). DTI metrics included fractional anisotropy (FA), mean diffusivity (MD), radial (RD), and axial (AD) diffusivity maps, global efficiency, path length, and clustering coefficients. Compared to HC, SCD patients had a lower FA (p = 0.0086) before HSCT. After HSCT, FA increased and was not different from healthy controls (p = 0.1769). Mean MD, RD, and AD decreased after HSCT (p = 0.0049; p = 0.0029; p = 0.0408, respectively). We confirm previous data of white matter lesions in SCD and present evidence that HSCT promotes recovery of brain injury with potential improvement of brain structural connectivity.

Effects of hydroxyurea on brain function in children with sickle cell anemia

INTRODUCTION

Sickle cell anemia (SCA) results in numerous adverse effects on the brain, including neurocognitive dysfunction. Hydroxyurea has been utilized extensively for management of SCA, but its effects on brain function have not been established.

METHODS

We examined prospectively the effects of 1 year of treatment with hydroxyurea on brain function in children with SCA (HbSS/HbSβ⁰ -thalassemia) by baseline and exit evaluations, including comprehensive neurocognitive testing, transcranial Doppler ultrasound (TCD), and brain MRI (silent cerebral infarcts [SCI], gray matter cerebral blood flow [GM-CBF], and blood oxygen level-dependent [BOLD] signal from visual stimulation).

RESULTS

Nineteen patients with SCA, mean age 12.4 years (range 7.2-17.8), were evaluated. At baseline, subjects had these mean values: full-scale IQ (FSIQ) 82.8, TCD velocity 133 cm/s, GM-CBF 64.4 ml/100 g/min, BOLD signal 2.34% increase, and frequency of SCI 47%. After 1 year of hydroxyurea, there were increases in FSIQ (+2, p = .059) and reading passage comprehension (+4, p = .033), a significant decrease in TCD velocity (-11 cm/s, p = .007), and no significant changes in GM-CBF, BOLD, or SCI frequency. Hemoglobin F (HbF) was associated with passage comprehension, hemoglobin with lower TCD velocity, and lower GM-CBF with greater working memory. Higher BOLD signal was associated with higher processing speed and lower TCD velocity with higher math fluency.

DISCUSSION

Improvements in neurocognition and decreased TCD velocity following 1 year of treatment support hydroxyurea use for improving neurocognitive outcomes in SCA. Understanding the mechanisms of benefit, as indicated by relationships of neurocognitive function with HbF, hemoglobin, and CBF, requires further evaluation.

Epidemiology of Stroke in Sickle Cell Disease

Sickle cell disease is the most common cause of stroke in childhood, both ischaemic and haemorrhagic, and it also affects adults with the condition. Without any screening or preventative treatment, the incidence appears to fall within the range 0.5 to 0.9 per 100 patient years of observation. Newborn screening with Penicillin prophylaxis and vaccination leading to reduced bacterial infection may have reduced the incidence, alongside increasing hydroxyurea prescription. Transcranial Doppler screening and prophylactic chronic transfusion for at least an initial year has reduced the incidence of stroke by up to 10-fold in children with time averaged mean of the maximum velocity >200 cm/s. Hydroxyurea also appears to reduce the incidence of first stroke to a similar extent in the same group but the optimal dose remains controversial. The prevention of haemorrhagic stroke at all ages and ischaemic stroke in adults has not yet received the same degree of attention. Although there are fewer studies, silent cerebral infarction on magnetic resonance imaging (MRI), and other neurological conditions, including headache, epilepsy and cognitive dysfunction, are also more prevalent in sickle cell disease compared with age matched controls. Clinical, neuropsychological and quantitative MRI screening may prove useful for understanding epidemiology and aetiology.

Low Rates of Cerebral Infarction after Hematopoietic Stem Cell Transplantation in Patients with Sickle Cell Disease at High Risk for Stroke

