Transcranial Doppler in hemoglobin SC disease

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.

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.

Unusually High Prevalence of Stroke and Cerebral Vasculopathy in Hemoglobin SC Disease: A Retrospective Single Institution Study

INTRODUCTION

Unlike homozygous hemoglobin SS (HbSS) disease, stroke is a rare complication in hemoglobin SC (HbSC) disease. However, recent studies have demonstrated a high prevalence of silent stroke in HbSC disease. The factors associated with stroke and cerebral vasculopathy in the HbSC population are unknown.

METHODS

We conducted a retrospective study of all patients with sickle cell disease treated at the University of Missouri, Columbia, over an 18-year period (2000-2018). The goal of the study was to characterize the silent, overt stroke, and cerebral vasculopathy in HbSC patients and compare them to patients with HbSS and HbS/β thalassemia1 (thal) in this cohort. We also analyzed the laboratory and clinical factors associated with stroke and cerebral vasculopathy in the HbSC population.

RESULTS

Of the 34 HbSC individuals, we found that the overall prevalence of stroke and cerebral vasculopathy was 17.7%. Only females had evidence of stroke or cerebral vasculopathy in our HbSC cohort (33.3%, p = 0.019). Time-averaged means of maximum velocities were lower in the HbSC group than the HbSS group and did not correlate with stroke outcome. Among HbSC individuals, those with stroke and cerebral vasculopathy had a marginally higher serum creatinine than those without these complications (0.77 mg/dL vs. 0.88 mg/dL, p = 0.08). Stroke outcome was associated with recurrent vaso-occlusive pain crises (Rec VOCs) (75 vs. 25%, p = 0.003) in HbSC patients. The predominant cerebrovascular lesions in HbSC included microhemorrhages and leukoencephalopathy.

CONCLUSION

There is a distinct subset of individuals with HbSC who developed overt, silent stroke, and cerebral vasculopathy. A female predominance and association with Rec VOCs were identified in our cohort; however, larger clinical trials are needed to identify and confirm specific clinical and laboratory markers associated with stroke and vasculopathy in HbSC disease.

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.

Distribution of sickle cell disease and assessment of risk factors based on transcranial Doppler values in the Gulf region

Background/Objective: Stroke is a potentially fatal complication of sickle cell disease (SCD). Transcranial Doppler (TCD) is useful at identifying increased risk of stroke in children with SCD and vasospasm after subarachnoid hemorrhage. The main aim of this study was to determine the proportion of patients with SCD in the Gulf region who are at a high risk of stroke, as determined by TCD.Methods: This multicenter (Oman, Qatar, and UAE), descriptive, cross-sectional study in patients (aged 2-16 years) with SCD included a baseline visit, 1 follow-up visit for patients with conditional TCD, and 3-year retrospective data analysis for all patients.Results: Of the 410 eligible patients (Oman, 86.5%; Qatar, 8.2%; UAE, 5.1%), most had a TCD finding (left side, 91.7%; right side, 92.0%) of normal velocity (<155 cm/s) at baseline. For 6 of 7 patients with conditional velocity (155-179 cm/s) and 1 patient with high velocity (≥180 cm/s), baseline TCD results were not confirmed at follow-up. As per bivariate linear regression, age, race, transfusion type, and transfusion frequency were significant predictors of the TCD velocities. Multivariate logistic regressions revealed that TCD velocities were significantly correlated with sex, race, and type of transfusion. No patients reported any adverse events at follow-up. No deaths occurred during the study.Discussion/Conclusions: The study results show that far fewer patients with SCD in the Gulf have abnormal TCD findings than the internationally reported. Larger studies are needed to identify the factors underlying this observation.

Clinical and hematological profile in a newborn cohort with hemoglobin SC

OBJECTIVES

Hemoglobin SC is the second most common variant of sickle-cell disease worldwide, after hemoglobin SS. The objectives of the study were to describe the clinical and laboratory characteristics of hemoglobin SC disease in children from a newborn screening program and treated at a blood center.

METHODOLOGY

This study assessed a cohort of 461 infants born between 01/01/1999 and 12/31/2012 and followed-up until 12/31/2014. Clinical events were expressed as rates for 100 patient-years, with 95% confidence intervals. Kaplan-Meier survival curves were created.