Hematopoietic stem cell transplantation (HSCT) can be curative for sickle cell disease (SCD). SCD patients with cerebrovascular disease are often referred for HSCT. The objective of this study was to describe neurologic outcomes after HSCT in patients with pre-existing SCD and cerebrovascular comorbidity. Patients with SCD treated with HSCT at a single center between 1996 and 2019 were identified. Patients with cerebral ischemia and/or vasculopathy before undergoing HSCT were included. Patients with graft failure were excluded. The cohort was divided into 3 groups: symptomatic stroke, vasculopathy without symptomatic stroke, and isolated silent cerebral infarction (SCI). Magnetic resonance imaging/angiography and neurologic assessments pre- and post-HSCT were analyzed to assess outcomes. In a cohort of 44 patients, there were 25 with symptomatic infarction, 10 with vasculopathy, and 9 with isolated SCI. Post-HSCT ischemic injury (2 symptomatic strokes, 2 SCIs) was identified in 4 patients, all with previous symptomatic infarction. Within this group (n = 25), the post-HSCT incidence of subsequent symptomatic infarction was 1.6 events/100 patient-years, and SCIs occurred at a rate of 2.2 events/100 patient-years. No patient had progression of vasculopathy post-HSCT. Our data show a low incidence of new ischemic injury after successful HSCT for SCD. Patients with a history of both symptomatic stroke and vasculopathy are at greatest risk for post-HSCT ischemic injury.

Progression of central nervous system disease from pediatric to young adulthood in sickle cell anemia

Silent cerebral infarcts and arteriopathy are common and progressive in individuals with sickle cell anemia. However, most data describing brain lesions in sickle cell anemia are cross-sectional or derive from pediatric cohorts with short follow-up. We investigated the progression of silent cerebral infarct and cerebral vessel stenosis on brain MRI and MRA, respectively, by describing the incidence of new or worsening lesions over a period of up to 25 years among young adults with sickle cell anemia and explored risk factors for progression. Forty-four adults with sickle cell anemia (HbSS or HbSβ⁰thalassemia), exposed to chronic transfusions (n = 12) or hydroxyurea (n = 32), median age 19.2 years (range 18.0-31.5), received a screening brain MRI/MRA and their results were compared with a clinical exam performed during childhood and adolescence. We used exact log-rank test to compare MRI and MRA progression among any two groups. The hazard ratio (HR) and 95% confidence interval (CI) were calculated from Cox regression analyses. Progression of MRI and MRA occurred in 12 (27%) and 4 (9%) young adults, respectively, relative to their pediatric exams. MRI progression risk was high among participants with abnormal pediatric exams (HR: 11.6, 95% CI: 2.5-54.7) and conditional or abnormal transcranial Doppler ultrasound velocities (HR: 3.9, 95% CI: 1.0-15.1). Among individuals treated with hydroxyurea, high fetal hemoglobin measured in childhood was associated with lower hazard of MRI progression (HR: 0.86, 95% CI: 0.76-0.98). MRA progression occurred more frequently among those with prior stroke (HR: 8.6, 95% CI: 1.2-64), abnormal pediatric exam (P = 0.00084), and elevated transcranial Doppler ultrasound velocities (P = 0.004). Brain MRI/MRA imaging in pediatrics can identify high-risk patients for CNS disease progression in young adulthood, prompting consideration for early aggressive treatments.

Neurologic and Cognitive Outcomes in Sickle Cell Disease from Infancy through Adolescence

Children with sickle cell disease (SCD) are at risk for neurologic and cognitive complications beginning in early childhood. Current treatment for SCD focuses on primary prevention of complications, such as hydroxyurea for prevention of pain and acute chest syndrome, and chronic transfusion therapy for children who are at high risk for strokes. In this article, the prevalence, pathophysiology, and available interventions to prevent and treat neurologic and cognitive complications of SCD will be reviewed.

Reduced global cerebral oxygen metabolic rate in sickle cell disease and chronic anemias

Anemia is the most common blood disorder in the world. In patients with chronic anemia, such as sickle cell disease or major thalassemia, cerebral blood flow increases to compensate for decreased oxygen content. However, the effects of chronic anemia on oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2 ) are less well understood. In this study, we examined 47 sickle-cell anemia subjects (age 21.7 ± 7.1, female 45%), 27 non-sickle anemic subjects (age 25.0 ± 10.4, female 52%) and 44 healthy controls (age 26.4 ± 10.6, female 71%) using MRI metrics of brain oxygenation and flow. Phase contrast MRI was used to measure resting cerebral blood flow, while T2 -relaxation-under-spin-tagging (TRUST) MRI with disease appropriate calibrations were used to measure OEF and CMRO2 . We observed that patients with sickle cell disease and other chronic anemias have decreased OEF and CMRO2 (respectively 27.4 ± 4.1% and 3.39 ± 0.71 ml O2 /100 g/min in sickle cell disease, 30.8 ± 5.2% and 3.53 ± 0.64 ml O2 /100 g/min in other anemias) compared to controls (36.7 ± 6.0% and 4.00 ± 0.65 ml O2 /100 g/min). Impaired CMRO2 was proportional to the degree of anemia severity. We further demonstrate striking concordance of the present work with pooled historical data from patients having broad etiologies for their anemia. The reduced cerebral oxygen extraction and metabolism are consistent with emerging data demonstrating increased non-nutritive flow, or physiological shunting, in sickle cell disease patients.