RESULTS

The median age of patients was 9.2 years; 47.5% were female. Mean values of blood tests were: hemoglobin, 10.5g/dL; reticulocytes, 3.4%; white blood cells, 11.24×10⁹/L; platelets, 337.1×10⁹/L; and fetal hemoglobin, 6.3%. Clinical events: acute splenic sequestration in 14.8%, blood transfusion 23.4%, overt stroke in 0.2%. The incidence of painful vaso-occlusive episodes was 51 (48.9-53.4) per 100 patient-years and that of infections, 62.2 episodes (59.8-64.8) per 100 patient-years. Transcranial Doppler ultrasonography (n=71) was normal given the current reference values for SS patients. Hydroxyurea was given to ten children, all of whom improvement of painful crises. Retinopathy was observed in 20.3% of 59 children who underwent ophthalmoscopy. Avascular necrosis was detected in seven of 12 patients evaluated, predominantly in the left femur. Echocardiogram compatible with pulmonary hypertension was recorded in 4.6% of 130 children, with an estimated average systolic pulmonary artery pressure of 33.5mmHg. The mortality rate from all causes was 4.3%.

CONCLUSIONS

Clinical severity is variable in SC hemoglobinopathy. Several children have severe manifestations similar to those with SS disease.

Pattern of Cerebral Blood Flow Velocity Using Transcranial Doppler Ultrasonography in Children with Sickle Cell Disorder in Lagos State, Nigeria

Cerebrovascular accident (CVA) is a common, devastating neurological complication of sickle cell disorder (SCD) with a high recurrent and mortality rate. The Stroke Prevention Trial in Sickle Cell Anaemia study (STOP) recommends routine screening with transcranial Doppler ultrasonography in children aged two to sixteen years with SCD. The present study assessed cerebral blood flow velocities of children with SCD in accordance with the recommendation of routine screening by the STOP study.

METHODS

Transcranial Doppler ultrasonography was done for children with SCD that attended Sickle Cell Foundation, Nigeria between July and November 2015.

RESULTS

In all, 388 subjects were screened within the study period (360 HbSS and 28 HbSC). The prevalence of abnormal Time-Averaged Maximum Mean Velocity (TAMMV) of at least 200 cm/second was 10.8%: this was seen solely in HbSS subjects. The mean Time-averaged mean of the maximum (TAMM) velocity were 163±25 cm/sec, 162±30 cm/sec and 150±30 cm/sec for children less than five years, five to ten years and eleven to sixteen years respectively.

CONCLUSION

The prevalence of abnormal TAMM velocity in children with HbSS is 10.8%. Identification of subjects at risk helped in primary CVA prevention by prompt therapy institution.

Laboratory and Genetic Biomarkers Associated with Cerebral Blood Flow Velocity in Hemoglobin SC Disease

Reference values for cerebral blood flow velocity (CBFV) in hemoglobin SC disease (HbSC) have not been established. We aimed to investigate associations between laboratory and genetic biomarkers associated with CBFV in HbSC children. Sixty-eight HbSC children were included; CBFV was analyzed by transcranial Doppler, and the time-averaged maximum mean velocity (TAMMV) was estimated. Hematological, biochemical, immunological, and genetic analyses were performed. TAMMV was negatively correlated with red blood cell count (RBC) count, hemoglobin, hematocrit, and direct bilirubin (DB), yet positively correlated with monocytes and ferritin. We found that children with TAMMV ≥ 128 cm/s had decreased red blood cell distribution width (RDW) and nitric oxide metabolite (NOx) concentration. Children with TAMMV ≥ 143.50 cm/s had decreased hemoglobin and hematocrit, as well as increased ferritin levels. Decreased hemoglobin, hematocrit, RDW, and NOx and increased ferritin were detected in children with TAMMV ≥ 125.75 cm/s. The CAR haplotype was associated with higher TAMMV. In association analyses, RBC, hemoglobin, hematocrit, RDW, monocyte, DB, NOx, and ferritin, as well as the CAR haplotype, were found to be associated with higher TAMMV in HbSC children. Multivariate analysis suggested that high TAMMV was independently associated with hematocrit, RDW, and NOx. Additional studies are warranted to validate the establishment of a cutoff value of 125.75 cm/s associated with elevated TAMMV in HbSC children.