Chronic organ injuries in children with sickle cell disease

Median life expectancy of patients with sickle cell disease has increased to up to 55 years but there are still frequent cases of premature death, mostly in patients with pre-existing organ failure such as pulmonary hypertension, kidney injury, and cerebral vasculopathy. Most organ injuries remain asymptomatic for a long time and can only be detected through early systematic screening. Protocols combining assessment of velocities on transcranial Doppler and regular transfusions in patients with abnormal velocities have been demonstrated to dramatically reduce the risk of stroke. In contrast, no consensus has been reached on systematic screening or therapy for silent cerebral infarcts. The prognostic significance of increased tricuspid regurgitant jet velocity on echocardiography has not yet been identified in children, whereas increased albuminuria is a good predictor of kidney injury. Finally, screening for hip and eye disorder is recommended; however, different countries adopt different screening strategies. Hydroxyurea is probably of potential benefit in preventing chronic organ damage but this requires further study in order to be fully demonstrated. Efficacy and safety of the other new drugs available are also under investigation.

American Society of Hematology 2020 guidelines for sickle cell disease: prevention, diagnosis, and treatment of cerebrovascular disease in children and adults

BACKGROUND

Central nervous system (CNS) complications are among the most common, devastating sequelae of sickle cell disease (SCD) occurring throughout the lifespan.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology are intended to support the SCD community in decisions about prevention, diagnosis, and treatment of the most common neurological morbidities in SCD.

METHODS

The Mayo Evidence-Based Practice Research Program supported the guideline development process, including updating or performing systematic evidence reviews. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including GRADE evidence-to-decision frameworks, to assess evidence and make recommendations.

RESULTS

The panel placed a higher value on maintaining cognitive function than on being alive with significantly less than baseline cognitive function. The panel developed 19 recommendations with evidence-based strategies to prevent, diagnose, and treat CNS complications of SCD in low-middle- and high-income settings.

CONCLUSIONS

Three of 19 recommendations immediately impact clinical care. These recommendations include: use of transcranial Doppler ultrasound screening and hydroxyurea for primary stroke prevention in children with hemoglobin SS (HbSS) and hemoglobin Sβ0 (HbSβ0) thalassemia living in low-middle-income settings; surveillance for developmental delay, cognitive impairments, and neurodevelopmental disorders in children; and use of magnetic resonance imaging of the brain without sedation to detect silent cerebral infarcts at least once in early-school-age children and once in adults with HbSS or HbSβ0 thalassemia. Individuals with SCD, their family members, and clinicians should become aware of and implement these recommendations to reduce the burden of CNS complications in children and adults with SCD.

Advances in neuroimaging to improve care in sickle cell disease

Sickle cell disease is associated with progressive and increased neurological morbidity throughout the lifespan. In people with sickle cell anaemia (the most common and severe type of sickle cell disease), silent cerebral infarcts are found in more than a third of adolescents by age 18 years and roughly half of young adults by age 30 years, many of whom have cognitive impairment despite having few or no conventional stroke risk factors. Common anatomical neuroimaging in individuals with sickle disease can assess structural brain injury, such as stroke and silent cerebral infarcts; however, emerging advanced neuroimaging methods can provide novel insights into the pathophysiology of sickle cell disease, including insights into the cerebral haemodynamic and metabolic contributors of neurological injury. Advanced neuroimaging methods, particularly methods that report on aberrant cerebral blood flow and oxygen delivery, have potential for triaging patients for appropriate disease-modifying or curative therapies before they have irreversible neurological injury, and for confirming the benefit of new therapies on brain health in clinical trials.

MRI detection of brain abnormality in sickle cell disease

Introduction: Over the past decades, neuroimaging studies have clarified that a significant proportion of patients with sickle cell disease (SCD) have functionally significant brain abnormalities. Clinically, structural magnetic resonance imaging (MRI) sequences (T2, FLAIR, diffusion-weighted imaging) have been used by radiologists to diagnose chronic and acute cerebral infarction (both overt and clinically silent), while magnetic resonance angiography and venography have been used to diagnose arteriopathy and venous thrombosis. In research settings, imaging scientists are increasingly applying quantitative techniques to shine further light on underlying mechanisms.Areas covered: From a June 2020 PubMed search of 'magnetic' or 'MRI' and 'sickle' over the previous 5 years, we selected manuscripts on T1-based morphometric analysis, diffusion tensor imaging, arterial spin labeling, T2-oximetry, quantitative susceptibility, and connectivity.Expert Opinion: Quantitative MRI techniques are identifying structural and hemodynamic biomarkers associated with risk of neurological and neurocognitive complications. A growing body of evidence suggests that these biomarkers are sensitive to change with treatments, such as blood transfusion and hydroxyurea, indicating that they may hold promise as endpoints in future randomized clinical trials of novel approaches including hemoglobin F upregulation, reduction of polymerization, and gene therapy. With further validation, such techniques may eventually also improve neurological and neurocognitive risk stratification in this vulnerable population.

Tract-specific analysis and neurocognitive functioning in sickle cell patients without history of overt stroke

INTRODUCTION

Sickle cell disease (SCD) is a hereditary blood disorder in which the oxygen-carrying hemoglobin molecule in red blood cells is abnormal. SCD patients are at increased risks for strokes and neurocognitive deficit, even though neurovascular screening and treatments have lowered the rate of overt strokes. Tract-specific analysis (TSA) is a statistical method to evaluate microstructural WM damage in neurodegenerative disorders, using diffusion tensor imaging (DTI).

METHODS

We utilized TSA and compared 11 major brain WM tracts between SCD patients with no history of overt stroke, anemic controls, and healthy controls. We additionally examined the relationship between the most commonly used DTI metric of WM tracts and neurocognitive performance in the SCD patients and healthy controls.

RESULTS

Disruption of WM microstructure orientation-dependent metrics for the SCD patients was found in the genu of the corpus callosum (CC), cortico-spinal tract, inferior fronto-occipital fasciculus, right inferior longitudinal fasciculus, superior longitudinal fasciculus, and left uncinate fasciculus. Neurocognitive performance indicated slower processing speed and lower response inhibition skills in SCD patients compared to controls. TSA abnormalities in the CC were significantly associated with measures of processing speed, working memory, and executive functions.

CONCLUSION

Decreased DTI-derived metrics were observed on six tracts in chronically anemic patients, regardless of anemia subtype, while two tracks with decreased measures were unique to SCD patients. Patients with WMHs had more significant FA abnormalities. Decreased FA values in the CC significantly correlated with all nine neurocognitive tests, suggesting a critical importance for CC in core neurocognitive processes.

Preventive measures for the critical postexercise period in sickle cell trait and disease

The immediate postexercise/physical activity period is critical for sickle cell trait (SCT) carriers and disease (SCD) patients. Exercise-related blood acidosis is known to trigger the cascade of HbS deoxygenation and polymerization, leading to red blood cell sickling and subsequent complications. Unfortunately, two facts worsen exercise-related blood acidosis during the initial postexercise period: First, blood lactate and H⁺ concentrations continue to increase for several minutes after exercise completion, exacerbating blood acidosis. Second, blood lactate concentration remains elevated and pH altered for 20-45 min during inactivity after intense exercise, keeping acid/base balance disturbed for a long period after exercise. Therefore, the risk of complications (including vasoocclusive crises and even sudden death) persists and even worsens several minutes after intense exercise completion in SCT carriers or SCD patients. Light physical activity following intense exercise (namely, active recovery) may, by accelerating lactate removal and acid/base balance restoration, reduce the risk of complications. Scientific evidence suggests that light exercise at or below the first lactate threshold is an appropriate strategy.

Diverse manifestations of a sickle cell crisis

We describe the case of a 21-year-old man with a background of sickle cell disease (SCD) who was on acute presentation in a sickle cell crisis required immediate intensive care admission with red blood cell exchange and ventilatory support. He had right frontal lobe infarcts and extensive bilateral deep white matter lesions most likely secondary to fat embolism. Inpatient investigations demonstrated a patent foramen ovale, explaining the route of spread of the fat embolus. He then had a transcatheter closure of the atrial defect. The patient needed prolonged inpatient rehabilitation. He was discharged from hospital in a wheelchair secondary to severe lower limb neurology and bilateral knee heterotopic ossification. He lives with the possibility of early onset dementia and cognitive decline, requiring constant care. The case highlights the multiple manifestations of SCD and their diverse and debilitating consequences.